A microwave molten salt preparation method for layered gradient Ti2AlC 0.5 N 0.5 Method

Abstract

This invention discloses a method for preparing layered gradient Ti2AlC using microwave molten salt. 0.5 N 0.5 This method relates to the field of new material synthesis and preparation technology. Several components selected from Ti powder, Al powder, organic fibers, and inorganic salts are weighed and subjected to one-step microwave molten salt heating to achieve pyrolysis of the organic fibers and preparation of MAX phase materials at a relatively low temperature. The product is washed with deionized water to remove inorganic salts, and the washed solid product is dried to obtain the MAX phase material. By controlling the reaction time, a layered gradient structure MAX phase material is prepared. This invention utilizes a microwave molten salt method to prepare layered gradient Ti2AlC... 0.5 N 0.5 The method for preparing stratified gradient MAX phase materials has high product purity, stable and efficient reaction, and can simultaneously achieve morphology and composition control of MAX phase materials. The method is simple, efficient and easy to industrialize.

Description

Technical Field

[0001] This invention relates to the field of novel material synthesis and preparation technology, specifically to a method for preparing layered gradient Ti2AlC using microwave molten salt. 0.5 N 0.5 The method. Background Technology

[0002] MAX phase materials are ternary layered ceramic materials with a hexagonal structure, where M is a transition metal element, A is a main group element, and X is C or N. In MAX phase materials, the M-site atoms and X-site atoms are connected by strong covalent bonds forming MXM covalent bonds, exhibiting advantages such as high strength and elastic modulus, good thermal stability, low coefficient of thermal expansion, strong resistance to acid and alkali corrosion, and good high-temperature oxidation resistance. On the other hand, the MX structure is bonded to the A atoms by weaker MA metallic covalent bonds, thus giving MAX phase materials good machinability while also possessing some of the properties of the A-layer metal, such as electrical conductivity, thermal conductivity, and ductility. Given these ceramic and metallic properties, MAX phase materials have enormous application potential in many high-tech fields such as aerospace, high-speed rail, nuclear industry, and microwave absorption stealth.

[0003] Currently, most domestic and international research on the preparation of MAX phase materials involves mixing raw material powders, cold pressing them into shape, and then sintering them at high temperatures. This method is not suitable for the efficient and rapid preparation of MAX phase powder materials. Related literature reports that the morphology and type of MAX phase materials have a significant impact on their physicochemical properties. CN202311651537 discloses a MAX phase material, its preparation method, and its applications. Specifically, M-source and X-source are mixed and electrospinned to prepare nanofibers, followed by preheating for 2-12 hours to obtain an MX nanofiber precursor template. Subsequently, the MX precursor is mixed with an A-source and heat-treated at 1100-1600℃ for 1-4 hours to obtain the MAX phase material. CN202410384549 discloses a high-purity gallium-based layered carbide / nitride MAX phase material and its preparation method. First, metal powder M is mixed with graphite powder or metal nitride powder MN, and pre-calcined at 1200-1400℃ to obtain an MX precursor. The obtained MX precursor is then impregnated with molten Ga metal and calcined at 1300-1600℃ for 100-250 min to obtain the gallium-based layered carbide / nitride MAX phase material. These techniques obtain carbide / nitride MAX phase materials by adding an additional N source, and require multiple high-temperature treatments with long reaction times. Special morphology and structure have a significant impact on the practical applications of MAX phase materials. For example, in the field of electromagnetic wave absorption, morphology and structure control can promote electromagnetic wave attenuation; therefore, morphology and structure control of MAX phase materials are necessary.

[0004] Therefore, it is crucial to develop a simple and efficient method that does not require the addition of additional C or N sources and can simultaneously control the morphology and structure of MAX phase materials, in order to meet the demand for mass production of high-quality carbonitride MAX phase materials. Summary of the Invention

[0005] The purpose of this invention is to provide a method for rapidly preparing layered gradient structure MAX phase materials by microwave molten salt pyrolysis, which solves the problems of long reaction time, uncontrollable morphology and structure, and difficulty in meeting the requirements of large-scale industrial production in existing MAX phase material preparation processes.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a microwave molten salt preparation method for layered gradient Ti2AlC 0.5 N 0.5 The method is characterized by comprising the following steps:

[0007] S1. Weigh Ti powder, Al powder, organic fiber and inorganic salt and place them in a mortar. Add anhydrous ethanol and grind to obtain material a. Place material a in a ball mill and ball mill until it is mixed evenly to obtain material b.

[0008] S2. Place material b in a microwave oven for rapid drying to remove anhydrous ethanol and obtain material c;

[0009] S3. Place the mixture c in a microwave oven and perform molten salt synthesis under a protective atmosphere. Through microwave selective activation heating, the rapid preparation of layered gradient carbonitride MAX phase materials is achieved.

