High-temperature-resistant aluminum oxide aerogel and preparation method thereof

Abstract

The invention relates to a high-temperature-resistant aluminum oxide aerogel and a preparation method thereof, and relates to the technical field of aluminum oxide aerogel preparation, the method comprises the following steps: industrial aluminum hydroxide is subjected to a solvothermal reaction, and then a solvothermal reaction product is ground to obtain a-type Al2O3.nH2O, where n is lt; 1.2; the preparation method comprises the following steps: carrying out heat treatment on industrial aluminum hydroxide, and carrying out solvothermal reaction on a product obtained by heat treatment and an acidic regulator to obtain an aluminum oxide substance containing a functional group; the preparation method comprises the following steps: mixing an aluminum oxide substance containing a functional group, a type Al2O3.nH2O, an acidity regulator and a solvent, and then freezing to obtain first aluminum oxide aerogel; and sequentially carrying out heat treatment on the first aluminum oxide aerogel in a non-oxidizing atmosphere and an air atmosphere to obtain the high-temperature-resistant aluminum oxide aerogel. The heat conductivity coefficient of the aluminum oxide aerogel provided by the invention under the condition of 25-1400 DEG C is not higher than 0.03 w / m.k.

Description

Technical Field

[0001] The present application relates to the technical field of alumina aerogel preparation, and in particular to a high temperature resistant alumina aerogel and a preparation method thereof. Background Art

[0002] Aerogel is an ultra-low density porous solid material composed of nanoparticles or polymer molecules that are aggregated together. It is currently the solid material with the lowest thermal conductivity. The unique structure and properties of aerogel make it have great application value in the fields of catalysis, thermal insulation, glass and ceramics. There are many types of aerogels, and oxide aerogel is one of them. Among oxide aerogels, alumina aerogel is favored because of its high temperature resistance and low price.

[0003] Alumina aerogel is mainly prepared by sol-gel method, and the raw materials used in the preparation are mainly inorganic aluminum salts and organic alcohol aluminum salts. However, the preparation process of alumina aerogel prepared by organic alcohol aluminum salt is lengthy, the sample shrinks severely during solvent exchange and drying, the product has poor mechanical strength, the organic alcohol aluminum salt is expensive, toxic, and the hydrolysis process is difficult to control, which limits its large-scale application; alumina aerogel prepared by inorganic aluminum salt usually has larger alumina particles, which affects the formability of aerogel. It is easier to form alumina aerogel in the form of fragments. At present, most of the alumina aerogels developed are amorphous alumina. Under high-temperature conditions, alumina will undergo crystal transformation, resulting in pore collapse and loss of the performance of alumina aerogel. In addition, the supercritical drying method of aerogel has the defects of long cycle and high cost; the atmospheric pressure drying method of aerogel has the defect that the product performance is difficult to meet the standard. Therefore, it is planned to develop a new process for preparing alumina aerogel. Summary of the invention

[0004] The present application provides a high temperature resistant alumina aerogel and a preparation method thereof to solve the following technical problems: providing a new preparation method of alumina aerogel.

[0005] In a first aspect, the present application provides a method for preparing a high temperature resistant alumina aerogel, the method comprising:

[0006] subjecting the first industrial aluminum hydroxide to a first solvothermal reaction to obtain aluminum oxide hydrate;

[0007] The alumina hydrate is ground to obtain alphah type Al2O3·nH2O, wherein n<1.2;

[0008] The second industrial aluminum hydroxide is subjected to a first heat treatment so as to cause a qualitative change in the microstructure of the second industrial aluminum hydroxide;

[0009] The second industrial aluminum hydroxide after the first heat treatment is subjected to a second solvent thermal reaction with the first acidic regulator to obtain an aluminum oxide substance containing a functional group;

[0010] The aluminum oxide material containing a functional group, the alphah type Al2O3·nH2O, a second acidic regulator and a solvent are mixed to obtain a slurry;

[0011] Freezing the slurry to obtain a first alumina aerogel;

[0012] The first alumina aerogel is sequentially subjected to a second heat treatment in a non-oxidizing atmosphere and a third heat treatment in an air atmosphere to obtain a high temperature resistant alumina aerogel.

[0013] Optionally, the process parameters of the first solvent thermal reaction include: temperature of 80°C to 300°C, and time of 3h to 10h.

[0014] Optionally, the particle size of the alumina hydrate is less than 10 μm.

[0015] Optionally, the process parameters of the first heat treatment include: temperature of 900° C. to 1200° C., and time of 3s to 10s.

[0016] Optionally, the process parameters of the second solvent thermal reaction include: temperature of 80°C to 250°C, time of 3h to 10h, and pH value <7.

