SiC whisker reinforced aluminum oxide ceramic material with directionally arranged whiskers and preparation method of SiC whisker reinforced aluminum oxide ceramic material

Abstract

The invention relates to the technical field of ceramic materials, and provides a SiC whisker reinforced alumina ceramic material with directionally arranged whiskers and a preparation method thereof.The SiC whiskers are magnetized and modified by coating the SiC whiskers with cobalt, then the magnetized and modified SiC whisker powder and ball-milled Al2O3 ceramic slurry are mixed, and the SiC whisker reinforced alumina ceramic material with directionally arranged whiskers is obtained. And then adding sodium polystyrenesulfonate and fully mixing in a dispersion machine. And then simultaneously applying an electric field and a magnetic field in the mixed solution, so that the SiC whiskers turn under the action of the electric field and the magnetic field, and directional arrangement of the SiC whiskers in a certain direction is realized. The preparation method comprises the following steps: preparing a solution containing Al2O3-Y2O3 and SiCw, timely transferring the solution into a freeze dryer to freeze and fix the directional arrangement, carrying out vacuum sublimation drying at a low temperature to prepare Al2O3-Y2O3-SiCw mixed powder with directional arrangement of SiC whiskers, and carrying out hot pressed sintering on the mixed powder to prepare the SiC whisker reinforced alumina ceramic material with remarkable directional arrangement of whiskers. The ceramic material can be used for preparing a ceramic cutting tool and is used for efficiently cutting nickel-based high-temperature alloy.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic materials, and in particular relates to a SiC whisker reinforced alumina ceramic material with directional whisker arrangement and a preparation method thereof. Background Art

[0002] Alumina ceramics are widely researched and applied due to their numerous advantages, including high hardness, high wear resistance, good high-temperature resistance, and excellent oxidation resistance. They are primarily used in extreme environments such as high temperatures, corrosion, and severe wear, as well as in some electronic components such as grinding balls, corrosion-resistant parts, cutting tools, and electronic substrates. However, the brittleness, low strength, and poor impact resistance of alumina ceramics have greatly limited their widespread application.

[0003] SiC whiskers are single-crystal fibers with a diameter ranging from nanometer to micrometer, with high strength, few chemical impurities in the crystal, few crystal structure defects, and have characteristics such as high melting point, low density, high strength, high modulus, low thermal expansion coefficient, as well as wear resistance, corrosion resistance, and strong resistance to high-temperature oxidation. Adding a certain amount of SiC whiskers to an Al2O3 ceramic matrix can significantly improve the toughness of the Al2O3 ceramic. However, if the SiC whiskers are randomly distributed in the Al2O3 matrix, they cannot fully exert the reinforcing effect of the whiskers. Only if the SiC whiskers are highly oriented and directional distribution is achieved can the high reinforcing effect of the whiskers be maximized. The prior art discloses a whisker-reinforced alumina composite ceramic and its preparation method and application. By using a hot-pressing flow sintering method, a sample is made to flow in one or two dimensions in a mold to prepare a whisker-reinforced alumina ceramic with whisker directional arrangement. However, since the whiskers are simply oriented by making the powder particles flow through hot-pressing sintering, the orientation degree of the whiskers is not high, and there are problems such as high sintering temperature and high energy consumption. There is also prior art that discloses a calcium sulfate whisker highly oriented reinforced functional composite material and preparation method, which comprises adding a sodium polyacrylate electrolyte aqueous solution, applying an electric field in the solution, and aligning the calcium sulfate whiskers through a filter, then introducing a crosslinking agent N,N-methylenebisacrylamide and an initiator ammonium persulfate to cause a crosslinking reaction and solidify the solution with the oriented calcium sulfate whiskers, and then removing organic matter at high temperature to obtain a dense inorganic oriented calcium sulfate whisker composite material. Although this method can achieve oriented arrangement of whiskers, the preparation method is relatively complicated, industrial production has certain limitations, and N,N-methylenebisacrylamide itself is toxic, and inhalation or accidental ingestion can cause damage to the human central nervous system. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention aims to provide a SiC whisker reinforced alumina ceramic material with oriented whisker arrangement and a preparation method thereof.

