Ingenieurwissenschaften und zugeordnete Tätigkeiten
Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (425) (entfernen)
Sprache
- Englisch (297)
- Deutsch (117)
- Russisch (6)
- Italienisch (2)
- Chinesisch (2)
- Mehrsprachig (1)
Referierte Publikation
- nein (425) (entfernen)
Schlagworte
- Additive manufacturing (23)
- KorroPad (18)
- Nichtrostender Stahl (18)
- Korrosionsschnelltest (17)
- Passivschicht (17)
- Electron backscatter diffraction (15)
- Corrosion (13)
- Laser beam welding (12)
- Nanoparticles (11)
- Korrosion (9)
- Additive Fertigung (8)
- Laser metal deposition (8)
- Steel (8)
- Additive Manufacturing (7)
- Electron microscopy (7)
- SEM (7)
- Composite (6)
- Heat treatment (6)
- Laser implantation (6)
- Microstructure (6)
- SAXS (6)
- TED-GC/MS (6)
- AFM (5)
- CCS (5)
- Friction (5)
- Laserstrahlschweißen (5)
- Mechanical properties (5)
- Microplastics (5)
- Porosity (5)
- Sicherheit (5)
- Simulation (5)
- Wear (5)
- Welding (5)
- Widerstandspunktschweißen (5)
- Cement (4)
- Druckgasbehälter (4)
- Feuerwehr (4)
- Hydrogen (4)
- Laser-induced periodic surface structures (LIPSS) (4)
- Niobium carbide (4)
- Phase identification (4)
- Quality assurance (4)
- Qualitätssicherung (4)
- TiO2 (4)
- Tribology (4)
- Applications (3)
- Aquifer (3)
- Carbon storage (3)
- Coating (3)
- Computed tomography (3)
- Corrosion Fatigue (3)
- Crystal orientation (3)
- Degradation (3)
- Diffusion (3)
- EDS (3)
- EPR (3)
- Faserverbundwerkstoff (3)
- Geothermie (3)
- High alloyed steel (3)
- High strength steel (3)
- Hot stamping (3)
- IgG (3)
- In situ measurement (3)
- Interface (3)
- Kurdjumov-Sachs (3)
- L-PBF (3)
- Laser processing (3)
- Laser welding (3)
- MALDI-TOF MS (3)
- Meteorite (3)
- Nickel (3)
- Nishiyama-Wassermann (3)
- Numerical modelling (3)
- Orientation relationship (3)
- Particle size distribution (3)
- Polylactide (3)
- Rheology (3)
- Sintering (3)
- Solidification cracking (3)
- Surface modification (3)
- Thick-walled steel (3)
- Tribofilm (3)
- Wasserstoff (3)
- Weld defects (3)
- Weld pool shape (3)
- XPS (3)
- Affinitätschromatographie (2)
- Alkali zinc borate glasses (2)
- Alkali-activated materials (2)
- Alterung (2)
- Alumina (2)
- Aluminium (2)
- Anlagensicherheit (2)
- Arbeitsschutz (2)
- Auftragschweißen (2)
- Austenitic stainless steels (2)
- Automation (2)
- Betoninstandsetzung (2)
- Binder Jetting (2)
- Cermet (2)
- Cladding parameter (2)
- Composites (2)
- Corrosion evolution (2)
- Corrosion fatigue (2)
- Corrosion rate (2)
- Crack propagation (2)
- Creep (2)
- Critical strain (2)
- DED (2)
- Design of experiments (2)
- Directed Energy Deposition (2)
- Directed energy deposition (2)
- Disposal repository (2)
- Distortion (2)
- Duplex stainless steels (2)
- Durability (2)
- EBSD (2)
- Embrittlement (2)
- End crater (2)
- Endurance limit (2)
- Energy dispersive x-ray spectroscopy (2)
- Explosionsgrenzen (2)
- Explosivstoffe (2)
- FEM (2)
- FIB (2)
- Fatigue (2)
- Fatigue crack propagation threshold (2)
- Festigkeit (2)
- Functionalized graphene (2)
- Gold (2)
- HAXPES (2)
- HPLC (2)
- Hardness (2)
- High Alloyed Steel (2)
- Hochfester Stahl (2)
- Hot cracking (2)
- Hybrid laser arc welding (2)
- Hybrid laser-arc welding (2)
- Hybrid welding (2)
- Imaging (2)
- Künstliche Intelligenz (2)
- LIBS (2)
- Laser cladding (2)
- Laser hybrid welding (2)
- Laser powder bed fusion (2)
- Laser-Pulver-Auftragschweißen (2)
- Laser-induced slip casting (2)
- Laserhybridschweißen (2)
- Layerwise Slurry Deposition (2)
- Lead borate glasses (2)
- Legierungen (2)
- Liquid Metal Embrittlement (2)
- Local critical strain (2)
- Lochkorrosion (2)
- Mass transport (2)
- Mathematical modeling (2)
- Mechanical Engineering (2)
- Mechanically mixed layer (2)
- Medical implants (2)
- Microstructures (2)
- Mikroplastik (2)
- Molecular Dynamics (2)
- NIR (2)
- Nanomaterial (2)
- Nanoparticle (2)
- Nanostructures (2)
- NbC (2)
- Neutron imaging (2)
- Ni-base superalloy (2)
- Nickel alloys (2)
- Non-destructive testing (2)
- Nuclear waste (2)
- Oberflächenintegrität (2)
- Optical flow (2)
- Orientation distribution (2)
- Pattern matching (2)
- Phase transformation (2)
- Pipe manufacturing (2)
- Pipeline (2)
- Pitting (2)
- Polysaccharides (2)
- Protein A (2)
- Protein G (2)
- Residual stress (2)
- Ring-opening polymerization (2)
- Rissbildung (2)
- Sample preparation (2)
- Schmiedeteile (2)
- Schutzgasschweißen (2)
- Semiconductor (2)
- Sensor (2)
- Single pass welding (2)
- Sliding simulation (2)
- Solidification (2)
- Superellipse (2)
- Surface structuring (2)
- Surface texturing (2)
- TEM (2)
- TIG welding (2)
- Temperature field (2)
- Thermography (2)
- Tool wear (2)
- Toxicology (2)
- Transesterification (2)
- Trinkwasser (2)
- Ultraschall (2)
- Ultraschallunterstütztes Fräsen (2)
- Ultrashort laser pulses (2)
- Ultrasound (2)
- Upconversion (2)
- Vacancies (2)
- Vakuum (2)
- Validation (2)
- Vaporization (2)
- Weldability (2)
- Wärmeführung (2)
- X-ray diffraction (2)
- X-ray scattering (2)
- Zerstörungsfreie Prüfung (2)
- laser welding (2)
- nanoparticle (2)
- 100Cr6 (AISI 52100) steel (1)
- 150 Years (1)
- 2D chromatography (1)
- 2D nanomaterials (1)
- 2PP (1)
- 316L (1)
- 3D (1)
- 3D Druck (1)
- 3D Fourier Transform (1)
- 3D-printing (1)
- AISI D2 (1)
- ASR (1)
- ATR-FTIR (1)
- ATZ (1)
- Ab initio calculations (1)
- Acicular ferrite (1)
- Acid-leaching (1)
- Additive manufactured Ni-base superalloys (1)
- Additive manufacturing, 3D printing (1)
- Additives (1)
- Adolf Martens (1)
- Adsorbates (1)
- Adsorbent (1)
- Advanced High-Strength Steel (AHSS) (1)
- Advanced Oxidation (1)
- Affinity chromatography (1)
- Affinitätsextraktion (1)
- Agarose (1)
- Agglomerates (1)
- Aggregate scattering (1)
- Aging (1)
- Air fragmentation (1)
- Aktiv-Passiv-Element (1)
- Aktivkohle (1)
- Akzeptanzwahrscheinlichkeit (1)
- Al-Composite (1)
- Al/SiO2 composite (1)
- Al2O3 (1)
- AlSi10Mg (1)
- AlSi10Mg alloy (1)
- Alkali-Kieselsäure-Reaktion (1)
- Alkali-silica-reaction (1)
- Alpha-tricalcium phosphate (1)
- Alumina toughened zirconia (1)
- Aluminiumlegierung (1)
- Aluminum alloy (1)
- Aluminum alloys (1)
- Ambient vibration measurements (1)
- Ammonium nitrate (1)
- Amorphous silica (1)
- Ancient document production (1)
- Anisotropy (1)
- Annealing (1)
- Anodization (1)
- Anpassung (1)
- Antibacterial agent (1)
- Antibody coating (1)
- Antifouling surface coatings (1)
- Antikörper (1)
- Antimicrobial (1)
- Antimony black (stibnite) (1)
- Anwendungsmöglichkeiten (1)
- Arbeitsanleitung (1)
- Artificial neural network (1)
- As-shielded arc welding (1)
- Atemschutz (1)
- Atomic force microscope (1)
- Atomic force microscopy (1)
- Austenite (1)
- Austenite-to-martensite transformation (1)
- Automatisation (1)
- Automatische Bildbewertung (1)
- Automobilindustrie (1)
- Automotive braking (1)
- Azimuthal projection (1)
- BPF-LB/M (1)
- BREXIT (1)
- Back scatter (1)
- Backlight (1)
- Backscattered electron imaging (1)
- Backscattered electrons (1)
- Bainitischer Schmiedestahl (1)
- Basin (1)
- Baustoffe (1)
- Bauteilauslegung (1)
- Bauteilschweißungen (1)
- Bead-on-plate welds (1)
- Beam oscillation (1)
- Belüftungselement (1)
- Bending modulus (1)
- Berstprüfung (1)
- Beständigkeit (1)
- Beton (1)
- Betonfahrbahndecke (1)
- Betonfahrbahndecken (1)
- Betriebsfestigkeit (1)
- Bildverarbeitung (1)
- Bimetallkorrosion (1)
- Bimodal size distribution (1)
- Bio-SAXS (1)
- Bio-based concrete (1)
- Bio-ceramic engineering (1)
- BioSAXS (1)
- Biobased (1)
- Bioconjugation (1)
- Biokraftstoffe (1)
- Biosensor (1)
- Bitumen (1)
- Bitumen und bitumenhaltige Bindemittel (1)
- Bituminous material (1)
- Bond energy (1)
- Bonding Analysis (1)
- Bone screws (1)
- Borosilicatglas (1)
- Borosilikatglas (1)
- Bragg-edge imaging (1)
- Bremse (1)
- Bremsleitung (1)
- Brightness (1)
- Bruchlastwechselzahlen (1)
- Bruchmechanik (1)
- Bulge effect (1)
- Bulging (1)
- CALPHAD (1)
- CALPHAD approach (1)
- CFRP (1)
- CLP-Verordnung (1)
- CLP-regulation (1)
- CMT welding (1)
- CO adsoprtion (1)
- CO2 lasers (1)
- Cabon capture and storage (1)
- Calcium phosphate (1)
- Cancer (1)
- Cantilever microprobe (1)
- Carbon capture and storage (1)
- Carbon ink (1)
- Carbon nanotube (1)
- Carbon nanotubes (1)
- Carbonation (1)
- Carbonitride (1)
- Carolingian (1)
- Carrier gas hot extraction (1)
- Carrier plasmas (1)
- Carrier-Material (1)
- Castings (1)
- Catalogues (1)
- Catalysis (1)
- Catalyst (1)
- Ccs (1)
- Cell adhesion (1)
- Cell-repellent surfaces (1)
- Ceramic (1)
- Ceramic nano particles (1)
- Ceramics (1)
- Ceramics 3D printing (1)
- Ceria (1)
- Chalcopyrite (1)
- Charakterisierung (1)
- Charpy impact toughness (1)
- Charpy toughness (1)
- Chemical admixtures (1)
- Chemical composition (1)
- Chemicals classification (1)
- Chemikalienrecht (1)
- Chemisch instabile Gase (1)
- Chemometrie (1)
- Chitosan (1)
- Chlorbutylkautschuk (1)
- Cimensional Accuracy (1)
- Circular economy (1)
- Circumferential weld (1)
- Classification (1)
- Cluster (1)
- Co2-Storage (1)
- Coarse-grained heat-affected zone (1)
- Coda wave interferometry (1)
- Cohesive zone (1)
- Cold cracking (1)
- Color key (1)
- Colourants (1)
- Colouring (1)
- Combined sewer system (1)
- Compatibility (1)
- Compatibility evaluation (1)
- Composite material (1)
- Compound semiconductors (1)
- Computational Materials Science (1)
- Computations (1)
- Computed Tomography (1)
- Computer simulation (1)
- Concrete (1)
- Concrete pavements (1)
- Concrete's porosity (1)
- Condition monitoring (1)
- Conductive carbon tape (1)
- Conference (1)
- Contact resistance (1)
- Contact resonance (1)
- Convolutional neural networks (1)
- Cooling rate (1)
- Coordinate transformation (1)
- Coptic papyri (1)
- Core-clusters (1)
- Corrosion environment (1)
- Corrosion mechanism (1)
- Corrosion product (1)
- Cosolute (1)
- Coulomb explosion (1)
- Cr(III) (1)
- CrMnFeCoNi (1)
- Crack (1)
- Crack closure effect (1)
- Crack growth (1)
- Crack initiation (1)
- Crack-tip constraint (1)
- Cracks (1)
- Creep damage (1)
- Creep models (1)
- Critical energy release rate (1)
- Critical strain rate (1)
- Cryogenic einvironment (1)
- Cryogenic steel (1)
- Crystal (1)
- Crystal class (1)
- Crystal lattice (1)
- Crystal plasticity (1)
- Crystalinity (1)
- Crystallization (1)
- Cube slip (1)
- Cubical shape (1)
- Cyclic R-curve (1)
- Cyclic traffic loading and mechanical pre-damage (1)
- Cylindrical turning (1)
- DED-LB (1)
- DEM (1)
- DICTRA modeling (1)
- DNA (1)
- DRIFTS (1)
- Damage (1)
- Damage tolerance (1)
- Dangerous goods (1)
- Data preparation (1)
- Data-driven material design (1)
- Dead Sea Scrolls (1)
- Debye-Waller-Faktor (1)
- Debye–Waller factor (1)
- Decarburization (1)
- Deep penetration (1)
- Defect detection (1)
- Degradation of polyethylene (1)
- Density functional theory (1)
- Density separation (1)
- Density-based Model (1)
- Dentine (1)
- Dichtungswerkstoffe (1)
- Diffraction analysis (1)
- Digital Image Correlation (1)
- Digital detector arrays (1)
- Digital radiography (1)
- Direct energy deposition (1)
- Directed Energy Depositio (1)
- Disc brakes (1)
- Discontinuities (1)
- Dislocation structure (1)
- Dislocations (1)
- Dispersion process (1)
- Dissimilar metal weld overlays (1)
- Dokumentation (1)
- Dosimetry (1)
- Downstream Processing (1)
- Drehen (1)
- Druck (1)
- Druckschwellenversuch (1)
- Druckstabilität (1)
- Dry sliding (1)
- Duplex (1)
- Duplex AISI 2205 (1)
- Duplex stainless steel (1)
- Durchstrahlungsprüfung (1)
- Dyes and pigments (1)
- Dynamic Light Scattering (1)
- Dynamical simulation (1)
- EBSD pattern (1)
- ECD-Aktorschicht (1)
- EDX (1)
- EPMA (Electron Probe Microanalysis) (1)
- EU-CLP (1)
- Earth block (1)
- Earth mortar (1)
- Ectoin (1)
- Ectoine (1)
- Editorial (1)
- Eigenspannungen (1)
- Eindeutige Kennzeichnung (1)
- Eindringtechnik (1)
- Eisenaluminid (1)
- Elastic waves (1)
- Elastomer Dichtung (1)
- Elastomere (1)
- Electrical conductivity (1)
- Electrochemical deposition (1)
- Electrochemical treatment (1)
- Electromagnetic backing (1)
- Electromagnetic forces (1)
- Electromagnetic weld pool support (1)
- Electromagnetic weld pool support system (1)
- Electron Rutherford backscattering (1)
- Electron beam cladding (1)
- Electron beam-induced fragmentation (1)
- Electron density map (1)
- Electron diffraction (1)
- Electron probe microanalysis (EPMA) (1)
- Elektrochemie (1)
- Elektromagnetische Badstütze (1)
- Elektromagnetische Schmelzbadunterstützung (1)
- Element transport (1)
- Elemental composition (1)
- Embedded electronics (1)
- Enamel (1)
- Endurance Limit (1)
- Energetic materials (1)
- Energy parameters of the arc (1)
- Energy systems (1)
- Entsorgung gefährlicher Stoffe (1)
- Entwicklung (1)
- Environmental conditions (1)
- Environmentally assisted cracking (1)
- Epoxy (1)
- Equal area projection (1)
- Equilibration (1)
- Ermüdungsverhalten (1)
- Error sources analysis (1)
- Eutectic (1)
- Evaporation (1)
- Evolution (1)
- Excitation (1)
- Experimental kinetics (1)
- Experimental procedure (1)
- Explosion (1)
- Explosionsgefährliche Eigenschaften (1)
- Explosionsschutz (1)
- Explosivbearbeitung (Plattieren, Härten) (1)
- Explosivstoffrichtlinie (1)
- Extreme environments (1)
- FAIR data (1)
- FAME (1)
- FEM simulation (1)
- FFT (1)
- FPLC (1)
- FT-IR (1)
- FT-Raman (1)
- FTIR (1)
- FTIR-Spektroskopie (1)
- Faseroptik-Sensoren (1)
- Fatigue behavior (1)
- Fatigue life (1)
- Fatigue properties (1)
- Fatigue strength (1)
- Fatigue tests (1)
- Fe3O4 (1)
- Femtosecond laser processing (1)
- Femtosecond laser-processing (1)
- Ferroic cooling (1)
- Feuchtesorption (1)
- Fiber Bragg grating (1)
- Fiber toxicology (1)
- Fiber-reinforced concrete (1)
- Fibre release (1)
- Field flow fractionation (1)
- Filler wire (1)
- Film replacement (1)
- Film thickness (1)
- Filmersatz durch digitale Detektoren (1)
- Fine-grained Steel (1)
- Finite Element Method (1)
- Finite-element method (1)
- Flaschenventile (1)
- Flexural rigidity (1)
- Fluorides (1)
- Force-distance curves (1)
- Fracture (1)
- Fracture mechanics (1)
- Fracture surface energy (1)
- Fragility (1)
- Fraktographie (1)
- Friction stir welding (1)
- Fräsbearbeitung (1)
- Functional fatigue (1)
- Fundamental zone (1)
- Fungicidal property (1)
- Funktionale Betonoberfläche (1)
- Fusion Zone (1)
- G5P (1)
- GAPSI 16 (1)
- GHS (1)
- GTR 13 (1)
- GVP (1)
- Gap bridgeability (1)
- Gas flow assisted powder deposition (1)
- Gas separation (1)
- Gas shielded arc welding (1)
- Gas sorption (1)
- Gas tungsten arc welding (1)
- Gas tungsten arc welding (GTAW) (1)
- Gase (1)
- Gaspermeation (1)
- Geant4 (1)
- Geant4-DNA (1)
- Gefahrgruppen (1)
- Gefahrstoff (1)
