CERAMIC COMPOSITE MATERIALS AND METHOD FOR PRODUCING SAME

Abstract

A prepreg for a ceramic matrix composite, a process for the preparation of a green body with the help of the prepreg, and a process for the preparation of the ceramic matrix composite from the green body prepared according to the present invention are provided. The inventive process comprises the following steps: a) impregnating an arrangement of ceramic fibers with a slurry, which slurry comprises the following components: (i) 10 to 40 vol.-%, based on the total volume of the slurry, of ceramic particles, (ii) an alcoholic organic solvent selected from: (ii-1) 21 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of glycerol, (ii-2) 10 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of an oligo or polyethylene glycol with an average molecular weight of at most 800 g/mol, (ii-3) 10 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of at least one C2-C6 alkane diol, and (ii-4) 10 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of a mixture of two or more components, selected from a C2-C6 alkane diol, an oligo or polyethylene glycol with an average molecular weight of at most 800 g/mol, and glycerol; and (iii) water; b) reducing the water content in the slurry in the impregnated fiber arrangement to obtain a prepreg for a ceramic matrix composite; c) providing a shaped composite material from one or more prepregs obtained according to step b); d) consolidating the shaped composite material by reducing the water content and the content of alcoholic organic solvent so that a green body is obtained.

Claims

1. Process for the preparation of a green body for a ceramic matrix composite comprising the steps of: a) impregnating an arrangement of ceramic fibers with a slurry, which slurry comprises the following components: (i) 10 to 40 vol.-%, based on the total volume of the slurry, of ceramic particles, (ii) an alcoholic organic solvent selected from: (ii-1) 21 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of glycerol, (ii-2) 10 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of an oligo or polyethylene glycol with an average molecular weight of at most 800 g/mol, (ii-3) 10 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of at least one C2-C6 alkane diol, and (ii-4) 10 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of a mixture of two or more components, selected from a C2-C6 alkane diol, an oligo or polyethylene glycol with an average molecular weight of at most 800 g/mol, and glycerol; and (iii) water; b) reducing the water content in the slurry in the impregnated fiber arrangement to obtain a prepreg for a ceramic matrix composite; c) providing a shaped composite material from one or more prepregs obtained according to step b); d) consolidating the shaped composite material by reducing the water content and the content of alcoholic organic solvent so that a green body is obtained.

2. The process of claim 1, wherein the slurry used in step a) comprises the following components: (i) 10 to 40 vol.-%, based on the total volume of the slurry, of ceramic particles, (ii) an alcoholic organic solvent selected from: (ii-1) 21 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of glycerol, (ii-2) 21 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of an oligo or polyethylene glycol with an average molecular weight of at most 800 g/mol, (ii-3) 21 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of at least one C2-C6 alkane diol, and (ii-4) 21 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of a mixture of two or more components, selected from a C2-C6 alkane diol, an oligo or polyethylene glycol with an average molecular weight of at most 800 g/mol, and glycerol; and (iii) water.

3. The process of claim 1 or 2, wherein the alcoholic organic solvent is selected from glycerol, at least one C2-C4 alkane diol, and mixtures thereof.

4. The process of claim 1 or 2, wherein the alcoholic organic solvent is glycerol.

5. The process of any of claims 1 to 4, wherein the slurry comprises a dispersant.

6. The process of claim 5, wherein the dispersant is an acrylic acid polymer or an acrylic acid copolymer.

7. The process of any of claim 5 or 6, wherein the slurry used in step a) contains the dispersant in an amount of up to 5 wt.-%, based on the total solid content of the slurry.

8. The process of any of claims 1 to 7, wherein the slurry used in step a) contains 0 to 10 wt.-%, based on the total weight of the ceramic particles in the slurry, of an organic binder.

9. The process of any of claims 1 to 8, wherein the slurry is free of organic binder.

10. The process of any of claims 1 to 9, wherein the slurry used in step a) has a viscosity of less than 10 Pas, determined at a shear rate of 1 s.sup.1 and at a temperature of 20 C. using a rotational coaxial cylinder viscometer.

