CN112979315A - Preparation method of high-temperature-resistant, antioxidant and heat-conducting graphene-based ceramic composite material - Google Patents

Preparation method of high-temperature-resistant, antioxidant and heat-conducting graphene-based ceramic composite material Download PDF

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CN112979315A
CN112979315A CN202110117738.6A CN202110117738A CN112979315A CN 112979315 A CN112979315 A CN 112979315A CN 202110117738 A CN202110117738 A CN 202110117738A CN 112979315 A CN112979315 A CN 112979315A
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邰晓倩
周珈羽
翟天戈
徐立宇
刁辰潇
张玉平
杜伟
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Yantai University
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Abstract

The invention relates to a preparation method of a high-temperature-resistant, antioxidant and heat-conducting graphene-based ceramic composite material, and belongs to the technical field of preparation of graphene-based ceramic composite materials. Preparing a supersaturated solution of fluosilicic acid by adopting fluosilicic acid solution and silica gel, preparing a mixed solution by adopting boric acid powder, graphene and water, dropwise adding the mixed solution into the supersaturated solution of fluosilicic acid, and stirring and reacting for 4-8 h at 50-70 ℃ to generate the high-temperature-resistant, antioxidant and heat-conducting graphene-based ceramic composite material. The invention applies the liquid phase deposition technology to the preparation of the graphene-based ceramic composite material, has the advantages of simple process operation, mild reaction conditions, low raw material cost, good repeatability and the like, and can ensure that a proper amount of SiO is prepared by regulating and controlling process parameters2The nano spherical particles are continuously and uniformly deposited on the surface of the graphene,the problem that graphene is easy to agglomerate is effectively solved, and the heat-conducting property of the graphene in a high-temperature aerobic environment can be improved.

Description

Preparation method of high-temperature-resistant, antioxidant and heat-conducting graphene-based ceramic composite material
Technical Field
The invention relates to a preparation method of a high-temperature-resistant, antioxidant and heat-conducting graphene-based ceramic composite material, and belongs to the technical field of preparation of graphene-based ceramic composite materials.
Background
Graphene is a novel heat conducting and radiating material, has the in-plane heat conductivity as high as 5300W/(m.K), has the excellent characteristics of low density, low thermal expansion coefficient, good mechanical property and the like, and is a novel heat conducting material with light weight, high heat conductivity and excellent performance. But it is difficult to use it alone as a heat conductive material because its thickness is too thin. In order to solve this problem, it is one of the effective methods to compound graphene and other materials as a heat conducting and dissipating material.
In the aspect of utilizing the combination of graphene, polymers and metals, some researches have been made at home and abroad to synthesize graphene/polymer composite materials, graphene/copper foil composite materials, graphene-aluminum-based composite materials and the like, and the composite materials show higher heat-conducting performance under the low-temperature condition. However, for the heat conduction material, the high-temperature and aerobic conditions are the basis of the working environment in which the material plays a heat conduction function, and graphene is easily oxidized in the high-temperature aerobic environment, so that the lattice structure of graphene is defective, and the conduction of phonons is seriously affected, so that the heat conduction performance of graphene is affected, and the potential application of graphene as the heat conduction material in the high-temperature aerobic environment is greatly limited.
Among many ceramic materials, silicon-based ceramic materials are often used as protective coatings on the surface of carbon materials. In one aspect, SiO2The thermal expansion coefficient of the ceramic oxide is generally smaller and is very close to that of the matrix carbonThe combination of the substrate and the coating can be promoted; on the other hand, in a high-temperature aerobic environment, SiO2The coating is in a glass state, thermal expansion cracks generated by the coating can be closed, and good oxidation resistance protection is provided for graphene. At present, the preparation method of the graphene-based ceramic composite material comprises a hydrothermal method, a high-temperature treatment method, a chemical treatment method and the like, and the graphene-based SiO with high temperature resistance, oxidation resistance and heat conduction can be prepared by compounding graphene and ceramic oxide by the methods2A ceramic composite material. However, these methods have complex processes, and cannot effectively solve the problem of easy aggregation of graphene, so that the performance advantages of graphene are difficult to be fully exerted.
