A method for preparing Ti2AlN powder based on multi-stage temperature rising and in-situ catalytic aluminothermic reaction

Abstract

The application provides a method for preparing Ti2AlN powder based on multi-stage temperature rising and in-situ catalytic aluminothermic reaction, and belongs to the technical field of ceramic powder preparation. TiN powder, Ti powder and Al powder are used as raw materials, NH4Cl and La2O3 are used as catalysts, are dispersed in an alcohol solvent, and are freeze-dried to obtain precursor powder agglomerates with a porous network structure; then, pre-activation treatment is carried out at 400-600 DEG C in a gas atmosphere containing ammonia, and multi-stage temperature rising reaction is carried out in an argon atmosphere to synthesize high-purity Ti2AlN powder; wherein the multi-stage temperature rising reaction conditions are as follows: 600-800 DEG C, heat preservation for 30-70 min; 1000-1200 DEG C, heat preservation for 120-160 min. The method has the advantages of low synthesis temperature, high purity of Ti2AlN powder, uniform and controllable particle size, and suitability for large-scale production. In addition, the silicon carbide composite refractory material prepared from the Ti2AlN powder has excellent normal-temperature mechanical properties and high-temperature mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of ceramic powder preparation technology, specifically to a method for preparing Ti2AlN powder based on multi-stage heating synergistic in-situ catalytic aluminothermic reaction. Background Technology

[0002] Ti2AlN, with its unique layered crystal structure and bonding characteristics, possesses both the machinability and high conductivity of metals and the high strength, high temperature resistance, and oxidation resistance of ceramics, demonstrating irreplaceable application potential in fields such as aerospace extreme conditions, high-temperature protective coatings, energy storage devices, and microelectronic devices.

[0003] However, due to the narrow stability region in the Ti-Al-N ternary system, synthesizing high-purity, single-phase Ti2AlN bulk or powder materials presents significant challenges. Existing Ti2AlN powder preparation processes generally suffer from limitations such as low purity and low yield. For example, Zhang et al. (ZX Zhang, Y. Zhou, W. Gao, et al. MS3 of Ti2AlN powder at 700 ℃ with controllable morphology and its formation mechanism analyzed by DFT-TST-SD [J]. Ceramics International, 2022, (48): 28471-28479) prepared Ti2AlN powder at 700~1000 ℃ using a mixed salt of NaCl and KCl as a medium. However, this method uses a mixed salt that accounts for 80% of the total mass of the raw materials and the mixed salt, resulting in a complex overall molten salt removal process, high cost, and low yield. The study by Liang Suying et al. (Liang Suying, Kang Ju, Zhao Xia. Phase and microstructure of hot-pressed Ti2AlN cermet materials[J]. Journal of Aeronautical Materials, 2017, 37(3): 73-77) pointed out that the microstructure of Ti2AlN bulk ceramic materials prepared by hot-pressing sintering exhibits anisotropy, but a small amount of TiN particles still remain in the sintered products, making it difficult to prepare high-purity Ti2AlN materials. Summary of the Invention

[0004] To address the shortcomings of the existing technologies, this invention provides a method for preparing Ti2AlN powder based on multi-stage heating synergistic in-situ catalytic aluminothermic reaction. The Ti2AlN powder prepared by this method has a smooth and rounded surface, good crystallinity, and high purity. Furthermore, silicon carbide composite refractory materials prepared using the obtained Ti2AlN powder exhibit excellent room temperature and high temperature mechanical properties.

[0005] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0006] This invention provides a method for preparing Ti2AlN powder based on multi-stage heating synergistic in-situ catalytic aluminothermic reaction, comprising the following steps:

[0007] TiN powder, Ti powder, Al powder and composite catalyst are uniformly dispersed in an alcohol solvent to obtain a precursor suspension; wherein, the composite catalyst is a mixture of NH4Cl and La2O3;

[0008] The precursor suspension was freeze-dried to obtain precursor powder agglomerates with a porous network structure.

[0009] The precursor powder agglomerates were subjected to aluminothermic activation treatment in a gas atmosphere containing ammonia to form a highly active ternary intermetallic compound coating structure.

[0010] The highly active ternary intermetallic compound coating structure was heated to 600-800 °C at a rate of 3-5 °C / min under an inert gas atmosphere and held for 30-70 min; then heated to 1000-1200 °C at a rate of 1-3 °C / min and held for 120-160 min; the furnace was then cooled to obtain the reaction product.

[0011] The reaction product was acid-washed, and then washed, dried, and air-separated to obtain Ti2AlN powder with different particle size ranges.

[0012] Optionally, the mass ratio of TiN powder, Ti powder, and Al powder is (41.92~45.2):(32.45~35):(19.8~25.63), and the amount of the composite catalyst is 1%~3% of the total mass of TiN powder, Ti powder, and Al powder.

[0013] Optionally, in the composite catalyst, the mass ratio of NH4Cl to La2O3 is (2~4):1.

[0014] Optionally, the TiN powder has a TiN content ≥ 98.5 wt%, the Ti powder has a Ti content ≥ 98.5 wt%, and the Al powder has an Al content ≥ 98.5 wt%; the TiN powder has a particle size ≤ 0.045 mm, the Ti powder has a particle size ≤ 0.045 mm, and the Al powder has a particle size ≤ 0.045 mm.

