CN101747049B - Preparation method of Nb4AlC3 bulk ceramics - Google Patents

Abstract

The invention relates to a preparation method of Nb ₄ AlC ₃ bulk ceramics, which relates to a preparation method of ternary layered compound single-phase bulk ceramics. The invention solves the problems of high synthesis temperature, long reaction time, complicated process, high cost and coarsening structure of the obtained Nb ₄ AlC ₃ bulk ceramics in the existing preparation method of Nb ₄ AlC ₃ bulk ceramics. The method of the present invention is as follows: 1. Mix niobium powder, aluminum powder and carbon powder by ball milling; 2. Prepare the preform, then put the preform and the mold into the combustion synthesis reactor, ignite and carry out the combustion synthesis reaction; 3. Combustion reaction Apply pressure after finishing, and then embed in quartz sand for cooling to obtain Nb ₄ AlC ₃ bulk ceramics. The method of the invention has the advantages of fast reaction speed, short synthesis time, low cost and high production efficiency, and the obtained Nb ₄ AlC ₃ bulk ceramics have high purity. The Nb ₄ AlC ₃ block ceramics obtained by the invention can be used in industries such as aviation, spaceflight, electronic industry and nuclear industry.

Description

Preparation method of Nb4AlC3 bulk ceramics

technical field

The invention relates to a preparation method of a ternary layered compound single-phase bulk ceramic.

Background technique

M _n+1 AX _n (M is a transition group metal, A is a main group element, X is C or N, n=1-3) has a layered hexagonal structure. Since MW Barsoum et al. (American Ceramic Society, J.Am.Ceram.Soc.79(1996)1953) synthesized bulk Ti ₃ SiC ₂ for the first time by reactive hot pressing technique, M _n+1 AX _n has attracted attention for its unique characteristics. There are more and more scientific researchers in the world. Specifically, it has many advantages of ceramics, such as high modulus and high strength. It also has certain properties of metals, such as low hardness, machinability, good electrical and thermal conductivity, high damage tolerance and good thermal shock resistance. It is a new structure/function integrated material that is very promising to be used in aviation, aerospace, electronics industry and nuclear industry.

Nb ₄ AlC ₃ is a newly discovered ternary layered compound M _n+1 AX _n ceramics, and its excellent high temperature performance has been paid more and more attention by people. Although Nb ₄ AlC ₃ has many excellent comprehensive properties and broad potential application prospects, the preparation of Nb ₄ AlC ₃ is extremely difficult, which limits its related basic research and application. At present, the ternary layered compound Nb ₄ AlC ₃ block is mainly prepared by hot pressing process. Zhou Yanchun et al. (Journal of the American Ceramic Society, J.Am.Ceram.Soc.91(2008)2258) successfully prepared Nb, Al and C powders by hot pressing at 1700°C and 30MPa for 1 hour by hot pressing Nb ₄ AlC ₃ single-phase bulk ceramics. The disadvantages of this preparation process are high preparation temperature (1700°C), long reaction time (1 hour), difficulty in obtaining large-scale materials, low production efficiency, and high cost; Continuous heating for a long time consumes a lot of electric energy; the process is complicated, and a vacuum environment or argon gas protection is required to prevent oxidation; at the same time, after a long period of heating, the structure of the material is coarsened, resulting in deterioration of its mechanical properties.

Contents of the invention

The purpose of the present invention is to solve the problems of high synthesis temperature, long reaction time, complex process, high cost and coarsening of the structure of the obtained Nb ₄ AlC ₃ bulk ceramics in the preparation method of the existing Nb ₄ AlC ₃ bulk ceramics. The invention provides a method for preparing Nb ₄ AlC ₃ bulk ceramics.

The preparation method of Nb ₄ AlC ₃ block ceramics of the present invention is realized through the following steps: 1. Put niobium powder, aluminum powder and carbon powder into a resin ball mill tank for ball milling for 5 to 30 hours, or add absolute ethanol ball mill and wet mix After 5 to 30 hours, dry naturally to obtain a mixed powder, wherein the molar ratio of niobium powder and aluminum powder is 4:0.7 to 1.3, and the molar ratio of niobium powder and carbon powder is 4:2.6 to 3.2; Press the mixed powder into a preform at a pressure of 15-45MPa for 10-20s, then put the preform into the mold, fill the gap between the mold and the preform with quartz sand, and then put the mold and the preform into the combustion synthesis In the reactor, the center of the upper surface of the preform is ignited, and a self-propagating combustion reaction occurs; 3. After the combustion reaction ends 1-5s, a pressure of 160-480MPa is applied, and the pressure is kept for 10-15s, and then the reaction product is embedded in the quartz The sand is cooled to room temperature to obtain Nb ₄ AlC ₃ bulk ceramics.

