Ultrasonic-assisted hot-pressed sintered SiC ceramic material and preparation method thereof

Abstract

The invention belongs to the technical field of high-temperature-resistant ceramic materials, and discloses a preparation method of an ultrasonic-assisted hot-pressed sintered SiC ceramic material, which comprises the following steps: step 1, mixing SiC powder, B4C powder and C powder, pouring into a ball milling tank, adding ethanol and WC alloy balls, and carrying out ball milling; step 2, putting the ball-milled mixed slurry into a constant-temperature drying oven, grinding after the ball-milled mixed slurry is completely dried, and sieving to obtain mixed powder; 3, the mixed powder is weighed and then put into a graphite mold; 4, the graphite mold is put into an ultrasonic-assisted hot-pressing sintering furnace to be sintered, ultrasonic vibration is applied in the heat preservation period, and the SiC ceramic material is obtained. The density of the material can be improved, and the mechanical property of the SiC ceramic material can be improved.

Description

Technical Field

[0001] This invention relates to the field of high-temperature resistant ceramic materials technology, specifically to a method for preparing ultrasonic-assisted hot-pressing sintering SiC ceramic materials. Background Technology

[0002] SiC ceramic materials possess high melting point, high hardness, good wear resistance, and high neutron absorption properties, making them widely used in machinery manufacturing, aerospace, nuclear industry, and defense. However, because SiC is a strongly covalent compound with a low diffusion coefficient, it is difficult to sinter and densify, which severely affects the hardness and strength of SiC materials, limiting their further development and application.

[0003] Currently, the main methods to improve SiC's performance include adding liquid-phase sintering aids and solid-phase sintering aids to lower the sintering temperature. Liquid-phase sintering aids (such as Y₂O₃, Al₂O₃, CaO, etc.) form a liquid phase during sintering, which can improve the sintering density of SiC. However, the addition of low-hardness materials reduces the overall hardness of the material. Solid-phase sintering aids (such as C, B, B₄C, etc.) can effectively remove the oxide layer on the SiC surface and promote the sintering density of SiC materials. However, they still require higher sintering temperatures and longer holding times, and can also lead to abnormal grain growth, reducing the material's mechanical properties.

[0004] In addition, SiC-based ceramic materials are commonly prepared by sintering methods such as pressureless sintering, hot pressing sintering, and spark plasma sintering, but their ability to improve the density of the material is limited. Summary of the Invention

[0005] To address the challenges of achieving dense SiC ceramic materials through sintering and the resulting low mechanical properties, this invention proposes a method for preparing SiC ceramic materials using ultrasonic-assisted hot pressing sintering, thereby improving the material's density.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for preparing ultrasonically assisted hot-pressing sintering SiC ceramic materials, comprising the following steps: Step 1: Mix SiC powder, B4C powder and C powder, pour into a ball mill jar, add ethanol and WC alloy balls, and ball mill; Step 2: Place the ball-milled slurry into a constant temperature drying oven, and after it is completely dry, grind and sieve it to obtain a mixed powder; Step 3: Weigh the mixed powder and then put it into the graphite mold; Step 4: Place the graphite mold into an ultrasonic-assisted hot pressing sintering furnace for sintering, and apply ultrasonic vibration during the heat preservation period to obtain SiC ceramic material.

[0007] In step 1, the mass percentage of SiC powder in the mixed powder is 95.2-97.7%, the mass percentage of B4C powder is 0.3-0.8%, and the mass percentage of C powder is 1.5-4.2%.

[0008] In step 4, the heating rate during sintering is 10℃ / min, the sintering pressure is 30MPa-50MPa, the sintering temperature is 1900℃-2000℃, and the holding time is 10min-30min.

[0009] In step 4, the temperature is raised to 1600℃ and ultrasonic vibration is applied.

[0010] In step 4, the applied ultrasonic vibration frequency is 20kHz and the amplitude is 5μm-15μm.

