| 摘要 |
The present invention relates to a process for preparing spheroidal boron carbide that is characterized in that a powder precursor consisting of boric acid, urea and carbonaceous compound adducts is brought into a stream of plasma being at least 1600 degC hot, under conditions preventing product oxidation. The flying powder product is heated to a temperature of at least 2450 degC, liquid boron carbide drops being formed are collected in a collecting vessel containing liquid nitrogen and an abruptly cooled down. The carbonaceous compound is represented by an organic monosaccharide, preferably saccharose. The precursor can be fixed on the surface or in pores of an inert powder carrier, preferably alumina or boron nitride, optionally annealed to the monosaccharide dehydration temperature. The preparation process is conditioned by prevention of the product oxidation. This can be achieved either by placing a plasma generator into a sealed cabin or by supplying the product into a cooling liquid, or enclosing the plasma stream containing the product by a protective gas (so called shrouding), or by using several plasma torches simultaneously and arranged parallel to each other so that the precursor can be supplied through the center of a plasma-formed flame. |
