Hydrophobic aerogel material with low combustion heat as well as preparation method and application thereof

Abstract

The invention relates to a hydrophobic aerogel material with low combustion heat as well as a preparation method and application thereof. The method comprises the following steps: 1) carrying out two-stage calcination on an aerogel material to be treated; (2) carrying out vacuum gas phase modification on the calcined aerogel material; and 3) etching the modified aerogel material to obtain the hydrophobic aerogel material with low combustion heat. The invention aims to solve the problems of controlling the content of combustible substances contained in aerogel and a composite material and improving the flame safety of the aerogel and the composite material at high temperature by combining two-stage high-temperature treatment, vacuum gas phase modification, nano-particle surface etching and partial hydroxyl reduction technical means.

Description

Technical Field

[0001] The present invention belongs to the field of thermal insulation materials, and particularly relates to a low combustion heat hydrophobic aerogel material, a preparation method thereof, and an application thereof. Background Art

[0002] Aerogel is a new type of lightweight porous material. However, during the traditional "sol-gel" preparation process, a large number of hydroxyl groups remain on the surface of its nanoparticle skeleton, resulting in its hydrophilicity. This hydrophilicity makes the aerogel material easily adsorb moisture in the environment, seriously damaging its pore structure and leading to a significant reduction in its thermal insulation performance, which has a serious impact on the long-term storage of the aerogel material and its application in high-humidity environments. In order to improve the hydrophobicity of aerogel, the currently more effective method is to replace the hydrophilic hydroxyl groups on the surface of the aerogel with organic hydrophobic groups during the aerogel preparation process to endow the aerogel material with hydrophobicity. For example, an organosilicon source containing hydrophobic functional groups is added during the aerogel preparation process, or a surface modification is carried out using an organic hydrophobic modifier after the gelation process is completed, and finally a hydrophobic aerogel material with a large number of hydrophobic functional groups on the surface of the nanoparticle skeleton is obtained. Such methods often require the consumption of a large amount of organic modifiers, in an excessive manner to achieve a relatively complete reaction. Although it can bring relatively good hydrophobicity, because the introduction amount of the hydrophobic organic groups on the surface of the aerogel nanoparticles by this method is uncontrollable, the content of organic components including hydrophobic functional groups is too high. As a result, the traditional hydrophobic aerogel material modified with organic groups will decompose and burn at high temperatures (greater than 400 °C), generating smoke and even flames. This not only has an adverse effect on the fire prevention performance, but also has a negative effect on its application in high-temperature thermal insulation scenarios. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a low combustion heat hydrophobic aerogel material, a preparation method thereof, and an application thereof, as well as a treatment method and an application for converting it into a low combustion heat hydrophobic aerogel material. The problem to be solved is to control the content of the introduced hydrophobic organic functional groups and reduce some hydroxyl groups, so that while having hydrophobic characteristics, its combustion heat release at high temperatures is controlled to prevent the generation of smoke and open fire, improve the flame safety, and improve its safety in high-temperature thermal insulation applications.

[0004] The purpose of the present invention and the solution to its technical problems are achieved by adopting the following technical solutions. A preparation method of a low combustion heat hydrophobic aerogel material proposed by the present invention includes the following steps:

[0005] 1) Calcining the aerogel material to be treated in two stages;

[0006] 2) Subjecting the calcined aerogel material to vacuum gas phase modification;

[0007] 3) Etch the modified aerogel material to obtain the low combustion heat hydrophobic aerogel material.

[0008] The object of the present invention and the technical problems to be solved can also be further realized by the following technical measures.

[0009] Preferably, in the preparation method of the aforementioned low combustion heat hydrophobic aerogel material, in step 1), the two-stage calcination of the aerogel material to be treated includes the following steps:

[0010] Calcine the aerogel material to be treated at a heating rate of 5-10 °C / min at 300-400 °C for 1-6 h to complete the first-stage calcination; then raise the temperature to 650-1000 °C at a heating rate of 10-20 °C / min, keep warm for 0.25-1 h, and cool to room temperature after completing the second-stage calcination.

[0011] Preferably, in the preparation method of the aforementioned low combustion heat hydrophobic aerogel material, in step 1), the aerogel material is selected from one of silica, zirconia aerogel, alumina aerogel, silicon-aluminum composite aerogel, silicon-zirconium composite aerogel, and composites formed by them and fiber reinforcing materials; the fiber reinforcing material includes one of glass fiber, alumina fiber, high silica fiber, and zirconia fiber.

[0012] Preferably, in the preparation method of the aforementioned low combustion heat hydrophobic aerogel material, in step 2), the vacuum gas phase modification of the calcined aerogel material includes the following steps:

[0013] Modify the calcined aerogel material with a modifier under low pressure conditions; then purge with an inert gas.

[0014] Preferably, in the preparation method of the aforementioned low combustion heat hydrophobic aerogel material, in step 2), the modifier is a two-component, including component A and component B; wherein component A is an organic modifier with a smaller steric hindrance hydrophobic group, which is selected from one of dichlorodimethylsilane, trimethylchlorosilane, and dimethylchlorosilane; component B is an organic modifier with a larger steric hindrance hydrophobic group, which is selected from phenyldimethylchlorosilane, (diphenylmethyl)-dimethylchlorosilane, p-chlorophenyldimethylchlorosilane, 4-biphenyldimethylchlorosilane, p-tolyldimethylchlorosilane, and benzyldimethylchlorosilane; the molar ratio of component A to component B is 1.5:1-2:1.

[0015] Preferably, in the preparation method of the aforementioned low combustion heat hydrophobic aerogel material, in step 2), the addition amount of the modifier is 1 / 30-1 / 10 of the mass of the calcined aerogel material;

[0016] Preferably, in the preparation method of the low combustion heat hydrophobic aerogel material described above, in step 2), the vacuum degree of the low pressure is -0.08 MPa to -0.06 MPa, and the modification time is 2 - 6 h.

[0017] Preferably, in the preparation method of the low combustion heat hydrophobic aerogel material described above, in step 2), the purging time is greater than 5 min.

[0018] Preferably, in the preparation method of the low combustion heat hydrophobic aerogel material described above, in step 3), the etching of the modified aerogel material includes the following steps:

[0019] Place the modified aerogel material, the etchant, and the desiccant in a closed environment so that the etchant volatilizes to etch the modified aerogel material; then heat the etched aerogel material to 100 - 250 °C and keep it warm for more than 1 h.

[0020] Preferably, in the preparation method of the low combustion heat hydrophobic aerogel material described above, in step 3), the etchant is an aqueous solution of hydrofluoric acid with a concentration of 4 - 8 wt%.

[0021] Preferably, in the preparation method of the low combustion heat hydrophobic aerogel material described above, in step 3), the etching time is 4 - 12 h.

[0022] The object of the present invention and the technical problems it solves are achieved by the following technical solutions. A low combustion heat hydrophobic aerogel material proposed by the present invention has a contact angle greater than 110° and a combustion heat value less than 4.5 MJ / kg; the low combustion heat hydrophobic aerogel material is prepared by the above method.

[0023] The object of the present invention and the technical problems it solves are achieved by the following technical solutions. A heat insulation material proposed by the present invention uses a low combustion heat hydrophobic aerogel material, and the low combustion heat hydrophobic aerogel material has a contact angle greater than 110° and a combustion heat value less than 4.5 MJ / kg.

[0024] By means of the above technical solutions, a low combustion heat hydrophobic aerogel material, its preparation method and application provided by the present invention have at least the following advantages:

[0025] The present invention combines two-stage calcination treatment, vacuum gas-phase modification, nanoparticle surface etching, and partial hydroxyl reduction techniques to control the content of combustible substances in aerogels and composites, improving their flame safety at high temperatures. The two-stage heat treatment first undergoes medium-high temperature calcination to oxidize and decompose residual alkoxy groups and other combustible organic groups inside and on the surface of aerogel nanoparticles, and promotes the condensation of some silanol groups, facilitating the fusion of primary aerogel particles, thereby densifying the secondary particles. Subsequently, high-temperature treatment is used to further promote the growth of secondary particle size, coarsen the skeleton structure of aerogel nanoparticles, reduce the external surface area of the aerogel material's skeleton structure, and decrease the number of surface sites that can react with modifiers during subsequent modification processes. Moreover, the densified and coarsened nanostructure can withstand subsequent etching processes, preventing the collapse of the nanostructure. The vacuum gas-phase modification method is used for gas-phase surface modification. The gas-phase modification process under low pressure can promote the gasification of high-boiling-point modifiers, enabling gas-phase reaction processes. At the same time, compared with the atmospheric-pressure gas-phase modification process, in a low-pressure environment, not only is the collision between other gas molecules and organic modifier molecules reduced, but also the adsorption characteristics of the aerogel material itself can be utilized, facilitating the diffusion process of modifier molecules in the internal pores of the aerogel. This can significantly reduce the usage amount of modifiers and improve the reaction efficiency. Due to the lower amount of modifiers used, the number of combustible hydrophobic groups introduced onto the surface of aerogel nanoparticles can be controlled. After the modification is completed, an inert gas can be introduced to restore atmospheric pressure, and the reaction by-products can be purged and taken out for tail gas treatment. Since a two-component modifier is used, two types of (sterically hindered / low steric hindrance) hydrophobic groups can be simultaneously modified on the surface of aerogel nanoparticles. The hydrogen fluoride gas generated by volatilization can etch the modified aerogel. On the one hand, it selectively reacts with the hydrophobic groups with low steric hindrance, breaking the silicon-oxygen bonds connected to the groups, partially reducing the content of surface organic groups. The hydrophobic groups with large steric hindrance tend to be retained, thus controlling the overall content of hydrophobic groups. On the other hand, the etched nanoparticles can also generate silanol groups, enabling the coexistence of hydrophobic organic groups and silanol groups on the surface. This not only controls the loading amount of organic groups, but the polycondensation process of the reduced hydroxyl groups at high temperatures can also absorb the combustion heat generated by the decomposition of organic groups. Thus, while achieving surface hydrophobicity, the flame safety is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 FIG. is a process flow diagram for the preparation of low-combustion hydrophobic aerogel / aerogel composites according to some embodiments of the present invention;

[0027] Figure 2Schematic diagram of the surface modification process of the low combustion heat aerogel / aerogel composite nanoparticles of the present invention; 1 - Unreacted residual organic groups; 2 - Aerogel nanoparticle skeleton to be treated; 3 - Calcined and densified aerogel nanoparticle skeleton; 4 - High steric hindrance hydrophobic groups; 5 - Low steric hindrance hydrophobic groups; 6 - Selectively etched low steric hindrance hydrophobic groups;

[0028] Figure 3 Schematic connection diagram of the vacuum gas phase modification device of the present invention; 10 - Pressure vessel; 20 - Buffer chamber; 30 - Valve; 40 - Gas cylinder; 50 - Tail gas treatment device; 60 - Aerogel sample to be treated; 70 - Vacuum pump.