11. The process of any of claims 1 to 10, wherein the ceramic particles are selected from particles formed from Al.sub.2O.sub.3, SiO.sub.2, ZrO.sub.2, Y.sub.2O.sub.3, ZrO.sub.2 stabilized by Y.sub.2O.sub.3, yttrium aluminum garnet, mullite, Si.sub.3N.sub.4, SiC or carbon, or from combinations of two or more types of such particles.

12. The process of any of claims 1 to 11, wherein the ceramic fibers are selected from (i) fibers formed from Al.sub.2O.sub.3, SiO.sub.2, ZrO.sub.2, Y.sub.2O.sub.3, ZrO.sub.2 stabilized by Y.sub.2O.sub.3, yttrium aluminum garnet, mullite, Si.sub.3N.sub.4, SiC, SiCN, SiBNC, or carbon, or from combinations of two or more types of such fibers; (ii) fibers formed from ceramic blends or composites of two or more of Al.sub.2O.sub.3, SiO.sub.2, ZrO.sub.2, Y.sub.2O.sub.3, ZrO.sub.2 stabilized with Y.sub.2O.sub.3, yttrium aluminum garnet, mullite, Si.sub.3N.sub.4, SiC, SiCN, SiBNC, and carbon; and (iii) combinations of different fibers, selected from (i), (ii) or (i) and (ii).

13. The process of any of claims 1 to 12, wherein the arrangement of ceramic fibers in step a) comprises rovings.

14. The process of any of claims 1 to 13, wherein the arrangement of ceramic fibers in step a) is formed from continuous fibers.

15. The process of any of claims 1 to 14, wherein the arrangement of ceramic fibers in step a) is a woven fabric or a non-woven.

16. The process of any of claims 1 to 15, wherein the arrangement of ceramic fibers in step a) is formed from chopped fibers with a length of less than 100 mm.

17. The process of any of claims 1 to 16, wherein the arrangement of ceramic fibers in step a) is a sheet.

18. The process of any of claims 1 to 17, wherein the slurry used in step a) contains preferably at least 24 wt.-% of the alcoholic organic solvent, based on the total weight of the ceramic particles in the slurry.

19. The process of any of claims 1 to 18, wherein the slurry used in step a) contains preferably at most 30 wt.-% of the alcoholic organic solvent, based on the total weight of the ceramic particles in the slurry.

20. The process of any of claims 1 to 19, wherein the slurry used in step a) contains at least 20 vol.-% of ceramic particles.

21. The process of any of claims 1 to 20, wherein the water content of the slurry in the prepreg provided in step b) is adjusted such that the volume fraction of the ceramic particles in the slurry, based on the total volume of the slurry in the prepreg, is at least 5 vol.-% higher after step b) than before step b).

22. The process of any of claims 1 to 21, wherein the water content of the slurry in the prepreg provided in step b) is adjusted such that the volume fraction of the ceramic particles in the slurry, based on the total volume of the slurry in the prepreg, is at least 45 vol.-%.

23. The process of any of claims 1 to 22, wherein the water content of the slurry in the prepreg provided in step b) is adjusted such that the volume fraction of the ceramic particles in the slurry, based on the total volume of the slurry in the prepreg, is at most 60 vol.-%.

24. The process of any of claims 1 to 23, wherein the water fraction of the slurry in the prepreg provided in step b) is 4 to 13 wt.-%, based on the total weight of the slurry in the prepreg.

25. The process of any of claims 1 to 24, wherein the volume fraction of the ceramic fibers in the prepreg is 15 to 60 vol.-%, based on the total volume of the prepreg.

26. The process of any of claims 1 to 25, wherein step b) of reducing the water content comprises keeping the impregnated fiber arrangement at conditions of a temperature of 50 to 150 C. and a relative humidity of 10 to 30% for a period of time of 1 min to 2 h.

