Preparation method of frame-type nitride ceramic whisker reinforced nitride ceramic-based composite material

Abstract

The invention relates to a preparation method of a frame-type nitride ceramic whisker reinforced nitride ceramic-based composite material, which comprises the following steps: firstly, based on a pulse-type aerodynamic vortex field, dispersing nitride whiskers in a polymer solution, and carrying out gradient heating evaporation coupling to obtain a nitride whisker dispersion liquid; carrying out ultralow-temperature instantaneous curing, freeze drying, pre-oxidation and carbonization on the nitride whisker dispersion liquid to obtain a nitride whisker / organic carbon composite framework; and filling the nitride crystal whisker / organic carbon frame with the nitride slurry through negative pressure suction, and carrying out multi-airflow variable-temperature pressureless sintering to obtain the frame-type nitride crystal whisker reinforced nitride ceramic-based composite material. Compared with the prior art, the frame type nitride whisker reinforced phase has low discrete distribution and high continuity, a continuous heat conduction network is formed in a nitride ceramic matrix, and the mechanical strength and the heat conduction performance of the nitride ceramic matrix composite material are greatly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic matrix composites, and relates to a preparation method of a frame type nitride ceramic whisker reinforced nitride ceramic matrix composite. BACKGROUND

[0002] Nitride ceramic materials have the advantages of high temperature resistance, corrosion resistance and wear resistance, and also have excellent thermal conductivity and electrical insulation, high frequency dielectric constant and small dielectric loss, and play a key role in the field of electronic packaging and semiconductors. However, the intrinsic brittleness and discontinuous thermal conduction path of nitride ceramic materials result in poor mechanical properties and thermal conductivity far lower than the theoretical value, which seriously limits their application and development.

[0003] At present, researchers add a second phase as a reinforcing phase in the ceramic matrix to improve the mechanical strength and thermal conductivity of the ceramic matrix composite by using the crack resistance, expansion capacity and bridging connection capacity of the reinforcing phase. The reinforcing phase for ceramic matrix composites includes particles, whiskers, chopped fibers and continuous fibers. The reinforcing effect of whiskers and continuous fibers on mechanical properties is the most significant. However, continuous fibers are difficult to uniformly penetrate the ceramic base paste due to the anisotropy and tightness of their woven structure, and the composite material has problems such as high porosity, low compressive strength, and easy peeling between layers. In addition, the existing continuous fiber reinforcing phase is carbide and oxide fiber, such as "a method for preparing a ceramic fiber reinforced quartz ceramic matrix composite at low temperature and application (CN114105664A)", "a preparation method of glass fiber reinforced quartz ceramic (CN109336632A)", and "carbon fiber reinforced ceramic composite material and preparation method thereof (CN116947516A)", which use carbon or oxide fiber woven pieces as reinforcing bodies, impregnate in ceramic paste, and are sintered at high temperature to form a continuous fiber reinforced ceramic matrix composite with good mechanical properties. However, the high electrical conductivity of carbon fiber and the low thermal conductivity of oxide fiber cannot meet the application requirements of high thermal conductivity and insulating ceramic matrix composites. In contrast, nitride whisker reinforced nitride ceramic can effectively solve the above problems due to its anisotropy, electrical insulation and single crystal intrinsic high thermal conductivity, and has great development potential.

[0004] Nitride whiskers are usually prepared by chemical vapor deposition, carbothermal reduction or combustion method, and are mostly discrete distribution phases. Therefore, the introduction of nitride whiskers into the ceramic matrix usually adopts an external method, such as "AlN whisker / Al2O3 ceramic matrix composite substrate and its preparation process (CN103086733A)", "aluminum nitride whisker reinforced aluminum nitride ceramic composite material for electronic packaging and preparation method (CN105777169A)", in order to uniformly disperse the whiskers in the ceramic matrix, the whiskers need to be mixed with the powder by dry mixing, hot pressing or through ball milling with the powder slurry liquid phase mixing, pouring forming, which inevitably damages the structure of the whiskers, such as crystal type damage, whisker fracture, etc., causing the reliability of the composite material to decrease, the heat conduction path to be shortened / broken, and the thermal conductivity to be far lower than the theoretical value. In addition, a small amount of whiskers cannot form a continuous heat conduction path, and a large amount of whiskers are prone to agglomeration and difficult to disperse uniformly.

[0005] Recently, researchers ball mill granulation, dry pressing of precursor powder, growth promoter powder, etc. After that, the short and thick whiskers can be grown in situ in the ceramic matrix, which avoids the damage of the whiskers during mixing, such as "preparation method of in-situ grown mullite whisker reinforced silicon carbide ceramic matrix composite (CN113292344A)" and in-situ grown tantalum carbide whisker material and its preparation method (CN102051676A)", but the in-situ grown whiskers are highly uncontrollable and have high dispersion, which causes poor connectivity of the heat conduction path in the composite material and low thermal conductivity.

[0006] Therefore, the existing whisker reinforced ceramic matrix composite material still faces the following problems: 1) when prepared by an external method, the whiskers are difficult to be dispersed and formed without damage and are prone to agglomeration; 2) the dispersion of the whiskers in the ceramic matrix is high, and it is difficult to form a continuous heat conduction path. SUMMARY

[0007] The purpose of the present application is to provide a preparation method of a framework type nitride ceramic whisker reinforced nitride ceramic matrix composite material. The nitride ceramic matrix composite material prepared by the present application is prepared by pulse gas vortex to uniformly disperse high content nitride whiskers in a polymer solution without damage, freeze-drying, pre-oxidation to prepare a low dispersion distribution, high continuity and high pore connectivity nitride whisker / organic carbon composite framework, and filling the composite framework with a high solid and low viscosity nitride slurry by negative pressure suction, and then multi-gas flow temperature sintering to obtain a low porosity, high heat conduction path nitride whisker reinforced nitride ceramic matrix composite material, which effectively improves the mechanical strength and thermal conductivity of the composite material.

