When performing X-ray diffraction (XRD) analysis of small powder sample volumes with the Bragg–Brentano setup, choosing an appropriate sample preparation method is important. This work provides practical information on the conventional top dusted sample preparation method and the top dusted adhesive tape sample preparation method. In the latter, the powder of interest is dusted onto an adhesive tape. Because adhesive tapes contribute to the measured XRD signal as background noise, care must be taken when using a particular adhesive tape. This work assists XRD users in selecting the most suitable adhesive tape for their purpose by providing the diffractograms (Cu Kα1 radiation) of 13 commercially available adhesive tapes used for office and packing applications. In general, tapes with a matte acetate or polyvinyl chloride backing are recommended as they cause a comparatively low background signal without high-intensity reflections.

In previous studies, chromium–silicon-based alloys have shown promising material properties for high-temperature applications. For chromium–silicon alloys to be processed on a large scale, primary shaping processes must be adapted to the requirements of these alloys. In this work, binary chromium–silicon alloys are primarily shaped using an investment casting process. Ceramic shell molds made of hafnium oxide stabilized zirconium oxide are developed to withstand the thermal, mechanical and chemical stresses resulting from pouring melts with liquidus temperatures of up to 1900 °C. The layered construction of the shell molds leads to a sufficient thermal shock stability. Energy-dispersive X-ray spectroscopy shows that chemical interactions between the shell mold and the melt do not occur, nor oxides are formed to a detectable extent. Microstructure investigations reveal that casting binary chromium–silicon alloys lead to a coarse grain structure with grain diameters above 300 µm. Strength-increasing precipitations of the intermetallic phase Cr3Si (A15 phase) can be detected from a silicon content of seven-atom percent in the as-cast state.

Aiming for an increased surface hardness and a better wear resistance of TiZrNbHfTa, we investigate a two-step process combining oxidation of rolled, ultrafine-grained, single-phase bcc TiZrNbHfTa in air at 550 °C with a vacuum heat treatment process at 1200 °C, including subsequent quenching. The first process step is associated with the formation of a surface oxide layer, a phase decomposition of the bulk, and oxygen ingress into the bulk, leading to an oxygen-enriched subsurface region containing internal oxides. The second process step is capable of restoring the single-phase nature of the bulk TiZrNbHfTa. At the same time, the presence of a compact surface oxide layer of 1–2 μm and an oxygen-enriched subsurface region underneath is preserved. The oxygen present in the subsurface region stabilizes a two-phase regime consisting of a Hf- and Zr-rich hcp phase and an Nb- and Ta-rich bcc phase, with the oxygen being interstitially dissolved predominantly in the hcp phase.

We investigate the oxidation of TiZrNbHfTa high entropy alloy between 550 degrees C and 650 degrees C as a surface hardening method. Coarse-grained specimens with grain boundaries perpendicular to the surface exhibit catastrophic oxidation, while ultrafine-grained, cold-rolled specimens show a continuous mass gain and the formation of an adherent, mu m-sized, vitreous oxide layer. Underneath, TiZrNbHfTa decomposes into a bcc- and an hcp-phase, while selective internal oxidation of hafnium and zirconium occurs upon oxygen inward diffusion. Oxygen concentration- and microhardness-depth profiles confirm an increase in oxygen concentration and hardness at the surface, raising the initial hardness by four times to 1522 +/- 64 HV0.5.

Thermal oxidation is a promising technique to improve the tribological properties of Ti6Al4V. Herein, a single‐step process consisting of oxidation in air, a two‐step process with an additional solid‐state oxide layer reduction step under vacuum, and a three‐step process with an appended final oxidation step in air are applied to Ti6Al4V. The oxide layer adhesion after the three‐step process is improved compared with the single‐step process. This improved adhesion is not due to a different nature of the oxide layers because oxide layers obtained during the single‐step and three‐step process show a similar morphology and composition. Instead, it is ascribed to the presence of an optimized oxygen diffusion zone with two distinct regions: a gradual decrease in oxygen concentration from the maximum possible oxygen concentration at the oxide–substrate interface until a depth of 20 μm followed by a near‐linear decrease until a depth of about 85 μm. Both regions are also visible in the correlated microhardness‐depth profile.

Reactive particles consisting of nickel and aluminum represent an adaptable heat source for joining applications, since each individual particle is capable of undergoing a self-sustaining exothermic reaction. Of particular interest are particles with intrinsic lamellar microstructures, as they provide large contact areas between the reactants nickel and aluminum. In this work, the exothermic reaction as well as the microstructure of such lamellar reactive particles produced by high energy planetary ball milling were investigated. Based on statistically designed experiments regarding the milling parameters, the heat of reaction was examined by means of differential scanning calorimetry (DSC). A statistical model was derived from the results to predict the heat of reaction as a function of the milling parameters used. This model can be applied to adjust the heat of reaction of the reactive particles depending on the thermal properties of the joining partners. The fabricated microstructures were evaluated by means of scanning electron microscopy (SEM). Through the development of a dedicated SEM image evaluation algorithm, a computational quantification of the contact area between nickel and aluminum was enabled for the first time. A weak correlation between the contact area and the heat of reaction could be demonstrated. It is assumed that the quantification of the contact areas can be further improved by a higher number of SEM images per sample. The findings obtained provide an essential contribution to enable reactive particles as a tailored heat source for joining applications.

Ziel dieser Arbeit ist, den Zusammenhang zwischen Viskositat und Brechungsindex eines Harzes mit einem faseroptischen Sensor zu untersuchen. Dieser ist die Grundlage um Viskositat faseroptisch messen zu konnen. Hierzu werden mit dem Epoxidharz Epicote System 600 isotherme Versuchsreihen im Wesentlichen bei 80 °C, 120 °C und 180 °C durchgefuhrt. Der Viskositatsverlauf wahrend der Harzaushartung wird mit einem Rheometer mit Kegel-Platte Messsystem bestimmt. Hierzu werden zunachst vorbereitende Versuche durchgefuhrt um die Parameter fur die anschliesende Durchfuhrung der kombinierten rotatorisch-/oszillatorischen Messungen zu ermitteln. In einem zweiten Versuch wird der Brechungsindexverlauf ermittelt. Hierfur wird ein faseroptisches Messsystem eingesetzt. Dieses basiert auf dem Prinzip der Fresnel-Reflexion. Gemessen wird die an einer Glasfaser-Harz-Grenzflache reflektierte Intensitat wahrend der Aushartung. Daraus wird der Brechungsindexverlauf berechnet. Viskositats- und Brechungsindexverlauf werden dann fur jede isotherme Versuchsreihe korreliert. Fur die Korrelationskurven Viskositat vs. Brechungsindex wird ein formelmasiger Zusammenhang gesucht. Uber die Standardabweichung des Brechungsindex wird ein dem gemessenen Brechungsindex zugehoriger Viskositatsbereich ermittelt. Abschliesend wird zudem das Viskositatsmodell nach KIUNA fur das vorliegende Harz angewendet.