WO2022204866A1 - 一种具有双取向网络的气凝胶及其制备方法和应用 - Google Patents

一种具有双取向网络的气凝胶及其制备方法和应用 Download PDF

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WO2022204866A1
WO2022204866A1 PCT/CN2021/083548 CN2021083548W WO2022204866A1 WO 2022204866 A1 WO2022204866 A1 WO 2022204866A1 CN 2021083548 W CN2021083548 W CN 2021083548W WO 2022204866 A1 WO2022204866 A1 WO 2022204866A1
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aerogel
cylindrical ring
metal cylindrical
filler
sintering
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PCT/CN2021/083548
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English (en)
French (fr)
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么依民
孙蓉
曾小亮
许建斌
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中国科学院深圳先进技术研究院
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Priority to PCT/CN2021/083548 priority Critical patent/WO2022204866A1/zh
Publication of WO2022204866A1 publication Critical patent/WO2022204866A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00—Nitrogen; Compounds thereof
    • C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
    • C01B21/064—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with boron
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
    • C08L1/08—Cellulose derivatives
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L29/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical; Compositions of hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Compositions of derivatives of such polymers
    • C08L29/02—Homopolymers or copolymers of unsaturated alcohols
    • C08L29/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D31/00—Other cooling or freezing apparatus

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  • the invention belongs to the technical field of porous materials, and in particular relates to an aerogel with a bidirectional network and a preparation method and application thereof.
  • Aerogel is a kind of porous material, because of its unique microstructure, it has broad application prospects in the fields of adsorption and environmental protection, energy storage, tissue engineering, structural composite materials, etc., and has received extensive attention in recent years.
  • the application of aerogels involves the mass transfer behavior of aerogels, and the microstructure of aerogels is the main factor affecting the mass transfer performance of aerogels.
  • the microstructure of conventional aerogels is disordered. In order to improve the mass transfer performance of aerogels in specific directions, researchers have conducted extensive research on aerogels with oriented and ordered microstructures.
  • the microstructure of aerogels is related to the assembly technique and the morphology of the assembled unit.
  • the most studied are aerogels with unidirectional networks. Freeze casting is a common method for preparing aerogels with unidirectional networks, which is simple and environmentally friendly.
  • the prepared aerogel has an oriented microstructure in the axial direction, thereby showing excellent mass transfer performance in the axial direction.
  • Single-oriented aerogels have shown great potential in both thermally conductive composites and adsorption. Shenzhen Advanced Institute of Chinese Academy of Sciences has published a number of related patents.
  • Aerogels with dual-oriented networks face greater application requirements and technical difficulties than aerogels with single-oriented networks.
  • aerogels with bi-oriented networks and their preparation methods and applications are rarely mentioned.
  • the purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art, and to provide a general method for preparing aerogels with bi-oriented networks, which is widely applicable to zero-dimensional particles, one-dimensional tubes /Linear materials and two-dimensional materials are not limited by material types and morphology.
  • This method provides a new idea for optimizing the microstructure of aerogels and solves the current technical bottleneck.
  • a first aspect of the present invention provides a method for preparing an aerogel with a bidirectional network, comprising the steps of:
  • Step 1 Mix the filler, polymer binder and water according to the mass ratio of 1:0.01-0.05:3-50 to obtain the filler mixture;
  • Step 2 Putting the bi-orientation molding device into a low-temperature refrigeration medium in advance, adding the filler mixture into the bi-orientation molding device, performing freezing treatment to form a frozen mixture, and then performing freeze-drying treatment to obtain an aerogel precursor;
  • Step 3 performing sintering heat treatment on the aerogel precursor to obtain an aerogel
  • the dual orientation forming device is a container composed of a metal cylindrical ring and a gasket located at the bottom of the metal cylindrical ring.
  • the filler is any substance that does not chemically react with water at room temperature, and the filler is zero-dimensional particles, one-dimensional tube/wire-like materials, two-dimensional material micro-nano materials, Three-dimensional granular material, the filler is a micro-nano material.
  • the size of the filler is 50 nm to 100 ⁇ m, such as 100 nm, 300 nm, 500 nm, 1 ⁇ m, 3 ⁇ m, 5 ⁇ m, 10 ⁇ m, 20 ⁇ m, 30 ⁇ m, 40 ⁇ m, 50 ⁇ m, 100 ⁇ m.
  • the filler is selected from at least one of aluminum oxide, magnesium oxide, zinc oxide, aluminum nitride, boron nitride, silicon carbide, and graphene.
  • the aerogel can be prepared based on the method of the present invention.
  • the filler is selected from, but not limited to, any one of particles, wires or flakes, or a free combination thereof. Any one of particles, threads or sheets, or a free combination thereof can be prepared into aerogels based on the method of the present invention.
  • the particle size of the filler is 50 nm ⁇ 100 ⁇ m.
  • the polymer binder is selected from polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, polyacrylamide, carboxymethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl cellulose. or at least one of hydroxypropyl methylcellulose.
  • the selection of these polymer binders can effectively increase the viscosity of the solution, thereby improving the dispersibility of the filler in water, avoiding the agglomeration of the filler, and improving the mechanical properties of the aerogel precursor to facilitate subsequent sintering heat treatment.
  • the mixing treatment adopts a planetary mixer to stir, and after mixing the filler, the polymer binder and the water according to a certain mass ratio, a uniform filler mixture in a short time is obtained.
  • the metal in the metal cylindrical ring is any metal substance that does not chemically react with water at normal temperature, preferably copper, silver, gold, platinum, molybdenum, tungsten, nickel, aluminum , at least one of iron, zinc, tin, lead.
  • the target metal does not chemically react with water, it can be used to prepare the metal cylindrical ring described in this patent.
  • the selection of these metals can effectively promote the formation of the temperature gradient in the radial direction, and improve the structural regularity of the aerogel precursor in the radial direction, so as to obtain an aerogel with a bidirectional network.
  • the length ratio of the outer diameter to the height of the metal cylindrical ring is 0.25-4:1.
  • the height of the metal cylindrical ring is 1-5 cm.
  • the wall thickness of the metal cylindrical ring is 50-500 ⁇ m.
  • the anisotropy and structural regularity of the aerogel microstructure can be controlled by controlling the length ratio of the outer diameter to the height of the metal cylindrical ring, and the height and wall thickness of the metal cylindrical ring.
