CN113929464B - CNT/graphene covalent modified high-thermal-conductivity carbide ceramic and preparation method thereof - Google Patents
CNT/graphene covalent modified high-thermal-conductivity carbide ceramic and preparation method thereof Download PDFInfo
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Abstract
The invention relates to CNT/graphene covalent modified high-thermal-conductivity carbide ceramic and a preparation method thereof. The method comprises the following steps: under the condition of vacuum auxiliary vibration, uniformly mixing multi-walled carbon nanotube powder, multi-layer graphene powder and a ceramic precursor solution to obtain a CNT/graphene modified ceramic precursor solution; sequentially solidifying and pyrolyzing the CNT/graphene modified ceramic precursor solution at high temperature to obtain CNT/graphene covalently modified ceramic powder; and sintering the CNT/graphene covalent modified ceramic powder at high temperature and high pressure to prepare the CNT/graphene covalent modified high-thermal conductivity carbide ceramic. The invention gives full play to the advantages of the carbon nano tube and the graphene respectively as one-dimensional and two-dimensional nano carbon materials, and forms the CNT/graphene covalent modified carbide ceramic through the carbon thermal reduction reaction of the carbon materials and the oxide ceramic, thereby improving the electrical conductivity and the thermal conductivity and effectively solving the problems of poor thermal conductivity of the carbide ceramic and the like.
Description
Technical Field
The invention relates to the technical field of ceramic composite material preparation, in particular to CNT/graphene covalent modified high-thermal-conductivity carbide ceramic and a preparation method thereof.
Background
When the aircraft flies at 5 times of sound velocity and faster speed, the thermal protection component of the aircraft needs to be tested under extreme conditions such as ultrahigh heat flux density and the like, and more rigorous requirements are put forward on materials. Ceramics, represented by metal carbides, tend to have relatively high melting points (> 1600 ℃) and are the most competitive candidate materials for thermal protective components. Carbide ceramics, however, tend to be brittle and, in the presence of high stresses, can form through-cracks in the interior, with serious consequences. In addition, the thermal conductivity of carbide ceramics is often poor and is generally lower than 2W/(m · K), so that the heat of the thermal protection component is accumulated and cannot be effectively diffused, and the temperature is too high and even exceeds the melting point of the thermal protection component, thereby affecting the service performance of the component.
Carbon Nanotubes (CNTs) and graphene, which are one-dimensional and two-dimensional Carbon nanomaterials, are known as "black metal" materials because of their ultrahigh mechanical strength, electrical conductivity and thermal conductivity, and thus have received much attention from scientists in the world. In the prior art, in order to improve the toughness and the thermal conductivity of carbide ceramics, carbon nano materials such as carbon nano tubes and graphene can be dispersed in the carbide ceramics, so that the brittleness and the thermal conductivity of the ceramics are improved. However, the currently adopted dispersion method mostly focuses on mechanical mixing, and only simple mechanical mixing is performed on the carbon nanotubes or graphene and the carbide ceramic powder. Because the carbon nano tubes or graphene are easy to agglomerate, the carbon nano tubes or graphene are not uniformly dispersed in the carbide ceramic, the effect of improving the brittleness of the ceramic is poor, meanwhile, covalent bonds are not formed between the carbon nano tubes or graphene and the carbide ceramic, the efficiency is still low when heat is transferred, and the heat conductivity is not obviously improved. In order to further improve the service performance of the thermal protection component, the problems of brittleness and poor heat conductivity of the carbide ceramic under the prior art condition need to be solved.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention provides a CNT/graphene covalent modified high-thermal conductivity carbide ceramic and a preparation method thereof.
The invention provides a preparation method of CNT/graphene covalent modified high thermal conductivity carbide ceramic in a first aspect, which comprises the following steps:
(1) Under the condition of vacuum-assisted vibration, uniformly mixing multi-walled carbon nanotube powder, multi-layer graphene powder and a ceramic precursor solution to obtain a CNT/graphene modified ceramic precursor solution;
(2) Sequentially solidifying and pyrolyzing the CNT/graphene modified ceramic precursor solution to obtain CNT/graphene covalent modified ceramic powder;
(3) And sintering the CNT/graphene covalent modified ceramic powder at high temperature and high pressure to prepare the CNT/graphene covalent modified high-thermal conductivity carbide ceramic.
Preferably, step (1) comprises the sub-steps of:
(a) Mixing multi-walled carbon nanotube powder and multi-layer graphene powder to obtain a mixture;
(b) Under the vacuum condition, adding an organic solvent into the mixture to obtain a mixed solution;
(c) Under the vacuum condition, simultaneously carrying out ultrasonic treatment and stirring treatment on the mixed solution to obtain a CNT/graphene solution;
(d) And under the vacuum condition, adding the CNT/graphene solution into a ceramic precursor solution consisting of a ceramic precursor and an organic solvent, and simultaneously carrying out ultrasonic treatment and stirring treatment to obtain the CNT/graphene modified ceramic precursor solution.
Preferably, the mass ratio of the sum of the usage amounts of the multi-walled carbon nanotube powder and the multi-layered graphene powder to the usage amount of the organic solvent in the step (b) is 1: (1-100); in step (b) and/or step (d), the organic solvent is one or more of xylene, diethyl oxalate, ethanol and methanol; in the step (b), adding an organic solvent into the mixture under the vacuum condition with the absolute pressure of 1-100 Pa; in the step (c), the mixed solution is simultaneously subjected to ultrasonic treatment and stirring treatment for 1-100 min under the vacuum condition with the absolute pressure of 1-100 Pa; and/or in the step (d), under the vacuum condition that the absolute pressure is 1-100 Pa, adding the CNT/graphene solution into a ceramic precursor solution consisting of a ceramic precursor and an organic solvent, and simultaneously carrying out ultrasonic treatment and stirring treatment for 1-120 min.
