INNOVACERA

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Materials

Boron Nitride

Boron Nitride Introductions
Boron Nitride[10043-11-5], exists as three different poly-morphs:
Alpha-boron nitride(α-BN), a soft and ductile polymorph with a hexagonal crystal lattice similar to that of graphite, also called hexagonal boron nitride(HBN) or white graphite;
Beta-boron nitride(β-BN), the hardest manmade material and densest polymorph, with a cubic crystal lattice similar to that of diamond, also called cubic boron nitride(CBN) or borazon;
Pyrolitic boron nitride(PBN), from a chemical point of view, boron nitride oxidizes readily in air at temperatures above 1100°C, forming a thing protective layer of boric acid(H3BO3) on its surface that prevents further oxidation as long as it coats the material. Boron nitride is stable in reducing atmospheres up to 1500°C.

INNOVACERA Material Grades
HPBN
High purity hot pressed boron nitrides
Diffusion bonded (no binder)
Low dielectric constant & loss tangent
Minimal moisture pick-up
Chemically purified
Thermally purified

ZRBN
Boric oxide binder
Highest density
Highest strength

CABN
Calcium borate binder
High density
Best moisture resistance

Thermal Management
The unique combination of excellent electrical insulation and thermal conductivity makes BN very useful as a heat sink in high power electronic applications. Its properties compare favorably with beryllium oxide, aluminum oxide and other electronic packaging materials, yet is easier to form and finish.

High Temperature Environments
Temperature stability and excellent resistance to thermal shock makes BN the material of choice in the toughest high temperature environments such as equipment for plasma arc welding, diffusion source wafers, and semiconductor crystal growth equipment & processing.

Molten Metal Handling
BN is inorganic, inert, nonreactive with halide salts and reagents, and is not wet by most molten metals and slags. These characteristics, combined with low thermal expansion, make it ideal for interface materials used in various molten metal processes.

Industrial Preparation
Cubic BN or Borazon, is produced by subjecting hexagonal BN to extreme pressure and heat in a process similar that used to produce synthetic diamonds.Melting of either phase is possible only with a high nitrogen over pressure. The alpha-phase decomposes above 2700°C. at atmospheric pressure and at ca.1980°C in a vacuum.
Hexagonal BN is manufactured using hot pressing or pyrolytic deposition techniques.These processes cause orientation of the hexagonal crystals, resulting in varying degrees of anisotropy. There is one pyrolytic technique that forms a random crystal orientation and an isotropic body; however, the density reaches only 50 to 60% of the theoretical density. Both manufacturing processes yield high purity, usually greater than 99wt.% BN. The major impurity in the hot-pressed materials is boric oxide, which tends to hydrolyze in the presence of water, degrading the dielectric and thermal-shock properties of the material. The addition of calcia reduces the water absorption. Hexagonal hot-pressed BN is available in a variety of sizes and shapes, while the pyrolytic hexagonal materials is currently available in thin layers only.

Sourcing: Francois Cardarelli 2008 Springer London [Materials Handbook, A Concise Desktop Reference] 2nd Edition ISBN 978-7-5603-4451-5