Metal matrix composite based on modified boron nitride nanotubes and method of preparation

Abstract

The application relates to the technical field of metal composite material preparation, in particular to a metal matrix composite material based on modified boron nitride nanotube reinforcement and a preparation method, which comprises the following steps: S1, adding boron nitride nanotube powder into ethanol for dispersion, filtering and drying and grinding treatment to obtain uniformly dispersed boron nitride nanotube powder; S2, depositing Ti or W on the boron nitride nanotube powder by using a physical deposition method or a chemical deposition method to obtain modified boron nitride nanotubes; S3, wetly mixing the modified boron nitride nanotubes with pure metal powder, and then performing drying treatment, drying treatment and ball milling treatment to obtain uniformly dispersed mixed powder; and S4, treating the mixed powder by using a 3D printing technology or by compression, sintering or short-time melting to prepare the metal matrix composite material; the mechanical performance of the metal matrix composite material is improved by introducing the modified boron nitride nanotube powder and retaining the structure of the boron nitride nanotube in the three-dimensional printing process.

Description

Technical Field

[0001] This invention relates to the field of metal composite material preparation technology, and in particular to a metal matrix composite material based on modified boron nitride nanotube reinforcement and its preparation method. Background Technology

[0002] Aluminum (Al)-based composites are materials that use aluminum or aluminum alloys as a matrix and incorporate reinforcing agents such as carbon fibers and ceramic particles to significantly improve the strength, hardness, and wear resistance of the material. Due to their lightweight, good corrosion resistance, and high thermal and electrical conductivity, they are highly attractive in structural applications and are widely used in aerospace, automotive manufacturing, electronics manufacturing, and transportation. The Chinese publication "Carbon Nanotubes: Reinforcing Metal Matrix Composites" (CRC Press, 2018, A. Agarwal, D. Lahiri, SRBakshi) reported that adding high aspect ratio tubular reinforcing particles, such as carbon nanotubes, to an aluminum matrix can improve material performance. Unfortunately, the difficulty in using nanoparticles to reinforce metal composites lies in the insufficient adhesion between the matrix and the substrate, leading to poor bonding between the nanoparticles and the matrix. Furthermore, insufficient stability of the nanoparticles and uneven dispersion within the matrix, resulting in agglomeration, are also important factors affecting the performance of metal composites. Unlike other additives, boron nitride nanotubes (BNNTs) exhibit high chemical stability, and their reaction with the matrix can produce beneficial reinforcing phases. However, a common problem is that the structure of boron nitride nanotubes cannot be preserved during the 3D printing of aluminum alloys; and the complex reactions during additive manufacturing, coupled with the lack of diffusion in the alloy, result in numerous voids at the interface. These voids become stress concentration areas and reduce mechanical properties. To preserve the structure of boron nitride nanotubes and maintain uniform dispersion, titanium (Ti) or tungsten (W) metal compound coating techniques can be used to protect the surface of the boron nitride nanotube particles.

[0003] Although there is currently no research on the direct deposition and coating of metals such as Ti and W on powdered boron nitride nanotubes, boron nitride has two crystal forms: diamond and graphite. Graphite boron nitride crystals are also known as "white graphite" because their structure is similar to graphene. Therefore, it might be possible to design a method that allows for the direct deposition and coating of metals such as Ti and W on powdered boron nitride nanotubes, referencing methods used to prepare metal coatings on graphene surfaces, such as chemical vapor deposition (CVD) and physical vapor deposition (PVD).

[0004] This invention provides a metal matrix composite material based on modified boron nitride nanotubes and its preparation method, in order to solve the problems in the prior art, such as the inability to retain the structure of boron nitride nanotubes during the 3D printing process of aluminum alloy materials, and the lack of diffusion in the alloy leading to a large number of voids at the interface. Summary of the Invention

[0005] The purpose of this invention is to provide a metal matrix composite material based on modified boron nitride nanotubes and its preparation method, in order to solve the problems in the prior art where the structure of boron nitride nanotubes cannot be preserved in the 3D printing process of aluminum alloy materials, and the lack of diffusion in the alloy leads to a large number of voids at the interface.