[0010] S4. Take out the mixture c after the reaction in S3, add 5 to 8 times the volume of deionized water to remove inorganic salts, filter to obtain solid product, wash repeatedly with deionized water and dry, take the solid product and dry to obtain black powder, which is the layered gradient MAX phase material.

[0011] A further technical solution is that in step S1, the organic fiber is one or more of polyamide fiber, polyester fiber, polyacrylonitrile fiber, polypropylene fiber, and polyvinyl alcohol fiber, and the inorganic salt is one or two of NaCl and KCl.

[0012] A further technical solution is that in step S1, the molar ratio of Ti powder, Al powder, NaCl, and KCl is (2-3):1:(1-4):(1-4), the amount of organic fiber is 1-5 g / mol M-site metal, the purity of Ti powder is 99%-99.99%, the purity of Al powder is 99%-99.99%, and the amount of anhydrous ethanol added is 200-400 ml / mol M-site metal.

[0013] A further technical solution is that the ball milling process in step S1 has a rotation speed of 300-400 r / min and a ball milling time of 1-2 h.

[0014] A further technical solution is that in step S2, the microwave heating power is 600W, the microwave frequency is 2450±50MHz, and the heating time is 30min.

[0015] A further technical solution is that in step S3, the reaction temperature is 1000-1100℃, the heating rate is 30-50℃ / min, the holding time is 10-30min, the microwave heating power is 4000-5000W, the microwave frequency is 2450±50 or 915±50MHz, and the protective atmosphere is argon or nitrogen.

[0016] A further technical solution is that in step S4, drying is carried out using a forced-air drying oven at a temperature of 80-90°C for 30-60 minutes.

[0017] Reaction mechanism

[0018] Pyrolysis of organic fibers → Nitrogen-containing carbon fibers (N-CF)

[0019] Ti + N - CF → TiC 0.5 N 0.5

[0020] Ti+Al+TiC 0.5 N 0.5 →Ti2AlC 0.5 N 0.5

[0021] Several components of Ti powder, Al powder, organic fibers, and inorganic salts were weighed and subjected to one-step microwave molten salt heating to achieve pyrolysis of the organic fibers and preparation of MAX phase materials at a relatively low temperature. The product was washed with deionized water to remove inorganic salts, and the washed solid product was dried to obtain the MAX phase material. After pyrolysis, the organic fibers act as C and N sources, rapidly diffusing into the reaction system under microwave and molten salt conditions, and reacting with Ti to form a metal carbonitride mesophase. The metal carbonitride further reacts with Al to obtain the carbonitride MAX phase material. By controlling the reaction time, Ti₂AlC₂ was achieved. 0.5 N 0.5 / TiC 0.5 N 0.5 Preparation of MAX phase materials with a layered gradient structure of / cavity / amorphous carbon / microcrystalline carbon. This invention prepares layered gradient Ti2AlC using a microwave molten salt. 0.5 N 0.5The method for preparing stratified gradient MAX phase materials has high product purity, stable and efficient reaction, and can simultaneously achieve morphology and composition control of MAX phase materials. The method is simple, efficient and easy to industrialize.

[0022] Compared with existing technologies, the advantages of this invention are: Microwave heating is used, and the rapid pyrolysis of organic fibers provides C and N sources and rapidly raises the temperature, allowing inorganic salts to quickly enter the molten state, providing a uniform polar liquid phase environment for the reaction, thereby reducing the activation energy. After pyrolysis, the organic fibers serve as C and N sources and as a template; with the diffusion of C and N elements, Ti2AlC is achieved. 0.5 N 0.5 / TiC 0.5 N 0.5 Preparation of layered gradient strongly absorbing MAX phase materials from hollow / amorphous carbon / microcrystalline carbon. No additional N or C source is required; the layered gradient structure and morphology can be precisely controlled by adjusting the reaction time. The reaction is carried out under a protective atmosphere, resulting in a clearly defined layered gradient structure in the MAX phase materials. The entire process is safe, efficient, clean, and environmentally friendly, with low energy consumption suitable for large-scale industrial production. Attached Figure Description

[0023] Figure 1 The Ti2AlC obtained in Example 1 0.5 N 0.5 SEM image of the image.

[0024] Figure 2 The Ti2AlC obtained in Example 1 0.5 N 0.5 Cross-sectional SEM image.

[0025] Figure 3 The Ti2AlC obtained in Example 3 0.5 N 0.5 Cross-sectional SEM image.

