CN109627029B - Preparation method of high-thermal-conductivity CNTs (carbon nanotubes) oriented modified ceramic matrix composite - Google Patents
Preparation method of high-thermal-conductivity CNTs (carbon nanotubes) oriented modified ceramic matrix composite Download PDFInfo
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Abstract
The invention relates to a preparation method of a high-thermal-conductivity CNTs oriented modified ceramic matrix composite, which comprises the steps of preparing an interface layer and a matrix of a prefabricated body in a high-temperature furnace to enable the relative density of the prefabricated body to reach 30-70%; preparing a directional hole in the thickness direction of the ceramic matrix composite by using ultrashort pulse laser; preparing a CNTs solution by utilizing ultrasonic dispersion, and sealing and filling the CNTs solution by combining a vacuum impregnation method to form a CNTs oriented column; and further compacting the prefabricated body by using a CVI method to finally obtain the high-thermal-conductivity CNTs oriented modified ceramic matrix composite. The process has the advantages that: (1) the CNTs oriented column structure with high heat conductivity greatly improves the heat conductivity of the composite material in the thickness direction; (2) the CNTs interlayer dispersion structure and the CNTs directional columns form a strong heat conduction network, so that the overall heat conductivity of the composite material is improved; (3) the directional holes have designability, can design size, interval and distribution according to engineering requirements, and are simple to operate.
Description
Technical Field
The invention belongs to a preparation method of a ceramic matrix composite, and relates to a preparation method of a high-thermal-conductivity CNTs oriented modified ceramic matrix composite. Specifically, an oriented hole is designed and processed in the thickness direction of a preform by combining ultrashort pulse laser, a CNTs solution vacuum impregnation process is adopted to modify the ceramic matrix composite, a CNTs oriented packing column and a CNTs interlayer dispersion structure are formed inside the ceramic matrix composite, and a CNTs heat conduction network is finally constructed, so that the prepared modified ceramic matrix composite has excellent compactness and heat conductivity, the relative density is improved by 10-33%, and the heat conductivity is improved by 10-40 times.
Background
The ceramic matrix composite is a thermal structure/function integrated material integrating the properties of metal materials, ceramic materials and fiber materials, and is widely applied to the fields of aviation and aerospace engine hot end parts, aerospace craft thermal protection systems, deep space exploration ultra-light structures and the like. The development of a new generation of hypersonic aircraft has taken ceramic matrix composite materials as the first choice of heat-proof structural materials for design, and the ceramic matrix composite materials are mainly used for key thermal structures of the aircraft. When the flying speed of the aircraft reaches above 5Ma, the pneumatic heating of the aircraft can generate high temperature above 2000 ℃ and high thermal gradient. Because the thermal conductivity of the ceramic matrix composite material is only 10W/m.K, the thermal loads are easily concentrated on the tip part of the heat-proof structure, so that the ultrahigh temperature thermal ablation is caused, and the heat-proof material is caused to lose efficacy too quickly. Therefore, the high-thermal-conductivity ceramic matrix composite is continuously developed in the field, and the local overhigh heat load is quickly transferred to a low-temperature area by improving the thermal conductivity of the heat-proof structure material, so that the damage of the ultrahigh-temperature ablation to the local structure is reduced, the heat-proof effect is improved, and the service life is prolonged.
At present, commercial high-thermal conductivity mesophase pitch fibers developed and developed by Amoco company in the United states and Mitsubishi Chemical company in Japan run at the frontier of the world, the high thermal conductivity is derived from a highly preferred orientation structure of microcrystals along the axial direction of the fibers, but key raw materials of the mesophase pitch-based carbon fibers and mesophase pitch belong to strategic materials and are blocked for the technology of China. Therefore, the modification of ceramic matrix composites with highly thermally conductive materials is becoming the mainstream direction. The Gong MQ and the like permeate CNTs into single-layer carbon fiber cloth by using slurry impregnation, and then each layer of the carbon fiber cloth is laminated and pressed to prepare the CNTs-carbon fiber multi-scale preform, but the CNTs are not uniformly dispersed in the whole. Bekyarova and the like in the composite material center of the university of Delaware in the United states utilize electrophoretic deposition to prepare a multi-scale preform with CNTs uniformly dispersed on the surface of carbon fibers, and the process can realize the engineering scale production of the multi-scale preform, but the CNTs and the carbon fibers are only simply physically attached and are easy to fall off. In 2009, the rough layer pyrolytic carbon generated by Chen et al in Materials Chemistry and Physics by using in-situ growth CNTs induction leads to the great improvement of the heat-conducting property of the C/C composite material, but is not suitable for mass production.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides a preparation method of a high-thermal-conductivity CNTs oriented modified ceramic matrix composite, solves the technical problem of poor thermal conductivity of the ceramic matrix composite, provides the high-thermal-conductivity CNTs oriented modified ceramic matrix composite capable of realizing engineering application and mass production and the preparation method thereof, and obviously improves the thermal conductivity of the ceramic matrix composite.