[0008] The purpose of the present application can be achieved by the following technical solutions:

[0009] A preparation method of a framework type nitride ceramic whisker reinforced nitride ceramic matrix composite material, comprising the following steps:

[0010] 1) Based on pulsed pneumatic vortex field, nitride whiskers are dispersed in low-concentration polymer solution, and high-solid-content and high-fidelity nitride whisker homogeneous dispersion liquid is obtained through gradient temperature evaporation coupling;

[0011] 2) The nitride whisker homogeneous dispersion liquid is poured into a specially designed freezing mold, and after ultra-low temperature instantaneous solidification, freeze-drying, pre-oxidation and carbonization, a low-dispersion-distribution and high-continuity nitride whisker / organic carbon composite framework is obtained;

[0012] 3) The nitride slurry is filled into the nitride whisker / organic carbon framework by negative pressure suction, and a framework-type nitride whisker reinforced nitride ceramic matrix composite material with low porosity and three-dimensional interpenetrating heat conduction network is obtained through multi-gas flow variable temperature pressureless sintering.

[0013] The preparation method of the nitride slurry comprises: adding nano-sized nitride particles and sintering additives to an aqueous solution, inducing directional reconstruction of the charge density of the hydroxylated sites on the surface of the nanoparticles by liquid interfacial engineering strategy, and obtaining high-solid and low-viscosity nitride slurry by ball milling.

[0014] In some specific embodiments, in step 1), the pulse frequency in the pulsed pneumatic vortex field is 10-50 Hz, the vortex shear rate is 500-2000 s -1 , the stirring speed is 100-2000 rpm, the stirring time is 0.5-3 h, and the dispersion atmosphere is inert gas.

[0015] In some specific embodiments, in step 1), the nitride whiskers are selected from at least one of aluminum nitride, boron nitride, silicon nitride, gallium nitride or titanium nitride, the average diameter of the whiskers is 30-300 nm, and the aspect ratio is >1000;

[0016] In the polymer solution, the polymer is selected from at least one of polyacrylonitrile, polyimide, phenolic resin or aryl acetylene polymer, the concentration is 0.1-5 wt%, and the solvent is selected from at least one of methanol, ethanol, dimethylformamide, dimethyl sulfoxide, sulfolane, ethylene nitrate, tetrahydrofuran, acetone, chloroform or toluene;

[0017] The mass ratio of the nitride whiskers to the polymer is (2-5):5.

[0018] In some specific embodiments, in step 1), the gradient temperature evaporation coupling comprises: first fluidization shear dispersion at 25-110℃, then standing at 110-135℃, and then evaporation concentration at 135-155℃.

[0019] In some specific embodiments, in step 2), in the ultra-low temperature instantaneous solidification, the temperature is -196℃ to -40℃, and the solidification time is 5-60 s;

[0020] The drying temperature in the freeze drying is -10℃ to -50℃, and the solidification time is 24-48h;

[0021] The pre-oxidation atmosphere in the pre-oxidation is air, the pre-oxidation temperature is 100-300℃, and the pre-oxidation time is 0.5-5h;

[0022] The carbonization atmosphere in the carbonization is inert gas, the carbonization temperature is 600-1000℃, and the carbonization time is 1-5h.

[0023] In some specific embodiments, in step 3), the feeding ratio of the nitride slurry to the nitride whisker / organic carbon framework is (1-10)mL:(0.5-1)g.

[0024] In some specific embodiments, in step 3), the suction pressure in the negative pressure suction is -0.06MPa to -0.1MPa, and the suction time is 1-4h.

[0025] In some specific embodiments, in step 3), the multi-gas flow variable-temperature pressureless sintering includes:

[0026] First, calcining at 500-1000℃ for 1-3h in an air atmosphere; then calcining at 1500-2000℃ for 0.5-1h in an inert gas atmosphere; and then calcining at 1200-1400℃ for 1-5h.

[0027] In some specific embodiments, the nanoscale nitride particles are selected from at least one of aluminum nitride, boron nitride, silicon nitride, gallium nitride or titanium nitride, and the average particle size is 50-500nm;

[0028] The sintering aid is selected from at least one of yttrium oxide, calcium oxide, dysprosium oxide, boron oxide, calcium fluoride, titanium oxide, aluminum oxide or lithium oxide, and the amount is 0.5-5wt% of the amount of the nanoscale nitride particles;

[0029] The pH of the aqueous solution is 1-3 or 10-12.

[0030] In some specific embodiments, in the ball milling, the ball milling rotation speed is 300-500rad / min, the ball milling time is 0.5-5h, and the ball-to-material ratio is (1-5):1.

[0031] In the nitride slurry, the solid content of the nitride particles is 40-70wt%, and the viscosity is <200mpa·s.

[0032] The mechanism of the application is introduced as follows:

[0033] The pulse pneumatic vortex field is used to replace the traditional ball milling dispersion process, and the multi-scale spatial steric hindrance of the whisker is controlled through the fluid shear stress of the pulse and the pneumatic vortex field and the cavitation effect, so that the whisker can be uniformly dispersed in the polymer solution, the damage of the whisker morphology structure is greatly reduced, and the intrinsic mechanical and thermal conductivity properties of the whisker reinforcing phase are reserved. However, the continuous thermal conduction network of the whisker reinforcing phase with low solid content is difficult to form, therefore, the gradient temperature evaporation coupling process is introduced, the interface energy barrier between the whisker and the solution is broken through through the effects of stage fluidization dispersion, interface stabilization and polymerization concentration, and a high-solid-content and high-fidelity nitride whisker homogeneous dispersion liquid is obtained.

