Highly porous ceramics fabricated from preceramic polymer and expandable microspheres, and method for fabricating the same

• US 20050012233A1
• Filed: 09/23/2003
• Published: 01/20/2005
• Est. Priority Date: 07/16/2003
• Status: Active Grant

• Current Assignee: Korea Institute of Machinery and Materials (Dawonsys Co., Ltd.)
• Original Assignee: Korea Institute of Machinery and Materials (Dawonsys Co., Ltd.)
• Inventors: Park, Chul-B, Kim, Young-Wook, Kim, Hai-Doo, Kim, Shin-Han
• Granted Patent: US 7,033,527 B2
• Time in Patent Office: Days
• US Class Current: 264/43
• CPC Class Codes: C04B 2111/2046 Shock-absorbing materials
• CPC Class Codes: C04B 2235/3206 Magnesium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/465 Ammonia
• 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 2235/5436 micrometer sized, i.e. from 1 to 100 micron
• CPC Class Codes: C04B 2235/658 Atmosphere during thermal treatment
• CPC Class Codes: C04B 2235/77 Density
• 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 35/01 based on oxide ceramics
• CPC Class Codes: C04B 35/117 Composites
• CPC Class Codes: C04B 35/14 based on silica
• CPC Class Codes: C04B 35/488 Composites
• CPC Class Codes: C04B 35/56 based on carbides or oxycarbides containing free metal binder C22C29/00
• CPC Class Codes: C04B 35/5611 based on titanium carbides
• CPC Class Codes: C04B 35/5626 based on tungsten carbides
• CPC Class Codes: C04B 35/565 based on silicon carbide
• CPC Class Codes: C04B 35/58 based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides containing free binder metal C22C29/00
• CPC Class Codes: C04B 35/58014 based on titanium nitrides, e.g. TiAlON
• CPC Class Codes: C04B 35/58092 based on refractory metal silicides
• CPC Class Codes: C04B 35/581 based on aluminium nitride
• CPC Class Codes: C04B 35/584 : based on silicon nitride
• CPC Class Codes: C04B 35/632 : Organic additives
• CPC Class Codes: C04B 38/0054 : the pores being microsized or nanosized
• CPC Class Codes: C04B 38/0074 : expressed as porosity percentage
• CPC Class Codes: C04B 38/0655 : Porous materials C04B38/0625 takes precedence
• CPC Class Codes: C04B 38/067 : Macromolecular compounds C04B38/062 takes precedence; polysaccharides C04B38/0645
• CPC Class Codes: Y10T 428/249953 : Composite having voids in a component [e.g., porous, cellular, etc.]

Abstract

Disclosed herein are a highly porous ceramic having a high porosity of not less than 60% and a pore density of not less than 10⁸ pores/cm³ fabricated from expandable microspheres and a preceramic polymer, and a method for fabricating highly porous ceramic. The method for fabricating highly porous ceramic from expandable microspheres and a preceramic polymer comprises the steps of: homogeneously mixing a preceramic polymer powder and expandable hollow microspheres, if necessary, a ceramic powder, and molding the mixture to form a molded body; heating the molded body to expand it; curing the expanded molded body; and pyrolyzing the cured molded body. Since the highly porous ceramic has a higher porosity and pore density than conventional porous ceramics, it can be suitably used for various high temperature structure materials, kiln furniture, bulletproof materials, shock-absorbing materials, insulating materials, refractory materials, lightweight structure materials, etc.

Claims

1. A method for fabricating a highly porous ceramic from expandable microspheres and a preceramic polymer, comprising the steps of:

homogeneously mixing a preceramic polymer powder, expandable hollow microspheres and a ceramic powder, and molding the mixture to form a molded body;

heating the molded body to expand it;

curing the expanded molded body; and

pyrolyzing the cured molded body.

2. The method for fabricating a highly porous ceramic from expandable microspheres and a preceramic polymer according to claim 1, wherein the ceramic powder is at least one material selected from the group consisting of Al₂O₃, ZrO₂, MgO, SiC, TiC, Si₃N₄, AlN, TiN, MoSi₂, WC and mixtures thereof.

3. The method for fabricating a highly porous ceramic from expandable microspheres and a preceramic polymer as according to claim 1, wherein the ceramic powder is added in an amount of 50% by weight or less, based on the total weight of the starting materials.

5. The method for fabricating a highly porous ceramic from expandable microspheres and a preceramic polymer according to claim 1, wherein the expansion of the molded body is carried out by heating at a temperature of 110˜

200°

C., the temperature range between the softening point and the melting point of the preceramic polymer, to expand the expandable hollow microspheres.

6. The method for fabricating a highly porous ceramic from expandable microspheres and a preceramic polymer according to claim 1, wherein the preceramic polymer is at least one polymer selected from the group consisting of polycarbosilane, polysiloxane, polysilazane and mixtures thereof.

7. The method for fabricating a highly porous ceramic from expandable microspheres and a preceramic polymer according to claim 1, wherein the preceramic polymer powder is added in an amount of 20% by weight or more, based on the total weight of the starting materials.

8. The method for fabricating a highly porous ceramic from expandable microspheres and a preceramic polymer according to claim 1, wherein the expandable hollow microspheres are added in an amount of 20% by weight or more, based on the total weight of the starting materials.

9. The method for fabricating a highly porous ceramic from expandable microspheres and a preceramic polymer according to claim 1, wherein upon heating the expandable hollow microspheres to 110˜

200°

C. at atmospheric pressure, the shell is softened and the inner medium is expanded to form spherical hollow spheres having an average diameter of 10-200 μ

m.

10. A highly porous ceramic fabricated from expandable microspheres and a preceramic polymer, in accordance with the method according to claim 1 wherein the highly porous ceramic has a high porosity of not less than 60% and a pore density of not less than 10⁸ pores/cm³.

4. A method for fabricating a highly porous ceramic from expandable microspheres and a preceramic polymer, comprising the steps of:

homogeneously mixing a preceramic polymer powder and expandable hollow microspheres, and molding the mixture to form a molded body;

heating the molded body to expand it;

curing the expanded molded body; and

pyrolyzing the cured molded body.

11. The method for fabricating a highly porous ceramic from expandable microspheres and a preceramic polymer according to claim 4, wherein the expansion of the molded body is carried out by heating at a temperature of 110˜

200°

C., the temperature range between the softening point and the melting point of the preceramic polymer, to expand the expandable hollow microspheres.

12. The method for fabricating a highly porous ceramic from expandable microspheres and a preceramic polymer according to claim 4, wherein the preceramic polymer is at least one polymer selected from the group consisting of polycarbosilane, polysiloxane, polysilazane and mixtures thereof.

13. The method for fabricating a highly porous ceramic from expandable microspheres and a preceramic polymer according to claim 4, wherein the preceramic polymer powder is added in an amount of 20% by weight or more, based on the total weight of the starting materials.

14. The method for fabricating a highly porous ceramic from expandable microspheres and a preceramic polymer according to claim 4, wherein the expandable hollow microspheres are added in an amount of 20% by weight or more, based on the total weight of the starting materials.

15. The method for fabricating a highly porous ceramic from expandable microspheres and a preceramic polymer according to claim 4, wherein upon heating the expandable hollow microspheres to 110˜

200°

C. at atmospheric pressure, the shell is softened and the inner medium is expanded to form spherical hollow spheres having an average diameter of 10-200 μ

m.

16. A highly porous ceramic fabricated from expandable microspheres and a preceramic polymer, in accordance with the method according to claim 4 wherein the highly porous ceramic has a high porosity of not less than 60% and a pore density of not less than 10⁸ pores/cm³.