Preferably, in the step (2), the curing is carried out in an inert atmosphere, and/or the curing temperature is 100-500 ℃, and the curing time is 1-360 min.
Preferably, in the step (2), pyrolysis is carried out in an inert atmosphere, and/or the pyrolysis temperature is 1000-1500 ℃, and the pyrolysis time is 1-360 min.
Preferably, in the step (3), sintering is carried out at high temperature and high pressure under the conditions of vacuum and inert gas introduction, wherein the flow rate of the introduced inert gas is 1-50 sccm; and/or in the step (3), the temperature of the high-temperature high-pressure sintering is 1500-1900 ℃, and the time of the high-temperature high-pressure sintering is 1-360 min.
Preferably, the mass ratio of the used amount of the multi-walled carbon nanotube powder to the used amount of the multi-layered graphene powder is (1-10): (1-10); and/or the mass ratio of the sum of the using amounts of the multi-walled carbon nanotube powder and the multilayer graphene powder to the ceramic precursor contained in the ceramic precursor solution is 1: (10-1000).
Preferably, the ceramic precursor contained in the ceramic precursor solution is one or more of poly-hafnoxane, poly-tantalaxane, poly-zirconyl-siloxane, and poly-tungstoxane.
Preferably, the multi-walled carbon nanotube powder is of a coaxial multi-layer structure, and the number of walls is 10-500; and/or the multilayer graphene powder is in a layer-by-layer parallel stacking structure, and the number of layers is 10-500.
The invention provides in a second aspect a CNT/graphene covalently modified high thermal conductivity carbide ceramic prepared by the preparation method according to the first aspect of the invention.
Compared with the prior art, the invention at least has the following beneficial effects:
(1) The invention adopts the multi-walled carbon nanotube and the multi-layer graphene as the reinforcing phases, and realizes the uniform dispersion in the ceramic precursor solution by means of vacuum vibration assistance, thereby solving the problem of brittleness of the carbide ceramic and obviously increasing the toughness of the prepared high-thermal-conductivity carbide ceramic; the invention discovers that the dispersion uniformity of the multi-walled carbon nanotube and the multi-layer graphene can be remarkably improved by introducing a vacuum condition compared with the mode of only adopting ultrasonic treatment and stirring treatment.
(2) In the prior art, the carbon nano tube or graphene and the carbide ceramic are mixed by adopting the traditional mechanical mixing, on one hand, the carbon nano tube or graphene is easy to agglomerate, on the other hand, the carbon nano tube or graphene and the ceramic particles are only in physical contact, and chemical covalent bond connection is not formed, so that heat conduction is not facilitated; according to the invention, a carbon thermal reduction reaction is adopted, and the covalent bond connection is constructed through the reaction of outer layer carbon of the multi-wall carbon nano tube and the multi-layer graphene and metal oxide, so that compared with non-covalent bond connection, the thermal conductivity of the ceramic can be improved to a greater extent through the covalent bond connection, the heat conduction speed is greatly improved, and the high-thermal-conductivity ceramic is obtained.
(3) The invention combines the characteristics of the carbon nano tube and the graphene as one-dimensional and two-dimensional nano materials respectively, gives full play to the excellent radial and in-plane transmission performance of the carbon nano tube and the graphene, obviously improves the heat conduction performance of the three-dimensional microstructure in the carbide ceramic, and effectively solves the problem of poor heat conduction performance of the carbide ceramic.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The invention provides a preparation method of CNT/graphene covalent modified high thermal conductivity carbide ceramic in a first aspect, which comprises the following steps:
(1) Under the condition of vacuum-assisted vibration, uniformly mixing multi-walled carbon nanotube powder, multi-layer graphene powder and a ceramic precursor solution to obtain a CNT/graphene modified ceramic precursor solution; the multi-wall carbon nanotube powder and the multi-layer graphene powder have no special requirements and can be directly purchased from the market; in the invention, it is preferable that the multi-walled carbon nanotube has a coaxial multi-layer structure, the number of walls is 10 to 500, the multi-layered graphene has a layer-by-layer parallel stacking structure, and the number of layers is 10 to 500; in the present invention, it is preferable that the ceramic precursor contained in the ceramic precursor solution is one or more of poly hafnium siloxane, poly tantalum siloxane, poly zirconium siloxane and poly tungsten siloxane; the sources of the hafnocene, the polytantalkane, the polynicosyloxane, the polytungstoxane and the like are not particularly limited, and the hafnocene, the polytantalkane, the polynicosyloxane, the polytungstoxane and the like can be purchased directly from the market or prepared by the existing method, the ceramic precursors can be dispersed in an organic solvent to form a ceramic precursor solution, the organic solvent is preferably one or more of dimethylbenzene, oxalic acid diethyl ether, ethanol and methanol, and the solid content of the ceramic precursor solution is preferably 60-80%; in the present invention, the ceramic precursor is, for example, poly hafnium siloxane, which is a high molecular polymer mainly containing hafnium, and can be converted into hafnium oxide by heat treatment under a certain condition.