[0015] Optionally, the alcohol solvent includes, but is not limited to, at least one of ethanol and isopropanol.

[0016] Optionally, the precursor suspension is prepared by adding TiN powder, Ti powder, and Al powder to an alcohol solvent, adding a composite catalyst, and then mechanically stirring with ultrasonic oscillation for 40-60 min to obtain the precursor suspension; the ultrasonic power is 340-360 W, and the stirring speed is 440-450 rpm.

[0017] Optionally, the freeze-drying operation is as follows: add an appropriate amount of water to the precursor suspension, rapidly freeze it in a liquid nitrogen environment (-196℃) for 10~30 min, and then freeze-dry it in a freeze dryer at -50 to -30℃ for 24~48 h to obtain precursor powder agglomerates with a porous network structure.

[0018] Optionally, the aluminothermic activation treatment is performed at a temperature of 400~600 ℃ for a time of 10~30 min.

[0019] Optionally, the ammonia-containing gas is a mixture of ammonia and an inert gas, with the ammonia content being 10% to 15%; the inert gas includes, but is not limited to, at least one of nitrogen and argon.

[0020] Optionally, the acid washing process is performed by placing the reaction product in a reflux condenser and refluxing it with 0.5-2 mol / L dilute hydrochloric acid for 2-10 h.

[0021] Optionally, the drying process is performed at 100-120°C for 12-20 hours.

[0022] Optionally, the airflow classification is performed under conditions of compressed air pressure of 0.3~0.5 MPa and classification wheel speed of 3000~4000 rpm.

[0023] Specifically, the method for preparing Ti2AlN powder based on multi-stage heating synergistic in-situ catalytic aluminothermic reaction includes the following steps:

[0024] Step 1: Add TiN powder, Ti powder, and Al powder in a mass ratio of (41.92~45.2):(32.45~35):(19.8~25.63) to an alcohol solvent. At the same time, add 1%~3% of the total mass of TiN powder, Ti powder, and Al powder of NH4Cl and La2O3 composite catalyst. Stir the mixture with ultrasonic oscillation for 40~60 min to obtain a precursor suspension.

[0025] Step 2: Add an appropriate amount of deionized water to the precursor suspension, rapidly freeze it in a liquid nitrogen environment for 10-30 min, and then freeze-dry it in a freeze dryer for 24-48 h to obtain precursor powder agglomerates with a porous network structure; the volume ratio of the deionized water to the alcohol solvent in Step 1 is (7-8):(2-3).

[0026] Step 3: Place the precursor powder agglomerates in a high-temperature atmosphere furnace and heat them to 400-600 ℃ in a mixed gas of ammonia and inert gas at a rate of 4-6 ℃ / min for aluminothermic activation treatment for 10-30 min to form a highly active ternary intermetallic compound coating structure.

[0027] Step 4: Close the ammonia gas valve. Under an inert gas protective atmosphere, raise the temperature to 600-800℃ at a rate of 3-5℃ / min and hold for 30-70 min, with a gas flow rate of 400-600 mL / min during this period to facilitate the removal of volatile substances. Then raise the temperature to 1000-1200℃ at a rate of 1-3℃ / min and hold for 120-160 min, with a gas flow rate of 120-160 mL / min during this period to avoid erosion and loss of powder by the gas flow. Cool the furnace to obtain the reaction product.

[0028] Step 5: Place the reaction product in a reflux condenser and reflux it with 0.5-2 mol / L dilute hydrochloric acid for 2-10 h. Then wash it with deionized water until neutral and dry it at 120 ℃ for 12-20 h. Finally, obtain Ti2AlN powder with different particle size ranges by air classification.

[0029] The present invention also provides Ti2AlN powder prepared by the above preparation method.

[0030] This invention also provides the application of the Ti2AlN powder in refractory materials. For example, using the Ti2AlN powder in silicon carbide refractory material systems significantly improves the performance of the refractory materials.

[0031] Compared with the prior art, the advantages of the present invention are:

[0032] This invention introduces a catalyst precursor in situ, utilizing the decomposition of NH4Cl to generate active ions. During the aluminothermic activation stage, these ions form a trace amount of low-melting-point eutectic liquid phase with the TiAl3 / TiAl mesophase, significantly shortening the long-range diffusion distance between Ti and N atoms in the solid phase. This results in a significant reduction in the nucleation reaction energy barrier of Ti2AlN. Simultaneously, the ammonia-containing atmosphere in the aluminothermic activation stage performs synergistic pre-activation of the precursor through "atomic nitrogen chemical adsorption for nitrogen supply" and "in-situ reduction and deoxidation by active hydrogen." Compared to conventional inert protection or N2 nitriding processes, the ammonia-containing atmosphere can advance the surface activation temperature window by approximately 300-400 °C, thereby reducing the synthesis temperature of Ti2AlN to 1000-1200 °C and significantly reducing energy consumption.

