A carbon dot-reinforced titanium matrix composite material based on microwave sintering and its preparation method

Abstract

This invention discloses a carbon dot-reinforced titanium-based composite material based on microwave sintering and its preparation method, belonging to the field of metal matrix composite material preparation technology. The method includes: preparing carbon dots; mixing, ball milling, drying, and microwave sintering the carbon dots with TC4 powder. This invention uses carbon dots as a carbon source to synthesize in-situ TiCp reinforcing phases with fine grain size, significantly improving the comprehensive performance of the matrix material and further enhancing the mechanical properties of the composite material. Simultaneously, the use of a hydrothermal method to process agricultural waste for batch preparation of carbon dots is low-cost, achieves resource utilization, and provides a new direction for the green treatment of agricultural waste. Furthermore, the use of microwave technology for sintering has the characteristics of uniform heating, rapid and efficient operation, simple operation, and no pollution. The prepared titanium-based composite material has fine grains, strong interfacial bonding with the matrix, and excellent mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of metal matrix composite material preparation technology, and in particular relates to a carbon dot reinforced titanium matrix composite material based on microwave sintering and its preparation method. Background Technology

[0002] Titanium-based composite materials are prepared by cold isostatic pressing-microwave sintering using ceramics as reinforcement and titanium or titanium alloys as the matrix material. Due to their high specific stiffness and specific strength, excellent high-temperature performance, wear resistance, and strong corrosion resistance, titanium-based composite materials have been extensively studied by materials experts worldwide in recent years and have wide applications in aerospace, shipbuilding, automotive manufacturing, and biomedicine.

[0003] TiC particles possess high melting points, high elastic modulus, and similar density and Poisson's ratio to titanium alloys. Their coefficient of thermal expansion is also not significantly different from that of titanium alloys. Furthermore, they exhibit good chemical stability in the matrix material, minimal interfacial reactions, and strong interfacial bonding. However, existing methods for preparing TiC-reinforced titanium matrix composites using ordinary carbon sources in situ suffer from problems such as coarse-sized and unevenly distributed TiC reinforcing phase grains, leading to poor mechanical properties. Simultaneously, with increasing TiC reinforcing phase content, TiC particles tend to transform into dendritic morphologies, significantly reducing the mechanical properties of the reinforced titanium matrix composites and making it difficult to meet application requirements. Therefore, there is an urgent need for a novel reinforced titanium matrix composite material with superior mechanical properties. Summary of the Invention

[0004] 1. The problem to be solved

[0005] This invention addresses the issue that traditional methods for in-situ synthesis of TiCp-reinforced titanium matrix composites with large grain sizes using common carbon sources do not significantly improve the mechanical properties of these composites, especially given the dendritic morphology of the TiC particles. This invention provides a microwave-sintered carbon dot-reinforced titanium matrix composite and its preparation method. The technical solution of this invention can significantly enhance the mechanical properties of titanium matrix composites, while using agricultural waste as raw material to prepare biomass carbon dots achieves resource utilization, fully aligning with the concept of sustainable development.

[0006] 2. Technical Solution

[0007] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0008] The present invention discloses a method for preparing a carbon dot-reinforced titanium-based composite material based on microwave sintering, comprising the following steps:

[0009] Step S1: Preparation of carbon dots:

[0010] After crushing and grinding the raw materials, they were dissolved in deionized water, ultrasonically mixed, and then placed in a high-pressure reactor. The mixture was then dried in a forced-air drying oven at 140–220°C for 6–13 hours to obtain a dark yellow solution. The solution was then poured into a centrifuge tube and centrifuged at high speed. This operation was repeated three times. The supernatant obtained was placed in a dialysis bag for dialysis. After dialysis, the solution was freeze-dried to obtain biomass carbon dots.

[0011] Step S2, Ingredients: The carbon dots and TC4 powder obtained in step S1 are mixed according to a certain mass ratio. When mixing, the amount of carbon dots added accounts for 0.5 to 2.35% of the total weight of the raw material powder.

[0012] Step S3, Mixing: Weigh stainless steel balls according to a certain ball-to-material ratio, and add an appropriate amount of alcohol to the ball mill jar for mixing;

[0013] Step S4, ball milling: The powder mixed in step S3 is ball milled;

[0014] Step S5, Drying: Dry the ball-milled powder from step S4 in a vacuum drying oven;

[0015] Step S6, pressing: Press the dried mixed powder from step S5 into a sample using a cold isostatic pressing device;

[0016] Step S7, Microwave Sintering: The cold-pressed blank from step S6 is microwave sintered. SiC is used as an auxiliary heating material during sintering to surround the blank containing the mixed powder. After sintering, the blank is cooled in the furnace. After the sample is removed, it is cooled at room temperature to obtain the titanium-based composite material.