The preparation method of Nb ₄ AlC ₃ bulk ceramics of the present invention is characterized in that the preparation method of Nb ₄ AlC ₃ bulk ceramics is realized through the following steps: 1. Putting niobium powder, aluminum powder and carbon powder into a resin ball mill jar Ball mill for 5 to 30 hours, or add absolute ethanol ball mill and wet mix for 5 to 30 hours and then dry naturally to obtain a mixed powder, wherein the molar ratio of niobium powder and aluminum powder is 4:0.7~1.3, and the molar ratio of niobium powder and carbon powder The ratio is 4:2.6~3.2; 2. Put the mixed powder into a steel mold, apply a pressure of 15~45MPa for 20~25s, make the mixed powder form a cylindrical green body, and then press the center point on the upper surface of the green body , or place igniting agent and resistance wire on the midpoints of the three radii at an angle of 120° to each other on the upper surface, then place a sand cake on the green body, place a steel pad with a thickness of 30mm on the sand cake, and place the resistance wire The lead wire is led out from the edge of the pad and connected to the ignition device; 3. Turn on the ignition device to ignite and energize the resistance wire to heat and ignite the preform. Immediately apply an axial pressure of 2000kN to 5000kN on the preform after the combustion reaction stops for 1 to 5 seconds. ~50 seconds, take out the product, embed quartz sand within 30 seconds to cool, and cool for 20 to 30 hours to obtain Nb ₄ AlC ₃ bulk ceramics; the steel mold in step 2 is the patent " A steel mold in a combustion synthesis reactor.

The purity of the niobium powder, aluminum powder and carbon powder of the present invention is above 98%.

In step 1 of the present invention, absolute ethanol is added as a dispersant to mix the materials uniformly, so that the liquid level of the absolute ethanol does not cover the materials.

The preparation method of Nb ₄ AlC ₃ bulk ceramics of the present invention utilizes the combustion synthesis/quasi-isostatic pressing in-situ synthesis process to prepare high-purity single-phase Nb ₄ AlC ₃ with low-cost niobium powder, aluminum powder and carbon powder as raw materials Ceramic block; the synthesis and densification of block ceramics is completed in one step, and the cost of the preparation process is low, without the need for long-term high-temperature heating, which can save a lot of energy and reduce energy consumption; the production efficiency is high, and the combustion synthesis reaction can be completed within 5 minutes , the obtained Nb ₄ AlC ₃ bulk ceramics have a fine structure and improved compactness; Nb ₄ AlC ₃ bulk ceramics with diameters of 50mm and 80-300mm can be obtained.

The Nb ₄ AlC ₃ bulk ceramic obtained by the preparation method of the present invention is composed of single-phase Nb ₄ AlC ₃ and has high purity. The Nb ₄ AlC ₃ bulk ceramic belongs to the hexagonal crystal system, the space group is P6 ₃ /mmc, and the crystal structure is Al and Nb-C chains are combined with weak covalent bonds, resulting in shear deformation of the ductile (0001) basal plane of Nb ₄ AlC ₃ , which makes the grains of Nb ₄ AlC ₃ prone to kinks and laminations, which appear macroscopically microplastic. It can be used in industries such as aviation, aerospace, electronics industry and nuclear industry.

Compared with the traditional high-temperature solid-state reaction method, the preparation method of the present invention has the advantage of utilizing the chemical energy of the chemical reaction of the raw material, and only needs a small amount of energy to ignite during the reaction process, and the energy required for the combustion process comes from the raw material The chemical energy released by combustion greatly reduces energy consumption and improves production efficiency; and the temperature of combustion synthesis is very high, up to 2000-3000 ° C, high temperature is conducive to the volatilization of impurities, so the Nb ₄ AlC ₃ bulk ceramics The purity is very high. In summary, the present invention adopts combustion synthesis technology to prepare Nb ₄ AlC ₃ bulk ceramics, which has outstanding advantages such as short reaction time, fast reaction rate, less energy consumption, high production efficiency, low cost, simple process, etc., and obtains The Nb ₄ AlC ₃ bulk ceramics have a fine structure and broad application prospects. The use of this technology will have obvious social and economic benefits.