[0029] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly and implement it in accordance with the content of the specification, the following describes the preferred embodiments of the present invention in detail. Detailed implementation manners

[0030] To further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following combines preferred embodiments to detail the specific implementation manners, structures, features and effects of a low combustion heat hydrophobic aerogel material, its preparation method and its application proposed according to the present invention. In the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0031] The following materials or reagents, unless otherwise specified, are all commercially available.

[0032] As Figure 1 shown, some embodiments of the present invention provide a preparation method of a low combustion heat hydrophobic aerogel material, including the following steps:

[0033] S1 Calcining the aerogel material to be treated in two stages

[0034] S11 Place the aerogel material to be processed in a muffle furnace. The first-stage calcination temperature is 300 - 400 °C, the calcination time is 1 - 6 h, and the heating rate is 5 - 10 °C / min. If the first-stage calcination temperature is too low (less than 300 °C) or the time is too short (less than 2 h), the combustible organic components remaining in the aerogel during preparation cannot be completely burned out. If the temperature is too high (greater than 400 °C) or the time is too long (greater than 6 h), it will lead to too high a degree of fusion of the nanoparticle framework particles, which is not conducive to the subsequent second-stage calcination process. Subsequently, perform the second-stage temperature calcination. Heat the furnace body to 650 - 1000 °C, with a heating rate of 10 - 20 °C / min and a holding time of 0.25 - 1 h. After completion of the calcination, cool to room temperature. If the second-stage calcination temperature is too low (less than 650 °C) or the calcination time is too short (less than 0.5 h), it cannot promote the fusion and densification of the primary particles in the aerogel nanoparticles; it will also result in insufficient framework strength, and the framework structure is prone to collapse under the etching of the subsequent etchant. If the temperature is too high (greater than 1000 °C) or the calcination time is too long (greater than 1 h), it will lead to too high a degree of sintering of the aerogel, excessive sintering of the secondary particles, and severe shrinkage.

[0035] S12 In step S11, for the second-stage heating process, different calcination temperatures are adopted for different types of aerogel materials. For aerogels composed of single-element inorganic oxide nanoparticles such as silica, zirconia, and alumina, and their composites with fiber-reinforced materials, the fiber-reinforced materials include one of inorganic fiber materials such as glass fiber, alumina fiber, high-silica fiber, and zirconia fiber; the calcination temperature should be designed to be 650 - 800 °C. If the temperature is too high (greater than 800 °C), it is easy to cause too high a degree of sintering of this type of aerogel; if the temperature is too low (lower than 650 °C), it cannot promote the fusion and densification of the primary particles in this type of aerogel nanoparticles; for aerogels composed of multi-element inorganic oxide nanoparticles such as silicon-aluminum composite aerogel and silicon-zirconium composite aerogel, and their composites with fiber-reinforced materials, the calcination temperature should be designed to be 800 - 1000 °C. If the calcination temperature is too low (lower than 800 °C), it cannot promote the fusion and densification of the primary particles in this type of aerogel nanoparticles. If the calcination temperature is too high (greater than 1000 °C), it is easy to cause too high a degree of sintering of this type of aerogel.

[0036] S2 Vacuum gas-phase modification

[0037] S21 Place the calcined aerogel or composite material as a whole in the pressure vessel 10 of the vacuum gas-phase modification device. The pressure vessel 10 is connected to a vacuum pump 70, a small-size buffer chamber 20 connected by a valve, an exhaust gas treatment device 50, and a gas cylinder 40. Specifically, the exhaust gas treatment device 50 is connected to the pressure vessel 10 through a first pipeline, and the pressure vessel 10 is connected to the buffer chamber 20, the gas cylinder 40, and the vacuum pump 70 through a second pipeline, a third pipeline, and a fourth pipeline respectively; a bracket 60 for placing the aerogel sample to be processed is provided in the pressure vessel 10, and the buffer chamber 20 and the gas cylinder 40 are connected through a fifth pipeline; a first valve is provided on the first pipeline between the exhaust gas treatment device 50 and the pressure vessel 10, a second valve is provided on the second pipeline between the pressure vessel 10 and the buffer chamber 20, a third valve is provided on the third pipeline between the pressure vessel 10 and the gas cylinder 40, a fourth valve is provided on the fourth pipeline between the pressure vessel 10 and the vacuum pump 70, and a fifth valve 30 is provided on the fifth pipeline between the buffer chamber 20 and the gas cylinder 40, see Figure 3 .

[0038] S22 A modifier can be placed in the buffer chamber 20. The modifier is a two-component. Component A is an organic modifier with a small steric hindrance hydrophobic group. The small steric hindrance hydrophobic group is methyl. The organic modifier with a small steric hindrance hydrophobic group is selected from one of dichlorodimethylsilane, trimethylchlorosilane, and dimethylchlorosilane. Component B is an organic modifier with a large steric hindrance hydrophobic group. The large steric hindrance hydrophobic group is an aromatic group such as phenyl, benzyl, or biphenyl. The organic modifier with a large steric hindrance hydrophobic group is selected from one of phenyldimethylchlorosilane, (dibenzyl)-dimethylchlorosilane, p-chlorophenyldimethylchlorosilane, 4-biphenyldimethylchlorosilane, p-tolyldimethylchlorosilane, and benzyldimethylchlorosilane. The molar ratio of the two components is 1.5:1 - 2:1. Since the etchant will preferentially react with the hydrophobic group with a small steric hindrance during the subsequent etching process, when the molar ratio of component A to component B modifier is greater than 2:1, the number of hydrophobic groups remaining after the etching is too low, resulting in poor hydrophobicity. When the molar ratio of component A to component B modifier is less than 1.5:1, the number of hydrophobic groups remaining after the etching is too high, which is likely to cause a high combustion heat at high temperatures.

[0039] The addition amount of the liquid modifier mixture directly placed in S23 is 1 / 30 - 1 / 10 of the mass of the treated aerogel / aerogel composite material. When the amount of the modifier described in step S22 is too low (less than 1 / 30 of the material mass), it is likely that insufficient hydrophobic groups cannot be retained after the subsequent etching step, resulting in poor hydrophobicity. When the amount of the modifier described in step S22 is too high (greater than 1 / 10 of the material mass), the excessive modifier is difficult to remove by purging with inert gas, affecting the subsequent treatment process.

[0040] S24 Fill the buffer chamber 20 with an inert gas that does not react with the modifier. The inert gas is one of pure nitrogen or pure argon. Subsequently, use a vacuum pump 70 to pump the pressure vessel 10 to below -0.08 MPa, close the valve at the air extraction port, and then open the valve between the buffer chamber 20 and the pressure vessel 10. If the pressure is higher than -0.08 MPa, the vacuum degree is insufficient, resulting in too low an equilibrium vacuum degree after the gas in the buffer chamber enters the pressure vessel, which is not conducive to the rapid modification process; the pressure in the buffer chamber 20 will decrease accordingly. Under low-pressure (below atmospheric pressure) conditions, the modifier in the buffer chamber 20 will turn into a gas state and enter the pressure vessel along with the inert gas. At this time, as the gas in the buffer chamber 20 enters to reach pressure equilibrium, the vacuum degree in the pressure vessel 10 will partially drop to -0.08 MPa to -0.06 MPa, and the gas-phase modification of the aerogel or composite material will be carried out in the pressure vessel 10 under low pressure. If the vacuum degree during the vacuum pumping process is insufficient (pressure higher than -0.08 MPa), it is easy to cause too high an equilibrium pressure after opening the valve of the buffer chamber 20, which is not conducive to the modifier turning into a gas state. At the same time, under too high an equilibrium pressure condition (pressure higher than -0.06 MPa), there are still a large number of gas molecules hindering the molecular diffusion of the modifier, and it is also impossible to promote the modifier to complete the rapid reaction by virtue of the self-adsorption characteristics of the aerogel material under low pressure, slowing down the reaction efficiency. Keep the pressure vessel 10 in a closed state to complete the gas-phase modification process, and the modification time is 2 - 6 h.

[0041] S25 After the modification is completed, introduce an inert gas into the pressure vessel 10. After reaching atmospheric pressure, the gas is discharged through the tail gas treatment device, and the purging time is greater than 5 min; when it is less than 5 min, it is not conducive to ensuring the effective collection of by-products; so that the reaction by-products can be effectively collected to avoid environmental hazards.

