The preparation of high purity boron compounds products

According to the different types of products, select the method and technological conditions are different, several commonly used techniques are summarized as follows: recrystallization method. This method generally used for preparing the purity of less than 99.9% of boric acid and borate compound. The general process is dissolved the crude product in a solvent (such as water, methanol, ethanol, acetone, chloroform ), when necessary, by appropriate heating to increase solubility; and filtering the insoluble and the solution concentration or cooling, so that the solution after saturation to produce crystal. If necessary, can be conducted two crystallization or recrystallization, the more times of crystallization, the more purity of the product, but the cost increased. Boric acid recrystallization in dissolving tank with a temperature of 95 DEG C, after ion exchange resin processing industrial boric acid mother liquor to dissolve, solution using sand stick filter, liquid cooling crystallization, precipitation boric acid crystal; centrifugal separation and removal of mother liquor of boric acid wet; crystallization and high purity saturated borate aqueous washing, removing the crystal surface adsorption the impurities in ultra-pure water for liquor, and then again after washing; air drying is finished.

Adsorption distillation method. The method is suitable for low boiling point or gaseous boron compound purification, can make the product purity over 99.999%. In two boron trichloride as the example, this material at room temperature and atmospheric pressure is a colorless, flammable corrosive, toxic gases, choking smell. Method of preparing is using crude three boron chloride as raw material, after cooling, adsorption, cryogenic distillation, collection and other processes have a purity of more than 99.999% of three boron chloride molten and zone melting method. The method is suitable for preparing carbide and boride with high melting point of boron compounds, such as boron carbide, boron nitride, zirconium diboride, titanium diboride, the purity of the product will be based on raw materials and process to adjust, under certain conditions, can make the product purity over 99.99%. The basic principle is putting the raw material into the reactor, generated the communion or zone melting under the heat, and the products because the high melting point crystallization in the melt; but some products are not through melting, at a high temperature by reaction sintering or vapor deposition can also get a certain purity boron compounds. If the raw material purity is high enough, the micro crystal purity can reach above 99.9%.

Thermal reduction method. The method is generally used for preparing boron or amorphous boron powder. According to the selection of raw materials and reducing agent is different, the purity of the obtained product is different. The main use of several kinds of reducing agent and process are: use active metal pyrogen reduction of boron oxide; by hydrogen reduction of boron halides; by carbon thermal reduction; electrolytic molten borax borate or other boron compounds of boron and hydrogen compounds; thermal decomposition. The product by the vacuum degassing or control of halogenated to get pure boron powder, can also be used as ethanol, high purity water on the amorphous boron powder to make purification process. According to metal powder exporter, in order to obtain the 99.999% purity ultra pure boron powder, a successful technique is reduced by hydrogen boron tribromide, basic steps: boron and bromine vapor in quartz distillation kettle when the temperature reached 900chemical reaction occurs: 2B+3Br2=BBr3. Place the resulting BBr3 vapor is condensed into liquid into quartz distillation tower, at 95 distillation and purification; the purified BBr3 and H2 respectively into the quartz reaction tube, at 900 reduce into boron powder, the product was dark brown, purity is greater than 99.999%.

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