Process for making chemically bonded sol-gel ceramics

• US 6,284,682 B1
• Filed: 08/26/1999
• Issued: 09/04/2001
• Est. Priority Date: 08/26/1999
• Status: Expired due to Term

• Current Assignee: University of British Columbia
• Original Assignee: University of British Columbia
• Inventors: Yang, Quanzu, Troczynski, Tomasz
• Primary Examiner(s): GROUP, KARL E
• Application Number:
  US09/383,074
• Time in Patent Office: 740 Days
• Field of Search: 501/127, 501/128, 501/118, 501/12, 501/111
• US Class Current: 501/12
• CPC Class Codes: C04B 35/62222 obtaining ceramic coatings coating of mortars, concrete, artificial or natural stone or ceramics C04B41/45; laminated ceramic products B32B18/00; coating metallic materials C23; coating of glass C03C17/00, applying ceramic coatings on silicon for semi-conductor purposes H01L
• CPC Class Codes: C04B 35/624 Sol-gel processing
• CPC Class Codes: C23C 18/1208 Oxides, e.g. ceramics
• CPC Class Codes: C23C 18/1225 Deposition of multilayers of inorganic material
• CPC Class Codes: C23C 18/1254 Sol or sol-gel processing
• CPC Class Codes: C23C 18/1295 with after-treatment of the deposited inorganic material

Abstract

This invention relates to a novel method of decreasing porosity of ceramics produced by sol-gel processing. The process of preparing chemically bonded sol-gel ceramics comprises phosphating a sol-gel derived oxide or hydrated oxide and polymerizing the phosphated product with heat treatment. Such combined sol-gel/chemical bonding process can be used to fabricate dense, thick ceramics or ceramic coatings for a variety of applications, including high temperature corrosion protection, wear resistance, dielectric properties, non-sticky surfaces, bio-active ceramics, thermal barrier ceramics, non-wetted surfaces, and others.

Claims

1. A process of preparing a chemically bonded sol-gel ceramic comprising:

(a) preparing an oxide or hydrated oxide ceramic from a sol-gel process;

(b) impregnating the oxide or hydrated oxide ceramic with a phosphating agent to produce system components; and

(c) heat treating the system components at a temperature between about 300°

C. and about 1200°

C. to produce a chemically bonded sol-gel ceramic.

2. A process as claimed in claim 1 wherein the oxide or hydrated oxide ceramic prepared using the sol-gel process is a first phase and the oxide or hydrated oxide ceramic in the first phase is impregnated with a secondary phosphate phase which reacts with the oxide or hydrated oxide ceramic first phase.

3. A process as claimed in claim 2 wherein the first phase is a mixture of calcined alumina and alumina prepared using a sol-gel process, which mixture is impregnated with the second phase comprising a mixture of metal phosphate and phosphorus acid to form complex amorphous or crystalline phosphates under heat treatment according to step (c).

4. A process as claimed in claim 1 wherein the oxide or hydrated oxide ceramic can be one or more of SiO₂, Al₂O₃, ZrO₂, TiO₂, BeO, SrO, BaO, CoO, NiO, ZnO, PbO, CaO, MgO, CeO₂, Cr₂O₃, Fe₂O₃, Y₂O₃, Sc₂O₃, HfO₂ or La₂O₃.

5. A process as claimed in claim 1 wherein the phosphating agent is a metal phosphate, phosphoric acid, or mixtures thereof.

6. A process as claimed in claim 5 wherein the metal phosphate comprises a metal selected from one or more of Al, Zr, Ti, Mg, Cu, Fe, Ca, Sr, Hf or Cr.

7. A process as claimed in 4 wherein a calcined ceramic filler comprised of powders or fibres of oxides, carbidcs, nitrides, borides, sulphides or mixtures thereof is incorporated in the chemicallly bonded sol-gel ceramic.