A recycled carbon-ceramic composite thermal protection material based on photovoltaic thermal field recovery of carbon-carbon materials and its preparation method

Abstract

The application discloses a recycled carbon ceramic composite heat protection material based on photovoltaic thermal field recycled carbon carbon material and a preparation method thereof. Through processes such as crushing, mixing, hot pressing, carbonization and silicon melting, the waste C / C material is converted into a quaternary composite system heat protection material containing recycled short carbon fibers, pyrolytic carbon, silicon carbide and silicon. The material realizes full-component recycling of the waste composite material, reduces the cost by more than 60%, has a waste utilization rate of 95% or more, and reduces CO2 emission by 70%. The thermal conductivity of the material is 200 W / (m*K) or more, the temperature resistance is 1600 DEG C or more, the material has excellent ablation resistance and oxidation resistance, and provides a green high-performance solution for the photovoltaic and aerospace fields.

Description

Technical Field

[0001] This invention relates to the field of high-temperature composite materials technology, specifically to a recycled carbon-ceramic composite thermal protection material based on photovoltaic thermal field recovery of carbon-carbon materials and its preparation method. Background Technology

[0002] With the rapid development of the photovoltaic industry, a large number of photovoltaic thermal field components, such as single-crystal furnace crucibles and insulation cylinders, generate a significant amount of carbon-carbon composite (C / C) waste after completing their life cycle. Research reveals that current research in the field of high-temperature composite materials focuses over 70% on preparing high-performance materials from virgin raw materials, with less than 10% involving recycling technologies. Furthermore, these recycling technologies primarily target carbon-carbon composite materials used in the aerospace industry. Aerospace carbon-carbon composite material recycling emphasizes restoring the high strength and high modulus properties of the materials, while photovoltaic thermal field component recycling focuses more on low cost, high thermal conductivity, and compatibility with photovoltaic industry production processes. The two differ significantly in their recycling needs and technological approaches.

[0003] C / C composites possess excellent high-temperature performance, but traditional disposal methods, such as landfilling or incineration, present numerous problems. On the one hand, these methods lead to the loss of high-value carbon fiber resources, as carbon fiber is difficult to degrade naturally, and landfilling results in long-term resource idleness and land occupation. On the other hand, the incineration process not only releases large amounts of carbon dioxide, exacerbating the greenhouse effect, but also generates pollutants such as dust, imposing a serious burden on the environment and contradicting global carbon reduction goals.

[0004] Currently, most existing C / C composite material recycling technologies are limited to the extraction of single components, making it difficult to achieve efficient utilization throughout the material's entire life cycle. For example, existing technology A extracts only carbon fibers through chemical dissolution, resulting in the resin matrix and other components being treated as waste. Technology B, while attempting overall recycling, lacks effective methods for component reconstruction, resulting in recycled materials with a thermal conductivity of only 120 W / (m·K), far below the 180 W / (m·K) or higher required for practical photovoltaic thermal applications. Moreover, these recycling technologies have complex processes that consume significant amounts of energy, leading to high recycling costs and severely hindering the development of the circular economy in this field.

[0005] The introduction of silicon carbide (SiC) offers a new approach to solving the aforementioned problems. Studies have shown that SiC possesses multiple superior properties in material systems. During high-temperature service, a dense silicon oxide layer (SiO2) forms on the SiC surface, which significantly inhibits oxygen diffusion, providing long-term antioxidant protection. As a rigid reinforcement, SiC inhibits crack propagation through a pinning effect, thereby improving the mechanical strength of the composite material. Furthermore, SiC exhibits excellent interfacial compatibility with carbon fibers and pyrolytic carbon matrices, optimizing the material's thermal conductivity path and reducing interfacial thermal resistance. In the recycled materials involved in this invention, residual silicon (5-10%) can react with free carbon in the melt infiltration process to generate a new SiC phase, further filling the material's pores and achieving self-repair through densification. By transforming decommissioned photovoltaic thermal field materials into a short carbon fiber-pyrolytic carbon-SiC multi-component system, not only can waste C / C materials be given a second life, but material performance can also be upgraded through component reconstruction, while reducing recycling costs, providing a green and sustainable development path for high-temperature industries. Summary of the Invention

[0006] To address the aforementioned technical problems, this application resolves the issues of resource waste, environmental pollution, high recycling costs, and low efficiency associated with existing photovoltaic thermal field decommissioning C / C material processing methods. It also overcomes the traditional misconception that recycled materials cannot achieve high performance.

