Carbon aerogel-tantalum pentoxide interface evaporation composite, preparation method and application thereof

Abstract

The application discloses a carbon aerogel-tantalum pentoxide interface evaporation composite material, a preparation method and application thereof, relates to the technical field of carbon aerogel, and first synthesizes an alkali catalyzed phenolic resin sol, after the fluidity of the sol is reduced, under the action of ultrasonic waves, a photocatalyst Ta2O5 is added to make it fully dispersed, then the sol-gel process is completed through acid catalysis and heat treatment to obtain a phenolic resin-Ta2O5 wet gel, secondly, the wet gel is aged, washed and replaced, and dried at normal pressure to obtain a phenolic resin-Ta2O5 organic composite aerogel, and finally, the organic composite aerogel is carbonized at high temperature. The carbon aerogel-tantalum pentoxide interface evaporation composite material prepared by the application has the advantages of complete structure, no cracking, no powder and slag falling, good heat insulation performance, simple preparation process, low raw material cost, low toxicity, low requirement for heat treatment equipment and molds, short preparation period, high safety degree in the production process, and is expected to be applied to industrialized large-scale production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon aerogel, in particular to a carbon aerogel-tantalum pentoxide interface evaporation composite material, a preparation method and applications thereof. BACKGROUND

[0002] The carbon aerogel has a micro-pore structure of nanometer scale of traditional aerogel materials, and has high broadband absorption, high efficient light-heat conversion rate, excellent thermal stability, heat insulation and heat preservation performance and hydrophilicity. After being combined with Ta2O5, the band structure can be converted from direct to indirect, which promotes the non-radiative transition of electron generation and improves the light-heat conversion efficiency. The carbon aerogel is an ideal material for forming a local thermal effect of an absorption light-heat conversion layer and an insulation layer of a core component of a solar seawater evaporation system, and has high hydrophilicity and high open pore structure, which can provide water for a heat accumulation core part, and greatly improve the water evaporation efficiency. However, the carbon aerogel prepared by a traditional preparation method has high cost, low strength and is easy to break, and it is difficult to prepare a large volume, non-cracking and complete sample, and the raw materials and solvents used are easy to produce a large amount of volatile toxic gases, and it is difficult to realize large-scale engineering production and application. Therefore, it is urgent to explore a new preparation method to solve the defects of the carbon aerogel, such as easy to break, large shrinkage rate, difficult to prepare a large volume, non-cracking and complete sample, and to realize low-cost, safe and rapid preparation of a large volume of carbon aerogel light-heat conversion material with high mechanical properties and wide application.

[0003] Jian Li et al. (Fabrication of Large Aerogel-Like Carbon / Carbon Composites with Excellent LoadBearing Capacity and Thermal-Insulating Performance at 1800℃) introduces a preparation method of large aerogel-like carbon / carbon composite material with excellent load-bearing performance and thermal-insulating performance. Phenol formaldehyde resin and hexamethylenetetramine are used as reaction precursors and crosslinking agents, respectively, and a large composite material with aerogel-like carbon matrix and low crystallinity fiber reinforcement is prepared by high-pressure assisted polymerization combined with environmental pressure drying technology. The preparation method has wide adaptability, and the raw materials are easy to obtain. However, there are many problems in application. On the one hand, the interface between the fiber and the aerogel is easy to crack, and the phenomena of "interface peeling" and "serious slagging and powdering" are easy to occur under pressure. And the composite fiber process is only a simple physical composite, the interface is physically combined, which is not conducive to the improvement of high-temperature resistance and the increase of solid thermal conductivity in the composite aerogel to improve the thermal conductivity. On the other hand, it needs to use high-temperature and high-pressure assisted polymerization method which requires high equipment and instruments, so that the preparation cost is greatly increased, which is not conducive to industrialized low-cost production.

[0004] The Chinese invention patent with publication number CN108609606B discloses a preparation method of carbon aerogel thermal insulation material. The invention uses sol-gel process, acid-base two-step method, and high-pressure environment provided by pre-charged nitrogen or argon protective gas to prepare organic gel by solvent thermal process, and then carbonizes to obtain carbon aerogel. The invention has the characteristics of wide adaptability, easy-to-obtain raw materials, and high sample strength, and solves the problems of easy breaking and cracking of samples dried at normal pressure. However, the carbon aerogel prepared by the invention has high density, low porosity and low thermal conductivity, and needs to be treated at high temperature and high pressure with pre-charged nitrogen or argon. The volume of the prepared sample is limited by the volume of the autoclave, and the equipment for high-temperature and high-pressure production has high requirements. The production process is complicated, the risk coefficient is large, and the cost is high. SUMMARY

[0005] The purpose of the present application is to overcome the problems of the prior art, and to provide a large-size carbon aerogel-tantalum pentoxide (Ta2O5) interface evaporation composite material with good heat accumulation effect, high porosity, excellent light-heat conversion efficiency, good mechanical properties, no cracking, fast preparation speed and low cost, a preparation method thereof and applications thereof.

[0006] To achieve the above-mentioned purpose, the present application provides the following solutions:

[0007] Technical solution one:

[0008] A preparation method of a carbon aerogel-Ta2O5 interface evaporation composite material, comprising the following steps:

[0009] 1) Synthesis of base-catalyzed phenolic resin sol: mix phenolic organic matter and aldehyde organic matter raw materials, stir at a speed of 15-25 r / min at 50-80°C until completely soluble, accelerate the stirring speed to 30-50 r / min, add solvent and basic catalyst, stir until completely dissolved, continue to stir in a sealed state, perform base catalysis until a brown-yellow solution is formed, and mark it as sol A;

[0010] 2) Synthesis of composite phenolic resin sol: add photocatalyst Ta2O5 to the sol A, after compounding, coordinate with carbon atoms to enable the band structure to be converted from direct to indirect, promote non-radiative transition of electron generation to improve photo-thermal conversion efficiency, ultrasonic, form a uniformly dispersed composite phenolic resin sol, mark it as sol B;

[0011] 3) Synthesis of acid-catalyzed gel phenolic resin sol: keep the sol B at 50-80°C, accelerate the stirring speed to 40-60 r / min (accelerate the stirring speed to prevent local acid concentration from being too large when the acid catalyst solution is added, so that the organic raw material molecules locally rapidly condense to cause serious phase separation), add solvent to it, and dropwise add acid catalyst solution, continue to stir in a sealed state until a dark green solution is formed, mark it as sol C;

[0012] 4) Polymerization heat treatment: seal the sol C, keep the gel at 60-84°C, form a dark brown gel after 6.5-8 hours, then add a protective liquid to seal; continue to seal and age after liquid sealing, and form a phenolic resin-Ta2O5 wet gel;

[0013] 5) Normal pressure drying pretreatment: replace the solvent of the phenolic resin-Ta2O5 wet gel by washing and replacing multiple times, each time for 4 hours, and keep it in an environment at 60-84°C;

[0014] 6) Normal pressure drying: perform gradient temperature drying of the wet gel obtained in step 5) at 40°C, 60°C and 80°C until the weight does not change, and obtain a phenolic resin-Ta2O5 aerogel;

[0015] 7) High-temperature carbonization: carbonize the phenolic resin-Ta2O5 aerogel obtained in step 6), fill N2 inert gas protection gas during the carbonization process, first increase the temperature from room temperature to 300°C at a speed of 2-4°C / min, then increase the temperature to 800-900°C within 125-180 min, keep it for 120-300 min, cool it to room temperature after the carbonization is completed, and obtain an intact and non-cracked carbon aerogel-Ta2O5 interface evaporation composite material.

