CARBON MADE REACTION FURNACE AND PRODUCTION OF PYROLYTIC BORON NITRIDE FORMED BODY

PROBLEM TO BE SOLVED: To produce a pyrolytic boron nitride formed body free from contamination and to prolong the service life of a reaction furnace by coating at least a part of the surface of a reaction vessel and a heating heater, which constitute a carbon made reaction furnace for carrying out CVD method with a pyrolytic boron nitride film. SOLUTION: The reaction furnace 10 arranged in a water cooling chamber 17 is constituted so that the carbon made heating heater 12 and a carbon made core bar 21 at the center are provided in a carbon made reactor 11 provided with a heat insulating material 16 and if necessary, a partition heat insulating material 13 for uniformly heating is arranged between the heater 12 and the core bar 21. Boron halide and ammonia are introduced into the reactor 11 through a gas introducing pipe 14 and allowed to react with each other under a condition of about 2000 deg.C and 0.1-10 Torr to CVD-form the pyrolytic baron nitride formed body 20. In such a case, the pyrolytic boron nitride film having 10 μm to 6 mm film thickness is formed on a part of or the whole surface of the reactor 11 and/or the heater 12 by CVD method.