Technical scheme
A preparation method of a high-thermal-conductivity CNTs oriented modified ceramic matrix composite is characterized by comprising the following steps:
step 1, preparing a ceramic matrix composite material preform: after the fibers are sequentially laminated and sewn in a two-dimensional mode, a fiber preform with the volume fraction of about 25-35% is obtained; placing the fiber prefabricated part in a high-temperature vacuum furnace, depositing at 850-1000 ℃, at the atmosphere pressure of 0.2KPa, at the propylene flow rate of 30ml/min and at the Ar flow rate of 300ml/min, depositing for 50-60 h, and cooling to prepare a composite material interface;
then placing the fiber prefabricated part in a high-temperature vacuum furnace, depositing at 1000-1100 ℃, and keeping the atmosphere pressure at 2KPa, H2With MTS flow of 200ml/min, Ar flow of 300ml/min, H2The mol mass ratio of the powder to MTS is 10:1, and the density formed after deposition for 200-230 h and temperature reduction is 1.4-2.0 g/cm3The composite preform of (1);
step 2: processing a plurality of micro directional holes with the aperture of 0.2-1 mm on the composite material by adopting ultrashort pulse laser equipment with the wavelength of 400-1500 nm, the pulse width of 80-500 fs and the power of 5-20W;
and step 3: performing ultrasonic dispersion on 0.1-1.0% of CNTs, 1.0-2.5% of deionized water solvent, 0.7-2.5% of pH value regulator, anionic surfactant and 95-98% of dispersant by weight percent to prepare a CNTs solution;
the pH value regulator and the anionic surfactant are tetramethylammonium hydroxide;
the dispersant is triton X-100;
and 4, step 4: soaking the whole prefabricated body to be soaked in the CNTs solution by adopting a vacuum soaking method, pressurizing, drying, repeatedly soaking until the oriented holes are sealed and filled by the CNTs until the light-tight oriented columns are formed in the tiny oriented holes;
and 5: further densifying the modified composite material by adopting a chemical vapor infiltration method, placing the prefabricated body in a high-temperature vacuum furnace, depositing at 1000-1100 ℃, and keeping the atmosphere pressure at 2KPa and H2Flow 200ml/min, Ar flow 300ml/min, H2The mol mass ratio of the carbon nano tubes to MTS is 10:1, and the carbon nano tubes are deposited for 100-120 h and cooled to finally prepare the high-thermal-conductivity CNTs oriented modified ceramic matrix composite material, wherein the relative density reaches 85-95%.
The fiber is as follows: carbon fibers, silicon carbide fibers, boron fibers, oxide fibers, or other high temperature ceramic fibers.
The whisker is: ceramic whiskers, oxide whiskers, or boride whiskers.
The preform woven structure is: 2-dimensional, 2.5-dimensional, 3-dimensional, or other dimensional preforms.
The preparation method of the preform comprises the following steps: lamination, knitting, needling, or other fabrication methods.
The shape of the micro directional hole is as follows: round holes, square holes, and micro holes of other shapes.
The arrangement of the micro directional holes is as follows: equidistant, non-equidistant, ordered, disordered, widely spaced, or closely spaced.