[0016] Further, the molar ratio of the phenolic organic matter, the aldehyde organic matter, the solvent and the basic catalyst in step 1) is 1:2:5-15:(0.09-0.15).

[0017] Further, the phenolic organic matter in step 1) is resorcinol, and the aldehyde organic matter is furfural; the solvent is methanol, ethanol or tert-butanol; and the basic catalyst is hexamethylenetetramine (HMTA), wherein the resorcinol and the furfural can generate a nanoparticle phenolic resin monomer sol under the catalysis of the HMTA, and a small amount of solvent (such as methanol, anhydrous ethanol or tert-butanol) is added to dilute the sol.

[0018] Further, the reaction time in step 1) is 30-60 min, which can prevent the sol A from being solidified or forming a dense solid phenolic resin when the reaction time is too long. If the reaction time is too short, the catalysis by the base is insufficient, and too many organic raw material molecules are left, which causes the subsequent acid catalysis to form linear phenolic resin monomers with a nanometer network structure that is not easy to crosslink, and too many linear phenolic resin monomers cause slow gelation, poor mechanical properties after gelation, and easy powder falling and cracking.

[0019] Further, the amount of the photocatalyst added in step 2) is 0.6%-10.4% of the mass of the sol A.

[0020] Further, the molar ratio of the solvent and the acid catalyst solution in step 3) to the phenolic organic matter and the aldehyde organic matter in step 1) is 25-55:(1.5-3×10 -4 )∶1∶2.

[0021] Further, the solvent in step 3) is methanol, ethanol or tert-butanol; and the acid catalyst solution is an HCl-ethanol solution, an HCl-methanol solution or an HCl-tert-butanol solution, and the concentration is 0.1-0.3 mol / L. The raw materials are easy to obtain and low in price, and are non-toxic, which can reduce the preparation cost of the carbon aerogel and improve the production safety.

[0022] Further, the stirring time in step 3) is 5-15 min, so that the acid catalyst solution is fully mixed with the sol B.

[0023] Further, the protective liquid in step 4) is methanol, ethanol or tert-butanol, which can reduce the shrinkage of the sample during the heat treatment process, and prevent the sample from being damaged due to the incomplete growth and enhancement of the gel skeleton caused by excessive evaporation of the solvent and other factors.

[0024] Further, the aging time in step 4) is 16-48 h, which can ensure that the resorcinol and furfural are fully crosslinked under the catalyst; the aging temperature is 60-84 DEG C, which can ensure that the gel reaction process is stable below the boiling point of the solvent, and the formed gel skeleton is more rigid and has better mechanical properties; at the same time, 60-84 DEG C has low requirements for high-temperature equipment and sample molds, which can reduce the cost of industrial production equipment, and the preparation is safer at a lower temperature.

[0025] Further, the displacement solvent in step 5) is ethanol or n-heptane, and the displacement is washed 3-8 times. The surface tension of the solvent is prevented from being too large, so that the pore structure is collapsed during the normal pressure drying process, and the sample is shrunk too much and cracked. The n-heptane washing can remove excess reactants, acid and base catalysts and impurities, and the n-heptane after displacement can be reused by fractional distillation to reduce the production cost.

[0026] Further, the gradient temperature of each gradient in step 6) is kept for 3-8 h, and the gradient temperature is helpful for the solvent to volatilize from the outside to the inside in turn, which reduces the shrinkage rate of the sample. Each temperature gradient is kept for a period of time, so that the phenolic resin-Ta2O5 aerogel with complete block shape, large volume, no cracking and small shrinkage rate can be prepared.

[0027] Technical solution two:

[0028] A carbon aerogel-Ta2O5 interface evaporation composite material prepared by the preparation method.

[0029] Technical solution three:

[0030] The carbon aerogel-Ta2O5 interface evaporation composite material is used for preparing a local thermal core component of a seawater evaporation device, preferably for a light-heat conversion layer, an adiabatic layer and a water conveying layer of a solar seawater evaporation system.

[0031] The present application discloses the following technical effects:

[0032] 1. The present application selects low-cost resorcinol, lower toxicity of furfural compared with formaldehyde, selects methanol, ethanol, tert-butyl alcohol and 0.1-0.3 mol / L HCl-ethanol solution, HCl-methanol solution, HCl-tert-butyl alcohol solution, HMTA and Ta2O5, under acid-base catalytic conditions, through mild thermal reaction process crosslinking to form a nano-porous network gel skeleton structure. After compounding amorphous Ta2O5, the band structure can be changed from direct to indirect by coordination with carbon atoms, which promotes non-radiative transition of electron generation and improves light-heat conversion efficiency, and effectively enhances light absorption. At the same time, it has high hydrophilicity and high open porosity structure, which can provide water supplement for the polythermal core part, and the temperature gradient formed spontaneously promotes the transformation of water molecules from liquid phase to gas phase to improve the evaporation efficiency. Through simple aging, solvent washing replacement, normal pressure drying, carbonization and other processes, low-cost and rapid preparation of complete large-size block carbon aerogel high-efficiency light-heat conversion composite material is realized, which overcomes the defects of traditional carbon aerogel such as "powder falling", "cracking", "large shrinkage" and the like.

[0033] 2. The aging temperature is 60-84℃, which is below the boiling point of the solvent, so that the reaction process is stable and the reaction conditions are mild, which effectively strengthens the interface bonding between the primary particles to form a high-strength skeleton, and at the same time, high-temperature and high-pressure heat treatment process is not required, which reduces the requirements for heat treatment equipment. The size of the prepared sample is not limited by the autoclave and the tube furnace. The addition of protective liquid can prevent sample shrinkage due to incomplete growth of the skeleton and solvent evaporation. Washing with n-heptane and ethanol can remove excess impurities and volatile corrosive substances such as acid and base, reducing the corrosion of normal pressure drying equipment, and the waste liquid after washing and replacement can be reused by fractional distillation. This production process simplifies the production equipment and greatly reduces the cost of large-scale industrial production.

[0034] 3. The present application utilizes acid-base catalysis to prepare carbon aerogel, which combines "necked" structure and "pearl chain" staggered connection to construct a developed three-dimensional network structure. It solves the problem that linear phenolic resin monomer formed by simple acid catalysis is not easy to condense, and the nano-porous network has large shrinkage and is easy to form a dense structure, and at the same time, it also solves the problem that nano-particle phenolic resin monomer formed by simple base catalysis is crosslinked into a pearl chain structure nano-porous network structure, which leads to poor mechanical properties, easy powder falling, easy cracking during normal pressure drying, and low yield. By combining acid-base catalysis, reasonably controlling the amount of acid and base, and combining the advantages of good mechanical properties of linear phenolic resin and good pore-forming properties of granular phenolic resin, the prepared sample has good mechanical properties, good block formation, high porosity, small shrinkage, low thermal conductivity, good heat preservation performance and wide light waveband absorption range.

[0035] 4、The radial shrinkage rate of the composite aerogel prepared by the method is about 4-12% after normal pressure drying, and the radial shrinkage rate after carbonization is about 20-23%, and the density is 0.16-0.24 g / cm 3 ; under the condition of a high-diameter ratio of 1:1, the compression modulus can be up to 9.73 MPa, the thermal conductivity coefficient at room temperature is 0.0326-0.0627 W / (m·K), and the composite aerogel has good heat insulation performance. Under one solar light intensity, the evaporation rate of pure water can be up to 3.563 kg / (m 2 ·h), and stable evaporation and excellent cycle stability can be maintained under strong light and high salinity water.

