Silica-silicon carbon mineral phase change heat storage material, and preparation method and application thereof

Abstract

The application provides a phytolith silicocarbon mineral phase change heat storage material and a preparation method and application thereof, and belongs to the technical field of light-heat conversion materials. The preparation method comprises the following steps: crushing and grinding phytolith silicocarbon mineral raw ore, and then screening and drying to obtain a first solid product; uniformly mixing the first solid product and an alkaline hydroxide, and calcining under an inert atmosphere to obtain a second solid product; washing the second solid product to neutral, and then drying to obtain a third solid product; uniformly mixing the third solid product and stearic acid, and then performing immersion treatment under vacuum, and then removing excessive stearic acid on the surface of the third solid product, and then grinding after cooling to obtain the phytolith silicocarbon mineral phase change heat storage material. The heat storage material has a high enthalpy value of 106.93 J / g, excellent leakage prevention effect, a high light-heat conversion efficiency of 98.86%, no obvious change in phase change enthalpy after 200 times of melting / freezing cycles, and high cycle stability, and can be used for absorbing light energy and converting the light energy into heat energy and electric energy.

Description

Technical Field

[0001] This application belongs to the field of photothermal conversion materials technology, and more specifically, relates to a siliceous silica carbide phase change thermal storage material and its preparation method and application. Background Technology

[0002] Solar energy is the most abundant renewable and clean energy source on Earth, but its discontinuity and unpredictability hinder its effective utilization. Therefore, solar energy conversion and storage are crucial for achieving efficient and sustainable energy use. Phase change materials (PCMs) are advanced thermal storage materials that can store and release large amounts of latent heat during phase change processes, and are commonly used in industrial waste heat recovery, construction, temperature-controlled textiles, and solar energy utilization. However, to promote the practical application of organic phase change materials in solar energy conversion and storage, two major problems urgently need to be addressed: severe leakage of molten phase change materials during the phase change process and the inability to achieve photothermal conversion.

[0003] Currently, people have tried various solutions to solve the leakage problem of pure phase change materials by introducing phase change materials into porous support materials to prepare composite shape-stable phase change materials. At the same time, they have also tried to solve the photothermal conversion problem by adding light-absorbing materials such as carbon black nanoparticles, carbon nanotubes, graphene, graphite and biomass carbon materials. Whether it is possible to make an integrated phase change thermal storage material without adding porous support materials and light-absorbing materials is a hot topic today. Summary of the Invention

[0004] The purpose of this application is to provide a phytosilica phase change thermal storage material, its preparation method and application. The phase change thermal storage material of this application does not require the addition of additional light-absorbing materials and has the characteristics of an integrated photothermal phase change thermal storage material.

[0005] To achieve the above objectives, the first aspect of this application provides a method for preparing a phytolithic silicon carbide phase change thermal storage material, comprising the following steps:

[0006] S1: The phytolith silicate ore is crushed, ground, sieved, and dried to obtain the first solid product;

[0007] S2: Mix the first solid product with the alkaline hydroxide and calcine it under an inert atmosphere to obtain the second solid product;

[0008] S3: Wash the second solid product with water until neutral and dry it to obtain the third solid product;

[0009] S4: Mix the third solid product with stearic acid, impregnate it under vacuum, remove excess stearic acid from the surface of the third solid product, cool and grind to obtain phytosilicic carbide phase change thermal storage material.

[0010] Further, the alkaline hydroxide is sodium hydroxide or potassium hydroxide, and the mass ratio of the first solid product to the alkaline hydroxide is 1:0.75 to 4.

[0011] Furthermore, the calcination temperature is 600–1000℃, and the time is 2–4 hours.

[0012] Furthermore, the mass ratio of the third solid product to the stearic acid is 1:2 to 4.

[0013] Furthermore, the soaking time is 20–60 min.

[0014] Furthermore, the mesh size of the first solid product is 70 to 200 mesh.

[0015] Furthermore, the inert atmosphere is nitrogen.

[0016] In a second aspect, this application provides a phytolithic silicon carbide phase change thermal storage material, obtained by any of the preparation methods described above.

[0017] A third aspect of this application provides the application of a phytolithic silicon carbide phase change thermal storage material in photothermal conversion.

