Phosphate-based ceramic

• US 20020061811A1
• Filed: 10/01/2001
• Published: 05/23/2002
• Est. Priority Date: 10/03/2000
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Merkel, Gregory A.
• Granted Patent: US 6,576,579 B2
• Time in Patent Office: Days
• US Class Current: 501/106
• CPC Class Codes: C04B 35/447 based on phosphates , e.g. hydroxyapatite
• CPC Class Codes: Y10S 55/30 Exhaust treatment

Abstract

A ceramic including a first phase having a general formula R_1+(x/2)Zr₄P_6−xSi_xO₂₄ where R is selected from the group consisting of Ba, Ca, and Sr and 0≦x≦2, wherein the first phase has a volumetric heat capacity (C_p1), and at least 10 weight percent of a second phase having a volumetric heat capacity (C_p2), wherein C_p2>C_p1. The ceramic has a coefficient of thermal expansion from 22° to 1000° C. of −15×10⁻⁷/° C. to +15×10⁻⁷/° C., a permeability of at least 0.25×10⁻¹² m², a total porosity of at least 35% by volume, and a median pore diameter of at least 6 micrometers, and a volumetric heat capacity of the solid C_p(solid) of at least 3.15 J/cm³ K.

Claims

1. A ceramic comprising a first phase having a general formula R_1+(x/2)Zr₄P₆₋

xSi_xO₂₄ where R is selected from the group consisting of Ba, Ca, and Sr and 0≦

x≦

2, wherein the first phase has a volumetric heat capacity (C_p1), and at least 10 weight percent of a second phase having a volumetric heat capacity (C_p2), wherein C_p2>

C_p1, wherein the ceramic has a coefficient of thermal expansion from 22°

to 1000°

C. of −

15×

10<sup>−

7</sup>/°

C. to +15×

10<sup>−

7</sup>/°

C., a permeability of at least 0.25×

10<sup>−

12</sup> m², a total porosity of at least 35% by volume, a median pore diameter of at least 6 micrometers, and a volumetric heat capacity C_p(solid) of at least 3.15 J/cm³ K.

2. The ceramic of claim 1 wherein the first phase is CaZr₄P₆O₂₄.

3. The ceramic of claim 1 wherein the first phase is Sr_1.5Zr₄P₅SiO₂₄.

4. The ceramic of claim 1 wherein C_p2 is 3.3 J/cm³ K.

5. The ceramic of claim 4 wherein the second phase is about 10 to 90% by weight of the ceramic.

6. The ceramic of claim 5 wherein the second phase is about 20 to 80% by weight of the ceramic.

7. The ceramic of claim 6 wherein the second phase is about 50 to 80% by weight of the ceramic.

8. The ceramic of claim 4 wherein the second phase is selected from the group consisting of zircon (ZrSiO₄) and zirconia (ZrO₂).

9. The ceramic of claim 8 wherein the second phase is zircon.

10. The ceramic of claim 1 wherein the permeability is at least about 0.8×

10<sup>−

12</sup> m².

11. The ceramic of claim 9 wherein the permeability is at least about 1.2×

10<sup>−

12</sup> m².

12. The ceramic of claim 1 wherein the total porosity is at least about 42%.

13. The ceramic of claim 1 wherein the median pore diameter is at least about 9 micrometers.

14. The ceramic of claim 13 wherein the median pore diameter is at least about 13 micrometers.

15. The ceramic of claim 1 wherein the second phase has a grain size of at least about 10 micrometers.

16. The ceramic of claim 15 wherein the second phase has a grain size of at least about 25 micrometers.

17. The ceramic of claim 1 wherein the first phase is CaZr₄P₆O₂₄ and the second phase is zircon.

18. The ceramic of claim 1 wherein the first phase is Sr_1.5Zr₄P₅SiO₂₄ and the second phase is zircon.

19. The structure of claim 1 wherein the structure is used for filtering particulates from diesel engine exhaust.

20. A diesel particulate filter comprising a ceramic comprising a first phase having a general formula R_1+(x/2)Zr₄P₆₋

xSi_xO₂₄ where R is selected from the group consisting of Ba, Ca, and Sr and 0≦

x≦

2, wherein the first phase has a volumetric heat capacity (C_p1), and at least 10 weight percent of a second phase having a volumetric heat capacity (C_p2), wherein C_p2>