[0005] According to the first aspect of the present invention, the present invention provides the following technical solutions: A method for preparing a SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement comprises the following steps: S1. Magnetization treatment of SiC whiskers: Disperse SiC whiskers in ethanol, add cobalt nitrate hexahydrate and citric acid, adjust the pH to acidic, ball mill for 2-3 hours and then dry. After drying, reduce in H2 at 400-600°C to obtain magnetic Co-coated SiC whisker powder; S2. Slurry preparation: Weigh a certain amount of Al2O3 powder and Y2O3 powder, add anhydrous ethanol, and ball-mill for 2-4 hours to obtain Al2O3-Y2O3 ceramic slurry; S3, mixing: the Al2O3-Y2O3 ceramic slurry obtained in step S2, the Co-coated SiC whisker powder obtained in step S1, and the sodium polystyrene sulfonate powder are fully mixed in a disperser to obtain Al2O3-Y2O3-SiC w Mixing solution; S4, electric field-magnetic field assisted alignment: to the Al2O3-Y2O3-SiC obtained in step S3 w An electric field and a magnetic field are applied to the mixed solution for 3 to 5 minutes, with the angle between the electric and magnetic fields being 80 to 100 degrees. The arrangement direction of the SiC whiskers in the EB plane is controlled by adjusting the ratio E / B of the electric field intensity E to the magnetic field intensity B. S5, freeze molding: the solution after step S4 is promptly transferred to a freeze dryer for freeze drying to obtain Al2O3-Y2O3-SiC with oriented SiC whiskers. w powder; S6, sintering: the Al2O3-Y2O3-SiC w The powder is placed in a graphite mold and hot-pressed and sintered to obtain a SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement.

[0006] As a preferred embodiment of the method for preparing a SiC whisker reinforced alumina ceramic material with oriented whisker arrangement according to the present invention, wherein: Al2O3-Y2O3-SiC with oriented SiC whiskers w In the powder, the content of the Al2O3 powder is 68~84.5wt%, the SiC w The content of the powder is 15-30 wt %; the content of the Y2O3 powder is 0.5-2 wt %.

[0007] As a preferred embodiment of the method for preparing a SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement described in the present invention, wherein: in step S1, the mass ratio of cobalt nitrate hexahydrate to SiC whiskers is 1:3-5; the pH value is 3-5; the diameter of the SiC whiskers is 0.2-1 μm, and the aspect ratio is 20-100.

[0008] As a preferred embodiment of the method for preparing a SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement described in the present invention, in step S2, the particle size of the Al2O3 powder is less than 1 μm; and the particle size of the Y2O3 powder is less than 2 μm.

[0009] As a preferred embodiment of the method for preparing a SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement described in the present invention, in which: in step S3, the mass ratio of sodium polystyrene sulfonate powder to Co-coated SiC whisker powder is 1:(80~150), the speed of the disperser is 600~1000 rpm, and the mixing time is 2~4 hours.

[0010] As a preferred embodiment of the method for preparing a SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement described in the present invention, in step S4, the electric field strength E is 0.5-2.0 V / cm, and the magnetic field strength B is 0.1-3.0 T.

[0011] As a preferred embodiment of the method for preparing a SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement described in the present invention, in which: in the step S5, freeze-drying comprises two stages: the first stage is freeze-drying, wherein the freezing temperature of freeze-drying is -40~-50°C and the freezing time is 1~3 hours; the second stage is sublimation drying, wherein the vacuum degree of sublimation drying is 5~20 Pa, the temperature is -40~-50°C, and the time is 20~30 hours.

