A high-temperature resistant magnesium aluminum spinel aerogel and its preparation method

Abstract

This invention specifically relates to a high-temperature resistant magnesium aluminum spinel aerogel and its preparation method. The technical solution is as follows: M1 parts by mass of basic magnesium sulfate whiskers, M2 parts by mass of aluminum sol, and M3 parts by mass of deionized water are mixed to obtain 100 parts by mass of wet gel. Wherein: the sum of the mass parts of AlOOH in the basic magnesium sulfate whiskers and aluminum sol is M1+m=10~30; the mass part of aluminum sol is M2=(15~50)M1 / Y. The preparation process is as follows: the wet gel is frozen into a gel block using liquid nitrogen, and then freeze-dried to obtain a magnesium aluminum spinel aerogel precursor. Magnesia olivine powder and carbon black are ground and pressed into sheets to obtain flakes; the magnesium aluminum spinel aerogel precursors of equal volume are placed on the flakes and kept at 400~600℃ for 1~3h in a N2 atmosphere; then kept at 1400~1600℃ for 3~8h to obtain the high-temperature resistant magnesium aluminum spinel aerogel. The products manufactured by this invention not only have low bulk density, high porosity, good high temperature resistance and thermal insulation performance, but also high strength.

Description

Technical Field

[0001] This invention belongs to the field of magnesium aluminum spinel aerogel technology. Specifically, it relates to a high-temperature resistant magnesium aluminum spinel aerogel and its preparation method. Background Technology

[0002] Aerogels are low-density, high-porosity materials widely used in energy storage, adsorption separation, and thermal insulation due to their unique three-dimensional network structure and excellent properties. Compared with other thermal insulation materials, aerogels offer better thermal protection performance and require less weight and smaller volume. However, existing oxide aerogels face several limitations in practical production and use, such as poor high-temperature stability. They are prone to structural collapse at certain temperatures, causing volume shrinkage and thus losing their advantages of low thermal conductivity and high porosity.

[0003] Magnesium aluminum spinel is a commonly used functional material with many advantages. Firstly, it possesses high thermal and chemical stability, maintaining its structural stability and performance even at high temperatures, making it ideal for high-temperature applications such as catalysts and ceramic materials. Secondly, it exhibits good mechanical properties, with high hardness and a low coefficient of thermal expansion, allowing for applications in high-strength and wear-resistant materials. Furthermore, as the only substance in the magnesium-aluminum binary system, it exhibits no phase transformation. However, its high bulk density results in poor thermal insulation performance, hindering its large-scale application in thermal insulation fields. Therefore, the development of aerogels with the characteristics of magnesium aluminum spinel has attracted the attention of those skilled in the art.

[0004] The patented technology, "A High-Temperature Resistant High-Performance Aerogel Composite Material and Its Preparation Method" (Publication No.: CN111925194A), uses anhydrous ethanol as the supercritical drying medium. During supercritical drying of ethanol, the pressure inside the high-pressure reactor can reach 50 MPa, and the drying time is 5–72 hours. Although this technology synthesizes magnesium aluminum spinel aerogel using supercritical drying at a relatively low synthesis temperature, the preparation of the aerogel requires multiple solution replacements, each lasting 2–5 days. This multi-step preparation process is time-consuming, complex, and poses safety hazards, making industrial-scale production difficult.

[0005] The patented technology, "A method for preparing fiber-reinforced high-temperature resistant magnesium aluminum spinel aerogel" (publication number: CN107805064A), uses the sol-gel method to prepare magnesium aluminum spinel aerogel. However, the acetone used in the aging stage of the preparation process is toxic and poses a significant safety hazard. Furthermore, the aging solution needs to be replaced multiple times during the aging process, which is complex and time-consuming, making continuous production impossible.

[0006] Wu Xiaodong et al. (Wu X, Shao G, Shen X, et al. The low temperature fabrication of nanocrystalline MgAl2O4 spinel aerogel by anon-alkoxide sol-gelroute[J]. Materials Letters, 2017, 207(nov.15):137-140.) from Nanjing University of Technology prepared nanorod magnesium aluminum spinel aerogels using a sol-gel method combined with supercritical drying technology. Ethanol was used as the aging solution, and multiple replacements were performed in an oven, each lasting 12–24 hours, making the process complex and time-consuming. Furthermore, the supercritical drying process, using ethanol as the medium, involved high-pressure reactors with pressures as high as 8–17 MPa. The propylene oxide used in the preparation process is a flammable and explosive chemical, posing significant safety hazards and incurring high costs.

