Composite aerogel having a multiscale porous structure, method for producing the same, and seawater desalination apparatus

Abstract

To provide silicon-containing inorganic-organic composite aerogels having a reproducible multi-scale pore structure that is used in materials for converting and utilizing solar energy, and methods for preparing them.SOLUTION: Using silicon-containing nano-inorganic materials as a freezing motif, biomass polymers as a cross-linking agent, and deionized water as the solvent, these three are mixed uniformly, allowing the mixture to leave to solidify to form a hydrogel. The hydrogel is frozen to form a cryohydrate. Then, using freeze-drying technology, the cryohydrate is removed to form a micro-nano scale porous aerogel. Finally, using a pulsed laser technology, the resultant micro-nano scale aerogel is subjected to customized punching of milli-pores to finally obtain a milli-micro-nano multi-scale pore structure aerogel.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a composite aerogel having a multiscale porous structure composed of vertically oriented millipores and micro- and nanopores that are interconnected in three dimensions, a method for producing the same, and a seawater desalination apparatus using such a composite aerogel.

Background Art

[0002] As the consumption of non-renewable energy increases, converting energy using renewable energy has become an important future development trend. Solar energy is characterized by abundant resources, cleanliness, and no pollution. Replacing some of the consumption of fossil energy by utilizing and converting solar energy has important significance for environmental protection and sustainable development. Designing and developing lightweight, highly efficient, and mass-producible solar energy conversion and utilization materials is an important way to realize the practical application of solar energy.

[0003] Aerogel materials possess excellent characteristics such as low linear density, light weight, low thermal conductivity, large specific surface area, and high porosity, and are widely used in daily life and production. Aerogel materials are usually formed under supercritical drying or freeze-drying conditions and have a three-dimensional porous network skeletal structure. The pore structure characteristics are often influenced by both freeze motifs and crosslinking strength. Chemical crosslinking or physical crosslinking is commonly used to ensure the strength of aerogels. Chemical crosslinking means that monomers undergo polycondensation or copolymerization reactions under the action of a chemical crosslinking agent, forming covalent bonds and constructing a three-dimensional network structure. Physical crosslinking is a three-dimensional polymer network formed by crosslinking through physical forces such as hydrogen bonds, coordination bonds, van der Waals forces, and intermolecular entanglement. By selecting crosslinking agents with different characteristics, the pore structure and crosslinking strength of aerogels can be controlled to meet the needs of various usage environments. Polyvinyl alcohol is a versatile, water-soluble polymer with abundant hydroxyl groups, possessing good film-forming properties, thermal stability, adhesion, abrasion resistance, self-healing properties, and good mechanical strength. It also exhibits excellent biocompatibility, biodegradability, and non-toxicity, giving it unique advantages in the field of environmental protection. Agar, a polysaccharide substance with excellent biocompatibility, contains abundant carboxyl groups, dissolves at 90°C, and can be cured at room temperature, thus possessing excellent recyclability. Therefore, by selecting an appropriate crosslinking agent and utilizing multiple crosslinking mechanisms, the crosslinking strength of aerogels can be effectively improved.

[0004] Aerogel materials possess controllable pore structures and high porosity. When used in solar-powered water evaporation applications, they offer a significant light-absorbing surface area for sunlight absorption, as well as abundant pathways for water transport and vapor release. Therefore, aerogel materials have broad application potential in fields such as seawater desalination, wastewater treatment, and photothermal catalysts using solar-powered interfacial water evaporation. However, aerogels often have mesopores with internal pore diameters of 2-50 nm. While aerogels with single-pore structures have many limitations in water transport, light absorption, heat conduction, and energy utilization, aerogels with multi-scale pore structures offer a larger specific surface area for sunlight absorption and, simultaneously, can exhibit capillary action through controlled pore diameters, improving water supply rates. Furthermore, by constructing through-pore structures within the aerogel, a surface tension gradient can be formed by utilizing longitudinal salt concentration differences, thereby exhibiting the Marangoni effect, promoting salt ion movement, and enabling the design of aerogel materials with anti-salting-out functionality. By synergistically utilizing the light absorption and material exchange capabilities of multi-scale pore structures ranging from millimeters to micrometers and nanometers, aerogels offer a wider range of applications in environmental protection fields such as seawater desalination, wastewater treatment, and air purification. Therefore, to ensure structural properties while achieving multifunctionality, it is necessary to further control and optimize the pore size distribution and pore structure of aerogels.

