| 摘要 |
Carbonizing refractory moulds by exposing the moulds to a carbonizing material while heated to a critical temperature range extending from the minimum temperature required for dissociation of the carbonizing material to a higher temperature which is below the lowest temperature at which the carbonizing material dissociates to form soot. The preferred mould structure is made by forming a slurry containing refractory material, a binder and a gelling agent which is then heated to form a crazed structure. The crazed structure is strengthened by the addition of a further binder and the strengthened structure is carbonized. Also disclosed are moulds formed from a mixture of a refractory material and a silicate solution which is hardened by means of carbon dioxide before being impregnated with the pyrolytic graphite. In another embodiment, a phosphoric acid bond is formed in addition to carbonizing by impregnating the mould with a furfuryl alcohol solution containing 2 percent by volume phosphoric acid and then heating to 1000 DEG C. or higher in an inert atmosphere.
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