[0036] 5、The raw materials are easy to obtain, low in price and low in toxicity, the preparation process is simple, the preparation conditions are mild, part of the solvent can be recycled, the equipment cost is low, and the method is safe, and compared with the prior art, the overall production cost is lower, the method can be applied to large-scale industrial production, and the bulk carbon aerogel composite material prepared by the method is not cracked and does not fall off, and has excellent performance, and can be widely applied to local thermal core components of seawater evaporation devices. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0038] Figure 1 Nitrogen adsorption-desorption curve (left) and pore size distribution curve (right) of the phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material of Example 1;

[0039] Figure 2 Scanning electron microscope (SEM) photograph of the phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material of Example 4;

[0040] Figure 3 Sample photograph of the phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material of Example 5;

[0041] Figure 4 Compression stress-strain diagram of the phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material of Example 9. DETAILED DESCRIPTION

[0042] Now, various exemplary embodiments of the present application will be described in detail, which should not be considered as limiting the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0043] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of, for example, concentrations, amounts, and so forth, is to be understood as specifically encompassing each and every value falling within the range. Additionally, a number of ranges with respect to a given value or a given range are intended to include each and every value falling within the range, as well as each and every subrange that can be formed using the values within the range.

[0044] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All patents, patent applications, and publications mentioned herein are incorporated by reference for the disclosure and description thereof to the extent that such incorporation does not conflict with the explicit teachings of this specification. In case of conflict, the present specification will control.

[0045] Various modifications and changes can be made to the specific embodiments of the present application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples herein. The description and examples are illustrative of the application and are not intended to limit the scope of the application in any way.

[0046] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having" and the like are open-ended terms that are intended to permit but not limit the inclusion of elements or the number of elements, and that do not on their own recite an exclusive list of elements that can be included.

[0047] Room temperature in the embodiments of the present application refers to 25±2℃, and normal pressure refers to 0.1 MPa (101325 Pa, one standard atmosphere).

[0048] Example 1

[0049] The preparation method of the high-efficiency photo-thermal conversion phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material is prepared by the following steps:

[0050] 1) Synthesis of base-catalyzed phenolic resin sol: add phenolic organic matter (resorcinol) and aldehyde organic matter (furfural) raw materials into a container, stir at 60℃ and a low speed of 20 r / min until the two are completely miscible, increase the stirring speed to 40 r / min, add methanol and HMTA until completely dissolved, continue to maintain the stirring state under a sealed condition for 30 min of base catalysis, and record as sol A. The mass ratio of resorcinol, furfural, methanol, and HMTA is 5.51 g: 9.16 g: 12 g: 0.65 g;

[0051] 2) Synthesis of composite phenolic resin sol: 0.3 g of photocatalyst Ta2O5 is added to sol A and dispersed uniformly in sol A by ultrasonic dispersion to form a uniformly dispersed composite phenolic resin sol, which is denoted as sol B.

[0052] 3) Synthesis of acid-catalyzed gel phenolic resin sol: sol B is kept at 60°C and the stirring speed is increased to 60 r / min, methanol is added, and 0.1 mol / L HCl-methanol solution is added dropwise, and the stirring is continued for 10 min under a sealed condition to form a dark green solution, which is denoted as sol C, and the obtained sol C can be used for molding. The mass ratio of resorcinol, furfural, methanol, and HCl-methanol solution is 5.51 g: 9.16 g: 56 g: 0.1 g;

[0053] 4) Polymerization heat treatment: sol C is placed in a sealed plastic box mold and kept at 64°C for gelation. After about 6.5-8 h of gelation, 15 g of protective liquid methanol is added for sealing. After sealing, the sealing is continued for 48 h to form a phenolic resin-Ta2O5 wet gel;

[0054] 5) Atmospheric pressure drying pretreatment: the phenolic resin-Ta2O5 wet gel obtained in step 4) is subjected to solvent replacement by replacing n-heptane three times, each time for 4 h, and kept at 64°C;

[0055] 6) Atmospheric pressure drying: the wet gel obtained in step 5) is placed in an oven at 40°C, 60°C, and 80°C for gradient temperature drying until the weight does not change. Each temperature gradient is kept for 3 h, and a complete block, large volume, non-cracking, and small shrinkage phenolic resin-Ta2O5 aerogel is prepared;

[0056] 7) High-temperature carbonization: the phenolic resin-Ta2O5 aerogel obtained in step 6) is placed in a well-type carbonization furnace, and N2 inert gas protection gas is filled, and the temperature is increased from room temperature to 300°C at a rate of 2°C / min, and then increased to 800°C at a rate of 125 min, and kept for 120 min. After carbonization, the temperature is cooled to room temperature, and a complete and non-cracking phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material is prepared.

[0057] The nitrogen adsorption and desorption curve (left) and the pore size distribution curve (right) of the phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material prepared in Example 1 are shown in Figure 1The nitrogen adsorption-desorption curve (left) shows that the carbon aerogel-Ta2O5 interface evaporation composite material has micropore, mesopore and macropore structure. There is a higher adsorption volume in the early stage of adsorption (P / P0<0.1), indicating the presence of more micropores. The adsorption isotherm rises gently at a low relative pressure (P / P0<0.9). The hysteresis curve between nitrogen adsorption and desorption indicates the presence of typical mesoporous structure. At a high relative pressure (P / P0>0.9), the adsorption isotherm becomes steep, there is a hysteresis ring and no saturated adsorption platform, which proves the existence of macropores. According to the classification of the International Union of Pure and Applied Chemistry on adsorption-desorption isotherm, the isotherm of carbon aerogel belongs to the typical type IV of IUPAC classification, H3 hysteresis ring. From the pore size distribution curve (right), it can be seen that the mesoporous and nanoscale macroporous structure of the sample is mainly concentrated in 20-100 nm, and such pore size is beneficial to the heat preservation effect of carbon aerogel. Figure 1

[0058] The radial shrinkage rate of the phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material prepared by the above method after drying at 0.1 MPa atmospheric pressure is 8.31%, and the radial shrinkage rate after carbonization is 20.83%. The volume density before carbonization is 0.181 g / cm 3 , and the volume density of the carbon aerogel-Ta2O5 composite material is 0.210 g / cm 3 ; under the condition of high-diameter ratio of 1:1, the compression modulus is 2.59 MPa, and the thermal conductivity tested by the transient hot wire method at room temperature is 0.0392 W / (m·K), which has good heat insulation and heat preservation performance; under the condition of one solar light intensity, the evaporation rate of pure water is 1.823 kg / (m 2 ·h).

[0059] Example 2

[0060] The preparation method of the high-efficiency light-heat conversion phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material is prepared by the following steps:

[0061] 1) Synthesis of base-catalyzed phenolic resin sol: add phenolic organic matter (resorcinol) and aldehyde organic matter (furfural) raw materials to a container, stir at 50°C and low speed of 25 r / min until the two are completely soluble, increase the stirring speed to 45 r / min, add methanol and HMTA until completely dissolved, continue to maintain the stirring state under a sealed condition, and base catalysis for 40 min, which is recorded as sol A. The mass ratio of resorcinol, furfural, methanol and HMTA is 2.75 g:4.58 g:6 g:0.42 g;

[0062] ​2) Synthesis of composite phenolic resin sol: 1.375 g of photocatalyst Ta2O5 is added to the sol A and dispersed uniformly in the sol A by ultrasonic dispersion to form a uniformly dispersed composite phenolic resin sol, which is denoted as sol B.