[0005] Currently, relatively mature aerogels include polymer-based aerogels and biomass aerogels. However, such organic aerogels are flammable, severely limiting their pore formation technology and applications, and making it difficult to accurately control and optimize pore size. Reported methods for constructing multiscale pore structures typically use one or two pore formation methods in combination. For example, the method for preparing nitrogen-doped hierarchical pore graphene aerogel disclosed in Patent Document 1 (Chinese Patent Application Publication No. 109243849) uses CaCO3@polydopamine particles as a template and removes the CaCO3 by acid washing to form pores. However, this method requires the introduction of a template agent and subsequent removal of the template agent, making the process complex and failing to control the pore morphology and structure. Patent Document 2 (Chinese Patent Application Publication No. 110064347) discloses an inorganic nanofiber / organic polymer composite aerogel prepared by freeze-casting, which has a "layer-stack-layer" structure but can only provide micro-channels, and has certain limitations in terms of water and gas flux, and substance exchange and movement. Patent Document 3 (Chinese Patent Application Publication No. 113578282) discloses an emulsion template method for preparing aerogel materials, but this method has poor control performance over the pore size distribution and pore structure of the aerogel, and it is difficult to accurately control the number and distribution of various pore types. Therefore, the development of a technology that does not require a pore-forming agent template, is easy to use, can be prepared efficiently, and can accurately control the characteristics and distribution of the pore structure to prepare a multiscale pore structure aerogel with optimized pore size is of great significance for improving the evaporation efficiency of solar energy-driven water and expanding its range of application. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Chinese Patent Application Publication No. 109243849 Specification [Patent Document 2] Chinese Patent Application Publication No. 110064347 Specification [Patent Document 3] Chinese Patent Application Publication No. 113578282 Specification [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] To precisely control the properties and distribution of the pore structure of aerogels, the present invention provides a pulsed laser-based multiscale pore aerogel that not only simultaneously possesses pore diameters of three scales—millimeter, micrometer, and nanometer—but also does not require a pore-forming agent template during preparation. [Means for solving the problem]

[0008] The present invention also provides a method for preparing and using this aerogel.

[0009] To achieve the above objectives, the overall concept of the technical solutions employed by the present invention is as follows. First, utilizing the advantages of silicon-containing nanoinorganic materials such as high melting point, excellent high-temperature stability, and high-temperature oxidation resistance, polyvinyl alcohol, agar, and glutaraldehyde are used as crosslinking agents, and a silicon-containing nanoinorganic-organic composite porous double-mesh aerogel is prepared by synergistically utilizing physical and chemical crosslinking mechanisms such as hydrogen bonding and polycondensation reactions. This aerogel not only ensures the mechanical properties of the aerogel by utilizing the strength and toughness of the polymer material, but also improves the hardness and flame retardancy of the polyvinyl alcohol / agar aerogel by utilizing the properties of the inorganic material, and provides processing versatility based on its enhanced ablation resistance. Next, after preparing the flame-retardant silicon-containing nanoinorganic-organic aerogel, pulse laser technology with high pulse energy and high processing efficiency is used to make the process simple and highly efficient, allowing for precise control of the number and distribution of millimeter pores, and customizable pore patterns.

[0010] The specific technical solution is as follows: A multiscale pore structure aerogel based on pulsed lasers, in which silicon-containing nano-inorganic material is used as a freezing motif, biomass polymer as a crosslinking agent, and deionized water as a solvent. These three are uniformly mixed and allowed to stand to solidify, forming a silicon-containing inorganic-organic composite hydrogel. This is then frozen to form ice crystals, and subsequently freeze-drying is used to remove the ice crystals and form a micro- and nanoscale silicon-containing inorganic-organic composite aerogel. Finally, pulsed laser technology is used to perform customized millimeter-sized pore punching on the obtained micro- and nanoscale silicon-containing inorganic-organic composite aerogel. By utilizing the high speed, high energy, and designable punching pattern characteristics of the laser, the pore diameter, pore shape, and number of millimeter-sized pores in the aerogel can be designed, resulting in a milli-, micro-, and nanoscale multiscale pore silicon-containing inorganic-organic composite aerogel with a controllable process that can meet the needs of multiple scenes and complex usage environments.