[0042] S3 Etching with an etchant

[0043] S31 Place the modified aerogel material in a closed container.

[0044] An open container containing an etchant is placed inside an S32 airtight container. The etchant is an aqueous solution of hydrofluoric acid, and the concentration of the aqueous solution of hydrofluoric acid is 4 - 8 wt%. Using hydrofluoric acid as the etchant can react with the hydrophobic groups on the surface of aerogel nanoparticles to eliminate some hydrophobic organic functional groups; at the same time, it can also reduce the etched surface groups to hydroxyl groups. Therefore, the etchant is limited to hydrofluoric acid. Using an aqueous solution of hydrofluoric acid with a concentration of 4 - 8 wt% as the etchant can utilize the slow release process of hydrofluoric acid from the aqueous solution to prevent the reaction from being too violent. If the concentration of the aqueous solution of hydrofluoric acid is too low (less than 4 wt%), it may lead to insufficient etching. If the concentration of the aqueous solution of hydrofluoric acid is too high (more than 8 wt%), it is likely to cause a violent reaction and pose a potential environmental hazard. At the same time, a desiccant is placed inside the airtight container, and the desiccant is one of anhydrous calcium chloride and phosphorus pentoxide. The etching is completed by sealing the airtight container for 4 - 12 h. If the sealing time is too short (less than 4 h), it is easy to result in insufficient etching and too high content of remaining organic hydrophobic functional groups. If the sealing time is too long (more than 12 h), it is likely to cause over-etching, resulting in insufficient content of surface hydrophobic functional groups and poor hydrophobicity.

[0045] The aerogel material after the etching treatment is placed in a hot air oven and kept at 100 - 250 °C for more than 1 h. If the temperature is too low (such as less than 100 °C) or the heat preservation time is too short (such as less than 1 h), it is not conducive to removing the etching by-products. If the temperature is too high (such as more than 250 °C), it is easy to cause partial decomposition of the hydrophobic functional groups and reduce the hydrophobicity.

[0046] Some embodiments of the present invention also provide a low heat of combustion hydrophobic aerogel material. The contact angle of the low heat of combustion hydrophobic aerogel material is greater than 110°, the heat of combustion value is less than 4.5 MJ / kg, and no obvious smoke and open flame are generated at high temperatures; the low heat of combustion hydrophobic aerogel material is obtained by Figure 1 the method shown.

[0047] Some embodiments of the present invention also provide a heat insulation material. The heat insulation material can use the above-mentioned low heat of combustion hydrophobic aerogel material. The contact angle of the low heat of combustion hydrophobic aerogel material is greater than 110°, the heat of combustion value is less than 4.5 MJ / kg, and no obvious smoke and open flame are generated at high temperatures.

[0048] In the above technical solution, for the aerogel material prepared by the traditional "sol-gel" method, the present invention converts it into a low heat of combustion hydrophobic aerogel material, that is, converts the hydrophilic aerogel into a low heat of combustion hydrophobic aerogel material. The conversion process specifically includes: the combined action of two-stage calcination treatment, vacuum gas phase modification, surface etching of nanoparticles, and partial hydroxyl reduction technical means. As Figure 2As shown in the figure, first, a two-stage high-temperature treatment is adopted to eliminate the unreacted residual organic groups 1 inside and outside the aerogel nanoparticle framework 2, obtaining a densified aerogel nanoparticle framework 3, and reducing the external surface area of the nanoparticles. Subsequently, combined with a vacuum gas-phase modification method, two types of hydrophobic groups with high and low steric hindrances are simultaneously modified on the surface of the densified aerogel nanoparticle framework 3, obtaining a hydrophobic group 4 with high steric hindrance and a hydrophobic group 5 with low steric hindrance. Finally, an aqueous hydrofluoric acid solution is used as a dual-functional etching agent. Through the etching process, while eliminating part of the hydrophobic group 5 with low steric hindrance, part of the surface hydroxyl groups are restored, obtaining a selectively etched hydrophobic group 6 with low steric hindrance. Further reduce the loading amount of organic groups and control the combustion heat release. Moreover, the polycondensation process of the restored hydroxyl groups at high temperature can also absorb the combustion heat generated by the decomposition of organic groups, further reducing the overall combustion heat release (making the total combustion heat release below 4.5 MJ / kg). Thus, an aerogel material with both hydrophobic properties and no smoke and open flames at high temperatures, and having high flame safety is obtained.

[0049] The following further details the specific implementation manners of the present invention in conjunction with embodiments, but it should not be construed as a limitation on the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art to the present invention based on the above content of the present invention still fall within the protection scope of the present invention.

[0050] Unless otherwise specified, the materials, reagents, etc. involved below are all commercially available products well-known to those skilled in the art; unless otherwise specified, the methods are all well-known methods in the art. Unless otherwise defined, the technical terms or scientific terms used should have the ordinary meaning understood by those of ordinary skill in the art to which the present invention belongs.

[0051] Example 1

[0052] This example provides a preparation method for a low-combustion-heat hydrophobic aerogel material, including the following steps:

[0053] (1) Put the silica aerogel to be treated (with a volume of 100 cm 3 , and a mass of 10.2 g) into a muffle furnace, set the first calcination temperature at 350 °C, the heating rate at 10 °C / min, and the calcination time at 2 h.

[0054] (2) Subsequently, perform the second-stage temperature calcination, continue to raise the temperature of the furnace body to 650 °C, the heating rate at 15 °C / min, the holding time at 0.5 h, and cool to room temperature after completion of the calcination.

[0055] (3) Place the silica aerogel calcined in step (2) into the pressure vessel 10 of the vacuum gas-phase modification device. The pressure vessel 10 is connected to a vacuum pump 70, a small-sized buffer chamber 20 (the volume of the buffer chamber 20 is 1 / 100 of the volume of the pressure vessel 10) connected by valves, a tail gas treatment device 50, and a gas cylinder 40. Specifically, the tail gas treatment device 50 is connected to the pressure vessel 10 through a first pipeline, and the pressure vessel 10 is connected to the buffer chamber 20, the gas cylinder 40, and the vacuum pump 70 through a second pipeline, a third pipeline, and a fourth pipeline respectively; a bracket 60 for placing the aerogel sample to be treated is arranged in the pressure vessel 10, and the buffer chamber 20 and the gas cylinder 40 are connected through a fifth pipeline; a first valve is arranged on the first pipeline between the tail gas treatment device 50 and the pressure vessel 10, a second valve is arranged on the second pipeline between the pressure vessel 10 and the buffer chamber 20, a third valve is arranged on the third pipeline between the pressure vessel 10 and the gas cylinder 40, a fourth valve is arranged on the fourth pipeline between the pressure vessel 10 and the vacuum pump 70, and a fifth valve 30 is arranged on the fifth pipeline between the buffer chamber 20 and the gas cylinder 40, see Figure 3 .

[0056] (4) Close the second valve between the pressure vessel 10 and the buffer chamber 20, and put 0.32 g of phenyl dimethyl chlorosilane and 0.18 g of trimethyl chlorosilane into an open container in the buffer chamber 20.

[0057] (5) Fill the buffer chamber 20 with pure nitrogen (purity 99.9%) by sweeping, and the purging time is 10 s.

[0058] (6) Use the vacuum pump 70 to evacuate the pressure vessel 10 to -0.09 MPa, close the valve at the air extraction port, and then open the valve between the buffer chamber 20 and the pressure vessel 10. After opening the valve, the gas in the buffer chamber 20 enters the pressure vessel 10 to start the modification, and maintain the pressure in the pressure vessel 10 at about -0.07 MPa, and the modification time is 4 h.

[0059] (7) After the modification is completed, introduce pure nitrogen (purity 99.9%) into the pressure vessel 10. After reaching atmospheric pressure, open the valve between the pressure vessel 10 and the tail gas treatment device 50, and the gas (pure nitrogen) in the pressure vessel 10 is discharged through the tail gas treatment device 50 containing activated carbon, and the purging time is 5 min; the tail gas treatment device is a gas filter containing 100 g of activated carbon.

[0060] (8) Place the modified silica aerogel into another sealed container. Add 4.5 g of 5 wt% hydrofluoric acid aqueous solution to an open container in the container, and place 20 g of anhydrous calcium chloride in another open container. Wait for 6 h to complete the etching process.

[0061] (9) Put the etched aerogel material into a hot air oven, heat it to 150 °C at a heating rate of 5 °C / min, keep it warm for 1 h, and then take it out to obtain the treated silica aerogel material.

[0062] The contact angle of the silica aerogel material obtained in this example is 110.6°, showing hydrophobicity, and the calorific value of combustion is 4.12 MJ / kg. In an environment of 600 °C, there is no open fire and a large amount of smoke.

[0063] Example 2

[0064] This example provides a preparation method of a low-combustion-heat hydrophobic aerogel material, including the following steps:

[0065] (1) Put the silica aerogel to be treated (with a volume of 100 cm 3 , and a mass of 10.2 g) into a muffle furnace, set the first-stage calcination temperature to 400 °C, the heating rate to 10 °C / min, and the calcination time to 2 h.

[0066] (2) Subsequently, perform the second-stage temperature calcination, continue to raise the temperature of the furnace body to 700 °C, the heating rate is 20 °C / min, the holding time is 0.5 h, and after the calcination is completed, cool it to room temperature.

