Lightweight flexible wide-temperature-range thermal insulation material and preparation method thereof

Abstract

The invention belongs to the technical field of composite material preparation, and discloses a lightweight flexible wide-temperature-range thermal insulation material and a preparation method thereof. A clear solution is used for preparing a boron nitride aerogel thin layer; the clear solution is prepared from melamine, boric acid, deionized water and tert-butyl alcohol; growing graphene on the boron nitride aerogel thin layer by adopting a chemical vapor deposition process to obtain a boron nitride / graphene hybrid aerogel thin layer; floating a boron nitride / graphene hybrid aerogel thin layer on the clear solution, and preparing a boron nitride aerogel heat insulation layer on the surface of the boron nitride / graphene hybrid aerogel thin layer to obtain a graphene / boron nitride-boron nitride layered composite material; and gold particles are subjected to ion sputtering on the surface of the graphene / boron nitride-boron nitride layered composite material, then annealing treatment is conducted, and the nanogold / graphene / boron nitride composite material of the multi-layer structure is obtained. According to the invention, the aerogel can still keep excellent heat insulation performance in a high-temperature environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite material preparation, and specifically relates to a lightweight, flexible, wide-temperature-range thermal insulation material and a preparation method thereof. Background Art

[0002] With the rapid development of aerospace technology, the demand for high-performance thermal insulation materials for aerospace vehicles has become increasingly urgent. During the rocket launch and manned spacecraft return phases, the aerodynamic heating effect can cause the surface temperature to rise sharply to thousands of degrees Celsius. It is necessary to rely on an efficient thermal insulation layer to block the penetration of heat flow to ensure the safety of internal structures and equipment. Satellites and space stations serving in outer space are faced with a high and low temperature alternating environment of -200 to 200°C, requiring thermal insulation materials to have high thermal shock resistance to maintain thermal balance. At the same time, aerospace vehicles are faced with broadband vibrations and impact loads generated at high Mach numbers, which requires thermal insulation materials to have both good mechanical properties and impact resistance. In addition, since the weight and size of the aircraft are strictly restricted, the thermal insulation material should be as light as possible to reduce its mass share in the entire temperature control system, which is of great significance to improving the aircraft's payload, flight speed and range. However, the existing thermal insulation materials are mainly fiber porous felts (such as glass fiber, ceramic fiber, carbon fiber and metal fiber), and their density is generally greater than 0.1g / cm 3 , thermal conductivity above 25mW / (m·K), high rigidity, and a large volume are required to meet the thermal insulation requirements of aerospace vehicles. This means that thermal insulation materials with ultra-low density, ultra-low thermal conductivity over a wide temperature range, and high strength and toughness over a wide temperature range will be an important development direction for thermal protection of future aerospace vehicles.

[0003] Aerogel is the best known thermal insulation material (only 12-16 mW / (m·K)) and has the lowest density (as low as 2 mg / cm 3) solid material. 90% of the interior of aerogel is air, the solid skeleton accounts for a very small proportion, and the pore size is mostly smaller than the mean free path of air molecules (i.e. <70nm), which can effectively reduce the thermal conductivity of the solid, inhibit the convective heat transfer of the gas, and produce a thermal insulation effect lower than the thermal conductivity of air. The use of aerogel can greatly improve the thermal insulation efficiency of the thermal protection system of aerospace vehicles, and is more conducive to the lightweight and miniaturization of aircraft. Aerogels can be divided into: 0D nanoparticle-based aerogels, 1D nanofiber-based aerogels, and 2D nanosheet / belt-based aerogels based on the network skeleton structure. Among them, 0D nanoparticle-based aerogels generally have the problems of low strength, high brittleness and poor high-temperature thermal insulation performance. Even if a reinforcing phase is introduced, there are still structural powdering and high-temperature sintering collapse phenomena; although 1D nanofiber-based aerogels have flexible rebound characteristics, due to the weak "point-point" contact mode between the fibers, aerogels still face serious problems of mechanical property degradation under rapid thermal shock or high-temperature environments. In addition, the interwoven pore structure of 1D nanofibers cannot effectively inhibit gas convection, resulting in the thermal conductivity of nanofiber-based aerogels being higher than that of air (i.e., 24 mW / (m·K)). Compared with 0D nanoparticles and 1D nanofibers, 2D nanosheets / ribbons have a stable "face-to-face" overlap pattern, which is more conducive to the effective transfer and uniform distribution of loads, giving the aerogel greater deformation recovery ability. In addition, the "face-to-face" overlap between 2D nanosheets / ribbons can also divide the 3D aerogel into separate pores, which can effectively reduce gas conduction and convection, making the thermal conductivity of the aerogel lower than that of air. However, at high temperatures, the thermal conductivity of aerogels is mainly determined by radiative heat conduction. Near-infrared light (wavelength 2.5-8 μm) generated at high temperatures (300-1300 K) can almost all penetrate the aerogel, causing the thermal conductivity of the aerogel to rise sharply at high temperatures. Therefore, how to ensure that aerogels still maintain excellent thermal insulation properties in high-temperature environments is a major problem that needs to be solved urgently. Summary of the Invention