[0017] Optionally, the weight M1 of the aluminum oxide substance containing functional groups, the weight M2 of the alphah-type Al2O3·nH2O, the weight M3 of the second acidic regulator and the volume V of the solvent satisfy the relationship: M1:M2:M3:V=(1.5~10):(2~15):(0.1~10):500; wherein, if the unit of weight is gram, the unit of volume is milliliter.

[0018] Optionally, the freezing includes a first freezing and a second freezing; wherein the temperature of the first freezing is -50°C to -60°C, and the temperature of the second freezing is -50°C to -80°C.

[0019] Optionally, the first acidic regulator and the second acidic regulator respectively include at least one of the following: an inorganic acid, an organic acid, and an aluminum salt.

[0020] Optionally, the temperature of the second heat treatment is 600° C. to 750° C.; and / or,

[0021] The temperature of the third heat treatment is 650°C to 700°C.

[0022] In a second aspect, the present application provides a high temperature resistant alumina aerogel, wherein the high temperature resistant alumina aerogel is prepared by any method described in the first aspect.

[0023] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0024] The preparation method of the high temperature resistant alumina aerogel provided in an embodiment of the present application comprises the following steps: subjecting a first industrial aluminum hydroxide to a first solvent thermal reaction to obtain an alumina hydrate; grinding the alumina hydrate to obtain an alphah type Al2O3·nH2O; wherein n<1.2; subjecting a second industrial aluminum hydroxide to a first heat treatment to cause a qualitative change in the microstructure of the second industrial aluminum hydroxide; subjecting the second industrial aluminum hydroxide after the first heat treatment to a second solvent thermal reaction with a first acidic regulator to obtain an aluminum oxide substance containing a functional group; mixing the aluminum oxide substance containing a functional group, the alphah type Al2O3·nH2O, a second acidic regulator and a solvent to obtain a slurry; freezing the slurry to obtain a first alumina aerogel; subjecting the first alumina aerogel to a second heat treatment in a non-oxidizing atmosphere and a third heat treatment in an air atmosphere in sequence to obtain a high temperature resistant alumina aerogel. The first industrial aluminum hydroxide undergoes a first solvent thermal reaction, which can convert the trihydrate aluminum hydroxide in the industrial aluminum hydroxide into aluminum oxide hydrate and regulate the microscopic characteristics of the aluminum oxide hydrate; the aluminum oxide hydrate is ground to make the aluminum oxide hydrate refined and uniform. Due to its internal structure and internal water, the aluminum oxide hydrate will be converted into alphah-type Al2O3·nH2O, and Al2O3 is alphah-type, thus having excellent thermal stability; n is <1.2, and a lower degree of hydration can make the alphah-type Al2O3·nH2O have higher thermal stability and improve the reaction activity of the alphah-type Al2O3·nH2O; the second industrial aluminum hydroxide undergoes a first heat treatment, which can cause a qualitative change in the attached water, crystal water content and internal microstructure of the second industrial aluminum hydroxide, which will reshape the physical and chemical properties and functional group types of the second industrial aluminum hydroxide. The product obtained by the first heat treatment is subjected to a second solvent thermal reaction with the first acidic regulator, and the generated functional group-containing aluminum oxide substances and alphah-type Al2O3·nH2O have high activity. Under the action of the second acidic regulator and freezing conditions, the functional group-containing aluminum oxide substances and alphah-type Al2O3·nH2O can undergo a gluing chain reaction, thereby forming a first alumina aerogel with a three-dimensional network structure; the first alumina aerogel with a three-dimensional network structure is subjected to a second heat treatment in a non-oxidizing atmosphere, and the elements that will be oxidized in the first alumina aerogel can be retained, and the functional group elements that have not been oxidized in the first alumina aerogel can provide a skeleton effect to form an inorganic alumina gel; when the inorganic alumina gel is subjected to a third heat treatment in an air atmosphere, the elements that will be oxidized will be oxidized and calcined, while the original skeleton structure of the first alumina aerogel is retained, thereby preparing a high-temperature resistant alumina aerogel. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0027] Figure 1 A schematic flow chart of a method for preparing a high temperature resistant alumina aerogel provided in an embodiment of the present application;

[0028] Figure 2 This is a scanning electron microscope image of a high temperature resistant alumina aerogel provided in Example 1 of the present application;

[0029] Figure 3 This is a scanning electron microscope image of a high temperature resistant alumina aerogel provided in Example 2 of the present application;

[0030] Figure 4 This is a scanning electron microscope image of a high temperature resistant alumina aerogel provided in Example 3 of the present application;

[0031] Figure 5 This is a scanning electron microscope image of a high temperature resistant alumina aerogel provided in Example 4 of the present application;

[0032] Figure 6 This is a scanning electron microscope image of a high temperature resistant alumina aerogel provided in Example 5 of the present application. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0034] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0035] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present specification, the terms "including", "comprising", etc. refer to "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of the associated objects, indicating that there may be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A, B can be singular or plural. In this article, "at least one" refers to one or more, and "plural" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc or abc, where a, b, c can be single or plural, respectively.

