Titanium boride

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CASNo = 12045-63-5
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Formula = TiB₂
MolarMass = 69.5 g/mol
Appearance = metallic grey
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CrystalStruct = Hexagonal, Space group P6/mmm. Lattice parameters at room temperature: "a"=302.36 pm, "C"=322.04 pm
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Titanium Diboride (chemical formula TiB₂) is an extremely hard ceramic compound (33 GPa) composed of titanium and boron that has very good wear resistance. It is resistant to oxidation in air at temperatures up to 1000C, and to hydrochloric and hydrofluoric acids, but reacts with alkalis, nitric acid and sulphuric acid. Unusually for a ceramic, it is a reasonable electrical conductor (about 10⁵ Siemens per centimetre), so can be used as an anode material in aluminium smelting; this also means it can be shaped by electrical discharge machining.

It does not occur naturally in the earth; syntheses include heating a mixture of titanium dioxide and boron carbide to high temperature, followed by mechanical grinding, or reduction by the thermite reaction of a mixture of titanium dioxide, boron oxide and magnesium powders followed by dissolving magnesium oxide from the reaction mix [http://gtresearchnews.gatech.edu/newsrelease/TIB2.html] which produces a finer powder.

Many TiB₂ applications are inhibited by economic factors, particularly the costs of densifying a high melting point material - the melting point is about 2970C, and, thanks to a layer of titanium dioxide that forms on the surface of the particles of a powder, it is very resistant to sintering, though an admixture of about 10% silicon nitride helps with this [http://www.patentgenius.com/patent/6420294.html] . Current use of this material appears to be limited to specialized applications in such areas as impact resistant armor, cutting tools, crucibles and wear resistant coatings. It is also used as an inoculant to refine the grain size when casting aluminium alloys.

Thin films of TiB₂ have a wide range of potential industrial applications due to the wear and corrosion resistance properties that TiB₂ can provide to a cheap and/or tough substrate. The electroplating of TiB₂ layers possess two main advantages compared with plasma (PVD, CVD) methods: the growing rate of the layer is 200 times higher (up to 5 μm·s⁻¹) and the inconveniences of covering complex shaped products are dramatically reduced.