Disclosure of Invention
Aiming at the problems of complex preparation process and graphene agglomeration in the preparation process of the existing graphene-based ceramic composite material, the invention provides a preparation method of a high-temperature-resistant, oxidation-resistant and heat-conducting graphene-based ceramic composite material2The ceramic oxide particles solve the problem of graphene agglomeration, so that the prepared graphene-based ceramic composite material has good high-temperature resistance, oxidation resistance and thermal conductivity, and the method is simple to operate, controllable in reaction and good in repeatability.
The purpose of the invention is realized by the following technical scheme.
A preparation method of a high-temperature-resistant, oxidation-resistant and heat-conducting graphene-based ceramic composite material comprises the following steps:
(1) preparing a supersaturated solution of fluosilicic acid by adopting fluosilicic acid solution and silica gel;
preparing a mixed solution by adopting boric acid powder, graphene and water;
(2) under the ultrasonic condition, dropwise adding the mixed solution into a supersaturated solution of fluosilicic acid, and uniformly mixing to obtain a precursor solution;
wherein the mass ratio of the fluosilicic acid to the boric acid is (7-13) g: 1mg, wherein the mass ratio of the fluosilicic acid to the graphene is (1.8-5) g: 1 mg;
(3) and transferring the precursor solution into a water bath kettle at the temperature of 50-70 ℃, stirring and reacting for 4-8 h, collecting a solid product in a reaction system, and drying to obtain the high-temperature-resistant, antioxidant and heat-conducting graphene-based ceramic composite material.
Furthermore, in the supersaturated solution of the fluosilicic acid in the step (1), the concentration of the fluosilicic acid is preferably 3 mol/L-3.2 mol/L.
Further, in the step (1), a fluorosilicic acid solution with the mass fraction of 30-32% and silica gel are preferably adopted to prepare a supersaturated solution of fluorosilicic acid;
further, the concentration of boric acid in the mixed solution in the step (1) is preferably 60 mg/L-115 mg/L, and the concentration of graphene is preferably 0.1 g/L-0.5 g/L;
further, the ultrasonic frequency in the step (2) is preferably 40 kHz-60 kHz;
further, in the step (2), the mixed solution is preferably added dropwise to the supersaturated solution of fluorosilicic acid at a dropping rate of from 6mL/min to 10 mL/min.
Further, the stirring rate in the step (3) is preferably 120 to 200 r/min.
The reaction principle for preparing the graphene-based ceramic composite material is as follows: in the liquid phase deposition process, H is in solution2SiF6Under supersaturation by H2O attack to form SiO2And HF; h3BO3As a consuming agent for HF, indirectly promoting H2SiF6The hydrolysis reaction of (2) proceeds in the forward direction, and the involved reactions are shown in the formulas (1) and (2). When oxide SiO in the reaction system2When the amount of the nano-particles exceeds the solubility of the nano-particles in the reaction solution, the nano-particles begin to precipitate and are deposited on the surface of the graphene to form uniformly distributed nano-particles, and finally dense SiO is formed2A film. In addition, H is selected in the reaction3BO3Can be dissolved in reaction liquid, the addition amount is easy to control, post-treatment is convenient, and SiO product can not be treated2The film causes an influence.
Figure BDA0002920969880000031
Figure BDA0002920969880000032
Has the advantages that:
(1) the invention applies the liquid phase deposition technology to the preparation of the graphene-based ceramic composite material, the technology is a mild liquid phase reaction under the low temperature condition, and the preparation method has the advantages of simple process operation, controllable reaction, simple equipment, low raw material cost, good repeatability and the like.
(2) The graphene-based ceramic composite material with a specific morphology is obtained by regulating and controlling process parameters, the surface morphology of the graphene-based ceramic composite material directly influences the heat-conducting property of the graphene-based ceramic composite material in a high-temperature aerobic environment, and a proper amount of SiO2The continuous and uniform deposition of the nano spherical particles on the surface of the graphene not only effectively solves the problem that the graphene is easy to agglomerate, but also can prevent the graphene from being oxidized under the high-temperature aerobic condition, thereby improving the heat-conducting property of the graphene under the high-temperature aerobic environment, and excessive or small amount of SiO2The deposition of the nano particles can affect the heat conducting performance of the composite material in a high-temperature aerobic environment.
