A method for preparing a nickel-titanium alloy reinforced nanometer silicon carbide composite ceramic part by vacuum hot casting

Abstract

The application discloses a kind of nickel-titanium alloy reinforced nanometer silicon carbide composite ceramic part vacuum hot pouring forming preparation method, belong to ceramic preparation technical field.The present application is used to solve the technical problems of poor chemical stability and thermal stability of silicon nitride ceramic in the prior art, low density of single silicon nitride sintered ceramic, and large ceramic brittleness caused by matrix doping component.A kind of nickel-titanium alloy reinforced nanometer silicon carbide composite ceramic part vacuum hot pouring forming preparation method, comprising the following steps: mixing uniformly coated nanometer silicon carbide, inorganic binder and deionized water, to obtain mixed slurry;Mixed slurry vacuum hot pouring, to obtain reinforced nanometer silicon carbide composite ceramic part;The surface of reinforced nanometer silicon carbide composite ceramic part is coated with modified nickel-titanium alloy coating mixture, and then dried and cured, to obtain nickel-titanium alloy reinforced nanometer silicon carbide composite ceramic part.The composite ceramic prepared by the application has the advantages of high mechanical performance, high density, good thermal stability and chemical stability.

Description

Technical Field

[0001] This invention relates to the field of ceramic technology, specifically to a method for preparing nickel-titanium alloy reinforced nano-silicon carbide composite ceramic parts by vacuum hot casting. Background Technology

[0002] With the booming development of fields closely related to national development, such as aerospace, national defense, and nuclear industries, natural materials can no longer meet their needs in extremely harsh environments, especially under extreme high temperatures and pressures. Ceramic materials can be widely used not only in national defense and aerospace industries, but also in 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. Furthermore, maintaining high density, thermal stability, and chemical stability while ensuring high strength is key to synthesizing high-performance silicon nitride ceramic materials.

[0003] Patent application CN109293374A discloses a method for preparing a quaternary refractory ceramic of "andalusite-boron carbide-silicon nitride-silicon carbide". The slurry is vacuum-vibrated to form a green body; the green body is then placed in a nitriding furnace for nitriding treatment, and finally cooled to room temperature to obtain a ceramic with excellent thermal shock resistance and oxidation resistance. However, the mixing of multiple components in the above-mentioned ceramic material matrix will increase the brittleness of the prepared ceramic, thereby impairing its bending strength and fracture toughness, which is detrimental to the processing and preservation of the ceramic.

[0004] Patent application CN109320276A discloses a method for preparing silicon nitride-based microwave-transparent ceramics reinforced with silicon nitride whiskers and silicon nitride nanowires. Different volumes of Si3N... 4w The silicon nitride powder was used to prepare green bodies, which were then processed to obtain ceramics. However, the purpose of doping the silicon nitride powder was to improve its wave transmission properties, rather than to enhance the mechanical properties and chemical stability of the ceramic material.

[0005] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a vacuum hot casting method for preparing nickel-titanium alloy reinforced nano-silicon carbide composite ceramic parts, which addresses the poor chemical and thermal stability of silicon nitride ceramics in the prior art.

[0007] The technical problems of low density and high brittleness of single silicon nitride sintered ceramics and matrix doping components.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A method for preparing nickel-titanium alloy reinforced nano-silicon carbide composite ceramic parts by vacuum hot casting includes the following steps:

[0010] S1. Mix the coated nano-silicon carbide, inorganic binder and deionized water to obtain a mixed slurry;

[0011] S2. The mixed slurry is poured into a metal mold using a vacuum hot casting process. Under a vacuum of 20-30 kPa, it is vacuum hot cast at 1350-1500℃ for 3-5 hours to synthesize nano-silicon carbide composite ceramic parts.

[0012] The nano-silicon carbide, inorganic binder and water are uniformly mixed and then vacuum hot casting molding technology is used to prepare reinforced nano-silicon carbide composite ceramic parts.

