Inst. Werkstoffwissenschaften und -technologien

132 Items

Recent Submissions
An X-ray tomographic study of rechargeable Zn/MnO2 batteries

Osenberg, Markus ; Manke, Ingo ; Hilger, André ; Kardjilov, Nikolay ; Banhart, John (2018-08-21)

We present non-destructive and non-invasive in operando X-ray tomographic investigations of the charge and discharge behavior of rechargeable alkaline-manganese (RAM) batteries (Zn-MnO2 batteries). Changes in the three-dimensional structure of the zinc anode and the MnO2 cathode material after several charge/discharge cycles were analyzed. Battery discharge leads to a decrease in the zinc parti...

Analyse der Mikrostrukturentwicklung von CuInSe2 mittels in-situ Röntgenbeugung

Stange, Anna Helena (2018)

Die Reduzierung der Absorberschichtdicke auf wenige Mikrometer eröffnet neue Anwendungsmöglichkeiten für die Photovoltaik. Der Verbindungshalbleiter Cu(In,Ga)Se2 (CIGSe) hat sich als besonders geeignet für solche Dünnschichtsolarzellen herausgestellt. Mit CIGSe-Absorbern aus einem mehrstufigen Syntheseprozess werden die bisher höchsten Effizienzen im Bereich der Dünnschichttechnologie erreicht....

Preparation, characterization and electrical properties of nanocomposites based on hyperbranched polymers

Omara, Shereen Said Shabaan (2018)

Nanocomposites based on hyperbranched polymers (HBPs) and layered silicates as nanofillers are a relatively new class of nanocomposites. Due to their unique physical/chemical properties, they have attracted scientific interests. This study provides to a better understand the structure-dynamics-properties relationship, for different types of HBP/ kaolinite (Ka) nanocomposites. Two different me...

Microscopic aspects of ageing in Al-Mg-Si alloys

Madanat, Mazen Adel (2018)

Al-Mg-Si alloys with a low solute content (0.4 %Mg, 0.4 %Si) and higher contents (Mg+Si=1.4 %, all in wt.%) were solutionized, quenched and then either artificially aged (AA) at 180 °C or naturally pre-aged (NPA) for 2 weeks at room temperature and then reverse aged (RA) at 250 °C. Subsequently, positron annihilation lifetime spectroscopy was applied with the objective of obtaining information ...

Mechanical properties in crumple-formed paper derived materials subjected to compression

Hanaor, D.A.H. ; Flores Johnson, E.A. ; Wang, S. ; Quach, S. ; Dela-Torre, K.N. ; Gan, Y. ; Shen, L. (2017-06)

The crumpling of precursor materials to form dense three dimensional geometries offers an attractive route towards the utilisation of minor-value waste materials. Crumple-forming results in a mesostructured system in which mechanical properties of the material are governed by complex cross-scale deformation mechanisms. Here we investigate the physical and mechanical properties of dense compacte...

Structure-function relationships in Macadamia integrifolia seed coats – fundamentals of the hierarchical microstructure

Schüler, Paul ; Speck, Thomas ; Bührig-Polaczek, Andreas ; Fleck, Claudia (2014-08-07)

The shells/coats of nuts and seeds are often very hard to crack. This is particularly the case with Macadamia seed coats, known to exhibit astoundingly high strength and toughness. We performed an extensive materials science characterization of the complex hierarchical structure of these coats, using light and scanning electron microscopy in 2D as well as microCT for 3D characterization. We dif...

Surface chemistry and stability of metastable corundum-type In2O3

Köck, Eva-Maria ; Kogler, Michaela ; Zhuo, Chen ; Schlicker, Lukas ; Bekheet, Maged F. ; Doran, Andrew ; Gurlo, Aleksander ; Penner, Simon (2017)

To account for the explanation of an eventual sensing and catalytic behavior of rhombohedral In2O3 (rh-In2O3) and the dependence of the metastability of the latter on gas atmospheres, in situ electrochemical impedance spectroscopic (EIS), Fourier-transform infrared spectroscopic (FT-IR), in situ X-ray diffraction and in situ thermogravimetric analyses in inert (helium) and reactive gases (hydro...

