Ingenieurwissenschaften und zugeordnete Tätigkeiten
Filtern
Erscheinungsjahr
Dokumenttyp
- Posterpräsentation (798) (entfernen)
Sprache
- Englisch (664)
- 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 (204)
- 5 Werkstofftechnik (97)
- 8 Zerstörungsfreie Prüfung (95)
- 6.3 Strukturanalytik (65)
- 8.5 Röntgenbildgebung (60)
- 6.6 Physik und chemische Analytik der Polymere (56)
- 9 Komponentensicherheit (53)
- 1 Analytische Chemie; Referenzmaterialien (45)
- 6.1 Oberflächen- und Dünnschichtanalyse (45)
- 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 (14)
- 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)
Bioglass® 45S5 is mainly used clinically as powders, granules or pastes instead of sintered compacts. This is due to the inherent problem of crystallization during sintering. Recently, new bioactive glasses with improved crys-tallization stability have been developed as promising candidates for manufacturing of sintered powder compacts for bone regeneration, which combine improved sintering behavior with bioactivity. Compared with the well-known Bioglass® 45S5 (SiO2-P2O5-CaO-Na2O) the calcium/alkali oxide ratio was increased, sodium oxide was partially replaced by potassium oxide and up to 3 mol% calcium fluoride were added, in order to stabilize the glass against crystallization. Sintering and crystallization were characterized by heating microscopy, XRD, FTIR, SEM, and DTA. The results show that a sintered density of 88-99 % is achieved in contrast to only 57-67% for Bioglass® 45S5. Whereas Bioglass® 45S5 powder compacts crystallize during sintering, for the new glasses no crystalline phases were detected. Additionally the influence of grain size was characterized. These studies showed that full densification can be attained for particle size < 32 µm, whereas coarser particles pro-gressively increase residual porosity. Observed foaming phenomena, are strongly retarded by crystallization.
Ferritic steels with Cr-contents up to 13 wt. % are used as heat exchanger or boiler tube materials in combustion based power plants. These materials are subject to aggressive corrosion caused by the reaction of the steel with highly corrosive gases under high temperatures up to 650°C. The early stages of corrosion and sulfidation especially and the influence of the Cr-content in the alloy are thereby not understood but of fundamental interest.
Our work shows corrosion mechanisms and presents corrosion models for Fe and different Fe-Cr-alloys under pure SO2 und SO2+O2 atmospheres for different time scales. Modell alloys of high purity are used to focus on the reaction of the intended elements: Fe, Cr, S, and O. Long-time experiments (≥12h) took place in tube furnaces and short-time experiments (≥5min) in a special designed light furnace. Heating and cooling took place under inert atmosphere. The reactive gases were added not until the experimental temperature was reached. Samples were analyzed using high resolution synchrotron X-ray diffraction using a micro focus setup and electron microscopy including FIB.
Many earlier studies on corrosion and sulfidation on iron based alloys show a higher corrosion rate and material loss when sulfur was present in the atmosphere. In contrast, later studies propose an inhibiting effect of sulfur containing atmospheres. On the one side, most likely due to the formation of a protective layer of Mx(SO4)y -phases at the scale-gas interface. On the other side, a very recent study proposes the theory that MxSy-phases limit the further diffusion of elements. Up to now, no Mx(SO4)y –phases were detected in our samples, but sulfide phases nucleated within the oxide phases. For pure Fe our samples show FeS at the scale-metal interface working as a diffusion barrier for Fe-Cations from the base material in to the oxide scale. The above lying spalled off oxide-sulfide scale shows a wide area of small voids and accumulations of FeS-Crystals at the bottom. Under the main oxide scale a second generation of oxide-sulfide scale starts to form. For the Fe-Cr-alloys the inner oxide scale only shows FeS- and CrS-phases surrounded by hollow space. The here presented study will explain and discuss a new growth model for the shown phenomenon.
Bioglass® 45S5 is mainly used clinically as powders, granules or pastes instead of sintered compacts. This is due to the inherent problem of crystallization during the sintering, which results in poor mechanical properties and reduced bioactivity. Recently, new bioactive glasses with improved crystallization stability have been developed as promising candidates for manufacturing of sintered powder compacts for bone regeneration, which combine improved sintering behavior with bioactivity. Compared with the well-known Bioglass® 45S5 (SiO2-P2O5-CaO-Na2O) the calcium/alkali oxide ratio was increased, sodium oxide was partially replaced by potassium oxide and up to 3 mol% calcium fluoride were added, in order to stabilize the glass against crystallization. The aim of this study was to investigate the sintering and crystallization behavior of these new bioactive glasses.
Sintering and crystallization were characterized by heating microscopy, XRD, FTIR, SEM, and DTA. The results show that a sintered density of 88-99 % is achieved in contrast to only 57-67% for Bioglass® 45S5. In addition, FTIR and XRD analyses show that Bioglass® 45S5 crystallized during sintering while for the new glasses no crystalline phases are detected. The thermal properties of all glasses were studied by DTA measurements, and the influence of grain size was characterized. These studies showed that full densification can be attained for particle size < 32 µm, whereas coarser particles progressively increase residual porosity. Observed foaming phenomena, are strongly retarded by crystallization of beta-HAp.