[0033] This invention replaces traditional mechanical ball milling with freeze-drying granulation to obtain a precursor with a porous network structure. The formation of the porous network increases the permeability of gas, allowing an atmosphere containing ammonia to flow evenly through the entire agglomerate. This ensures that each precursor particle undergoes the same pre-activation conditions, ultimately resulting in a significant improvement in the uniformity of the product phase.

[0034] This invention utilizes the intrinsic chemical inertness of Ti2AlN in dilute hydrochloric acid medium through a controlled condensation reflux-airflow classification synergistic treatment to achieve targeted leaching of catalyst residues and trace impurities. At the same time, by replacing traditional mechanical crushing with gas dynamic classification, a finished powder with a highly concentrated particle size distribution is obtained while completely avoiding lattice distortion and external force contamination. This achieves both fine classification and avoids over-grinding.

[0035] The Ti2AlN powder prepared by this invention has a good continuous morphology. When introduced into silicon carbide composite refractory materials, it can promote in-situ interfacial reaction between Ti2AlN powder and silicon carbide matrix during sintering, effectively filling the pores between silicon carbide particles, eliminating matrix interface defects and interconnected pores, strengthening the interfacial bonding strength between the two phases, and improving the overall density and structural strength of the material. Test results show that the room temperature compressive strength of the silicon carbide composite refractory material prepared using the Ti2AlN powder of this invention is 140~180 MPa, and the high temperature flexural strength is 24~32 MPa.

[0036] In summary, the method for preparing Ti2AlN powder based on multi-stage heating synergistic in-situ catalytic aluminothermic reaction provided by this invention achieves low-temperature, high-efficiency, and high-purity preparation of Ti2AlN powder. The silicon carbide composite refractory material prepared using this powder exhibits excellent room-temperature and high-temperature mechanical properties, demonstrating significant technological innovation and industrial application value. Attached Figure Description

[0037] Figure 1 The image shows the XRD pattern of Ti2AlN powder prepared in Example 3 of this invention.

[0038] Figure 2 This is a SEM image of the Ti2AlN powder prepared in Example 3 of the present invention;

[0039] Figure 3 The image shows the XRD pattern of Ti2AlN powder prepared in Comparative Example 1 of this invention.

[0040] Figure 4 The image shows the XRD pattern of Ti2AlN powder prepared in Comparative Example 2 of this invention. Detailed Implementation

[0041] To enable those skilled in the art to clearly and completely understand the technical solution of the present invention, the present invention will be further described in detail below with reference to embodiments. Obviously, the embodiments described herein are only for explaining the present invention and are not intended to limit the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0042] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the raw materials, methods and equipment used in this invention are conventional raw materials, methods and equipment in the art.

[0043] This invention provides a method for preparing Ti2AlN powder based on multi-stage heating synergistic in-situ catalytic aluminothermic reaction, comprising the following steps:

[0044] TiN powder, Ti powder, Al powder and composite catalyst are uniformly dispersed in an alcohol solvent to obtain a precursor suspension; wherein, the composite catalyst is a mixture of NH4Cl and La2O3;

[0045] The precursor suspension was freeze-dried to obtain precursor powder agglomerates with a porous network structure.

[0046] The precursor powder agglomerates were subjected to aluminothermic activation treatment in a gas atmosphere containing ammonia to form a highly active ternary intermetallic compound coating structure.

[0047] The highly active ternary intermetallic compound-coated structure was heated to 600-800 °C at a rate of 3-5 °C / min under an inert gas atmosphere and held for 30-70 min, during which the gas flow rate was 400-600 mL / min; then heated to 1000-1200 °C at a rate of 1-3 °C / min and held for 120-160 min, during which the gas flow rate was 120-160 mL / min; the furnace was then cooled to obtain the reaction product.

[0048] The reaction product was acid-washed, and then washed, dried, and air-separated to obtain Ti2AlN powder with different particle size ranges.

[0049] In some embodiments, the mass ratio of TiN powder, Ti powder, and Al powder is (41.92~45.2):(32.45~35):(19.8~25.63), and the amount of the composite catalyst is 1%~3% of the total mass of TiN powder, Ti powder, and Al powder; the TiN content in the TiN powder is ≥98.5 wt%, the Ti content in the Ti powder is ≥98.5 wt%, and the Al content in the Al powder is ≥98.5 wt%; the particle size of the TiN powder is ≤0.045 mm, the particle size of the Ti powder is ≤0.045 mm, and the particle size of the Al powder is ≤0.045 mm.

[0050] In some embodiments, the mass ratio of NH4Cl to La2O3 in the composite catalyst is (2~4):1.

[0051] In some embodiments, the alcohol solvent includes, but is not limited to, at least one of ethanol and isopropanol.

[0052] In some embodiments, the precursor suspension is prepared by adding TiN powder, Ti powder, and Al powder to an alcohol solvent, along with a composite catalyst, and then mechanically stirring with ultrasonic oscillation for 40-60 min to obtain the precursor suspension; the ultrasonic power is 340-360 W, and the stirring speed is 440-450 rpm.

[0053] In some embodiments, the freeze-drying process involves adding an appropriate amount of water to the precursor suspension, rapidly freezing it in a liquid nitrogen environment (-196 °C) for 10-30 min, and then freeze-drying it in a freeze dryer at -50 to -30 °C for 24-48 h to obtain precursor powder agglomerates with a porous network structure.