[0018] Furthermore, it is used in solar thermal generators.

[0019] Compared with the prior art, this application has the following technical effects:

[0020] This application discloses a method for preparing a phytolithic silicon carbide phase change thermal energy storage material. Using phytolithic silicon carbide as raw material, it produces an integrated phase change thermal energy storage material with high conversion efficiency and leak-proof properties. The phase change thermal energy storage material prepared in this application differs from traditional composite thermal energy storage materials. It utilizes the carbon content of silicon carbide and the nano-micro particle characteristics of the mineral powder, eliminating the need for additional porous support materials and light-absorbing materials to prepare an integrated phase change thermal energy storage material. Furthermore, the prepared phase change thermal energy storage material exhibits good morphological stability. When this material is used to prepare a photothermal-electric energy storage device, it absorbs light energy and converts it into heat and electricity. After the sunlight exposure ends, it can continuously generate electricity using the heat stored in the energy storage material.

[0021] The thermal storage material prepared in this application has an enthalpy value as high as 106.93 J / g, excellent leakage prevention effect, and a photothermal conversion efficiency as high as 98.86%. After 200 melt / freeze cycles, the phase change enthalpy does not change significantly, and the cycle stability is high.

[0022] The preparation method of this application is simple and easy to implement, has low requirements for equipment, and is inexpensive to produce. It is easy to industrialize and is a low-cost alternative to battery-coupled photovoltaic power generation. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a scanning electron microscope image of the integrated phase change thermal storage material SA / Phy-800 prepared in Example 3;

[0025] Figure 2 These are the material XRD patterns of the integrated phase change thermal storage materials prepared in Examples 1-4;

[0026] Figure 3 These are FTIR images of the integrated phase change thermal storage materials prepared in Examples 1-4;

[0027] Figure 4 These are DSC curves of the integrated phase change thermal storage materials prepared in Examples 1-4;

[0028] Figure 5 These are DSC cycle test diagrams of the integrated phase change thermal storage materials prepared in Examples 1-4;

[0029] Figure 6 These are leakage prevention test diagrams of the integrated phase change thermal storage materials prepared in Examples 1-4;

[0030] Figure 7 These are temperature change curves of the integrated phase change thermal storage materials prepared in Examples 1-4;

[0031] Figure 8 The integrated phase change thermal storage material prepared in Example 3 is at 200 mV / cm 2 Temperature-current and temperature-voltage curves under light intensity;

[0032] Figure 9 The integrated phase change thermal storage material prepared in Example 3 is at 300 mV / cm 2 Temperature-current and temperature-voltage curves under light intensity;

[0033] Figure 10 The integrated phase change thermal storage material prepared in Example 3 is at 400 mV / cm 2 Temperature-current and temperature-voltage curves under light intensity;

[0034] Figure 11 This is an experimental diagram showing the integrated phase change thermal energy storage material prepared in Example 3 converting solar energy into thermal energy into electrical energy to power a 1.5V light bulb.

[0035] Figure 12 This is an experimental diagram of the integrated phase change thermal energy storage material prepared in Example 3, used to power a 3V light bulb through the conversion of solar energy to thermal energy to electrical energy. Detailed Implementation

[0036] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0037] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0038] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0039] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0040] This application provides a method for preparing a phytosilica phase change thermal storage material, including the following steps:

[0041] S1: The phytolith silicate ore is crushed, ground, sieved, and dried to obtain the first solid product;

[0042] S2: Mix the first solid product with the alkaline hydroxide and calcine it under an inert atmosphere to obtain the second solid product;

[0043] S3: Wash the second solid product with water until neutral and dry it to obtain the third solid product;

[0044] S4: Mix the third solid product with stearic acid, impregnate it under vacuum, remove excess stearic acid from the surface of the third solid product, cool and grind to obtain phytosilicic carbide phase change thermal storage material.

[0045] In step S1 above, the crushed and ground phytolith silicate ore is placed in a vibrating screen and its particle size is reduced to 70-200 mesh through physical sieving.

[0046] In step S2 above, the mass ratio of the first solid product to the alkaline hydroxide is 1:0.75-4. The alkaline hydroxide can be sodium hydroxide or potassium hydroxide. Nitrogen is used as the calcination atmosphere, and the heating rate is controlled at 5-10℃ / min.