[0013] S3. A modified nickel-titanium alloy coating mixture is coated on the surface of the nano-silicon carbide composite ceramic part with a coating thickness of 10-20μm, and then calcined to obtain a nickel-titanium alloy reinforced nano-silicon carbide composite ceramic part.

[0014] A nickel-titanium alloy-reinforced nano-silicon carbide composite ceramic part is prepared by coating the surface of the reinforced nano-silicon carbide composite ceramic part with a nickel-titanium alloy-doped coating solution, followed by drying and curing.

[0015] Further, in step S1, the preparation process of the coated nano-silicon carbide includes the following steps:

[0016] A1. Under a nitrogen atmosphere, diphenylchlorosilane and chlorobenzene are mixed to obtain a mixture; methylimidazole is added dropwise to the mixture, and after the addition is complete, a reaction system is obtained; the reaction system is heated to 75-85℃ and reacted for 3-4 hours, then allowed to stand and cool to room temperature, and the lower organic liquid is collected.

[0017] Using methylimidazole as a catalyst, diphenylchlorosilane and chlorobenzene undergo a nucleophilic substitution reaction to yield a silane compound and produce hydrogen chloride gas. The reaction equation is as follows:

[0018]

[0019] A2. Add deionized water to the organic liquid to obtain the hydrolysis product; add the hydrolysis product and nano-silicon carbide in a mass ratio of 1:5-10 into a granulator for coating to obtain coated nano-silicon carbide.

[0020] Organic liquid and water undergo a hydrolysis reaction to obtain a hydrolysis product containing hydroxyl groups; using the hydrolysis product as a coating liquid, coated nano-silicon carbide is prepared through a coating process without the need for coupling agents.

[0021] Further, in step A1, the ratio of diphenylchlorosilane, chlorobenzene and methylimidazole is 10.9-21.8g:5.6-11.2g:0.2-0.4g; in step A2, the ratio of organic liquid to deionized water is 10-15g:2-5mL; the granulator speed is 1000-2000r / min, the coating temperature is 70-80℃, and the coating time is 20-30min.

[0022] Further, in step S3, the preparation method of the modified nickel-titanium alloy coating solution includes the following steps:

[0023] B1. Mix dried polyethylene glycol 2000, toluene diisocyanate and diphenylmethane diisocyanate, then add catalyst and mix well to obtain a mixture; react the mixture at 65-75℃ for 1-1.5h to obtain polyurethane prepolymer;

[0024] The reaction of toluene diisocyanate, diphenylmethane diisocyanate, and polyethylene glycol 2000 under the action of a catalyst yields a polyurethane prepolymer, as shown in the following reaction formula:

[0025]

[0026] B2 and 4-formylphenylboronic acid were added dropwise to the polyurethane prepolymer and stirred at 65-75℃ for 1-2 hours. Then, the mixture was cured in a drying oven at 70-80℃ for 20-24 hours to obtain a dynamically reversible polyurethane material.

[0027] The reaction formula for the reaction of 4-formylphenylboronic acid and polyurethane prepolymer to obtain dynamically reversible polyurethane material is as follows:

[0028]

[0029] B3. The nickel-titanium alloy powder was ultrasonically cleaned with anhydrous ethanol and deionized water in sequence, and then dried at room temperature to obtain the surface-pretreated nickel-titanium alloy powder.

[0030] B4. Dynamic reversible polyurethane material and calcium phosphate solution are mixed at a mass ratio of 2-3:1 to obtain a coating solution; the surface-pretreated nickel-titanium alloy powder is immersed in the coating solution and then vacuum dried to obtain modified nickel-titanium alloy powder.

[0031] Pretreated nickel-titanium alloy powder is immersed in a coating solution to form a coating, thus preparing modified nickel-titanium alloy powder.