[0063] 3) Synthesis of acid-catalyzed gel phenolic resin sol: the stirring speed of the sol B is increased to 60 r / min at 50°C, methanol is added, and 0.3 mol / L HCl-methanol solution is added dropwise, and the stirring is continued for 5 min in a sealed state to form a dark green solution, which is denoted as sol C, and the solution can be poured into a mold. The mass ratio of resorcinol, furfural, methanol, and HCl-methanol solution is 2.75 g: 4.58 g: 28 g: 0.1 g;

[0064] 4) Polymerization heat treatment: the sol C is placed in a sealed plastic box mold to form a gel at 64°C for about 6.5-8 h, and then 8 g of protective liquid methanol is added for sealing; after the sealing, the sealing is continued for 24 h to form a phenolic resin-Ta2O5 wet gel;

[0065] 5) Normal pressure drying pretreatment: the phenolic resin-Ta2O5 wet gel obtained in step 4) is subjected to solvent replacement by replacing ethanol three times, each time for 4 h, and the replacement is carried out at 64°C;

[0066] 6) Normal pressure drying: the wet gel obtained in step 5) is placed in an oven at 40°C, 60°C, and 80°C for gradient temperature drying until the weight does not change. Each temperature gradient is maintained for 3 h, and a complete block-shaped, large-volume, non-cracked, and small-shrinkage phenolic resin-Ta2O5 aerogel is prepared;

[0067] 7) High-temperature carbonization: the phenolic resin-Ta2O5 aerogel obtained in step 6) is placed in a well-type carbonization furnace, N2 inert gas protection gas is filled, the temperature is increased from room temperature to 300°C at a rate of 2°C / min, and then increased to 800°C at a rate of 125 min and maintained for 120 min. After cooling to room temperature after carbonization, a complete and non-cracked phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material is prepared.

[0068] The radial shrinkage rate of the phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material prepared by the above method after normal pressure drying at 0.1 MPa is 6.56%, the radial shrinkage rate after carbonization is 20.88%, the volume density before carbonization is 0.169 g / cm 3 , and the volume density of the carbon aerogel-Ta2O5 composite material is 0.186 g / cm 3; under the condition of a height-diameter ratio of 1:1, a compression modulus of 1.83 MPa, and a thermal conductivity of 0.0373 W / (m·K) tested by a transient hot-wire method at room temperature, the material has good heat insulation performance; under the condition of one solar light intensity, the evaporation rate of pure water is 3.221 kg / (m 2 ·h).

[0069] Example 3

[0070] The preparation method of the high-efficiency photo-thermal conversion phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material is prepared by the following steps:

[0071] 1) Synthesis of base-catalyzed phenolic resin sol: add phenolic organic matter (resorcinol) and aldehyde organic matter (furfural) raw materials into a container, stir at 60°C and a low speed of 25 r / min until the two are completely miscible, increase the stirring speed to 45 r / min, add methanol and HMTA until completely dissolved, continue to maintain the stirring state under a sealed condition for 60 min of base catalysis, and mark as sol A. The mass ratio of resorcinol, furfural, methanol, and HMTA is 11.02 g: 18.32 g: 48 g: 0.42 g;

[0072] 2) Synthesis of composite phenolic resin sol: add 1.375 g of photocatalyst Ta2O5 to sol A, disperse it uniformly in sol A by ultrasonic dispersion, form a uniformly dispersed composite phenolic resin sol, mark as sol B.

[0073] 3) Synthesis of acid-catalyzed gel phenolic resin sol: keep the temperature at 60°C, increase the stirring speed of sol B to 60 r / min, add methanol, and drop 0.2 mol / L HCl-methanol solution dropwise, continue to maintain the stirring state under a sealed condition for 15 min to form a dark green solution, mark as sol C, and pour the mold. The mass ratio of resorcinol, furfural, methanol, and HCl-methanol solution is 11.02 g: 18.32 g: 170 g: 0.75 g;

[0074] 4) Polymerization heat treatment: place sol C in a sealed plastic box mold, keep the gel at 64°C, after about 6.5-8 h of gelation, add 30 g of protective liquid methanol for sealing; continue to seal for 48 h after liquid sealing to form a phenolic resin-Ta2O5 wet gel;

[0075] 5) Normal pressure drying pretreatment: replace the phenolic resin-Ta2O5 wet gel obtained in step 4) with n-heptane solvent by replacing 5 times, 4 h each time, and keep it in a 64°C environment;

[0076] 6) Ambient pressure drying: the wet gel obtained in step 5) is placed in an oven at 40℃, 60℃, 80℃ for gradient temperature drying until the weight does not change. Each temperature gradient is kept for 5h, so that the phenolic resin-Ta2O5 aerogel with complete block shape, large volume, no cracking, and small shrinkage rate can be prepared;

[0077] 7) High-temperature carbonization: the phenolic resin-Ta2O5 aerogel obtained in step 6) is placed in a well-type carbonization furnace, and N2 inert gas protection gas is filled, and then the temperature is increased from room temperature to 300℃ at a speed of 4℃ / min, and then increased to 900℃ at a speed of 150in, and kept for 200min. After carbonization, the phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material with complete and no cracking can be prepared after cooling to room temperature.

[0078] The radial shrinkage rate of the phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material prepared by the above method is 12.34% after ambient pressure drying at 0.1MPa, and the radial shrinkage rate after forming is 21.07% after carbonization, and the volume density before carbonization is 0.241g / cm 3 , and the volume density of the carbon aerogel-Ta2O5 composite material is 0.256g / cm 3 ; under the condition of high-diameter ratio of 1:1, the compression modulus is 5.36MPa, and the thermal conductivity tested by the transient hot wire method at room temperature is 0.0412W / (m·K), which has good heat insulation performance; under the condition of one solar light intensity, the evaporation rate of pure water is 1.321kg / (m 2 ·h).

[0079] Example 4

[0080] The preparation method of the high-efficiency photo-thermal conversion phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material is prepared by the following steps:

[0081] 1) Synthesis of base-catalyzed phenolic resin sol: add phenolic organic resorcinol and aldehyde organic furfural raw materials to a container, stir at 50℃ low speed 25r / min until they are completely soluble, increase the stirring speed to 45r / min, add ethanol and HMTA until they are completely dissolved, continue to keep the stirring state under sealed condition for 30min of base catalysis, and mark it as sol A. The mass ratio of resorcinol, furfural, ethanol and HMTA is 2.75g:4.58g:6g:0.38g;

[0082] 2) Synthesis of composite phenolic resin sol: add 0.12g of photocatalyst Ta2O5 to sol A, and disperse it uniformly in sol A by ultrasonic dispersion to form a uniformly dispersed composite phenolic resin sol, marked as sol B.

