Low-heat-conduction heat preservation cylinder and preparation method thereof

Abstract

The preparation method comprises the following steps: crushing a carbon fiber material to 1000 meshes, and carrying out high-temperature purification treatment to obtain carbon fiber powder; the preparation method comprises the following steps: dispersing and stirring carbon fiber powder, carbon powder, graphite powder and a binder according to a mass ratio of (0.1-0.3): 1: (0.4-0.6): (0.4-0.6), and uniformly mixing to obtain slurry; slurry is laid at the bottom of a preset mold to form a first slurry layer, then filler is laid at the center of the mold to form a filling layer, slurry is laid on the filling layer to form a second slurry layer, then hot-pressing curing and demolding are conducted, and a blank is obtained; carbonizing the blank body in an inert atmosphere, and keeping the temperature for 2 hours; carrying out high-temperature purification treatment on the carbonized blank body, and then carrying out vapor deposition densification treatment; and machining the blank body subjected to vapor deposition densification treatment to obtain the low-heat-conduction thermal insulation cylinder. The prepared heat preservation cylinder has the advantages of being low in heat conduction and low in cost.

Description

Technical Field

[0001] The present invention relates to the technical field of heat insulation materials, and particularly relates to a low thermal conductivity heat preservation cylinder and a preparation method thereof. Background Art

[0002] In recent years, with the rapid development of the new energy photovoltaic industry and semiconductor material preparation technology, the efficient preparation of crystalline silicon materials has put forward higher requirements for the performance of the thermal field system. In high-temperature equipment such as single-crystal silicon growth furnaces and vacuum smelting furnaces, as the core component of the thermal field system, the thermal conductivity of the heat preservation cylinder directly affects the equipment energy consumption and crystal growth quality. At present, traditional heat preservation materials mostly use graphite felt or carbon felt composite materials, and their thermal conductivity is generally higher than 1.5 W / (m·K), resulting in significant heat loss problems in the thermal field system. Especially under high-temperature conditions above 1500 °C, the radiative heat transfer of existing heat preservation materials intensifies, causing the operating power of the single-crystal furnace to remain high, and the energy consumption cost accounting for more than 40% of the total production cost.

[0003] Although attempts have been made in the prior art to improve the heat preservation performance by increasing the thickness of the heat preservation layer or adopting a multi-layer composite structure, such improvements have led to an increase in equipment volume and thermal inertia, which instead affects the temperature control accuracy. At the same time, the cost of the original carbon fiber material used in the traditional process is high, and a large amount of waste materials are generated during the processing and are difficult to effectively recycle, and the comprehensive utilization rate of the materials is less than 60%, which not only does not meet the requirements of circular economy but also raises the environmental protection treatment cost of manufacturing enterprises. Summary of the Invention

[0004] Aiming at the defects existing in the prior art, the present invention provides a low thermal conductivity heat preservation cylinder and a preparation method thereof.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides a preparation method of a low thermal conductivity heat preservation cylinder, including the following steps: S1. After crushing the carbon fiber material to 1000 meshes, carbon fiber powder is obtained through high-temperature purification treatment; S2. The carbon fiber powder, carbon powder, graphite powder, and binder are dispersed and stirred according to the mass ratio of (0.1 - 0.3):1:(0.4 - 0.6):(0.4 - 0.6), and mixed evenly to obtain a slurry; S3. First, the slurry is laid at the bottom of a preset mold to form a first slurry layer, then a filler is laid at the central part of the mold to form a filling layer, and the slurry is laid on the filling layer to form a second slurry layer, and then hot-pressed and cured, and demolded to obtain a blank; S4. The blank is carbonized in an inert atmosphere and kept warm for 2 h; S5. After the carbonized blank is subjected to high-temperature purification treatment, gas-phase deposition densification treatment is carried out; S6. Machine-process the green body after gas deposition densification treatment to obtain a low thermal conductivity insulating cylinder.

[0006] Preferably, the carbonization temperature is 700°C - 1100°C.

[0007] Preferably, the binder includes epoxy resin and phenolic resin.

[0008] Preferably, in S2, the stirring speed is 800 rpm - 1000 rpm.

[0009] Preferably, the gas deposition densification time is 80 h - 120 h.

