A long-life high-thermal-conductivity carbon-carbon crucible rib for photovoltaic thermal field and its preparation method and device

Abstract

The present invention discloses a long-life high thermal conductivity carbon-carbon crucible side for photovoltaic thermal field and a preparation method and device thereof, which belongs to the technical field of single crystal furnace thermal field material preparation in the photovoltaic field, including: using needle-punched non-woven cloth and mesh carbon fiber as raw materials to make a crucible carbon fiber preform blank, using natural gas as a carbon source, low molecular weight mixed hydrocarbon gas as an auxiliary gas, and argon or nitrogen as a protective gas, subjecting the crucible carbon fiber preform blank to isothermal chemical vapor deposition treatment, and then subjecting it to graphitization treatment to prepare a long-life high thermal conductivity carbon fiber reinforced carbon matrix crucible side for photovoltaic thermal field. The full vapor deposition thermal field crucible side prepared by the preparation method of the present invention has a high thermal conductivity, greatly improved mechanical properties, a uniform and continuous matrix carbon structure, good overall corrosion resistance, and greatly improved service life. Combined with the above advantages, the full vapor deposition thermal field product prepared by the present invention has excellent economic and social benefits in the field of photovoltaic thermal field.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of thermal field materials of single crystal furnaces in the photovoltaic field, and specifically relates to a long-life high-density crucible side for photovoltaic thermal fields and a preparation method and device thereof. Background Art

[0002] The crucible side is an important component of the crucible assembly, and is usually used in conjunction with the crucible tube, crucible bowl and other components to form a complete crucible system. The main function of the crucible side is to support and protect the crucible. In the photovoltaic field, the crucible side is the core component of the photovoltaic thermal field single crystal furnace, which mainly provides strength support for the quartz crucible during the crystal pulling process. The early crucible side was mainly made of graphite. With the large-scale photovoltaic crystal pulling thermal field, the early graphite crucible side was replaced by a carbon-carbon composite crucible side. The main reason is that the mechanical strength of the carbon-carbon composite material at high temperature is much higher than that of graphite, thereby increasing the service life of the crucible side.

[0003] The market demand for carbon-carbon crucible ribs is very large. It is a consumable product and the market demand is increasing year by year. According to user surveys, conventional carbon-carbon crucible ribs usually have the following problems: (1) Low density. The density of conventional carbon-carbon crucible is only 1.35~1.4g / cm3, and the average service life is about 6 months; (2) The thermal conductivity is generally low. The thermal conductivity of conventional carbon-carbon crucible is about 10W / (m·K); (3) Pollution of the environment and waste of energy. Due to their short service life, the carbon crucibles that are scrapped every year are usually disposed of by landfill and other methods, which will cause environmental pollution and is very wasteful. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a long-life and high-thermal conductivity carbon-carbon (carbon fiber reinforced carbon matrix composite material) crucible rib for photovoltaic thermal field and a preparation method and device thereof, so as to solve the technical problems of low density, short service life, poor thermal conductivity and easy pollution caused by scrapping of carbon-carbon composite material crucible rib in the prior art.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: The invention discloses a method for preparing a long-life high-thermal-conductivity carbon-carbon crucible rib for photovoltaic thermal field, comprising: using needle-punched non-woven cloth and mesh carbon fiber as raw materials to prepare a crucible rib carbon fiber preform blank, using natural gas as a carbon source, low-molecular mixed hydrocarbon gas as an auxiliary gas, and argon or nitrogen as a protective gas, subjecting the crucible rib carbon fiber preform blank to isothermal chemical vapor deposition treatment, and then subjecting the preform to graphitization treatment to prepare a long-life high-thermal-conductivity carbon fiber reinforced carbon matrix crucible rib for photovoltaic thermal field.

[0006] Preferably, the mass ratio of the non-woven fabric to the web is 1.7-2.7:1, and the non-woven fabric and the web are alternately layered.

[0007] More preferably, the non-woven fabric is made of carbon fiber grade T400 or above, and the mesh tire is made of carbon fiber grade T700 or above.

[0008] Preferably, the density of the carbon fiber preform is 0.45±0.03 g / cm 3 .

[0009] Preferably, when performing isothermal chemical vapor deposition treatment, the deposition gas flow flows from bottom to top, and after being kept at a certain treatment temperature for a period of time, a carbon source, a protective gas and an auxiliary gas are introduced to perform the deposition treatment.

