Highly dense and highly heat-conductive quartz crucible and preparation method thereof

Abstract

The present application relates to the technical field of quartz crucible, and particularly relates to a high-density and high-thermal-conductivity quartz crucible and a preparation method thereof. The star-shaped polyethylene glycol dispersant is prepared by adding polyethylene glycol, butanediol, toluene, thionyl chloride and D-sorbitol. Then, the star-shaped polyethylene glycol dispersant, deionized water and high-purity quartz sand powder are mixed to obtain quartz crucible raw materials. The quartz crucible raw materials are placed in a crucible mold, and the quartz sand crucible blank is obtained by pre-molding. The quartz sand crucible blank is placed in a melting furnace to obtain the quartz crucible. The coating is prepared by taking triboric acid, silicon nitride powder and silicon powder as raw materials. The coating is uniformly brushed on the inner surface of the quartz crucible to obtain the finished product. The quartz crucible prepared by the present application has good dispersibility, stability and viscosity. Meanwhile, the preparation of the surface coating also enhances the corrosion resistance and the polysilicon yield of the quartz crucible, so the present application has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of quartz crucibles, in particular to a high-density and high-thermal-conductivity quartz crucible and a preparation method thereof. Background Art

[0002] As traditional energy consumption and its negative environmental impact intensify, crystalline silicon solar cells play a vital role in transforming the energy mix and reducing environmental pressure. As a key material for crystalline silicon solar cells, polycrystalline silicon (polysilicon) is in widespread market demand. Quartz crucibles are often used as containers for melting and purifying the silicon material during polysilicon production. Quartz crucibles, with their high-temperature resistance, chemical stability, and low ion content, can withstand high-temperature melting and reaction processes while maintaining purity and stability, ensuring the quality and crystal structure integrity of polysilicon. However, quartz crucibles still face several technical challenges. First, the high cost of preparing quartz crucibles, primarily due to the high price and difficulty of processing the quartz material itself, has limited their widespread application in certain fields. Second, current quartz crucible production technology has certain size limitations, making it difficult to produce large and complex crucibles, which poses certain limitations in certain application scenarios. Third, quartz crucibles are relatively fragile and susceptible to mechanical and thermal shock, leading to cracking and damage. This can affect the accuracy of experimental results, increase experimental costs, and pose safety risks.

[0003] In order to overcome the defects of the prior art, the present invention provides a high-density and high-thermal-conductivity quartz crucible and a preparation method thereof. Summary of the Invention

[0004] The object of the present invention is to provide a high-density and high-thermal-conductivity quartz crucible and a preparation method thereof, so as to solve the problems in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for preparing a high-density and high-thermal-conductivity quartz crucible comprises the following steps:

[0007] Step 1: Mix polyethylene glycol, butanediol and toluene, heat and reflux for 5-7h, add chloroform after the reaction, shake and filter, adjust the pH of the filtrate to 2-3 with concentrated hydrochloric acid, extract, dry, filter, rotary evaporate and purify to obtain carboxyl-terminated polyethylene glycol; mix carboxyl-terminated polyethylene glycol, thionyl chloride and toluene, react at 70-90℃ for 20-

[0008] 30h, then distill under reduced pressure and dry to obtain chlorinated polyethylene glycol; mix chlorinated polyethylene glycol and D-sorbitol, react at 80-100°C for 6-10h, then cool, hydrolyze, extract, dry, and rotary evaporate to obtain a star-shaped polyethylene glycol dispersant;

[0009] Step 2: Mixing a star-shaped polyethylene glycol dispersant, deionized water, and high-purity quartz sand powder, and stirring them thoroughly to prepare a quartz crucible raw material; placing the quartz crucible raw material in a crucible mold, and preforming it to obtain a quartz casserole blank; placing the quartz casserole blank in a melting furnace, and sequentially performing inner layer melting and outer layer melting to obtain a quartz crucible;

[0010] Step 3: Add triboric acid to the polyvinyl pyrrolidone solution, stir thoroughly, then add silicon nitride powder, silicon powder and n-octanol, and obtain a coating by ball milling; apply the coating evenly on the inner surface of the quartz crucible, and obtain the finished product after natural air drying and calcination.