[0006] The technical solution of this invention is: a method for preparing a metal matrix composite material reinforced with modified boron nitride nanotubes, comprising the following steps: S1. Add the boron nitride nanotube powder to be deposited and the dispersant to ethanol for dispersion treatment. After stirring for 0.5-2 hours, filter to obtain boron nitride nanotube particles. Then, dry, grind or ball mill the boron nitride nanotube particles to obtain uniformly dispersed boron nitride nanotube powder. S2. Using physical deposition or chemical deposition, Ti or W is deposited on boron nitride nanotube powder to obtain modified boron nitride nanotubes. S3. The modified boron nitride nanotubes and pure metal powder are wet-mixed in proportion to obtain a mixture. Then, the mixture is dried by a blower under heating conditions of 45-55℃, and then transferred to a vacuum furnace to dry the mixture at 90-110℃. After drying, the mixture is ball-milled to obtain a uniformly dispersed mixed powder. S4. Metal matrix composites are prepared by using 3D printing technology or by processing the mixed powder through compression, sintering or short-time melting.

[0007] Preferably, in step S2, the physical deposition method includes the following specific steps: a. Using magnetron sputtering at a temperature of 20-30℃ and a power of 10-50W, Ti or W is pre-deposited onto boron nitride nanotube powder, with the pre-deposition time controlled within the range of 5-30s. b. Under the conditions of 20-30℃ and 80-120W, continue to deposit Ti or W on boron nitride nanotube powder; during the deposition process, the pressure in the vacuum chamber is controlled at 3-8 mTorr; the deposition time is controlled within the range of 5-30 min.

[0008] Preferably, during the deposition process, argon gas is introduced into the vacuum chamber at a flow rate of 25-40 sccm.

[0009] Preferably, in step S2, the chemical deposition method includes the following steps: a. Add boron nitride nanotube powder and hydrogen peroxide to a reaction vessel at a mass ratio of (4-5):1. Then, seal the reaction vessel and perform ultrasonic treatment followed by water bath heating treatment. The water bath heating temperature is 100-120℃ and the water bath heating time is 20-30h. b. After water bath heating treatment, the liquid phase in the reaction vessel is evaporated, and then an acidic solution is added to the reaction vessel and stirred evenly to form a mixture. Then, the mixture is filtered and the filter residue obtained by filtration is cleaned with pure water and acetone, and then dried to obtain functionalized boron nitride nanotube powder. c. Under a high-purity nitrogen atmosphere, functionalized boron nitride nanotube powder, oleic acid, and trioctylphosphine oxide are added to a solvent and mixed evenly. The mixture is then preheated to 100-150°C. Next, titanium isopropoxide or tungsten hexacarbonyl is added to the solvent at a molar ratio of 1:(1-2) of functionalized boron nitride nanotube powder to titanium isopropoxide or tungsten hexacarbonyl. The mixture is heated under reflux and reacted for 20-50 minutes. The reaction is then stopped, and the reaction solution is cooled to room temperature. After filtration, washing, and vacuum drying, modified boron nitride nanotubes are obtained.

[0010] Preferably, in step S3, the wet mixing includes the following steps: a) adding the modified boron nitride nanotubes to an organic solvent for dispersion treatment, stirring for 0.5-2 hours until uniformly dispersed to form a dispersion; the organic solvent is any one of ethanol, isopropanol, and n-butanol; b. Weigh out pure metal powder according to the proportion, add the weighed pure metal powder to the dispersion, and stir for 0.5-1h to obtain a mixture.

[0011] Preferably, in the metal matrix composite material, the modified boron nitride nanotubes account for 1-10% of the total mass of the metal matrix composite material.

[0012] The present invention also provides a metal matrix composite material based on modified boron nitride nanotube reinforcement, which is prepared by the above-described preparation method.