[0083] 3) Synthesis of acid catalyzed gel phenolic resin sol: keep the sol B at 55 °C, accelerate the stirring speed to 60 r / min, add ethanol, and dropwise add 0.3 mol / L HCl-ethanol solution, continue to keep the stirring state for 5 min in a sealed state, form a dark green solution, record as sol C, and pour into a mold. The mass ratio of resorcinol, furfural, anhydrous ethanol and HCl-ethanol solution is 2.75 g: 4.58 g: 28 g: 0.1 g;

[0084] 4) Polymerization heat treatment: place the sol C in a sealed plastic box mold, keep the gel at 75 °C, after about 6.5-8 h of gelation, add 8 g of anhydrous ethanol liquid seal; continue to seal for 32 h after liquid sealing, and form a phenolic resin-Ta2O5 wet gel;

[0085] 5) Normal pressure drying pretreatment: the phenolic resin-Ta2O5 wet gel obtained in step 4) is replaced by replacing the solvent n-heptane for 5 times, each time for 4 h, and kept at 75 °C environment;

[0086] 6) Normal pressure drying: the wet gel obtained in step 5) is placed in an oven at 40 °C, 60 °C, 80 °C for gradient temperature drying until the weight does not change. Each temperature gradient is kept for 5 h, and a complete block, large volume, non-cracking, small shrinkage phenolic resin-Ta2O5 aerogel is prepared;

[0087] 7) High temperature carbonization: the phenolic resin-Ta2O5 aerogel obtained in step 6) is placed in a well type carbonization furnace, filled with N2 inert gas protection gas, and the temperature is raised from room temperature to 300 °C at a rate of 4 °C / min, and then raised to 800 °C at a rate of 125 min. After cooling to room temperature after carbonization, a complete and non-cracking phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material is prepared.

[0088] The scanning electron microscope photos of the carbon aerogel composite material of Example 4 are shown in Figure 2 , and Figure 2 It can be seen that the carbon aerogel-Ta2O5 interface evaporation composite material is prepared by acid-base two-step catalysis principle, and the "oblate ellipsoid" and "pearl chain" structure is connected, and a three-dimensional network structure with high porosity is constructed. The sample nanometer skeleton particle size is about 50-100 nm, and the skeleton pore structure is uniform, which is beneficial to heat insulation and the formation of high-efficiency optical microcavity for light-heat conversion.

[0089] The radial shrinkage rate of the phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material prepared by the above method after 0.1 MPa normal pressure drying is 6.83%, the radial shrinkage rate after carbonization is 21.01%, and the volume density before carbonization is 0.221 g / cm 3, the volume density of the carbon aerogel-Ta2O5 composite material is 0.240 g / cm 3 ; under the condition of a height-diameter ratio of 1:1, the compression modulus is 4.31 MPa, and the thermal conductivity coefficient is 0.472 W / (m·K) tested by a transient hot wire method at room temperature, and the composite material has good heat insulation performance; under one solar light intensity, the evaporation rate of pure water is 1.656 kg / (m 2 ·h).

[0090] Example 5

[0091] The preparation method of the high-efficiency photo-thermal conversion phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material is prepared by the following steps:

[0092] 1) Synthesis of base-catalyzed phenolic resin sol: add phenolic organic resorcinol and aldehyde organic material furfural into a container, stir at 70°C and a low speed of 25 r / min until they are completely soluble, increase the stirring speed to 50 r / min, add ethanol and HMTA until they are completely dissolved, continue to stir in a sealed state for 50 min, and record it as sol A. The mass ratio of resorcinol, furfural, ethanol, and HMTA is 11.02 g: 18.32 g: 30 g: 1.7 g;

[0093] 2) Synthesis of composite phenolic resin sol: add 4.89 g of photocatalyst Ta2O5 to sol A, disperse it uniformly in sol A by ultrasonic dispersion, and form a uniformly dispersed composite phenolic resin sol, which is recorded as sol B.

[0094] 3) Synthesis of acid-catalyzed gel phenolic resin sol: keep sol B at 70°C, increase the stirring speed to 60 r / min, add ethanol, and drop 0.1 mol / L HCl-ethanol solution dropwise, continue to stir in a sealed state for 10 min, form a dark green solution, and record it as sol C, which can be poured into a mold. The mass ratio of resorcinol, furfural, anhydrous ethanol, and HCL ethanol solution is 11.02 g: 18.32 g: 120 g: 2 g;

[0095] 4) Polymerization heat treatment: place sol C in a sealed plastic box mold, keep the gel at 75°C, and after about 6.5-8 h of gelation, add 30 g of protective liquid anhydrous ethanol liquid seal; continue to seal for 48 h after liquid sealing to form a phenolic resin-Ta2O5 wet gel;

[0096] 5) Normal pressure drying pretreatment: replace the phenolic resin-Ta2O5 wet gel obtained in step 4) with n-heptane solvent by replacing it 8 times, 4 h each time, and keep it in a 75°C environment;

[0097] 6) Normal pressure drying: the wet gel obtained in step 5) is placed in an oven at 40℃, 60℃, 80℃ for gradient temperature drying until the weight does not change. Each temperature gradient is kept for 5h, so that the phenolic resin-Ta2O5 aerogel with complete block shape, large volume, no cracking, and small shrinkage rate is prepared;

[0098] 7) High temperature carbonization: the phenolic resin-Ta2O5 aerogel obtained in step 6) is placed in a well-type carbonization furnace, N2 inert gas protection gas is filled, the temperature is raised from room temperature to 300℃ at a rate of 2℃ / min, and then raised to 900℃ at a rate of 2℃ / min for 150min. After carbonization, the temperature is cooled to room temperature, and the phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material without cracking is prepared.

[0099] The radial shrinkage rate of the phenolic resin carbon aerogel-Ta2O5 interface evaporation composite material prepared by the above method after normal pressure drying at 0.1MPa is 7.66%, the radial shrinkage rate after carbonization is 20.11%, the volume density before carbonization is 0.204g / cm 3 , the volume density of the carbon aerogel-Ta2O5 composite material is 0.211g / cm 3 , the compression modulus is 2.65MPa under the condition of high diameter ratio of 1:1, the thermal conductivity coefficient is 0.0386W / (m·K) by transient hot wire method thermal test at room temperature, and the thermal insulation performance is good; under the condition of one solar light intensity, the evaporation rate of pure water is 2.103kg / (m 2 ·h), and the sample photo is shown in Figure 3 .

[0100] Example 6

[0101] The preparation method of the high-efficiency light-heat conversion phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material is prepared by the following steps:

[0102] 1) Synthesis of base-catalyzed phenolic resin sol: add phenolic organic resorcinol and aldehyde organic furfural raw materials to a container, stir at 60℃ and a low speed of 25r / min until they are completely soluble, increase the stirring speed to 35r / min, add ethanol and HMTA until they are completely dissolved, continue to stir in a sealed state for 50min of base catalysis, and record it as sol A. The mass ratio of resorcinol, furfural, ethanol and HMTA is 5.51g:9.16g:34.5g:1.05g;

[0103] 2) Synthesis of composite phenolic resin sol: add 4.02g of photocatalyst Ta2O5 to sol A, disperse it uniformly in sol A by ultrasonic wave to form a uniformly dispersed composite phenolic resin sol, and record it as sol B.