Detailed ways

The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

Specific Embodiment 1: The preparation method of Nb ₄ AlC ₃ bulk ceramics in this embodiment is realized through the following steps:

1. Put niobium powder, aluminum powder and carbon powder into a resin ball mill tank and mill for 5-30 hours, or add anhydrous ethanol ball mill to wet mix for 5-30 hours and then dry naturally to obtain a mixed powder. Among them, niobium powder and aluminum powder The molar ratio of niobium powder and carbon powder is 4:0.7～1.3, and the molar ratio of niobium powder and carbon powder is 4:2.6～3.2; 2. Apply a pressure of 15～45MPa to the mixed powder for 12～20s, press the mixed powder into a preform, and then The preform is put into the mold, and the gap between the mold and the preform is filled with quartz sand, and then the mold and the preform are put into the combustion synthesis reactor, and then the center of the upper surface of the preform is ignited to carry out the self-propagating combustion reaction 3. Apply a pressure of 160-480MPa 1-5s after the combustion reaction, hold the pressure for 10-15s, then embed the reaction product in quartz sand and cool to room temperature to obtain Nb ₄ AlC ₃ bulk ceramics.

In step 1 of this embodiment, absolute ethanol is added as a dispersant to mix the materials evenly, so that the liquid level of the absolute ethanol is submerged by 1-5 mm of the materials.

The purity of the niobium powder, aluminum powder and carbon powder in step 1 of this embodiment is above 98%.

In this embodiment, a high-purity single-phase Nb ₄ AlC ₃ ceramic block is prepared from low-cost niobium powder, aluminum powder and carbon powder by using the combustion synthesis/quasi-isostatic in-situ synthesis process; the synthesis of bulk ceramics and densification in one step, and the cost of the preparation process is low, without the need for long-term high-temperature heating, which can save a lot of energy and reduce energy consumption; the production efficiency is high, and the combustion synthesis reaction can be completed within 5 minutes, and the obtained Nb ₄ AlC ₃ block The ceramic structure is fine, and the compactness is improved; the diameter of the Nb ₄ AlC ₃ bulk ceramic obtained in this embodiment is 50 mm.

Embodiment 2: This embodiment differs from Embodiment 1 in that the molar ratio of niobium powder and aluminum powder in step 1 is 4:0.9-1.2, and the molar ratio of niobium powder and carbon powder is 4:2.7-3.1. Other steps and parameters are the same as those in Embodiment 1.

Embodiment 3: The difference between this embodiment and Embodiment 1 is that the molar ratio of niobium powder and aluminum powder in step 1 is 4:1.1, and the molar ratio of niobium powder and carbon powder is 4:2.8. Other steps and parameters are the same as those in Embodiment 1.

Embodiment 4: The difference between this embodiment and Embodiment 1, 2 or 3 is that in step 1, put it into a resin ball mill jar and mill it for 12-24 hours, or add absolute ethanol and ball-mill it for wet mixing for 12-24 hours. Other steps and parameters are the same as those in Embodiment 1, 2 or 3.

Embodiment 5: The difference between this embodiment and Embodiment 1, 2 or 3 is that in step 1, put it into a resin ball mill jar for ball milling for 16 hours, or add absolute ethanol and ball mill for wet mixing for 16 hours. Other steps and parameters are the same as those in Embodiment 1, 2 or 3.

Embodiment 6: This embodiment differs from Embodiments 1 to 5 in that in step 2, a pressure of 25-38 MPa is applied to the mixed powder. Other steps and parameters are the same as those in Embodiments 1 to 5.

Embodiment 7: This embodiment differs from Embodiments 1 to 5 in that a pressure of 32 MPa is applied to the mixed powder in step 2. Other steps and parameters are the same as those in Embodiments 1 to 5.

Embodiment 8: The difference between this embodiment and Embodiments 1 to 7 is that ignition in step 2 requires 3 to 7 g of igniting agent to be placed at the ignition point, and the igniting agent is a mixed powder mixed with Ti and C in a molar ratio of 1:1. , Ti and B in a molar ratio of 1:2 mixed powder or Ti and B ₄ C in a molar ratio of 3:1 mixed powder.

In this embodiment, Ti is Ti powder with a particle size of less than 300 mesh and a mass purity of 99%.

Specific embodiment nine: This embodiment is different from specific embodiments one to eight in that the mold in step two is the self-propagating high-temperature synthesis of TiC-TiB ₂ /Cu composite materials published in the fourth issue of "Journal of Inorganic Materials" in 2003 " in the mold. Other steps and parameters are the same as those in Embodiments 1 to 8.