C_p1, wherein the ceramic has a coefficient of thermal expansion from 22°

to 1000°

C. of −

15×

10<sup>−

7</sup>/°

C. to +15×

10<sup>−

7</sup>/°

C., a permeability of at least 0.25×

10<sup>−

12</sup> m², a total porosity of at least 35% by volume, a median pore diameter of at least 6 micrometers, and a volumetric heat capacity C_p(solid) of at least 3.15 J/cm³ K.

21. The diesel particulate filter of claim 20 wherein the filter has the shape of a honeycomb, the honeycomb having an inlet end and an outlet end, and a multiplicity of cells extending from the inlet end to the outlet end, the cells having porous walls, wherein part of the total number of cells at the inlet end are plugged along a portion of their lengths, and the remaining part of cells that are open at the inlet end are plugged at the outlet end along a portion of their lengths, so that an engine exhaust stream passing through the cells of the honeycomb from the inlet end to the outlet end flows into the open cells, through the cell walls, and out of the structure through the open cells at the outlet end.

22. The ceramic of claim 20 wherein the first phase is CaZr₄P₆O₂₄.

23. The ceramic of claim 20 wherein the first phase is Sr_1.5Zr₄P₅SiO₂₄.

24. The ceramic of claim 20 wherein C_p2 is at least 3.3 J/cm³ K.

25. The ceramic of claim 24 wherein the second phase is selected from the group consisting of zircon (ZrSiO₄) and zirconia (ZrO₂).

26. The ceramic of claim 25 wherein the second phase is zircon.

27. The ceramic of claim 20 wherein the permeability is at least about 0.8×

10<sup>−

12</sup> m².

28. The ceramic of claim 27 wherein the permeability is at least about 1.2×

10<sup>−

12</sup> m².

29. The ceramic of claim 20 wherein the total porosity is at least about 42%.

30. The ceramic of claim 20 wherein the median pore diameter is at least about 9 micrometers.

31. The ceramic of claim 30 wherein the median pore diameter is at least about 13 micrometers.

32. The ceramic of claim 20 wherein the second phase has a grain size of at least about 10 micrometers.

33. The ceramic of claim 32 wherein the second phase has a grain size of at least about 25 micrometers.

34. The ceramic of claim 20 wherein the first phase is CaZr₄P₆O₂₄ and the second phase is zircon.

35. The ceramic of claim 20 wherein the first phase is Sr_1.5Zr₄P₅SiO₂₄ and the second phase is zircon.

37. The method of claim 36 wherein the raw materials for the first phase comprise compounds of metals selected from the group consisting of zirconium, phosphorous, and combinations thereof.

38. The method of claim 37 wherein phosphorus compounds are included in the mixture and have a median particle diameter of at least about 15 micrometers.

39. The method of claim 38 wherein the phosphorus compounds have a median particle diameter of at least about 35 micrometers.

40. The method of claim 39 wherein the phosphorus compounds have a median particle diameter of at least about 50 micrometers.

41. The method of claim 40 wherein the compounds are selected from the group consisting of Zr₂P₂O₉, ZrP₂O₇, Zr₂P_2+2yO_9+5y, Zr(HPO₄)₂₋

y.xH₂O and combinations thereof, wherein 0≦

y≦

1 and 0≦

x≦

2.

42. The method of claim 36 wherein the raw materials for the first phase comprise compounds selected from the group consisting of calcium carbonate, calcium sulfate, strontium carbonate, strontium sulfate, barium carbonate, barium sulfate, and combinations thereof.