[0004] In order to solve the problem of sudden increase in thermal conductivity of aerogel at high temperature, the purpose of the present invention is to provide a lightweight, flexible, wide-temperature range thermal insulation material and a preparation method thereof. The present invention can enable aerogel to maintain excellent thermal insulation performance in a high-temperature environment.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a lightweight, flexible, wide-temperature-range thermal insulation material comprises the following steps:

[0007] A boron nitride aerogel thin layer is prepared using a clear solution. The preparation process of the clear solution comprises: mixing melamine, boric acid, deionized water and tert-butanol, and stirring at 80-85° C. for 20-30 minutes to obtain the clear solution, wherein the mixing ratio of melamine, boric acid, deionized water and tert-butanol is: (0.2-1 g): (0.2-1 g): (20-30 ml): (20-30 ml);

[0008] Using chemical vapor deposition technology, graphene is grown on a boron nitride aerogel thin layer to obtain a boron nitride / graphene hybrid aerogel thin layer;

[0009] floating the boron nitride / graphene hybrid aerogel thin layer on the clear solution, preparing a boron nitride aerogel thermal insulation layer on the surface of the boron nitride / graphene hybrid aerogel thin layer, and obtaining a graphene / boron nitride-boron nitride layered composite material;

[0010] Gold particles are ion-sputtered on the surface of a graphene / boron nitride-boron nitride layered composite material, and then annealed to obtain a nano-gold / graphene / boron nitride composite material with a multilayer structure.

[0011] Preferably, the process of preparing a boron nitride aerogel thin layer using a clarified solution comprises:

[0012] The clear solution was sonicated at room temperature to obtain a white supramolecular wet gel;

[0013] The supramolecular wet gel is freeze-dried and then heat-treated to obtain a boron nitride aerogel thin layer.

[0014] Preferably, the process of heat-treating the freeze-dried supramolecular wet gel comprises:

[0015] The freeze-dried supramolecular wet gel is heated to 1100-1500° C. in a protective atmosphere, kept warm for 2-4 hours, and cooled to obtain a boron nitride aerogel thin layer.

[0016] Preferably, the process of growing graphene on a boron nitride aerogel thin layer using a chemical vapor deposition process includes:

[0017] Using methanol as a carbon source, graphene is grown on a boron nitride aerogel thin layer at a growth temperature of 1100-1200° C. for a growth time of 4-12 hours.

[0018] Preferably, the process of floating the boron nitride / graphene hybrid aerogel thin layer on the clear solution and preparing a boron nitride aerogel thermal insulation layer on the surface of the boron nitride / graphene hybrid aerogel thin layer comprises:

[0019] At room temperature, the boron nitride / graphene hybrid aerogel thin layer is floated on the clear solution, and then ultrasonic treatment is performed to form a white supramolecular wet gel on the surface of the boron nitride / graphene hybrid aerogel thin layer. Thereafter, freeze-drying and heat treatment are performed to obtain a graphene / boron nitride-boron nitride layered composite material.

[0020] Preferably, the heat treatment process for preparing the boron nitride aerogel insulation layer on the surface of the boron nitride / graphene hybrid aerogel thin layer includes:

[0021] In a protective atmosphere, the freeze-dried supramolecular wet gel is heated to 1100-1500° C. and kept warm for 2-4 hours, and then cooled to obtain a graphene / boron nitride-boron nitride layered composite material.

[0022] Preferably, the protective atmosphere is a mixture of one or more of argon, nitrogen, and ammonia, and the protective atmosphere flow rate is 8 to 10 L / h.

[0023] Preferably, when gold particles are ion sputtered on the surface of the graphene / boron nitride-boron nitride layered composite material, the sputtering voltage is 4.5-5.5 mA and the sputtering time is 200-500 s.