  • the gasket is prepared by curing a polymer matrix, and the polymer matrix is epoxy resin, polyurethane, phenolic resin, unsaturated polyester, amino resin, polyethylene, polypropylene, At least one of polyvinyl chloride, polystyrene or polysiloxane.
  • the diameter of the polymer circular gasket is equal to the inner diameter of the metal cylindrical ring, and the length ratio of the thickness of the polymer circular gasket to the height of the metal cylindrical ring is 0.01-0.5:1.
  • the bidirectional molding device is to put the polymer gasket into the metal cylindrical ring and place it on the bottom to form a container that can hold liquid.
  • the low-temperature refrigeration medium is at least one of liquid nitrogen or liquid helium
  • the freezing treatment is to add the filler mixture into the bidirectional molding device and indirectly contact with the low-temperature refrigeration medium, thereby triggering a continuous self-assembly molding process.
  • the water in the filler mixture freezes and squeezes the filler to form a microstructure of a bi-oriented network.
  • ice crystals grow in two directions simultaneously, a radial direction from the periphery to the center, and an axial direction from the bottom to the top.
  • at least one quarter of the metal cylindrical ring in the bidirectional forming device is immersed in the cryogenic refrigeration medium.
  • the metal cylindrical ring can be rapidly heated, and only a quarter of immersion can ensure that the metal cylindrical ring is rapidly cooled to a temperature close to that of the freezing medium.
  • the freeze-drying process is to put the frozen product into a freeze-drying machine to sublimate the ice.
  • sintering is performed at a temperature of 300°C to 2500°C for 1h to 12h;
  • pre-sintering is performed at a temperature of 300° C. ⁇ 400° C. before the sintering heat treatment, and the pre-sintering time is 4 h ⁇ 6 h.
  • the second aspect of the present invention provides an aerogel, which is prepared by the preparation method of the present invention, and the ratio of the thermal conductivity measured in the radial and axial directions of the aerogel is: 0.4-1.2, and the anisotropy coefficient of the aerogel is 0.4-1.2.
  • a third aspect of the present invention provides a system for preparing a bi-oriented network aerogel, the system comprising a bi-orientation forming device, the bi-orientation forming device is composed of a metal cylindrical ring and a bottom of the metal cylindrical ring Containers made of gaskets.
  • the metal in the metal cylindrical ring is any metal substance that does not chemically react with water at room temperature, preferably copper, silver, gold, platinum, molybdenum, tungsten, nickel, aluminum, iron, zinc, At least one of tin and lead.
  • the length ratio of the outer diameter to the height of the metal cylindrical ring is 0.25-4:1.
  • the height of the metal cylindrical ring is 1-5 cm.
  • the wall thickness of the metal cylindrical ring is 50-500 ⁇ m.
  • the gasket is prepared by curing a polymer matrix, and the polymer matrix is epoxy resin, polyurethane, phenolic resin, unsaturated polyester, amino resin, polyethylene, polypropylene, polyvinyl chloride, polyvinyl chloride, etc. At least one of styrene or polysiloxane.
  • the diameter of the polymer circular gasket is equal to the inner diameter of the metal cylindrical ring, and the length ratio of the thickness of the polymer circular gasket to the height of the metal cylindrical ring is 0.01-0.5:1.
  • the system further includes a low-temperature refrigeration medium, preferably, the low-temperature refrigeration medium is liquid nitrogen or liquid helium.
  • the system further includes a freeze-drying device.
  • the system further includes a sintering device.
  • the sintering device can provide a temperature of 300°C-3000°C.
  • the system further includes a mixing device.
  • the mixing device is selected from planetary mixers.
  • a fourth aspect of the present invention provides the use of the aerogel prepared by the method of the present invention as a thermally conductive composite material.
  • the present invention has the following beneficial effects:
  • the aerogel prepared by the present invention is different from the traditional aerogel.
  • the aerogel prepared by the invention has the microstructure of a double-oriented network, and has regular channels in both radial and axial directions, thereby showing good mass transfer performance.
  • the aerogel prepared by the method of the invention has excellent comprehensive structural properties and controllability, and therefore, it can be more widely used in the fields of thermally conductive composite materials, environmental protection, sensors, military and aerospace.
  • the preparation method of an aerogel with a bi-oriented network proposed by the present invention mixes the filler, the polymer binder and water to form a uniform filler mixture, and only needs to subject the filler mixture to freezing treatment, freeze drying and sintering heat treatment That is, the method has a wide range of applicable materials, controllable size of aerogel, simple preparation process, and relatively mild reaction conditions, effectively solving the technical bottleneck of narrow applicable material range and complex preparation process of the existing common methods, and broadening the scope of aerogels.
  • Fig. 1 is the general preparation method flow chart of the method for preparing a kind of aerogel with bi-oriented network of the present invention
  • Fig. 2 is the general schematic diagram of the present invention for preparing a kind of bi-orientation molding device for aerogel with bi-orientation network;
  • Fig. 3 is the electron photograph during the freezing process of the boron nitride aerogel prepared in Example 1;
  • FIG. 4 is an electronic photograph of the graphene aerogel prepared in Example 2.
  • the present invention provides a method for preparing aerogels with bi-oriented networks.
  • the general process steps of the method for preparing an aerogel with a bi-oriented network of the present invention are shown in Figure 1, which includes the following steps:
  • S02. put the bidirectional molding device into a low-temperature refrigeration medium in advance, drop the filler mixture into the bidirectional molding device, perform freezing treatment to form a frozen mixture, and perform freeze drying treatment to obtain an aerogel precursor;
  • the dual-orientation molding device used in the present invention is improved on the traditional single-orientation device.
  • a radial temperature gradient is introduced to guide the ice crystals in the radial and axial directions during the freezing process.
  • the wall thickness of the metal cylindrical ring affects the radial temperature gradient
  • the thickness of the polymer gasket affects the axial temperature gradient.
  • FIG. 2 is an explanatory diagram of the principle of a general bi-oriented molding device for preparing an aerogel with a bi-oriented network in accordance with the present invention.
  • the bi-orientation molding device is pre-cooled in a low-temperature refrigeration medium, and the filler mixture is dropped into the bi-orientation molding device, and the local freeze-casting self-assembly process occurs immediately. Ice crystals grow along a temperature gradient in both radial and axial directions. As the ice crystals become larger, the fillers in the mixture are repelled and agglomerated between adjacent ice crystals. Freezing promotes the formation of oriented skeletons in the direction of the temperature gradient, giving the material anisotropic properties. As the freeze-casting self-assembly process continued until all the water in the filler mixture turned to ice. The ice is sublimed by freeze-drying to obtain aerogel precursors with bi-oriented networks.
