A carbon-carbon thermal field composite material and its preparation method and application

Abstract

The present invention belongs to the technical field of crucible materials, and provides a carbon-carbon thermal field composite material and its preparation method and application. The present invention obtains a densified material by sequentially subjecting a carbon fiber preform to a first heat treatment and a densification treatment; then, after the densified material is impregnated in a resin solution, cross-linking curing and cracking carbonization are sequentially performed to obtain a high-density carbon / carbon composite material. After the carbon / carbon composite material is impregnated in a polysilazane solution, it is sequentially dried and heat-treated to form a silicon nitride coating on the surface of the carbon / carbon composite material; after the surface of the silicon nitride coating is sequentially sprayed with Al2O3 powder and Si3N4-SiC mixed powder, it is heat-treated, and the surface of the carbon / carbon composite material reacts in situ to generate a dense composite coating, and finally forms a carbon-carbon thermal field composite material; when the carbon-carbon thermal field composite material is used as a crucible, it can prevent the high-temperature silicon liquid from infiltrating and reacting with the carbon-carbon thermal field composite material, thereby protecting the carbon-carbon thermal field composite material.

Description

Technical Field

[0001] The present invention relates to the technical field of crucible materials, and in particular to a carbon-carbon thermal field composite material and a preparation method and application thereof. Background Art

[0002] Currently, quartz crucibles are commonly used in single-crystal silicon pulling furnaces. However, in recent years, high-purity quartz sand has been in short supply and imports have been restricted. Furthermore, quartz crucibles only last about 15 days, resulting in a short service life and frequent replacement, significantly increasing production costs. As the size of single-crystal silicon continues to increase, the size requirements for thermal field components are also increasing. Carbon-carbon composites, due to their dimensional stability and excellent mechanical properties, have become the preferred thermal field material for single-crystal silicon.

[0003] During the Czochralski process, the melting of silicon material produces silicon vapor and molten silicon splash, which can cause silicidation and corrosion of the carbon-carbon composite material (hereinafter referred to as the carbon-carbon thermal field material) used as the thermal field material. This seriously affects the mechanical properties and service life of the carbon-carbon thermal field material. Therefore, how to reduce silicidation and corrosion of the carbon-carbon thermal field material and extend its service life has become a common concern for single crystal silicon manufacturers and carbon-carbon thermal field material manufacturers. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a carbon-carbon thermal field composite material and its preparation method and application. The carbon-carbon thermal field composite material provided by the present invention will not be corroded by silicification.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a carbon-carbon thermal field composite material, comprising the following steps:

[0007] preparing a carbon fiber preform;

[0008] performing a first heat treatment and a densification treatment on the carbon fiber preform in sequence to obtain a densified material;

[0009] After the densification material is immersed in a resin solution, cross-linking and curing and cracking and carbonizing are sequentially performed to obtain a carbon / carbon composite material;

[0010] The carbon / carbon composite material is immersed in a polysilazane solution, and then dried and subjected to a second heat treatment to obtain a silicon nitride coating-carbon / carbon composite material;

[0011] Spraying Al2O3 powder and Si3N4-SiC mixed powder on the surface of the silicon nitride coating-carbon / carbon composite material in sequence to obtain a carbon-carbon thermal field composite material precursor;

[0012] The carbon-carbon thermal field composite material precursor is subjected to a third heat treatment to obtain the carbon-carbon thermal field composite material.

[0013] Preferably, the woven structure of the carbon fiber preform is a needle-punched structure; and the method for preparing the carbon fiber preform comprises the following steps:

[0014] The carbon fiber preform is obtained by needle-punching the alternately stacked layers of the non-woven fabric and the ultra-thin mesh, and weaving the two-way through with Z-direction fibers;

[0015] The density of the carbon fiber preform is 0.2 to 0.4 g / cm 3 .

[0016] Preferably, the temperature of the first heat treatment is 1800-2300° C., the rate of heating to the temperature of the first heat treatment is 80-120° C. / h, the holding time is 1-4 hours, and the first heat treatment is performed under a protective atmosphere.

[0017] Preferably, the densification process is chemical vapor deposition; the parameters of the chemical vapor deposition include: the carbon source gas is methane or propylene, the flow rate of the carbon source gas is 2.0 to 20 m 3 / h, the deposition temperature is 1000-1200°C, the rate of heating to the deposition temperature is 40-80°C / h, the deposition pressure is 2.0-10.0 kPa, and the deposition time is 100-300 h.

[0018] Preferably, the resin in the resin solution is phenolic resin; the solvent of the resin solution is xylene, the solid content of the resin solution is 60-85%, the pressure of the densifying material immersed in the resin solution is 5-10 kPa, and the time is 1-3 hours; the temperature of the cross-linking and curing is 100-200°C, the pressure is 1-3 MPa, and the time is 2-4 hours; the temperature of the cracking and carbonization is 600-1200°C, and the time is 10-36 hours.

