METHOD FOR PRODUCING GRAPHITE-TYPE BORON NITRIDE

摘要

The present invention relates to a method which comprises preparing a mixture of primary component powders, wherein said mixture contains magnesium, boron oxide and from 10 to 20 wt.% of a base additive selected from a boron-nitride synthesis product, boron nitride or magnesium oxide. The mixture of components thus prepared is placed in an envelope which is made of the same material as the base additive and which has a layer whose thickness ranges preferably from 3 to 5 mm. The mixture is then submitted to a thermal treatment according to a high-temperature self-propagating synthesis mode and under a nitrogen pressure of between 8 and 10 MPa. The graphite-type boron nitride is then extracted by processing the synthesis product in a mineral sulphuric acid at a concentration of between 10 and 26 %. An ammonia- or hydrogen-based additive can also be added to the nitrogen in an amount not exceeding 10 vol. %, while the synthesis product of boron nitride includes an amount of graphite-type boron nitride not exceeding 30 wt.%.