- Gefahrstoffrecht (1)
- Gefahrstoffverordnung (1)
- Gefährlicher Stoff (1)
- General Chemistry (1)
- General Materials Science (1)
- Geometrical effect (1)
- Geometrical factors (1)
- Geometrical model (1)
- Geteilte Infrastruktur (1)
- Getting started (1)
- Giulio Romano (1)
- Glasmonolith (1)
- Glass (1)
- Glass powder (1)
- Glasses (1)
- Globally harmonized system of classification and labelling of chemicals (1)
- Gnomonic projection (1)
- Grafting (1)
- Grain boundary engineering (1)
- Grain boundary sliding (1)
- Grain growth (1)
- Grain size (1)
- Graphen (1)
- Graphene powder (1)
- Graphit (1)
- Graphitization (1)
- Greens function method (1)
- Ground penetrating radar (1)
- Growth competition (1)
- Gussteilprüfung (1)
- Gutachten (1)
- HAZPRED (1)
- HCF (1)
- HTMS (1)
- Hard X-ray photoelectron spectroscopy (HAXPES) (1)
- Hard materials (1)
- Hardening (1)
- Hardness measurement (1)
- Hausbockkäfer (1)
- Hazardous chemicals (1)
- Hazardous substances (1)
- Heat Input (1)
- Heat Treatment (1)
- Heat conduction (1)
- Heat flux estimation (1)
- Heat saturation function (1)
- Heating oil with 10 % FAME (1)
- Hebrew studies (1)
- Heterostructure field effect transistor (1)
- Heusler alloys (1)
- Hi-Tension (1)
- Hibbingite (1)
- Hierarchical micro-nanostructures (1)
- High Cycle Fatigue (1)
- High energy synchrotron diffraction (1)
- High entropy alloy (1)
- High power laser beam welding (1)
- High resolution (1)
- High temperature (1)
- High-power fibre laser (1)
- High-strength fine-grained steels (1)
- High-temperature properties (1)
- Highspeed (1)
- Hochfeste Feinkornbaustähle (1)
- Hochleistungskeramik (1)
- Holy Family (1)
- Holzschutz (1)
- Holzschutzmittel (1)
- Hot cracking test (1)
- Hot isostatic pressing (HIP) (1)
- Hot working tool steel (1)
- Hot-Stamping (1)
- Human umbilical cell adhesion (1)
- Hybrid Laser Arc Welding (1)
- Hybrid Manufacturing (1)
- Hybrid metrology (1)
- Hybridschweißen (1)
- Hydration (1)
- Hydrogen measurement (1)
- Hydrophobic interaction (1)
- Hylotrupes bajulus, Anobium punctatum, natural durability, tropical wood, native wood. (1)
- Härteprüfung (1)
- ICP-MS (1)
- IR spectroscopy (1)
- ISO 3690 (1)
- ISO 6892-1 (1)
- Identifizierung von Additiven (1)
- Image segmentation (1)
- Image-based analysis (1)
- Imaging plates (1)
- Immobilisierung (1)
- Immunglobulin (1)
- Immunglobuline (1)
- Immunoaffinity extraction (1)
- Immunoassay (1)
- Immunocapture (1)
- Immunoglobulins (1)
- Immunoprecipitation (1)
- Immunosensor (1)
- Implant material (1)
- In-line Monitoring (1)
- In-situ (1)
- Inconel 625 (1)
- Inconel 718 (1)
- Indentation hardness (1)
- Induction heating (1)
- Industrial and Manufacturing Engineering (1)
- Inertisierung (1)
- Infrared spectroscopy (1)
- Infrared thermography (1)
- Initial shear strength (1)
- Ink (1)
- Ink analyses (1)
- Ink analysis (1)
- Ink corrosion (1)
- Innenhydrophobierung (1)
- Innovationsrecht (1)
- Instrumental analysis of ink (1)
- Intelligent tribological material characterization (1)
- Intelligente tribologische Werkstoffcharakterisierung (1)
- Intensity (1)
- Inter layer time (1)
- Inter-laboratory comparison (1)
- Interfacial shear strength (1)
- Intergranular strain (1)
- Interlaboratory comparison (1)
- Intermetallic phases (1)
- Interphase residual stress (1)
- Inverse design techniques (1)
- Inverse heat transfer problem (1)
- IoT (1)
- Ionic liquid (1)
- Ionizing radiation damage (1)
- Iridium-titanium mixed oxides (1)
- Iron aluminide (1)
- Iron meteorites (1)
- Iron nanoparticles (1)
- Iron oxide (1)
- Iron-gall ink (1)
- Isotope dilution analysis (1)
- Joining dissimilar materials (1)
- K+ doped (1)
- K-nearest neighbor (1)
- Kaltrisse (1)
- Kaltzähe Stähle (1)
- Keramik (1)
- Kikuchi diffraction (1)
- Kikuchi pattern (1)
- Kinematic approach (1)
- Kitagawa-Takahashi diagram (1)
- Kl (1)
- Knudsen Effusion Mass Spectrometry (KEMS) (1)
- Kokillenguss (1)
- Konferenzbericht (1)
- Konzentrationselement (1)
- Korrosionsschutz (1)
- Korund (1)
- Kreislaufwirtschaft (1)
- Kupferazid (1)
- Kupferlegierungen (1)
- Kältemittel (1)
- Körperschall (1)
- LC-MS (1)
- LCF (1)
- LEE (1)
- LIBS TIG welding (1)
- LPSO (1)
- LTCC (1)
- LTT weld filler materials (1)
- Lab-to-field up-scaling (1)
- Lab-to-field upscaling (1)
- Laboratory energy-dispersive X-ray diffraction (EDXRD) (1)
- Laminography (1)
- Langsame Berstprüfung (1)
- Lanthanide (1)
- Large volume samplers (1)
- Laser (1)
- Laser Beam Welding (1)
- Laser Infrared thermography (1)
- Laser Metal Deposition (1)
- Laser Metal Deposition (LMD) (1)
- Laser Welding (1)
- Laser beam Welding (1)
- Laser beam melting (1)
- Laser dispersing (1)
- Laser metal fusion (1)
- Laser-Pulver-Auftragsschweißen (1)
- Laser-hybrid welding (1)
- Laser-induced micro- and nanostructures (1)
- Laser-metal-deposition (1)
- Laserschweißen (1)
- Lastwechselprüfung (1)
- Lattice misfit (1)
- Lattice structure (1)
- Lattices (1)
- Layered double hydroxide (1)
- Lebensdauer (1)
- Lebensdauervorhersage (1)
- Legierungsmodifikation (1)
- Lifetime (1)
- Lifetime prediction (1)
- Linear polyglycerol (1)
- Liquid Crystal (1)
- Liquid Metal Embrittlement (LME) (1)
- Liquid crystal (1)
- Lithium (1)
- Lithography-based technologies (1)
- Local fatigue spproaches (1)
- Localized Laser Dispersing (1)
- Localized laser dispersing (1)
- Lokale Effekte (1)
- Longitudinal weld (1)
- Lorenz transmission electron microscopy (1)
- Lotuseffekt (1)
- Low heat input GMA welding (1)
- Low themperature (1)
- Low transformation temperature (1)
- Low transformation temperature (LTT) steel (1)
- Low-cost (1)
- Lubricants (1)
- Lubricated sliding (1)
- Lötrissigkeit (1)
- Lüftung (1)
- MALDI (1)
- MALDI TOF MS (1)
- MCA-modeling (1)
- MIC (1)
- Machine learning optimization (1)
- Magnesium alloy (1)
- Magnetic bath support (1)
- Magnetic hyperthermia (1)
- Magnetic nanoparticles (1)
- Magneto-structural transition (1)
- Magnetocaloric materials (1)
- Magnéli phase (1)
- Manganese (1)
- Manuscript (1)
- Manuscript studies (1)
- Map production and publishing (1)
- Mapping for unseparable load (1)
- Maps and colours (1)
- Martensite (1)
- Martensitic steel (1)
- Maskinteknik (1)
- Masonry (1)
- Masonry tower (1)
- Mass contents (1)
- Mass spectrometry (1)
- Material defects (1)
- Material design (1)
- Material properties (1)
- Materialkennwerte (1)
- Materials (1)
- Materials Chemistry (1)
- Materials Properties (1)
- Materials Science (1)
- Materials database (1)
- Materialuntersuchung (1)
- McSAS3 (1)
- Mechanical Properties (1)
- Mechanical properties of the joints (1)
- Mechanical strength (1)
- Mechanics of Materials (1)
- Mechanische Eigenschaften (1)
- Mechanochemistry (1)
- Medium entropy alloy (1)
- Melt pool depth (1)
- Melting (1)
- Membrane polymers (1)
- Mesoporous thin films (1)
- Metadata (1)
- Metal halides (1)
- Metal organic framework (1)
- Metal-semiconductor (1)
- Metallschutzgasschweißen (1)
- Metals and Alloys (1)
- Metastable phases (1)
- Methanogene (1)
- Methods of scientific analysis (1)
- Microalloyed steel (1)
- Microarray printing (1)
- Microdosimetry (1)
- Micromechanical model (1)
- Microplastic analysis (1)
- Microplastic pathways (1)
- Microplastic pollution (1)
- Microplastics reference material (1)
- Microporous polymers (1)
- Microsegregation (1)
- Microstructure Design (1)
- Microwave (1)
- Middle Ages (1)
- Mikroplasik (1)
- Mikroplastik-Analyse (1)
- Mikroplastik-Analytik (1)
- Mikroplastik-Massengehalte (1)
- Mikrostruktur (1)
- Mikrostrukturierung (1)
- Misalignment of edges (1)
- Misorientation (1)
- Mixed Inks (1)
- Mixed ink (1)
- MoS2 (1)
- Model order reduction (MOR) (1)
- Model tuning (1)
- Modell der konstanten Flammentemperaturen (1)
- Modellierung (1)
- Modified spray arc (1)
- Molecular dynamics (1)
- Molecular mobility (1)
- Molybdenum carbide (1)
- Monte Carlo simulation (1)
- Monte-Carlo (1)
- Monte-Carlo simulation (1)
- Monte-Carlo simulations (1)
- Movable cellular automata (1)
- Multi-core particles (1)
- Multiphase microstructure (1)
- Multiple reflections (1)
- Multiple-layered scaffold (1)
- Multivariate Analysemethoden (1)
- Museumsschädling (1)
- Mussel-inspired adhesives (1)
- NDT (1)
- NaI (1)
- Nahtgeometrie (1)
- Nano (1)
- Nano CRM (1)
- Nano-ceramic-additive-manufacturing photoresin (1)
- Nano-powder (1)
- NanoCAM (1)
- NanoSIMS (1)
- Nanokomposite (1)
- Nanoparticle concentration (1)
- Nanopartikel (1)
- Nanoplastics (1)
- Nanowear (1)
- Naturbaustoffe (1)
- Neozoon (1)
- Networking (1)
- Neuronales Netz (1)
- Neutron Diffraction (1)
- Neutron radiography (1)
- Neutron tomography (1)
- Ni-Mn-Ga (1)
- Nicht lineare Prozesse (1)
- Nickel alloy (1)
- Nickel-/Nickel-Eisen- Magnetostriktion (1)
- Nickel-base superalloy (1)
- Nickelbasis (1)
- Niobcarbid (1)
- Niobcarbid (NbC) (1)
- Niobium carbide (NbC) (1)
- Non-destructive characterisation (1)
- Non-invasive scientific methods (1)
- Normung (1)
- Novel metrology (1)
- Novel optical measurement (1)
- Nucleation tendency (1)
- Numeric modelling (1)
- Numerical Simulation (1)
- Numerical process simulation (1)
- Numerical simulation (1)
- Numerical simulation of welding (1)
- Numerische Simulation (1)
- O-ring (1)
- OH Radical (1)
- OH radical scavenger (1)
- Oberflächenausführung (1)
- Oberflächentechnik (1)
- Online monitoring (1)
- Optical properties of ink (1)
- Optical temperature sensing (1)
- Organic peroxides (1)
- Orientation mapping (1)
- Orientation relationships (1)
- Oriented immobilization (1)
- Orientierungsverteilung (1)
- Oscillating ball-on-disc test (1)
- PBF-LB/M (1)
- PBFLB/M AlSi10Mg alloy (1)
- PCA (1)
- PDF (1)
- PEEK-Komposite (1)
- POD (1)
- PVD-Haftfestigkeit (1)
- Pacemaker (1)
- Paper sizings (1)
- Partial penetration (1)
- Particle (1)
- Particle erosion (1)
- Particle scatterin simulations (1)
- Particle transfer (1)
- Patch (1)
- Pattern quality (1)
- Pattern simulation (1)
- Pentimenti (1)
- Persian historical recipes (1)
- Phase distribution (1)
- Phase field model (1)
- Phase shifter (1)
- Phase-field (1)
- Photocatalysis (1)
- Photocatalyst (1)
- Photoluminescence (1)
- Photon counting detectors (1)
- Photophysics (1)
- Physical and optical characteristics (1)
- Physical hazards (1)
- Physical properties (1)
- Phytolith (1)
- Piezoresistive (1)
- Piezoresistive cantilever (1)
- Plane crystalization (1)
- Plasma (1)
- Plasma-cut samples (1)
- Plasticity (1)
- Platinum (1)
- Pollen (1)
- Polyaniline (1)
- Polycaprolactone (1)
- Polycrystal (1)
- Polyethylene Fibres (1)
- Polyethylene glycol (1)
- Polyglycolide (1)
- Polylactides (1)
- Polymer (1)
- Polymer Testing (1)
- Polymer intrinsischer Mikroporosität (1)
- Polymer matrix composites (1)
- Polymer-ceramic mixtures (1)
- Polymers (1)
- Polymorphism (1)
- Polyurethane acetate vinyl acrylate (1)
- Porous carbons (1)
- Porous film (1)
- Portrayal of St Joseph (1)
- Powder analysis (1)
- Powder bed density (1)
- Powder-based processes (1)
- Power density (1)
- Ppreheating temperature (1)
- Preceramic polymers (1)
- Preheating (1)
- Prill (1)
- Principal component analysis (1)
- Probability of detection (1)
- Probekörpergeometrien (1)
- Probennahme (1)
- Process (1)
- Process Monitoring (1)
- Process chain (1)
- Process monitoring (1)
- Projection imaging (1)
- Proper generalized decomposition (PGD) (1)
- Protection (1)
- Protein (1)
- Protein unfolding (1)
- Proximity-enhanced reaction (1)
- Prozessüberwachung (1)
- Präzision (1)
- Prüfmaschine (1)
- Prüfraster (1)
- Prüfung und Simulation (1)
- Prüfverfahren (1)
- Pseudosymmetry (1)
- Pufferschichten (1)
- Pull-out composite materials (1)
- Pulse electric current sintering (1)
- Pulse shaping (1)
- Pulsed laser beam welding (1)
- Push-out test (1)
- Pyrotechnik (1)
- QSPR (1)
- Qualität (1)
- Quantenausbeute (1)
- Quantum yield (1)
- REACH (1)
- RT (1)
- Radiation damage (1)
- Radical Scavenger (1)
- Radiography (1)
- Raman (1)
- Raman spectroscopy (1)
- Raphael school (1)
- Real-time rotation (1)
- Rebar (1)
- Recipes (1)
- Rectangular cross-section (1)
- Recyclability (1)
- Recyclingfähigkeit (1)
- Reference Material (1)
- Reference Method (1)
- Reference material (1)
- Reference nanoparticles (1)
- Refraction (1)
- Refractive index engineering (1)
- Regeneration (1)
- Reibung (1)
- Reinigung (1)
- Reliability (1)
- Renewable copolymers (1)
- Repair welding (1)
- Reparability (1)
- Reparierbarkeit (1)
- Reproducible data processing (1)
- Residual stresses (1)
- Resistance Spot Welding (RSW) (1)
- Resistance stress (1)
- Resonance frequency (1)
- Review (1)
- Reworking (1)
- Rheometry (1)
- Ring-expansion polymerization (1)
- Ripples (1)
- Rissanfälligkeit (1)
- Road inspection (1)
- Rohrleitungen (1)
- Rotational (1)
- Roughness (1)
- Round robin test (1)
- Rückverfolgbarkeit (1)
- SDB (1)
- SEC (1)
- Sample pretreatment (1)
- Sand-lime block (1)
- Scaffold (1)
- Scanning Probe Microscopy (1)
- Scanning electron microscopy (1)
- Scattering (1)
- Schadensanalyse (1)
- Schadstoffemission (1)
- Schadstoffsorption (1)
- Schallerzeuger (1)
- Schichtprüfung (1)
- Schiffsmotorbauteile (1)
- Schleifen (1)
- Schlickerdeposition (1)
- Schneidstoff (1)
- Schneidwaren (1)
- Schutzgas (1)
- SchwarzP cells (1)
- Schwarzpulverähnliches Reinigungspulver (1)
- Schweißeignung (1)
- Schweißsimulation (1)
- Schweißunregelmäßigkeiten (1)
- Schädigung (1)
- Scientific software (1)
- Scientific workflows (1)
- Seam geometry (1)
- Segregation Engineering (1)
- Selbstreinigende Oberfläche (1)
- Selective laser beam melting (1)
- Selektive-laser-melting (1)
- Self-healing (1)
- Self-reactive substances (1)
- Semantic web (1)
- Sensitivity analysis (1)
- Separate sewer system (1)
- Serum (1)
- Sets of archaeometric data (1)
- Shape memory polymer (1)
- Shape-memory alloys (1)
- Shared infrastruture (1)
- Shear bond test (1)
- Shielding gases (1)
- Short cracks (1)
- SiO2 (1)
- SiO2 Nanoparticle (1)
- Sicherheitsdatenblatt (1)
- Silica (1)
- Silica support (1)
- Silicon nitride (1)
- Silikatkeramik (1)
- Silver nanoparticles (1)
- Single asperity contact (1)
- Single crystal (1)
- Single crystal superalloys (1)
- Single particle (1)
- Single-pass welding (1)
- Single-shot XAFS (1)
- Single-stranded DNA-binding proteins (1)
- Sinter retardation (1)
- Sixteenth-century painting technique (1)
- Size (1)
- Size distribution (1)
- Sliding behaviour (1)
- Slurry (1)
- Small angle scattering (1)
- Small-angle X-ray scattering (1)
- Small-angle xray scattering (1)
- Small-scale specimens (1)
- Software (1)
- Solid lubricant (1)
- Solid lubrication (1)
- Space (1)
- Specific surface area (1)
- Spectral imaging (1)
- Spectroscopic Ellipsometry (1)