[0007] The patented technology, "Preparation Method of High-Temperature and Low-Temperature Resistant Synthetic Bulk Spinel Aerogel Material" (Publication No.: CN106478134A), uses carbon dioxide or ethanol as the supercritical drying medium. When using ethanol for supercritical drying, the pressure inside the high-pressure reactor can reach 8-17 MPa, and the drying time is 1-8 h. When using carbon dioxide for supercritical drying, the pressure inside the high-pressure reactor can reach 8-12 MPa, and the drying time is 8-15 h. This method requires multiple solution replacements to prepare magnesium-aluminum spinel aerogel, with each replacement taking 12-24 h. It requires multiple steps, is time-consuming, has a relatively complex preparation process, and poses safety hazards, making it difficult to achieve industrial production. Summary of the Invention

[0008] The present invention aims to overcome the defects of the prior art and provides a method for preparing high-temperature resistant magnesium aluminum spinel aerogel that is low in cost, simple in process, short in production cycle and high in safety. The high-temperature resistant magnesium aluminum spinel aerogel prepared by this method not only has good high temperature resistance and thermal insulation performance, but also has high strength.

[0009] To achieve the above objectives, the specific steps employed by this invention are as follows:

[0010] Step 1: Mix M1 parts by weight of basic magnesium sulfate whiskers, M2 parts by weight of aluminum sol, and M3 parts by weight of deionized water to obtain 100 parts by weight of wet gel. Wherein:

[0011] The solid content of the aluminum sol is Y = 20-60 wt%.

[0012] The mass ratio of the basic magnesium sulfate whiskers to AlOOH in the aluminum sol, M1:m, is 1:15-50.

[0013] The sum of the mass fractions of AlOOH in the basic magnesium sulfate whiskers and aluminum sol is M1+m = 10~30.

[0014] but:

[0015] The mass fraction of AlOOH in the aluminum sol is m = M2·Y;

[0016] The mass fraction of the basic magnesium sulfate whiskers is M1 = (10-30) / (16-51);

[0017] The mass fraction of the aluminum sol is M2 = (15~50)M1 / Y;

[0018] The mass fraction of the deionized water is M3 = 100 - M1 - M2.

[0019] Step 2: Freeze the wet gel with liquid nitrogen until it becomes a gel block.

[0020] Step 3: Place the gel block into a vacuum freeze dryer and freeze dry for 24-96 hours to obtain the magnesium aluminum spinel aerogel precursor.

[0021] Step 4: Mix the magnesium olivine powder (N1 by mass) and the carbon black (N2 by mass) at a ratio of 2 to 4:1, and grind them to obtain 100 parts by mass of mixed powder.

[0022] Step 5: Place the mixed powder in a tablet press and press it into tablets to obtain tablets.

[0023] Step 6: According to the requirement of the same or similar volume, place a single piece of the magnesium aluminum spinel aerogel precursor on one or more of the sheet-like materials, or place one or more pieces of the magnesium aluminum spinel aerogel precursor on a single sheet-like material, and then transfer them together into a tube furnace or a vertical furnace; in a N2 atmosphere, heat to 400-600℃ at a rate of 2-10℃ / min and hold for 1-3 hours; then heat to 1400-1600℃ at a rate of 1-3℃ / min and hold for 3-8 hours to obtain high-temperature resistant magnesium aluminum spinel aerogel.

[0024] The basic magnesium sulfate whiskers have a MgSO4·5Mg(OH)2·3H2O content ≥90% and an aspect ratio ≥5.

[0025] The particle size of AlOOH in the aluminum sol is ≤20nm.

[0026] The purity of the forsterite powder is ≥90%.

[0027] The particle size of the carbon black is ≤1μm.

[0028] The pressure of the tablet is ≥10MPa.

[0029] The cold trap temperature of the vacuum freeze dryer is -80℃ to -30℃.

[0030] The terms "same or similar volume" mean that the volume difference between the magnesium aluminum spinel aerogel precursor and the sheet material is less than or equal to 40% of the volume of the magnesium aluminum spinel aerogel precursor.

