Institut für Werkstoffwissenschaften und -technologien

111 Items

Recent Submissions
Untersuchungen zum Strangpressen von Aluminiumhohlprofilen mit axial variabler Wandstärke

Negendank, Maik (2017)

Ein möglichst ressourcenschonender Umgang mit den auf der Erde vorhandenen natürlichen Rohstoffen, insbesondere den fossilen Energieträgern, dem Ziel einer Minderung der globalen CO2-Emmissionen und einer Begrenzung der Erderwärmung machen im industriellen Transportsektor innovative Leichtbauentwicklungen notwendig. Aluminiumlegierungen sind derzeit im Leichtbaubereich der am häufigsten eingese...

Radiographic and tomographic investigation of water transport in operating polymer electrolyte membrane fuel cells

Alrwashdeh, Saad Sabe' (2017)

Fuel cells are foreseen to play a leading role in many future sustainable energy strategies as they allow for environmental friendly and locally pollutant-free energy conversion systems. One of the most important and prevalent types is the polymer electrolyte membrane fuel cell (PEMFC). One of the key issues of the PEM fuel cell is the water management since efficiency, cell performance and...

Changes of valence state and local structure in anode materials for lithium-ion batteries by X-ray absorption spectroscopy

Zhou, Dong (2017)

Electronic and local structural changes in three different promising anode materials (porous NiSi2/Si composite, nano-crystalline NiFe2O4 and ZnFe2O4) for lithium ion batteries are investigated by X-ray absorption spectroscopy. The lithium storage mechanism and associated structural changes are derived not only from the average valence states of the absorption atoms (Ni, Fe and Zn) estimated fr...

Optimierung der mechanischen Eigenschaften von 7xxx-Aluminiumlegierungen durch gezielte Einstellung der Mikrostruktur

Paulisch, Melanie Cornelia (2017)

In der vorliegenden Arbeit werden die Einflüsse des Strangpressens und Wärmebehandelns auf die Mikrostruktur und die mechanischen Eigenschaften vier verschiedener ausscheidungshärtbarer 7xxx-Legierungen (7108, 7020, 7021B und 7175) untersucht. Darüber hinaus wurde das quasistatische und dynamische Verformungsverhalten bezüglich Veränderungen in der Kornmorphologie und Textur analysiert. Dazu wu...

X-ray radiographic and tomographic investigations of cycled lithium ion batteries

Sun, Fu (2017)

Lithium ion batteries (LIBs) have become the predominant power supplies in portable electronic devices such as cell phones, laptops and tablets. They are regarded as promising candidates to power future electric vehicles and to store the intermittent and fluctuating energy harvested from solar and wind sources. Unfortunately, the current LIB technology fails to meet the growing energy demand re...

Alterung und Lebensdauervorhersage von O-Ring-Dichtungen

Kömmling, Anja (2017)

In some applications, elastomer seals have to remain leak tight over extended time periods (up to several decades) as an exchange of the seals is not practical. Therefore, it is necessary to be able to predict the lifetime of such seals reliably. For this reason, ageing experiments with O-rings and sheets based on hydrogenated acrylonitrile butadiene rubber (HNBR), ethylene propylene diene rubb...

Charakterisierung von Glas-Polymer Verbundmaterialien für die Hochdruckspeicherung von Wasserstoff

Prewitz, Marc (2017)

This thesis investigates glass capillaries and structures consisting of borosilicate glass (Simax) for high pressure hydrogen storage. The finite element method (FEM) is used for the mechanical analyses and the design optimization. The necessary characteristic values for the material descriptions are determined by experimental tests. The strength, the shear strength of the interface glass/adhe...

Flame retardant materials based on BDM/DBA resin and organic-inorganic additives

Wang, Zheng (2017)

2,2’-diallyl bisphenol A (DBA) modified bismaleimide resins (BDM) are widely used as polymer matrix of high-performance composites in the field of aerospace, transportation, machinery, and electronics. This kind of resin has excellent properties, including good thermal stability, good processing performance, high mechanical strength, excellent dielectric properties, etc. However, as for most or...

From linear to long-chain branched poly(ethylene terephthalate) – reactive extrusion, rheology and molecular characterization

Kruse, Matthias (2017)

Poly(ethylene terephthalate) is one of the most widely used polymers in packaging industry, due to its high mechanical strength, chemical resistance, and barrier functions. However, its processing is determined by degradation and low viscosity. In particular, foaming and film blowing is restricted by the linear structure of the molecule and low melt strength. The stability of three linear com...

Formation of intermetallic phases in Al-10Si-0.3Fe based alloys

Yu, Jiamin (2016)

The emphasis of the work lies on finding out how impurities and the addition of Sr influence the formation of Fe-rich intermetallic phases and the formation of the eutectic Si phase in Al-Si casting alloys. A further objective of this study was the understanding of the influence of the cooling rate on the formation of intermetallic phases. For this purpose, four Al-10Si-0.3Fe-based casting allo...

