| 摘要 |
PURPOSE:To obtain blocky cubic system BN in a high yield by giving a temp. gradient to a sample so that the lower temp. part becomes a region where cubic system BN is stable and the higher temp. part becomes a region where hexagonal system BN is stable when cubic system BN is synthesized from hexagonal system BN by a static pressure method. CONSTITUTION:Sample 6 is put in container 7, and graphite cylinder 8 as a heating element is placed outside container 7. Heating is carried out by supplying an electric current to cylinder 8 through electrically conductive rings 10 and electrically conductive plates 9. A temp. gradient is given to sample 6 between central part A and peripheral part B, and heatig and pressurizing conditions are set so that lower temp. part A becomes a region where cubic system BN is stable and higher temp. part B becomes a rigion where hexagonal system BN is stable. The temp. difference between points A and B is about 100-300 deg.C. The pressure is controlled by obtaining the relation between it and additional load by a general method utilizing the transition of metal at a temp. The state is held for about 2-10min, and then container 7 is slowly cooled to shift the higher temp. side to a region where cubic system BN is stable. The slow cooling rate is <=about 20 deg.C/min. |
