Novel light thermal insulation material and preparation method thereof

Abstract

The invention discloses a novel light heat prevention and insulation material and a preparation method thereof, and particularly relates to a method for rapidly preparing zirconium oxide sol and preparing the novel light heat prevention and insulation material by using the sol. The method comprises the following steps: by taking zirconium oxychloride, sodium hydroxide, strong acid and the like as raw materials, dropwise adding alkali liquor into a zirconium oxychloride aqueous solution until the whole mixture is in an alkaline state, separating zirconium from chlorine in a complex precipitate form, carrying out suction filtration and cleaning, removing impurity elements to obtain a wet filter cake, dissolving the wet filter cake by using deionized water, adding strong acid, and carrying out vacuum drying to obtain the zirconium-based composite material. And putting the mixture into a closed container, and carrying out heat preservation for more than 15 hours at the temperature of more than 100 DEG C, so as to prepare the zirconium oxide sol. The zirconia sol and silica sol are mixed according to a volume ratio, a gradient fiber cotton felt is impregnated for 5-6 times and then treated at the temperature of 600-1000 DEG C, and the novel light high-temperature-resistant heat-proof and heat-insulating material is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic composite materials, and in particular relates to a novel lightweight heat-insulating material and a preparation method thereof. Background Art

[0002] At present, the aerospace industry is developing rapidly, and the flight speed of aircraft is getting faster and faster. High-speed aircraft produce intense friction with the air in the atmosphere. The faster the speed, the more intense the friction, the more heat generated, and the higher the surface temperature. In order to better protect the safety of the internal components of the aircraft, the internal temperature of the aircraft must be kept within a certain range. If this goal is to be achieved without increasing the weight of the aircraft itself, materials with better heat insulation performance and higher temperature resistance must be used. The traditional approach is to use raw materials with higher temperature resistance instead of conventional materials, but this approach significantly increases the overall material cost. On the basis of not changing the original materials, it is undoubtedly a feasible solution to achieve higher temperature resistance requirements through partial fine-tuning.

[0003] At present, there are studies on zirconium sol, CN201780052950.0, in which the preparation of zirconium sol adopts the method of mixing zirconium oxychloride solution with alkaline solution, and after a long period of aging, the preparation cycle is relatively long. CN200810109057.X, in which zirconium sol is prepared by using organic matter as raw material, zirconium sol can be prepared, and organic solvent type zirconium sol can be prepared by changing the solvent, but organic solvent has many problems to be solved in waste liquid treatment. CN202111060662.4, in which zirconium sol is prepared by a one-step method, and all impurities in the raw materials are retained in the sol, and it takes a long time to remove impurities using a dialysis membrane.

[0004] There are also related studies on heat-insulating materials. CN202210736953.9 proposes a 1500°C heat-insulating integrated composite structure ceramic and its preparation method. The composite material uses Al 2 O 3 Aerogel composite materials are porous ceramic structure insulation materials prepared for the core layer, but the process requires a lot of manual labor, a long preparation cycle, low production efficiency, and many human factors. At the same time, in the preparation of this material, the mold sizes required for the aerogel stage and the later material molding stage are not the same, which invisibly increases the material cost.

[0005] Therefore, it is necessary to develop lightweight, high-temperature resistant and heat-insulating materials that can be prepared quickly and at low cost. Summary of the invention

[0006] Aiming at the problems of insufficient temperature resistance and long preparation cycle of the heat insulation material prepared from the raw materials used in the existing technology, the present invention provides a new type of lightweight heat insulation material and its preparation method, specifically an impregnation zirconium sol and a lightweight heat insulation material and its preparation method. In view of the traditional process of only changing a single raw material or impregnating solution, the present invention uses a self-made zirconium sol to carry out overall impregnation of the prefabricated parts, taking into account both the change of the impregnating solution and the change of the prefabricated parts, shortening the process cycle, reducing the preparation cost, and improving the material performance.

[0007] The technical solution of the present invention is as follows: A preparation method of a new type of lightweight heat insulation material is a method for quickly preparing zirconium oxide sol and using this sol to prepare a new type of lightweight heat insulation material. First, zirconium oxychloride, sodium hydroxide, strong acid, etc. are used as raw materials. By dropping an alkali solution into an aqueous solution of zirconium oxychloride until the whole mixture is alkaline, zirconium is separated from chlorine in the form of a complex precipitate. After suction filtration and washing, impurity elements are removed to obtain a wet filter cake, which is then dissolved with deionized water, and strong acid is added to make it return to an acidic state. It is placed in a closed container and kept at a temperature above 100 °C for more than 15 h to prepare zirconium oxide sol. After mixing this zirconium oxide sol and silica sol by volume ratio, gradient fiber cotton felt is impregnated. After 5 to 6 impregnations, it is then treated at 600 °C - 1000 °C to obtain a new type of lightweight high-temperature heat insulation material.