[0104] 3) Synthesis of acid catalyzed gel of phenolic resin sol: keep the sol B at 60℃, accelerate the stirring speed to 40 r / min, add ethanol, and drop 0.2 mol / L HCl-ethanol solution drop by drop, continue to keep the stirring state for 10 min in a sealed state, form a dark green solution, mark as sol C, and pour the mold. The mass ratio of resorcinol, furfural, anhydrous ethanol and HCl-ethanol solution is 5.51 g: 9.16 g: 126 g: 0.15 g;

[0105] 4) Polymerization heat treatment: place the sol C in a sealed plastic box mold, keep the gel at 75℃, after about 6.5-8 h of gelation, add 15 g of protective liquid anhydrous ethanol liquid seal; continue to seal for 32 h after liquid sealing to form a phenolic resin-Ta2O5 wet gel;

[0106] 5) Normal pressure drying pretreatment: replace the solvent ethanol of the phenolic resin-Ta2O5 wet gel obtained in step 4) for 8 times, 4 h each time, and keep it in a 75℃ environment;

[0107] 6) Normal pressure drying: place the wet gel obtained in step 5) in an oven at 40℃, 60℃ and 80℃ for gradient temperature drying until the weight does not change. Keep each temperature gradient for 5 h, and a complete block, large volume, non-cracking, small shrinkage phenolic resin-Ta2O5 aerogel can be prepared;

[0108] 7) High temperature carbonization: place the phenolic resin-Ta2O5 aerogel obtained in step 6) in a well type carbonization furnace, fill in N2 inert gas protection gas, and increase the temperature from room temperature to 300℃ at a speed of 2℃ / min, then increase the temperature to 900℃ for 150 min. After cooling to room temperature after carbonization, a complete and non-cracking phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material can be prepared.

[0109] The radial shrinkage rate of the phenolic resin carbon aerogel-Ta2O5 interface evaporation composite material prepared by the above method after normal pressure drying at 0.1 MPa is 4.12%, the forming radial shrinkage rate after carbonization is 19.68%, the volume density before carbonization is 0.156 g / cm 3 , the volume density of the carbon aerogel-Ta2O5 composite material is 0.161 g / cm 3 , the compression modulus is 0.84 MPa under the condition of high diameter ratio of 1:1, the thermal conductivity coefficient is 0.0326 W / (m·K) by transient hot wire method thermal test at room temperature, and it has good heat insulation performance; under the condition of one solar light intensity, the evaporation rate of pure water is 3.563 kg / (m 2 ·h).

[0110] Example 7

[0111] The application relates to a preparation method of a high-efficiency photo-thermal conversion phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material, which is prepared by the following steps:

[0112] 1) synthesizing an alkali-catalyzed phenolic resin sol: raw materials of a phenolic organic matter, resorcinol, and an aldehyde organic matter, furfural, are added into a container, stirring is carried out at 55 DEG C and a low speed of 15 r / min until the two are completely soluble, the stirring speed is increased to 30 r / min, t-butyl alcohol and HMTA are added until completely dissolved, and the stirring state is continuously maintained in a sealed state for 40 min of alkali catalysis, and the sol is recorded as sol A. The mass ratio of resorcinol, furfural, t-butyl alcohol and HMTA is 11.02g:18.32g:110g:2.1g;

[0113] 2) synthesizing a composite phenolic resin sol: 7.07g of a photocatalyst Ta2O5 is added into the sol A, ultrasonic dispersion is carried out to uniformly disperse the photocatalyst Ta2O5 in the sol A, a uniformly dispersed composite phenolic resin sol is formed, and the sol is recorded as sol B.

[0114] 3) synthesizing an acid-catalyzed gel phenolic resin sol: the sol B is kept at 55 DEG C, the stirring speed is increased to 50 r / min, t-butyl alcohol is added, and 0.2mol / L of an HCl-t-butyl alcohol solution is added drop by drop, the stirring state is continuously maintained in a sealed state for 10 min, a dark green solution is formed, the sol is recorded as sol C, and the sol C can be poured into a mold. The mass ratio of resorcinol, furfural, t-butyl alcohol and the HCL t-butyl alcohol solution is 11.02g:18.32g:185.3g:0.7g;

[0115] 4) polymerization heat treatment: the sol C is placed in a sealed plastic box mold, a gel is kept at 84 DEG C, after about 6.5-8h of gelation, 30g of a protective liquid, t-butyl alcohol, is added for liquid sealing, and after liquid sealing, the sealed state is continuously maintained for 16h to form a phenolic resin-Ta2O5 wet gel;

[0116] 5) normal-pressure drying pretreatment: the phenolic resin-Ta2O5 wet gel obtained in the step 4) is replaced by replacing solvents, ethanol is replaced for 3 times, and n-heptane is replaced for 5 times, each time for 4h, and the replacement is carried out in an environment kept at 84 DEG C;

[0117] 6) normal-pressure drying: the wet gel obtained in the step 5) is placed in an oven at 40 DEG C, 60 DEG C and 80 DEG C for gradient temperature drying until the weight does not change, each temperature gradient is kept for 8h, and a complete blocky, large-volume, non-cracking, small-shrinkage phenolic resin-Ta2O5 aerogel is prepared;

[0118] 7) High temperature carbonization: the phenolic resin-Ta2O5 aerogel obtained in step 6) is placed in a well-type carbonization furnace, N2 inert gas protection gas is filled, the temperature is raised from room temperature to 300℃ at a rate of 3℃ / min, and then raised to 800℃ in 180min and kept for 150min. After carbonization, cooling to room temperature, the complete and non-cracked phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material is prepared.

[0119] The radial shrinkage rate of the phenolic resin carbon aerogel-Ta2O5 interface evaporation composite material prepared by the above method after drying at 0.1MPa normal pressure is 10.31%, the radial shrinkage rate after carbonization is 23.13%, the volume density before carbonization is 0.271g / cm 3 , the volume density of the carbon aerogel-Ta2O5 composite material is 0.293g / cm 3 , the compression modulus is 7.31MPa under the condition of high aspect ratio of 1:1, the thermal conductivity coefficient is 0.0573W / (m·K) by transient hot wire method thermal test at room temperature, and has good heat insulation performance; under the condition of one solar light intensity, the evaporation rate of pure water is 1.012kg / (m 2 ·h).

[0120] Example 8

[0121] The preparation method of the high-efficiency light-heat conversion phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material is prepared by the following steps:

[0122] 1) Synthesis of base-catalyzed phenolic resin sol: add phenolic organic resorcinol and aldehyde organic furfural raw materials to the container, stir at 70℃ low speed 20r / min until they are completely soluble, increase the stirring speed to 35r / min, add t-butyl alcohol and HMTA until completely dissolved, continue to keep the stirring state under sealed condition for 60min of base catalysis, and record it as sol A. The mass ratio of resorcinol, furfural, t-butyl alcohol and HMTA is 16.53g:27.48g:55.6g:3.15g;

[0123] 2) Synthesis of composite phenolic resin sol: add 10.68g of photocatalyst Ta2O5 to sol A, disperse it uniformly in sol A by ultrasonic dispersion to form a uniformly dispersed composite phenolic resin sol, record it as sol B.

[0124] 3) Synthesis of acid catalyzed gel phenolic resin sol: keep the sol B at 70 °C, accelerate the stirring speed to 50 r / min, add t-butyl alcohol, and dropwise add 0.1 mol / L HCl-t-butyl alcohol solution, continue to keep the stirring state for 15 min in a sealed state, form a dark green solution, mark as sol C, and pour into a mold. The mass ratio of resorcinol, furfural, t-butyl alcohol, and HCl ethanol solution is 16.53 g: 27.48 g: 310 g: 1.0 g;

[0125] 4) Polymerization heat treatment: place the sol C in a sealed plastic box mold, keep the gel at 84 °C, after about 6.5-8 h of gelation, add 50 g of protective liquid t-butyl alcohol liquid seal; continue to seal for 48 h after liquid sealing to form a phenolic resin-Ta2O5 wet gel;

[0126] 5) Atmospheric pressure drying pretreatment: replace the phenolic resin-Ta2O5 wet gel obtained in step 4) with ethanol by replacing the solvent 8 times, 4 h each time, and keep it in an environment at 84 °C;

[0127] 6) Atmospheric pressure drying: place the wet gel obtained in step 5) in an oven at 40 °C, 60 °C, and 80 °C for gradient temperature drying until the weight does not change. Keep each temperature gradient for 8 h, and a complete block, large volume, non-cracking, and small shrinkage phenolic resin-Ta2O5 aerogel can be prepared;

[0128] 7) High temperature carbonization: place the phenolic resin-Ta2O5 aerogel obtained in step 6) in a well type carbonization furnace, fill in N2 inert gas protection gas, and increase the temperature from room temperature to 300 °C at a rate of 4 °C / min, then increase the temperature to 900 °C at a rate of 180 min and keep it for 300 min. After cooling to room temperature after carbonization, a complete and non-cracking phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material can be prepared.

