Synthesis of metal borides

1. A method for producing a metal boride, the method comprising:

(a) carbon-coating a first compound comprising a metal and carbon-coating a second compound comprising a boron, wherein the carbon-coating comprises

(i) decomposing a first hydrocarbon gas in the presence of the first compound so as to form a first carbon-coated compound; and

(ii) decomposing a second hydrocarbon gas in the presence of the second compound so as to form a second carbon-coated compound; and

(b) reacting the first carbon-coated compound and the second carbon-coated compound at a predetermined temperature for a predetermined time sufficient to form a metal boride;

wherein (a) occurs before (b).

2. The method of claim 1 , wherein carbon-coating the first compound and carbon-coating the second compound comprises:

(i) providing the first compound;

(ii) providing the second compound; and

(iii) decomposing the first hydrocarbon gas and the second hydrocarbon gas in the presence of the first compound and the second compound so as to form the first carbon-coated compound and the second carbon-coated compound.

3. A method according to claim 1 , wherein the first compound is selected from the group consisting of Ca, CaO, CaCO 3 , Al(OH) 3 , Al 3 (BO 3 ) 4 , Al 2 O 3 , Aluminum borohydrite, an Aluminum salt, ZrO 2 , and Al 2 O 3 .

4. A method according to claim 1 , wherein the second compound is selected from the group consisting of B, B 4 C, B 2 O 3 , and H 3 BO 3 .

5. The method of claim 1 , wherein:

the first compound comprises calcium; and

the metal boride comprises calcium hexaboride.

6. The method of claim 1 , wherein the first hydrocarbon gas or the second hydrocarbon gas is independently selected from the group consisting of methane, ethane, propane, butane, propylene, 1,3 butadiene, acetylene, allene, butene, neopentane, ethylene, methylacetylene, and natural gas.

7. The method of claim 1 , wherein carbon-coating the first compound or carbon-coating the second compound occurs at a pressure of about 15 psi to about 50 psi.

8. The method of claim 1 , wherein carbon-coating the first compound or carbon-coating the second compound occurs at a temperature of about 100 degrees C. to about 1000 degrees C.

9. The method of claim 1 , wherein carbon-coating the first compound or carbon-coating the second compound occurs in an inert atmosphere.

10. A method claim 1 , wherein

repeating carbon-coating of the first compound from about 10 to about 30 times; or

repeating carbon-coating of the second compound from about 10 to about 30 times.

11. A method of claim 10 , wherein one cycle of carbon-coating the first compound or carbon-coating the second compound, wherein the predetermined time is about 10 minutes to about 30 minutes.

12. A method according to claim 1 , wherein reacting the first carbon-coated compound and the second carbon-coated compound occurs at a temperature of at least about 1000 degrees C.

13. A method according to claim 1 , wherein reacting the first carbon-coated compound and the second carbon-coated compound occurs at a temperature increase or decrease rate of about 1 degrees C. per minute to about 10 degrees C. per minute.

14. A method according to claim 1 , wherein reacting the first carbon-coated compound and the second carbon-coated compound occurs in an inert atmosphere.

15. A method according to claim 1 , wherein reacting the first carbon-coated compound and the second carbon-coated compound occurs for about 1 hour to about 6 hours.

16. A method according to claim 1 , wherein reacting the first carbon-coated compound and the second carbon-coated compound comprises:

reacting the first carbon-coated compound, the second carbon-coated compound, and about 1% Fe or about 1% Ni.

17. A method according to claim 1 , wherein

decomposing the first hydrocarbon gas in the presence of the first compound comprises decomposing the first hydrocarbon gas in the presence of the first compound and about 1% Fe or about 1% Ni; or

decomposing the second hydrocarbon gas in the presence of the second compound comprises decomposing the second hydrocarbon gas in the presence of the second compound and about 1% Fe or about 1% Ni.

18. A method according to claim 1 , wherein the metal boride comprises an average particle size diameter of about 100 nm to about 1000 nm.

19. A method according to claim 1 , wherein the metal boride comprises an average specific surface area of about 0.1 m 2 g −1 to about 10 m 2 g −1 .

20. The method of claim 1 , wherein:

the first compound comprises oxygen; or

the second compound comprises oxygen.

21. The method of claim 1 , wherein

the first compound comprises a carbonate; or

the second compound comprises a borate.

22. The method of claim 1 , wherein carbon-coating the first compound and the second compound and reacting the first carbon-coated compound and the second carbon-coated compound are at different temperatures.

23. The method of claim 22 , wherein the temperature of carbon-coating the first compound and the second compound is lower than the temperature of reacting the first carbon-coated compound and the second carbon-coated compound.

24. The method of claim 1 , wherein carbon-coating the first compound or second compound occurs at a temperature of at least about 100 degrees C.

25. The method of claim 1 , wherein reacting the first carbon-coated compound and the second carbon-coated compound occurs at a temperature of at least about 1000 degrees C.

26. The method of claim 1 , wherein the metal of the first compound and the boron of the second compound do not substantially react during carbon-coating.

27. The method of claim 1 , wherein the first hydrocarbon gas and the second hydrocarbon gas are the same.

28. The method of claim 1 , wherein the first hydrocarbon gas and the second hydrocarbon gas are different.

29. The method of claim 1 , wherein the first compound and the second compound are carbon-coated separately.

30. The method of claim 1 , wherein the first hydrocarbon gas or the second hydrocarbon gas comprise a plurality of hydrocarbon gases.

31. The method of claim 1 , wherein the first compound and the second compound are carbon-coated together.