Directional solidification advantages

In directional solidification, growth occurs in close contact with the crucible, and if the expansion coefficient of the crucible material differs from that of the crystal, severe stresses may be induced during cooling, especially when the expansion is anisotropic The advantage is that the crucible may be sealed to permit the growth of crystals of volatile materials. It has also been used for refractories that do not require a sealed crucible, as in the examples shown in Table 1. ... 

Principal advantages of gas-pressure infiltration over other mechanically driven pressure infiltration processes are that infiltration parameters are controlled with precision and that weak molds can be used, which can be used to minimise impurities in the composite. It is thus an attractive method for academic research however, it is also used industrially, to produce electronic substrates for example. After infiltration, the metal is solidified. We use directional solidification, induced by lowering the mold onto a chill (Fig. 1), to avoid shrinkage cavity formation in the composite. The applied... 

The most suitable solvents for extracting SPA from fats are acetonitrile (113,125,126, 139,142) and water-alcohol mixtures. The fat is usually dissolved in hexane or petroleum ether, and SPA are extracted into acetonitrile (105,110-113,125,126,128). The disadvantages of acetonitrile extraction are that (a) BHT recovery is low and (b) moderately high levels of interfering compounds are coextracted. The advantage of aqueous methanolic extraction of SPA from nonpolar solvent is that the fat is mostly excluded (99,114). Hammond (99) described a methanolic extraction of a melted fat sample, heated to 40-50°C, followed by transfer of the mixture to a deep freeze for a few hours to aid the solidification of any excess fat from methanol. The methanol layer was then decanted and filtered prior to the addition of an internal standard and direct injection. 

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