[0054] In some embodiments, the aluminothermic activation treatment is performed at a temperature of 400-600 °C for a time of 10-30 min.

[0055] In some embodiments, the ammonia-containing gas is a mixture of ammonia and an inert gas, with the ammonia content being 10% to 15%; the inert gas includes, but is not limited to, at least one of nitrogen and argon.

[0056] In some embodiments, the acid washing process is performed by placing the reaction product in a reflux condenser and refluxing it with 0.5-2 mol / L dilute hydrochloric acid for 2-10 h.

[0057] In some embodiments, the drying operation is performed by drying at 100~120 °C for 12~20 h.

[0058] In some embodiments, the airflow classification is performed under conditions of compressed air pressure of 0.3~0.5 MPa and classification wheel speed of 3000~4000 rpm.

[0059] Example 1

[0060] A Ti2AlN powder prepared based on a multi-stage heating synergistic in-situ catalytic aluminothermic reaction, the preparation steps are as follows:

[0061] Step 1: Mix 45.2 parts by weight of TiN powder, 35 parts by weight of Ti powder, and 19.8 parts by weight of Al powder evenly, add the mixture to anhydrous ethanol, and simultaneously add 1 wt% of the NH4Cl and La2O3 composite catalyst; under ultrasonic oscillation-assisted mechanical stirring conditions of 350 W and 450 rpm for 60 min to obtain a precursor suspension; wherein the mass ratio of NH4Cl to La2O3 is 2:1.

[0062] Step 2: Add an appropriate amount of deionized water to the precursor suspension, rapidly freeze it in a liquid nitrogen environment for 10 min, and then freeze-dry it in a freeze dryer for 24 h to obtain precursor powder agglomerates with a porous network structure.

[0063] Step 3: Place the precursor powder agglomerates in a high-temperature atmosphere furnace and perform aluminothermic activation treatment at a rate of 5 °C / min to 600 °C for 10 min under an atmosphere of ammonia / argon mixed gas (ammonia volume percentage of 10%) to form a highly active ternary intermetallic compound coating structure.

[0064] Step 4: Close the ammonia gas valve, and under an argon protective atmosphere, raise the temperature to 800 ℃ at a rate of 4 ℃ / min, hold for 30 min, and control the argon gas flow rate at 500 mL / min during this period; then raise the temperature to 1000 ℃ at a rate of 2 ℃ / min, hold for 120 min, and control the argon gas flow rate at 150 mL / min during this period; cool with the furnace to obtain the reaction product;

[0065] Step 5: Place the reaction product in a reflux condenser and reflux it with 0.5 mol / L dilute hydrochloric acid for 2 h. Then wash it with deionized water until neutral and dry it at 120 ℃ for 12 h. Finally, perform air classification under the conditions of compressed air pressure of 0.3 MPa and classifier speed of 3000 rpm to obtain Ti2AlN powder with different particle size ranges.

[0066] Application Example 1

[0067] The Ti2AlN powder prepared in Example 1 was used to prepare silicon carbide composite refractory materials, and the steps are as follows:

[0068] Two parts by weight of Ti2AlN powder and three parts by weight of polyvinyl acetal modified phenolic resin (purchased from Shanghai Sixi Chemical Co., Ltd.) were added to anhydrous ethanol and stirred until homogeneous to obtain a slurry. 53 parts by weight of silicon carbide particles, 30 parts by weight of silicon carbide fine powder, and 15 parts by weight of silicon powder were added to a mixer and stirred for 20 min. The slurry was then added and the mixture was stirred for another 20 min. The mixture was then allowed to stand at 25 °C for 12 h, pressed into shape at 140 MPa, and cured at 100 °C for 24 h to obtain a molded sample. The molded sample was placed in a high-temperature atmosphere furnace and heated to 1250 °C under a nitrogen atmosphere, held for 120 min, and cooled with the furnace to obtain a silicon carbide composite refractory material with added Ti2AlN powder.

[0069] Testing revealed that the silicon carbide composite refractory material with added Ti2AlN powder described in Example 1 has a room temperature compressive strength of 140 MPa and a high temperature flexural strength of 24 MPa.

[0070] Example 2

[0071] A Ti2AlN powder prepared based on a multi-stage heating synergistic in-situ catalytic aluminothermic reaction, the preparation steps are as follows:

[0072] Step 1: Mix 44.4 parts by weight of TiN powder, 34.4 parts by weight of Ti powder, and 21.2 parts by weight of Al powder evenly, add the mixture to anhydrous ethanol, and simultaneously add 1.5 wt% of the NH4Cl and La2O3 composite catalyst; under ultrasonic oscillation-assisted mechanical stirring conditions of 350 W and 450 rpm for 60 min to obtain a precursor suspension; wherein the mass ratio of NH4Cl to La2O3 is 2:1.

[0073] Step 2: Add an appropriate amount of deionized water to the precursor suspension, rapidly freeze it in a liquid nitrogen environment for 15 min, and then freeze-dry it in a freeze dryer for 30 h to obtain precursor powder agglomerates with a porous network structure.