[0031] Due to the adoption of the above technical solution, the present invention has the following positive effects and outstanding features compared with the prior art:

[0032] 1. This invention uses basic magnesium sulfate whiskers and aluminum sol as the main raw materials. By reasonably controlling the ratio of raw materials, mixing them evenly, and then placing them on the sheet obtained by pressing, heat treatment is carried out to obtain high-temperature resistant magnesium aluminum spinel aerogel. The process is simple, the operation is controllable, and the safety is high.

[0033] 2. The raw materials used in this invention are basic magnesium sulfate whiskers, aluminum sol, magnesium olivine powder and carbon black, which are inexpensive and have low production costs; and are non-toxic and highly safe.

[0034] 3. This invention uses basic magnesium sulfate whiskers and aluminum sol to build an aerogel structure, and generates magnesium aluminum spinel aerogel in situ through calcination. During the calcination process, magnesium aluminum spinel whiskers are deposited in the gas phase of the generated magnesium aluminum spinel aerogel, which further increases the strength of the high-temperature resistant magnesium aluminum spinel aerogel.

[0035] 4. This invention employs a sol-gel method combined with vapor deposition to prepare high-temperature resistant magnesium aluminum spinel aerogel. During calcination, magnesium vapor escapes from the flake-like material and enters the magnesium aluminum spinel aerogel precursor, reacting with it. No other impurities are introduced during this process, resulting in a high-purity high-temperature resistant magnesium aluminum spinel aerogel.

[0036] 5. This invention prepares high-temperature resistant magnesium aluminum spinel aerogel using a two-step calcination method. First, basic magnesium sulfate whiskers decompose and release gas at 400–600℃, and the whisker morphology is preserved after 1–3 hours of holding at this temperature. Then, heating is continued to 1400–1600℃ for holding to generate magnesium aluminum spinel and deposit magnesium aluminum spinel whiskers. Therefore, the prepared magnesium aluminum spinel aerogel not only has a high operating temperature but also high strength.

[0037] 6. This invention employs a vacuum freeze-drying method to prepare high-temperature resistant magnesium aluminum spinel aerogel. By eliminating the gas-liquid interface, surface tension is reduced or surface pressure is prevented, thus avoiding shrinkage and collapse of the magnesium aluminum spinel aerogel precursor during drying and maximizing the preservation of the pore structure of the high-temperature resistant magnesium aluminum spinel aerogel. Therefore, the prepared high-temperature resistant magnesium aluminum spinel aerogel has low density, high porosity, and is in a complete block shape, overcoming the problem of weak block formation in existing aerogels. This results in products with excellent high-temperature resistance and thermal insulation properties, making them widely applicable in aerospace, high-temperature gas filters, industrial kilns, and other fields.

[0038] The high-temperature resistant magnesium aluminum spinel aerogel prepared by this invention was tested and found to have a bulk density of 0.25–0.3 g / cm³. 3 Porosity: 90.5–92.4%; Thermal conductivity: 0.08–0.13 W·m -1 ·K -1 .

[0039] Therefore, the present invention has a simple process, short production cycle, low cost and high safety. The high-temperature resistant magnesium aluminum spinel aerogel prepared has not only low bulk density, high porosity, good high temperature resistance and thermal insulation performance, but also high strength. Attached Figure Description

[0040] Figure 1 The XRD diffraction pattern of a high-temperature resistant magnesium aluminum spinel aerogel prepared according to the present invention. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments, but this is not intended to limit the scope of protection thereof.

[0042] A high-temperature resistant magnesium aluminum spinel aerogel and its preparation method. The preparation method described in this specific embodiment is as follows:

[0043] Step 1: Mix M1 parts by weight of basic magnesium sulfate whiskers, M2 parts by weight of aluminum sol, and M3 parts by weight of deionized water to obtain 100 parts by weight of wet gel. Wherein:

[0044] The solid content of the aluminum sol is Y = 20-60 wt%.

[0045] The mass ratio of the basic magnesium sulfate whiskers to AlOOH in the aluminum sol, M1:m, is 1:15-50.

[0046] The sum of the mass fractions of AlOOH in the basic magnesium sulfate whiskers and aluminum sol is M1+m = 10~30.

