Vacuum hot casting molding preparation method of nickel-titanium alloy reinforced nano silicon carbide composite ceramic part

Abstract

The invention discloses a vacuum hot casting molding preparation method of a nickel-titanium alloy reinforced nano silicon carbide composite ceramic part, and belongs to the technical field of ceramic preparation. The invention is used for solving the technical problems of poor chemical stability and thermal stability of silicon nitride ceramic, low density of single silicon nitride sintered ceramic and high brittleness of ceramic caused by matrix doped components in the prior art. A vacuum hot casting molding preparation method of a nickel-titanium alloy reinforced nano silicon carbide composite ceramic part comprises the following steps: uniformly mixing coated nano silicon carbide, an organic binder and deionized water to obtain mixed slurry; carrying out vacuum hot casting on the mixed slurry to obtain a reinforced nano silicon carbide composite ceramic part; and the surface of the enhanced nano silicon carbide composite ceramic part is coated with the modified nickel-titanium alloy coating mixture, then drying and curing are conducted, and the nickel-titanium alloy enhanced nano silicon carbide composite ceramic part is prepared. The composite ceramic prepared by the invention has the advantages of high mechanical property, high density, good thermal stability and good chemical stability.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramics, and specifically relates to a method for preparing nickel-titanium alloy reinforced nano-silicon carbide composite ceramic parts by vacuum hot casting molding. Background Art

[0002] With the booming development of fields closely related to national development such as the aerospace industry, national defense and military industry, and nuclear industry, natural materials can no longer meet their needs for extremely harsh environments, especially in extremely high-temperature and high-pressure environments. Ceramic materials can be used not only in the national defense and military industries and the aviation industry, but also widely applied in fields such as transport aircraft, rockets, and satellites. Among them, silicon nitride ceramics, as engineering structural ceramic materials, have the advantages of high temperature resistance and high strength; however, single silicon nitride is difficult to sinter densely. In addition, how to maintain high density, thermal stability, and chemical stability while still having high strength is the key to synthesizing high-performance silicon nitride ceramic materials.

[0003] Patent application CN109293374A discloses a preparation method of "andalusite-boron carbide-silicon nitride-silicon carbide" quaternary refractory ceramics. The slurry is used to prepare a green body by vacuum vibration casting molding; then the green body is put into a nitriding furnace for nitriding treatment, and finally cooled to room temperature to prepare a ceramic with excellent thermal shock resistance and oxidation erosion resistance. However, the mixing of multiple components in the matrix of the above ceramic materials will increase the brittleness of the prepared ceramics, thereby reducing their own flexural strength and fracture toughness, which is not conducive to the processing and preservation of ceramics.

[0004] Patent application CN109320276A discloses a preparation method of silicon nitride whisker and silicon nitride nanowire reinforced silicon nitride-based wave-transparent ceramics. Green bodies are prepared by selecting different volumes of Si3N 4w and Si powder, and then processed into ceramics. However, the purpose of doping the above silicon nitride powder materials is to improve their own wave-transparent properties; and the mechanical properties and chemical stability of the ceramic materials have not been improved.

[0005] In view of the technical deficiencies in this regard, a solution is proposed now. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing nickel-titanium alloy reinforced nano-silicon carbide composite ceramic parts by vacuum hot casting molding, which is used to solve the technical problems in the prior art that the chemical stability and thermal stability of silicon nitride ceramics are poor, the density of single silicon nitride sintered ceramics is low, and the matrix doping components result in high brittleness of ceramics.

[0007] The purpose of the present invention can be achieved by the following technical solutions: A method for preparing a nickel-titanium alloy reinforced nano-silicon carbide composite ceramic part by vacuum hot casting molding, comprising the following steps: S1. Mix the coated nano-silicon carbide, organic binder and deionized water to obtain a mixed slurry; S2. Pour the mixed slurry into a metal mold by vacuum hot casting process. Under a vacuum degree of 20 - 30 kPa, vacuum hot cast at 1350 - 1500 °C for 3 - 5 h to synthesize a titanium alloy reinforced nano-silicon carbide composite ceramic part; Uniformly mix the coated nano-silicon carbide, organic binder and water, and adopt the vacuum hot casting molding technology to prepare a reinforced nano-silicon carbide composite ceramic part.