[0074] Step 3: Place the precursor powder agglomerates in a high-temperature atmosphere furnace and perform aluminothermic activation treatment at a rate of 5 °C / min to 600 °C for 15 min under an atmosphere of ammonia / argon mixed gas (ammonia volume percentage of 10%) to form a highly active ternary intermetallic compound coating structure.

[0075] Step 4: Close the ammonia gas valve, and under an argon protective atmosphere, raise the temperature to 800 ℃ at a rate of 4 ℃ / min, hold for 40 min, and control the argon gas flow rate at 500 mL / min during this period; then raise the temperature to 1050 ℃ at a rate of 2 ℃ / min, hold for 130 min, and control the argon gas flow rate at 150 mL / min during this period; cool with the furnace to obtain the reaction product;

[0076] Step 5: Place the reaction product in a reflux condenser and reflux it with 0.5 mol / L dilute hydrochloric acid for 4 h. Then wash it with deionized water until neutral and dry it at 120 ℃ for 14 h. Finally, perform air classification under the conditions of compressed air pressure of 0.35 MPa and classifier speed of 3250 rpm to obtain Ti2AlN powder with different particle size ranges.

[0077] Application Example 2

[0078] The Ti2AlN powder prepared in Example 2 was used to prepare silicon carbide composite refractory materials, and the steps are as follows:

[0079] Four parts by weight of Ti2AlN powder and 3.5 parts by weight of polyvinyl acetal modified phenolic resin were added to anhydrous ethanol and stirred until homogeneous to obtain a slurry. 48 parts by weight of silicon carbide particles, 33 parts by weight of silicon carbide fine powder, and 15 parts by weight of silicon powder were added to a mixer and stirred for 20 min. The slurry was then added and the mixture was stirred for another 30 min. The mixture was then allowed to stand at 25 °C for 12 h, pressed into shape at 150 MPa, and cured at 105 °C for 24 h to obtain a molded sample. The molded sample was placed in a high-temperature atmosphere furnace and heated to 1300 °C under a nitrogen atmosphere, held for 120 min, and then cooled in the furnace to obtain a silicon carbide composite refractory material with added Ti2AlN powder.

[0080] Testing revealed that the silicon carbide composite refractory material with added Ti2AlN powder described in Example 1 has a room temperature compressive strength of 150 MPa and a high temperature flexural strength of 26 MPa.

[0081] Example 3

[0082] A Ti2AlN powder prepared based on a multi-stage heating synergistic in-situ catalytic aluminothermic reaction, the preparation steps are as follows:

[0083] Step 1: Mix 43.6 parts by weight of TiN powder, 33.6 parts by weight of Ti powder, and 22.8 parts by weight of Al powder evenly, add them to anhydrous ethanol, and simultaneously add 2 wt% of the NH4Cl and La2O3 composite catalyst; under ultrasonic oscillation-assisted mechanical stirring conditions of 350 W and 450 rpm for 60 min to obtain a precursor suspension; wherein the mass ratio of NH4Cl to La2O3 is 2:1.

[0084] Step 2: Add an appropriate amount of deionized water to the precursor suspension, rapidly freeze it in a liquid nitrogen environment for 20 min, and then freeze-dry it in a freeze dryer for 36 h to obtain precursor powder agglomerates with a porous network structure.

[0085] Step 3: Place the agglomerates in a high-temperature atmosphere furnace and, under an atmosphere of ammonia / argon mixed gas (ammonia volume percentage of 10%), heat the aluminothermic activation treatment to 600 ℃ at a rate of 5 ℃ / min for 20 min to form a highly active ternary intermetallic compound coating structure.

[0086] Step 4: Close the ammonia gas valve, and under an argon protective atmosphere, raise the temperature to 800 ℃ at a rate of 4 ℃ / min, hold for 50 min, and control the argon flow rate at 500 mL / min during this period; then raise the temperature to 1100 ℃ at a rate of 2 ℃ / min, hold for 140 min, and control the argon flow rate at 150 mL / min during this period; cool with the furnace to obtain the reaction product.

[0087] Step 5: Place the reaction product in a reflux condenser and reflux it with 0.5 mol / L dilute hydrochloric acid for 6 h. Then wash it with deionized water until neutral and dry it at 120 ℃ for 16 h. Finally, perform air classification under the conditions of compressed air pressure of 0.4 MPa and classifier speed of 3500 rpm to obtain Ti2AlN powder with different particle size ranges.

[0088] Application Example 3

[0089] The Ti2AlN powder prepared in Example 3 was used to prepare silicon carbide composite refractory materials, and the steps are as follows:

[0090] Six parts by weight of Ti2AlN powder and four parts by weight of polyvinyl acetal-modified phenolic resin were added to anhydrous ethanol and stirred until homogeneous to obtain a slurry. Forty-two parts by weight of silicon carbide particles, 37 parts by weight of silicon carbide fine powder, and 15 parts by weight of silicon powder were added to a mixer and stirred for 20 min. The slurry was then added and stirred for another 40 min. The mixture was allowed to stand at 25 °C for 12 h, pressed into shape at 160 MPa, and cured at 110 °C for 24 h to obtain a molded sample. The molded sample was placed in a high-temperature atmosphere furnace and heated to 1350 °C under a nitrogen atmosphere, held for 120 min, and then cooled in the furnace to obtain a silicon carbide composite refractory material with added Ti2AlN powder.