[0047] but:

[0048] The mass fraction of AlOOH in the aluminum sol is m = M2·Y;

[0049] The mass fraction of the basic magnesium sulfate whiskers is M1 = (10-30) / (16-51);

[0050] The mass fraction of the aluminum sol is M2 = (15~50)M1 / Y;

[0051] The mass fraction of the deionized water is M3 = 100 - M1 - M2.

[0052] Step 2: Freeze the wet gel with liquid nitrogen until it becomes a gel block.

[0053] Step 3: Place the gel block into a vacuum freeze dryer and freeze dry for 24-96 hours to obtain the magnesium aluminum spinel aerogel precursor.

[0054] Step 4: Mix the magnesium olivine powder (N1 by mass) and the carbon black (N2 by mass) at a ratio of 2 to 4:1, and grind them to obtain 100 parts by mass of mixed powder.

[0055] Step 5: Place the mixed powder in a tablet press and press it into tablets to obtain tablets.

[0056] Step 6: According to the requirement of the same or similar volume, place a single piece of the magnesium aluminum spinel aerogel precursor on one or more of the sheet-like materials, or place one or more pieces of the magnesium aluminum spinel aerogel precursor on a single sheet-like material, and then transfer them together into a tube furnace or a vertical furnace; in a N2 atmosphere, heat to 400-600℃ at a rate of 2-10℃ / min and hold for 1-3 hours; then heat to 1400-1600℃ at a rate of 1-3℃ / min and hold for 3-8 hours to obtain high-temperature resistant magnesium aluminum spinel aerogel.

[0057] The pressure of the tablet is ≥10MPa.

[0058] The cold trap temperature of the vacuum freeze dryer is -80℃ to -30℃.

[0059] In this specific implementation:

[0060] The basic magnesium sulfate whiskers have a MgSO4·5Mg(OH)2·3H2O content ≥90% and an aspect ratio ≥5.

[0061] The particle size of AlOOH in the aluminum sol is ≤20nm.

[0062] The purity of the forsterite powder is ≥90%.

[0063] The particle size of the carbon black is ≤1μm.

[0064] The terms "same or similar volume" mean that the volume difference between the magnesium aluminum spinel aerogel precursor and the sheet material is less than or equal to 40% of the volume of the magnesium aluminum spinel aerogel precursor.

[0065] The details will not be repeated in the examples.

[0066] Example 1

[0067] A high-temperature resistant magnesium aluminum spinel aerogel and its preparation method. The preparation method described in this embodiment is as follows:

[0068] Step 1: Mix M1 parts by weight of basic magnesium sulfate whiskers, M2 parts by weight of aluminum sol, and M3 parts by weight of deionized water to obtain 100 parts by weight of wet gel. Wherein:

[0069] The solid content of the aluminum sol is Y = 20 wt%.

[0070] The mass ratio of the basic magnesium sulfate whiskers to AlOOH in the aluminum sol, M1:m, is 1:15.

[0071] The sum of the mass fractions of AlOOH in the basic magnesium sulfate whiskers and aluminum sol is M1+m=18.

[0072] but:

[0073] The mass fraction of the basic magnesium sulfate whiskers, M1 = 18 / 16 = 1.12;

[0074] The mass fraction of the aluminum sol is M2 = 15·1.12 / 0.2 = 84.

[0075] The mass fraction of AlOOH in the aluminum sol is m = M²·Y = 84·0.2 = 16.8.

[0076] The mass fraction of the deionized water is M3 = 100 - M1 - M2 = 100 - 1.12 - 84 = 14.88.

[0077] Step 2: Freeze the wet gel with liquid nitrogen until it becomes a gel block.

[0078] Step 3: Place the gel block into a vacuum freeze dryer and freeze dry for 24 hours to obtain the magnesium aluminum spinel aerogel precursor.

[0079] Step 4: Mix the magnesium olivine powder (N1 by mass) and the carbon black (N2 by mass) at a ratio of 4:1, and grind them to obtain 100 parts by mass of mixed powder.

[0080] Step 5: Place the mixed powder in a tablet press and press it into tablets to obtain tablets.

[0081] Step 6: According to the requirement of the same or similar volume, place a single piece of the magnesium aluminum spinel aerogel precursor on a sheet, and then transfer them together into a tube furnace; in N2 atmosphere, heat to 600℃ at a rate of 5℃ / min and hold for 1h; then heat to 1600℃ at a rate of 2℃ / min and hold for 3h to obtain high-temperature resistant magnesium aluminum spinel aerogel.

