Preparation method of a sensible-latent heat composite heat storage material based on alloy@SiC whisker@mullite structure and product prepared by the method

Abstract

This invention discloses a method for preparing a sensible-latent heat composite thermal storage material based on an alloy@SiC whisker@mullite structure, and the resulting product. The method involves pre-treating an Al-Si alloy by encapsulating it with silica sol and alumina sol to form an Al-Si alloy particle precursor with an alloy@SiO2 gel layer@Al2O3 gel layer structure. This precursor is then combined with an aluminosilicate mineral-Si-Al-C matrix material system and sintered with embedded carbonaceous materials, thus obtaining the sensible-latent heat composite thermal storage material through in-situ synthesis and reducing atmosphere sintering. This invention effectively improves the material's stability, thermal conductivity, and energy storage density. Furthermore, the raw materials are readily available, the process is simple, and the sintering temperature is low. This is of great significance for improving the quality, safety, and stability of thermal storage materials, as well as saving product costs, and therefore has broad market prospects, which is conducive to its promotion and application and the advancement and development of industry technology.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, and in particular to a method for preparing a composite thermal storage material and the product obtained therefrom. Background Technology

[0002] Concentrated solar thermal power generation, industrial waste heat recovery, and industrial kiln thermal storage are among the new energy and environmental protection technologies receiving increasing attention. The key to these technologies lies in efficient and stable thermal storage to address the mismatch between heat supply and demand, and to improve energy efficiency. Thermal storage technologies include sensible heat storage, chemical reaction heat storage, and phase change latent heat storage. Among these, phase change latent heat storage has been widely applied and researched due to its strong heat storage capacity, small temperature fluctuation range, and good chemical stability.

[0003] According to existing literature, common metal / alloy phase change thermal energy storage materials (PCMs) are mainly inorganic salts and metal alloys. For inorganic salts, their low phase change temperature, low thermal conductivity, and chemical incompatibility limit their widespread application. However, metals and alloys, due to their excellent high-temperature melting properties, high thermal conductivity, and high thermal energy storage density, overcome the shortcomings of inorganic salts and have become very promising alternative materials in high-temperature fields.

[0004] Metals and alloys possess advantages such as high heat storage density, good thermal stability, and high thermal conductivity, making them highly advantageous in medium- and high-temperature latent heat energy storage systems, with Al-Si alloys showing particularly significant benefits. However, metals and alloys are prone to solid-liquid transitions at high temperatures, and liquid-phase metals and alloys expand and become fluid. Furthermore, liquid metals and alloys exhibit strong reactivity and corrosiveness, capable of undergoing various complex physicochemical reactions with container materials, all of which pose bottlenecks to their application and development. Therefore, to achieve comprehensive utilization of metal and alloy PCMs, further research is needed to encapsulate metals and their alloys into encapsulated PCMs. Ceramics are chemically incompatible with metals, and while ceramics possess excellent mechanical properties and density, their coefficients of thermal expansion are mismatched. During heating, the alloy exerts stress on the ceramic encapsulation layer, which is the primary factor contributing to the instability of the encapsulation structure. Solving the problem of this mismatch in coefficients of thermal expansion remains an urgent issue. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing a sensible-latent heat composite thermal storage material based on an alloy@SiC whisker@mullite structure. This method involves pre-treating an Al-Si alloy by encapsulating it with silica sol and alumina sol to form an Al-Si alloy particle precursor with an alloy@SiO2 gel layer@Al2O3 gel layer structure. This precursor is then combined with an aluminosilicate mineral-Si-Al-C matrix system and sintered with embedded carbonaceous materials. This process, using in-situ synthesis and reducing atmosphere sintering, yields a composite thermal storage material with a core-shell-shell latent heat microcapsule structure formed by alloy@SiC whiskers@mullite and a mullite-SiC ceramic sensible heat matrix. Another objective of this invention is to provide a product obtained using the above-described method for preparing a sensible-latent heat composite thermal storage material based on an alloy@SiC whisker@mullite structure.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] This invention provides a method for preparing a sensible-latent heat composite thermal storage material based on an alloy@SiC whisker@mullite structure, comprising the following steps:

[0008] (1) A base material is obtained by mixing 50-70 wt% of aluminosilicate minerals, 0-15 wt% of siliceous raw materials, 5-15 wt% of metallic aluminum raw materials, 5-15 wt% of metallic silicon raw materials and 5-15 wt% of carbonaceous raw materials, and adding a binder to mix evenly.