[0024] Preferably, after ion sputtering gold particles on the surface of the graphene / boron nitride-boron nitride layered composite material, the process of performing annealing treatment comprises:

[0025] In an argon atmosphere, heating to 400-800° C., keeping the temperature for 30-120 minutes, and then cooling to obtain a nano-gold / graphene / boron nitride composite material with a multilayer structure; wherein the argon flow rate is 8-10 L / h.

[0026] The present invention also provides a lightweight, flexible, wide-temperature-range thermal insulation material, which is prepared by the above-mentioned preparation method of the present invention.

[0027] The present invention has the following beneficial effects:

[0028] The present invention utilizes melamine and boric acid as initial components, water and tert-butanol as co-solvents, and adjusts the molar ratio of the two components to prepare supramolecular wet gel. Boron nitride nanoribbon aerogels are synthesized on a large scale through a high-temperature pyrolysis process. It is found that the nanoribbons have a larger aspect ratio and bending flexibility than other conventional nanosheets. Boron nitride nanoribbons divide the interior of the aerogel into several unconnected single pores through a "face-to-face" overlapping method, effectively reducing gas conduction and convection, making its thermal conductivity lower than that of air. Through a low-pressure pyrolysis process, "edge-rich graphene" (ERG) is grown on the surface of the boron nitride nanoribbons. Compared with conventional graphene sheets with complete structure and continuous in-plane and reduced graphene oxide with more defects, ERG is composed of a large number of graphene fragments with a large number of open edges around it and a certain distance between the fragments. This structure gives ERG excellent infrared shading effect and phonon scattering ability, making it very suitable for suppressing high-temperature radiation heat transfer of aerogels without causing an increase in the solid thermal conductivity of the system. In addition, compared to infrared light-shielding nanoparticles such as TiO2 and Fe2O3, which cannot form a good interface bond with 2D nano-elements and will fall off due to repeated mechanical deformation, ERG growth does not require a metal catalyst, so the growth process will not damage the surface structure and intrinsic flexibility of the BNNR substrate, making it an ideal 2D high-temperature infrared light-shielding agent. By ion sputtering gold particles on the surface of graphene / boron nitride nanobelts and then annealing, the particles are homogenized. Because ERG is composed of a large number of fragments and has open edges, the loading area and loading number of gold particles are increased. At the same time, the gold nanoparticles are wrapped by the graphene layer, which firmly locks the gold particles so that they will not fall off the nanobelts during service processes such as mechanical vibration and thermal fatigue (see Figure 6 、 Figure 7 ). In addition, in the near-infrared band, the surface plasmon resonance of gold can be effectively excited (especially for gold nanoparticles, this phenomenon is more significant), and the surface of gold will produce an extremely high local electromagnetic field, thereby significantly enhancing the absorption of near-infrared light. The multi-layered nanogold / graphene / boron nitride composite material has a functional layer with a sandwich structure, in which the upper layer is a nanogold particle layer, which can absorb near-infrared light on the outermost surface and effectively block a part of the near-infrared light from penetrating to the lower layer; the middle layer is a thin layer of graphene / boron nitride aerogel, which acts as an infrared sunscreen layer and can effectively absorb mid-infrared and far-infrared bands; the lower layer is a boron nitride nanobelt aerogel, which acts as the main thermal insulation layer to block external heat from transferring to the inside. In addition, the upper and middle layers wrap the gold nanoparticles with graphene, and the nanobelts at the junction of the middle and lower layers are interwoven to form an "interlocking" structure (see Figure 8Without compromising the overall lightweight and flexible material, this method addresses the issue of aerogel's thermal conductivity increasing dramatically at high temperatures, effectively improving its thermal insulation properties. This preparation process utilizes inexpensive raw materials, is simple and easily scalable, offers high yield, low cost, is environmentally friendly and pollution-free, and is not restricted by the shape or size of the composite material, demonstrating strong industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic cross-sectional view of the nano-gold / graphene / boron nitride composite material according to an embodiment of the present invention;

[0030] Figure 2 This is a curved and flexible optical image of the boron nitride nanoribbon aerogel prepared in Example 1 of the present invention;

[0031] Figure 3 This is a scanning electron microscope image of the boron nitride nanoribbon aerogel prepared in Example 1 of the present invention;

[0032] Figure 4 This is a transmission electron microscopy image of the graphene / boron nitride nanoribbon aerogel prepared in Example 1 of the present invention;

[0033] Figure 5 This is a curved and flexible optical image of the graphene / boron nitride nanoribbon aerogel prepared in Example 1 of the present invention;