  • these aerogel materials are prepared by the above-mentioned general method for preparing aerogels with bi-oriented network. Specifically include the following embodiments:
  • Example 1 The preparation method of boron nitride aerogel provided in Example 1 is shown in FIG. 1 , and includes the following specific steps:
  • the dual orientation forming device includes a copper cylindrical ring and an epoxy resin gasket at the bottom of the copper cylindrical ring, the length ratio of the outer diameter to the height of the copper cylindrical ring is 0.5:1, the height of the copper cylindrical ring is 4.5cm, and the copper cylindrical ring is 4.5cm high.
  • the wall thickness of the ring is 200 ⁇ m
  • the thickness of the epoxy gasket is 2 cm
  • the diameter of the epoxy gasket is equal to the inner diameter of the copper cylindrical ring. At least a quarter of the copper cylindrical rings were immersed in liquid nitrogen.
  • the boron nitride aerogel precursor is subjected to a sintering heat treatment process, the first sintering heat treatment temperature is 350°C, and the sintering time is 4h; the second sintering temperature is 900°C, and the sintering time is 10h.
  • the boron nitride aerogel prepared in Example 1 of the present invention is analyzed, and the electron photo of the boron nitride aerogel during the freezing process is shown in Figure 3. It can be seen that the growth of radial ice crystals dominates during the freezing process. Therefore, more radial networks are formed inside the aerogel, while the proportion of axial networks decreases.
  • the measured thermal conductivities of the boron nitride aerogel-filled epoxy resin composite in the radial and axial directions are 3.56 W/mK and 3.43 W/mK, respectively, and the anisotropy coefficient of the aerogel is 1.04.
  • the dual orientation molding device includes a silver cylindrical ring and a polysiloxane gasket at the bottom of the silver cylindrical ring.
  • the length ratio of the outer diameter to the height of the silver cylindrical ring is 0.3:1, the height of the silver cylindrical ring is 3 cm, and the silver cylindrical ring is 3 cm in height.
  • the wall thickness of the ring is 100 ⁇ m, the thickness of the silicone gasket is 1 cm, and the silicone gasket diameter is equal to the inner diameter of the silver cylindrical ring. At least a quarter of the silver cylindrical rings were immersed in liquid nitrogen.
  • the graphene aerogel precursor is subjected to a sintering heat treatment process, the first sintering heat treatment temperature is 300° C., and the sintering time is 4 hours; the second sintering treatment is not performed.
  • the graphene aerogel prepared in Example 2 of the present invention is analyzed, and the electronic photo of the graphene aerogel is shown in Figure 4, and an obvious radial network structure can be seen.
  • the measured thermal conductivities of the graphene aerogel-filled epoxy resin composites in the radial and axial directions are 0.52 W/mK and 0.49 W/mK, respectively, and the anisotropy coefficient of the aerogel is 1.06 .
  • Example 3 The preparation method of the alumina aerogel provided in Example 3 is shown with reference to accompanying drawing 1, and comprises the following specific steps:
  • the double orientation molding device includes a tin cylindrical ring and a phenolic resin gasket, the length ratio of the outer diameter to the height of the tin cylindrical ring is 3:1, the height of the tin cylindrical ring is 1cm, the wall thickness of the tin cylindrical ring is 400 ⁇ m, and the phenolic resin gasket The thickness of the sheet is 0.1 cm, and the diameter of the phenolic resin spacer is equal to the inner diameter of the tin cylindrical ring. At least a quarter of the tin cylindrical rings were immersed in liquid nitrogen.
  • the alumina aerogel precursor is subjected to a sintering heat treatment process, the first sintering heat treatment temperature is 400°C, and the sintering time is 6h; the second sintering temperature is 1300°C, and the sintering time is 10h. .
  • the alumina aerogel prepared in Example 3 of the present invention was analyzed, and the thermal conductivity of the composite material filled with alumina aerogel in the radial and axial directions was 0.72W/mK and 1.25 respectively. W/mK, the anisotropy coefficient of the aerogel was 0.58.
  • Example 4 The preparation method of boron nitride aerogel provided in Example 4 is shown in FIG. 1 and includes the following specific steps:
  • the dual orientation forming device includes a copper cylindrical ring and an epoxy resin gasket at the bottom of the copper cylindrical ring, the length ratio of the outer diameter to the height of the copper cylindrical ring is 0.5:1, the height of the copper cylindrical ring is 4.5cm, and the copper cylindrical ring is 4.5cm high.
  • the wall thickness of the ring is 200 ⁇ m
  • the thickness of the epoxy gasket is 2 cm
  • the diameter of the epoxy gasket is equal to the inner diameter of the copper cylindrical ring. At least a quarter of the copper cylindrical rings were immersed in liquid nitrogen.
  • the boron nitride aerogel precursor is subjected to a sintering heat treatment process, the first sintering heat treatment temperature is 350°C, and the sintering time is 4h; the second sintering temperature is 900°C, and the sintering time is 10h.
  • the boron nitride aerogel prepared in Example 4 of the present invention is analyzed, and the measured thermal conductivity of the boron nitride aerogel-filled epoxy resin composite material in the radial and axial directions is 3.85W/mK, respectively. and 3.38 W/mK, the anisotropy coefficient of the aerogel is 1.14.
  • Example 5 The preparation method of boron nitride aerogel provided in Example 5 is shown in FIG. 1 and includes the following specific steps:
  • the dual orientation molding device includes a copper cylindrical ring and an epoxy resin gasket at the bottom of the copper cylindrical ring, the length ratio of the outer diameter to the height of the copper cylindrical ring is 1:1, the height of the copper cylindrical ring is 4.5cm, and the copper cylindrical ring is 4.5cm high.
  • the wall thickness of the ring is 200 ⁇ m, the thickness of the epoxy gasket is 2 cm, and the diameter of the epoxy gasket is equal to the inner diameter of the copper cylindrical ring. At least a quarter of the copper cylindrical rings were immersed in liquid nitrogen.
  • the boron nitride aerogel precursor is subjected to a sintering heat treatment process, the first sintering heat treatment temperature is 350°C, and the sintering time is 4h; the second sintering temperature is 900°C, and the sintering time is 10h.
