5 Werkstofftechnik
Filtern
Erscheinungsjahr
- 2019 (55) (entfernen)
Dokumenttyp
- Zeitschriftenartikel (55) (entfernen)
Sprache
- Englisch (55)
Schlagworte
- Corrosion (7)
- Carbon steel (3)
- Crystallization (3)
- 3D printing (2)
- Additive Manufacturing (2)
- Additive manufacturing (2)
- Bioactive glass (2)
- Condensate (2)
- Corrosion Fatigue (2)
- Degradation (2)
- Ductile iron (2)
- Fatigue (2)
- High Alloyed Steel (2)
- Impurities (2)
- NMR spectroscopy (2)
- Niobium alloying (2)
- Oxidation (2)
- Pitting (2)
- AISI 304L (1)
- Abrasion (1)
- Alkali-activated materials (1)
- Alumina (1)
- Aluminosilicate glasses (1)
- Aquifer (1)
- Artificial weathering (1)
- Bioceramics (1)
- Biodiesel (1)
- Biogeochemical cycling (1)
- Biomineralisation (1)
- Biopolymer (1)
- Bubble formation (1)
- C. lap-shear (1)
- CCS (1)
- CCUS (1)
- CFRP (1)
- CO2 (1)
- CO2 separation membranes (1)
- Calcination (1)
- Calcium cobaltite (1)
- Carbidic austempered ductile iron (1)
- Carbon capture (1)
- Carbon capture, utilization and storage technology (1)
- Carbon fibres (1)
- Carbon storage (1)
- Cavitation (1)
- Cellulose (1)
- Ceramic (1)
- Ceramics (1)
- Chalcogenides (1)
- Characterisation (1)
- Coefficient of thermal expansion (1)
- Contact angle (1)
- Contact fatigue (1)
- Copper vacancies (1)
- Corrosion pits (1)
- Crack arrest (1)
- Crack propagation (1)
- Crosslinking (1)
- Crystal Texture (1)
- Cyclic softening (1)
- D. aging (1)
- D. creep D. viscoelasticity (1)
- Defects (1)
- Deuterium (1)
- Dielectric breakdown (1)
- Diesel (1)
- Diesel Fuel (1)
- Distributed fiber optic sensing (1)
- EBSD (1)
- Early oxidation (1)
- Early sulfidation (1)
- Elastic constants (1)
- Electrochemical characterisation (1)
- Electrochemical deposition (1)
- Electrochemical impedance spectroscopy (1)
- Electron energy (1)
- Electron microscopy (1)
- Endurance Limit (1)
- Energy distribution (1)
- Environment (1)
- Environmentally assisted cracking (1)
- Exposed metal sites (1)
- FSDC (1)
- Fabrication (1)
- Facilitated activation (1)
- Fatigue Testing (1)
- Fatigue crack propagation stages (1)
- Ferritic steels (1)
- Ferritic–martensitic steel (1)
- Finite element analysis (1)
- Four-point bending test (1)
- Fracture (1)
- Fracture mechanics (1)
- Freeze casting (1)
- Friction Stir Welding (1)
- Frozen state photopolymerization (1)
- GFRP (1)
- Geothermal (1)
- Glass (1)
- Glass-ceramic (1)
- Gold (1)
- Grain boundary (1)
- Heat treatment (1)
- Hierarchical porosities (1)
- High pressure (1)
- High temperature corrosion (1)
- High-temperature oxidation (1)
- High-temperature properties (1)
- High-voltage testing (1)
- Hydrogel (1)
- Hydrogen (1)
- Hydrogen diffusivity (1)
- Hygrothermal (1)
- Impact damage (1)
- In-situ Process Monitoring (1)
- Inclusion cluster (1)
- Inclusion size (1)
- Inconel 625 (1)
- Incremental lifetime models (1)
- Infrared nano AFM (1)
- Infrared spectroscopy (1)
- Intermodulation AFM (1)
- Internal Surfaces (1)
- Internal oxidation (1)
- Interphase (1)
- Ionic porosity (1)
- Iron meteorite (1)
- Kikuchi pattern (1)
- LSD print (1)
- Laser beam melting (1)
- Laser-induced slip casting (1)
- Layerwise slurry deposition (1)
- Long-term storage (1)
- Low cycle fatigue (1)
- MOF-74 (1)
- Magmatic and hydrothermal processes (1)
- Martensite (1)
- Mass transport (1)
- Material degradation (1)
- Micro-shrinkages (1)
- Microhardness (1)
- Mis-match (1)
- Mixed Ca-K-Na phosphates (1)
- Mixed-linkers (1)
- Moisture (1)
- Multiple cracks (1)
- Na and K rhenanites (1)
- Nanocomposites (1)
- Natural (1)
- Neutron diffraction (1)
- Nitride (1)
- Non-destructive Materials (1)