- Spectroscopic ellipsometry (1)
- Sphalerite (1)
- Sprengarbeiten (1)
- SrTiO3 (1)
- Stability (1)
- Stainless Steel (1)
- Standardisation (1)
- Standardisierung (1)
- Stationäre Phase (1)
- Statistical analysis (1)
- Steel and aluminium (1)
- Steel bar (1)
- Steel billets (1)
- Steels (1)
- Stereographic projection (1)
- Stichprobenumfang (1)
- Stormwater retention tank (1)
- Strain gauge factor (1)
- Strain measurement (1)
- Stress exponent (1)
- Stress-relief heat-treatments (1)
- String metal support interaction (1)
- Structural identification (1)
- Subgroup (1)
- Submerged arc welding (1)
- Superalloy (1)
- Superelasticity (1)
- Superlattice extrinsic stacking faults (1)
- Supermartensitic steel (1)
- Superplasticizers (1)
- Surface (1)
- Surface Integrity (1)
- Surface coating (1)
- Surface integrity (1)
- Surface structures (1)
- Surface-induced Melting (1)
- Survey (1)
- Sustainable concrete (1)
- Synchrotron X-ray diffraction (1)
- Synchrotron X-ray diffraction (SXRD) (1)
- Synchrotron X-ray refraction (1)
- Synchrotron computed tomography (1)
- TENSTAND WP4 Report (1)
- TKD (1)
- TRBS (1)
- TRGS (1)
- TRIS (1)
- TaC (1)
- Tafel Plot (1)
- Tannins (1)
- Tantalum carbide (1)
- Tauchen (1)
- Teaching (1)
- Technical Ceramics (1)
- Technical crack detection (1)
- Technical lignin (1)
- Technikrecht (1)
- Technische Regeln (1)
- Temperature (1)
- Temperature and humidity (1)
- Temperature sensitivity (1)
- Tensile properties (1)
- Termiten (1)
- Termites (1)
- Terpolymer (1)
- Test method (1)
- Testing (1)
- Textile binder (1)
- Textilschädling (1)
- Thermal coupling energy level (1)
- Thermal cycles (1)
- Thermal transient problem (1)
- Thermischer Ausdehnungkoeffizient (1)
- Thermoanalytische Verfahren (1)
- Thermochemistry (1)
- Thermoelectrics (1)
- Thermogravimetrie (1)
- Thermoplastic (1)
- Thick plate welding (1)
- Thick plates (1)
- Thick steel plates (1)
- Thick-plate welding (1)
- Thick-walled Structures (1)
- Thin film contact layer (1)
- Thin films (1)
- Thin steel plates (1)
- Thin tribofilm (1)
- Third body (1)
- Three-dimensional crystallization (1)
- Ti-6Al-4V (1)
- Ti-6Al-4V alloy (1)
- TiB2 (1)
- TiO2 nanoparticles (1)
- Time resolution (1)
- Time-of-flight secondary ion mass spectrometry (ToF-SIMS) (1)
- Tin acetates (1)
- Titan-Halterung (1)
- Titanaluminid (1)
- Titanium alloy (1)
- Titanium alloys (1)
- Titanium aluminides (1)
- Titanium carbide (1)
- Tnsile testing (1)
- Tooth wear (1)
- Topas-MC (1)
- Topas-nBio (1)
- TopasMC (1)
- Topographic analysis (1)
- Topographie (1)
- Torsion (1)
- Total scattering (1)
- Trabecular structures (1)
- Traceability (1)
- Transformation (1)
- Transmission Kikuchi Diffraction (TKD) (1)
- Transmission electron microscopy (1)
- Trennung (1)
- Tribo-Analytik (1)
- Tribo-analytics (1)
- Tribologie (1)
- Trilobite compound eyes (1)
- Triobology (1)
- Triplet test (1)
- Tubular X-joints (1)
- Tunable antenna (1)
- Tungsten carbide (WC) (1)
- Turbine blade (1)
- Two-photon adsorption (1)
- Two-photon polymerization (1)
- UN-GHS (1)
- UV-VIS (1)
- Ultrafast laser excitation (1)
- Ultrahochleistungsbeton (1)
- Ultrasonic Assisted Machining (1)
- Ultrasonic vibration (1)
- Ultrasonic-assisted milling (1)
- Umlaufkühler (1)
- Umweltsimulation (1)
- Unterpulverschweißen (1)
- Upconversion luminescence (1)
- V-notch impact toughness (1)
- VAMAS (1)
- Varestraint testing (1)
- Vasari (1)
- Ventile (1)
- Verarbeitung (1)
- Vererbung (1)
- Vergleichuntersuchung (1)
- Verkehrslasten (1)
- Verschleiß (1)
- Verzug (1)
- Vinyl monomer (1)
- Viscosity (1)
- Viscosity modifying agents (1)
- Viscous sintering (1)
- WRC 1992 diagram (1)
- Washing machine (1)
- Wasseraufbereitung (1)
- Wear particles (1)
- Weld filler (1)
- Weld imperfections (1)
- Weld metal (1)
- Weld pool (1)
- Weld pool dynamics (1)
- Weld pool modeling (1)
- Welding Current (1)
- Welding Simulation (1)
- Welding thermal cycle (1)
- Werkstoffauswahl (1)
- Werkstoffdatenbank (1)
- Werkstofffragen (1)
- Werkstoffranking (1)
- Werkzeug (1)
- White light interferometry (1)
- White-light Interference Microscopy (1)
- Widerstandspressschweißen (1)
- Windkraftanlagen (1)
- Workflow (1)
- Working mechanism (1)
- Wärmebehandlung (1)
- X-ray (1)
- X-ray absorption spectroscopy (1)
- X-ray photoelectron spectroscopy (1)
- X-ray tomography (1)
- X38CrMoV5-3 (1)
- XANES (1)
- XRD (1)
- YAG lasers (1)
- Yb(III) complex (1)
- Young’s Modulus (1)
- Zero wear (1)
- Zinc (1)
- Zinkbeschichtung (1)
- Zirconia (1)
- Zündenergie (1)
- Zündquellen (1)
- a-C:H (1)
- amorphous carbon film (1)
- amorphous silica film (1)
- bioactive (1)
- biokompatibel (1)
- biomaterials (1)
- bone (1)
- cascade reaction (1)
- catalysis (1)
- contact resonance (1)
- corrosion (1)
- cryogenic steel (1)
- dry friction (1)
- enatioselective (1)
- gesintert (1)
- glass-like carbon (1)
- hardness (1)
- high entropy alloys (1)
- hochfeste Stähle (1)
- hot-embossing (1)
- local effects (1)
- low temperature co-fired ceramics (1)
- machining (1)
- martensitisch (1)
- microstructure (1)
- molecular dynamics (1)
- nichtrostender Stahl (1)
- niobium carbide (1)
- optimale Überdeckungshöhe (1)
- organocatalysis (1)
- oxidation (1)
- plasticity (1)
- pressure-assisted sintering (1)
- quality assurance (1)
- resistance spot welding (1)
- scanning electron microscopy (1)
- sliding simulation (1)
- square amide (1)
- ssDNA (1)
- strength (1)
- sulfidation (1)
- tensile strength (1)
- vacuum (1)
- wear (1)
- Ökodesign (1)
- Ökonomische und ökologische Vorteile (1)
- Überlebenswahrscheinlichkeit (1)
- μCT-analysis (1)
- ГИДРОДИНАМИКА (1)
- КОНВЕКЦИЯ (1)
- ЛАЗЕРНАЯ СВАРКА (1)
- МЕТОД КОНЕЧНЫХ ЭЛЕМЕНТОВ (1)
- СВАРОЧНАЯ ВАННА (1)
- ТЕМПЕРАТУРНОЕ ПОЛЕ (1)
- ТЕПЛОПРОВОДНОСТЬ (1)
- ЧИСЛЕННОЕ МОДЕЛИРОВАНИЕ (1)
- кратер шва (1)
- кристаллизация, (1)
- плавление, (1)
- сварочная ванна (1)
- температурное поле (1)
- функция теплонасыщения (1)
Organisationseinheit der BAM
- 9 Komponentensicherheit (98)
- 6 Materialchemie (63)
- 9.3 Schweißtechnische Fertigungsverfahren (57)
- 5 Werkstofftechnik (49)
- 7 Bauwerkssicherheit (42)
- 7.6 Korrosion und Korrosionsschutz (25)
- 8 Zerstörungsfreie Prüfung (23)
- 4 Material und Umwelt (18)
- 6.6 Physik und chemische Analytik der Polymere (18)
- 9.4 Integrität von Schweißverbindungen (17)
Paper des Monats
- ja (1)
A method of solving the thermo-fluid dynamics problem is presented, enabling the prediction of the shape and dimensions of the weld pool during keyhole laser welding of thick plates. It is shown that the rear weld pool boundary can be satisfactorily approximated by a set of superellipses (Lamé curves). The presence of a convex rear weld pool boundary in the mid-plane has been observed experimentally and reproduced numerically. It was shown that in this zone the concentration of liquating impurities increases and the local solidification temperature decreases, contributing to the susceptibility to hot cracking.
Glycolide was polymerized in bulk by means of four different ROPPOC catalysts: tin(II) 2-ethylhexanoate (SnOct2), dibutyltin bis(pentafluoro-phenoxide) (BuSnOPF),zinc biscaproate (ZnCap), and zinc bis(pentafluoro-phenyl sulfide) (ZnSPF). The temperature was varied between 110 and 180°C and the time between 3 h and 7 days. For the few polyglycolides (PGAs) that were soluble extremely high molecular masses were obtained. The MALDI TOF mass spectra had all a low signal-to-noise ration and displayed the peaks of cyclic PGAs with a“saw-tooth pattern ”indicating formation of extended-ring crystallites in the mass range below m/z 2500. The shape of DSC curves varied considerably with catalyst and reaction conditions, whereas the long-distance values measured by SAXS were small and varied little with the polymeriza-tion conditions.
A giant Zn segregation transition is revealed using CALPHAD-integrated density-based modeling of segregation into Fe grain boundaries (GBs). The results show that above a threshold of only a few atomic percent Zn in the alloy, a substantial amount of up to 60 at.% Zn can segregate to the GB. We found that the amount of segregation abruptly increases with decreasing temperature, while the Zn content in the alloy required for triggering the segregation transition decreases. Direct evidence of the Zn segregation transition is obtained using high-resolution scanning transmission electron microscopy. Base on the model, we trace the origin of the segregation transition back to the low cohesive energy of Zn and a miscibility gap in Fe-Zn GB, arising from the magnetic ordering effect, which is confirmed by ab-initio calculations. We also show that the massive Zn segregation resulting from the segregation transition greatly assists with liquid wetting and reduces the work of separation along the GB. The current predictions suggest that control over Zn segregation, by both alloy design and optimizing the galvanization and welding processes, may offer preventive strategies against liquid metal embrittlement.
The stress-induced tetragonal to monoclinic (t-m) zirconia phase transformation can provide a certain degree of plasticity to Ceria-stabilized (Ce-TZP) zirconia-based composites. Characterizing and monitoring this phase transition on a millimeter-size range, within the bulk and in-situ remains a challenge. In this work, the mechanical behavior of Ce-TZP based composite was studied in tension, combining microscopy and synchrotron Xray refraction techniques. In contrast with microscopy methods, which only provide surface information, X-ray refraction radiography (SXRR) allowed the visualization of all the transformation bands, over the entire length and thickness of tested specimens, opening up new avenues for in-situ stress-induced t-m transformation studies.
Thermal transient problems, essential for modeling applications like welding and additive metal manufacturing, are characterized by a dynamic evolution of temperature. Accurately simulating these phenomena is often computationally expensive, thus limiting their applications, for example for model parameter estimation or online process control. Model order reduction, a solution to preserve the accuracy while reducing the computation time, is explored. This article addresses challenges in developing reduced order models using the proper generalized decomposition (PGD) for transient thermal problems with a specific treatment of the moving heat source within the reduced model. Factors affecting accuracy, convergence, and computational cost, such as discretization methods (finite element and finite difference), a dimensionless formulation, the size of the heat source, and the inclusion of material parameters as additional PGD variables are examined across progressively complex examples. The results demonstrate the influence of these factors on the PGD model’s performance and emphasize the importance of their consideration when implementing such models. For thermal example, it is demonstrated that a PGD model with a finite difference discretization in time, a dimensionless representation, a mapping for a moving heat source, and a spatial domain non-separation yields the best approximation to the full order model.
In this work we instigated the fragmentation of Au microparticles supported on a thin amorphous carbon film by irradiating them with a gradually convergent electron beam inside the Transmission Electron Microscope. This phenomenon has been generically labeled as “electron beam-induced fragmentation” or EBIF and its physical origin remains contested. On the one hand, EBIF has been primarily characterized as a consequence of beam-induced heating. On the other, EBIF has been attributed to beam-induced charging eventually leading to Coulomb explosion. To test the feasibility of the charging framework for EBIF, we instigated the fragmentation of Au particles under two different experimental conditions. First, with the magnetic objective lens of the microscope operating at full capacity, i.e. background magnetic field B = 2 T, and with the magnetic objective lens switched off (Lorenz mode), i.e. B = 0 T. We observe that the presence or absence of the magnetic field noticeably affects the critical current density at which EBIF occurs. This strongly suggests that magnetic field effects play a crucial role in instigating EBIF on the microparticles. The dependence of the value of the critical current density on the absence or presence of an ambient magnetic field cannot be accounted for by the beam-induced heating model. Consequently, this work presents robust experimental evidence suggesting that Coulomb explosion driven by electrostatic charging is the root cause of EBIF.
Functional fatigue of shape-memory alloys is a considerable threat to the reliable service of actuation devices. Here, we demonstrate the essentially degradation-free cyclic phase-transformation behavior of Ni-Mn-Ga microcrystals up to one million stress-driven superelastic cycles. Cyclic dissipation amounts to about 1/5 of the bulk counterpart and remains unaffected during cycling, even after the introduction of dislocation structures via plastic straining. Plastic yielding and the transformation stress largely exceed the known bulk values. However, the transformation-stress is found to depend on plastic pre-straining, which suggests that the size-affected transformation stress is sensitive to the initial defect structure and that it can be tuned by a targeted introduction of dislocations. These findings demonstrate the high suitability of Ni-Mn-Ga as a robust shape-memory alloy in small-scale functional device engineering.
Rotational rheometry test of Portland cement-based materials - A systematic literature review
(2024)
This study systematically reviews 62 papers on the use of rotational rheometry to assess the fresh state behavior of Portland cement-based materials. The research highlights the wide variation in test methods and aims to provide a comprehensive overview. Findings reveal that 50.0% of studies employed vane geometry, despite its limitations in providing transformation equations. Regarding dynamic shearing tests, 67.0% followed a consensus using a pre-shearing step and a step-wise routine with stabilization times ≥ 10 s. While the Bingham model is commonly used, the study emphasizes the importance of considering shear-thinning behavior in cementitious materials. Models like Herschel-Bulkley and modified Bingham may be more appropriate. This review offers insights into testing conditions for rotational rheometry of cementitious materials, serving as a foundation for future research in the field.