[0082] The cold trap temperature of the vacuum freeze dryer is -30℃.

[0083] The pressure of the tablet press is 10 MPa.

[0084] The high-temperature resistant magnesium aluminum spinel aerogel prepared in this embodiment was tested and found to have a bulk density of 0.3 g / cm³. 3 Porosity: 90.5%; Thermal conductivity: 0.13 W·m -1 ·K -1 .

[0085] Example 2

[0086] A high-temperature resistant magnesium aluminum spinel aerogel and its preparation method. The preparation method described in this embodiment is as follows:

[0087] Step 1: Mix M1 parts by weight of basic magnesium sulfate whiskers, M2 parts by weight of aluminum sol, and M3 parts by weight of deionized water to obtain 100 parts by weight of wet gel. Wherein:

[0088] The solid content of the aluminum sol is Y = 60 wt%.

[0089] The mass ratio of the basic magnesium sulfate whiskers to AlOOH in the aluminum sol, M1:m, is 1:40.

[0090] The sum of the mass fractions of AlOOH in the basic magnesium sulfate whiskers and aluminum sol is M1+m=10.

[0091] but:

[0092] The mass fraction of the basic magnesium sulfate whiskers is M1 = 10 / 41 = 0.24;

[0093] The mass fraction of the aluminum sol is M2 = 40·0.24 / 0.6 = 16.

[0094] The mass fraction of AlOOH in the aluminum sol is m = M²·Y = 16·0.6 = 9.6.

[0095] The mass fraction of the deionized water is M3 = 100 - M1 - M2 = 100 - 0.24 - 16 = 83.76.

[0096] Step 2: Freeze the wet gel with liquid nitrogen until it becomes a gel block.

[0097] Step 3: Place the gel block into a vacuum freeze dryer and freeze dry for 48 hours to obtain the magnesium aluminum spinel aerogel precursor.

[0098] Step 4: Mix the magnesium olivine powder (N1 by mass) and the carbon black (N2 by mass) at a ratio of 2:1, and grind them to obtain 100 parts by mass of mixed powder.

[0099] Step 5: Place the mixed powder in a tablet press and press it into tablets to obtain tablets.

[0100] Step 6: According to the requirement of the same or similar volume, place a single piece of the magnesium aluminum spinel aerogel precursor on 3 of the sheet-like materials, and then transfer them together into a vertical furnace; in a N2 atmosphere, heat to 500°C at a rate of 2°C / min and hold for 2 hours; then heat to 1500°C at a rate of 1°C / min and hold for 5 hours to obtain high-temperature resistant magnesium aluminum spinel aerogel.

[0101] The cold trap temperature of the vacuum freeze dryer is -45℃.

[0102] The pressure of the tablet is 20 MPa.

[0103] The high-temperature resistant magnesium aluminum spinel aerogel prepared in this embodiment was tested and found to have a bulk density of 0.29 g / cm³. 3 Porosity: 91.6%; Thermal conductivity: 0.11 W·m -1 ·K -1 .

[0104] Example 3

[0105] A high-temperature resistant magnesium aluminum spinel aerogel and its preparation method. The preparation method described in this embodiment is as follows:

[0106] Step 1: Mix M1 parts by weight of basic magnesium sulfate whiskers, M2 parts by weight of aluminum sol, and M3 parts by weight of deionized water to obtain 100 parts by weight of wet gel. Wherein:

[0107] The solid content of the aluminum sol is Y = 30 wt%.

[0108] The mass ratio of the basic magnesium sulfate whiskers to AlOOH in the aluminum sol, M1:m, is 1:50.

[0109] The sum of the mass fractions of AlOOH in the basic magnesium sulfate whiskers and aluminum sol is M1+m=30.

[0110] but:

[0111] The mass fraction of the basic magnesium sulfate whiskers is M1 = 30 / 51 = 0.59.

[0112] The mass fraction of the aluminum sol is M2 = 50·0.59 / 0.3 = 98.

[0113] The mass fraction of AlOOH in the aluminum sol is m = M²·Y = 98·0.3 = 29.4.

[0114] The mass fraction of the deionized water is M3 = 100 - M1 - M2 = 100 - 0.59 - 98 = 1.41.

