| 摘要 |
1319330 Carbides KANEBO Ltd 30 Dec 1970 [23 Jan 1970] 61837/70 Heading C1A Carbide whiskers are made by heating at 800‹ C. or higher, in substantial absence of O 2 and N 2 , a mixture of containing (A) an oxide of an element of groups IIa, IIb, IIIa, IIIb, IVa, IVb (except for C), Va, Vb (except for W and P), VIa, VIb (except for O and S), VIIa or VIII, the oxide having a particle size of not more than 300 Ám; and (B) at least one organic halogen compound containing at least 10 wt. per cent halogen, the weight ratio of A to B being 90/10 to 10/90. The oxide powder may be in a pure form or may be a compound oxide e.g. feldspar or kaolin, an ore, an artificial cement or brick, or a glass. The halogen compound may be of low mol. wt. e.g. CH 3 Cl or a high mol. wt. polymer such as PVC. Many halogen compounds are specified. The oxide and halogen compound may be mixed before or after charging to the reaction system. The system may be evacuated or provided with an atmosphere of H 2 or group O element, and exhaust gases may be recycled to the system. The system may be raised to 800‹ C. or more from room temperature over a period of 3 mins. to 5 hours, and the preferred reaction time at 800‹ C. or more is also 5 mins. to 5 hours. The carbide whiskers may be condensed on a cooler surface inserted into the reaction system. Substrates of carbon, refractory oxides, carbides, nitrides and heat-resisting metals are specified. In Examples (1): silicon carbide whiskers are made at 1600‹ C. in an electric furnace from a mixture of Portland cement and benzyl chloride in an alumina crucible, the whiskers being condensed on a carbon rod; (2) titanium carbide whiskers are made at 1400‹ C. from TiO 2 and polyvinyl chloride; (3) boron carbide whiskers are made at 1800‹ C. from 1,1,2-trichloroethane and a boron-containing glass made from B 2 O 3 , V 2 O 5 and ZnO, the whiskers being condensed on an aluminium plate; (4) aluminium carbide whiskers are made from alumina and chlorinated paraffin at 1300 in a mullite tube, the whiskers being condensed on a platinum wire; (5) silicon carbide whiskers are made at 1500‹ C. in a mullite tube from silica and chlorinated paraffin; (6) Zirconium carbide whiskers are made from ZrO 2 and chlorinated polyvinyl chloride in a graphite tube at 1900‹ C., the whiskers being condensed on a graphite rod. In all the examples, the electric furnace containing the cold reactants is evacuated before heating to reaction temperature. |