[0032] Further, in step B1, the dried polyethylene glycol 2000 is obtained by drying polyethylene glycol 2000 at 100-105℃ for 1-2 hours, and the catalyst is dibutyltin dilaurate; the ratio of dried polyethylene glycol 2000, toluene diisocyanate, diphenylmethane diisocyanate and catalyst is 20-30g:1.74-3.48g:2.5-5g:0.01-0.02g; in step B2, the ratio of 4-formylphenylboronic acid and polyurethane prepolymer is 1.5-3g:20-25g; in step B3, the frequency of the two ultrasonic cleanings is 20-30KHz and the ultrasonic duration is 10-20min; the drying temperature is 25℃ and the drying time is 20-30min.

[0033] Further, in step B4, the concentration of the calcium phosphate solution is 0.01-0.02 g / mL; the mass ratio of the pretreated nickel-titanium alloy powder to the coating solution is 1:5-10; the immersion temperature is 25℃ and the immersion time is 1-2 h; the surface coating thickness of the modified nickel-titanium alloy powder is 10-20 μm.

[0034] Further, in step S1, the inorganic binder is clay; the weight ratio of coating nano-silicon carbide, inorganic binder and deionized water is 40-50:10-20:30-50; in step S3, the drying and curing temperature is 70-80℃ and the drying and curing time is 1-2h.

[0035] The present invention has the following beneficial effects:

[0036] 1. This invention involves mixing coated nano-silicon carbide, an inorganic binder, and deionized water to obtain a slurry for ceramic preparation. The slurry is then used to prepare nano-silicon carbide composite ceramic parts using a vacuum hot casting process. A modified nickel-titanium alloy coating mixture is then applied to the surface of the nano-silicon carbide composite ceramic parts, followed by drying and curing, ultimately yielding nickel-titanium alloy-reinforced nano-silicon carbide composite ceramic parts. The vacuum hot casting process helps eliminate air bubbles in the casting material, reducing porosity in the prepared ceramics and forming a uniformly distributed silicon-containing silicon carbide ceramic matrix. The high bulk density of the ceramic powder reduces porosity during stacking, lowers the compression ratio during molding, and thus results in a high and uniform density of the pressed green body. Finally, applying a modified nickel-titanium alloy coating mixture to the surface of the nano-silicon carbide composite ceramic parts further improves the hardness, thermal stability, and other mechanical properties of the prepared ceramic products.

[0037] 2. Polyurethane prepolymers were synthesized using polyethylene glycol 2000, toluene diisocyanate, and diphenylmethane diisocyanate as monomers. The polyurethane prepolymers were modified with 4-formylphenylboronic acid to obtain dynamically reversible polyurethane materials. Through structural design of the polyurethane molecular chains, the synthesized polyurethane possessed excellent mechanical properties and dynamic bonds were introduced between the molecular chains. The dynamically reversible polyurethane material was mixed with calcium phosphate solution to obtain a coating solution. Immersing nickel-titanium alloy powder in the coating solution allowed a coating to form on the surface of the nickel-titanium alloy powder. This porous structure and dynamically reversible bonds enabled the nickel-titanium alloy to maintain its shape memory effect during heating, thereby improving the mechanical and chemical stability of the coated modified nickel-titanium alloy mixture ceramic.

[0038] 3. This invention uses nanoscale silicon carbide to prepare ceramics. The technical principle of nanotechnology toughening is that the matrix contains nanoparticles, which can act as a reinforcing phase, inhibiting the growth of ceramic grains and significantly increasing the size of the grain surface and grain boundaries. Quantum and interfacial effects improve the mechanical properties of nanomaterials. The hydrolysis product of the reaction between 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. Furthermore, during the vacuum casting process, the coated nanoscale silicon carbide disperses silicon elements within the ceramic matrix, playing a toughening and reinforcing role, and significantly improving the mechanical properties of the prepared composite ceramic material. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] The nano-silicon carbide used in Examples 1-3 of this 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 / cm³. 3 The polyethylene glycol 2000 used in Examples 4-6 of this invention was purchased from Haian Petrochemical Plant in Jiangsu Province, 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 this invention was purchased from Ruili Alloy Welding Materials in Nangong City, with a nickel content of 56% and a particle size of 75-225 μm. The clay used in Examples 7-9 of this invention was purchased from Yuexin Metallurgical Casting Materials Factory in Sishui County, with a product number of 2301.