  • the boron nitride aerogel prepared in Example 5 of the present invention is analyzed, and the measured thermal conductivity of the boron nitride aerogel-filled epoxy resin composite material in the radial and axial directions is 3.34W/mK, respectively. and 2.96 W/mK, the anisotropy coefficient of the aerogel is 1.13.
  • Example 6 The preparation method of boron nitride aerogel provided in Example 6 is shown in FIG. 1 , and includes the following specific steps:
  • the dual orientation forming device comprises a copper cylindrical ring and an epoxy resin gasket at the bottom of the copper cylindrical ring, the length ratio of the outer diameter to the height of the copper cylindrical ring is 0.3:1, the height of the copper cylindrical ring is 5cm, and the copper cylindrical ring is 5cm high.
  • the wall thickness is 100 ⁇ m, the thickness of the epoxy gasket is 2.5 cm, and the diameter of the epoxy gasket is equal to the inner diameter of the copper cylindrical ring. At least a quarter of the copper cylindrical rings were immersed in liquid nitrogen.
  • the boron nitride aerogel precursor is subjected to a sintering heat treatment process, the first sintering heat treatment temperature is 350°C, and the sintering time is 4h; the second sintering temperature is 900°C, and the sintering time is 10h.
  • the boron nitride aerogel prepared in Example 6 of the present invention is analyzed, and the thermal conductivity measured in the radial and axial directions of the boron nitride aerogel-filled epoxy resin composite material is 3.77W/mK, respectively. and 3.70 W/mK, the anisotropy coefficient of the aerogel is 1.02.
  • Example 7 The preparation method of boron nitride aerogel provided in Example 7 is shown in FIG. 1, and includes the following specific steps:
  • the dual orientation molding device includes a copper cylindrical ring and an epoxy resin gasket at the bottom of the copper cylindrical ring, the length ratio of the outer diameter to the height of the copper cylindrical ring is 3.5:1, the height of the copper cylindrical ring is 2cm, and the copper cylindrical ring is 2cm high.
  • the wall thickness is 400 ⁇ m, the thickness of the epoxy gasket is 0.1 cm, and the diameter of the epoxy gasket is equal to the inner diameter of the copper cylindrical ring. At least a quarter of the copper cylindrical rings were immersed in liquid nitrogen.
  • the boron nitride aerogel precursor is subjected to a sintering heat treatment process, the first sintering heat treatment temperature is 350°C, and the sintering time is 4h; the second sintering temperature is 900°C, and the sintering time is 10h.