27. The process of any of claims 1 to 26, wherein step b) of reducing the water content comprises keeping the impregnated fiber arrangement at conditions of a temperature of 50 to 150 C. and a relative humidity of 10 to 30% for a period of time of 1 to 30 min.

28. The process of any of claims 1 to 27, wherein step b) of reducing the water content comprises hydrothermal conditioning of the impregnated fiber arrangement.

29. The process of claim 28, wherein the hydrothermal conditioning is carried out at a temperature in the range of 10 to 30 C., particularly preferably 20 to 30 C., a relative humidity of 30 to 80%, and for a period of time of 1 to 20 hours.

30. The process of claim 28 or 29, wherein the hydrothermal conditioning is carried out at a temperature in the range of 10 to 30 C., a relative humidity of 30 to 60%, and for a period of time of 1 to 10 hours.

31. The process of any of claims 1 to 30, wherein after step b), the process comprises a re-humidification of the prepreg(s) by means of hydrothermal conditioning.

32. The process of claim 31, wherein the hydrothermal conditioning is carried out at a temperature in the range of 10 to 30 C., a relative humidity of 30 to 60%, and for a period of time of 1 to 10 hours.

33. The process of any of claims 1 to 32, wherein the process comprises storing the prepreg obtained in step b) at a relative humidity of at most 60%.

34. The process of any of claims 1 to 33, wherein the provision of a shaped composite material in step c) comprises applying one or more of the prepregs obtained in step b) onto a shaped support.

35. The process of any of claims 1 to 34, wherein the shaped composite material is a laminate and wherein the provision of a shaped composite material in step c) comprises laminating two or more of the prepregs provided in step b).

36. The process of claim 35, wherein the laminate is applied onto a shaped support material so that a laminate with a predetermined three-dimensional shape is obtained.

37. The process of claim 35, wherein the two or more prepregs are laminated on a shaped support material so that a laminate with a predetermined three-dimensional shape is obtained.

38. The process of claim 34, wherein in step c) one or more of the prepregs obtained in step b) are wound around a shaped support material.

39. The process of any of claims 2 to 38, wherein in step d) the content of alcoholic organic solvent in the shaped composite material is reduced to such a degree that after consolidation the content of alcoholic organic solvent in the matrix material of the green body is 20 wt.-% or less, based on the total weight of the ceramic particles in the matrix material.

40. The process of any of claims 1 to 39, wherein the reduction of the water content and the content of alcoholic organic solvent in step d) is carried out by heating the shaped composite material to 100 C. or more and at reduced pressure or in a gas stream.

41. Process for the preparation of a ceramic matrix composite comprising the steps for the preparation of a green body according to the process of any of claims 1 to 40, and sintering the green body.

42. The process of claim 41, wherein the ceramic matrix composite has a fiber volume content of at least 30 vol.-%, based on the total volume of the material.

43. Prepreg for a ceramic matrix composite comprising an arrangement of ceramic fibers impregnated with a slurry wherein the slurry comprises (i) ceramic particles, (ii) an alcoholic organic solvent and (iii) water, and wherein the alcoholic organic solvent is selected from: (ii-1) 21 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of glycerol, (ii-2) 10 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of an oligo or polyethylene glycol with an average molecular weight of at most 800 g/mol, (ii-3) 10 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of at least one C2-C6 alkane diol, and (ii-4) 10 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of a mixture of two or more components, selected from a C2-C6 alkane diol, an oligo or polyethylene glycol with an average molecular weight of at most 800 g/mol, and glycerol.

44. The prepreg of claim 43, wherein the alcoholic organic solvent is selected from: (ii-1) 21 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of glycerol, (ii-2) 21 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of an oligo or polyethylene glycol with an average molecular weight of at most 800 g/mol, (ii-3) 21 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of at least one C2-C6 alkane diol, and (ii-4) 21 to 35 wt.-%, based on the total weight of the ceramic particles in the slurry, of a mixture of two or more components, selected from a C2-C6 alkane diol, an oligo or polyethylene glycol with an average molecular weight of at most 800 g/mol, and glycerol.