[0034] In the compounding process of the nitride whisker dispersion liquid and the nitride ceramic substrate, the nitride whisker is randomly and discretely distributed in a low-continuity state, and cannot play the maximum role of the reinforcing and thermal conduction. Therefore, the nitride whisker dispersion liquid is poured into a freezing mold, the nitride whisker is directionally and closely distributed by using the extrusion effect of ice crystals on the whisker through the ultra-low temperature instantaneous solidification technology, and the solvent phase is removed by using the freeze-drying technology, so that a low-discrete-distribution and high-continuity multi-level structure nitride whisker / polymer framework is obtained. The un-crosslinked whisker framework structure is easy to collapse, and thus a multi-level structure nitride whisker / organic carbon composite framework reinforcing phase is obtained after low-temperature pre-oxidation and high-temperature carbonization. However, the high-concentration ceramic substrate slurry as the substrate is difficult to disperse and has poor fluidity, and the low-concentration slurry cannot be densely formed and has poor mechanical strength. Therefore, a mediator is introduced to control the surface charge density of the ceramic nanoparticles through the liquid phase interface engineering strategy, the repulsive force of the double electric layer of the nanoparticles is increased, and the agglomeration phenomenon of the nanoparticles caused by the van der Waals force is inhibited, so that a high-solid-content and low-viscosity nitride ceramic particle slurry is obtained. The nitride ceramic particle slurry is penetrated into the nitride whisker / organic carbon composite framework by using a negative pressure suction impregnation process, so that a green body is obtained. Combined with the multi-gas flow variable-temperature pressureless sintering technology, the organic carbon material in the framework is removed, the temperature is then increased to stimulate the explosive growth of the substrate grains, so that the residual space of the organic carbon material is filled, and finally the coherent interface between the whisker and the substrate is constructed, so that the composite material is densified, the defect density of the composite material is reduced, and a high-strength and high-thermal-conductivity nitride whisker reinforced nitride ceramic composite material with a three-dimensional interpenetrating thermal conduction network is formed.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] (1) The nitride whisker reinforcing phase in the present application is in a low-discrete-distribution and high-continuity framework state, which overcomes the problems of random and discrete distribution of the whisker reinforcing phase in the ceramic matrix and the inability to form a continuous thermal conduction path in the external method and the in-situ growth method, and the framework of the whisker reinforcing phase has high porosity and pore connectivity, which solves the problem of reliability reduction of the composite material caused by the difficulty of uniform penetration of the continuous reinforcing phase.

[0037] (2) In the material preparation, the high-content nitride whisker is uniformly and non-destructively dispersed in the polymer solution by using pulse pneumatic vortex, and the nitride whisker / organic carbon composite framework is prepared by freeze-drying and pre-oxidation. The high-solid and low-viscosity nitride slurry is filled into the composite framework through negative pressure suction, and finally the nitride ceramic matrix composite material is obtained by multi-gas flow temperature sintering without pressure, which solves the problem of damage to the crystal structure and morphology of the whisker caused by liquid phase ball milling mixing process and dry mixing hot pressing forming.

[0038] (3) The preparation method of the present application is simple, one-step forming, short preparation period and wide raw material adaptability, which can be used for preparing aluminum nitride, boron nitride, silicon nitride and other whisker reinforced ceramic matrix composites. The mechanical strength and thermal conductivity of the prepared material are high, and it can be widely used in electronic packaging and semiconductor field. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 SEM image of the cross-section of the framework type aluminum nitride whisker / organic carbon framework in Example 1;

[0040] Figure 2 SEM image of the cross-section of the aluminum nitride whisker reinforced aluminum nitride ceramic matrix composite material in Example 1;

[0041] Figure 3 Fracture bending-displacement curve of the aluminum nitride whisker reinforced aluminum nitride ceramic matrix composite material in Example 1;

[0042] Figure 4 SEM image of the cross-section of the aluminum nitride whisker reinforced aluminum nitride ceramic matrix composite material in Comparative Example 1;

[0043] Figure 5 Fracture bending-displacement curve of the aluminum nitride whisker reinforced aluminum nitride ceramic matrix composite material in Comparative Example 1.

[0044] Figure 6 SEM image of the cross-section of the aluminum nitride whisker reinforced aluminum nitride ceramic matrix composite material in Comparative Example 2. DETAILED DESCRIPTION

[0045] The present application will be described in detail below in combination with the drawings and specific examples. The present embodiment is implemented on the premise of the technical solution of the present application, and detailed implementation and specific operation process are given, but the protection scope of the present application is not limited to the following examples.

[0046] The present application provides a framework type nitride ceramic whisker reinforced nitride ceramic matrix composite material and a preparation method thereof, comprising the following steps:

[0047] (1) Disperse nitride whiskers in a low-concentration polymer solution, realize multi-scale spatial steric hindrance regulation of the whiskers by pulsed pneumatic vortex field, and obtain a high-solid-content and high-fidelity nitride whisker homogeneous dispersion liquid by gradient temperature evaporation coupling and breaking through the energy barrier of the whisker-solution interface;

[0048] (2) Pour the nitride whisker dispersion liquid into a freezing mold to realize ultra-low temperature instantaneous solidification, remove the solvent phase by freeze-drying, and obtain an uncrosslinked three-dimensional nitride whisker / polymer framework;

[0049] (3) Obtain a low-dispersion-distribution and high-continuity multi-level structure nitride whisker / organic carbon composite framework by a low-temperature pre-oxidation and high-temperature carbonization process of the uncrosslinked framework;

[0050] (4) Add nanoscale nitride particles and sintering aids to an aqueous solution, induce directional reconstruction of the charge density of the surface hydroxyl sites of the nanoparticles by liquid interfacial engineering strategy, and obtain a high-solid-content, low-viscosity and low-nitride slurry by ball milling dispersion;

[0051] (5) Penetrate the nitride slurry into the multi-level pores of the nitride whisker / organic carbon framework by a negative pressure suction impregnation process to obtain a framework-type nitride whisker reinforced nitride ceramic matrix composite body;

[0052] (6) Build a coherent interface between the whiskers and the matrix by multi-gas flow variable-temperature pressureless sintering of the composite body to prepare a nitride whisker reinforced nitride ceramic matrix composite material with low defect density and three-dimensional interpenetrating thermal conduction network.

[0053] In step (1), the nitride whiskers include one or more of aluminum nitride, boron nitride, silicon nitride, gallium nitride, titanium nitride, etc., the whisker diameter is nanoscale (50-300 nm), and the whisker aspect ratio is >1000;

[0054] The polymers in the low-concentration polymer solution include one or more of polyacrylonitrile, polyimide, phenolic resin, aryl acetylene polymer, etc.; the solution includes one or more of methanol, ethanol, dimethylformamide, dimethyl sulfoxide, sulfolane, ethylene nitrate, tetrahydrofuran, acetone, chloroform, toluene, etc.; and the polymer content in the low-concentration polymer solution is 0.1-5 wt%;

[0055] The pulsed pneumatic vortex has a pulse frequency of 10-50 Hz, a stirring speed of 100-2000 rpm, a vortex shear speed of 500-2000 s -1 , a stirring time of 0.5-3 h, and a gas type of compressive inert gas;

[0056] The gradient temperature evaporation is coupled with three gradient stages, respectively, fluidized shear dispersion stage (25-110℃), interface stabilization stage (110-135℃) and polymerization concentration stage (135-155℃); in the high solid content and high fidelity nitride whisker mean dispersion liquid, the solid content of the whisker in the solution is increased from 5-10wt% to 20-50wt%, and the length-diameter ratio of the whisker is reduced by less than 5%.

