| 摘要 |
PURPOSE:To produce fine powder of hexagonal boron nitride having high purity and high sintering characteristic by heat-treating fine powder of crude hexagonal boron nitride having an appropriate particle size at an appropriate temp. in a specified density of layer or under reduced pressure in nonoxidizing atmosphere. CONSTITUTION:Fine powder of crude hexagonal boron nitride having <=1mum primary particle size obtd. by synthesizing from borax and urea, etc., is heat- treated at 1,500-3,000 deg.C, pref. 1,600-2,000 deg.C under 0.001-0.25g/cm<3> layer density and/or reduced pressure in nonoxidizing atmosphere such as N2, Ar, etc. By this treatment, impurities such as B2O3, borates, ammonium borate, etc., are removed by evaporation without causing the growth of the particle size. By this method, fine powder of hexagonal boron nitride having high purity of >=ca. 90wt% purity and <=1mum primary particle size is obtd.
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