Alumina-based ceramic materials and process for the production thereof
The present invention provides a process for producing a ceramic material, which comprises: (a) forming a green compact by compacting a powder comprising alumina and carbon, wherein the powder is substantially free of silicon carbide and wherein the amount of carbon present in the powder does not exceed 0.1% by weight of the powder; and (b) sintering the green compact under non-oxidising conditions to form a ceramic material comprising alumina and carbon, wherein the green compact is sintered at a temperature of less than 1550° C. Ceramic materials obtainable by said process are also provided.
1. A process for producing a ceramic material, which comprises:
(a) forming a green compact by compacting a powder comprising alumina and carbon, wherein the powder is substantially free of silicon carbide and wherein the amount of carbon present in the powder does not exceed 0.1% by weight of the powder; and
(b) sintering the green compact under non-oxidising conditions to form a ceramic material comprising alumina and carbon, wherein the green compact is sintered at a temperature of less than 1550° C.;
wherein the powder contains carbon in the form of carbon particles and wherein the ceramic material exhibits a predominantly transgranular mode of fracture.
2. A process according to claim 1 , wherein the powder comprises alumina particles having an average diameter of from about 1 nm to about 1 μm.
3. A process according to claim 1 , wherein the carbon particles have an average diameter of from about 1 nm to about 1 μm.
4. A process according to claim 3 , wherein the particles are in the form of graphite particles.
5. A process according to claim 1 , wherein the powder contains carbon in the form of an organic precursor.
6. A process according to claim 1 , wherein the carbon is present in the powder in an amount of from about 0.01% to about 0.05% by weight of the powder.
7. A process according to claim 1 , wherein the green compact is sintered at a temperature of from about 1350° C. to about 1500° C.
8. A process according to claim 1 , wherein the green compact is sintered by pressureless sintering.
9. A process according to claim 8 , wherein the green compact is sintered in vacuo.
10. A process according to claim 1 , which further comprises forming the material as, or converting the material into, a wear resistant product.
11. A process according to claim 1 , wherein the ceramic material is substantially free of discrete particles of carbon.