[0008] S3. Coating the surface of the reinforced nano-silicon carbide composite ceramic part with a modified nickel-titanium alloy coating mixture, with a coating thickness of 10 - 20 μm, and then roasting to obtain a nickel-titanium alloy reinforced nano-silicon carbide composite ceramic part.

[0009] Coat the surface of the reinforced nano-silicon carbide composite ceramic part with a coating solution doped with nickel-titanium alloy, and then dry and cure to prepare a nickel-titanium alloy reinforced nano-silicon carbide composite ceramic part.

[0010] Further, in step S1, the preparation process of the coated nano-silicon carbide comprises the following steps: A1. Under a nitrogen atmosphere, mix diphenylchlorosilane and chlorobenzene to obtain a mixture; drop methylimidazole into the mixture, and after dropping, obtain a reaction system; heat the reaction system to 75 - 85 °C and react for 3 - 4 h, then let it stand and cool to room temperature, and collect the lower-layer organic liquid; Using methylimidazole as a catalyst, diphenylchlorosilane and chlorobenzene undergo a nucleophilic substitution reaction to obtain a silane compound and generate hydrogen chloride gas. The reaction formula is as follows:

[0011] A2. Add deionized water to the organic liquid to obtain a hydrolysis product; add the hydrolysis product and nano-silicon carbide to a granulator for coating according to a mass ratio of 1:5 - 10 to obtain coated nano-silicon carbide.

[0012] The organic liquid and water undergo a hydrolysis reaction to obtain a hydrolysis product containing hydroxyl groups; using the hydrolysis product as a coating solution, without the action of a coupling agent, and through a coating process, coated nano-silicon carbide is prepared.

[0013] Further, in step A1, the dosage ratio of diphenylchlorosilane, chlorobenzene and methylimidazole is 10.9 - 21.8 g: 5.6 - 11.2 g: 0.2 - 0.4 g; in step A2, the dosage ratio of the organic liquid and deionized water is 10 - 15 g: 2 - 5 mL; the rotational speed of the granulator is 1000 - 2000 r / min, the coating temperature is 70 - 80 °C, and the coating duration is 20 - 30 min.

[0014] Further, in step S3, the preparation method of the modified nickel-titanium alloy coating solute liquid includes the following steps: B1. Mix the dried polyethylene glycol 2000, toluene diisocyanate and diphenylmethane diisocyanate, then add a catalyst and mix well to obtain a mixture; the mixture reacts at 65 - 75 °C for 1 - 1.5 h to obtain a polyurethane prepolymer; Under the action of a catalyst, the reaction of toluene diisocyanate, diphenylmethane diisocyanate and polyethylene glycol 2000 to obtain a polyurethane prepolymer is as follows:

[0015] B2. Drop 4-formylphenylboronic acid into the polyurethane prepolymer, stir and react at 65 - 75 °C for 1 - 2 h, and then cure in an oven at 70 - 80 °C for 20 - 24 h to obtain a dynamic reversible polyurethane material; The reaction of 4-formylphenylboronic acid and the polyurethane prepolymer to obtain a dynamic reversible polyurethane material is as follows:

[0016] B3. Ultrasonically clean the nickel-titanium alloy powder successively with absolute ethanol and deionized water, and then dry it at room temperature to obtain the surface-pretreated nickel-titanium alloy powder; B4. Mix the dynamic reversible polyurethane material and the calcium phosphate solution according to a mass ratio of 2 - 3:1 to obtain a coating solution; immerse the surface-pretreated nickel-titanium alloy powder in the coating solution, and then dry it under vacuum to obtain the modified nickel-titanium alloy powder.

[0017] The surface-pretreated nickel-titanium alloy powder is immersed in the coating solution to form a coating, and the modified nickel-titanium alloy powder is prepared.

[0018] Further, in step B1, the dried polyethylene glycol 2000 is obtained by drying polyethylene glycol 2000 at 100 - 105°C for 1 - 2 h, and the catalyst is dibutyltin dilaurate; the dosage ratio of the dried polyethylene glycol 2000, toluene diisocyanate, diphenylmethane diisocyanate, and the catalyst is 20 - 30 g : 1.74 - 3.48 g : 2.5 - 5 g : 0.01 - 0.02 g; in step B2, the dosage ratio of 4-formylphenylboronic acid and the polyurethane prepolymer is 1.5 - 3 g : 20 - 25 g; in step B3, the frequency of the two ultrasonic cleanings is 20 - 30 KHz, and the ultrasonic duration is 10 - 20 min; the drying temperature is 25°C, and the drying duration is 20 - 30 min.