[0007] To achieve the above objectives, the technical solution adopted in this application is as follows: a regenerated carbon-ceramic composite thermal protection material based on photovoltaic thermal field recovery of carbon-carbon materials, which is composed of the following quaternary composite system by mass percentage:

[0008] Recycled short carbon fibers: 30%, wherein the length of the recycled short carbon fibers is 50-300 μm and the diameter is 5-10 μm; when the length of the recycled short carbon fibers is less than 50 μm, a three-dimensional skeleton reinforcement structure cannot be effectively formed, and the mechanical properties of the material decrease by more than 20%; when the length is greater than 300 μm, agglomeration is prone to occur during mixing and molding, resulting in uneven material properties. This invention selects this length and diameter range, which allows for full synergy with other components. Compared to the simple use of recycled carbon fibers in existing technologies, this application improves the thermal shock resistance of the material by 35% through precise control of fiber size.

[0009] Pyrolytic carbon: 45%, wherein the pyrolytic carbon has a graphitization degree ≥80% and a specific surface area of ​​10-50 m². 2 / g; The pyrolyzed carbon originates from the high-temperature pyrolysis products of the resin matrix of waste carbon fiber composites, exhibiting significant high graphitization and porous structure formation. During the high-temperature pyrolysis process, by controlling the heating rate and pyrolysis time, the resin matrix is ​​orderly transformed into structured pyrolyzed carbon. This structure can not only serve as a filler to reduce material density by up to 15%, but also form chemical bonds with fibers through surface active sites, resulting in a 40% increase in interfacial bonding strength compared to ordinary carbon fillers in existing technologies.

[0010] Silicon carbide: 20%, wherein the average particle size of the silicon carbide is 0.5-5 μm; silicon carbide within this particle size range can be uniformly dispersed in the material and fully exert its synergistic effect with other components. Unlike the prior art that uses silicon carbide with a single particle size, this application improves the high-temperature strength of the material by 25% by optimizing the particle size distribution.

[0011] Silicon: 5%, with a purity ≥99.9% and a particle size of 1-10 μm. During sintering, silicon undergoes an in-situ reaction with pyrolyzed carbon to generate nano-SiC whiskers that fill the pores, while simultaneously consuming free carbon. When the silicon purity is below 99.9%, impurities affect the in-situ reaction, leading to an 8% increase in material porosity and a significant decrease in performance. This invention strictly controls the purity and particle size of silicon, achieving precise control over material densification.

[0012] To better realize the present invention, the recycled short carbon fiber is further used as a three-dimensional skeleton reinforcement.

[0013] To better realize the present invention, the pyrolyzed carbon is further derived from the high-temperature pyrolysis products of the resin matrix of waste carbon fiber composite material, and has a high degree of graphitization and a porous structure.

[0014] To better realize the present invention, the silicon further reacts in situ with pyrolyzed carbon during the sintering process to generate nano-SiC whiskers that fill the pores, while consuming free carbon.

[0015] A method for preparing the aforementioned recycled carbon-ceramic composite thermal protection material includes the following steps:

[0016] Crushing: The recovered photovoltaic thermal field decommissioned C / C material is mechanically crushed into powder with a particle size ≤200μm. The powder composition includes 25-35wt% short carbon fibers, 35-50wt% pyrolyzed carbon, 15-25wt% SiC, and 5-10wt% silicon. When the crushed particle size is greater than 200μm, the uniformity of subsequent mixing decreases, leading to a larger fluctuation range in material properties. When the sieving rate is less than 95%, coarse particles will affect the molding quality and final performance of the material. This invention strictly controls the crushed particle size and sieving rate, laying the foundation for subsequent processes.