Advanced methods for 3D green density characterization like computed tomography and 3D FE sinter modeling can be utilized for increasing the reliability of sintered components. The experimental in situ observation of sintering, however, is currently restricted to silhouette methods, i.e. heating microscopy. For complex shaped samples, in situ shape screening during shrinkage would allow much better validation of 3D sinter simulation models. Further, by revealing temporary sinter warpage, 3D high-temperature shape screening allows to locate potential defects of complex sintered components. Against this background, BAM developed a testing device for in situ 3D high-temperature shape screening for ceramic and glass-ceramic tapes up to 1000°C [1-3]. Current work is focused on dropping this restriction in sample shape and temperature. The poster illustrates the current state of this work and possible applications of the method e.g. in detecting sinter warpage of metallized glass-ceramic LTCC tapes.
We investigated the efficiency of phase gratings, i.e., the visibility upon variation of different parameters. Rotating around an axis parallel to the grid lines of the phase grating changes the grating’s shape and thereby the initial distribution of phase shifts. This yields high visibilities for shorter propagation distances than derived from box shapes. Tilting the grating in the scattering plane allows continuous tuning of the grating’s height that corresponds to an ideal phase shift for a particular photon energy. This opens the way for tuning the design energy suitable for the material under investigation
Mechanical characterization of high-density polyethylene in contact with diesel and biodiesel fuels
(2016)
Renewable resources become more and more relevant to maintain energy demands for an increasing global population. Biosynthetic fuels like biodiesel might replace conventional petrochemical fuels, such as diesel. However, more research is needed to characterize the interaction between the different fuels and polymeric materials widely used in the fuel infrastructure as well as for automotive parts. Especially changes in the structural properties and mechanical behavior of the polyethylene (PE-HD) have to be addressed.
The presented work comprises the direct interaction of high density polyethylene (PE-HD) with diesel and biodiesel, resulting in swelling and plasticization. Also long-term degradation phenomena will be discussed.
The chosen PE-HD types are typical thermoplastic resins for container and storage tank applications. The impact of diesel and biodiesel in PE-HD is investigated by changes in the mechanical properties with emphasis on the Charpy impact strength. Furthermore, structural and dynamic influences on the polymeric material induced by diesel and biodiesel are proven in Dynamic Mechanical Analysis (DMA). Both methods, Charpy impact strength and DMA, reveal softening effects due to the migration of diesel and biodiesel into the amorphous regions of PE-HD.
Since biodiesel is more prone to oxidative degradation compared to diesel, the fuel/air/polymer-interaction is studied for partly immersed tensile test specimens. Main focus of the evaluation is the co-oxidation. Here, the accelerated deterioration of PE caused by the sorption of the facile oxidation of biodiesel into the solid polymer might be a major degradation mechanism in this context.
The formation of biofilms on different materials provokes high costs in industrial processes, as well as in medical applications. Therefore, the interest in development of new materials with improved surfaces to reduce bacterial colonization rises. In order to evaluate the quality and safety of these new materials, it is highly important to ensure world-wide comparable tests that are relying on statistical evidence. The only way to reach this statistical safety is through a high-throughput Screening under standardized test conditions.
We developed a flow through system for cultivation of biofilm-forming bacteria under controlled conditions with a total capacity for testing up to 32 samples in parallel. Quantification of the surface colonization was done by staining the bacterial cells with a fluorescence marker, followed by epifluorescence microscopy. More than 100 images of each sample were automatically taken and the surface coverage was estimated with the free open source software gmic (http://gmic.eu), followed by a precise statistical evaluation. Overview images of all gathered pictures of the whole material coupon were generated to illuminate the colonization characteristics of the selected bacteria on certain materials.
With this method, differences in bacterial colonization on different materials can be quantified in a statistically validated manner. The innovative and solid test procedure will support the design of improved materials for medical and industrial applications such as implants, ship hulls, pipelines, heat exchangers, aquaculture equipments, photovoltaic-panels and fundaments of wind power plants.
Due to their chemical structure, a rigid disk-like aromatic core and flexible alkyl chains attached to the core, discotic liquid crystals (DLCs) can organize and stack themselves into columns in a hexagonal columnar mesophase, a mesophase in between the plastic crystalline and isotropicphase. The overlap of the π orbitals of the aromatic core in the hexagonal columnar mesophase leads to a high charge-carrier mobilitie along the column axis – these columns can be considered as “moleculer nanowires” making liquid crystals a promising class of materials for electronic applications. Previous studies on DLCs showed that the phase behavior of DLCs is susceptible to nano confinement. Here in this study, the thermotropic collective orientational order of 2,3,6,7,10,11 hexakis[hexyloxy] triphenylene (HAT6), a triphenylene based DLC, and the effects of nano confinment on of its phase behavior were investigated by broadband dielectric spectroscopy (BDS) and differential scanning calorimetry (DSC). HAT6 was embedded into nanoporous anodic aluminum oxide membranes by melt infiltration in the isotropic phase under argon atmosphere. The filled membranes have the thickness of 80 µm and the diameter of 15mm and parallel aligned tubular nanopores having the pore diameters of 25, 40, 80 and 180 nm. The filling degree for each sample was checked by thermogravimetric analysis (TGA) in order to ensure complete filling. The bulk HAT6 forms, a hexagonal columnar phase between the isotropic phase above 371 K, and the plastic crystalline phase below 340 K. Unlike the bulk, the confined HAT6 forms two peaks in the heat flow during the plastic crystalline-to-hexagonal columnar phase transition, which might be the evidence of two different phase structures close to the wall and in the pore center. Moreover, the isotropic-to-columnar transition of the confined HAT6 shifts with decreasing pore diameter to lower temperatures.