[0011] Furthermore, the silicon-containing nanoinorganic material includes, but is not limited to, MoSi2, SiO2, Si3N4, and the like.

[0012] Furthermore, the crosslinking agent comprises at least polyvinyl alcohol, agar, and glutaraldehyde.

[0013] The following provides a method for preparing aerogels with a multiscale pore structure based on the pulsed laser described above, comprising steps 1 to 3. Step 1: Preparation of silicon-containing inorganic-organic composite hydrogel First, polyvinyl alcohol and agar are weighed, deionized water is added and heated to dissolve the two powders and obtain a homogeneous solution. Then, glutaraldehyde solution is added to the solution to crosslink it, and silicon-containing nano-inorganic powder is added to the crosslinked solution to obtain a homogeneous silicon-containing inorganic-organic composite sol. After the silicon-containing inorganic-organic composite sol is allowed to stand and solidify, a silicon-containing inorganic-organic hydrogel with a certain toughness is formed. Furthermore, the concentration of polyvinyl alcohol in the silicon-containing inorganic-organic composite sol system is 1-4 wt%, the concentration of agar in the silicon-containing inorganic-organic composite sol system is 1-2 wt%, and the concentration of silicon-containing nanoinorganic powder in the silicon-containing inorganic-organic composite sol system is 0.02-1 wt%. Furthermore, the concentration of the glutaraldehyde solution is 50 wt%. Step 2: Preparation of micro- and nanoscale silicon-containing inorganic-organic composite aerogels After freezing the silicon-containing inorganic-organic composite hydrogel obtained in Step 1 to obtain ice crystals, vacuum freeze-drying is performed to obtain a micro--nanoscale silicon-containing inorganic-organic composite aerogel. Furthermore, the freezing temperature range of silicon-containing inorganic-organic composite hydrogels is -30 to -80°C, with pore sizes decreasing as the freezing temperature decreases and increasing as the temperature increases. Step 3: Synthesis of silicon-containing inorganic-organic composite aerogels with multiscale pores at the millimeter, micrometer, and nanometer scales. Using pulsed laser processing technology, the obtained micro- and nanoscale silicon-containing inorganic-organic composite aerogel was subjected to a structure treatment of millipores, and the specific treatment method is as follows: The pulse laser frequency is set to 20, pulse width to 5000, scanning speed to 50-150 mm / s, laser power to 3-8%, and laser spot to 1 mm. The shape of the millipores is designed, and matrix punching programming is performed. Subsequently, the laser light source punches millipores from top to bottom into the micro- and nanoscale silicon-containing inorganic-organic composite aerogel. Utilizing the high efficiency, high speed, high energy, and designable punching pattern characteristics of the laser, the pore diameter, pore shape, and number of millipores in the aerogel are designed to obtain a milli-, micro-, and nanoscale multiscale pore silicon-containing inorganic-organic composite aerogel with vertically oriented millipore shapes and adjustable porosity. In principle, the pore diameter of the millipores is controlled and unrestricted by self-programming, and the number of millipores is determined by the pore density and the area of ​​the aerogel, also controlled and unrestricted by self-programming. The porosity may be greater than 98%.

[0014] Furthermore, the shape of the millipores includes, but is not limited to, square, circular, and polygonal shapes, and the distribution pattern of the millipores is not limited.

[0015] The pulsed laser-based multiscale pore structure aerogel of the present invention can be used for solar energy-driven seawater desalination. The method of use involves assembling an evaporator by combining the aerogel with polystyrene foam and absorbent fiber paper. The silicon-containing inorganic-organic composite aerogel absorbs and converts solar energy to evaporate seawater and obtain fresh water, the polystyrene foam acts as an insulating layer for thermal management and suppresses heat conduction loss during the photothermal evaporation process, and the hydrophilic fiber paper transports seawater by capillary force.