For the hydrogen-based energy economy of tomorrow, the construction of the necessary infrastructure will play a central role. Most materials used to date, such as welded steels, can be prone to hydrogen embrittlement under certain conditions. This includes the classic delayed cold cracking during welding as well as degradation phenomena during service of components in hydrogen-containing environment. For the evaluation of any hydrogen effect, for example, on the mechanical properties of a welded metallic material, the hydrogen content must be precisely determined. In the case of weld seams, the carrier gas hot extraction (CGHE) according to ISO 3690 is meanwhile state-of-the-art. CGHE is based on accelerated hydrogen degassing due to the thermal activation of hydrogen at elevated temperatures. In addition to the quantification of hydrogen, thermal desorption analysis (TDA) with varying heating rates can be used to determine and evaluate the hydrogen trapping at microstructural defects in the material. For both techniques, experimental and metrological influences must be considered, which have a major effect on the result. For example, ISO 3690 suggests different sample geometries and minimum extraction times for CGHE. This study summarizes the results and experiences of numerous investigations at the Federal Institute for Materials Research and Testing (BAM) with different sample temperatures and geometries (ISO 3690 type B and cylindrical TDA samples) regarding the influence of the sample surface (polished/welded), measurement accuracy depending on the sample volume and the insufficient monitoring of the effect of PI control on the extraction temperature. A deviating extraction temperature from the target temperature can significantly falsify the measurement results. Based on the results, methods are shown which allow the desired extraction temperature to be reached quickly without physically interfering with the measuring equipment. This serves to significantly improve the reliability of the hydrogen measurement through increased signal stability and accelerated hydrogen desorption. In general, an independent temperature measurement with dummy samples is recommended for the heating procedure of choice to exclude possible undesired temperature influences before the measurement. The methods described can be transferred directly to industrial applications
The production of plastics is rising since they have been invented. Micro, submicro- and nanoplastics are produced intentionally or generated by environmental processes, and constitute ubiquitous contaminants which are ingested orally by consumers. Reported health concerns include intestinal translocation, inflammatory response, oxidative stress and cytotoxicity. Every digestive milieu in the gastrointestinal tract does have an influence on the properties of particles and can cause changes in their effect on biological systems. In this study, we subjected plastic particles of different materials (polylactic acid, polymethylmethacrylate, melamine formaldehyde) and sizes (micro- to nano-range) to a complex artificial digestion model consisting of three intestinal fluid simulants (saliva, gastric and intestinal juice). We monitored the impact of the digestion process on the particles by performing Dynamic Light Scattering, Scanning Electron Microscopy and Asymmetric Flow Field-Flow Fractionation. An in vitro model of the intestinal epithelial barrier was used to monitor cellular effects and translocation behavior of (un)digested particles. In conclusion, artificial digestion decreased cellular interaction and slightly increased transport of all particles across the intestinal barrier. The interaction with organic matter resulted in clear differences in the agglomeration behavior. Moreover, we provide evidence for polymer-, size- and surface-dependent cellular effects of the test particles.
Durch Auslagerungs- und elektrochemische Tests im Labor kann das Korrosionsverhalten verschiedener metallener Werkstoffe beurteilt werden. Aus den Versuchsergebnissen, die in verschiedenen synthetischen Geothermalwässern im Labor erzielt wurden, lassen sich die folgenden Schlussfolgerungen ziehen:
• Die Anfälligkeit für Spaltkorrosion wurde als wichtigster Aspekt für die Werkstoffqualifizierung ermittelt.
• Der niedriglegierte Stahl 25CrMo4 zeigte bei niedrigem Salzgehalt in MB-Geothermalwasser eine gleichmäßige Korrosion unterhalb der akzeptierten Schwelle von 0,3 mm/Jahr. Daher kann er als geeignet für geothermische Bedingungen mit niedrigem Salzgehalt angesehen werden, wie sie für MB getestet wurden. Es besteht keine Notwendigkeit, auf höherlegierte (teurere) Werkstoffe auszuweichen. Ein niedrigerer pH-Wert (wie bei LHD) führt zu Korrosionsraten oberhalb der akzeptablen Grenzwerte, so dass die niedriglegierten Werkstoffe nicht für Flüssigkeiten mit niedrigem pH-Wert geeignet sind.
• Stark salzhaltige Geothermalwässer erfordern höherlegierte Werkstoffe, da die Korrosionsrate von niedriglegiertem Stahl zu hoch ist.
• Der Duplexstahl X2CrNiMo22-5-3 und der Superduplexstahl X2CrNiMoCuWN25-7-4 wurden aufgrund ihrer kritischen Anfälligkeit für örtliche Korrosion in Form von Loch- und Spaltkorrosion unter Betriebsbedingungen nicht als geeignet für geothermische Anwendungen in Geothermalwässern mit einer mit NDB und ORG vergleichbaren Zusammensetzung angesehen.
• Der superaustenitische Stahl X1CrNiMoCu32-28-7 eignet sich für ORG und salzarme Wässer. In NDB-Geothermalwasser wurde er bei 100 °C als geeignet angesehen. Jedoch schränkt seine Anfälligkeit für Spaltkorrosion seine Anwendbarkeit ein. Neben seiner guten Korrosionsbeständigkeit ist sein Repassivierungsverhalten für seine begrenzte Anwendbarkeit in Geothermalwässern mit niedrigem pH-Wert verantwortlich.
• Die Nickelbasislegierung NiCr23Mo16Al wurde als geeignet erachtet und stellt eine sichere Option für den Einsatz in geothermischen Anlagen dar, selbst wenn mit stark salzhaltigem Geothermalwasser gearbeitet wird.
Durch Auslagerungs- und elektrochemische Tests im Labor kann das Korrosionsverhalten verschiedener metallener Werkstoffe beurteilt werden. Aus den Versuchsergebnissen, die in verschiedenen synthetischen Geothermalwässern im Labor erzielt wurden, lassen sich die folgenden Schlussfolgerungen ziehen:
• Die Anfälligkeit für Spaltkorrosion wurde als wichtigster Aspekt für die Werkstoffqualifizierung ermittelt.
• Der niedriglegierte Stahl 25CrMo4 zeigte bei niedrigem Salzgehalt in MB-Geothermalwasser eine gleichmäßige Korrosion unterhalb der akzeptierten Schwelle von 0,3 mm/Jahr. Daher kann er als geeignet für geothermische Bedingungen mit niedrigem Salzgehalt angesehen werden, wie sie für MB getestet wurden. Es besteht keine Notwendigkeit, auf höherlegierte (teurere) Werkstoffe auszuweichen. Ein niedrigerer pH-Wert (wie bei LHD) führt zu Korrosionsraten oberhalb der akzeptablen Grenzwerte, so dass die niedriglegierten Werkstoffe nicht für Flüssigkeiten mit niedrigem pH-Wert geeignet sind.
• Stark salzhaltige Geothermalwässer erfordern höherlegierte Werkstoffe, da die Korrosionsrate von niedriglegiertem Stahl zu hoch ist.
• Der Duplexstahl X2CrNiMo22-5-3 und der Superduplexstahl X2CrNiMoCuWN25-7-4 wurden aufgrund ihrer kritischen Anfälligkeit für örtliche Korrosion in Form von Loch- und Spaltkorrosion unter Betriebsbedingungen nicht als geeignet für geothermische Anwendungen in Geothermalwässern mit einer mit NDB und ORG vergleichbaren Zusammensetzung angesehen.
• Der superaustenitische Stahl X1CrNiMoCu32-28-7 eignet sich für ORG und salzarme Wässer. In NDB-Geothermalwasser wurde er bei 100 °C als geeignet angesehen. Jedoch schränkt seine Anfälligkeit für Spaltkorrosion seine Anwendbarkeit ein. Neben seiner guten Korrosionsbeständigkeit ist sein Repassivierungsverhalten für seine begrenzte Anwendbarkeit in Geothermalwässern mit niedrigem pH-Wert verantwortlich.
• Die Nickelbasislegierung NiCr23Mo16Al wurde als geeignet erachtet und stellt eine sichere Option für den Einsatz in geothermischen Anlagen dar, selbst wenn mit stark salzhaltigem Geothermalwasser gearbeitet wird.
AbstractIn this study, we compare the residual stress state in a laser powder bed fusion (PBF‐LB/M) AlSi10Mg alloy in the as‐built (AB) condition with that after two different heat treatments (265 °C for 1 h, HT1; and 300 °C for 2 h, HT2). The bulk residual stress (RS) is determined using synchrotron X‐ray diffraction (SXRD), and near‐surface profiles are determined using laboratory energy‐dispersive X‐ray diffraction (EDXRD). The EDXRD results do not reveal any notable difference between the conditions at a depth of 350 μm, suggesting that the machining process yields a comparable residual stress state in the near‐surface regions. On the other hand, the SXRD results show that HT1 is more effective in relieving the bulk RS. It is observed that HT1 reduces the RS state in both the aluminium matrix and the silicon network. In addtion, HT2 does not have a significant impact on relaxing the RS as‐built state of the matrix, although it does induce a reduction in the RS magnitudes of the Si phase. It is concluded that the heat treatment stress relieving is effective as long as the Si‐network is not disaggregated.
A corrosion study is performed on six variations of titanium grade 5 (Ti6Al4V) samples. Samples are prepared in different conditions by variation of preanodization, postanodization, and picosecond-laser (ps-laser) surface treatment, while polished and anodized samples serve as reference. Microcones and nanosized periodic surface features are successfully produced on Ti6Al4V samples. The morphology and topography of the structures are visualized by scanning electron microscopy and white light interference microscopy. Furthermore, the relative electrochemically active surface area (ECSA) is determined for the ps-laser-treated samples. It is determined that the preanodized and laser-treated sample has 3.5 times larger ECSA than a polished sample, and that the laser-treated sample has 4.1 times larger area. Moreover, Tafel analysis is performed to determine the corrosion properties of the samples. It is shown that the corrosion resistance improves for both laser-structured samples after the anodization. To further study the surface of the samples, electrochemical impedance spectroscopy measurements are conducted. The study indicates that the ps-laser-treated and anodized Ti6Al4V is suitable to be used for the fabrication of bone screws and plates due to its improved corrosion resistance as compared to nonanodized samples.
The LOBSTER (Deringer et al., 2011;Maintz et al., 2013 ,2016 ;Nelson et al., 2020 ) software aids in extracting quantum-chemical bonding information from materials by projecting the plane-wave based wave functions from density functional theory (DFT) onto an atomic orbital basis. LobsterEnv, a module implemented in pymatgen (Ong et al., 2013) by some of the authors of this package, facilitates the use of quantum-chemical bonding information obtained from LOBSTER calculations to identify neighbors and coordination environments. LobsterPy is a Python package that offers a set of convenient tools to further analyze and summarize the LobsterEnv outputs in the form of JSONs that are easy to interpret and process. These tools enable the estimation of (anti) bonding contributions, generation of textual descriptions, and visualization of LOBSTER computation results. Since its first release, both LobsterPy and LobsterEnv capabilities have been extended significantly. Unlike earlier versions, which could only automatically analyze Crystal Orbital Hamilton Populations (COHPs) (Dronskowski & Blöchl, 1993), both can now also analyze Crystal Orbital Overlap Populations (COOP) (Hughbanks & Hoffmann, 1983) and Crystal Orbital Bond Index (COBI) (Müller et al., 2021). Extracting the information about the most important orbitals contributing to the bonds is optional, and users can enable it as needed. Additionally, bonding-based features for machinelearning (ML) studies can be engineered via the sub-packages “featurize” and “structuregraphs”. Alongside its Python interface, it also provides an easy-to-use command line interface (CLI) that runs automatic analysis of the computations and generates a summary of results and publication-ready figures. LobsterPy has been used to produce the results in Ngo et al. (2023), Chen et al. (2024), Naik et al. (2023), and it is also part of Atomate2 (2023) bonding analysis workflow for generating bonding analysis data in a format compatible with the Materials Project (Jain et al., 2013) API.
Die additive Fertigung mittels Schweißverfahren bietet große ökonomische Vorteile für eine ressourceneffiziente Bauteilherstellung. Offene Fragen bezüglich Homogenität, Anisotropie der Schweißgefüge und den damit verbundenen Bauteileigenschaften stehen einer wirtschaftlichen Verarbeitung oftmals im Wege. Finale Bauteilgeometrie und Oberflächengüte erfordern meist komplementäre subtraktive Fertigungsschritte. Werkstoffe für hochbelastbare Komponenten sind oftmals schwer spanbar. In einem Vorhaben der BAM und des ISAF wurde untersucht, wie die Modifikation der AM-Schweißzusätze und das ultraschallunterstützte Fräsen (US) die Zerspanungssituation verbessern. Der vorliegende Artikel stellt wesentliche Zusammenhänge zwischen Legierung, Gefüge und Zerspanung zweier schwer spanbarer Hochleistungslegierungen (FeNi und CoCr) dar. Großes Potenzial zeigte neben dem US die Modifikation mit Zr und Hf bei Zulegierung in das Schweißgut mittels Beschichtung von Massivdrähten bzw. Herstellung von Fülldrähten.
Beim Unterpulverschweißen sind die Prozessgeräusche ein Indikator für eine gute Fügequalität. Diese Beurteilung kann i.d.R. nur von einer erfahrenen Fachkraft durchgeführt werden. Eine kürzlich entwickelte künstliche Intelligenz kann automatisch das akustische Prozesssignal anhand vortrainierter Merkmale klassifizieren und die Fügequalität anhand des Geräuschs beurteilen. Der Algorithmus, einmal richtig trainiert, kann den Prüfaufwand beim Unterpulverschweißen deutlich reduzieren.
We present Jobflow, a domain-agnostic Python package for writing computational workflows tailored for high-throughput computing applications. With its simple decorator-based approach, functions and class methods can be transformed into compute jobs that can be stitched together into complex workflows. Jobflow fully supports dynamic workflows where the full acyclic graph of compute jobs is not known until runtime, such as compute jobs that launch
other jobs based on the results of previous steps in the workflow. The results of all Jobflow compute jobs can be easily stored in a variety of filesystem- and cloud-based databases without the data storage process being part of the underlying workflow logic itself. Jobflow has been intentionally designed to be fully independent of the choice of workflow manager used to dispatch the calculations on remote computing resources. At the time of writing, Jobflow
workflows can be executed either locally or across distributed compute environments via an adapter to the FireWorks package, and Jobflow fully supports the integration of additional workflow execution adapters in the future.
AbstractThe high-temperature corrosion behaviors of the equimolar CrCoNi medium-entropy alloy and CrMnFeCoNi high-entropy alloy were studied in a gas atmosphere consisting of a volumetric mixture of 10% H2O, 2% O2, 0.5% SO2, and 87.5% Ar at 800 °C for up to 96 h. Both alloys were initially single-phase fcc with a mean grain size of ~ 50 μm and a homogeneous chemical composition. The oxide layer thickness of CrMnFeCoNi increased linearly with exposure time while it remained constant at ~ 1 μm for CrCoNi. A Cr2O3 layer and minor amounts of (Co,Ni)Cr2O4 developed on the latter while three oxide layers were detected on the former, i.e., a thin and continuous chromium rich oxide layer at the oxide/alloy interface, a dense (Mn,Cr)3O4 layer in the center and a thick and porous layer of Mn3O4 and MnSO4 at the gas/oxide interface. Additionally, a few metal sulfides were observed in the CrMnFeCoNi matrix. These results were found to be in reasonable agreement with thermodynamic calculations.
Abstract. In power electronics, compound semiconductors with large bandgaps, like silicon carbide (SiC), are increasingly being used as material instead of silicon. They have a lot of advantages over silicon but are also intolerant of nanoscale material defects, so that a defect inspection with high accuracy is needed. The different defect types on SiC samples are measured with various measurement methods, including optical and tactile methods. The defect types investigated include carrots, particles, polytype inclusions and threading dislocations, and they are analysed with imaging ellipsometry, coherent Fourier scatterometry (CFS), white light interference microscopy (WLIM) and atomic force microscopy (AFM). These different measurement methods are used to investigate which method is most sensitive for which type of defect to be able to use the measurement methods more effectively. It is important to be able to identify the defects to classify them as critical or non-critical for the functionality of the end product. Once these investigations have been completed, the measurement systems can be optimally distributed to the relevant defects in further work to realize a hybrid analysis of the defects. In addition to the identification and classification of defects, such a future hybrid analysis could also include characterizations, e.g. further evaluation of ellipsometric data by using numerical simulations.
Recent publications indicate that the order of electrochemical anodization (before or after the laser processing step) plays an important role for the response of bone-forming osteoblasts—an effect that can be utilized for improving permanent dental or removable bone implants. For exploring these different surface functionalities, multimethod morphological, structural, and chemical characterizations are performed in combination with electrochemical pre- and postanodization for two different characteristic microspikes covered by nanometric laser-induced periodic surface structures on Ti–6Al–4V upon irradiation with near-infrared ps-laser pulses (1030 nm wavelength, ≈1 ps pulse duration, 67 and 80 kHz pulse repetition frequency) at two distinct sets of laser fluence and beam scanning parameters. This work involves morphological and topographical investigations by scanning electron microscopy and white light interference microscopy, structural material examinations via X-ray diffraction, and micro-Raman spectroscopy, as well as near-surface chemical analyses by X-ray photoelectron spectroscopy and hard X-ray photoelectron spectroscopy. The results allow to qualify the mean laser ablation depth, assess the spike geometry and surface roughness parameters, and provide new detailed insights into the near-surface oxidation that may affect the different cell growth behavior for pre- or postanodized medical implants.
The current lack of quantitative knowledge on processing-microstructure–property relationships is one of the major bottlenecks in today’s rapidly expanding field of additive manufacturing. This is centrally rooted in the nature of the processing, leading to complex microstructural features. Experimentally-guided modeling can offer reliable solutions for the safe application of additively manufactured materials. In this work, we combine a set of systematic experiments and modeling to address creep anisotropy and its correlation with microstructural characteristics in laser-based powder bed fusion (PBF-LB/M) additively manufactured Inconel-738LC (IN738LC). Three sample orientations (with the tensile axis parallel, perpendicular, and 45° tilted, relative to the building direction) are crept at 850 °C, accompanied by electron backscatter secondary diffraction (EBSD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigations. A crystal plasticity (CP) model for Ni-base superalloys, capable of modeling different types of slip systems, is developed and combined with various polycrystalline representative volume elements (RVEs) built on the experimental measurements. Besides our experiments, we verify our modeling framework on electron beam powder bed fusion (PBF-EB/M) additively manufactured Inconel-738LC. The results of our simulations show that while the crystallographic texture alone cannot explain the observed creep anisotropy, the superlattice extrinsic stacking faults (SESF) and related microtwinning slip systems play major roles as active deformation mechanisms. We confirm this using TEM investigations, revealing evidence of SESFs in crept specimens. We also show that the elongated grain morphology can result in higher creep rates, especially in the specimens with a tilted tensile axis.
In this study, we investigated the diverse range of materials used for sizing in Iranian paper manuscripts during the Timurid (fifteenth century) to Safavid (sixteenth century) and Qajar (nineteenth century) periods. Our approach combined historical analysis with scientific examination of reconstructed sizings. We reconstructed 15 sizing materials based on identified Persian historical recipes and analysed their physical, optical, and spectral characteristics. Additionally, we assessed their behaviour against the mould fungus Aspergillus flavus. The results revealed distinctive properties for each sizing material, shedding light on their potential applications in paper preservation. Furthermore, our investigation demonstrated variations in hygroscopicity, thickness, grammage, and ash content post-sizing. The sizing materials also exhibited different effects on paper reflectance properties. Additionally, our study revealed insights into the impact of sizing on burnished papers, indicating that the mechanical process of burnishing did not significantly alter the chemical composition or spectral properties of the paper, with only minor changes in brightness observed in specific cases. All tested sizing materials supported varying levels of mould growth, indicating potential implications for paper conservation. Our findings provide valuable insights into the historical practices of Iranian paper sizing and offer practical considerations for the preservation of paper manuscripts.