[0067] (3) Place the silica aerogel calcined in step (2) in the pressure vessel 10 of the vacuum gas-phase modification device. The pressure vessel 10 is connected to a vacuum pump 70, a small-size buffer chamber 20 (the volume of the buffer chamber 20 is 1 / 100 of the volume of the pressure vessel 10) connected by valves, a tail gas treatment device 50 and a gas cylinder 40; specifically, the tail gas treatment device 50 is connected to the pressure vessel 10 through a first pipeline, and the pressure vessel 10 is connected to the buffer chamber 20, the gas cylinder 40 and the vacuum pump 70 through a second pipeline, a third pipeline and a fourth pipeline respectively; a bracket 60 for placing the aerogel sample to be treated is arranged in the pressure vessel 10, and the buffer chamber 20 and the gas cylinder 40 are connected through a fifth pipeline; a first valve is provided on the first pipeline between the tail gas treatment device 50 and the pressure vessel 10, a second valve is provided on the second pipeline between the pressure vessel 10 and the buffer chamber 20, a third valve is provided on the third pipeline between the pressure vessel 10 and the gas cylinder 40, a fourth valve is provided on the fourth pipeline between the pressure vessel 10 and the vacuum pump 70, and a fifth valve 30 is provided on the fifth pipeline between the buffer chamber 20 and the gas cylinder 40, see Figure 3 .

[0068] (4) Close the valve between the pressure vessel 10 and the buffer chamber 20, and put 0.32 g of phenyldimethylchlorosilane and 0.18 g of trimethylchlorosilane into the open container in the buffer chamber 20.

[0069] (5) The buffer chamber 20 is purged and filled with pure nitrogen gas (purity 99.9%), and the purging time is 10 s.

[0070] (6) Using a vacuum pump 70, the pressure inside the pressure vessel 10 is pumped down to -0.09 MPa. The valve at the gas extraction port is closed, and then the valve between the buffer chamber 20 and the pressure vessel 10 is opened. After opening the valve, the gas in the buffer chamber 20 enters the pressure vessel 10 to start modification, and the pressure inside the pressure vessel 10 is maintained at about -0.07 MPa for a modification time of 4 h.

[0071] (7) After completion of the modification, pure nitrogen gas (purity 99.9%) is introduced into the pressure vessel 10. After reaching atmospheric pressure, the valve between the pressure vessel 10 and the tail gas treatment device 50 is opened, and the gas (pure nitrogen) inside the pressure vessel 10 is discharged through the tail gas treatment device 50 containing activated carbon. The purging time is 5 min; the tail gas treatment device is a gas filter containing 100 g of activated carbon.

[0072] (8) The modified silica aerogel is placed in another sealed container. In an open container inside the container, 4.5 g of a 5 wt% hydrofluoric acid aqueous solution is added, and 20 g of anhydrous calcium chloride is placed in another open container. After waiting for 6 h, the etching process is completed.

[0073] (9) The etched aerogel material is placed in a hot air oven, heated to 150 °C at a heating rate of 5 °C / min, held for 1 h, and then taken out to obtain the treated aerogel material.

[0074] The contact angle of the silica aerogel material obtained in this example was measured to be 118.2°, showing hydrophobicity, and the calorific value of combustion was 3.84 MJ / kg. In an environment of 600 °C, no open flame and a large amount of smoke appeared.

[0075] Example 3

[0076] This example provides a method for preparing a low combustion heat hydrophobic aerogel material, including the following steps:

[0077] (1) The silica aerogel to be treated (volume 100 cm 3 , mass 10.2 g) is placed in a muffle furnace. The first-stage calcination temperature is set to 350 °C, the heating rate is 10 °C / min, and the calcination time is 2 h.

[0078] (2) Subsequently, the second-stage temperature calcination is carried out. The furnace body is further heated to 650 °C at a heating rate of 15 °C / min, held for 0.5 h, and after completion of the calcination, it is cooled to room temperature.

[0079] (3) Place the silica aerogel calcined in step (2) into the pressure vessel 10 of the vacuum gas-phase modification device. The pressure vessel 10 is connected to a vacuum pump 70, a small-sized buffer chamber 20 (the volume of the buffer chamber 20 is 1 / 100 of the volume of the pressure vessel 10) connected by valves, an exhaust gas treatment device 50, and a gas cylinder 40. Specifically, the exhaust gas treatment device 50 is connected to the pressure vessel 10 through a first pipeline, and the pressure vessel 10 is connected to the buffer chamber 20, the gas cylinder 40, and the vacuum pump 70 through a second pipeline, a third pipeline, and a fourth pipeline respectively. A bracket 60 for placing the aerogel sample to be processed is provided in the pressure vessel 10. The buffer chamber 20 and the gas cylinder 40 are connected through a fifth pipeline. A first valve is provided on the first pipeline between the exhaust gas treatment device 50 and the pressure vessel 10, a second valve is provided on the second pipeline between the pressure vessel 10 and the buffer chamber 20, a third valve is provided on the third pipeline between the pressure vessel 10 and the gas cylinder 40, a fourth valve is provided on the fourth pipeline between the pressure vessel 10 and the vacuum pump 70, and a fifth valve 30 is provided on the fifth pipeline between the buffer chamber 20 and the gas cylinder 40, as shown in Figure 3 .

[0080] (4) Close the second valve between the pressure vessel 10 and the buffer chamber 20, and place 0.41 g of benzyldimethylchlorosilane and 0.20 g of dichlorodimethylsilane into the open container in the buffer chamber 20.

[0081] (5) Fill the buffer chamber 20 with pure nitrogen (purity 99.9%) by sweeping, and the purging time is 15 s.

[0082] (6) Use the vacuum pump 70 to evacuate the pressure vessel 10 to -0.09 MPa, close the valve at the air extraction port, and then open the valve between the buffer chamber 20 and the pressure vessel 10. After opening the valve, the gas in the buffer chamber 20 enters the pressure vessel 10 to start the modification, and maintain the pressure in the pressure vessel 10 at about -0.08 MPa, and the modification time is 4 h.

[0083] (7) After the modification is completed, introduce pure nitrogen (purity 99.9%) into the pressure vessel 10. After reaching atmospheric pressure, open the valve between the pressure vessel 10 and the exhaust gas treatment device 50, and the gas (pure nitrogen) in the pressure vessel 10 is discharged through the exhaust gas treatment device 50 containing activated carbon, and the purging time is 5 min; the exhaust gas treatment device is a gas filter containing 100 g of activated carbon.

[0084] (8) Place the modified silica aerogel into another sealed container. Add 4.5 g of 5 wt% hydrofluoric acid aqueous solution to an open container in the container, and place 20 g of anhydrous calcium chloride in another open container, and wait for 6 h to complete the etching process.

[0085] (9) Put the etched aerogel material into a hot air oven, heat it to 150 °C at a heating rate of 5 °C / min, keep it warm for 1 h, and then take it out to obtain the processed aerogel material.

[0086] The contact angle of the silica aerogel material obtained in this example was measured to be 121.4°, showing hydrophobicity, and the calorific value of combustion was 4.36 MJ / kg. In an environment of 600 °C, there was no open flame and a large amount of smoke.

[0087] Example 4

[0088] This example provides a preparation method of a low-combustion heat hydrophobic aerogel material, including the following steps:

[0089] (1) Put the silica aerogel to be processed (with a volume of 100 cm 3 , and a mass of 10.2 g) into a muffle furnace, set the first-stage calcination temperature to 350 °C, the heating rate to 10 °C / min, and the calcination time to 2 h.

[0090] (2) Subsequently, perform the second-stage temperature calcination, continue to raise the temperature of the furnace body to 650 °C at a heating rate of 15 °C / min, keep it warm for 0.5 h, and cool it to room temperature after the calcination is completed.

[0091] (3) Place the silica aerogel calcined in step (2) in the pressure vessel 10 of the vacuum gas-phase modification device. The pressure vessel 10 is connected to a vacuum pump, a small-size buffer chamber (the volume of the buffer chamber is 1 / 100 of the volume of the pressure vessel) connected by a valve, a tail gas treatment device 50, and a gas cylinder 40. Specifically, the tail gas treatment device 50 is connected to the pressure vessel 10 through a first pipeline, and the pressure vessel 10 is connected to the buffer chamber 20, the gas cylinder 40, and the vacuum pump 70 through a second pipeline, a third pipeline, and a fourth pipeline respectively; a support 60 for placing the aerogel sample to be processed is arranged in the pressure vessel 10; the buffer chamber 20 and the gas cylinder 40 are connected through a fifth pipeline; a first valve is provided on the first pipeline between the tail gas treatment device 50 and the pressure vessel 10, a second valve is provided on the second pipeline between the pressure vessel 10 and the buffer chamber 20, a third valve is provided on the third pipeline between the pressure vessel 10 and the gas cylinder 40, a fourth valve is provided on the fourth pipeline between the pressure vessel 10 and the vacuum pump 70, and a fifth valve 30 is provided on the fifth pipeline between the buffer chamber 20 and the gas cylinder 40, as shown in Figure 3 .

[0092] (4) Close the valve between the pressure vessel 10 and the buffer chamber 20, and put 0.32 g of phenyl dimethyl chlorosilane and 0.18 g of trimethyl chlorosilane into the open container in the buffer chamber 20.

[0093] (5) Fill the buffer chamber 20 with pure nitrogen (purity 99.9%) and purge for 10 s.

[0094] (6) Use a vacuum pump 70 to evacuate the pressure vessel 10 to -0.09 MPa. ， Close the valve at the air extraction port, and then open the valve between the buffer chamber 20 and the pressure vessel 10. After opening the valve, the gas in the buffer chamber 20 enters the pressure vessel 10 to start modification, maintaining the pressure in the pressure vessel 10 at about -0.07 MPa for 4 h.