[0011] More optimally, in step 1, the mass ratio of polyethylene glycol, butanediol and toluene is 2-3:1:11.

[0012] More optimally, in step 1, the mass ratio of carboxyl-terminated polyethylene glycol, thionyl chloride and toluene is 3-4:7:13.

[0013] More optimally, in step 1, the mass ratio of chlorinated polyethylene glycol to D-sorbitol is 3-4:10.

[0014] More optimally, in step 2, the mass ratio of the star-shaped polyethylene glycol dispersant, deionized water and high-purity quartz sand powder is 3-4:6:2.

[0015] More optimally, in step 2, during prefabrication, the rotation speed is 70-90 r / min and the radius of the forming rod is 230-300 mm.

[0016] More optimally, in step 2, when the inner layer is melted, the power is 280-330W and the time is 40-80s; when the outer layer is melted, the power is 600-650W and the time is 40-80s.

[0017] More optimally, in step three, the contents of the coating components are: by mass fraction, 5-8% triboric acid, 8-10% polyvinyl pyrrolidone solution, 25-30% silicon nitride powder, 2-4% n-octanol, and the balance is silicon powder.

[0018] More optimally, in step three, the calcination process parameters are: calcination temperature is 550-650°C, and calcination time is 100-150min.

[0019] More optimally, in step three, the ball-to-grinding ratio is 1:1.5-2.5; and the coating thickness is 1-2 mm.

[0020] Beneficial effects of the present invention:

[0021] The present invention prepares a star-shaped polyethylene glycol dispersant by adding polyethylene glycol, butanediol, toluene, thionyl chloride, and D-sorbitol. The star-shaped polyethylene glycol dispersant, deionized water, and high-purity quartz sand powder are then mixed to obtain a quartz crucible raw material. The quartz crucible raw material is placed in a crucible mold and preformed to obtain a quartz casserole blank. The quartz casserole blank is placed in a melting furnace and sequentially melted through inner and outer layers to obtain a quartz crucible. A coating is then prepared using triboric acid, silicon nitride powder, and silicon powder as raw materials. The coating is evenly applied to the inner surface of the quartz crucible, naturally air-dried, and calcined to obtain a finished product.

[0022] By adding polyethylene glycol, butylene glycol, toluene, thionyl chloride and D-sorbitol, prepare a star-shaped polyethylene glycol dispersant. Star-shaped polyethylene glycol has multiple branches, by connecting multiple branched chains to a central core, forming a kind of highly cross-linked molecular structure, compared with linear polymers, can provide more active end groups, increase reaction sites, improve reaction rate. Therefore, this step can form a three-dimensional network structure by adding star-shaped polyethylene glycol as dispersant, effectively coats and disperses solid particles, thereby providing larger dispersion interface area and stronger dispersibility, making it possible to disperse particles better, and prevent particle reaggregation. In addition, the star-shaped structure polymer has the characteristic of higher molecular weight and narrow molecular weight distribution, which makes it possible to provide powerful dispersion stability in dispersion system, thereby effectively preventing particle deposition, aggregation and precipitation, and keeping the stability and uniformity of dispersion system. In step three, by adding triboric acid to the coating, chemical connections are generated between the particles inside the coating, and the bonding strength of the coating is enhanced; by adding silicon powder to the coating as the crystal nucleus at the crystallization center, and then growing into crystals based on the crystal nucleus, the yield of polycrystalline silicon prepared using a quartz crucible can be significantly improved; in addition, the coating uses silicon nitride powder as the main material, and silicon nitride is a ceramic material with high thermal conductivity and relatively high density. Therefore, applying a silicon nitride coating can form a coating with good thermal conductivity and density on the surface of the quartz crucible. DETAILED DESCRIPTION