[0012] As a preferred embodiment of the method for preparing a SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement described in the present invention, in step S6, the hot pressing sintering temperature is 1750-1850°C, the holding time is 1-2 hours, and the pressure is 25-40 MPa.

[0013] According to the second aspect of the present invention, the present invention provides the following technical solutions: A SiC whisker reinforced alumina ceramic material with directional whisker arrangement is prepared by adopting the above-mentioned method for preparing the SiC whisker reinforced alumina ceramic material with directional whisker arrangement.

[0014] As a preferred embodiment of the SiC whisker reinforced alumina ceramic material with oriented whisker arrangement according to the present invention, wherein: the relative density of the SiC whisker reinforced alumina ceramic material with oriented whisker arrangement is ≥98%, the hardness HV3 is ≥2050, the bending strength is ≥700MPa, and the fracture toughness Kic is ≥6.5MPa·m 1 / 2 .

[0015] The beneficial effects of the present invention are as follows: The present invention provides a SiC whisker reinforced alumina ceramic material with oriented whisker arrangement and a preparation method thereof. The SiC whisker is magnetized and modified by coating the SiC whisker with cobalt. Then, the magnetized SiC whisker powder is mixed with ball-milled Al2O3 ceramic slurry and sodium polystyrene sulfonate in a disperser and fully mixed. Then, an electric field and a magnetic field are simultaneously applied to the mixed solution, so that the SiC whiskers are turned under the action of the electric and magnetic fields, thereby achieving oriented arrangement in a certain direction. The solution is then promptly transferred to a freeze dryer to freeze and fix the oriented arrangement. Then, vacuum sublimation drying is performed at a low temperature to prepare Al2O3-Y2O3-SiC with oriented SiC whisker arrangement. w The mixed powder is subjected to hot pressing and sintering to prepare SiC whisker reinforced alumina ceramic material with significant whisker orientation. The ceramic material can be used to prepare ceramic cutting tools for efficient cutting of nickel-based high-temperature alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0017] Figure 1 Schematic diagram of applying electric and magnetic fields to a solution.

[0018] Figure 2 Al2O3-Y2O3-SiC prepared in Example 1 w SEM morphology of mixed powder.

[0019] Figure 3 Al2O3-Y2O3-SiC prepared in Comparative Example 5 w SEM morphology of mixed powder.

[0020] Figure 4 This is the SEM morphology of the fracture of the SiC whisker reinforced Al2O3 ceramic material prepared in Example 1.

[0021] Figure 5 This is the SEM morphology of the fracture of the SiC whisker reinforced Al2O3 ceramic material prepared in Example 5.

[0022] Figure 6 This is the SEM morphology of the fracture of the SiC whisker reinforced Al2O3 ceramic material prepared in Comparative Example 1.

[0023] Figure 7 This is the SEM morphology of the fracture of the SiC whisker reinforced Al2O3 ceramic material prepared in Comparative Example 5.

[0024] In the figure, 1-electrode, 2-container.

[0025] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0026] The following will be a clear and complete description of the technical solutions in the embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] The present invention provides a SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement and a preparation method thereof, which has the following advantages: (1) After adding cobalt nitrate to SiC whiskers and ball milling, the cobalt nitrate is reduced to cobalt in a hydrogen atmosphere, and the SiC whiskers are coated with cobalt, thereby achieving magnetic modification of the SiC whiskers. At the same time, the presence of cobalt can form a liquid phase at high temperature, improve the wettability of SiC whiskers with Al2O3, and enhance the interfacial bonding strength between SiC whiskers and Al2O3.

