Introduction to Materials Processing in Large Centrifuges

Effect of Temperature on Segregation Coefficients of Impurities in Tellurium

“…This increase of K eff with T was well understood by the particular anomaly of molten tellurium [4] related to its quasi-polymer chain structure. The chains were destroyed immediately upon melting.…”

“…Therefore, the entropy increases in the molten zone which becomes more homogeneous. Nevertheless, this high temperature gradient induces a formation of lattice and defects of about 10 13 cm À3 of hole concentrations [4,6] with an acceptable behavior but not clear nature [18]. It also produces a higher rate of irreversible diffusion of impurities and micro segregation due to the instability of the systems.…”

“…Recent studies [4] on the effect of high and microgravity on the growth and purification of tellurium showed a perturbation of K eff for S b in tellurium of À25% for 5g and þ25% for 10gðg ¼ 9:81 m=s 2 Þ: A decrease of hole mobility was observed at a gravity of 10g due to the formation of additional defects. In addition, higher values of K eff for the samples refer to a tendency toward a lower convective mass transport of impurities in the molten zone in space [5].…”

Formation and Characterization of TiO2/CNT Nanomaterials Dried under Supergravity Conditions

“…Materials processing in centrifuges have two interesting motivations: first, opportunities for production of unique and improved materials that cannot be prepared under normal earth conditions or in space; second, such research improves our understanding of the influence of acceleration and thermophysical mechanisms on materials processing. Research on processing materials in high gravity has been increased in the last twenty years due to the fact that even a modest increase in acceleration gives dramatic effects on the physical properties of the materials [1]. Few examples are the improved compositional homogeneity of semiconductors [2,3]: the increased nucleation rates, growth rates, and coverage area for diamond film deposition [4,5]; the improved quality of protein and high-energy crystals [6]; the large-scale production of nanoparticles [7,8].…”

Invariant and univariant eutectic solidification in ternary alloys

“…The thermal buoyancy can be negated by orienting directional growth antiparallel to the gravity, since the less dense fluid will then float over the colder one which at the solid/liquid interface. Although there are contradictory reports in the literature on the effect of convection on coupled growth [135][136][137][138][139][140][141][142][143][144], due to very limited solute boundary layer, regular binary eutectics are not much affected from the effect of convection.…”