Self-healing polymers have been developed to improve durability and reduce costs associated with maintenance during service. The addition of thermoplastics to thermosets to produce mendable polymers appears as a promising selfhealing technique. In this study, poly (ethylene-co-methacrylic acid) (EMAA) was added to epoxy resin and the effects of EMAA addition on epoxy properties were evaluated. Specimens with two different contents of thermoplastic and particles sizes were manufactured. A two-level full factorial experimental design was used to evaluate the effect of particle size and particle content on properties of epoxy modified with addition of EMAA. Tensile tests and dynamic mechanical analysis (DMA) were used and the evaluated responses were tensile strength, modulus of elasticity, and glass transition temperature (Tg). X-ray computed tomography (XCT) was used to investigate particle size and concentration after manufacturing. It was found that the particle concentration has greater effects on stress–strain behavior of epoxy while Tg was not significantly affected by neither of the analyzed entrance variables.
Optical Thermometry is popular among researchers because of its non-contact, high sensitivity, and fast measurement properties. In the present experiment, Er3+/Yb3+/K+ co-doped NaYF4 nanoparticles with different K+ concentrations were synthesized by solvothermal method, and the samples showed bright upconversion green emission under the excitation of a 980 nm laser. The powder X-ray diffractometer and transmission electron microscope were used to characterize the crystal structure and its surface morphology, respectively. The spectral characteristics of nanoparticles with K+ doping concentration from 10% to 30% (Molar ratio) were investigated by fluorescence spectroscopy, and it was observed that the fluorescence intensity reached the maximum at the K+ concentration of 20%, after which the intensity weakened when the K+ content continued to increase. According to the dependence between the luminescence intensity of the sample and the laser power density and fluorescence lifetime, the intrinsic mechanism was carefully investigated. Temperature-dependent spectra of the samples were recorded in the temperature range of 315–495 K, and the maximum values of absolute sensitivity (Sa) and relative sensitivity (Sr) were measured at 0.0041 K−1 (455 K) and 0.9220%K−1 (315 K). The experimental results show that K+/Er3+/Yb3+ triple-doped NaYF4 green fluorescent nanoparticles (GFNs) have good prospects for applications in display devices, temperature sensing, and other fields.
Duplex stainless steels (DSS) are frequently used, especially in applications requiring high strength combined with high corrosion resistance in aggressive media. Examples include power plant components and maritime structures. During welding of these steels, local variations in chemical composition can occur. This results in ferritization of the material and negatively affects the mechanical properties of the components. In this work, tungsten inert gas (TIG) welding experiments were performed with DSS. Chemical composition analysis was realized in situ by using Laser Induced Breakdown Spectroscopy (LIBS). The aim of the work is to quantitatively measure the chemical composition in the weld seam of various DSS and to identify possible influences of welding parameters on the microstructure of the material. The chemical concentrations of the main alloying elements Cr, Ni, Mn on the surface of the sample during the welding process and the cooling process were measured. Mn and Ni are austenite stabilizers and their content increases during welding by using certain high alloyed filler material. Spectra were recorded every 1.3 s at a spacing of approximately 2 mm. During the cooling process the location of the measurement was not changed. The LIBS method is proofed to be suitable for the quantitative representation of the chemical compositions during the welding process.
It is proposed to model the experimentally observed weld pool boundary with superellipses (Lamé curves) and to find the unknown parameters of the curves using optimization methods. It has been shown experimentally that during laser welding of austenitic stainless steel with a thickness of 2 mm at a speed of 20 mm/s, the rear weld pool part has a shape close to triangular which can be accurately approximated by a superellipse. Analytical dependences of the trajectory and growth rate of the crystal and its cross-sectional area on the geometry of the rear weld pool part are obtained.
In this article, we present two Coptic papyri, P 11934 and P 11935 from the Berlin collection excavated in Ashmunein (ancient Hermopolis) by Otto Rubensohn in 1906. We employ a multi-disciplinary approach that takes into account both their materiality – writing support as well as ink – and their content, as has become ‘best practice’. 1 Material aspects of written documents have traditionally been the purview of papyrologists. Recently developed methods of scientific analysis generate sets of archaeometric data with the potential to improve understanding of the materiality of ancient document production, as well as to yield new evidence for genuine papyrological research questions. To achieve this, a large corpus of comparative data needs to be built. Our contribution offers a first step in this direction. We aim at presenting the papyri, which were selected because of the ink corrosion during conservation work at the Berlin collection, in a format that is exhaustive both for material and textual aspects. The inks from both papyri were analysed using a combination of techniques, contributing to our better understanding of the development of ink technology in Late Antiquity.
Iron aluminides, already reported in the late 19th century, did not cease to attract the interest of scientists and engineers ever since. Besides good oxidation resistance, low density and resource availability, potentials for hightemperature strengths that compete with high-alloy steels were unlocked by low alloy contents. Still, research on alloy design continues, as alloying usually comes at the price of brittleness in low-temperature regimes. A potential candidate is the quinary Fe–Al–Mo–Ti–B system which is strengthened by solid solution and eutectic borides. It was shown to have good strength and outstanding creep resistance under compressive loading up to elevated temperatures. Although the individual effect of alloy additions is well understood in iron aluminides, little is known about the combined effects of alloying concentrations on microstructure, phase stability and mechanical properties. Therefore a systematic study of two Ti-doped near-Fe3Al alloys with varying contents of Mo (2–4 at.%) and B (0.5–1 at.%) was conducted. In total eight different alloys were fabricated by investment casting into ceramic shell molds. Alloys were characterized and compared by grain size, phase transitions, microstructure evolution as well as elemental compositions and volume fractions of phases. For mechanical characterization, macrohardness and microhardness tests as well as tensile tests at ambient and high tempera tures were conducted. Independent of alloy additions, alloys with 24–25 at.% Al exhibit superior proof strength due to a higher matrix hardness. Decreasing B content generally decreases strength by lower secondary phase fractions which contribute via particle hardening. Reducing Mo content decreases both the solute concentration in the matrix and secondary phase fractions. Surprisingly, strength is similar or even superior to alloys with higher Mo content. Strength relations are discussed with a focus on solid-solution hardening theory and other competing strengthening mechanisms.
Titanium and its alloys are known to allow the straightforward laser-based manufacturing of ordered surface nanostructures, so-called high spatial frequency laser-induced periodic surface structures (HSFL). These structures exhibit sub-100 nm spatial periods – far below the optical diffraction limit. The resulting surface functionalities are usually enabled by both, topographic and chemical alterations of the nanostructured surfaces. For exploring these effects, multi-method characterizations were performed here for HSFL processed on Ti–6Al–4V alloy upon irradiation with near-infrared ps-laser pulses (1030 nm, ≈1 ps pulse duration, 1–400 kHz) under different laser scan processing conditions, i.e., by systematically varying the pulse repetition frequency and the number of laser irradiation passes. The sample characterization involved morphological and topographical investigations by scanning electron microscopy (SEM), atomic force microscopy (AFM), tactile stylus profilometry, as well as near-surface chemical analyses hard X-ray photoelectron spectroscopy (HAXPES) and depth-profiling time-of-flight secondary ion mass spectrometry (ToF-SIMS). This provides a quantification of the laser ablation depth, the geometrical HSFL characteristics and enables new insights into the depth extent and the nature of the non-ablative laser-induced near-surface oxidation accompanying these nanostructures. This allows to answer the questions how the processing of HSFL can be industrially scaled up, and whether the latter is limited by heat-accumulation effects.
Die Fourier-Transformations-Infrarot-Spektroskopie (FTIR-Spektroskopie) stellt eine innovative und wirkungsvolle Methode zur Charakterisierung von Bitumen und bitumenhaltigen Bindemitteln dar. So erlaubt die FTIRCharakterisierung nicht nur eine Bewertung des Alterungsfortschritts eines Bindemittels, sondern zudem auch die Identifizierung von im Bitumen enthaltenen Additiven und Schadstoffen wie z. B. polyzyklischen aromatischen Kohlenwasserstoffen (PAK), die Ableitung verschiedener physikalischer und chemischer Kennwerte sowie weiterhin eine Klassifizierung von Bindemitteln nach verschiedenen übergeordneten Eigenschaften wie der Raffinerie, dem Alterungszustand und auch der Alterungsempfindlichkeit.
FAIR (findable, accessible, interoperable and reusable) data usage is one of the main principals that many of the research and funding organizations include in their strategic plans, which means that following the main principals of FAIR data is required in many research projects. The definition of data being FAIR is very general. When implementing that for a specific application or project or even setting a standardized procedure within a working group, a company or a research community, many challenges arise. In this contribution, an overview about our experience with different methods and tools is outlined.
We begin with a motivation on potential use cases for the application of FAIR data with increasing complexity starting from a reproducible research paper over collaborative projects with multiple participants such as Round-Robin tests up to data-based models within standardization codes, applications in machine learning or parameter estimation of physics-based simulation models.
In a second part, different options for structuring the data (including metadata schema) are discussed. The first one is the openBIS system, which is an open-source lab notebook and PostgreSQL based data management system. A second option is a semantic representation using RDF based on ontologies for the domain of interest.
In a third section, requirements for workflow tools to automate data processing are discussed and their integration into reproducible data analysis is presented with an outlook on required information to be stored as metadata in the database.
Finally, the presented procedures are exemplarily demonstrated for the calibration of a temperature dependent constitutive model for additively manufactured mortar. A metadata schema for a rheological measurement setup is derived and implemented in an openBIS database. After a short review of a potential numerical model predicting the structural build-up behavior, the automatic workflow to use the stored data for model parameter estimation is demonstrated.
Black writing materials of different types and compositions have varied in use over time and different geographical regions. With this paper, we would like to contribute to their study by listing and reviewing recipes for black writing inks that were in circulation in the Carolingian Empire as well as by referencing the archaeometric analyses of the black inks used in the manuscripts. The studies presented here that involved the humanities and natural sciences provide new insights into how the scholars of the early Medieval Ages organized manuscripts.
Colours on East Asian Maps
(2023)
Maps and colours have a close connection. Drawn or printed in black on white, subsequently added colours enhance maps with additional information. Colours were not just there to improve maps aesthetically, but they regulated how they were read and thus reinforced their meanings, significances and ideas. Colour is an important key to a more precise understanding of the map’s purposes and uses; moreover, colours are also an important aspect of a map’s materiality. The material scientific analysis makes it possible to find out more about the making of colours and the process of colouring maps. By skillfully deploying colours, map colourists were able to create mimetic representations of nature or codify information in an abstract form. The use of colours involved many considerations as to the materials. ‘Reading’ colours in this way gives a glimpse into the social lives of mapmakers as well as map users and reveals the complexity of the historical and social context in which maps were produced and how the maps were actually made. Within the scope of the three-year joint research project Coloured Maps (2018–2021), we undertook an in-depth and systematic study of hand-drawn and hand-coloured maps from East Asia in the Museum am Rothenbaum (MARKK) in Hamburg and produced between the seventeenth and twentieth centuries.
With a multi-perspective approach and transdisciplinary methods (humanities and the sciences), we were able to pool and compare the research results from different fields of research on Asian maps. The aim of this publication is to provide a first general overview of the subject of colours on maps in East Asia in the period from the seventeenth to the early twentieth century and to stimulate further research on the topic.
Showcasing research from the Federal Institute for Material Research and Testing Berlin and Fraunhofer Institute for Celltherapy and Immunology Branch Bioanalytics and Bioprocesses Potsdam.
Bio-SAXS of single-stranded DNA-binding proteins: Radiation protection by the compatible solute ectoine.
We aimed to increase the possible undisturbed exposure time during bio-SAXS measurements of single-stranded DNA-binding proteins. Therefore small angle X-ray scattering was performed on Gene-V Protein (G5P/GVP), which is involved in DNA repair processes. To achieve this, irradiations were performed in presence and absence of the hydroxyl-radical scavenger and osmolyte Ectoine, which showed efficient radiation protection and prevented protein aggregation, thus allows for a non-disturbing way to improve structure-determination of biomolecules.
Die Begriffe gefährlicher Stoff und Gefahrstoff werden häufig nicht unterschieden – in vielen Fällen resultieren aber durch den Kontext auch keine Missverständnisse. Tatsächlich bestehen aber Unterschiede – sowohl inhaltlich als auch bezüglich des Rechtsbereichs, der jeweils für sie gilt.
Stoffe sind gefährlich, wenn sie den Kriterien der CLP-Verordnung für physikalische Gefahren, Gesundheitsgefahren oder Umweltgefahren entsprechen. Sie werden dann im Sinne der CLP-Verordnung entsprechend eingestuft und es ergeben sich Pflichten bezüglich des Inverkehrbringens innerhalb der EU.
Gefahrstoffe sind in der Gefahrstoffverordnung definiert. Sie beinhalten die gefährlichen Stoffe und weitere nicht notwendigerweise als gefährlich eingestufte Stoffe. Das Ziel ist vor allem der Schutz von Beschäftigten bei Tätigkeiten mit Gefahrstoffen – es handelt sich also um eine Arbeitsschutzvorschrift.
Dieser Aufsatz stellt gefährliche Stoffe in ihrem Kontext vor, gibt einen Überblick über die Prinzipien und Rechtsfolgen sowie Hinweise auf weiterführende Informationen und stellt ihnen die Gefahrstoffe gegenüber.
This study was carried out to investigate the neutron transmission signal as a function of sample temperature during a welding process. A theoretical description that includes the Debye-Waller factor was used to describe the temperature influence on the neutron crosssections. Neutron imaging using a monochromatic beam helps to observe transmission variations related to the material temperature. In-situ neutron imaging of welding experiments show the distribution of the temperature in bulk steel samples. The performed finite element modelling of expected temperature distributions shows good agreement with the obtained experimental data.
Die heute in der Anwendung befindlichen Bemessungskonzepte für Ermüdung von Beton stammen zum Teil noch aus den 1990er Jahren und sind speziell hinsichtlich hochfester Betone konservativ ausgelegt. Um die Vorteile von Türmen für Windkraftanlagen, vor allem auch aus hochfesten Betonen, im Zuge des geplanten Ausbaus der Windenergieversorgung in Deutschland wirtschaftlich nutzbar zu machen, müssen diese Bemessungskonzepte weiterentwickelt werden. Dafür sind umfangreiche Untersuchungen zur Ermittlung von Bruchlastwechselzahlen und zur Charakterisierung der Schädigungsentwicklung unter Ermüdungsbeanspruchung erforderlich. Allgemein anerkannte bzw. verbindliche Regelwerke oder Verfahren zur experimentellen Bestimmung der Ermüdungsfestigkeit (Bruchlastwechselzahlen) an Betonproben gibt es zurzeit aber nicht und die bisher durchgeführten Untersuchungen variieren in Parametern wie Probengeometrie, Probengröße und Prüffrequenz. Eine vergleichende Analyse der Ergebnisse der Studien und insbesondere die Übertragbarkeit auf bauteilrelevante Abmessungen ist auf dieser Grundlage nur sehr eingeschränkt möglich.
In this study, a wound dressing composed of an alginate dialdehyde−gelatin (ADA-GEL) hydrogel incorporated by astaxanthin (ASX) and 70B (70:30 B2O3/CaO in mol %) borate bioactive glass (BBG) microparticles was developed through 3D printing. ASX and BBG particles sti.ened the composite hydrogel construct and delayed its in vitro degradation compared to the pristine hydrogel construct, mainly due to their cross-linking role, likely arising from hydrogen bonding between the ASX/BBG particles and ADA-GEL chains. Additionally, the composite hydrogel construct could hold and deliver ASX steadily. The composite hydrogel constructs codelivered biologically active ions (Ca and B) and ASX, which should lead to a faster, more e.ective wound-healing process. As shown through in vitro tests, the ASX-containing composite hydrogel promoted fibroblast (NIH 3T3) cell adhesion, proliferation, and vascular endothelial growth factor expression, as well as keratinocyte (HaCaT) migration, thanks to the antioxidant activity of ASX, the release of cell-supportive Ca2+ and B3+ ions, and the biocompatibility of ADA-GEL. Taken together, the results show that the ADA-GEL/BBG/ASX composite is an attractive biomaterial to develop multipurposed wound-healing constructs through 3D printing.
Im Additive Manufacturing Verfahren Directed Energy Deposition (DED) wird bei der Verarbeitung von Werkzeugstahl in der Regel reines Argon als Schutzgas verwendet. Dabei kann die Verwendung von speziellen Schutzgasgemischen, auch bei geringen Anteilen zugemischter Gase, durchaus die Bauteilqualität positiv beeinflussen.
In Vorarbeiten der Messer SE & Co. KGaA zeigte ein gewisser Sauerstoffanteil im Schutzgas die Tendenz, den Flankenwinkel von Schweißspuren beim DED zu verbessern. In der vorliegenden Studie wurde daher detailliert untersucht in wie weit unterschiedliche Schutzgasgemische einen Einfluss auf die Qualität sowie die geometrischen Eigenschaften der additiv gefertigten Strukturen des Werkzeugstahls 1.2709 beim Laser-DED ausüben. Es erfolgten zunächst Testschweißungen in Form von Einzelspuren mit unterschiedlichen Gemischen aus dem Basisschutzgas Argon mit geringen Anteilen verschiedener Gase. Dabei wurde der Einfluss der Zusätze auf die Spurgeometrie und Aufbauqualität untersucht. Auf Basis dieser Vorversuche wurde eine Auswahl vielversprechender Gasgemische getroffen und Detailuntersuchungen in Form von Spuren, Flächen und Quadern unter Zugabe verschiedener Mengen an Zusätzen durchgeführt. Zur Bewertung des Einflusses der Schutzgasbeimengungen wurden der Flankenwinkel, die Porosität und das Gefüge der Proben anhand metallografischer Schliffe untersucht. Es zeigte sich, dass eine Zugabe von geringen Anteilen an Zusätzen zunächst zu einer Vergrößerung des Flankenwinkels im Vergleich zu reinem Argon führt. Mit steigendem Anteil der Gase nimmt dieser Winkel jedoch ab. So kann je nach Menge des zugesetzten Gases eine individuelle Benetzung des aufgetragenen Materials an der Oberfläche erreicht werden. Auch die Porosität ließ sich durch Schutzgasgemische beeinflussen und zeigt ein abweichendes Verhalten im Vergleich zu reinem Argon.