[0019] Further, in step B4, the concentration of the calcium phosphate solution is 0.01 - 0.02 g / mL; the mass ratio of the nickel-titanium alloy powder after surface pretreatment to the coating solution is 1 : 5 - 10; the soaking temperature is 25°C, and the soaking duration is 1 - 2 h; the surface coating thickness of the modified nickel-titanium alloy powder is 10 - 20 μm.

[0020] Further, in step S1, the organic binder is clay; the weight ratio of the coated nano-silicon carbide, the organic binder, and deionized water is 40 - 50 : 10 - 20 : 30 - 50; in step S3, the drying and curing temperature is 70 - 80°C, and the drying and curing duration is 1 - 2 h.

[0021] The present invention has the following beneficial effects: 1. In the present invention, the coated nano-silicon carbide, the organic binder, and deionized water are mixed to obtain a mixed slurry for preparing ceramics; the mixed slurry is used to prepare a nano-silicon carbide composite ceramic part by a vacuum hot casting process. Then, a modified nickel-titanium alloy coating mixture is coated on the surface of the nano-silicon carbide composite ceramic part, and then dried and cured to finally obtain a nickel-titanium alloy-reinforced nano-silicon carbide composite ceramic part. The vacuum hot casting process helps to remove the bubbles in the casting material, reduce the pores in the prepared ceramics, and form a silicon carbide ceramic matrix with uniformly distributed silicon elements. The packing density of the ceramic powder is large to reduce the porosity during packing, lower the compression ratio during molding, so that the density of the green body after pressing is large and uniform. Then, a modified nickel-titanium alloy coating mixture is coated on the surface of the nano-silicon carbide composite ceramic part, which can further improve the mechanical properties such as the hardness and thermal stability of the prepared ceramic products.

[0022] 2. Polyethylene glycol 2000, toluene diisocyanate and diphenylmethane diisocyanate are used as monomers to synthesize a polyurethane prepolymer; the polyurethane prepolymer is modified with 4-formylphenylboronic acid to obtain a dynamic reversible polyurethane material. Through the structural design of the polyurethane molecular chain, the synthesized polyurethane has good mechanical properties and can introduce dynamic bonds between the molecular chains. The dynamic reversible polyurethane material is mixed with a calcium phosphate solution to obtain a coating solution; nickel-titanium alloy powder is immersed in the coating solution, and a coating can be formed on the surface of the nickel-titanium alloy powder; this porous structure and dynamic reversible bonds can enable the nickel-titanium alloy to maintain the shape memory effect during the heating process, and can improve the mechanical stability and chemical stability of the coated and modified nickel-titanium alloy coating mixture ceramics themselves.

[0023] 3. The present invention selects nanoscale silicon carbide to prepare ceramics. The technical principle of toughening by nanotechnology is that the matrix contains nanoparticles, which can be used as reinforcing phases to inhibit the growth of ceramic grains, and the surface and grain boundary sizes of the grains increase exponentially. The quantum effect and interface effect improve the mechanical properties of the nanomaterials. The hydrolysis product of the reaction product of diphenylchlorosilane and chlorobenzene is used to replace the coupling agent to coat the nanoscale silicon carbide, thereby improving the dispersibility of the coated nanoscale silicon carbide in the mixed slurry. In addition, during the vacuum casting process, the coated nanoscale silicon carbide is dispersed in the ceramic matrix with silicon elements, playing a role in toughening and strengthening, and can significantly improve the mechanical properties of the prepared composite ceramic materials. Specific embodiments

[0024] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present invention.

[0025] The nanoscale silicon carbide used in Examples 1-3 of the present invention was purchased from Haixu Abrasives, specifically black silicon carbide, with a SiC content of 97.5%, a particle size of 100-200 nm, a Mohs hardness of 9.2, and a true density of 3.2-3.45 g / cm 3 ; the polyethylene glycol 2000 used in Examples 4-6 of the present invention was purchased from Jiangsu Haian Petrochemical Factory, with a hydroxyl value of 51-63 mgKOH / g and a molecular weight of 1800-2200; the nickel-titanium alloy powder used in Examples 4-6 of the present invention was purchased from Nangong Sharp Alloy Welding Materials, with a nickel content of 56% and a particle size of 75-225 μm; the clay used in Examples 7-9 of the present invention was purchased from Sishui Yuexin Foundry Materials Factory, with a product number of 2301.