[0034] Figure 6 This is a scanning electron microscope image of the gold nanoparticles prepared in Example 1 of the present invention and wrapped by a graphene layer;

[0035] Figure 7 This is a transmission electron micrograph of the gold nanoparticles prepared in Example 1 of the present invention and wrapped by a graphene layer;

[0036] Figure 8 This is a scanning electron microscope image of the junction of two layers of aerogel prepared in Example 1 of the present invention;

[0037] Figure 9 The thermal insulation performance of the nano-gold / graphene / boron nitride composite material prepared in Example 1 of the present invention;

[0038] Figure 10 This is a scanning electron microscope image of the graphene / boron nitride nanoribbon aerogel prepared in Comparative Example 1 of the present invention;

[0039] Figure 11 This is a scanning electron micrograph of graphene fragments loaded with gold nanoparticles prepared in Comparative Example 1 of the present invention;

[0040] Figure 12 This is a scanning electron microscope image of graphene fragments loaded with gold nanoparticles prepared in Comparative Example 2 of the present invention.

[0041] In the figure, 1-nano-gold particle layer, 2-boron nitride / graphene hybrid aerogel thin layer, 3-boron nitride aerogel thermal insulation layer. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0043] To address the issue of aerogels experiencing a sudden increase in thermal conductivity at high temperatures, this paper proposes a lightweight, flexible, wide-temperature-range thermal insulation material and its preparation method. This material utilizes CVD to grow edge-structured graphene on boron nitride nanoribbons to form a thin hybrid aerogel layer. This layer is then physically entangled with the boron nitride nanoribbon aerogel. Finally, the surface of the hybrid aerogel layer is ion-sputtered with gold nanoparticles and then homogenized. The gold nanoparticle layer absorbs near-infrared light, the hybrid aerogel layer serves as a flexible infrared sunscreen, and the boron nitride nanoribbon aerogel serves as the primary thermal insulation layer, resulting in a multilayered gold nanoparticle / graphene / boron nitride composite material.

[0044] The preparation method of the lightweight, flexible, wide-temperature-range thermal insulation material of the present invention comprises the following steps:

[0045] Step 1: Preparation of boron nitride aerogel thin layer:

[0046] 0.2-1g of melamine, 0.2-1g of boric acid, 20-30ml of deionized water, and 20-30ml of tert-butyl alcohol were stirred in a water bath at 80-85°C for 20-30 minutes to obtain a clear solution. The clear solution was cooled to room temperature and then sonicated for 20-30 minutes to obtain a white supramolecular wet gel. The white supramolecular wet gel was then freeze-dried for 48 hours and then heat-treated in a tubular furnace to obtain a thin layer of boron nitride aerogel. The tubular furnace heat treatment temperature was 1100-1500°C for 2-4 hours in an atmosphere of one or a mixture of argon, nitrogen, and ammonia at a flow rate of 8-10 L / h.

[0047] Step 2: Growing edge-rich graphene on boron nitride nanoribbons:

[0048] Graphene is grown on boron nitride nanoribbons using chemical vapor deposition (CVD): methanol with a high O / C ratio is selected as the carbon source, and a boron nitride aerogel thin layer is placed in a CVD furnace at a growth temperature of 1100-1200°C for 4-12 hours to obtain a boron nitride / graphene hybrid aerogel thin layer.

[0049] Step 3: Combining the hybrid aerogel layer with the boron nitride aerogel insulation layer:

[0050] The boron nitride / graphene hybrid aerogel thin layer is floated on the same clarified solution as in step 1. After the clarified solution is cooled to room temperature, it is sonicated for 20 to 30 minutes, followed by freeze drying for 48 hours. After freeze drying, it is heat treated to obtain a graphene / boron nitride-boron nitride layered composite material. The heat treatment temperature is 1100 to 1500°C, the heat treatment time is 2 to 4 hours, and the heat treatment atmosphere is a mixture of one or more of argon, nitrogen, and ammonia at an atmosphere flow rate of 8 to 10 L / h.

[0051] Step 4: Ion sputtering of gold particles on the surface of the layered composite material:

[0052] Gold particles were ion-sputtered onto the surface of a graphene / boron nitride-boron nitride layered composite material at a sputtering voltage of 5 mA for 200 to 500 seconds. This was followed by annealing in a tube furnace to produce a multilayered nano-gold / graphene / boron nitride composite material. The annealing temperature was 400 to 800°C for 30 to 120 minutes in an argon atmosphere at a flow rate of 8 to 10 L / h.