Ring-expansion polymerizations (REPs) catalyzed by two cyclic tin catalysts (2-stanna-1.3-dioxa-4,5,6,7-dibenzazepine [SnBiph] and
2,2-dibutyl-2-stanna-1,3-dithiolane [DSTL]) are performed at 140 °C in bulk.
Small amounts (4 vol%) of chlorobenzene or other solvents are added to
facilitate transesterification reactions (ring–ring equilibration) in the solid poly(l-lactide)s. In the mass range up to m/z 13 000 crystalline PLAs displaying a so-called saw-tooth pattern in the MALDI-TOF mass spectra are obtained indicating the formation of extended-ring crystals. The characteristics of extended-ring crystallites and folded-ring crystallites are discussed. Furthermore, extremely high melting temperatures (Tm’s up to 201.2 °C) and melting enthalpies (𝚫Hm’s up to 106 J g−1)) are found confirming that 𝚫Hm max, the 𝚫Hm of a perfect crystal, is around or above 115 J g−1 in contrast to literature data.
Abstract
In the post-processing of large maritime components, a considerable amount of waste in the form of milling and grinding chips is produced. At the same time, additive manufacturing technologies have shown great potential in producing high-volume parts for maritime applications, allowing novel design approaches and short lead times. In this context, this study presents a sustainable approach to recycle and use aluminium bronze waste material, generated during post-processing of large cast ship propellers, as feedstock for laser-powder directed energy deposition. The recycling technology used to produce powder batches is inductive re-melting in combination with ultrasonic atomization. The derived metal powders are characterized using digital image analysis, powder flowability tests, scanning electron microscopy as well as energy dispersive X-ray spectroscopy. Compared to conventional metal powders produced by gas atomization, the recycled material shows excellent sphericity and a powder size distribution with a higher content of finer and coarser particles. Metallographic sections of deposited additively produced specimens show an increased hardness and reduced ductility, but also competitive densities and higher yield and ultimate tensile strength compared to cast material. The process chain shows high potential for the maritime sector to enable circular and sustainable manufacturing.
In recent decades, the number of components in concrete has grown, particularly in formulations aimed at reducing carbon footprints. Innovations include diverse binders, supplementary cementitious materials, activators, concrete admixtures, and recycled aggregates. These developments target not only the enhancement of material properties but also the mitigation of the ecological and economic impacts of concrete — the most extensively used material by humankind. However, these advancements also introduce a greater variability in the composition of raw materials. The material’s behavior is significantly influenced by its nanoscale properties, which can pose challenges in accurate characterization. Consequently, there’s an increasing need for experimental tuning of formulations. This is accompanied by a more inconsistent composition of raw materials, which makes an experimental tuning of formulations more and more necessary. However, the increased complexity in composition presents a challenge in finding the ideal formulation through trial and error. Inverse design (ID) techniques offer a solution to this challenge by allowing for a comprehensive search of the entire design space to create new and improved concrete formulations. In this publication, we introduce the concept of ID and demonstrate how our open-source app “SLAMD” provides all necessary steps of the workflow to adapt it in the laboratory, lowering the application barriers. The intelligent screening process, guided by a predictive model, leads to a more efficient and effective data-driven material design process resulting in reduced carbon footprint and improved material quality while considering socio-economic factors in the materials design.
The process of viscous flow sintering is a phenomenon that is closely linked to the surface properties of the glass particles. In this work, we studied the extreme case of acid-leaching of soda-lime-silicate glass beads of two different particle size distributions and its effects on non-isothermal viscous sintering of powder compacts. Depth profiling of the chemical composition after leaching revealed a near-surface layer depleted in alkali and alkaline earth ions, associated with concurrent hydration as mass loss was detected by thermogravimetry. Heating microscopy showed that acid treatment of glasses shifted the sinter curves to higher temperatures with increasing leaching time. Modelling of the shrinkage with the cluster model predicted a higher viscosity of the altered surface layer, while analysis of the time scales of mass transport of mobile species (Na+, Ca2+ and H2O) during isochronous sintering revealed that diffusion of Na+ can compensate for concentration gradients before sintering begins. Also, exchanged water species can diffuse out of the altered layer, but the depletion of Ca2+ in the altered surface layer persists during the sinter interval, resulting in a glass with higher viscosity, which causes sintering to slow down.
Die neue Generation von bainitischen Schmiedestählen bietet auf der einen Seite ein erhebliches Festigkeitspotenzial, das es im Sinne des Leichtbaus auch für zyklisch belastete Sicherheitsbauteile zu heben gilt. Auf der anderen Seite geht mit dieser Festigkeitssteigerung im Vergleich zu Vergütungsstählen ein Verlust an Duktilität und Zähigkeit einher. Am Beispiel des Demonstratorbauteils Achsschenkel ging das Forschungsvorhaben der Frage nach, wie ein Freigabeprozess zu gestalten ist, damit das Festigkeitspotenzial der neuen Stähle zuverlässig ausgenutzt werden kann. Als Ergebnis wird eine Vorgehensweise dargestellt, die den Eigenschaften der neuen Generation von Schmiedestählen Rechnung trägt, um den sicheren Betrieb der Komponenten zu gewährleisten.
We demonstrate a strategy for simulating wide-range X-ray scattering patterns, which spans the small- and wide scattering angles as well as the scattering angles typically used for Pair Distribution Function (PDF) analysis. Such simulated patterns can be used to test holistic analysis models, and, since the diffraction intensity is on the same scale as the scattering intensity, may offer a novel pathway for determining the degree of crystallinity.
The "Ultima Ratio" strategy is demonstrated on a 64-nm Metal Organic Framework (MOF) particle, calculated from Q < 0.01 1/nm up to Q < 150 1/nm, with a resolution of 0.16 Angstrom. The computations exploit a modified 3D Fast Fourier Transform (3D-FFT), whose modifications enable the transformations of matrices at least up to 8000^3 voxels in size. Multiple of these modified 3D-FFTs are combined to improve the low-Q behaviour. The resulting curve is compared to a wide-range scattering pattern measured on a polydisperse MOF powder. While computationally intensive, the approach is expected to be useful for simulating scattering from a wide range of realistic, complex structures, from (poly-)crystalline particles to hierarchical, multicomponent structures such as viruses and catalysts.
AbstractMicroplastics (MP) can be detected in all environmental systems. Marine and terrestrial aquatic systems, especially the transported suspended solids, have often been the focus of scientific investigations in the past. Sediments of aquatic river systems, on the other hand, were often ignored due to the time‐consuming sample preparation and analysis procedures. Spectroscopic measurement methods counting particle numbers are hardly suitable as detection methods, because there are plenty of natural particles next to a small number of MP particles. Integral methods, such as thermoanalytical methods are determining the particle mass independently of the inorganic components.In this study, a workflow for sample preparation via density separation and subsequent analysis by thermal extraction desorption‐gas chromatography/mass spectrometry is presented, which leads to representative and homogeneous samples and allows fast and robust MP mass content measurements suitable for routine analysis. Polymers were identified and quantified in all samples. Polyethylene and styrene‐butadiene rubber are the dominant polymers, besides polypropylene and polystyrene. Overall, total polymer masses between 1.18 and 337.0 µg/g could be determined. Highest MP concentrations in riverbed sediment are found in sites characterized by low flow velocities in harbors and reservoirs, while MP concentrations in sandy/gravelly bed sediments with higher flow velocities are small.
Tracking waterborne microplastic (MP) in urban areas is a challenging task because of the various sources and transport pathways involved. Since MP occurs in low concentrations in most wastewater and stormwater streams, large sample volumes need to be captured, prepared, and carefully analyzed. The recent research in urban areas focused mainly on MP emissions at wastewater treatment plants (WWTPs), as obvious entry points into receiving waters. However, important transport pathways under wet-weather conditions are yet not been investigated thoroughly. In addition, the lack of comprehensive and comparable sampling strategies complicated the attempts for a deeper understanding of occurrence and sources. The goal of this paper is to (i) introduce and describe sampling strategies for MP at different locations in a municipal catchment area under dry and wet-weather conditions, (ii) quantify MP emissions from the entire catchment and two other smaller ones within the bigger catchment, and (iii) compare the emissions under dry and wet-weather conditions. WWTP has a high removal rate of MP (>96%), with an estimated emission rate of 189 kg/a or 0.94 g/[population equivalents (PEQ · a)], and polyethylene (PE) as the most abundant MP. The specific dry-weather emissions at a subcatchment were ≈30 g/(PEQ · a) higher than in the influent of WWTP with 23 g/(PEQ · a). Specific wet-weather emissions from large sub-catchment with higher traffic and population densities were 1952 g/(ha · a) higher than the emissions from smaller catchment (796 g/[ha · a]) with less population and traffic. The results suggest that wet-weather transport pathways are likely responsible for 2–4 times more MP emissions into receiving waters compared to dry-weather ones due to tire abrasion entered from streets through gullies. However, more investigations of wet-weather MP need to be carried out considering additional catchment attributes and storm event characteristics.
In recent years, thermoextraction/desorption-gas chromatography/mass spectrometry (TED-GC/MS) has been developed as a rapid detection method for the determination of microplastics (MP) mass contents in numerous environmentally relevant matrices and, in particular, for the measurement of polymers in water samples without time-consuming sample preparation. The TED-GC/MS method was applied to investigate a typical European municipal wastewater system for possible MP masses. Such investigations are important in view of the recent revision of the Urban Wastewater Treatment Directive. Four different representative sampling sites were selected: greywater (domestic wastewater without toilet), combined sewer, and influent and effluent of a wastewater treatment plant (WWTP). All samples were collected by fractional filtration. Filtration was carried out over mesh sizes of 500, 100, 50, and in some cases, 5 µm. Polyethylene (PE), polypropylene (PP), and polystyrene (PS) were detected in all samples, with the PE fraction dominating in all cases. Styrene-butadiene rubber which serves as an indication of tire abrasion, was only found in the influent of the WWTP. The highest MP mass contents were found in the combined sewer, so MP can become a source of pollution during heavy rain events when the capacity limits of the effluent are reached, and the polluted effluent is released uncontrolled into the environment. Based on the studies, MP retention from the WWTP could be estimated to be approximately 96%. Few trends in polymer type or mass contents were detected within the different fractions of the samples or when comparing samples to each other.
This study reflects typical consumer textile washing behaviour while taking into account existing standards in the household appliance and garment industries. Two garments were washed repeatedly with artificial dirt and detergent 30 times. The collected washing water was separated using fractional filtration. Textile physical tests were used to follow property changes of the garments, the microplastic release is determined using thermoextraction/desorbtion–gas chromatography/mass spectrometry and the total organic carbon was measured as a sum parameter for the organic bonded carbon. This article shows the importance of a reality‐based approach when investigating microplastics of textile origin in the laundry care process. Deposits of detergent and dirt on the textiles were detected. The total mass of sieve residues was much higher than the release of synthetic polymers. The cotton content of the garments causes a much higher fibre release than synthetic fibres. Both will lead to false results by purely gravimetric analysis because nonpolymer fibres will be included microplastic mass. The results cannot be generalised only by the main polymer type, knowledge of the textile construction must be included for final evaluation.
Microplastic particles with sizes between 1 to 1000 μm are widely distributed worldwide. Origin, transport pathways and fate are poorly known, as sampling, sample preparation and detection methods are major challenges. In addition, reference materials that mimic environmental particles are lacking. Most challenging is the yield of MP particle production and the need for resource-intensive grinding with liquid nitrogen. In this paper, a machine is designed to produce aged microplastic particles as reference material candidates with high yield. The machine is based on ultraviolet aging of a thin foil and mechanical fragmentation using clean air. An example of aging and fragmentation of high density polyethylene with additional physical and chemical characterization of shape, size, aging state by carbonyl index and density is presented.
Laser powder bed fusion of metallic components (PBF-LB/M) is gaining acceptance in industry. However, the high costs and lengthy qualification processes required for printed components create the need for more effective in-situ monitoring and testing methods. This article proposes multispectral Optical Tomography (OT) as a new approach for monitoring the PBF-LB/M process. Compared to other methods, OT is a low-cost process monitoring method that uses long-time exposure imaging to observe the build process. However, it lacks time resolution compared to expensive thermographic sensor systems. Monochromatic OT (1C-OT) is already commercially available and observes the building process layer-wise using a single wavelength window in the NIR range. Multispectral OT (nC-OT) utilizes a similar setup but can measure multiple wavelength ranges per location simultaneously. By comparing the classical 1C-OT and nC-OT approaches, this article examines the advantages of nC-OT (two channel OT and RGB-OT) in reducing the false positive rate for process deviations and approximating maximum temperatures for a better comparison between different build processes and materials. This could ultimately reduce costs and time for part qualification. The main goal of this contribution is to assess the advantages of nC-OT compared to 1C-OT for in-situ process monitoring of PBF-LB/M.
Admixtures are important constituents to enhance the performance of concrete. They allow for more efficient use of binders which can mitigate negative environmental impacts from producing cement-based materials. Commonly used rheology modifying agents like polycarboxylate ethers or cellulose ethers are synthetic or semi-synthetic, respectively. This requires additional energy consumption for their production and global supply chains particularly for many developing regions, which will be large consumers of concrete in the future. However, many locally available bio-based polysaccharides could be effectively used instead. These polymers are often overlooked by engineers and scientists due to their limited distribution and inherent complexity, yet they represent an underleveraged source of precursors for admixtures. This study investigates the action mechanisms of some bio-based rheology modifying agents, i.e., acacia gum and miscanthus gum, and provides a comparison to a conventionally modified starch. The results show that the mechanism of action of these polymers is closely related to the composition of the mixture, mixing regime, and the composition of the aqueous phase. Depending on the agent, either plasticizing or stabilizing effects on rheology can be revealed.
Recently, additive manufacturing of ceramics has achieved the maturity to be transferred from scientific laboratories to industrial applications. At the same time, research is progressing to expand the boundaries of this field into the territory of novel materials and applications. This feature issue addresses current progress in all aspects of additive manufacturing of ceramics, from parts design to feedstock selection, from technological development to characterization of printed components.
We present an easy-to-apply method to predict structural trends in the internal nucleation tendency of oxide glasses. The approach is based on calculated crystal fracture surface energies derived from easily accessible diatomic bond energy and crystal lattice data. The applicability of the method is demonstrated on literature nucleation data for isochemically crystallizing oxide glasses.
Mechanochemistry offers a unique opportunity to modify and manipulate crystal forms, often providing new products as compared with conventional solution methods. While promising, there is little known about how to control the solid form through mechanochemical means, demanding dedicated investigations. Using a model organic cocrystal system (isonicotinamide:glutaric acid), we here demonstrate that with mechanochemistry, polymorphism can be induced in molecular solids under conditions seemingly different to their conventional thermodynamic (thermal) transition point. Whereas Form II converts to Form I upon heating to 363 K, the same transition can be initiated under ball milling conditions at markedly lower temperatures (348 K). Our results indicate that mechanochemical techniques can help to reduce the energy barriers to solid form transitions, offering new insights into controlling polymorphic forms. Moreover, our results suggest that the nature of mechanochemical transformations could make it difficult to interpret mechanochemical solid form landscapes using conventional equilibrium-based tools.
Prognose von Qualitätsmerkmalen durch Anwendung von KI-Methoden beim Directed 10 Energy Deposition
(2022)
Dieser Beitrag enthält die Ergebnisse eines im Rahmen der DVS Forschung entwickelten Ansatzes zur Qualitätssicherung im Directed Energy Deposition. Es basiert auf der Verarbeitung verschiedener während des Prozesses gesammelter Sensordaten unter Anwendung Künstlicher Neuronale Netze (KNN). So ließen sich die Qualitätsmerkmale Härte und Dichte auf der Datenbasis von 50 additiv gefertigten Probenwürfel mit einer Abweichung < 2 % vorhersagen. Des Weiteren wurde die Übertragbarkeit des KNN auf eine Schaufelgeometrie untersucht. Auch hier ließen sich Härte und Dichte hervorragend prognostizieren (Abweichung < 1,5 %), sodass der Ansatz als validiert betrachtet werden kann.
In an interdisciplinary collaboration, restorers, art historians, and scientists examined Guilio Romano’s The Madonna with the Wash-Basin of 1525 (Dresden State Art Collections). Insights into the painting technique along with art historical comparisons provided the opportunity for a better understanding of the painting’s genesis, in particular concerning an early reworking of the background by the artist. A recovery and reconstruction of the earlier version of the background is now possible. The discovery of zinc in distinct passages of the painting, as well as the grey-black pigment stibnite and glass particles used as a supplement in paint layers are of special interest. The technological investigation initiated a discussion about the circumstances of the revision, as well as the painting’s relation to Vasari’s Lives of Artists.
The Gay-Berne model is studied numerically with a choice of parameters allowing for the formation of a discotic liquid crystal at low temperatures. We show that the model has strong virial potential-energy correlations in the isotropic phase at high temperatures, i.e., it obeys the criterion for the existence of isomorphs, which are curves of approximately invariant structure and dynamics. These properties are demonstrated to be approximately invariant in reduced units along the isomorph studied. The isomorph is described well by the constant density-scaling exponent 11.5, a number that is significantly larger than the density-scaling exponents of various Lennard-Jones models that are always below 6.
