Carbon mineralization-based thermoelectric composite material and preparation method thereof

Abstract

The application provides a carbon-mineralized-based thermoelectric composite material and a preparation method thereof. The preparation raw materials comprise the following components in parts by weight: 70-90 parts of a carbon-mineralized precursor material, 0-20 parts of an electrically-conductive reinforcing filler, 1-20 parts of a thermoelectric functional filler and a certain amount of water. The carbon-mineralized material is used as a matrix to form a high-strength calcium carbonate and low-calcium silica gel structure, so that the mechanical properties of the material are enhanced. A stable three-dimensional conductive network is constructed through ball milling pre-dispersion and in-situ fixation in the carbonization process. The prepared carbon-mineralized-based thermoelectric composite material simultaneously has high compressive strength and excellent thermoelectric properties.

Description

Technical Field

[0001] This invention relates to the field of thermoelectric materials technology, specifically to a carbon mineralization-based thermoelectric composite material and its preparation method. Background Technology

[0002] With societal development, human demand for energy is increasing daily. Traditional fossil fuels are not only facing depletion, but their large-scale combustion also releases excessive greenhouse gases into the atmosphere, causing serious environmental damage. Therefore, the need to find alternative energy sources is growing, and thermoelectric materials, which convert heat energy into electrical energy, have become a research hotspot in recent years. The thermoelectric effect refers to the directional thermal diffusion of charge carriers within a material under a temperature gradient, thereby generating a potential difference across its terminals.

[0003] Traditional thermoelectric materials are mainly metals and semiconductors. Although they possess high thermoelectric performance, their low mechanical strength and brittleness make them unsuitable for direct use in applications requiring structural strength or durability, thus limiting their engineering applications. In recent years, researchers have introduced functional fillers (such as metal oxides and carbon materials) into cement matrices to obtain thermoelectric composite materials with thermoelectric effects. However, problems such as difficulty in dispersing the fillers and low thermoelectric efficiency of the devices still exist. In cement-based thermoelectric composites, the introduced functional fillers are prone to agglomeration or uneven distribution, leading to unstable material properties, reduced thermoelectric efficiency, and poor controllability in the preparation process. The complex preparation process of thermoelectric materials also limits their application. The preparation of traditional thermoelectric materials often requires high-temperature sintering or complex processes, while cement-based composites have long curing cycles and high energy consumption, increasing production costs and environmental burden.

[0004] Therefore, how to prepare a thermoelectric material based on novel materials that possesses both excellent mechanical and thermoelectric properties, improves the uniformity of filler dispersion, and simplifies the preparation process is an urgent problem to be solved. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present invention provides a carbon mineralization-based thermoelectric composite material and its preparation method, aiming to solve the technical problem of poor comprehensive thermoelectric and mechanical properties of thermoelectric materials in the prior art.

[0006] In a first aspect, the present invention provides a carbon mineralization-based thermoelectric composite material, the raw materials for which, by weight, include the following components: 70-90 parts of carbon mineralization precursor material, 0-20 parts of conductive reinforcing filler, 1-20 parts of thermoelectric functional filler, and several parts of water.

[0007] Preferably, the carbon mineralization precursor material includes at least one of C3S, γ-C2S, β-C2S, C3S2, and CS.

[0008] Preferably, the particle size of the carbon mineralization precursor material is 0.5~80 μm, and the apparent density is 2500~3500 kg / m³. 3 Specific surface area is 250~300m² 2 / kg.

[0009] Preferably, the conductive reinforcing filler includes graphite and / or carbon black.

[0010] Preferably, the thermoelectric functional filler includes at least one of bismuth telluride, graphene, and carbon fiber.

[0011] Preferably, the thermoelectric functional filler is graphene.

[0012] Preferably, the mass of water is 8% to 15% of the total mass of the carbon mineralization precursor, the conductive reinforcing filler, and the thermoelectric functional filler.

[0013] Secondly, the present invention provides a method for preparing a carbon mineralization-based thermoelectric composite material, comprising the following steps: After vacuum drying pretreatment, carbon mineralization precursor material, conductive reinforcing filler, and thermoelectric functional filler are ball-milled and mixed, and then water is added and stirred evenly to obtain wet material. Wet material is placed in a mold and pressed to form a blank. The blank is then placed in a CO2 atmosphere for carbonization curing to obtain a carbon mineralized thermoelectric composite material.

[0014] Preferably, the vacuum drying temperature is 180~220℃ and the vacuum drying time is 2~4h.

