| 摘要 |
1,158,628. Aluminium nitride. PECHINEY COMPAGNIE DE PRODUITS CHEMIQUES ET ELECTROMETALLURGIQUES. 10 Aug., 1966 [10 Aug., 1965], No. 35814/66. Heading C1A. Aluminium nitride is produced practically free from impurities of iron, silicon and titanium in elementary or combined form by treating impure aluminous material such as bauxite containing silica, iron oxide and titanium oxide with carbon, sulphur, and nitrogen at a temperature rising from a minimum between 275‹ C. and 1000‹ C. to a maximum between 1600‹ C. and 1750‹ C., the quantity of carbon used being between 1 and 1.6 times the quantity required to convert the oxides of aluminium, iron, silicon and titanium present to aluminium nitride, iron, silicon and titanium respectively, the carbon being eliminated as carbon monoxide. The quantity of sulphur used is at least equal to the quantity required to convert the silicon present in the aluminous material to silicon monosulphide, and at the most equal to 1.6 times the quantity required to convert the silicon, iron and titanium into the corresponding higher sulphides, the oxygen combined with the iron and titanium being removed as sulphur dioxide. The product obtained after nitridation as described above, may be subjected to treatment with gaseous chlorine at a temperature of 200 to 650‹ C., preferably 450 to 550‹ C. The nitrogen flow in the nitridation process may be controlled in such a way as to keep the nitrogen content of the gas mixture leaving the reaction zone at least equal to that corresponding to the thermodynamic equilibrium data within the temperature range of nitridation. The residual carbon in the aluminium nitride may be eliminated substantially by selective oxidation whereby the nitride is contacted with a gas containing oxygen at a temperature in the range from 600‹ C. to 800‹ C., the optional step of chlorination being completed before the selective oxidation step. |