Advantageous effects
The invention provides a preparation method of a high-thermal-conductivity CNTs oriented modified ceramic matrix composite, which comprises the steps of preparing an interface layer and a matrix of a prefabricated body in a high-temperature furnace to enable the relative density of the prefabricated body to reach 30-70%; preparing a directional hole in the thickness direction of the ceramic matrix composite by using ultrashort pulse laser; preparing a CNTs solution by utilizing ultrasonic dispersion, and sealing and filling the CNTs solution by combining a vacuum impregnation method to form a CNTs oriented column; and further compacting the prefabricated body by using a CVI method to finally obtain the high-thermal-conductivity CNTs oriented modified ceramic matrix composite. The process has the advantages that: (1) the CNTs oriented column structure with high heat conductivity greatly improves the heat conductivity of the composite material in the thickness direction; (2) the CNTs interlayer dispersion structure and the CNTs directional columns form a strong heat conduction network, so that the overall heat conductivity of the composite material is improved; (3) the directional holes have designability, can design size, interval and distribution according to engineering requirements, and are simple to operate.
The invention has the beneficial effects that: from the composite law of thermal conductivity of two composites, it can be speculated that: the thermal conductivity of the composite increases with increasing CNTs content. The CNTs column is formed in the thickness direction of the ceramic matrix composite, so that the introduction amount of the CNTs can be remarkably increased, the section of the oriented column is compact, and the packed CNTs and the composite realize crack-free combination, as shown in figure 2. The CNTs heat-conducting network formed between and within the ceramic matrix composite layers, as shown in FIG. 3, enables the heat-conducting network of the composite material to be formed to the maximum extent to achieve effective heat conduction, and obtains the high heat-conducting composite material.
Compared with the ceramic matrix composite prepared by the prior art, the relative density of the composite is improved by 10-33%, and the thermal conductivity is improved by 10-40 times, as shown in figure 4. The density is 1.4-2.0 g/cm3The ceramic matrix composite material is prepared by preparing an oriented hole with the diameter of 0.5mm in the thickness direction of a preform by adopting ultrashort pulse laser, and sealing and filling the oriented hole by vacuum impregnation of a CNTs solution to obtain the composite material with the density of 2.2-2.4 g/cm3The heat conductivity is improved by 15-25 times.
Drawings
FIG. 1: preparation process flow of CNTs (carbon nanotubes) oriented modified ceramic matrix composite
FIG. 2: SEM image of CNTs oriented modified ceramic matrix composite
FIG. 3: CNTs heat conduction layer of modified ceramic matrix composite material
FIG. 4: graph comparing thermal conductivity before and after modification of CNTs
Detailed Description
The invention will now be further described with reference to the following examples and drawings:
the preparation method provided by the invention is the CNTs directional modified ceramic matrix composite. The technical scheme of the method is as follows: preparing a ceramic matrix composite preform by using a laser processing assisted chemical vapor infiltration method, and using CNTs as a directional hole processed in the thickness direction of a second phase-sealed filling preform by using a vacuum impregnation method. The high-thermal-conductivity CNTs directional modified ceramic matrix composite has two characteristics: on one hand, the method forms the periodic CNTs directional packing column in the thickness direction of the ceramic matrix composite material, increases the CNTs introduction amount and improves the heat conductivity; on the other hand, the CNTs are dispersed and infiltrated into the surface of the fiber bundles or fiber filaments of the ceramic matrix composite, and a continuous heat conducting network is formed between the layers of the composite and in the in-layer direction. The specific steps are shown in figure (1):
step 1, preparing a ceramic matrix composite material preform: the fiber preform with the volume fraction of about 25-35% is obtained after 1K carbon fibers are sequentially overlapped and sewn in a two-dimensional mode. And (3) placing the fiber prefabricated part in a high-temperature vacuum furnace, depositing at 850-1000 ℃, under the atmosphere pressure of 0.2KPa, under the propylene flow of 30ml/min and the Ar flow of 300ml/min, depositing for 50-60 h, and cooling to prepare a composite material interface. Then placing the fiber prefabricated part in a high-temperature vacuum furnace, depositing at 1000-1100 ℃, and keeping the atmosphere pressure at 2KPa, H2Flow 200ml/min, Ar flow 300ml/min, H2The mol mass ratio of the powder to MTS is 10:1, and the density formed after deposition for 200-230 h and temperature reduction is 1.4-2.0 g/cm3The composite preform of (1).
The interface layer material may be pyrolytic carbon, boron nitride, or other ceramic interface layer.