[0010] Preferably, the temperature of the purification treatment is 1800°C - 2200°C.

[0011] Preferably, the temperature of the hot pressing and curing is 200°C - 240°C.

[0012] Preferably, first lay 2 cm of slurry at the bottom of the preset mold to form a first slurry layer, then lay a filler at the center of the mold to form a 1 cm filler layer, and lay 2 cm of slurry on the filler layer to form a second slurry layer and then perform hot pressing and curing.

[0013] Preferably, the carbon fiber material includes carbon fiber offcuts and carbon-carbon product offcuts.

[0014] On the other hand, the present invention also provides a low thermal conductivity insulating cylinder prepared by the above preparation method.

[0015] Compared with the prior art, the beneficial technical effects of the present invention are as follows: A low-thermal-conductivity heat preservation cylinder and its preparation method provided by the present invention involve crushing carbon fiber materials to 1000 meshes so that they can be evenly dispersed and stirred to obtain better bonding strength. Then, high-temperature purification treatment is carried out to remove impurities in the carbon fiber powder. By controlling the mass ratio of carbon fiber powder, carbon powder, graphite powder, and binder to be (0.1 - 0.3):1:(0.4 - 0.6):(0.4 - 0.6), under this mass ratio, carbon fibers can bridge graphite lamellae to optimize the conductive network. Specifically, through the bridging of carbon fibers, the interfacial contact resistance between graphite lamellae can be reduced, promoting the transmission of electrons between graphite lamellae and carbon fibers, thereby improving the conductive efficiency of the entire conductive network. At the same time, under this mass ratio, excessive carbon fibers can be avoided, preventing uneven dispersion and thus cracks in the prepared heat preservation cylinder. By controlling the carbonization time to 2h, it is prevented that the embryo undergoes graphitization due to insufficient carbonization degree, and at the same time, it is also prevented that due to too long carbonization time, the graphite crystals in the embryo grow excessively, resulting in larger crystal sizes and thus poorer uniformity of the overall performance. Moreover, too long carbonization will make the internal structure of the embryo loose, leading to a reduction in mechanical properties such as the strength and toughness of the prepared heat preservation cylinder. Through gas-phase deposition densification treatment, the strength of the embryo is enhanced. Specifically, through 80h - 120h of gas-phase deposition densification treatment, pyrolytic carbon seals the surface pores, reducing gas convection heat transfer, thereby enhancing the strength of the embryo. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0017] Figure 1 Schematic diagram of the low-thermal-conductivity heat preservation cylinder provided for one embodiment; Figure 2 Cross-sectional view of the low-thermal-conductivity heat preservation cylinder provided for one embodiment.

[0018] Reference numerals in the drawings: 1. First slurry layer; 2. Filling layer; 3. Second slurry layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0020] Example 1: After crushing the carbon fiber scraps to 1000 mesh, carbon fiber powder is obtained through high-temperature purification treatment at 2000 °C; the carbon fiber powder, carbon powder, graphite powder, and epoxy resin are dispersed according to a mass ratio of 0.2:1:0.5:0.5, and stirred at a rotation speed of 900 rpm until evenly mixed to obtain a slurry, where the carbon powder and graphite powder are carbon powder and graphite powder that can be purchased in the market; referring to Figure 1 , Figure 2 , first lay 2 cm of the slurry at the bottom of a preset mold to form a first slurry layer, then lay a filler at the center of the mold to form a 1 cm filler layer, lay 2 cm of the slurry on the filler layer to form a second slurry layer, and then perform hot pressing and curing, and demold to obtain a blank; in an inert atmosphere at a carbonization temperature of 900 °C, carbonize the blank and keep it warm for 2 h; after the carbonized blank is subjected to high-temperature purification treatment at 2000 °C, perform a gas-phase deposition densification treatment for 100 h; perform machining on the blank after the gas-phase deposition densification treatment to obtain a low-thermal-conductivity heat-insulating cylinder.

[0021] Example 2: Compared with Example 1, the mass ratio of the carbon fiber powder, carbon powder, graphite powder, and epoxy resin is 0.15:1:0.5:0.5, and other settings are the same as those in Example 1.

[0022] Example 3: Compared with Example 1, the mass ratio of the carbon fiber powder, carbon powder, graphite powder, and epoxy resin is 0.2:1:0.55:0.5, and other settings are the same as those in Example 1.