[0129] The phenolic resin carbon aerogel-Ta2O5 interface evaporation composite material prepared by the above method has a radial shrinkage rate of 10.56% after atmospheric pressure drying at 0.1 MPa, a radial shrinkage rate of 22.81% after carbonization, a volume density of 0.296 g / cm3 before carbonization, a volume density of 0.312 g / cm3 of the carbon aerogel-Ta2O5 composite material, a compression modulus of 8.61 MPa under the condition of a high aspect ratio of 1:1, a thermal conductivity of 0.0601 W / (m·K) by transient hot wire method thermal test at room temperature, and good heat insulation performance; under the condition of a solar light intensity, the evaporation rate of pure water is 0.931 kg / (m 2 ·h).

[0130] Example 9

[0131] The application relates to a preparation method of a high-efficiency photo-thermal conversion phenolic resin-based carbon aerogel-Ta2O5 interface evaporation composite material, which is prepared through the following steps:

[0132] 1) synthesizing an alkali-catalyzed phenolic resin sol: raw materials of a phenolic organic matter, resorcinol, and an aldehyde organic matter, furfural, are added into a container, stirring is carried out at 80 DEG C and a low speed of 15 r / min until the two are completely soluble, the stirring speed is increased to 30 r / min, t-butyl alcohol and HMTA are added until completely dissolved, and the stirring state is continuously maintained in a sealed state for 30 min of alkali catalysis, and the obtained product is recorded as sol A. The mass ratio of resorcinol, furfural, t-butyl alcohol and HMTA is 5.51 g:9.16 g:30 g:0.75 g;

[0133] 2) synthesizing a composite phenolic resin sol: 0.27 g of a photocatalyst Ta2O5 is added into the sol A, ultrasonic dispersion is carried out to uniformly disperse the photocatalyst Ta2O5 in the sol A, a uniformly dispersed composite phenolic resin sol is formed, and the obtained product is recorded as sol B.

[0134] 3) synthesizing an acid-catalyzed gel phenolic resin sol: the sol B is kept at 80 DEG C, the stirring speed is increased to 50 r / min, t-butyl alcohol is added, and 0.3 mol / L of an HCl-t-butyl alcohol solution is added drop by drop, the stirring state is continuously maintained in a sealed state for 5 min, a dark green solution is formed, the obtained product is recorded as sol C, and the sol C can be used for mold pouring. The mass ratio of resorcinol, furfural, t-butyl alcohol and the HCL ethanol solution is 16.53 g:27.48 g:200 g:0.1 g;

[0135] 4) polymerization heat treatment: the sol C is placed in a sealed plastic box mold, a gel is kept at 84 DEG C, after about 6.5-8 h of gelation, 30 g of a protective liquid, t-butyl alcohol, is added for liquid sealing, and after the liquid sealing, the sealing is continuously kept for 48 h to form a phenolic resin-Ta2O5 wet gel;

[0136] 5) normal-pressure drying pretreatment: the phenolic resin-Ta2O5 wet gel obtained in the step 4) is replaced with solvent ethanol for 5 times, 4 h each time, and the replacement is kept in an environment at 84 DEG C;

[0137] 6) normal-pressure drying: the wet gel obtained in the step 5) is placed in an oven at 40 DEG C, 60 DEG C and 80 DEG C for gradient temperature rising drying until the weight does not change. Each temperature gradient is kept for 4 h, and a complete blocky, large-volume, non-cracking and small-shrinkage phenolic resin-Ta2O5 aerogel is prepared;

[0138] 7) High-temperature carbonization: The phenolic resin-Ta2O5 aerogel obtained in step 6) is placed in a pit-type carbonization furnace, and N2 inert gas is introduced as a protective gas. The temperature is increased from room temperature to 300℃ at a rate of 2℃ / min, and then increased to 800℃ over 180 min and held for 300 min. After carbonization, the mixture is cooled to room temperature to prepare a complete and crack-free phenolic resin-based carbon aerogel-Ta2O5 interfacial evaporation composite material.

[0139] The phenolic resin carbon aerogel-Ta2O5 interfacial evaporation composite material prepared by the above method exhibits a radial shrinkage rate of 12.86% after drying at 0.1 MPa atmospheric pressure and a radial shrinkage rate of 22.62% after carbonization. The bulk density before carbonization is 0.313 g / cm³, and the bulk density of the carbon aerogel-Ta2O5 composite material is 0.332 g / cm³. Under a height-to-diameter ratio of 1:1, the compressive modulus is 9.73 MPa. The thermal conductivity, measured by the transient hot-wire method at room temperature, is 0.0627 W / (m·K), indicating good thermal insulation performance. Under a certain solar irradiance, the evaporation rate of pure water is 0.861 kg / (m²·K). 2 •h). The compressive stress-strain of the sample in this embodiment is as follows: Figure 4 As shown. By Figure 4 It can be seen that the maximum pressure that the sample can withstand reaches 9.73 MPa, which proves that the composite material has excellent mechanical properties.

[0140] Comparative Example 1

[0141] Same as Example 1, except that the sealing time after liquid sealing in step 4) is 60 hours.

[0142] The phenolic resin carbon aerogel-Ta2O5 interfacial evaporation composite material prepared by the above method had a radial shrinkage rate of 8.32% after atmospheric pressure drying, and a radial shrinkage rate of 20.76% after carbonization. The density before carbonization was 0.183 g / cm³. 3 The density of the carbon aerogel-Ta2O5 composite material is 0.213 g / cm³. 3 Under a height-to-diameter ratio of 1:1, the compressive modulus is 2.57 MPa, and the thermal conductivity at room temperature is 0.0396 W / (m·K); under a certain solar radiation intensity, the evaporation rate of pure water is 1.819 kg / (m²·K). 2 •h). After an aging time of 60h, the performance parameters of the sample are basically the same as those of the original example after 48h. However, the excessively long aging time increases the energy and time costs of the preparation process, which is not conducive to industrial production.

[0143] Comparative Example 2

[0144] Same as Example 1, except that the sealing time after liquid sealing in step 4) is 10 hours.

[0145] The radial shrinkage rate of the phenolic resin carbon aerogel-Ta2O5 interface evaporation composite material prepared by the above method after normal pressure drying was 19.12%, the forming radial shrinkage rate after carbonization was 20.48%, and the density before carbonization was 0.46 g / cm 3 The density of the carbon aerogel-Ta2O5 composite material was 0.61 g / cm 3 Under the condition of a height-diameter ratio of 1:1, the compression modulus was 1.02 MPa, the thermal conductivity coefficient at room temperature was 0.856 W / (m·K), and the evaporation rate of pure water under one solar light intensity was 0.562 kg / (m 2 ·h). Due to the too short aging time (10 h), the sample was not completely gelled, the internal skeleton was not completely grown, the sample strength was weak at this time, and thus the sample could not resist the surface tension generated during the normal pressure drying process, resulting in an increase in the normal pressure drying radial shrinkage rate. The increase in the drying shrinkage rate resulted in a dense sample and an increase in the density, which was not conducive to the evaporation of water vapor after evaporation, and thus the evaporation rate was reduced. And due to the too large drying shrinkage rate, the sample was prone to crack and difficult to form a complete block, and thus the mechanical properties were reduced.