The micromechanical behavior of an annealed Ti-6Al-4V material produced by Laser Powder Bed Fusion was characterized by means of in-situ synchrotron X-ray diffraction during a tensile test. The lattice strain evolution was obtained parallel and transversal to the loading direction. The elastic constants were determined and compared with the conventionally manufactured alloy. In the plastic regime, a lower plastic anisotropy exhibited by the lattice planes was observed along the load axis (parallel to the building direction) than in the transverse direction.
Also, the load transfer from α to β phase was observed, increasing global ductility of the material. The material seems to accumulate a significant amount of intergranular strain in the transverse direction.
The ease with which an energetic material can be initiated by mechanical impact is a critical parameter directing material safety and application. While impact sensitivity metrics are traditionally derived experimentally, recent developments have highlighted that the phenomenon is amenable to first principles simulation. In this chapter, we will outline a fully ab initio approach to predict the relative impact sensitivities of energetic materials based on the mechanochemical principles that link the impact event to vibrational energy transfer.
This mechanism is key to rationalizing how a mechanical impact—which deposits energy into the low-frequency lattice vibrations—results in a molecular response. By simulating the vibrational energy levels (the so-called phonon density of states, PDOS) using first-principles computational methods (typically dispersion-corrected plane-wave density functional theory, PW-DFT) we can calculate the relative rate of energy propagation from the delocalized low-energy lattice vibrations through to the localized molecular modes. The latter traps the energy, which eventually results in bond rupture through heightened vibrational excitation.
This method, based on vibrational up-pumping, offers a route toward predicting the impact sensitivities of a broad range of energetic materials, provided the crystal structure of the compound (or salt or co-crystal) is known. While it does not offer insight into the sensitizing roles undoubtedly played by crystal defects or grain boundaries, it does provide a level of understanding at the molecular and crystal packing levels. Correspondingly, this approach offers a feedback mechanism to chemists and materials scientists to guide the design of new materials with desired impact sensitivity behavior.
Laserstrahlhybridschweissen von Türmen für Windkraftanlagen Ökonomische und ökologische Vorteile
(2022)
Das Laserstrahlhybridschweißen ist beim Schweißen von Türmen für Windkraftanlagen eine Alternative zum Unterpulverschweißen von Dickblechen in Mehrlagentechnik und bietet hier ökonomische und ökologische Vorteile. Der industrielle Einsatz des Verfahrens ist jedoch durch prozessspezifische Herausforderungen eingeschränkt. Die im Beitrag beschriebene kontaktlose elektromagnetische Badstütze dient zur Erweiterung des Verfahrenspotenzials im Dickblechbereich >15 mm.
The study deals with the influence of the heat input and the resulting cooling times on the microstructure and Charpy impact toughness of single-pass laser hybrid welded 20-mm thick high-strength steel S690QL. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured in-situ using a pyrometer and an optical fibre in three different depths of the seam where Charpy impact test specimens were also later taken. Thereby, three different heat inputs from 1.3 kJ/mm to 2 kJ/mm were investigated. Despite the observed decreased values of both t8/5-cooling time and the Charpy impact toughness in the root part of the seam, the required impact toughness of 38 J/cm2 could be reached in dependance on applied heat input, especially at the heat input of 1.6 kJ/mm.
With additive manufacturing in the powder bed, the component size is limited by the installation space. Joint welding of additively manufactured parts offers a possibility to remove this size limitation. However, due to the specific stress and microstructure state in the additively built material, it is unclear to what extent existing evaluation rules of joint welding are also suitable for welds on additive components. This is investigated using laser beam welding of additively manufactured pipe joints. The welds are evaluated by means of visual inspection, metallographic examinations as well as computed tomography. The types of defects found are comparable to conventional components. This is an indicator that existing evaluation regulations also map the possible defects occurring for weld seams on additive components.
Solidification cracking is still a serious problem in laser beam welding, especially in the welding of thick-walled plates. The influence of weld pool geometry on solidification cracking in partial penetration welding of thick plates is investigated within scope of this study. Therefore, a specific experimental setup of steel and quartz glass in butt configuration and on the side with high-speed camera were used to record the weld pool shape. In addition, the influence of laser inclination angle on the weld pool geometry and on solidification crack formation was investigated. The results show a bulge in the weld pool root, which is separated from an upper region by a necking region. This leads to a case where there are three different longitudinal region lengths with different solidification zones. This temporal sequence of solidification strongly promotes the formation of solidification cracks in the weld root.
Ensuring the required mechanical-technological properties of welds is a critical issue in the application of multi-wire submerged arc welding processes for welding high-strength fine-grained steels. Excessive heat input is one of the main causes for microstructural zones with deteriorated mechanical properties of the welded joint, such as a reduced notched impact strength and a lower structural robustness. A process variant is proposed which reduces the weld volume as well as the heat input by adjusting the welding wire configuration as well as the energetic parameters of the arcs, while retaining the advantages of multiwire submerged arc welding such as high process stability and production speed.
The effect of the environmental conditions on the threshold against fatigue crack propagation
(2022)
The threshold against fatigue crack propagation (ΔKth) is a crucial parameter for the damage tolerance assessment of engineering components subjected to cyclic loading and it is composed by two distinct components, one intrinsic, dependent on the elastic material properties and the lattice type, and one extrinsic, related to the occurrence of crack closure effects. An important issue is that several factors can influence ΔKth and, in general, the fatigue crack propagation behavior. In this work, the influence of the experimental procedure, air humidity, stress ratio and test frequency on da/dN-ΔK data has been investigated. Results are discussed with their potential causes and consequences on the calculations of the residual lifetime.
In order to find a resource efficient approach for the fatigue lifetime prediction of laser powder bed fusion (L-PBF) processed AlSi10Mg material, results of tensile and fatigue tests were compared. The specimens were manufactured with three different L-PBF machines and studied in different heat treatment conditions (as-built, annealed, T6 heat treated). The investigations showed that the high attainable tensile strength properties after the manufacturing process are not beneficial in the high cycle fatigue (HCF) regime. In contrast, the applied heat treatments, which lead typically to a decrease of ultimate tensile strength, improved dramatically the fatigue behavior. Additionally, a clear correlation between the elongation at fracture and HCF resistance has been found for individual heat treatment conditions. This empiric relationship provides an estimation of the fatigue resistance in the presence of material defects and can be implemented in part and process approvals.
The Kitagawa-Takahashi (KT) diagram is a proven concept for describing the fatigue limit in presence of a defect or crack. It can be determined empirically with great experimental effort. It can also be estimated by means of the El Haddad relationship if the endurance limit and the long fatigue crack propagation threshold are available in reasonable accuracy. A third option is the determination using the cyclic R-curve, which describes the dependency of the fatigue crack propagation threshold on the crack growth at the short crack propagation stage. This can be experimentally determined using a closure-free initial pre-crack. It can then be applied to the determination of crack arrest for a given applied load and a given defect or crack size. Compared to the other two methods mentioned above, this option has considerable advantages: It can be applied to any component and any stress ratio. It allows the treatment of multiple cracks and provides estimations of the S-N curve in the finite life regime as well as at the endurance limit. Compared to the empirical determination of the KT diagram, the experimental effort is significantly lower and compared to the El Haddad approach it avoids problems such as the use of non-conservative long fatigue crack propagation thresholds (when the conventional load reduction method is applied to materials prone to corrosion) and the mathematical predetermination of the curve shape. The work introduces the method and provides a critical discussion as well as quantitative comparison between the different methods.
Al-Si alloys produced by Laser Powder Bed Fusion (L-PBF) techniques allow the fabrication of lightweight free-shape components that find space in aerospace, automotive, biomedical and military applications. Due to the high cooling rates occurring during the building process, L-PBF AlSi10Mg alloys exhibit an ultra-fine microstructure that leads to superior mechanical properties in the as-built condition compared to conventional cast Al-Si materials. Nevertheless, L-PBF processing induces high thermal gradients, leading to deleterious residual stress levels that must be considered to avoid part distortion and unpredicted failures. In order to relax detrimental residual stress and to increase the ductility, post-processing stress relief treatments are generally performed. In as-built condition the hypoeutectic AlSi10Mg microstructure consist of fine α-Al cells containing uniformly dispersed silicon nanoparticles, which are, in addition, surrounded by a eutectic Si network. Above 260°C the silicon interconnectivity starts to breakdown into spheroidized particles and to coarsen. At the same time, the heating residual stresses are relieved.
The objective of the contribution is to investigate, under different heat treatment conditions, the evolution of microstructure and residual stresses in view of optimizing the fatigue performance of the alloy. To this purpose various heat treatments in a range of temperatures between 265°C and 300°C for a duration between 15 minutes and 2 hours are performed. The microstructure modifications are analysed using a scanning electron microscope and the residual stress state is measured by laboratory X-ray diffraction.
Additive manufacturing (AM) is becoming increasingly important in engineering applications due to the possibility of producing components with a high geometrical complexity allowing for optimized forms with respect to the in-service functionality. Despite the promising potential, AM components are still far from being used in safety-relevant applications, mainly due to a lack of understanding of the feedstock-process-properties-performance relationship. This work aims at providing a full characterization of the fatigue behavior of the additively manufactured AISI 316L austenitic stainless steel and a direct comparison with the fatigue performance of the wrought steel. To this purpose, a set of specimens has been produced by laser powder bed fusion (L-PBF) and subsequently heat treated at 900 °C for 1 hour for complete stress relief, whereas a second set of specimens has been machined out of hot-rolled plates. Low cycle fatigue (LCF) and high cycle fatigue (HCF) tests have been conducted for characterizing the fatigue behavior. The L-PBF material had a higher fatigue limit and better finite life performance compared to wrought material. Both, LCF and HCF-testing revealed an extensive cyclic softening.
The damage tolerance approach is widely used in the design and estimation of inspection intervals of safety-relevant metallic components subject to fatigue loading. The approach relies on the knowledge of the fatigue crack propagation characteristics, wherein a relevant role is played by the fatigue crack propagation threshold. Nevertheless, the use of material data determined by testing on conventional specimens is not straightforward in the case of thin-walled components such as turbine blades or additively manufactured parts, in which the local variation of material properties in highly stressed regions must be considered. In these cases, the possibility of investigating the fatigue crack propagation properties on a limited portion of material is crucial. For this purpose, a new test procedure has been developed for small-scale specimens which allows the determination of the intrinsic fatigue crack propagation threshold and the near-threshold regime. The validity and limitations of the method are demonstrated on the high strength steel S960QL, along with a comparison with data determined by testing on conventional geometries.
Many applications in industry require a material-to-material joining process of Duplex Stainless Steels (DSS). Therefore, it is essential to investigate the material’s properties during a welding process to control the weld quality. With the help of Laser-Induced Breakdown Spectroscopy (LIBS), the chemical composition during the Tungsten Inert Gas (TIG) welding process of DSS could be monitored in situ. The chemical composition could be quantitatively measured using pre-established calibration curves. Although the surface temperature and the welding plasma have a high influence on the spectral intensities, reliable composition measurements were possible. The concentration of alloying elements could be mapped during the TIG welding process.
In the automotive industry, the development of electrically powered vehicles has become a major forward-looking topic. For improving the range and thus the efficiency of electric cars, lightweight construction has gained even more importance. In this regard, hot stamping has been established as a suitable and resource efficient process to manufacture high-strength and lightweight body-in-white components. This method combines hot forming and quenching of boron-manganese steel 22MnB5 in a single process step. As a result, complex structures with thin sheet thicknesses and high ultimate tensile strength up to 1500 MPa are generated. However, the use of lubricants is not possible at elevated temperatures, which subsequently leads to high thermo-mechanical tool stresses. As a side effect, high friction and severe wear occur during the forming process, which affect the resulting part quality and maximum tool life. Therefore, the aim of this study is to improve the tribological performance of hot stamping tools by using a laser implantation process. This technique is based on manufacturing highly wear resistant, separated and elevated structures in micrometer range by embedding hard ceramic particles into the tool material via pulsed laser radiation. As a result, highly stressed areas on the tool surface can be modified locally, which in turn influence the tribological and thermal behavior during the forming process. In this regard, laser implanted and conventionally tool surfaces were investigated under hot stamping conditions. A modified pin-on-disk test was used to analyze the friction coefficient and occuring wear mechanisms. Furthermore, quenching tests as well as hardness measurements were carried out to gain in-depth knowledge about the cooling behavior of the modified tool surfaces and its impact to the resulting mechanical part properties.
We report dielectric and calorimetric studies on metathesis and addition-type polytricyclononenes, both based on the same monomer bearing three pendant OSiMe3 groups. For the addition-type polymer, dielectric spectroscopy reveals a β*-process related to the microporosity, whereas for its metathesis counterpart, the segmental dynamics manifests as an α-process related to a glass transition. Besides active dielectric processes, a significant conductivity contribution is detected for both samples which for the microporous additiontype polymer is three orders of magnitude greater than for the metathesis polymer. The broadband dielectric spectroscopy is complemented by detailed calorimetric investigations, comprising DSC, FSC, and TMDSC. The calorimetric methods detected the glass transition for the metathesis polymer in agreement with the observed dielectric α-process. Furthermore, the already reported gas transport properties for both polymers are compared, setting them in correlation with the observed molecular mobility and conductivity behavior. The discussed results reflect significant differences in molecular mobility of the two polymers affecting the appearance of microporosity which strongly determines the gas transport properties.
Instead of foreseeing and preparing for all possible scenarios of machine failures, accidents, and other challenges arising in space missions, it appears logical to take advantage of the flexibility of additive manufacturing for “in-space manufacturing” (ISM). Manned missions into space rely on complicated equipment, and their safe operation is a great challenge. Bearing in mind the absolute distance for manned missions to the Moon and Mars, the supply of spare parts for the repair and replacement of lost equipment via shipment from Earth would require too much time. With the high flexibility in design and the ability to manufacture ready-to-use components directly from a computer-aided model, additive manufacturing technologies appear to be extremely attractive in this context. Moreover, appropriate technologies are required for the manufacture of building habitats for extended stays of astronauts on the Moon and Mars, as well as material/feedstock. The capacities for sending equipment and material into space are not only very limited and costly, but also raise concerns regarding environmental issues on Earth. Accordingly, not all materials can be sent from Earth, and strategies for the use of in-situ resources, i.e., in-situ resource utilization (ISRU), are being
envisioned. For the manufacturing of both complex parts and equipment, as well as for large infrastructure, appropriate technologies for material processing in space need to be developed.
Glasses in the systems Me2O-ZnO-B2O3 with Me = Li, Na, K, Rb (MeZB), Na2O-ZnO-CuO-B2O3 (NZCuB), CaO-ZnO-B2O3 (CaZB), and Li2O-PbO-B2O3 (LPbB) as a reference, were studied by differential thermal analysis, dilatometry, rotational viscometry, and heating microscopy. A decrease of viscosity and sintering range was found with decreasing number of fourfold coordinated boron. The viscosity of the alkali zinc borate glasses varies only slightly. LPbB and CaZB stand out by their reduced and increased viscosities, respectively. Sodium, potassium, and calcium zinc borate glasses possess a fragility above 76. All glasses were sintered to full density before crystallization. Mostly binary zinc borate phases govern crystallization. A ternary crystalline phase was detected only in the potassium containing sample. The Weinberg glass stability parameter ranges between 0.07 and 0.12. This is caused by the presence of several crystalline phases and varying melting points of even the same crystalline phase in different glass matrices.
Ein Umlaufkühler ist im Betrieb explodiert. Splitter des zerborstenen Gehäuses aus Kunststoff wurden mit dem Kühlwasser in die Umgebung geschleudert, am Betriebsort entstand Personenschaden. Bei Funktionsprüfungen am beschädigten Gerät traten unerwartet - aber reproduzierbar - Knalleffekte bei Berührung der Außenoberfläche der Kupfer-Kühlschlange auf. Ein möglicher Mechanismus konnte im Labor durch Synthese von Kupferazid auf Kupferproben und Auslösung vergleichbarer Knalleffekte nachgestellt werden. Damit ist die Plausibilität des beschriebenen Schadensereignisses mit diesem oder einem ähnlich reagierenden Stoff belegt. Ein eindeutiger Nachweis darüber, dass bei dem aufgetretenen Schadensfall dieselbe chemische Reaktion stattgefunden hat, war nicht möglich, da die Belag-Überreste aus dem explodierten Kühlgerät für eine Analyse nicht mehr in ausreichender Menge verfügbar gewesen sind.
In order to bridge the gap between lab-scale and industrial-scale production of graphene it is necessary to develop processes, equipment and measurement procedures to control the material features. One of the crucial reasons of graphene’s limited commercialization is the lack of standard procedures to properly characterize and define the material chemical and structural properties down to the nanometer level. This leads to many issues regarding material synthesis repeatability, inappropriateness choice of measurands and measurement reproducibility which heavily affect the consistency of the material performance.
In our study, a comparative analysis is performed on two different series (G5 and G6) of industrial graphene powders, each series produced with four types of functionalization: raw graphene, oxygen-functionalized, nitrogen-functionalized and fluorine-functionalized. All the 8 sample variants were analyzed from a chemical and morphological point of view in the form of powders prepared as slightly pressed in metallic sample holders.
The results of the comparative chemical analyses XPS and EDS show a good agreement in the concentration values for all the elements present in the samples, despite the different analysis volumes addressed by the two techniques. For this reason, the samples can be considered homogeneous in both lateral and vertical direction.
A clear influence of the morphology on the composition is evident. Therefore, such correlative measurements of morphology and composition are necessary for a comprehensive characterization of industrial graphene flakes.
During resistance spot welding of zinc-coated advanced high-strength steels (AHSSs) for automotive production, liquid metal embrittlement (LME) cracking may occur in the event of a combination of various unfavorable influences. In this study, the interactions of different welding current levels and weld times on the tendency for LME cracking in third-generation AHSSs were investigated. LME manifested itself as high penetration cracks around the circumference of the spot welds for welding currents closely below the expulsion limit. At the same time, the observed tendency for LME cracking showed no direct correlation with the overall heat input of the investigated welding processes. To identify a reliable indicator of the tendency for LME cracking, the local strain rate at the origin of the observed cracks was analyzed over the course of the welding process via finite element simulation. While the local strain rate showed a good correlation with the process-specific LME cracking tendency, it was difficult to interpret due to its discontinuous course. Therefore, based on the experimental measurement of electrode displacement during welding, electrode indentation velocity was proposed as a descriptive indicator for quantifying cracking tendency.