[0010] Further preferably, the temperature of the isothermal chemical vapor deposition treatment is 950-1050 °C, the holding time is 2 h, the volume ratio of the carbon source, the protective gas and the auxiliary gas is (1-2): (1-3): (0.5-1), and the deposition time is 200 h.

[0011] Preferably, the graphitization treatment is carried out at a temperature of 1800-2200° C. for 2 hours.

[0012] The present invention also discloses a long-life high thermal conductivity carbon-carbon crucible for photovoltaic thermal field prepared by the above-mentioned preparation method, wherein the density of the long-life high thermal conductivity carbon-carbon crucible for photovoltaic thermal field is 1.5-1.7g / cm 3 , thermal conductivity ≥30W / (m·K).

[0013] The present invention also discloses a device for realizing the preparation method of the long-life high-density crucible side for the photovoltaic thermal field, comprising a deposition furnace, in which several layers of solid felt support seats are laid, the crucible side to be processed is placed on the solid felt support seats, and packaged by tooling; air flow holes are opened at the bottom of each layer of solid felt support seats, and the proportions of the air flow holes opened in the several layers of solid felt support seats are different.

[0014] Preferably, the number of air flow holes provided at the bottom of the solid felt support seat arranged from bottom to top gradually decreases.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The method for preparing a long-life high-thermal-conductivity carbon-carbon crucible for photovoltaic thermal field disclosed in the present invention has the following characteristics: (1) the carbon matrix is ​​a uniform and continuous structure, which avoids cracking caused by thermal stress mismatch between pyrolytic carbon and resin carbon or asphalt carbon during high-temperature use. In particular, needle-punched non-woven cloth and mesh carbon fiber are selected as raw materials to prepare needle-punched carbon fiber preforms, which can effectively ensure uniform pores between fiber bundles, facilitate rapid densification, and uniform pores within the bundle to prevent defects from increasing due to deposition and sealing. On the other hand, based on the isothermal chemical vapor deposition process, natural gas is used as the carbon source, low-molecular mixed hydrocarbon gas is used as the auxiliary gas, and argon or nitrogen is used as the protective gas to carry out full chemical vapor deposition. The low-molecular mixed hydrocarbon gas can assist in improving the deposition efficiency, and the premature sealing of the blank surface can be delayed under the action of concentration gradient and temperature gradient during the deposition process, so as to achieve deposition of the product blank from the inside out.

[0016] Furthermore, the non-woven fabric uses carbon fiber grades of T400 and above, and the mesh tire uses conventional carbon fiber grades of T700 and above, mainly polyacrylonitrile-based (PAN-based) fibers. This requires the fiber to have good flexibility to prevent defects such as broken wires during the molding process.

[0017] Furthermore, the weight ratio of the non-woven fabric to the mesh is controlled between 1.7-2.7, the non-woven fabric and the mesh are alternately laid, and the density of the preform is controlled at 0.45±0.03g / cm 3 , high thermal conductivity and mechanical strength can improve the thermal conductivity of the product and enhance its corrosion resistance.

[0018] The full vapor deposition thermal field crucible prepared by the preparation method of the present invention has high thermal conductivity, greatly improved mechanical properties, uniform and continuous matrix carbon structure, good overall corrosion resistance, and greatly improved service life. Combined with the above advantages, the full vapor deposition thermal field product prepared by the present invention has excellent economic and social benefits in the field of photovoltaic thermal fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of the photovoltaic thermal field crucible full chemical vapor deposition device of the present invention; Figure 2 Polarized light microscope image (a) and scanning electron microscope image (b) of the carbon-carbon crucible substrate with long life and high thermal conductivity for photovoltaic thermal field prepared by the present invention; Figure 3 The thermal conductivity and silicon material melting rate of the product obtained by the full vapor phase deposition crucible rib method of the present invention and the conventional hot field crucible rib preparation method are compared.