[0013] Compared with the prior art, the advantages of the present invention are: (1) This invention provides a metal matrix composite material based on modified boron nitride nanotube reinforcement and its preparation method. By introducing modified boron nitride nanotube powder into aluminum matrix material as reinforcement, it can not only retain the structure of boron nitride nanotubes in the three-dimensional printing process of aluminum alloy material, but also improve the mechanical properties of metal matrix composite material. This solves the problems in the prior art that the structure of boron nitride nanotubes cannot be retained in the three-dimensional printing process of aluminum alloy material, and the lack of diffusion in the alloy will lead to a large number of voids at the interface.

[0014] (2) This invention provides a metal matrix composite material reinforced with modified boron nitride nanotubes and its preparation method. Ti or W is chosen as the dopant during the preparation process because Ti or W can form intermediate phases at the boron nitride nanotube interface in aluminum alloys. For example, titanium deposited on boron nitride nanotubes in aluminum alloys can form TiB2 and TiAl3 phases. Therefore, titanium can act as a bridge between the reinforcing particles and the metal matrix, thereby improving mechanical properties. Simultaneously, the Ti or W coating method not only promotes heat transfer in boron nitride nanotubes and prevents thermal degradation of these particles, but also improves the hardness of the final alloy by forming new phases. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram illustrating the drying process of the mixture using a blower as described in this invention; Figure 2 The images show TEM images and EDX analysis results of the modified boron nitride nanotubes prepared in Example 1 of this invention. Figure 3 The images shown are TEM images and EDX diagrams of the modified boron nitride nanotubes prepared in Example 2 of this invention. Figure 4 The images shown are TEM images and EDX analysis diagrams of the modified boron nitride nanotubes prepared in Example 3 of this invention. Figure 5 EDX analysis images of different sites of the modified boron nitride nanotubes prepared in Example 3 of the present invention; Figure 6 The images shown are TEM images and EDX diagrams of the modified boron nitride nanotubes prepared in Example 4 of this invention. Figure 7 The images shown are TEM images and EDX diagrams of the modified boron nitride nanotubes prepared in Example 5 of this invention. Figure 8 The images shown are TEM images and EDX diagrams of the modified boron nitride nanotubes prepared in Example 6 of this invention. Figure 9 This is a schematic diagram of the structure in Embodiment 7 of the present invention, in which the mixed powder is pressed into shape using an instrument; Figure 10 The images show the external appearance of the aluminum-based materials prepared in Examples 7, 8, and Comparative Example 1 of this invention. Figure 11 The results of hardness testing of the compressed mixed powder in Examples 7, 8 and Comparative Example 1 of this invention; Figure 12 The hardness test results are for the sintered mixed powders in Examples 7, 8 and Comparative Example 1 of this invention. Figure 13 The results of thermal stability testing of the compressed mixed powders in Examples 7, 8 and Comparative Example 1 of this invention; Detailed Implementation

[0016] The present invention will be further described in detail below with reference to specific embodiments: It should be noted that the titanium and tungsten targets used in this application are both 99.99% pure and were purchased from EzziVision; the aluminum powder was provided by Deakin University; and the boron nitride nanotube particles were provided by PPK Group Ltd.

[0017] A method for preparing a metal matrix composite material reinforced with modified boron nitride nanotubes, specifically including the following steps: S1. The boron nitride nanotube powder to be deposited and the dispersant are added to ethanol for dispersion treatment. After stirring for 0.5-2 hours, the boron nitride nanotube particles are obtained by filtration. The boron nitride nanotube particles are then dried, ground or ball-milled to obtain uniformly dispersed boron nitride nanotube powder. The dispersant is commercially available ammonium oleate or polyethyleneimine (PEI), and the optimal usage of PEI is no more than 1.5%, and the usage of ammonium oleate is no more than 3%.

