Processing of non-oxide ceramics from sol-gel methods
A general procedure applied to a variety of sol-gel precursors and solvent systems for preparing and controlling homogeneous dispersions of very small particles within each other. Fine homogenous dispersions processed at elevated temperatures and controlled atmospheres make a ceramic powder to be consolidated into a component by standard commercial means: sinter, hot press, hot isostatic pressing (HIP), hot/cold extrusion, spark plasma sinter (SPS), etc.
1. A method, comprising:
a) forming an intimate mixture of an inorganic oxide and an organic polymer,
b) reaction heat treating the mixture to form particles of a non-oxide ceramic; and
c) consolidating the particles into a solid ceramic object,
wherein the solid ceramic object is characterized by a domain size of 100 nm or less wherein the organic polymer comprises a copolymer of an aldehyde and a mono-, di-, or trihydroxy substituted aromatic ring.
2. A method according to claim 1 , wherein the non-oxide ceramic comprises a carbide.
3. A method according to claim 1 , wherein the non-oxide ceramic comprises a nitride.
4. A method according to claim 1 , wherein the non-oxide ceramic comprises a boride.
5. A method according to claim 1 , wherein the polymer comprises a copolymer of resorcinol and formaldehyde.
6. A method according to claim 1 , wherein the polymer is a polymer of trihydroxybenzene and formaldehyde.
7. A method according to claim 1 , wherein the polymer is a polymer of phenol and formaldehyde.
8. A method according to claim 1 , wherein step a) comprises
a1) forming a first sol comprising an inorganic gel intermediate in a solution;
a2) forming a second sol comprising an organic gel intermediate in the solution;
a3) further reacting the solution until at least one of the first sol and second sol forms a sol gel comprising the respective inorganic oxide or organic polymer; and
a4) removing solvent from the solution to form the intimate mixture.
9. A method according to claim 1 , wherein step a) comprises
a1) reacting precursors of a first sol in a solution;
a2) reacting precursors of a second sol in the solution;
a3) carrying out the reaction in the solution for a time sufficient to form a sol gel from at least one of the first and second sols; and
a4) removing solvent from the solution to form the intimate mixture,
wherein the first sol comprises an inorganic oxide and the second sol comprises a copolymer of an aldehyde and a mono-, di-, or trihydroxy substituted aromatic ring.
10. A method according to claim 1 , wherein step a) comprises forming an interpenetrating network of two sol gel chemistries in a solution and then removing solvent from the solution to form the intimate mixture.
11. A method comprising
a) reacting first starting monomers of a first sol gel in a solution;
b) reacting second starting monomers of a second sol gel in the solution;
c) reacting the first and second starting monomers until at least one of the first sol gel and second sol gel is formed in the solution to form a gel mixture;
d) removing solvent from the gel mixture to form a mixture of inorganic oxide and organic polymer; and
e) reaction heat treating the mixture to form particles of a non-oxide ceramic selected from carbides, nitrides, and borides, wherein the first sol gel comprises an inorganic sol gel and the second sol gel comprises a copolymer of an aldehyde and a mono-, di-, or trihydroxy substituted aromatic ring.
12. A method according to claim 11 , wherein the inorganic oxide is an oxide of boron, silicon, aluminum, magnesium, titanium, zirconium, or tungsten.
13. A method according to claim 11 , wherein reaction heat treating is carried out in a hydrogen stream to form particles in the form of a carbide.
14. A method according to claim 11 , wherein reaction heat treating is carried out in a nitrogen or ammonia stream to form particles in the form of a nitride.
15. A method according to claim 11 , wherein the gel mixture further comprises a nitrogen compound, and the reaction heat treating produces particles of a nitride.
16. A method according to claim 11 , wherein the gel mixture further comprises a boron compound, and the reaction heat treating produces particles of a boride.
17. A method comprising forming particles by the method of claim 11 and consolidating the particles to form a solid object.
18. A method according to claim 17 , comprising consolidating by sintering.
19. A method according to claim 17 , comprising consolidating by hot press.
20. A method according to claim 17 , comprising consolidating by spark plasma sinter.
21. A method comprising
a) forming a first gel comprising an inorganic oxide in a solution;
b) forming an second gel comprising an organic polymer in the solution to form a gel mixture;
c) removing solvent from the gel mixture to form a mixture of an inorganic oxide and organic polymer; and
d) reaction heat treating the mixture to form particles of a non-oxide ceramic selected from carbides, nitrides, and borides, wherein the organic polymer comprises a copolymer of an aldehyde and a mono-, di-, or trihydroxy substituted aromatic ring.
22. A method according to claim 21 , wherein in step a) the first and second gels are formed simultaneously.
23. A method according to claim 21 , wherein in step a) the first gel is formed first in the solution, and then the second gel is formed in the presence of the first gel.
24. A method according to claim 21 , wherein in step a) the second gel is formed first in the solution and then the first gel is formed in the presence of the second gel.
25. A method according to claim 21 , wherein the polymer is a polymer of trihydroxybenzene.
26. A method according to claim 21 , wherein the polymer is a polymer of dihydroxybenzene.
27. A method according to claim 21 , wherein reaction heat treating is carried out in the presence of hydrogen gas and the particles comprise carbides.
28. A method according to claim 21 , wherein reaction heat treating is carried out in the presence of nitrogen or ammonia, and the particles comprise nitrides.
29. A method according to claim 21 , wherein reaction heat treating is carried out in the presence of a boron compound, and the particles comprises borides.
30. A method according to claim 21 , wherein the gel mixture further comprises a nitrogen compound and the particles comprise nitrides.
31. A method according to claim 21 , wherein the gel mixture further comprises a boron compound and the particles comprise borides.
32. A method according to claim 21 , wherein the gel mixture further comprises a soluble metal cation, and the reaction heat treating is carried out under reducing conditions to form particles comprising a carbide and particles of the metal in the ground state.
33. A method comprising forming particles by the method of claim 21 and consolidating the particles to form a solid object.
34. A method according to claim 33 , comprising consolidating by sintering.
35. A method according to claim 33 , comprising consolidating by hot press.
36. A method according to claim 33 , comprising consolidating by spark plasma sinter.