A combined structure fully enclosed carbon ceramic thermal insulation screen and its preparation method

Abstract

The present invention discloses a fully enclosed carbon-ceramic thermal insulation screen with a combined structure and a preparation method thereof. The key is that the thermal insulation screen is cylindrical, a composite thermal insulation layer (3) is provided between an inner cylinder (1) of carbon / ceramic material and an outer cylinder (2) of carbon / ceramic material, and a circular ring-shaped reinforcing cover plate (4) is provided at the end of the composite thermal insulation layer (3). The present invention adopts composite materials and a combined structure for preparation, has the advantages of high temperature ablation resistance, heat radiation resistance, and powdering resistance, and has a long service life, and realizes the preparation of large (or large-sized) thin-wall thermal insulation screens.

Description

Technical field:

[0001] The present invention relates to a heat-insulating material for industrial high-temperature furnaces and a preparation method thereof, in particular to a heat-insulating material and a preparation method thereof which can be used for single crystal silicon furnaces, polycrystalline silicon furnaces and ultra-high temperature induction furnaces (>1500°C). Background technology:

[0002] Photovoltaic power generation is a key industry for the development of new energy in my country. In recent years, the single crystal materials for photovoltaic cells have developed rapidly. The single crystal materials for cells are prepared by the direct method (CZ method). The single crystal silicon pulling furnace consists of four parts: furnace body, heating element, control system and insulation system with carbon / carbon insulation cylinder and carbon / carbon insulation material. Among them, the insulation system is related to the single crystal production quality, thermal efficiency, production cost and energy saving and environmental protection.

[0003] As the size of crystalline silicon cells increases, single crystal silicon furnaces develop towards large-scale development and adopt continuous crystal pulling technology, which puts forward higher requirements on the performance (insulation, corrosion resistance and service life) and manufacturing technology of the insulation system. For example, the diameter of the carbon / carbon (C / C) insulation tube is required to be greater than 1200mm, and the wall thickness is required to be less than 10mm. It is very difficult to prepare the above-mentioned large thin-walled insulation tube by the C / C material preform-CVD method in the prior art, and the production cycle is long and the preparation cost is high. If the components are prepared separately and then spliced ​​together as a whole, the process is complicated and the manufacturing cycle is long. The key is that the quality is difficult to guarantee. If the waste material insert splicing method is adopted, the prepared insulation tube has gaps, which affects the thermal efficiency and the life of the insulation layer. At the same time, the production process is complicated and the preparation cost is high. In the insulation tube prepared by the above-mentioned various preparation methods, the C / C material in the insulation tube has the problem of pulverization during long-term high-temperature use, which in turn affects the service life of the insulation tube. Therefore, there are still many problems to be solved in the preparation of large thin-walled insulation tubes with excellent performance. Summary of the invention:

[0004] The invention aims to disclose a fully enclosed carbon-ceramic thermal insulation screen with a combined structure and excellent comprehensive performance and a preparation method thereof.

[0005] The technical solution to realize the present invention is: the key is that the heat preservation screen is cylindrical, there is a composite heat insulation layer between the inner cylinder of carbon / ceramic material and the outer cylinder of carbon / ceramic material, and an annular strengthening cover plate is provided at the end of the composite heat insulation layer.

[0006] A first adhesive structure layer is provided between the outer cylinder and the composite heat insulation layer, and a second adhesive structure layer is provided between the composite heat insulation layer and the annular reinforced cover plate.

[0007] A connecting structure is provided between the end of the inner cylinder and the annular strengthening cover plate.

[0008] The steps of the preparation method of the thermal insulation screen are:

[0009] a. Prepare the inner tube body and the outer tube body;

[0010] b. Preparing a preform of a composite insulation layer on the outer wall of the inner tube;

[0011] c. Preparing a cover plate preform of a circular reinforced cover plate;

[0012] d. The products obtained in steps a, b, and c are fired at high temperature in a high temperature furnace to obtain a composite insulation layer integrated with the inner cylinder, an outer cylinder, and an annular strengthening cover plate;

[0013] e. The inner wall of the outer cylinder is coated with adhesive and sleeved on the surface of the composite insulation layer. The end of the composite insulation layer is connected to the annular reinforcement cover plate through the adhesive, and then heated and cured at 150℃~180℃ for 2 hours to obtain the combined structure fully enclosed carbon ceramic insulation screen.

