Claims
- 1. A method of fabricating metal-ceramic composites from previously formed ceramic precursor starting constituents selected from boron-carbide, boron and borides and metals reactive therewith selected from reactive metals, alloys thereof, and compounds thereof which reduce to reactive metals or alloys thereof, comprising:
- chemically pretreating the previously formed starting constituents of a ceramic precursor;
- consolidating the chemically pretreated starting constituents into a porous ceramic precursor;
- infiltrating molten reactive metal into the chemically pretreated ceramic precursor;
- wherein the step of chemically pretreating the starting constituents of the ceramic precursor alters the surface chemistry to enhance infiltration of the precursor by the molten reactive metal by slowing the kinetics of reaction relative to the kinetics of densification.
- 2. The method of claim 1 wherein the step of chemically pretreating the starting constituents comprises chemically altering the surface chemistry of the starting constituents to eliminate phases which inhibit infiltration.
- 3. The method of claim 2 wherein the step of chemically pretreating the starting constituents comprises chemically converting phases which inhibit infiltration to phases which promote infiltration.
- 4. The method of claim 3 further including pyrolyzing the chemically converted phases at low temperature.
- 5. The method of claim 1 further comprising forming the starting constituents into particles prior to chemically pretreating.
- 6. The method of claim 5 further comprising forming the particles with a controlled polymodal size distribution.
- 7. The method of claim 1 wherein the step of consolidating the starting constituents is performed by colloidal consolidation.
- 8. The method of claim 6 wherein the step of consolidating the starting constituents is performed by colloidal consolidation.
- 9. The method of claim 1 wherein the steps of pretreating and consolidating the starting constitutents are performed by injection molding the starting constituents using a binder containing chemical pretreatment agents.
- 10. The method of claim 1 wherein the step of pretreatment is performed by immersing the starting constituents in a chemical solution to produce chemical reactions at the surface of the starting constituents.
- 11. The method of claim 10 for boron-carbide starting constituents comprising changing the boron to carbon ratio at the surface of the starting constituents.
- 12. The method of claim 1 comprising chemically removing B.sub.2 O.sub.3, BH.sub.3 O.sub.3 and B.sub.2 O.sub.3 .multidot.H.sub.2 O from the surface of the starting constituents.
- 13. The method of claim 10 comprising immersing the starting constituents in any of the following:
- a. methanol (CH.sub.4 O or CH.sub.3 OH);
- b. anhydrous alcohol (C.sub.2 H.sub.6 OH);
- c. n-propyl alcohol (C.sub.3 H.sub.8 O or CH.sub.3 CH.sub.2 CH.sub.2 OH);
- d. isopropyl alcohol (C.sub.3 H.sub.8 O or CH.sub.3 HOHCH.sub.3);
- e. n-butyl alcohol (C.sub.4 H.sub.10 O or CH.sub.3 CH.sub.2 CH.sub.2 CH.sub.2 OH);
- f. sec-butyl alcohol (C.sub.4 H.sub.10 O or CH.sub.3 CH.sub.2 CH(OH)CH.sub.3);
- g. tert-butyl alcohol C.sub.4 H.sub.10 O or (CH.sub.3).sub.3 COH);
- h. any azeotrope of the above;
- i. any dilution of the the above;
- j. any higher alcohol (C.sub.n H.sub.m O), where n .gtoreq.4 and m .gtoreq.10), or azeotrope or dilution thereof;
- k. glycerol (C.sub.3 H.sub.8 O.sub.3 or CH.sub.20 OHCHOHCH.sub.2 OH);
- 1. any glycerol derivative (C.sub.n H.sub.m O.sub.p, where n .gtoreq.3,m .gtoreq.6,and p .gtoreq.2), including glyceraldehyde (C.sub.3 H.sub.6 O.sub.3), glyceric acid (C.sub.3 H.sub.6 O.sub.4 or CH.sub.2 OHCH(OH)COOH), glycerol formal (C.sub.4 H.sub.8 O.sub.3), and glycidol (C.sub.3 H.sub.6 O.sub.2);
- m. any methyl--abietate (C.sub.21 H.sub.32 O.sub.2), acetate (C.sub.3 H.sub.6 O.sub.2 or CH.sub.3 COOCH.sub.3), acetoacetate (C.sub.3 H.sub.8 O.sub.3 or CH.sub.3 COCH.sub.2 COOCH.sub.3), acetylsalicylate (C.sub.10 H.sub.10 O.sub.4), acrylate (C.sub.4 H.sub.6 O.sub.2 or CH.sub.2 =CHCOOCH.sub.3), benzoate (C.sub.8 H.sub.8 O.sub.2 or C.sub.6 H.sub.5 COOCH.sub.3), benzoylsalicylate (C.sub.15 H.sub.12 O.sub.4), butyl ketone (C.sub.6 H.sub.12 O.sub. or CH.sub.3 COC.sub.4 H.sub.9), butyrate (C.sub.5 H.sub.10 O.sub.2 or CH.sub.3 (CH.sub.2).sub.2 COOCH.sub.3), carbitol (C.sub.5 H.sub.12 O.sub.3 or CH.sub.3 OCH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2 OH), carbonate (C.sub.3 H.sub.6 O.sub.3 or CO(OCH.sub.3).sub.2), cellosolve (C.sub.3 H.sub.8 O.sub.2 or HOCH.sub.2 CH.sub.2 OCH.sub.3), cellosolve acetate (C.sub.5 H.sub.10 O.sub.3 or CH.sub.3 OCH.sub.2 CH.sub.2 OOCCH.sub.3), or methylcellulose, or methylal (C.sub.3 H.sub. 8 O.sub.2 or CH.sub.2 (OCH.sub.3).sub.2);
- n. boiling water;
- o. cold water;
- p. any combination of the above, in part or whole;
- q. any binder, for the purpose of injection molding, containing any of the above, in part or whole.
- 14. The method of claim 1 wherein the step of infiltrating the metal into the precursor comprises:
- placing the metal adjacent to the precursor;
- heating the metal and precursor to a temperature which promotes wetting of the precursor by the metal.
- 15. The method of claim 14 wherein the heating step is performed in a vacuum.
- 16. The method of claim 14 wherein the heating step is performed in an inert atmosphere.
- 17. The method of claim 14 further comprising further heating to a temperature which promotes microstructural enhancement of the composite.
- 18. The method of claim 1 further comprising forming a graded microstructure.
- 19. The method of claim 7 further comprising forming a graded microstructure.
- 20. The method of claim 1 further comprising consolidating the starting constituents into a precursor having a substantially disconnected microstructure.
- 21. A composite formed by the method of claim 1.
- 22. A composite formed by the method of claim 13.
- 23. A composite formed by the method of claim 18.
- 24. A composite formed by the method of claim 20.
BACKGROUND OF THE INVENTION
The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-48 between the U. S. Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory.
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