[0018] S2. Modified boron nitride nanotubes are obtained by depositing Ti or W nanoparticles onto boron nitride nanotube powder using physical deposition or chemical deposition methods. A challenge of directly using PVD sputtering technology is the inability to retain the powdered boron nitride nanotubes within the vacuum chamber. In this application, to overcome this challenge, the gas flow direction within the vacuum chamber is changed, and the N2 purge gas flow rate is reduced. Alternatively, in the physical deposition method, BNNT powder can be mixed with Al metal powder first, and then a coating can be applied to the mixed powder. The physical deposition method specifically includes the following steps: a. Adjusting the internal pressure of the vacuum chamber to a vacuum state and injecting an appropriate amount of argon gas into the vacuum chamber. Under conditions of a temperature of 20-30℃ and a power of 10-50W, the generated Ar...+ a) Ion bombardment of a Ti or W target pre-deposits Ti or W onto boron nitride nanotube powder, with the pre-deposition time controlled within the range of 5-30 s; b) After pre-deposition, Ti or W is further deposited onto the boron nitride nanotube powder under conditions of 20-30℃ and 80-120 W power. During the deposition process, argon gas is introduced into the vacuum chamber at a flow rate of 25-40 sccm; and the pressure inside the vacuum chamber is controlled within 3-8 mTorr; the deposition time is controlled within the range of 5-30 min. The chemical deposition method specifically includes the following steps: a) Weigh boron nitride nanotube powder and hydrogen peroxide reagent at a mass ratio of (4-5):1, and add the weighed boron nitride nanotube powder and hydrogen peroxide reagent to a reaction vessel; then, seal the reaction vessel and place it in an ultrasonic instrument for ultrasonic treatment. After ultrasonic treatment for 3-10 minutes, transfer it to a water bath at a temperature of 100-120℃ and heat it in a water bath for 20-30 hours to functionalize the boron nitride nanotube powder; b) After the water bath heating treatment is completed, evaporate the liquid phase in the reaction vessel to separate the solid and liquid phases, then add an acidic solution to the reaction vessel, stir or sonicate for 5-20 minutes to mix the acidic solution with the solid phase in the reaction vessel to form a mixed liquid. Then, filter the mixed liquid to obtain a filter residue containing functionalized boron nitride nanotube powder. Then, use pure water and acetone to clean and dry the filtered filter residue several times to obtain the functionalized boron nitride nanotube powder. Functionalized boron nitride nanotube powder; wherein, the acidic solution is one or a combination of HNO3, H2SO4, and fuming sulfuric acid; c, under a high-purity nitrogen atmosphere, the functionalized boron nitride nanotube powder and surfactant are added to the solvent, mixed evenly, and preheated to 100-150℃; then, the metal source precursor is weighed according to a molar ratio of functionalized boron nitride nanotube powder to metal source precursor of 1:(1-2) and added to the solvent, heated under reflux, reacted for 20-50 min, then the reaction was stopped and the reaction solution was cooled to room temperature; then, the reaction solution was filtered to obtain a solid containing modified boron nitride nanotubes, then the solid was washed with deionized water, and then vacuum filtered and vacuum dried in sequence to obtain modified boron nitride nanotubes; wherein, the surfactant is oleic acid and trioctylphosphine oxide; the solvent is one of THF, diphenyl ether, and toluene; the metal source precursor is titanium isopropoxide and tungsten hexacarbonyl.

[0019] S3. The modified boron nitride nanotubes and pure metal powder are wet-mixed according to a specified ratio. First, the modified boron nitride nanotubes are added to an organic solvent, such as ethanol, isopropanol, or n-butanol, and dispersed by stirring for 0.5-2 hours until uniformly dispersed, forming a dispersion. Then, pure metal powder is weighed out according to the specified ratio and added to the dispersion, stirring for 0.5-1 hour until uniformly mixed, obtaining a mixture. Afterwards, as... Figure 1As shown, the mixture is first dried by a blower under heating conditions of 45-55℃, and then transferred to a vacuum furnace for drying at 90-110℃. After drying, the mixture is ball-milled to obtain a uniformly dispersed mixed powder. The pure metal powder can be pure aluminum powder, pure nickel powder, etc.

[0020] S4. Using 3D printing technology, Ti and W deposited boron nitride nanotubes are introduced into an Al matrix, or the mixed powder is processed by compression, sintering, or short-time melting to prepare a metal matrix composite material. In this metal matrix composite material, modified boron nitride nanotubes account for 1-10% of the total mass of the metal matrix composite material.