[0014] The steps for preparing the inner barrel blank and the outer barrel blank in step a are:

[0015] a1. The carbon fiber cloth is immersed in the glue solution and then taken out and dried at 90 ℃ ~ 110 ℃ to obtain a modified carbon fiber prepreg;

[0016] a2. Wind the carbon fiber prepreg on the cylindrical molds of different diameters of the winding machine in multiple layers, place the mold in a heating furnace for isostatic curing, and obtain the inner cylinder blank and the outer cylinder blank with the mold.

[0017] The steps for preparing the preform of the composite thermal insulation layer in step b are:

[0018] b1. The carbon fiber felt is immersed in the modified liquid and then taken out and dried at 70 ℃ to 90 ℃ to obtain a carbon fiber felt prepreg;

[0019] b2. The prepreg felt body is wound on the aforementioned inner tube blank in multiple layers by a winding machine to obtain a preform of a composite thermal insulation layer.

[0020] The steps for preparing the cover plate preform in step c are as follows:

[0021] c1. The disordered carbon fiber is immersed in the glue solution and then taken out and baked at 60 ℃ ~ 90 ℃ to obtain a disordered carbon fiber prepreg;

[0022] c2. The above-mentioned disordered carbon fiber prepreg is prepared into a ring shape after being left to stand for 24 hours, and then cured by heating and pressure to obtain a cover plate preform.

[0023] The high temperature firing in step d is to raise the temperature in a high temperature furnace to 1500°C to 1800°C under the protection of nitrogen (N2), keep it warm for 4 hours, and then cool it to 150°C to 250°C in the furnace.

[0024] The components of the glue solution by weight percentage are:

[0025]

[0026] The modified liquid comprises the following components by weight percentage:

[0027]

[0028] The adhesive comprises the following components by weight percentage:

[0029]

[0030] The isostatic pressing curing process of the step ax is as follows: evacuate the heating furnace to -0.098MPa, maintain the pressure for 2 hours, the vacuum rate is <50Pa / h, then pressurize with an air compressor, the pressurizing medium is air, the pressurization rate is 0.08MPa / min, pressurize to 2.0MPa and then maintain the pressure, while heating the heating furnace at a heating rate of 2°C to 7°C / min, heating to 180°C to 200°C and then maintaining the temperature for 2 hours; in the step c2, the annular product prepared from the disordered carbon fiber prepreg is placed on the mold plate of the press, the mold plate is preheated to 80°C to 110°C, the mold plate is pressurized and the mold plate is heated at a heating rate of 2°C to 5°C / min, heating to 180°C to 200°C, maintaining the temperature for 2 hours, and cooling to a temperature of the mold plate below 100°C to obtain a cover plate preform.

[0031] The thermal insulation screen in the above technical solution disclosed in the present invention is a thermal insulation screen made of composite materials and combined structures. The inner and outer tubes of the carbon / ceramic material make the thermal insulation screen resistant to high-temperature ablation, heat radiation, and pulverization, and have a long service life. At the same time, the composite thermal insulation layer makes the thermal insulation screen have good thermal insulation performance, high thermal effect and energy saving. Therefore, the thermal insulation screen has good environmental performance, prevents pollution, reduces the carbon and oxygen content of crystalline silicon, and improves the quality of crystalline silicon. In addition to ensuring the above advantages, the preparation method can achieve the best path for the full closure of the thermal insulation screen, and while reducing the preparation cost, it also conveniently realizes the preparation of large (or large-size) thin-walled thermal insulation screens. Therefore, the thermal insulation screen of the present invention has excellent comprehensive performance. Description of the drawings:

[0032] Figure 1 It is a schematic cross-sectional structure diagram of an embodiment of the present invention. Specific implementation method:

[0033] A detailed description of the specific embodiments of the present invention is given in conjunction with the drawings of the specification. It should be noted that the detailed description of the specific embodiments of the present invention is for facilitating the understanding of the technical essence of the present invention and should not be regarded as limiting the scope of protection of the claims of the present invention.