[0020] Among them: 1-deposition furnace; 2-insulation felt; 3-heating element; 4-tooling; 5-solid felt support seat; 6-thermal field product, 7-deposition airflow. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0022] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings: The invention discloses a method for preparing a long-life high-thermal-conductivity carbon fiber reinforced carbon matrix crucible lining for photovoltaic thermal field, comprising: using needle-punched non-woven cloth and mesh carbon fiber as raw materials to prepare a needle-punched carbon fiber preform blank, using natural gas as a carbon source, low-molecular mixed hydrocarbon gas as an auxiliary gas, and argon or nitrogen as a protective gas, subjecting the needle-punched carbon fiber preform blank to isothermal chemical vapor deposition treatment, and then subjecting the preform to graphitization treatment to prepare a long-life high-thermal-conductivity carbon fiber reinforced carbon matrix crucible lining for photovoltaic thermal field.

[0024] First, the conventional mesh and non-woven fabric composite needle punching process technology is used, which requires: the non-woven fabric uses carbon fiber grades of T400 and above, and the mesh uses conventional carbon fiber grades of T700 and above, mainly polyacrylonitrile-based (PAN-based) fibers. This requires the fiber to have good flexibility to prevent defects such as broken wires during the molding process; high thermal conductivity and mechanical strength can improve the thermal conductivity of the product and enhance its corrosion resistance. The weight ratio of non-woven fabric to mesh is controlled between 1.7-2.7, the non-woven fabric and mesh are alternately laid, and the density of the preform is controlled at 0.45±0.03g / cm 3 ,Different from the preforms required for deposition + resin / asphalt impregnation, the preforms required for full vapor deposition need to ensure uniform pores between fiber bundles to facilitate rapid densification, and uniform pores within bundles to prevent an increase in defects due to deposition sealing.

[0025] Based on the isothermal chemical vapor deposition process, natural gas is used as the carbon source, low molecular weight mixed hydrocarbon gas is used as the auxiliary gas, argon or nitrogen is used as the protective gas, and the volume density is 0.45±0.03g / cm 3 PAN-based needle-punched carbon fiber preforms are fully chemically vapor deposited. Low-molecular-weight mixed hydrocarbon gases can help improve deposition efficiency, and under the action of concentration gradient and temperature gradient, they can delay the early sealing of the blank surface during the deposition process, thus achieving deposition of the product blank from the inside out.

[0026] Preferably, the deposition process is to heat the temperature to 950-1050°C and then keep it for 2 hours, then introduce natural gas, nitrogen or argon, and low molecular weight mixed hydrocarbon gas mixture, and the volume ratio of the three is controlled at (1-2): (1-3): (0.5-1). The deposition pressure is set to 3-4.0 kPa, and the deposition time is 200 hours.

[0027] Preferably, during deposition, the total flow rate of the gas introduced is controlled at 30-50 m 3 / h.

[0028] Preferably, the low molecular weight mixed hydrocarbon gas used in the present invention refers to a mixed gas composed of a variety of low molecular weight hydrocarbon compounds, mainly composed of alkanes, alkenes, alkynes, etc. with a small number of carbon atoms, including alkanes such as methane, ethane, propane, butane, etc.; olefins such as ethylene, propylene, butene, butadiene, etc.

[0029] See also Figure 1 The present invention also discloses a deposition device for realizing the above-mentioned photovoltaic thermal field with a long life and high thermal conductivity carbon-carbon crucible. Like the existing deposition device, it includes a deposition furnace 1, a thermal insulation felt 2 is provided close to the inner wall of the furnace body, a heating body 3 is provided in the furnace body, and a thermal field product 6 is placed in a packaging tool 4 inside the furnace body for processing.

[0030] Different from the prior art, several layers of solid felt support seats 5 are laid in the deposition furnace 1, the crucible to be processed is placed on the solid felt support seats 5, and packaged by the tooling 4; air flow holes are opened at the bottom of each layer of solid felt support seats 5, and the proportions of the air flow holes opened in several layers of solid felt support seats 5 are different.

[0031] Example 1 A method for preparing a long-life high-thermal-conductivity carbon-carbon crucible rib for photovoltaic thermal field, comprising: 1) Preparation of carbon fiber preform The composite needle punching technology of conventional mesh and non-woven fabric is adopted. The non-woven fabric uses carbon fiber grade T400 and above, and the mesh uses conventional carbon fiber grade T700 and above, mainly polyacrylonitrile-based (PAN-based) fiber. The weight ratio of non-woven fabric to mesh is controlled at 1.7, and the non-woven fabric and mesh are alternately laid. The volume density of the preform is 0.43g / cm 3 .

