The authors have performed crystal growth experiments on the NASA Long duration Exposure Facility. The crystal growth process investigated is a solute diffusion process, in which liquid reactant solutions diffuse into pure solvent and react chemically to form single crystals. They grew CaCO3 (calcite-type) single crystals from solutions of CaCl2 and NH4HCO3 in water, and TTF-TCNQ single crystals from solutions of TTF and TCNQ in acetonitrile. The CaCO3 experiment produced numerous clear, well-formed single or twinned crystals ranging between 1 and 6 mm in longest dimension, which is substantially larger than previous solution growth results. These crystals have an acute scalenohedral habit very different from the habits that we have obtained previously. Their habit is like that of some natural calcite crytals, but very unlike the familiar rhombohedral habit if Iceland spar. The twinning is like that of natural calcite. The TTF-TCNQ experiment also produced numerous well formed single crystals. They are smmaller than the largest crystals grown previously, but are adequate in size and quality from analysis. Their habit is also very different from that obtained previously. The crystals are thin rectangular plates with the crystallographic b axis perpendicular to the plate.That is contrary to all our previous crystals growth experiments, in which the b axis has been the preferred direction of growth.
Crystal growth by solute diffusion in earth-orbit
Kristallwachstum durch Lösungsdiffusion im Erdorbit
1991
12 Seiten, 5 Bilder, 1 Tabelle, 17 Quellen
Conference paper
English
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