Low melting Li2O-PbO-B2O3, Me2O-ZnO-B2O3, Me = Li, Na, K, Rb and CaO-ZnO-B2O3 glasses were studied with Raman and infrared spectroscopies to advance the structural understanding of zinc borate glasses as potential candidates for substitution of lead containing glasses. Although the effect of type of alkali ions on the number (N4) of fourfold coordinated boron (B4) in the glasses is small, the alkali ions direct the type of borate groups, i.e., pentaborate in lithium, sodium, and calcium zinc borate glasses, as well as diborate in potassium and rubidium containing ones. Both groups were simultaneously found in Li2O-PbO-B2O3. Alkali ions are mainly responsible for the formation of B4-units and metaborate. Zinc ions favorably compensate non-bridging oxygen and partially form ZnO4. With decreasing N4 and field strength of the alkali ions the atomic packing density, glass transition temper ature and Young’s Modulus also decrease. The coefficient of thermal expansion increases with decreasing N4.
With regard to efficient production, it is desirable to combine the respective advantages of additively and conventionally manufactured components. Particularly in the case of large-volume components that also include filigree or complex structures, it makes sense to divide the overall part into individual elements, which afterwards have to be joined by welding.
The following research represents a first step in fundamentally investigating and characterizing the joint welding of Laser Powder Bed Fusion (L-PBF) components made of Inconel 718. For this purpose, bead-on-plate welds were performed on plates manufactured using the L-PBF process and compared with the conventionally manufactured material. Conventional laser beam welding was used as welding process. The weld geometry was investigated as a function of the L-PBF build-up orientation. It was found that the welding depth and weld geometry differ depending on this orientation and in comparison to the conventional material.
BAM! This issue of Advanced Engineering Materials celebrates 150 years of scientific and technical research at the interface between academia, industry and politics. Rooted in 1871 at the birth of the German Empire and at that time located in simple basements and barracks, the institutional development began around mechanical metallurgy of iron and steel and represents today a diverse portfolio of fore-front research that orients itself along tomorrow's societal challenges and long-term research horizons.
The Directed Energy Deposition process is used in a wide range of applications including the repair, coating or modification of existing structures and the additive manufacturing of individual parts. As the process is frequently applied in the aerospace industry, the requirements for quality assurance are extremely high. Therefore, more and more sensor systems are being implemented for process monitoring. To evaluate the generated data, suitable methods must be developed. A solution, in this context, was the application of artificial neural networks (ANNs). This article demonstrates how measurement data can be used as input data for ANNs. The measurement data were generated using a pyrometer, an emission spectrometer, a camera (Charge-Coupled Device) and a laser scanner. First, a concept for the extraction of relevant features from dynamic measurement data series was presented. The developed method was then applied to generate a data set for the quality prediction of various geometries, including weld beads, coatings and cubes. The results were compared to ANNs trained with process parameters such as laser power, scan speed and powder mass flow. It was shown that the use of measurement data provides additional value. Neural networks trained with measurement data achieve significantly higher prediction accuracy, especially for more complex geometries.
Laser metal deposition (LMD) as an additive manufacturing technique became increasingly important in recent years and thus the demand for component safety. This is the reason, for the need for reliable in-situ defect detection techniques. For laser beam weld seams an optical measurement technique based on an optical flow algorithm was successfully used to define the critical straining conditions that lead to hot cracking. This algorithm was adapted for bead-on-plate weld seams on LMD deposited layers of IN718 alloy while performing external strain on the specimen in an externally loaded hot cacking test facility. The resulting transversal hot cracks along the weld seam were localized via X-Ray inspection and the type of cracking confirmed by Scanning Electron Microscopy (SEM). The strain distribution was measured in the vicinity of the solidification front and correlated to the detected hot cracks. Based on the results this technique could be adopted for LMD experiments.
Nanosafety is becoming increasingly important as nanomaterials are widely used in industrial processes and consumer products. For nanotoxicity measurements prior sterilization of the samples is necessary, but as structure activity relationships are made with properties of pristine particles, the question arises, if the sterilization process has an impact on the physico-chemical properties of nanoparticles and thus on the biological behavior.
This question will be addressed in this talk. For this purpose, results from SEM and EDS measurements are combined with those of a novel lab-based HAXPES spectrometer in order to obtain a more complete picture. At the end, an influence of sterilization will be evident, which indicates a restructuring of the nanoparticles owing to sterilization.
Duplex stainless steels combine the positive properties of its two phases, austenite and ferrite. Due to its good corrosion resistance, high tensile strength and good ductility it has multiple applications. But laser beam welding of duplex steels changes the balanced phase distribution in favor of ferrite. This results in a higher vulnerability to corrosion and a lower ductility. In this study different powder combinations consisting of duplex and nickel for coating layers by laser metal deposition are investigated. Afterwards laser tracks are welded, and the temperature cycles measured. The ferrite content of the tracks are analyzed by feritscope, metallographic analysis and Electron Backscatter Diffraction. The goal is the development of a powder mixture allowing for a duplex microstructure in a two-step process, where firstly the edges of the weld partners are coated with the powder mixture by LMD and secondly those edges are laser beam welded. The powder mixture identified by the pretests is tested in the two-step process and analyzed by metallographic analysis, energy dispersive X-ray spectroscopy and Vickers hardness tests. The resulting weld seams show a balanced duplex microstructure with a homogenous nickel distribution and a hardness of the weld seam similar to the base material.
The thickness of thin films can be measured by various methods, e.g., profilometry, ellipsometry, atomic force microscopy (AFM), or X-ray reflectometry. For the additional determination of thin film composition, techniques like X-ray photoelectron spectroscopy (XPS) or mass spectrometry-based techniques can be used. An alternative non-destructive technique is electron probe microanalysis (EPMA). This method assumes a sample of homogenous (bulk) chemical composition, so that it cannot be usually applied to thin film samples. However, in combination with the thin film software StrataGEM, the thickness as well as the composition of such films on a substrate can be determined.
This has been demonstrated for FeNi on Si and SiGe on Al2O3 film systems. For both systems five samples with different elemental composition and a reference were produced and characterised by Korean research institute KRISS using inductively coupled plasma mass spectrometry (ICP-MS), Rutherford backscattering (RBS), and transmission electron microscopy (TEM). These samples were used for an international round robin test.
In 2021, a new and open-source thin film evaluation programme called BadgerFilm has been released. It can also be used to determine thin film composition and thickness from intensity ratios of the unknown sample and standards (k-ratios).
In this contribution, we re-evaluated the data acquired for the FeNi and SiGe systems using the BadgerFilm software package and compared the resulting composition and thickness with the results of the established StrataGEM software and other reference methods. With the current evaluation, the BadgerFilm software shows good agreement with the composition and thickness calculated by StrataGEM and as the reference values provided by the KRISS.
Medium and High Entropy Alloys (MEA/HEA) are recently developed material classes, providing manifold applications, e.g., due to extraordinary structural properties. In that connection, the machinability as important issue for the processing of these materials was not in the scientific focus. This study focusses on experimental analysis of milling process conditions including ultrasonic assisted milling (USAM) and their effects on the resulting surface integrity of equiatomic CoCrFeNi-MEA specimens. For that reason, milling parameters (cutting speed, feed per cutting edge) were systematically varied for both conventional milling and USAM. The surface integrity was analyzed in terms of topography, defects, and residual stresses. Especially USAM leads to a decrease of occurring cutting forces and, hence, to an improvement of the surface integrity. Beneficial effects were observed in terms of lower tensile residual stresses at high cutting speed and feed per cutting edge.
The conversion of solar energy into electricity and solar fuels is of crucial importance for a green and sustainable future. Water splitting using semiconductor photo-catalysts is considered a sustainable method to produce clean hydrogen (H2) fuel. Nevertheless, H2 photo-production efficiency remains still low, although extensive research works to understand better the mechanisms of the Hydrogen Evolution Reaction (HER) and the Oxygen Evolution Reaction (OER) are being carried out. In this respect, TiO2 is a key photoactive material, usually employed with a co-catalyst deposited onto the surface to enhance charge carriers’ separation and catalyze surface charge transfer reactions. The deposition of a co-catalyst on the TiO2 nanoparticle surface represents one successful way to enhance the activity of the photocatalyst through a modification of its surface and redox properties. In this context, high-resolution scanning electron microscopy coupled with elemental analysis by energy-dispersive X-ray spectroscopy (EDS) is fundamental for studying and understanding the effect of the nanoparticle morphology on the functional properties of shape-controlled TiO2 crystals (bipyramides, platelets, and elongated particles). Different types of metal-semiconductor combinations, TiO2 shapes and dopant metals (Ag, Pt, etc) and metal concentrations will be discussed.
The importance of high-temperature materials made of iron aluminides (FeAl) has been increasing in light weight applications, e.g., airplane turbines, due to the high material’s specific strength. However, the highly economic production by means of permanent mold casting involves special microstructures for Fe26Al4Mo0.5Ti1B alloy components leading to difficult machinability for subsequent finishing milling and low surface qualities. Major effects of tool and machining parameter variation incorporating ultrasonic assistance on the milling process and surface integrity are shown. Loads for tool and component surface are significantly adjustable to enable an economic process chain regarding the surface integrity of safety-relevant components.
To mitigate carbon dioxide emissions CO2 is compressed and sequestrated into deep geological layers (Carbon Capture and Storage CCS). The corrosion of injection pipe steels is induced when the metal is in contact with CO2 and at the same time the geological saline formation water. Stainless steels X35CrMo17 and X5CrNiCuNb16-4 with approximately 17% Cr show potential as injection pipes to engineer the Northern German Basin geological onshore CCS-site. Static laboratory experiments (T = 60 ◦C, p = 100 bar, 700–8000 h exposure time, aquifer water, CO2-flow rate of 9 L/h) were conducted to evaluate corrosion kinetics. The anomalous surface corrosion phenomena were found to be independent of heat treatment prior to exposure. The corrosion process is described as a function of the atmosphere and diffusion process of ionic species to explain the precipitation mechanism and better estimate the reliability of these particular steels in a downhole CCS environment.
Trace elements play an important role in the fine-tuning of complex material properties. This study focuses on the correlation of microstructure, lattice misfit and creep properties. The compositionally complex alloy Al10Co25Cr8Fe15Ni36Ti6 (in at. %) was tuned with high melting trace elements Hf and W. The microstructure consists of a γ matrix, γ' precipitates and the Heusler phase and it is accompanied by good mechanical properties for high temperature applications. The addition of 0.5 at.% Hf to the Al10Co25Cr8Fe15Ni36Ti6 alloy resulted in more sharp-edged cubic γ′ precipitates and an increase in the Heusler phase amount. The addition of 1 at.% W led to more rounded γ′ precipitates and the dissolution of the Heusler phase. The shapes of the γ' precipitates of the alloys Al9.25Co25Cr8Fe15Ni36Ti6Hf0.25W0.5 and Al9.25Co25Cr8Fe15Ni36Ti6Hf0.5W0.25, that are the alloys of interest in this paper, create a transition from the well-rounded precipitates in the alloy with 1% W containing alloy to the sharp angular particles in the alloy with 0.5% Hf. While the lattice misfit has a direct correlation to the γ' precipitates shape, the creep rate is also related to the amount of the Heusler phase. The lattice misfit increases with decreasing corner radius of the γ' precipitates. So does the creep rate, but it also increases with the amount of Heusler phase. The microstructures were investigated by SEM and TEM, the lattice misfit was calculated from the lattice parameters obtained by synchrotron radiation measurements.
BAM is currently building up a platform of novel nanoRMs relying on iron oxide nanoparticles of different shape, size and surface chemistry. Iron oxide was chosen as a core material because of its relevance to the material and life sciences.
As a first candidate of this series, we present cubic iron oxide nanoparticles with a nominal edge length of 8 nm. These particles were synthesized by thermal decomposition of iron oleate in high boiling organic solvents adapting well-known literature procedures. After dilution to a concentration suitable for electron microscopy (TEM and SEM) as well as for small-angle X-ray scattering (SAXS) measurements, the candidate nanoRM was bottled and assessed for homogeneity and stability by both methods following the guidelines of ISO 17034 and ISO Guide 35.
The particle sizes obtained by both STEM-in-SEM and TEM are in excellent agreement with a minimum Feret of 8.3 nm ± 0.7 nm. The aspect ratio (AR) of the iron oxide cubes were extracted from the images as the ratio of minimum Feret to Feret resulting in an AR of 1.18 for TEM to 1.25 for SEM. Alternatively, a rectangular bounding box was fitted originating from the minimum Feret and the longest distance through the particle in perpendicular direction. This led to AR values of 1.05 for TEM and 1.12 for SEM, respectively. The results confirm the almost ideal cubic shape.
The large surface-to-volume ratio of nanoparticles is understood to be the source of many interesting phenomena. The melting temperature of nanoparticles is shown to dramatically reduce compared to bulk material. Yet, at temperatures below this reduced melting point, a liquid-like atomic arrangement on the surface of nanoparticles is still anticipated to influence its properties. To understand such surface effects, here, we study the coalescence of Au nanoparticles of various sizes using molecular dynamics simulations. Analysis of the potential energy and Lindemann index distribution across the nanoparticles reveals that high-energy, high-mobility surface atoms can enable the coalescence of nanoparticles at temperatures much lower than their corresponding melting point. The smaller the nanoparticles, the larger the difference between their melting and coalescence temperatures. For small enough particles and/or elevated enough temperatures, we found that the coalescence leads to a melting transition of the two nominally solid nanoparticles, here discussed in relation to the heat released due to the surface reduction upon the coalescence and the size dependence of latent heat. Such discontinuous melting transitions can lead to abrupt changes in the properties of nanoparticles, important for their applications at intermediate temperatures.
The continuously increasing use of plastics is supposed to result in a rising exposure of MNPs to humans. Available data on human health risks of microplastics after oral uptake increased immensely in the past years and indicates very likely only low risks after oral consumption. Concerning nanoplastics, uptake, transport and potential adverse effects after oral uptake are less well understood. This study aims to investigate differences between microplastic particles and particles in the submicron- and nanoscaled size derived from food-relevant polymers with a particle size range consistent with higher potential for cellular uptake, fate, and effects when applied to human intestinal and liver cells. This work includes the development of cellular and subcellular detection methods for synthetic polymeric particles in the micro- and nanometer-range, using Scanning Electron Microscopy, Small-Angle X-ray and Dynamic Light Scattering methods, Asymmetric Flow Field Flow Fractionation, octanol-water fractionation, fluorescence microscopy and flow cytometry. Polylactic acid (250 nm and 2 μm (polydisperse)), melamine formaldehyde (366 nm) and polymethylmethacrylate (25 nm) were thoroughly characterized. The submicro- and nanoplastic test particles showed an increased uptake and transport quantity through intestinal cells. Both types of particles resulted in observed differences of uptake behavior, most likely influenced by different lipophilicity, which varied between the polymeric test materials. Toxic effects were detected after 24 h only in overload situations for the particles in the submicrometer range. This study provides further evidence for gastrointestinal uptake of submicro- and nanoplastics and points towards differences regarding bioavailability between microplastics and smaller plastic particles that may result following the ingestion of contaminated food and beverages. Furthermore, the results reinforce the importance for studying nanoplastics of different materials of varying size, surface properties, polymer composition and hydrophobicity.
Laser beam welding is a widely used joining technique in many industrial applications. This is mainly due to its many unique advantages, especially compared to conventional arc welding processes. These advantages include, among others, highly concentrated energy deposition, low total heat input and a capacity to penetrate deep into the material while causing only small welding distortions.
However, at the same time, the small dimension of the laser spot, high solidification rates, and small dimensions of the weld pool itself can provoke issues regarding the assembly tolerances of the workpiece, the hot-cracking phenomena, as well as keyhole-induced bubbles escaping from the melt.
Weld pool shapes in laser beam welding are elongated at the external, free surfaces under the action of the main driving forces in the melt – such as recoil pressure and surface tension forces – while being shorter in the internal areas of the weld pool. This leads to a regular solidification sequence from the internal zones toward the free surfaces, e.g. from the bottom to the top in partial penetration welding. However, in recent studies reported in the literature and seen in the experimental and numerical investigations of BAM Bundesanstalt für Materialforschung und -prüfung in Berlin, it was found that an internal narrowing phenomenon can occur that is often accompanied by a distinct bulging of the weld bead in deeper zones.
As the internal behaviour of the melt during the process is hardly optically accessible, several numerical models and experimental techniques were established to visualise the mechanisms of the formation of the bulging and the narrowing phenomenon and to reveal the consequences on the solidification sequence, pore formation, and filler metal dilution.
Metastable austenitic stainless steel (304L) samples with a rectangular cross-section were plastically deformed in torsion during which they experienced multiaxial stresses that led to a complex martensitic phase distribution owing to the transformation induced plasticity effect. A three-dimensional characterization of the phase distributions in these cm-sized samples was carried out by wavelength-selective neutron tomography. It was found that quantitatively correct results are obtained as long as the samples do not exhibit any considerable preferential grain orientation. Optical microscopy, electron backscatter diffraction, and finite element modeling were used to verify and explain the results obtained by neutron tomography. Altogether, neutron tomography was shown to extend the range of microstructure characterization methods towards the meso- and macroscale.
In diesem Artikel werden die verschiedenen additiven Fertigungsverfahren und ihre Anwendungsmöglichkeiten vorgestellt. Der Fokus liegt hierbei auf Silikatkeramik. Für jedes 3D Druckverfahren werden die Möglichkeiten mit Silikatkeramik, Hochleistungskeramik und Dentalkeramik aufgezeigt. Auf den Nutzen der verschiedenen 3D Druckverfahren für industrielle Anwendungen, den privaten Bereich, sowie die Verwendung für Kunst und Design wird eingegangen. Das Potenzial der Additiven Fertigung wird auch für den Bereich der Keramik in der dentalen Anwendung bewertet.