The matrix material can be a silicon carbide matrix, a silicon nitride matrix, a boron carbide matrix, a silicon carbon nitride matrix or other ceramic matrixes.
Step 2, preparing the directional hole by ultrashort pulse laser: and preparing directional micro holes in the thickness direction of the composite material preform by using ultrashort pulse laser equipment and adopting the wavelength of 400-1500 nm, the pulse width of 80-500 fs and the power of 5-20W.
Step 3, preparing the CNTs solution: an ultrasonic dispersion emulsifier is adopted, and the solution comprises the following components in percentage by weight: 0.1-1.0% of CNTs, 1.0-2.5% of deionized water solvent, 0.7-2.5% of pH regulator and anionic surfactant and 95-98% of dispersant are ultrasonically dispersed to prepare a CNTs solution; CNTs is used as a solute, deionized water is used as a solvent, tetramethylammonium hydroxide is used as a pH regulator and an anionic surfactant, and Triton X-100 is used as a dispersant to be mixed to prepare a CNTs solution. And (2) dissolving and dispersing the CNTs by using an ultrasonic dispersion emulsifier to prepare a CNTs solution with the weight percentage of 0.1-1 wt.%.
Step 4, filling the directional holes of the prefabricated body with CNTs: and (2) adopting a vacuum impregnation method, manufacturing negative pressure in the impregnation cavity, vacuumizing the CNTs slurry through the negative pressure to remove bubbles, and simultaneously extracting byproduct gas generated after deposition reaction in the prefabricated body in time. And (3) soaking the whole prefabricated body to be soaked in the CNTs soaking liquid all the time, finishing soaking after half an hour, taking out the sample for about 2 hours, basically curing the soaking liquid, drying, and repeatedly circulating for 7-8 times until the oriented column is light-proof. Thus, the CNTs can quickly and smoothly penetrate into the pores in the deep inside of the prefabricated body, and the CNTs are indicated to completely seal the oriented pores.
And 5, further densifying the preform. Placing the prefabricated body in a high-temperature vacuum furnace, depositing at 1000-1100 ℃, and keeping the atmosphere pressure at 2KPa, H2Flow 200ml/min, Ar flow 300ml/min, H2The mol mass ratio of the carbon nano tubes to MTS is 10:1, and the CNTs oriented modified ceramic matrix composite material with high thermal conductivity is finally prepared after deposition for 100-120 h and cooling.
The relative density of the prepared composite material is improved by 10-33%, and the thermal conductivity is improved by 10-40 times.
The specific embodiment is as follows:
example 1:
the modified density of the CNTs is 1.40g/cm3The C/SiC composite material comprises the following specific processes:
(1) the density is 1.40g/cm3The preform of (2): selecting T300-1K carbon fiber to weave two-dimensional plain cloth, superposing 24 layers and sewing to prepare the plain cloth with the volume density of 0.74g/cm3And a carbon fiber preform having a carbon fiber volume fraction of 33.0%. And (3) placing the prefabricated body in a CVI vacuum furnace, wherein the deposition temperature is 900 ℃, the atmosphere pressure is 0.2KPa, the propylene flow is 30ml/min, and the Ar flow is 300ml/min, and preparing a pyrolytic carbon interface layer (PyC) with the pyrolytic thickness of about 200 nm. Placing the prefabricated body in a CVI vacuum furnace, wherein the deposition temperature is 1100 ℃, and the atmosphere pressure is 2KPa, H2The flow rate is 200ml/min, the Ar flow rate is 300ml/min, and the deposition is carried out for 200-230 hNaturally cooling to obtain the product with density of 1.40g/cm3The C/SiC preform of (1).
(2) And preparing micropores by using ultrashort pulse laser. Processing parameters by using ultrashort pulse laser: the wavelength is 800nm, the pulse width is 300fs, the repetition frequency is 100KHz, the line scanning speed is 800 mu m/s, the line spacing is 30 mu m, the laser power is 10W, and directional holes with certain arrangement are prepared in the C/SiC prefabricated body.