  • the boron nitride aerogel prepared in Example 7 of the present invention is analyzed, and the thermal conductivity measured in the radial and axial directions of the composite material of the boron nitride aerogel filled epoxy resin is 1.63W/mK, respectively. and 3.66 W/mK, the anisotropy coefficient of the aerogel is 0.45.

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Abstract

本发明涉及具有双取向网络的气凝胶及其制备方法和应用，具体公开了一种具有双取向网络的气凝胶的制备方法，包括如下步骤：1)将填料、聚合物粘结剂与水混合处理，得到填料混合物；2)将双取向成型装置预先放入低温制冷介质中，将填料混合物加入到双取向成型装置中，进行冷冻处理形成冰冻混合物，然后进行冷冻干燥处理，得到气凝胶前驱体；3)将所述气凝胶前驱体进行烧结热处理，得到气凝胶；其中，所述双取向成型装置为由金属圆柱环和位于金属圆柱环底部的垫片构成的容器。本发明适用材料范围广、气凝胶结构具有鲜明的双取向特征、制备过程简单、反应条件相对温和以及产率高，气凝胶的各向异性系数可控，在诸多领域具有良好的应用前景。

Description

一种具有双取向网络的气凝胶及其制备方法和应用 技术领域
本发明属于多孔材料技术领域，具体地讲，涉及一种具有双取向网络的气凝胶及其制备方法和应用。
背景技术
气凝胶是一种多孔材料，因其独特的微观结构在吸附环保、能源储存、组织工程、结构型复合材料等领域具有广阔的应用前景，在近年来受到了广泛关注。气凝胶的应用涉及到气凝胶的传质行为，而气凝胶的微观结构是气凝胶传质性能的主要影响因素。常规气凝胶的微观结构是无序的，为了提高气凝胶在特定方向上的传质性能，研究者们对具有取向、有序的微观结构的气凝胶进行了大量研究。
如何优化气凝胶的微观结构一直是制备气凝胶的关键技术问题。气凝胶的微观结构与组装技术和组装单元的形貌有关。目前研究最多的是具有单取向网络的气凝胶。冷冻铸造是制备具有单取向网络的气凝胶的常用方法，这种方法操作简单、绿色环保。制备得到的气凝胶在轴向方向上具有取向的微观结构，从而在轴向方向上表现出优异的传质性能。单取向气凝胶在导热复合材料和吸附领域都已经展现了巨大的应用潜力。中国科学院深圳先进院公开了多篇相关专利。
然而，很多应用场合对气凝胶的性能提出了更严格的要求。气凝胶不仅需要在轴向方向上表现出良好的传质行为，在平面方向上也要保证传质通道的规整性。因此，具有双取向网络的气凝胶比具有单取向网络的气凝胶面临着更大的应用需求和技术难度。目前公开的专利文件中，鲜有提及具有双取向网络的气凝胶及其制备方法和应用。
因此，发明一种简单、快速和通用的制备具有双取向网络的气凝胶的方法具有十分重要的意义。
发明内容
针对上述背景技术中提出的问题，本发明目的在于克服现有技术的上述不足，提供了一种通用的制备具有双取向网络的气凝胶的方法，广泛地适用于零维颗粒、一维管/线状材料以及二维材料，不受限于材料种类和形貌，该方法为优化气凝胶的微观结构提供了新思路，解决了当前的技术瓶颈。
为了达到上述发明目的，本发明的技术方案如下：
本发明第一个方面提供一种具有双取向网络的气凝胶的制备方法，包括如下步骤：
步骤一、将填料、聚合物粘结剂与水按照质量比1：0.01～0.05：3～50混合处理，得到填料混合物；
步骤二、将双取向成型装置预先放入低温制冷介质中，将填料混合物加入到双取向成型装置中，进行冷冻处理形成冰冻混合物，然后进行冷冻干燥处理，得到气凝胶前驱体；
步骤三、将所述气凝胶前驱体进行烧结热处理，得到气凝胶；
其中，所述双取向成型装置为由金属圆柱环和位于金属圆柱环底部的垫片构成的容器。
在本发明的技术方案中，所述填料为不与水在常温下发生化学反应的任一种物质，所述填料为零维颗粒、一维管/线状材料、二维材料微纳材料、三维颗粒材料，所述填料为微纳材料。优选地，填料的尺寸为50nm～100μm，例如100nm、300nm、500nm、1μm、3μm、5μm、10μm、20μm、30μm、40μm、50μm、100μm。
在一些实施例中，所述填料选自氧化铝、氧化镁、氧化锌、氮化铝、氮化 硼、碳化硅、石墨烯中的至少一种。只要目标填料不与水发生化学反应且可以在水中分散，就可以基于本发明方法制备成气凝胶。
优选的，所述填料选用但不仅限于颗粒、线状或者片状的任意一种，或其自由组合。颗粒、线状或者片状的任意一种，或其自由组合都可以基于本发明方法制备成气凝胶。所述填料的粒径为50nm～100μm。
在本发明的技术方案中，所述聚合物粘结剂选用聚乙烯醇、聚乙烯吡咯烷酮、聚乙二醇、聚丙烯酰胺、羧甲基纤维素、羟甲基纤维素、羟乙基纤维素或羟丙基甲基纤维素中的至少一种。选用该些聚合物粘结剂能有效增加溶液的粘度，从而提高填料在水中的分散性、避免发生填料的团聚现象，并提高气凝胶前驱体的机械性能，以便于后续的烧结热处理。
在本发明的技术方案中，所述的混合处理采用的是行星式混合机搅拌，将填料、聚合物粘结剂与水按照一定质量比例进行混合处理后，得到短时间均匀的填料混合物。
在本发明的技术方案中，所述金属圆柱环中的金属为不与水在常温下发生化学反应的任一种金属物质，优选为铜、银、金、铂、钼、钨、镍、铝、铁、锌、锡、铅中的至少一种。只要目标金属不与水发生化学反应，就可以用来制备本专利所述的金属圆柱环。选用该些金属能有效促进径向上温度梯度的形成，提高气凝胶前驱体在径向上的结构规整度，以便于得到具有双取向网络的气凝胶。
在本发明的技术方案中，所述金属圆柱环的外径与高度的长度比为0.25～4：1。例如0.3:1、0.4:1、0.5:1、0.6:1、0.7:1、0.8:1、0.9:1、1:1、1.5:1、2:1、2.5:1、3:1、3.5:1。
在本发明的技术方案中，所述金属圆柱环的高度为1～5cm。例如1cm、2cm、3cm、4cm、5cm。
在本发明的技术方案中，所述金属圆柱环的壁厚为50～500μm。例如， 100μm、200μm、300μm、400μm、450μm。
将金属圆柱环的外径与高度的长度比、金属圆柱环的高度和壁厚进行控制，可以控制气凝胶微观结构的各向异性以及结构规整度。