[0019] Preferably, the solvent of the polysilazane solution is xylene, the solid content of the polysilazane solution is ≥90%, the carbon / carbon composite material is immersed in the polysilazane solution at a pressure of 1 to 10 MPa, for 12 to 24 hours, and for 1 to 3 cycles;

[0020] The drying temperature is 80-100°C and the humidity is 40-75% RH;

[0021] The temperature of the second heat treatment is 1800-2300° C., the rate of heating to the temperature of the second heat treatment is 80-120° C. / h, the holding time is 1-4 hours, and the second heat treatment is carried out under a protective atmosphere.

[0022] Preferably, the spraying parameters of the Al2O3 powder include: the purity of the Al2O3 powder is 99.99%, the particle size is 150-300 μm, the binder is silica sol, the spraying temperature is 2000-2300°C, and the spraying thickness of the Al2O3 powder is 10-40 μm;

[0023] The spraying parameters of the Si3N4-SiC mixed powder include:

[0024] The mass ratio of Si3N4 powder to SiC powder in the Si3N4-SiC mixed powder is 1:1 to 4:1, the purity of the Si3N4-SiC mixed powder is 99.999%, the particle size is 150 to 300 μm, the spraying temperature is 1500 to 1800°C, and the spraying thickness of the Si3N4-SiC mixed powder is 10 to 40 wires.

[0025] Preferably, the temperature of the third heat treatment is 2000-2500° C., the rate of heating to the temperature of the third heat treatment is 80-120° C. / h, the holding time is 1-4 hours, and the third heat treatment is carried out under a protective atmosphere.

[0026] The present invention also provides a carbon-carbon thermal field composite material obtained by the preparation method described in the above technical solution.

[0027] The present invention also provides the use of the carbon-carbon thermal field composite material described in the above technical solution in a crucible for a single crystal silicon pulling furnace.

[0028] The present invention provides a preparation method of a carbon-carbon thermal field composite material, comprising the following steps: preparing a carbon fiber preform; sequentially performing a first heat treatment and a densification treatment on the carbon fiber preform to obtain a densified material; immersing the densified material in a resin solution, and sequentially performing cross-linking curing and cracking carbonization to obtain a carbon / carbon composite material; immersing the carbon / carbon composite material in a polysilazane solution, and sequentially performing drying and a second heat treatment to obtain a silicon nitride coating-carbon / carbon composite material; sequentially spraying Al2O3 powder and Si3N4-SiC mixed powder on the surface of the silicon nitride coating-carbon / carbon composite material to obtain a carbon-carbon thermal field composite material precursor; and performing a third heat treatment on the carbon-carbon thermal field composite material precursor to obtain the carbon-carbon thermal field composite material.

[0029] The present invention obtains a densified material by sequentially subjecting a carbon fiber preform to a first heat treatment and a densification treatment; then, after the densified material is impregnated in a resin solution, cross-linking and curing and cracking and carbonization are sequentially performed to obtain a high-density carbon / carbon composite material. The carbon / carbon composite material is then impregnated in a polysilazane solution, followed by drying and heat treatment, to form a silicon nitride coating on the surface of the carbon / carbon composite material; the surface of the silicon nitride coating is sequentially sprayed with Al2O3 powder and Si3N4-SiC mixed powder, and then heat-treated, and the surface of the carbon / carbon composite material reacts in situ to form a dense composite coating, ultimately forming a carbon-carbon thermal field composite material; when the carbon-carbon thermal field composite material is used as a crucible, the composite coating in the carbon-carbon thermal field composite material can prevent the high-temperature silicon liquid from infiltrating and reacting with the carbon-carbon thermal field composite material, thereby protecting the carbon-carbon thermal field composite material. Using the carbon-carbon thermal field composite material provided by the present invention as a crucible material to replace the quartz crucible can alleviate the problem of domestic quartz sand shortage, while also increasing the service life of the single crystal silicon pulling crucible and reducing the production cost of the enterprise. It can be seen that the preparation method provided by the present invention has the advantages of simple process, convenient operation, short preparation cycle and low production cost. The obtained carbon-carbon thermal field composite material has the advantages of excellent mechanical properties and strong interlayer bonding force, which provides a practical and effective method for large-scale industrial production. DETAILED DESCRIPTION

[0030] The present invention provides a method for preparing a carbon-carbon thermal field composite material, comprising the following steps:

[0031] preparing a carbon fiber preform;

[0032] performing a first heat treatment and a densification treatment on the carbon fiber preform in sequence to obtain a densified material;

[0033] After the densification material is immersed in a resin solution, cross-linking and curing and cracking and carbonizing are sequentially performed to obtain a carbon / carbon composite material;

[0034] The carbon / carbon composite material is immersed in a polysilazane solution, and then dried and subjected to a second heat treatment to obtain a silicon nitride coating-carbon / carbon composite material;

[0035] Spraying Al2O3 powder and Si3N4-SiC mixed powder on the surface of the silicon nitride coating-carbon / carbon composite material in sequence to obtain a carbon-carbon thermal field composite material precursor;

[0036] The carbon-carbon thermal field composite material precursor is subjected to a third heat treatment to obtain the carbon-carbon thermal field composite material.