[0036] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0037] In a first aspect, the present application provides a method for preparing a high temperature resistant alumina aerogel. Figure 1 A schematic diagram of a method for preparing a high temperature resistant alumina aerogel provided in an embodiment of the present application; see Figure 1 , the method comprising:

[0038] S1. subjecting the first industrial aluminum hydroxide to a first solvothermal reaction to obtain aluminum oxide hydrate;

[0039] In the embodiment of the present application, the first industrial aluminum hydroxide is subjected to a first solvothermal reaction, which can convert aluminum hydroxide trihydrate in the industrial aluminum hydroxide into aluminum oxide hydrate, and regulate the particle size, internal structure and other microscopic characteristics of the aluminum oxide hydrate.

[0040] In some embodiments, the process parameters of the first solvothermal reaction include: temperature of 80° C. to 300° C., and time of 3 h to 10 h.

[0041] In the embodiment of the present application, the temperature of the first solvent thermal reaction can be 80℃~300℃. Within this temperature range, sufficient energy can be provided for the first solvent thermal reaction to promote the transformation of the first industrial aluminum hydroxide to form aluminum oxide hydrate, while ensuring the crystal structure, particle size and crystallinity of the product. The time of the first solvent thermal reaction can be 3h~10h, and sufficient time can ensure that the reactants are fully converted into products and improve the yield and purity of the products. Exemplarily, the temperature can be 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, etc.; the time can be 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, etc.

[0042] In some embodiments, the particle size of the alumina hydrate is less than 10 μm.

[0043] In the embodiment of the present application, the particle size of the alumina hydrate may be less than 10 μm, so as to increase the specific area of ​​the alumina hydrate and improve the reactivity of the alumina hydrate. For example, the particle size of the alumina hydrate may be 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, etc.

[0044] Specifically, in step S1, if the first industrial aluminum hydroxide is less than 10 μm, the first industrial aluminum hydroxide can be directly subjected to the first solvent thermal reaction; if the first industrial aluminum hydroxide is greater than 10 μm, an auxiliary agent needs to be added to the first solvent thermal reaction, and the first solvent thermal reaction may be performed multiple times until the particle size of the product of the first solvent thermal reaction reaches less than 10 μm, similar to the micron-grade industrial aluminum hydroxide powder or close to the product produced by the hydrothermal treatment of the micron-grade industrial aluminum hydroxide powder; or the first industrial aluminum hydroxide greater than 10 μm is ground and subjected to the first solvent thermal reaction. In addition, the product after the first solvent thermal reaction needs to be filtered and dried, and the product drying temperature is 50°C to 200°C, and the drying time is 1h to 20h.

[0045] S2, grinding the alumina hydrate to obtain alphah type Al2O3·nH2O, wherein n<1.2;

[0046] In the embodiments of the present application, grinding alumina hydrate can make alumina hydrate more refined and uniform. Due to the interaction between the internal structure of alumina hydrate and internal water, the alumina hydrate is further converted into alphah-type Al2O3·nH2O. Alphah-type Al2O3·nH2O, also known as α_Al2O3·nH2O, is a form of aluminum oxide containing crystal water. Among them, α_Al2O3·nH2O is a crystal form of aluminum oxide with a trigonal crystal structure. The presence of crystal water (nH2O, n represents the molar content of crystal water) will affect its physical and chemical properties. For example, crystal water will gradually be lost during the heating process, thereby changing the form and properties of the substance. Alumina contains the elements aluminum and oxygen. The aluminum ions and oxygen ions in this structure are arranged according to a specific crystal structure. Under the α_Al2O3 crystal form, its atomic arrangement gives it higher hardness, melting point and other characteristics. When combined with crystal water, its solubility and other properties will change to a certain extent. It is usually a white solid that is difficult to dissolve in water, odorless, tasteless, extremely hard, easy to absorb moisture but not deliquescent (non-hygroscopic after burning), and α_Al2O3·nH2O has excellent thermal stability. The grinding process helps to adjust the position and bonding mode of water molecules in the alumina crystal structure, so that it exists more stably in the alphah-type Al2O3·nH2O structure; n is <1.2, and a lower degree of hydration can make alphah-type Al2O3·nH2O have higher thermal stability and improve the reactivity of alphah-type Al2O3·nH2O. Exemplarily, the n can be 1.15, 1.1, 1.0, 0.9, 0.8, etc., and the grinding time can be more than 10 hours.

[0047] S3, subjecting the second industrial aluminum hydroxide to a first heat treatment so as to cause a qualitative change in the microstructure of the second industrial aluminum hydroxide;

[0048] In some embodiments, the process parameters of the first heat treatment include: a temperature of 900° C. to 1200° C., and a time of 3 s to 10 s.

