| 摘要 |
<p>1430144 Ceramic material BABCOCK & WILCOX CO 19 April 1973 [12 May 1972] 19159/73 Heading C1A A ceramic material comprises grains of sintered aluminium oxide having grains with a size distribution observed on a fracture surface with a scanning electron microscope at 10,000 magnifications as follows: less than 0À3 Á = 0%, between 0À3 and 0À5 Á = 25%, between 0À3 and 0À7 Á = 54%, between 0À3 and 0À9 Á = 80% and between 0À3 and 1À5 Á = 100%. A suitable method of converting a sinterable powder into a fine grain ceramic metal oxide of the above type comprises a first step of heating the powder to a temperature that produces an onset of powder shrinkage, a step of applying a maximum process physical pressure to the powder with the onset of shrinkage, a step of raising the temperature of the powder, with the onset of shrinkage, at a lower rate than the first heating step, to a temperature of more than 800‹ C. and holding the pressure and attained temperature for more than two minutes. It is preferred to heat the powder in the first heating step to more than 400‹ C. at a rate of at least 400‹ C. per minute and to use a maximum hot process pressure of 2000-6000 lbs./sq. inch. The preparation of Al 2 O 3 and UO 2 ceramic materials are exemplified.</p> |