- Non-metallic inclusions (1)
- Orientation relationship (1)
- Oxidation protection (1)
- P92 (1)
- PE-HD Sorption (1)
- Parabolic flight (1)
- Permeability (1)
- Phase diagram (1)
- Phase transformations (1)
- Phase-field (1)
- Phosphate (1)
- Pitting corrosion (1)
- Plastic deformation (1)
- Platinum-group-metals (1)
- Polyaniline (1)
- Polymer (1)
- Polyurethane (1)
- Pores (1)
- Preceramic polymer (1)
- Pressure-assisted sintering (1)
- Process development (1)
- Processing window (1)
- Pultruded fiber rods (1)
- Relaxation fatigue (1)
- Resonance testing (1)
- Roughness (1)
- SDC (1)
- STEM (1)
- Safety (1)
- Samarium doped ceria (1)
- Sandwich (1)
- Scaffolds (1)
- Scavenging effect of iron (1)
- Scratches (1)
- Silicoborate glasses (1)
- Silicon Carbide (1)
- Simulation (1)
- Sintering (1)
- Slip-rolling (1)
- Soda-lime-silica (1)
- Soda-lime-silica glass (1)
- Sodium ion batteries (1)
- Sol-gel coating (1)
- Sorption (1)
- Spar cap design (1)
- Standardisation (1)
- Statistics (1)
- Steel (1)
- Stress intensity factor (1)
- Stress-strain behavior (1)
- Structural composites (1)
- Structural defects (1)
- Structural health monitoring (1)
- Subcritical crack growth (1)
- Sulfidation (1)
- Superconducting magnet (1)
- Surface (1)
- Surface treatments (1)
- Swept wavelength interferometry (1)
- Synthesis (1)
- Thermoelectric properties (1)
- Thiol-ene click chemistry (1)
- ToF-SIMS (1)
- Tungsten-Rhenium (1)
- Utilization, and storage (CCUS) technology (1)
- Vickers indentation (1)
- Viscoelastic model (1)
- Viscous sintering (1)
- WAXS (1)
- Water content (1)
- Water speciation (1)
- Wetting (1)
- X-ray absorption spectroscopy (1)
- X-ray refraction (1)
- Young´s modulus (1)
- ZnO (1)
- arbidic austempered ductile iron (1)
- bioactive (1)
- biomaterials (1)
- bone (1)
- high pressure (1)
- infrared spectroscopy (1)
- phosphate glasses (1)
- water speciation (1)
- µ-gravity (1)
Organisationseinheit der BAM
- 5 Werkstofftechnik (55)
- 5.1 Mikrostruktur Design und Degradation (22)
- 5.4 Multimateriale Fertigungsprozesse (12)
- 5.6 Glas (11)
- 7 Bauwerkssicherheit (9)
- 9 Komponentensicherheit (8)
- 5.3 Polymere Verbundwerkstoffe (7)
- 5.2 Metallische Hochtemperaturwerkstoffe (5)
- 6 Materialchemie (5)
- 5.0 Abteilungsleitung und andere (4)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (4)
- 7.6 Korrosion und Korrosionsschutz (4)
- 9.0 Abteilungsleitung und andere (4)
- 9.4 Integrität von Schweißverbindungen (4)
- 5.5 Materialmodellierung (3)
- 6.3 Strukturanalytik (3)
- 8 Zerstörungsfreie Prüfung (3)
- 8.5 Röntgenbildgebung (3)
- 6.1 Oberflächen- und Dünnschichtanalyse (2)
- 6.6 Physik und chemische Analytik der Polymere (2)
- 9.3 Schweißtechnische Fertigungsverfahren (2)
- 9.5 Tribologie und Verschleißschutz (2)
- 1 Analytische Chemie; Referenzmaterialien (1)
- 1.2 Biophotonik (1)
- 1.7 Organische Spuren- und Lebensmittelanalytik (1)
- 4 Material und Umwelt (1)
- 4.2 Material-Mikrobiom Wechselwirkungen (1)
- 7.4 Baustofftechnologie (1)
- 8.0 Abteilungsleitung und andere (1)
- S Qualitätsinfrastruktur (1)
- S.0 Abteilungsleitung und andere (1)
The crystallization behavior of sodium ion conductive Na2MnP2O7 glass was examined to clarify the crystallization mechanism. The formation of thermodynamically metastable phase, layered Na2MnP2O7, at the surface of the glass occurred. Heat treatment at 430 °C for 3 h lead to surface crystals of Na2MnP2O7 oriented with the (101) direction perpendicular to the sample surface. As the heat treatment temperature increased, the glass-ceramic samples deformed, and the presence numerous micro bubbles due to dissolved water was detected.