[0032] 2) Full chemical vapor deposition process, including: A. Sample loading. Press the lifting button of the sample loading platform to move the platform to the sample loading room. Use the lifting fixture to lift the carbon fiber preform blank into the sample loading room. Figure 1 Sample loading as shown. Pay attention to the order of loading. First, place the crucible carbon fiber preform blank on the solid felt support seat to ensure that there is deposition airflow inside and outside the crucible carbon fiber preform blank; then put the tooling on the outside of the crucible carbon fiber preform blank to ensure that the airflow passes through the inside of the tooling; repeat this cycle until the products are stacked. It is worth noting that the deposition airflow aperture area ratio from the bottom solid felt support seat to the top solid felt support seat is 5:4:3:2:1. Then move the platform containing the sample to the inside of the furnace and lock the bottom.

[0033] B. Gas washing. Open the vacuum pump to suck the air out of the furnace cavity, close the pump valve; introduce nitrogen or argon into the furnace cavity; open the vacuum pump valve again, and perform gas washing three times to exhaust the air in the furnace cavity and the pores of the preform.

[0034] C. Maintain pressure. Turn on the vacuum pump and pump the pressure in the furnace chamber to 1kPa. Maintain the pressure for 2 hours until the vacuum degree remains unchanged.

[0035] D. Parameter setting. Start the water cooling device, turn on the circulating water button, and set the parameters according to the cooling capacity of the equipment. Use argon or nitrogen as the carrier gas and set the flow rate to 10m 3 / h; start the heating button, the heating rate is 10℃ / min.

[0036] E. Deposition. After the temperature rises to 950℃ and is kept for 2h, a mixture of natural gas, nitrogen or argon and low molecular weight hydrocarbon gas is introduced, with the volume ratio controlled at 2:3:1. The total gas flow rate is controlled at 50m 3 / h, the deposition pressure was set to 3.5 kPa, and the deposition time was 200 hours. The low molecular weight mixed hydrocarbon gas used in Example 1 is a mixed gas of methane and butane in a volume ratio of 3:1.

[0037] F. Cooling down. After the deposition is completed, stop introducing low molecular weight hydrocarbon gas mixture, and keep introducing argon or nitrogen. After the temperature drops to room temperature, dismantle the furnace and take samples.

[0038] 3) Graphitization treatment According to the product placement method during the deposition process, the product and tooling are placed in the graphitization furnace and the deposition process is performed again, including: A. Sample loading. Activate the sample loading platform moving button, move the platform out, and place the crucible containing the tooling on the platform using a lifting fixture, etc. until it is full according to the equipment furnace chamber volume. Then move the platform containing the sample into the furnace body and lock the side door.

[0039] B. Gas washing. Open the vacuum pump to suck the air out of the furnace cavity, close the pump valve; introduce argon gas into the furnace cavity; open the vacuum pump valve again, and perform gas washing three times to exhaust the air in the furnace cavity and the pores of the preform.

[0040] C. Maintain pressure. Turn on the vacuum pump and pump the pressure in the furnace chamber to 1-2kPa. Maintain the pressure for 2 hours until the vacuum degree remains unchanged.

[0041] Parameter setting: The heating rate varies with the equipment capacity. After the temperature rises to 2200℃, keep warm for 2 hours; the furnace chamber pressure is set to 3kPa; turn on the circulating water button and cool according to the equipment capacity; take samples after cooling to room temperature.

[0042] See also Figure 2 , is a microscopic photograph of the carbon of the crucible base of the long-life and high-thermal-conductivity carbon fiber reinforced carbon matrix for photovoltaic thermal field prepared in this embodiment. It can be seen that the introduction of low-molecular mixed hydrocarbon gas to assist deposition through the natural gas deposition process avoids the occurrence of crusting on the product surface; the different pore proportions of the solid felt support seat are used to bind the alkane free radical molecules in different positions, thereby improving the densification efficiency of the product and ensuring the quality consistency of products in different regions.

[0043] Example 2 A method for preparing a long-life high-thermal-conductivity carbon-carbon crucible rib for photovoltaic thermal field, comprising: 1) Preparation of carbon fiber preform The composite needle punching technology of conventional mesh and non-woven fabric is adopted. The non-woven fabric uses carbon fiber grade T400 and above, and the mesh uses conventional carbon fiber grade T700 and above, mainly polyacrylonitrile-based (PAN-based) fiber. The weight ratio of non-woven fabric to mesh is controlled at 1.5, and the non-woven fabric and mesh are alternately laid. The volume density of the preform is 0.45 g / cm 3 .