Drawings
Fig. 1 is a graph comparing an X-ray diffraction pattern of the graphene-based ceramic composite prepared in example 1 with that of untreated graphene.
Fig. 2 is a graph comparing thermogravimetric curves of the graphene-based ceramic composite prepared in example 1 and untreated graphene.
Fig. 3 is a low power Scanning Electron Microscope (SEM) image of the graphene-based ceramic composite prepared in example 1.
Fig. 4 is a high-power scanning electron microscope image of the graphene-based ceramic composite prepared in example 1.
Fig. 5 is a scanning electron microscope image of the graphene-based ceramic composite prepared in example 2.
Fig. 6 is a scanning electron microscope image of the graphene-based ceramic composite prepared in example 3.
Fig. 7 is a scanning electron microscope image of the graphene-based ceramic composite prepared in comparative example 1.
Fig. 8 is a scanning electron microscope image of the graphene-based ceramic composite prepared in comparative example 2.
Fig. 9 is a scanning electron microscope image of the graphene-based ceramic composite prepared in comparative example 3.
Fig. 10 is a scanning electron microscope image of the graphene-based ceramic composite prepared in comparative example 4.
Detailed Description
The present invention is further illustrated by the following detailed description, wherein the processes are conventional unless otherwise specified, and the starting materials are commercially available from a public source without further specification.
In the following examples:
fluosilicic acid: analytically pure (AR), 30.0% -32.0%, Macklin;
boric acid: analytically pure (AR) of not less than 99.5%, Macklin;
silica gel: analytical purification (AR), 300-400 mesh, Aladdin;
graphene: diameter of 0.5-5 μm, thickness of 0.8-1.2 nm, purity of 99%, Jiangsu Xiancheng nanometer material science and technology Limited;
scanning Electron Microscope (SEM): JSM-7610F, JEOL, Japan;
transmission Electron Microscope (TEM): JEM-2100F, JEOL, Japan;
x-ray diffractometer (XRD): 7000X, Shimadzu, Japan;
differential Scanning Calorimetry (DSC): sta 449F3, Netzsch, Germany;
thermal conductivity meter: hot Disk TPS2500S, Sweden.
Example 1
(1) Adding 10g of silica gel into 200mL of fluorosilicic acid solution, stirring for 20h to completely saturate the fluorosilicic acid solution, stopping stirring, standing for 30min, filtering the silica gel in the fluorosilicic acid solution by using a vacuum filtration system to obtain a clarified supersaturated solution of fluorosilicic acid, wherein the concentration of fluorosilicic acid is about 3.09 mol/L;
dissolving 0.0095g of boric acid powder in 60mL of deionized water, and uniformly stirring to obtain a boric acid solution; adding 0.03g of graphene into 49mL of deionized water, and performing ultrasonic dispersion for 30min to obtain a graphene solution; uniformly mixing the boric acid solution and the graphene solution by ultrasonic waves to obtain a mixed solution;
(2) under the ultrasonic frequency of 48kHz, 109mL of mixed solution is dropwise added into 200mL of supersaturated solution of fluosilicic acid at the dropwise adding rate of 8mL/min to obtain precursor solution;
(3) preheating a water bath to 60 ℃, then putting the precursor solution into the water bath, adjusting the stirring speed to 160r/min, stirring and reacting for 6 hours, then performing suction filtration by using a vacuum filtration system, and drying the collected solid product in a vacuum drying oven at 70 ℃ for 12 hours to obtain the graphene-based ceramic composite material.
As can be seen from the XRD spectrum of fig. 1, in addition to the diffraction peak in which the carbon peak appears at 2 θ ═ 26 °, a distinct diffraction peak appears at 2 θ ═ 21 °, corresponding to SiO2Peak, proof production of graphene-based SiO2A ceramic composite material.
As can be seen from fig. 2, the prepared graphene-based SiO was compared to the untreated graphene2The initial weightlessness temperature of the ceramic composite material is delayed by about 100 ℃, the weightlessness is started only when the temperature is 620 ℃, the weightlessness rate is greatly reduced, the ceramic composite material is basically kept stable when the temperature is 780 ℃, and the final retention rate reaches 78%.
