Ingenieurwissenschaften und zugeordnete Tätigkeiten
Filtern
Erscheinungsjahr
Dokumenttyp
- Posterpräsentation (797) (entfernen)
Sprache
- Englisch (663)
- Deutsch (133)
- Französisch (1)
Schlagworte
- Corrosion (36)
- Additive manufacturing (30)
- Mechanochemistry (24)
- Additive Manufacturing (20)
- Glass (20)
- Nanoparticles (19)
- Crystallization (17)
- Degradation (14)
- Fluorescence (14)
- In situ (14)
Organisationseinheit der BAM
- 6 Materialchemie (203)
- 5 Werkstofftechnik (97)
- 8 Zerstörungsfreie Prüfung (95)
- 6.3 Strukturanalytik (65)
- 8.5 Röntgenbildgebung (60)
- 6.6 Physik und chemische Analytik der Polymere (55)
- 9 Komponentensicherheit (53)
- 1 Analytische Chemie; Referenzmaterialien (45)
- 6.1 Oberflächen- und Dünnschichtanalyse (44)
- 4 Material und Umwelt (36)
- 7 Bauwerkssicherheit (34)
- 5.1 Mikrostruktur Design und Degradation (28)
- 6.0 Abteilungsleitung und andere (26)
- 1.2 Biophotonik (25)
- 5.4 Multimateriale Fertigungsprozesse (22)
- 8.0 Abteilungsleitung und andere (21)
- 9.4 Integrität von Schweißverbindungen (20)
- 4.1 Biologische Materialschädigung und Referenzorganismen (19)
- 5.2 Metallische Hochtemperaturwerkstoffe (19)
- 5.6 Glas (19)
- 6.2 Material- und Oberflächentechnologien (19)
- 9.3 Schweißtechnische Fertigungsverfahren (19)
- 2 Prozess- und Anlagensicherheit (14)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (13)
- 7.1 Baustoffe (13)
- 6.7 Materialsynthese und Design (12)
- 3 Gefahrgutumschließungen; Energiespeicher (11)
- 4.2 Material-Mikrobiom Wechselwirkungen (11)
- 7.6 Korrosion und Korrosionsschutz (11)
- 5.3 Polymere Verbundwerkstoffe (8)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (8)
- 9.6 Additive Fertigung metallischer Komponenten (8)
- 1.9 Chemische und optische Sensorik (7)
- 8.4 Akustische und elektromagnetische Verfahren (7)
- 1.4 Prozessanalytik (6)
- 9.0 Abteilungsleitung und andere (6)
- 2.5 Konformitätsbewertung Explosivstoffe/Pyrotechnik (5)
- 3.1 Sicherheit von Gefahrgutverpackungen und Batterien (5)
- 4.5 Kunst- und Kulturgutanalyse (5)
- 8.1 Sensorik, mess- und prüftechnische Verfahren (5)
- 9.5 Tribologie und Verschleißschutz (5)
- 1.6 Anorganische Referenzmaterialien (4)
- 2.0 Abteilungsleitung und andere (4)
- 5.5 Materialmodellierung (4)
- 8.3 Thermografische Verfahren (4)
- 9.2 Versuchsanlagen und Prüftechnik (4)
- 2.1 Sicherheit von Energieträgern (3)
- 4.0 Abteilungsleitung und andere (3)
- 7.2 Ingenieurbau (3)
- 8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen (3)
- 8.6 Faseroptische Sensorik (3)
- VP Vizepräsident (3)
- VP.1 eScience (3)
- 1.1 Anorganische Spurenanalytik (2)
- 1.5 Proteinanalytik (2)
- 2.2 Prozesssimulation (2)
- 3.2 Gefahrguttanks und Unfallmechanik (2)
- 3.4 Sicherheit von Lagerbehältern (2)
- 1.8 Umweltanalytik (1)
- 3.0 Abteilungsleitung und andere (1)
- 3.3 Sicherheit von Transportbehältern (1)
- 3.6 Elektrochemische Energiematerialien (1)
- 5.0 Abteilungsleitung und andere (1)
- 6.4 Materialinformatik (1)
- 7.4 Baustofftechnologie (1)
- MP Mitglied des Präsidiums (1)
- MP.0 Mitglied des Präsidiums und andere (1)
- P Präsident (1)
- PST Präsidiale Stabsstelle (1)
Eingeladener Vortrag
- nein (1)
We report on the in situ investigation of the Al13 sulfate synthesis by WAXS. Al13 sulfates were crystallized by precipitating hydrolyzed aluminum solutions by the addition of sodium sulfate. The measurements were performed using an acoustic levitator. The study provides information about the intermediates during the crystallization process.