[0021] The following example uses the preparation of aluminum matrix composite material reinforced with modified boron nitride nanotubes. Other metal matrix composite materials reinforced with modified boron nitride nanotubes can be prepared by referring to the preparation method of aluminum matrix composite material reinforced with modified boron nitride nanotubes.

[0022] Example 1

[0023] S1. Add the boron nitride nanotube powder to be deposited and the dispersant to ethanol for dispersion treatment. After stirring for 0.5, filter to obtain boron nitride nanotube particles. Then, dry, grind or ball mill the boron nitride nanotube particles to obtain uniformly dispersed boron nitride nanotube powder. S2. Ti was deposited on boron nitride nanotube powder using physical deposition to obtain modified boron nitride nanotubes. The vacuum chamber pressure was first adjusted to a vacuum state, and an appropriate amount of argon gas was injected into the vacuum chamber. Under conditions of 20℃ and 20W, the generated Ar... + Ion bombardment of a Ti target led to Ti pre-deposition on boron nitride nanotube powder; the pre-deposition time was 20 s; after pre-deposition, argon gas was introduced into the vacuum chamber at a flow rate of 35 sccm, and the pressure inside the vacuum chamber was controlled at approximately 5 mTorr; then, under conditions of 25 °C and 100 W power, Ti deposition continued on the boron nitride nanotube powder; after 5 minutes of deposition, modified boron nitride nanotubes with a Ti deposition thickness of 19 ± 2 nm were obtained, P1; Figure 2 As shown, the modified boron nitride nanotube P1 was detected and analyzed using transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX).

[0024] Example 2

[0025] The difference between this embodiment and Example 1 is that the deposition time is 10 min; modified boron nitride nanotubes with a Ti deposition thickness of 22±2 nm are obtained on the surface, P2; as shown. Figure 3As shown, the modified boron nitride nanotube P2 was detected and analyzed using transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX).

[0026] Example 3

[0027] The difference between this embodiment and Example 1 is that the deposition time is 15 min; modified boron nitride nanotubes with a Ti deposition thickness of 33±3 nm are obtained on the surface, P3; as shown. Figure 4 As shown, the modified boron nitride nanotube P3 was detected and analyzed using transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX).

[0028] Example 4

[0029] S1. Add the boron nitride nanotube powder to be deposited and the dispersant to ethanol for dispersion treatment. After stirring for 0.5, filter to obtain boron nitride nanotube particles. Then, dry, grind or ball mill the boron nitride nanotube particles to obtain uniformly dispersed boron nitride nanotube powder. S2. Modified boron nitride nanotubes are obtained by depositing W onto boron nitride nanotube powder using physical deposition. Specifically, the internal pressure of the vacuum chamber is first adjusted to a vacuum state, and an appropriate amount of argon gas is injected into the vacuum chamber. Under conditions of 25℃ and 20W, Ar gas is generated... + Ion bombardment of a W target caused W to be pre-deposited onto boron nitride nanotube powder; the pre-deposition time was 20 s; after pre-deposition, argon gas was introduced into the vacuum chamber at a flow rate of 35 sccm, and the pressure inside the vacuum chamber was controlled at approximately 5 mTorr; then, under conditions of 25 °C and 100 W power, Ti was further deposited onto the boron nitride nanotube powder; after 5 minutes of deposition, modified boron nitride nanotubes with a W deposition thickness of 15 ± 2 nm were obtained, P4; Figure 6 As shown, the modified boron nitride nanotube P4 was detected and analyzed using transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX).

[0030] Example 5

[0031] The difference between this embodiment and Example 4 is that the deposition time is 10 min; modified boron nitride nanotubes with a W deposition thickness of 19.3 ± 5 nm are obtained on the surface, P5; as shown. Figure 7 As shown, the modified boron nitride nanotube P5 was detected and analyzed using transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX).

[0032] Example 6

[0033] The difference between this embodiment and Embodiment 4 is that the deposition time is 15 min; modified boron nitride nanotubes with a W deposition thickness of 41 ± 12 nm are obtained on the surface, P6; as shown. Figure 8 As shown, the modified boron nitride nanotube P6 was detected and analyzed using transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX).

