Metal melting-point depression

The behavior of K2Tip6 in the alkali metal halides LiP, NaP, LiCl, NaCl, KCl, and in the LiCl-KCl and LiP-LiCl eutectic mixtures was studied using the cryoscopic method by Danbk et al. (1975). The experimentally determined dependency of the melting point depression on molality and molar fraction of K2T1P6, in the proximity of the melting point of the above mentioned solvents were compared with the liquidus curves calculated according to the equation... 

Melting endotherms Melting point depression Melting temperature, Memory effect Metal plating Metallocene catalyst... 

An opinion which is frequently voiced as far as nanofibers formation by electrospinning is concerned is that the structure in nanofibers and the properties of the growing crystals should deviate strongly from the one of bulk systems due to rapid structure formation and confinement effects imposed by the small diameter of the fibers. Melting point depressions originating from a reduction in size of the crystals are well known from metals or semi-conductor systems. Yet, no such effects actually seem to be of general significance in electrospun polymer nanofibers. One has to take into account in this con-... 

It is usual to use a mixture of salts (in the case of sodium, 60% NaCl + 40% CaCy so as to depress the melting point and permit electrolysis at a lower temperature (600 °C, instead of 801 °C for pure NaCl), but obviously the second metal ion (Ca2+) must be less readily reduced than the one of interest. 

Sodium metal is produced by the electrolysis of molten rock salt (impure sodium chloride) and calcium chloride. Calcium chloride lowers the melting point of sodium chloride (recall freezing point depression), increasing the energy efficiency of the process. 

The simplest approach to obtain ILs from natural sources is surely the direct use of quaternary ammonium salts. Choline chloride, a salt melting at 302 °C, has been transformed recently by Davies and co-workers in a fluid at room temperature by mixing the organic salt with metal chlorides or other simple organic compounds (such as, urea or polyalcohols), which depress the melting point producing liquids with significant ionic character (Scheme 2). These liquids systems are known as eutectic mixtures. 

The starting point for the analysis of the freezing-point depression phenomenon is the observation that when a solid freezes out from a mixture, it generally is pure and it is the component that is concentrated in the solution, that is, the pure solvent. [Indeed, this is the basis for zone refining, in which melting and resolidification (or recrystallization) are used to purify metals.] The equilibrium condition when the first crystal of pure solvent forms is... 

Liquid solutions usually freeze at lower temperatures than the pure liquids, with the freezing point depression (for aqueous solutions) being directly related to the amount of solute dissolved. Certain proportions of two metals often freeze at a temperature much lower than for other proportions. The proportions of these two metals that freeze at the minimum temperature is called the eutectic mixture. One useful eutectic mixture is tin/lead in a 60/40 mixture. Pure lead melts at 327°C pure tin melts at 232°C. The 60/40 mixture, called solder, melts at 190°C, lower than for either metal alone. For this reason, 60/40 solder is often used for constructing electric circuits. 

Molten metal poured above its melting point is chilled at the walls and bottom of the ingot mold and begins to solidify. The molten metal in the center cools more slowly and contracts as it cools. As the metal solidifies at the exterior of the molten zone and contraction continues a depression or in its worst condition a pipe develops in the center of the ingot. 

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