Dispersible barium titanate-based particles and methods of forming the same

• US 20030059366A1
• Filed: 09/16/2002
• Published: 03/27/2003
• Est. Priority Date: 09/21/2001
• Status: Abandoned Application

• Current Assignee: Hoover Company (Whirlpool Corporation)
• Original Assignee: Cabot Corporation
• Inventors: Venigalla, Sridhar, Kerchner, Jeffrey A.
• Application Number:
  US10/244,828
• Publication Number:
  US 20030059366A1
• Time in Patent Office: Days
• US Class Current: 423/598
• CPC Class Codes: C01G 23/006 Alkaline earth titanates
• CPC Class Codes: C01P 2004/62 Submicrometer sized, i.e. from 0.1-1 micrometer
• CPC Class Codes: C04B 2235/3215 Barium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3236 Alkaline earth titanates
• CPC Class Codes: C04B 2235/483 Si-containing organic compounds, e.g. silicone resins, (poly)silanes, (poly)siloxanes or (poly)silazanes
• CPC Class Codes: C04B 35/62625 Wet mixtures
• CPC Class Codes: C04B 35/6263 characterised by their solids loadings, i.e. the percentage of solids
• CPC Class Codes: C04B 35/6264 Mixing media, e.g. organic solvents
• CPC Class Codes: C04B 35/6269 Curing of mixtures
• CPC Class Codes: C04B 35/63 using additives specially adapted for forming the products , e.g.. binder binders
• CPC Class Codes: C04B 35/632 Organic additives
• CPC Class Codes: C09C 1/36 Compounds of titanium C09C1/0009, C09C1/0015, C09C1/0078 take precedence

Abstract

Dispersible barium titanate-based particles and methods of forming the same are provided. One method involves subjecting the barium titanate-based particles to a heating step which removes hydroxyl groups from particle surfaces. Another method involves attaching a coupling agent to surfaces of the barium titanate-based particles. Both methods reduce the tendency of particles to agglomerate and/or aggregate when subsequently dispersed in a fluid. Thus, the methods enable production of dispersions that have a relatively uniform distribution of particles throughout. Such dispersions may be further processed as desired to form, for example, dielectric layers, polymer/dielectric composites or other structures. The structure may also include a uniform distribution of barium titanate-based particles which can improve properties amongst other advantages.

Claims

1. A method of processing barium titanate-based particles comprising:

providing a mixture comprising barium titanate-based particles, a coupling agent, and a first fluid;

removing the fluid to form a barium titanate-based particle composition, wherein the coupling agent is attached to surfaces of at least a portion of the barium titanate-based particles; and

dispersing the barium titanate-based particle composition in a second fluid to form a dispersion.

2. The method of claim 1, wherein the second fluid is a non-aqueous fluid.

3. The method of claim 1, wherein the second fluid is a solvent having a precursor of polymeric material dissolved therein.

4. The method of claim 1, further comprising forming a layer from the dispersion.

5. The method of claim 1, further comprising forming a composite structure from the dispersion.

6. The method of claim 5, wherein the composite structure includes a polymer matrix having the barium titanate-based particles distributed therein.

7. The method of claim 1, further comprising adjusting the pH of the mixture to acidic conditions.

8. The method of claim 1, wherein the first fluid comprises alcohol and water.

9. The method of claim 1, wherein the coupling agent is silane-based.

10. The method of claim 1, further comprising producing the barium titanate-based particles in a hydrothermal process prior to providing the mixture.

11. The method of claim 10, further comprising drying the barium titanate-based particles prior to providing the mixture.

12. The method of claim 1, wherein removing the water comprises filtering the dispersion.

13. The method of claim 12, wherein removing the water further comprises drying the barium titanate-based particles after filtering the dispersion.

14. The method of claim 1, further comprising heating the barium titanate-based particles prior to providing the mixture.

15. The method of claim 14, comprising heating the barium titanate-based particles to a maximum temperature of between about 300°

C. and about 500°

C.

16. The method of claim 1, wherein the mixture is provided by adding barium titanate-based particles to the fluid followed by adding the coupling agent to the fluid.

17. A method of processing barium titanate-based particles comprising removing hydroxyl groups from surfaces of the barium titanate-based particles by heating the barium titanate-based particles to a maximum temperature of greater than about 300°

C. and less than about 500°

C.

18. The method of claim 17, further comprising hydrothermally producing the barium titanate-based particles prior to removing hydroxyl groups from surfaces of the barium titanate-based particles.

19. The method of claim 18, further comprising drying the hydrothermally-produced barium titanate-based particles prior to removing hydroxyl groups from surfaces of the barium titanate-based particles.

20. The method of claim 17, further comprising cooling the barium titanate-based particles to room temperature.

21. The method of claim 17, further comprising dispersing the barium titanate-based particles in a fluid to form a dispersion after removing hydroxyl groups from surfaces of the barium titanate-based particles.

22. The method of claim 21, wherein the fluid is non-aqueous.

23. The method of claim 21, wherein the fluid is a solvent having a precursor of polymeric material dissolved therein.

24. The method of claim 21, further comprising forming a layer from the dispersion.

25. The method of claim 21, further comprising forming a composite structure from the dispersion.

26. The method of claim 21, wherein the composite structure includes a polymer matrix having the barium titanate-based particles distributed therein.

27. The method of claim 25, wherein forming the composite structure comprises casting the dispersion and evaporating the fluid.

28. The method of claim 17, comprising heating the barium titanate-based particles to a maximum temperature of greater than about 350°

C. and less than about 450°

C.

29. A particulate composition including a plurality of dried barium titanate-based particles, wherein a coupling agent is attached to surfaces of at least a portion of the barium titanate-based particles.

30. The particulate composition of claim 29, wherein the barium titanate-based particles are hydrothermally-produced.

31. The particulate composition of claim 29, wherein the barium titanate-based particles are substantially spherical.

32. The particulate composition of claim 29, wherein the barium titanate-based particles have an average particle size of less than 0.5 micron.

33. The particulate composition of claim 29, wherein the barium titanate-based particles include a dopant coating layer.

34. The particulate composition of claim 29, wherein the coupling agent is silane-based.