[0034] A comparison of the modified boron nitride nanotubes P1-P3 prepared in Examples 1-3 shows that, Figure 1 , Figure 2 , Figure 3 As shown, the Ti nanoparticles deposited on the surface of boron nitride nanotubes have a columnar morphology and a relatively smooth "fine dome" surface; furthermore, by increasing the deposition time, the gaps between the particles begin to be filled, and the structure becomes more tightly packed, as shown in the figure. Figure 4 As shown, this is especially true after 15 minutes of deposition. Similarly, comparing the modified boron nitride nanotubes P4-P6 prepared in Examples 4-6 also yields the same conclusion: with increasing deposition time, the gaps between grains begin to be filled, and the structural morphology becomes more compact. Furthermore, compared to Ti, W has a lower deposition rate, possibly due to the lower molecular weight of the dopant, making it difficult for the plasma to knock out the W target. Additionally, Examples 1-6 also investigated the ability of this physical deposition method to control the deposition thickness of Ti and W nanoparticles (non-oxide) at a constant sputtering power (100W). Since the coating thickness on the boron nitride nanotube surface should be sufficient to protect the boron nitride nanotube particle surface from the high temperatures generated by the external laser energy during printing, the deposition coating thickness is crucial. Moreover, an appropriate coating thickness can enhance the opportunity for Ti or W particles to diffuse into B atoms, increasing the possibility of forming interfacial phases such as TiB2 and TiB.

[0035] Example 7

[0036] S1. Add the boron nitride nanotube powder to be deposited and the dispersant to ethanol for dispersion treatment. After stirring for 0.5, filter to obtain boron nitride nanotube particles. Then, dry, grind or ball mill the boron nitride nanotube particles to obtain uniformly dispersed boron nitride nanotube powder. S2. Ti was deposited on boron nitride nanotube powder using physical deposition to obtain modified boron nitride nanotubes. The vacuum chamber pressure was first adjusted to a vacuum state, and an appropriate amount of argon gas was injected into the vacuum chamber. Under conditions of 25℃ and 20W, the generated Ar... +Ti was pre-deposited onto boron nitride nanotube powder by ion bombardment of a Ti target for 20 s. After pre-deposition, argon gas was introduced into the vacuum chamber at a flow rate of 30 sccm, and the pressure inside the vacuum chamber was controlled at around 5 mTorr. Then, Ti was deposited onto the boron nitride nanotube powder at a temperature of 25 °C and a power of 100 W for 15 minutes to obtain modified boron nitride nanotubes, P7. S3. Modified boron nitride nanotubes P7 and pure Al powder are wet-mixed in proportion to obtain a mixture. Then, the mixture is dried by a blower under heating conditions of about 50°C, and then transferred to a vacuum furnace for drying at 100°C. After drying, the mixture is ball-milled to obtain a uniformly dispersed mixed powder. S4. The mixed powder is processed by compression, sintering, or short-time melting, and, as... Figure 9 As shown, a 2wt% Ti-BNNT-Al composite material was prepared by pressing and molding with an instrument; at the same time, steps S3 and S4 were repeated to prepare a 5wt% Ti-BNNT-Al composite material.

[0037] Example 8

[0038] S1. Add the boron nitride nanotube powder to be deposited and the dispersant to ethanol for dispersion treatment. After stirring for 0.5, filter to obtain boron nitride nanotube particles. Then, dry, grind or ball mill the boron nitride nanotube particles to obtain uniformly dispersed boron nitride nanotube powder. S2. Modified boron nitride nanotubes are obtained by depositing W onto boron nitride nanotube powder using physical deposition. Specifically, the internal pressure of the vacuum chamber is first adjusted to a vacuum state, and an appropriate amount of argon gas is injected into the vacuum chamber. Under conditions of 25℃ and 20W, Ar gas is generated... + Ion bombardment of a W target caused W to be pre-deposited onto boron nitride nanotube powder for 10 seconds. After pre-deposition, argon gas was introduced into the vacuum chamber at a flow rate of 30 sccm, and the pressure inside the vacuum chamber was adjusted to approximately 5 mTorr. Then, W was deposited onto the boron nitride nanotube powder at a temperature of 25°C and a power of 100 W for 15 minutes to obtain modified boron nitride nanotubes, P8. S3. Modified boron nitride nanotubes and pure Al powder are wet-mixed in proportion to obtain a mixture. Then, as follows: Figure 1 As shown, the mixture is first dried by a blower under heating conditions of about 50°C, and then transferred to a vacuum furnace for drying at 100°C. After drying, the mixture is ball-milled to obtain a uniformly dispersed mixed powder. S4. The mixed powder is processed by compression, sintering or short-time melting to prepare a 2wt% W-BNNT-Al composite material; at the same time, steps S3 and S4 are repeated to prepare a 5wt% W-BNNT-Al composite material.