Selective Electron Beam Melting (SEBM) is a promising powder bed Additive Manufacturing (AM) technique for near net-shape manufacturing of high-value titanium components. However, as with every emerging technique, the manufacturing processes can still be greatly improved and optimised. In particular, the links between AM settings and the resulting sample porosity is of great interest, as the fatigue life of SEBM parts is currently dominated by the presence of porosity. In this study, the size, volume fraction, and spatial distribution of the pores in model samples have been characterised in 3D, using X-ray Computed Tomography (CT), and correlated to the SEBM process variables. A strong relationship was found with the different beam strategies used to contour, and infill by hatching, a part section. The majority of pores were found to be small spherical gas pores, concentrated in the infill hatched region. Rarer irregular shaped pores were mostly located in the contour region and have been attributed to a lack of fusion between powder particles.
By means of an effective medium (EMA) based approach, it is possible to use spectroscopic ellipsometry to determine the mixing ratios between air and material in porous dielectrics and calculate a quantitative value of the porosity for these materials. As this method is model-based, it is very difficult to provide a quantitative measure for the accuracy of porosity values determined by this method. Valuable additional information can often be obtained by combining ellipsometry with other complementary methods. In the present study, the ellipsometry results were validated by Electron Probe Microanalysis (EPMA) with the option of layer analysis (by the socalled “STRATAGem” approach), gravimetry, and electron microscopy. We analysed porous TiO2 thin layers synthesised by means of a template synthesis Approach (evaporation induced self assembly).
Ellipsometry measurements on porous samples are difficult to analyse due to the complexity of the models necessary. Often it is difficult to decide if the measured data contains enough information to successfully determine the target quantities (mixing ratio, dielectric function of the matrix material). One method to decrease the complexity of the fit and therefore use the measurement data most efficiently is a multi-sample analysis. In the present case, multi-sample analysis was used for determining the porosity factors of the individual layers while using one common set of dielectric function values for the matrix in all cases.
While the results of the fit analysis in this case can be used to show the feasibility and also the limitations of the multi-method approach, the porosity values themselves show a promising agreement between the Independent methods. It can therefore be concluded that determining porosity values with ellipsometry is in accordance to other methods to the level of accuracy provided by the complementary methodologies.
Evaluation of nano-sized internal oxidation in a Fe-13Cr alloy exposed to water vapor atmosphere
(2016)
The topotactic formation of nano-sized precipitates immediately under the internal oxide layer in a Fe-13Cr alloy exposed to oxidizing water vapor atmosphere was recently reported. The precipitates were identified as lath-shaped Fe-Cr spinel exhibiting a crystallographic orientation relationship with the ferritic matrix. The authors proposed that these precipitates could act as a precursor to the formation of the spinel layer observed in the adjacent part of the oxide scale.The occurrence of internal oxidation in Fe–Cr alloys subjected to similar conditions had been previously identified and directly correlated to the presence of water vapor. In the present work, we attempt to rationalize the processes occurring during the oxidation of this alloy through thermodynamic and kinetic analyses based on the CALPHAD approach, using the geometrical representation of phase equilibria and concepts developed to describe internal oxidation. The influence of water vapor on the mechanism and kinetics of formation of the nano-sized precipitates and its role in the overall oxidation process is also considered.