[0026] Example 1 This embodiment provides a preparation process for coating nano-silicon carbide used in nickel-titanium alloy reinforced nano-silicon carbide composite ceramic materials, comprising the following steps: A1. In a 500 mL three-necked flask, add 10.9 g of diphenylchlorosilane and 5.6 g of chlorobenzene, mix well to obtain a mixture; then introduce nitrogen into the three-necked flask to place the three-necked flask in a nitrogen atmosphere. The three-necked flask is connected to a dropping funnel, and 0.2 g of methylimidazole is added to the three-necked flask through the dropping funnel. After the addition is complete, a reaction system is obtained. The three-necked flask is transferred to a water bath, heated to 75 °C, reacted at this temperature for 3 h, then left to stand and cooled to room temperature, and the lower-layer organic liquid is collected.

[0027] A2. Add 2 mL of deionized water to 10 g of the organic liquid to obtain a hydrolysis product. The hydrolysis product and nano-silicon carbide are added to a granulator for coating according to a mass ratio of 1:5. The rotation speed of the granulator is 1000 r / min, the coating temperature is 70 °C, and the coating duration is 20 min to obtain coated nano-silicon carbide.

[0028] Example 2 This embodiment provides a preparation process for coating nano-silicon carbide used in nickel-titanium alloy reinforced nano-silicon carbide composite ceramic materials, comprising the following steps: A1. In a 500 mL three-necked flask, add 15.5 g of diphenylchlorosilane and 8.4 g of chlorobenzene, mix well to obtain a mixture; then introduce nitrogen into the three-necked flask to place the three-necked flask in a nitrogen atmosphere. The three-necked flask is connected to a dropping funnel, and 0.3 g of methylimidazole is added to the three-necked flask through the dropping funnel. After the addition is complete, a reaction system is obtained. The three-necked flask is transferred to a water bath, heated to 80 °C, reacted at this temperature for 3.5 h, then left to stand and cooled to room temperature, and the lower-layer organic liquid is collected.

[0029] A2. Add 3 mL of deionized water to 12 g of the organic liquid to obtain a hydrolysis product. The hydrolysis product and nano-silicon carbide are added to a granulator for coating according to a mass ratio of 1:8. The rotation speed of the granulator is 1500 r / min, the coating temperature is 75 °C, and the coating duration is 25 min to obtain coated nano-silicon carbide.

[0030] Example 3 This embodiment provides a preparation process for coating nano-silicon carbide used in nickel-titanium alloy reinforced nano-silicon carbide composite ceramic materials, comprising the following steps: A1. In a 500 mL three-necked flask, add 21.8 g of diphenylchlorosilane and 11.2 g of chlorobenzene, mix well to obtain a mixture. Then, introduce nitrogen into the three-necked flask to place the three-necked flask in a nitrogen atmosphere. The three-necked flask is connected to a dropping funnel, and 0.4 g of methylimidazole is added to the three-necked flask through the dropping funnel. After the addition is complete, a reaction system is obtained. The three-necked flask is transferred to a water bath, heated to 85 °C, reacted at this temperature for 4 h, and then allowed to stand and cool to room temperature. The lower-layer organic liquid is collected.

[0031] A2. Add 5 mL of deionized water to 15 g of the organic liquid to obtain a hydrolysis product. The hydrolysis product and nano-silicon carbide are added to a granulator for coating according to a mass ratio of 1:10. The rotation speed of the granulator is 2000 r / min, the coating temperature is 80 °C, and the coating duration is 30 min to obtain coated nano-silicon carbide.

[0032] Example 4 This example provides a preparation process for a modified nickel-titanium alloy coating mixture for a nickel-titanium alloy reinforced nano-silicon carbide composite ceramic material, including the following steps: B1. Place polyethylene glycol 2000 in a vacuum oven and dry it at 30 °C for 1 h to obtain dried polyethylene glycol 2000. Add 1.74 g of toluene diisocyanate, 2.5 g of diphenylmethane diisocyanate, and 20 g of polyethylene glycol 2000 to a 500 mL beaker. Place the beaker on a water bath, and then add 0.01 g of the catalyst dibutyltin dilaurate, mix well to obtain a mixture; the mixture is reacted at 65 °C for 1 h to obtain a polyurethane prepolymer.