Embodiment 10: This embodiment differs from Embodiments 1 to 9 in that in step 3, after the combustion synthesis reaction is completed, a pressure of 240-380 MPa is applied, and the pressure is maintained for 11-14 seconds. Other steps and parameters are the same as those in Embodiments 1 to 9.

Embodiment 11: This embodiment differs from Embodiments 1 to 9 in that in Step 3, after the combustion synthesis reaction is completed, a pressure of 280-340 MPa is applied and the pressure is maintained for 12-13 seconds. Other steps and parameters are the same as those in Embodiments 1 to 9.

Embodiment 12: This embodiment differs from Embodiments 1 to 9 in that in step 3, after the combustion synthesis reaction is completed, a pressure of 300 MPa is applied and the pressure is maintained for 12 s. Other steps and parameters are the same as those in Embodiments 1 to 9.

Embodiment 13: The difference between this embodiment and Embodiment 1 is that the mold in step 2 is the mold in "Research on Self-propagating High Temperature Synthesis of TiC-TiB ₂ /Cu Composite Materials". Other steps and parameters are the same as those in Embodiment 1.

Embodiment 15: The method for preparing high-purity Nb ₄ AlC ₃ bulk material in this embodiment is carried out as follows: 1. Put niobium powder, aluminum powder and carbon powder into a resin ball mill tank, and then add absolute ethanol for ball milling After wet mixing for 24 hours, dry naturally to obtain mixed powder, wherein the mol ratio of niobium powder and aluminum powder is 4: 1.1, and the mol ratio of niobium powder and carbon powder is 4: 2.8;

2. Apply a pressure of 32MPa to the mixed powder for 20s, press the mixed powder into a preform, then put the preform into the mold, fill the gap between the mold and the preform with quartz sand, and put the mold and the preform together In the combustion synthesis reactor, ignite at the center of the upper surface of the preform to carry out the combustion reaction; 3. After the combustion synthesis reaction is completed 5s, start to apply a pressure of 300MPa, keep the pressure for 12s, and then embed the reaction product in quartz sand to cool to room temperature. That is, Nb ₄ AlC ₃ bulk ceramics are obtained.

In step 1 of this embodiment, absolute ethanol is added as a dispersant to mix the materials evenly, so that the liquid level of the absolute ethanol is submerged by 1-5 mm of the materials.

The purity of the niobium powder, aluminum powder and carbon powder in step 1 of this embodiment is above 98%.

Ignition in step 2 of this embodiment needs to place 5 g of igniting agent at the ignition point. The igniting agent is a mixed powder of Ti and C in a molar ratio of 1:1; the mold in step 2 is "TiC-TiB ₂ /Cu composite Die in Self-Propagating High-Temperature Synthesis of Materials.

The Nb ₄ AlC ₃ bulk ceramic obtained in this embodiment has a diameter of 50 mm and a height of 10 to 20 mm.

The Nb ₄ AlC ₃ bulk ceramic obtained in this embodiment has a single-phase Nb ₄ AlC ₃ composition, high purity, good microplasticity, and good mechanical properties.

Specific Embodiment Sixteen: The preparation method of Nb ₄ AlC ₃ bulk ceramics in this embodiment is realized through the following steps:

1. Put niobium powder, aluminum powder and carbon powder into a resin ball mill tank and mill for 5-30 hours, or add anhydrous ethanol ball mill to wet mix for 5-30 hours and then dry naturally to obtain a mixed powder. Among them, niobium powder and aluminum powder The molar ratio of niobium powder and carbon powder is 4:0.7~1.3, and the molar ratio of niobium powder and carbon powder is 4:2.6~3.2; 2. Put the mixed powder into a steel mold, and apply a pressure of 15~45MPa to the steel mold for 20~25s , so that the mixed powder forms a cylindrical green body, and then place the igniter and resistance wire on the center point of the upper surface of the green body, or on the midpoints of the three radii that form an angle of 120° each other on the upper surface, and then place the igniter and resistance wire on the green body Place a sand cake, place a steel block with a thickness of 30mm on the sand cake, lead the resistance wire lead from the edge of the block and connect it to the ignition device; 3. Turn on the ignition device to ignite and make the resistance wire energize and heat to ignite the preform , Immediately after the combustion reaction stops for 1-5s, an axial pressure of 2000kN-5000kN is applied to the green body for 10-50 seconds, the product is taken out, embedded in quartz sand within 30 seconds and cooled for 20-30 hours, and Nb ₄ AlC ₃ bulk ceramics are obtained ; The steel mold in step 2 is the steel mold in the patent "combustion synthesis reactor" with Chinese patent number ZL03132642.0.