[0039] Comparative Example 1 Pure aluminum-based materials are prepared by purchasing pure aluminum powder on the market and then compressing, sintering, or melting it for a short time.

[0040] The partial morphologies of the 2wt% Ti-BNNT-Al composite material, 5wt% Ti-BNNT-Al composite material, 2wt% W-BNNT-Al composite material, 5wt% W-BNNT-Al composite material prepared in Examples 7 and 8, and the pure aluminum-based material prepared in Comparative Example 1 are shown below. Figure 10 As shown; the properties of the compressed mixed powders from Examples 7, 8, and Comparative Example 1, as well as the powders after heat treatment, were tested respectively; the test results are as follows. Figure 11 As shown, there was no significant difference in hardness between pure Al and the 5wt% W-BNNT-Al composite, while the 5wt% Ti-BNNT-Al alloy had a slightly lower hardness. This difference can be attributed to the difference in density between Ti and W. Due to the lower strength of Ti, there are more boron nitride nanotube particles coated with Ti compared to the W-BNNT-Al composite. This leads to poorer compatibility of the titanium-coated boron nitride nanotube powder, resulting in a slightly lower hardness of the Ti-BNNT-Al alloy. Meanwhile, as... Figure 12 As shown, after heat treatment, the hardness of the aluminum matrix composite reinforced by Ti / W deposited boron nitride nanotubes increased by approximately 40% and 50%, respectively. This is due to the sintering of the Ti / W deposited boron nitride nanotube-reinforced aluminum matrix composite during the heat treatment process. This also indicates that Ti / W deposited boron nitride nanotubes have significant potential for mechanical reinforcement of pure Al.

[0041] In this application, 3D printing is simulated using compression disks made of pure aluminum and its aluminum-based composite materials; the disks obtained by compression in Examples 7, 8 and Comparative Example 1 were heat-treated at 900°C to examine their thermal stability under the high-temperature conditions mainly required in the 3D printing process. Figure 13 The results show that pure aluminum melts while the aluminum-based composite material reinforced with boron nitride nanotubes based on Ti / W deposition remains, confirming the crucial role of the metal coating; therefore, when the Lens 3D printer is put back into service, the Ti / W-deposited boron nitride nanotubes are ready to be fed into the printer.

[0042] In this application, Ti / W nanoparticles are deposited on the surface of boron nitride nanotubes. In addition to maintaining the microstructure of the boron nitride nanotubes during 3D printing, the deposition of Ti / W nanoparticles also leads to the formation of a strong TiB2 or WB2 phase at the interface between the boron nitride nanotube powder particles and the Ti / W nanometal layer, thereby improving the hardness and tensile strength of the composite material. Furthermore, another interfacial phase, Al-AlB2, is also prevalent along with the formation of AlN on the surface of the boron nitride nanotubes. Therefore, through these intermediate phases and the refinement of the Al grain size, the mechanical properties of the prepared composite material can be significantly improved after 3D printing.

[0043] The above embodiments are merely illustrative of the technical concept and features of the present invention, intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and should not be construed as limiting the scope of protection of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and thus all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention.

