| 摘要 |
PROBLEM TO BE SOLVED: To obtain BN powder with a high crystallinity that has excellent shape retention and handling properties with high N2 gas permeability via bulk B2 O3 , as an intermediate, that can suitably cope with blocking of the production process by dehydrating a mixture containing an orthoboric acid powder and a carbonaceous powder having an average particle size, respectively and heating the mixture. SOLUTION: A mixture of an orthoboric acid powder with an average particle size of >=100μm, preferably >=500μm, particularly 700-1,000μm and a carbonaceous powder (for example, acetylene black), in a preferred embodiment, the average diameter of the powders other than orthoboric acid is less than 1/5 that of the orthoboric acid particle, is dehydrated, preferably at 300-450 deg.C to prepare bulk boron oxide, preferably with a density of 0.4-0.7g/cm<3> , particularly of 0.5-0.6g/cm<3> , then fired in a nitrogen atmosphere, preferably over 1,600 deg.C.
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