Ultrasonic echo testing has become a common method in civil engineering for the investigation of concrete structures. The detection of inhomogeneities, reinforcing elements and the geometry of the object is required for quality assurance and Inspection. This assessment depends on the quality of ultrasonic images which can be improved by using Reverse Time Migration (RTM) rather than the standard method, Synthetic Aperture Focusing Technique (SAFT). Although RTM provides a better mapping of circular objects and (dipping) reflectors, the image is corrupted by migration noise. To suppress the image noise, we have tested various filter methods in the spatial domain, frequency domain as well as in the curvelet domain on ultrasonic RTM images. We found that either a spatial edge detection filter in combination with a lowpass filter (Laplacian of Gaussian filter) or two lowpass filter with different filter parameters (Difference of Gaussian filter) removed artefacts. An additional smoothing was obtained by applying the first generation curvelet transform after downsampling the image matrix and adding Gaussian noise. The proposed filter scheme is able to suppress RTM noise and enhance the image quality such that the objective interpretation of ultrasonic images for Quality assessment of concrete specimen is simplified.
A test campaign was launched to determine the mechanical properties of the HL-LHC 11 T Nb₃Sn magnet components in order to accurately model the mechanical properties in Finite Element simulations that predict the stress and strain distribution in these magnets. Static and dynamic test methods have been applied for determining elastic materials behavior, and highly accurate Young’s moduli are obtained with the dynamic methods resonance and impulse excitation. These non-destructive methods also enable temperature dependent modulus measurements during in situ heat cycles.
Materials that respond to the environment by changing their properties are critical for developing
autonomously adaptive systems. However, to reversibly influence a material's inherent characteristics, such as its ability to self-heal, from distance without continuously expending energy, remains a challenging task. Herein, we report on the modul at ion of imine exchange kinetics by light, manifested in a remote controllable dynamic covalent polymer network. Simple mixing of a commercially available amino-functionalized polysiloxane with small amounts of a photoswitchable diarylethene cross-linker, carrying two aldehyde groups, yields a rubbery material. Its viscoelastic and self-healing properties can be reversibly tuned with everyday light sources, such as sunlight. Our two-component system offers the unique advantage that self-healing takes place continuously without any additives at ambient conditions and is neither dependent on continuous illumination nor does it require recent damage. Overall, our approach allows for the local amplification of intrinsic material properties in a permanent yet reversible fashion. The availability of the inexpensive sta1ting materials on a multi-gram scale, the easy synthesis of the polymer network, and its convenient handling paired with high versatility make our Approach highly applicable to create custom-tailored adaptive materials.
Healable materials are able to repair inflicted damages, herin often applied: dynamic covalent polymer networks. We have shown in this study that light of different colors shift the Diels-Alder and retro Diels-Alder crosslinking and decrosslinking equilibrium. This effect was utilized for self-healing of a polymer film. Small-angle X-ray scattering was used to quantifiy the polymeric mesh size on a nanoscale.
Characterization of silver nanoparticles in cell culture medium containing fetal bovine serum
(2016)
Nanoparticles are being increasingly used in consumer products worldwide, and their toxicological effects are currently being intensely debated. In vitro tests play a significant role in nanoparticle risk assessment, but reliable particle characterization in the cell culture medium with added fetal bovine serum (CCM) used in these tests is not available. As a step toward filling this gap, we report on silver ion release by silver nanoparticles, and changes in the particle radii and in their protein corona when incubated in CCM. Particles of a certified reference material (CRM), p1, and particles of a commercial silver nanoparticle material, p2, were investigated. The colloidal stability of p1 is provided by the surfactants polyethylene glycole-25 glyceryl trioleate and polyethylene glycole-20 sorbitan monolaurate, whereas p2 is stabilized by polyvinylpyrrolidone (PVP). Dialysis of p1 and p2 reveal that their silver ion release rates in CCM are much larger than in water. Particle characterization was performed with asymmetrical flow field-flow fractionation (FFF), small-angle X-ray scattering (SAXS), dynamic light scattering (DLS) and electron microscopy. p1 and p2 have similar hydrodynamic radii of 15 nm and 16 nm, respectively. The silver core radii are 9.2 and 10.2 nm. Gel electrophoresis and subsequent peptide identification reveal that albumin is the main corona component of p1 and p2 after incubation in CCM, which consists of Dulbeccos Modified Eagle Medium with 10% fetal bovine serum added.