[0057] In step (2), the freezing mold is composed of or combined with super-high or super-low thermal conductivity materials; the super-high thermal conductivity materials include one of copper plate, aluminum plate, aluminum nitride plate, etc., and the super-low thermal conductivity materials include one of polytetrafluoroethylene, polycarbonate plate, polyvinyl chloride plate, heat insulation cotton, etc.; the shape can be made according to the requirements of the composite materials, including tetrahedron, cylinder, cone, variable-structure geometric body, etc.

[0058] The freezing temperature is -196℃ to -40℃, and the freezing time is 5-60s; the freeze-drying is under the conditions of vacuum and low temperature (-10 to -50℃) for 24-48h.

[0059] In step (3), the low-temperature pre-oxidation is calcined at 100-300℃ for 0.5-5h in air atmosphere; the high-temperature carbonization is calcined at 600-1000℃ for 1-5h in inert atmosphere, and the inert gas is argon or nitrogen; the multi-level structure nitride whisker / organic carbon composite framework has a porosity of more than 99%, a micron-level directional or random pore channel and a nano-pore channel wall structure composed of whiskers.

[0060] In step (4), the nano-scale nitride particles are spherical particles including one or more of aluminum nitride, boron nitride, silicon nitride, gallium nitride, titanium nitride, etc., with a particle size of 50-500nm; the sintering aid includes one or more of yttrium oxide, calcium oxide, dysprosium oxide, boron oxide, calcium fluoride, titanium oxide, aluminum oxide, lithium oxide; the liquid phase interface engineering strategy is to change the surface charge density of the nanoparticles by introducing a mediator substance, to enhance the double electric layer repulsion and to inhibit the agglomeration of nanoparticles caused by van der Waals force; the mediator substance is a strong acid or a strong base solvent, wherein the strong acid solvent includes one of concentrated nitric acid, concentrated hydrochloric acid, concentrated sulfuric acid, perchloric acid, hydrobromic acid, hydroiodic acid, etc.; the strong base solvent includes one of ammonia water, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, with the pH value of the solution adjusted to 1-3 or 10-12; the high solid content and low viscosity nitride slurry has a solid content of the nitride particles of 40-70wt%, a sintering aid of 0.5-5wt% of the nitride particles, a ball milling speed of 300-500rad / min, a ball milling time of 0.5-5h, a ball-to-material ratio of (1-5):1, a viscosity of less than 200mpa·s after ball milling, and a Zeta potential absolute value of the slurry of more than 20 without sedimentation for 24h.

[0061] In step (5), the negative pressure suction is vacuum suction, the pressure is -0.06 to -0.1 MPa, the suction time is 1 to 4 hours, and the room temperature drying time after suction is 24 to 48 hours;

[0062] In step (6), the multi-gas flow temperature-swing pressureless sintering process includes a carbon removal stage, in which the polymers in the whisker / polymer framework are removed by passing air at 500 to 1000°C for 1 to 3 hours; a grain growth stage, in which the particles are subjected to explosive grain growth to fill the polymer residual pores, by passing an inert gas (nitrogen or argon) to replace the air, rapidly heating to 1500 to 2000°C for calcination for 0.5 to 1 hour at a heating rate of 50 to 100°C / min and a gas flow rate of 10 to 40 mL / min; and a densification stage, in which the particles and the whiskers are sintered at a coherent interface, by slowly cooling to 1200 to 1400°C for calcination for 1 to 5 hours at a gas flow rate of 50 to 100 mL / min.

[0063] The final nitride ceramic matrix composite has a porosity of less than 5%, an in-plane thermal conductivity of 170 to 280 W / (m·K), an out-of-plane thermal conductivity of 150 to 300 W / (m·K), a bending strength of 300 to 600 MPa, and a fracture toughness of 5 to 15 MPa·m 1 / 2 .

[0064] In the following examples, unless otherwise specified, the raw reagents or processing techniques are conventional commercially available products or conventional processing techniques in the art.

[0065] In the following examples, the pulsed pneumatic vortex field is provided by a Vortex-Genie series SI-P256 laboratory vortex mixer from Scientific Industries, USA. The fluidized shear dispersion is achieved by a MagicLAB multifunctional emulsifying disperser from IKA, Germany.

[0066] The aluminum nitride whiskers are prepared by a gas deposition method. Specifically, aluminum particles (Beijing Zhongke Yannuo New Material Technology Co., Ltd., 99%, 1 cm*1 cm), anhydrous aluminum chloride powder (Macklin, AR 99%), ammonium chloride powder (Macklin, 99.99%), and iron powder (Beijing Zhongke Yannuo New Material Technology Co., Ltd., 99%, 80 mesh) with a mass ratio of 6:3:4:10 are uniformly mixed in a corundum crucible, and then the temperature is raised to 1100°C under a high-purity argon (99.99%) atmosphere for 1 hour. Subsequently, the temperature is raised to 1650°C for half an hour, during which the argon is replaced with high-purity nitrogen (99.99%), and then the temperature is maintained for 5 hours to obtain crude aluminum nitride nanofibers. After alcohol ultrasonic treatment and drying, the aluminum nitride nanofibers are obtained.

[0067] Polyacrylonitrile is a product of Aladdin Company, Mw 85000 type.

[0068] Polyimide is a product of Aladdin Company, 500-800 mesh type.