[0041] Example 1

[0042] This embodiment provides a process for preparing coated nano-silicon carbide for nickel-titanium alloy reinforced nano-silicon carbide composite ceramic materials, including the following steps:

[0043] 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 purge the three-necked flask with nitrogen gas to place it in a nitrogen atmosphere. Connect the three-necked flask to a dropping funnel, and add 0.2 g of methylimidazole to the three-necked flask through the dropping funnel. After the addition is complete, the reaction system is obtained. Transfer the three-necked flask to a water bath, heat to 75 °C, react at this temperature for 3 h, then allow to cool to room temperature, and collect the lower organic liquid layer.

[0044] A2. 10g of organic liquid was mixed with 2mL of deionized water to obtain a hydrolysis product. The hydrolysis product and nano-silicon carbide were added to a granulator at a mass ratio of 1:5 for coating. The granulator speed was 1000r / min, the coating temperature was 70℃, and the coating time was 20min to obtain coated nano-silicon carbide.

[0045] Example 2

[0046] This embodiment provides a process for preparing coated nano-silicon carbide for nickel-titanium alloy reinforced nano-silicon carbide composite ceramic materials, including the following steps:

[0047] 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 purge the three-necked flask with nitrogen gas to place it in a nitrogen atmosphere. Connect the three-necked flask to a dropping funnel, and add 0.3 g of methylimidazole to the three-necked flask through the dropping funnel. After the addition is complete, the reaction system is obtained. Transfer the three-necked flask to a water bath, heat to 80 °C, react at this temperature for 3.5 h, then allow it to cool to room temperature, and collect the lower organic liquid layer.

[0048] A2. 12g of organic liquid was mixed with 3mL of deionized water to obtain a hydrolysis product. The hydrolysis product and nano-silicon carbide were added to a granulator at a mass ratio of 1:8 for coating. The granulator speed was 1500r / min, the coating temperature was 75℃, and the coating time was 25min to obtain coated nano-silicon carbide.

[0049] Example 3

[0050] This embodiment provides a process for preparing coated nano-silicon carbide for nickel-titanium alloy reinforced nano-silicon carbide composite ceramic materials, including the following steps:

[0051] 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, purge the three-necked flask with nitrogen gas to place it in a nitrogen atmosphere. Connect the three-necked flask to a dropping funnel, and add 0.4 g of methylimidazole to the three-necked flask through the dropping funnel. After the addition is complete, the reaction system is obtained. Transfer the three-necked flask to a water bath, heat to 85 °C, react at this temperature for 4 h, then allow it to cool to room temperature, and collect the lower organic liquid layer.

[0052] A2. 15g of organic liquid was mixed with 5mL of deionized water to obtain a hydrolysis product. The hydrolysis product and nano-silicon carbide were added to a granulator at a mass ratio of 1:10 for coating. The granulator speed was 2000r / min, the coating temperature was 80℃, and the coating time was 30min to obtain coated nano-silicon carbide.

[0053] Example 4

[0054] This embodiment provides a preparation process for a modified nickel-titanium alloy coating mixture for use in nickel-titanium alloy-reinforced nano-silicon carbide composite ceramic materials, including the following steps:

[0055] B1. Polyethylene glycol 2000 was placed in a vacuum oven and dried at 30°C for 1 hour to obtain dried polyethylene glycol 2000. 1.74 g of toluene diisocyanate, 2.5 g of diphenylmethane diisocyanate, and 20 g of polyethylene glycol 2000 were added to a 500 mL beaker, which was placed on a water bath. Then, 0.01 g of dibutyltin dilaurate catalyst was added and mixed well to obtain a mixture. The mixture was reacted at 65°C for 1 hour to obtain a polyurethane prepolymer.