[0008] The object of the present invention is achieved through the following technical solutions: A preparation method of a new type of lightweight heat insulation material includes the following steps: S1. Preparation of zirconium oxide sol: Prepare zirconium oxide sol from zirconium-containing raw materials. The main component of the prepared zirconium oxide sol is zirconia, and the sol is a light blue or milky white liquid with a concentration of 2% - 8% and a density of 1.01 g / cm 3 , and the viscosity ≤ 15 mPa·s; The zirconium-containing raw materials selected from zirconium oxychloride (ZrOCl 2 ), zirconium oxynitrate (ZrO(NO 3 ) 2 ), zirconium tetrachloride (ZrCl 4 ), zirconium nitrate (Zr(NO 3 ) 4 ), zirconium sulfate (Zr(SO 4 ) 2 ), zirconium oxalate (ZrOCO 3 ), etc., or any proportion mixture of one or several of them; S2. Use the zirconia sol prepared in S1 and mix it with silica sol in a volume ratio of ≤5:1. After mixing, impregnate the fiber preform. This fiber preform has a gradient structure. The gradient fiber preform is a silica fiber cotton felt, which is divided into upper and lower surface layers and an intermediate core layer. The fiber cotton felt is an integral structure. The upper and lower surface layers are composed of a mixture of fiber cloth and fiber cotton, and the intermediate core layer is entirely composed of fiber cotton. The thickness of the upper surface layer is 0.5 mm - 10.0 mm, the thickness of the lower surface layer is 0.3 mm - 2.0 mm, and the thickness of the intermediate core layer is 10 m - 30 mm; S3. After the impregnation is completed, perform high-temperature treatment on the obtained gradient fiber preform to obtain a new type of lightweight heat-insulating material with a thickness of 10 mm - 35 mm and a density of 0.5 g / cm 3 - 0.8 g / cm 3 , and the thermal conductivity is 0.047 W / m·K; it has strong oxidation resistance, can withstand the burning of oxygen - liquefied petroleum gas flame at 1600 °C, can withstand the temperature of a quartz lamp ≥1500 °C, and the heat-resistant temperature in a typical ballistic heating environment ≥1500 °C.

[0009] Furthermore, in step S1, during the preparation of the zirconia sol, an alkali solution is used for adjustment. The amount of the alkali solution should be higher than the amount of zirconium so that zirconium can be completely precipitated and separated; the alkali solution used is one or more of LiOH, NaOH, KOH, or ammonia water, the concentration of the hydroxide is 5% - 20%, and the concentration of ammonia water is 15% - 27%.

[0010] Furthermore, in step S1, the acid used during the preparation of the zirconia sol is an inorganic strong acid, selected from one or more of hydrochloric acid, nitric acid, and sulfuric acid, with a concentration of 30% - 60%; or organic acids such as acetic acid, oxalic acid, lactic acid, and tartaric acid are used.

[0011] Furthermore, in step S1, during the preparation of the zirconia sol, the dissolution temperature of the zirconium-containing raw material is room temperature.

[0012] Furthermore, in step S1, during the preparation of the zirconia sol, some stabilizers need to be added, which can be compounds of yttrium.

[0013] Furthermore, in step S1, during the preparation of the zirconia sol, after the dissolution is completed, a closed container is used for the subsequent reaction.

[0014] Further, in step S2, for the impregnation, the impregnation liquid is a mixed solution of self-made zirconia sol and silica sol. Both sols are acidic. After mixing, the sol is homogeneous and the viscosity remains unchanged. The mixing ratio is ≤ 5:1 in terms of volume ratio. The impregnation method is vacuum impregnation. The impregnation also includes a curing step. The curing atmosphere is air. The curing temperature is 100°C - 300°C, and the curing time is 30 min - 120 min. During curing, a mold is used to fix the shape of the material. Different molds are used according to the different shapes of the material. After the shape of the material is fixed, the mold can be no longer used.

[0015] Further, in step S2, the fiber cotton felt is the fiber cotton felt body developed in the previous experiment. In step S2, except for curing and high-temperature treatment, all are carried out at room temperature.

[0016] Further, in step S2, the gradient fiber preform is a silica fiber cotton felt. The thickness of the upper surface layer is 0.5 mm - 10.0 mm, the thickness of the lower surface layer is 0.3 mm - 2.0 mm, and the thickness of the middle core layer is 10 m - 30 mm. The proportion of each part can also be adjusted according to the use requirements, and the subsequent forming methods are generally the same.

[0017] Further, in step S3, for the high-temperature treatment, the temperature is 600°C - 1000°C, the time is 30 min - 120 min, and the atmosphere is air.