As can be seen from the combination of FIGS. 3 and 4, the prepared graphene-based SiO2In ceramic composite materials, SiO2Uniformly dispersed on the surface of graphene in the form of spherical particles to form a layer of uniform, continuous and compact SiO on the surface of graphene2And the coating layer is coated, and the lamination phenomenon of the matrix graphene does not occur.
Testing of the prepared graphene-based SiO2The thermal conductivity of the ceramic composite material and the untreated graphene at 25 ℃, 300 ℃ and 600 ℃ respectively are shown in table 1. Graphene-based SiO in contrast to untreated graphene2The decreasing rate of the thermal conductivity of the ceramic composite material along with the temperature rise is greatly reduced, and the thermal conductivity can still reach 112W/(m.K) at 600 ℃. Thus, the prepared graphene-based SiO2Ceramic composite materialThe heat conductivity coefficient of the graphene material at medium and high temperature is greatly improved.
TABLE 1
Sample (I) 25℃ 300℃ 600℃
Graphene-based SiO2Ceramic composite material W/(m.K) 223 217 112
Graphene W/(m.K) 289 115 13
Example 2
(1) Adding 5g of silica gel into 100mL of fluorosilicic acid solution, stirring for 18h to completely saturate the fluorosilicic acid solution, stopping stirring, standing for 30min, filtering the silica gel in the fluorosilicic acid solution by using a vacuum filtration system to obtain a clarified supersaturated solution of fluosilicic acid, wherein the concentration of the fluosilicic acid is about 3.09 mol/L;
dissolving 0.0057g of boric acid powder in 30mL of deionized water, and uniformly stirring to obtain a boric acid solution; adding 0.01g of graphene into 25mL of deionized water, and performing ultrasonic dispersion for 30min to obtain a graphene solution; uniformly mixing the boric acid solution and the graphene solution by ultrasonic waves to obtain a mixed solution;
(2) dripping 55mL of mixed solution into 100mL of supersaturated solution of fluosilicic acid at the dripping rate of 6mL/min under the ultrasonic frequency of 60kHz to obtain precursor solution;
(3) preheating a water bath to 50 ℃, then putting the precursor solution into the water bath, adjusting the stirring speed to 120r/min, stirring and reacting for 8 hours, then performing suction filtration by using a vacuum filtration system, and drying the collected solid product in a vacuum drying oven at 70 ℃ for 12 hours to obtain the graphene-based ceramic composite material.
The XRD characterization revealed that the XRD spectrum showed a diffraction peak with a carbon peak at 26 ° 2 θ and a SiO peak at 21 ° 2 θ2The diffraction peak of (2) proves that the graphene-based SiO is prepared2A ceramic composite material. DSC tests show that the prepared graphene-based SiO2The ceramic composite material begins to lose weight from 618 ℃, and basically keeps stable until 776 ℃, and the final retention rate reaches 75%. According to SEM characterization, SiO2Uniformly dispersed on the surface of graphene in the form of spherical particles to form a layer of uniform, continuous and compact SiO on the surface of graphene2The cladding layer, and the matrix graphene does not show the lamination phenomenon, as shown in fig. 5.
Tests show that the prepared graphene-based SiO2The thermal conductivity of the ceramic composite material at 25 ℃, 300 ℃ and 600 ℃ is 212W/(mK), 193W/(mK) and 101W/(mK), respectively. Graphene-based SiO in contrast to untreated graphene2The rate of the decrease of the thermal conductivity of the ceramic composite material along with the increase of the temperature is greatly reduced, namely the prepared graphene-based SiO2The ceramic composite material greatly improves the heat conductivity coefficient of the graphene material at medium and high temperature.