(3) Preparing a CNTs solution: CNTs (diameter of 8-15 nm, length of 500 mu m, more than 95 wt.%) is used as a solute, and a solvent (deionized water), a pH regulator, an anionic surfactant (tetramethylammonium hydroxide (C4H13NO, 25 wt.% aqueous solution)) and a dispersant (Triton X-100, purity of more than 99.0%)) are mixed in a ratio of 0.5: 1.5: 1: 97 to prepare the CNTs solution. CNTs were dissolved by an ultrasonic dispersion emulsifier (BILON-1500 type, 300-.
(4) Vacuum impregnation of CNTs solution: the CNTs impregnation liquid is placed below the dried preform, a vacuum pump is used for producing negative pressure in an impregnation cavity, air bubbles in the CNTs solution are removed through negative pressure vacuumizing, and meanwhile, byproduct gas generated after deposition reaction in the preform can be timely pumped out. And (3) soaking the whole prefabricated body to be soaked in the CNTs soaking solution all the time, finishing soaking after half an hour, taking out the sample for about 2 hours, basically curing the soaking solution, drying, repeatedly circulating for 7-8 times, and repeating until the packed directional column is light-tight. Thus, the CNTs can quickly and smoothly penetrate into the pores in the deep inside of the prefabricated body, and the CNTs are indicated to completely seal the oriented pores.
(5) Densifying the preform by a CVI process: placing the prefabricated body in a high-temperature vacuum furnace, depositing at 1000-1100 ℃, and keeping the atmosphere pressure at 2KPa, H2Flow 200ml/min, Ar flow 300ml/min, H2The molar mass ratio of the MTS to the MTS is 10:1, and the sample preparation is completed after deposition for 110 hours and temperature reduction.
(6) The volume density of the CNTs modified C/SiC composite material prepared by the embodiment is 2.35g/cm3The thermal diffusivity of the composite material is detected by using a thermal diffusivity instrument (laser flash method thermal conductivity instrument, LFA 427) according to the ASTM E-1461 standard to obtain the thermal diffusivityThe thermal conductivity of the composite material is up to 150.423 W.m-1·K-1And the improvement is nearly 25 times.
Example 2:
the modified density of the CNTs is 1.80g/cm3The C/SiC composite material comprises the following specific processes:
(1) the density is 1.80g/cm3The preform of (2): selecting T300-1K carbon fiber to weave two-dimensional plain cloth, superposing 24 layers and sewing to prepare the plain cloth with the volume density of 0.74g/cm3And a carbon fiber preform having a carbon fiber volume fraction of 33.0%. And (3) placing the prefabricated body in a CVI vacuum furnace, wherein the deposition temperature is 900 ℃, the atmosphere pressure is 0.2KPa, the propylene flow is 30ml/min, and the Ar flow is 300ml/min, and preparing a pyrolytic carbon interface layer (PyC) with the pyrolytic thickness of about 200 nm. Placing the prefabricated body in a CVI vacuum furnace, wherein the deposition temperature is 1100 ℃, and the atmosphere pressure is 2KPa, H2The flow rate is 200ml/min, the Ar flow rate is 300ml/min, the mixture is naturally cooled after being deposited for 300 to 400 hours, and the density is 1.80g/cm3The C/SiC preform of (1).
(2) And preparing micropores by using ultrashort pulse laser. Processing parameters by using ultrashort pulse laser: the wavelength is 800nm, the pulse width is 300fs, the repetition frequency is 100KHz, the line scanning speed is 800 mu m/s, the line spacing is 30 mu m, the laser power is 10W, and directional holes with certain arrangement are prepared in the C/SiC prefabricated body.
(3) Preparing a CNTs solution: CNTs (diameter of 8-15 nm, length of 500 mu m, more than 95 wt.%) is used as a solute, and a solvent (deionized water), a pH regulator, an anionic surfactant (tetramethylammonium hydroxide (C4H13NO, 25 wt.% aqueous solution)) and a dispersant (Triton X-100, purity of more than 99.0%)) are mixed in a ratio of 0.5: 1.5: 1: 97 to prepare the CNTs solution. CNTs were dissolved by an ultrasonic dispersion emulsifier (BILON-1500 type, 300-.