[0018] The present invention also relates to a new type of lightweight heat-insulating and heat-protecting material, which is obtained according to the preparation method of the above-mentioned new type of lightweight heat-insulating and heat-protecting material. For the prepared new type of lightweight heat-insulating and heat-protecting material, the preparation period of zirconia sol is 20 h - 80 h, the material forming period is 4 d - 8 d, the thickness is 10 mm - 35 mm, and the density is 0.5 g / cm 3 - 0.8 g / cm 3 , and the thermal conductivity is 0.047 W / m·K; it has strong antioxidant properties, can resist the burning of oxygen - liquefied petroleum gas flame at 1600°C, can resist the temperature of quartz lamp ≥ 1500°C, and the heat-resistant temperature in a typical ballistic heating environment ≥ 1500°C.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. The new type of lightweight heat-insulating and heat-protecting material prepared by the present invention is a nano-level zirconia sol. The sol particles are relatively uniform in size, and the appearance is light blue or milky white. It can be stored for a long time. The sol can be continuously prepared, which can meet its own needs and greatly save the material preparation cost.

[0020] 2. The preparation method of a novel lightweight heat-insulating material according to the present invention uses the sol developed in step S1 to prepare a novel lightweight heat-insulating material, providing a ceramic composite preform with controllable thickness and adjustable system. By controlling the impregnation efficiency, the density of the material is effectively controlled, and this method effectively shortens the preparation cycle of the material, greatly reducing the production cost and delivery cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 is a flowchart of the preparation method of the novel lightweight heat-insulating material provided by the present invention; Figure 2 is an appearance view of the zirconia sol prepared in Example 1 of the present invention; Figure 3 is an appearance view of the novel lightweight heat-insulating material prepared in Example 1 of the present invention; Figure 4 is a view of the novel lightweight heat-insulating material prepared in Example 1 of the present invention under the treatment of oxygen - liquefied petroleum gas flame at 1600°C; Figure 5 is a view of the novel lightweight heat-insulating material prepared in Example 1 of the present invention under the assessment of a quartz lamp at 1500°C; Figure 6 is a comparison view of the novel lightweight heat-insulating material prepared in Example 1 of the present invention before and after the assessment of a quartz lamp at 1500°C; wherein, Figure 6 (a) is a comparison view before ablation, Figure 6 (b) is a comparison view after ablation. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The following details the preparation of the novel lightweight heat-insulating material of the present invention, but the present invention can be implemented in many different ways defined and covered by the claims.

[0023] As Figure 1 shown, it is a flowchart of the preparation method of the novel lightweight heat-insulating material provided by the present invention. The present invention provides a preparation method of a novel lightweight heat-insulating material, mainly including two major parts. One part is the preparation of zirconia sol, and the other part is to use the prepared zirconia sol to prepare a lightweight heat-insulating material, which specifically includes the following steps: S1: Preparation of zirconia sol. The prepared sol has a certain concentration and a relatively low viscosity; S2: Using the self-made zirconia sol, after mixing with silica sol, impregnate the fiber preform, and this fiber preform has a gradient structure; S3: After the impregnation is completed, the gradient fiber preform is subjected to high-temperature treatment, and a lightweight heat-insulating material can be obtained after the high-temperature treatment; Further, in step S1, the raw materials selected can be zirconium oxychloride (ZrOCl 2 ), zirconyl nitrate (ZrO(NO 3 2 ), zirconium tetrachloride (ZrCl 4 ), zirconium nitrate (Zr(NO 3 4 ), zirconium sulfate (Zr(SO 4 2 ), zirconium oxalate carbonate (ZrOCO 3 ), etc., one or several of them; Further, in step S1, during the preparation of the zirconia sol, an alkali solution is used for adjustment. The alkali solution used is one or several of LiOH, NaOH, KOH, or ammonia water. The amount of the alkali solution should be higher than the amount of zirconium. The concentration of the hydroxide is 5%-20%, and the concentration of ammonia water is 15%-27%; Further, in step S1, the acid used in the sol preparation is an inorganic strong acid, which can be one or several of hydrochloric acid, nitric acid, and sulfuric acid, with a concentration of 30%-60%; organic acids such as acetic acid, oxalic acid, lactic acid, and tartaric acid can also be used; Further, in step S1, during the sol preparation, the required dissolution temperature of the raw materials is room temperature; Further, in step S1, some stabilizers need to be added during the sol preparation, which can be compounds of yttrium; Further, in step S1, after the dissolution is completed during the sol preparation, a closed container is used for the subsequent reaction; Further, in step S2, the gradient fiber preform is silica fiber felt, which is divided into an upper and lower surface layer and a middle core layer. The fiber felt is an integral structure. The upper and lower surface layers are composed of a mixture of fiber cloth and fiber cotton, and the middle core layer is entirely composed of fiber cotton; Further, in step S2, the thickness of the upper surface layer is 0.5 mm - 10.0 mm, the thickness of the lower surface layer is 0.3 mm - 2.0 mm, and the thickness of the middle core layer is 10 m - 30 mm. The proportion of each part can also be adjusted according to the usage requirements, and the subsequent forming methods are generally the same; Further, in step S2, the impregnating solution is a mixed solution of self-made zirconia sol and silica sol. The sols are all acidic. After mixing, the sols are homogeneous and the viscosity remains unchanged. The mixing ratio ≤ 5:1 (volume ratio), and the impregnation method is vacuum impregnation; ​​​Further, in step S2, a curing step is included. The curing atmosphere is air, the curing temperature is 100°C - 300°C, and the curing time is 30 min - 120 min. During curing, a mold is used to fix the shape of the material. Different molds are used according to the different shapes of the material. After the shape of the material is fixed, the mold can be no longer used. Further, in step S3, the high-temperature treatment atmosphere is air, the high-temperature treatment temperature is 600°C - 1000°C, and the time is 30 min - 120 min. Before high-temperature treatment, the excess part of the material is cut neatly. Further, the thickness of the novel lightweight heat-insulating material is 10 mm - 35 mm, and the density is 0.5 - 0.8 g / cm 3 ; This heat-insulating material has a gradient distribution. The upper and lower surface layers have good compactness and high strength. The middle core layer is a porous structure, having good heat-insulating performance and being able to effectively block heat. Further, the novel lightweight heat-insulating material has strong antioxidant properties, can resist the burning of oxygen - liquefied petroleum gas flame at 1600°C, and can resist the temperature of the quartz lamp ≥1500.