[0026] Figure 4 Ti2AlC obtained in Examples 1-3 0.5 N 0.5 XRD pattern.

[0027] Figure 5 The Ti2AlC obtained in Example 1 0.5 N 0.5 The electromagnetic wave absorption performance diagram. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0029] Example 1

[0030] Weigh the raw materials as follows: Ti powder 19.14g; Al powder 2.69g; polyacrylonitrile fiber 2g; NaCl 46.7g; KCl 59.6g.

[0031] (1) First, place the above raw materials in a mortar, add 150ml of anhydrous ethanol and grind to obtain material a. Place material a in a ball mill and ball mill at 300r / min for 1h until it is mixed evenly to obtain material b.

[0032] (2) Place material b in a microwave oven for rapid drying to remove anhydrous ethanol. The microwave power is 600W, the microwave frequency is 2450±50MHz, and the heating time is 30 minutes to obtain material c.

[0033] (3) Transfer material c to a microwave oven under an argon atmosphere for molten salt synthesis. The reaction temperature is 1000℃, the microwave power is 4500W, the microwave frequency is 2450±50MHz, the heating rate is 30℃ / min, and the holding time is 10min.

[0034] (4) Take out the reactants, add 8 times the volume of deionized water to remove inorganic salts, filter to obtain solid product, wash repeatedly with deionized water and dry, use a forced-air drying oven to dry at 90℃ for 45min to obtain the processed reaction product.

[0035] Example 2

[0036] Weigh the raw materials as follows: Ti powder 19.14g; Al powder 2.69g; polyacrylonitrile fiber 2g; NaCl 46.7g; KCl 59.6g.

[0037] (1) First, place the above raw materials in a mortar, add 150ml of anhydrous ethanol and grind to obtain material a. Place material a in a ball mill and ball mill at 300r / min for 1h until it is mixed evenly to obtain material b.

[0038] (2) Place material b in a microwave oven for rapid drying to remove anhydrous ethanol. The microwave power is 600W, the microwave frequency is 2450±50MHz, and the heating time is 30 minutes to obtain material c.

[0039] (3) Transfer material c to a microwave oven under an argon atmosphere for molten salt synthesis. The reaction temperature is 1000℃, the microwave power is 4500W, the microwave frequency is 2450±50MHz, the heating rate is 30℃ / min, and the holding time is 20min.

[0040] (4) Take out the reactants, add 8 times the volume of deionized water to remove inorganic salts, filter to obtain solid product, wash repeatedly with deionized water and dry, use a forced-air drying oven to dry at 90℃ for 45min to obtain the processed reaction product.

[0041] Example 3

[0042] Weigh the raw materials as follows: Ti powder 19.14g; Al powder 2.69g; polyacrylonitrile fiber 2g; NaCl 46.7g; KCl 59.6g.

[0043] (1) First, place the above raw materials in a mortar, add 150ml of anhydrous ethanol and grind to obtain material a. Place material a in a ball mill and ball mill at 300r / min for 1h until it is mixed evenly to obtain material b.

[0044] (2) Place material b in a microwave oven for rapid drying to remove anhydrous ethanol. The microwave power is 600W, the microwave frequency is 2450±50MHz, and the heating time is 30 minutes to obtain material c.

[0045] (3) Transfer material c to a microwave oven under an argon atmosphere for molten salt synthesis. The reaction temperature is 1000℃, the microwave power is 4500W, the microwave frequency is 2450±50MHz, the heating rate is 30℃ / min, and the holding time is 30min.

[0046] (4) Take out the reactants, add 8 times the volume of deionized water to remove inorganic salts, filter to obtain solid product, wash repeatedly with deionized water and dry, use a forced-air drying oven to dry at 90℃ for 45min to obtain the processed reaction product.

[0047] Example 4

[0048] Weigh the raw materials as follows: Ti powder 28.7g; Al powder 2.69g; polyester fiber 4g; NaCl 46.7g; KCl 59.6g.

[0049] (1) First, place the above raw materials in a mortar, add 150ml of anhydrous ethanol and grind to obtain material a. Place material a in a ball mill and ball mill at 300r / min for 2h until it is mixed evenly to obtain material b.

[0050] (2) Place material b in a microwave oven for rapid drying to remove anhydrous ethanol. The microwave power is 600W, the microwave frequency is 2450±50MHz, and the heating time is 30 minutes to obtain material c.

[0051] (3) Transfer material c to a microwave oven under an argon atmosphere for molten salt synthesis. The reaction temperature is 1050℃, the microwave power is 5000W, the microwave frequency is 2450±50MHz, the heating rate is 40℃ / min, and the holding time is 30min.