[0016] The method for testing the seawater desalination rate of an evaporator involves placing the evaporator on an analytical balance, irradiating it with a simulated xenon lamp light source, continuously recording the mass change of the evaporator at different times through a computer connected to the balance, monitoring the mass loss, and calculating the evaporation rate. [Effects of the Invention]

[0017] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects. (1) The present invention uses polyvinyl alcohol, agar, and glutaraldehyde as crosslinking agents. Polyvinyl alcohol has a large number of hydroxyl functional groups on its molecular chain, and agar contains a large number of carboxyl functional groups. The hydroxyl groups and carboxyl groups form hydrogen bonds between the molecular chains to form a physical crosslinking network, and the carboxyl groups and aldehyde groups also undergo polycondensation reactions to form covalent bonds, forming a chemical crosslinking network. The double network structure can not only form a stable three-dimensional porous structure during freeze-drying, but also further improve the strength of the aerogel. These properties not only help to ensure the macroformability of the aerogel and avoid volume shrinkage, but also increase the compressive strength, improve the swelling resistance, and achieve excellent mechanical properties. (2) By preparing an inorganic-organic composite aerogel, the present invention improves the flame retardancy of the aerogel by adding a silicon-containing inorganic nanomaterial and endows it with pulse laser processing properties. Compared with the prior art, for the first time, pulse laser shock is used to perform customized optimization and control of millimeter-scale pores on the aerogel. It is not limited by the size and shape of the template, and a variety of designs of millimeter pores can be realized with only simple programming. The method is simple, the process is stable, the reproducibility is good, it is convenient and efficient, the cost is low, it is environmentally friendly and pollution-free, the control range of the pore structure is wide, and an accurate structural matching design can be carried out according to different usage usage scenes scenes. It has good commercial application prospects in multiple fields and the potential for large-scale popularization and application. (3) The present invention combines multi-component materials and combines a clever multi-scale pore structure design to obtain a silicon-containing inorganic-organic composite aerogel with a multi-scale pore structure of milli-micro-nano that has both vertical orientation and three-dimensional connectivity, optimizes the pore size distribution, increases the specific surface area, improves its anti-swelling property, and improves the water transport performance, mass exchange efficiency and self-cleaning function. It has a good evaporation rate in the field of solar energy-driven seawater desalination and shows prospects for application in the field of solar energy conversion and utilization, including but not limited to fields such as seawater desalination and sewage treatment.

Brief Description of the Drawings

[0018] In order to more clearly explain the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly described below. The drawings described below are only a part of the embodiments of the present invention. A person skilled in the art can obtain other drawings based on these drawings without creative labor.

[0019] [Figure 1] It is a schematic diagram of the preparation process of the MoSi2 aerogel with a multi-scale pore structure of milli-micro-nano of the present invention. [Figure 2] It is a macroscopic photograph of the MoSi2 aerogel with a multi-scale pore structure of milli-micro-nano before and after pulsed laser punching in Examples 1 to 3 of the present invention. [Figure 3] It is a SEM diagram of the MoSi2 aerogel with a multi-scale pore structure in Example 1 of the present invention, which is composed of four photos a, b, c, and d. Photo a represents the micro-nano scale pore structure on the surface of the MoSi2 aerogel, photo b represents the microscopic structure in the channel of the milli-scale pores after laser punching of the MoSi2 aerogel, photo c represents the internal pore structure of the original MoSi2 aerogel, and photo d is an enlarged view of the microscopic structure in the channel of the milli-scale pores of the MoSi2 aerogel. [Figure 4]This shows the density diagrams of the original MoSi2 aerogel of the present invention and the multiscale pore structure MoSi2 aerogels synthesized in Examples 1-3. [Figure 5] This figure shows the swelling performance of the original MoSi2 aerogel of the present invention and the multiscale pore structure MoSi2 aerogels synthesized in Examples 1-3. [Figure 6a] This is a diagram showing the actual flame retardancy test of the aerogel before the addition of the MoSi2 nanomaterial of the present invention. [Figure 6b] This is a diagram showing the actual flame retardancy test of an aerogel after the addition of the MoSi2 nanomaterial of the present invention. [Figure 7a] This diagram shows the mass loss and evaporation rate of the original MoSi2 aerogel of the present invention at 1x solar intensity within 60 min of multiscale pores. [Figure 7b] These are diagrams showing the mass loss and evaporation rate of multiscale pore MoSi2 aerogels of Examples 1-3 of the present invention at 1x solar intensity over 60 minutes. [Figure 8] These are actual diagrams showing the time-dependent self-dissolution of salts in the original MoSi2 aerogel of the present invention and the multiscale pore MoSi2 aerogels of Examples 1-3. [Modes for carrying out the invention]

[0020] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings, so that the advantages and features of the present invention may be easily understood by those skilled in the art, and the scope of protection of the present invention may be more clearly defined.