Volatile organic compounds (VOC) are ubiquitous in the indoor air, since they emit from materials used indoors. Investigations of these materials are mostly carried out in test chambers under controlled climatic conditions. Quality control of these test chamber measurements is important but there is a lack of commercially available homogenous reference materials. The approach of this study is to dope a supporting material with VOCs, which are then reproducibly released in measurable chamber air concentrations between 30 to 300 µg m ³. From several tested supporting materials vacuum grease (APIEZON M) was selected because of its very low own emissions. First tests were conducted with styrene. For the estimation of the initial emission and the emission over time FEM (finite element methods) modelling was used. Based on this, five samples with a surface of 7 cm2 and a thickness of 12 mm with a content of 1 ‰ styrene were investigated at (23 ± 2) °C and (50 ± 5) % relative humidity in the µ-chamber (3 samples) and 24 L test chambers (2 samples) for 28 days. Air samples were taken after 24 hours, 3, 7, 14, 21 and 28 days on Tenax TA® sorption tubes and analyzed by TD-GC-MS. The area specific emission rate (SERa) was calculated to compare the results from both chamber types. After 24 hours SERa was between 0.8 0.9 µg cm 2 h 1 (3800 4000 µg m 3) for the µ-chamber samples and between 0.9 1.1 µg cm 2 h 1 (300-370 µg m 3) for the 24 L test chamber samples. After 28 days the SERa was at 0.2 µg cm 2 h 1 for all samples. The relative standard deviation of the SERa was between 1 26 %. These results show the applicability of vacuum grease as supporting material and the favored starting concentration range could be achieved in the 24 L test chambers.
In the last years, secondary low-energy electrons (LEE) emerged as important, if not predominant, reductive pathway in ionizing damage of biomolecules. These electrons are created in copious amount as result of inelastic scattering of high energy radiation at water. Until now, all experiments the quantification of the effects of LEEs on the biomolecular damage was either performed in vacuum with LEE sources or with DNA on surfaces in humid atmosphere.
We present a new experimental setup to irradiate biomolecules with electrons under physiological conditions. In combination with monte carlo simulations this setup makes it possible to determine microdosimetric quantities for biomolecules in liquid environment under electron irradiation.
This opens up new possibilities in radiation research to access the LEE damage under well defined physiological condition, for more complex systems, such as DNA-Protein complexes and even living cells.
Were prepared four unsubstituted Pc - C60 fullerene systems, using two different synthetic strategies, via Prato (1,3 - dipolar cycloaddition) or Bingel reactions. The precursor Pcs 1 and 2 were successfully synthesized by cyclotetramerization reaction between TBDPS - protected and unsubstituted phthalonitriles. The surface studies are currently ongoing.
Additive Manufacturing by Selective Laser Melting (SLM) offers ample scope for producing geometrically complex parts as compared to the traditional subtractive manufacturing strategies. However, the residual stresses (RS) developed during the processing can reduce the load bearing capacity as well as induce unwanted distortion, limiting the application of SLM parts. In the present work, residual stresses in additivly manufactured IN718 part were analised by means of neutron diffraction and synchrotron X-ray diffraction.
The work presents the microstructure, chemical composition and mechanical properties of Inconel 686 coatings after high - temperature corrosion in environment of aggressive gases. To produce the Ni - base weld overlays the QS Nd:YAG laser beam was used. The substrates were 13Mo4-5 boilers plate steel. Ni - base alloys characterize the excellent high temperature corrosion resistance, good strength and good ability to work in aggressive environments. Applied overlays had a proper combination of the metal substrate in particular small amount of Fe. This could be achieved by the reduction of the melting of the substrate and its dissolution into the overlays. The microstructure, chemical composition of the obtained overlays were investigated by means of a light microscope, a scanning electron microscope (SEM) equipped with the EDS detector. The overlays had cellular-dendritic structure. The variations of the chemical composition (especially Mo, Ni and W ) in the interdendritic and dendritic regions were observed. The interdendritic regions were enriched during solidifications in Mo and W and had lower content of Ni.