[0037] In the present invention, unless otherwise specified, the raw materials used in the present invention are preferably commercially available products.

[0038] The present invention prepares a carbon fiber preform.

[0039] In the present invention, the woven structure of the carbon fiber preform is preferably a needle-punched structure. In the present invention, the density of the carbon fiber preform is preferably 0.2 to 0.4 g / cm 3 .

[0040] In the present invention, the method for preparing the carbon fiber preform comprises the following steps: needle-punching the alternately stacked layers of the non-woven fabric and the ultra-thin web, and weaving them bidirectionally through the Z-direction fibers.

[0041] After obtaining the carbon fiber preform, the present invention sequentially performs a first heat treatment and a densification treatment on the carbon fiber preform to obtain a densified material.

[0042] In the present invention, the temperature of the first heat treatment is preferably 1800-2300°C, more preferably 1900-2200°C, and more preferably 2000-2100°C; the rate of heating to the temperature of the first heat treatment is preferably 80-120°C / h, and the holding time is preferably 1-4h, more preferably 2-3h; the first heat treatment is preferably carried out under a protective atmosphere, and the protective atmosphere is preferably high-purity argon.

[0043] In the present invention, the densification process is chemical vapor deposition; the parameters of the chemical vapor deposition include: the carbon source gas is preferably methane or propylene, more preferably methane; the flow rate of the carbon source gas is preferably 2.0 to 20 m 3 / h, more preferably 5 to 15m 3 / h, more preferably 10m 3 / h; the deposition temperature is preferably 1000-1200°C; the rate of heating to the deposition temperature is preferably 40-80°C / h, more preferably 50-70°C / h, more preferably 60°C / h; the deposition pressure is preferably 2.0-10.0kPa, more preferably 4-8kPa; the deposition time is preferably 100-300h, more preferably 150-250h, more preferably 200h.

[0044] In the present invention, the density of the densifying material is preferably 1.3 to 1.5 g / cm 3 .

[0045] In the present invention, when the prepared carbon-carbon thermal field composite material is used to prepare a crucible, it is preferably subjected to machining after the first heat treatment and before the densification treatment; that is, the material after the first heat treatment is mechanically processed into the shape of a crucible.

[0046] In the present invention, chemical vapor deposition is used for initial densification, which can maximize the connectivity of open pores, which is beneficial to shortening the subsequent resin carbon densification cycle, quickly reaching the predetermined volume density, greatly shortening the preparation cycle, and reducing production costs.

[0047] After obtaining the densified material, the present invention immerses the densified material in a resin solution, and then sequentially performs cross-linking curing and cracking carbonization to obtain a carbon / carbon composite material.

[0048] In the present invention, the resin in the resin solution is preferably phenolic resin; the solvent of the resin solution is preferably xylene, and the solid content of the resin solution is preferably 60-85%, further preferably 65-80%, and more preferably 70-75%; the pressure of the densifying material immersed in the resin solution is preferably 5-10 kPa, and the time is preferably 1-3 hours.

[0049] In the present invention, the cross-linking and curing temperature is preferably 100 to 200° C., the pressure is preferably 1 to 3 MPa, and the time is preferably 2 to 4 hours.

[0050] In the present invention, the temperature of the cracking and carbonization is preferably 600 to 1200° C., and the time is preferably 10 to 36 hours, more preferably 12 to 30 hours.

[0051] In the present invention, the density of the carbon / carbon composite material is preferably 1.75 to 1.85 g / cm 3 .

[0052] In the present invention, when the obtained carbon-carbon thermal field composite material is prepared for use in preparing a crucible, it is preferably subjected to fine processing after cracking and carbonization; the present invention does not specifically limit the operation and parameters of the fine processing, as long as the surface of the obtained crucible-shaped carbon / carbon composite material is flat, smooth and free of residue.

[0053] In the present invention, the resin solution is used for impregnation and cracking and carbonization, which is beneficial to further improve the density of the material.

[0054] After obtaining the carbon / carbon composite material, the present invention immerses the carbon / carbon composite material in a polysilazane solution, and sequentially performs drying and a second heat treatment to obtain a silicon nitride coating-carbon / carbon composite material.