[0023] The following will provide a clear and complete description of the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] Source of raw materials:

[0025] Polyethylene glycol 1000, provided by Yixing Jiateng Chemical Co., Ltd., model PEG1000; high-purity quartz sand powder, provided by Lingshou County Anda Mineral Powder Factory, with a particle size of 10-120 mesh; silicon nitride powder, provided by Zhejiang Zhiti Nano Micro New Materials Co., Ltd., with an average particle size of 50-100nm; silicon powder, provided by Hebei Wenlun Metal Materials Co., Ltd., with a particle size of 100 mesh.

[0026] Example 1: Step 1: 24 g of polyethylene glycol, 12 g of butanediol and 150 mL of toluene were mixed, heated under reflux for 7 h, 50 mL of chloroform was added after the reaction was completed, the mixture was shaken and filtered, and the pH of the filtrate was adjusted to 3 with concentrated hydrochloric acid. After extraction, drying, filtration, rotary evaporation and purification, carboxyl-terminated polyethylene glycol was obtained; 12 g of carboxyl-terminated polyethylene glycol, 28 g of thionyl chloride and 60 mL of toluene were mixed, reacted at 90 ° C for 30 h, and then vacuum distilled and dried to obtain chlorinated polyethylene glycol; 12 g of chlorinated polyethylene glycol and 40 g of D-sorbitol were mixed, reacted at 100 ° C for 10 h, and then cooled, hydrolyzed, extracted, dried and rotary evaporated to obtain a star-shaped polyethylene glycol dispersant;

[0027] Step 2: 3 parts of star-shaped polyethylene glycol dispersant, 6 parts of deionized water and 2 parts of high-purity quartz sand powder are mixed and stirred thoroughly to prepare a quartz crucible raw material; the quartz crucible raw material is placed in a crucible mold, and preformed at a speed of 90 r / min and a forming rod radius of 300 mm to obtain a quartz casserole blank; the quartz casserole blank is placed in a melting furnace, and the inner layer is melted for 80 seconds at a power of 330 W and the outer layer is melted for 80 seconds at a power of 650 W to obtain a quartz crucible;

[0028] Step 3: Add 5wt% triboric acid to 8wt% polyvinyl pyrrolidone solution by mass fraction, stir thoroughly, then add 25wt% silicon nitride powder, 60wt% silicon powder and 2wt% n-octanol, and ball mill at a ball milling ratio of 1:1.5 to obtain a coating; apply the coating evenly on the inner surface of a quartz crucible, dry it naturally, and calcine it at 650℃ for 150min to obtain a finished product with a coating thickness of 1mm.

[0029] Example 2: Step 1: 24 g of polyethylene glycol, 12 g of butanediol and 150 mL of toluene were mixed, heated under reflux for 6.5 h, and after the reaction, 50 mL of chloroform was added for shaking and suction filtration. The pH of the filtrate was adjusted to 2.7 with concentrated hydrochloric acid, and the mixture was extracted, dried, filtered, rotary evaporated and purified to obtain carboxyl-terminated polyethylene glycol; 12 g of carboxyl-terminated polyethylene glycol, 28 g of thionyl chloride and 60 mL of toluene were mixed, reacted at 85 ° C for 27 h, and then distilled under reduced pressure and dried to obtain chlorinated polyethylene glycol; 12 g of chlorinated polyethylene glycol and 40 g of D-sorbitol were mixed, reacted at 95 ° C for 9 h, and then cooled, hydrolyzed, extracted, dried and rotary evaporated to obtain a star-shaped polyethylene glycol dispersant;