[0069] Example 1:

[0070] A kind of aluminum nitride whisker reinforced aluminum nitride ceramic matrix composite, its preparation method includes the following steps:

[0071] S1: 2wt% of polyacrylonitrile (Mw=150000) is dissolved in N,N-dimethylformamide solution, and magnetic stirring is obtained for 12h to obtain a polyacrylonitrile polymer solution. 5wt% of aluminum nitride whisker with an average diameter of 120.5nm and an average aspect ratio of 4000 is added to the polyacrylonitrile polymer solution, argon is introduced, and the vortex shear rate is 1000s -1 , stirring speed 1000rpm, room temperature dispersion for 1h, aluminum nitride whisker is initially uniformly dispersed. To improve the whisker solid content and dispersion liquid stability, 3000rpm, auxiliary heating to 80℃ fluidized shear dispersion for 1h, then the temperature is increased to 120℃ and kept for 0.5h to improve the whisker interface stability, finally the temperature is increased to 135℃ to make the organic solvent continuously evaporate and concentrate for 1h, finally the solid content of the aluminum nitride whisker homogeneous dispersion liquid is 40wt%, and the aspect ratio of the whisker is reduced by 1%;

[0072] S2: the aluminum nitride whisker homogeneous dispersion liquid is poured into a freezing mold (the bottom plate is a copper plate, and the periphery is polytetrafluoroethylene), and placed in an ultra-low temperature refrigerator (-50℃) for 30s, then moved to a freeze dryer at -40℃, vacuumized to -0.1Pa, and vacuum dried for 48h to obtain a non-crosslinked three-dimensional aluminum nitride whisker / polymer framework;

[0073] S3: the whisker / polymer framework is placed in a muffle furnace, pre-oxidized at 220℃ for 2h in an air atmosphere, then moved to a tube furnace, and carbonized at 800℃ for 5h in an argon atmosphere to obtain an aluminum nitride whisker / organic carbon framework with vertically oriented microporous channels and submicron whisker fiber walls, as shown in Figure 1 , the porosity of the framework is 99.6%;

[0074] S4: after adjusting the pH value of the deionized water solution to 2.3 with concentrated nitric acid to obtain an acidic solution, the aluminum nitride spherical powder with an average particle size of 50nm (final concentration 50wt%) and yttria powder (final concentration 3wt%) are mixed and added to the acidic solution in batches, and the mixed solution is continuously stirred by magnetic force during the process. After the aluminum nitride powder is completely added, it is moved to a ball mill jar, 2 times the mass of zirconia ball milling beads of the aluminum nitride powder is added, and ball milling is carried out at a speed of 500rad / min for 4h to obtain an aluminum nitride slurry with a viscosity of 105mpa·s.

[0075] S5: 5 mL of high solid and low viscosity aluminum nitride slurry was infiltrated into 1 g of aluminum nitride whisker / organic carbon frame by negative pressure suction, the suction pressure was-0.1 MPa, the suction time was 4 h, and the frame type aluminum nitride whisker reinforced aluminum nitride ceramic composite blank was obtained after room temperature drying for 24 h;

[0076] S6: The dried composite blank was placed in a plasma sintering furnace, first in an air atmosphere, the temperature was increased to 1000℃, carbon was removed for 2 h, the heating rate was 2℃ / min, and the gas flow was 200 mL / min; then vacuum was drawn, nitrogen was introduced, the temperature was increased to 1700℃ at a rate of 100℃ / min, and the temperature was kept for 1 h, the gas flow was 40 mL / min; the temperature was decreased to 1400℃ at a rate of 1℃ / min, and the densification was performed for 3 h, the gas flow was 100 mL / min.

[0077] Finally, an aluminum nitride whisker reinforced aluminum nitride ceramic matrix composite was obtained, as shown in Figure 2 The frame type whisker reinforced phase formed a three-dimensional fully interpenetrated heat conducting network, the porosity of the composite was 3.5% (Archimedes method, GB / T 25995-2010, Test method for density and apparent porosity of fine ceramics, the same as the test method of the following examples), the in-plane thermal conductivity was 170 W / (m·K), and the thermal conductivity in the direction was 240 W / (m·K) (flash method, GB / T 39862-2021, Detection of thermal conductivity of high thermal conductivity ceramics, the same as the test method of the following examples), in addition, as shown in Figure 3 The bridging and crack deflection of the whiskers changed the brittle fracture of the composite to ductile fracture, the fracture strength was 450 MPa (three-point bending method, GB / T 6569-2006, Test method for bending strength of fine ceramics, the same as the test method of the following examples), and the fracture toughness was improved to 5.1 MPa·m 1 / 2 (single-edge notched beam method, GB / T 23806-2009, Test method for fracture toughness of fine ceramics-single edge pre-cracked beam method, the same as the test method of the following examples).

[0078] Example 2:

[0079] A silicon nitride whisker reinforced silicon nitride ceramic matrix composite, the preparation method comprising the following steps:

[0080] S1: 5wt% of polyimide was dissolved in N,N-dimethylacetamide solution, and magnetic stirring was performed for 8 h to obtain a polyimide polymer solution. 5wt% of silicon nitride whiskers with an average diameter of 80 nm and an average aspect ratio of 5000 were added to the polyimide polymer solution, argon was introduced, and the vortex shear rate was 2000 s -1, stirring speed 2000 rpm, dispersion at room temperature for 2 h, and the silicon nitride whiskers were initially uniformly dispersed. Subsequently, the silicon nitride whiskers were dispersed at 3000 rpm, and fluidized shear dispersion was performed at an auxiliary temperature of 80 °C for 1 h. Then, the temperature was increased to 120 °C and kept constant for 0.5 h to improve the interface stability of the whiskers. Finally, the temperature was increased to 150 °C, and the organic solvent was continuously evaporated and concentrated for 1 h. Finally, a silicon nitride whisker homogeneous dispersion liquid with a solid content of 48 wt% was obtained, in which the aspect ratio of the whiskers was reduced by 0.8%.

[0081] S2: The silicon nitride whisker homogeneous dispersion liquid was poured into a freezing mold (the bottom plate and the surrounding copper plate), placed in liquid nitrogen (-196 °C) for 10 s, and then moved to a freeze dryer at -40 °C. Vacuum drying was performed for 48 h by vacuumizing to -0.1 Pa, and an uncrosslinked three-dimensional silicon nitride whisker / polymer framework was obtained.