[0055] In the present invention, the solvent of the polysilazane solution is preferably xylene, and the solid content of the polysilazane solution is preferably ≥90%, more preferably 90-99%; the pressure of the carbon / carbon composite material immersed in the polysilazane solution is preferably 1-10 MPa, more preferably 2-8 MPa, and more preferably 4-6 MPa; the time is preferably 12-24 h, and the number of cycles is preferably 1-3 times.

[0056] In the present invention, the drying temperature is preferably 80-100° C., and the humidity is preferably 40-75% RH, more preferably 50-70% RH, and even more preferably 55-60% RH.

[0057] In the present invention, the temperature of the second heat treatment is preferably 1800-2300°C, more preferably 1900-2200°C, and more preferably 2000-2100°C; the rate of heating to the temperature of the second heat treatment is preferably 80-120°C / h, and the holding time is preferably 1-4h, more preferably 2-3h; the second heat treatment is preferably carried out under a protective atmosphere, and the protective atmosphere is preferably high-purity argon.

[0058] After the polysilazane solution is impregnated, the present invention first performs drying to allow the polysilazane to completely cover the carbon / carbon composite material. Then, a second heat treatment is performed to decompose the polysilazane to generate a silicon nitride coating, which can protect the formed material from reacting with silicon liquid and prevent silicon liquid contamination. At the same time, the silicon nitride coating can block the macropores of the carbon / carbon composite material, improve the density of the carbon / carbon composite material, and when used as a crucible material, can effectively prevent silicon liquid leakage during single crystal pulling.

[0059] After obtaining the silicon nitride coating-carbon / carbon composite material, the present invention sequentially sprays Al2O3 powder and Si3N4-SiC mixed powder on the surface of the silicon nitride coating-carbon / carbon composite material to obtain a carbon-carbon thermal field composite material precursor.

[0060] In the present invention, the spraying parameters of the Al2O3 powder include: the purity of the Al2O3 powder is preferably 99.99%, the particle size is preferably 150-300 μm, the binder is preferably silica sol, the solid content of the silica gel is preferably 50-65%, more preferably 55-60%, the spraying temperature is preferably 2000-2300°C, more preferably 2100-2200°C; the spraying thickness of the Al2O3 powder is preferably 10-40 wires, more preferably 20-30 wires.

[0061] After the Al2O3 powder is sprayed and before the Si3N4-SiC mixed powder is sprayed, the present invention preferably also includes standing, and the standing temperature is preferably 120-180°C, more preferably 140-160°C, and more preferably 150°C; the humidity is preferably 40-75RH%, more preferably 50-70RH%, and more preferably 60-65RH%; and the time is preferably 6-10h.

[0062] In the present invention, after Al2O3 powder is sprayed, the Al2O3 powder self-heals under the subsequent third heat treatment, thereby bridging and blocking micropores to form a first coating layer.

[0063] In the present invention, the spraying parameters of the Si3N4-SiC mixed powder include:

[0064] The mass ratio of Si3N4 powder and SiC powder in the Si3N4-SiC mixed powder is preferably 1:1 to 4:1, the purity of the Si3N4-SiC mixed powder is preferably 99.999%, the particle size is preferably 150 to 300 μm, the spraying temperature is preferably 1500 to 1800°C, and more preferably 1600 to 1700°C; the spraying thickness of the Si3N4-SiC mixed powder is preferably 10 to 40 wires, and more preferably 20 to 30 wires.

[0065] After the Si3N4-SiC mixed powder is sprayed, the present invention preferably further comprises standing, and the standing temperature is preferably 120-180°C, more preferably 130-170°C, and more preferably 140-160°C; the humidity is preferably 40-75RH%, more preferably 50-70RH%, and more preferably 60-65RH%; and the time is preferably 6-10h.

[0066] In the present invention, the material covered with the first coating is sprayed with a Si3N4+SiC mixed powder, wherein the binder is silica sol, and Si3N4 and SiC can react with the material coated with the first coating at high temperature to obtain a reactive silicon-carbon-nitrogen coating through an in-situ chemical reaction. The interlayer bonding force is stronger, and the surface of the obtained carbon-carbon thermal field composite material can be made denser, preventing silicon liquid from penetrating, and preventing silicon vapor from chemically reacting with the carbon-carbon thermal field composite material, effectively preventing the carbon-carbon thermal field composite material from being corroded and damaged, and effectively improving the high-temperature mechanical properties and anti-silicification corrosion performance of the carbon-carbon thermal field composite material, thereby extending the service life of the carbon-carbon thermal field composite material.

[0067] After obtaining the carbon-carbon thermal field composite material precursor, the present invention performs a third heat treatment on the carbon-carbon thermal field composite material precursor to obtain the carbon-carbon thermal field composite material.