[0030] Step 2: 3 parts of star-shaped polyethylene glycol dispersant, 6 parts of deionized water and 2 parts of high-purity quartz sand powder are mixed and stirred thoroughly to prepare a quartz crucible raw material; the quartz crucible raw material is placed in a crucible mold, and preformed at a speed of 85 r / min and a forming rod radius of 283 mm to obtain a quartz casserole blank; the quartz casserole blank is placed in a melting furnace, and the inner layer is melted for 70 seconds at a power of 317 W and the outer layer is melted for 70 seconds at a power of 637 W to obtain a quartz crucible;

[0031] Step 3: Add 5wt% triboric acid to 8wt% polyvinyl pyrrolidone solution by mass fraction, stir thoroughly, then add 25wt% silicon nitride powder, 60wt% silicon powder and 2wt% n-octanol, and ball mill at a ball milling ratio of 1:1.5 to obtain a coating; apply the coating evenly on the inner surface of a quartz crucible, air dry naturally, and calcined at 625℃ for 139min to obtain a finished product with a coating thickness of 1mm.

[0032] Example 3: Step 1: 24 g of polyethylene glycol, 12 g of butanediol and 150 mL of toluene were mixed, heated under reflux for 6 h, and after the reaction, 50 mL of chloroform was added for shaking and suction filtration, and the pH of the filtrate was adjusted to 2.5 with concentrated hydrochloric acid. After extraction, drying, filtering, rotary evaporation and purification, carboxyl-terminated polyethylene glycol was obtained; 12 g of carboxyl-terminated polyethylene glycol, 28 g of thionyl chloride and 60 mL of toluene were mixed, reacted at 80 ° C for 25 h, and then vacuum distilled and dried to obtain chlorinated polyethylene glycol; 12 g of chlorinated polyethylene glycol and 40 g of D-sorbitol were mixed, reacted at 90 ° C for 8 h, and then cooled, hydrolyzed, extracted, dried and rotary evaporated to obtain a star-shaped polyethylene glycol dispersant;

[0033] Step 2: 3 parts of star-shaped polyethylene glycol dispersant, 6 parts of deionized water and 2 parts of high-purity quartz sand powder are mixed and stirred thoroughly to prepare a quartz crucible raw material; the quartz crucible raw material is placed in a crucible mold, and preformed at a speed of 80 r / min and a forming rod radius of 265 mm to obtain a quartz casserole blank; the quartz casserole blank is placed in a melting furnace, and the inner layer is melted for 60 seconds at a power of 305 W, and the outer layer is melted for 60 seconds at a power of 625 W to obtain a quartz crucible;

[0034] Step 3: Add 5wt% triboric acid to 8wt% polyvinyl pyrrolidone solution by mass fraction, stir thoroughly, then add 25wt% silicon nitride powder, 60wt% silicon powder and 2wt% n-octanol, and ball mill at a ball milling ratio of 1:1.5 to obtain a coating; apply the coating evenly on the inner surface of a quartz crucible, dry it naturally, and calcine it at 600℃ for 125min to obtain a finished product with a coating thickness of 1mm.

[0035] Example 4: Step 1: 24 g of polyethylene glycol, 12 g of butanediol and 150 mL of toluene were mixed, heated under reflux for 5.5 h, and after the reaction, 50 mL of chloroform was added for shaking and suction filtration. The pH of the filtrate was adjusted to 2.3 with concentrated hydrochloric acid, extracted, dried, filtered, rotary evaporated and purified to obtain carboxyl-terminated polyethylene glycol; 12 g of carboxyl-terminated polyethylene glycol, 28 g of thionyl chloride and 60 mL of toluene were mixed, reacted at 75 ° C for 23 h, and then distilled under reduced pressure and dried to obtain chlorinated polyethylene glycol; 12 g of chlorinated polyethylene glycol and 40 g of D-sorbitol were mixed, reacted at 85 ° C for 7 h, and then cooled, hydrolyzed, extracted, dried and rotary evaporated to obtain a star-shaped polyethylene glycol dispersant;