[0009] (2) The Al-Si alloy particles were immersed in silica sol and stirred and coated. After one filtration and one drying, Al-Si alloy particles with a pre-coated SiO2 shell were obtained. Then, they were immersed in aluminum sol and stirred and coated. After two filtrations and two dryings, Al-Si alloy particle precursor with a double gel shell structure of first coating SiO2 and then coating Al2O3 was obtained.

[0010] (3) The Al-Si alloy particle precursor and the base material are mixed in a mass ratio of 1:1. The Al-Si alloy particle precursor is mixed into the base material and then granulated, pressed and dried to obtain a green body. The green body is then embedded in a carbonaceous material for reducing atmosphere sintering treatment, i.e., held at 1050℃ for 0.5-1h, held at 1050-1150℃ for 1-2h, and held at 1250-1400℃ for 1-3h to obtain a sensible-latent heat composite thermal storage material based on alloy@SiC whisker@mullite structure. The matrix of the composite thermal storage material is mullite-SiC ceramic, and the matrix contains a double-shell microcapsule structure with an alloy core, an inner layer of SiC whisker layer and an outer layer of mullite shell.

[0011] Further, the aluminosilicate minerals of this invention are one or a combination of kaolin, spheroidal clay, andalusite, sillimanite, kyanite, and bauxite, with a particle size of 80-700 mesh; the siliceous raw materials are one or a combination of fly ash, quartz powder, and quartz glass powder, with a particle size of 80-325 mesh; the metallic aluminum raw materials are metallic aluminum powder and / or aluminum shavings, with a particle size of 80-325 mesh; the metallic silicon raw materials are one or a combination of metallic silicon powder, polycrystalline silicon waste, and monocrystalline silicon waste, with a particle size of 80-700 mesh; the carbonaceous raw materials are one or a combination of graphite, carbon powder, and carbon black, with a particle size of 325-1000 mesh; the Si content in the Al-Si alloy is 12-40%, the particle size of the Al-Si alloy is 100-200 mesh, and the shape is spherical. The binder is carboxymethyl cellulose and / or polyvinyl alcohol solution, and the amount of binder is 3-5 wt% of the base raw materials.

[0012] Furthermore, in step (2) of this invention, the concentrations of both silica sol and alumina sol are 7.5–15%; the process conditions for secondary filtration and secondary drying are the same as those for primary filtration and primary drying. In step (3), the moisture content of the green body is <1%.

[0013] The product obtained by the present invention using the above-mentioned preparation method of sensible-latent heat composite thermal storage material based on alloy@SiC whisker@mullite structure has a thermal storage density >850J / g (room temperature~800℃), thermal conductivity >17W / (mK), compressive strength >110MPa, and does not crack after 200 thermal cycles at room temperature~800℃.

[0014] The present invention has the following beneficial effects:

[0015] (1) In view of the problem of thermal expansion mismatch in the prior art, the present invention adopts a novel alloy@SiC whisker@mullite double-shell encapsulated latent heat microcapsule structure. The flexible buffer intermediate layer is formed by in-situ synthesis of SiC whiskers with sponge structure to buffer the thermal stress and volume expansion generated by the phase transformation of Al-Si alloy during heating, overcome the structural damage of thermal stress to mullite shell, and avoid stress transmission to sensible heat ceramic substrate, thereby playing a role in stable encapsulation.

[0016] (2) The microcapsule structure of the present invention with double shell encapsulation forms a buffer layer in the middle part, which can also enhance the thermal conductivity between the alloy core and the mullite shell. Therefore, it is preferred to form a high thermal conductivity buffer middle layer in situ using SiC whiskers with high thermal conductivity.

[0017] (3) This invention employs a two-step pretreatment process for the alloy particles: first, they are immersed in silica sol to form a SiO2 gel layer, and then immersed in aluminum sol to form an Al2O3 gel layer. This is to better form the SiC whisker intermediate layer. When the first layer of SiO2 gel is held at 1050–1150°C, the Al metal in the Al-Si alloy undergoes a displacement reaction with SiO2. Utilizing the density difference between the reactants and products, a gap is formed between the alloy and the SiO2 layer, providing space for whisker growth and forming a buffer layer. The second layer of Al2O3 gel then combines with the outermost base material at the highest firing temperature to form a mullite shell layer.