[0028] (2) After the magnetically modified SiC whiskers and Al2O3-Y2O3 ceramic slurry are fully dispersed and mixed with sodium polystyrene sulfonate, the SO3 2- It will be adsorbed on the surface of SiC whiskers, making it easier for SiC whiskers to combine with positively charged ions and increase the bonding strength between SiC whiskers and cobalt. At the same time, sodium polystyrene sulfonate is an organic electrolyte solution. Under the action of electric and magnetic fields (the schematic diagram of applying electric and magnetic fields to the solution is as shown in the figure), Figure 1 As shown in the figure, 1 is the electrode and 2 is the container), the SiC whisker particles can be turned to achieve directional arrangement in a certain direction. The solution is transferred to a freeze dryer for immediate freeze drying. Since it is dried in a frozen state, the volume will hardly change, maintaining the Al2O3-Y2O3-SiC wThe original directional arrangement orientation of SiC whiskers in the mixed powder.

[0029] (3) Al2O3-Y2O3-SiC w After hot pressing and sintering, the mixed powder can be used to prepare a SiC whisker-reinforced alumina ceramic material with a microstructure with significant SiC whisker orientation, high fracture toughness and bending strength. This material can be used to make ceramic tools for efficient cutting of nickel-based high-temperature alloys.

[0030] The technical solution of the present invention is further described below with reference to specific embodiments.

[0031] The specific preparation parameters of the SiC whisker reinforced alumina ceramic materials of Examples 1-5 are shown in Table 1 below.

[0032] Table 1 Preparation parameters of SiC whisker reinforced alumina ceramic materials of Examples 1-5 Example 1-5 According to the process parameter conditions of Table 1, weighed SiC whiskers, cobalt nitrate hexahydrate and citric acid are first added and ball-milled in a ball mill, and then dried. The dried powder is reduced in a hydrogen atmosphere to obtain cobalt-coated magnetically modified SiC whisker powder. Weigh Al2O3 powder and Y2O3 powder and pour them into a ball mill jar. According to the ball-to-material ratio of 6:1, φ5mm Al2O3 grinding balls are added, and anhydrous ethanol is poured into the ball mill to mix the Al2O3 powder and Y2O3 powder to prepare Al2O3-Y2O3 ceramic slurry. After the ball-milled Al2O3-Y2O3 ceramic slurry is fully dispersed and mixed with the cobalt-coated SiC whisker powder and sodium polystyrene sulfonate powder in a disperser, the SiC whiskers are turned under the action of an external electric field and a magnetic field. After 3 to 5 minutes, the Al2O3-Y2O3-SiC w The mixed solution container was transferred to a freeze dryer for freeze drying. The freeze-dried powder was then placed in a graphite mold and hot-pressed to produce a SiC whisker-reinforced alumina ceramic sample. This ceramic sample was then laser cut, surface ground, and sharpened to produce a ceramic cutting tool of the desired shape.

[0033] The specific preparation parameter conditions of the SiC whisker reinforced alumina ceramic materials of Comparative Examples 1-5 are shown in Table 2 below.

[0034] Table 2 Preparation parameters of SiC whisker reinforced alumina ceramic materials of Comparative Examples 1-5 The difference between Comparative Example 1 and Example 1 is that: during the SiC whisker magnetization treatment stage, the mass ratio of cobalt nitrate to SiC whiskers is 1:2, and the pH value is 6; The difference between Comparative Example 2 and Example 2 is that the mass ratio of sodium polystyrene sulfonate to SiC whiskers is 1:70, and the electric field intensity E is 0.4 V / cm; Comparative Example 3 differs from Example 3 in that the particle size of the Al2O3 powder is 1.2 μm, the mass ratio of sodium polystyrene sulfonate to SiC whiskers is 1:160, and the hot pressing sintering temperature is 1700°C; The difference between Comparative Example 4 and Example 4 is that: during the SiC whisker magnetization treatment stage, the pH value is 2; the electric field strength is 2.5 V / cm; The difference between Comparative Example 5 and Example 5 is that the mass ratio of cobalt nitrate to SiC whiskers is 1:6, and the magnetic field intensity is 3.5T.