[0091] Testing revealed that the silicon carbide composite refractory material with added Ti2AlN powder described in Example 1 has a room temperature compressive strength of 160 MPa and a high temperature flexural strength of 28 MPa.

[0092] Example 4

[0093] A Ti2AlN powder prepared based on a multi-stage heating synergistic in-situ catalytic aluminothermic reaction, the preparation steps are as follows:

[0094] Step 1: Mix 42.75 parts by weight of TiN powder, 33.03 parts by weight of Ti powder, and 24.22 parts by weight of Al powder evenly, add the mixture to anhydrous ethanol, and simultaneously add 2.5 wt% of the NH4Cl and La2O3 composite catalyst; under ultrasonic oscillation-assisted mechanical stirring conditions of 350 W and 450 rpm for 60 min to obtain a precursor suspension; wherein the mass ratio of NH4Cl to La2O3 is 2:1.

[0095] Step 2: Add an appropriate amount of deionized water to the precursor suspension, rapidly freeze it in a liquid nitrogen environment for 25 min, and then freeze-dry it in a freeze dryer for 42 h to obtain precursor powder agglomerates with a porous network structure.

[0096] Step 3: Place the precursor powder agglomerates in a high-temperature atmosphere furnace and perform aluminothermic activation treatment at a rate of 5 °C / min to 600 °C for 25 min under an atmosphere of ammonia / argon mixed gas (ammonia volume percentage of 10%) to form a highly active ternary intermetallic compound coating structure.

[0097] Step 4: Close the ammonia gas valve, and under an argon protective atmosphere, raise the temperature to 800 ℃ at a rate of 4 ℃ / min, hold for 60 min, and control the argon gas flow rate at 500 mL / min during this period; then raise the temperature to 1150 ℃ at a rate of 2 ℃ / min, hold for 150 min, and control the argon gas flow rate at 150 mL / min during this period; cool with the furnace to obtain the reaction product;

[0098] Step 5: Place the reaction product in a reflux condenser and reflux it with 0.5 mol / L dilute hydrochloric acid for 8 h. Then wash it with deionized water until neutral and dry it at 120 ℃ for 18 h. Finally, perform air classification under the conditions of compressed air pressure of 0.45 MPa and classifier speed of 3750 rpm to obtain Ti2AlN powder with different particle size ranges.

[0099] Application Example 4

[0100] The Ti2AlN powder prepared in Example 4 was used to prepare silicon carbide composite refractory materials, and the steps are as follows:

[0101] Eight parts by weight of Ti2AlN powder and 4.5 parts by weight of polyvinyl acetal modified phenolic resin were added to anhydrous ethanol and stirred until homogeneous to obtain a slurry. 38 parts by weight of silicon carbide particles, 39 parts by weight of silicon carbide fine powder, and 15 parts by weight of silicon powder were added to a mixer and stirred for 20 min. The slurry was then added and stirred for another 50 min. The mixture was allowed to stand at 25 °C for 12 h, pressed into shape at 170 MPa, and cured at 115 °C for 24 h to obtain a molded sample. The molded sample was placed in a high-temperature atmosphere furnace and heated to 1400 °C under a nitrogen atmosphere, held for 120 min, and then cooled in the furnace to obtain a silicon carbide composite refractory material with added Ti2AlN powder.

[0102] Testing revealed that the silicon carbide composite refractory material with added Ti2AlN powder described in Example 1 has a room temperature compressive strength of 170 MPa and a high temperature flexural strength of 30 MPa.

[0103] Example 5

[0104] A Ti2AlN powder prepared based on a multi-stage heating synergistic in-situ catalytic aluminothermic reaction, the preparation steps are as follows:

[0105] Step 1: Mix 41.92 parts by weight of TiN powder, 32.45 parts by weight of Ti powder, and 25.63 parts by weight of Al powder evenly, add the mixture to anhydrous ethanol, and simultaneously add 3 wt% of the NH4Cl and La2O3 composite catalyst; under ultrasonic oscillation-assisted mechanical stirring conditions of 350 W and 450 rpm for 60 min to obtain a precursor suspension; wherein the mass ratio of NH4Cl to La2O3 is 2:1.

[0106] Step 2: Add an appropriate amount of deionized water to the precursor suspension, rapidly freeze it in a liquid nitrogen environment for 30 min, and then freeze-dry it in a freeze dryer for 48 h to obtain precursor powder agglomerates with a porous network structure.

[0107] Step 3: Place the agglomerates in a high-temperature atmosphere furnace and, under an atmosphere of ammonia / argon mixed gas (ammonia volume percentage of 10%), heat the aluminothermic activation treatment to 600 ℃ at a rate of 5 ℃ / min for 30 min to form a highly active ternary intermetallic compound coating structure.

[0108] Step 4: Close the ammonia gas valve. Under an argon protective atmosphere, raise the temperature to 800℃ at a rate of 4℃ / min and hold for 70 min, controlling the argon flow rate at 500 mL / min during this period. Then raise the temperature to 1200℃ at a rate of 2℃ / min and hold for 160 min, controlling the argon flow rate at 150 mL / min during this period. Cool the furnace to obtain the reaction product.