Example 3
(1) Adding 15g of silica gel into 300mL of fluorosilicic acid solution, stirring for 24h to completely saturate the fluorosilicic acid solution, stopping stirring, standing for 30min, filtering the silica gel in the fluorosilicic acid solution by using a vacuum filtration system to obtain a clarified supersaturated solution of fluosilicic acid, wherein the concentration of the fluosilicic acid is about 3.09 mol/L;
dissolving 0.0114g of boric acid powder in 90mL of deionized water, and uniformly stirring to obtain a boric acid solution; adding 0.06g of graphene into 74mL of deionized water, and performing ultrasonic dispersion for 30min to obtain a graphene solution; uniformly mixing the boric acid solution and the graphene solution by ultrasonic waves to obtain a mixed solution;
(2) under the ultrasonic frequency of 40kHz, 164mL of mixed solution is dripped into 300mL of supersaturated solution of fluosilicic acid at the dripping rate of 10mL/min to obtain precursor solution;
(3) preheating a water bath to 70 ℃, then putting the precursor solution into the water bath, adjusting the stirring speed to 200r/min, stirring and reacting for 4 hours, then performing suction filtration by using a vacuum filtration system, and drying the collected solid product in a vacuum drying oven at 70 ℃ for 12 hours to obtain the graphene-based ceramic composite material.
The XRD characterization revealed that the XRD spectrum showed a diffraction peak with a carbon peak at 26 ° 2 θ and a SiO peak at 21 ° 2 θ2The diffraction peak of (2) proves that the graphene-based SiO is prepared2A ceramic composite material. DSC tests show that the prepared graphene-based SiO2The ceramic composite material begins to lose weight from 619 ℃, basically keeps stable until 778 ℃, and finally has a retention rate of 76%. According to SEM characterization, SiO2Uniformly dispersed on the surface of graphene in the form of spherical particles to form a layer of uniform, continuous and compact SiO on the surface of graphene2The cladding layer, and the matrix graphene does not show the lamination phenomenon, as shown in fig. 6.
Tests show that the prepared graphene-based SiO2The thermal conductivity of the ceramic composite material at 25 ℃, 300 ℃ and 600 ℃ is 217W/(mK), 203W/(mK) and 109W/(mK), respectively. Graphene-based SiO in contrast to untreated graphene2The rate of the decrease of the thermal conductivity of the ceramic composite material along with the increase of the temperature is greatly reduced, namely the prepared graphene-based SiO2The ceramic composite material greatly improves the heat conductivity coefficient of the graphene material at medium and high temperature.
Comparative example 1
(1) Adding 5g of silica gel into 80mL of fluorosilicic acid solution, stirring for 20h to completely saturate the fluorosilicic acid solution, stopping stirring, standing for 30min, filtering the silica gel in the fluorosilicic acid solution by using a vacuum filtration system to obtain a clarified supersaturated solution of fluorosilicic acid, wherein the concentration of fluorosilicic acid is about 3.09 mol/L;
dissolving 0.0025g of boric acid powder in 25mL of deionized water, and uniformly stirring to obtain a boric acid solution; adding 0.03g of graphene into 25mL of deionized water, and performing ultrasonic dispersion for 30min to obtain a graphene solution; uniformly mixing the boric acid solution and the graphene solution by ultrasonic waves to obtain a mixed solution;
(2) under the ultrasonic frequency of 50kHz, dripping 50mL of mixed solution into 50mL of supersaturated solution of fluosilicic acid at the dripping rate of 8mL/min to obtain precursor solution;
(3) preheating a water bath to 50 ℃, then putting the precursor solution into the water bath, adjusting the stirring speed to 200r/min, stirring and reacting for 4 hours, then performing suction filtration by using a vacuum filtration system, and drying the collected solid product in a vacuum drying oven at 70 ℃ for 12 hours to obtain the graphene-based ceramic composite material.
The XRD characterization revealed that the XRD spectrum showed a diffraction peak with a carbon peak at 26 ° 2 θ and a SiO peak at 21 ° 2 θ2The diffraction peak of (2) proves that the graphene-based SiO is prepared2A ceramic composite material. DSC tests show that the prepared graphene-based SiO2The ceramic composite material is weightless from 560 ℃ and basically keeps stable to 760 ℃, and the final retention rate reaches 42%. According to SEM characterization, SiO2The graphene is dispersed on the surface of graphene in a particle form, but the bare graphene exists and is not completely coated, as shown in fig. 7, under the high-temperature oxidation condition, the bare graphene is firstly oxidized, and the graphene-based SiO is directly influenced2The heat-conducting property of the ceramic composite material.