The microstructure of weld overlay Ni - base alloy deposited on carbon steel by laser QS-Nd:YAG
(2017)
Ni- base alloys are used as a one of the most important coating material and can be applied in a different environments and elements of devices having various applications. To protect the surface of the material from aggressive gases at high temperature, there are use different kinds of the Ni- base alloys. One of such alloy is Ni-Cr-Mo-W called commercial Inconel 686. This alloy based on NiCr22Mo9Nb (Inconel 625), in which content of molybdenum increased and niobium was replaced with the addition of tungsten, in order to counteract the strong segregation in the microstructure, which results in homogeneity of the chemical composition of the structure. Inconel 686 is also characterized by greater resistance to high temperature corrosion and heat resistance than Inconel 625. The Inconel 686 alloy was deposited on 13CrMo4-5 steel by laser QS - Nd:YAG. In the poster the microstructure (SEM) and chemical composition (EDS) of obtained weld overlays were investigated.
Up to now, the mechanisms of surface nucleation and surface-induced texture formation are far from being understood. Corresponding phenomena are discussed hypothetically or even controversial, and related studies are restricted to very few glasses. As a main drawback, the vast majority of previous work on oriented growth of surface crystals do not consider the possible effects of glass surface treatments (like polishing defects, adhered particles and cracks, …) or ambient annealing conditions (vacuum or atmospheric pressure) which both can influence crystal nucleation and growth. Moreover, very few observations of crystal orientation related to surface crystallization were focused on separately growing crystals. In conclusion, up to now, no systematic studies on initially oriented crystal growth or nucleation from defined active nucleation sites have been pursued.
Therefore, the main objective of the proposed project is to gain a basic understanding of the mechanisms of surface-induced microstructure formation in glass ceramics. We shall answer the question whether preferred orientation of surface crystals is the result of oriented nucleation or caused by other orientation selection mechanisms acting during early crystal growth. In both cases, crystal orientation may be caused by the orientation of the glass surface itself or the anisotropy and orientation of active surface nucleation defects.
New techniques of experimental characterization of surface-crystallized glasses shall be applied to find answers to the questions posed above. Based on a controlled preparation and annealing of the glass sample surfaces, that includes the defined creation of active nucleation defects, and followed by the microstructural characterization especially during the very early growth stages of separated surface crystals, the orientation relations between defect and initiated surface crystal will be analyzed. In order to gain new insights, a couple of entirely new microstructure diagnostics techniques, including chemically contrasted XRM, laser-based sample preparation for XRM, and 3D electron backscatter diffraction shall be developed or applied.
This way, using X-ray microscopy as a pivotal technique for the non-destructive 3D characterization of relatively large samples at superior spatial resolution (but also complemented by other microstructure diagnostics techniques, e.g. TEM elemental mappings at cross-sectioned samples) unprecedented insights into the microstructure evolution upon surface crystallization of model glasses will be gained.
Absorption edge tomography is a method which exploits the sudden change of the attenuation coefficient, when the photon energy crosses the absorption edge of an element. The beamline BAMline at BESSY II, which is operated by the Federal Institute for Materials Research and Testing, can provide a monochromatized beam in a photon energy range from 5 keV up to 80 keV with a bandwidth of 2%. Together with the microtomography setup, this enables differential tomography sensitive to any element with N >= 24 (Cr) by using an appropriate K- or L-edge in this range. Here, absorption edge tomography at the Yttrium edge is employed to perform a non-destructive 3D characterization of the microstructure of a high strength Mg-Y-Zn alloy. The long period stacking ordered (LPSO) phase which forms fibres in this material was extracted based on the Yttrium content and the fibre length distribution was analysed.
P92 is one of the important steels for super heater tubes used in combustion plants. However, in fossil fuel fired environments the formation of oxides and sulfides are challenging the material. To understand early corrosion mechanisms, which are important for process prediction, high temperature in-situ ageing experiments of Fe-Cr-Mn alloys in SO2 and SO2+H2O atmosphere were performed, applying energy dispersive X-ray diffraction (EDXRD) analysis.