Diffusion measurements on a liquid monotectic alloy PbGa using the shear cell technique under μg in the Foton-M2 mission and under 1G

Shinsuke Suzuki, Kurt Helmut Kraatz, Günter Frohberg

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Abstract

Diffusion experiments of a liquid monotectic alloy PbGa were performed under 1g-conditions at 623, 773 and 903K, and under μg-conditions at 903K. As a measurement tool the shear cell specially designed for Russian satellite Foton missions within the AGAT-furnace was used to have a homogenization time before the diffusion and to avoid the influence of decomposition into two liquid phases during cooling-down. The experiment type was diffusion from a thick layer of PbGa5at% into pure Pb. The liquid sample in the capillary was pressurized using a reservoir system in order to minimize Marangoni convection. In 1g-experiments the diffusion axis was arranged vertically and the sample was set such that the density increases monotonously parallel to the gravity vector in order to suppress buoyancy convection. Four experiments were performed simultaneously for each set-up. The μg-experiment was performed in the AGAT facility during the Foton-M2 mission (June 2005) where one capillary was assigned for the PbGa-Pb experiment (PbGa was containing an enriched Pb-isotope tracer). The concentration profiles were obtained by AAS (1g) and by ICP-MS (μg). The diffusion coefficients were evaluated by fitting with the thick layer solution. For the evaluation a correction method was used for the shear convection and the averaging effect inside each cell. As a result, the obtained concentration curves agreed well with the fitting function. The reproducibility of the diffusion coefficients among four parallel 1g-experiments was good with a standard deviation among four capillaries smaller than 5.5% including the standard temperature deviation. The diffusion coefficients agreed well between 1g- and μg-experiments. The temperature dependence of the diffusion coefficients could be fitted well to a power law with an exponent about 2.4. From these results we conclude that the 1g-experimental method in this study for diffusion measurement is effective also for monotectic systems.

Original languageEnglish
Pages (from-to)82-85
Number of pages4
JournalMicrogravity Science and Technology
Volume18
Issue number3-4
DOIs
Publication statusPublished - 2006 Jan 1

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ASJC Scopus subject areas

  • Modelling and Simulation
  • Engineering(all)
  • Physics and Astronomy(all)
  • Applied Mathematics

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