[0017] As a further improvement of the present invention, in step S1, agricultural waste is used as raw material, such as straw or wheat straw. The agricultural waste is crushed and ground to about 100 mesh and then dissolved in 20-50 ml of deionized water for ultrasonic mixing.

[0018] During the reaction, the temperature of the drying oven is controlled at 140-220℃, and the reaction time is 6-13 hours.

[0019] When centrifuging after the reaction is complete, control the speed of the high-speed centrifuge to be 5000-10000 r / min and the centrifugation time to be 6-12 min.

[0020] When using dialysis bags for dialysis, the selected dialysis bag size is 500-1000 kDa, and the dialysis time is 12-24 hours.

[0021] When performing freeze drying, the freeze drying temperature is -80℃ and the freeze drying time is 32 to 50 hours.

[0022] This invention enables the mass production of high-quality biomass carbon dots using a hydrothermal method. These carbon dots can be added to TC4 powder as a carbon source to create titanium-based composite materials with excellent mechanical properties. Furthermore, this invention effectively solves the problem of difficult agricultural waste treatment and establishes a simple, inexpensive, and effective treatment and recycling system.

[0023] As a further improvement of the present invention, in step S2, the particle size of TC4 is 30-150 μm, the particle size of carbon dots is less than 10 nm, and the amount of carbon dots added accounts for 0.5-2.35% of the total weight of the raw material powder. The present invention, through optimized design of the amount of carbon dots added and supplemented by microwave treatment, can effectively ensure the mechanical properties of the prepared titanium-based composite material. Through multiple experiments, the applicant found that the amount of carbon dots added is crucial. Adding too many carbon dots not only fails to significantly improve performance but also greatly reduces the plasticity of the composite material, while adding too few carbon dots provides little reinforcing effect and has poor microwave absorption capacity, ultimately leading to prolonged sintering time. Research has shown that controlling the amount of carbon dots added in the present invention, supplemented by the microwave treatment process of the present invention, and ensuring that the reinforcing phase content is around 1.7%, yields the best reinforcing effect.

[0024] As a further improvement of the present invention, in step S3, the ball-to-powder ratio is (3-5):1, the ball milling speed is 150-250 r / min, and the ball milling time is 6-20 h. By adjusting the ball milling speed and time, carbon dots can be adhered to the surface of TC4 powder without damaging the TC4 powder. During sintering, the carbon dots react with TC4 to form a TiC reinforcing phase, which conforms to the HS theory of hard reinforcing phase surrounding the matrix, greatly improving the mechanical properties of the material.

[0025] As a further improvement of the present invention, the drying temperature is 65-80℃ and the drying time is 8-22h.

[0026] As a further improvement of the present invention, the cold isostatic pressure is 280-350 MPa, and the holding time is 2-8 min.

[0027] As a further improvement of the present invention, in step S7, the microwave sintering power is controlled to be 500-1000W and the sintering time is 10-50min. After sintering, the sample is taken out after cooling in the furnace for about 2min and then cooled at room temperature to obtain the titanium-based composite material.

[0028] It should be noted that when adding the carbon dots of this invention for microwave sintering, the excellent microwave absorption properties of the carbon dots effectively compensate for the poor microwave absorption properties of metal powders. During sintering, they act as both a reinforcing phase and absorb microwave radiation for heating. Furthermore, because the biomass carbon dots in this invention are extremely small (below 10 nm), they have a larger specific surface area than traditional carbon sources, resulting in stronger microwave absorption and shorter sintering time. To further improve microwave sintering efficiency, this invention uses SiC with excellent microwave absorption properties as an auxiliary heating material to surround the bulk of the mixed powder, thereby further shortening the sintering time and ensuring the mechanical properties of the material. Moreover, thanks to the unique non-thermal effect of microwaves, the reinforcing phase generated after adding carbon dots is finer and has a stronger interfacial bond with the matrix, enabling it to withstand greater loads and significantly improving the mechanical properties of the material.

[0029] In existing technologies, titanium-based composite materials prepared using traditional sintering methods and conventional carbon sources typically have a hardness of around 350 HV and a compressive strength of around 1600 MPa. However, this invention utilizes microwave sintering technology and adds biomass carbon dots. Carbon dots, as a reinforcing phase, offer numerous advantages, such as small grain size and high load-bearing capacity. Furthermore, by controlling the amount of carbon dots added and the sintering process parameters, the resulting titanium-based composite material can achieve a hardness of up to 480 HV and a compressive strength of up to 2231 MPa. Compared to titanium-based composite materials reinforced with traditional carbon sources, this represents an increase in hardness and compressive strength of 37.14% and 39.44%, respectively.