[0082] S3: The whisker / polymer framework was placed in a muffle furnace and pre-oxidized at 300 °C for 1 h in an air atmosphere. Then, the framework was moved to a tube furnace and carbonized at 900 °C for 3 h in an argon atmosphere. A silicon nitride whisker / organic carbon framework with random channels was obtained, and the porosity of the framework was 99.7%.

[0083] S4: An alkaline solution was obtained by adjusting the pH value of a deionized water solution to 10.7 with ammonia water. Silicon nitride spherical powder with an average particle size of 100 nm (final concentration 50 wt%) and yttrium oxide (final concentration 1.5 wt%) and cerium oxide powder (final concentration 1.5 wt%) were mixed and added to the alkaline solution in batches. The mixed solution was continuously stirred by magnetic stirring during the process. After the silicon nitride powder was completely added, the solution was moved to a ball mill tank, 1.5 times the mass of the mixed solution of zirconium oxide milling beads was added, and ball milling was performed at a speed of 500 rad / min for 6 h. A silicon nitride slurry with a viscosity of 94 mpa·s was obtained.

[0084] S5: 2 mL of the high-solid and low-viscosity silicon nitride slurry was infiltrated into 0.8 g of the silicon nitride whisker / organic carbon framework by negative pressure suction. The suction pressure was -0.1 MPa, and the suction time was 4 h. After suction, the framework was dried at room temperature for 24 h, and a framework-type silicon nitride whisker-reinforced silicon nitride ceramic matrix composite green body was obtained.

[0085] S6: The dried composite green body was placed in a plasma sintering furnace. First, the temperature was increased to 1000 °C in an air atmosphere, and carbon was removed for 2 h at a heating rate of 2 °C / min and a gas flow rate of 200 mL / min. Then, the furnace was evacuated to a vacuum state, nitrogen was introduced, the temperature was increased to 1500 °C at a rate of 100 °C / min, and the temperature was kept constant for 1 h at a gas flow rate of 40 mL / min. The temperature was decreased to 1200 °C at a rate of 1 °C / min, and densification was performed for 3 h at a gas flow rate of 100 mL / min.

[0086] The silicon nitride whisker reinforced silicon nitride ceramic matrix composite material is finally obtained, the frame type whisker reinforced phase forms a three-dimensional full interpenetrating heat conducting network, the porosity of the composite material is 4.2%, the in-plane thermal conductivity is 190 W / (m·K), the normal phase thermal conductivity is 185 W / (m·K), the fracture strength is 380 MPa, and the fracture toughness is increased to 6.3 MPa·m 1 / 2 .

[0087] Example 3

[0088] An aluminum nitride whisker reinforced silicon nitride ceramic matrix composite material, a preparation method thereof comprises the following steps:

[0089] S1: 5wt% of polyimide is dissolved in an N,N-dimethylacetamide solution, and magnetic stirring is carried out for 8h to obtain a polyimide polymer solution. 5wt% of aluminum nitride whiskers with an average diameter of 120.5nm and an average aspect ratio of 4000 are added to the polyacrylonitrile polymer solution, argon is introduced, and pulse frequency is 50Hz, vortex shear rate is 1000s -1 , stirring speed is 1000rpm, and the aluminum nitride whiskers are uniformly dispersed at room temperature for 1h. Subsequently, the temperature is increased to 80℃ and sheared and dispersed for 1h at 3000rpm to assist the temperature increase, then the temperature is increased to 120℃ and kept constant for 0.5h to improve the interface stability of the whiskers, and finally the temperature is increased to 150℃, and the organic solvent is continuously evaporated and concentrated for 1h to obtain a silicon nitride whisker homogeneous dispersion liquid with a solid content of 48wt%, wherein the aspect ratio of the whiskers is reduced by 0.8%;

[0090] S2: The aluminum nitride whisker homogeneous dispersion liquid is poured into a freezing mold (the bottom plate is a copper plate, and the periphery is polytetrafluoroethylene), and is placed in an ultra-low temperature refrigerator (-50℃) for rapid freezing for 30s, then is moved to a freeze dryer at -40℃, is vacuumized to -0.1Pa, and is vacuum dried for 48h to obtain a three-dimensional aluminum nitride whisker / polymer frame which is not crosslinked;

[0091] S3: The whisker / polymer frame is placed in a muffle furnace, is pre-oxidized at 220℃ for 2h in an air atmosphere, is then moved to a tube furnace, and is carbonized at 800℃ for 5h in an argon atmosphere to obtain an aluminum nitride whisker / organic carbon frame with vertically oriented microporous channels and submicron whisker fiber walls, and the porosity of the frame is 99.6%;

[0092] S4: After adjusting the pH value of the deionized water solution to 10.7 with ammonia water to obtain an alkaline solution, the silicon nitride spherical powder with an average particle size of 100 nm (final concentration 50 wt%) and yttrium oxide (final concentration 1.5 wt%) and cerium oxide powder (final concentration 1.5 wt%) were mixed and added into the alkaline solution in batches. The mixed solution was continuously stirred by magnetic force during the process. After the silicon nitride powder was completely added, it was moved to a ball mill tank, 1.5 times the mass of the mixed solution of zirconium oxide milling beads was added, and it was ball milled at a speed of 500 rad / min for 6 h to obtain a silicon nitride slurry with a viscosity of 94 mpa·s;

[0093] S5: 3 mL of high-solid and low-viscosity silicon nitride slurry was infiltrated into 1 g of aluminum nitride whisker / organic carbon frame by negative pressure suction. The suction pressure was -0.1 MPa, the suction time was 5 h, and the frame type aluminum nitride whisker reinforced silicon nitride ceramic matrix composite blank was obtained after drying at room temperature for 48 h.

[0094] S6: The dried composite blank was placed in a plasma sintering furnace. First, in an air atmosphere, the temperature was increased to 1000℃, the carbon was removed for 2 h at a heating rate of 2℃ / min and a gas flow rate of 200 mL / min. Then, it was pumped to a vacuum state and nitrogen was introduced. The temperature was increased to 1600℃ at a rate of 100℃ / min and held for 1 h at a gas flow rate of 40 mL / min. The temperature was decreased to 1400℃ at a rate of 1℃ / min and densified for 5 h at a gas flow rate of 100 mL / min.