[0023] Comparative Example 1: After crushing the carbon fiber scraps to 800 mesh, carbon fiber powder is obtained through high-temperature purification treatment at 2000 °C; the carbon fiber powder, carbon powder, graphite powder, and epoxy resin are dispersed according to a mass ratio of 0.2:1:0.5:0.5, and stirred at a rotation speed of 900 rpm until evenly mixed to obtain a slurry; first lay 2 cm of the slurry at the bottom of a preset mold to form a first slurry layer, then lay a filler at the center of the mold to form a 1 cm filler layer, lay 2 cm of the slurry on the filler layer to form a second slurry layer, and then perform hot pressing and curing, and demold to obtain a blank; in an inert atmosphere at a carbonization temperature of 900 °C, carbonize the blank and keep it warm for 2 h; after the carbonized blank is subjected to high-temperature purification treatment at 2000 °C, perform a gas-phase deposition densification treatment for 100 h; perform machining on the blank after the gas-phase deposition densification treatment to obtain a low-thermal-conductivity heat-insulating cylinder.

[0024] Comparative Example 2: Compared with Comparative Example 1, the carbon fiber scraps are crushed to 1200 mesh, and other settings are the same as those in Comparative Example 1.

[0025] Comparative Example 3: The carbon fiber scraps are crushed to 1000 mesh and then purified at a high temperature of 2000 °C to obtain carbon fiber powder; the carbon fiber powder, carbon powder, graphite powder, and epoxy resin are dispersed according to a mass ratio of 0:1:0.5:0.5, stirred at a rotation speed of 900 rpm, and mixed evenly to obtain a slurry; first, 2 cm of the slurry is laid at the bottom of a preset mold to form a first slurry layer, then a filler is laid at the center of the mold to form a 1 cm filling layer, and 2 cm of the slurry is laid on the filling layer to form a second slurry layer, and then hot-pressed and cured, and demolded to obtain a blank; the blank is carbonized in an inert atmosphere at a carbonization temperature of 900 °C and kept warm for 2 h; after the carbonized blank is purified at a high temperature of 2000 °C, a gas-phase deposition densification treatment is carried out for 100 h; the blank after the gas-phase deposition densification treatment is machined to obtain a low thermal conductivity heat preservation cylinder.

[0026] Comparative Example 4: Compared with Example 1, the mass ratio of carbon fiber powder, carbon powder, graphite powder, and epoxy resin is 0.5:1:0.5:0.5, and other settings are the same as those in Example 1.

[0027] Comparative Example 5: Compared with Example 1, the mass ratio of carbon fiber powder, carbon powder, graphite powder, and epoxy resin is 0.2:1:0.5:1, and other settings are the same as those in Example 1.

[0028] At 2300 °C, the performance indexes of Examples 1-3 are shown in Table 1, and the performance indexes of Comparative Examples 1-5 are shown in Table 2.

[0029] Table 1 Data Sheet of Performance Indexes of Examples

[0030] Table 2 Data Sheet of Performance Indexes of Comparative Examples

[0031] As can be seen from the table, the performance indicators of Example 1 and Comparative Example 4 are the best. However, due to the addition of excessive carbon fiber powder in Comparative Example 4, the cost increases, but the increase amplitude is relatively small. Therefore, the cost performance is relatively low, and the coefficient of thermal expansion increases compared with Example 1. Generally speaking, the performance effect of Example 1 is the best. Compared with Example 1, the surface of the heat preservation cylinder prepared in Comparative Example 1 is rough after demolding, and cracks appear. The surface of the heat preservation cylinder prepared in Comparative Example 2 shows delamination and cracking problems after demolding. This is caused by too low or too high crushing mesh number when preparing carbon fiber powder. Specifically, when the mesh number of carbon fiber powder is too low (large particle size), it cannot fully fill the mold cavity, resulting in uneven local accumulation, affecting the density consistency of the product, rough surface after demolding, and crack phenomenon. When the mesh number of carbon fiber powder is too high (small particle size), the fluidity of carbon fiber powder is poor, and less carbon fiber length is retained, weakening the reinforcement effect of carbon fiber itself, and delamination and cracking phenomena appear on the surface after demolding. Compared with Example 1, no carbon fiber powder is added in Comparative Example 3. From its performance indicators, it can be seen that Comparative Example 3 is inferior to Example 1 in terms of compressive strength, flexural strength, thermal conductivity, and coefficient of thermal expansion. This is because carbon fiber powder directly affects the mechanical properties, thermal properties, densification efficiency, and final application performance of the product. Specifically, carbon fiber powder forms a three-dimensional network structure in the molded embryo, acting as a rigid skeleton to resist external forces, significantly improving the strength and modulus of the product. Moreover, during the high-temperature carbonization process, the binder matrix will shrink, and carbon fiber powder reduces the shrinkage deformation of the binder through its high modulus characteristics, preventing cracking of the heat preservation cylinder after demolding. At the same time, when the carbon fiber powder is at 1000 mesh, it can form connected pores in the embryo, enabling better infiltration of gas during subsequent gas-phase deposition densification treatment and improving the densification efficiency. Compared with Example 1, due to the too high binder content in Comparative Example 5, the brittleness of the heat preservation cylinder increases, and both the compressive strength and flexural strength decrease compared with Example 1.