[0044] 2) Full chemical vapor deposition process, including: A. Sample loading. Press the lifting button of the sample loading platform to move the platform to the sample loading room. Use the lifting fixture to lift the carbon fiber preform blank into the sample loading room. Figure 1 As shown in the sample loading. Pay attention to the order of sample loading. First, place the crucible carbon fiber preform blank on the solid felt support seat to ensure that there is deposition airflow inside and outside the crucible carbon fiber preform blank; then put the tooling on the outside of the crucible carbon fiber preform blank to ensure that the airflow passes through the inside of the tooling; repeat this cycle until the products are stacked. It is worth noting that the deposition airflow aperture area ratio from the bottom solid felt support seat to the top solid felt support seat is 5:4.2:3.5:2.5:1. Then move the platform containing the sample to the inside of the furnace and lock the bottom.

[0045] B. Gas washing. Open the vacuum pump to suck the air out of the furnace cavity, close the pump valve; introduce nitrogen or argon into the furnace cavity; open the vacuum pump valve again, and perform gas washing three times to exhaust the air in the furnace cavity and the pores of the preform.

[0046] C. Maintain pressure. Turn on the vacuum pump and pump the pressure in the furnace chamber to 2kPa. Maintain the pressure for 2 hours until the vacuum degree remains unchanged.

[0047] D. Parameter setting. Start the water cooling device, turn on the circulating water button, and set the parameters according to the cooling capacity of the equipment. Use argon or nitrogen as the carrier gas and set the flow rate to 20 m 3 / h; start the heating button, the heating rate is 20℃ / min.

[0048] E. Deposition. After the temperature rises to 1000℃ and is kept for 2h, a mixture of natural gas, nitrogen or argon and low molecular weight hydrocarbon gas is introduced, with the volume ratio controlled at 2:2:0.5. The total gas flow rate is controlled at 40m 3 / h, the deposition pressure was set to 3.0 kPa, and the deposition time was 200 hours. The low molecular weight mixed hydrocarbon gas used in Example 1 is a mixed gas of methane and propylene in a volume ratio of 5:1.

[0049] F. Cooling down. After the deposition is completed, stop introducing low molecular weight hydrocarbon gas mixture, and keep introducing argon or nitrogen. After the temperature drops to room temperature, dismantle the furnace and take samples.

[0050] 3) Graphitization treatment According to the product placement method during the deposition process, the product and tooling are placed in the graphitization furnace and the deposition process is performed again, including: A. Sample loading. Activate the sample loading platform moving button, move the platform out, and place the crucible containing the tooling on the platform using a lifting fixture, etc. until it is full according to the equipment furnace chamber volume. Then move the platform containing the sample into the furnace body and lock the side door.

[0051] B. Gas washing. Open the vacuum pump to suck the air out of the furnace cavity, close the pump valve; introduce argon gas into the furnace cavity; open the vacuum pump valve again, and perform gas washing three times to exhaust the air in the furnace cavity and the pores of the preform.

[0052] C. Maintain pressure. Turn on the vacuum pump and pump the pressure in the furnace chamber to 1-2kPa. Maintain the pressure for 2 hours until the vacuum degree remains unchanged.

[0053] Parameter setting: The heating rate varies with the equipment capacity. After the temperature rises to 2000℃, keep warm for 2 hours; the furnace chamber pressure is set to 3.5kPa; turn on the circulating water button and cool according to the equipment capacity; take samples after cooling to room temperature.

[0054] Example 3 A method for preparing a long-life high-thermal-conductivity carbon-carbon crucible rib for photovoltaic thermal field, comprising: 1) Preparation of carbon fiber preform The conventional mesh and non-woven fabric composite needle punching technology is adopted. The non-woven fabric uses T400 grade and above carbon fiber grades, and the mesh uses conventional T700 grade and above carbon fiber, mainly polyacrylonitrile-based (PAN-based) fiber. The weight ratio of non-woven fabric to mesh is controlled at 2.0, and the non-woven fabric and mesh are alternately laid. The volume density of the preform is 0.48 g / cm 3 .

