Magnus Rohde

Tungsten as a Structural Divertor Material

Refractory materials, in particular tungsten base materials are considered as primary candidates for structural high heat load applications in future nuclear fusion power plants. Promising helium-cooled divertor design outlines make use of their high heat conductivity and strength. The upper operating temperature limit is mainly defined by the onset of recrystallization but also by loss of creep strength. The lower operating temperature range is restricted by the use of steel parts for the in- and outlets as well as for the back-bone. Therefore, the most critical issue of tungsten materials in connection with structural divertor applications is the ductile-to-brittle transition. Another problem consists in the fact that especially refractory alloys show a strong correlation between microstructure and their manufacturing history. Since physical and mechanical properties are influenced by the underlying microstructure, refractory alloys can behave quite different, even if their chemical composition is the same. Therefore, creep and thermal conductivity have been investigated using typical commercial tungsten materials. Moreover, the fracture behavior of different tungsten based semi-finished products was characterized by standard Charpy tests which have been performed up to 1100 °C in vacuum. Due to their fabrication history (powder mixing, pressing, sintering, rolling, forging, or swaging) these materials have specific microstructures which lead different fracture modes. The influence of the microstructure characteristics like grain size, anisotropy, texture, or chemical composition has been studied.

Heating Concepts for Ceramic Microreactors

For high-temperature applications of a microreactor system the precise temperature control inside the reactor is important to optimize the yield of chemical reactions. If a microreactor system is operated inside a tube furnace, at best a homogeneous temperature distribution will be achieved inside the reactor. Heating elements that are integrated in the reactor have the potential to realize localized heating. Moreover, integrated heaters offer an efficient heating and a more convenient handling. Ohmic resistance heating for a modular ceramic microreactor system was investigated by direct connection and induction heating. The ceramic reactor system was modeled with FEM methods. Heat transfer and stress were calculated and compared with measurements taken.

Laser Micro and Nano Processing of Metals, Ceramics, and Polymers

Laser -based material processing is well investigated for structuring , modification , and bonding of metals , ceramics , glasses, and polymers . Especially for material processing on micrometer, and nanometer scale laser-assisted processes will very likely become more prevalent as lasers offer more cost-effective solutions for advanced material research, and application. Laser ablation , and surface modification are suitable for direct patterning of materials and their surface properties. Lasers allow rapid prototyping and small-batch manufacturing . They can also be used to pattern moving substrates, permitting fly-processing of large areas at reasonable speed. Different types of laser processes such as ablation, modification, and welding can be successfully combined in order to enable a high grade of bulk and surface functionality. Ultraviolet lasers favored for precise and debris-free patterns can be generated without the need for masks, resist materials, or chemicals. Machining of materials, for faster operation, thermally driven laser processes using NIR and IR laser radiation, could be increasingly attractive for a real rapid manufacturing .

Microwave Crystallization of Lithium Aluminum Germanium Phosphate Solid-State Electrolyte

Lithium aluminum germanium phosphate (LAGP) glass-ceramics are considered as promising solid-state electrolytes for Li-ion batteries. LAGP glass was prepared via the regular conventional melt-quenching method. Thermal, chemical analyses and X-ray diffraction (XRD) were performed to characterize the prepared glass. The crystallization of the prepared LAGP glass was done using conventional heating and high frequency microwave (MW) processing. Thirty GHz microwave (MW) processing setup were used to convert the prepared LAGP glass into glass-ceramics and compared with the conventionally crystallized LAGP glass-ceramics that were heat-treated in an electric conventional furnace. The ionic conductivities of the LAGP samples obtained from the two different routes were measured using impedance spectroscopy. These samples were also characterized using XRD and scanning electron microscopy (SEM). Microwave processing was successfully used to crystallize LAGP glass into glass-ceramic without the aid of susceptors. The MW treated sample showed higher total, grains and grain boundary ionic conductivities values, lower activation energy and relatively larger-grained microstructure with less porosity compared to the corresponding conventionally treated sample at the same optimized heat-treatment conditions. The enhanced total, grains and grain boundary ionic conductivities values along with the reduced activation energy that were observed in the MW treated sample was considered as an experimental evidence for the existence of the microwave effect in LAGP crystallization process. MW processing is a promising candidate technology for the production of solid-state electrolytes for Li-ion battery.