High resolution pore size analysis in metallic powders by X-ray tomography

Heim, Korbinian ; Bernier, F. ; Pelletier, R. ; Lefebvre, L.-P. (2016)

The deployment of additive manufacturing processes relies on part quality, specifically the absence of internal defects. Some of those defects have been associated with porosities in the powder feedstock. Since the level of porosity in the powder is generally very low, standard characterisation techniques such as pycnometry and metallography are not suitable for quantification. However, the qua...

Ordered mesoporous silica COK-12: mesoscale tailoring, upscaling, continuous synthesis and application in the oxidative coupling of Methane

Colmenares, Maria (2018)

Ordered mesoporous silica (OMS) materials are a family of silica nanomaterials with pores ranging in size from 2 to 50 nm which are arranged periodically within the silica matrix. They have expanding applications in various fields of research, such as drug delivery, adsorption, separation and catalysis. COK-12 is an OMS produced by the soft-templating method, using the block copolymer P123 as a...

Structure and molecular dynamics of thin films of homopolymers and miscible polymer blends

Madkour, Sherif A. (2018)

In recent years, research on nanoscale confinement of polymers has witnessed topical investigations in attempt to tune polymer properties on demand. One of the most studied forms of nanoconfinement are thin films, where 1D confinement results from the reduction of the film thickness. For these systems, it is crucial to understand how confinement affects the glass transition phenomenon and the a...

Variotherme Verarbeitung von Epoxidharz zur Zyklusverkürzung im RTM Prozess

Ai, Qingfeng (2018)

Im Rahmen dieser Arbeit wurde ein dynamischer, variothermer RTM-Prozess zur gezielten Beeinflussung und Steuerung der Vernetzungsreaktion eines Epoxidharzsystems unter praxisnahen Bedingungen entwickelt, mit dem Ziel, den Produktionszyklus stark zu verkürzen und gleichzeitig hochwertige Formteile mit geforderten Eigenschaften herzustellen. Als Grundlage für den praktischen Verarbeitungsprozess...

Der Schäumprozess von Aluminiumlegierungen: Tomoskopische Untersuchung der Gasnukleation

Kamm, Paul Hans (2018)

Die Verbesserung der Struktur metallischer Schäume und damit ihrer Eigenschaften bedarf eines tieferen Verständnisses der während des Schäumens und der späteren Degradation ablaufenden Mechanismen. Um diesen dynamischen Prozess in seiner dreidimensionalen Komplexität und zeitlichen Veränderung zu erfassen wurde in dieser Arbeit das Verfahren der zeitaufgelösten Tomographie (Tomoskopie: Ein Kuns...

Tribologisch induzierte Oberflächenveränderungen im Reib-Verschleiß-Kontakt Kolbenring gegen Zylinderlaufbahn

Biberger, Julian (2017)

In Verbrennungsmotoren ist der Tribokontakt Topring gegen Zylinderlaufbahn einer der am höchsten beanspruchten Kontakte. Die Anforderungen an Reibungsoptimierung und geringen Verschleiß bei gleichzeitig hoher Laufzeit erfordern ein detailliertes Verständnis dieses tribologischen Kontaktes. Aus diesem Grund ist es erforderlich, unterschiedliche Kolbenringbeschichtungen auf ihr tribologisches Ver...

Ultramicroporous silicon nitride ceramics for CO2 capture

Schitco, Cristina ; Seifollahi Bazarjani, Mahdi ; Riedel, Ralf ; Gurlo, Aleksander (2015)

Carbon dioxide (CO2) capture is regarded as one of the biggest challenges of the 21st century; therefore, intense research effort has been dedicated in the area of developing new materials for efficient CO2 capture. Here, we report high CO2 capture capacity in the low region of applied CO2 pressures observed with ultramicroporous silicon nitride-based material. The latter is synthesized by a fa...

Suitability of various complex hydrides for foaming aluminum alloys

Kamm, Paul H. ; García-Moreno, Francisco ; Jiménez, Catalina ; Banhart, John (2013)

Some hydrides that could replace TiH2 as the hitherto most suitable blowing agent for foaming aluminum alloys were investigated. Hydrides taken from the group MBH4 (M = Li, Na, K) and LiAlH4 were selected since these have not been studied in the past although their decomposition characteristics appear to be suitable. Foamable precursors of alloy AlSi8Mg4 were manufactured by pressing blends of ...