[0095] (7) After completion of the modification, introduce pure nitrogen (purity 99.9%) into the pressure vessel 10. After reaching atmospheric pressure, open the valve between the pressure vessel 10 and the tail gas treatment device 50, and the gas (pure nitrogen, purity 99.9%) in the pressure vessel 50 is discharged through the tail gas treatment device containing activated carbon. The purge time is 5 min; the tail gas treatment device is a gas filter containing 100 g of activated carbon.

[0096] (8) Place the modified silica aerogel in another airtight container. Add 6.6 g of a 4 wt% hydrofluoric acid aqueous solution to an open container in the container, and place 20 g of anhydrous calcium chloride in another open container. Wait for 8 h to complete the etching process.

[0097] (9) Put the etched aerogel material into a hot air oven, heat it to 120 °C at a heating rate of 5 °C / min, keep it warm for 1.5 h, and then take it out to obtain the processed aerogel material.

[0098] The contact angle of the silica aerogel material obtained in this example was measured to be 107.8°, showing hydrophobicity, and the calorific value of combustion was 3.48 MJ / kg. In an environment of 600 °C, there was no open flame and a large amount of smoke.

[0099] Example 5

[0100] This example provides a method for preparing a low combustion heat hydrophobic aerogel material, including the following steps:

[0101] (1) Place the aluminosilicate fiber-reinforced silica aerogel to be treated (volume 100 cm 3 , mass 22 g) into a muffle furnace, set the first-stage calcination temperature to 400 °C, the heating rate to 10 °C / min, and the calcination time to 3 h.

[0102] (2) Subsequently, perform the second-stage temperature calcination. Continue to raise the temperature of the furnace body to 700 °C at a heating rate of 15 °C / min, keep it warm for 1 h, and after completion of the calcination, cool it to room temperature.

[0103] (3) Place the aluminosilicate fiber-reinforced silica aerogel calcined in step (2) into the pressure vessel 10 of the vacuum gas-phase modification device. The pressure vessel 10 is connected to a vacuum pump 70, a small-sized buffer chamber 20 (the volume of the buffer chamber 20 is 1 / 100 of the volume of the pressure vessel 10) connected by valves, a tail gas treatment device 50, and a gas cylinder 40. Specifically, the tail gas treatment device 50 is connected to the pressure vessel 10 through a first pipeline, and the pressure vessel 10 is connected to the buffer chamber 20, the gas cylinder 40, and the vacuum pump 70 through a second pipeline, a third pipeline, and a fourth pipeline respectively; a support 60 for placing the aerogel sample to be treated is arranged in the pressure vessel 10, and the buffer chamber 20 and the gas cylinder 40 are connected through a fifth pipeline; a first valve is provided on the first pipeline between the tail gas treatment device 50 and the pressure vessel 10, a second valve is provided on the second pipeline between the pressure vessel 10 and the buffer chamber 20, a third valve is provided on the third pipeline between the pressure vessel 10 and the gas cylinder 40, a fourth valve is provided on the fourth pipeline between the pressure vessel 10 and the vacuum pump 70, and a fifth valve 30 is provided on the fifth pipeline between the buffer chamber 20 and the gas cylinder 40, as shown in Figure 3 .

[0104] (4) Close the second valve between the pressure vessel 10 and the buffer chamber 20, and place 0.48 g of phenyldimethylchlorosilane and 0.26 g of trimethylchlorosilane into the open container in the buffer chamber 20.

[0105] (5) Fill the buffer chamber 20 with pure nitrogen (purity 99.9%) by sweeping, and the purging time is 10 s.

[0106] (6) Use the vacuum pump 70 to evacuate the pressure vessel 10 to -0.09 MPa, close the valve at the air extraction port, and then open the valve between the buffer chamber 20 and the pressure vessel 10. After opening the valve, the gas in the buffer chamber 20 enters the pressure vessel 10 to start the modification, and maintain the pressure in the pressure vessel 10 at about -0.07 MPa, and the modification time is 5 h.

[0107] (7) After the modification is completed, introduce pure nitrogen (purity 99.9%) into the pressure vessel 10. After reaching atmospheric pressure, open the valve between the pressure vessel 10 and the tail gas treatment device 50, and the gas (pure nitrogen, purity 99.9%) in the pressure vessel 10 is discharged through the tail gas treatment device containing activated carbon, and the purging time is 5 min; the tail gas treatment device is a gas filter containing 100 g of activated carbon.

[0108] (8) Place the modified aluminosilicate fiber-reinforced silica aerogel into another closed container. Add 7 g of 4 wt% hydrofluoric acid aqueous solution to an open container in the container, and place 30 g of anhydrous calcium chloride in another open container. Wait for 8 h to complete the etching process.

[0109] (9) Put the etched aluminosilicate fiber reinforced silica aerogel into a hot air oven, heat it to 150 °C at a heating rate of 5 °C / min, keep it warm for 1 h, and then take it out to obtain the treated aerogel material.

[0110] The contact angle of the aluminosilicate fiber reinforced silica aerogel material obtained in this example was measured to be 124.6°, showing hydrophobicity, and the calorific value of combustion was 4.03 MJ / kg. In an environment of 600 °C, there is no open flame and a large amount of smoke.

[0111] Example 6

[0112] This example provides a preparation method of a low combustion heat hydrophobic aerogel material, including the following steps:

[0113] (1) Put the to-be-treated high silica fiber reinforced silica aerogel (with a volume of 100 cm3 and a mass of 19 g) into a muffle furnace, set the first-stage calcination temperature to 330 °C, the heating rate to 10 °C / min, and the calcination time to 2 h.

[0114] (2) Subsequently, carry out the second-stage temperature calcination, continue to raise the furnace temperature to 600 °C at a heating rate of 15 °C / min, keep it warm for 0.5 h, and cool it to room temperature after the calcination is completed.

[0115] (3) Place the high silica fiber reinforced silica aerogel calcined in step (2) in the pressure vessel 10 of the vacuum gas phase modification device. The pressure vessel 10 is connected to a vacuum pump 70, a small-sized buffer chamber 20 (the volume of the buffer chamber 20 is 1 / 100 of the volume of the pressure vessel 10) connected by valves, a tail gas treatment device 50, and a gas cylinder 40. Specifically, the tail gas treatment device 50 is connected to the pressure vessel 10 through a first pipeline, and the pressure vessel 10 is connected to the buffer chamber 20, the gas cylinder 40, and the vacuum pump 70 through a second pipeline, a third pipeline, and a fourth pipeline respectively; a bracket 60 for placing the to-be-treated aerogel sample is arranged in the pressure vessel 10, and the buffer chamber 20 and the gas cylinder 40 are connected through a fifth pipeline; a first valve is arranged on the first pipeline between the tail gas treatment device 50 and the pressure vessel 10, a second valve is arranged on the second pipeline between the pressure vessel 10 and the buffer chamber 20, a third valve is arranged on the third pipeline between the pressure vessel 10 and the gas cylinder 40, a fourth valve is arranged on the fourth pipeline between the pressure vessel 10 and the vacuum pump 70, and a fifth valve 30 is arranged on the fifth pipeline between the buffer chamber 20 and the gas cylinder 40, see Figure 3 .

[0116] (4) Close the second valve between the pressure vessel 10 and the buffer chamber 20, and put 0.48 g of phenyldimethylchlorosilane and 0.26 g of trimethylchlorosilane into the open container in the buffer chamber.

[0117] (5) Fill the buffer chamber 20 with pure nitrogen (purity 99.9%) by purging, with a purging time of 10 s.

[0118] (6) Use a vacuum pump 70 to evacuate the pressure vessel 10 to -0.09 MPa, close the valve at the air extraction port, and then open the valve between the buffer chamber 20 and the pressure vessel 10. After opening the valve, the gas in the buffer chamber 20 enters the pressure vessel 10 to start modification, maintaining the pressure in the pressure vessel 10 at approximately -0.07 MPa, and the modification time is 4 h.

[0119] (7) After completion of the modification, introduce pure nitrogen (purity 99.9%) into the pressure vessel 10. After reaching atmospheric pressure, open the valve between the pressure vessel 10 and the tail gas treatment device 50, and the gas (pure nitrogen, purity 99.9%) in the pressure vessel 10 is discharged through the tail gas treatment device 50 containing activated carbon, with a purging time of 5 min; the tail gas treatment device is a gas filter containing 100 g of activated carbon.

[0120] (8) Place the modified high-silica fiber reinforced silica aerogel in another airtight container. Add 6 g of a 5 wt% hydrofluoric acid aqueous solution to an open container in the container, and place 25 g of anhydrous calcium chloride in another open container. Wait for 6 h to complete the etching process.

[0121] (9) Put the etched high-silica fiber reinforced silica aerogel into a hot air oven, heat it to 150 °C at a heating rate of 5 °C / min, hold for 1 h, and then take it out to obtain the processed aerogel material.

[0122] The contact angle of the high-silica fiber reinforced silica aerogel material obtained in this example was measured to be 113.5°, showing hydrophobicity, and the calorific value of combustion was 3.96 MJ / kg. In an environment of 600 °C, no open flame and a large amount of smoke appeared.

[0123] Example 7

[0124] This example provides a method for preparing a low-combustion-heat hydrophobic aerogel material, including the following steps:

[0125] (1) Place the glass fiber reinforced silica aerogel to be treated (volume 100 cm3, mass 18 g) in a muffle furnace, set the first-stage calcination temperature to 330 °C, the heating rate to 10 °C / min, and the calcination time to 2 h.

[0126] (2) Subsequently, perform the second-stage temperature calcination. Continue to raise the temperature of the furnace body to 600 °C, with a heating rate of 15 °C / min and a holding time of 0.5 h. After completion of the calcination, cool to room temperature.