[0053] The schematic diagram of the structure of the nano-gold / graphene / boron nitride composite material with a multilayer structure prepared by the method of the present invention is as follows Figure 1 As shown, the gold nanoparticle layer 1 can be used as an infrared absorption layer, the boron nitride / graphene hybrid aerogel thin layer 2 can be used as an infrared light-shielding layer and a transition layer, and the boron nitride aerogel thermal insulation layer 3 can be used as a thermal insulation layer.

[0054] Example 1:

[0055] The preparation method of the lightweight, flexible, wide-temperature-range thermal insulation material of this embodiment comprises the following steps:

[0056] Step 1: Stir 0.244g of melamine, 0.716g of boric acid, 22ml of deionized water and 26ml of tert-butanol in a water bath at 80°C for 30min to obtain a clear solution. Cool the clear solution to room temperature and ultrasonicate for 20min to obtain a white supramolecular wet gel. The white supramolecular wet gel is then freeze-dried for 48h and then placed in a tubular furnace for heat treatment to obtain a boron nitride aerogel thin layer. The tubular furnace heat treatment temperature is 1400°C, the heat treatment time is 2h, the heat treatment atmosphere is argon, and the atmosphere flow rate is 2L / h. After heat treatment, the bandwidth of the boron nitride nanobelt is 2-2.5μm, the ribbon length is hundreds of microns, and it has a high aspect ratio (see Figure 3 ) and bending flexibility (see Figure 2 ).

[0057] Step 2: Graphene was grown on boron nitride nanoribbons using chemical vapor deposition (CVD) technology. Methanol with a high O / C ratio was selected as the carbon source. The boron nitride aerogel thin layer was placed in a CVD furnace with a growth temperature of 1120°C and a growth time of 12 hours to obtain a boron nitride / graphene hybrid aerogel thin layer.

[0058] Step 3: Float the boron nitride / graphene hybrid aerogel thin layer on the same clarified solution as in step 1. After the clarified solution cools to room temperature, sonicate for 20 minutes, then freeze-dry for 48 hours. After freeze-drying, heat treat the mixture to obtain a graphene / boron nitride-boron nitride layered composite material. The heat treatment temperature is 1400°C, the heat treatment time is 2 hours, and the heat treatment atmosphere is argon at a flow rate of 2 L / h.

[0059] Step 4: Gold particles were ion-sputtered onto the surface of the graphene / boron nitride-boron nitride layered composite material at a sputtering voltage of 5 mA for 300 seconds. This was followed by annealing in a tube furnace to produce a multilayered nano-gold / graphene / boron nitride composite material. The annealing temperature was 800°C for 60 minutes in an argon atmosphere at a flow rate of 2 L / h.

[0060] The results show that a large number of graphene fragments are randomly distributed on the BN nanoribbons in the middle layer of the hybrid aerogel, while maintaining good bending flexibility (see Figure 4 、 Figure 5 ); the upper layer of gold nanoparticles has a particle size of 100-150 nm and is firmly locked by graphene (see Figure 6 、 Figure 7 ), and at the same time, an interlocking structure is formed between the nanoribbons at the junction of the lower layer and the middle layer (see Figure 8 ). The test results show that the thermal conductivity is 0.025W / m·k and the density is 35mg / cm 3 , stable mechanical properties and excellent thermal insulation performance (see Figure 9 ).

[0061] Example 2:

[0062] The preparation method of the lightweight, flexible, wide-temperature-range thermal insulation material of this embodiment comprises the following steps:

[0063] Step 1: 0.324g of melamine, 0.646g of boric acid, 20ml of deionized water, and 28ml of tert-butyl alcohol were stirred in a water bath at 80°C for 30 minutes to obtain a clear solution. The clear solution was cooled to room temperature and sonicated for 20 minutes to obtain a white supramolecular wet gel. The white supramolecular wet gel was then freeze-dried for 48 hours and then heat-treated in a tube furnace at 1300°C for 2 hours in an argon atmosphere at a flow rate of 2 L / h to obtain a thin layer of boron nitride aerogel.

[0064] Step 2: Use chemical vapor deposition (CVD) to grow graphene on boron nitride nanoribbons. Use methanol with a high O / C ratio as the carbon source. Place the boron nitride aerogel thin layer in a CVD furnace with a growth temperature of 1100°C and a growth time of 8 hours to obtain a boron nitride / graphene hybrid aerogel thin layer.