[0030] 3. Beneficial effects

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] (1) The present invention provides a method for preparing carbon dot-reinforced titanium-based composite materials based on microwave sintering. On the one hand, it provides a new carbon source by using agricultural waste (such as straw, wheat straw, etc.) as raw materials to prepare high-quality biomass carbon dots in batches through hydrothermal method, which solves the problem of difficult treatment of agricultural waste and establishes a simple, cheap and effective treatment and recycling system, truly realizing the development concept of solid waste utilization. On the other hand, the prepared biomass carbon dots are used as carbon source and combined with cold isostatic pressing-microwave sintering technology to generate fine-grained TiC reinforcing phase in situ, which significantly enhances the mechanical properties of the matrix material.

[0033] (2) The present invention provides a method for preparing carbon dot-reinforced titanium-based composite materials based on microwave sintering. Through microwave sintering technology, titanium-based composite materials with high density, effective carbon dot composite and excellent mechanical properties can be prepared quickly. Moreover, microwave sintering technology can heat uniformly and is a fast, economical and environmentally friendly sintering method. The method of the present invention follows the concepts of saving costs, reducing energy consumption and recycling, and realizes the maximum utilization of resources.

[0034] (3) The present invention provides a carbon dot reinforced titanium-based composite material based on microwave sintering, which has a grain size of less than 40 μm, a density of more than 99.6%, a compressive strength of 1876 MPa to 2231 MPa, and a hardness of 368 HV to 480 HV, and has excellent mechanical properties. Attached Figure Description

[0035] Figure 1 This is an external view of the titanium-based composite material sample obtained in Example 1 of the present invention;

[0036] Figure 2 This is a diagram showing the compressive properties of the titanium-based composite material sample obtained in Example 1 of the present invention;

[0037] Figure 3 This is a microstructure (SEM) image of the titanium-based composite material sample obtained in Example 1 of the present invention. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments.

[0039] Example 1

[0040] Step 1: Preparation of carbon dots;

[0041] 4.67g of wheat straw was crushed and ground to about 100 mesh, then dissolved in 35ml of deionized water. After ultrasonic mixing, the mixture was placed in a high-pressure reactor and reacted at 160℃ for 8 hours in a forced-air drying oven to obtain a deep yellow solution. The solution was then poured into centrifuge tubes and centrifuged at 7000r / min for 8 minutes. This operation was repeated three times. The supernatant was placed in an 800KD dialysis bag and dialyzed for 17 hours. After dialysis, the solution was freeze-dried at -80℃ for 37 hours to obtain 0.64g of carbon dots.

[0042] Step 2: Preparation of a mixed sample of carbon dots and TC4 powder;

[0043] 11.76 g of TC4 (particle size 45-75 μm) and 0.24 g of carbon dots obtained in step one were mixed together in a ball mill jar; stainless steel balls were weighed at a ball-to-particle ratio of 5:1, and an appropriate amount of alcohol was added. The mixture was ball-milled at 200 r / min for 10 h; the ball-milled powder was placed in a drying oven and dried at 70 °C for 15 h; the dried powder was then subjected to cold isostatic pressing at a pressure of 300 MPa for 4 min to obtain a green body.

[0044] Step 3: Microwave sintering;

[0045] The cold-pressed blank was placed in a microwave oven for microwave sintering at 800W for 20 minutes. After cooling for about 2 minutes, the sample was removed and then cooled to room temperature to obtain the specimen, which appeared as follows. Figure 1 As shown, the compression performance is as follows Figure 2 As shown, the titanium-based composite material exhibits a yield strength of 1615 MPa, a compressive strength of 2231 MPa, and an engineering strain of 27.8%, demonstrating excellent mechanical properties. SEM images of the sample surface morphology are shown below. Figure 3 As shown, after sintering, the reinforcing phase is distributed in a quasi-continuous network, and the hard reinforcing phase surrounds the matrix, which is consistent with the HS theory, and the generated reinforcing phase is relatively uniformly dispersed.

[0046] The mechanical properties of the samples obtained in this embodiment were tested, and the test results are shown in Table 1.

[0047] Example 2

[0048] Step 1: Preparation of carbon dots;

[0049] 3.35g of wheat straw was crushed and ground to about 100 mesh and dissolved in 40ml of deionized water. After ultrasonic mixing, the mixture was placed in a high-pressure reactor and reacted at 140℃ for 6 hours in a forced-air drying oven to obtain a dark yellow solution. The solution was then poured into centrifuge tubes and centrifuged at 5000r / min for 6 minutes. This operation was repeated three times. The supernatant was placed in a 500KD dialysis bag and dialyzed for 14 hours. After dialysis, the solution was freeze-dried at -80℃ for 32 hours to obtain 0.57g of carbon dots.