[0017] Mixing: Add 2-5 wt% phenolic resin as a binder and ball mill for 2-4 hours to ensure uniform composition. If the binder addition is below 2 wt%, the material is difficult to mold; if it exceeds 5 wt%, it will increase the impurity content and reduce material performance. By optimizing the ball milling time and speed, this application achieves thorough and uniform mixing of the components, improving material performance consistency by 30%.

[0018] Hot pressing: The preform is cured in a vacuum hot press at a pressure of 30-60 MPa and a temperature of 180-220°C for 1-2 hours. When the pressure is below 30 MPa, the preform has insufficient density and low strength; pressure above 60 MPa may damage the internal structure of the material. Temperatures below 180°C result in incomplete resin curing; temperatures above 220°C cause resin decomposition, affecting material properties. The hot pressing pressure determined in this invention is 50 MPa. Under this condition, the preform exhibits the best overall performance, with a 25% increase in strength compared to other pressure settings.

[0019] Carbonization: Under a nitrogen atmosphere, the temperature is increased to 900℃ at 5℃ / min and held for 2 hours to cause the resin to decompose and generate a porous carbon skeleton.

[0020] Molten silicon infiltration: Under argon protection at 1420-1600℃, molten silicon infiltrates the pores and reacts with free carbon to form SiC. The reaction time is 2-4 hours, ultimately resulting in a material porosity ≤3%. When the silicon infiltration temperature is below 1420℃, the silicon's fluidity is insufficient, preventing it from fully infiltrating the pores; above 1600℃, excessive reaction occurs, leading to performance degradation. The silicon infiltration temperature determined in this application is 1550℃. At this temperature, the reaction rate is maximized, and the thermal conductivity of the material is increased by 20% compared to other temperature settings.

[0021] To better realize the present invention, further, in the crushing step, the crushed particle size is ≤200μm and the sieving rate is ≥95%.

[0022] To better realize the present invention, further, in the hot pressing molding step, the hot pressing pressure is 50 MPa.

[0023] To better realize the present invention, further, in the melt silicon infiltration step, the silicon infiltration temperature is 1550°C.

[0024] The recycled carbon-ceramic composite thermal protection material can be applied to photovoltaic thermal field components or aerospace high-temperature resistant composite materials.

[0025] The technical solution provided by this invention has the following advantages compared with the prior art:

[0026] 1. This invention directly utilizes short carbon fibers from photovoltaic thermal field recycled materials and generates silicon carbide in situ, avoiding the high-energy-consuming process of synthesizing SiC separately and the procurement of new fibers, thus reducing raw material costs by 60%.

[0027] 2. In the preparation method of this invention, the waste utilization rate is ≥95%, and CO2 emissions are reduced by 70% compared with traditional processes, effectively reducing the impact on the environment.

[0028] 3. The recycled material prepared by this invention has a thermal conductivity ≥200W / (m·K) and a temperature resistance ≥1600℃. It has excellent multi-level structure anti-ablation performance and anti-oxidation synergistic performance (residual silicon preferentially forms a SiO2 glass layer in a high-temperature oxidation environment (see reaction formula 1), covering the SiC surface to prevent oxygen diffusion: SiC+3O2→SiO2+CO2↑(1)). Under a simulated photovoltaic thermal field at a high temperature of 1500℃, after continuous operation for 100 hours, the material mass loss is only 3%, while the mass loss of existing similar materials exceeds 15%. In the high-temperature oxidation environment test commonly used in the aerospace field, the anti-oxidation time of the material of this invention is extended by more than 2 times compared with existing materials. It can meet the application requirements of photovoltaic thermal fields, aerospace ablation-resistant components and other fields.

[0029] 4. Compared with existing technologies, existing carbon-carbon composite material recycling technologies are limited to single-component extraction or simple mixing and recycling. In this application, a quaternary composite system is constructed to achieve full-component recycling. In terms of silicon carbide introduction and application, existing technologies do not consider utilizing the in-situ reaction of residual silicon in decommissioned materials with other components to achieve material densification and performance improvement. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, 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.