Tests show that the prepared graphene-based SiO2The ceramic composite material has thermal conductivity coefficients of 269W/(mK), 112W/(mK) and 26W/(mK) at 25 ℃, 300 ℃ and 600 ℃, respectively. Graphene-based SiO in contrast to untreated graphene2The ceramic composite had a reduced rate of decrease in thermal conductivity with an increase in temperature, but the graphene-based SiO prepared under this condition was comparable to the sample prepared in the example2Ceramic composite material having oxygen at high temperatureThe thermal conductivity coefficient under the condition is obviously reduced, which is in accordance with the SiO deposited on the surface of the graphene2The states are directly related.
Comparative example 2
(1) Adding 18g of silica gel into 350mL of fluorosilicic acid solution, stirring for 20h to completely saturate the fluorosilicic acid solution, stopping stirring, standing for 30min, filtering the silica gel in the fluorosilicic acid solution by using a vacuum filtration system to obtain a clarified supersaturated solution of fluorosilicic acid, wherein the concentration of fluorosilicic acid is about 3.09 mol/L;
dissolving 0.0192g of boric acid powder in 120mL of deionized water, and uniformly stirring to obtain a boric acid solution; adding 0.02g of graphene into 55mL of deionized water, and performing ultrasonic dispersion for 30min to obtain a graphene solution; uniformly mixing the boric acid solution and the graphene solution by ultrasonic waves to obtain a mixed solution;
(2) under the ultrasonic frequency of 50kHz, dropwise adding 175mL of mixed solution into 350mL of supersaturated solution of fluosilicic acid at the dropwise adding rate of 8mL/min to obtain precursor solution;
(3) preheating a water bath to 70 ℃, then putting the precursor solution into the water bath, adjusting the stirring speed to 180r/min, stirring and reacting for 6 hours, then performing suction filtration by using a vacuum filtration system, and drying the collected solid product in a vacuum drying oven at 70 ℃ for 12 hours to obtain the graphene-based ceramic composite material.
The XRD characterization revealed that the XRD spectrum showed a diffraction peak with a carbon peak at 26 ° 2 θ and a SiO peak at 21 ° 2 θ2The diffraction peak of (2) proves that the graphene-based SiO is prepared2A ceramic composite material. DSC tests show that the prepared graphene-based SiO2The ceramic composite material starts to lose weight from 570 ℃, basically keeps stable from 757 ℃, and finally the retention rate reaches 78%. According to SEM characterization, SiO2Densely deposited on graphene, but now SiO2Obvious fusion phenomenon exists among particles, the particles are not deposited on the graphene in the form of spherical particles, and SiO2The thickness of the ceramic layer is significantly increased as shown in fig. 8.
Tests show that the prepared graphene-based SiO2The ceramic composite material has thermal conductivity at 25 deg.C, 300 deg.C and 600 deg.C157W/(mK), 83W/(mK) and 39W/(mK), respectively. Graphene-based SiO in contrast to untreated graphene2The ceramic composite had a reduced rate of decrease in thermal conductivity with an increase in temperature, but the graphene-based SiO prepared under this condition was comparable to the sample prepared in the example2The heat conductivity coefficient of the ceramic composite material is obviously reduced under the conditions of normal temperature and high temperature and oxygen, and the heat conductivity coefficient is combined with the SiO deposited on the surface of the graphene2The states are directly related.
Comparative example 3
(1) Adding 10g of silica gel into 200mL of fluorosilicic acid solution, stirring for 20h to completely saturate the fluorosilicic acid solution, stopping stirring, standing for 30min, filtering the silica gel in the fluorosilicic acid solution by using a vacuum filtration system to obtain a clarified supersaturated solution of fluorosilicic acid, wherein the concentration of fluorosilicic acid is about 3.09 mol/L;
dissolving 0.0095g of boric acid powder in 60mL of deionized water, and uniformly stirring to obtain a boric acid solution; adding 0.03g of graphene into 49mL of deionized water, and performing ultrasonic dispersion for 30min to obtain a graphene solution; uniformly mixing the boric acid solution and the graphene solution by ultrasonic waves to obtain a mixed solution;
(2) under the ultrasonic frequency of 48kHz, 109mL of mixed solution is dropwise added into 200mL of supersaturated solution of fluosilicic acid at the dropping rate of 5mL/min to obtain precursor solution;
(3) preheating a water bath to 40 ℃, then putting the precursor solution into the water bath, adjusting the stirring speed to 110r/min, stirring and reacting for 9 hours, then performing suction filtration by using a vacuum filtration system, and drying the collected solid product in a vacuum drying oven at 70 ℃ for 12 hours to obtain the graphene-based ceramic composite material.
