Carbothermic reduction boron oxide

Research-grade material may be prepared by reaction of pelleted mixtures of titanium dioxide and boron at 1700°C in a vacuum furnace. Under these conditions, the oxygen is eliminated as a volatile boron oxide (17). Technical grade (purity > 98%) material may be made by the carbothermal reduction of titanium dioxide in the presence of boron or boron carbide. The endothermic reaction is carried out by heating briquettes made from a mixture of the reactants in electric furnaces at 2000°C (11,18,19). 

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. 

Boron carbide (B4C) is one of the hardest known materials with excellent properties of low density, very high chemical and thermal stability, and high neutron absorption cross-section. Bulk B4C is conventionally synthesized by high temperature (up to 2400 °C) reactions, such as the carbothermal reduction of boric acid or boron oxide. Nanocrystalline B4C was solvothermally synthesized in CCI4 at 600 °C (Reaction (32)). 

The carbothermic reduction processes are usually strongly endothermic and require high temperatures. For example, carbothermic reduction of uranium (U), boron (B), zirconium (Zr), niobium (Nb), and tantalum (Ta) from their oxides requires 2000 000 K and, therefore, application of thermal plasma. In most plasma-chemical carbothermic reduction processes, an arc electrode is prepared from well-mixed and pressed oxide and carbon particles. The arc provides heating of the mixture, stimulating the reduction process on the electrode. Carbon oxides leave the electrode, finalizing the reduction process. 

Boron carbide powder is produced on a technical scale by the carbothermic reduction of boron oxide with graphite or petroleum coke... 

Joly [21] reported the preparation of boron carbide in 1883, labeling the product as B3C, whilst in 1899 Moisson [22] labeled the compound as BeC. Yet, another 50 years passed until Ridgeway [23] suggested the stoichiometry to be 4 to 1. Today, it is well established that the composition of boron carbide has no exact stoichiometric composition but ranges from B4 3C to B10.4C. The composition of commercially produced boron carbide, using the carbothermal reduction of boron oxide in arc furnaces, is usually close to B4C, which corresponds to the stoichiometric limit on the high-carbon side. 

The high-volume production of boron carbide powder was made available by the carbothermal reduction of boron oxide in huge electric arc or resistance furnaces. 

In order to synthesize boron carbide nanostructures, several techniques have been developed which include CNT template-mediated growth [149-152], CVD, and plasma-enhanced CVD (PECVD) [147,153,154], carbothermal reductions of boron oxides [155-159], a porous alumina templating technique [160], and electrostatic... 

Our work aims to developed a scientific and engineering background in the production of Nickel boron alloys (NiB) which can be used as a brazing material, wear-corrosion-oxidation resistive applications via carbothermic reduction that is the effective and attractive process technique regarding high mass of production for industry such as brazing, automotive, electronics, aircrafts, coatings etc. 

Alizadeh, A., Taheri-Nassaj, E., Ehsani, N., and Baharvandi, H.R. (2005) Production of boron carbide powder by carbothermic reduction from boron oxide and petroleum coke or carbon active. 

Carbide and nitride powders are conventionally prepared by the carboreduction of oxide powder with subsequent nitridation in a nitrogen atmosphere or carborization in an inert gas. Diboride powders are synthesized by carbothermal reduction, where boron needs to form the boride and carbon aids in the removal of oxygen. These processes require a high temperature and a long heating time. Fine powders of these compounds are prepared by the thermite method by reduction with Mg. 

A powder with good characteristics (high purity, good homogeneity, fine particle size, narrow particle size distribution, absence of hard agglomerates) is a must to get the desired properties and microstructure in the final component and thus synthesis of high quality powder is extremely important. Powders of ZrB and HfB are synthesized by (a) reaction between elements (Brochu et al., 2008 Tamburini et al., 2008) (b) borothermic reduction of metal oxide (Peshev et al., 1968), (c) boron carbide reduction of metal oxide in presence of carbon (Sonber et al, 2010 2011) (d) carbothermic reduction of metal oxide and B Oj (Fahrenholtz et al., 2007) (e) Metallothermic reduction of metal oxide and B Oj (Setoudeh et al., 2006 Kobayashi et al., 1993),(f) molten salt electrolysis (Frazer et al.,1975) (g) solution based techniques (Yan et al., 2006) and (h) s3mthesis from polymer precursors (Suetal., 1991). 

Carbothermic Reduction of Metal Oxide and Boron Oxide... 

Metal borides are generally prepared by the direct reaction of the elanents at high temperatures or by the reduction of metal oxides or halides. Thus, reduction of mixtures of BjOj and metal oxides by carbothermic reaction yields metal borides. Reaction of metal oxides with boron or with a mixture of carbon and boron carbide is another route. Some metal borides are prepared by fused salt electrolysis (e.g. TaBj). Borides of IVA-VIIA elements as well as ternary borides have been reviewed by Nowomy [1], The method employed to prepare TiB starting with TiCl is interesting [2], TiCl and BCI3 react with sodium in a nonpolar solvent (e.g. heptane) to produce an amorphous precursor powder along with NaCl. NaCl is distilled off and the precursor crystallized at relatively low temperatures (-970 K). 

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