METHOD OF SYNTHESIZING MULTI-IPHASE OXIDE CERAMICS WITH SMALL PHASE DOMAIN SIZES

• US 20120322645A1
• Filed: 12/16/2011
• Published: 12/20/2012
• Est. Priority Date: 12/17/2010
• Status: Active Grant

• Current Assignee: University of Connecticut Through Its Center For Science & Technology Commercialization
• Original Assignee: University of Connecticut Through Its Center For Science & Technology Commercialization
• Inventors: Suib, Steven L., Jordan, Eric H., Iyer, Aparna, Garofano, Jacquelynn, Chen, Chun-Hu
• Granted Patent: US 8,877,119 B2
• Time in Patent Office: Days
• US Class Current: 501/1
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: C01B 13/18 by thermal decomposition of compounds, e.g. of salts or hydroxides
• CPC Class Codes: C01B 13/185 Preparing mixtures of oxides
• CPC Class Codes: C01F 17/218 Yttrium oxides or hydroxides
• CPC Class Codes: C01F 5/06 by thermal decomposition of magnesium compounds calcining magnesite or dolomite C04B2/10
• CPC Class Codes: C01F 7/162 Magnesium aluminates
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2004/04 obtained by TEM, STEM, STM or AFM
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: C04B 2235/3206 Magnesium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3225 Yttrium oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3244 Zirconium oxides, zirconates, hafnium oxides, hafnates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/447 Phosphates or phosphites calcium phosphates C04B2235/3212, e.g. orthophosphate, hypophosphite
• CPC Class Codes: C04B 2235/80 Phases present in the sintered or melt-cast ceramic products other than the main phase
• CPC Class Codes: C04B 2235/9653 Translucent or transparent ceramics other than alumina
• CPC Class Codes: C04B 35/053 Fine ceramics
• CPC Class Codes: C04B 35/505 based on yttrium oxide
• CPC Class Codes: C04B 35/624 Sol-gel processing
• CPC Class Codes: C04B 35/6267 Pyrolysis, carbonisation or auto-combustion reactions
• CPC Class Codes: C04B 35/62675 : characterised by the treatment temperature
• CPC Class Codes: C04B 35/632 : Organic additives
• CPC Class Codes: C04B 35/636 : Polysaccharides or derivatives thereof
• CPC Class Codes: C04B 35/645 : Pressure sintering

Abstract

Nanocomposites of multi-phase metal oxide ceramics have been produced from water soluble salts of the resulting metal oxides by a foaming esterification sol-gel method. The evolution of volatile gases at elevated temperature during the esterification reaction causes the formation of a foam product. Nanocomposites of multi-phase metal oxide ceramics have also been produced by a cation polymer precursor method. In this second method, the metal cations are chelated by the polymer and the resulting product is gelled and foamed. Calcination of the resulting foams gives nanocomposite powders with extremely fine, uniform grains and phase domains. These microstructures are remarkably stable both under post-calcination heat treatment and during consolidation by hot-pressing.

Claims

1. A method of making a multi-phase nanocomposite comprising:

preparing a first aqueous solution of water-soluble organic acid and water-soluble organic alcohol which will form an ester under appropriate conditions;

adding to the first solution a combination of more than one water-soluble metal salts which do not form a combined phase when heated, to obtain a second aqueous solution of acid, alcohol and metal salts;

heating the second aqueous solution at a temperature and for a time sufficient to produce a foam comprised of (i) the ester of the acid and the alcohol and (ii) the metal salts;

treating the foam under conditions to obtain a powder; and

heating the powder at a temperature and for a time sufficient to obtain a calcined powder comprised of metal oxides of the metal salts.

2. The method of claim 1, wherein in the preparing step the water-soluble organic acid is comprised of carboxylic acid and the water-soluble organic alcohol is comprised of diol.

3. The method of claim 2, wherein the soluble organic carboxylic acid is comprised of citric acid and the water-soluble diol is comprised of ethylene glycol.

4. The method of claim 1, wherein in the adding step the cation of the water-soluble metal salts is selected from yttrium, magnesium, zirconium, cesium, zinc, calcium, copper, chromium, titanium, manganese and any combination thereof.