[0095] Finally, an aluminum nitride whisker reinforced silicon nitride ceramic matrix composite material was obtained. The porosity of the composite material was 2.1%, the in-plane thermal conductivity was 205 W / (m·K), the out-of-plane thermal conductivity was 221 W / (m·K), the fracture strength was 410 MPa, and the fracture toughness was increased to 5.8 MPa·m 1 / 2 .

[0096] Comparative Example 1:

[0097] A traditional aluminum nitride whisker reinforced aluminum nitride ceramic matrix composite material, the preparation method comprising the following steps:

[0098] S1: After adjusting the pH value of the deionized water solution to 2.3 with concentrated nitric acid, 40 wt% of aluminum nitride whiskers (average diameter 120.5 nm, average aspect ratio 4000) and 50 wt% of aluminum nitride spherical powder (average particle size 120.5 nm) and 3 wt% of yttrium oxide powder were mixed and added into the acidic solution in batches. After the aluminum nitride mixture was completely added, it was moved to a ball mill tank, 2 times the mass of the aluminum nitride powder of zirconium oxide milling beads was added, and it was ball milled at a speed of 500 rad / min for 4 h to obtain an aluminum nitride whisker / particle mixed slurry with a viscosity of 500 mpa·s;

[0099] S2: Pour the aluminum nitride whisker / particle mixture into a square mold and dry at room temperature for 24 hours to obtain a conventional aluminum nitride whisker-reinforced aluminum nitride ceramic matrix composite preform;

[0100] S3: The dried composite material preform is placed in a plasma sintering furnace. First, under an air atmosphere, the temperature is raised to 1000℃ for 2 hours to remove carbon, with a heating rate of 2℃ / min and a gas flow rate of 200mL / min. Then, the furnace is evacuated to a vacuum state, nitrogen is introduced, and the temperature is raised to 1700℃ at 100℃ / min and held for 1 hour at a gas flow rate of 40mL / min. Finally, the temperature is lowered to 1400℃ at 1℃ / min for densification for 3 hours at a gas flow rate of 100mL / min.

[0101] like Figure 4 As shown, the final product is a traditional aluminum nitride whisker-reinforced aluminum nitride ceramic matrix composite. In the composite prepared by ball milling, the aspect ratio of the whiskers is severely damaged and sintered with the powder to form large particles. The composite has a porosity of 10.3%, an in-plane thermal conductivity of 80 W / (m·K), and a normal phase thermal conductivity of 85 W / (m·K), which is less than half of the thermal conductivity of the frame-type aluminum nitride whisker-reinforced aluminum nitride ceramic matrix composite prepared in Example 1 of this invention. Furthermore, as... Figure 5 As shown, the whiskers did not exhibit bridging or crack deflection due to fracture; the composite material exhibited brittle fracture with a fracture strength of 325 MPa and a fracture toughness of 2.1 MPa·m. 1 / 2 The strength and thermal conductivity are significantly lower than those in Embodiment 1 of this invention. Therefore, it can be seen that the nitride whisker-reinforced nitride ceramic matrix composite material and its preparation method provided by this invention significantly improve the mechanical strength and thermal conductivity of the nitride ceramic matrix composite material.

[0102] Comparative Example 2

[0103] An aluminum nitride whisker-reinforced aluminum nitride ceramic matrix composite material, the preparation method of which differs from that of Example 1 only in that:

[0104] In step S4, an equal mass of deionized water is used to replace the acidic solution.

[0105] The rest is the same as in Example 1.

[0106] like Figure 6 As shown, the final aluminum nitride whisker-reinforced aluminum nitride ceramic matrix composite material was obtained. However, it lacked a mediating agent to regulate the surface charge density of the aluminum nitride particles, resulting in severe agglomeration and an inability to achieve uniform distribution within the aluminum nitride whisker / organic carbon framework. The composite material exhibited a porosity of 15%, an in-plane thermal conductivity of 75 W / (m·K), a normal phase thermal conductivity of 70 W / (m·K), a fracture strength of 200 MPa, and a fracture toughness of 3.4 MPa·m. 1 / 2, which is much lower than the thermal conductivity and mechanical properties of the framework aluminum nitride whisker reinforced aluminum nitride ceramic matrix composite prepared in the embodiment 1 of the present application. It can be seen that the nitride whisker reinforced nitride ceramic matrix composite and the preparation method thereof provided by the present application greatly improve the mechanical strength and thermal conductivity of the nitride ceramic matrix composite.

[0107] Comparative example 3:

[0108] An aluminum nitride whisker reinforced aluminum nitride ceramic matrix composite, the preparation method of which is only different from that of the embodiment 1 in that:

[0109] In step S6, the dried composite body is placed in a plasma sintering furnace, first in an air atmosphere, the temperature is raised to 1000℃, carbon is removed for 2h, the heating rate is 2℃ / min, and the gas flow is 200mL / min; then it is pumped to a vacuum state, nitrogen is introduced, the temperature is raised to 1700℃ at a rate of 100℃ / min, and the temperature is kept for 4h, and the gas flow is 40mL / min.

[0110] The rest is the same as the embodiment 1.

[0111] Finally, an aluminum nitride whisker reinforced aluminum nitride ceramic matrix composite is obtained, the high-temperature long-time calcination causes the grain to grow and the adjacent grains to fuse, the porosity of the composite is 1.5%, the in-plane thermal conductivity is 203W / (m·K), the normal phase thermal conductivity is 201W / (m·K), the fracture strength is 390Mpa, and the fracture toughness is 0.4MPa·m 1 / 2 Although the thermal conductivity and fracture strength of the framework aluminum nitride whisker reinforced aluminum nitride ceramic matrix composite prepared in the embodiment 1 of the present application are maintained, the fracture toughness is greatly reduced and shows brittle fracture, which is easy to cause devastating damage.

[0112] Comparative example 4:

[0113] An aluminum nitride whisker reinforced aluminum nitride ceramic matrix composite, the preparation method of which is only different from that of the embodiment 1 in that:

[0114] In step S6, the dried composite body is placed in a plasma sintering furnace, first in an air atmosphere, the temperature is raised to 1000℃, carbon is removed for 2h, the heating rate is 2℃ / min, and the gas flow is 200mL / min; then it is pumped to a vacuum state, nitrogen is introduced, the temperature is raised to 1700℃ at a rate of 100℃ / min, and the temperature is kept for 4h, and the gas flow is 40mL / min.