在本发明的技术方案中，所述垫片是由聚合物基体固化制备得到，所述聚合物基体为环氧树脂、聚氨酯、酚醛树脂、不饱和聚酯、氨基树脂、聚乙烯、聚丙烯、聚氯乙烯、聚苯乙烯或聚硅氧烷中的至少一种。
在一实施例中，所述聚合物圆形垫片的直径等于金属圆柱环的内径，所述聚合物圆形垫片的厚度与金属圆柱环的高度的长度比为0.01～0.5：1。
在本发明的技术方案中，所述双取向成型装置是将聚合物垫片放入金属圆柱环中并置于底部，形成可以盛放液体的容器。
在本发明的技术方案中，所述低温制冷介质为液氮或液氦中的至少一种；
在本发明的技术方案中，所述冷冻处理为将填料混合物加入在双取向成型装置并与低温制冷介质间接接触，从而引发连续的自组装成型过程。冰冻过程中，是为了使得填料混合物中的水结冰并对填料形成挤压，形成双取向网络的微观结构。冰冻时，冰晶同时沿着两个方向生长，分别是从外围向中心的径向方向，以及从底部向顶部的轴向方向。其中双取向成型装置中的金属圆柱环的至少四分之一浸入低温制冷介质中。金属圆柱环能够快速进行温度，只浸入四分之一即可保证金属圆柱环迅速降温至温度与冷冻介质相近。
在本发明的技术方案中，所述冷冻干燥处理为将冰冻产物放入冷冻干燥机，将冰升华。
在本发明的技术方案中，300℃～2500℃温度下烧结1h～12h；
优选地，在烧结热处理前以300℃～400℃的温度进行预烧结，预烧结时间为4h～6h。
本发明第二个方面提供一种气凝胶，所述气凝胶是由本发明所述的制备方法制备得到，根据气凝胶在径向和轴向方向上测得的热导率之比为0.4～1.2， 所述气凝胶的各向异性系数为0.4～1.2。
本发明第三个方面提供了一种用于制备双取向网络的气凝胶的系统，所述系统包括双取向成型装置，所述双取向成型装置为由金属圆柱环和位于金属圆柱环底部的垫片构成的容器。
优选地，所述金属圆柱环中的金属为不与水在常温下发生化学反应的任一种金属物质，优选为铜、银、金、铂、钼、钨、镍、铝、铁、锌、锡、铅中的至少一种。
优选地，所述金属圆柱环的外径与高度的长度比为0.25～4：1。
优选地，所述金属圆柱环的高度为1～5cm。
优选地，所述金属圆柱环的壁厚为50～500μm。
优选地，所述垫片是由聚合物基体固化制备得到，所述聚合物基体为环氧树脂、聚氨酯、酚醛树脂、不饱和聚酯、氨基树脂、聚乙烯、聚丙烯、聚氯乙烯、聚苯乙烯或聚硅氧烷中的至少一种。
优选地，所述聚合物圆形垫片的直径等于金属圆柱环的内径，所述聚合物圆形垫片的厚度与金属圆柱环的高度的长度比为0.01～0.5：1。
在本发明的技术方案中，所述的系统中还包括低温制冷介质，优选地，所述低温制冷介质为液氮或液氦。
在本发明的技术方案中，所述的系统中还包括冷冻干燥装置。在本发明的技术方案中，所述的系统中还包括烧结装置。优选地，所述的烧结装置能提供300℃-3000℃的温度。
在本发明的技术方案中，所述的系统中还包括混合装置。优选地，所述的混合装置选自行星式混合机。
本发明第四个方面提供由本发明的方法制备的气凝胶作为导热复合材料中的应用。
与现有技术相比，本发明具有以下有益效果：
1、本发明制备的气凝胶不同于传统气凝胶。本发明制备的气凝胶具有双取向网络的微观结构，在径向和轴向方向上都具有规整的通道，从而表现出良好的传质性能。本发明方法制备的气凝胶具有优异的综合结构特性和可调控性，因此，其可以更加广泛地应用于导热复合材料、环境保护、传感器、军事及航天等领域。
2、本发明提出的一种具有双取向网络的气凝胶的制备方法将填料、聚合物粘结剂与水混合形成均匀的填料混合物，只需将填料混合物经冷冻处理、冷冻干燥和烧结热处理即可，使得本方法适用材料范围广、气凝胶尺寸可控、制备过程简单、反应条件相对温和，有效解决了现有通常方法适用材料范围窄、制备过程复杂的技术瓶颈，并拓宽了气凝胶在各领域的应用前景。
附图说明
图1为本发明通用的制备一种具有双取向网络的气凝胶的方法的制备方法流程图；
图2为本发明通用的制备一种具有双取向网络的气凝胶的双取向成型装置的原理说明图；
图3为实施例1制备的氮化硼气凝胶冰冻过程中的电子照片；
图4为实施例2制备的石墨烯气凝胶的电子照片。
具体实施方式
下面结合实施例以及对比例，对本发明作进一步地详细说明，但本发明的实施方式不限于此。具体包括以下实施例：
为了使本发明要解决的技术问题、技术方案及有益效果更加清楚明白，以下结合实施例与附图，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅用以解释本发明，并不用于限定本发明。
本发明提供了一种制备具有双取向网络的气凝胶的方法。本发明通用的制备具有双取向网络的气凝胶的方法工艺步骤如图1所示，其包括如下步骤：
S01.将填料、聚合物粘结剂与水按照质量比1：0.01～0.05：3～50混合处理，得到填料混合物；
S02.将双取向成型装置预先放入低温制冷介质，将填料混合物滴入到双取向成型装置中，进行冷冻处理形成冰冻混合物，进行冷冻干燥处理，得到气凝胶前驱体；
S03.将所述气凝胶前驱体进行第一、第二烧结热处理，得到气凝胶。
本发明所采用的双取向成型装置是在传统的单取向装置上进行了改进，在保证轴向温度梯度存在的条件下，引入径向温度梯度，引导冰晶在冰冻过程中同时沿径向和轴向生长，构造具有双取向网络的微观结构。金属圆柱环的壁厚影响径向温度梯度，聚合物垫片的厚度影响轴向温度梯度，结合金属圆柱环的外径和高度的长度比等参数，可以调控气凝胶结构的各向异性。具体地，图2为本发明通用的制备一种具有双取向网络的气凝胶的双取向成型装置的原理说明图。首先将双取向成型装置放在低温制冷介质中预冷，将填料混合物滴入双取向成型装置中，局部的冷冻铸造自组装过程立即发生。冰晶同时沿径向和轴向方向、顺着温度梯度进行生长。随着冰晶体积变大，混合物中的填料被排斥、团聚在相邻的冰晶之间。冰冻会促进在温度梯度方向上取向骨架的形成，赋予材料各向异性的性质。随着冷冻铸造自组装过程的不断进行，直到填料混合物中所有的水都变成了冰。通过冷冻干燥将冰升华，得到具有双取向网络的气凝胶前驱体。
在上文所述的通用的制备具有双取向网络的气凝胶的方法的基础上，本发明以下实施例还提供了几种气凝胶材料。理所当然的是，这几种气凝胶材料是采用上文通用的制备具有双取向网络的气凝胶的方法制备获得。具体包括以下实施例：
实施例1
实施例1提供的氮化硼气凝胶的制备方法参照附图1所示，包括如下具体步骤：
S11：将尺寸为5μm的氮化硼微米片、聚乙烯醇与水按照质量比1：0.01：5混合后在行星式混合机中搅拌，得到均匀的氮化硼混合物；
