METHOD FOR PRODUCING A CERAMIC COMPONENT

Abstract

A method for producing a ceramic component from a composite material containing at least one hard material and plastic, to the component produced by said method and to the use of said component. Hie method includes the following steps: a) providing a green body comprising at least one hard material, which has been produced by means of a 3D printing method, b) impregnating the green body with at least one liquid resin system and c) curing the impregnated green body to form a synthetic resin matrix. The hard material is preferably SiC and/or B4C.

Claims

1-15. (canceled)

16. A method for producing a ceramic component from a composite material containing at least one hard material and plastic, comprising the following steps: a) providing a green body comprising at least one hard material produced by a 3D printing process. b) impregnating the green body with at least one liquid resin system and c) curing the impregnated green body to form a synthetic resin matrix.

17. The method according to claim 16, wherein the at least one hard material in step a) represents silicon carbide (SiC), boron carbide (B.sub.4C) or any mixture of SiC and B.sub.4C.

18. The method according to claim 16, wherein at least one hard material having a grain size (d50) between 10 μm and 500 μm is used for the production of the green body.

19. The method according to claim 16, wherein the at least one liquid resin system in step b) is a resin system which is converted into a synthetic resin matrix by means of a polycondensation reaction or a polyaddition reaction.

20. The method according to claim 19, wherein the at least one synthetic resin matrix produced by means of a polyaddition reaction represents an epoxy resin, a polyurethane resin or a benzoxazine resin, or the at least one synthetic resin matrix produced by means of a polycondensation reaction represents a phenolic resin or a furan resin, or the at least one synthetic resin matrix represents any mixture of these resins.

21. The method according to claim 16, wherein the impregnation with at least one liquid resin system in step b) is carried out by spraying, dipping, brushing, vacuum impregnation or by vacuum pressure impregnation.

22. The method according to claim 16, wherein the curing in step c) is carried out at room temperature or by applying a temperature in a range of 60° C. to 250° C.

23. The method according to claim 16, wherein the steps of impregnation with at least one liquid resin system which is converted into a synthetic resin matrix by means of polycondensation according to step b) and of curing according to step c) arc repeated at least once.

24. The method according to claim 16, wherein in step b) an impregnation with at least one liquid resin system which is converted into a synthetic resin matrix by means of a polycondensation reaction is carried out, and, after step c) of curing, a step d) of carbonising the cured component is earned out, followed by the steps of e) impregnating the carbonised body with a liquid resin system which is converted into a synthetic resin matrix by means of a polyaddition reaction or a polycondensation reaction, and f) curing the impregnated body to form a synthetic resin matrix.

25. A Ceramic component made of a composite material containing at least one hard material and plastic produced by a method for producing a ceramic component from a composite material containing at least one hard material and plastic, comprising the following steps: a) providing a green body comprising at least one hard material produced by a 3D printing process. b) impregnating the green body with at least one liquid resin system and c) curing the impregnated green body to form a synthetic resin matrix.

26. The ceramic component according 10 claim 25, wherein the component has a specific resistance of less than 10,000 μOhm*m.

27. The ceramic component according to claim 25, wherein the component has a Shore hardness D of greater than/equal to 90.

28. The ceramic component according to claim 25, wherein the component has a thermal conductivity of at least 2 W/(m.Math.K).

29. The ceramic component according to claim 25, wherein the component has a strength of at least 80 MPa when impregnated with at least one liquid resin system which reacts by means of a polyaddition reaction, or has a strength of at least 40 MPa when impregnated with at least one liquid resin system which reacts by means of polycondensation.

30. A use of a ceramic component according to claim 25 as an impeller and shut-off or rotary valve in pumps and compressors, as a pump casing, as internals in columns, as static mixing elements, as turbulators, as spray nozzles, as an electrical heating element, as a classifier wheel, as a lining element for protecting against wear and in corrosive applications or as an oxidation-stable high-temperature mould.

Description

EXAMPLES

[0034] The production of a green body using silicon carbide as hard material according to step a) of our method according to the Invention can be carried out as described below.

[0035] A silicon carbide with grain size F80 (grain size according to FEPA standard) was used. This was first mixed with 0.1 % by weight of a sulphuric acid liquid activator for phenolic resin. based on the total weight of silicon carbide and activator, and processed with a 3D printing powder bed machine. A doctor blade unit placed a thin layer of silicon carbide powder (approximately 0.3 mm high) on a flat powder bed, and an inkjet printing unit printed an alcoholic phenolic resin solution onto the silicon carbide powder bed according to the desired component geometry. The printing table was then lowered by the thickness of the layers, and another layer of silicon carbide was applied and phenolic resin was again printed on locally. By repeating this procedure, cuboidal test specimens with dimensions of, for example, 120 mm (length)×20 mm (width)×20 mm (height) were constructed. Once the complete “component” was printed, the powder bed was placed in an oven preheated to 160° C. and held there for approximately 20 hours, during which time the phenolic resin completely cured and formed a dimensionally stable green body. The excess silicon carbide powder was then vacuumed off after cooling, and the green body was removed. The geometric density of the test specimen was determined to be 1.45 g/cm.sup.3.

Example 1 According to the Invention

[0036] The silicon carbide-based green body, produced by a 3D printing process, was vacuum impregnated with a liquid epoxy resin system The epoxy resin from Ebalta consisted of 100 parts of a resin with a room temperature (RT) viscosity of approximately 800 mPas and 30 parts of the corresponding fast-curing hardener with an RT viscosity of approximately 55 mPas. The pot life of the epoxy resin system is stated as 50-60 minutes according to the manufacturer's specifications. The test specimen was completely immersed in the liquid resin system and evacuated to approx. 100 mbar. The test specimen was impregnated in the resin system under vacuum for a further 30 minutes, and, after this time, it was brought to ambient pressure, removed from the container and cleaned superficially of the adhering resin. After storage at room temperature and subsequent curing at 60° C., the corresponding test specimen geometries for the physical tests were worked out mechanically from the rods. The density of the test specimens was 2.0 g/cm.sup.3. The test specimen surfaces were finally available in a ground quality.