(2) Sequentially solidifying and pyrolyzing the CNT/graphene modified ceramic precursor solution to obtain CNT/graphene covalent modified ceramic powder; according to the invention, a CNT/graphene modified ceramic precursor solution is used as a reactant, curing and pyrolysis process treatment are carried out, and CNT/graphene covalent modified ceramic powder is obtained through a carbothermic reduction reaction; in the present invention, the CNT/graphene modified ceramic precursor solution is first cured as a reactant, and the preferable curing conditions are: the curing temperature is 100-500 ℃, the curing time is 1-360 min, and an inert atmosphere is introduced to ensure that the CNT/graphene and a ceramic precursor (such as hafnoxane) contained in the ceramic precursor solution are subjected to a crosslinking reaction, so that the CNT/graphene is prevented from agglomerating and preparation is made for a subsequent high-temperature pyrolysis carbon thermal reduction reaction; after the cured product is obtained by curing, the high-temperature cracking is carried out, a ceramic precursor such as poly hafnium siloxane and the like is firstly converted into an oxide, and then undergoes a carbothermic reduction reaction with CNT/graphene to form a carbide, and the preferable conditions of the high-temperature cracking are as follows: the pyrolysis temperature is 1000-1500 ℃, the pyrolysis time is 1-360 min, and inert atmosphere is introduced; in the carbothermic reduction reaction, due to the fact that CNT/graphene has the structural characteristics of multi-wall/multi-layer and is limited by the number of local oxides, partial carbon of the CNT/graphene can react and form covalent bonds with carbides by controlling the ratio of the CNT/graphene to a ceramic precursor (such as poly hafnium siloxane) (preferably, the mass ratio of the sum of the using amount of the multi-wall carbon nanotube and the multi-layer graphene powder to the ceramic precursor contained in the ceramic precursor solution is 1 (10-1000)); the CNT and the graphene respectively have one-dimensional and two-dimensional structural characteristics, can fully exert radial and in-plane performances in carbide ceramics, realize advantage complementation and construct and form CNT/graphene covalent modified ceramic powder.
(3) Sintering the CNT/graphene covalent modified ceramic powder at high temperature and high pressure to prepare CNT/graphene covalent modified high-thermal conductivity carbide ceramic; in the present invention, in the high-temperature high-pressure sintering, it is preferable to extract vacuum (absolute pressure is 1 to 100 Pa), introduce a small amount of inert gas such as nitrogen (flow rate is preferably 1 to 50 sccm), and perform high-temperature high-pressure sintering for 1 to 360min at a temperature of 1500 to 1900 ℃ and a high pressure of 35 to 45MPa (e.g., 40 MPa) to sinter and mold the CNT/graphene covalent-modified ceramic powder (ceramic particles) to obtain the CNT/graphene covalent-modified high thermal conductivity carbide bulk ceramic.
The method adopts the multi-walled carbon nanotube and the multi-layer graphene as the reinforcing phase, and realizes the uniform dispersion in the ceramic precursor solution by means of vacuum vibration assistance, thereby solving the problem of brittleness of the carbide ceramic and obviously increasing the toughness of the prepared high-thermal-conductivity carbide ceramic; in addition, the method fully exerts the advantages of the carbon nano tube and the graphene respectively as the one-dimensional and two-dimensional nano carbon materials, and forms CNT/graphene covalent modified HfC and other carbide ceramic powder through the carbon thermal reduction reaction of the carbon materials and the oxide ceramic, thereby improving the electrical conductivity and the thermal conductivity of the HfC and other carbide ceramic matrix, and effectively solving the problems of poor thermal conductivity and the like of the HfC and other carbide ceramic; the CNT/graphene covalent modified high-thermal-conductivity carbide ceramic prepared by the method has the advantages of obviously improved toughness and thermal conductivity.
According to some preferred embodiments, step (1) comprises the following sub-steps:
(a) Mixing multi-walled carbon nanotube powder and multi-layer graphene powder to obtain a mixture;
(b) Under the vacuum condition, adding an organic solvent into the mixture to obtain a mixed solution;
(c) Under the vacuum condition, simultaneously carrying out ultrasonic treatment and stirring treatment on the mixed solution to obtain a CNT/graphene solution;
(d) And under the vacuum condition, adding the CNT/graphene solution into a ceramic precursor solution consisting of a ceramic precursor and an organic solvent, and simultaneously carrying out ultrasonic treatment and stirring treatment to obtain the CNT/graphene modified ceramic precursor solution.
According to some preferred embodiments, the mass ratio of the sum of the amounts of the multiwalled carbon nanotube powder and the multilayer graphene powder to the amount of the organic solvent in step (b) is 1: (1-100) (e.g. 1: (60-100); in step (b) and/or step (d), the organic solvent is one or more of xylene, diethyl ether oxalate, ethanol and methanol; in step (b), adding an organic solvent to the mixture under vacuum at an absolute pressure of 1 to 100Pa (e.g., 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 Pa); in step (c), the mixed solution is subjected to ultrasonic treatment and stirring treatment simultaneously for 1 to 100min (e.g., 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90 or 100 min), preferably 30 to 100min, more preferably 30 to 60min, under a vacuum condition with an absolute pressure of 1 to 100Pa (e.g., 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90 or 100 Pa); and/or in step (d), adding the CNT/graphene solution to a ceramic precursor solution composed of a ceramic precursor and an organic solvent under a vacuum condition with an absolute pressure of 1 to 100Pa (e.g., 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 Pa) and simultaneously performing ultrasonic treatment and stirring treatment for 1 to 120min (e.g., 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, or 120 min), preferably 30 to 120min, and more preferably 30 to 60min.