[0109] Step 5: Place the reaction product in a reflux condenser and reflux it with 0.5 mol / L dilute hydrochloric acid for 10 h. Then wash it with deionized water until neutral and dry it at 120 ℃ for 20 h. Finally, perform air classification under the conditions of compressed air pressure of 0.5 MPa and classifier speed of 4000 rpm to obtain Ti2AlN powder with different particle size ranges.

[0110] Application Example 5

[0111] The Ti2AlN powder prepared in Example 5 was used to prepare silicon carbide composite refractory materials, and the steps are as follows:

[0112] Ten parts by weight of Ti2AlN powder and five parts by weight of polyvinyl acetal-modified phenolic resin were added to anhydrous ethanol and stirred until homogeneous to obtain a slurry. Thirty-three parts by weight of silicon carbide particles, 42 parts by weight of silicon carbide fine powder, and 15 parts by weight of silicon powder were added to a mixer and stirred for 20 min. The slurry was then added and stirred for another 60 min. The mixture was allowed to stand at 25 °C for 12 h, pressed into shape at 180 MPa, and cured at 120 °C for 24 h to obtain a molded sample. The molded sample was placed in a high-temperature atmosphere furnace and heated to 1450 °C under a nitrogen atmosphere, held for 120 min, and cooled with the furnace to obtain a silicon carbide composite refractory material with added Ti2AlN powder.

[0113] Testing revealed that the silicon carbide composite refractory material with added Ti2AlN powder described in Example 1 has a room temperature compressive strength of 180 MPa and a high temperature flexural strength of 32 MPa.

[0114] Comparative Example 1

[0115] A Ti2AlN powder is prepared by the following steps:

[0116] Step 1: Mix 41.92 parts by weight of TiN powder, 32.45 parts by weight of Ti powder and 25.63 parts by weight of Al powder evenly, and add them to anhydrous ethanol; under the conditions of ultrasonic power of 350 W and stirring speed of 450 rpm, mechanical stirring is assisted by ultrasonic oscillation for 60 min to obtain the precursor suspension.

[0117] Step 2: Add an appropriate amount of deionized water to the precursor suspension, rapidly freeze it in a liquid nitrogen environment for 30 min, and then freeze-dry it in a freeze dryer for 48 h to obtain precursor powder agglomerates.

[0118] Step 3: Place the agglomerates in a high-temperature atmosphere furnace and perform aluminothermic activation treatment for 30 min at a rate of 5 °C / min in an atmosphere of ammonia / argon mixed gas (ammonia volume percentage of 10%), heating to 600 °C.

[0119] Step 4: Close the ammonia gas valve. Under an argon protective atmosphere, raise the temperature to 800℃ at a rate of 4℃ / min and hold for 70 min, controlling the argon flow rate at 500 mL / min during this period. Then raise the temperature to 1200℃ at a rate of 2℃ / min and hold for 160 min, controlling the argon flow rate at 150 mL / min during this period. Cool the furnace to obtain the reaction product.

[0120] Step 5: The reaction product was placed in a reflux condenser and refluxed with 0.5 mol / L dilute hydrochloric acid for 10 h, then washed with deionized water until neutral, and dried at 120 ℃ for 20 h. Finally, air classification was performed under compressed air pressure of 0.5 MPa and classifier speed of 4000 rpm to obtain Ti2AlN powders with different particle size ranges. The XRD pattern of the Ti2AlN powder prepared in this comparative example is shown below. Figure 3 .

[0121] Comparative Example 2

[0122] A Ti2AlN powder is prepared by the following steps:

[0123] Step 1: Mix 41.92 parts by weight of TiN powder, 32.45 parts by weight of Ti powder, and 25.63 parts by weight of Al powder evenly, add the mixture to anhydrous ethanol, and simultaneously add 3 wt% of the NH4Cl and La2O3 composite catalyst; under ultrasonic oscillation-assisted mechanical stirring conditions of 350 W and 450 rpm for 60 min to obtain a precursor suspension; wherein the mass ratio of NH4Cl to La2O3 is 2:1.

[0124] Step 2: Add an appropriate amount of deionized water to the precursor suspension, rapidly freeze it in a liquid nitrogen environment for 30 min, and then freeze-dry it in a freeze dryer for 48 h to obtain precursor powder agglomerates with a porous network structure.

[0125] Step 3: Place the precursor powder agglomerates in a high-temperature atmosphere furnace, and under an argon protective atmosphere, heat to 1200 ℃ at a rate of 5 ℃ / min, hold for 180 min, and control the argon flow rate at 150 mL / min during this period; cool with the furnace to obtain the reaction product;

[0126] Step 4: The reaction product was placed in a reflux condenser and refluxed with 0.5 mol / L dilute hydrochloric acid for 10 h, then washed with deionized water until neutral, and dried at 120 ℃ for 20 h. Finally, air classification was performed under compressed air pressure of 0.5 MPa and classifier speed of 4000 rpm to obtain Ti2AlN powders with different particle size ranges. The XRD pattern of the Ti2AlN powder prepared in this comparative example is shown below. Figure 4 .