[0047] In step S4 above, the third solid product and stearic acid are mixed evenly and placed in a vacuum flask. The vacuum flask is then evacuated to a vacuum state and placed in a water bath for heating, causing the stearic acid to melt into a liquid state. Under vacuum conditions, the liquid stearic acid is more likely to impregnate the porous third solid product. In the embodiments of this application, stearic acid is used to impregnate the third solid product. The inventors found in their experiments that, compared with commonly used phase change materials such as paraffin and lauric acid, the phytolithic silicon carbide phase change thermal storage material obtained by impregnation with stearic acid has a higher photothermal-electric conversion efficiency.

[0048] In this embodiment, excess stearic acid on the surface of the third solid product is removed by the following method: the impregnated third solid product is placed on funnel-shaped filter paper and placed in an 80°C oven for hot filtration for 48–120 hours. During the filtration process, the filter paper is replaced every 2 hours for the first 24 hours, and then every 24 hours thereafter, until no residual stearic acid remains on the filter paper surface, indicating that the excess stearic acid on the surface of the third solid product has been sufficiently removed.

[0049] The phytolithic silicon carbide integrated phase change thermal storage material prepared in this application embodiment can be used as a thermal measurement material in a self-made photothermal conversion device to convert collected solar energy into thermal energy. The structure of the self-made photothermal conversion device is based on the inventor's previously published article, "3D porous copper foam-based shape-stabilized composite phase change materials for high photothermal conversion, thermal conductivity and storage," and will not be repeated here. The simulated solar light intensity is 100 mV / cm². 2 After the light exposure was stopped, the corresponding temperature-time curves were generated on the Keysight34972A and the assembled thermocouple, and the photothermal conversion efficiency was obtained.

[0050] The phytosilicone-based integrated phase change thermal storage material prepared in this application embodiment can also be used in a solar thermoelectric generator (STEG) system to convert collected solar energy into electrical energy. The structure of the solar thermoelectric generator system is described in CN218917254U and will not be repeated here. Specifically, the two ends of the thermoelectric semiconductor engine are connected to experimental light bulbs for photothermal-electric conversion. The light intensity is 200–400 mW / cm². 2 The light bulb used in the experiment was 1.5 to 3.0V.

[0051] The following examples illustrate a silicon carbide phase change thermal storage material, its preparation method, and its application, based on several specific embodiments.

[0052] Example 1

[0053] Embodiment 1 of this application provides a phytosilica-based silicon carbide phase change thermal storage material and its preparation method, including the following steps:

[0054] Phytolithic silicate ore was crushed and ground, then placed in a 200-mesh sieve for physical sieving to obtain phytolithic silicate (Phy). This was then dried in a 60℃ oven for 24 hours. 2g of the dried powder and 8g of stearic acid (SA) were weighed and mixed evenly in a vacuum flask. The flask was evacuated to a vacuum and held for 10 minutes. Under vacuum, the flask was placed in a 90℃ water bath for 30 minutes of immersion reaction. The resulting reactant was placed on filter paper and placed in an 80℃ oven for hot filtration for 120 hours. The filter paper was replaced every 2 hours from 0 to 24 hours, and every 12 hours from 24 to 120 hours. After hot filtration, the mixture was ground evenly to obtain the integrated phase change thermal storage material SA / Phy.

[0055] Example 2

[0056] Embodiment 2 of this application provides a phytosilica-based silicon carbide phase change thermal storage material and its preparation method, including the following steps:

[0057] After crushing and grinding the raw phytolith silicate ore, it was placed in a 200-mesh sieve for physical sieving to obtain phytolith silicate ore, which was then dried in an oven at 60℃ for 24 hours. 6g of the dried phytolith silicate ore and 6g of... The NaOH mixture was ground evenly. The resulting powder was placed in a tube furnace and calcined at 600℃ for 2 hours under a N2 atmosphere at a heating rate of 10℃ / min. The powder was then placed in a beaker, 1000ml of deionized water was added, and the mixture was stirred at room temperature for 2 hours. After filtration, the powder was repeatedly washed until neutral and placed in an 80℃ oven for 24 hours. The resulting powder was Phy-600. 2g of the powder and 8g of stearic acid were weighed and mixed evenly in a vacuum flask. The flask was evacuated to a vacuum and held for 10 minutes. Under vacuum, the flask was placed in a 90℃ water bath and immersed for 30 minutes. The resulting reactant was placed on filter paper and placed in an 80℃ oven for hot filtration for 120 hours. The filter paper was replaced every 2 hours from 0 to 24 hours and every 12 hours from 24 to 120 hours. After hot filtration, the mixture was ground evenly to obtain the integrated phase change thermal storage material SA / Phy-600.

[0058] Example 3

[0059] Embodiment 3 of this application provides a phytosilica-based silicon carbide phase change thermal storage material and its preparation method, including the following steps:

[0060] After crushing and grinding the raw phytolith silicate ore, it was placed in a 200-mesh sieve for physical sieving to obtain phytolith silicate ore, which was then dried in an oven at 60℃ for 24 hours. 6g of the dried phytolith silicate ore and 6g of... The NaOH mixture was ground evenly. The resulting powder was placed in a tube furnace and calcined at 800℃ for 2 hours under a N2 atmosphere at a heating rate of 10℃ / min. The powder was then placed in a beaker, 1000ml of deionized water was added, and the mixture was stirred at room temperature for 2 hours. After filtration, the powder was repeatedly washed until neutral and placed in an 80℃ oven for 24 hours. The resulting powder was Phy-800. 2g of the powder and 8g of stearic acid were weighed and mixed evenly in a vacuum flask. The flask was evacuated to a vacuum and held for 10 minutes. Under vacuum, the flask was placed in a 90℃ water bath and immersed for 30 minutes. The resulting reactant was placed on filter paper and placed in an 80℃ oven for hot filtration for 120 hours. The filter paper was replaced every 2 hours from 0 to 24 hours and every 12 hours from 24 to 120 hours. After hot filtration, the mixture was ground evenly to obtain the integrated phase change thermal storage material SA / Phy-800.

[0061] Example 4

[0062] Embodiment 4 of this application provides a phytosilica-based silicon carbide phase change thermal storage material and its preparation method, including the following steps:

[0063] After crushing and grinding the raw phytolith silicate ore, it was placed in a 200-mesh sieve for physical sieving to obtain phytolith silicate ore, which was then dried in an oven at 60℃ for 24 hours. 6g of the dried phytolith silicate ore and 6g of... The NaOH mixture was ground evenly. The resulting powder was placed in a tube furnace and calcined at 1000℃ for 2 hours under a N2 atmosphere at a heating rate of 10℃ / min. The powder was then placed in a beaker, 1000ml of deionized water was added, and the mixture was stirred at room temperature for 2 hours. After filtration, the powder was repeatedly washed until neutral and placed in an 80℃ oven for 24 hours. The resulting powder was Phy-1000. 2g of the powder and 8g of stearic acid were weighed and mixed evenly in a vacuum flask. The flask was evacuated to a vacuum and held for 10 minutes. Under vacuum, the flask was placed in a 90℃ water bath and immersed for 30 minutes. The resulting reactant was placed on filter paper and placed in an 80℃ oven for hot filtration for 120 hours. The filter paper was replaced every 2 hours from 0 to 24 hours and every 12 hours from 24 to 120 hours. After hot filtration, the mixture was ground evenly to obtain the integrated phase change thermal storage material SA / Phy-1000.

[0064] Figure 1 This is a scanning electron microscope image of the integrated phase change thermal storage material SA / Phy-800 prepared in Example 3;

[0065] Figure 2 These are the material XRD patterns of the integrated phase change thermal storage materials prepared in Examples 1-4;

[0066] Figure 3 These are FTIR images of the integrated phase change thermal storage materials prepared in Examples 1-4;

[0067] Figure 4 These are DSC curves of the integrated phase change thermal storage materials prepared in Examples 1-4. Figure 4 The melting and solidification phase transition enthalpies of SA / Phy, SA / Phy-600, SA / Phy-800 and SA / Phy-1000 are 39.36 J / g and 39.03 J / g, 56.88 J / g and 55.48 J / g, 106.93 J / g and 100.87 J / g, and 78.24 J / g and 77.64 J / g, respectively.