[0011] Compared with the prior art, the present invention has the following advantages: 1. This invention provides a method for preparing SiC ceramic materials by ultrasonic-assisted hot pressing sintering. Adding B4C to SiC ceramic materials can introduce dislocation defects, improve the hardness of the material, and improve the strength and toughness of the material. Adding C can remove the oxide layer on the surface of SiC, enhance the contact and diffusion between particles, reduce residual porosity, and promote the densification of the material, with a relative density of over 99.2.

[0012] 2. This invention enhances particle rearrangement, promotes the formation and growth of sintering necks, accelerates material densification, and improves material density by applying ultrasonic vibration during the sintering process. Simultaneously, ultrasonic vibration can shorten the holding time, inhibit abnormal grain growth, obtain uniform grain size, and improve the mechanical properties of the material.

[0013] In summary, the present invention uses ultrasonic-assisted hot pressing sintering of SiC ceramic materials, which can effectively reduce the densification temperature of SiC ceramic materials and improve the density of SiC ceramic materials; the prepared SiC ceramic materials have uniform grain size and excellent comprehensive mechanical properties. Attached Figure Description

[0014] Figure 1 This is a scanning electron microscope (SEM) image of the fracture surface of the SiC ceramic material prepared in an embodiment of the present invention. Figure 1 As can be seen, the SiC ceramic material prepared by ultrasonic-assisted hot pressing sintering technology has a relatively uniform microstructure and no obvious pore defects, indicating that the material is relatively dense. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Example 1 Embodiment 1 of the present invention provides a method for preparing ultrasonically assisted hot-pressing sintered SiC ceramic materials, comprising the following steps: (1) Material preparation: Weigh out the required raw material powder according to the designed material composition ratio, pour the powder into the ball mill jar, add an appropriate amount of ethanol and WC alloy balls into the ball mill jar, and perform ball milling.

[0017] In the mixed powder of the present invention, the mass percentage of SiC powder is 95.2-97.7%, the mass percentage of B4C powder is 0.3-0.8%, and the mass percentage of C powder is 1.5-4.2%.

[0018] Specifically, in this embodiment, the raw materials are composed of the following mass percentages: SiC 97.7%, B4C 0.8%, C 1.5%, and the total thickness of the test sample is designed to be 4 mm, with a diameter of 35 mm.

[0019] (2) Drying: Place the ball-milled slurry into a constant temperature drying oven and grind and sieve it after it is completely dry.

[0020] (3) Loading: Weigh the required SiC powder and load it into the graphite mold.

[0021] (4) Ultrasonic-assisted hot pressing sintering: The graphite mold with the blank is placed in the ultrasonic-assisted hot pressing sintering furnace. Under the conditions of heating rate of 10℃ / min, sintering pressure of 50MPa, sintering temperature of 1900℃, the holding time is 30min. During the holding time, ultrasonic vibration of 20kHz with an amplitude of about 15μm is applied to obtain SiC ceramic material.

[0022] Example 2 Embodiment 2 of the present invention provides a method for preparing SiC ceramic materials by ultrasonic-assisted hot pressing sintering, comprising the following steps: (1) Material preparation: Weigh out the required raw material powder according to the designed material composition ratio, pour the powder into the ball mill jar, add an appropriate amount of ethanol and WC alloy balls into the ball mill jar, and perform ball milling.

[0023] Specifically, in this embodiment, the raw materials are composed of the following mass percentages: SiC 96.5%, B4C 0.5%, C 3%, and the total thickness of the test sample is designed to be 4 mm, with a diameter of 35 mm.

[0024] (2) Drying: Place the ball-milled slurry into a constant temperature drying oven and grind and sieve it after it is completely dry.

[0025] (3) Loading: Weigh the required SiC powder and load it into the graphite mold.

[0026] (4) Ultrasonic-assisted hot pressing sintering: The graphite mold with the blank is placed in the ultrasonic-assisted hot pressing sintering furnace. Under the conditions of heating rate of 10℃ / min, sintering pressure of 40MPa, sintering temperature of 2000℃, the holding time is 10min. During the holding time, ultrasonic vibration of 20kHz with an amplitude of about 10μm is applied to obtain SiC ceramic material.

