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)
When assessing the performance of welded components residual stresses are vital. The possibilities of transferring the real boundary conditions of welding, which influence the residual stress, into the laboratory are highlighted in this contribution. The potentials of a test system specially developed for this purpose are demonstrated. The component design induces global process-, geometry- and material-dependent stresses, which can be simulated and quantified in the system. In addition, the resulting local residual stress distribution can be exactly determined with high spatial resolution with the aid of X-ray diffraction. Examples are presented of how the conditions to be found during production are simulated in the laboratory.
Casks for storage and transportation of used fuel rods of radioactive material are equipped with polyethylene (PE) for improved neutron flux shielding. The embedded PE structures are additionally exposed to gamma radiation and heat flow due to the specific high activity of the fission products. 60Co γ-radiation and heat load experiments at 125°C has been performed to evaluate PE degradation during the ageing process. FAR-FTIR-experiments were subsequently performed at differently aged PE test samples to characterize the oxidation process and morphological changes in the samples during the ageing at 125°C.
We report the synthesis and characterization of carbon nanodots (CDs) with high quantum yield (>50%) and tailored optical absorption as well as emission properties. A well-described protocol with polyethyleneimine (PEI) as amine precursor is used as a reference to a new CD system which is stabilized by aromatic 2,3-diaminopyridine (DAP) molecules instead. The DAP stabilizer is installed in order to red-shift the absorption peak of the n-π* electron transition allowing efficient radiative recombination and light emission. Size, shape, and chemical composition of the samples are determined by (HR)TEM, EDX and FTIR-spectroscopy. Optical parameters are investigated using UV-VIS, PL and QY measurements. Several parameters such as concentration, excitation wavelength and pH are studied. Zeta-potential analysis indicate that pH-induced (de-)protonation processes of functional moieties directly affect the n-π* energy bands. This results in unique pH-dependent absorption and emission characteristics which are discussed on the specific chemical composition of each CD system.
Kaltrissprüfung hochfester Feinkornbaustähle beim Schweißen mit modifiziertem Sprühlichtbogen
(2019)
Sind in Stahlkonstruktionen hohe Tragfähigkeiten bei geringem Eigengewicht gefordert, finden hochfeste Feinkornbaustähle mit Streckgrenzen ≥ 960 MPa Anwendung. In der Vergangenheit wurde der konventionelle Übergangslichtbogen (Konv. LB) zur schweißtechnischen Fertigung von hochfesten Stählen eingesetzt. In den letzten Jahren wurde der modifizierte Sprühlichtbogen (Mod. SLB) entwickelt, welcher reduzierte Nahtöffnungswinkel bei erhöhter Abschmelzleistung ermöglicht. Jedoch treten höhere Wasserstoffkonzentrationen verbunden mit Mikro-(Kalt-)rissen unter reduziertem Nahtöffnungswinkel mit Mod. SLB auf. In diesem Beitrag wird die Kaltrissempfindlichkeit des hochfesten Feinkornbaustahles S960QL mit artgleichem Schweißzusatzwerkstoff untersucht.
The motivation and the measurement setup for large fast-scanning piezoresistive cantilevers are presented. The theory behind the measurements of mechanical properties through contact resonance is explained. Results of such measurements on two kinds of polymer are compared to results from force distance curves. Noise, time-dependency and dependency of the results on the vibration mode are identified as challenges of contact resonance.
The geometry of the melt pool in laser beam welding plays a major role to understand the dynamics of the melt and its solidification behavior. In this study, a butt configuration of 20 mm thick structural steel and transparent quartz glass was used to observe the weld pool geometry in the partial penetration mode by means of a high-speed camera. The observations show that the dimensions of the weld pool vary depending on the depth. The areas close to the weld pool surface take a teardrop-shape. A bulge-region and its temporal evolution were observed approximately in the weld pool root. Additionally, a 3D transient thermal-fluid numerical simulation was performed to obtain the weld pool shape and to understand the formation mechanism of the observed bulging effect. The model considers the local temperature field, the effects of phase transition, thermo-capillary convection, natural convection and temperature-dependent material properties. The numerical results showed good accordance and were furthermore used to improve the understanding of the experimentally observed bulging effect.
Degradation of thermal barrier coatings (TBCs) in gas‐turbine engines due to calcium–magnesium–aluminosilicate (CMAS) glassy deposits from various sources has been a persistent issue since many years. In this study, state of the art electron microscopy was correlated with X‐ray refraction techniques to elucidate the intrusion of CMAS into the porous structure of atmospheric plasma sprayed (APS) TBCs and the formation and growth of cracks under thermal cycling in a burner rig. Results indicate that the sparse nature of the infiltration as well as kinetics in the burner rig are majorly influenced by the wetting behavior of the CMAS. Despite the obvious attack of CMAS on grain boundaries, the interaction of yttria‐stabilized zirconia (YSZ) with intruded CMAS has no immediate impact on structure and density of internal surfaces. At a later stage the formation of horizontal cracks is observed in a wider zone of the TBC layer.