45. The prepreg of claim 43 or 44, wherein the alcoholic organic solvent is selected from glycerol, at least one C2-C4 alkane diol, and mixtures thereof.

46. The prepreg of any of claims 43 to 45, wherein the alcoholic organic solvent is glycerol.

47. The prepreg of any of claims 43 to 46, wherein the slurry comprises a dispersant.

48. The prepreg of claim 47, wherein the dispersant is an acrylic acid polymer or an acrylic acid copolymer.

49. The prepreg of claim 47 or 48, wherein the slurry comprises the dispersant in an amount of up to 5 wt.-%, based on the total solid content of the slurry.

50. The prepreg of any of 43 to 49, wherein the slurry comprises 0 to 10 wt.-%, based on the total weight of the ceramic particles in the slurry, of an organic binder.

51. The prepreg of any of claims 43 to 50, wherein the slurry is free of organic binder.

52. The prepreg of any of claims 43 to 51, wherein the ceramic particles are selected from particles formed from Al.sub.2O.sub.3, SiO.sub.2, ZrO.sub.2, Y.sub.2O.sub.3, ZrO.sub.2 stabilized by Y.sub.2O.sub.3, yttrium aluminum garnet, mullite, Si.sub.3N.sub.4, SiC or carbon, or from combinations of two or more types of such particles.

53. The prepreg of any of claims 43 to 52, wherein the ceramic fibers are selected from (i) fibers formed from Al.sub.2O.sub.3, SiO.sub.2, ZrO.sub.2, Y.sub.2O.sub.3, ZrO.sub.2 stabilized by Y.sub.2O.sub.3, yttrium aluminum garnet, mullite, Si.sub.3N.sub.4, SiC, SiCN, SiBNC, or carbon, or from combinations of two or more types of such fibers; (ii) fibers formed from ceramic blends or composites of two or more of Al.sub.2O.sub.3, SiO.sub.2, ZrO.sub.2, Y.sub.2O.sub.3, ZrO.sub.2 stabilized with Y.sub.2O.sub.3, yttrium aluminum garnet, mullite, Si.sub.3N.sub.4, SiC, SiCN, SiBNC, and carbon; and (iii) combinations of different fibers, selected from (i), (ii) or (i) and (ii).

54. The prepreg of any of claims 43 to 53, wherein the arrangement of ceramic fibers comprises rovings.

55. The prepreg of any of claims 43 to 54, wherein the arrangement of ceramic fibers is formed from continuous fibers.

56. The prepreg of any of claims 43 to 55, wherein the arrangement of ceramic fibers is a woven fabric or a non-woven.

57. The prepreg of any of claims 43 to 54, wherein the arrangement of ceramic fibers is formed from chopped fibers with a length of less than 100 mm.

58. The prepreg of any of claims 43 to 57, wherein the arrangement of ceramic fibers in step a) is a sheet.

59. The prepreg of any of claims 43 to 58, wherein the slurry contains at least 24 wt.-% of the alcoholic organic solvent, based on the total weight of the ceramic particles in the slurry.

60. The prepreg of any of claims 43 to 59, wherein the slurry used in step a) contains at most 30 wt.-% of the alcoholic organic solvent, based on the total weight of the ceramic particles in the slurry.

61. The prepreg of any of claims 43 to 60, wherein the volume fraction of the ceramic particles in the slurry is at least 45 vol.-%, based on the total volume of the slurry in the prepreg.

62. The prepreg of any of claims 43 to 61, wherein the volume fraction of the ceramic particles in the slurry is at most 60 vol.-%, based on the total volume of the slurry in the prepreg.

63. The prepreg of any of claims 43 to 62, wherein the water fraction of the slurry is 4 to 13 wt.-%, based on the total weight of the slurry in the prepreg.

64. Shaped composite material comprising one or more prepregs according to any of claims 43 to 63.

65. The shaped composite material of claim 64, wherein the composite material is a laminate of two or more of the prepregs according to any of claims 43 to 63.