[0065] Step 3: Float the boron nitride / graphene hybrid aerogel thin layer on the same clarified solution as in step 1. After the clarified solution cools to room temperature, sonicate for 20 minutes, then freeze-dry for 48 hours. After freeze-drying, heat treat the mixture to obtain a graphene / boron nitride-boron nitride layered composite material. The heat treatment temperature is 1300°C, the heat treatment time is 2 hours, and the heat treatment atmosphere is argon at a flow rate of 2 L / h.

[0066] Step 4: Gold particles were ion-sputtered onto the surface of the graphene / boron nitride-boron nitride layered composite material at a sputtering voltage of 5 mA for 200 seconds. This was followed by annealing in a tube furnace to produce a multilayered nano-gold / graphene / boron nitride composite material. The annealing temperature was 800°C for 80 minutes, and the furnace atmosphere was argon at a flow rate of 2 L / h.

[0067] The test results show that the thermal conductivity is 0.030W / m·k and the density is 34mg / cm 3 , stable mechanical properties and excellent thermal insulation performance.

[0068] Example 3:

[0069] The preparation method of the lightweight, flexible, wide-temperature-range thermal insulation material of this embodiment comprises the following steps:

[0070] Step 1: 0.384g of melamine, 0.576g of boric acid, 24ml of deionized water, and 24ml of tert-butyl alcohol were stirred in a water bath at 80°C for 30 minutes to obtain a clear solution. The clear solution was cooled to room temperature and sonicated for 20 minutes to obtain a white supramolecular wet gel. The white supramolecular wet gel was then freeze-dried for 48 hours and then heat-treated in a tube furnace at 1200°C for 4 hours in an argon atmosphere at a flow rate of 2 L / h to obtain a thin layer of boron nitride aerogel.

[0071] Step 2: Graphene was grown on boron nitride nanoribbons using chemical vapor deposition (CVD) technology. Methanol with a high O / C ratio was selected as the carbon source. The boron nitride aerogel thin layer was placed in a CVD furnace with a growth temperature of 1130°C and a growth time of 10 hours to obtain a boron nitride / graphene hybrid aerogel thin layer.

[0072] Step 3: Float the boron nitride / graphene hybrid aerogel layer on the same clarified solution as in step 1. After the clarified solution cools to room temperature, sonicate for 20 minutes, then freeze-dry for 48 hours. After freeze-drying, heat treat the mixture to obtain a graphene / boron nitride-boron nitride layered composite material. The heat treatment temperature is 1200°C, the heat treatment time is 4 hours, and the heat treatment atmosphere is argon at a flow rate of 2 L / h.

[0073] Step 4: Gold particles were ion-sputtered onto the surface of the graphene / boron nitride-boron nitride layered composite material at a sputtering voltage of 5 mA for 300 seconds. This was followed by annealing in a tube furnace to produce a multilayered nano-gold / graphene / boron nitride composite material. The annealing temperature was 650°C for 30 minutes in an argon atmosphere at a flow rate of 2 L / h.

[0074] The test results show that the thermal conductivity is 0.028W / m·k and the density is 36mg / cm 3 , stable mechanical properties and excellent thermal insulation performance.

[0075] Comparative Example 1:

[0076] The preparation method of the composite material of this comparative example comprises the following steps:

[0077] Step 1: 0.244g of melamine, 0.716g of boric acid, 22ml of deionized water, and 26ml of tert-butyl alcohol were stirred in a water bath at 80°C for 30 minutes to obtain a clear solution. The clear solution was cooled to room temperature and sonicated for 20 minutes to obtain a white supramolecular wet gel. The white supramolecular wet gel was then freeze-dried for 48 hours and then heat-treated in a tube furnace at 1400°C for 2 hours in an argon atmosphere at a flow rate of 2 L / h to obtain a thin layer of boron nitride aerogel.

[0078] Step 2: Use chemical vapor deposition (CVD) to grow graphene on boron nitride nanoribbons. Use methanol with a high O / C ratio as the carbon source. Place the boron nitride aerogel thin layer in a CVD furnace with a growth temperature of 1500°C and a growth time of 4 hours to obtain a boron nitride / graphene hybrid aerogel thin layer.

[0079] Step 3: Float the boron nitride / graphene hybrid aerogel thin layer on the same clarified solution as in step 1. After the clarified solution cools to room temperature, sonicate for 20 minutes, then freeze-dry for 48 hours. After freeze-drying, heat treat the mixture to obtain a graphene / boron nitride-boron nitride layered composite material. The heat treatment temperature is 1400°C, the heat treatment time is 2 hours, and the heat treatment atmosphere is argon at a flow rate of 2 L / h.