[0033] B2. Drop 1.5 g of 4-formylphenylboronic acid into 20 g of the polyurethane prepolymer at a rate of 0.5 g / min, stop heating after stirring and reacting at 65 °C for 1 h, and then cure in a forced-air drying oven at 70 °C for 20 h to obtain a dynamic reversible polyurethane material.

[0034] B3. The nickel-titanium alloy powder is ultrasonically cleaned with anhydrous ethanol and then with deionized water successively. The frequency of both ultrasonic cleanings is 20 KHz, and the ultrasonic duration is 10 min. Then, it is dried at 25 °C for 20 min to obtain the surface-pretreated nickel-titanium alloy powder.

[0035] B4. Mix the dynamic reversible polyurethane material and a calcium phosphate solution of 0.01 g / mL according to a mass ratio of 2:1 to obtain a coating solution. At 25 °C, immerse the surface-pretreated nickel-titanium alloy powder in the coating solution for 1 h and mix well. The mass ratio of the nickel-titanium alloy powder to the coating solution is 1:5 to obtain a modified nickel-titanium alloy coating mixture.

[0036] Example 5 This embodiment provides a preparation process for a modified nickel-titanium alloy coating mixture for nickel-titanium alloy reinforced nano-silicon carbide composite ceramics, comprising the following steps: B1. Place polyethylene glycol 2000 in a vacuum oven and dry it at 33 °C for 1.5 h to obtain dried polyethylene glycol 2000. Add 2.8 g of toluene diisocyanate, 3.5 g of diphenylmethane diisocyanate and 25 g of polyethylene glycol 2000 into a 500 mL beaker. Place the beaker on a water bath, and then add 0.015 g of the catalyst dibutyltin dilaurate, and mix well to obtain a mixture. React the mixture at 70 °C for 1.2 h to obtain a polyurethane prepolymer.

[0037] B2. Drop 2.5 g of 4-formylphenylboronic acid into 22 g of the polyurethane prepolymer at a rate of 0.8 g / min. Stop heating after stirring and reacting at 70 °C for 1.5 h, and then cure in a forced air drying oven at 75 °C for 22 h to obtain a dynamic reversible polyurethane material.

[0038] B3. Clean the nickel-titanium alloy powder successively by ultrasonic cleaning with anhydrous ethanol and ultrasonic cleaning with deionized water. The frequency of both ultrasonic cleanings is 25 KHz and the ultrasonic duration is 15 min. Then dry it at 25 °C for 23 min to obtain the nickel-titanium alloy powder after surface pretreatment.

[0039] B4. Mix the dynamic reversible polyurethane material and a calcium phosphate solution of 0.015 g / mL according to a mass ratio of 2.7:1 to obtain a coating solution. At 25 °C, immerse the nickel-titanium alloy powder after surface pretreatment in the coating solution for 1.5 h and mix well. The mass ratio of the nickel-titanium alloy powder to the coating solution is 1:8 to obtain a modified nickel-titanium alloy coating mixture.

[0040] Example 6 This embodiment provides a preparation process for a modified nickel-titanium alloy coating mixture for nickel-titanium alloy reinforced nano-silicon carbide composite ceramics, comprising the following steps: B1. Place polyethylene glycol 2000 in a vacuum oven and dry it at 40 °C for 2 h to obtain dried polyethylene glycol 2000. Add 3.48 g of toluene diisocyanate, 5 g of diphenylmethane diisocyanate and 30 g of polyethylene glycol 2000 into a 500 mL beaker. Place the beaker on a water bath, and then add 0.02 g of the catalyst dibutyltin dilaurate, and mix well to obtain a mixture. React the mixture at 75 °C for 1.5 h to obtain a polyurethane prepolymer.

[0041] B2. Drop 3 g of 4-formylphenylboronic acid into 25 g of the polyurethane prepolymer at a rate of 1 g / min. Stop heating after stirring and reacting at 75 °C for 2 h, and then cure in a forced air drying oven at 80 °C for 24 h to obtain a dynamic reversible polyurethane material.