[0034] See also Figure 1 The structure shown in the figure, the technical solution of the specific embodiment of the present invention is: the heat preservation screen is cylindrical, in fact, the heat preservation screen can also be other shapes with connected cross sections, such as rectangle, which can be realized according to actual needs, there is a composite heat insulation layer 3 between the inner tube 1 of carbon / ceramic material and the outer tube 2 of carbon / ceramic material, the inner and outer tubes (1, 2) and the composite heat insulation layer 3 together constitute the tube wall of the heat preservation screen, and the end of the composite heat insulation layer 3 is provided with a circular ring-shaped strengthening cover plate 4; the above-mentioned inner and outer tubes (1, 2) and the strengthening cover plate 4 completely cover the composite heat insulation layer 3, avoiding direct contact between the composite heat insulation layer 3 and the high temperature environment, and the inner and outer tubes (1, 2) and the strengthening cover plate 4 have excellent high temperature resistance and corrosion resistance, so that the heat preservation screen has good heat insulation performance and greatly increases the service life.

[0035] There is a first adhesive structural layer 5 between the outer cylinder 2 and the composite heat insulation layer 3, and a second adhesive structural layer 6 between the composite heat insulation layer 3 and the annular reinforced cover plate 4; through the above-mentioned first adhesive structural layer 5 and second adhesive structural layer 6, the connection strength between the outer cylinder 2 and the reinforced cover plate 4 and the composite heat insulation layer 3 is further improved, and at the same time, the gaps that may exist between the outer cylinder 2, the reinforced cover plate 4 and the composite heat insulation layer 3 can be completely filled. The above-mentioned first and second adhesive structural layers (5, 6) are formed by the adhesive after high-temperature firing, and they themselves are a structural layer with ceramic components, which have good heat resistance, corrosion resistance and high strength. A connection structure is provided between the end of the inner cylinder 1 and the annular reinforced cover plate 4, and the connection structure is a buckle structure or a sleeve structure. The above-mentioned connection structure is a technology in the general technical field. The connection strength between the inner cylinder 1 and the reinforced cover plate 4 is increased through the connection structure, and a better comprehensive coverage effect of the composite heat insulation layer 3 is achieved.

[0036] The structure of the combined structure fully enclosed carbon-ceramic thermal insulation screen of the present invention has been described above. The specific steps of the preparation method of the combined structure fully enclosed carbon-ceramic thermal insulation screen are: a. preparing a blank of an inner tube 1 and a blank of an outer tube 2; b. preparing a preform of a composite thermal insulation layer 3 on the outer wall surface of the blank of the inner tube 1; c. preparing a cover plate preform of an annular reinforced cover plate 4; d. firing the products of steps a, b, and c at high temperature in a high-temperature furnace to obtain a composite thermal insulation layer 3, an outer tube 2, and an annular reinforced cover plate 4 integrated with the inner tube 1; e. coating the inner wall surface of the outer tube 2 with an adhesive and fitting it on the surface of the composite thermal insulation layer 3, connecting the end of the composite thermal insulation layer 3 to the annular reinforced cover plate 4 via an adhesive, and then heating and curing at 150°C to 180°C for 2 hours to obtain the combined structure fully enclosed carbon-ceramic thermal insulation screen. After the above steps b to c, a composite structure with the inner tube 1 blank and the composite insulation layer 3 preform is obtained, and a cover plate preform of a circular reinforced cover plate 4 is also obtained. After high-temperature firing in step c, the composite insulation layer 3, the outer tube 2 and the reinforced cover plate 4 integrated with the inner tube 1 are obtained. Under the action of high temperature, the inner tube 1 and the outer tube 2 are sintered into carbon / ceramic materials, and the composite insulation layer 3 is formed into another structure of hard carbon-ceramic insulation material. The reinforced cover plate 4 is also sintered into a cover plate of carbon-ceramic properties after high temperature sintering. After the above components are assembled into one body through step e, the combined structure fully enclosed carbon-ceramic insulation screen of the present invention is obtained after 150℃~180℃ and heat preservation for 2 hours. Since the inner tube 1, the outer tube 2 and the reinforced cover plate 4 are all carbon / ceramic materials, which have excellent strength, high temperature resistance and corrosion resistance, they can be prepared thinner or with smaller thickness. The finally prepared insulation screen has large dimensions such as diameter and height, while still having excellent comprehensive performance. The above steps will be described in detail later.