According to some specific embodiments, step (1) comprises the following sub-steps:
(a) Mixing multi-wall carbon nano tube powder and multi-layer graphene powder according to the mass ratio of (1-10): (1-10) adding the mixture into a round-bottom flask and mixing to obtain a mixture;
(b) Adding an organic solvent (such as dimethylbenzene) into the separating funnel, wherein the mass ratio of the sum of the used amount of the multi-wall carbon nano tube powder and the multi-layer graphene powder to the organic solvent is 1: (1-100), and vacuumizing the round-bottom flask filled with the multi-walled carbon nanotube powder and the multi-layer graphene powder in the step (a); after the round-bottom flask is in a stable vacuum state (for example, the round-bottom flask is preferably in a stable vacuum state of 1-100 Pa), dropwise adding the organic solvent in the separating funnel into the round-bottom flask filled with the multi-walled carbon nanotube and the multi-layer graphene powder to obtain a mixed solution; in the invention, the round-bottom flask is in a stable vacuum state of 1-100 Pa, namely the absolute pressure in the round-bottom flask is 1-100 Pa;
(c) Placing the round-bottom flask containing the mixed solution in the step (b) in a vacuum state in an ultrasonic device, starting mechanical stirring, and simultaneously performing ultrasonic treatment and stirring (mechanical stirring) treatment on the mixed solution for 1-100 min under the vacuum condition to ensure that the multi-walled carbon nanotube and the multi-layer graphene powder are uniformly dispersed in the organic solvent to obtain a uniformly dispersed CNT/graphene solution; the conditions for the ultrasonic treatment and the stirring treatment are not particularly limited;
(d) Collecting the CNT/graphene solution obtained in the step (c), adding the CNT/graphene solution into a ceramic precursor solution consisting of a ceramic precursor and an organic solvent under a vacuum condition, and simultaneously performing ultrasonic treatment and stirring treatment for 1-120 min to obtain a CNT/graphene modified ceramic precursor solution, thereby realizing uniform dispersion of the multi-walled carbon nanotube and the multi-layer graphene in the ceramic precursor solution; in the present invention, the solid content (mass percentage content of the ceramic precursor) of the ceramic precursor solution is preferably 60 to 80%.
According to some preferred embodiments, in step (2), the curing is performed in an inert atmosphere (e.g., an argon atmosphere), and/or the curing is performed at a temperature of 100 to 500 ℃ (e.g., 100 ℃, 150 ℃, 200 ℃, 250 ℃, 300 ℃, 350 ℃, 400 ℃, 450 ℃ or 500 ℃), and the curing is performed for a time of 1 to 360min (e.g., 1, 5, 10, 30, 60, 120, 180, 240, 300 or 360 min); in some more preferred embodiments, the curing temperature is 150 to 300 ℃ and the curing time is 60 to 180min.
According to some preferred embodiments, in step (2), the pyrolysis is carried out in an inert atmosphere, and/or the pyrolysis temperature is from 1000 to 1500 ℃ (e.g., 1000 ℃, 1100 ℃, 1200 ℃, 1300 ℃, 1400 ℃ or 1500 ℃), the pyrolysis time is from 1 to 360min (e.g., 1, 5, 10, 30, 60, 120, 180, 240, 300 or 360 min); in some more preferred embodiments, the pyrolysis temperature is 1300 to 1500 ℃, and the pyrolysis time is 60 to 180min.
In the present invention, when the curing is performed in an inert atmosphere and/or the pyrolysis is performed in an inert atmosphere, the flow rate of the inert gas to be introduced may be, for example, 1 to 50sccm.
According to some preferred embodiments, in step (3), the high-temperature high-pressure sintering is performed under vacuum (for example, at an absolute pressure of 1 to 100 Pa) and inert gas is introduced at a flow rate of 1 to 50sccm; in the present invention, the unit "sccm" represents standard milliliters per minute; and/or in step (3), the temperature of the high-temperature high-pressure sintering is 1500-1900 ℃ (such as 1500 ℃, 1600 ℃, 1700 ℃, 1800 ℃ or 1900 ℃), and the time of the high-temperature high-pressure sintering is 1-360 min (such as 1, 5, 10, 30, 60, 120, 180, 240, 300 or 360 min); in some more preferred embodiments, the high-temperature high-pressure sintering temperature is 1700-1900 ℃, and the high-temperature high-pressure sintering time is 30-120 min.
According to some preferred embodiments, the mass ratio of the used amount of the multi-walled carbon nanotube powder to the used amount of the multi-layered graphene powder is (1-10): (1 to 10) (e.g. 1, 1; and/or the mass ratio of the sum of the using amounts of the multi-walled carbon nanotube powder and the multilayer graphene powder to the ceramic precursor contained in the ceramic precursor solution is 1: (10-1000) (e.g. 1: (100 to 500); in the carbothermic reduction reaction, as CNT/graphene has the structural characteristics of multi-wall/multi-layer and is limited by the local oxide quantity, the mass ratio of CNT/graphene to ceramic precursor is controlled to be 1: (10-1000), partial carbon of the CNT/graphene can react and form covalent bond connection with the carbide, and the good modification effect of the carbon nanotube and the graphene on the carbide is realized, if the mass ratio of the CNT/graphene to the ceramic precursor is lower than 1: (10-1000) this range, will result in the carbon nanotube and graphene in its content too low, can't realize higher thermal conductivity promotion effect and toughness reinforcing effect, and if the proportion is higher than the above-mentioned range, will result in the carbon nanotube and graphene in its volume content too high, the ceramic content is too low, can't realize the ceramic briquetting, can't guarantee to get complete pottery.
According to some preferred embodiments, the ceramic precursor contained in the ceramic precursor solution is one or more of poly-hafnioxane, poly-tantaloxane, poly-zirconioxane, and poly-tungstoxane.
According to some preferred embodiments, the multi-walled carbon nanotube powder has a coaxial multi-layer structure, and the number of walls is 10 to 500; and/or the multilayer graphene powder is in a layer-by-layer parallel stacking structure, and the number of layers is 10-500.
The invention provides in a second aspect a CNT/graphene covalently modified high thermal conductivity carbide ceramic prepared by the preparation method according to the first aspect of the invention.