[0068] DSC cycle experiments were conducted on the integrated phase change thermal storage materials prepared in Examples 1-4 of this application: the integrated phase change thermal storage materials of each example were placed in a circulating metal bath for rapid heating and cooling cycles, with an upper limit temperature of 80°C and a lower limit temperature of 20°C, for 50-200 cycles. The results are as follows: Figure 5 As shown, from Figure 5As observed, the DSC curves of the materials after 50, 100, 150, and 200 heating and cooling cycles basically overlapped with the DSC curves of the uncycled materials, indicating that the phase transition temperature and phase transition enthalpy of the materials prepared in Examples 1-4 did not change significantly before and after the cycles.

[0069] Leakage prevention experiments were conducted on the integrated phase change thermal storage materials prepared in Examples 1-4 of this application: the integrated phase change thermal storage materials of each example were pressed into 25mm tablets, placed on a stainless steel constant temperature plate, and heated at 80℃ for 1 hour. Leakage on filter paper during the heating process was observed. The results are as follows: Figure 6 As shown, from Figure 6 As can be seen, after 60 minutes on a heating platform at 80℃, SA completely melted, SA / Phy showed slight leakage, while SA / Phy-600, SA / Phy-800, and SA / Phy-1000 showed no leakage, indicating good leak-proof performance.

[0070] Photothermal conversion application experiments were conducted on the integrated phase change thermal storage materials prepared in Examples 1-4 of this application: the integrated phase change thermal storage materials of each example were pressed into 25mm tablets and placed on a self-made device to simulate a solar radiation intensity of 100mV / cm. 2 The illumination time was 620 seconds. After the illumination was stopped, corresponding temperature-time curves were generated on the Keysight 34972A and the assembled thermocouple. The temperature change curves of SA and the materials prepared in Examples 1-4 are shown below. Figure 7 As shown in (a), with increasing illumination time, the composite phase change material gradually rises above the phase change temperature, and a thermal storage plateau appears. Photothermal conversion efficiency is an important indicator for evaluating the photothermal conversion capability of thermal storage materials. The photothermal conversion efficiency (η) of the integrated phase change thermal storage material was calculated using the following formula:

[0071]

[0072] Where m is the mass of the integrated phase change thermal storage material; S is the light-receiving area of ​​the integrated phase change thermal storage material; ΔH is the phase change enthalpy obtained from DSC analysis; I is the simulated light intensity; T t and T f These represent the start and end times of the phase change process, respectively. The start and end times of the phase change process in an integrated phase change thermal storage material can be calculated using the tangent method, and the difference Δt is shown below. Figure 7As shown in (b), the photothermal conversion efficiencies of SA / Phy, SA / Phy-600, SA / Phy-800, and SA / Phy-1000, calculated using the above formula, are 54.5%, 65.9%, 98.9%, and 80.9%, respectively. Among them, the material SA / Phy-800 prepared in Example 3 has the highest photothermal conversion efficiency of 98.9%, exhibiting high photothermal conversion performance.

[0073] Photothermal-electric conversion application experiment of the integrated phase change thermal storage material prepared in Example 3 of this application: The integrated phase change thermal storage material of Example 3 was pressed into a 25mm tablet and placed on the STEG system, simulating a solar radiation intensity of 200mV / cm. 2 300mV / cm 2 400mV / cm 2 The illumination time was 860 seconds. After the illumination was stopped, corresponding temperature-time curves were generated on the Keysight 34972A and the assembled thermocouple, and the current and voltage at the corresponding times were recorded using a multimeter. The results are as follows: Figure 8-10 As shown, Figure 8 The display shows that at 200mV / cm 2 Under intense sunlight, the solar thermal power device generates sustained output power, with a maximum output voltage of 134mV and a current of 19mA. The curves of Ut and It show the same trend as the curve of Tt. When sunlight stops, the SA / Phy-800 extends the operating time by generating output power through thermal discharge. This makes the system superior to traditional photovoltaic power generation and a low-cost alternative to battery-coupled photovoltaic power generation.