[0037] The steps for preparing the blank of the inner cylinder 1 and the blank of the outer cylinder 2 in the step a are: a1. After the carbon fiber cloth is immersed in the glue, it is taken out and dried at 90℃~110℃ to obtain a modified carbon fiber prepreg cloth; a2. The carbon fiber prepreg cloth is wound on a cylindrical mold of different diameters of a winding machine in multiple layers, and the mold is placed in a heating furnace for isostatic curing to obtain the blank of the inner cylinder 1 and the blank of the outer cylinder 2 with the mold. In the above step a1, after taking a carbon fiber cloth of appropriate size and immersing it in the glue, it is left for a suitable time to allow the glue to fully penetrate the inside of the carbon fiber cloth, then taken out and dried at 90℃~110℃ to obtain a modified carbon fiber prepreg cloth, and the amount of glue is 30~45% of the carbon fiber prepreg cloth by weight percentage; after step a2, the inner cylinder 1 and the outer cylinder 2 are cylindrical blanks formed by multiple layers of winding.

[0038] The preparation steps of the preform of the composite thermal insulation layer 3 in the step b are: b1. After immersing the carbon fiber felt in the modification liquid, take it out and dry it at 70℃~90℃ to obtain a carbon fiber felt prepreg body; b2. Wind the prepreg body on the blank of the aforementioned inner tube 1 in multiple layers through a winding machine to obtain a preform of the composite thermal insulation layer 3. In the above-mentioned step b1, a carbon fiber felt of suitable size is taken and immersed in the modifying liquid. It is also left for a suitable time to allow the modifying liquid to fully penetrate the interior of the carbon fiber felt, then taken out and dried at 70°C to 90°C to obtain a carbon fiber felt impregnated felt body; multiple layers of the above-mentioned carbon fiber felt preimpregnated felt body are wound on the aforementioned inner cylinder 1 blank by a winding machine, and the multi-layer structure of the preimpregnated felt body is the preform of the composite thermal insulation layer 3. Since the density of the carbon fiber felt is relatively low, for example, compared with conventional carbon fiber cloth, its density after high-temperature firing is lower than that of the aforementioned inner cylinder 1 and outer cylinder 2, and the thermal insulation effect is better; or the above-mentioned step b2 is: after the preimpregnated felt body is wound on the aforementioned inner cylinder 1 blank by a winding machine, a layer of graphite paper is wound, and the winding is repeated to obtain a preform of the composite thermal insulation layer 3 of multiple layers of preimpregnated felt and multiple layers of graphite paper spaced apart, which can further improve the thermal insulation effect of the composite thermal insulation layer 3.

[0039] The preparation steps of the cover plate preform in step c are as follows: c1. The disordered carbon fiber is immersed in the glue solution and then taken out, and then baked at 60℃~90℃ to obtain a disordered carbon fiber prepreg; c2. The above-mentioned disordered carbon fiber prepreg is prepared into a ring shape after standing for 24 hours, and then heated and pressure cured to obtain a cover plate preform. After steps c1 to c2, the disordered carbon fiber is waste in the preparation process of carbon fiber or carbon fiber cloth. After step c2, a cover plate preform with a certain density is obtained.

