Process for producing platelet .alpha.-Al.sub.2 O.sub.3 based ceramic composite
AssigneeMitsubishi Materials Corporation
InventorsTakashi Koyama, Koichi Niihara
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Abstract
A platelet .alpha.-Al.sub.2 O.sub.3 based ceramic composite consists of Al.sub.2 O.sub.3 powder, promoters and controllers. The composite is prepared by mixing aluminum oxide powder with promoters and controllers. The mixture is shaped and sintered to form an object. In one embodiment of the invention, the promoters are either salts or oxides of alkaline metals and alkaline earth metals. The salts are oxidized during sintering.
Claims14
A process for producing platelet .alpha.-Al.sub.2 O.sub.3 based ceramic composite, which comprises:
- blending Al.sub.2 O.sub.3 powder with from 0.02 to 4 weight percent of a first additive for promoting platelet formation in .alpha.-Al.sub.2 O.sub.3 grains, wherein said first additive is at least one oxide of a member selected from the group, consisting of Li, K, Na, Ca, Sr, Si, and Ba;
- adding from 5 to 40 weight percent of a second additive for controlling grain growth of said .alpha.-Al.sub.2 O.sub.3 platelets, wherein said second additive is at least one member selected from the group consisting of ZrO.sub.2 HfO.sub.2, SiC whiskers, SiC particles and carbides, nitrides or carbonitrides of IVa, Va or VIa metals;
- said Al.sub.2 O.sub.3, said first additive and said second additive forming a mixture;
- and
- sintering said mixture to produce said platelet .alpha.-Al.sub.2 O.sub.3 based ceramic composite.
A process for producing platelet .alpha.-Al.sub.2 O.sub.3 based ceramic composite, comprising:
- blending Al.sub.2 O.sub.3 powder with from 0.02 to 4 weight percent of a first additive for promoting platelet formation in .alpha.-Al.sub.2 O.sub.3 grains and from 5 to 40 weight percent of a second additive for controlling grain growth of said .alpha.-Al.sub.2 O.sub.3 selected from the group consisting of ZrO.sub.2, HfO.sub.2, SiC whickers, SiC particles and carbides, nitrides or carbonitrides of IVa, Va and VIa metals, to form a raw powder composition;
- said first additive is selected from the group consisting of salts of alkali metals, salts of alkaline earth metals which upon heating decompose into oxides, SiO.sub.2 and a compound which produces SiO.sub.2 ;
- heat treating a portion said raw powder composition at a temperature 1000.degree. C. to about 1500.degree. C., to produce a liquid phase component;
- grinding said liquid phase component to produce a liquid phase powder;
- mixing the remainder of said raw powder composition and said liquid phase powder forming a powder shape;
- and
- sintering said powder shape to produce platelet .alpha.-Al.sub.2 O.sub.3 based ceramic composite.
Dependencies are inferred from the claim text.