[0036] Step 2: 3 parts of star-shaped polyethylene glycol dispersant, 6 parts of deionized water and 2 parts of high-purity quartz sand powder are mixed and stirred thoroughly to prepare a quartz crucible raw material; the quartz crucible raw material is placed in a crucible mold, and preformed at a speed of 75 r / min and a forming rod radius of 248 mm to obtain a quartz casserole blank; the quartz casserole blank is placed in a melting furnace, and the inner layer is melted for 50 seconds at a power of 292 W, and the outer layer is melted for 50 seconds at a power of 612 W to obtain a quartz crucible;

[0037] Step 3: Add 5wt% triboric acid to 8wt% polyvinyl pyrrolidone solution by mass fraction, stir thoroughly, then add 25wt% silicon nitride powder, 60wt% silicon powder and 2wt% n-octanol, and ball mill at a ball milling ratio of 1:1.5 to obtain a coating; apply the coating evenly on the inner surface of a quartz crucible, air dry naturally, and calcined at 575℃ for 112 minutes to obtain a finished product with a coating thickness of 1mm.

[0038] Example 5: Step 1: 24 g of polyethylene glycol, 12 g of butanediol and 150 mL of toluene were mixed, heated under reflux for 5 h, and after the reaction, 50 mL of chloroform was added for shaking and suction filtration, and the pH of the filtrate was adjusted to 2 with concentrated hydrochloric acid. After extraction, drying, filtration, rotary evaporation and purification, carboxyl-terminated polyethylene glycol was obtained; 12 g of carboxyl-terminated polyethylene glycol, 28 g of thionyl chloride and 60 mL of toluene were mixed, reacted at 70 ° C for 20 h, and then vacuum distilled and dried to obtain chlorinated polyethylene glycol; 12 g of chlorinated polyethylene glycol and 40 g of D-sorbitol were mixed, reacted at 80 ° C for 6 h, and then cooled, hydrolyzed, extracted, dried and rotary evaporated to obtain a star-shaped polyethylene glycol dispersant;

[0039] Step 2: 3 parts of star-shaped polyethylene glycol dispersant, 6 parts of deionized water and 2 parts of high-purity quartz sand powder are mixed and stirred thoroughly to prepare a quartz crucible raw material; the quartz crucible raw material is placed in a crucible mold, and preformed to obtain a quartz casserole blank at a rotation speed of 70 r / min and a forming rod radius of 230 mm; the quartz casserole blank is placed in a melting furnace, and the inner layer is melted for 40 seconds at a power of 280 W and the outer layer is melted for 40 seconds at a power of 600 W to obtain a quartz crucible;

[0040] Step 3: Add 5wt% triboric acid to 8wt% polyvinyl pyrrolidone solution by mass fraction, stir thoroughly, then add 25wt% silicon nitride powder, 60wt% silicon powder and 2wt% n-octanol, and ball mill at a ball milling ratio of 1:1.5 to obtain a coating; apply the coating evenly on the inner surface of a quartz crucible, dry it naturally, and calcine it at 550℃ for 100min to obtain a finished product with a coating thickness of 1mm.

[0041] Comparative Example 1: The preparation step of the star-shaped polyethylene glycol dispersant was removed, and the rest was the same as in Example 1, and the specific steps were as follows: Step 1: 6 parts of deionized water and 2 parts of high-purity quartz sand powder were mixed and stirred thoroughly to prepare a quartz crucible raw material; the quartz crucible raw material was placed in a crucible mold, and preformed at a speed of 90 r / min and a forming rod radius of 300 mm to obtain a quartz casserole blank; the quartz casserole blank was placed in a melting furnace, and the inner layer was melted for 80 s at a power of 330 W, and the outer layer was melted for 80 s at a power of 650 W to obtain a quartz crucible;

[0042] Step 2: Add 5wt% triboric acid to 8wt% polyvinyl pyrrolidone solution by mass fraction, stir thoroughly, then add 25wt% silicon nitride powder, 60wt% silicon powder and 2wt% n-octanol, and ball mill at a ball milling ratio of 1:1.5 to obtain a coating; apply the coating evenly on the inner surface of a quartz crucible, dry it naturally, and calcine it at 650℃ for 150min to obtain a finished product with a coating thickness of 1mm.

