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Re: nike sb (Score: 0)
by Anonymous on Tuesday, February 23, 2010 @ 20:49:25 CST | Hafnium is a shiny, silvery, ductile metal that is corrosion-resistant and chemically similar to zirconium. The melting points and boiling points of the compounds and the solubility in solvents are the major differences in the chemistry of these twin elements. The physical properties of hafnium metal samples are markedly affected by zirconium impurities, as these two elements are among the most difficult ones to separate because of their tantalum [www.stanfordmaterials.com] chemical similarity. A notable physical difference between them is their density ( zirconium [www.stanfordmaterials.com] being about half as dense as hafnium). The metal is resistant to concentrated alkalis, but halogens react with it to form hafnium tetra halides. As a tetravalent transition metal, hafnium [www.stanfordmaterials.com] forms various inorganic compounds, generally in the oxidation state of +4. The chemistry of hafnium is so similar to that of zirconium that a separation on chemical reactions was not possible, only the physical properties of the compounds differ.
Zirconium silicate is used for manufacturing refractory materials for applications where resistance to corrosion by alkali materials is required. Another use of zirconium oxide [www.stanfordmaterials.com] is as beads for milling and grinding. In enamels and glazes it serves as an pacifier. It is also used in production of some ceramics, enamels, and ceramic glazes grinding media [www.stanfordmaterials.com]. It is able to be also present in some cements. Thin films of zirconium silicate and YSZ [www.stanfordmaterials.com] hafnium silicate produced by chemical vapor deposition, most often MOCVD, can be used as a high-k dielectric as a replacement for silicon dioxide in semiconductors. |
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