Borides from boron oxide

Hafnium Boride. Hafnium diboride [12007-23-7] HfB2, is a gray crystalline soHd. It is usually prepared by the reaction of hafnium oxide with carbon and either boron oxide or boron carbide, but it can also be prepared from mixtures of hafnium tetrachloride, boron trichloride, and hydrogen above 2000°C, or by direct synthesis from the elements. Hafnium diboride is attacked by hydrofluoric acid but is resistant to nearly all other reagents at room temperature. Hafnium dodecaboride [32342-52-2] has been prepared by direct synthesis from the elements (56). 

The main chemical products produced from these minerals are (a) boron oxides, boric acid and borates, (b) esters of boric acid, (c) refractory boron compounds (borides, eu .), (d) boron halides, (e) boranes and carbaboranes and (f) organoboranes. The main industrial and domestic uses of boron compounds in Europe (USA in parentheses) are ... 

Titanium borides have been reviewed66,67 and optimum conditions given for then-preparation from boron and titanium oxides.68 Electrolysis of a solution containing cryolite, NaOH, sodium borate, NaCl, and rutile at 1100°C results in the crystallization of TiB2 at the cathode.69 Mixtures of boride and nitride phases are formed during the interaction of BN with TiB2 at 1200—2000 °C.70... 

Borides of Nb and Ta have been reviewed67 and a method for their preparation from boron and metal oxide has been reported.68... 

Boron has a great affinity for oxygen and occurs in nature only in boric acid or borates. Borates are composed from clusters of flat trigonal BO3 and tetrahedral BO4 groups. The structural chemistry of borates is as rich and complicated as those of silicates, borides, or boranes. Boron oxide is an essential part of borosilicate glasses such as Pyrex. Boron halides are volatile molecular compounds. They are Lewis acids and react violently with water. The subhalides consist of boron chains or clusters that have terminally bound halogen atoms. They are substitution derivatives of the lower boranes. 

Various metal borides can be prepared by molten salt electrolysis. Frazer et al. (1975) have deposited ZrB on nickel cathode from ZrO and B Oj dissolved in molten NajAlF at 1020°C. A graphite crucible was used as anode. A series of nickel boride diffusion compounds were also noticed by electron microprobe analysis. The ZrB deposit was found to be scaly or dendritic and was usually non-adherent. Devyatkin (2001) has also obtained ZrB on nickel cathode from cryolite- alumina melts containing zirconium and boron oxide. 

Devyatkin, S. V. (2001). Electrosynthesis of zirconium boride from cryolite-alumina melts containing zirconium and boron oxides. Russian Journal of Electrochemistry, 37(12), 1308-1311. doi 10.1023/A 1013295931573. 

Borides. Zirconium forms two borides zirconium diboride [12045-64-6] ZrB2, and zirconium dodecabotide [12046-91 -2] ZtB 2- Th diboride is synthesized from the elements, by vapor-phase coreduction of zirconium and boron hahdes, or by the carbothermic reduction of zirconium oxide and boron carbide boric oxide is avoided because of its relatively high vapor pressure at the reaction temperature. 

Numerous ceramics are deposited via chemical vapor deposition. Oxide, carbide, nitride, and boride films can all be produced from gas phase precursors. This section gives details on the production-scale reactions for materials that are widely produced. In addition, a survey of the latest research including novel precursors and chemical reactions is provided. The discussion begins with the mature technologies of silicon dioxide, aluminum oxide, and silicon nitride CVD. Then the focus turns to the deposition of thin films having characteristics that are attractive for future applications in microelectronics, micromachinery, and hard coatings for tools and parts. These materials include aluminum nitride, boron nitride, titanium nitride, titanium dioxide, silicon carbide, and mixed-metal oxides such as those of the perovskite structure and those used as high To superconductors. 

Boron compounds with nonmetals, i.e., boron hydrides, carbides, nitrides, oxides, silicides, and arsenides, show simple atomic structures. For example, boron nitride (BN) can be found in layered hexagonal, rhombohedral, and turbostratic or denser cubic and wurtzite-like structures, as well as in the form of nanotubes and fullerenes. Boron compounds with metalloids also differ from borides by electronic properties being semiconductors or wide-gap insulators. 

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