[0042] B3. The NiTi alloy powder was ultrasonically cleaned with anhydrous ethanol and then with deionized water successively. The frequency of both ultrasonic cleanings was 30 KHz, and the ultrasonic duration was 20 min. Then it was dried at 25 °C for 30 min to obtain the NiTi alloy powder with surface pretreatment.

[0043] B4. The dynamic reversible polyurethane material and the calcium phosphate solution with a concentration of 0.02 g / mL were mixed evenly according to a mass ratio of 3:1 to obtain a coating solution. At 25 °C, the NiTi alloy powder with surface pretreatment was immersed in the coating solution for 2 h and mixed evenly. The mass ratio of the NiTi alloy powder to the coating solution was 1:10 to obtain a modified NiTi alloy coating mixture.

[0044] Example 7 This example provides a method for vacuum hot casting and molding of a NiTi alloy reinforced nano-silicon carbide composite ceramic part, which includes the following steps: S1. By weight, 40 parts of the coated nano-silicon carbide prepared in Example 1, 10 parts of the organic binder clay, and 30 parts of deionized water were evenly mixed to obtain a mixed slurry.

[0045] S2. The mixed slurry was poured into a metal mold, and a titanium alloy reinforced nano-silicon carbide composite ceramic part with dimensions of Φ60 mm × Φ40 mm × Φ1600 mm was prepared by using the vacuum hot casting process; among them, the vacuum degree was 20 - 30 kPa, the temperature of the vacuum hot casting was 1350 °C, and the duration of the vacuum hot casting was 3 h.

[0046] S3. The modified NiTi alloy coating mixture prepared in Example 4 was coated on the surface of the nano-silicon carbide composite ceramic part, and the coating thickness was 10 μm; then it was transferred to a vacuum drying oven and dried and cured at 70 °C for 1 h to prepare a NiTi alloy reinforced nano-silicon carbide composite ceramic part.

[0047] Example 8 This example provides a method for vacuum hot casting and molding of a NiTi alloy reinforced nano-silicon carbide composite ceramic part, which includes the following steps: S1. By weight, 45 parts of the coated nano-silicon carbide prepared in Example 2, 15 parts of the organic binder clay, and 40 parts of deionized water were evenly mixed to obtain a mixed slurry.

[0048] S2. The mixed slurry was used for vacuum hot casting to prepare a titanium alloy reinforced nano-silicon carbide composite ceramic part with dimensions of Φ60 mm × Φ40 mm × Φ1600 mm; among them, the temperature of the vacuum hot casting was 1450 °C, and the duration of the vacuum hot casting was 4 h.

[0049] S3. Coat the surface of the nano - silicon carbide composite ceramic part with the modified nickel - titanium alloy coating mixture prepared in Example 5, with a coating thickness of 15 μm; then transfer it to a vacuum drying oven and dry and cure it at 75 °C for 1.5 h to prepare a nickel - titanium alloy reinforced nano - silicon carbide composite ceramic part.

[0050] Example 9 This example provides a method for preparing a nickel - titanium alloy reinforced nano - silicon carbide composite ceramic part by vacuum hot casting molding, including the following steps: S1. By weight, uniformly mix 50 parts of the coated nano - silicon carbide prepared in Example 3, 20 parts of the organic binder clay, and 50 parts of deionized water to obtain a mixed slurry.

[0051] S2. Use the mixed slurry to prepare a nano - silicon carbide composite ceramic part with dimensions of Φ60mm×Φ40mm×Φ1600mm by vacuum hot casting; among them, the temperature of vacuum hot casting is 1500 °C, and the duration of vacuum hot casting is 5 h.

[0052] S3. Coat the surface of the nano - silicon carbide composite ceramic part with the modified nickel - titanium alloy coating mixture prepared in Example 6, with a coating thickness of 20 μm; then transfer it to a vacuum drying oven and dry and cure it at 80 °C for 2 h to prepare a nickel - titanium alloy reinforced nano - silicon carbide composite ceramic part.

[0053] Comparative Example 1 The difference between this comparative example and Example 9 is that in step S1, nano - silicon carbide of the same mass is used to replace the coated nano - silicon carbide.

[0054] Comparative Example 2 The difference between this comparative example and Example 9 is that when preparing the modified nickel - titanium alloy coating mixture, 4 - formylphenylboronic acid modification is not added to the synthesized polyurethane prepolymer, and then it is directly cured to obtain a polyurethane material.