[0068] In the present invention, the temperature of the third heat treatment is preferably 2000-2500°C, more preferably 2100-2400°C, and more preferably 2200-2300°C; the rate of heating to the temperature of the third heat treatment is preferably 80-120°C / h, more preferably 90-110°C / h, and more preferably 100°C / h; the holding time is preferably 1-4h, and the third heat treatment is preferably carried out under a protective atmosphere, and the protective atmosphere is preferably high-purity nitrogen.

[0069] In the present invention, after the third heat treatment, a Si / C / N coating is formed on the outer surface, which further improves the density of the material, prevents contamination by silicon liquid, and prevents leakage of silicon liquid.

[0070] The present invention also provides a carbon-carbon thermal field composite material obtained by the preparation method described in the above technical solution.

[0071] In the present invention, the carbon-carbon thermal field composite material includes a carbon / carbon composite material and a composite coating, wherein the composite coating is obtained by heat-treating a silicon nitride coating, sprayed Al2O3 powder, and Si3N4-SiC mixed powder.

[0072] The present invention also provides for the use of the carbon-carbon thermal field composite material described in the above technical solution in a crucible for a single crystal silicon pulling furnace. When the carbon-carbon thermal field composite material is used in a crucible for a single crystal silicon pulling furnace, the present invention does not specifically limit its application, and those skilled in the art can configure it according to actual circumstances.

[0073] The carbon-carbon thermal field composite material provided by the present invention, its preparation method and application are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0074] Example 1

[0075] The preparation method of the carbon-carbon thermal field composite material comprises the following steps:

[0076] 1. Preparation of high-density carbon / carbon composite crucibles

[0077] The density of the material is 0.31g / cm2 by using alternating lamination of non-woven fabric and ultra-thin mesh and bidirectional weaving of Z-direction fibers. 3 The carbon fiber preform was treated at 2000℃ for 3 hours and then machined according to the drawing requirements. A specific graphite set was used to build the tooling, and chemical vapor deposition was performed in a chemical vapor deposition furnace to obtain a densified crucible. The chemical vapor deposition densification conditions included: the carbon source gas was methane, and the methane flow rate was 10m 3 / h, the deposition temperature is 1200℃, the heating rate is 60℃ / h, the deposition time is 200h, and the deposition pressure is 5kPa. Then the densified crucible is placed in a phenolic resin solution (solid content is 75%, solvent is xylene), vacuum impregnated for 3h under 10kPa conditions, cross-linked and cured at 200℃ and 3MPa for 4h, and cracked and carbonized in a carbonization furnace at 1200℃ for 12h to obtain a density of 1.78g / cm 3 Finally, the crucible is machined and polished until the outer surface is smooth and free of residue, and the residue on the surface is cleaned to obtain a carbon / carbon composite crucible.

[0078] 2. Impregnation-heat treatment

[0079] A carbon / carbon composite crucible was pressure-impregnated with a polysilazane solution having a solid content of 95% and a xylene solvent for three times at a pressure of 5 MPa for 24 hours. After impregnation, the carbon / carbon composite crucible was dried at 100°C and 55% relative humidity for 8 hours. The carbon / carbon composite crucible was then subjected to a second heat treatment in a high-temperature furnace at 2000°C for 3 hours at a heating rate of 60°C / hour. The protective atmosphere in the heat treatment equipment was high-purity argon, yielding a silicon nitride-coated carbon / carbon composite crucible.

[0080] 3. Ultrasonic spraying

[0081] Ultrasonic spraying of Al2O3 powder was performed on the entire silicon nitride coating-carbon / carbon composite crucible. The Al2O3 powder had a purity of 99.99% and a particle size of 150-300 μm. The binder was silica sol (solid content of 60%). The spraying temperature was 2200°C, and the Al2O3 coating thickness was 20 μm. After spraying, the crucible was left to stand for 8 hours at a temperature of 150°C and a humidity of 60%.

[0082] A Si3N4+SiC mixed powder (99.999% purity, 150-300μm particle size, Si3N4:SiC mass ratio of 2:1) was sprayed onto a silicon nitride-coated carbon / carbon composite crucible sprayed with an Al2O3 coating. The spraying temperature was 1700°C, and the coating thickness was 20 μm. After spraying, the Si3N4+SiC mixed powder was allowed to stand for 8 hours at a temperature of 150°C and a humidity of 60%.

[0083] 4. High temperature treatment

[0084] The sprayed material was placed in a high-temperature furnace and heated to 2300°C at a rate of 100°C / min in an argon environment for high-temperature heat treatment. The temperature was kept for 4 hours, and the carbon / carbon composite crucible and the silicon nitride coating, Al2O3 coating and Si3N4+SiC mixed powder coating reacted in situ to obtain a carbon-carbon thermal field composite crucible. Among them, the thickness of the composite coating obtained by the reaction of silicon nitride coating, Al2O3 coating and Si3N4+SiC mixed powder coating was about 150μm.

