HOLLOW CARBONACEOUS MICROSPHERES FOR USE IN CARBON MICROPHONES

摘要

1366159 Aftertreated carbonaceous microspheres KUREHA KAGAKU KOGYO KK 22 Dec 1971 [29 Dec 1970] 59658/71 Heading C1A Hollow carbonaceous microspheres having a particle size of 50 to 1000 Á, a wall thickness of 2 to 50 Á and a particle density of 0À15 to 1À0 g./c.c. are heat-treated at a temperature of 900‹ to 2000‹ C. in an inert or carbonizing atmosphere. The atmosphere may be nitrogen, argon or helium, or a gaseous organic aliphatic or aromatic hydrocarbon. The starting microspheres are preferably made as described in Specification 1,318,324 and the aftertreated product used in electro-acoustic transducers.