[0032] From the above examples and comparative examples, it can be known that the low thermal conductivity heat preservation cylinder provided by the present invention has high compressive and flexural strengths; low thermal conductivity, which helps to form a larger temperature gradient and improve the crystal growth rate; good heat preservation performance, which helps to construct a thermal field space and effectively insulate and keep warm; and low cost.

[0033] Matters not covered by the present invention are well-known technologies.

[0034] The technical features of the above examples can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above examples are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0035] The above-described embodiments merely represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims.

[0036] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a low thermal conductivity heat preservation cylinder, characterized in that: The following steps are involved: S1, crushing the carbon fiber material into 1000 meshes, and then subjecting it to high temperature purification treatment to obtain carbon fiber powder; S2, dispersing and stirring carbon fiber powder, carbon powder, graphite powder and binder according to the mass ratio of (0.1-0.3):1:(0.4-0.6):(0.4-0.6), mixing evenly to obtain slurry; S3, firstly lay slurry on the bottom of the preset mold to form a first slurry layer, then lay filler on the center of the mold to form a filling layer, lay slurry on the filling layer to form a second slurry layer, then heat-press and solidify, and demold to obtain an embryo body; S4, carbonizing the embryo under an inert atmosphere and keeping it warm for 2 hours; S5, the carbonized embryo body is subjected to high temperature purification treatment and then to vapor deposition densification treatment; S6. Mechanically process the embryo body after the vapor deposition densification treatment to obtain a low thermal conductivity insulation tube.

2. The method for preparing the low thermal conductivity heat preservation cylinder according to claim 1, characterized in that: The carbonization temperature is 700℃-1100℃.

3. The method for preparing the low thermal conductivity heat preservation cylinder according to claim 1, characterized in that: The adhesive includes epoxy resin and phenolic resin.

4. The method for preparing the low thermal conductivity heat preservation cylinder according to claim 1, characterized in that: In S2, the stirring speed is 800 rpm-1000 rpm.

5. The method for preparing the low thermal conductivity heat preservation cylinder according to claim 1, characterized in that: The vapor deposition densification time is 80h-120h.

6. The method for preparing the low thermal conductivity heat preservation cylinder according to claim 1, characterized in that: The temperature of the purification treatment is 1800°C-2200°C.

7. The method for preparing the low thermal conductivity heat preservation cylinder according to claim 1, characterized in that: The temperature of hot pressing curing is 200℃-240℃.

8. The method for preparing the low thermal conductivity heat preservation cylinder according to claim 1, characterized in that: First, 2 cm of slurry is spread on the bottom of the preset mold to form the first slurry layer, and then filler is spread on the center of the mold to form a 1 cm filling layer. 2 cm of slurry is spread on the filling layer to form the second slurry layer and then hot-pressed and cured.

9. The method for preparing the low thermal conductivity heat preservation cylinder according to claim 1, characterized in that: The carbon fiber material includes carbon fiber scraps and carbon-carbon product scraps.

10. A low thermal conductivity heat preservation cylinder, characterized in that: The low thermal conductivity heat preservation tube is prepared by the preparation method of any one of claims 1 to 9.

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