Analysis of poly(L-lactide) nanocomposites based on layered double hydroxides

Leng, Jing (2016)

This work focuses on the analysis of the poly (L-lactide) nanocomposites based on modified MgAl and NiAl layered double hydroxides (LDH) characterized by measurements such as size exclusion chromatography (SEC), differential scanning calorimetry (DSC), small- and wide-angle X-ray scattering (SAXS and WAXS) and broadband dielectric spectroscopy (BDS). The polymer based nanocomposites were ...

Characterization of epoxy/copper interphases using nanoindentation

Elabshihy, Karim (2016)

Characterization of the size and mechanical properties of interphases is essential when designing multicomponent materials. Polymer/metal composites, often found in microelectronics, are an example of such multicomponent materials, where understanding the interphase properties can provide vital information about the durability of a finished product. When nanoindentation is used to investigate t...

Untersuchungen zur Photo-Degradation von Kohlenstoff-Nanoröhren-gefüllten Polymerkompositen

Barthel, Anne-Kathrin (2016)

Durch eine Additivierung von Kunststoffen mit Kohlenstoff-Nanoröhren (CNT) lassen sich ihre Eigenschaften gezielt optimieren. Die erzielten Leistungsverbesserungen können über steigende Nachfrage zu einem höheren Materialeinsatz der CNT-Polymerkomposite in den unterschiedlichsten technologischen Bereichen führen. CNT sind faserförmige Nanomaterialien und müssen nach WHO-Regularien (Weltgesundhe...

Untersuchungen zur Spanbildung metallischer Werkstoffe anhand von in situ Röntgenbeugungsexperimenten

Brömmelhoff, Katrin Stefanie (2016)

Zur Optimierung der Zerspanprozesse mit geometrisch bestimmter Schneide ist ein fundiertes Wissen über den Spanbildungsprozess notwendig, welches jedoch aufgrund der erschwerten messtechnischen Erfassbarkeit der Wirkzone stark limitiert ist. Moderne Quellen für hochenergetische Synchrotronröntgenstrahlung und neue Detektionsmöglichkeiten ermöglichen es nun, in situ Diffraktionsexperimente währe...

Assessing microstrain in polycrystalline thin films by means of various diffraction and spectroscopy techniques

Schäfer, Norbert (2016)

Die vorliegende Arbeit behandelt die Möglichkeit von Dehnungsmessungen innerhalb einzelner Körner der CuInSe2-Absorberschicht einer Dünnschichtsolarzelle. Ausgedehnte strukturelle Defekte und deren möglicher Einfuss auf optoelektronische Eigenschaften der Absorberschicht, und damit auch auf die Effizienz der kompletten Solarzelle, sind verbunden mit Änderungen in der periodischen Kristallstrukt...

Friction in long bearing channels during multi-hole extrusion of aluminum alloy

Sanabria Rosas, Vidal R. (2016)

The friction behavior between the aluminum alloy EN AW-6060 and the hot working steel AISI H13 was investigated under extrusion conditions. The visco-plastic response of the EN AW-6060 was determined by means of hot compression tests at high different temperatures and strain rates. The Garofalo or Zener-Hollomon relationship was applied to model the flow stress. Furthermore, tribo-torsion-tests...

Particle-stabilised foams: structure and aging

Stocco, Antonio ; Garcia-Moreno, Francisco ; Manke, Ingo ; Banhart, John ; Langevin, Dominique (2011)

We show that aqueous foams stabilised by nanoparticles can be easily imaged using an X-ray laboratory source. We have used hydrophobically modified silica nanoparticles that confer to the foam a remarkable stability. The X-ray tomography observations were compared with the information obtained using a multiple light scattering technique. Both techniques confirm that provided the concentration o...

Kinetics of coalescence in liquid aluminium foams

Garcia-Moreno, Francisco ; Solorzano, E. ; Banhart, Jon (2011)

The cell wall rupture kinetics for a collection of AlSi9 foam samples kept at a constant temperature over the melting point for a long time period (700 s) has been characterized by in situ X-ray radioscopy. The images obtained have been computed by using image analysis algorithms allowing the identification of the cell wall ruptures in the molten state. The time evolution, the spatial distribut...

The rupture of a single liquid aluminium alloy film

Heim, K. ; Garcia-Moreno, F. ; Kumar, G. S. Vinod ; Rack, A. ; Banhart, J. (2014)

The present study is based on the idea of understanding the rupture of films in metal foams by studying free standing metallic films as a model system. Liquid dynamics, the velocity of the rupturing material as well as the behaviour of ceramic particles inside the melt were analysed optically ex situ and by synchrotron X-ray radiography in situ. It was found that the resistance of films to rupt...

On the structural integrity and electrochemical activity of a 0.5Li(2)MnO(3)center dot 0.5LiCoO(2) cathode material for lithium-ion batteries

Rana, Jatinkumar ; Klöpsch, Richard ; Li, Jie ; Scherb, Tobias ; Schumacher, Gerhard ; Winter, Martin ; Banhart, John (2014)

Structural changes in a 0.5Li2MnO3·0.5LiCoO2cathode material were investigated by X-ray absorption spectroscopy. It is observed that both Li2MnO3and LiCoO2components of the material exist as separate domains, however, with some exchange of transition metal (TM) ions in their slab layers. A large irreversible capacity observed during activation of the material in the 1stcycle can be attributed t...