[0052] (4) Take out the reactants, add 8 times the volume of deionized water to remove inorganic salts, filter to obtain solid product, wash repeatedly with deionized water and dry, use a forced-air drying oven to dry at 90℃ for 45min to obtain the processed reaction product.

[0053] This invention prepares layered gradient Ti2AlC using a microwave molten salt. 0.5 N 0.5 The method, Figure 1 Ti2AlC was prepared as described in Example 1. 0.5 N 0.5 The scanning electron microscope image shows that the product retains its fibrous morphology. Figure 2 Ti2AlC was prepared as described in Example 1. 0.5 N 0.5 Cross-sectional SEM image, the product is Ti2AlC 0.5 N 0.5 / TiC 0.5 N 0.5 A hierarchical gradient structure of hollow / amorphous carbon / microcrystalline carbon; Figure 3 Ti2AlC was prepared as described in Example 3. 0.5 N 0.5 Cross-sectional SEM image, the product is Ti2AlC 0.5 N 0.5 / TiC 0.5 N 0.5 / Hollow tubular structure with layered cavities. Figure 4 Ti2AlC was obtained in Examples 1-3 0.5 N 0.5 The XRD pattern shows that the product has high purity and the reaction is stable. Figure 5 Ti2AlC was obtained in Example 1 0.5 N 0.5 The electromagnetic wave absorption performance diagram shows that the product exhibits superior electromagnetic wave absorption performance. This demonstrates that the method, by controlling the reaction time, effectively controls the number of layers and the gradient structure of the layered gradient MAX phase material, offering significant advantages in preparation efficiency and reaction stability. It enables the efficient and rapid preparation of high-quality MAX phase materials, meeting the needs of various fields such as aerospace, energy catalysis, and electromagnetic wave absorption.

[0054] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A microwave molten salt preparation method for layered gradient Ti2AlC 0.5 N 0.5 The method is characterized by: Includes the following steps: S1. Weigh Ti powder, Al powder, organic fiber and inorganic salt and place them in a mortar. Add anhydrous ethanol and grind to obtain material a. Place material a in a ball mill and ball mill until it is mixed evenly to obtain material b. S2. Place material b in a microwave oven for rapid drying to remove anhydrous ethanol and obtain material c; S3. Place material c in a microwave oven and perform molten salt synthesis under a protective atmosphere. Through microwave selective activation heating, the rapid preparation of layered gradient carbonitride strong microwave absorbing MAX phase materials is achieved. S4. Take out the material c after the reaction in S3, add 5 to 8 times the volume of deionized water to remove inorganic salts, filter to obtain solid product, wash repeatedly with deionized water and dry, take the solid product and dry to obtain black powder, which is the layered gradient MAX phase material.

2. The microwave molten salt preparation method for layered gradient Ti2AlC according to claim 1 0.5 N 0.5 The method is characterized by: In step S1, the organic fiber is one or more of polyamide fiber, polyester fiber, polyacrylonitrile fiber, polypropylene fiber, and polyvinyl alcohol fiber, and the inorganic salt is one or two of NaCl and KCl.

3. The method for preparing layered gradient Ti2AlC using microwave molten salt according to claim 2 0.5 N 0.5 The method is characterized by: In step S1, the molar ratio of Ti powder, Al powder, NaCl, and KCl is (2-3):1:(1-4):(1-4), the amount of organic fiber is 1-5 g / mol M-site metal, the purity of Ti powder is 99%-99.99%, the purity of Al powder is 99%-99.99%, and the amount of anhydrous ethanol added is 200-400 ml / mol M-site metal.

4. The microwave molten salt preparation method for layered gradient Ti2AlC according to claim 1 0.5 N 0.5 The method is characterized by: In step S1, the ball milling process involves a rotation speed of 300–400 r / min and a milling time of 1–2 h.

5. The microwave molten salt preparation method for layered gradient Ti2AlC according to claim 1 0.5 N 0.5 The method is characterized by: In step S2, the microwave heating power is 600W, the microwave frequency is 2450±50 MHz, and the heating time is 30min.

6. The method for preparing layered gradient Ti2AlC using microwave molten salt according to claim 1 0.5 N 0.5 The method is characterized by: In step S3, the reaction temperature is 1000–1100 °C, the heating rate is 30–50 °C / min, the holding time is 10–30 min, the microwave heating power is 4000–5000 W, the microwave frequency is 2450±50 or 915±50 MHz, and the protective atmosphere is argon or nitrogen.

7. The microwave molten salt preparation method for layered gradient Ti2AlC according to claim 1 0.5 N 0.5 The method is characterized by: In step S4, drying is performed using a forced-air drying oven at a temperature of 80–90°C for 30–60 minutes.

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