Novel high thermal conductivity composite crucible for polycrystalline silicon ingot casting and preparation method thereof

Abstract

The present invention relates to a novel high thermal conductivity composite crucible for polysilicon ingot casting and a preparation method thereof, belonging to the technical field of crucibles for polysilicon ingot casting, comprising a crucible body, wherein the crucible body is a cavity-shaped structure with an upper end opening, a graphene-silicon dioxide composite material layer is laid on the bottom of the inner cavity of the crucible body, and a quartz ceramic structure layer is laid on the top of the graphene-silicon dioxide composite material layer. A novel high thermal conductivity composite crucible for polysilicon ingot casting of the present invention and a preparation method thereof, by adding a graphene-silicon dioxide composite material layer in the crucible, can effectively enhance the mechanical properties and thermal properties of the material, so that the novel composite crucible has high strength and good toughness, can effectively reduce the overflow rate of the crucible, and at the same time, the use of the composite crucible can reduce the energy consumption of the ingot casting process, improve the quality of polysilicon crystals, and meet market demand.

Description

Technical Field

[0001] The present invention relates to a novel composite crucible for polycrystalline ingot casting and a preparation method thereof, and in particular to a novel high thermal conductivity composite crucible for polycrystalline silicon ingot casting and a preparation method thereof, which belongs to the technical field of crucibles for polycrystalline silicon ingot casting. Background Art

[0002] During the preparation of polysilicon ingots, quartz ceramic crucibles are important supplies that must be used in the polysilicon ingot casting stage. The silicon material is melted, crystals grow, annealed and cooled in the crucible to cast a polysilicon ingot. The silicon ingot is cut into silicon wafers according to technical requirements, which become the matrix material for the production of solar cells.

[0003] At present, quartz ceramic crucibles are mainly prepared into green bodies by slip casting, and then sintered at about 1200℃ to obtain a density of about 1.92g / cm 3 Ceramic crucible. The thermal conductivity of this ceramic crucible is low, generally only 0.86-0.88W / mK. During the directional solidification stage of the ingot, the thermal conductivity is low and the heat dissipation is slow, which will cause a large difference in the heat dissipation between the side wall and the bottom. In order to obtain high-quality ingot polycrystalline, a relatively flat crystal growth interface is required. Heat loss from the side will lead to a concave crystal growth interface, which seriously affects the quality of the crystal. The material matrix of the ceramic crucible is ceramic, and its crystal phase is crystal and glass. When preparing cast polycrystalline silicon, during the melting of the raw materials and the growth of the crystal, the silicon melt and the crucible are in contact for a long time, which will produce a viscosity effect. Due to the different thermal expansion coefficients of the two materials, if the silicon material and the crucible wall are tightly combined, it is likely to cause the crystalline silicon or the crucible to rupture and overflow when the crystal is cooled. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a novel high thermal conductivity composite crucible for polycrystalline silicon ingot casting and a preparation method thereof.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] A novel high thermal conductivity composite crucible for polycrystalline silicon ingot casting comprises a crucible body, wherein the crucible body is a cavity structure with an upper end open, a graphene-silicon dioxide composite material layer is laid on the bottom of the inner cavity of the crucible body, and a quartz ceramic structure layer is laid above the graphene-silicon dioxide composite material layer.

[0007] Furthermore, the thickness of the graphene-silicon dioxide composite material layer is 8-10 mm, the thickness of the quartz ceramic structure layer is 5-8 mm, and the total thickness of the crucible bottom, the graphene-silicon dioxide composite material layer and the quartz ceramic structure layer is 22-25 mm.

[0008] Furthermore, the components for making the graphene-silicon dioxide composite material layer include graphene oxide, toluene and monomer siloxane.

[0009] A method for preparing a novel high thermal conductivity composite crucible for polycrystalline silicon ingot casting comprises the following steps:

[0010] (1) Preparation of graphene-silicon dioxide composite material: dissolving graphene oxide in water and ultrasonically dispersing to obtain a graphene oxide aqueous solution, then adding toluene for emulsification to obtain a graphene oxide emulsion; adding monomer siloxane to the obtained graphene oxide emulsion, then adjusting the pH value to 9 with ammonia water and stirring, and performing emulsion polymerization for 6 hours. After the reaction is completed, washing and filtering to obtain a graphene-silicon dioxide composite material;

[0011] (2) Preparation of quartz ceramic crucible: The crucible body is prepared by a novel injection molding technology. After the crucible body is dried, a layer of graphene-silicon dioxide composite material solution is brushed on the bottom of the crucible body, and then a special lid is covered and compacted to form a graphene-silicon dioxide composite material layer. Then a layer of silicon dioxide slurry is poured on top, and the lid is covered and compacted to form a quartz ceramic structure layer. After drying, the crucible body is demolded, cured and sintered at high temperature.