S12：将双取向成型装置预先放入液氮中，将氮化硼混合物滴入到双取向成型装置中，进行冷冻处理形成冰冻混合物，进行冷冻干燥处理，得到氮化硼气凝胶前驱体。所述双取向成型装置包括铜圆柱环以及位于铜圆柱环底部的环氧树脂垫片，铜圆柱环的外径与高度的长度比为0.5：1，铜圆柱环的高度为4.5cm，铜圆柱环的壁厚为200μm，环氧树脂垫片的厚度为2cm，环氧树脂垫片直径等于铜圆柱环的内径。其中至少四分之一的铜圆柱环浸入到液氮中。
S13：将氮化硼气凝胶前驱体进行烧结热处理过程，第一烧结热处理温度为350℃，烧结时间为4h；第二烧结温度为900℃，烧结时间为10h。
将本发明实施例1制备的氮化硼气凝胶进行分析，氮化硼气凝胶冰冻过程中的电子照片如图3所示，可以看到在冰冻过程中径向冰晶的生长占主导，因此气凝胶内部形成更多的径向网络，而相比之下轴向网络的占比会下降。氮化硼气凝胶填充环氧树脂的复合材料在径向和轴向方向上测得的热导率分别为3.56W/mK和3.43W/mK，所述气凝胶的各向异性系数为1.04。
实施例2
实施例2提供的石墨烯气凝胶的制备方法参照附图1所示，包括如下具体步骤：
S21：将尺寸为20μm的石墨烯、羧甲基纤维素与水按照质量比1：0.01：40混合后在行星式混合机中搅拌，得到均匀的石墨烯混合物；
S22：将双取向成型装置预先放入液氮中，将石墨烯混合物滴入到双取向成型装置中，进行冷冻处理形成冰冻混合物，进行冷冻干燥处理，得到石墨烯 气凝胶前驱体。所述双取向成型装置包括银圆柱环以及位于银圆柱环底部的聚硅氧烷垫片，银圆柱环的外径与高度的长度比为0.3：1，银圆柱环的高度为3cm，银圆柱环的壁厚为100μm，聚硅氧烷垫片的厚度为1cm，聚硅氧烷垫片直径等于银圆柱环的内径。其中至少四分之一的银圆柱环浸入到液氮中。
S23：将石墨烯气凝胶前驱体进行烧结热处理过程，第一烧结热处理温度为300℃，烧结时间为4h；不做第二烧结处理。
将本发明实施例2制备的石墨烯气凝胶进行分析，石墨烯气凝胶的电子照片如图4所示，可以看到明显的径向网络结构。石墨烯气凝胶填充环氧树脂的复合材料在径向和轴向方向上测得的热导率分别为0.52W/mK和0.49W/mK，所述气凝胶的各向异性系数为1.06。
实施例3
实施例3提供的氧化铝气凝胶的制备方法参照附图1所示，包括如下具体步骤：
S31：将尺寸为500nm的氧化铝颗粒、聚乙烯吡咯烷酮与水按照质量比1：0.03：10混合后在行星式混合机中搅拌，得到均匀的氧化铝混合物；
S32：将双取向成型装置预先放入液氮中，将氧化铝混合物滴入到双取向成型装置中，进行冷冻处理形成冰冻混合物，进行冷冻干燥处理，得到氧化铝气凝胶前驱体。双取向成型装置包括锡圆柱环和酚醛树脂垫片，锡圆柱环的外径与高度的长度比为3：1，锡圆柱环的高度为1cm，锡圆柱环的壁厚为400μm，酚醛树脂垫片的厚度为0.1cm，酚醛树脂垫片直径等于锡圆柱环的内径。其中至少四分之一的锡圆柱环浸入到液氮中。
S33：将氧化铝气凝胶前驱体进行烧结热处理过程，第一烧结热处理温度为400℃，烧结时间为6h；第二烧结温度为1300℃，烧结时间为10h。。
将本发明实施例3制备的氧化铝气凝胶进行分析，氧化铝气凝胶填充环氧树脂的复合材料在径向和轴向方向上测得的热导率分别为0.72W/mK和1.25 W/mK，所述气凝胶的各向异性系数为0.58。
实施例4
实施例4提供的氮化硼气凝胶的制备方法参照附图1所示，包括如下具体步骤：
S41：将尺寸为15μm的氮化硼微米片、聚乙烯醇与水按照质量比1：0.01：5混合后在行星式混合机中搅拌，得到均匀的氮化硼混合物；
S42：将双取向成型装置预先放入液氮中，将氮化硼混合物滴入到双取向成型装置中，进行冷冻处理形成冰冻混合物，进行冷冻干燥处理，得到氮化硼气凝胶前驱体。所述双取向成型装置包括铜圆柱环以及位于铜圆柱环底部的环氧树脂垫片，铜圆柱环的外径与高度的长度比为0.5：1，铜圆柱环的高度为4.5cm，铜圆柱环的壁厚为200μm，环氧树脂垫片的厚度为2cm，环氧树脂垫片直径等于铜圆柱环的内径。其中至少四分之一的铜圆柱环浸入到液氮中。
S43：将氮化硼气凝胶前驱体进行烧结热处理过程，第一烧结热处理温度为350℃，烧结时间为4h；第二烧结温度为900℃，烧结时间为10h。
将本发明实施例4制备的氮化硼气凝胶进行分析，氮化硼气凝胶填充环氧树脂的复合材料在径向和轴向方向上测得的热导率分别为3.85W/mK和3.38W/mK，所述气凝胶的各向异性系数为1.14。
实施例5
实施例5提供的氮化硼气凝胶的制备方法参照附图1所示，包括如下具体步骤：
S51：将尺寸为5μm的氮化硼微米片、聚乙烯醇与水按照质量比1：0.01：5混合后在行星式混合机中搅拌，得到均匀的氮化硼混合物；
S52：将双取向成型装置预先放入液氮中，将氮化硼混合物滴入到双取向成型装置中，进行冷冻处理形成冰冻混合物，进行冷冻干燥处理，得到氮化硼气凝胶前驱体。所述双取向成型装置包括铜圆柱环以及位于铜圆柱环底部的环 氧树脂垫片，铜圆柱环的外径与高度的长度比为1：1，铜圆柱环的高度为4.5cm，铜圆柱环的壁厚为200μm，环氧树脂垫片的厚度为2cm，环氧树脂垫片直径等于铜圆柱环的内径。其中至少四分之一的铜圆柱环浸入到液氮中。
S53：将氮化硼气凝胶前驱体进行烧结热处理过程，第一烧结热处理温度为350℃，烧结时间为4h；第二烧结温度为900℃，烧结时间为10h。
将本发明实施例5制备的氮化硼气凝胶进行分析，氮化硼气凝胶填充环氧树脂的复合材料在径向和轴向方向上测得的热导率分别为3.34W/mK和2.96W/mK，所述气凝胶的各向异性系数为1.13。
实施例6
实施例6提供的氮化硼气凝胶的制备方法参照附图1所示，包括如下具体步骤：
S61：将尺寸为5μm的氮化硼微米片、聚乙烯醇与水按照质量比1：0.01：5混合后在行星式混合机中搅拌，得到均匀的氮化硼混合物；
S62：将双取向成型装置预先放入液氮中，将氮化硼混合物滴入到双取向成型装置中，进行冷冻处理形成冰冻混合物，进行冷冻干燥处理，得到氮化硼气凝胶前驱体。所述双取向成型装置包括铜圆柱环以及位于铜圆柱环底部的环氧树脂垫片，铜圆柱环的外径与高度的长度比为0.3：1，铜圆柱环的高度为5cm，铜圆柱环的壁厚为100μm，环氧树脂垫片的厚度为2.5cm，环氧树脂垫片直径等于铜圆柱环的内径。其中至少四分之一的铜圆柱环浸入到液氮中。
S63：将氮化硼气凝胶前驱体进行烧结热处理过程，第一烧结热处理温度为350℃，烧结时间为4h；第二烧结温度为900℃，烧结时间为10h。