The purity of the niobium powder, aluminum powder and carbon powder of the present invention is above 98%.

In step 1 of this embodiment, absolute ethanol is added as a dispersant to mix the materials evenly, so that the liquid level of the absolute ethanol is submerged by 1-5 mm of the materials.

In this embodiment, a high-purity single-phase Nb ₄ AlC ₃ ceramic block is prepared from low-cost niobium powder, aluminum powder and carbon powder by using the combustion synthesis/quasi-isostatic in-situ synthesis process; the synthesis of bulk ceramics and densification in one step, and the cost of the preparation process is low, without the need for long-term high-temperature heating, which can save a lot of energy and reduce energy consumption; the production efficiency is high, and the combustion synthesis reaction can be completed within 5 minutes, and the obtained Nb ₄ AlC ₃ block The ceramic structure is fine, and the compactness is improved; the diameter of the Nb ₄ AlC ₃ bulk ceramic obtained in this embodiment is 80 mm to 300 mm, and the height is 10 mm to 300 mm.

Specific embodiment seventeen: the difference between this embodiment and specific embodiment sixteen is that the molar ratio of niobium powder and aluminum powder in step 1 is 4: 0.9～1.2, and the molar ratio of niobium powder and carbon powder is 4: 2.7～3.1 . Other steps and parameters are the same as those in Embodiment 16.

Embodiment 18: This embodiment differs from Embodiment 16 in that the molar ratio of niobium powder to aluminum powder in step 1 is 4:1.1, and the molar ratio of niobium powder to carbon powder is 4:2.8. Other steps and parameters are the same as those in Embodiment 16.

Specific Embodiment Nineteen: The difference between this embodiment and specific embodiments sixteen, seventeen or eighteen is that in step one, put it into a resin ball mill tank for ball milling for 12 to 24 hours, or add anhydrous ethanol ball mill to wet mix for 12 to 24 hours. Hour. Other steps and parameters are the same as those in Embodiment 16, 17 or 18.

Embodiment 20: This embodiment differs from Embodiment 16, 17 or 18 in that in step 1, put it into a resin ball mill tank for 16 hours of ball milling, or add anhydrous ethanol ball mill and wet mix for 16 hours. Other steps and parameters are the same as

The specific embodiments are the same as sixteen, seventeen or eighteen.

Embodiment 21: This embodiment differs from Embodiments 16 to 20 in that in step 2, a pressure of 25-38 MPa is applied to the steel mold. Other steps and parameters are the same as those in Embodiments 16 to 20.

Embodiment 22: This embodiment differs from Embodiments 16 to 20 in that in step 2, a pressure of 32 MPa is applied to the steel mold. Other steps and parameters are the same as those in Embodiments 16 to 20.

Specific embodiment 23: The difference between this embodiment and specific embodiments 16 to 22 is that the ignition in step 2 needs to place 3 to 7 g of igniting agent at the ignition point, and the igniting agent is Ti and C with a molar ratio of 1. :1 mixed powder, Ti and B mixed powder with a molar ratio of 1:2, or Ti and B ₄ C mixed powder with a molar ratio of 3:1.

Other steps and parameters are the same as those in Embodiments 16 to 22.

Embodiment 24: This embodiment differs from Embodiments 16 to 23 in that the diameter of the sand cake placed on the body in step 2 is consistent with the diameter of the cylindrical body. Other steps and parameters are the same as those in Embodiments 16 to 23.

Embodiment 25: This embodiment differs from Embodiments 16 to 24 in that the ignition device in step 2 is composed of a power supply capable of instantly providing a current up to 100A and a copper wire, and the copper wire is connected to a resistance wire. Other steps and parameters are the same as those in Embodiments 16 to 24.

Embodiment 26: This embodiment differs from Embodiments 16 to 25 in that an axial pressure of 2800kN-4200kN is applied to the green body for 15-35 seconds immediately after the combustion stops in step 3. Other steps and parameters are the same as those in Embodiments 16 to 25.

Specific Embodiment 27: This embodiment differs from specific embodiments 16 to 25 in that an axial pressure of 3600 kN is applied to the green body for 30 seconds immediately after the combustion stops in step 3. Other steps and parameters are the same as those in Embodiments 16 to 25.