[0021] It should be explained that the original MoSi2 aerogel described in this invention refers to a micro- to nanoscale MoSi2 aerogel that has not undergone laser punching.

[0022] Example 1 Example 1 illustrates the preparation method and use of the milli-micro-nanometer multiscale pore structure of the present invention, with reference to Figure 1, using the preparation of a MoSi2 aerogel with a macroscopic pore matrix of 5 × 5 circular pores as an example, and includes the following steps 1 to 3. Step 1: Preparation of MoSi2 hydrogel First, 2 wt% agar and 1 wt% polyvinyl alcohol powder were weighed and placed in a beaker. 100 ml of deionized water was added, and the mixture was heated to 90°C. Magnetic stirring was maintained for 1 hour to dissolve the two powders and obtain a homogeneous solution. Next, 100 μl of 50 wt% glutaraldehyde solution was added to the solution, and stirring was continued for 10 minutes. Subsequently, 0.02 wt% MoSi2 powder was weighed and slowly added to the above solution, and magnetic stirring was continued until a homogeneous black solution was obtained. The black solution obtained above was poured into a prefabricated mold measuring 100 x 100 x 10 mm, and after standing for 5 minutes, the solution solidified, forming a MoSi2 hydrogel with a certain degree of toughness. Step 2: Preparation of MoSi2 aerogel with micro- and nanoscale pore structures The MoSi2 hydrogel obtained in Step 1 was placed in a refrigerator at -80°C and frozen for 24 hours to allow ice crystals to condense. Subsequently, the frozen gel was removed and vacuum-dried in a freeze-dryer at -80°C for 48 hours before being removed to obtain a MoSi2 aerogel with a micro--nanoscale pore structure. Step 3: Synthesis of multiscale pore MoSi2 aerogels ranging from millimeters to micrometers and nanometers. In Step 2, the aerogel was cut to obtain a 30 × 30 mm square aerogel. A customized punching process with millipore patterns was performed on the obtained micro- and nanoscale MoSi2 aerogel using a pulsed laser. The pulse laser frequency was set to 20, the pulse width to 5000, the speed to 100 mm / s, and the laser power to 8%. The pore shape was set to a circle with a diameter of 1 mm, and the pore spacing was set to program a 5 × 5 matrix circular pore pattern. The laser was then activated, and the laser light source punched millipores into the MoSi2 aerogel from top to bottom. After approximately 30 seconds, when the laser punching was complete, a multiscale pore MoSi2 aerogel with milli- and nanoscale pores, including a P5 × 5 pattern as shown in Figure 2 and vertically oriented through-holes as shown in Figure 3, was obtained. (5) Use of photothermal seawater desalination After testing, the water evaporation rate of the P5×5 multiscale pore MoSi2 aerogel of Example 1 was 1.39 kg·m³. -2 ·h -1 That was the case.

[0023] Example 2 Example 2 uses the preparation of a MoSi2 aerogel with a 6x6 circular pore matrix as an example. The preparation method is basically the same as in Example 1, the only difference being that, in order to verify the adjustability of the millimeter pore mesh count of the aerogel in the present invention under conditions that ensure the macroscopic shape does not collapse, the programming design for a 5x5 matrix circular pore in step 3 of Example 1 is changed to programming for a 6x6 matrix circular pore. Other parameters of the pulsed laser and operating steps remain unchanged, and a multiscale pore aerogel with a P6x6 millimeter pore mesh count as shown in Figure 2 was obtained. After testing, the water evaporation rate of the P6×6 multiscale pore MoSi2 aerogel in Example 2 was 1.26 kg·m³. -2 ·h -1 That was the case.

