| 摘要 |
1,135,713. Boron nitride. DEUTSCHE GOLDUND SILBER SCHEIDEANSTALT. 14 Feb., 1967 [19 Feb., 1966], No. 6991/67. Heading C1A. Boron nitride is prepared by reacting alkalimetal borates, or mixtures of alkali-metal oxide and alkali-metal borates or boron trioxide, with silicon and/or aluminium or their alloys in a stream of nitrogen, ammonia, or gases which give off nitrogen under reaction conditions, at 200‹ to 1200‹ C., and working up the crude product, consisting of a mixture of boron nitride and water-soluble alkali-metal salts, by treatment with water. Preferably alkali-metal borates are used whose M 2 O: B 2 O 3 ratio (M representing the alkali-metal) is such that water-soluble silicates or aluminates are formed. A sodium borate of composition Na 2 O: B 2 O 3 = 3: 2, preferably obtained from sodium tetraborate and sodium monoxide, is preferably used for the reaction with silicon, while sodium metaborate is preferably used for the reaction with aluminium. Silicon and aluminium are preferably used in a 5 to 20% deficit in relation to the borate. Specified nitrogen donors are nitrogen and ammonia gas. According to an example, the crude product from reactants Na 6 B 4 O 9 and silicon is purified, after size-reduction, by treatment with distilled water to remove soluble sodium silicate, and with dilute HC1 to remove trivalent hydroxides, e.g. Fe(OH) 3 , which may be derived from impurities in the Na 6 B 4 O 9 . |