[0127] This specific implementation method has the following advantages compared with the prior art:

[0128] This invention reduces the synthesis temperature of Ti2AlN to 1000~1200℃ by introducing the catalyst precursor in situ, which is much lower than the 1300~1500℃ of the traditional hot pressing sintering method and the 1400~1600℃ of the hot isostatic pressing method, thus significantly reducing energy consumption.

[0129] The composite catalysts used in this invention are produced in small amounts of NH4Cl and La2O3, resulting in less residue and meeting the requirements of green chemistry. Furthermore, by controlling the multi-stage heating and gas flow rate, impurities are effectively eliminated, and the purity of the powder is improved.

[0130] This invention obtains a precursor with a porous network structure through freeze-drying granulation, which increases the reaction contact area; the composite catalyst and gradient atmosphere work together to achieve in-situ nitridation of Ti powder surface; at the same time, it can guide the orderly transformation of the intermediate phase, resulting in powder with regular morphology, high crystallinity and few internal crystal defects.

[0131] This invention removes catalyst residue through controlled condensation reflux; and achieves effective control of Ti2AlN powder particle size through a combined freeze-drying-airflow classification process, obtaining D... 50 It produces uniform powder with a particle size of 1~10 μm, overcoming the shortcomings of traditional crushing-ball milling methods, such as wide particle size distribution and easy introduction of impurities.

[0132] In summary, the method for preparing Ti2AlN powder based on multi-stage heating synergistic in-situ catalytic aluminothermic reaction of the present invention achieves low-temperature, high-efficiency and high-purity preparation of Ti2AlN powder, and has significant technological innovation and industrial application value.

[0133] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A method for preparing Ti2AlN powder based on multi-stage heating synergistic in-situ catalytic aluminothermic reaction, characterized in that, Includes the following steps: TiN powder, Ti powder, Al powder and composite catalyst are uniformly dispersed in an alcohol solvent to obtain a precursor suspension; wherein the composite catalyst is a mixture of NH4Cl and La2O3; The precursor suspension was freeze-dried to obtain precursor powder agglomerates with a porous network structure. The precursor powder agglomerates were subjected to aluminothermic activation treatment in a gas atmosphere containing ammonia to form a highly active ternary intermetallic compound coating structure. The highly active ternary intermetallic compound coating structure was heated to 600-800 °C at a rate of 3-5 °C / min under an inert gas atmosphere and held for 30-70 min; then heated to 1000-1200 °C at a rate of 1-3 °C / min and held for 120-160 min; the furnace was then cooled to obtain the reaction product. The reaction product was acid-washed, and then washed, dried, and air-separated to obtain Ti2AlN powder with different particle size ranges.

2. The method for preparing Ti2AlN powder based on multi-stage heating synergistic in-situ catalytic aluminothermic reaction according to claim 1, characterized in that, The mass ratio of TiN powder, Ti powder, and Al powder is (41.92~45.2):(32.45~35):(19.8~25.63), and the amount of the composite catalyst is 1%~3% of the total mass of TiN powder, Ti powder, and Al powder.

3. The method for preparing Ti2AlN powder based on multi-stage heating synergistic in-situ catalytic aluminothermic reaction according to claim 1, characterized in that, In the composite catalyst, the mass ratio of NH4Cl to La2O3 is (2~4):

1.

4. The method for preparing Ti2AlN powder based on multi-stage heating synergistic in-situ catalytic aluminothermic reaction according to claim 1, characterized in that, The precursor suspension is prepared by adding TiN powder, Ti powder, and Al powder to an alcohol solvent, adding a composite catalyst, and then mechanically stirring with ultrasonic oscillation for 40-60 min to obtain the precursor suspension; the ultrasonic power is 340-360 W, and the stirring speed is 440-460 rpm.

5. The method for preparing Ti2AlN powder based on multi-stage heating synergistic in-situ catalytic aluminothermic reaction according to claim 1, characterized in that, The freeze-drying process is as follows: add an appropriate amount of water to the precursor suspension, rapidly freeze in a liquid nitrogen environment for 10-30 min, and then freeze-dry in a freeze dryer for 24-48 h to obtain precursor powder agglomerates with a porous network structure.

6. The method for preparing Ti2AlN powder based on multi-stage heating synergistic in-situ catalytic aluminothermic reaction according to claim 1, characterized in that, The aluminothermic activation treatment is performed at a temperature of 400~600 ℃ for a time of 10~30 min.

7. The method for preparing Ti2AlN powder based on multi-stage heating synergistic in-situ catalytic aluminothermic reaction according to claim 6, characterized in that, The ammonia-containing gas is a mixture of ammonia and an inert gas, with the ammonia content being 10% to 15%.

8. The method for preparing Ti2AlN powder based on multi-stage heating synergistic in-situ catalytic aluminothermic reaction according to claim 1, characterized in that, The acid washing process is as follows: the reaction product is placed in a reflux condenser and refluxed with 0.5~2mol / L dilute hydrochloric acid for 2~10 h.

9. Ti2AlN powder prepared by any one of claims 1-8.

10. The application of Ti2AlN powder prepared by any one of claims 1-8 or Ti2AlN powder according to claim 9 in refractory materials.

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