The invention will be further described by way of example only, without the scope of protection of the invention being limited to these examples. The present invention is capable of other embodiments, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention.
Example 1
(1) CNT/graphene modified hafnoxane solution: adding multi-wall carbon nanotube powder and multi-layer graphene powder into a round-bottom flask according to a mass ratio (abbreviated as the mass ratio of the carbon nanotubes to the graphene in table 1) of 10. Then adding dimethylbenzene into a separating funnel, wherein the mass ratio of the sum of the using amounts of the multi-walled carbon nanotube powder and the multilayer graphene powder to the dimethylbenzene is 1; after the vacuum is stable (the absolute pressure is 20 Pa), dropwise adding dimethylbenzene in the separating funnel into a round-bottom flask filled with the multi-walled carbon nanotube and the multi-layer graphene powder to obtain a mixed solution. And (2) placing the round-bottom flask containing the mixed solution in a vacuum state (the absolute pressure is 20 Pa) into an ultrasonic device, starting mechanical stirring, and simultaneously carrying out ultrasonic treatment (ultrasonic treatment in the ultrasonic device with the frequency of 40kHz and the power of 100W) and stirring treatment (the stirring rotating speed is 600 r/min) on the mixed solution under the vacuum condition of the absolute pressure of 20Pa for 30min to ensure that the multi-wall carbon nano tube powder and the multi-layer graphene powder are uniformly dispersed in xylene to obtain the CNT/graphene solution. Collecting the CNT/graphene solution, adding the CNT/graphene solution into a hafnocene solution consisting of hafnocene and xylene (the solid content of the hafnocene solution is 70%) under the condition that the absolute pressure is 20Pa, and simultaneously performing ultrasonic treatment (ultrasonic treatment is performed in an ultrasonic device with the frequency of 40kHz and the power of 100W) and stirring treatment (the rotating speed of stirring is 600 r/min) for 30min to obtain a CNT/graphene modified hafnocene solution, thereby realizing the uniform dispersion of multi-walled carbon nanotubes and multi-layer graphene in the hafnocene solution; wherein the number of walls of the multi-wall carbon nanotube powder is 100, the number of layers of the multi-layer graphene powder is 100, and the mass ratio of the sum of the amounts of the multi-wall carbon nanotube powder and the multi-layer graphene powder to the mass ratio of the poly (hafnoxane) contained in the poly (hafnoxane) solution (abbreviated as CNT/graphene/poly (hafnoxane mass ratio in table 1) is 1.
(2) CNT/graphene covalent modified HfC ceramic powder: and (2) curing by taking the CNT/graphene modified poly hafnoxane solution as a reactant (the curing temperature is 200 ℃, the curing time is 120min, the inert atmosphere is argon, and the argon flow is 10 sccm), so that the CNT/graphene and the poly hafnoxane are ensured to generate a crosslinking reaction, and the CNT/graphene is prevented from agglomerating. And then, carrying out pyrolysis on the cured product obtained by curing, wherein the poly-hafnoxane can be firstly converted into an oxide, and then the oxide and the CNT/graphene undergo a carbothermic reduction reaction, wherein the pyrolysis temperature is 1400 ℃, the pyrolysis time is 120min, and the inert atmosphere is argon (argon flow is 10 sccm), so that hafnium carbide is formed. Therefore, partial carbon of the CNT/graphene can react and form covalent bond connection with hafnium carbide, and the CNT/graphene covalent modified HfC ceramic powder is constructed.
(3) CNT/graphene covalently modified high thermal conductivity HfC carbide bulk ceramic: carrying out high-temperature high-pressure sintering treatment on the CNT/graphene covalent modified HfC ceramic powder obtained in the step (2); the high-temperature high-pressure sintering comprises the following steps: vacuum pumping (absolute pressure of 20 Pa), introducing nitrogen (flow rate of 10 sccm), sintering at 1800 deg.C under 40MPa for 60min to obtain sintered product with density of 12.8g/cm 3 The CNT/graphene covalently modified HfC carbide bulk ceramic with high thermal conductivity.
The CNT/graphene covalent modified high thermal conductivity HfC carbide bulk ceramic prepared in the embodiment is subjected to toughness and thermal conductivity tests, and the fracture toughness is 3.89 MPa-m 1/2 The thermal conductivity was 8.6W/(mK).
Example 2
(1) CNT/graphene modified hafnoxane solution: adding the multi-wall carbon nanotube powder and the multilayer graphene powder into a round-bottom flask according to the mass ratio of 10. Then adding dimethylbenzene into a separating funnel, wherein the mass ratio of the sum of the using amounts of the multi-walled carbon nanotube powder and the multilayer graphene powder to the dimethylbenzene is 1; after the vacuum is stable (the absolute pressure is 20 Pa), the dimethylbenzene in the separating funnel is dripped into the round-bottom flask filled with the multi-walled carbon nanotube and the multilayer graphene powder, and a mixed solution is obtained. And (2) placing the round-bottom flask containing the mixed solution in a vacuum state (the absolute pressure is 20 Pa) in an ultrasonic device, starting mechanical stirring, and simultaneously carrying out ultrasonic treatment (ultrasonic treatment in the ultrasonic device with the frequency of 40kHz and the power of 100W) and stirring (the stirring rotating speed is 600 r/min) treatment on the mixed solution for 30min under the vacuum condition of the absolute pressure of 20Pa to ensure that the multi-wall carbon nano tube powder and the multi-layer graphene powder are uniformly dispersed in xylene to obtain the CNT/graphene solution. Collecting the CNT/graphene solution, adding the CNT/graphene solution into a hafnocene solution consisting of hafnocene and xylene (the solid content of the hafnocene solution is 70%) under the condition that the absolute pressure is 20Pa, and simultaneously carrying out ultrasonic treatment (ultrasonic treatment is carried out in an ultrasonic device with the frequency of 40kHz and the power of 100W) and stirring (the rotating speed of stirring is 600 r/min) for 30min to obtain a CNT/graphene modified hafnocene solution, thereby realizing the uniform dispersion of multi-walled carbon nanotubes and multi-layer graphene in the hafnocene solution; the mass ratio of the sum of the using amounts of the multi-wall carbon nanotube powder and the multi-layer graphene powder to the poly-hafnoxane contained in the poly-hafnoxane solution is 1.