[0115] Step 2: Freeze the wet gel with liquid nitrogen until it becomes a gel block.

[0116] Step 3: Place the gel block into a vacuum freeze dryer and freeze dry for 96 hours to obtain the magnesium aluminum spinel aerogel precursor.

[0117] Step 4: Mix the magnesium olivine powder (N1 by mass) and the carbon black (N2 by mass) at a ratio of 3:1, and grind them to obtain 100 parts by mass of mixed powder.

[0118] Step 5: Place the mixed powder in a tablet press and press it into tablets to obtain tablets.

[0119] Step 6: According to the requirement of having the same or similar volume, place two pieces of the magnesium aluminum spinel aerogel precursor on a single sheet and then transfer them together into a vertical furnace; in a N2 atmosphere, heat to 400°C at a rate of 10°C / min and hold for 3 hours; then heat to 1400°C at a rate of 3°C / min and hold for 8 hours to obtain high-temperature resistant magnesium aluminum spinel aerogel.

[0120] The cold trap temperature of the vacuum freeze dryer is -80℃.

[0121] The pressure of the tablet is 30 MPa.

[0122] The high-temperature resistant magnesium aluminum spinel aerogel prepared in this embodiment was tested and found to have a bulk density of 0.25 g / cm³. 3 Porosity: 92.4%; Thermal conductivity: 0.08 W·m -1 ·K -1 .

[0123] Compared with the prior art, this specific implementation method has the following positive effects and outstanding features:

[0124] 1. This specific embodiment uses basic magnesium sulfate whiskers and aluminum sol as the main raw materials. By reasonably controlling the ratio of raw materials, they are mixed evenly and then placed on the sheet obtained by pressing for heat treatment to obtain high temperature resistant magnesium aluminum spinel aerogel. The process is simple, the operation is controllable, and the safety is high.

[0125] 2. The raw materials used in this specific implementation method are basic magnesium sulfate whiskers, aluminum sol, magnesium olivine powder and carbon black, which are inexpensive and have low production costs; and are non-toxic and highly safe.

[0126] 3. In this specific embodiment, basic magnesium sulfate whiskers and aluminum sol are used to construct an aerogel structure. Magnesium aluminum spinel aerogel is generated in situ by calcination. During the calcination process, magnesium aluminum spinel whiskers are deposited in the gas phase of the generated magnesium aluminum spinel aerogel, which further increases the strength of the high-temperature resistant magnesium aluminum spinel aerogel.

[0127] 4. The high-temperature resistant magnesium aluminum spinel aerogel prepared by the sol-gel method combined with vapor deposition in this specific embodiment is shown in the attached figure. Figure 1 The XRD diffraction pattern of the high-temperature resistant magnesium aluminum spinel aerogel prepared in Example 3 is shown below. Figure 1 It can be seen that during the calcination process, magnesium vapor escapes from the flakes and enters the magnesium aluminum spinel aerogel precursor, reacting with it. No other impurities are introduced during this process, resulting in a high-purity high-temperature resistant magnesium aluminum spinel aerogel.

[0128] 5. This specific embodiment of the preparation of high-temperature resistant magnesium aluminum spinel aerogel adopts a two-step calcination method. At 400–600℃, basic magnesium sulfate whiskers decompose and release gas; after holding at this temperature for 1–3 hours, the whisker morphology is preserved. Further heating to 1400–1600℃ and holding at this temperature generates magnesium aluminum spinel and deposits magnesium aluminum spinel whiskers. Therefore, the prepared magnesium aluminum spinel aerogel not only has a high operating temperature but also high strength.

[0129] 6. This specific embodiment uses a vacuum freeze-drying method to prepare high-temperature resistant magnesium aluminum spinel aerogel. By eliminating the gas-liquid interface, surface tension is reduced or surface pressure is prevented, thus avoiding shrinkage and collapse of the magnesium aluminum spinel aerogel precursor during drying, and greatly preserving the pore structure of the high-temperature resistant magnesium aluminum spinel aerogel. Therefore, the prepared high-temperature resistant magnesium aluminum spinel aerogel has low density, high porosity, and is in a complete block shape, overcoming the problem of weak block formation in existing aerogels. This results in products with excellent high-temperature resistance and thermal insulation properties, and is widely used in aerospace, high-temperature gas filters, industrial kilns, and other fields.