[0080] Step 4: Gold particles were ion-sputtered onto the surface of the graphene / boron nitride-boron nitride layered composite material at a sputtering voltage of 5 mA for 300 seconds. The composite material was then annealed in a tube furnace to obtain the composite material of this comparative example. The annealing temperature was 800°C for 60 minutes in an argon atmosphere at a flow rate of 2 L / h.

[0081] Depend on Figure 10 It can be seen that the growth time of graphene on boron nitride nanoribbons is short, the growth temperature is high, and the grown graphene fragments are short. After sputtering gold nanoparticles, the gold particles cannot be loaded on the graphene fragments, and the phenomenon of graphene wrapping gold particles does not occur (see Figure 11 ). The test results show that the thermal conductivity is 0.045W / m·k and the density is 41mg / cm 3 Compared with the embodiment, the thermal insulation performance is poor.

[0082] Comparative Example 2:

[0083] The preparation method of the composite material of this comparative example comprises the following steps:

[0084] Step 1: 0.544g of melamine, 0.816g of boric acid, 22ml of deionized water, and 26ml of tert-butyl alcohol were stirred in a water bath at 80°C for 30 minutes to obtain a clear solution. The clear solution was cooled to room temperature and sonicated for 20 minutes to obtain a white supramolecular wet gel. The white supramolecular wet gel was then freeze-dried for 48 hours and then heat-treated in a tube furnace at 1400°C for 2 hours in an argon atmosphere at a flow rate of 2 L / h to obtain a thin layer of boron nitride aerogel.

[0085] Step 2: Graphene was grown on boron nitride nanoribbons using chemical vapor deposition (CVD) technology. Methanol with a high O / C ratio was selected as the carbon source. The boron nitride aerogel thin layer was placed in a CVD furnace with a growth temperature of 1120°C and a growth time of 2 hours to obtain a boron nitride / graphene hybrid aerogel thin layer.

[0086] Step 3: Float the boron nitride / graphene hybrid aerogel thin layer on the same clarified solution as in step 1. After the clarified solution cools to room temperature, sonicate for 20 minutes, then freeze-dry for 48 hours. After freeze-drying, heat treat the mixture to obtain a graphene / boron nitride-boron nitride layered composite material. The heat treatment temperature is 1400°C, the heat treatment time is 2 hours, and the heat treatment atmosphere is argon at a flow rate of 2 L / h.

[0087] Step 4: Gold particles were ion-sputtered onto the surface of the graphene / boron nitride-boron nitride layered composite material at a sputtering voltage of 5 mA and a sputtering time of 500 seconds. This was then annealed in a tube furnace to obtain the composite material of this comparative example. The annealing temperature was 1000°C, the annealing time was 60 minutes, and the tube furnace atmosphere was argon at a flow rate of 2 L / h.

[0088] Depend on Figure 12 It can be seen that the graphene growth time on the boron nitride nanoribbons is short and the growth temperature is high, resulting in shorter graphene fragments. After sputtering gold nanoparticles, annealing found that the gold particles aggregated into flakes and loaded on the nanoribbon surface. Test results show that the thermal conductivity value is 0.047W / m·K and the density is 39mg / cm 3 Compared with the embodiment, the thermal insulation performance is poor.

[0089] In summary, the present invention divides the functionality of aerogels through multi-layer structural design, constructs infrared absorption layer, infrared light-shielding layer, transition layer and heat-insulating layer, and collaboratively realizes the preparation of highly flexible, wide temperature range and strong heat-insulating aerogel. Specifically, by growing graphene with rich edge structure on flexible boron nitride nanobelts, a composite aerogel thin layer with high efficiency infrared light-shielding property is obtained, and the absorption and reflection of infrared light by graphene light-shielding agent is used to reduce the radiant heat conductivity at high temperature, thereby reducing the thermal conductivity of aerogel at high temperature, and then the composite aerogel thin layer and boron nitride nanobelt aerogel are combined by physical entanglement of nanobelts, and nano-gold particles are ion-sputtered onto the surface of the composite aerogel thin layer and then homogenized, which can absorb the near-infrared band and reduce the penetration of infrared light, thereby obtaining a nano-gold / graphene / boron nitride composite material with a multi-layer structure.