Embodiment 28: This embodiment differs from Embodiments 16 to 27 in that in Step 3, quartz sand is embedded and cooled for 22 to 28 hours. Other steps and parameters are the same as those in Embodiments 16 to 27.

Specific embodiment 29: The difference between this embodiment and specific embodiments 16 to 27 is: in step 3, embed quartz sand and cool for 25 hours. Other steps and parameters are the same as those in Embodiments 16 to 27.

Specific Embodiment Thirty: The preparation method of Nb ₄ AlC ₃ bulk ceramics in this embodiment is realized through the following steps:

One, niobium powder, aluminum powder and carbon powder are put into resin ball mill tank and ball milled for 24 hours, wherein, the mol ratio of niobium powder and aluminum powder is 4: 1.1, and the mol ratio of niobium powder and carbon powder is 4: 2.8; Two 1. Put the mixed powder into the steel mold, apply a pressure of 32MPa to the steel mold for 20s, make the mixed powder form a cylindrical green body, then place the igniter and resistance wire at the center of the upper surface of the green body, and then Place a sand cake on the green body, and place a steel block with a thickness of 30mm on the sand cake. The lead wire of the resistance wire is drawn from the edge of the block and connected to the ignition device; 3. Turn on the ignition device to ignite and make the resistance wire energize and generate heat. Immediately after the combustion stops, apply an axial pressure of 3600kN to the green body for 25 seconds, take out the product, embed it in quartz sand within 30 seconds and cool it for 25 hours to obtain Nb ₄ AlC ₃ bulk ceramics; the steel mold in step 2 is a Chinese patent number It is the steel mold in the patent "combustion synthesis reactor" of ZL03132642.0.

The purity of the niobium powder, aluminum powder and carbon powder of the present invention is above 98%.

In step 1 of this embodiment, absolute ethanol is added as a dispersant to mix the materials evenly, so that the liquid level of the absolute ethanol is submerged by 1-5 mm of the materials.

In step 2 of this embodiment, 7 g of igniting agent needs to be placed at the ignition point for ignition. The igniting agent is a mixed powder of Ti and C in a molar ratio of 1:1.

The Nb ₄ AlC ₃ bulk ceramic obtained in this embodiment has a diameter of 300 mm and a height of 20 mm.

The Nb ₄ AlC ₃ bulk ceramic obtained in this embodiment is composed of single-phase Nb ₄ AlC ₃ , has high purity, good microplasticity, and good mechanical properties.

Claims (4)

1. The preparation method of Nb ₄ AlC ₃ bulk ceramics is characterized in that the preparation method of Nb ₄ AlC ₃ bulk ceramics is realized through the following steps: one, niobium powder, aluminum powder and carbon powder are put into the resin ball mill jar Ball mill for 5 to 30 hours, or add absolute ethanol ball mill and wet mix for 5 to 30 hours and then dry naturally to obtain a mixed powder, wherein the molar ratio of niobium powder and aluminum powder is 4:0.7~1.3, and the molar ratio of niobium powder and carbon powder The ratio is 4:2.6~3.2; 2. Apply a pressure of 15~45MPa to the mixed powder for 10~20s, press the mixed powder into a preform, and then put the preform into the mold. The gap between the mold and the preform is made of quartz Sand filling, then put the mold and the preform together into the combustion synthesis reactor, and then ignite at the center of the upper surface of the preform, and a self-propagating combustion reaction occurs; 3. After the combustion reaction ends 1-5s, start to apply a pressure of 160-480MPa , hold the pressure for 10-15s, and then embed the reaction product in quartz sand and cool to room temperature to obtain Nb ₄ AlC ₃ bulk ceramics. 2. the preparation method of Nb ₄ AlC ₃ bulk ceramics according to claim 1 is characterized in that the mol ratio of niobium powder and aluminum powder is 4: 0.9～1.2 in the step 1, and the mol ratio of niobium powder and carbon powder is 4: 2.7 ~ 3.1. 3. the preparation method of Nb ₄ AlC ₃ bulk ceramics according to claim 1, it is characterized in that the mol ratio of niobium powder and aluminum powder is 4: 1.1 in the step 1, and the mol ratio of niobium powder and carbon powder is 4: 2.8. 4. The method for preparing Nb ₄ AlC ₃ bulk ceramics according to claim 1, 2 or 3, characterized in that in step 3, after the combustion synthesis reaction is completed, a pressure of 240-380 MPa is applied and the pressure is kept for 11-14s.