[0024] The present invention will be explained and illustrated below with specific embodiments.

[0025] Example 1: A preparation method of a novel lightweight heat-insulating material includes the following steps: First, zirconia sol is prepared. Zirconium oxychloride is used to prepare a solution. The usage amount of zirconium oxychloride is 20 g, and the usage amount of deionized water is 180 g. After the solution is prepared, 0.8 g of yttrium nitrate is added thereto. After stirring evenly and completely dissolving, 10% NaOH solution is dropped into it, and stirring is continued until the pH reaches 10 and then stopped. After stirring evenly, it is left standing for 3 h for suction filtration, and is washed several times with deionized water. The wet filter cake obtained is 80 g. Then it is dissolved with deionized water, and 50% nitric acid is added to adjust its pH to 1 and then stopped. Then it is put into a closed container and kept at 150°C for 15 h, or kept at 100°C for 45 h. After taking out, zirconia sol can be obtained, and the color is light blue or milky white. As Figure 2 shown, it is the appearance diagram of the zirconia sol prepared in Example 1; Another gradient fiber preform is prepared. The preform is a silica fiber cotton felt, having upper and lower surface layers and a middle core layer, and the materials of all are silica fibers. The thickness of the upper surface layer is 2 - 5 mm; the thickness of the lower surface layer is 1 mm; the thickness of the above-mentioned middle core layer is 20 mm. The preform is fixed with a fitting mold and vacuum impregnated with a mixed sol. The mixed sol is a mixture of zirconium oxide sol and silicon oxide sol. The zirconium oxide sol is a homemade sol in the previous step, and the silicon oxide sol is purchased. The mixing ratio is 2:1 by volume. After the impregnation, the material is solidified at a temperature of 180°C for 4 hours. This process is repeated 5 times. The material after the impregnation and solidification is treated at 800°C for 80 minutes to obtain a new lightweight heat-insulating material.

[0026] like Figure 3 Shown is the appearance of the new lightweight heat-insulating material prepared in Example 1.

[0027] The basic properties of various materials obtained in the preparation of the new lightweight heat-insulating material in Example 1 are as follows: (1) The density of zirconium oxide sol is 1.01g / cm 3 , concentration is 5%, viscosity is ≤15mPa·s, and it is light blue or milky white. The sol particles prepared by this method are 50nm and can transmit red light; (2) The density of the prepared new lightweight thermal insulation material is 0.71 g / cm 3 , panel tensile strength 60MPa, panel bending strength 40MPa; (3) If Figure 5 As shown, this is a diagram of the assessment of the new lightweight heat-insulating material prepared in Example 1 under a quartz lamp at 1500°C. The new lightweight heat-insulating material prepared in Example 1 was subjected to a quartz lamp single-sided radiation heating test at 1500°C for 1 hour. After the test, the surface structure of the material was intact without obvious damage, indicating that the material system can be used normally for a long time at 1500°C; like Figure 6 As shown, it is a comparison diagram of the new lightweight heat-insulating material prepared in Example 1 before and after the 1500°C quartz lamp test, and a comparison diagram of the new lightweight heat-insulating material prepared in Example 1 before and after the 1500°C quartz lamp test (a is a comparison diagram before ablation, and b is a comparison diagram after ablation); like Figure 4 As shown, this is a diagram of the new lightweight heat-insulating material prepared in Example 1 treated with an oxygen-liquefied petroleum gas flame at 1600°C. After being ablated for 5 minutes under the conditions of an oxygen-liquefied petroleum gas flame at 1600°C, there is no obvious change, indicating that the material has strong oxidation resistance.