The XRD characterization revealed that the XRD spectrum showed a diffraction peak with a carbon peak at 26 ° 2 θ and a SiO peak at 21 ° 2 θ2The diffraction peak of (2) proves that the graphene-based SiO is prepared2A ceramic composite material. DSC tests show that the prepared graphene-based SiO2The ceramic composite material is weightless from 572 ℃ and basically keeps stable to 755 ℃, and the final retention rate reaches 46%. According to SEM characterization, SiO2Dispersed on the surface of graphene in the form of particles, but with naked particlesIn the presence of graphene, the graphene is not completely coated, as shown in fig. 9, under the high-temperature oxidation condition, the bare graphene is firstly oxidized, and graphene-based SiO is directly affected2The heat-conducting property of the ceramic composite material.
Tests show that the prepared graphene-based SiO2The thermal conductivity of the ceramic composite material at 25 ℃, 300 ℃ and 600 ℃ is 237W/(mK), 152W/(mK) and 51W/(mK), respectively. Graphene-based SiO in contrast to untreated graphene2The ceramic composite had a reduced rate of decrease in thermal conductivity with an increase in temperature, but the graphene-based SiO prepared under this condition was comparable to the sample prepared in the example2The thermal conductivity coefficient of the ceramic composite material is obviously reduced under the high-temperature aerobic condition, which is in cooperation with SiO deposited on the surface of graphene2The states are directly related.
Comparative example 4
(1) Adding 10g of silica gel into 200mL of fluorosilicic acid solution, stirring for 20h to completely saturate the fluorosilicic acid solution, stopping stirring, standing for 30min, filtering the silica gel in the fluorosilicic acid solution by using a vacuum filtration system to obtain a clarified supersaturated solution of fluorosilicic acid, wherein the concentration of fluorosilicic acid is about 3.09 mol/L;
dissolving 0.0095g of boric acid powder in 60mL of deionized water, and uniformly stirring to obtain a boric acid solution; adding 0.03g of graphene into 49mL of deionized water, and performing ultrasonic dispersion for 30min to obtain a graphene solution; uniformly mixing the boric acid solution and the graphene solution by ultrasonic waves to obtain a mixed solution;
(2) under the ultrasonic frequency of 48kHz, 109mL of mixed solution is dropwise added into 200mL of supersaturated solution of fluosilicic acid at the dropping rate of 11mL/min to obtain precursor solution;
(3) preheating a water bath to 80 ℃, then putting the precursor solution into the water bath, adjusting the stirring speed to 210r/min, stirring and reacting for 2 hours, then performing suction filtration by using a vacuum filtration system, and drying the collected solid product in a vacuum drying oven at 70 ℃ for 12 hours to obtain the graphene-based ceramic composite material.
The XRD shows that the diffraction pattern has a diffraction peak with a carbon peak at 26 degrees 2 theta and 21 degrees 2 thetaSiO appears2The diffraction peak of (2) proves that the graphene-based SiO is prepared2A ceramic composite material. DSC tests show that the prepared graphene-based SiO2The ceramic composite material starts to lose weight from 580 ℃, basically keeps stable to 762 ℃, and finally has a retention rate of 76%. According to SEM characterization, SiO2Densely distributed on graphene mainly in the form of small particles, and SiO2The thickness of the ceramic layer is significantly increased as shown in fig. 10.