Electrochemical deposition of polyaniline on carbon steel for corrosion study in geothermal solution
(2019)
Polyaniline has been widely developed for many applications, e.g. sensor, supercapacitor components, electrochromic devices, and anticorrosion pigments. Although the addition of polyaniline pigment in organic coatings has been an alternative for corrosion protection in industrial applications, the protection mechanism is still not fully understood. Herein in this study, as a part of the development of polyaniline/silicon dioxide coating for geothermal application, polyaniline has been deposited electrochemically on carbon steel surface in oxalic acid medium and tested in geothermal solution to understand the contribution of polyaniline to the corrosion protection of a polyaniline-based composite in the geothermal system. To observe the surface/interface reaction between the electrolyte and electrode surface during the electrochemical polymerization, electrochemical impedance spectroscopy (EIS) was applied after each cycle. For corrosion study in the geothermal application, an artificial geothermal solution was used with the composition of 1,500 mg/l Cl⁻, 20 mg/l SO₄²⁻, 15 mg/l HCO₃⁻, 200 mg/l Ca²⁺, 250 mg/l K⁺, and 600 mg/l Na⁺, and pH 4 to simulate a geothermal brine found in Sibayak, Indonesia. An electrochemical measurement was performed by monitoring the open circuit potential over seven days, with the interruption by EIS every 22 hours. The experiments were performed at room temperature and 150 °C (1 MPa) in an oxygen-free environment. Impedance spectra showed a reduction of the total impedance value of approximately 10 times for specimens measured at 150 °C compared to the specimens measured at room temperature, suggesting a less stable layer at high temperature.
This study focuses on the corrosion mechanism of carbon steel exposed to an artificial geothermal brine influenced by carbon dioxide (CO2) gas. The tested brine simulates a geothermal source in Sibayak, Indonesia, containing 1500 mg/L of Cl-, 20 mg/L of SO4 2-, and 15 mg/L of HCO3-with pH 4. To reveal the temperature effect on the corrosion behavior of carbon steel, exposure and electrochemical tests were carried out at 70 °C and 150 °C. Surface analysis of corroded specimens showed localized corrosion at both temperatures, despite the formation of corrosion products on the surface. After 7 days at 150 °C, SEM images showed the formation of an adherent, dense, and crystalline FeCO3 layer. Whereas at 70 °C, the corrosion products consisted of chukanovite (Fe2(OH)2CO3) and siderite (FeCO3), which are less dense and less protective than that at 150 °C.
Control experiments under Ar-environment were used to investigate the corrosive effect of CO2. Free corrosion potential (Ecorr) and electrochemical impedance spectroscopy (EIS) confirm that at both temperatures, the corrosive effect of CO2 was more significant compared to that measured in the Ar-containing solution. In terms of temperature effect, carbon steel remained active at 70 °C, while at 150 °C, it became passive due to the FeCO3 formation. These results suggest that carbon steel is more susceptible to corrosion at the near ground surface of a geothermal well, whereas at a deeper well with a higher temperature, there is a possible risk of scaling (FeCO3 layer). A longer exposure test at 150 °C with a stagnant solution for 28 days, however, showed the unstable FeCO3 layer and therefore a deeper localized corrosion compared to that of seven-day exposed specimens.
Dissolved water has major impact on the physical and chemical properties of phosphate glasses. In the present study we have investigated the structural response to water incorporation for glasses in the system Li2O–MgO–Al2O3–P2O5.