[0050] Step 2: Preparation of a mixed sample of carbon dots and TC4 powder;

[0051] 11.94 g of TC4 powder (particle size 30-60 μm) and 0.06 g of carbon dots obtained in step one were mixed together in a ball mill jar. Stainless steel balls were weighed at a ball-to-particle ratio of 3:1, and an appropriate amount of alcohol was added. The mixture was ball-milled at 250 r / min for 6 h. The ball-milled powder was placed in a drying oven and dried at 65 °C for 18 h. The dried powder was then subjected to cold isostatic pressing at a pressure of 280 MPa for 2 min to obtain a green body.

[0052] Step 3: Microwave sintering;

[0053] The cold-pressed blank was placed in a microwave oven for microwave sintering at a power of 1000W for 10 minutes. After cooling for about 2 minutes, the sample was removed and then cooled to room temperature to obtain the specimen.

[0054] The mechanical properties of the obtained samples in this embodiment were tested, and the test results are shown in Table 1.

[0055] Example 3

[0056] Step 1: Preparation of carbon dots;

[0057] 5.81g of wheat straw was crushed and ground to about 100 mesh, then dissolved in 30ml of deionized water. After ultrasonic mixing, the mixture was placed in a high-pressure reactor and reacted at 180℃ for 10h in a forced-air drying oven to obtain a dark yellow solution. The solution was then poured into a centrifuge tube and centrifuged at 9000r / min for 9min. This operation was repeated three times. The supernatant was placed in a 900KD dialysis bag and dialyzed for 20h. After dialysis, the solution was freeze-dried at -80℃ for 42h to obtain 0.79g of carbon dots.

[0058] Step 2: Preparation of a mixed sample of carbon dots and TC4 powder;

[0059] 11.82 g of TC4 powder (particle size 50-80 μm) and 0.18 g of carbon dots obtained in step one were mixed together in a ball mill jar. Stainless steel balls were weighed at a ball-to-particle ratio of 4:1, and an appropriate amount of alcohol was added. The mixture was ball-milled at 180 r / min for 14 h. The ball-milled powder was placed in a drying oven and dried at 75 °C for 11 h. The dried powder was then subjected to cold isostatic pressing at a pressure of 330 MPa for 2 min to obtain a green body.

[0060] Step 3: Microwave sintering;

[0061] The cold-pressed blank was placed in a microwave oven for microwave sintering at 700W for 30 minutes. After cooling for about 2 minutes, the sample was removed and then cooled to room temperature to obtain the specimen.

[0062] The mechanical properties of the samples obtained in this embodiment were tested, and the test results are shown in Table 1.

[0063] Example 4

[0064] Step 1: Preparation of carbon dots;

[0065] 6.99g of wheat straw was crushed and ground to about 100 mesh, then dissolved in 25ml of deionized water. After ultrasonic mixing, the mixture was placed in a high-pressure reactor and reacted at 210℃ for 12h in a forced-air drying oven to obtain a dark yellow solution. The solution was then poured into centrifuge tubes and centrifuged at 10000r / min for 10min. This operation was repeated three times. The supernatant was placed in a 1000KD dialysis bag and dialyzed for 23h. After dialysis, the solution was freeze-dried at -80℃ for 47h to obtain 0.77g of carbon dots.

[0066] Step 2: Preparation of a mixed sample of carbon dots and TC4 powder;

[0067] 11.72g of TC4 powder (particle size 60-100μm) and 0.28g of carbon dots obtained in step one were mixed together in a ball mill jar; stainless steel balls were weighed at a ball-to-particle ratio of 5:1, and an appropriate amount of alcohol was added. The mixture was ball-milled at 150r / min for 18h; the ball-milled powder mixture was placed in a drying oven and dried at 80℃ for 8h; the dried powder mixture was then subjected to cold isostatic pressing at a pressure of 350MPa for 2min to obtain a green body.

[0068] Step 3: Microwave sintering;

[0069] The cold-pressed blank was placed in a microwave oven for microwave sintering at 600W for 35 minutes. After cooling for about 2 minutes, the sample was removed and then cooled to room temperature to obtain the specimen.

[0070] The mechanical properties of the samples obtained in this embodiment were tested, and the test results are shown in Table 1.