[0115] The rest is the same as the embodiment 1.

[0116] The finally obtained aluminum nitride whisker reinforced aluminum nitride ceramic matrix composite material has a porosity of 7.5%, an in-plane thermal conductivity of 105 W / (m·K), a normal plane thermal conductivity of 112 W / (m·K), a fracture strength of 190 MPa, and a fracture toughness of 5.5 MPa·m 1 / 2 , which is far lower than the thermal conductivity and fracture strength of the frame type aluminum nitride whisker reinforced aluminum nitride ceramic matrix composite material prepared in Embodiment 1.

[0117] The above description of the embodiments is for the purpose of facilitating the understanding and use of the present application by those of ordinary skill in the art. Those skilled in the art can obviously make various modifications to the embodiments and apply the general principles described herein to other embodiments without having to make creative efforts. Therefore, the present application is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present application without departing from the scope of the present application should be within the protection scope of the present application.

Claims

1. A method for preparing a framework-type nitride ceramic whisker-reinforced nitride ceramic matrix composite material, characterized in that, Includes the following steps: 1) Nitride whiskers are dispersed in a polymer solution based on a pulsed aerodynamic vortex field, and then nitride whisker dispersion is obtained by gradient heating and evaporation coupling. 2) The nitride whisker dispersion was subjected to ultra-low temperature instantaneous solidification, freeze drying, pre-oxidation, and carbonization to obtain a nitride whisker / organic carbon composite framework; 3) Nitride slurry is filled into nitride whiskers / organic carbon framework by negative pressure suction, and then subjected to multi-flow temperature-variable pressureless sintering to obtain framework-type nitride whisker-reinforced nitride ceramic matrix composite material. The method for preparing the nitride slurry includes: adding nano-sized nitride particles and sintering aids to an aqueous solution and ball milling to obtain the nitride slurry.

2. The method for preparing the framework-type nitride ceramic whisker-reinforced nitride ceramic matrix composite material according to claim 1, characterized in that, In step 1), the pulsed aerodynamic vortex field has a pulse frequency of 10–50 Hz and an vortex shear rate of 500–2000 s⁻¹. -1 The stirring speed is 100-2000 rpm, the stirring time is 0.5-3 h, and the dispersion atmosphere is inert gas.

3. The method for preparing the framework-type nitride ceramic whisker-reinforced nitride ceramic matrix composite material according to claim 1, characterized in that, In step 1), the nitride whiskers are selected from at least one of aluminum nitride, boron nitride, silicon nitride, gallium nitride, or titanium nitride, and the average diameter of the whiskers is 30-300 nm, with an aspect ratio >1000. In the polymer solution, the polymer is selected from polyacrylonitrile, polyimide, phenolic resin or arylaceyne polymer, and the concentration is 0.1-5 wt%. The solvent is selected from at least one of methanol, ethanol, dimethyl diamide, dimethyl sulfoxide, sulfolane, ethyl nitrate, tetrahydrofuran, acetone, chloroform or toluene. The mass ratio of the nitride whiskers to the polymer is (2-5):

5.

4. The method for preparing the framework-type nitride ceramic whisker-reinforced nitride ceramic matrix composite material according to claim 1, characterized in that, In step 1), the gradient temperature rise evaporation coupling includes: first, fluidized shear dispersion at 25-110℃ for 1-2 hours, then standing at 110-135℃ for 0.5-1 hours, and then evaporation concentration at 135-155℃.

5. The method for preparing the framework-type nitride ceramic whisker-reinforced nitride ceramic matrix composite material according to claim 1, characterized in that, In step 2), the temperature during the ultra-low temperature instantaneous curing is -196℃ to -40℃, and the curing time is 5 to 60 seconds. In the freeze-drying process, the drying temperature is -10℃ to -50℃, and the curing time is 24 to 48 hours. In the pre-oxidation process, the pre-oxidation atmosphere is air, the pre-oxidation temperature is 100–300°C, and the pre-oxidation time is 0.5–5 hours. During the carbonization process, the carbonization atmosphere is an inert gas, the carbonization temperature is 600–1000℃, and the carbonization time is 1–5 hours.

6. The method for preparing the framework-type nitride ceramic whisker-reinforced nitride ceramic matrix composite material according to claim 1, characterized in that, In step 3), the feed ratio of the nitride slurry to the nitride whiskers / organic carbon framework is (1-10) mL:(0.5-1) g.

7. The method for preparing the framework-type nitride ceramic whisker-reinforced nitride ceramic matrix composite material according to claim 1, characterized in that, In step 3), the suction pressure is -0.06MPa to -0.1MPa and the suction time is 1 to 4 hours.

8. The method for preparing the framework-type nitride ceramic whisker-reinforced nitride ceramic matrix composite material according to claim 1, characterized in that, In step 3), the multi-flow variable temperature pressureless sintering includes: First, calcine at 500–1000℃ for 1–3 hours in air; then calcine at 1500–2000℃ for 0.5–1 hour in an inert gas atmosphere; and finally calcine at 1200–1400℃ for 1–5 hours.

9. The method for preparing the framework-type nitride ceramic whisker-reinforced nitride ceramic matrix composite material according to claim 1, characterized in that, The nanoscale nitride particles are selected from at least one of aluminum nitride, boron nitride, silicon nitride, gallium nitride, or titanium nitride, with an average particle size of 50–500 nm. The sintering aid is selected from at least one of yttrium oxide, calcium oxide, dysprosium oxide, boron oxide, calcium fluoride, titanium oxide, aluminum oxide or lithium oxide, and the amount used is 0.5 to 5 wt% of the amount of nano-sized nitride particles. The pH of the aqueous solution is 1-3 or 10-12.

10. The method for preparing the framework-type nitride ceramic whisker-reinforced nitride ceramic matrix composite material according to claim 1, characterized in that, In the ball mill, the ball milling speed is 300-500 rad / min, the ball milling time is 0.5-5 h, and the ball-to-material ratio is (1-5):1; The nitride slurry contains 40–70 wt% nitride particles with a viscosity of <200 mPa·s.

Images