Mg is a very promising material for lightweight construction and biomedical applications. However, the applicability of Mg and its alloys is hindered by its high corrosion susceptibility. Moreover, due to the toxicity of most inorganic conversion coating systems, the development of novel pre-treatment strategies for technical alloys are of vital importance. Recently, the application of intrinsically conducting polymers (ICPs) have been introduced as an alternative approach for corrosion protection of Mg alloys. ICPs with electronic conductivity are known to be able to passivate small defects, however they fail in the presence of large defects due to fast coating reduction and increased cation transport if macroscopically extended percolation networks exist.
The aim of this study is to develop graphene-polymer nanocomposite thin films for corrosion protection of Mg-alloys. As polymer matrix, poly(4-vinyl pyridine) (P4VP) was selected due to its semiconducting properties and protonic conductivity. In contrast to ICPs with electronic conductivity, the pH-dependant, reversible protonation/de-protonation capability of the P4VP has been utilized to synthesize environment-responsive coatings. The presentation summarizes our recent results on the synthesis and characterization of this novel coating system with a special focus on their interfacial stability and corrosion protection properties.
Mg is a very promising material for lightweight construction and biomedical applications. However, the applicability of Mg and its alloys is hindered by its high corrosion susceptibility. Moreover, due to the toxicity of most inorganic conversion coating systems, the development of novel pre-treatment strategies for technical alloys are of vital importance. The aim of this study is to develop polymeric bilayer thin films for corrosion protection of Mg-alloys. As polymer matrix, poly(4-vinyl pyridine) (P4VP) was selected due to its semiconducting properties and protonic conductivity. In contrast to ICPs with electronic conductivity, the pH-dependant, reversible protonation/de-protonation capability of the P4VP has been utilized to synthesize environment-responsive coatings. Polyacrylicacid (PAA) was tested as crosslinking layers to improve interfacial interactions between the polymeric layers. The macroscopic corrosion properties of the bilayer coatings were investigated by means of electrochemical methods such as linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) in corrosive media simulating technical and biomedical applications. The presentation summarizes our recent results on the synthesis and characterization of this novel coating system with a special focus on their interfacial stability and corrosion protection properties.
CEQAT-DGHS Interlaboratory tests for method validation and measurement uncertainty determination
(2019)
An explosion in a chemical plant or a fire on a dangerous goods vessel - the reason for such accidents can be numerous. Prevention starts in the laboratory where chemicals are tested for their hazardous properties in order to be able to assess the risks involved in their handling. For this purpose, test methods have been developed and published. They are applied globally nowadays. Safety experts, manufacturers, suppliers, importers, employers or consumers must be able to rely on the validity of safety-related test methods and on correct test results and assessments in the laboratory.
Interlaboratory tests play a decisive role in assessing the reliability of test results. Participation in interlaboratory tests is not only a crucial element of the quality assurance of laboratories; as such it is explicitly recommended in DIN EN ISO/IEC 17025. In addition, interlaboratory tests are also used to develop and validate test methods and can be used for the determination of the measurement uncertainty.
Interlaboratory tests on different test methods have been performed by Bundesanstalt für Materialforschung und –prüfung (BAM) and Physikalisch-Technische Bundesanstalt (PTB) in collaboration with the QuoData GmbH during the last 10 years. Significant differences between the results of the participating laboratories were observed in all interlaboratory tests. The deviations of the test results were not caused only by laboratory faults but also by deficiencies of the test method (see interlaboratory test reports of the CEQAT-DGHS Centre for quality assurance for testing of dangerous goods and hazardous substances: www.ceqat-dghs.bam.de).
In view of the interlaboratory test results the following conclusions can be drawn:
• To avoid any discrepancy on classification and labelling of chemicals it should become state of the art to use validated test methods and the results accompanied by the measurement uncertainty.
• A need for improvement is demonstrated for all examined test methods. Thus, interlaboratory tests shall initially aim at the development, improvement and validation of the test methods (including the determination of the measurement uncertainty) and not on proficiency tests.
• The laboratory management and the practical execution of the tests need to be improved in many laboratories.
• The term "experience of the examiner" must be seen critically: A "long experience with many tests" is not necessarily a guarantee for correct results.
aRTist is an easy-to-use and practical simulation tool to generate realistic radiographic images from CAD objects. A dedicated add-on module makes CT simulation easy (virtual computer tomography). Just choose the number of projections.
Unlike in the practice, simulation can separately image the primary and scatter radiation. This allows studying the scattering artefacts in CT (gray-level variations in regions of homogeneous material).
The WelDX research project aims to foster the exchange of scientific data inside the welding community by developing and establishing a new open source file format suitable for documentation of experimental welding data and upholding associated quality standards. In addition to fostering scientific collaboration inside the national and international welding community an associated advisory committee will be established to oversee the future development of the file format. The proposed file format will be developed with regards to current needs of the community regarding interoperability, data quality and performance and will be published under an appropriate open source license.