Tests show that the prepared graphene-based SiO2The thermal conductivity of the ceramic composite material at 25 ℃, 300 ℃ and 600 ℃ is 156W/(mK), 76W/(mK) and 21W/(mK), respectively. Graphene-based SiO in contrast to untreated graphene2The ceramic composite had a reduced rate of decrease in thermal conductivity with an increase in temperature, but the graphene-based SiO prepared under this condition was comparable to the sample prepared in the example2The heat conductivity coefficient of the ceramic composite material is obviously reduced under the conditions of normal temperature and high temperature and oxygen, and the heat conductivity coefficient is combined with the SiO deposited on the surface of the graphene2The states are directly related.
In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (7)

1. A preparation method of a high-temperature-resistant, oxidation-resistant and heat-conducting graphene-based ceramic composite material is characterized by comprising the following steps: the method comprises the following steps:
(1) preparing a supersaturated solution of fluosilicic acid by adopting fluosilicic acid solution and silica gel;
preparing a mixed solution by adopting boric acid powder, graphene and water;
(2) under the ultrasonic condition, dropwise adding the mixed solution into a supersaturated solution of fluosilicic acid, and uniformly mixing to obtain a precursor solution;
(3) transferring the precursor solution into a water bath kettle at the temperature of 50-70 ℃, stirring and reacting for 4-8 h, collecting a solid product in a reaction system, and drying to obtain the high-temperature-resistant, antioxidant and heat-conducting graphene-based ceramic composite material;
wherein the mass ratio of the fluosilicic acid to the boric acid is (7-13) g: 1mg, wherein the mass ratio of the fluosilicic acid to the graphene is (1.8-5) g: 1 mg.
2. The preparation method of the high-temperature-resistant, antioxidant and heat-conductive graphene-based ceramic composite material according to claim 1, characterized by comprising the following steps: in the supersaturated solution of the fluosilicic acid in the step (1), the concentration of the fluosilicic acid is 3 mol/L-3.2 mol/L.
3. The preparation method of the high-temperature-resistant, antioxidant and heat-conducting graphene-based ceramic composite material according to claim 1 or 2, characterized by comprising the following steps: in the step (1), a fluosilicic acid solution with the mass fraction of 30-32% and silica gel are adopted to prepare a supersaturated solution of fluosilicic acid.
4. The preparation method of the high-temperature-resistant, antioxidant and heat-conducting graphene-based ceramic composite material according to claim 1 or 2, characterized by comprising the following steps: in the mixed solution in the step (1), the concentration of boric acid is 60-115 mg/L, and the concentration of graphene is 0.1-0.5 g/L.
5. The preparation method of the high-temperature-resistant, antioxidant and heat-conductive graphene-based ceramic composite material according to claim 1, characterized by comprising the following steps: the ultrasonic frequency in the step (2) is 40 kHz-60 kHz.
6. The preparation method of the high-temperature-resistant, antioxidant and heat-conducting graphene-based ceramic composite material according to claim 4, wherein the preparation method comprises the following steps: and (2) dropwise adding the mixed solution into the supersaturated solution of the fluosilicic acid at the dropwise adding rate of 6 mL/min-10 mL/min.
7. The preparation method of the high-temperature-resistant, antioxidant and heat-conductive graphene-based ceramic composite material according to claim 1, characterized by comprising the following steps: the stirring speed in the step (3) is 120 r/min-200 r/min.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102701191A (en) * 2012-06-06 2012-10-03 渤海大学 Preparation method of fluorosilane surface finished grapheme for supercapacitor
CN104045346A (en) * 2014-06-30 2014-09-17 中国科学技术大学 Graphene-ceramic composite material prepared by sol-gel process and preparation method thereof
CN105777124A (en) * 2016-02-29 2016-07-20 中原工学院 Method for preparing graphene in-situ growth silicon-carbide nanometer materials

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102701191A (en) * 2012-06-06 2012-10-03 渤海大学 Preparation method of fluorosilane surface finished grapheme for supercapacitor
CN104045346A (en) * 2014-06-30 2014-09-17 中国科学技术大学 Graphene-ceramic composite material prepared by sol-gel process and preparation method thereof
CN105777124A (en) * 2016-02-29 2016-07-20 中原工学院 Method for preparing graphene in-situ growth silicon-carbide nanometer materials

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