Boron nitride shear-cell for high temperature diffusion experiments.

For long time diffusion experiments, shear-cell techniques offer more favourable terms than the traditional long capillary techniques. Graphite shear-cells have successfully been tested on Al-Cu and Al-Cu-Ag interdiffusion experiments at 973 K. However, graphite is not applicable for high melting Al-Ni diffusion samples because of chemical reactions between the melt and the container material. Here, we present a further developed shear-cell version made of boron nitride containing ZrO2, that enables the measurement of diffusion coefficients on Al-Ni alloys up to temperatures of 1873 K. The modified shear-cell combines the capabilities and advantages of the graphite cell with the chemical durability of the boron nitride. It is operated in an isothermal furnace insert which can be accommodated in the Materials Science Laboratory of the International Space Station. This provides the opportunity that the shear-cell can be applied to µg- and to ground based experiments respectively. Temperature homogeneity along the boron nitride sample compartment is better than 2.1 K at 1673 K. We report on the new design and first successfully performed experiments. [ABSTRACT FROM AUTHOR]