[0056] B2. 1.5g of 4-formylphenylboronic acid was added dropwise to 20g of polyurethane prepolymer at a rate of 0.5g / min. The mixture was stirred at 65℃ for 1h and then heating was stopped. The mixture was then cured in a forced-air drying oven at 70℃ for 20h to obtain a dynamically reversible polyurethane material.

[0057] B3. The nickel-titanium alloy powder was ultrasonically cleaned with anhydrous ethanol and then ultrasonically cleaned with deionized water. The frequency of the two ultrasonic cleanings was 20KHz and the duration was 10min. After that, it was dried at 25℃ for 20min to obtain the nickel-titanium alloy powder with surface pretreatment.

[0058] B4. Mix the dynamic reversible polyurethane material and 0.01 g / mL calcium phosphate solution at a mass ratio of 2:1 to obtain a coating solution. Immerse the surface-pretreated nickel-titanium alloy powder in the coating solution at 25°C for 1 hour and mix well. The mass ratio of nickel-titanium alloy powder to coating solution is 1:5 to obtain a modified nickel-titanium alloy coating mixture.

[0059] Example 5

[0060] This embodiment provides a preparation process for a modified nickel-titanium alloy coating mixture for use in nickel-titanium alloy-reinforced nano-silicon carbide composite ceramic materials, including the following steps:

[0061] B1. Polyethylene glycol 2000 was placed in a vacuum oven and dried at 33°C for 1.5 hours to obtain dried polyethylene glycol 2000. 2.8 g of toluene diisocyanate, 3.5 g of diphenylmethane diisocyanate, and 25 g of polyethylene glycol 2000 were added to a 500 mL beaker placed in a water bath. Then, 0.015 g of dibutyltin dilaurate catalyst was added and mixed thoroughly to obtain a mixture. The mixture was reacted at 70°C for 1.2 hours to obtain a polyurethane prepolymer.

[0062] B2. 2.5g of 4-formylphenylboronic acid was added dropwise to 22g of polyurethane prepolymer at a rate of 0.8g / min. The mixture was stirred at 70℃ for 1.5h and then heating was stopped. The mixture was then cured in a forced-air drying oven at 75℃ for 22h to obtain a dynamically reversible polyurethane material.

[0063] B3. The nickel-titanium alloy powder was sequentially ultrasonically cleaned with anhydrous ethanol and ultrasonically cleaned with deionized water. The frequency of the two ultrasonic cleanings was 25KHz and the duration was 15min. Then, it was dried at 25℃ for 23min to obtain the nickel-titanium alloy powder with surface pretreatment.

[0064] B4. Mix the dynamic reversible polyurethane material and 0.015 g / mL calcium phosphate solution at a mass ratio of 2.7:1 to obtain a coating solution. Immerse the surface-pretreated nickel-titanium alloy powder in the coating solution at 25°C for 1.5 h and mix well. The mass ratio of nickel-titanium alloy powder to coating solution is 1:8 to obtain a modified nickel-titanium alloy coating mixture.

[0065] Example 6

[0066] This embodiment provides a preparation process for a modified nickel-titanium alloy coating mixture for use in nickel-titanium alloy-reinforced nano-silicon carbide composite ceramic materials, including the following steps:

[0067] B1. Polyethylene glycol 2000 was placed in a vacuum oven and dried at 40°C for 2 hours to obtain dried polyethylene glycol 2000. 3.48 g of toluene diisocyanate, 5 g of diphenylmethane diisocyanate, and 30 g of polyethylene glycol 2000 were added to a 500 mL beaker, which was placed in a water bath. Then, 0.02 g of dibutyltin dilaurate catalyst was added and mixed thoroughly to obtain a mixture. The mixture was reacted at 75°C for 1.5 hours to obtain a polyurethane prepolymer.

[0068] B2. 3g of 4-formylphenylboronic acid was added dropwise to 25g of polyurethane prepolymer at a rate of 1g / min. The mixture was stirred at 75℃ for 2h and then heating was stopped. The mixture was then cured in a forced-air drying oven at 80℃ for 24h to obtain a dynamically reversible polyurethane material.