[0015] Preferably, the carbonization curing conditions are: carbonization temperature at room temperature, carbon dioxide volume concentration ≥99.8%, gas pressure 0.2~0.4MPa, and curing time 24~36h.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a carbon mineralization-based thermoelectric composite material that achieves a synergistic improvement in mechanical and thermoelectric properties. Based on the high-strength, dense matrix of the carbon mineralization material, it provides stable support for brittle thermoelectric fillers, enabling the material to maintain good thermoelectric performance while possessing high compressive strength, thus achieving structural-functional integration. This invention constructs a stable three-dimensional conductive network through ball milling pre-dispersion and in-situ fixation during the carbonization process, effectively overcoming the problems of filler agglomeration and performance inhomogeneity, ensuring the long-term stability and reliability of thermoelectric output. Compared to the complex preparation process of traditional thermoelectric materials, the carbon mineralization-based thermoelectric composite material of this invention adopts a dry mixing, compression molding, and low-temperature carbonization curing process. Room temperature / near room temperature, low-pressure carbonization curing replaces traditional high-temperature sintering, significantly reducing energy consumption and equipment requirements, achieving short-cycle, low-cost manufacturing. Simultaneously, the carbonization process actively consumes and solidifies CO2, making the preparation process itself carbon negative, thus providing environmental benefits. Attached Figure Description

[0017] Figure 1 This is a SEM image of the carbon mineralization-based thermoelectric composite material obtained in Example 2 of the present invention. Detailed Implementation

[0018] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0019] To address the technical problem of poor combined thermoelectric and mechanical properties of existing thermoelectric materials, this invention provides a carbon mineralization-based thermoelectric composite material and its preparation method. The method involves using a carbon mineralization material as the matrix to form a high-strength calcium carbonate and low-calcium silicate gel structure, thereby enhancing the material's mechanical properties. Through ball milling pre-dispersion and in-situ fixation during the carbonization process, a stable three-dimensional conductive network is constructed. The resulting carbon mineralization-based thermoelectric composite material possesses both high compressive strength and excellent thermoelectric properties.

[0020] In a first aspect, embodiments of the present invention provide a carbon mineralization-based thermoelectric composite material, the raw materials for which, by weight, include the following components: 70-90 parts of carbon mineralization precursor material, 0-20 parts of conductive reinforcing filler, 1-20 parts of thermoelectric functional filler, and several parts of water.

[0021] In the technical solution of this invention, the carbon mineralization precursor material has high carbonization activity. Under a CO2 atmosphere, it can rapidly undergo a carbonization reaction to generate interwoven calcium carbonate crystals and low-calcium silicate gel, forming a high-strength, high-density, and stable matrix. This matrix provides excellent mechanical properties and a stable carrier for the dispersion and functional performance of thermoelectric fillers and conductive reinforcing fillers. The conductive reinforcing filler forms a conductive network in the matrix, significantly improving the electrical conductivity of the composite material and further realizing efficient thermoelectric conversion. The thermoelectric functional filler is the core of generating the thermoelectric effect, providing a high Seebeck coefficient and enabling the generation of a significant voltage under a temperature gradient. The carbon mineralization matrix provides a stable, robust, and well-bonded dispersion environment for the conductive reinforcing component and the thermoelectric functional filler. The conductive reinforcing component compensates for the insufficient electrical conductivity of the thermoelectric functional filler and the matrix itself, while the thermoelectric functional filler ensures that the entire composite material possesses the intrinsic ability to convert thermal energy into electrical energy. The synergy of these three components achieves a balance and optimization of the mechanical and thermoelectric properties of the carbon mineralization-based thermoelectric composite material.

[0022] Furthermore, in some embodiments, the carbon mineralization precursor material includes at least one of C3S, γ-C2S, β-C2S, C3S2, and CS.

[0023] Furthermore, in some embodiments, the particle size of the carbon mineralization precursor material is 0.5–80 μm, and the apparent density is 2500–3500 kg / m³. 3 Specific surface area is 250~300m² 2 / kg.

[0024] Furthermore, in some embodiments, the conductive reinforcing filler comprises graphite and / or carbon black.

[0025] Furthermore, in some embodiments, the thermoelectric functional filler includes at least one of bismuth telluride, graphene, and carbon fiber.

[0026] Furthermore, in some embodiments, the thermoelectric functional filler is graphene.

[0027] In the technical solution of this invention embodiment, graphene possesses both excellent electrical and thermal properties. Its unique two-dimensional honeycomb crystal structure endows it with extremely high carrier mobility and thermal conductivity. Furthermore, graphene sheets have a large specific surface area and good mechanical flexibility, allowing for more uniform dispersion in the carbon mineralization precursor material during ball milling pre-dispersion. During carbonization curing, it interacts with in-situ generated calcium carbonate crystals to form a stable interfacial bond, further enhancing the mechanical properties of the composite material, thereby achieving a better synergistic improvement in both thermoelectric and mechanical properties.