[0049] In the embodiment of the present application, in the embodiment of the present application, the second industrial aluminum hydroxide is subjected to the first heat treatment, which can cause the attached water, crystal water content and internal microstructure of the second industrial aluminum hydroxide to undergo qualitative changes, and this qualitative change will reshape the physical and chemical properties and functional group types of the second industrial aluminum hydroxide. In the first heat treatment, the temperature can be 900°C to 1200°C, and the time can be 3s to 10s. This instantaneous high-temperature heat treatment can fully cause the microstructure of the second industrial aluminum hydroxide to undergo qualitative changes, and obtain the target first heat treatment product (modified second industrial aluminum hydroxide). Exemplarily, in the first heat treatment, the temperature can be 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, etc.; the time can be 3s, 4s, 5s, 6s, 7s, 8s, 9s, 10s, etc.

[0050] S4, subjecting the second industrial aluminum hydroxide after the first heat treatment to a second solvent thermal reaction with the first acidic regulator to obtain an aluminum oxide substance containing a functional group;

[0051] In some embodiments, the process parameters of the second solvothermal reaction include: temperature of 80° C. to 250° C., time of 3 h to 10 h, and pH value <7.

[0052] In the embodiment of the present application, in the second solvent thermal reaction, the temperature can be 80℃~250℃, the time can be 3h~10h, and the pH value can be <7. Within this temperature, time and pH value range, sufficient energy and time can be provided for the first solvent thermal reaction to promote the chemical reaction of the second industrial aluminum hydroxide and the organic functional groups in the first acidic regulator, thereby generating aluminum oxide substances with high activity and containing functional groups. Exemplarily, in the second solvent thermal reaction, the temperature can be 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, etc.; the time can be 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, etc., and the pH value can be 6, 5, 4, 3, etc. The first industrial aluminum hydroxide and the second industrial aluminum oxide can both be aluminum hydroxide obtained in the form of seed hydrogenation aluminum, carbon hydrogenation aluminum, neutralized hydrogen aluminum or other forms.

[0053] S5, mixing the aluminum oxide material containing a functional group, the alphah type Al2O3·nH2O, a second acidic regulator and a solvent to obtain a slurry;

[0054] In some embodiments, the weight M1 of the aluminum oxide substance containing functional groups, the weight M2 of the alphah-type Al2O3·nH2O, the weight M3 of the second acidic regulator, and the volume V of the solvent satisfy the relationship: M1:M2:M3:V=(1.5-10):(2-15):(0.1-10):500; wherein, if the unit of weight is gram, the unit of volume is milliliter.

[0055] In the embodiment of the present application, M1:M2:M3:V can be = (1.5-10): (2-15): (0.1-10): 500, which can ensure the density and temperature resistance of alumina aerogel. The aluminum oxide substances containing functional groups provide a skeleton, functional groups and aluminum oxide components for the later formation of inorganic alumina colloid; alphah-type Al2O3·nH2O provides the high temperature resistant components of alumina aerogel and provides a sufficient number of functional groups; the second acidic regulator adjusts the pH value of the slurry to <7, and the solvent fully disperses and dilutes the aluminum oxide substances containing functional groups and alphah-type Al2O3·nH2O, and lays the basic conditions for the subsequent formation of alumina aerogel, facilitating the formation of a porous skeleton structure, and the solvent can be water. Exemplarily, the above M1:M2:M3:V can be 1.5:2:0.1:500, 3:10:5:500, 8:5:1:500, 10:15:10:500, etc. Therefore, 1.5 to 10 grams of alumina material containing functional groups can be added to every 500 ml of water, and 2 to 15 grams of alphah type Al2O3·nH2O and 0.1 to 10 grams of a second acidic regulator can be added at the same time.

[0056] S6, freezing the slurry to obtain a first alumina aerogel;

[0057] In the embodiment of the present application, under the action of the second acidic regulator and freezing conditions, the aluminum oxide substance containing functional groups can react with alphah-type Al2O3·nH2O to form a first alumina aerogel with a three-dimensional network structure, and retain the pore structure formed by the first alumina aerogel and strengthen the alumina aerogel skeleton.

[0058] In some embodiments, the freezing includes a first freezing and a second freezing; wherein the temperature of the first freezing is -50°C to -60°C, and the temperature of the second freezing is -50°C to -80°C.