[0012] Furthermore, the mass ratio of the toluene and graphene oxide aqueous solution is 1:2-1:5, and the ratio of the amount of the monomer siloxane to the amount of graphene oxide is 50:1-100:1.

[0013] Furthermore, the concentration of the graphene oxide aqueous solution is 1-5 mg / ml.

[0014] Furthermore, the crucible body is a quartz ceramic structure.

[0015] The beneficial effects of the present invention are as follows: by adding a graphene-silicon dioxide composite material layer inside the crucible, the composite material has the characteristics of light weight, high strength, good thermal conductivity and high temperature resistance. It combines the respective advantages of graphene material and silicon dioxide, can effectively enhance the mechanical properties and thermal properties of the material, so that the new composite crucible has high strength and good toughness, and can effectively reduce the overflow rate of the crucible; graphene has very good thermal conductivity, and the thermal conductivity of pure defect-free single-layer graphene is as high as 5300W / mK, which is the carbon material with the highest thermal conductivity so far. When it is used as a carrier, the thermal conductivity can also reach 600W / mK, but when graphene is exposed to a high temperature environment, graphene will usually degrade, but ceramic materials have the characteristics of high temperature resistance and fire resistance, which are very helpful for the high temperature resistance of graphene. Using the crucible combined with the two to carry out polycrystalline silicon ingot casting can reduce the energy consumption of the ingot casting process and improve the quality of polycrystalline silicon crystals in the ingot casting process, which is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the present invention.

[0017] In the figure, 1. crucible body; 2. quartz ceramic structure layer; 3. graphene-silicon dioxide composite material layer. DETAILED DESCRIPTION

[0018] The following is combined with Figure 1 The principles and features of the present invention are described, and the examples given are only used to explain the present invention, rather than to limit the scope of the present invention.

[0019] A novel high thermal conductivity composite crucible for polycrystalline silicon ingot casting comprises a crucible body 1, wherein the crucible body 1 is a cavity structure with an upper end open, a graphene-silicon dioxide composite material layer 3 is laid on the bottom of the inner cavity of the crucible body 1, and a quartz ceramic structure layer 2 is laid above the graphene-silicon dioxide composite material layer 3; the crucible body 1 is a quartz ceramic structure.

[0020] The thickness of the graphene-silicon dioxide composite material layer 3 is 8-10 mm, the thickness of the quartz ceramic structure layer 2 is 5-8 mm, and the total thickness of the bottom of the crucible body 1, the graphene-silicon dioxide composite material layer 3 and the quartz ceramic structure layer 2 is 22-25 mm.

[0021] The components for making the graphene-silicon dioxide composite material layer 3 include graphene oxide, toluene and monomer siloxane.

[0022] The mass ratio of the toluene and graphene oxide aqueous solution is 1:2-1:5, the usage ratio of the monomer siloxane to the graphene oxide is 50:1-100:1; and the concentration of the graphene oxide aqueous solution is 1-5 mg / ml.

[0023] Example

[0024] A method for preparing a novel high thermal conductivity composite crucible for polycrystalline silicon ingot casting comprises the following steps:

[0025] (1) Preparation of graphene-silicon dioxide composite material: dissolving graphene oxide in water and ultrasonically dispersing to obtain a graphene oxide aqueous solution, wherein the concentration of the graphene oxide aqueous solution is 1 mg / ml, and then emulsifying toluene in a mass ratio of toluene to the graphene oxide aqueous solution of 1:2 to obtain a graphene oxide emulsion; then adding monomer siloxane to the graphene oxide emulsion in a ratio of 50:1, and then adjusting the pH value to 9 with ammonia water and stirring, and performing emulsion polymerization for 6 hours. After the reaction is completed, washing and filtering are performed to obtain a graphene-silicon dioxide composite material;

[0026] (2) Preparation of quartz ceramic crucible: A crucible body 1 is prepared by a novel injection molding technology. After the crucible body 1 is dried, a layer of graphene-silicon dioxide composite material solution is brushed on the bottom of the crucible body 1, and then a special lid is covered and compacted to form a graphene-silicon dioxide composite material layer 3. Then, a layer of silicon dioxide slurry is poured on top, and the lid is covered and compacted to form a quartz ceramic structure layer 2. After drying, the crucible body 1 is demolded, cured and sintered at high temperature.