[0028] Furthermore, in some embodiments, the mass of water is 8% to 15% of the total mass of the carbon mineralization precursor, the conductive reinforcing filler, and the thermoelectric functional filler.

[0029] Secondly, embodiments of the present invention provide a method for preparing a carbon mineralization-based thermoelectric composite material, comprising the following steps: After vacuum drying pretreatment, carbon mineralization precursor material, conductive reinforcing filler, and thermoelectric functional filler are ball-milled and mixed, and then water is added and stirred evenly to obtain wet material. Wet material is placed in a mold and pressed to form a blank. The blank is then placed in a CO2 atmosphere for carbonization curing to obtain a carbon mineralized thermoelectric composite material.

[0030] In the technical solution of this invention embodiment, vacuum drying can effectively remove adsorbed moisture and volatile impurities from the raw materials, avoiding material agglomeration or affecting mixing uniformity during subsequent ball milling. Ball milling uses high-speed rotating grinding balls to grind and shear the materials, further refining the raw material particles. The purpose is to ensure that each component, especially the trace amounts of added thermoelectric filler and conductive phase, is fully and uniformly dispersed in the matrix, initially constructing a thermally and electrically conductive connection path, laying the foundation for the formation of a stable three-dimensional network during subsequent carbonization. The wet material is pressed into a compact green body with a certain shape. Carbonization curing of the green body is a key step in the preparation process. Under these conditions, CO2 gas penetrates into the interior of the green body and reacts chemically with the active component carbon mineralization precursor material to generate calcium carbonate and silica gel, firmly bonding the loose powder particles together. The originally dispersed conductive reinforcing filler and thermoelectric functional filler particles are fixed by the in-situ generated carbide matrix, further improving the conductive and thermally conductive network structure, forming the final high-strength thermoelectric composite material.

[0031] Furthermore, in some embodiments, the vacuum drying temperature is 180~220℃, and the vacuum drying time is 2~4h.

[0032] Furthermore, in some embodiments, the carbonization curing conditions are as follows: carbonization temperature is room temperature, carbon dioxide volume concentration is ≥99.8%, gas pressure is 0.2~0.4MPa, and curing time is 24~36h.

[0033] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0034] In the following embodiments of the present invention, the carbon mineralization precursor material is γ-C2S powder with a particle size of 0.5~80μm and an apparent density of approximately 3000 kg / m³. 3 Specific surface area is 260m² 2 / kg, purity >99%.

[0035] Example 1 A carbon mineralization-based thermoelectric composite material, the raw materials for which are prepared include the following components by weight: 79 parts of carbon mineralization precursor material, 10 parts of graphite, 1 part of carbon fiber, and 10 parts of water.

[0036] The specific steps for preparing this carbon mineralization-based thermoelectric composite material are as follows: (1) After drying the carbon mineralization precursor material, graphite and carbon fiber in a vacuum drying oven at 200°C for 2 hours, the three materials are ball-milled in a ball mill for 1 hour to fully mix them. Then, the mixture is taken out and water is added and stirred until uniform to obtain wet material. (2) The wet material is placed in a stainless steel carbonization mold and pressed to form a blank. The blank is then immediately placed in a carbonization box for carbonization. The CO2 purity in the carbonization box is 99.9%, the carbonization pressure is 0.3 MPa, and the carbonization time is 24 h. After carbonization, carbon mineralization-based thermoelectric composite material is obtained.

[0037] Example 2 A carbon mineralization-based thermoelectric composite material, the raw materials for which are prepared include the following components by weight: 79 parts of carbon mineralization precursor material, 11 parts of graphene, and 10 parts of water.

[0038] The specific steps for preparing this carbon mineralization-based thermoelectric composite material are as follows: (1) After drying the carbon mineralization precursor material and graphene in a vacuum drying oven at 200°C for 2 hours, the two materials were ball-milled for 1 hour to fully mix them. Then, the mixture was taken out and water was added and stirred until uniform to obtain wet material. (2) The wet material is placed in a stainless steel carbonization mold and pressed to form a blank. The blank is then immediately placed in a carbonization box for carbonization. The CO2 purity in the carbonization box is 99.9%, the carbonization pressure is 0.3 MPa, and the carbonization time is 24 h. After carbonization, carbon mineralization-based thermoelectric composite material is obtained.

[0039] The SEM image of the carbon mineralization-based thermoelectric composite material prepared in this embodiment is as follows: Figure 1 As shown.