[0127] (3) Place the glass fiber reinforced silica aerogel calcined in step (2) into the pressure vessel 10 of the vacuum gas phase modification device. The pressure vessel 10 is connected to a vacuum pump 70, a small-sized buffer chamber 20 (the volume of the buffer chamber 20 is 1 / 100 of the volume of the pressure vessel 10) connected by valves, a tail gas treatment device 50, and a gas cylinder 40. Specifically, the tail gas treatment device 50 is connected to the pressure vessel 10 through a first pipeline. The pressure vessel 10 is connected to the buffer chamber 20, the gas cylinder 40, and the vacuum pump 70 through a second pipeline, a third pipeline, and a fourth pipeline respectively. A support 60 for placing the aerogel sample to be treated is provided inside the pressure vessel 10. The buffer chamber 20 and the gas cylinder 40 are connected through a fifth pipeline. A first valve is provided on the first pipeline between the tail gas treatment device 50 and the pressure vessel 10. A second valve is provided on the second pipeline between the pressure vessel 10 and the buffer chamber 20. A third valve is provided on the third pipeline between the pressure vessel 10 and the gas cylinder 40. A fourth valve is provided on the fourth pipeline between the pressure vessel 10 and the vacuum pump 70. A fifth valve 30 is provided on the fifth pipeline between the buffer chamber 20 and the gas cylinder 40, see Figure 3 。

[0128] (4) Close the second valve between the pressure vessel 10 and the buffer chamber 20, and place 0.52 g of benzyldimethylchlorosilane and 0.19 g of dichlorodimethylsilane into an open container inside the buffer chamber 20.

[0129] (5) Fill and purge the buffer chamber 20 with pure nitrogen (purity 99.9%), and the purging time is 10 s.

[0130] (6) Use the vacuum pump 70 to evacuate the pressure vessel 10 to -0.08 MPa, close the valve at the air extraction port, and then open the valve between the buffer chamber 20 and the pressure vessel 10. After opening the valve, the gas in the buffer chamber 20 enters the pressure vessel 10 to start the modification, and maintain the pressure in the pressure vessel 10 at about -0.06 MPa, and the modification time is 5 h.

[0131] (7) After the modification is completed, introduce pure nitrogen (purity 99.9%) into the pressure vessel 10. After reaching atmospheric pressure, open the valve between the pressure vessel 10 and the tail gas treatment device 50. The gas (pure nitrogen, purity 99.9%) in the pressure vessel 10 is discharged through the tail gas treatment device 50 containing activated carbon, and the purging time is 5 min. The tail gas treatment device is a gas filter containing 100 g of activated carbon.

[0132] (8) Place the glass fiber reinforced silica aerogel after the modification into another sealed container. Add 6 g of a 5 wt% hydrofluoric acid aqueous solution to an open container inside the container, and place 25 g of anhydrous calcium chloride in another open container. Wait for 6 h to complete the etching process.

[0133] (9) Place the etched aerogel material into a hot air oven, heat it to 150 °C at a heating rate of 5 °C / min, keep it warm for 1 h, and then take it out to obtain the processed aerogel material.

[0134] The contact angle of the glass fiber reinforced silica aerogel material obtained in this example was measured to be 117.4°, showing hydrophobicity, and the calorific value of combustion was 4.11 MJ / kg. In an environment of 800 °C, there was no open flame and a large amount of smoke.

[0135] Example 8

[0136] This example provides a preparation method of a low combustion heat and hydrophobic aerogel material, including the following steps:

[0137] (1) Place the silicon-aluminum composite aerogel to be processed (with a volume of 100 cm3 and a mass of 9.8 g) into a muffle furnace, set the first-stage calcination temperature to 350 °C, the heating rate to 10 °C / min, and the calcination time to 1 h.

[0138] (2) Subsequently, perform the second-stage temperature calcination. Continue to raise the temperature of the furnace body to 900 °C at a heating rate of 15 °C / min, keep it warm for 0.5 h, and after completion of the calcination, cool it to room temperature.

[0139] (3) Place the silicon-aluminum composite aerogel calcined in step (2) into the pressure vessel 10 of the vacuum gas phase modification device. The pressure vessel 10 is connected to a vacuum pump 70, a small-size buffer chamber 20 (the volume of the buffer chamber 20 is 1 / 100 of the volume of the pressure vessel 10) connected by valves, a tail gas treatment device 50, and a gas cylinder 40; specifically, the tail gas treatment device 50 is connected to the pressure vessel 10 through a first pipeline, and the pressure vessel 10 is connected to the buffer chamber 20, the gas cylinder 40, and the vacuum pump 70 through a second pipeline, a third pipeline, and a fourth pipeline respectively; a bracket 60 for placing the aerogel sample to be processed is provided inside the pressure vessel 10, and the buffer chamber 20 and the gas cylinder 40 are connected through a fifth pipeline; a first valve is provided on the first pipeline between the tail gas treatment device 50 and the pressure vessel 10, a second valve is provided on the second pipeline between the pressure vessel 10 and the buffer chamber 20, a third valve is provided on the third pipeline between the pressure vessel 10 and the gas cylinder 40, a fourth valve is provided on the fourth pipeline between the pressure vessel 10 and the vacuum pump 70, and a fifth valve 30 is provided on the fifth pipeline between the buffer chamber 20 and the gas cylinder 40, as shown in Figure 3 .

[0140] (4) Close the valve between the pressure vessel 10 and the buffer chamber 20, and place 0.45 g of phenyldimethylchlorosilane and 0.18 g of trimethylchlorosilane into the open container inside the buffer chamber 20.

[0141] (5) Fill the buffer chamber 20 with pure nitrogen gas (purity 99.9%) by purging, with a purging time of 10 s.

[0142] (6) Use a vacuum pump 70 to evacuate the pressure vessel 10 to -0.08 MPa, close the valve at the air extraction port, and then open the valve between the buffer chamber 20 and the pressure vessel 10. After opening the valve, the gas inside the buffer chamber 20 enters the pressure vessel 10 to start modification, maintaining the pressure inside the pressure vessel 10 at approximately -0.06 MPa, with a modification time of 4 h.

[0143] (7) After completion of the modification, introduce pure nitrogen gas (purity 99.9%) into the pressure vessel 10. After reaching atmospheric pressure, open the valve between the pressure vessel 10 and the tail gas treatment device 50, and the gas inside the pressure vessel 10 (pure nitrogen gas, purity 99.9%) is discharged through the tail gas treatment device 50 containing activated carbon, with a purging time of 5 min; the tail gas treatment device is a gas filter containing 100 g of activated carbon.

[0144] (9) Place the modified silicon-aluminum composite aerogel in another sealed container. Add 5 g of a 4 wt% hydrofluoric acid aqueous solution to an open container inside the container, and place 20 g of anhydrous calcium chloride in another open container. Wait for 4 h to complete the etching process.

[0145] (9) Put the etched silicon-aluminum composite aerogel into a hot air oven, heat it to 150 °C at a heating rate of 5 °C / min, hold for 1 h, and then take it out to obtain the processed aerogel material.

[0146] The contact angle of the silicon-aluminum composite aerogel material obtained in this example was measured to be 109.1°, showing hydrophobicity, and the calorific value of combustion was 3.91 MJ / kg. In an environment of 800 °C, no open flame and a large amount of smoke appeared.

[0147] Example 9

[0148] This example provides a method for preparing a low-combustion-heat hydrophobic aerogel material, including the following steps:

[0149] (1) Place the silicon-aluminum composite aerogel reinforced with aluminosilicate fibers to be processed (volume 100 cm 3 , mass 18.8 g) into a muffle furnace, set the first-stage calcination temperature to 350 °C, the heating rate to 10 °C / min, and the calcination time to 1 h.

[0150] (2) Subsequently, perform the second-stage temperature calcination. Continue to raise the temperature of the furnace body to 900 °C at a heating rate of 20 °C / min, hold for 0.25 h, and after completion of the calcination, cool to room temperature.

[0151] (3) Place the calcined aluminum silicate fiber-reinforced silicon-aluminum composite aerogel in the pressure vessel 10 of the vacuum gas-phase modification device. The pressure vessel 10 is connected to a vacuum pump 70, a small-sized buffer chamber 20 (the volume of the buffer chamber 20 is 1 / 100 of the volume of the pressure vessel 10) connected by valves, an exhaust gas treatment device 50, and a gas cylinder 40. Specifically, the exhaust gas treatment device 50 is connected to the pressure vessel 10 through a first pipeline, and the pressure vessel 10 is connected to the buffer chamber 20, the gas cylinder 40, and the vacuum pump 70 through a second pipeline, a third pipeline, and a fourth pipeline respectively. A support 60 for placing the aerogel sample to be treated is arranged in the pressure vessel 10. The buffer chamber 20 and the gas cylinder 40 are connected through a fifth pipeline. A first valve is arranged on the first pipeline between the exhaust gas treatment device 50 and the pressure vessel 10, a second valve is arranged on the second pipeline between the pressure vessel 10 and the buffer chamber 20, a third valve is arranged on the third pipeline between the pressure vessel 10 and the gas cylinder 40, a fourth valve is arranged on the fourth pipeline between the pressure vessel 10 and the vacuum pump 70, and a fifth valve 30 is arranged on the fifth pipeline between the buffer chamber 20 and the gas cylinder 40. See Figure 3 .

[0152] (4) Close the valve between the pressure vessel 10 and the buffer chamber 20, and put 0.54 g of phenyl dimethyl chlorosilane and 0.22 g of trimethyl chlorosilane into the open container in the buffer chamber 20.