[0028] Embodiment 2: A method for preparing a novel lightweight heat-insulating material comprises the following steps: First, prepare zirconia sol. Prepare a solution with zirconium oxychloride. The amount of zirconium oxychloride used is 30 g, and the amount of deionized water used is 170 g. After preparing the solution, add 1.5 g of yttrium nitrate to it. Stir evenly until completely dissolved, then dropwise add 26% ammonia water to it and keep stirring until the pH reaches 10 and stop. After stirring evenly, let it stand for 3 h and then perform suction filtration, and wash it several times with deionized water to obtain 130 g of wet filter cake. Then dissolve it with deionized water, add 50% nitric acid to adjust the pH to 1 and stop, and then put it into a closed container and keep it warm at 150 °C for 15 h, or keep it warm at 100 °C for 45 h. After taking it out, zirconia sol can be obtained, and the color is light blue or milky white; Prepare a gradient fiber preform separately. The preform is a silica fiber felt, which has upper and lower surface layers and a middle core layer, and the materials are all silica fibers; the thickness of the upper surface layer of the preform is 5 mm; the thickness of the lower surface layer of the preform is 1 mm; the thickness of the middle core layer of the above preform is 30 mm; Fix the above preform with a fitting mold, and perform vacuum impregnation with a mixed sol. The mixed sol is a mixed solution of zirconia dissolution and silica sol. The zirconia sol is the self-made sol in the previous step, and the silica sol is obtained by purchase; the mixing ratio is 4:1 by volume. After the impregnation is completed, cure the material. The curing temperature is 180 °C and the time is 4 h. This process is repeated 4 times. Treat the impregnated and cured material at 800 °C for 80 min to obtain a new type of lightweight heat-insulating and heat-protecting material.

[0029] The basic properties of various materials obtained in the preparation of the new type of lightweight heat-insulating and heat-protecting material in Example 2 are as follows: (1) The density of the zirconia sol is 1.01 g / cm 3 , the concentration is 6.5%, the viscosity ≤ 15 mPa·s, it is light blue or milky white, and the sol particles prepared by this method are 40 nm and can transmit red light; (2) The density of the prepared new type of lightweight heat-insulating and heat-protecting material is 0.69 g / cm 3 , the panel tensile strength is 56 MPa, and the panel bending strength is 41 MPa; (3) Conduct a 1-hour quartz lamp single-sided radiation heating test on the new type of lightweight heat-insulating and heat-protecting material prepared in this example at 1500 °C. After the test, the surface structure of the material is complete and there is no obvious damage, indicating that the material system can be used normally for a long time at 1500 °C; under the condition of oxy-liquid petroleum gas flame at 1600 °C for 5 min, there is no obvious change, indicating that the material has strong oxidation resistance.

[0030] Example 3: A preparation method of a new type of lightweight heat-insulating and heat-protecting material, including the following steps: First, prepare zirconia sol. Configure a solution with zirconium oxychloride. The amount of zirconium oxychloride used is 20 g, and the amount of deionized water used is 180 g. After configuring the solution, add 0.8 g of yttrium nitrate to it, stir evenly until completely dissolved, and set aside; separately prepare 200 g of 5% NaOH solution, stir evenly, and set aside. Add the zirconium oxychloride solution to the NaOH solution in multiple batches, and keep stirring. After complete addition, continue stirring for 2 h and then stop. Then, perform suction filtration. After suction filtration, obtain 130 g of wet filter cake. After rinsing several times, dissolve it with deionized water, add 50% nitric acid to adjust its pH to 1, continue stirring for 2 h, then put it into a sealed container, take it out after keeping it at 150 °C for 15 h, and completely form sol. The sol is acidic and its color is light blue or milky white. Prepare a gradient fiber preform separately. The preform is a silica fiber felt, which has upper and lower surface layers and a middle core layer, and the materials are all silica fibers; the thickness of the upper surface layer of the preform is 2 - 5 mm; the thickness of the lower surface layer of the preform is 1 mm; the thickness of the middle core layer of the above preform is 20 mm. Fix the above preform with a fitting mold, and perform vacuum impregnation with a mixed sol. The mixed sol is a mixed solution of zirconia sol and silica sol. The zirconia sol is the self-made sol in the previous step, and the silica sol is obtained by purchasing; the mixing ratio is 3:1 by volume. After impregnation, cure the material. The curing temperature is 180 °C and the time is 4 h. This process is repeated 5 times. Treat the impregnated and cured material at 800 °C for 80 min to obtain a new type of lightweight heat insulation material.