(4) Vacuum impregnation of CNTs solution: the CNTs impregnation liquid is placed below the dried preform, a vacuum pump is used for producing negative pressure in an impregnation cavity, air bubbles in the CNTs solution are removed through negative pressure vacuumizing, and meanwhile, byproduct gas generated after deposition reaction in the preform can be timely pumped out. And (3) soaking the whole prefabricated body to be soaked in the CNTs soaking liquid all the time, finishing soaking after half an hour, taking out the sample for about 2 hours, basically curing the soaking liquid, drying, and repeatedly circulating for 6-7 times until the directional hole is opaque. Thus, the CNTs can quickly and smoothly penetrate into the pores in the deep inside of the prefabricated body, and the CNTs are indicated to completely seal the oriented pores.
(5) Densifying the preform by a CVI process: placing the prefabricated body in a high-temperature vacuum furnace, depositing at 1000-1100 ℃, and keeping the atmosphere pressure at 2KPa, H2The flow rate is 200ml/min, the Ar flow rate is 300ml/min, the molar mass ratio of H2 to MTS is 10:1, and the sample preparation is completed after deposition for 110H and temperature reduction.
(6) The volume density of the CNTs modified C/SiC composite material prepared by the embodiment is 2.30g/cm3.The thermal diffusivity of the composite material is detected by using a thermal diffusivity instrument (LFA 427) according to the ASTM E-1461 standard, and the thermal conductivity of the composite material is obtained to be 120.635 W.m-1·K-1And the improvement is nearly 17 times.
Example 3:
(1) the density is 1.40g/cm3The preform of (2): the Nicalon-0.5K silicon carbide fiber is selected to be woven into two-dimensional plain cloth, 12 layers are superposed and sewn, and then the carbon fiber preform with the volume density of 0.65g/cm3 and the carbon fiber volume fraction of 34.6 percent is prepared. And (3) placing the prefabricated body in a CVI vacuum furnace, wherein the deposition temperature is 950 ℃, the total system pressure is 5kPa, the propylene flow is 15ml/min, and the Ar flow is 200ml/min, and preparing a pyrolytic carbon interface layer (PyC) with the pyrolytic thickness of about 150 nm. Placing the prefabricated body in a CVI vacuum furnace, depositing at the temperature of 1000 ℃, the atmospheric pressure of 5KPa, the flow rate of H2 of 200ml/min and the flow rate of Ar of 300ml/min, naturally cooling after depositing for 200-230H, and preparing the composite material with the density of 1.40g/cm3SiC/SiC preform of (1).
(2) And preparing micropores by using ultrashort pulse laser. Processing parameters by using ultrashort pulse laser: the wavelength is 800nm, the pulse width is 300fs, the repetition frequency is 100KHz, the line scanning speed is 600 mu m/s, the line spacing is 20 mu m, the laser power is 25W, and directional holes with certain arrangement are prepared in the SiC/SiC prefabricated body.
(3) Preparing a CNTs solution: CNTs (diameter of 8-15 nm, length of 500 mu m, more than 95 wt.%) is used as a solute, and a solvent (deionized water), a pH regulator, an anionic surfactant (tetramethylammonium hydroxide (C4H13NO, 25 wt.% aqueous solution)) and a dispersant (Triton X-100, purity of more than 99.0%)) are mixed in a ratio of 0.5: 1.5: 1: 97 to prepare the CNTs solution. CNTs were dissolved by an ultrasonic dispersion emulsifier (BILON-1500 type, 300-.
(4) Vacuum impregnation of CNTs solution: and (2) placing the CNTs impregnation liquid below the dried preform, making negative pressure in an impregnation cavity by a vacuum pump, removing bubbles in the CNTs solution by negative pressure vacuumizing, and simultaneously extracting byproduct gas generated after deposition reaction in the SiC/SiC preform in time. And (3) soaking the whole SiC/SiC prefabricated body to be soaked in the CNTs soaking liquid all the time, finishing soaking after half an hour, taking out the sample for about 2 hours, basically curing the soaking liquid, drying, repeatedly circulating for 7-8 times, and repeating the steps until the oriented column is opaque. Thus, the CNTs can quickly and smoothly penetrate into the deep pores in the SiC/SiC prefabricated body, and the CNTs are indicated to completely seal the oriented pores.
(5) Densifying the preform by a CVI process: placing the SiC/SiC prefabricated body in a high-temperature vacuum furnace, depositing at 1000-1100 ℃, and keeping the atmosphere pressure at 2KPa, H2Flow 200ml/min, Ar flow 300ml/min, H2The molar mass ratio of the MTS to the MTS is 10:1, and the sample preparation is completed after deposition for 110 hours and temperature reduction.