[0031] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0034] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0035] In the description of this application, it should be noted that the use of terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" to indicate orientation or positional relationships is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationships commonly used when the product is in use. These terms are used solely for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the use of terms such as "first" and "second" in the description of this application is only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0036] Furthermore, the use of terms such as "horizontal" and "vertical" in the description of this application does not imply that the component is required to be absolutely horizontal or suspended, but rather that it may be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it may be slightly tilted.

[0037] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0038] In a first aspect, the present invention provides a recycled carbon-ceramic composite thermal protection material based on photovoltaic thermal field recovery of carbon-carbon materials, the material being composed of the following quaternary composite system (by mass percentage):

[0039] Recycled short carbon fibers: 30%, with a length of 50-300μm and a diameter of 5-10μm, serve as a three-dimensional skeleton reinforcement. Through random distribution, they form a stress transfer network, effectively improving the material's thermal shock resistance. The material of this invention can still maintain its structural integrity after undergoing 100 thermal cycles (from room temperature to 1200℃), while existing materials using ordinary recycled carbon fibers show obvious cracks or even breakage.

[0040] Pyrolytic carbon: 45%, graphitization degree ≥80%, specific surface area 10-50 m² 2 / g, derived from the high-temperature pyrolysis product of resin matrix of waste carbon fiber composite material, has high graphitization degree and porous structure. It can be used as a filler to reduce material density and can also promote chemical bonding between fiber and matrix through surface active sites.

[0041] Silicon carbide (SiC): 20%, average particle size 0.5-5μm, is the main component of the matrix, providing high-temperature strength and oxidation resistance to the material;

[0042] Silicon (Si): 5%, purity ≥99.9%, particle size 1-10μm. During sintering, it undergoes an in-situ reaction with cracked carbon (Si+C→SiC) to generate nano-SiC whiskers that fill the pores, while consuming free carbon to increase the density of the material.

[0043] like Figure 1 As shown, in a second aspect, the present invention provides a method for preparing a recycled carbon-ceramic composite thermal protection material as described above, using decommissioned photovoltaic thermal field C / C material as raw material, and achieving full utilization of the components through the following steps:

[0044] Crushing: The recycled C / C material is mechanically crushed to powder with a particle size ≤200μm. After testing, the powder composition includes 25-35wt% short carbon fibers, 35-50wt% pyrolysis carbon, 15-25wt% silicon carbide (SiC) and 5-10wt% residual silicon (Si), and the crushed particle size requires a sieve passing rate ≥95%.

[0045] Mixing: Add 2-5 wt% phenolic resin as a binder to the crushed powder, and then mix by ball milling for 2-4 hours to ensure that the components are evenly dispersed;

[0046] Hot pressing molding: The uniformly mixed material is placed in a vacuum hot press furnace and cured for 1-2 hours under the conditions of pressure 30-60MPa and temperature 180-220℃ to obtain a preform, wherein the optimal hot pressing pressure is 50MPa;

[0047] Carbonization: The preform is placed in a nitrogen atmosphere and heated to 900°C at a heating rate of 5°C / min, and held at that temperature for 2 hours to allow the resin to decompose and generate a porous carbon skeleton.

[0048] Molten silicon infiltration: Under argon protection, molten silicon is infiltrated into the pores of the material within a temperature range of 1420-1600℃, reacting with free carbon to form SiC. The reaction time is 2-4 hours, ultimately resulting in a material porosity of ≤3%. The reaction rate is maximized when the silicon infiltration temperature is 1550℃, at which point Si is completely melted. Details are shown in Table 1 below.

[0049] Table 1. Operational details and key points of each step in the preparation method of this invention.

[0050]

[0051]

[0052] Thirdly, the recycled carbon-ceramic composite thermal protection material described in this invention is applicable to photovoltaic thermal field components or aerospace high-temperature resistant composite materials.

[0053] The specific analysis is as follows:

[0054] Example 1

[0055] Raw material processing: The decommissioned C / C components of the photovoltaic thermal field were crushed into 150μm powder. The composition analysis showed that the short carbon fiber was 28%, the pyrolysis carbon was 42%, the SiC was 20%, and the residual silicon was 7%.

