Undercooled fluids

According to H. Bruhl, the melting point of lithium chlorate, LiC103. H20, is 63°-65°—A. Potilitzin gives 50° the molten mass readily forms an undercooled fluid. The hydrate becomes anhydrous in dry air at 90°, and melts at 129°. Lithium chlorate begins to decompose at 270°, and at higher temp, the decomposition is more rapid. The rate of decomposition reaches a maximum with rise of temp.,... 

Hatley RHM, Franks F, Day H, Byth B. Subzero temperature preservation of reactive fluids in the undercooled state. I. The reduction of potassium ferricya-nide by potassium cyanide. Biophys Chem 1986a 24 41-46. 

Liquid carbon dioxide (purity 99, 95 Vol %) was undercooled (W2) to avoid cavitation in the membran pump (P). After the compression to pre-expansion pressure, the fluid is heated to the extraction temperature (W3). The supercritical fluid loaded with anthracene leaves the extractor (V = 0,6 1). With a additional heat exchanger (W4), the solution is heated to pre-expansion temperature. In the separation vessel, the supercritical solution is expanded through a nozzle. The expanded gas will be condensed (Wl) and recompressed or let off. After the experiment, the separation vessel is opened and the particles were collected. The particle size is measured by laser diffraction spectroscopy (Malvern Master Sizer X). 

Figure 11 Undercooling and droplet freezing of water in saline solution ( ), aqueous solution of polygalacturonic acid (k.), fluids extracted from the efflorescence of L. telekii (M) and their polysaccharide fraction (o). Reproduced with permission from the Royal Society of Chemistry from Franks" ...

Because of the multiplicity of phases (any of which may be more fluid or more undercooled than the homogeneous system) and the extensive interfacial boundary, after phase separation one (or more) of the phases is likely to be more unstable with respect to crystallization than was the initially homogeneous system. Thus phase separation can result in enhanced crystallization kinetics. Cahn (1969) also describes conditions in which crystallization must be preceded by phase separation the crystallization being thermodynamically prohibited until phase separation occurs. 

Fig. 2 Schematic phase diagram of a single flexible polymer chain in the thermodynamic limit (Af —> Qo) as a function of temperature T and range of attractive monomer-monomer interaction X. For 2 > At, there occurs a transition at T = 6 X) from the swollen coil to the collapsed fluid globule. At TcystCiV = < ) the globule crystalhzes. Due to slow crystallization kinetics, this transition may be undercooled and at FcystW the collapsed globule freezes into a glassy slate. Since it was assumed that the transition lines vary linearly with the interaction volume A, A rather than A has been chosen as an abscissa variable. Adapted from Binder et al. [4]...

Glass is a transparent, sometimes colored, inorganic material, which is fragile and predominantly noncrystalline. It has no well-defined melting point, but with continuous heating, it changes from being viscous to a soft and finally thin fluid state (i.e., an undercooled melt without crystallization). 

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