The volume density of the CNTs oriented modified SiC/SiC composite material prepared by the embodiment is 2.48g/cm3The thermal diffusivity of the composite material is detected by using a thermal diffusivity instrument (LFA 427) according to the ASTM E-1461 standard, and the thermal conductivity of the composite material is obtained to be 167.568 W.m-1·K-1And the lifting is improved by nearly 23 times.
Claims (6)
1. A preparation method of a high-thermal-conductivity CNTs oriented modified ceramic matrix composite is characterized by comprising the following steps:
step 1, preparing a ceramic matrix composite material preform: after the fibers are sequentially laminated and sewn in a two-dimensional mode, a fiber preform with the volume fraction of 25-35% is obtained; placing the fiber prefabricated member in a high-temperature vacuum furnace, depositing at 850-1000 ℃, at an atmosphere pressure of 0.2kPa, at a propylene flow rate of 30ml/min and at an Ar flow rate of 300ml/min, depositing for 50-60 h, and cooling to prepare a composite material interface;
then placing the fiber prefabricated member in a high-temperature vacuum furnace, depositing at 1000-1100 ℃, and keeping the atmosphere pressure at 2kPa, H2With MTS flow of 200ml/min, Ar flow of 300ml/min, H2The mol ratio of the mixed solution to MTS is 10:1, and the density formed after deposition for 200-230 h and temperature reduction is 1.4-2.0 g/cm3The composite preform of (1);
step 2: processing a plurality of micro directional holes with the aperture of 0.2-1 mm on the composite material by adopting ultrashort pulse laser equipment with the wavelength of 400-1500 nm, the pulse width of 80-500 fs and the power of 5-20W;
and step 3: performing ultrasonic dispersion on 0.1-1.0% of CNTs, 1.0-2.5% of deionized water solvent, 0.7-2.5% of pH value regulator, anionic surfactant and 95-98% of dispersant by weight percent to prepare a CNTs solution;
the pH value regulator and the anionic surfactant are tetramethylammonium hydroxide;
the dispersant is triton X-100;
and 4, step 4: soaking the whole prefabricated body to be soaked in a CNTs solution by adopting a vacuum soaking method, pressurizing, drying, and repeatedly soaking until the oriented holes are sealed and filled by the CNTs and the micro oriented holes form a lightproof oriented column;
and 5: further densifying the modified composite material by adopting a chemical vapor infiltration method, placing the prefabricated body in a high-temperature vacuum furnace, depositing at 1000-1100 ℃, and keeping the atmosphere pressure at 2kPa and H2Flow 200ml/min, Ar flow 300ml/min, H2The mol ratio of the carbon nano tubes to MTS is 10:1, the carbon nano tubes are deposited for 100-120 h and cooled to finally prepare the high-thermal-conductivity CNTs oriented modified ceramic matrix composite material, and the relative density reaches 85-95%;
the fiber is as follows: carbon fibers, silicon carbide fibers, boron fibers, oxide fibers, or other high temperature ceramic fibers.
2. The method for preparing the oriented modified ceramic matrix composite of CNTs with high thermal conductivity according to claim 1, wherein: the preform woven structure is: 2-dimensional, 2.5-dimensional, 3-dimensional, or other dimensional preforms.
3. The method for preparing the oriented modified ceramic matrix composite of CNTs with high thermal conductivity according to claim 1, wherein: the preparation method of the preform comprises the following steps: lamination, knitting, needling, or other fabrication methods.
4. The method for preparing the oriented modified ceramic matrix composite of CNTs with high thermal conductivity according to claim 1, wherein: the shape of the micro directional hole is as follows: round holes, square holes or micro holes with other shapes.
5. The method for preparing the CNTs oriented modified ceramic matrix composite with high thermal conductivity according to any one of claims 1-4, wherein: the arrangement of the micro directional holes is as follows: equally spaced or unequally spaced.
6. The method for preparing the CNTs oriented modified ceramic matrix composite with high thermal conductivity according to any one of claims 1-4, wherein: the arrangement of the micro directional holes is as follows: ordered or disordered.
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