[0153] (5) Fill the buffer chamber 20 with pure nitrogen (purity 99.9%) by sweeping, and the purging time is 10 s.

[0154] (6) Use the vacuum pump 70 to evacuate the pressure vessel 10 to -0.08 MPa, close the valve at the air extraction port, and then open the valve between the buffer chamber 20 and the pressure vessel 10. After opening the valve, the gas in the buffer chamber 20 enters the pressure vessel 10 to start the modification, and maintain the pressure in the pressure vessel 10 at about -0.06 MPa, and the modification time is 5 h.

[0155] (7) After the modification is completed, introduce pure nitrogen (purity 99.9%) into the pressure vessel 10. After reaching atmospheric pressure, open the valve between the pressure vessel 10 and the exhaust gas treatment device 50, and the gas in the pressure vessel 10 (pure nitrogen, purity 99.9%) is discharged through the exhaust gas treatment device containing activated carbon, and the purging time is 5 min; the exhaust gas treatment device is a gas filter containing 100 g of activated carbon.

[0156] (8) Place the modified aluminum silicate fiber-reinforced silicon-aluminum composite aerogel material in another sealed container. Add 5 g of 4 wt% hydrofluoric acid aqueous solution to an open container in the container, and place 20 g of anhydrous calcium chloride in another open container. Wait for 4 h to complete the etching process.

[0157] (9) Place the etched aluminosilicate fiber reinforced silicon-aluminum composite aerogel material into a hot air oven, heat it to 150 °C at a heating rate of 5 °C / min, keep it warm for 1 h, and then take it out to obtain the processed aerogel material.

[0158] The aluminosilicate fiber reinforced silicon-aluminum composite aerogel material obtained in this example has a measured contact angle of 122.9°, showing hydrophobicity, and a combustion heat value of 4.23 MJ / kg. In an 800 °C environment, there is no open flame and a large amount of smoke.

[0159] Example 10

[0160] This example provides a method for preparing a low combustion heat and hydrophobic aerogel material, which includes the following steps:

[0161] (1) Place the to-be-treated mullite fiber reinforced silicon-aluminum composite aerogel (with a volume of 100 cm 3 , and a mass of 19.8 g) into a muffle furnace, set the first-stage calcination temperature to 350 °C, the heating rate to 10 °C / min, and the calcination time to 1 h.

[0162] (2) Subsequently, perform the second-stage temperature calcination. Continue to raise the temperature of the furnace body to 950 °C at a heating rate of 20 °C / min, keep it warm for 0.25 h, and after completion of calcination, cool it to room temperature.

[0163] (3) Place the mullite fiber reinforced silicon-aluminum composite aerogel calcined in step (2) into the pressure vessel 10 of the vacuum gas-phase modification device. The pressure vessel 10 is connected to a vacuum pump 70, a small-size buffer chamber 20 (the volume of the buffer chamber 20 is 1 / 100 of the volume of the pressure vessel 10) connected by valves, a tail gas treatment device 50, and a gas cylinder 40; specifically, the tail gas treatment device 50 is connected to the pressure vessel 10 through a first pipeline, and the pressure vessel 10 is connected to the buffer chamber 20, the gas cylinder 40, and the vacuum pump 70 through a second pipeline, a third pipeline, and a fourth pipeline respectively; a bracket 60 for placing the to-be-treated aerogel sample is arranged in the pressure vessel 10, and the buffer chamber 20 and the gas cylinder 40 are connected through a fifth pipeline; a first valve is provided on the first pipeline between the tail gas treatment device 50 and the pressure vessel 10, a second valve is provided on the second pipeline between the pressure vessel 10 and the buffer chamber 20, a third valve is provided on the third pipeline between the pressure vessel 10 and the gas cylinder 40, a fourth valve is provided on the fourth pipeline between the pressure vessel 10 and the vacuum pump 70, and a fifth valve 30 is provided on the fifth pipeline between the buffer chamber 20 and the gas cylinder 40, see Figure 3 .

[0164] (4) Close the valve between the pressure vessel 10 and the buffer chamber 20, and place 0.52 g of benzyldimethylchlorosilane and 0.19 g of dichlorodimethylsilane into an open container within the buffer chamber 20.

[0165] (5) Fill the buffer chamber 20 with pure nitrogen (purity 99.9%) by purging, and the purging time is 10 s.

[0166] (6) Use a vacuum pump 70 to evacuate the pressure vessel 10 to -0.08 MPa, close the valve at the air extraction port, and then open the valve between the buffer chamber 20 and the pressure vessel 10. After opening the valve, the gas in the buffer chamber 20 enters the pressure vessel 10 to start modification, maintain the pressure in the pressure vessel 10 at about -0.06 MPa, and the modification time is 5 h.

[0167] (7) After completion of the modification, introduce pure nitrogen (purity 99.9%) into the pressure vessel 10. After reaching atmospheric pressure, open the valve between the pressure vessel 10 and the tail gas treatment device 50, and the gas in the pressure vessel 10 (pure nitrogen, purity 99.9%) is discharged through the tail gas treatment device 50 containing activated carbon, and the purging time is 5 min; the tail gas treatment device is a gas filter containing 100 g of activated carbon.

[0168] (8) Place the modified mullite fiber reinforced silicon-aluminum composite aerogel into another closed container. Add 5 g of 4 wt% hydrofluoric acid aqueous solution to an open container within the container, and place 20 g of anhydrous calcium chloride in another open container. Wait for 4 h to complete the etching process.

[0169] (9) Put the etched mullite fiber reinforced silicon-aluminum composite aerogel into a hot air oven, heat it to 150 °C at a heating rate of 5 °C / min, hold for 1 h and then take it out to obtain the processed aerogel material.

[0170] The contact angle of the mullite fiber reinforced silicon-aluminum composite aerogel material obtained in this example is measured to be 126.2°, showing hydrophobicity, and the calorific value of combustion is 4.41 MJ / kg. In an environment of 800 °C, there is no open flame and a large amount of smoke.

[0171] Comparative Example 1

[0172] This comparative example uses methoxytrimethylsilane (MTMS) and tetraethyl orthosilicate (TEOS) as composite silicon sources to prepare hydrophobic silica aerogel by the co-precursor method.

[0173] The specific steps are as follows: Mix methoxytrimethylsilane (MTMS), tetraethyl orthosilicate (TEOS), absolute ethanol, and water in a molar ratio of 1:0.5:8:6. Add 1 mol / L nitric acid to adjust the pH value to 3. After stirring at room temperature for 4 hours, add 1 mol / L ammonia water to adjust the pH value to 8 to obtain silica sol. Put the above silica sol into a mold, wait for it to gel, then seal the mold, and age it at 60 °C for 3 days. After aging, take out the gel and soak it in ethanol for 12 hours, and repeat this three times. Use a carbon dioxide supercritical drying equipment to dry and obtain a hydrophobic silica aerogel material.

[0174] Use the hydrophobic silica aerogel without any treatment as Comparative Example 1. After testing, the hydrophobic angle of the hydrophobic silica aerogel is 132.5°, and the calorific value of combustion is 18.6 MJ / kg. In an environment of 600 °C, there is an open flame during combustion and smoke is generated.

[0175] Comparative Example 2

[0176] This comparative example provides a preparation method of an aerogel material, including the following steps:

[0177] (1) Place the silica aerogel to be treated (with a volume of 100 cm 3 , and a mass of 10.2 g) directly into a pressure vessel, which is connected to a vacuum pump, a small-sized buffer chamber (the volume of the buffer chamber is 1 / 100 of the volume of the pressure vessel) connected by a valve, a tail gas treatment device, and a gas cylinder.

[0178] (2) Close the valve between the pressure vessel and the buffer chamber, and put 0.32 g of phenyldimethylchlorosilane and 0.18 g of trimethylchlorosilane into an open container in the buffer chamber.

[0179] (3) Fill the buffer chamber with pure nitrogen (purity of 99.9%) by sweeping, and the purging time is 10 s.

[0180] (4) Use a vacuum pump to pump the pressure vessel to -0.09 MPa, close the air extraction port valve, and then open the valve between the buffer chamber and the pressure vessel. After opening the valve, the gas in the buffer chamber enters the pressure vessel to start modification, maintain the pressure in the pressure vessel at about -0.07 MPa, and the modification time is 4 h.

[0181] (5) After the modification is completed, introduce pure nitrogen (purity of 99.9%) into the pressure vessel. After reaching atmospheric pressure, open the valve between the pressure vessel and the tail gas treatment device. The gas in the pressure vessel (pure nitrogen, purity of 99.9%) is discharged through the tail gas treatment device containing activated carbon, and the purging time is 5 min; the tail gas treatment device is a gas filter containing 100 g of activated carbon.

[0182] (6) Place the modified silica aerogel in another sealed container. Add 4.5 g of 5 wt% hydrofluoric acid aqueous solution to an open container inside the container, and place 20 g of anhydrous calcium chloride in another open container. Wait for 4 h to complete the etching process.

[0183] (7) Put the etched silica aerogel into a hot air oven, heat it to 150 °C at a heating rate of 5 °C / min, keep it warm for 1 h, and then take it out to obtain the treated aerogel material as Comparative Example 2.

[0184] The contact angle of the silica aerogel material obtained in Comparative Example 2 was measured to be 118.7°, showing hydrophobicity, and the calorific value of combustion was 8.93 MJ / kg. In an environment of 600 °C, there was an indistinct flame, but no obvious smoke appeared.

