Papers by Author: Annegret Brendel

Abstract: Copper matrix composites reinforced with silicon carbide fibres (SiCf/Cu) are considered as heat sink materials for the divertor of DEMO as they combine high thermal conductivity and good mechanical strength at high temperature. A new method was developed to synthesise a metal matrix composite (MMC) consisting of about 3-6 unidirectional reinforced layers (UD-layers). The UD-layers were prepared by two subsequent electroplating processes which allow to adjust various fibre volume fractions. These single UD layers were stacked with different relative fibre orientations (0°/0° and 0°/90°) and consolidated by vacuum hot pressing to form the MMC specimen. The thermal conductivity perpendicular to fibre direction was obtained by laser flash apparatus (LFA) measurements. It is about 310 Wm-1K-1 for electroplated copper (Cu) and above 200 Wm-1K-1 for MMC specimens with a fibre volume fraction of 8-13%. Due to the manufacturing process, boundaries within the matrix were found resulting in a reduction of the values. In addition, DSC (differential scanning calorimetry) measurements were performed which gave similar results.

Abstract: The mechanical properties of a SiC-fiber/copper matrix composite, reinforced with SCS-0 SiC-fibers ( 140µm, Specialty Materials), can significantly be increased by applying a Ti-Ta-C multilayer between fiber and matrix. This interlayer is deposited with a magnetron sputter device directly on the single fibers. By changing the deposition parameters of this sputter process the Ti-Ta-C interlayer can be optimized regarding fiber strength and fiber/matrix adhesion. Experiments with different deposition pressures, bias voltages and layer thickness’ were performed to increase the bond strength and the ultimate tensile strength when compared to the Ti-Ta-C reference sample.