Prepn. of composite for electrodes at high temps. - by hot-isostatically pressing an electrically conducting material with a ceramic material

摘要

Prepn. of a composite (I) comprises an initial material, esp. an electrically conducting material, and at least one further ceramic material, esp. an electrically non-conducting material. The novelty is that the initial material and the ceramic material are hot-isostatically pressed together. Pref. the electrically conducting material is selected from carbon, MoSI2, B4C, SiC, metals or their mixt. Carbon is used in the form of graphite carbon or carbon-fibre reinforced carbon. The ceramic material is selected from boron nitride, aluminium nitride, oxides, nitrides or their mixt. pref. hexagonal boron nitride. A defined electrical resistance in the ceramic material is achieved by adding up to 10 wt.% conducting material. The first material together with the ceramic material is surrounded by a gas-tight shell. The shell is evacuated and the material within it is subjected to 30-200 MPa and 1000-2500 deg.C. After isostatistical pressing, the shell is melted by increasing the temp. above the m.p. of the shell material. During hot-isostatistical pressing, the first moulding is used as the solid which is surrounded by a powder forming the ceramic moulding. An additional material is applied between the materials to improve diffusion. USE/ADVANTAGE - (I) is used as electrodes at high temps. It is prepd. inexpensively and exhibits strong adhesion over the whole composite zone. It has sufficient electrical insulation.