[0035] Al2O3-Y2O3-SiC prepared in Example 1 w The SEM morphology of the mixed powder is shown in Figure 2 As shown. Al2O3-Y2O3-SiC prepared in Comparative Example 5 w The SEM morphology of the mixed powder is shown in Figure 3 As shown. Figure 2 and Figure 3 It can be seen that Figure 2 The SiC whiskers have obvious directional alignment along a certain direction. Figure 3 The SiC whiskers have no orientation. This means that when the mass ratio of cobalt nitrate to SiC whiskers exceeds 1:5, that is, when the cobalt content is low, even if the magnetic field strength is increased, the SiC whiskers cannot be oriented.

[0036] The fracture SEM morphology of the SiC whisker reinforced Al2O3 ceramic material prepared in Example 1 is shown in FIG. Figure 4 The fracture SEM morphology of the SiC whisker reinforced Al2O3 ceramic material prepared in Example 5 is shown in FIG. Figure 5 The fracture SEM morphology of the SiC whisker reinforced Al2O3 ceramic material prepared in Comparative Example 1 is shown in FIG. Figure 6 The fracture SEM morphology of the SiC whisker reinforced Al2O3 ceramic material prepared in Comparative Example 5 is shown in FIG. Figure 7 As shown. Figure 4-7 It can be seen that the SiC whiskers are clearly oriented in a certain direction in the fracture SEM of Example 1 and Example 5, while the SiC whiskers of Comparative Example 1 and Comparative Example 5 are disorderly distributed in the Al2O3 matrix and have no orientation.

[0037] The SiC whisker reinforced alumina ceramic materials prepared in each embodiment and the comparative example are tested for bending strength, hardness and density, and the results are shown in Table 3. It can be seen that the relative density of the SiC whisker reinforced alumina ceramic material prepared in the application is ≥98%, the hardness HV3 is ≥2050, the bending strength is ≥700 MPa, and the fracture toughness Kic is ≥6.5 MPa·m 1 / 2 .

[0038] The detection of the bending strength, hardness and fracture toughness is performed according to the method for testing the performance of ceramic cutting tool materials (JB / T 12613-2016). The sample bar size for the bending strength is 4 mm x 3 mm x 46 mm, the span is 30 mm, and the loading rate is 0.5 mm / min; the density is tested by the Archimedes drainage method, and the hardness and fracture toughness are tested by the indentation method, and the loading pressure is 3 kg.

[0039] Table 3 Performance of SiC whisker reinforced alumina ceramic prepared in each embodiment and the comparative example The ceramic samples of Example 1, Example 5, Comparative Example 1 and Comparative Example 5 are prepared into ceramic turning inserts of RNGN120700T01020, and the prepared ceramic inserts are subjected to turning test, the test material is nickel-based high-temperature alloy GH4169 (HRC 35-45), the turning mode is dry turning, and the cutting parameters are: cutting speed Vc is 300 m / min, feed f is 0.18 mm / rev, and cutting depth Ap is 0.5 mm, and the tool failure is judged when the relief wear VB reaches 0.2 mm; the cutting tool life results are shown in Table 4. It can be seen that the cutting tool life of the SiC whisker reinforced alumina ceramic cutting tool prepared by the method of the application is obviously better than that of the comparative example.

[0040] Table 4 Tool cutting life The above only describes the preferred embodiments of the application, and does not limit the patent scope of the application, and any equivalent structural transformation made according to the content of the application specification, or direct / indirect application in other related technical fields is included in the patent protection scope of the application.