[0055] Comparative Example 3 The difference between this comparative example and Example 9 is that when preparing the modified nickel - titanium alloy coating mixture, the polyurethane prepolymer and deionized water are mixed evenly according to a mass ratio of 3:1 to obtain a coating solution.

[0056] Performance test: 1. Sequentially measure the strength values of the nickel - titanium alloy reinforced nano - silicon carbide composite ceramic materials prepared in Examples 7 - 9 and Comparative Examples 1 - 3 by a three - point bending strength test.

[0057] 2. Use the single - edge notched beam method and sequentially measure the fracture toughness of the nickel - titanium alloy reinforced nano - silicon carbide composite ceramic materials prepared in Examples 7 - 9 and Comparative Examples 1 - 3 with a universal mechanical testing machine.

[0058] 3. The surface microhardness of the nickel-titanium alloy reinforced nano-silicon carbide composite ceramic materials prepared in Examples 7-9 and Comparative Examples 1-3 was tested successively using a micro Vickers hardness instrument; the loading load was 4.9 N, the pressure was maintained for 10 s, and the average value was obtained by measuring five times.

[0059] 4. The density and porosity of the nickel-titanium alloy reinforced nano-silicon carbide composite ceramic materials prepared in Examples 7-9 and Comparative Examples 1-3 were calculated successively using the Archimedes drainage method.

[0060] 5. A thermogravimetric analyzer was used to analyze and record the thermal weight loss rate of the nickel-titanium alloy reinforced nano-silicon carbide composite ceramic materials prepared in Examples 7-9 and Comparative Examples 1-3 at 800 °C successively.

[0061] Table 1 - Data sheet for performance detection of specimens

[0062] Data analysis: By comparing and analyzing the data in Table 1 above, the nickel-titanium alloy reinforced nano-silicon carbide composite ceramic parts prepared in Examples 7-9 of the present invention using the vacuum hot casting process all have excellent mechanical properties, including high hardness, density, fracture toughness and flexural strength; the prepared ceramic parts have a low porosity and good thermal stability (low thermal weight loss rate at 800 °C).

[0063] However, in Comparative Example 1, nano-silicon carbide of the same mass was used to replace the coated nano-silicon carbide; the nano-silicon carbide coated with silicone has better compatibility and dispersibility in the mixed slurry; in addition, the silicon element in the silicone can be dispersed in the ceramic matrix through the calcination process, playing a role in toughening and strengthening. Therefore, the mechanical properties such as flexural strength, fracture toughness, hardness, and density of the ceramic parts prepared in Comparative Example 1 decreased.

[0064] In Comparative Example 2, when preparing the modified nickel-titanium alloy coating mixture, 4-formylphenylboronic acid modification was not added to the synthesized polyurethane prepolymer, making the prepared modified nickel-titanium alloy coating mixture not have dynamic reversibility, thereby reducing the mechanical properties of the prepared ceramic parts. In Comparative Example 3, calcium phosphate solution was not added to the coating solution, and the mechanical properties of the synthesized ceramic parts increased slightly, but their own thermal stability decreased.

[0065] The above content is only an example and explanation of the structure of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined by the claims of the present invention, they should all fall within the protection scope of the present invention.

[0066] In the description of this specification, the descriptions referring to the terms "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0067] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not exhaust all the details and do not limit the present invention to only the specific embodiments. Obviously, many modifications and variations can be made according to the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the present invention, so that those skilled in the relevant technical fields can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for preparing a nickel-titanium alloy reinforced nano-silicon carbide composite ceramic part by vacuum hot casting molding, characterized in that, It includes the following steps: S1. Mix nano silicon carbide, organic binder and deionized water to obtain a mixed slurry. S2. Pour the mixed slurry into a metal mold by vacuum hot casting process. Under a vacuum degree of 20 - 30 kPa, vacuum hot cast at 1350 - 1500 °C for 3 - 5 h to synthesize a titanium alloy reinforced nano silicon carbide composite ceramic part. S3. Coat the surface of the titanium alloy reinforced nano silicon carbide composite ceramic part with a modified nickel - titanium alloy coating mixture with a coating thickness of 10 - 20 μm, and then dry and cure it to obtain a nickel - titanium alloy reinforced nano silicon carbide composite ceramic part.