[0059] In the embodiment of the present application, the functional group-containing aluminum oxide substance and alphah-type Al2O3·nH2O both have high activity. Under the action of the second acidic regulator and the first freezing condition, the functional group-containing aluminum oxide substance and alphah-type Al2O3·nH2O can form a glue chain, thereby forming a first alumina aerogel with a three-dimensional network structure, and retaining the pore structure formed by the first alumina aerogel and strengthening the alumina aerogel skeleton; the second freezing removes the moisture in the alumina aerogel while strengthening the alumina aerogel skeleton, and at the same time strengthens and retains the pore structure formed by the alumina aerogel. In order to fully achieve the above-mentioned freezing effect, and taking into account the morphology, pore size and performance of the alumina aerogel, the temperature of the first freezing can be -50°C to -60°C, and the temperature of the second freezing can be -50°C to -80°C. For example, the temperature of the first freezing can be -50°C, -52°C, -54°C, -56°C, -58°C, -60°C, etc.; the temperature of the second freezing can be -50°C, -60°C, -70°C, -80°C, etc. The first freezing time can be 4h to 6h, and the second freezing time can be 12h to 48h.

[0060] In some embodiments, the first acidic regulator and the second acidic regulator each include at least one of the following: an inorganic acid, an organic acid, and an aluminum salt.

[0061] In the embodiment of the present application, the first acidic regulator and the second acidic regulator can be a combination of one or more of an inorganic acid, an organic acid, and an aluminum salt.

[0062] S7. Subjecting the first alumina aerogel to a second heat treatment in a non-oxidizing atmosphere and a third heat treatment in an air atmosphere in sequence to obtain a high temperature resistant alumina aerogel.

[0063] In some embodiments, the temperature of the second heat treatment is 600° C. to 750° C.; and / or,

[0064] The temperature of the third heat treatment is 650°C to 700°C.

[0065] In the embodiment of the present application, the first alumina aerogel is subjected to a second heat treatment in a non-oxidizing atmosphere, which can retain the elements that will be oxidized in the first alumina aerogel, and the functional group elements that have not been oxidized in the first alumina aerogel can provide a skeleton effect, forming an inorganic alumina gel, and increasing the strength of the pore skeleton of the first alumina aerogel; when the inorganic alumina gel is subjected to a third heat treatment in an air atmosphere, the elements that will be oxidized will be oxidized and calcined, thereby improving the purity of the first alumina aerogel, while retaining the original skeleton structure of the first alumina aerogel, and preparing a high-temperature resistant alumina aerogel. In order to achieve the above effect, and considering the performance of the alumina aerogel and the production energy consumption cost, the temperature of the second heat treatment can be 600℃~750℃, and the temperature of the third heat treatment can be 650℃~700℃. Exemplarily, the temperature of the second heat treatment may be 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, 720°C, 750°C, etc.; the temperature of the third heat treatment may be 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, etc. The time of the second heat treatment and the time of the third heat treatment may be 4h to 8h, respectively, and the heating rate of the second heat treatment and the third heat treatment may be 3°C / min to 5°C / min.

[0066] In a second aspect, the present application provides a high temperature resistant alumina aerogel, wherein the high temperature resistant alumina aerogel is prepared by any method described in the first aspect.

[0067] The high temperature resistant alumina aerogel is realized based on the preparation method of the high temperature resistant alumina aerogel. The specific steps of the preparation method of the high temperature resistant alumina aerogel can refer to the above embodiment. Since the high temperature resistant alumina aerogel adopts part or all of the technical solutions of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment, which will not be repeated here one by one.

[0068] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0069] Example 1

[0070] A method for preparing high-temperature resistant alumina aerogel specifically comprises: forming a slurry with a mass concentration of 40% by weight with industrial aluminum hydroxide and water at room temperature, and reacting at 180° C. for 5 hours to obtain an alumina hydrate slurry, wherein the particle size of the alumina hydrate is less than 10 μm; filtering and drying the alumina hydrate slurry; and adding the dried product to a grinding device at room temperature for 12 hours to obtain alphah-type Al2O3·nH2O (n is 0.67).

[0071] Industrial aluminum hydroxide is modified at 900°C for 10 seconds, and the modified industrial aluminum hydroxide is stirred into a slurry by adding water, and formic acid is added to control the pH value at 2, and hydrothermally treated at 130°C for 4 hours to obtain a slurry of aluminum oxide substances containing functional groups; the slurry of aluminum oxide substances containing functional groups is diluted, and the dilution standard is 1.5 grams of aluminum oxide substances containing functional groups per 500 ml of water, and 5 grams of alphah type Al2O3·nH2O are added at the same time, and 1 gram of aluminum chloride is added, and mixed evenly to obtain a mixed slurry; the mixed slurry is frozen at -50°C for 4 hours, and then freeze-dried at -50°C for 48 hours to obtain a frozen composite; the frozen composite is heated at 700°C in a non-oxidizing atmosphere for 5 hours, and the heating rate is 5°C / min; in an air atmosphere, the temperature is increased to 650°C at a heating rate of 4°C / min, and the temperature is kept for 5 hours to obtain a high-temperature resistant aluminum oxide aerogel. The thermal conductivity of the aluminum oxide aerogel prepared in Example 1 at different temperatures is shown in Table 1:

[0072] Table 1 Thermal conductivity of high temperature resistant alumina aerogel of Example 1 at different temperatures (w / (mk)

[0073]

[0074] Example 2

[0075] A method for preparing high-temperature resistant alumina aerogel specifically comprises: forming a slurry with a mass concentration of 40% by weight with industrial aluminum hydroxide and water at room temperature, and reacting at 180° C. for 5 hours to obtain an alumina hydrate slurry, wherein the particle size of the alumina hydrate is less than 10 μm; filtering and drying the alumina hydrate slurry; and adding the dried product to a grinding device at room temperature for 12 hours to obtain alphah-type Al2O3·nH2O (n is 0.67).

[0076] Industrial aluminum hydroxide is modified at 1100℃ for 3 seconds, and the modified industrial aluminum hydroxide is stirred into slurry by adding water, and formic acid is added to control the pH value at 2, and hydrothermally treated at 150℃ for 4 hours to obtain a slurry of aluminum oxide substances containing functional groups; the slurry of aluminum oxide substances containing functional groups is diluted, and the dilution standard is 2.5 grams of aluminum oxide substances containing functional groups per 500 ml of water, and 5 grams of alpha-type new aluminum oxide obtained in the first step and 5 grams of aluminum chloride are added at the same time, and mixed evenly to obtain a mixed slurry; the mixed slurry is frozen at -50℃ for 4 hours, and then freeze-dried at -50℃ for 48 hours to obtain a frozen composite; the frozen composite is heated at 700℃ in a non-oxidizing atmosphere for 5 hours, and the heating rate is 5℃ / min; in an air atmosphere, the temperature is increased to 660℃ at a heating rate of 3-5℃ / min, and then kept warm for 5 hours to obtain a high-temperature resistant aluminum oxide aerogel. The thermal conductivity of the aluminum oxide aerogel prepared in Example 2 at different temperatures is shown in Table 2:

[0077] Table 2 Thermal conductivity of high temperature resistant alumina aerogel of Example 2 at different temperatures (w / (mk)

[0078]

[0079]

[0080] Example 3

[0081] A method for preparing a high-temperature resistant alumina aerogel specifically comprises: forming a slurry with a mass concentration of 40% by industrial aluminum hydroxide and water at room temperature, and heat-retaining the mixture at 200°C for 3 hours to obtain an alumina hydrate slurry, wherein the particle size of the alumina hydrate is less than 10 μm; filtering and drying the alumina hydrate slurry, adding the dried product to a grinding device, and grinding for 14 hours to obtain alphah-type Al2O3·nH2O (n is 0.73).

[0082] Industrial aluminum hydroxide is modified at 1100°C for 3 seconds, and the modified industrial aluminum hydroxide is stirred into a slurry by adding water, and acetic acid is added to control the pH value at 2, and hydrothermally treated at 140°C for 4 hours to obtain a slurry of aluminum oxide substances containing functional groups; the slurry of aluminum oxide substances containing functional groups is diluted, and the dilution standard is 2.5 grams of aluminum oxide substances containing functional groups per 500 ml of water, and 7 grams of alphah type Al2O3·nH2O and 3 grams of aluminum chloride are added at the same time, and mixed evenly to obtain a mixed slurry; the mixed slurry is frozen at -50°C for 4 hours, and then freeze-dried at -50°C for 48 hours to obtain a frozen composite; the frozen composite is heated at 700°C in a non-oxidizing atmosphere for 5 hours, and the heating rate is 5°C / min; in an air atmosphere, the temperature is increased to 680°C at a heating rate of 4°C / min, and then kept warm for 5 hours to obtain a high-temperature resistant aluminum oxide aerogel. The thermal conductivity of the aluminum oxide aerogel prepared in Example 3 at different temperatures is shown in Table 3:

[0083] Table 3 Thermal conductivity of high temperature resistant alumina aerogel of Example 3 at different temperatures (w / (mk)

[0084]

[0085] Example 4

[0086] A method for preparing a high-temperature resistant alumina aerogel specifically comprises: forming a slurry with a mass concentration of 20% with industrial aluminum hydroxide and water at room temperature, adding 3.5wt% of a grain control agent, and reacting at 180°C for 3 hours to obtain an alumina hydrate slurry, wherein the particle size of the alumina hydrate is less than 10μm; filtering and drying the alumina hydrate slurry, adding the dried product into a grinding device, and grinding for 13 hours to obtain alphah-type Al2O3·nH2O (n is 0.68).