[0069] B3. The nickel-titanium alloy powder was ultrasonically cleaned with anhydrous ethanol and ultrasonically cleaned with deionized water in sequence. The frequency of the two ultrasonic cleanings was 30KHz and the duration of the ultrasonic cleaning was 20min. Then it was dried at 25℃ for 30min to obtain the nickel-titanium alloy powder with surface pretreatment.

[0070] B4. Mix the dynamic reversible polyurethane material and 0.02 g / mL calcium phosphate solution at a mass ratio of 3:1 to obtain a coating solution. Immerse the surface-pretreated nickel-titanium alloy powder in the coating solution at 25°C for 2 hours and mix well. The mass ratio of nickel-titanium alloy powder to coating solution is 1:10 to obtain a modified nickel-titanium alloy coating mixture.

[0071] Example 7

[0072] This embodiment provides a method for preparing nickel-titanium alloy reinforced nano-silicon carbide composite ceramic parts by vacuum hot casting, including the following steps:

[0073] S1. According to the weight, 40 parts of the coated nano-silicon carbide prepared in Example 1, 10 parts of inorganic binder clay and 30 parts of deionized water are mixed evenly to obtain a mixed slurry.

[0074] S2. The mixed slurry is poured into a metal mold, and a nano-silicon carbide composite ceramic part with dimensions of Φ60mm×Φ40mm×Φ1600mm is prepared by vacuum hot casting process; wherein, the vacuum degree is 20-30kPa, the vacuum hot casting temperature is 1350℃, and the vacuum hot casting time is 3h.

[0075] S3. The modified nickel-titanium alloy coating mixture prepared in Example 4 is coated on the surface of the nano-silicon carbide composite ceramic part with a coating thickness of 10 μm; then it is transferred to a vacuum drying oven and dried and cured at 70°C for 1 h to obtain the nickel-titanium alloy reinforced nano-silicon carbide composite ceramic part.

[0076] Example 8

[0077] This embodiment provides a method for preparing nickel-titanium alloy reinforced nano-silicon carbide composite ceramic parts by vacuum hot casting, including the following steps:

[0078] S1. According to the weight, 45 parts of the coated nano-silicon carbide prepared in Example 2, 15 parts of inorganic binder clay and 40 parts of deionized water are uniformly mixed to obtain a mixed slurry.

[0079] S2. The mixed slurry was used to prepare nano-silicon carbide composite ceramic parts with dimensions of Φ60mm×Φ40mm×Φ1600mm by vacuum hot casting; wherein, the vacuum hot casting temperature was 1450℃ and the vacuum hot casting time was 4h.

[0080] S3. The modified nickel-titanium alloy coating mixture prepared in Example 5 was coated on the surface of the nano-silicon carbide composite ceramic part with a coating thickness of 15 μm; then it was transferred to a vacuum drying oven and dried and cured at 75°C for 1.5 h to obtain the nickel-titanium alloy reinforced nano-silicon carbide composite ceramic part.

[0081] Example 9

[0082] This embodiment provides a method for preparing nickel-titanium alloy reinforced nano-silicon carbide composite ceramic parts by vacuum hot casting, including the following steps:

[0083] S1. According to the weight, 50 parts of the coated nano-silicon carbide prepared in Example 3, 20 parts of inorganic binder clay and 50 parts of deionized water are uniformly mixed to obtain a mixed slurry.

[0084] S2. The mixed slurry was used to prepare nano-silicon carbide composite ceramic parts with dimensions of Φ60mm×Φ40mm×Φ1600mm by vacuum hot casting; wherein, the vacuum hot casting temperature was 1500℃ and the vacuum hot casting time was 5h.

[0085] S3. The modified nickel-titanium alloy coating mixture prepared in Example 6 was coated on the surface of the nano-silicon carbide composite ceramic part with a coating thickness of 20 μm; then it was transferred to a vacuum drying oven and dried and cured at 80°C for 2 h to obtain the nickel-titanium alloy reinforced nano-silicon carbide composite ceramic part.

