The free growth of ice crystals in supercooled bulk water containing an impurity of glycoprotein, a bio-macromolecule that functions as ‘antifreeze’ in living organisms in a subzero environment, was observed under microgravity conditions on the International Space Station. We observed the acceleration and oscillation of the normal growth rates as a result of the interfacial adsorption of these protein molecules, which is a newly discovered impurity effect for crystal growth. As the convection caused by gravity may mitigate or modify this effect, secure observations of this effect were first made possible by continuous measurements of normal growth rates under long-term microgravity condition realized only in the spacecraft. Our findings will lead to a better understanding of a novel kinetic process for growth oscillation in relation to growth promotion due to the adsorption of protein molecules and will shed light on the role that crystal growth kinetics has in the onset of the mysterious antifreeze effect in living organisms, namely, how this protein may prevent fish freezing.
Understanding the liquid structure provides information that is crucial to uncovering the nature of the glass-liquid transition. We apply an aerodynamic levitation technique and high-energy X-rays to liquid (l)-Er 2 O 3 to discover its structure. The sample densities are measured by electrostatic levitation at the International Space Station. Liquid Er 2 O 3 displays a very sharp diffraction peak (principal peak). Applying a combined reverse Monte Carlomolecular dynamics approach, the simulations produce an Er-O coordination number of 6.1, which is comparable to that of another nonglass-forming liquid, l-ZrO 2. The atomic structure of l-Er 2 O 3 comprises distorted OEr 4 tetraclusters in nearly linear arrangements, as manifested by a prominent peak observed at~180°in the Er-O-Er bond angle distribution. This structural feature gives rise to long periodicity corresponding to the sharp principal peak in the X-ray diffraction data. A persistent homology analysis suggests that l-Er 2 O 3 is homologically similar to the crystalline phase. Moreover, electronic structure calculations show that l-Er 2 O 3 has a modest band gap of 0.6 eV that is significantly reduced from the crystalline phase due to the tetracluster distortions. The estimated viscosity is very low above the melting point for l-ZrO 2 , and the material can be described as an extremely fragile liquid.
Density of gadolinium oxide in its liquid phase was measured using a containerless technique under microgravity environment in the International Space Station (ISS). An electrostatically levitated sample was melted using high power semiconductor lasers. Pictures of a molten spherical sample were analyzed and corresponding volumes were obtained as afunction of temperature. After weighing the returned sample mass, the density of the Gd2O3 was found to be 7240 kg/m3 at its melting temperature (Tm = 2693 K).
The use of levitation (containerless) techniques can enable new scientific discoveries because deeply undercooled and metastable liquids can be achieved over a wide temperature range. This review article summarizes the state-of-art instrumentation for structure measurements at synchrotron radiation/neutron sources and for thermophysical property measurements not only on the ground but also in microgravity utilizing the International Space Station (ISS). Furthermore, we introduce recent scientific topics on high-temperature oxide liquids and oxide glasses synthesized from levitated undercooled liquids by the use of quantum beam measurements analyzed using advanced computation.
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