[0040] The high temperature firing in step d is to raise the temperature in a high temperature furnace to 1500°C to 1800°C under the protection of nitrogen (N2), keep it warm for 4 hours, and then cool it to 150°C to 250°C with the furnace. The above-mentioned insulation time is the best or most suitable time. Of course, it can be appropriately increased or decreased according to the thickness of each preform. In the high temperature firing process of step c, a support frame is placed inside the inner tube 1 and the outer tube 2 according to the size or need to avoid deformation of the inner tube 1 and the outer tube 2 at high temperature. At the same time, a heavy object can be applied after the cover plate preform is laid flat to avoid deformation of the cover plate preform.

[0041] The composition of the adhesive solution by weight percentage is: 30-40% phenolic resin, 35-45% alcohol, 5-10% carbon fiber powder, 10-20% silicon powder, 5-10% carbonized silicon powder, 4-10% graphite powder and 5-15% short carbon fiber. The composition of the modified liquid by weight percentage is: 20-30% phenolic resin, 40-60% alcohol, 10-20% silicon powder, 5-10% carbonized silicon powder, 4-10% graphite powder, 5-10% zirconium oxide powder and 4-8% mullite powder. The adhesive comprises the following components by weight percentage: 20-40% phenolic resin, 30-50% silicon powder, 5-15% silicon dioxide powder, 10-20% carbonized silicon powder, 10-20% graphite powder and 5-15% zirconium oxide powder. The common feature of the above-mentioned glue, modified liquid and adhesive is that they all form a solid structure containing ceramic components after high-temperature sintering, and are respectively combined with carbon fiber cloth, carbon fiber felt and disordered carbon fiber to form carbon ceramic materials with different microstructures. However, based on the different arrangement positions and different functions of the inner and outer cylinders (1, 2), the composite heat insulation layer 3 and the reinforced cover plate 4, the glue, modified liquid and adhesive have substantially different formulas and proportions.

[0042] The aforementioned modified carbon fiber prepreg and carbon fiber felt prepreg bodies both require heating and curing during preparation. The isostatic pressing curing process of step a2 is as follows: evacuate the heating furnace to -0.098 MPa, maintain the pressure for 2 hours, and the vacuum rate is <50 Pa / h. Then, pressurize with an air compressor, the pressurizing medium is air, the pressurizing rate is 0.08 MPa / min, pressurize to 2.0 MPa and then maintain the pressure. At the same time, heat and heat the furnace at a heating rate of 2℃~7℃ / min, heating to 180℃~200℃ and keeping warm for 2 hours; and in the step c2, the annular product prepared by the disordered carbon fiber prepreg is placed on the mold plate of the press, the mold plate is preheated to 80℃~110℃, the mold plate is pressurized and the mold plate is heated, the heating rate is 2℃~5℃ / min, the temperature is raised to 180℃~200℃, kept warm for 2 hours, and cooled to the mold plate temperature below 100℃ to obtain the cover plate preform. Through the above preparation process, the density of the blank of the inner tube 1 and the outer tube 2 and the cover plate preform is further improved, and the volatile matter has sufficient time to volatilize a part.

[0043] From the foregoing description, the combined structure fully enclosed carbon ceramic thermal insulation screen disclosed in the present invention has excellent comprehensive performance, especially good high temperature corrosion resistance while also having good strength and thermal insulation performance, and can realize a thin-wall thermal insulation screen of large structure (or size).