[0018] (4) The present invention uses a double-shell structure of SiC whiskers + mullite shell to encapsulate the alloy. The non-wetting properties of the metal with the SiC whisker layer and the mullite shell reduce wetting and penetration. In addition, the outside is further encapsulated by the mullite-SiC whisker sensible ceramic matrix generated by the aluminosilicate mineral-Si-Al-C base material system, which is a double insurance and can further improve the stability of the encapsulation structure.

[0019] (5) This invention uses an aluminosilicate mineral-Si-Al-C system as the base material. During the firing process, through a series of displacement and reduction reactions, Al is converted into Al2O3. Combined with the generation of various gas phases, the volume expands synchronously with the alloy, mitigating the alloy expansion behavior during firing and preventing damage to the outermost matrix and alloy leakage. The generated gas phase enters the gap between the alloy and the mullite shell, replenishing the gas phase required for the formation of the whisker layer. Simultaneously, SiC whiskers are also generated in situ within the sensible heat-generating material, enhancing and increasing thermal conductivity.

[0020] (6) The Al-Si alloy used in this invention serves as both a latent heat material and a reducing agent for generating the whisker intermediate layer. In order to better form the microcapsule encapsulation structure, small-diameter Al-Si alloy particles with regular morphology (spherical) and better reactivity are used.

[0021] (7) This invention presents a sensible-latent heat composite thermal storage material with an alloy@SiC whisker@mullite double-shell microcapsule structure. This material exhibits a dense structure, high energy density, high thermal conductivity, high strength, and a high stability cycle life. Furthermore, the raw materials are readily available, the process is simple, and the firing temperature is low. This is of great significance for improving the quality, safety, stability, and cost savings of thermal storage materials. Through the design and preparation of a flexible interlayer, this invention optimizes the interface bonding, ultimately solving a problem that has plagued the industry for many years. It has broad market prospects and is conducive to promotion, application, and the advancement and development of industry technology. Attached Figure Description

[0022] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings:

[0023] Figure 1 This is a schematic diagram of the encapsulation structure of the composite thermal storage material according to an embodiment of the present invention;

[0024] Figure 2 These are scanning electron microscope images of the composite thermal storage material prepared according to the embodiments of the present invention;

[0025] Figure 3 These are photos comparing six samples. Detailed Implementation

[0026] Example 1:

[0027] This embodiment describes a method for preparing a sensible-latent heat composite thermal storage material based on an alloy@SiC whisker@mullite structure, the steps of which are as follows:

[0028] (1) A base material is prepared by mixing 20 wt% of kaolin (80 mesh), 10 wt% of ball clay (325 mesh), 20 wt% of andalusite (700 mesh), 5 wt% of quartz powder (180 mesh), 5 wt% of quartz glass powder (80 mesh), 11 wt% of metallic aluminum powder (180 mesh), 4 wt% of aluminum shavings (180 mesh), 15 wt% of metallic silicon powder (700 mesh), and 10 wt% of graphite (325 mesh). Carboxymethyl cellulose (CMC, 4 wt% of the base material) is added as a binder and mixed evenly.

[0029] (2) Al-12Si alloy (100 mesh, spherical) particles were immersed in silica sol (concentration 7.5%, pH 7.2) and stirred to coat them. After one filtration and one drying (temperature 60℃, drying time 24 h), Al-Si alloy particles with a pre-coated SiO2 gel layer were obtained. Then, they were immersed in aluminum sol (concentration 7.5%, pH 7.2) and stirred to coat them. After a second filtration and a second drying (temperature 60℃, drying time 24 h), Al-Si alloy particle precursor with a double gel layer structure of first coating SiO2 and then coating Al2O3 was obtained.

[0030] (3) The Al-Si alloy particle precursor and the base material were mixed in a mass ratio of 1:1. The Al-Si alloy particle precursor was incorporated into the base material, granulated, pressed, and dried (at 100℃ for 24 h) to obtain a green body (moisture content <1%). The green body was then placed in an electric furnace and embedded in graphite for sintering treatment, i.e., held at 1050℃ for 0.5 h, at 1100℃ for 1 h, and at 1300℃ for 3 h, to obtain a sensible-latent heat composite thermal storage material based on the alloy@SiC whisker@mullite structure; wherein, as shown in the figure Figure 1As shown, the matrix of the composite thermal storage material is mullite-SiC ceramic, and the matrix contains a double-shell microcapsule structure with an alloy core, an inner layer of SiC whisker layers, and an outer layer of mullite (see...). Figure 2 ).