2. The vacuum hot casting forming preparation method of a nickel-titanium alloy reinforced nano-silicon carbide composite ceramic part according to claim 1, characterized in that, In step S1, the preparation process of the coated nano silicon carbide includes the following steps: A1. Under a nitrogen atmosphere, mix diphenylchlorosilane and chlorobenzene to obtain a mixture. Drop methylimidazole into the mixture. After dropping, obtain a reaction system. Heat the reaction system to 75 - 85 °C and react for 3 - 4 h, then let it stand and cool to room temperature, and collect the lower - layer organic liquid. A2. Add deionized water to the organic liquid to obtain a hydrolysis product. The hydrolysis product and nano silicon carbide are added to a granulator in a mass ratio of 1:5 - 10 for coating to obtain coated nano silicon carbide.

3. The vacuum hot casting forming preparation method of a nickel-titanium alloy reinforced nano-silicon carbide composite ceramic part according to claim 2, characterized in that, In step A1, the dosage ratio of diphenylchlorosilane, chlorobenzene and methylimidazole is 10.9 - 21.8 g:5.6 - 11.2 g:0.2 - 0.4 g; in step A2, the dosage ratio of the organic liquid and deionized water is 10 - 15 g:2 - 5 mL; the rotation speed of the granulator is 1000 - 2000 r / min, the coating temperature is 70 - 80 °C, and the coating duration is 20 - 30 min.

4. A method for preparing a nickel-titanium alloy reinforced nano-silicon carbide composite ceramic part by vacuum hot casting molding, characterized in that, In step S3, the preparation method of the modified nickel - titanium alloy coating mixture includes the following steps: B1. Mix dried polyethylene glycol 2000, toluene diisocyanate and diphenylmethane diisocyanate, then add a catalyst and mix well to obtain a mixture. React the mixture at 65 - 75 °C for 1 - 1.5 h to obtain a polyurethane prepolymer. B2. Drop 4 - formylphenylboronic acid into the polyurethane prepolymer, stir and react at 65 - 75 °C for 1 - 2 h, then cure in an oven at 70 - 80 °C for 20 - 24 h to obtain a dynamic reversible polyurethane material. B3. Ultrasonically clean nickel - titanium alloy powder successively with absolute ethanol and deionized water, and then dry it at room temperature to obtain surface - pretreated nickel - titanium alloy powder. B4. Mix the dynamic reversible polyurethane material and calcium phosphate solution in a mass ratio of 2 - 3:1 to obtain a coating solution. Immerse the surface - pretreated nickel - titanium alloy powder in the coating solution to obtain a modified nickel - titanium alloy coating mixture.

5. The vacuum hot casting forming preparation method of a nickel-titanium alloy reinforced nano-silicon carbide composite ceramic part according to claim 4, characterized in that, In step B1, the dried polyethylene glycol 2000 is obtained by drying polyethylene glycol 2000 at 30 - 40 °C for 1 - 2 h, and the catalyst is dibutyltin dilaurate; the dosage ratio of the dried polyethylene glycol 2000, toluene diisocyanate, diphenylmethane diisocyanate and the catalyst is 20 - 30 g: 1.74 - 3.48 g: 2.5 - 5 g: 0.01 - 0.02 g; in step B2, the dosage ratio of 4-formylphenylboronic acid and the polyurethane prepolymer is 1.5 - 3 g: 20 - 25 g; in step B3, the frequency of the two ultrasonic cleanings is 20 - 30 KHz, and the ultrasonic duration is 10 - 20 min; the drying temperature is 25 °C, and the drying duration is 20 - 30 min.

6. A method for preparing a nickel-titanium alloy reinforced nano-silicon carbide composite ceramic part by vacuum hot casting molding according to claim 4, characterized in that, In step B4, the concentration of the calcium phosphate solution is 0.01 - 0.02 g / mL; the mass ratio of the surface-pretreated nickel-titanium alloy powder to the coating solution is 1: 5 - 10; the soaking temperature is 25 °C, and the soaking duration is 1 - 2 h.

7. A method for preparing a nickel-titanium alloy reinforced nano-silicon carbide composite ceramic part by vacuum hot casting molding, characterized in that, In step S1, the organic binder is clay; the weight ratio of the coated nano silicon carbide, the organic binder and deionized water is 40 - 50: 10 - 20: 30 - 50; in step S3, the drying and curing temperature is 70 - 80 °C, and the drying and curing duration is 1 - 2 h.

Images