[0043] Comparative Example 2: The preparation step of the coating is removed, and the rest is the same as Example 1, and the specific steps are as follows: Step 1: 24g of polyethylene glycol, 12g of butanediol and 150mL of toluene are mixed, and the mixture is heated under reflux for 7h. After the reaction is completed, 50mL of chloroform is added for shaking and filtration, and the pH of the filtrate is adjusted to 3 with concentrated hydrochloric acid. After extraction, drying, filtration, rotary evaporation and purification, carboxyl-terminated polyethylene glycol is obtained; 12g of carboxyl-terminated polyethylene glycol, 28g of thionyl chloride and 60mL of toluene are mixed, reacted at 90°C for 30h, and then distilled under reduced pressure and dried to obtain chlorinated polyethylene glycol; 12g of chlorinated polyethylene glycol and 40g of D-sorbitol are mixed, reacted at 100°C for 10h, and then cooled, hydrolyzed, extracted, dried and rotary evaporated to obtain a star-shaped polyethylene glycol dispersant;

[0044] Step 2: 3 parts of star-shaped polyethylene glycol dispersant, 6 parts of deionized water and 2 parts of high-purity quartz sand powder are mixed and stirred thoroughly to prepare a quartz crucible raw material; the quartz crucible raw material is placed in a crucible mold, and preformed at a rotation speed of 90 r / min and a forming rod radius of 300 mm to obtain a quartz casserole blank; the quartz casserole blank is placed in a melting furnace, and the inner layer is melted for 80 seconds at a power of 330 W, and the outer layer is melted for 80 seconds at a power of 650 W to obtain a finished product.

[0045] Detection test:

[0046] Compressive strength test: According to GB / T 5072.2-2004, the finished product prepared in the present invention was cut into specimens with a side length of 52×52 mm. The test was performed using a mechanical compressive strength testing machine. Pressure was continuously and uniformly applied at a rate of 1.1 MPa / s until the specimen broke. The maximum load was recorded, and the tensile index was finally calculated using a formula.

[0047] Bond Strength Test: The finished product prepared in this invention was cut into samples with a diameter of 3 cm and a thickness of 1 cm. Epoxy resin glue was applied to both ends of the metal nut. When the glue was almost dry, it was adhered to the sample. The samples were tested using a CSS-44100 universal mechanical testing machine from the Changchun Testing Machine Research Institute. After the test, the data was entered into a formula to calculate the bond strength. The results are shown in the following table.

[0048] Compressive strength / MPa Bonding strength / Pa Example 1 72 <![CDATA[6.47×10 5 ]]> Example 2 71 <![CDATA[6.46×10 5 ]]> Example 3 71 <![CDATA[6.45×10 5 ]]> Example 4 70 <![CDATA[6.43×10 5 ]]> Example 5 70 <![CDATA[6.42×10 5 ]]> Comparative Example 1 52 <![CDATA[6.35×10 5 ]]> Comparative Example 2 63 <![CDATA[5.16×10 5 ]]>

[0049] Conclusion: The dosage of Examples 1 to 5 remains unchanged, and only some reaction parameters are modified. The experimental data show that there is no significant fluctuation in the performance. Comparative Example 1: The preparation steps of the star-shaped polyethylene glycol dispersant are removed, and the rest are the same as Example 1. The experimental data show that compared with Example 1, the compressive strength is reduced to 52 MPa and the bonding strength is reduced to 6.35×10 5The reason for this is that after removing the star-shaped polyethylene glycol dispersant, the dispersibility of the quartz crucible raw material decreases, and the particles may re-aggregate, resulting in the formation of larger pores and voids. These pores and voids will weaken the material's density and mechanical properties, thereby reducing the compressive strength.