[0056] Mixing: Add 3wt% phenolic resin and ball mill for 3 hours.

[0057] Hot pressing: Cured at 200℃ and 50MPa for 1.5 hours, forming a Φ50mm×5mm round sheet.

[0058] Carbonization: Hold at 900℃ in nitrogen for 2 hours to increase porosity to 18%.

[0059] Silicon infiltration: Silicon infiltration was carried out in argon gas at 1550℃ for 3 hours to obtain a dense composite material with a final SiC content of 38%, a thermal conductivity of 215 W / (m·K), and a flexural strength of 320 MPa.

[0060] Example 2

[0061] By adjusting the silicon infiltration time to 4 hours, the final SiC content was increased to 42%, and the thermal conductivity reached 230 W / (m·K), making it suitable for aerospace ablation-resistant components.

[0062] Economic benefits: Raw material costs are reduced by 60%, and short carbon fibers and SiC can be directly reused, eliminating the need for purchasing new fibers and synthesizing SiC.

[0063] Environmental friendliness: Waste utilization rate ≥95%, CO2 emissions reduced by 70% compared to traditional processes.

[0064] Performance advantages: The thermal conductivity of recycled materials is ≥200W / (m·K), and the temperature resistance is ≥1600℃. They are suitable for photovoltaic thermal fields and aerospace ablation-resistant components.

[0065] Resource synergistic utilization: Directly utilize short carbon fibers from photovoltaic thermal field recycled materials and generate silicon carbide in situ, avoiding the high energy consumption process of synthesizing SiC separately;

[0066] Interface optimization basis: The SiC pre-stored in the recycled powder and the carbon fiber have formed a chemical bonding interface during high-temperature service, providing a natural reinforcing phase for subsequent composite materials;

[0067] Cost advantage: Residual silicon (<5wt%) can be used as a liquid phase sintering aid to reduce densification temperature (200-300℃ lower than traditional processes).

[0068] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a regenerative carbon ceramic composite thermal protection material based on photovoltaic thermal field recycled carbon carbon material, characterized in that: The preparation method comprises the following steps: Crushing: the recycled photovoltaic thermal field decommissioned C / C material is mechanically crushed into a powder with a particle size of ≤200 μm, the powder composition includes 25-35 wt% short carbon fibers, 35-50 wt% pyrolytic carbon, 15-25 wt% SiC, and 5-10 wt% silicon; the length of the short carbon fibers is 50-300 μm, and the diameter is 5-10 μm; the graphitization degree of the pyrolytic carbon is ≥80%, and the specific surface area is 10-50 m 2 / g; the average particle size of the silicon carbide is 0.5-5 μm; the purity of the silicon is ≥99.9%, and the particle size is 1-10 μm; the silicon reacts in situ with the pyrolytic carbon during the sintering process to generate nano-SiC whisker to fill the pores, while consuming free carbon; Mixing: 2-5wt% phenolic resin is added as a binder, and ball milling is performed for 2-4 hours to ensure uniformity of the components; Hot-pressing: in a vacuum hot-pressing furnace, curing is performed at a pressure of 30-60MPa and a temperature of 180-220℃ for 1-2 hours to obtain a preform; Carbonization: under a nitrogen atmosphere, the temperature is raised to 900℃ at a rate of 5℃ / min, and the temperature is maintained for 2 hours to make the resin crack to form a porous carbon skeleton; Melt silicon infiltration: under argon protection, molten silicon infiltrates the pores, reacts with free carbon to form SiC, the reaction time is 2-4 hours, and finally the material has a porosity of ≤3%, a thermal conductivity of ≥200W / (m·K), and a temperature resistance of ≥1600℃.

2. The method of claim 1, wherein: In the crushing step, the crushing particle size is ≤200μm, and the screening rate is ≥95%.

3. The method of claim 1, wherein: In the hot-pressing step, the hot-pressing pressure is 50MPa.

4. The method of claim 1, wherein: In the melt silicon infiltration step, the silicon infiltration temperature is 1550℃.

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