[0027] Example 3 Embodiment 3 of the present invention provides a method for preparing ultrasonically assisted hot-pressing sintered SiC ceramic materials, comprising the following steps: (1) Material preparation: Weigh out the required raw material powder according to the designed material composition ratio, pour the powder into the ball mill jar, add an appropriate amount of ethanol and WC alloy balls into the ball mill jar, and perform ball milling.

[0028] Specifically, in this embodiment, the raw materials are composed of the following mass percentages: SiC 95.2%, B4C 0.8%, C 4%, and the total thickness of the test sample is designed to be 4 mm, with a diameter of 35 mm.

[0029] (2) Drying: Place the ball-milled slurry into a constant temperature drying oven and grind and sieve it after it is completely dry.

[0030] (3) Loading: Weigh the required SiC powder and load it into the graphite mold.

[0031] (4) Ultrasonic-assisted hot pressing sintering: The graphite mold with the blank is placed in the ultrasonic-assisted hot pressing sintering furnace. Under the conditions of heating rate of 10℃ / min, sintering pressure of 30MPa, sintering temperature of 2000℃, and holding time of 10min, ultrasonic vibration of 20kHz is applied at 1600℃ and ultrasonic vibration of 20kHz is applied during the holding period. The amplitude is about 5μm, and SiC ceramic material is obtained.

[0032] Example 3 Example 3 of the present invention provides a SiC ceramic material, which is prepared according to the preparation methods in Examples 1 to 3.

[0033] Specifically, the SiC ceramic material has a relative density between 99.2% and 99.9%, a hardness between 29.63 and 31.33 GPa, a flexural strength between 701 and 927 GPa, and a fracture toughness between 7.53 and 10.43 MPa·m. 1 / 2 .

[0034] like Figure 1 The image shown is a scanning electron microscope (SEM) image of the fracture surface of the SiC ceramic material prepared according to the present invention. Figure 1 As can be seen, the SiC ceramic material prepared by ultrasonic-assisted hot pressing sintering technology has a relatively uniform microstructure and no obvious pore defects, indicating that the material is relatively dense.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing SiC ceramic materials by ultrasonic-assisted hot pressing sintering, characterized in that, Includes the following steps: Step 1: Mix SiC powder, B4C powder and C powder, pour into a ball mill jar, add ethanol and WC alloy balls, and ball mill; Step 2: Place the ball-milled slurry into a constant temperature drying oven, and after it is completely dry, grind and sieve it to obtain a mixed powder; Step 3: Weigh the mixed powder and then put it into the graphite mold; Step 4: Place the graphite mold into an ultrasonic-assisted hot pressing sintering furnace for sintering, and apply ultrasonic vibration during the heat preservation period to obtain SiC ceramic material.

2. The method for preparing ultrasonically assisted hot-pressing sintered SiC ceramic material according to claim 1, characterized in that, In step 1, the mass percentage of SiC powder in the mixed powder is 95.2-97.7%, the mass percentage of B4C powder is 0.3-0.8%, and the mass percentage of C powder is 1.5-4.2%.

3. The method for preparing ultrasonically assisted hot-pressing sintered SiC ceramic material according to claim 1, characterized in that, In step 4, the heating rate during sintering is 10℃ / min, the sintering pressure is 30MPa-50MPa, the sintering temperature is 1900℃-2000℃, and the holding time is 10min-30min.

4. The method for preparing ultrasonically assisted hot-pressing sintered SiC ceramic material according to claim 1, characterized in that, In step 4, the temperature is raised to 1600℃ and ultrasonic vibration is applied.

5. The method for preparing ultrasonically assisted hot-pressing sintered SiC ceramic material according to claim 1, characterized in that, In step 4, the applied ultrasonic vibration frequency is 20kHz and the amplitude is 5μm-15μm.

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