[0031] Example 2:

[0032] This embodiment describes a method for preparing a sensible-latent heat composite thermal storage material based on an alloy@SiC whisker@mullite structure, the steps of which are as follows:

[0033] (1) A mixture of 20 wt% kaolin (80 mesh), 10 wt% bauxite (325 mesh), 20 wt% sillimanite (325 mesh), 20 wt% spherical clay (700 mesh), 10 wt% quartz glass powder (325 mesh), 5 wt% aluminum powder (325 mesh), 5 wt% polysilicon waste (180 mesh), 3 wt% graphite (500 mesh), 3 wt% carbon black (1000 mesh), and 4 wt% carbon powder (325 mesh) was used as the base material. A 5% polyvinyl alcohol solution (PVA solution, 3 wt% of the base material) was added and mixed evenly to obtain the base material.

[0034] (2) Al-12Si alloy (100 mesh, spherical) particles were immersed in silica sol (concentration 9%, pH 7.2) and stirred to coat them. After one filtration and one drying (temperature 60℃, drying time 24 h), Al-Si alloy particles with a pre-coated SiO2 gel layer were obtained. Then, they were immersed in aluminum sol (concentration 9%, pH 7.2) and stirred to coat them. After a second filtration and a second drying (temperature 60℃, drying time 24 h), Al-Si alloy particle precursor with a double gel layer structure of first coating SiO2 and then coating Al2O3 was obtained.

[0035] (3) The Al-Si alloy particle precursor and the base material were mixed in a mass ratio of 1:1. The Al-Si alloy particle precursor was incorporated into the base material, granulated, pressed, and dried (at 100℃ for 24 h) to obtain a green body (moisture content <1%). The green body was then placed in an electric furnace and sintered in carbon black, i.e., held at 1050℃ for 0.5 h, at 1100℃ for 1.5 h, and at 1350℃ for 2 h, to obtain a sensible-latent heat composite thermal storage material based on an alloy@SiC whisker@mullite structure; wherein, as Figure 1 As shown, the matrix of the composite thermal storage material is mullite-SiC ceramic, and the matrix contains a double-shell microcapsule structure with an alloy core, an inner layer of SiC whisker layers, and an outer layer of mullite (see...). Figure 2 ).

[0036] Example 3:

[0037] This embodiment describes a method for preparing a sensible-latent heat composite thermal storage material based on an alloy@SiC whisker@mullite structure, the steps of which are as follows:

[0038] (1) A mixture of 50 wt% kaolin (500 mesh), 20 wt% kyanite (700 mesh), 15 wt% aluminum powder (150 mesh), 10 wt% silicon powder (325 mesh), and 5 wt% graphite (400 mesh) was used as the base material. Carboxymethyl cellulose (CMC, 3 wt% of the base material) and a 5% polyvinyl alcohol solution (PVA solution, 2 wt% of the base material) were added and mixed evenly to obtain the base material.

[0039] (2) Al-30Si alloy (150 mesh, spherical) particles were immersed in silica sol (concentration 12%, pH 7.2) and stirred to coat them. After one filtration and one drying (temperature 60℃, drying time 24 h), Al-Si alloy particles with a pre-coated SiO2 gel layer were obtained. Then, they were immersed in aluminum sol (concentration 12%, pH 7.2) and stirred to coat them. After a second filtration and a second drying (temperature 60℃, drying time 24 h), Al-Si alloy particle precursor with a double gel shell structure of first coating SiO2 and then coating Al2O3 was obtained.

[0040] (3) The Al-Si alloy particle precursor and the base material were mixed in a mass ratio of 1:1. The Al-Si alloy particle precursor was incorporated into the base material, granulated, pressed, and dried (at 100℃ for 24 h) to obtain a green body (moisture content <1%). The green body was then placed in an electric furnace and buried in carbon powder for sintering treatment, i.e., held at 1050℃ for 1 h, held at 1150℃ for 2 h, and held at 1400℃ for 1 h to obtain a sensible-latent heat composite thermal storage material based on the alloy@SiC whisker@mullite structure; wherein, as Figure 1 As shown, the matrix of the composite thermal storage material is mullite-SiC ceramic, and the matrix contains a double-shell microcapsule structure with an alloy core, an inner layer of SiC whisker layers, and an outer layer of mullite (see...). Figure 2 ).