[0031] The basic properties of various materials obtained in the preparation of the new type of lightweight heat insulation material in Example 3 are as follows: (1) The density of the zirconia sol is 1.01 g / cm 3 , the concentration is 4.5%, the viscosity ≤ 15 mPa·s, it is light blue or milky white, and the sol particles prepared by this method are 30 nm and can transmit yellow light. (2) The density of the prepared new type of lightweight heat insulation material is 0.68 g / cm 3 , the tensile strength of the panel is 53 MPa, and the bending strength of the panel is 40 MPa. (3) Conduct a 1-hour quartz lamp single-sided radiation heating test on the new type of lightweight heat insulation material prepared in this example at 1500 °C. After the test, the surface structure of the material is complete and there is no obvious damage, indicating that the material system can be used normally for a long time at 1500 °C; under the condition of oxy - liquefied petroleum gas flame at 1600 °C for 5 min, there is no obvious change, indicating that the material has strong oxidation resistance.

[0032] Comparative Example 1: The zirconia sol was prepared by the method of Example 1. The color of the sol was light blue or milky white, and it was mixed with silica sol for use. The mixing ratio was 2:1 by volume. Another split preform was prepared. The split preform was a composite structure made of silica material, which was divided into upper and lower panels and an intermediate heat-insulating core layer. The upper panel was a 2.5D woven body of silica fiber with a thickness of 1 mm - 3 mm. The lower panel was a silica fiber cloth with a twill weaving pattern and a thickness of 0.2 mm - 1 mm. The intermediate heat-insulating core layer was a silica aerogel material with a thickness of 10 mm - 30 mm. Comparative Example 1 was the same as Example 1 except for the preform. The prepared lightweight heat-insulating material had the following properties: (1) It was substantially the same as that of Example 1 for the zirconia sol. (2) The density of the prepared novel lightweight heat-insulating material was 0.65 g / cm 3 , the tensile strength of the panel was 70 MPa, and the bending strength of the panel was 45 MPa. (3) The novel lightweight heat-insulating material prepared in Comparative Example 1 was subjected to a quartz lamp single-sided radiation heating test at 1500 °C for 1 hour. After the test, the surface structure of the material was complete and there was no obvious damage, indicating that the material system could be used normally at 1500 °C for a long time. It was ablated for 5 min under the condition of an oxygen - liquefied petroleum gas flame at 1600 °C, and there was no obvious change, indicating that the material had strong oxidation resistance.

[0033] The results showed that the materials prepared in Comparative Example 1 and Example 1 had similar heat resistance, and the mechanical properties were slightly better than those of Example 1. However, for the split preform, it was necessary to first prepare the intermediate heat-insulating core layer, and then manually combine the upper and lower panels and the intermediate heat-insulating core layer after the preparation of the intermediate heat-insulating core layer was completed. This combination process required multiple manual operations and a long preparation cycle. While the gradient fiber preform used a machine instead of manual labor, and the steps were simple, which greatly shortened the preparation cycle and avoided the interference of manual differences. In addition, in the split preform, the raw material costs of the upper and lower panels and the intermediate heat-insulating core layer were much higher than those of the fiber cloth and fiber cotton in the gradient fiber preform. In summary, by comparing the two heat-insulating materials, the gradient fiber preform scheme had higher advantages in terms of preparation cycle and raw material price, and the difference in mechanical properties was not significant. The overall cost was much lower than that of the split preform, and the scheme of Example 1 was superior to Comparative Example 1.

[0034] Comparative Example 2: The gradient fiber preform was impregnated with silica sol alone. The preform was a silica fiber cotton felt with upper and lower surface layers and an intermediate core layer, and the materials were all silica fibers. The thickness of the upper surface layer was 2 mm - 5 mm; the thickness of the lower surface layer was 1 mm; the thickness of the above intermediate core layer was 20 mm. The sol used in Comparative Example 2 is different from that in Example 1. In Example 1, a mixed sol of zirconia and silica is used, and the mixing ratio is 2:1 by volume. In Comparative Example 2, only silica sol is used, and the others are the same as in Example 1; The prepared lightweight heat-insulating material has the following properties: (1) The density of the prepared heat-insulating material is 0.68 g / cm 3 , the tensile strength of the panel is 58 MPa, and the bending strength of the panel is 41 MPa; (2) A 1-hour single-sided radiation heating test with a quartz lamp at 1500 °C was carried out on the new lightweight heat-insulating material prepared in Comparative Example 2. After the test, the structure of the material was deformed and partial collapse occurred on the surface, indicating that the material system was damaged at 1500 °C; under the condition of oxy-liquefied petroleum gas flame at 1600 °C for 5 minutes of ablation, collapse occurred around the material, indicating that the material could not withstand high temperature of 1600 °C; (3) The thermal conductivity of the tested material is 0.056 W / m·k.

