Sinterable structures and method

• US 20050239628A1
• Filed: 06/30/2005
• Published: 10/27/2005
• Est. Priority Date: 04/06/1999
• Status: Active Grant

• Current Assignee: Phillips Plastics Corporation
• Original Assignee: Phillips Plastics Corporation
• Inventors: Johnson, James R., Frencl, Michael Edward
• Granted Patent: US 7,482,390 B2
• Time in Patent Office: Days
• US Class Current: 501/81
• CPC Class Codes: B22F 3/1121 by using decomposable, meltable or sublimatable fillers
• CPC Class Codes: C04B 14/366 Phosphates, e.g. apatite
• CPC Class Codes: C04B 2111/00793 as filters or diaphragms
• CPC Class Codes: C04B 2111/0081 as catalysts or catalyst carriers
• CPC Class Codes: C04B 2235/5436 micrometer sized, i.e. from 1 to 100 micron
• CPC Class Codes: C04B 2235/5445 submicron sized, i.e. from 0,1 to 1 micron
• CPC Class Codes: C04B 2235/602 Making the green bodies or pre-forms by moulding
• CPC Class Codes: C04B 2235/6021 Extrusion moulding
• CPC Class Codes: C04B 2235/658 Atmosphere during thermal treatment
• CPC Class Codes: C04B 2235/9661 Colour
• CPC Class Codes: C04B 24/12 Nitrogen containing compounds organic derivatives of hydrazine hydrazine C04B22/00
• CPC Class Codes: C04B 26/28 Polysaccharides or derivatives thereof
• CPC Class Codes: C04B 35/00 Shaped ceramic products characterised by their composition porous ceramic products C04B38/00; ceramic articles characterised by particular shape, see the relevant classes, e.g. linings for casting ladles, tundishes, cups or the like B22D41/02; ceramic substrates for microelectronic semi-conductors H01L23/15; Ceramics compositions containing free metal bonded to carbides, diamond, oxides, borides, nitrides, silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides or sulfides other than as macroscopic reinforcing agents C22C; shaping of ceramics B28B; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products chemical preparation of powders of inorganic compounds C01; infiltration of sintered ceramic preforms with molten metal C04B41/51
• CPC Class Codes: C04B 35/111 Fine ceramics
• CPC Class Codes: C04B 35/447 based on phosphates , e.g. hydroxyapatite
• CPC Class Codes: C04B 35/624 Sol-gel processing
• CPC Class Codes: C04B 35/6365 Cellulose or derivatives thereof
• CPC Class Codes: C04B 38/0054 the pores being microsized or nanosized
• CPC Class Codes: C04B 38/0058 open porosity
• CPC Class Codes: C04B 38/062 the burned-out substance being formed in situ, e.g. by polymerisation of a prepolymer composition containing ceramic powder
• CPC Class Codes: C04B 38/0635 : Compounding ingredients C04B38/0615 takes precedence
• CPC Class Codes: C04B 40/0028 : Aspects relating to the mixing step of the mortar preparation
• CPC Class Codes: C04B 40/0268 : Heating up to sintering temperatures C04B41/0072 takes precedence

Abstract

A method of producing an open, porous structure having an outer surface defining a shape having a bulk volume and having interconnecting openings extending throughout said volume and opening through said surface, and products resulting from the method. The method comprises preparing a viscous mixture comprising a sinterable powder dispersed in a sol of a polymer in a primary solvent, replacing the primary solvent with a secondary liquid in which the polymer is insoluble to produce a gel comprising an open polymeric network having the sinterable powder arranged therein, removing the secondary liquid from the gel; removing the polymer network, and sintering the sinterable powder to form the open, porous structure. Also disclosed are shaped, porous products resulting from methods of the invention.

Claims

1-19. -19. (canceled)

20. Method of producing an open, porous structure having an outer surface defining a shape having a bulk volume and having interconnecting openings extending throughout said volume and opening through said surface comprising

a. preparing a viscous mixture comprising a sinterable powder dispersed in a sol of a polymer in a primary solvent wherein the polymer weight per volume ratio of polymer to liquid in the sol is not greater than about 4.2:

100 g/cc,

b. contacting said viscous mixture with a secondary liquid in which the polymer is insoluble to replace said primary solvent with said secondary liquid and to produce a gel comprising an open polymeric network comprised of microfibrils and having said sinterable powder arranged therein,

c. removing said secondary liquid from said gel; and

d. sintering said sinterable powder to form said open, porous structure.

21. The method of claim 20 including, after step (c), the step of removing said polymeric network.

22. The method of claim 21 wherein said viscous mixture is prepared by heating said polymer in a mixture of said primary solvent and a liquid non-solvent for said polymer to remove at least part of said non-solvent and to form said viscous sol.

