| 摘要 |
An article of uranium monocarbide is produced by heating an approximately stoichiometric mixture of carbon and uranium powders in a mould at or near vacuum pressure, from a first temperature at which uranium hydride (UH3) decomposes (about 250 DEG C.) to a final temperature at which solid phase diffusion of the uranium monocarbide takes place (about 1200 DEG C.), the heating being carried out at different rates between successively higher temperatures, and the article being then cooled and removed from the mould. Prior to the heating the mixture of powders may be mechanically packed in the mould, e.g. by vibration, until its density is 5 grams/c.c. The heating may comprise the following steps:-(a) preheating from ambient temperature to the initial temperature of about 250 DEG C., e.g. at 100 DEG C. per hour, (b) heating from about 250 DEG C. to about 450 DEG C. at a fast rate, e.g. 200 DEG C. per hour, (c) heating from about 450 DEG C. to about 900 DEG C. at a slower rate, e.g. 100 DEG C. per hour, and (d) finally heating to about 1200 DEG C. at a fast rate, e.g. 200 DEG C. per hour. Stage (c) may be divided into two parts, i.e. heating from 450 DEG C. to 750 DEG C. at 100 DEG C. per hour and then from 750 DEG C. to 900 DEG C. at 50 DEG C. per hour. The article is maintained at the final temperature for about 2 hours and may be cooled at the rate of 300 DEG C. per hour. The density of the finished product is about 7,5 grams/c.c., and the density may be further increased by electrothermal treatment, e.g. by electromagnetic induction, by the Joule effect, or by treatment in tanks in which the article acts as an electrode. |