[0086] Comparative Example 1

[0087] The difference between this comparative example and Example 9 is that, in step S1, nano-silicon carbide of the same mass is used instead of coated nano-silicon carbide.

[0088] Comparative Example 2

[0089] The difference between this comparative example and Example 9 is that, in preparing the modified nickel-titanium alloy coating mixture, the synthesized polyurethane prepolymer was not modified with 4-formylphenylboronic acid and was directly cured to obtain the polyurethane material.

[0090] Comparative Example 3

[0091] The difference between this comparative example and Example 9 is that, in preparing the modified nickel-titanium alloy coating mixture, the polyurethane prepolymer and deionized water were mixed at a mass ratio of 3:1 to obtain the coating solution.

[0092] Performance testing:

[0093] 1. 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 were determined by a three-point bending strength test.

[0094] 2. 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 was measured using the single-sided notched beam method and a universal testing machine.

[0095] 3. The surface of the nickel-titanium alloy reinforced nano-silicon carbide composite ceramic materials prepared in Examples 7-9 and Comparative Examples 1-3 was tested using a micro hardness tester. The load was 4.9 N, the holding time was 10 s, and the average value was obtained after five measurements.

[0096] 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 using Archimedes' water displacement method.

[0097] 5. The 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℃.

[0098] Table 1 - Performance Test Data of Samples

[0099]

[0100] Data Analysis:

[0101] Comparative analysis of the data in Table 1 above shows that the nickel-titanium alloy reinforced nano-silicon carbide composite ceramic parts prepared by vacuum hot casting process in Examples 7-9 of this invention all have excellent mechanical properties, including high hardness, density, fracture toughness and bending strength; the prepared ceramic parts have low porosity and good thermal stability (low thermal weight loss rate at 800℃).

[0102] However, in Comparative Example 1, nano-silicon carbide of the same mass was used instead of coated nano-silicon carbide. The nano-silicon carbide coated with organosilicon exhibits better compatibility and dispersibility in the mixed slurry. Furthermore, the silicon element in the organosilicon, after calcination, can be dispersed in the ceramic matrix, playing a role in toughening and strengthening. Therefore, the mechanical properties of the ceramic parts prepared in Comparative Example 1, such as bending strength, fracture toughness, hardness, and density, decreased.

[0103] In Comparative Example 2, the polyurethane prepolymer synthesized without 4-formylphenylboronic acid modification resulted in a non-dynamically reversible modified nickel-titanium alloy coating mixture, thus reducing the mechanical properties of the prepared ceramic parts. In Comparative Example 3, calcium phosphate solution was not added to the coating solution, resulting in a slight increase in the mechanical properties of the synthesized ceramic parts, but a decrease in their thermal stability.

[0104] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, 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 in the claims, all of which should fall within the protection scope of the present invention.