[0087] The industrial aluminum hydroxide is modified at 1100°C for 3 seconds, water is added to the modified industrial aluminum hydroxide and stirred into a slurry, formic acid and acetic acid are added to control the pH value at 2, and hydrothermal treatment is performed at 135°C for 4 hours to obtain a slurry of aluminum oxide substances containing functional groups; the slurry of aluminum oxide substances containing functional groups is diluted, and the dilution standard is 5 grams of aluminum oxide substances containing functional groups per 500 ml of water, and 10 grams of alphah type Al2O3·nH2O and 3 grams of aluminum chloride and aluminum nitrate mixture are added at the same time, and mixed evenly to obtain a mixed slurry; the mixed slurry is frozen at -50°C for 4 hours, and then freeze-dried at -50°C for 48 hours to obtain a frozen composite; the frozen composite is heated at 700°C in a non-oxidizing atmosphere for 5 hours, and the heating rate is 5°C / min; in an air atmosphere, the temperature is increased to 680°C at a heating rate of 3°C / min, and then kept warm for 5 hours to obtain a high-temperature resistant aluminum oxide aerogel. The thermal conductivity of the alumina aerogel prepared in Example 4 at different temperatures is shown in Table 4:

[0088] Table 4 Thermal conductivity of high temperature resistant alumina aerogel of Example 4 at different temperatures (w / (mk)

[0089]

[0090] Example 5

[0091] A method for preparing a high-temperature resistant alumina aerogel specifically comprises: forming a slurry with a mass concentration of 20% with industrial aluminum hydroxide and water at room temperature, adding 3.5wt% of a grain control agent, and reacting at 180°C for 3 hours to obtain an alumina hydrate slurry, wherein the particle size of the alumina hydrate is less than 10μm; filtering and drying the alumina hydrate slurry, adding the dried product into a grinding device, and grinding for 15 hours to obtain alphah-type Al2O3·nH2O (n is 0.76).

[0092] Industrial aluminum hydroxide is modified at 1100°C for 3 seconds, and the modified industrial aluminum hydroxide is stirred into a slurry by adding water, and formic acid is added to control the pH value at 2, and hydrothermally treated at 160°C for 4 hours to obtain a slurry of aluminum oxide substances containing functional groups; the slurry of aluminum oxide substances containing functional groups is diluted, and the dilution standard is 2.5 grams of aluminum oxide substances containing functional groups per 500 ml of water, and 5 grams of alphah type Al2O3·nH2O and 1 gram of aluminum nitrate are added at the same time, and mixed evenly to obtain a mixed slurry; the mixed slurry is frozen at -50°C for 4 hours, and then freeze-dried at -50°C for 48 hours to obtain a frozen composite; the frozen composite is heated at 700°C in a non-oxidizing atmosphere for 5 hours, and the heating rate is 5°C / min; in an air atmosphere, the temperature is raised to 700°C at a heating rate of 5°C / min, and then kept warm for 5 hours to obtain a high-temperature resistant aluminum oxide aerogel. The thermal conductivity of the aluminum oxide aerogel prepared in Example 5 at different temperatures is shown in Table 5:

[0093] Table 5 Thermal conductivity of high temperature resistant alumina aerogel of Example 5 at different temperatures (w / (mk)

[0094]

[0095] Comparative Example 1

[0096] A method for preparing a high-temperature resistant alumina aerogel specifically comprises: forming a slurry with a mass concentration of 40% by weight with industrial aluminum hydroxide and water at room temperature, and reacting at 180° C. for 5 hours to obtain an alumina hydrate slurry, wherein the particle size of the alumina hydrate is less than 10 μm; filtering and drying the alumina hydrate slurry; and adding the dried product to a grinding device at room temperature for 13 hours to obtain alphah-type Al2O3·nH2O (n is 1).

[0097] Add water to industrial aluminum hydroxide and stir to form a slurry, add formic acid to control the pH value at 2, and hydrothermally treat at 130°C for 4 hours; dilute the aluminum hydroxide slurry after hydrothermally treatment, the dilution standard is 1.5 grams of aluminum oxide per 500 ml of water, and at the same time add 5 grams of alphah type Al2O3·nH2O, add 1 gram of aluminum chloride, mix evenly, and obtain a mixed slurry; freeze the mixed slurry at -50°C for 4 hours, and then freeze-dry at -50°C for 48 hours to obtain a frozen composite; heat the frozen composite at 700°C in a non-oxidizing atmosphere for 5 hours, with a heating rate of 5°C / min; in an air atmosphere, heat to 650°C at a heating rate of 4°C / min, and keep warm for 5 hours to obtain a high-temperature resistant aluminum oxide aerogel. The thermal conductivity of the aluminum oxide aerogel prepared in Comparative Example 1 at different temperatures is shown in Table 6:

[0098] Table 6 Thermal conductivity of high temperature resistant alumina aerogel of Comparative Example 1 at different temperatures (w / (mk)

