Composite article and related method

1. A method for making a composite, comprising:

combining a strengthening agent and an aluminum compound to form a first solution;

precipitating an Al(OH) 3 gel from the first solution by:

providing a second solution comprising ammonia and water; and

adding the first solution to the second solution while maintaining the pH of the second solution in a range of from about 8 to about 14,

wherein strengthening agent particles are dispersed within the gel;

washing the Al(OH) 3 gel with an alcohol;

contacting the Al(OH) 3 gel with a salt;

drying the Al(OH) 3 gel to form a powder;

calcining the powder to convert Al(OH) 3 to Al 2 O 3 ; and

sintering the powder to form a composite article comprising beta double prime alumina.

2. The method as defined in claim 1 , wherein contacting the Al(OH) 3 gel with an alcohol comprises removal of terminal hydroxy groups.

3. The method as defined in claim 1 , wherein the alcohol comprises methanol, ethanol, propanol, isopropanol, or a combination of two or more thereof.

4. The method as defined in claim 1 , wherein the strengthening agent comprises zirconium oxide, cerium zirconate, silicon carbide, boron carbide, titanium carbide, titanium diboride, silicon nitride, boron nitride or a combination of two or more thereof.

5. The method as defined in claim 4 , wherein the strengthening agent comprises ZrO 2 .

6. The method as defined in claim 1 , wherein combining the strengthening agent and the aluminum compound comprises:

dissolving the aluminum compound in a solvent to form an aluminum compound solution; and

ultrasonically dispersing the strengthening agent in the aluminum compound solution.

7. The method as defined in claim 1 , wherein the aluminum compound comprises aluminum nitrate, aluminium chloride, aluminum isopropoxide or aluminium-sec-butoxide.

8. The method as defined in claim 7 , wherein the aluminum compound comprises aluminum nitrate.

9. The method as defined in claim 1 , wherein the first solution is a slurry.

10. The method as defined in claim 1 , wherein the salt comprises NaOH, LiOH, or a combination of two or more thereof.

11. The method as defined in claim 1 , wherein drying the Al(OH) 3 gel comprises:

a first drying step to remove alcohol from the gel; and

a second drying step to form a powder.

12. The method as defined in claim 1 , wherein drying the gel comprises heating the gel to a temperature between about 70 degrees Celsius and about 300 degrees Celsius.

13. The method as defined in claim 1 , wherein after drying the gel the method further comprises:

calcining the powder at a temperature in a range of from about 300 degrees Celsius to about 1000 degrees Celsius.

14. The method as defined in claim 1 , wherein the powder is sintered at a temperature in a range of from about 1450 degrees Celsius to about 1650 degrees Celsius.

15. The method as defined in claim 1 , wherein the strengthening agent particles are substantially uniformly distributed within the composite.

16. The method as defined in claim 1 , wherein the composite has a density in a range of from about 70 percent to about 90 percent of theoretical density.

17. The method as defined in claim 1 , wherein the composite has a density in a range of from about 91 percent to about 100 percent of theoretical density.

18. The method as defined in claim 1 , wherein the composite comprises beta double prime Al 2 O 3 particles having an average diameter less than about 15 micrometers.

19. The method as defined in claim 1 , wherein the composite comprises strengthening agent particles having an average diameter less than about 10 micrometers.

20. The method as defined in claim 1 , wherein the composite comprises from about 10 percent to about 30 percent by volume of the strengthening agent.

21. The method as defined in claim 1 , wherein the composite comprises from about 50 percent to about 95 percent by volume of beta double prime Al 2 O 3 .