[0050] Comparative Example 2: The preparation steps of the coating were removed, and the rest were the same as in Example 1. The experimental data showed that compared with Example 1, the compressive strength was reduced to 63 MPa and the bonding strength was reduced to 5.16×10 5 Pa, the reason is: after removing the coating of the finished quartz crucible, the surface of the quartz crucible is exposed to the external environment, and micro defects and cracks may be more easily formed and expanded, so the compressive strength and bonding strength are reduced.

[0051] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include," "comprise," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0052] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-density and high-thermal-conductivity quartz crucible, characterized in that: The following steps are involved: Step 1: Mix polyethylene glycol, butanediol and toluene, heat and reflux for 5-7 hours, add chloroform after the reaction, shake and filter, adjust the pH of the filtrate to 2-3 with concentrated hydrochloric acid, extract, dry, filter, rotary evaporate and purify to obtain carboxyl-terminated polyethylene glycol; mix carboxyl-terminated polyethylene glycol, thionyl chloride and toluene, react at 70-90°C for 20-30 hours, and then distill and dry under reduced pressure to obtain chlorinated polyethylene glycol; mix chlorinated polyethylene glycol and D-sorbitol, react at 80-100°C for 6-10 hours, and then cool, hydrolyze, extract, dry and rotary evaporate to obtain a star-shaped polyethylene glycol dispersant; Step 2: Mixing a star-shaped polyethylene glycol dispersant, deionized water, and high-purity quartz sand powder, and stirring thoroughly to prepare a quartz crucible raw material; placing the quartz crucible raw material in a crucible mold, and preforming to obtain a quartz casserole blank; placing the quartz casserole blank in a melting furnace, and sequentially performing inner layer melting and outer layer melting to obtain a quartz crucible; the mass ratio of the star-shaped polyethylene glycol dispersant, deionized water, and high-purity quartz sand powder is 3-4:6:2; Step 3: Add triboric acid to the polyvinyl pyrrolidone solution, stir thoroughly, then add silicon nitride powder, silicon powder and n-octanol, and ball mill to obtain a coating; the coating is evenly brushed on the inner surface of a quartz crucible, and after natural air drying and calcination, a finished product is obtained; the content of each component of the coating is: by mass fraction, 5-8% triboric acid, 8-10% polyvinyl pyrrolidone solution, 25-30% silicon nitride powder, 2-4% n-octanol, and the balance is silicon powder.

2. The method for preparing a high-density and high-thermal-conductivity quartz crucible according to claim 1, wherein: In step 1, the mass ratio of polyethylene glycol, butanediol and toluene is 2-3:1:

11.

3. The method for preparing a high-density and high-thermal-conductivity quartz crucible according to claim 1, wherein: In step 1, the mass ratio of carboxyl-terminated polyethylene glycol, thionyl chloride and toluene is 3-4:7:

13.

4. The method for preparing a high-density and high-thermal-conductivity quartz crucible according to claim 1, wherein: In step 1, the mass ratio of acyl chloride polyethylene glycol to D-sorbitol is 3-4:

10.

5. The method for preparing a high-density and high-thermal-conductivity quartz crucible according to claim 1, wherein: In step 2, during prefabrication, the rotation speed is 70-90 r / min and the radius of the forming rod is 230-300 mm.

6. The method for preparing a high-density and high-thermal-conductivity quartz crucible according to claim 1, wherein: In step 2, when the inner layer is melted, the power is 280-330W and the time is 40-80s; when the outer layer is melted, the power is 600-650W and the time is 40-80s.

7. The method for preparing a high-density and high-thermal-conductivity quartz crucible according to claim 1, wherein: In step 3, the calcination process parameters are: calcination temperature is 550-650°C, and calcination time is 100-150 minutes.

8. The method for preparing a high-density and high-thermal-conductivity quartz crucible according to claim 1, wherein: In step 3, the ball-to-grinding ratio is 1:1.5-2.5; and the coating thickness is 1-2 mm.