[0040] Example 3 A carbon mineralization-based thermoelectric composite material, the raw materials for which are prepared include the following components by weight: 79 parts of carbon mineralization precursor material, 11 parts of high-purity bismuth telluride powder, and 10 parts of water.

[0041] The specific steps for preparing this carbon mineralization-based thermoelectric composite material are as follows: (1) After drying the carbon mineralization precursor material and the high-purity bismuth telluride powder in a vacuum drying oven at 200°C for 2 hours, the two materials were ball-milled for 1 hour to fully mix them. Then, the mixture was taken out and water was added and stirred until uniform to obtain a wet material. (2) The wet material is placed in a stainless steel carbonization mold and pressed to form a blank. The blank is then immediately placed in a carbonization box for carbonization. The CO2 purity in the carbonization box is 99.9%, the carbonization pressure is 0.3 MPa, and the carbonization time is 24 h. After carbonization, carbon mineralization-based thermoelectric composite material is obtained.

[0042] Comparative Example 1 The difference between this comparative example and Example 1 is that vacuum drying was not performed in step (1), and ball milling was performed directly.

[0043] Performance testing The compressive strength and Seebeck coefficient of the carbon mineralized thermoelectric composite materials prepared in each embodiment and comparative example were tested; the test method was in accordance with the international standard ASTM E1225, and the results are shown in Table 1.

[0044] Table 1

[0045] Table 1 shows that the carbon-based thermoelectric composite materials prepared in the embodiments of the present invention have high compressive strength and Seebeck coefficient, exhibiting excellent mechanical and thermoelectric properties. Among them, Example 2 has the best overall performance, which is due to the mechanical reinforcement effect of graphene itself, which further improves the mechanical strength of the composite material. At the same time, the excellent electrical conductivity of graphene is also the reason for its superior thermoelectric properties. In Example 1, the electrical conductivity and mechanical properties of graphite and carbon fiber are significantly weaker than those of graphene. In Example 3, bismuth telluride is only introduced as a thermoelectric component and cannot form a three-dimensional conductive network well, so its effect on improving the mechanical and thermoelectric properties of the composite material is limited.

[0046] In Comparative Example 1, because the raw materials were not dried, the moisture during the ball milling process may cause the raw materials to agglomerate, affecting the uniformity of mixing and thus adversely affecting the final material properties.

[0047] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A carbon mineralization-based thermoelectric composite material, characterized in that, The raw materials for preparation include the following components by weight: 70-90 parts of carbon mineralization precursor material, 0-20 parts of conductive reinforcing filler, 1-20 parts of thermoelectric functional filler, and a certain amount of water.

2. The carbon mineralization-based thermoelectric composite material according to claim 1, characterized in that, The carbon mineralization precursor material includes at least one of C3S, γ-C2S, β-C2S, C3S2, and CS.

3. The carbon mineralization-based thermoelectric composite material according to claim 2, characterized in that, The carbon mineralization precursor material has a particle size of 0.5~80μm and an apparent density of 2500~3500kg / m³. 3 Specific surface area is 250~300m² 2 / kg.

4. The carbon mineralization-based thermoelectric composite material according to claim 1, characterized in that, The conductive reinforcing filler includes graphite and / or carbon black.

5. The carbon mineralization-based thermoelectric composite material according to claim 1, characterized in that, The thermoelectric functional filler includes at least one of bismuth telluride, graphene, and carbon fiber.

6. The carbon mineralization-based thermoelectric composite material according to claim 5, characterized in that, The thermoelectric functional filler is graphene.

7. The carbon mineralization-based thermoelectric composite material according to claim 1, characterized in that, The mass of the water is 8% to 15% of the total mass of the carbon mineralization precursor, conductive reinforcing filler, and thermoelectric functional filler.

8. The method for preparing the carbon mineralization-based thermoelectric composite material according to any one of claims 1 to 7, characterized in that, Includes the following steps: After vacuum drying pretreatment, carbon mineralization precursor material, conductive reinforcing filler, and thermoelectric functional filler are ball-milled and mixed, and then water is added and stirred evenly to obtain wet material. The wet material is placed in a mold and pressed to form a blank. The blank is then placed in a CO2 atmosphere for carbonization curing to obtain the carbon mineralized thermoelectric composite material.

9. The method for preparing the carbon mineralization-based thermoelectric composite material according to claim 8, characterized in that, The vacuum drying temperature is 180~220℃, and the vacuum drying time is 2~4h.

10. The method for preparing the carbon mineralization-based thermoelectric composite material according to claim 8, characterized in that, The carbonization curing conditions are as follows: carbonization temperature is room temperature, carbon dioxide volume concentration is ≥99.8%, gas pressure is 0.2~0.4MPa, and curing time is 24~36h.

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