Claims

1. A method for preparing a SiC whisker reinforced alumina ceramic material with oriented whisker arrangement, characterized in that: The steps include: S1. Magnetization treatment of SiC whiskers: disperse SiC whiskers in ethanol, add cobalt nitrate hexahydrate and citric acid, adjust the pH to acidic, ball mill in a ball mill and dry, and then reduce in H2 to obtain magnetic Co-coated SiC whisker powder; S2. Slurry preparation: Weigh a certain amount of Al2O3 powder and Y2O3 powder, add anhydrous ethanol, and ball mill to obtain Al2O3-Y2O3 ceramic slurry; S3, mixing: the Al2O3-Y2O3 ceramic slurry obtained in step S2, the Co-coated SiC whisker powder obtained in step S1, and the sodium polystyrene sulfonate powder are fully mixed in a disperser to obtain Al2O3-Y2O3-SiC w Mixing solution; S4, electric field-magnetic field assisted alignment: to the Al2O3-Y2O3-SiC obtained in step S3 w The mixed solution is subjected to an electric field and a magnetic field, and the arrangement direction of the SiC whiskers in the EB plane is controlled by adjusting the ratio E / B of the electric field intensity E to the magnetic field intensity B; S5, freeze molding: the solution after step S4 is promptly transferred to a freeze dryer for freeze drying to obtain Al2O3-Y2O3-SiC with oriented SiC whiskers. w powder; S6, sintering: the Al2O3-Y2O3-SiC w The powder is placed in a graphite mold and hot-pressed and sintered to obtain a SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement.

2. The method for preparing the SiC whisker reinforced alumina ceramic material with oriented whisker arrangement according to claim 1, characterized in that: Al2O3-Y2O3-SiC with oriented SiC whiskers w In the powder, the content of the Al2O3 powder is 68~84.5wt%, the SiC w The content of the powder is 15-30 wt %; the content of the Y2O3 powder is 0.5-2 wt %.

3. The method for preparing the SiC whisker reinforced alumina ceramic material with oriented whisker arrangement according to claim 1, characterized in that: In step S1, the mass ratio of cobalt nitrate hexahydrate to SiC whiskers is 1:3-5; the pH value is 3-5; the diameter of the SiC whiskers is 0.2-1 μm, and the aspect ratio is 20-100.

4. The method for preparing the SiC whisker reinforced alumina ceramic material with oriented whisker arrangement according to claim 1, characterized in that: In the step S2, the particle size of the Al2O3 powder is less than 1 μm; the particle size of the Y2O3 powder is less than 2 μm.

5. The method for preparing the SiC whisker reinforced alumina ceramic material with oriented whisker arrangement according to claim 1, characterized in that: In step S3, the mass ratio of sodium polystyrene sulfonate powder to Co-coated SiC whisker powder is 1:(80-150), the speed of the disperser is 600-1000 rpm, and the mixing time is 2-4 hours.

6. The method for preparing the SiC whisker reinforced alumina ceramic material with oriented whisker arrangement according to claim 1, characterized in that: In step S4, the electric field intensity E is 0.5-2.0 V / cm, and the magnetic field intensity B is 0.1-3.0 T.

7. The method for preparing the SiC whisker reinforced alumina ceramic material with oriented whisker arrangement according to claim 1, characterized in that: In step S5, freeze drying includes two stages: the first stage is freeze drying, wherein the freezing temperature of freeze drying is -40~-50°C and the freezing time is 1~3 hours; the second stage is sublimation drying, wherein the vacuum degree of sublimation drying is 5~20Pa, the temperature is -40~-50°C, and the time is 20~30 hours.

8. The method for preparing the SiC whisker reinforced alumina ceramic material with oriented whisker arrangement according to claim 1, characterized in that: In step S6, the hot pressing sintering temperature is 1750-1850° C., the holding time is 1-2 hours, and the pressure is 25-40 MPa.

9. A SiC whisker reinforced alumina ceramic material with oriented whisker arrangement, characterized in that: The SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement is prepared by the preparation method of any one of claims 1 to 8.

10. The SiC whisker reinforced alumina ceramic material with oriented whisker arrangement according to claim 9, characterized in that: The SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement has a relative density of ≥98%, a hardness HV3 ≥2050, a bending strength ≥700 MPa, and a fracture toughness Kic ≥6.5 MPa·m 1 / 2 .

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