[0071] Table 1 Performance test indicators of titanium-based composite material samples obtained in each embodiment

[0072] project Grain size Density Yield strength compressive strength hardness Engineering strain Example 1 34μm 99.61％ 1615MPa 2231MPa 480HV 27.8％ Example 2 38μm 99.68％ 1532MPa 2134MPa 426HV 25.6％ Example 3 38μm 99.71％ 1436MPa 2065MPa 381HV 28.1％ Example 3 37μm 99.81％ 1566MPa 1876MPa 368HV 27.4％

[0073] More specifically, although exemplary embodiments of the invention have been described herein, the invention is not limited to these embodiments, but includes any and all embodiments modified, omitted, such as combinations between various embodiments, adaptive changes, and / or substitutions, as would be apparent to those skilled in the art from the foregoing detailed description. The limitations in the claims are to be interpreted broadly as used in the language of the claims and are not limited to the examples described in the foregoing detailed description or during the implementation of this application, which should be considered non-exclusive. Any step listed in any method or process claim may be performed in any order and is not limited to the order set forth in the claims. Therefore, the scope of the invention should be determined solely by the appended claims and their legal equivalents, and not by the description and examples given above.

[0074] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the definitions in this specification shall prevail. When a rate, pressure, temperature, time, or other value or parameter is expressed as a range, preferred range, or a range defined by a series of upper and lower preferred values, this shall be understood to specifically disclose all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether such range is disclosed individually. For example, the range 1-50 should be understood to include any number, combination of numbers, or subrange selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, as well as all decimal values ​​between the integers mentioned above, such as 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. Regarding subranges, specifically consider "nested subranges" extending from any endpoint of the range. For example, nested sub-ranges of the exemplary range 1-50 may include 1-10, 1-20, 1-30 and 1-40 in one direction, or 50-40, 50-30, 50-20 and 50-10 in another direction.

Claims

1. A method for preparing a microwave sintering based carbon dots enhanced titanium matrix composite material, characterized in that, The method comprises the following steps: Step S1, preparing carbon dots; Step S2, batching: the carbon dots obtained in step S1 and TC4 powder are batched, and the addition amount of the carbon dots accounts for 0.5% to 2.35% of the total weight of the raw material powder; Step S3, mixing: the batched material in step S2 is weighed according to the ball-to-material ratio, and a proper amount of alcohol is added in the ball milling tank for mixing; Step S4, ball milling: the mixed powder in step S3 is subjected to ball milling treatment; Step S5, drying: the spherically shaped powder subjected to ball milling in step S4 is dried in a vacuum drying box; Step S6, sample pressing: the mixed powder dried in step S5 is subjected to sample pressing through a cold isostatic pressing device; Step S7, microwave sintering: the green body subjected to cold pressing in step S6 is subjected to microwave sintering, and SiC is used as auxiliary heating material to surround the green body of the mixed powder, and after sintering, the sample is subjected to furnace cooling and then cooled at room temperature, thereby obtaining a titanium-based composite material.

2. The method according to claim 1, wherein the method is characterized by: The particle size of the TC4 is 15 to 130 μm.

3. The method according to claim 1, wherein the method is characterized by: In step S1, agricultural waste is used as raw material, and biomass carbon dots are prepared by using a hydrothermal method.

4. The method according to claim 1, wherein the method is characterized by: In step S3, the ball-to-material ratio is (3-5):

1.

5. The method for preparing a microwave sintering based carbon dots enhanced titanium matrix composite material according to any one of claims 1-4, characterized in that: In step S4, the ball milling speed is 150-250 r / min, and the ball milling time is 6-20 h.

6. The method for preparing a microwave sintering based carbon dots enhanced titanium matrix composite material according to any one of claims 1-4, characterized in that: In step S5, the drying temperature is 60-75 ℃, and the drying time is 10-24 h.

7. The method for preparing a microwave sintering based carbon dots enhanced titanium matrix composite material according to any one of claims 1-4, characterized in that: In step S6, the cold isostatic pressing pressure is 280-350 MPa, and the pressure maintaining time is 2-8 min.

8. The method for preparing a microwave sintering based carbon dots enhanced titanium matrix composite material according to any one of claims 1-4, characterized in that: In step S7, the microwave power is 500-1000 W, the sintering time is 10-50 min, and the furnace cooling time is 2-3 min.

9. A microwave sintering based carbon dots reinforced titanium matrix composite, characterized by: The titanium-based composite material is prepared by the method in any one of claims 1-8, the grain size of the prepared titanium-based composite material is less than 40 μm, the density is more than 99.6%, the compressive strength is 1876 MPa-2231 MPa, and the hardness is 368 HV-480 HV.

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