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Research Containing: SCN

Precise Measurements of Dendrite Growth of Ice Crystals in Microgravity

by on 9 June 2015in Physical Sciences No comment

An ice crystal growth experiment was performed on board the International Space Station. The experiment was repeated 134 times with various undercooling conditions. Dendrite crystal growth velocity and tip radius were precisely measured by using a newly developed software. The results are compared with those obtained previously on the ground as well as with those reported by Glicksman et al. for Succinonitrile (SCN). The plot of the dimensionless velocity V as a function of the dimensionless undercooling Δ under microgravity revealed values that were consistently lower than those obtained under 1-G which indicates that thermal convection was suppressed. The plot of the dimensionless radius R0 as a function of Δ showed a less scattered value. The stability factor σ* became close to that of SCN when it was calculated using the geometrical mean radius.

Related URLs:
http://dx.doi.org/10.1007/s12217-012-9306-9

Observation of an Aligned Gas – Solid Eutectic during Controlled Directional Solidification aboard the International Space Station – Comparison with Ground-based Studies

by on 9 June 2015in Physical Sciences No comment

Direct observation of the controlled melting and solidification of succinonitrile was conducted in the glovebox facility of the International Space Station (ISS). The experimental samples were prepared on ground by filling glass tubes, 1 cm ID and approximately 30 cm in length, with pure succinonitrile (SCN) in an atmosphere of nitrogen at 450 millibar pressure for eventual processing in the Pore Formation and Mobility Investigation (PFMI) apparatus in the glovebox facility (GBX) on board the ISS. Real time visualization during controlled directional melt back of the sample showed nitrogen bubbles emerging from the interface and moving through the liquid up the imposed temperature gradient. Over a period of time these bubbles disappear by dissolving into the melt. Translation is stopped after melting back of about 9 cm of the sample, with an equilibrium solid-liquid interface established. During controlled re-solidification, aligned tubes of gas were seen growing perpendicular to the planar solid/liquid interface, inferring that the nitrogen previously dissolved into the liquid SCN was now coming out at the solid/liquid interface and forming the little studied liquid = solid + gas eutectic-type reaction. The observed structure is evaluated in terms of spacing dimensions, interface undercooling, and mechanisms for spacing adjustments. Finally, the significance of processing in a microgravity environment is ascertained in view of ground-based results.

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