[0024] Example 3 Example 3 uses the preparation of a MoSi2 aerogel with a macroscopic pore matrix of 7 × 7 square pores as an example. The preparation method is basically the same as in Example 1, the only difference being that, in order to verify that the milliscale pore pattern of the aerogel in the present invention can be precisely customized, the programming design for a 5 × 5 matrix of circular pores in step 3 of Example 1 is changed to a programming design for a 7 × 7 matrix of square pores. Other parameters of the pulsed laser and operating steps remain unchanged, and a multiscale pore aerogel with a mesh count of P7 × 7 millimeters, as shown in Figure 2, was obtained. After testing, the water evaporation rate of the P7×7 multiscale pore MoSi2 aerogel of Example 3 was 1.13 kg·m³. -2 ·h -1 That was the case. Figure 2 shows macroscopic images of multi-scale pore structure MoSi2 aerogels with millimeter-micrometer-nanometer pores before and after pulsed laser punching in Examples 1-3 of the present invention. As can be seen from the figure, the MoSi2 aerogels prepared according to the present invention have good macroscopic moldability, no cracks or obvious shrinkage deformation on the surface, and good cutting properties. After pulsed laser punching, the aerogels do not undergo fracture phenomena such as ablation or structural collapse. As the mesh count of the millimeter pores increases and the pore shape changes, the aerogels still retain the characteristics of a stable macroscopic structure, enabling advantages such as customized processing of the millimeter pore pattern, adjustability of the mesh count, and controllability of the pore size distribution. When the multi-scale pore structure MoSi2 aerogels are immersed in water, the surface turns black, which is due to the removal of gel. However, since no collapse phenomenon occurs in the pore shape and no fracture occurs in the macroscopic shape of the aerogel, it has been proven that the multi-scale pore structure aerogels retain excellent strength and toughness. Figure 3 is an SEM image of a multiscale pore structure MoSi2 aerogel in Example 1 of the present invention. From photograph a in the figure, it can be seen that the surface of the MoSi2 aerogel that was not laser punched has an elliptical micropore structure, and that a large number of nanopores are uniformly distributed in the network framework. From photograph b in the figure, it can be seen that after pulsed laser processing, the pore framework of the through-holes carbonizes at high temperature, the surface turns black, the cross-linking bonds are broken, and a layered microscopic structure is formed. Photograph d in the figure is a local magnified view of photograph b, and as can be seen from the figure, there are wrinkles on the surface of the pore framework after fracture, and it has a gap structure assembled layer by layer. Photograph c in the figure is the internal pore structure of the MoSi2 aerogel that was not laser punched, and as can be seen from the figure, the aerogel framework has grown significantly and has through-holes in one direction. Figure 4 shows the density diagrams of the original MoSi2 aerogel of the present invention and the multiscale pore MoSi2 aerogels of Examples 1-3. Their densities are 0.039, 0.036, 0.034, and 0.033 g / cm³, respectively. 3As can be seen from the figure, the density of the aerogel gradually decreases as the number of millimeter-sized pores increases, but the difference is small, indicating that laser punching has little effect on the quality of the aerogel. Figure 5 shows the swelling rates of the original MoSi2 aerogel of the present invention and the multiscale pore MoSi2 aerogels of Examples 1-3. The swelling rates were 17.3%, 18.8%, 19.3%, and 21.4%, respectively. As can be seen from the figure, the swelling rate gradually increased with increasing millimeter pore mesh of the aerogel, demonstrating that the water absorption capacity of the aerogel was enhanced and the water saturation level increased. The reason for this is that, compared to the original MoSi2 aerogel with a large degree of crosslinking, the presence of millimeter pores provides more penetration pathways to the aqueous solution, and the breakage of crosslinking bonds reduces the penetration resistance of the aqueous solution, thus promoting the absorption of more water in the multiscale pore structure aerogel with more millimeter pores in the same amount of time. Figures 6a and 6b are actual diagrams of flame retardancy tests of aerogels before and after the addition of the MoSi2 nanomaterial of the present invention. As can be seen from the figures, before the addition of the MoSi2 nanomaterial, the polyvinyl alcohol / agar aerogel continued to burn within 14 seconds. However, the polyvinyl alcohol / agar / MoSi2 aerogel self-stopped burning after 14 seconds, demonstrating that the flame retardancy of the aerogel was improved by the addition of the MoSi2 nanomaterial. This is because MoSi2 has high-temperature stability, functions as an insulator, forms a good physical barrier during the combustion process, and can effectively prevent adjacent parts from continuing to burn. Figures 7a and 7b show the mass loss and evaporation rate diagrams for the original MoSi2 aerogel of the present invention and the multiscale pore MoSi2 aerogels of Examples 1-3 at 1x solar intensity over 60 minutes, respectively. As can be seen from the mass loss diagram in Figure 7a and the evaporation rate diagram in Figure 7b, the original MoSi2 aerogel maintained a fast mass loss within the first 30 minutes of evaporation, but the mass loss clearly slowed down within 30-60 minutes. This is because the high degree of crosslinking in the original MoSi2 aerogel slowed down water supply, and the water supply rate could not keep up with the evaporation rate. However, when the number of milliscale through-pores increased to P5×5, the evaporation rate increased significantly because the water supply rate became faster. When the number of milliscale through-pores increased further, the evaporation rate decreased. This is because the increase in the mesh number of milliscale pores leads to a decrease in the light absorption area. As can be seen from the above, by controlling the appropriate number of millimeter pores and minimizing area loss while ensuring improved water supply rate and water supply capacity, the solar energy evaporation performance of multiscale pore structure MoSi2 aerogel can be effectively improved. Figure 8 shows the actual self-dissolution of salt in the original MoSi2 aerogel of the present invention and the multiscale pore MoSi2 aerogels of Examples 1-3. As can be seen from the figure, when salts are deposited on the surface of aerogels with different concentrations, the salt dissolution efficiency over time is in the order of P7×7 > P6×6 > P5×5 > original MoSi2 aerogel. Compared to the original micro-nano structure aerogel, the increase in the number of millipores improves the internal mass transport efficiency of the MoSi2 aerogel, imparts a self-cleaning function, and further demonstrates the necessity of designing and constructing milli-micro-nano multiscale pore structure aerogels.