[0130] The high-temperature resistant magnesium aluminum spinel aerogel prepared according to this specific embodiment was tested and found to have a bulk density of 0.25–0.3 g / cm³. 3 Porosity: 90.5–92.4%; Thermal conductivity: 0.08–0.13 W·m -1 ·K -1 .

[0131] Therefore, this specific embodiment has a simple process, short production cycle, low cost and high safety. The high-temperature resistant magnesium aluminum spinel aerogel prepared has not only low bulk density, high porosity, good high temperature resistance and thermal insulation performance, but also high strength.

Claims

1. A method for preparing high-temperature resistant magnesium aluminum spinel aerogel, characterized in that, The specific steps of the preparation method are as follows: Step 1: Mix M1 parts by weight of basic magnesium sulfate whiskers, M2 parts by weight of aluminum sol, and M3 parts by weight of deionized water to obtain 100 parts by weight of wet gel; wherein: The solid content of the aluminum sol is Y = 20~60wt%. The mass ratio of the basic magnesium sulfate whiskers to AlOOH in the aluminum sol, M1:m, is 1:15~50. The sum of the mass fractions of AlOOH in the basic magnesium sulfate whiskers and aluminum sol is M1+m=10~30; but: The mass fraction of AlOOH in the aluminum sol is m = M2·Y. The mass fraction of the basic magnesium sulfate whiskers, M1, is (10~30) / (16~51). The mass fraction of the aluminum sol is M2 = (15~50)M1 / Y. The mass fraction of the deionized water is M3 = 100 - M1 - M2; Step 2: Freeze the wet gel with liquid nitrogen until it forms a gel block; Step 3: Place the gel block into a vacuum freeze dryer and freeze dry for 24-96 hours to obtain magnesium aluminum spinel aerogel precursor; Step 4: Mix the forsterite powder and the carbon black according to the mass ratio of N1 to N2 of the forsterite powder being 2 to 4 to 1, and grind them to obtain 100 parts by mass of mixed powder. Step 5: Place the mixed powder in a tablet press and compress it to obtain tablets; Step 6: According to the requirement of the same or similar volume, place a single piece of the magnesium aluminum spinel aerogel precursor on one or more of the sheet-like materials, or place one or more pieces of the magnesium aluminum spinel aerogel precursor on a single sheet-like material, and then transfer them together into a tube furnace or a vertical furnace; in a N2 atmosphere, heat to 400-600℃ at a rate of 2-10℃ / min and hold for 1-3 hours; then heat to 1400-1600℃ at a rate of 1-3℃ / min and hold for 3-8 hours to obtain high-temperature resistant magnesium aluminum spinel aerogel.

2. The method for preparing high-temperature resistant magnesium aluminum spinel aerogel according to claim 1, characterized in that, The basic magnesium sulfate whiskers have a MgSO4·5Mg(OH)2·3H2O content ≥90% and an aspect ratio ≥5.

3. The method for preparing high-temperature resistant magnesium aluminum spinel aerogel according to claim 1, characterized in that, The particle size of AlOOH in the aluminum sol is ≤20nm.

4. The method for preparing high-temperature resistant magnesium aluminum spinel aerogel according to claim 1, characterized in that, The purity of the forsterite powder is ≥90%.

5. The method for preparing high-temperature resistant magnesium aluminum spinel aerogel according to claim 1, characterized in that, The particle size of the carbon black is ≤1μm.

6. The method for preparing high-temperature resistant magnesium aluminum spinel aerogel according to claim 1, characterized in that, The pressure of the tablet is ≥10 MPa.

7. The method for preparing high-temperature resistant magnesium aluminum spinel aerogel according to claim 1, characterized in that, The cold trap temperature of the vacuum freeze dryer is -80℃ to -30℃.

8. The method for preparing high-temperature resistant magnesium aluminum spinel aerogel according to claim 1, characterized in that, The terms "same or similar volume" mean that the volume difference between the magnesium aluminum spinel aerogel precursor and the sheet material is less than or equal to 40% of the volume of the magnesium aluminum spinel aerogel precursor.

9. A high-temperature resistant magnesium aluminum spinel aerogel, characterized in that, The high-temperature resistant magnesium aluminum spinel aerogel is prepared by the preparation method of the high-temperature resistant magnesium aluminum spinel aerogel according to any one of claims 1 to 8.

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