5. The method of claim 4, wherein the cation is selected from yttrium, magnesium, zirconium and combinations thereof.

6. The method of claim 1, wherein in the adding step the anion of the water-soluble metal salts is selected from nitrate, carbonate, sulfate, sulfite, nitrite, acetate, citrate, chloride, phosphate and combinations thereof.

7. The method of claim 1, wherein in the first heating step the temperature is in the range of 100°

C.-300°

C. and the time is in the range of 1-5 hours.

8. The method of claim 7, wherein in the temperature is about 200°

C. and the time is about 3 hours.

9. The method of claim 1, wherein in the treating step the treatment is comprised of grinding, milling, pulverizing or combinations thereof.

10. The method of claim 1, wherein in the second heating step the temperature is from about 300°

C.-to about 500°

C. and the time is in the range of 12-36 hours.

11. The method of claim 10, wherein the temperature is about 400°

C. and the time is about 24 hours.

12. The method of claim 1, further comprising the step of heating the calcined powder obtained from the second heating step in a post-calcination heat treatment at a temperature and for a time sufficient to obtain a multi-phase nanocomposite comprised of metal oxides.

13. The method of claim 12, wherein the temperature is from about 700°

C. to about 1200°

C. and the time is from about 0.5 to about 2 hours.

14. The method of claim 13, wherein the temperature is in the range of 800°

C.-1100°

C. and the time is about 1 hour.

15. The method of claim 1, further comprising the step of consolidating the calcined powder of the second heating step by hot pressing.

16. The method of claim 15, wherein the consolidating is by vacuum hot pressing at a temperature of from about 900°

C. to about 1300°

C.

21. A metal oxide nanocomposite composition made by the method of claim 1.

22. A multi-phase metal oxide ceramic composition made by the method of claim 1.

23. An optically transparent nanocomposite ceramic material made from the composition of claim 1.

17. A method of making a multi-phase nanocomposite comprising:

a. preparing an aqueous solution of citric acid and ethylene glycol;

b. adding to the solution of step a. a combination of water-soluble salts of yttrium and magnesium to obtain an aqueous solution of citric acid, ethylene glycol and yttrium and magnesium salts;

c. heating the solution of step b. at a temperature of about 200°

C. for between about 2-4 hours to produce a foam comprised of (i) the ester of citric acid and ethylene glycol and (ii) the yttrium and magnesium salts;

d. milling the foam to obtain a powder;

e. heating the powder at a temperature between about 300°

C.-500°

C. for a time between about 12-36 hours to obtain a calcined powder comprised of metal oxides of the metal salts; and

f. heating the calcined powder in a post-calcination heat treatment at a temperature between about 700°

C.-1200°

C. for a time between about 0.5-2.0 hours to obtain a multi-phase nanocomposite comprised of the metal oxides.

18. The method of claim 17, further comprising the step of consolidating the post calcined nanocomposite by vacuum hot pressing at a temperature of about 1300°

C. for a time of about 0.5 hour.

19. A method of making a multi-phase nanocomposite comprising:

preparing an aqueous solution of one or more non-polymeric mono-and/or disaccharides;

adding to the solution a combination of more than one water-soluble metal salts which do not form a combined phase when heated, to obtain a combined aqueous solution of mono- and/or disaccharides and metal salts;

heating the combined solution at a temperature and for a time sufficient to produce a gel comprised of (i) the mono- and/or disaccharides and (ii) the metal salts;

heating the gel to form a foam;

treating the foam under conditions to obtain a powder;

heating the powder at a temperature and for a time sufficient to obtain a calcined powder comprised of metal oxides of the metal salts.

20. The method of claim 19, further comprising the step of heating the calcined powder obtained from the second heating step in a post-calcination heat treatment at a temperature and for a time sufficient to obtain a multi-phase nanocomposite comprised of the metal oxides.

24. A metal oxide nanocomposite composition made by the method of claim 19.

25. A multi-phase metal oxide ceramic composition made by the method of claim 19.

26. An optically transparent nanocomposite ceramic material made from the composition of claim 19.