Claims

1. A method for preparing a fully enclosed carbon ceramic thermal insulation screen with a combined structure, characterized in that: The heat-insulating screen is cylindrical, and a composite heat-insulating layer (3) is provided between an inner cylinder (1) made of carbon / ceramic material and an outer cylinder (2) made of carbon / ceramic material, and an annular reinforcing cover plate (4) is provided at the end of the composite heat-insulating layer (3); A first adhesive structure layer (5) is provided between the outer cylinder (2) and the composite heat insulation layer (3), and a second adhesive structure layer (6) is provided between the composite heat insulation layer (3) and the annular reinforced cover plate (4); A connection structure is provided between the end of the inner cylinder (1) and the annular strengthening cover plate (4); The steps of the preparation method of the thermal insulation screen are: a. Preparing a green body of the inner cylinder (1) and an outer cylinder (2); a1. The carbon fiber cloth is immersed in the glue solution and then taken out and dried at 90 ℃ ~ 110 ℃ to obtain a modified carbon fiber prepreg; a2. The carbon fiber prepreg is wound on a cylindrical mold of different diameters in a winding machine and multiple layers are wound. The mold is placed in a heating furnace and isostatically cured to obtain a green body with an inner cylinder (1) and an outer cylinder (2) of the mold; b. Preparing a preform of a composite insulation layer (3) on the outer wall of the inner tube (1); b1. The carbon fiber felt is immersed in the modified liquid and then taken out and dried at 70 ℃ to 90 ℃ to obtain a carbon fiber felt prepreg; b2. The prepreg felt body is wound on the inner tube (1) of the blank by a winding machine in multiple layers to obtain a preform of a composite insulation layer (3); c. Preparing a cover plate preform of a circular reinforced cover plate (4); c1. The disordered carbon fiber is immersed in the glue solution and then taken out and baked at 60 ℃ ~ 90 ℃ to obtain a disordered carbon fiber prepreg; c2. The above-mentioned disordered carbon fiber prepreg was allowed to stand for 24 hours to form a ring shape, and then heated and pressure cured to obtain a cover plate preform; d. The products obtained in steps a, b, and c are fired at high temperature in a high temperature furnace to obtain a composite heat insulation layer (3) integrated with the inner tube (1), an outer tube (2), and an annular strengthening cover plate (4); e. The inner wall surface of the outer cylinder (2) is coated with adhesive and mounted on the surface of the composite insulation layer (3). The end of the composite insulation layer (3) is connected to the annular reinforcing cover plate (4) via adhesive, and then heated and cured at 150°C to 180°C for 2 hours to obtain the composite structure fully enclosed carbon ceramic insulation screen; The isostatic pressing curing process of step a2 is as follows: evacuate the heating furnace to -0.098MPa, maintain the pressure for 2 hours, and the vacuum rate is <50Pa / h, then pressurize with an air compressor, the pressurizing medium is air, the pressurization rate is 0.08MPa / min, pressurize to 2.0MPa and then maintain the pressure, and heat and heat the heating furnace at a heating rate of 2°C to 7°C / min, and heat to 180°C to 200°C and then keep warm for 2 hours; in step c2, the annular product prepared by the disordered carbon fiber prepreg is placed on the mold plate of the press, the mold plate is preheated to 80°C to 110°C, the mold plate is pressurized and the mold plate is heated, the heating rate is 2°C to 5°C / min, the temperature is raised to 180°C to 200°C, and the temperature is kept for 2 hours, and the temperature is lowered to a mold plate temperature below 100°C to obtain a cover plate preform.

2. The method for preparing the combined structure fully enclosed carbon ceramic thermal insulation screen according to claim 1, characterized in that: The high temperature firing in step d is to raise the temperature in a high temperature furnace to 1500°C to 1800°C under the protection of nitrogen (N2), keep it warm for 4 hours, and then cool it to 150°C to 250°C in the furnace.

3. The method for preparing the combined structure fully enclosed carbon ceramic thermal insulation screen according to claim 2, characterized in that: The composition of the adhesive solution by weight percentage is: 30-40% phenolic resin, 35-45% alcohol, 5-10% carbon fiber powder, 10-20% silicon powder, 5-10% carbonized silicon powder, 4-10% graphite powder, 5-15% short carbon fiber; the sum of the contents of each component is 100%; The modified liquid comprises the following components by weight percentage: 20-30% phenolic resin, 40-60% alcohol, 10-20% silicon powder, 5-10% carbonized silicon powder, 4-10% graphite powder, 5-10% zirconium oxide powder, 4-8% mullite powder; the sum of the contents of each component is 100%; The adhesive comprises the following components by weight percentage: 20-40% phenolic resin, 30-50% silicon powder, 5-15% silicon dioxide powder, 10-20% carbonized silicon powder, 10-20% graphite powder, 5-15% zirconium oxide powder; the sum of the contents of each component is 100%.

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