[0041] Example 4:

[0042] This embodiment describes a method for preparing a sensible-latent heat composite thermal storage material based on an alloy@SiC whisker@mullite structure, the steps of which are as follows:

[0043] (1) 50 wt% of spherical clay (700 mesh), 5 wt% of quartz powder (180 mesh), 5 wt% of quartz glass powder (80 mesh), 5 wt% of fly ash (325 mesh), 15 wt% of metallic aluminum powder (80 mesh), 3.5 wt% of polycrystalline silicon waste (80 mesh), 3.5 wt% of monocrystalline silicon waste (325 mesh), and 13 wt% of carbon powder (325 mesh) are mixed as the base material. Carboxymethyl cellulose (CMC, 2 wt% of the base material) and a 5% polyvinyl alcohol solution (PVA solution, 3 wt% of the base material) are added and mixed evenly to obtain the base material.

[0044] (2) Al-40Si alloy (200 mesh, spherical) particles were immersed in silica sol (concentration 15%, pH 7.2) and stirred to coat them. After one filtration and one drying (temperature 60℃, drying time 24 h), Al-Si alloy particles with a pre-coated SiO2 gel layer were obtained. Then, they were immersed in aluminum sol (concentration 15%, pH 7.2) and stirred to coat them. After a second filtration and a second drying (temperature 60℃, drying time 24 h), Al-Si alloy particle precursor with a double gel layer structure of first coating SiO2 and then coating Al2O3 was obtained.

[0045] (3) The Al-Si alloy particle precursor and the base material were mixed in a mass ratio of 1:1. The Al-Si alloy particle precursor was incorporated into the base material, granulated, pressed, and dried (at 100℃ for 24 h) to obtain a green body (moisture content <1%). The green body was then placed in an electric furnace and embedded in graphite for sintering treatment, i.e., held at 1050℃ for 0.5 h, at 1150℃ for 1 h, and at 1360℃ for 2 h, to obtain a sensible-latent heat composite thermal storage material based on the alloy@SiC whisker@mullite structure; wherein, as Figure 1 As shown, the matrix of the composite thermal storage material is mullite-SiC ceramic, and the matrix contains a double-shell microcapsule structure with an alloy core, an inner layer of SiC whisker layers, and an outer layer of mullite (see...). Figure 2 ).

[0046] Example 5:

[0047] This embodiment describes a method for preparing a sensible-latent heat composite thermal storage material based on an alloy@SiC whisker@mullite structure, the steps of which are as follows:

[0048] (1) 30 wt% of kaolin (325 mesh), 29 wt% of ball clay (700 mesh), 5 wt% of quartz powder (150 mesh), 10 wt% of aluminum powder (325 mesh), 2 wt% of polycrystalline silicon waste (240 mesh), 3 wt% of monocrystalline silicon waste (325 mesh), 5 wt% of silicon powder (700 mesh), 5 wt% of graphite (325 mesh), 5 wt% of carbon powder (325 mesh), and 6 wt% of carbon black (1000 mesh) are mixed as the base material. Carboxymethyl cellulose (CMC, 3 wt% of the base material) and a 5% polyvinyl alcohol solution (PVA solution, 2 wt% of the base material) are added and mixed evenly to obtain the base material.

[0049] (2) Al-40Si alloy (200 mesh, spherical) particles were immersed in silica sol (concentration 15%, pH 7.2) and stirred to coat them. After one filtration and one drying (temperature 60℃, drying time 24 h), Al-Si alloy particles with a pre-coated SiO2 gel layer were obtained. Then, they were immersed in aluminum sol (concentration 15%, pH 7.2) and stirred to coat them. After a second filtration and a second drying (temperature 60℃, drying time 24 h), Al-Si alloy particle precursor with a double gel layer structure of first coating SiO2 and then coating Al2O3 was obtained.