[0074] Figure 9 The display shows that at 300mV / cm 2 Under intense sunlight, the solar thermal power device generates sustained output power, with a maximum output voltage of 197mV and a current of 26mA. The curves of Ut and It show the same trend as the curve of Tt. When sunlight is cut off, the SA / Phy-800 extends the operating time by generating output power through thermal discharge. This makes the system superior to traditional photovoltaic power generation and a low-cost alternative to battery-coupled photovoltaic power generation.

[0075] Figure 10 The display shows that at 400mV / cm 2 Under intense sunlight, the solar thermal power device generates sustained output power, with a maximum output voltage of 241mV and a current of 33mA. The curves of Ut and It show the same trend as the curve of Tt. When sunlight stops, the SA / Phy-800 extends the operating time by generating output power through thermal discharge. This makes the system superior to traditional photovoltaic power generation and a low-cost alternative to battery-coupled photovoltaic power generation.

[0076] In addition, the integrated phase change thermal storage material of Example 3 was pressed into 25mm tablets and placed on the STEG system to simulate a solar radiation intensity of 300mV / cm. 2 Then, the two ends of the thermoelectric semiconductor engine were connected to a 1.5V light bulb for the experiment. The STEG system was used to convert solar energy into thermal energy into electrical energy to power the light bulb. The experiment was as follows. Figure 11 As shown, the time that the thermal energy stored in the SA / Phy-800 thermal spectral material could sustain electrical energy transmission after the light exposure was stopped was recorded. The experiment showed that the thermal energy stored in the SA / Phy-800 thermal spectral material could sustain electrical energy transmission for 21 seconds after the light exposure was stopped.

[0077] The integrated phase change thermal storage material from Example 3 was pressed into 25mm tablets and placed on an STEG system to simulate a solar radiation intensity of 300mV / cm. 2 Then, the two ends of the thermoelectric semiconductor engine were connected to a 3V light bulb used in the experiment. The STEG system was used to convert solar energy into thermal energy into electrical energy to power the light bulb. The experiment was as follows. Figure 12 As shown, the experiment recorded the time that the thermal energy stored in the SA / Phy-800 thermal spectral material could sustain electrical energy transmission after the light exposure was stopped. The experiment showed that the thermal energy stored in the SA / Phy-800 thermal spectral material could sustain electrical energy transmission for 18 seconds after the light exposure was stopped.

[0078] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a silica-based silicon carbide phase change thermal storage material, characterized in that, Includes the following steps: S1: The phytolith silicate ore is crushed, ground, sieved, and dried to obtain the first solid product; S2: Mix the first solid product with the alkaline hydroxide and calcine it under an inert atmosphere to obtain the second solid product; S3: Wash the second solid product with water until neutral and dry it to obtain the third solid product; S4: Mix the third solid product and stearic acid, impregnate under vacuum, remove excess stearic acid from the surface of the third solid product, cool and grind to obtain phytosilicic carbide phase change thermal storage material. Specifically, the mass ratio of the third solid product to the stearic acid is 1:2~4; the impregnation time is 20~60 min.

2. The preparation method of a silica-based silicon carbide phase change thermal storage material as described in claim 1, characterized in that, The alkaline hydroxide is sodium hydroxide or potassium hydroxide, and the mass ratio of the first solid product to the alkaline hydroxide is 1:0.75~4.

3. The method for preparing a silica-based silicon carbide phase change thermal storage material as described in claim 1, characterized in that, The calcination temperature is 600~1000 ℃, and the time is 2~4 h.

4. The preparation method of a silica-based silicon carbide phase change thermal storage material as described in claim 1, characterized in that, The first solid product has a mesh size of 70 to 200 mesh.

5. The method for preparing a silica-based silicon carbide phase change thermal storage material according to any one of claims 1-4, characterized in that, The inert atmosphere is nitrogen.

6. A silica-based silicon carbide phase change thermal storage material, characterized in that, It is obtained by the preparation method described in claim 5.

7. The application of the plant-based silica-carbide phase change thermal storage material as described in claim 6 in photothermal conversion.

8. The application of a plant-based silica-carbide phase change thermal storage material as described in claim 7 in photothermal conversion, characterized in that, Used in solar thermal generators.

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