[0085] Example 2

[0086] The preparation method of the carbon-carbon thermal field composite material comprises the following steps:

[0087] 1. Preparation of high-density carbon / carbon composite crucibles

[0088] The non-woven fabric and ultra-thin mesh were alternately laminated and needle-punched, and the Z-direction fiber was used for bidirectional weaving to obtain a density of 0.34g / cm3 The carbon fiber preform was treated at 2000℃ for 3 hours and then machined according to the drawing requirements. A specific graphite set was used to build the tooling, and chemical vapor deposition was performed in a chemical vapor deposition furnace to obtain a densified crucible. The chemical vapor deposition conditions were: the carbon source gas was methane, and the methane flow rate was 10m 3 / h, the deposition temperature is 1200℃, the heating rate is 60℃ / h, the deposition time is 200h, and the deposition pressure is 5kPa. Then the densified crucible is placed in a phenolic resin solution (solid content is 75%, solvent is xylene), vacuum impregnated for 3h under 10kPa conditions, cross-linked and cured at 200℃ and 3MPa for 4h; in a carbonization furnace, cracked and carbonized at 1200℃ for 12h, and a density of 1.82g / cm 3 Finally, the crucible is machined and polished until the outer surface is smooth and free of residue, and the residue on the surface is cleaned to obtain a carbon / carbon composite crucible.

[0089] 2. Impregnation-heat treatment

[0090] A carbon / carbon composite crucible was pressure-impregnated with a polysilazane solution having a solid content of 99% and a xylene solvent for three times at a pressure of 5 MPa for 24 hours. After impregnation, the carbon / carbon composite crucible was dried at 100°C and 55% relative humidity for 8 hours. The crucible was then subjected to a second heat treatment in a high-temperature furnace at 2000°C for 3 hours at a heating rate of 60°C / hour. The protective atmosphere in the heat treatment equipment was high-purity argon, yielding a silicon nitride-coated carbon / carbon composite crucible.

[0091] 3. Ultrasonic spraying

[0092] Ultrasonic spraying of Al2O3 powder was performed on the entire silicon nitride coating-carbon / carbon composite crucible. The Al2O3 had a purity of 99.99% and a particle size of 150-300 μm. The binder was silica sol (solid content of 60%). The spraying temperature was 2200°C, and the Al2O3 coating thickness was 20 μm. After spraying, the Al2O3 powder was allowed to stand for 8 hours in an environment with a temperature of 150°C and a humidity of 60%.

[0093] A Si3N4+SiC mixed powder (99.999% purity, 150-300μm particle size, Si3N4:SiC mass ratio of 2:1) was sprayed onto a silicon nitride-coated carbon / carbon composite crucible sprayed with an Al2O3 coating. The spraying temperature was 1700°C, and the coating thickness was 30 μm. After spraying, the Si3N4+SiC mixed powder was allowed to stand for 8 hours at a temperature of 150°C and a humidity of 60%.

[0094] 4. High temperature treatment

[0095] The sprayed material was placed in a high-temperature furnace and heated to 2300°C at a rate of 100°C / min under an argon environment for high-temperature heat treatment. The temperature was kept for 4 hours, and the carbon / carbon composite material crucible and the silicon nitride coating, Al2O3 coating and Si3N4+SiC mixed powder coating reacted in situ to obtain a carbon-carbon thermal field composite material crucible. Among them, the thickness of the composite coating obtained by the reaction of silicon nitride coating, Al2O3 coating and Si3N4+SiC mixed powder coating was about 250μm.

[0096] Example 3

[0097] The preparation method of the carbon-carbon thermal field composite material comprises the following steps:

[0098] 1. Preparation of high-density carbon / carbon composite crucibles

[0099] The non-woven fabric and ultra-thin mesh were alternately laminated and needle-punched, and the Z-direction fiber was used for bidirectional weaving to obtain a density of 0.32g / cm 3 The carbon fiber preform was treated at 2000℃ for 3 hours and then machined according to the drawing requirements. A specific graphite set was used to build the tooling and chemical vapor deposition was performed in a chemical vapor deposition furnace for densification. The chemical vapor deposition conditions were: the carbon source gas was methane, and the methane flow rate was 10m 3 / h, the deposition temperature is 1200℃, the heating rate is 60℃ / h, the deposition time is 200h, and the deposition pressure is 5kPa. Then the densified crucible is placed in a phenolic resin solution (solid content is 75%, solvent is xylene), vacuum impregnated for 3h under 10kPa, cross-linked and cured at 200℃ and 3MPa for 4h, and cracked and carbonized in a carbonization furnace at 1200℃ for 12h to obtain a density of 1.84g / cm 3 Finally, the crucible is machined and polished until the outer surface is smooth and free of residue, and the residue on the surface is cleaned to obtain a carbon / carbon composite crucible.