23. The method of claim 22 wherein said polymer is cellulose and said primary solvent comprises an amine oxide, the method including the step of heating said polymer in a mixture of said primary solvent and said non-solvent for cellulose to drive off at least a portion of said non-solvent to enable the cellulose to form a sol with said primary solvent.

24. The method of claim 20 including, after step (c), the step of forming said gel into a predetermined shape.

25. The method of any one of claims 20-23 including the step (f), following step (b) and before step (d), of forming the polymeric network into a predetermined shape.

26. The method of claim 25 wherein step (f) is performed after step (c).

27. The method of claim 21 wherein said polymeric network is removed by pyrolysis.

28. A formable product capable of being sintered to produce an open, porous, self-supporting structure having an outer surface defining a shape having a bulk volume and having interconnecting openings extending throughout said volume and opening through said surface, comprising, in combination, a viscous sol of a polymer in a primary solvent, the polymer weight per volume ratio of polymer to primary solvent in the sol not exceeding about 4.2:

100 g/cc, and a sinterable powder arranged in the sol.

29. The formable product of claim 28 wherein said polymer is a polysaccharide.

30. The formable product of claim 28 wherein said primary solvent is an amine oxide.

31. A shaped, porous product having an outer surface defining a shape having a bulk volume and having interconnecting openings extending throughout said volume and opening through said surface, said article being formed by a method comprising forming into a pre-determined shape the formable product of any one of claims 28, 29 and 30, and sintering said product.

32. Method of producing an open, porous structure having an outer surface defining a shape having a bulk volume and having interconnecting openings extending throughout said volume and opening through said surface comprising

a. preparing a viscous mixture comprising a sinterable powder comprised of particles dispersed in a sol of a polymer in a primary solvent, wherein the polymer weight per volume ratio of polymer to liquid in the sol is not greater than about 4.2:

100 g/cc,

b. immersing the viscous mixture in a secondary liquid in which the polymer is insoluble to produce a gel comprising an open polymeric network comprised of microfibrils and having said sinterable powder arranged therein with the positions of the particles being guided by the positions of the microfibrils,

c. removing said secondary liquid from said gel; and

d. sintering said sinterable powder to form said open, porous structure, the resulting reticulated, three dimensional configuration of the product following the position of the microfibrils.

33. The method of claim 32 including, after step (c), the step of removing said polymeric network.

34. The method of claim 33 wherein said viscous mixture is prepared by heating said polymer in a mixture of said primary solvent and a liquid non-solvent for said polymer to remove at least part of said non-solvent and to form said viscous sol.

35. The method of claim 34 wherein said polymer is cellulose and said primary solvent comprises an amine oxide, the method including the step of heating said polymer in a mixture of said primary solvent and said non-solvent for cellulose to drive off at least a portion of said non-solvent to enable the cellulose to form a sol with said primary solvent.

36. The method of claim 33 wherein said polymeric network is removed by pyrolysis.

37. Method of producing an open, porous structure having an outer surface defining a shape having a bulk volume and having interconnecting openings extending throughout said volume and opening through said surface comprising

a. preparing a viscous mixture comprising a sinterable powder dispersed in a sol of a polymer in a primary solvent, wherein the polymer weight per volume ratio of polymer to primary solvent is not greater than about 4.2:

100 g/cc,

b. allowing said viscous mixture to fall into a secondary liquid in which the polymer is insoluble to replace said primary solvent with said secondary liquid and to produce a gel comprising an open polymeric network comprised of microfibrils and having said sinterable powder arranged therein,

c. removing said secondary liquid from said gel; and

d. sintering said sinterable powder to form said open, porous structure.

38. A flat, porous, rigid disc having an outer surface defining a shape having a bulk volume and having interconnecting openings extending throughout said volume in a reticulated, three dimensional configuration and opening through said surface, said article being formed by a method comprising forming into a predetermined shape a shapeable, viscous mixture comprising a sinterable powder comprised of particles dispersed in a sol of a polymer in a primary solvent, wherein the polymer weight per volume ratio of polymer to primary solvent is not greater than about 4.2:

100 g/cc, allowing said sol in the primary solvent to fall into a secondary liquid in which the polymer is insoluble to produce a gel comprising an open polymeric network comprised of microfibrils and having said sinterable powder arranged therein with the positions of the particles guided by the positions of the microfibrils, removing said secondary liquid from the gel, and heating the gel to remove said polymeric network and to sinter said sinterable powder to form said shaped porous structure, the resulting reticulated, three dimensional configuration of the product following the position of the microfibrils.