| 摘要 |
PURPOSE:The addition of a Ca-containing compound to starting materials for synthesizing boron nitride is followed by heat treatment to cause nitridation and from a complete mixture of the boron nitride and the Ca-containing compound whereby hexagonal boron nitride with good sintering properties is obtained. CONSTITUTION:A mixture of a boron compound such as boric acid, ammonium borate and a nitrogen compound such as urea, ammonium chloride is combined with a Ca-containing compound such as its carbonate, hydroxide or oxide and the resultant mixture is heat-treated in a non-oxidative atmosphere at 250-600 deg.C to form lumps of the product. The product is crushed into particles of less than 50mm particle sizes, then the particles are heated in a non-oxidative atmosphere at 800-1,200 deg.C to obtain hexagonal boron nitride containing calcium compounds less than 9%, calculated as Ca atom and showing good sintering properties. The sintering process is preferably effected in a non-oxidative atmosphere under reduced pressure. |