[0025] The above are merely specific embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be conceived without requiring creative effort should also be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A composite aerogel having a multiscale porous structure consisting of a silicon-containing inorganic gel, polyvinyl alcohol, agar, and glutaraldehyde, A composite aerogel having a multiscale porous structure in which multiple millimeter-scale pores formed by a pulsed laser are arranged in a mesh-like pattern at predetermined intervals in the vertical direction.

2. Micropores are formed on the surface, and nanopores are distributed in a network structure inside, forming a layered structure. A composite aerogel having a multiscale porous structure according to claim 1, wherein the network framework of nanopores exposed on the walls of millimeter-scale pores is carbonized by a pulsed laser, thereby breaking the crosslinking bonds.

3. Density is 0.033 g / cm³ ３ From 0.039 g / cm³ ３ A composite aerogel having a multiscale porous structure as described in claim 1.

4. A step of mixing silicon-containing nano-inorganic gel material, polyvinyl alcohol, agar, and a crosslinking agent consisting of glutaraldehyde and deionized water as a solvent, The process involves allowing these mixtures to stand and solidify to form a silicon-containing inorganic-organic composite hydrogel, The process involves freezing the hydrogel to form ice crystals, removing the ice crystals using freeze-drying technology, and creating a micro- to nanoscale silicon-containing inorganic-organic composite gel. The process involves forming multiple millimeter-scale pores in a mesh-like structure at predetermined intervals in the vertical direction on the micro- to nanoscale silicon-containing inorganic-organic composite gel obtained in the above process, using pulsed laser technology. A method for producing a composite aerogel having a multiscale porous structure.

5. The step of forming the silicon-containing inorganic-organic composite hydrogel is as follows: A method for producing a composite aerogel having a multiscale porous structure according to claim 4, characterized in that polyvinyl alcohol powder and agar powder are heated with deionized water to obtain a solution of the two powders, glutaraldehyde solution is added to the solution to cause crosslinking, and silicon-containing nanoinorganic powder is added to the crosslinking solution to obtain the silicon-containing inorganic-organic composite sol.

6. The method for producing a composite aerogel having a multiscale porous structure according to claim 5, characterized in that the concentration of the polyvinyl alcohol is 1 to 4 wt%, the concentration of the agar is 1 to 2 wt%, and the concentration of the silicon-containing nanoinorganic powder is 0.02 to 1 wt%.

7. A solar-powered seawater desalination apparatus using a composite aerogel having a multiscale porous structure as described in any one of claims 1 to 3, as a seawater absorption and evaporation gel.

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