[0055] 2) Full chemical vapor deposition process, including: A. Sample loading. Press the lifting button of the sample loading platform to move the platform to the sample loading room. Use the lifting fixture to lift the carbon fiber preform blank into the sample loading room. Figure 1 Sample loading as shown. Pay attention to the order of loading. First, place the crucible carbon fiber preform blank on the solid felt support seat to ensure that there is deposition airflow inside and outside the crucible carbon fiber preform blank; then put the tooling on the outside of the crucible carbon fiber preform blank to ensure that the airflow passes through the inside of the tooling; repeat this cycle until the products are stacked. It is worth noting that the deposition airflow aperture area ratio from the bottom solid felt support seat to the top solid felt support seat is 5:4:3:2:1. Then move the platform containing the sample to the inside of the furnace and lock the bottom.

[0056] B. Gas washing. Open the vacuum pump to suck the air out of the furnace cavity, close the pump valve; introduce nitrogen or argon into the furnace cavity; open the vacuum pump valve again, and perform gas washing three times to exhaust the air in the furnace cavity and the pores of the preform.

[0057] C. Maintain pressure. Turn on the vacuum pump and pump the pressure in the furnace chamber to 1kPa. Maintain the pressure for 2 hours until the vacuum degree remains unchanged.

[0058] D. Parameter setting. Start the water cooling device, turn on the circulating water button, and set the parameters according to the cooling capacity of the equipment. Use argon or nitrogen as the carrier gas and set the flow rate to 40 m / s. 3 / h; start the heating button, the heating rate is 50℃ / min.

[0059] E. Deposition. After the temperature rises to 1050°C and is kept at this temperature for 2 hours, a mixture of natural gas, nitrogen or argon and low molecular weight hydrocarbon gas is introduced, with the volume ratio controlled at 1:1:1. The total gas flow rate is controlled at 30 m 3 / h, the deposition pressure was set to 4.0 kPa, and the deposition time was 200 hours. The low molecular weight mixed hydrocarbon gas used in Example 1 is a mixed gas of methane and acetylene in a volume ratio of 10:1.

[0060] F. Cooling down. After the deposition is completed, stop introducing low molecular weight hydrocarbon gas mixture, and keep introducing argon or nitrogen. After the temperature drops to room temperature, dismantle the furnace and take samples.

[0061] 3) Graphitization treatment According to the product placement method during the deposition process, the product and tooling are placed in the graphitization furnace and the deposition process is performed again, including: A. Sample loading. Activate the sample loading platform moving button, move the platform out, and place the crucible containing the tooling on the platform using a lifting fixture, etc. until it is full according to the equipment furnace chamber volume. Then move the platform containing the sample into the furnace body and lock the side door.

[0062] B. Gas washing. Open the vacuum pump to suck the air out of the furnace cavity, close the pump valve; introduce argon gas into the furnace cavity; open the vacuum pump valve again, and perform gas washing three times to exhaust the air in the furnace cavity and the pores of the preform.

[0063] C. Maintain pressure. Turn on the vacuum pump and pump the pressure in the furnace chamber to 1-2kPa. Maintain the pressure for 2 hours until the vacuum degree remains unchanged.

[0064] Parameter setting: The heating rate varies with the equipment capacity. After the temperature rises to 1800℃, keep warm for 2 hours; the furnace chamber pressure is set to 3 kPa; turn on the circulating water button and cool according to the equipment capacity; take samples after cooling to room temperature.

[0065] Take the carbon-carbon crucible with a density of 1.35g / cm3 produced by the conventional deposition + resin impregnation process in the market and the carbon-carbon crucible with a density of 1.6g / cm3 produced by our company's full vapor deposition process and put them into the single crystal furnace respectively, and record the melting time of the silicon materials in the two crucibles at the same power. Figure 3 ,from Figure 3 It can be seen that the long-life high thermal conductivity carbon fiber reinforced carbon matrix crucible for photovoltaic thermal field prepared by the present invention can melt 10 kg more silicon material per hour, the production efficiency is improved, and the power of a single furnace is reduced, and the energy consumption is reduced.

[0066] In summary, compared with the deposition + resin / asphalt impregnation process on the market, the crucible rib prepared by the full chemical vapor deposition process of the present invention has the following advantages: 1. The carbon matrix has a uniform and continuous structure, which avoids cracking caused by the mismatch of thermal stress between pyrolytic carbon and resin carbon or asphalt carbon during high-temperature use.