将本发明实施例6制备的氮化硼气凝胶进行分析，氮化硼气凝胶填充环氧树脂的复合材料在径向和轴向方向上测得的热导率分别为3.77W/mK和3.70W/mK，所述气凝胶的各向异性系数为1.02。
实施例7
实施例7提供的氮化硼气凝胶的制备方法参照附图1所示，包括如下具体步骤：
S71：将尺寸为5μm的氮化硼微米片、聚乙烯醇与水按照质量比1：0.01：5混合后在行星式混合机中搅拌，得到均匀的氮化硼混合物；
S72：将双取向成型装置预先放入液氮中，将氮化硼混合物滴入到双取向成型装置中，进行冷冻处理形成冰冻混合物，进行冷冻干燥处理，得到氮化硼气凝胶前驱体。所述双取向成型装置包括铜圆柱环以及位于铜圆柱环底部的环氧树脂垫片，铜圆柱环的外径与高度的长度比为3.5：1，铜圆柱环的高度为2cm，铜圆柱环的壁厚为400μm，环氧树脂垫片的厚度为0.1cm，环氧树脂垫片直径等于铜圆柱环的内径。其中至少四分之一的铜圆柱环浸入到液氮中。
S73：将氮化硼气凝胶前驱体进行烧结热处理过程，第一烧结热处理温度为350℃，烧结时间为4h；第二烧结温度为900℃，烧结时间为10h。
将本发明实施例7制备的氮化硼气凝胶进行分析，氮化硼气凝胶填充环氧树脂的复合材料在径向和轴向方向上测得的热导率分别为1.63W/mK和3.66W/mK，所述气凝胶的各向异性系数为0.45。
上述实施例为本发明较佳的实施方式，但本发明的实施方式并不受所述实施例的限制，其他的任何未背离本发明的精神实质与原理下所作的改变、修饰、替代、组合、简化，均应为等效的置换方式，都包含在本发明的保护范围之内。
显然，本领域的技术人员可以对本发明进行各种改动和变型而不脱离本发明的精神和范围。这样，倘若本发明的这些修改和变型属于本发明权利要求及其等同技术的范围之内，则本发明也意图包含这些改动和变型在内。

Claims (14)

  1. 一种具有双取向网络的气凝胶的制备方法，其特征在于，包括如下步骤：
    步骤一、将填料、聚合物粘结剂与水按照质量比1：0.01～0.05：3～50混合处理，得到填料混合物；
    步骤二、将双取向成型装置预先放入低温制冷介质中，将填料混合物加入到双取向成型装置中，进行冷冻处理形成冰冻混合物，然后进行冷冻干燥处理，得到气凝胶前驱体；
    步骤三、将所述气凝胶前驱体进行烧结热处理，得到气凝胶；
    其中，所述双取向成型装置为由金属圆柱环和位于金属圆柱环底部的垫片构成的容器。
  2. 根据权利要求1所述的具有双取向网络的气凝胶的制备方法，其特征在于：所述填料为不与水在常温下发生化学反应的任一种物质；
    优选的，所述填料包括氧化铝、氧化镁、氧化锌、氮化铝、氮化硼、碳化硅、石墨烯；
    优选的，所述填料的外观形貌为颗粒、线状或者片状的任意一种或多种；
    优选的，所述填料的粒径为50nm～100μm。
  3. 根据权利要求1所述的具有双取向网络的气凝胶的制备方法，其特征在于：所述聚合物粘结剂为聚乙烯醇、聚乙烯吡咯烷酮、聚乙二醇、聚丙烯酰胺、羧甲基纤维素、羟甲基纤维素、羟乙基纤维素或羟丙基甲基纤维素中的至少一种。
  4. 根据权利要求1所述的具有双取向网络的气凝胶的制备方法，其特征在于：所述金属圆柱环中的金属为不与水在常温下发生化学反应的任一种金 属物质，优选的，所述金属选自铜、银、金、铂、钼、钨、镍、铝、铁、锌、锡、铅中的至少一种；
    优选的，所述金属圆柱环的外径与高度的长度比为0.25～4：1；
    优选的，所述金属圆柱环的高度为1～5cm；
    优选的，所述金属圆柱环的壁厚为50～500μm。
  5. 根据权利要求1所述的具有双取向网络的气凝胶的制备方法，其特征在于：所述聚合物圆形垫片是由聚合物基体固化制备得到，所述聚合物基体选自环氧树脂、聚氨酯、酚醛树脂、不饱和聚酯、氨基树脂、聚乙烯、聚丙烯、聚氯乙烯、聚苯乙烯或聚硅氧烷中的至少一种；
    优选的，所述聚合物圆形垫片的厚度与金属圆柱环的高度的长度比为0.01～0.5：1。
  6. 根据权利要求5所述的具有双取向网络的气凝胶的制备方法，其特征在于：所述烧结热处理为300℃～2500℃温度下烧结1h～12h；
    优选地，在烧结热处理前以300℃～400℃的温度进行预烧结，预烧结时间为4h～6h。
  7. 根据权利要求1所述的具有双取向网络的气凝胶的制备方法，其特征在于：所述低温制冷介质为液氮或液氦中的至少一种；
    优选的，所述冷冻处理为将填料混合物滴入在双取向成型装置并与低温制冷介质间接接触，从而引发连续的自组装成型过程；
    所述冷冻干燥处理为将冰冻产物放入冷冻干燥机，将冰升华。
  8. 根据权利要求1-7任一项所述的制备方法，制备获得的具有双取向网络的气凝胶。
  9. 权利要求8所述的具有双取向网络的气凝胶作为导热复合材料中的应用。
  10. 一种用于制备双取向网络的气凝胶的系统，所述系统包括双取向成型装置，所述双取向成型装置为由金属圆柱环和位于金属圆柱环底部的垫片构成的容器；
    优选地，所述金属圆柱环中的金属为不与水在常温下发生化学反应的任一种金属物质；
    优选地，所述金属圆柱环的外径与高度的长度比为0.25～4：1；
    优选地，所述金属圆柱环的高度为1～5cm；
    优选地，所述金属圆柱环的壁厚为50～500μm；
    优选地，所述垫片是由聚合物基体固化制备得到，所述聚合物基体为环氧树脂、聚氨酯、酚醛树脂、不饱和聚酯、氨基树脂、聚乙烯、聚丙烯、聚氯乙烯、聚苯乙烯或聚硅氧烷中的至少一种；
    更优选地，所述聚合物圆形垫片的直径等于金属圆柱环的内径，所述聚合物圆形垫片的厚度与金属圆柱环的高度的长度比为0.01～0.5：1。
  11. 根据权利要求10所述的系统，其特征在于，所述的系统中还包括低温制冷介质，优选地，所述低温制冷介质为液氮或液氦。
  12. 根据权利要求10所述的系统，其特征在于，所述的系统中还包括冷冻干燥装置。
  13. 根据权利要求10所述的系统，其特征在于，所述的系统中还包括烧结装置；优选地，所述的烧结装置能提供300℃-3000℃的温度。
  14. 根据权利要求10所述的系统，其特征在于，所述的系统中还包括混合装置；优选地，所述的混合装置选自行星式混合机。
    。
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