[0050] (3) The Al-Si alloy particle precursor and the base material were mixed in a mass ratio of 1:1. The Al-Si alloy particle precursor was incorporated into the base material, granulated, pressed, and dried (at 100℃ for 24 h) to obtain a green body (moisture content <1%). The green body was then placed in an electric furnace and embedded in graphite for sintering treatment, i.e., held at 1050℃ for 0.5 h, held at 1100℃ for 2 h, and held at 1340℃ for 2.5 h to obtain a sensible-latent heat composite thermal storage material based on an alloy@SiC whisker@mullite structure; wherein, as Figure 1 As shown, the matrix of the composite thermal storage material is mullite-SiC ceramic, and the matrix contains a double-shell microcapsule structure with an alloy core, an inner layer of SiC whisker layers, and an outer layer of mullite (see...). Figure 2 ).

[0051] Comparative Example 1:

[0052] Compared with Example 1, the alloy particles were not pretreated with silica sol and aluminosilicate coating in step (2), and the other process conditions were the same as in Example 1.

[0053] Comparative Example 2:

[0054] Compared with Example 1, the alloy particles only undergo aluminum sol coating pretreatment in step (2), while the other process conditions are the same as in Example 1.

[0055] Comparative Example 3:

[0056] Compared with Example 1, the alloy particles only undergo silica sol encapsulation pretreatment in step (2), while the remaining process conditions are the same as in Example 1.

[0057] Comparative Example 4:

[0058] Compared with Example 2, step (3) did not involve heat preservation at 1050℃ and 1100℃, while the other process conditions were the same as in Example 2.

[0059] Comparative Example 5:

[0060] Compared with Example 3, the reducing atmosphere sintering with embedded carbon powder was not used; instead, a vacuum environment was used as the sintering environment, and the other process conditions were the same as in Example 3.

[0061] Comparative Example 6:

[0062] Compared with Example 3, the basic raw materials in step (1) do not contain any reducing agents, and only aluminosilicate minerals are used as the basic raw materials. The other process conditions are the same as in Example 3.

[0063] The performance and appearance of the samples prepared in the embodiments and comparative examples of the present invention are described in Table 1.

[0064] Table 1. Description of the performance and appearance of samples prepared in the embodiments and comparative examples of the present invention.

[0065] Example 1 19.2 131 913 none Example 2 17.2 111 872 none Example 3 18.4 125 854 none Example 4 18.5 120 868 none Example 5 18.7 118 865 none Comparative Example 1 15.4 95 715 Give way Comparative Example 2 15.7 91 721 Give way Comparative Example 3 16.4 99 731 Minor leak Comparative Example 4 16.7 88 710 Give way Comparative Example 5 15.7 82 668 Serious leak Comparative Example 6 8.2 35 564 Cracks, leaks

[0066] As shown in Table 1, the samples prepared in Examples 1 to 5 of the present invention all exhibited high thermal conductivity, high strength, and high stability; and did not crack after 200 thermal cycles at room temperature to 800°C.

[0067] Comparing the data of Example 1 and Comparative Example 1, it can be seen that Comparative Example 1 did not use sol-gel encapsulation treatment, the SiC whisker intermediate layer was not easy to obtain, the mullite shell layer was incomplete, the alloy was prone to leakage, the strength was reduced, and the middle was dented due to leakage because the structure of alloy@SiC whisker@mullite shell layer was incomplete.

[0068] Comparing the data of Example 1 and Comparative Example 2, it can be seen that Comparative Example 2, which only encapsulates aluminum sol, only obtains a mullite shell layer and lacks a SiC whisker intermediate layer. It cannot buffer the thermal stress generated by the expansion of the alloy, and is also prone to leakage, resulting in a decrease in strength.

[0069] Comparing the data of Example 1 and Comparative Example 3, it can be seen that after the SiC whisker intermediate layer was formed in Comparative Example 3, although the outer mullite shell was not complete, it was able to buffer most of the expansion. However, a high-strength mullite shell layer was not formed well during the firing process, and there was still slight leakage in the early stage of firing.

[0070] Comparing the data of Example 2 and Comparative Example 4, it can be seen that Comparative Example 4 lacks the substitution reaction at low temperature. Without the substitution reaction, cavities or gaps are not formed, and a SiC whisker intermediate layer with good morphology and structure cannot be formed. Similarly, the stability, thermal conductivity, strength and other properties will decrease, and leakage will also occur.

[0071] Comparing the data of Example 3 and Comparative Example 5, it can be seen that Comparative Example 5 did not use a reducing atmosphere with embedded carbon powder, and did not form an encapsulation structure of alloy core@whisker layer@ceramic shell, resulting in serious leakage.