[0105] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0106] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to any specific implementation. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for the vacuum hot cast forming of a nickel-titanium alloy reinforced nanosized silicon carbide composite ceramic part, characterized in that, The method comprises the following steps: S1, mixing coated nanometer silicon carbide, inorganic binder and deionized water to obtain a mixed slurry; S2, the mixed slurry is poured into a metal mold by a vacuum hot pouring process, and is subjected to vacuum hot pouring at 1350-1500 DEG C for 3-5 h under a vacuum degree of 20-30 kPa to synthesize a nanometer silicon carbide composite ceramic part; S3, the nanometer silicon carbide composite ceramic part is coated with a modified nickel-titanium alloy coating mixture, the coating thickness is 10-20 microns, and then drying and curing are performed to obtain a nickel-titanium alloy reinforced nanometer silicon carbide composite ceramic part; In step S1, the preparation process of the coated nanometer silicon carbide comprises the following steps: A1, under a nitrogen atmosphere, diphenyl monochloromonohydrosilane and chlorobenzene are mixed to obtain a mixture; methyl imidazole is added dropwise into the mixture, and after the dropwise addition is completed, a reaction system is obtained; the reaction system is heated to 75-85 DEG C and reacted for 3-4 h, and then is cooled to room temperature after standing; and the lower organic liquid is collected; A2, deionized water is added to the organic liquid to obtain a hydrolysis product; and the hydrolysis product and nanometer silicon carbide are added into a granulator according to a mass ratio of 1:5-10 to obtain coated nanometer silicon carbide; In step S3, the preparation method of the modified nickel-titanium alloy coating mixture comprises the following steps: B1, after drying, polyethylene glycol 2000, toluene diisocyanate and diphenyl methane diisocyanate are mixed, a catalyst is then added and mixed to obtain a mixture; the mixture is reacted at 65-75 DEG C for 1-1.5 h to obtain a polyurethane prepolymer; B2, 4-formyl phenyl boronic acid is added dropwise into the polyurethane prepolymer, and is stirred and reacted at 65-75 DEG C for 1-2 h; and then is cured in a drying oven at 70-80 DEG C for 20-24 h to obtain a dynamic reversible polyurethane material; B3, nickel-titanium alloy powder is ultrasonically cleaned with anhydrous ethanol and deionized water in sequence, and is then dried at room temperature to obtain surface pretreated nickel-titanium alloy powder; B4, the dynamic reversible polyurethane material and calcium phosphate solution are mixed according to a mass ratio of 2-3:1 to obtain a coating solution; and the surface pretreated nickel-titanium alloy powder is soaked in the coating solution to obtain a modified nickel-titanium alloy coating mixture.

2. The method of claim 1, wherein the method is a vacuum hot casting method for manufacturing a nickel-titanium alloy-reinforced nanoscale silicon carbide composite ceramic part, characterized in that, In step A1, the amount ratio of diphenyl monochloromonohydrosilane, chlorobenzene and methyl imidazole is 10.9-21.8 g:5.6-11.2 g:0.2-0.4 g; in step A2, the amount ratio of the organic liquid and deionized water is 10-15 g:2-5 mL; the rotating speed of the granulator is 1000-2000 r / min, the coating temperature is 70-80 DEG C, and the coating time is 20-30 min.

3. The method of claim 1, wherein the method is a vacuum hot casting method for manufacturing a nickel-titanium alloy-reinforced nanoscale silicon carbide composite ceramic part, characterized in that, In step B1, the dried polyethylene glycol 2000 is obtained by drying polyethylene glycol 2000 at 30-40℃ for 1-2h, and the catalyst is dibutyl tin dilaurate; the amount ratio of dried polyethylene glycol 2000, toluene diisocyanate, diphenyl methane diisocyanate and catalyst is 20-30g:1.74-3.48g:2.5-5g:0.01-0.02g; in step B2, the amount ratio of 4-formyl phenyl boronic acid and polyurethane prepolymer is 1.5-3g:20-25g; in step B3, the frequency of twice ultrasonic cleaning is 20-30KHz, and the ultrasonic time is 10-20min; the drying temperature is 25℃, and the drying time is 20-30min.

4. The method of claim 1, wherein the method is a vacuum hot casting method for manufacturing a nickel-titanium alloy-reinforced nanoscale silicon carbide composite ceramic part, characterized in that, In step B4, the concentration of calcium phosphate solution is 0.01-0.02g / mL; the mass ratio of surface pretreated nickel-titanium alloy powder and coating solution is 1:5-10; the soaking temperature is 25℃, and the soaking time is 1-2h.

5. The method of claim 1, wherein the method is a vacuum hot casting method for manufacturing a nickel-titanium alloy-reinforced nanoscale silicon carbide composite ceramic part, characterized in that, In step S1, the inorganic binder is clay; the weight ratio of coated nanometer silicon carbide, inorganic binder and deionized water is 40-50:10-20:30-50; in step S3, the drying and curing temperature is 70-80℃, and the drying and curing time is 1-2h.

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