[0146] Comparative Example 3

[0147] The same as Example 1, except that after step 3) aging was completed, step 6) normal pressure drying process was directly performed, and step 5) solvent replacement step was not performed.

[0148] The radial shrinkage rate of the phenolic resin carbon aerogel-Ta2O5 interface evaporation composite material prepared by the above method after normal pressure drying was 19.12%, the forming radial shrinkage rate after carbonization was 20.48%, and the density before carbonization was 0.46 g / cm 3 The density of the carbon aerogel-Ta2O5 composite material was 2.231 g / cm 3 Under the condition of a height-diameter ratio of 1:1, the compression modulus was 3.62 MPa, the thermal conductivity coefficient at room temperature was 0.413 W / (m·K), and the evaporation rate of pure water under one solar light intensity was 1.105 kg / (m 2 ·h). Utilizing a low surface tension liquid to replace the original solvent can reduce the surface tension required to be borne by the sample skeleton structure during drying, reduce the skeleton shrinkage rate, and not easily collapse.

[0149] Comparative Example 4

[0150] The same as Example 1, except that the aging temperature in step 4) was 100°C.

[0151] The phenolic resin carbon aerogel-Ta2O5 interface evaporation composite prepared by the above method cannot form a complete gel. The reason is that the aging temperature is above the boiling point of the solvent, and the solvent boils and volatilizes violently, so the sample cannot be successfully prepared.

[0152] Comparative Example 5

[0153] The same as Example 1, except that the drying process of step 6) is directly dried at 80℃ for 9h.

[0154] The radial shrinkage rate of the phenolic resin carbon aerogel-Ta2O5 interface evaporation composite prepared by the above method after atmospheric drying is 10.46%, the radial shrinkage rate after carbonization is 21.33%, the density before carbonization is 0.186g / cm 3 , and the density of the carbon aerogel-Ta2O5 composite is 0.215g / cm 3 , the compression modulus is 3.10MPa, the thermal conductivity coefficient at room temperature is 0.401W / (m·K) under the condition of high-diameter ratio of 1:1, and the evaporation rate of pure water under one solar light intensity is 1.693kg / (m 2 ·h). Gradient heating can make the solvent in the wet gel volatilize gradually from the outside to the inside. Direct drying at high temperature of 80℃ leads to too violent solvent volatilization, which destroys the pore structure, causing the sample shrinkage rate to increase sharply or crack, even break.

[0155] Comparative Example 6

[0156] The same as Example 1, except that after forming a dark brown gel in step 4), no protective liquid is added, and direct aging is carried out for the same time.

[0157] The radial shrinkage rate of the phenolic resin carbon aerogel-Ta2O5 interface evaporation composite prepared by the above method after atmospheric drying is 19.36%, the radial shrinkage rate after carbonization is 20.98%, the density before carbonization is 0.47g / cm 3 , and the density of the carbon aerogel-Ta2O5 composite is 0.63g / cm 3 , the compression modulus is 0.92MPa, the thermal conductivity coefficient at room temperature is 0.889W / (m·K) under the condition of high-diameter ratio of 1:1, and the evaporation rate of pure water under one solar light intensity is 0.553kg / (m 2 ·h). During the aging process, if there is no protective liquid covering the surface of the sample, the solvent volatilizes continuously during the sol-gel process of the sample, making the sample surface dry and the skeleton structure damaged.

[0158] The above described embodiments are only to illustrate the preferred modes of the present application, and are not intended to limit the scope of the present application. Any modification and improvement made by those skilled in the art to the technical solutions of the present application without departing from the design spirit of the present application shall fall within the protection scope of the present application as defined by the claims.

Claims

1. A method for preparing a carbon aerogel-tantalum pentoxide interface evaporative composite, characterized by, The method comprises the following steps: 1) Synthesis of base-catalyzed phenolic resin sol: mixing phenolic organic matter, aldehyde organic matter raw materials, stirring at 15-25 r / min at 50-80℃ until completely soluble, increasing the stirring speed to 30-50 r / min, adding solvent and base catalyst, stirring until completely dissolved, continuing to stir in a sealed state, carrying out base catalysis until a brown-yellow solution is formed, denoted as sol A; 2) Synthesis of composite phenolic resin sol: adding photocatalyst tantalum pentoxide to the sol A, ultrasonic treatment, forming a uniformly dispersed composite phenolic resin sol, denoted as sol B; 3) Synthesis of acid-catalyzed gel phenolic resin sol: keeping 50-80℃, increasing the stirring speed to 40-60 r / min, adding solvent, and simultaneously adding acid catalyst solution drop by drop, continuing to stir in a sealed state until a dark green solution is formed, denoted as sol C; 4) Polymerization heat treatment: sealing the sol C, keeping 60-84℃ gel, forming a dark brown gel after 6.5-8 h, adding a protective liquid to seal; continuing to seal and age after liquid sealing, forming a phenolic resin-tantalum pentoxide wet gel; 5) Normal pressure drying pretreatment: washing and replacing the phenolic resin-tantalum pentoxide wet gel by replacing solvent multiple times, each time for 4 h, keeping in a 60-84℃ environment; 6) Normal pressure drying: gradient temperature rising drying of the wet gel obtained in step 5) at 40℃, 60℃, and 80℃ until the weight does not change, obtaining a phenolic resin-tantalum pentoxide aerogel; 7) High-temperature carbonization: carbonizing the phenolic resin-tantalum pentoxide aerogel obtained in step 6), filling N2 inert gas protection gas during the carbonization process, first increasing the temperature from room temperature to 300℃ at a speed of 2-4℃ / min, then increasing the temperature to 800-900℃ within 125-180 min, keeping for 120-300 min, cooling to room temperature after carbonization, obtaining a carbon aerogel-tantalum pentoxide interface evaporation composite material.

2. The preparation method according to claim 1, characterized in that, The molar ratio of phenolic organic matter, aldehyde organic matter, solvent, and base catalyst in step 1) is 1:2:5-15:(0.09-0.15).

3. The preparation method according to claim 1, characterized in that, The amount of photocatalyst added in step 2) is 0.6%-10.4% of the mass of the sol A.

4. The preparation method according to claim 1, characterized in that, The molar ratio of the solvent and the acidic catalyst solution in step 3) to the phenolic organic compound and the aldehyde organic compound in step 1) is 25-55:(1.5-3 x 10 -4 ):1:

2.

5. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The protective liquid in step 4) is methanol, ethanol, or tert-butyl alcohol.

6. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The aging time in step 4) is 16-48 h, and the aging temperature is 60-84℃.

7. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The replacing solvent in step 5) is ethanol or n-heptane, and the washing and replacing is performed 3-8 times.

8. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The gradient temperature rising time in step 6) is 3-8 h for each gradient.

9. A carbon aerogel-tantalum pentoxide interface evaporation composite material prepared by the preparation method of any one of claims 1-8.

10. Application of the carbon aerogel-tantalum pentoxide interface evaporation composite material of claim 9 in preparing a local thermalization core component of a seawater evaporation device.

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