43. The method of claim 42 wherein the median particle diameter of the total of the selected compounds is at least about 5 micrometers.

44. The method of claim 43 wherein the median particle diameter of the total of the selected compounds is at least about 15 micrometers.

45. The method of claim 44 wherein the median particle diameter of the total of the selected compounds is at least about 35 micrometers.

46. The method of claim 36 wherein the raw materials for the first phase comprise compounds selected from the group consisting of CaZrO₃, SrZrO₃, BaZrO₃, and combinations thereof.

47. The method of claim 46 wherein the median particle diameter of the total of the selected compounds is at least about 15 micrometers.

48. The method of claim 47 wherein the median particle diameter of the total of the selected compounds is at least about 35 micrometers.

49. The method of claim 48 wherein the median particle diameter of the total of the selected compounds is at least about 50 micrometers.

50. The method of claim 49 wherein the median particle diameter of the total of the selected compounds is at least about 100 micrometers.

51. The method of claim 36 wherein at least one of the raw materials for the first phase is zirconium oxide powder having a median particle diameter of at least about 10 micrometers.

52. The method of claim 36 wherein the raw materials for the second phase include zircon powder.

53. The method of claim 52 wherein the median particle size of the zircon powder is at least about 15 micrometers.

54. The method of claim 53 wherein the median particle size of the zircon powder is at least about 35 micrometers.

55. The method of claim 53 wherein the median particle size of the zircon powder is at least about 50 micrometers.

56. The method of claim 36 wherein the second phase is zircon.

57. The method of claim 56 wherein the second phase is formed by reaction of a silica source and a zirconia source.

58. The method of claim 57 wherein the silica source is of a particulate form having a median particle size of at least 15 micrometers.

59. The method of claim 58 wherein the silica source is of a particulate form having a median particle size of at least 35 micrometers.

60. The method of claim 59 wherein the zirconia source is of a particulate form having a median particle size of at least 15 micrometers.

61. The method of claim 60 wherein the zirconia is of a particulate form having a median particle size of at least 35 micrometers.

62. The method of claim 61 wherein the median particle size of the zircon powder is at least about 50 micrometers.

63. The method of claim 36 wherein the firing temperature is about 1200°

C. to 1750°

C.

64. The method of claim 36 wherein the mixture is shaped by extrusion.

65. The method of claim 64 wherein the mixture is extruded into a honeycomb structure having an inlet and outlet end and a multiplicity of cells extending from inlet end to outlet end, the cells having porous walls.

36. A method of making a ceramic, the method comprising:

a) forming a mixture comprising raw material powders capable of reacting to form a ceramic comprising a first phase having a general formula R_1+(x/2)Zr₄P<sub>6−

x</sub>Si_xO₂₄ where R is selected from the group consisting of Ba, Ca, and Sr and 0≦

x≦

2, and a second phase selected from the group consisting of zircon and zirconia, wherein the second phase is about 10 to 90% based on weight of the final ceramic;

b) shaping the mixture into a green body;

c) firing the green body to produce a ceramic comprising a first phase having a general formula R_1+(x/2)Zr₄P<sub>6−

x</sub>Si_xO₂₄ where R is selected from the group consisting of Ba, Ca, and Sr and 0≦

x≦

2, wherein the first phase has a volumetric heat capacity (C_p1), and at least 10 weight percent of a second phase selected from the group consisting of zircon and zirconia, wherein the second phase has a volumetric heat capacity (C_p2), wherein C_p2>

C_p1, wherein the ceramic has a coefficient of thermal expansion from 22°

to 1000°

C. of −

15×

10<sup>−

7</sup>/°

C. to +15×

10<sup>−

7</sup>/°

C., a permeability of at least 0.25×

10<sup>−

12</sup> m², a total porosity of at least 35% by volume, a median pore diameter of at least 6 micrometers, and a volumetric heat capacity C_p(solid) of at least 3.15 J/cm³ K.