[0100] 2. Impregnation-heat treatment

[0101] A carbon / carbon composite crucible was pressure-impregnated with a polysilazane solution having a solid content of 99% and a xylene solvent. The impregnation was repeated three times at a pressure of 5 MPa for 24 hours. After impregnation, the carbon / carbon composite crucible was dried at 100°C and 55% relative humidity for 8 hours. The crucible was then subjected to a second heat treatment in a high-temperature furnace at 2000°C for 3 hours at a heating rate of 60°C / h. The protective atmosphere in the heat treatment equipment was high-purity argon, resulting in a silicon nitride coating-carbon / carbon composite crucible.

[0102] 3. Ultrasonic spraying

[0103] Ultrasonic spraying of Al2O3 powder was performed on the entire silicon nitride coating-carbon / carbon composite crucible. The Al2O3 powder had a purity of 99.99% and a particle size of 150-300 μm. The binder was silica sol (solid content of 60%). The spraying temperature was 2200°C, and the Al2O3 coating thickness was 20 μm. After spraying, the crucible was left to stand for 8 hours at a temperature of 150°C and a humidity of 60%.

[0104] A Si3N4+SiC mixed powder (99.999% purity, 150-300μm particle size, Si3N4:SiC mass ratio of 2:1) was sprayed onto a silicon nitride-coated carbon / carbon composite crucible sprayed with an Al2O3 coating. The spraying temperature was 1700°C, and the coating thickness was 40 μm. After spraying, the Si3N4+SiC mixed powder was allowed to stand for 8 hours at a temperature of 150°C and a humidity of 60%.

[0105] 4. High temperature treatment

[0106] The sprayed material was placed in a high-temperature furnace and heated to 2300°C at a rate of 100°C / min in an argon environment for high-temperature heat treatment. The temperature was kept for 4 hours, and the carbon / carbon composite material crucible and the silicon nitride coating, Al2O3 coating and Si3N4+SiC mixed powder coating reacted in situ to obtain a carbon-carbon thermal field composite material crucible. Among them, the thickness of the composite coating obtained by the reaction of silicon nitride coating, Al2O3 coating and Si3N4+SiC mixed powder coating was about 350μm.

[0107] A conventional commercially available carbon / carbon composite crucible (denoted as C / C crucible), a high-density carbon / carbon composite crucible (denoted as HC / C crucible), and the carbon-carbon thermal field composite crucible obtained in Examples 1 to 3 were tested, and the results are shown in Table 1. The high-density carbon / carbon composite crucible differs from the preparation method provided by the present invention in that only a carbon fiber preform is prepared; the carbon fiber preform is sequentially subjected to a first heat treatment and a densification treatment to obtain a densified material; the densified material is impregnated in a resin solution, followed by cross-linking and curing and cracking and carbonization to obtain a carbon / carbon composite material; and the subsequent polysilazane solution impregnation, Al2O3 powder spraying, Si3N4-SiC mixed powder spraying, and third heat treatment are not performed.

[0108] Table 1 Performance test results

[0109] <![CDATA[Density (g / cm 3 )]]> Opening rate (%) Silicone liquid contact angle (°) C / C Crucible 1.4～1.6 15～20 10～30 HC / C crucible 1.75～1.85 ＜15 10～30 Crucible prepared in Example 1 1.87 9.76 78 Crucible prepared in Example 2 1.92 4.21 84 Crucible prepared in Example 3 1.96 0.62 92

[0110] As can be seen from Table 1, the density of the carbon-carbon thermal field composite material crucible covered with the composite coating is increased by 25-40%, and the open porosity is greatly reduced, reflecting that the composite coating can effectively seal the pores. The carbon-carbon thermal field composite material crucible has the characteristics of high surface density and large contact angle with silicon liquid, which can better isolate the molten silicon, protect the silicon material, and prevent the silicon liquid from leaking and contaminating the carbon-carbon thermal field composite material crucible.

[0111] The compressive strength and flexural strength of the carbon-carbon thermal field composite material crucibles obtained in Examples 1 to 3 and conventional quartz crucibles on the market were tested using a three-point bending method. The results are shown in Table 2.

[0112] Table 2 Mechanical properties test results

[0113] Quartz crucible Example 1 Example 2 Example 3 Compressive strength / MPa 130～170 316 334 354 Bending strength / MPa 30～50 221 229 235

[0114] As can be seen from Table 2, the preparation method provided by the present invention can effectively improve the compressive strength and flexural strength of the carbon-carbon crucible itself, and improve its ability to carry molten silicon liquid. The carbon-carbon thermal field composite material crucibles prepared using Examples 1 to 3 and conventional quartz crucibles on the market are used to pull single crystal silicon under the same conditions. The service life of the carbon-carbon thermal field composite material crucibles prepared in Examples 1 to 3 is 177 days, 239 days, and 315 days, respectively, while the service life of conventional quartz crucibles is only 15 to 30 days. Therefore, the carbon-carbon thermal field composite material crucible prepared by the present invention has a long service life for pulling single crystal silicon and a low overall cost, and can meet the use requirements of the carbon / carbon composite material crucible force-bearing core structure of the single crystal silicon vertical pulling furnace for photovoltaic thermal fields.