Glasses containing 0–8 wt% H2O were synthesised at 500 MPa confining pressure in internally heated gas pressure vessels at 1323 K (LMP, Al-poor glass) and 1423 K (LMAP, Al-enriched glass). Water contents of glasses were determined by pyrolysis and subsequent Karl-Fischer titration (KFT) and/or by infrared spectroscopy. Density varies nonlinearly with water content implying large structural changes when adding up to 2 wt% H2O to the dry glass. Glass Transition temperatures measured by differential thermal analysis (DTA) continuously decrease with water content. The trend can be explained by depolymerisation of the phosphate network. Near-infrared spectroscopy shows that even in Al poor glasses only a minority of dissolved water is present as H2O molecules, but the largest amount is present as OH Groups formed by hydrolysis of P–O–P bonds. The network is stabilised by aluminium which is predominantly six-coordinated in these glasses as shown by 27Al MAS NMR spectroscopy. With increase of Al in the glasses, breaking up of the Phosphate network through hydrolysis is depressed, i.e. much lower OH Contents are formed at same total water content.
Network depolymerisation upon addition of H2O is evident also from 31P MAS NMR spectroscopy. While Phosphate tetraheda are crosslinked by two to three bridging oxygen in dry glasses, diphosphate Groups are dominant in glasses containing 8 wt% H2O.
To understand the impact of dissolved water on structure and properties, four boron-rich glasses of molar compositions 15-x Na2O x CaO 15 SiO2 70 B2O3 (with x=0, 7.5, 10) and 10 Na2O 15 SiO2 75 B2O3 were prepared and subsequently hydrated (up to 8 wt% H2O). Density measurements show a non-linear trend upon hydration implying large structural changes in particular at water contents<2 wt%. Near-infrared spectroscopy shows hydroxyl groups are the dominant species in all glasses upon the entire range of water content. Molecular H2O is detectable only at total water contents>2 wt%. 11B MAS NMR spectra show that the abundance of BO4 species is mainly controlled by ratio of (Na2O+CaO)/B2O3 while incorporation of water plays a minor role.
Compared to borate glasses, the efficiency of formation of BO4 tetrahedra is favored by crosslinking of the network by SiO4-units. The glass transition temperatures, determined by differential thermal analysis, decreases continuously with water content due to breakage of B-O-B bonds by hydrolysis. However, compared to Silicates and aluminosilicates, the effect of dissolved water is less pronounced which can be explained by weaker B-O-B bonds in comparison to Si-O-Si bonds.
The sintering of bioactive glasses allows for the preparation of complex structures, such as three‐dimensional porous scaffolds. Such 3D constructs are particularly interesting for clinical applications of bioactive glasses in bone regeneration, as the scaffolds can act as a guide for in‐growing bone cells, allowing for good Integration with existing and newly formed tissue while the scaffold slowly degrades. Owing to the pronounced tendency of many bioactive glasses to crystallize upon heat treatment, 3D scaffolds have not been much exploited commercially. Here, we investigate the influence of crystallization on the sintering behavior of several bioactive glasses. In a series of mixed‐alkali glasses an increased CaO/alkali metal oxide Ratio improved sintering compared to Bioglass 45S5, where dense sintering was inhibited.
Addition of small amounts of calcium fluoride helped to keep melting and sintering temperatures low. Unlike glass 13‐93, these new glasses crystallized during sintering but this did not prevent densification. Variation in bioactive glass particle size allowed for fine‐tuning the microporosity resulting from the sintering process.
Calcium cobaltite (Ca3Co4O9) is considered as one of the most promising thermoelectric p-type oxides for energy harvesting applications at temperatures above 500 °C. It is challenging to sinter this material as its stability is limited to 920 °C. To facilitate a practicable and scalable production of Ca3Co4O9 for multilayer generators, a systematic study of the influence of powder calcination, Bi-doping, reaction sintering, and pressure-assisted sintering (PAS) on microstructure and thermoelectric properties is presented. Batches of doped, undoped, calcined, and not calcined powders were prepared, tape-cast, and sintered with and without uniaxial pressure at 900 °C. The resulting phase compositions, microstructures and thermoelectric properties were analysed. It is shown that the beneficial effect of Bi-doping observed on pressureless sintered samples cannot be transferred to PAS. Liquid phase formation induces distortions and abnormal grain growth. Although the Seebeck coefficient is increased to 139 µV/K by Bi-doping, the power factor is low due to poor electrical conductivity. The best results were achieved by PAS of calcined powder. The dense and textured microstructure exhibits a high power factor of 326 µW/mK² at 800 °C but adversely high thermal conductivity in the relevant direction. The figure of merit is higher than 0.08 at 700 °C.