(2) CNT/graphene covalent modified HfC ceramic powder: and (2) curing by taking the CNT/graphene modified poly hafnoxane solution as a reactant (the curing temperature is 200 ℃, the curing time is 120min, the inert atmosphere is argon, and the argon flow is 10 sccm), so that the CNT/graphene and the poly hafnoxane are ensured to generate a crosslinking reaction, and the CNT/graphene is prevented from agglomerating. And then, carrying out pyrolysis on the cured product obtained by curing, wherein the poly-hafnoxane can be firstly converted into an oxide, and then the oxide and the CNT/graphene undergo a carbothermic reduction reaction, wherein the pyrolysis temperature is 1400 ℃, the pyrolysis time is 120min, and the inert atmosphere is argon (argon flow is 10 sccm), so that hafnium carbide is formed. Therefore, partial carbon of the CNT/graphene can react and form covalent bond connection with hafnium carbide, and the CNT/graphene covalent modified HfC ceramic powder is constructed.
(3) CNT/graphene covalently modified high thermal conductivity HfC carbide bulk ceramic: sintering the CNT/graphene covalent modified HfC ceramic powder obtained in the step (2) at high temperature and high pressure; the high-temperature high-pressure sintering comprises the following steps: extracting trueIntroducing nitrogen (flow rate 10 sccm) at 1800 deg.C under 40MPa for 60min to obtain a sintered product with density of 12.6g/cm 3 The CNT/graphene covalently modified HfC carbide bulk ceramic with high thermal conductivity.
The CNT/graphene covalent modified high thermal conductivity HfC carbide ceramic prepared in the embodiment is subjected to toughness and thermal conductivity tests, and the fracture toughness is measured to be 4.68 MPa-m 1/2 The thermal conductivity was 10.1W/(mK).
Compared with example 1, in example 2, when the CNT/graphene modified hafnoxane solution is prepared, the ratio of CNT/graphene to hafnoxane is adjusted, and the content of CNT/graphene is increased, so that the content of CNT/graphene in the finally prepared CNT/graphene covalent modified high thermal conductivity HfC bulk ceramic is increased, and the toughness and thermal conductivity of the high thermal conductivity HfC bulk ceramic are improved.
Examples 3 to 6
The specific process parameters of examples 3-6 and the performance index of the finally prepared CNT/graphene covalent modified high thermal conductivity HfC carbide bulk ceramic are shown in table 1, and the other preparation processes are the same as in example 1.
Table 1: the process parameters and performance index of examples 1-6.
As can be seen from table 1, when comparing example 1 with example 4, by adjusting the ratio of the multi-walled carbon nanotubes to the multi-layered graphene, when the content of graphene is increased, the fracture toughness and the thermal conductivity of the finally obtained HfC ceramic are also increased, because graphene is a two-dimensional nanomaterial, and has a higher specific surface area than a one-dimensional carbon nanotube, which shows a more significant advantage in improving the toughness of the material and the heat transfer rate.
Comparative example 1
(1) CNT/graphene modified hafnoxane solution: adding the multi-wall carbon nanotube powder and the multilayer graphene powder into a round-bottom flask according to the mass ratio of 10. And then adding xylene into a separating funnel, wherein the mass ratio of the sum of the using amounts of the multi-walled carbon nanotube and the multilayer graphene powder to the xylene is 1. And (2) placing the round-bottom flask containing the mixed solution into an ultrasonic device, starting mechanical stirring, and simultaneously carrying out ultrasonic treatment (ultrasonic treatment is carried out in the ultrasonic device with the frequency of 40kHz and the power of 100W) and stirring treatment (the rotating speed of stirring is 600 r/min) on the mixed solution for 30min to obtain the CNT/graphene solution. Collecting the CNT/graphene solution, adding the CNT/graphene solution into a hafnocene solution (the solid content of the hafnocene solution is 70%) consisting of hafnocene and xylene, and simultaneously performing ultrasonic treatment (ultrasonic treatment is performed in an ultrasonic device with the frequency of 40kHz and the power of 100W) and stirring treatment (the rotating speed of stirring is 600 r/min) for 30min to obtain a CNT/graphene modified hafnocene solution; wherein the number of walls of the multi-wall carbon nanotube powder is 100, the number of layers of the multi-layer graphene powder is 100, and the mass ratio of the sum of the usage amount of the multi-wall carbon nanotube powder and the multi-layer graphene powder to the mass ratio of the poly-hafnoxane contained in the poly-hafnoxane solution is 1.
(2) CNT/graphene covalent modified HfC ceramic powder: and (2) curing the CNT/graphene modified poly (hafnoxane) solution obtained in the step (1) as a reactant (the curing temperature is 200 ℃, the curing time is 120min, the inert atmosphere is argon, and the flow of the argon is 10 sccm). And then, carrying out pyrolysis on the cured product obtained by curing, wherein the poly-hafnium siloxane is converted into an oxide, and then is subjected to a carbothermic reduction reaction with CNT/graphene, wherein the pyrolysis temperature is 1400 ℃, the pyrolysis time is 120min, and the inert atmosphere is argon (the argon flow is 10 sccm), so that hafnium carbide is formed.