[0099]

[0100] It can be seen from Examples 1 to 5 that under the conditions of room temperature (25° C.) to 1400° C., the thermal conductivity of the high temperature resistant alumina aerogel is not higher than 0.03w / (mk), which reflects the excellent high temperature resistance. Figure 2 This is a scanning electron microscope image of a high temperature resistant alumina aerogel provided in Example 1 of the present application; Figure 3 This is a scanning electron microscope image of a high temperature resistant alumina aerogel provided in Example 2 of the present application; Figure 4 This is a scanning electron microscope image of a high temperature resistant alumina aerogel provided in Example 3 of the present application; Figure 5 This is a scanning electron microscope image of a high temperature resistant alumina aerogel provided in Example 4 of the present application; Figure 6 This is a scanning electron microscope image of a high temperature resistant alumina aerogel provided in Example 5 of the present application; see Figure 2 to Figure 6 , and combined with Tables 1 to 5, it is shown that the alumina aerogel prepared in the embodiment of the present application has good uniformity, unique internal structure, and good temperature resistance. In Comparative Example 1, the industrial aluminum hydroxide was not subjected to instantaneous heat treatment. Combined with Table 6, it is shown that the alumina aerogel obtained in Comparative Example 1 has poor temperature resistance.

[0101] One or more technical solutions in the embodiments of the present application also have at least the following technical effects or advantages:

[0102] (1) The raw materials used in the preparation method of the high temperature resistant alumina aerogel provided in the embodiment of the present application are all industrially produced aluminum hydroxide, and no organic aluminum salt or inorganic aluminum salt is used, which greatly reduces the production cost;

[0103] (2) The method for preparing high-temperature resistant alumina aerogel provided in the embodiment of the present application is resistant to high temperatures compared with other processes for preparing alumina aerogel; thirdly, compared with the currently commonly used supercritical drying method for preparing aerogel, this process does not require a high-cost, long-cycle supercritical drying process. The process has a short preparation cycle and low manufacturing cost, laying the foundation for large-scale industrial preparation of high-temperature resistant alumina aerogel.

[0104] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing high temperature resistant alumina aerogel, characterized in that: The method comprises: subjecting the first industrial aluminum hydroxide to a first solvothermal reaction to obtain aluminum oxide hydrate; The alumina hydrate is ground to obtain alphah type Al2O3·nH2O, wherein n<1.2; The second industrial aluminum hydroxide is subjected to a first heat treatment so as to cause a qualitative change in the microstructure of the second industrial aluminum hydroxide; The second industrial aluminum hydroxide after the first heat treatment is subjected to a second solvent thermal reaction with the first acidic regulator to obtain an aluminum oxide substance containing a functional group; The aluminum oxide material containing a functional group, the alphah type Al2O3·nH2O, a second acidic regulator and a solvent are mixed to obtain a slurry; Freezing the slurry to obtain a first alumina aerogel; The first alumina aerogel is sequentially subjected to a second heat treatment in a non-oxidizing atmosphere and a third heat treatment in an air atmosphere to obtain a high temperature resistant alumina aerogel.

2. The method according to claim 1, characterized in that The process parameters of the first solvent thermal reaction include: temperature of 80°C to 300°C and time of 3h to 10h.

3. The method according to claim 1 or 2, characterized in that: The particle size of the alumina hydrate is 10 μm or less.

4. The method according to claim 1, characterized in that: The process parameters of the first heat treatment include: a temperature of 900° C. to 1200° C. and a time of 3s to 10s.

5. The method according to claim 1, characterized in that The process parameters of the second solvent thermal reaction include: temperature of 80° C. to 250° C., time of 3 h to 10 h, and pH value <7.

6. The method according to claim 1, characterized in that The weight M1 of the aluminum oxide substance containing functional groups, the weight M2 of the alphah type Al2O3·nH2O, the weight M3 of the second acidic regulator and the volume V of the solvent satisfy the relationship: M1:M2:M3:V=(1.5~10):(2~15):(0.1~10):500; wherein, if the unit of weight is gram, the unit of volume is milliliter.

7. The method according to claim 1, characterized in that The freezing includes a first freezing and a second freezing; wherein the temperature of the first freezing is -50°C to -60°C, and the temperature of the second freezing is -50°C to -80°C.

8. The method according to claim 1, characterized in that The first acidic regulator and the second acidic regulator respectively include at least one of the following: an inorganic acid, an organic acid, and an aluminum salt.

9. The method according to claim 1, characterized in that: The temperature of the second heat treatment is 600° C. to 750° C.; and / or, The temperature of the third heat treatment is 650°C to 700°C.

10. A high temperature resistant alumina aerogel, characterized in that: The alumina aerogel is prepared by the method according to any one of claims 1 to 9.

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