[0115] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon-carbon thermal field composite material, characterized in that: The following steps are involved: preparing a carbon fiber preform; performing a first heat treatment and a densification treatment on the carbon fiber preform in sequence to obtain a densified material; After the densification material is immersed in a resin solution, cross-linking and curing and cracking and carbonizing are sequentially performed to obtain a carbon / carbon composite material; The carbon / carbon composite material is immersed in a polysilazane solution, and then subjected to drying and second heat treatments to obtain a silicon nitride coating-carbon / carbon composite material; Spraying Al2O3 powder and Si3N4-SiC mixed powder on the surface of the silicon nitride coating-carbon / carbon composite material in sequence to obtain a carbon-carbon thermal field composite material precursor; performing a third heat treatment on the carbon-carbon thermal field composite material precursor to obtain the carbon-carbon thermal field composite material; The solid content of the polysilazane solution is ≥90%, and the carbon / carbon composite material is immersed in the polysilazane solution at a pressure of 1 to 10 MPa for 12 to 24 hours, with a cycle number of 1 to 3 times; The temperature of the second heat treatment is 1800-2300°C, the rate of heating to the temperature of the second heat treatment is 80-120°C / h, and the holding time is 1-4h; The spraying parameters of the Al2O3 powder include: the particle size of the Al2O3 powder is 150-300 μm, the binder is silica sol, the spraying temperature is 2000-2300°C, and the spraying thickness of the Al2O3 powder is 10-40 μm; The spraying parameters of the Si3N4-SiC mixed powder include: The mass ratio of Si3N4 powder to SiC powder in the Si3N4-SiC mixed powder is 1:1-4:1, the particle size of the Si3N4-SiC mixed powder is 150-300 μm, the spraying temperature is 1500-1800° C., and the spraying thickness of the Si3N4-SiC mixed powder is 10-40 μm; The temperature of the third heat treatment is 2000-2500° C., the rate of heating to the temperature of the third heat treatment is 80-120° C. / h, and the holding time is 1-4 hours.

2. The preparation method according to claim 1, characterized in that The woven structure of the carbon fiber preform is a needle-punched structure; and the preparation method of the carbon fiber preform comprises the following steps: The carbon fiber preform is obtained by needle-punching the alternately stacked layers of the non-woven fabric and the ultra-thin mesh, and weaving the Z-direction fibers bidirectionally through the layers. The density of the carbon fiber preform is 0.2 to 0.4 g / cm 3 .

3. The preparation method according to claim 1 or 2, characterized in that The temperature of the first heat treatment is 1800-2300° C., the rate of heating to the temperature of the first heat treatment is 80-120° C. / h, the holding time is 1-4 hours, and the first heat treatment is carried out under a protective atmosphere.

4. The preparation method according to claim 1, characterized in that The densification process is chemical vapor deposition; the parameters of the chemical vapor deposition include: the carbon source gas is methane or propylene, the flow rate of the carbon source gas is 2.0 to 20m 3 / h, the deposition temperature is 1000-1200°C, the rate of heating to the deposition temperature is 40-80°C / h, the deposition pressure is 2.0-10.0 kPa, and the deposition time is 100-300 h.

5. The preparation method according to claim 1, characterized in that The resin in the resin solution is phenolic resin, the solvent of the resin solution is xylene, the solid content of the resin solution is 60-85%, the pressure of the densifying material immersed in the resin solution is 5-10 kPa, and the time is 1-3 hours; the temperature of the cross-linking and curing is 100-200°C, the pressure is 1-3 MPa, and the time is 2-4 hours; the temperature of the cracking and carbonization is 600-1200°C, and the time is 10-36 hours.

6. The preparation method according to claim 1, characterized in that The solvent of the polysilazane solution is xylene; The drying temperature is 80-100°C and the humidity is 40-75% RH; The second heat treatment is performed under a protective atmosphere.

7. The preparation method according to claim 1, characterized in that The purity of the Al2O3 powder is 99.99%; The purity of the Si3N4-SiC mixed powder is 99.999%.

8. The preparation method according to claim 1, characterized in that The third heat treatment is performed under a protective atmosphere.

9. The carbon-carbon thermal field composite material obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the carbon-carbon thermal field composite material according to claim 9 in a crucible for a single crystal silicon pulling furnace.