(3) CNT/graphene covalently modified HfC carbide bulk ceramic: sintering the CNT/graphene covalent modified HfC ceramic powder obtained in the step (2) at high temperature and high pressure; the high-temperature high-pressure sintering comprises the following steps: and (3) vacuumizing (the absolute pressure is 20 Pa), introducing nitrogen (the flow is 10 sccm), sintering at 1800 ℃ under high temperature and high pressure, and sintering at 40MPa for 60min to obtain the CNT/graphene covalent modified HfC carbide blocky ceramic.
The CNT/graphene covalent modified HfC carbide bulk ceramic prepared by the comparative example is tested for toughness and thermal conductivity, and the fracture toughness is measured to be 2.35 MPa.m 1/2 The thermal conductivity was 5.4W/(mK).
Comparative example 2
(1) CNT-modified hafnoxane solution: adding the multi-walled carbon nanotube powder into a round-bottom flask. Then adding dimethylbenzene into a separating funnel, and vacuumizing the round-bottom flask filled with the multi-walled carbon nanotube powder; after the vacuum is stable (the absolute pressure is 20 Pa), the dimethylbenzene in the separating funnel is dripped into the round-bottom flask filled with the multi-walled carbon nano-tubes, and the dimethylbenzene solution of the multi-walled carbon nano-tubes is obtained. Placing the round-bottom flask in a vacuum state (the absolute pressure is 20 Pa) in an ultrasonic device, starting mechanical stirring, and simultaneously carrying out ultrasonic treatment (ultrasonic treatment in the ultrasonic device with the frequency of 40kHz and the power of 100W) and stirring treatment (the rotating speed of stirring is 600 r/min) on the xylene solution of the multi-wall carbon nano tubes for 30min under the vacuum condition of the absolute pressure of 20Pa to obtain the CNT solution. Collecting the CNT solution, adding the CNT solution into a hafnocene solution (the solid content of the hafnocene solution is 70%) consisting of hafnocene and xylene under the vacuum condition of the absolute pressure of 20Pa, and simultaneously performing ultrasonic treatment (ultrasonic treatment is performed in an ultrasonic device with the frequency of 40kHz and the power of 100W) and stirring treatment (the rotating speed of stirring is 600 r/min) for 30min to obtain a CNT modified hafnocene solution; wherein the number of walls of the multi-walled carbon nanotube powder is 100, and the mass ratio of the multi-walled carbon nanotube powder to the poly-hafnoxane contained in the poly-hafnoxane solution is 1.
(2) CNT-covalently modified HfC ceramic powder: curing the CNT-modified hafnoxane solution obtained in the step (1) as a reactant (curing temperature 200 ℃, curing time 120min, inert atmosphere argon, argon flow 10 sccm). And then, carrying out pyrolysis on the cured product obtained by curing, wherein the poly-hafnoxane can be firstly converted into an oxide, and then, carrying out a carbothermic reduction reaction on the oxide and the CNT, wherein the pyrolysis temperature is 1400 ℃, the pyrolysis time is 120min, and the inert atmosphere is argon (argon flow is 10 sccm), so as to form the hafnium carbide. Therefore, partial carbon of the CNT can react and form covalent bond connection with hafnium carbide, and the CNT covalent modified HfC ceramic powder is constructed.
(3) CNT covalently modified HfC carbide bulk ceramic: sintering the CNT covalent modified HfC ceramic powder obtained in the step (2) at high temperature and high pressure; the high-temperature high-pressure sintering comprises the following steps: and (3) vacuumizing (the absolute pressure is 20 Pa), introducing nitrogen (the flow is 10 sccm), sintering at 1800 ℃ under 40MPa for 60min, and obtaining the CNT covalent modified HfC carbide blocky ceramic.
The CNT covalently modified HfC carbide bulk ceramic prepared by the comparative example was subjected to toughness and thermal conductivity tests and the fracture toughness was measured to be 3.26 MPa.m 1/2 The thermal conductivity was 6.9W/(mK).
Comparative example 3
(1) Graphene modified hafnoxane solution: adding the multilayer graphene powder into a round-bottom flask. Then adding dimethylbenzene into a separating funnel, and vacuumizing the round-bottom flask filled with the multilayer graphene powder; after the vacuum is stable (the absolute pressure is 20 Pa), the dimethylbenzene in the separating funnel is dripped into the round-bottom flask filled with the multilayer graphene, and the dimethylbenzene solution of the multilayer graphene is obtained. Placing the round-bottom flask in a vacuum state (the absolute pressure is 20 Pa) in an ultrasonic device, starting mechanical stirring, and simultaneously carrying out ultrasonic treatment (ultrasonic treatment is carried out in the ultrasonic device with the frequency of 40kHz and the power of 100W) and stirring treatment (the rotating speed of stirring is 600 r/min) on the xylene solution of the multilayer graphene for 30min under the vacuum condition of the absolute pressure of 20Pa to obtain the graphene solution. Collecting the graphene solution, adding the graphene solution into a hafnocene solution consisting of hafnocene and xylene under a vacuum condition with an absolute pressure of 20Pa, and simultaneously performing ultrasonic treatment (ultrasonic treatment is performed in an ultrasonic device with a frequency of 40kHz and a power of 100W) and stirring treatment (the rotating speed of stirring is 600 r/min) for 30min to obtain a graphene modified hafnocene solution; wherein the number of layers of the multilayer graphene powder is 100, and the mass ratio of the multilayer graphene powder to the hafnocene contained in the hafnocene solution is 1.