[0035] The results show that the materials prepared in Comparative Example 2 and Example 1 have similar mechanical properties, but the temperature resistance and heat insulation properties are much lower than those in Example 1. The scheme of Example 1 is superior to that of Comparative Example 2.

[0036] Comparative Example 3: Zirconia sol was prepared by the scheme of Example 1. The color of the sol is light blue or milky white, and it is mixed with silica sol for use. The mixing ratio is 8:1 by volume; Another gradient fiber preform was prepared. The preform is a silica fiber cotton felt, which has upper and lower surface layers and an intermediate core layer, and the materials are all silica fibers; the thickness of the upper surface layer is 2 mm - 5 mm; the thickness of the lower surface layer is 1 mm; the thickness of the above intermediate core layer is 20 mm; The difference between Comparative Example 3 and Example 1 lies in the different mixing ratio of zirconia sol and silica sol, and the others are the same as in Example 1; The prepared lightweight heat-insulating material has the following properties: (1) The zirconia sol is generally the same as that in Example 1; (2) The density of the prepared new lightweight heat-insulating material is 0.62 g / cm 3 , the tensile strength of the panel is 50 MPa, and the bending strength of the panel is 35 MPa; (3) A 1-hour single-sided radiation heating test with a quartz lamp at 1500 °C was carried out on the new lightweight heat-insulating material prepared in Comparative Example 3. After the test, the surface structure of the material was intact and there was no obvious damage, indicating that the material system could be used normally for a long time at 1500 °C; under the condition of oxy-liquefied petroleum gas flame at 1600 °C for 5 minutes of ablation, there was no obvious change, indicating that the material has strong oxidation resistance.

[0037] The results show that for the materials prepared in Comparative Example 3 and Example 1, although the density decreased, the mechanical properties also decreased, and the temperature resistance and heat insulation properties were similar to those of Example 1. Since the preparation cost of zirconia sol is higher than that of silica sol, using a larger proportion of zirconia sol not only increases the material preparation cost, but also reduces the material properties to some extent. Overall, the scheme of Example 1 is better after comprehensive comparison.

[0038] Results and Discussion: 1. Through the comprehensive comparison of the examples and comparative examples, it can be seen that adjusting the ratio of zirconia sol and silica sol within an appropriate range, or appropriately changing the thickness of the upper and lower surface layers and the middle core layer of the gradient fiber preform will not have a substantial impact on the final properties of the lightweight heat-insulating material. The prepared heat-insulating materials all have high mechanical properties and good ability to resist high temperatures.

[0039] 2. Through the comparison of the comparative examples and examples, it is found that when the mixed sol becomes a pure silica sol or the proportion of zirconia sol is greatly increased, the mechanical and temperature resistance properties of the obtained heat-insulating material will decrease to a certain extent or the cost will increase additionally; when the gradient fiber preform is changed to a split preform, the preparation cycle and cost of the material will increase significantly. Therefore, after comprehensive comparison of the material properties, the examples are the better schemes for the lightweight heat-insulating material, and Example 1 is the best.

[0040] 3. The preparation method of a novel lightweight heat-insulating material provided by the present invention can be used normally for a long time at 1500 °C, can be prepared rapidly, and has characteristics such as high temperature resistance and strong oxidation resistance.

[0041] In summary, a novel lightweight heat-insulating material prepared by the method of the present invention adopts a gradient structure, uses a silica fiber cotton felt with a porous structure as the middle core layer to obtain better heat insulation performance, uses a silica composite material as the upper and lower panels, the upper surface layer has a large thickness to undertake the heat protection task and resist the continuous high-temperature environment, the lower surface layer can be bonded to the cabin body during product application, and the thickness of the upper surface layer is designed to be greater than that of the lower surface layer. The combination of the middle core layer and the heat surface layer has good heat resistance and heat insulation effects, which can improve the overall heat-insulating performance.

[0042] In addition, a novel lightweight heat-resistant and heat-insulating material prepared by the present invention provides a ceramic composite material preform with controllable thickness and adjustable system, adopts a gradient distribution, effectively improves the bonding strength between layers, minimizes human factors, improves production efficiency and material stability. Shorten the entire research and development cycle and indirectly reduce the production cost.

