Crystals high-purity-metal

Fractional crystallization processes are also used commercially to produce high purity metal from lower grade alurninum. These processes rely on the... 

Crystals of high purity metals are very soft, while high purity diamond crystals are very hard. Why are they different What features of the atomic (molecular) structures of materials determine how hard any particular crystal, or aggregate of crystals, is Not only are crystals of the chemical elements to be considered, but also compounds and alloys. Glasses can also be quite hard. Is it for similar reasons What about polymeric materials ... 

Due to the great similarity of the chemical properties of the rare earth elements, their separation represented, especially in the past, one of the most difficult problems in metallic chemistry. Two principal types of process are available for the extraction of rare earth elements (i) solid-liquid systems using fractional precipitation, crystallization or ion exchange (ii) liquid-liquid systems using solvent extraction. The rare earth metals are produced by metallothermic reduction (high purity metals are obtained) and by molten electrolysis. 

Available forms (1) Chromium metal as lumps, granules, or powder (2) high- or low-carbon ferro-chromium (3) single crystals, high-purity crystals, or powder run 99.97% pure. 

Optical crystals of high purity lithium fluoride are grown by use of the Stockbarger process (10) in sizes to 25 cm dia x 25 cm high (14). Typical commercial material contains 99.2% LiF typical impurities include Li CO and Fe202 at <0.1% levels, and and heavy metals as Pb at <0.01%... 

The most widely employed thermal reduction process for preparing Mg metal uses PeSi as reducing agent. Mixtures of the substrate, usually calcined dolomite (i.e., MgO, CaO) and PeSi are fabricated into briquettes with a hydrocarbon binder and loaded into Ni-Cr steel (15/28) retorts. After evacuation the retort is subjected to a temperature gradient Mg distills from the hot mixture (at 1150°C) and high-purity Mg crystals collect at the water-cooled end of the retort ... 

Thorium sulfate, being less soluble than rare earth metals sulfates, can be separated by fractional crystallization. Usually, solvent extraction methods are applied to obtain high purity thorium and for separation from rare earths. In many solvent extraction processes, an aqueous solution of tributyl phosphate is the extraction solvent of choice. 

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