T92 steel was oxidized at 650 °C for 1000 h in dry and wet oxyfuel gases. The microstructure of inner oxide layer was investigated using scanning transmission electron microscopy and energy dispersive spectroscopy on thin lamellas of oxide cross-sections. The oxides were composed of fine equiaxed grains and separated into Fe-rich and Cr-rich regions. Fe-rich regions were wustite and iron sulphide while Cr-rich regions consisted of Fe-Cr spinel with different stoichiometries. Precipitates of (W,Mo)-rich oxides were formed within the oxide scale and beneath the oxide/alloy interface. Often iron sulphide and (W,Mo)-rich oxide were surrounded by Cr-rich spinel.
The aim of this research is to study the influence of moisture absorption at low moisture contents on the creep behaviour of an epoxy adhesive in steel bonded joints. Single lap joints were manufactured using high strength steel adherends and a two-component epoxy adhesive. The single lap joints were tested at load Levels corresponding to average lap shear stresses of±5%, 15%, 30% and 45% of the dry lap shear strength in both 40 °C air and 40 °C distilled water. Specimens were not pre-aged to be able to analyse the coupled effect of moisture and loading. The test results show that an increase in the load level resulted in an increase in the instantaneous strain and in the creep strain rate. The creep strain of single lap joints loaded in water was generally larger than for the ones loaded in air. For joints loaded in water the creep behaviour was found to be dependent on the moisture concentration in the adhesive. At low moisture percentages creep was suppressed, resulting in a lower instantaneous strain. At higher moisture percentages creep was promoted, resulting in a larger strain rate. The suppression of creep at low moisture percentages is attributed to water molecules bonding to the epoxy macromolecules, resulting in a reduction in molecular mobility and a smaller creep strain. At higher moisture percentages the plasticizing effect of the water dominates, resulting in a larger creep strain. The Maxwell threeelement solid model and Kelvin-Voigt three-element solid model were used to simulate the creep behaviour of the single lap joints loaded in air and water. The models gave good representations of the creep Response across the different load levels in both water and air, they were however unable to give a correct representation of the instantaneous strain of the single lap joints loaded in water. This is attributed to the models being unable to account for the present short-term relaxation process that is dependent on the moisture concentration.
Increasing Exposed Metal Site Accessibility in a Co-MOF-74 Material With Induced Structure-Defects
(2019)
Metal-organic frameworks (MOFs) are promising nanoporous materials with many practical applications. This owes largely to their remarkable porosity and the presence of specific chemical functionalities, such as exposed metal sites (EMS). The MOF-74 structure is known for exhibiting one of the highest EMS densities among porous materials. Moreover, the inclusion of structural defects has been proposed to enhance activity further. This was previously achieved by mixing the original linker together with a second one, having lower topology. The presence of structural defects was evidenced by the resulting crystalline properties and thermal stability. In this work, different mixtures of tetratopic 2,5-dihydroxyterephthalic acid with up to 60% of the tritopic hydroxyterephtalic acid were used to synthesize crystalline Co-MOF-74-like materials. Materials synthesized from higher proportions than 30% of hydroxyterephtalic acid in the synthesis media collapse upon partial removal of the solvent molecules. This indicates the presence of structural defects and the importance of the solvent molecules in stabilizing the crystalline structures. Electron microscope images show that crystal size reduces with inclusion of hydroxyterephtalic acid as the second linker. The presence of coordinated solvent molecules at the EMS was evaluated by Fourier-transform infrared spectra (FTIR) spectroscopy, so that a higher degree of solvent-exchange was observed during washing for defective structures. Furthermore, TG analysis suggests defective structures exhibit lower desolvation temperatures than the defect-free structures. Finally, N2 adsorption-desorption analyses at −196°C showed an enhanced accessibility of the gas to the inner porosity of the defective structures and therefore, the EMS of the material. All these finding make this pathway interesting to enhance the potential interest of these materials for an industrial application because of both a facilitated activation and a better access to the active sites.