Description

EXAMPLES

Example 1

[0176] The process is shown using the example of the preparation of oxide-ceramic prepregs. As reinforcement, Nextel610 DF19 fabrics (supplied by 3M) are used. Before processing, the sizing is burned out (700 C. for 2 h). The aqueous slurry has a solids content of 67 wt.-% and comprises an Al.sub.2O.sub.3ZrO.sub.2 powder mixture (80% MRS1, Albemarle; 20% TZ-3Y-E, Krahn Chemie), 1 wt.-% Dispergator Sokalan PA 15, 26 wt.-% glycerol, based on the solid. The woven fabrics are impregnated with slurry and the excess slurry is removed with a doctor blade. In order to obtain the tacky prepreg, different methods are used. In Variant A, the infiltrated fabric is stored in a climate chamber at 60% relative humidity and 25 C. for 24 hours. In Variant B, a partial removal of water is carried out at 50 C. (15 min, about 10% relative humidity) in a drying cabinet. The drying duration is selected such that the removal of water corresponds to the state of equilibrium of Variant A (see drawing 3). In Variant C (not shown in drawing 2), water is first partially removed at 50 C. (15 min) and followed by storage in the climate chamber at 60% relative humidity and 25 C. (24 h). Variant D is a combination of 60 minutes of water removal at 50 C. and storage in the climate chamber at 60% relative humidity and 25 C. (24 h). In that case, the prepreg was re-humidified in order to achieve the state of equilibrium.

[0177] FIG. 1 shows the change in the water content of the slurry in the prepreg during the course of conditioning or drying, with a view to the water content of the slurry after infiltration and as a function of the duration.

[0178] Then the tacky prepregs are laminated onto a form (lab conditioned to 25 C. and 60% relative humidity). After consolidating (100 C. with blower, 11 h), the green body is stable and no longer tacky due to the removal of water and glycerol. The composites are sintered at a temperature of 1,225 C. and a holding period of 2 hours. The bending strength in all methods is about 300 MPa and a uniform prepreg quality is obtained (Table 1).

TABLE-US-00001 TABLE 1 3-point bending strength of composite materials whose prepregs were conditioned differently Bending Method of Sintered Composites Fiber volume strength hydrothermal (4 layers DF19, 1111 cm.sup.2) content [vol.-%] [MPa] conditioning Climate chamber 60% rel. hum., 25 C. 44 334 25 Method A (24 h) Partial removal of water at 50 C. (15 min) 47 320 9 Method B Partial removal of water at 50 C. (15 min), 45 299 34 Method C climate chamber 60% rel. hum., 25 C. (24 h) Partial removal of water at 50 C. (60 min) 46 294 18 Method D and re-humidification climate chamber 60% rel. hum., 25 C. (24 h)

Example 2

[0179] The process is shown using the example of the preparation of oxide-ceramic prepregs. As reinforcement, Nextel610 DF19 fabrics (supplied by 3M) are used. Before processing, the sizing is burned out (700 C. for 2 h). The aqueous slurry has a solids content of 67 wt.-% and comprises an Al.sub.2O.sub.3ZrO.sub.2 powder mixture (80% MRS1, Albemarle; 20% TZ-3Y-E, Krahn Chemie), 1 wt.-% Dispergator Sokalan PA 15, 26 wt.-% ethane-1,2-diol, based on the solid. The woven fabrics are impregnated with slurry and the excess slurry is removed with a doctor blade.

[0180] In order to obtain the tacky prepreg, the infiltrated fabric is stored in the climate chamber at 60% relative humidity and 25 C. for 20 hours.

[0181] Then the tacky prepregs are laminated onto a form (lab conditioned to 25 C. and 60% relative humidity). After consolidating (100 C. with blower, 11 h), the green body is stable and no longer tacky due to the removal of water and ethane-1,2-diol. The composites are sintered at a temperature of 1,225 C. and a holding period of 2 hours.