[0027] Experimental data analysis

[0028] The flexural strength, elastic modulus, thermal conductivity, density and apparent porosity of the new type of high thermal conductivity composite crucible for polycrystalline silicon ingot produced in the embodiment were tested and compared with ordinary crucibles. The comparison results are as follows:

[0029] Table 1

[0030] Ordinary crucible High thermal conductivity composite crucible Flexural strength MPa 23 25 Elastic modulus GPa 20 30 Thermal conductivity W / mK 1.0 1.2 <![CDATA[Density g / cm 3 > 1.92 1.90 Apparent porosity% 12 11

[0031] As shown in Appendix 1, the comparative analysis between the high thermal conductivity composite crucible and the ordinary crucible leads to the conclusion that the high thermal conductivity composite crucible produced by the above method has stronger flexural strength, larger elastic modulus and thermal conductivity, lower apparent porosity and density, and longer service life.

[0032] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a high thermal conductivity composite crucible for polycrystalline silicon ingot casting, characterized in that: The following steps are involved: (1) Preparation of graphene-silicon dioxide composite material: dissolving graphene oxide in water and ultrasonically dispersing to obtain a graphene oxide aqueous solution, and then adding toluene to emulsify to obtain a graphene oxide emulsion; adding monomer siloxane to the obtained graphene oxide emulsion, and then adjusting the pH value to 9 with ammonia water and stirring, and performing emulsion polymerization for 6 hours. After the reaction is completed, washing and filtering to obtain a graphene-silicon dioxide composite material; (2) Preparation of quartz ceramic crucible: A crucible body (1) is prepared by gel injection molding technology. After the crucible body (1) is dried, a layer of graphene-silicon dioxide composite material solution is brushed on the bottom of the crucible body (1), and then a special lid is covered and compacted to form a graphene-silicon dioxide composite material layer (3). Then, a layer of silicon dioxide slurry is poured on top, and the lid is covered and compacted to form a quartz ceramic structure layer (2). After drying, the crucible body is demolded, cured and sintered at high temperature.

2. The method for preparing a high thermal conductivity composite crucible for polycrystalline silicon ingot casting according to claim 1, characterized in that: The mass ratio of the toluene and graphene oxide aqueous solution is 1:2-1:5, and the amount ratio of the monomer siloxane to the graphene oxide is 50:1-100:

1.

3. The method for preparing a high thermal conductivity composite crucible for polycrystalline silicon ingot casting according to claim 1, characterized in that: The concentration of the graphene oxide aqueous solution is 1-5 mg / ml.

4. The high thermal conductivity composite crucible for polycrystalline silicon ingots prepared by the method for preparing a high thermal conductivity composite crucible for polycrystalline silicon ingots according to claim 1 comprises a crucible body (1), wherein the crucible body (1) is a cavity-shaped structure with an upper end open, and is characterized in that: A graphene-silicon dioxide composite material layer (3) is laid on the bottom of the inner cavity of the crucible body (1), and a quartz ceramic structure layer (2) is laid on top of the graphene-silicon dioxide composite material layer (3).

5. The high thermal conductivity composite crucible for polycrystalline silicon ingot casting according to claim 4, characterized in that: The thickness of the graphene-silicon dioxide composite material layer (3) is 8-10 mm, the thickness of the quartz ceramic structure layer (2) is 5-8 mm, and the total thickness of the bottom of the crucible body (1), the graphene-silicon dioxide composite material layer (3) and the quartz ceramic structure layer (2) is 22-25 mm.

6. The high thermal conductivity composite crucible for polycrystalline silicon ingot casting according to claim 4, characterized in that: The crucible body (1) is a quartz ceramic structure.

7. A graphene-silicon dioxide composite material for making a high thermal conductivity composite crucible for polycrystalline silicon ingot casting as claimed in any one of claims 4 to 6, characterized in that: The components for making the graphene-silicon dioxide composite material include graphene oxide, toluene and monomer siloxane.

Images