Claims

1. A method for preparing a metal matrix composite material reinforced with modified boron nitride nanotubes, characterized in that, Includes the following steps: S1. Add the boron nitride nanotube powder to be deposited and the dispersant to ethanol for dispersion treatment. After stirring for 0.5-2 hours, filter to obtain boron nitride nanotube particles. Then, dry, grind or ball mill the boron nitride nanotube particles to obtain uniformly dispersed boron nitride nanotube powder. S2. Using physical deposition or chemical deposition, Ti or W is deposited on boron nitride nanotube powder to obtain modified boron nitride nanotubes. S3. The modified boron nitride nanotubes and pure metal powder are wet-mixed in proportion to obtain a mixture. Then, the mixture is dried by a blower under heating conditions of 45-55℃, and then transferred to a vacuum furnace to dry the mixture at 90-110℃. After drying, the mixture is ball-milled to obtain a uniformly dispersed mixed powder. S4. Metal matrix composites are prepared by using 3D printing technology or by processing the mixed powder through compression, sintering or short-time melting.

2. The method for preparing a metal matrix composite material reinforced with modified boron nitride nanotubes according to claim 1, characterized in that: In step S2, the physical deposition method includes the following specific steps: a. Using magnetron sputtering at a temperature of 20-30℃ and a power of 10-50W, Ti or W is pre-deposited onto boron nitride nanotube powder, with the pre-deposition time controlled within the range of 5-30s. b. Under the conditions of 20-30℃ and 80-120W, continue to deposit Ti or W on boron nitride nanotube powder; During the deposition process, the pressure inside the vacuum chamber is controlled at 3-8 mTorr; The deposition time should be controlled within the range of 5-30 minutes.

3. The method for preparing a metal matrix composite material reinforced with modified boron nitride nanotubes according to claim 2, characterized in that: During the deposition process, argon gas is introduced into the vacuum chamber at a flow rate of 25-40 sccm.

4. The method for preparing a metal matrix composite material reinforced with modified boron nitride nanotubes according to claim 1, characterized in that: In step S2, the chemical deposition method includes the following steps: a. Add boron nitride nanotube powder and hydrogen peroxide to a reaction vessel at a mass ratio of (4-5):

1. Then, seal the reaction vessel and perform ultrasonic treatment followed by water bath heating treatment. The water bath heating temperature is 100-120℃ and the water bath heating time is 20-30h. b. After water bath heating treatment, the liquid phase in the reaction vessel is evaporated, and then an acidic solution is added to the reaction vessel and stirred evenly to form a mixture. Then, the mixture is filtered and the filter residue obtained by filtration is cleaned with pure water and acetone, and then dried to obtain functionalized boron nitride nanotube powder. c. Under a high-purity nitrogen atmosphere, functionalized boron nitride nanotube powder, oleic acid, and trioctylphosphine oxide are added to a solvent and mixed evenly. The mixture is then preheated to 100-150°C. Next, titanium isopropoxide or tungsten hexacarbonyl is added to the solvent at a molar ratio of 1:(1-2) of functionalized boron nitride nanotube powder to titanium isopropoxide or tungsten hexacarbonyl. The mixture is heated under reflux and reacted for 20-50 minutes. The reaction is then stopped, and the reaction solution is cooled to room temperature. After filtration, washing, and vacuum drying, modified boron nitride nanotubes are obtained.

5. The method for preparing a metal matrix composite material reinforced with modified boron nitride nanotubes according to claim 1, characterized in that: In step S3, the wet mixing includes the following steps: a) adding the modified boron nitride nanotubes to an organic solvent for dispersion treatment, stirring for 0.5-2 hours until uniformly dispersed to form a dispersion; the organic solvent is any one of ethanol, isopropanol, and n-butanol; b. Weigh out pure metal powder according to the proportion, add the weighed pure metal powder to the dispersion, and stir for 0.5-1h to obtain a mixture.

6. The method for preparing a metal matrix composite material reinforced with modified boron nitride nanotubes according to claim 1, characterized in that: In the metal matrix composite material, the modified boron nitride nanotubes account for 1-10% of the total mass of the metal matrix composite material.

7. A metal matrix composite material reinforced with modified boron nitride nanotubes, characterized in that: The metal matrix composite material was prepared by the preparation method described in any one of claims 1-6.

Images