[0072] Comparing the data from Example 3 and Comparative Example 6, it can be seen that no reducing agent was added to the base material of Comparative Example 6. The outermost ceramic matrix did not expand with increasing temperature, failing to counteract the alloy's expansion. Consequently, the green body cracked, leading to alloy leakage (see...). Figure 3 ).

Claims

1. A preparation method of an apparent heat-latent heat composite heat storage material based on an alloy SiC whisker mullite structure, characterized by Includes the following steps: (1) A base material is obtained by mixing 50-70 wt% of aluminosilicate minerals, 0-15 wt% of siliceous raw materials, 5-15 wt% of metallic aluminum raw materials, 5-15 wt% of metallic silicon raw materials and 5-15 wt% of carbonaceous raw materials, and adding a binder to mix evenly. (2) The Al-Si alloy particles were immersed in silica sol and stirred and coated. After one filtration and one drying, Al-Si alloy particles with a pre-coated SiO2 shell were obtained. Then, they were immersed in aluminum sol and stirred and coated. After two filtrations and two dryings, Al-Si alloy particle precursor with a double gel shell structure of first coating SiO2 and then coating Al2O3 was obtained. (3) The Al-Si alloy particle precursor and the base material are mixed in a mass ratio of 1:

1. The Al-Si alloy particle precursor is mixed into the base material and then granulated, pressed and dried to obtain a green body. The green body is then embedded in a carbonaceous material for reducing atmosphere sintering treatment, i.e., held at 1050℃ for 0.5-1h, held at 1050-1150℃ for 1-2h, and held at 1250-1400℃ for 1-3h to obtain a sensible-latent heat composite thermal storage material based on alloy@SiC whisker@mullite structure. The matrix of the composite thermal storage material is mullite-SiC ceramic, and the matrix contains a double-shell microcapsule structure with an alloy core, an inner layer of SiC whisker layer and an outer layer of mullite shell. 2.The preparation method of the sensible-latent heat composite heat storage material based on alloy SiC whisker-mullite structure according to claim 1, characterized in that: The aluminosilicate mineral is one or a combination of kaolin, spheroidal clay, andalusite, sillimanite, kyanite, and bauxite; the siliceous raw material is one or a combination of fly ash, quartz powder, and quartz glass powder; the metallic aluminum raw material is metallic aluminum powder and / or aluminum shavings; the metallic silicon raw material is one or a combination of metallic silicon powder, polycrystalline silicon waste, and monocrystalline silicon waste; the carbonaceous raw material is one or a combination of graphite, carbon powder, and carbon black; and the Si content in the Al-Si alloy is 12-40%. 3.The preparation method of the sensible-latent heat composite heat storage material based on alloy SiC whisker-mullite structure according to claim 1, characterized in that: The aluminosilicate minerals have a particle size of 80–700 mesh; the siliceous raw materials have a particle size of 80–325 mesh; the metallic aluminum raw materials have a particle size of 80–325 mesh; the metallic silicon raw materials have a particle size of 80–700 mesh; the carbonaceous raw materials have a particle size of 325–1000 mesh; and the Al-Si alloy particles have a particle size of 100–200 mesh and are spherical in shape. 4.The preparation method of the sensible-latent heat composite heat storage material based on alloy SiC whisker-mullite structure according to claim 1, characterized in that: The binder is a carboxymethyl cellulose and / or polyvinyl alcohol solution, and the amount of binder used is 3 to 5 wt% of the base raw material. 5.The preparation method of the sensible-latent heat composite heat storage material based on alloy SiC whisker-mullite structure according to claim 1, characterized in that: In step (2), the concentrations of both silica sol and alumina sol are 7.5-15%; the process conditions for secondary filtration and secondary drying are the same as those for primary filtration and primary drying. 6.The preparation method of the sensible-latent heat composite heat storage material based on alloy SiC whisker-mullite structure according to claim 1, characterized in that: The moisture content of the green body in step (3) is <1%.

7. The product prepared by the method for preparing sensible-latent heat composite thermal storage material based on alloy@SiC whisker@mullite structure as described in any one of claims 1-6.

8. The product of claim 7, wherein: The composite thermal storage material has a thermal storage density of >850J / g (room temperature to 800℃), thermal conductivity of >17W / (mK), compressive strength of >110MPa, and does not crack after 200 thermal cycles at room temperature to 800℃.

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