By using the file format objectivity, comparability and reproducibility across different institutes and experimental setups can be improved.
Multiplexed encoding schemes of nano- and micrometer sized particles with fluorescent dyes or quantum dots (QDs) and their optical detection, are of increasing interest for applications in the life sciences, for example in flow cytometry. Almost all strategies utilizing fluorescence focus on spectrally distinguishable emission bands or colors and different intensity levels as fluorescence codes. The fluorescence parameter lifetime has been, however, barely exploited. In this work the goal is to perform multiplexing with encoding fluorophores with different fluorescence lifetimes (LTs). In comparison to the spectral multiplexing strategies this has the advantage, that the different fluorescence LT codes can be measured with the excitation and emission wavelength, thus reducing instrument costs. Moreover, LTs should not depend on emitter concentration. Unlike organic dyes, the LTs of which are typically < 10 ns, the fluorescence LTs of ternary semiconductor QDs that represent a “green” alternative to conventional Cd-containing QDs are in the range of several hundred ns, independent of oxygen concentration, and can be tuned to a certain extent by chemical composition and surface chemistry. This present a time region that can be barely covered by other emitters that have either much shorter or longer lifetimes. In this project, different encoding strategies will be assessed and the encoded particles will be then used for fluorescence assays for the analysis of several targets in parallel. Therefor the encoded particles will be functionalized with different target-specific bioligands and read out with a specifically designed flow cytometer enabling time-resolved fluorescence detection. With this instrument, the particles will be discriminated by their fluorescence LTs In one detection channel while the analytes will be quantified by fluorescence labels in a second channel in the intensity domain.
Multiplexed encoding schemes of nano- and micrometer sized polymer particles with fluorescent dyes or quantum dots (QDs) and their optical detection, are of increasing interest for applications in the life sciences, for example in flow cytometry. Almost all strategies utilizing fluorescence focus on spectrally distinguishable emission bands or colors and different intensity levels as fluorescence codes.
In this work the goal is to perform multiplexing with encoding fluorophores with different fluorescence lifetimes (LTs). In comparison to the spectral multiplexing strategies this has the advantage, that the different fluorescence LT codes can be measured with the same excitation and emission wavelength, thus reducing instrumental costs. Moreover, LTs should not depend on emitter concentration. Unlike organic dyes, the LTs of which are typically <10ns, the fluorescence LTs of ternary semiconductor QDs which represent a “green” alternative to conventional Cd-containing QDs are in the range of several hundred ns, independent of oxygen concentration, and can be tuned to a certain extent by chemical composition and surface chemistry. This presents a time region that can barely be covered by other emitters that have either much shorter or longer lifetimes. In this project, different encoding strategies will be assessed, and the encoded particles will then be used for fluorescence assays for the analysis of several targets in parallel. Therefore, the encoded particles will be functionalized with different target-specific bioligands and read out with a specifically designed flow cytometer enabling time-resolved fluorescence detection. With this instrument, the particles will be discriminated by their fluorescence LTs in one detection channel while the analytes will be quantified by fluorescence labels in a second channel in the intensity domain.
Depending on the specific plastic’s ageing sensitivities, the durations which plastic components remain in the environment can be very long. As, in the past, the advantages in ageing resistance and durability were highly evaluated, we now face the problem of quite stable plastic waste within the environment.
However, there is only little knowledge on the real timescales until macroscopic fragmentation for the different kinds of plastic under various environmental conditions.
Here, weathering methods are presented, which have been used for the failure prediction in specific outdoor conditions. Issues of uncertainty, reproducibility, or validation are discussed.
For the prediction of the plastic’s fragmentation, much longer time scales have to be considered. To do this within a limited project life span, various processes as well as their acceleration potential have to be evaluated separately, such as temperature increase or spectral shift.
The possibilities and limitations of such controlled acceleration will be discussed.
Non-linear optical emitters are promising materials for energy applications and biotechnologies. Solid-state multi-band emitters like lanthanide doped up-conversion nanoparticles (UCNPs) show excellent photostability, are excitable in the near infrared (NIR), and show emission bands from the UV to SWIR spectral regions. The optical properties of these materials strongly depend on the excitation power density, i.e., the number of photons absorbed per time interval. The upconversion (ΦUC) and downshifting quantum efficiencies (ΦDS) of these materials, the excitation power dependent population, and the deactivation dynamics are influenced by nanoparticle architecture, doping concentration, and the microenvironment. We studied the fundamental changes of the luminescence properties of ß-NaYF4 UCNPs doped with Yb3+ and Er3+ depending on size, different surroundings such as aqueous and organic media, and different surface chemistries. We obtained further insights into shelling procedures, FRET optimization, influence of doping concentration, and advantages of different sensitizer ions.