[0067] 2. The product is more corrosion-resistant as a whole. The surface of the conventional deposition + resin / asphalt process product is dense, but there are many pores inside. After the surface carbon shell corrodes, the crucible side thickness and weight reduction accelerate.

[0068] 3. Better thermal conductivity. The thermal conductivity of conventional thermal field products on the market is 10-15W / (m·K), and the fully vapor-deposited matrix carbon is a uniform and continuous structure. The thermal conductivity of the product produced by the present invention is 2-3 times that of conventional thermal field products. The high thermal conductivity helps to shorten the melting time of the powder, improve production efficiency and reduce equipment power consumption.

[0069] 4. The thermal damage is small. The fiber is deposited in a thermal field environment. The alkane free radical molecules grow along the fiber surface. The preform structure is not distorted, thus avoiding the formation of a carbon-rich layer.

[0070] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a long-life high thermal conductivity carbon-carbon crucible for photovoltaic thermal field, characterized in that: include: A crucible carbon fiber preform blank is made of needle-punched non-woven cloth and mesh carbon fiber as raw materials, natural gas is used as a carbon source, low-molecular mixed hydrocarbon gas is used as an auxiliary gas, and argon or nitrogen is used as a protective gas. The crucible carbon fiber preform blank is subjected to isothermal chemical vapor deposition treatment and then graphitized to obtain a long-life and high-thermal conductivity carbon fiber reinforced carbon matrix crucible for photovoltaic thermal field.

2. The method for preparing a long-life high thermal conductivity carbon-carbon crucible rib for photovoltaic thermal field according to claim 1, characterized in that: The mass ratio of the non-woven fabric to the mesh tire is 1.7-2.7:1, and the non-woven fabric and the mesh tire are laid alternately.

3. The method for preparing a long-life high thermal conductivity carbon-carbon crucible rib for photovoltaic thermal field according to claim 2, characterized in that: The non-woven fabric uses carbon fiber grade T400 and above, and the mesh tire uses carbon fiber grade T700 and above.

4. The method for preparing the long-life high thermal conductivity carbon-carbon crucible rib for photovoltaic thermal field according to claim 1, characterized in that: The density of the carbon fiber preform is 0.45±0.03 g / cm 3 .

5. The method for preparing a long-life high thermal conductivity carbon-carbon crucible rib for photovoltaic thermal field according to claim 1, characterized in that: During isothermal chemical vapor deposition, the deposition gas flows from bottom to top, and after being kept at a certain treatment temperature for a period of time, a carbon source, a protective gas and an auxiliary gas are introduced to carry out the deposition treatment.

6. The method for preparing the long-life high thermal conductivity carbon-carbon crucible rib for photovoltaic thermal field according to claim 5, characterized in that: The temperature of the isothermal chemical vapor deposition treatment is 950-1050 °C, the holding time is 2 h, the volume ratio of the carbon source, the protective gas and the auxiliary gas is (1-2): (1-3): (0.5-1), and the deposition time is 200 h.

7. The method for preparing a long-life high thermal conductivity carbon-carbon crucible rib for photovoltaic thermal field according to claim 1, characterized in that: The graphitization treatment is carried out at a temperature of 1800-2200°C for 2 hours.

8. The long-life high thermal conductivity carbon-carbon crucible for photovoltaic thermal field prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The density of the long-life high thermal conductivity carbon-carbon crucible used in the photovoltaic thermal field is 1.5-1.7g / cm 3 , thermal conductivity ≥30W / (m·K).

9. A device for realizing the method for preparing a long-life high-density crucible for photovoltaic thermal field according to any one of claims 1 to 7, characterized in that: The invention comprises a deposition furnace (1), wherein a plurality of layers of solid felt support seats (5) are laid in the deposition furnace (1), a crucible to be processed is placed on the solid felt support seats (5), and is packaged by a tooling (4); air flow holes are provided at the bottom of each layer of the solid felt support seats (5), and the proportions of the air flow holes provided in the plurality of layers of the solid felt support seats (5) are different.

10. The device according to claim 9, characterized in that The number of air flow holes provided at the bottom of the solid felt support seat (5) arranged from bottom to top gradually decreases.

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