[0043] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a novel lightweight heat-insulating material, characterized in that: The following steps are involved: S1. Preparation of zirconia sol: zirconia sol is prepared from zirconium-containing raw materials. The main component of the prepared zirconia sol is zirconium dioxide. The sol is light blue or milky white liquid with a concentration of 2%-8% and a density of 1.01g / cm 3 , viscosity ≤15mPa·s; The zirconium-containing raw material is selected from zirconium oxychloride, zirconium oxynitrate, zirconium tetrachloride, zirconium nitrate, zirconium sulfate, zirconium oxycarbonate, or a mixture of any proportions thereof; S2, using the zirconium oxide sol prepared in S1 and the silicon oxide sol, the volume ratio is ≤5:1, and the fiber preform is impregnated after mixing, the fiber preform has a gradient structure, the gradient fiber preform is a silicon oxide fiber cotton felt, which is divided into an upper and lower surface layer and a middle core layer, the fiber cotton felt is an integral structure, the upper and lower surface layers are a mixture of fiber cloth and fiber cotton, the middle core layer is composed entirely of fiber cotton, the thickness of the upper surface layer is 0.5mm-10.0mm, the thickness of the lower surface layer is 0.3mm-2.0mm, and the thickness of the middle core layer is 10m-30mm; S3. After the impregnation is completed, the obtained gradient fiber preform is subjected to high temperature treatment to obtain a new lightweight heat-insulating material with a thickness of 10mm-35mm and a density of 0.5g / cm 3 -0.8g / cm 3 , thermal conductivity is 0.047W / m·K; it has strong oxidation resistance, can withstand the burning of oxygen-liquefied petroleum gas flame at 1600℃, can withstand quartz lamp temperature ≥1500℃, and the heat resistance temperature of typical ballistic heating environment ≥1500℃.

2. The method for preparing a novel lightweight heat-insulating material according to claim 1, characterized in that: In step S1, alkali solution is used for adjustment in the process of preparing zirconium oxide sol, and the amount of alkali solution is higher than the amount of zirconium used, so that zirconium can be completely precipitated and separated; the alkali solution used is one or more of LiOH, NaOH, KOH or ammonia water, and the concentration of hydroxide in the alkali solution is 5%-20%, and the concentration of ammonia water is 15%-27%.

3. The method for preparing a novel lightweight heat-insulating material according to claim 1, characterized in that: In step S1, the acid used in the process of preparing the zirconium oxide sol is an inorganic strong acid, selected from one or more of hydrochloric acid, nitric acid, and sulfuric acid, with a concentration of 30%-60%; or acetic acid, oxalic acid, lactic acid, and tartaric acid are used.

4. The method for preparing a novel lightweight heat-insulating material according to claim 1, characterized in that: In step S1, during the process of preparing the zirconium oxide sol, the dissolution temperature of the zirconium-containing raw material is room temperature.

5. The method for preparing a novel lightweight heat-insulating material according to claim 1, characterized in that: In step S1, during the preparation of zirconium oxide sol, an yttrium compound needs to be added as a stabilizer.

6. The method for preparing a novel lightweight heat-insulating material according to claim 1, characterized in that: In step S2, the impregnation, wherein the impregnation liquid is a mixture of homemade zirconium oxide sol and silicon oxide sol, the sols are both acidic, the sols are uniform after mixing, the viscosity does not change, the mixing ratio is ≤5:1 by volume, and the impregnation method is vacuum impregnation; the impregnation also includes a curing step, the curing atmosphere is air, the curing temperature is 100°C-300°C, the curing time is 30min-120min, and a mold is used to fix the material shape during curing. Different molds are used according to different shapes of the materials. After the shape of the material is fixed, the mold is no longer used.

7. The method for preparing a novel lightweight heat-insulating material according to claim 1, characterized in that: In step S2, except for curing and high temperature treatment, all other steps are carried out at room temperature.

8. The method for preparing a novel lightweight heat-insulating material according to claim 1, characterized in that: In step S2, the gradient fiber preform is a silica fiber felt, and the proportion of each part is adjusted according to the use requirements, and the subsequent molding method is the same.

9. The method for preparing a novel lightweight heat-insulating material according to claim 1, characterized in that: In step S3, the high temperature treatment is carried out at a temperature of 600°C-1000°C, for a time of 30 min-120 min, in an air atmosphere.

10. A new type of lightweight heat-insulating material, characterized in that: According to the preparation method of a novel lightweight heat-insulating material according to any one of claims 1 to 9, the prepared novel lightweight heat-insulating material has a zirconium oxide sol preparation cycle of 20h-80h, a material molding cycle of 4d-8d, a thickness of 10mm-35mm, and a density of 0.5g / cm 3 -0.8g / cm 3 , thermal conductivity is 0.047 W / m·K; it has strong oxidation resistance, can withstand the burning of oxygen-liquefied petroleum gas flame at 1600℃, can withstand quartz lamp temperature ≥1500℃, and the heat resistance temperature of typical ballistic heating environment ≥1500℃.

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