(2) Graphene covalent modified HfC ceramic powder: and (2) curing the graphene modified poly hafnoxane solution obtained in the step (1) as a reactant (the curing temperature is 200 ℃, the curing time is 120min, the inert atmosphere is argon, and the argon flow is 10 sccm). And then, carrying out pyrolysis on the cured product obtained by curing, wherein the poly-hafnoxane can be firstly converted into an oxide, and then, carrying out a carbothermic reduction reaction with the graphene, wherein the pyrolysis temperature is 1400 ℃, the pyrolysis time is 120min, and the inert atmosphere is argon (argon flow is 10 sccm), so as to form the hafnium carbide. Therefore, partial carbon of the graphene can react and form covalent bond connection with hafnium carbide, and the graphene covalent modified HfC ceramic powder is constructed.
(3) Graphene covalently modified HfC carbide bulk ceramic: sintering the graphene covalent modified HfC ceramic powder obtained in the step (2) at high temperature and high pressure; the high-temperature high-pressure sintering comprises the following steps: and (3) vacuumizing (the absolute pressure is 20 Pa), introducing nitrogen (the flow is 10 sccm), sintering at 1800 ℃ under 40MPa for 60min, and obtaining the graphene covalent modified HfC carbide blocky ceramic.
The graphene covalent modified HfC carbide bulk ceramic prepared by the comparative example is subjected to toughness and thermal conductivity tests, and the fracture toughness is 3.55 MPa-m 1/2 The thermal conductivity was 7.6W/(mK).
The invention has not been described in detail and is not limited thereto.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A preparation method of CNT/graphene covalent modified high thermal conductivity carbide ceramic is characterized by comprising the following steps:
(1) Under the condition of vacuum-assisted vibration, uniformly mixing multi-walled carbon nanotube powder, multi-layer graphene powder and a ceramic precursor solution to obtain a CNT/graphene modified ceramic precursor solution; the mass ratio of the sum of the using amounts of the multi-walled carbon nanotube powder and the multi-layered graphene powder to the ceramic precursor contained in the ceramic precursor solution is 1: (10 to 1000);
(2) Sequentially solidifying and pyrolyzing the CNT/graphene modified ceramic precursor solution to obtain CNT/graphene covalent modified ceramic powder; carrying out pyrolysis in an inert atmosphere, wherein the pyrolysis temperature is 1000-1500 ℃;
(3) Sintering the CNT/graphene covalent modified ceramic powder at high temperature and high pressure to prepare CNT/graphene covalent modified high-thermal conductivity carbide ceramic; the temperature of the high-temperature high-pressure sintering is 1500-1900 ℃, and the pressure is 35-45MPa.
2. The method of claim 1, wherein step (1) comprises the substeps of:
(a) Mixing multi-walled carbon nanotube powder and multi-layer graphene powder to obtain a mixture;
(b) Under the vacuum condition, adding an organic solvent into the mixture to obtain a mixed solution;
(c) Under the vacuum condition, simultaneously carrying out ultrasonic treatment and stirring treatment on the mixed solution to obtain a CNT/graphene solution;
(d) And under the vacuum condition, adding the CNT/graphene solution into a ceramic precursor solution consisting of a ceramic precursor and an organic solvent, and simultaneously carrying out ultrasonic treatment and stirring treatment to obtain the CNT/graphene modified ceramic precursor solution.
3. The method of claim 2, wherein:
the mass ratio of the sum of the dosages of the multi-walled carbon nanotube powder and the multi-layer graphene powder to the dosage of the organic solvent in the step (b) is 1: (1 to 100);
in step (b) and step (d), the organic solvent is one or more of xylene, oxalic acid diethyl ether, ethanol and methanol;
in the step (b), adding an organic solvent into the mixture under the vacuum condition of absolute pressure of 1 to 100Pa;
in the step (c), the mixed solution is subjected to ultrasonic treatment and stirring treatment for 1 to 100min at the same time under the vacuum condition of the absolute pressure of 1 to 100Pa;
in the step (d), under the vacuum condition of the absolute pressure of 1 to 100Pa, adding the CNT/graphene solution into a ceramic precursor solution composed of a ceramic precursor and an organic solvent, and simultaneously carrying out ultrasonic treatment and stirring treatment for 1 to 120min.
4. The production method according to any one of claims 1 to 3, characterized in that:
and (2) curing in an inert atmosphere at the temperature of 100-500 ℃ for 1-360min.
5. The production method according to any one of claims 1 to 3, characterized in that:
in the step (2), the pyrolysis time is 1 to 360min.
6. The production method according to any one of claims 1 to 3, characterized in that:
in the step (3), sintering at high temperature and high pressure under the conditions of vacuum and inert gas introduction, wherein the flow rate of the introduced inert gas is 1 to 50sccm;
in the step (3), the time of high-temperature high-pressure sintering is 1 to 360min.
7. The production method according to any one of claims 1 to 3, characterized in that:
the mass ratio of the usage amount of the multi-walled carbon nanotube powder to the usage amount of the multi-layered graphene powder is (1 to 10): (1 to 10).
8. The production method according to any one of claims 1 to 3, characterized in that:
the ceramic precursor contained in the ceramic precursor solution is one or more of poly hafnium-oxygen alkane, poly tantalum-oxygen alkane, poly zirconium-oxygen alkane and poly tungsten-oxygen alkane.
9. The production method according to any one of claims 1 to 3, characterized in that:
the multi-wall carbon nano tube powder is of a coaxial multi-layer structure, and the wall number is 10 to 500;
the multilayer graphene powder is in a layer-by-layer parallel stacking structure, and the number of layers is 10 to 500.
10. CNT/graphene covalently modified high thermal conductivity carbide ceramic prepared by the preparation method of any one of claims 1 to 9.
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