[0090] Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a lightweight, flexible, wide-temperature-range thermal insulation material, characterized in that: The process includes the following: A boron nitride aerogel thin layer is prepared using a clear solution. The preparation process of the clear solution comprises: mixing melamine, boric acid, deionized water and tert-butanol, and stirring at 80-85° C. for 20-30 minutes to obtain the clear solution, wherein the mixing ratio of melamine, boric acid, deionized water and tert-butanol is: (0.2-1 g): (0.2-1 g): (20-30 ml): (20-30 ml); Using chemical vapor deposition technology, graphene is grown on a boron nitride aerogel thin layer to obtain a boron nitride / graphene hybrid aerogel thin layer; floating the boron nitride / graphene hybrid aerogel thin layer on the clear solution, preparing a boron nitride aerogel thermal insulation layer on the surface of the boron nitride / graphene hybrid aerogel thin layer, and obtaining a graphene / boron nitride-boron nitride layered composite material; Gold particles are ion-sputtered on the surface of a graphene / boron nitride-boron nitride layered composite material, and then annealed to obtain a nano-gold / graphene / boron nitride composite material with a multilayer structure.

2. The method for preparing a lightweight, flexible, wide-temperature-range thermal insulation material according to claim 1, characterized in that: The process for preparing a thin layer of boron nitride aerogel from a clear solution includes: The clear solution was sonicated at room temperature to obtain a white supramolecular wet gel; The supramolecular wet gel is freeze-dried and then heat-treated to obtain a boron nitride aerogel thin layer.

3. The method for preparing a lightweight, flexible, wide-temperature-range thermal insulation material according to claim 2, characterized in that: The process of heat treating the freeze-dried supramolecular wet gel includes: The freeze-dried supramolecular wet gel is heated to 1100-1500° C. in a protective atmosphere, kept warm for 2-4 hours, and cooled to obtain a boron nitride aerogel thin layer.

4. The method for preparing a lightweight, flexible, wide-temperature-range thermal insulation material according to claim 1, characterized in that: The process of growing graphene on a thin layer of boron nitride aerogel using chemical vapor deposition includes: Using methanol as a carbon source, graphene is grown on a boron nitride aerogel thin layer at a growth temperature of 1100-1200° C. for a growth time of 4-12 hours.

5. The method for preparing a lightweight, flexible, wide-temperature-range thermal insulation material according to claim 1, characterized in that: The process of floating the boron nitride / graphene hybrid aerogel thin layer on the clear solution and preparing a boron nitride aerogel thermal insulation layer on the surface of the boron nitride / graphene hybrid aerogel thin layer comprises: At room temperature, the boron nitride / graphene hybrid aerogel thin layer is floated on the clear solution, and then ultrasonic treatment is performed to form a white supramolecular wet gel on the surface of the boron nitride / graphene hybrid aerogel thin layer. Thereafter, freeze-drying and heat treatment are performed to obtain a graphene / boron nitride-boron nitride layered composite material.

6. The method for preparing a lightweight, flexible, wide-temperature-range thermal insulation material according to claim 5, characterized in that: The heat treatment process for preparing a boron nitride aerogel insulation layer on the surface of a boron nitride / graphene hybrid aerogel thin layer includes: In a protective atmosphere, the freeze-dried supramolecular wet gel is heated to 1100-1500° C. and kept warm for 2-4 hours, and then cooled to obtain a graphene / boron nitride-boron nitride layered composite material.

7. The method for preparing a lightweight, flexible, wide-temperature-range thermal insulation material according to claim 3 or 6, characterized in that: The protective atmosphere is a mixture of one or more of argon, nitrogen and ammonia, and the flow rate of the protective atmosphere is 8 to 10 L / h.

8. The method for preparing a lightweight, flexible, wide-temperature-range thermal insulation material according to claim 1, characterized in that: When gold particles are ion sputtered on the surface of the graphene / boron nitride-boron nitride layered composite material, the sputtering voltage is 4.5-5.5 mA and the sputtering time is 200-500 s.

9. The method for preparing a lightweight, flexible, wide-temperature-range thermal insulation material according to claim 1, characterized in that: After ion sputtering of gold particles on the surface of the graphene / boron nitride-boron nitride layered composite material, the annealing process includes: In an argon atmosphere, heating to 400-800° C., keeping the temperature for 30-120 minutes, and then cooling to obtain a nano-gold / graphene / boron nitride composite material with a multilayer structure; wherein the argon flow rate is 8-10 L / h.

10. A lightweight, flexible, wide-temperature-range thermal insulation material, characterized in that: The lightweight, flexible, wide-temperature-range thermal insulation material is prepared by any one of the preparation methods described in claims 1-9.

Images