Example 2 According to the Invention

[0037] The silicon carbide-based green body, produced by a 3D printing process, was subjected to vacuum pressure impregnation instead of an epoxy resin impregnation with a phenol formaldehyde resin (Hexion) with a viscosity at 20° C. of 700 mPas and a water content according to Karl Fischer (ISO 760) of approx. 15%. The procedure was as follows: the carbon bodies were placed in an impregnation vessel. The pressure in the vessel was reduced to 10 mbar and increased to 11 bar after the resin was applied. After a dwell time of 10 hours, the carbon test specimens were removed from the impregnation vessel and heated to 160° C. under pressure of 11 bar to cure the resin. The heating time was approximately 2 hours, and the dwell time at 160° C. was approximately 10 hours. After polycondensation curing, the cooled test specimens had a density of 2.0 g/cm.sup.3.

Example 3 According to the Invention

[0038] The silicon carbide-based green body, which was produced using a 3D printing process, was first subjected to dip impregnation with furan resin. The advantage of the furan resin impregnation is the extremely low viscosity of the furan resin system of less than 100 mPas, which means that pure impregnation can be implemented without the need for vacuum or pressure. The following procedure was used: the specimens were placed in a glass vessel and a pre-prepared solution of one part maleic anhydride (Aug. Hedinger GmbH 6 Co. KG) and 10 parts furfuryl alcohol (International Furan Chemicals B.V.) was poured thereover. The test specimens were immersed completely in the solution for the complete infiltration time of two hours (at room temperature). After infiltration of the furfuryl alcohol/maleic acid anhydride solution, the specimens were removed and cleaned superficially using a cell cloth. The specimens soaked with resin were then cured in a drying cabinet. The temperature was gradually increased from 50° C. to 150° C. The actual curing program was as follows: 19 hours at 50° C., 3 hours at 70° C., 3 hours at 100° C. and finally 1.5 hours at 150° C. The mean density of the furan resin-impregnated test specimens was determined to be 1.70-1.75 g/cm.sup.3 after curing. After curing, the impregnated SiC green body was carbonised at 900° C. in a nitrogen atmosphere. For the carbonisation treatment, a slow heating curve over 3 days at 900° C. was chosen to ensure that the green body would not burst duo to the sudden evaporation of the solvent, i.e. water. During the carbonisation treatment, the furan resin is converted into carbon and thus forms conductive binder bridges between the SiC grains. Finally, the carbonised bodies were impregnated with epoxy resin according to example 1 and further processed.

[0039] All test specimens of examples 1-3 were subjected to a material characterisation. The results of these tests are shown in the following table, where the measurement results of the pure epoxy resin are included as a comparison:

TABLE-US-00001 Example 2: Example 3: Example 1: Phenolic Conductive EP- resin- SiC body Pure epoxy impregnated impregnated with EP resin (EP) SiC SiC impregnation AD (g/cm.sup.3) 1.2 2.0 2.0 2.1 ER (Ohmμm) >10.sup.7 >10.sup.7 >10.sup.7 5500 YM 3p (GPa) 3.5 13 19 15 FS 3p (MPa) 105 95 57 40 CS (MPa) 101 121 134 91 Shore D 85 91 92 93 TC 0.2 2.4 3 4 (W/(m*K)) AD (g/cm.sup.3): density (geometric) according to ISO 12985-1 ER (Ohmμm): electrical resistance according to DIN 51911 YM 3p (GPa): modulus of elasticity (stiffness), determined from the 3-point bending test according to EN ISO 178 FS 3p (MPa): 3-point bending strength according to EN ISO 178 CS (MPa): compressive strength according to EN ISO 604 Shore D: Shore hardness according to DIN ISO 7619-1 TC (W/(m*K)): Thermal conductivity at room temperature according to DIN 51908

[0040] The SiC composite material with an epoxy matrix (Examples 1 and 3) shows a higher strength compared to the SiC composite material with the phenolic resin matrix, but the latter is more temperature-stable and more chemically stable. With regard to the effort required for impregnation, the SiC green bodies can be impregnated with furan resin simply by means of an immersion process (partial method step in Example 3), while phenolic resin and epoxy resin must be impregnated by means of a vacuum impregnation process or vacuum pressure impregnation process due to the usually higher viscosity. The curing mechanism of epoxy resin is a polyaddition which leads to comparatively dense composite materials. The polycondensation resins such as phenol or furan resins generally have a much less dense structure.

[0041] By intermediate impregnation with a carbon-donating resin (here: furan resin) and subsequent carbonisation treatment in Example 3, a conductive SiC network with carbon binder bridges is formed. The pores are filled by the subsequent epoxy resin impregnation, resulting in a penetration composite material with good mechanical properties and good electrical conductivity.

[0042] In comparison with the pure epoxy resin, the addition of a hard material significantly reduces the thermal expansion, which can be determined according to DIN 51909. The SiC composite material with an epoxy resin matrix according to Example 1 shows a high thermal expansion compared to an SiC composite material with a phenolic resin matrix according to Example 2. For this reason, if high dimensional stability is required and thus a low thermal expansion is needed, an SiC composite material with a phenolic resin matrix or furan resin matrix alone or with a subsequent carbonisation step and re-impregnation with a phenolic resin or furan resin is preferred.