A study on the thermal conversion of scheelite-type ABO(4) into perovskite-type AB(O,N)(3)

Li, Wenjie ; Li, Duan ; Gao, Xin ; Gurlo, Aleksander ; Zander, Stefan ; Jones, Philip ; Navrotsky, Alexandra ; Shen, Zhijian ; Riedel, Ralf ; Ionescu, Emanuel (2015)

Phase-pure scheelite AMoO(4) and AWO(4) (A = Ba, Sr, Ca) were thermally treated under an ammonia atmosphere at 400 to 900 degrees C. SrMoO4 and SrWO4 were shown to convert into cubic perovskite SrMoO2N and SrWO1.5N1.5, at 700 degrees C and 900 degrees C respectively, and to form metastable intermediate phases (scheelite SrMoO4-xNx and SrWO4-xNx), as revealed by X-ray diffraction (XRD), elementa...

Slow crystallisation of a monodisperse foam stabilised against coarsening

Meagher, Aaron J. ; Whyte, David ; Banhart, John ; Hutzler, Stefan ; Weaire, Denis ; García-Moreno, Francisco (2015)

The evolution of a three-dimensional monodisperse foam was investigated using X-ray tomography over the course of seven days. The coarsening of the sample was inhibited through the use of perfluorohexane gas. The internal configuration of bubbles is seen to change markedly, evolving from a disordered arrangement towards a more ordered state. We chart this ordering process through the use of the...

Annihilation of structural defects in chalcogenide absorber films for high-efficiency solar cells

Mainz, Roland ; Sanli, Ekin Simsek ; Stange, Helena ; Azulay, Doron ; Brunken, Stephan ; Greiner, Dieter ; Hajaj, Shir ; Heinemann, Marc D. ; Kaufmann, Christian A. ; Klaus, Manuela ; Ramasse, Quentin M. ; Rodriguez-Alvarez, Humberto ; Weber, Alfons ; Balberg, Isaac ; Millo, Oded ; Aken, Peter A. van ; Abou-Ras, Daniel (2016)

In polycrystalline semiconductor absorbers for thin-film solar cells, structural defects may enhance electron-hole recombination and hence lower the resulting energy conversion efficiency. To be able to efficiently design and optimize fabrication processes that result in high-quality materials, knowledge of the nature of structural defects as well as their formation and annihilation during film...

The contrasting effect of the Ta/Nb ratio in (111)-layered B-site deficient hexagonal perovskite Ba5Nb4-xTaxO15 crystals on visible-light-induced photocatalytic water oxidation activity of their oxynitride derivatives

Hojamberdiev, Mirabbos ; Bekheet, Maged F. ; Zahedi, Ehsan ; Wagata, Hajime ; Vequizo, Junie Jhon M. ; Yamakata, Akira ; Yubuta, Kunio ; Gurlo, Aleksander ; Domen, Kazunari ; Teshima, Katsuya (2016)

The effect of the Ta/Nb ratio in the (111)-layered B-site deficient hexagonal perovskite Ba5Nb4-xTaxO15 (0 <= x <= 4) crystals grown by a KCl flux method on visible-light-induced photocatalytic water oxidation activity of their oxynitride derivatives BaNb1-xTaxO2N (0 <= x <= 1) was investigated. The Rietveld refinement of X-ray data revealed that all Ba5Nb4-xTaxO15 samples were well crystallize...

Characterization and mechanical properties investigation of the cellulose/gypsum composite

Nindiyasari, Fitriana ; Griesshaber, Erika ; Zimmermann, Tanja ; Manian, Avinash Pradip ; Randow, Clemens ; Zehbe, Rolf ; Fernandez-Diaz, Lurdes ; Ziegler, Andreas ; Fleck, Claudia ; Schmahl, Wolfgang W. (2016)

We synthesized cellulose/gypsum composites in the presence and absence of sodium alginate and investigated the interaction between the composite components as well as the mechanical properties of the final composites. Four different types of cellulose fiber materials were used: cellulose UFC100, cellulose B400, nanofibrillated cellulose, and Lyocell fiber. For all investigated composites the to...