[0185] Comparative Example 3

[0186] This comparative example provides a preparation method of an aerogel material, including the following steps:

[0187] (1) Place the silica aerogel to be treated (with a volume of 100 cm 3 , and a mass of 10.2 g) into a muffle furnace, set the first-stage calcination temperature to 350 °C, the heating rate to 10 °C / min, and the calcination time to 2 h.

[0188] (2) Subsequently, perform the second-stage temperature calcination. Continue to raise the temperature of the furnace body to 650 °C at a heating rate of 15 °C / min, keep it warm for 0.5 h, and after completion of calcination, cool it to room temperature.

[0189] (3) Place the silica aerogel calcined in step (2) into a sealed container, and at the same time, put 0.32 g of phenyldimethylchlorosilane and 0.18 g of trimethylchlorosilane into an open container inside the sealed container.

[0190] (4) Seal the sealed container, keep the internal pressure at atmospheric pressure and modify the aerogel for 4 h.

[0191] (5) After completion of modification, open the valve between the sealed container 10 and the tail gas treatment device 50, introduce pure nitrogen (purity: 99.9%) into the pressure vessel, and the gas is discharged through the tail gas treatment device 50. The purging time is 5 min; the tail gas treatment device is a gas filter containing 100 g of activated carbon.

[0192] (6) Place the modified aerogel / aerogel composite material into another sealed container. Add 4.5 g of 5 wt% hydrofluoric acid aqueous solution to an open container inside the container, and place 20 g of anhydrous calcium chloride in another open container. Wait for 6 h to complete the etching process.

[0193] (7) Place the aerogel material after etching completion into a hot air oven, heat it to 150 °C at a heating rate of 5 °C / min, hold for 1 h and then take it out to obtain Comparative Example 3.

[0194] The silica aerogel material obtained in Comparative Example 3 shows obvious hydrophilicity. The liquid droplet directly penetrates into the interior of the material, and the contact angle cannot be measured. Its calorific value of combustion is 2.63 MJ / kg. In an environment of 600 °C, there is no open flame and a large amount of smoke.

[0195] Comparative Example 4

[0196] This comparative example provides a preparation method of an aerogel material, including the following steps:

[0197] (1) Place the silica aerogel to be treated (with a volume of 100 cm 3 , and a mass of 10.2 g) into a muffle furnace, set the first-stage calcination temperature to 350 °C, the heating rate to 10 °C / min, and the calcination time to 2 h.

[0198] (2) Subsequently, conduct the second-stage temperature calcination. Continue to raise the temperature of the furnace body to 650 °C at a heating rate of 15 °C / min, hold for 0.5 h, and after completion of calcination, cool it to room temperature.

[0199] (3) Place the silica aerogel calcined in step (2) into a pressure vessel, which is connected to a vacuum pump, a small-size buffer chamber (the volume of the buffer chamber is 1 / 100 of the volume of the pressure vessel) connected by a valve, a tail gas treatment device and a gas cylinder.

[0200] (4) Close the valve between the pressure vessel 10 and the buffer chamber 20, and place 0.32 g of phenyl dimethyl chlorosilane and 0.18 g of trimethyl chlorosilane into an open container in the buffer chamber 20.

[0201] (5) Fill the buffer chamber 20 with pure nitrogen (purity 99.9%) by sweeping, and the purging time is 10 s.

[0202] (6) Use the vacuum pump 70 to pump the pressure vessel 10 to -0.09 MPa, close the valve at the air extraction port, and then open the valve between the buffer chamber 20 and the pressure vessel 10; after opening the valve, the gas in the buffer chamber 20 enters the pressure vessel 10 to start modification, maintain the pressure in the pressure vessel 10 at about -0.07 MPa, and the modification time is 4 h.

[0203] (7) After the modification is completed, pure nitrogen gas (purity 99.9%) is introduced into the pressure vessel 10. After reaching normal pressure, the valve between the pressure vessel 10 and the tail gas treatment device 50 is opened, and the gas in the pressure vessel 10 (pure nitrogen gas, purity 99.9%) is discharged through the tail gas treatment device containing activated carbon, and the purging time is 5 min; the tail gas treatment device is a gas filter containing 100 g of activated carbon; the modified aerogel material is taken out to obtain Comparative Example 4.

[0204] The contact angle of the silica aerogel material obtained in Comparative Example 4 was measured to be 129.1°, showing hydrophobicity, and the calorific value of combustion was 11.32 MJ / kg. In an environment of 600 °C with an open flame, the combustion time was about 10 s, and a small amount of smoke appeared.

[0205] The test data of the hydrophobic properties and combustion properties of the aerogel materials of Examples 1-10 and Comparative Examples 1-4 are summarized in Table 1. It can be seen from the data in Table 1 that the aerogel materials obtained in Examples 1-10 all have good hydrophobicity (contact angle > 90°) after the completion of the treatment, and have a low calorific value of combustion (< 4.5 MJ / kg), and no open flame and a large amount of smoke appear in a high-temperature environment. The aerogel material of Comparative Example 1 has hydrophobicity, but has a high calorific value of combustion, and open flame and smoke are generated at high temperature. The aerogel material of Comparative Example 2 has obtained hydrophobicity, but the calorific value of combustion is on the high side and an open flame appears. The aerogel material of Comparative Example 3 has a low calorific value of combustion, but no obvious hydrophobic effect is obtained. The aerogel material of Comparative Example 4 has hydrophobicity, but has a high calorific value of combustion, and open flame and smoke are generated at high temperature.

[0206] Table 1

[0207]

[0208]

[0209] In the above embodiments, the descriptions of each embodiment have their own focuses. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0210] The numerical ranges described in the present invention include all the numerical values within this range, and include the range values composed of any two numerical values within this range. Different numerical values of the same index appearing in all embodiments of the present invention can be arbitrarily combined to form range values.

[0211] The technical features in the claims and / or the specification of the present invention can be combined, and the combination method is not limited to the combination obtained through the citation relationship in the claims. The technical solutions obtained by combining the technical features in the claims and / or the specification are also within the protection scope of the present invention.

[0212] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A preparation method of a low combustion heat hydrophobic aerogel material, characterized in that It includes the following steps: 1) Calcining the aerogel material to be processed in two stages; 2) Performing vacuum gas phase modification on the calcined aerogel material; 3) Etching the modified aerogel material to obtain the low combustion heat hydrophobic aerogel material.

2. The preparation method of the low combustion heat hydrophobic aerogel material according to claim 1, characterized in that In step 1), the two-stage calcination of the aerogel material to be processed includes the following steps: The aerogel material to be processed is calcined at a heating rate of 5 - 10 °C / min at 350 - 400 °C for 1 - 6 h to complete the first-stage calcination; then it is heated to 650 - 1000 °C at a heating rate of 10 - 20 °C / min, held for 0.25 - 1 h, and cooled to room temperature after the second-stage calcination is completed.

3. The preparation method of the low combustion heat hydrophobic aerogel material according to claim 2, characterized in that, In step 1), the aerogel material is selected from one of silica aerogel, zirconia aerogel, alumina aerogel, silicon-aluminum composite aerogel, silicon-zirconium composite aerogel, and their composites formed with fiber reinforcement materials; the fiber reinforcement material includes one of glass fiber, alumina fiber, high silica oxygen fiber, and zirconia fiber.

4. The preparation method of the low combustion heat hydrophobic aerogel material according to claim 1, characterized in that In step 2), the vacuum gas phase modification of the calcined aerogel material includes the following steps: The calcined aerogel material is modified under low-pressure conditions with a modifier; then an inert gas is introduced for purging.

5. The preparation method of the low combustion heat hydrophobic aerogel material according to claim 4, wherein, In step 2), the modifier is a two-component one, including component A and component B; wherein component A is an organic modifier with a smaller steric hindrance hydrophobic group, which is selected from one of dichlorodimethylsilane, trimethylchlorosilane, and dimethylchlorosilane; component B is an organic modifier with a larger steric hindrance hydrophobic group, which is selected from phenyldimethylchlorosilane, (diphenylmethyl)-dimethylchlorosilane, p-chlorophenyldimethylchlorosilane, 4-biphenyldimethylchlorosilane, p-tolyldimethylchlorosilane, and benzyldimethylchlorosilane; the molar ratio of component A to component B is 1.5:1 - 2:

1.

6. The preparation method of the low combustion heat hydrophobic aerogel material according to claim 4, characterized in that, In step 2), the addition amount of the modifier is 1 / 30 - 1 / 10 of the mass of the calcined aerogel material; the vacuum of the low pressure is -0.08 MPa to -0.06 MPa, the modification time is 2 - 6 h; the purging time is more than 5 min.

7. The preparation method of the low combustion heat hydrophobic aerogel material according to claim 1, characterized in that, In step 3), the etching of the modified aerogel material includes the following steps: The modified aerogel material, an etchant, and a desiccant are placed in a closed environment, so that the etchant volatilizes to etch the modified aerogel material; then the etched aerogel material is heated to 100 - 250 °C and held for more than 1 h.

8. The preparation method of the low combustion heat hydrophobic aerogel material according to claim 7, characterized in that In step 3), the etchant is a 4 - 8 wt% hydrofluoric acid aqueous solution; the etching time is 4 - 12 h.

9. A low combustion heat hydrophobic aerogel material, characterized in that, The contact angle of the low combustion heat hydrophobic aerogel material is greater than 110°, and the combustion heat value is less than 4.5 MJ / kg; the low combustion heat hydrophobic aerogel material is prepared by the method according to any one of claims 1 - 8.

10. A heat-insulating material, characterized in that, The thermal insulation material uses the low combustion heat hydrophobic aerogel material, and the contact angle of the low combustion heat hydrophobic aerogel material is greater than 110°, and the combustion heat value is less than 4.5 MJ / kg.

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