阅读说明：本技术 一种提纯多晶硅使用的石墨坩埚 (Graphite crucible for purifying polycrystalline silicon ) 是由 王庆辉 于 2019-10-25 设计创作，主要内容包括：本发明涉及石墨坩埚技术领域,且公开了一种提纯多晶硅使用的石墨坩埚,包括石墨坩埚基体,在石墨坩埚基体的表面上附着有Si-3N-4涂层,该Si-3N-4涂层的制备方法包括：制备Si-3N-4浆料；将石墨坩埚基体在45～60℃下预热；将Si-3N-4浆料分三次均匀涂刷在石墨坩埚基体的表面上,将涂刷Si-3N-4浆料的石墨坩埚基体放置在45～60℃的真空干燥箱内干燥；将表面固化有Si-3N-4浆料的石墨坩埚基体移到石英加热炉腔内,先通入氮气,在1050～1200℃下保温焙烧,即得到石墨坩埚。本发明解决了目前的石墨坩埚,在高温熔炼多晶硅的过程中,石墨炭素会与硅蒸汽发生反应生成SiC,导致坩埚与硅块发生粘合的技术问题。(The invention relates to the technical field of graphite crucibles, and discloses a graphite crucible for purifying polycrystalline silicon 3 N 4 Coating of Si 3 N 4 The preparation method of the coating comprises the following steps: preparation of Si 3 N 4 Sizing agent; preheating a graphite crucible matrix at 45-60 ℃; mixing Si 3 N 4 The slurry is evenly coated on the surface of the graphite crucible substrate in three times, and Si is coated 3 N 4 Placing the graphite crucible matrix of the slurry in a vacuum drying oven at 45-60 ℃ for drying;solidifying the surface with Si 3 N 4 And (3) moving the graphite crucible matrix of the slurry into a quartz heating furnace cavity, introducing nitrogen, and roasting at 1050-1200 ℃ in a heat preservation manner to obtain the graphite crucible. The invention solves the technical problem that in the process of smelting polycrystalline silicon at high temperature in the conventional graphite crucible, graphite carbon can react with silicon vapor to generate SiC, so that the crucible is bonded with a silicon block.)

1. The graphite crucible for purifying the polycrystalline silicon is characterized by comprising a graphite crucible base body, wherein Si is attached to the surface of the graphite crucible base body₃N₄Coating of Si₃N₄The preparation method of the coating comprises the following steps:

the method comprises the following steps: mixing Si₃N₄Adding the powder into a beaker filled with ultrapure water, wherein Si is contained₃N₄The weight ratio of the powder to the ultrapure water is 1: 4, firstly carrying out ultrasonic oscillation and then stirring to ensure that water and Si are mixed₃N₄The powders are fully mixed to obtain Si₃N₄Sizing agent;

step two: placing the graphite crucible matrix in a drying oven, preheating at 45-60 ℃, and then placing the Si obtained in the first step₃N₄The slurry is uniformly coated on the surface of the graphite crucible substrate for the first time, and Si is coated on the surface of the graphite crucible substrate for the first time₃N₄Placing the graphite crucible matrix of the slurry in a vacuum drying oven at 45-60 ℃ for drying;

then, the coating is coated with Si₃N₄Coating the graphite crucible matrix with the slurry for the second time, and coating Si for the second time₃N₄Placing the graphite crucible matrix of the slurry in a vacuum drying oven at 45-60 ℃ for drying;

then, the coating is coated with Si₃N₄Coating the graphite crucible matrix with the slurry for the third time, and coating Si for the third time₃N₄Placing the graphite crucible matrix of the slurry in a vacuum drying oven at 45-60 ℃ for drying to obtain the graphite crucible matrix with Si solidified on the surface₃N₄A graphite crucible base of the slurry;

step three: solidifying the surface of the second step with Si₃N₄And (3) moving the graphite crucible substrate of the slurry into a quartz heating furnace cavity, introducing nitrogen, heating to 1050-1200 ℃ within 2 hours, and preserving heat at 1050-1200 ℃ for 3 hours to obtain the graphite crucible.

2. Root of herbaceous plantThe graphite crucible for purifying polysilicon as set forth in claim 1, wherein the Si of the first step₃N₄Average particle diameter of powder<2.6um。

3. The graphite crucible as claimed in claim 2, wherein the graphite crucible base body comprises the following raw materials in parts by weight: 100 parts of regenerated graphite powder, 60 parts of white corundum particles, 20 parts of alumina clinker particles, 10 parts of alumina clinker fine powder and 10 parts of alpha-Al₂O₃Micropowder, 15 parts of Si₃N₄Powder, 40 parts of phenolic resin (PF).

4. The graphite crucible for purifying polysilicon as set forth in claim 3, wherein the preparation of the graphite crucible base body comprises the steps of:

the method comprises the following steps: adding white corundum particles and alumina clinker particles into a liquid bonding agent consisting of phenolic resin (PF) and absolute ethyl alcohol, mixing to wet the white corundum particles and the alumina clinker particles, and uniformly attaching the liquid resin to the particles to obtain a first mixing component;

step two: adding the regenerated graphite powder into the mixing component I in the step I, and continuously mixing to ensure that the regenerated graphite powder is completely wetted and well bonded with a bonding agent to obtain a mixing component II;

step three: mixing fine powder of alumina clinker and alpha-Al₂O₃Fine powder of Si₃N₄Adding the powder into the second mixing component in the second step, continuously mixing to make pug uniform, and then placing to make absolute ethyl alcohol fully volatilize to obtain a third mixing component;

step four: pressing the mixing component III in the step III into a crucible blank by using a mould, wherein the forming pressure is 30MPa, and the specification of a formed sample is 10 multiplied by 12 multiplied by 40 mm;

then, drying the crucible blank at the temperature of 100 ℃ for 1h, and then carrying out curing reaction on the crucible blank at the temperature of 200 ℃ for 6 h;

step five: and D, firing the crucible blank solidified and formed in the step four in a reducing atmosphere by adopting a carbon-buried firing process, wherein the firing temperature is 1450 ℃, the firing heat preservation time is 5 hours, and then naturally cooling to room temperature to obtain the graphite crucible matrix.

Technical Field

The invention relates to the technical field of graphite crucibles, in particular to a graphite crucible for purifying polycrystalline silicon.

Background

The crucible is needed in the process of preparing solar polycrystalline silicon, and Si-containing crucible is commonly used in industrial production₃N₄Coated quartz crucibles, or from coated quartz crucibles with Si₃N₄Coated quartz crucible and graphite crucible combinationA crucible is disclosed.

The phenomena of crystallization, softening and the like exist in the quartz crucible at high temperature, so that the service life of the quartz crucible is short, the loss is serious in the production of solar polycrystalline silicon, and the production cost is increased. The graphite crucible has no defects of crystallization, softening and the like of a quartz crucible at high temperature, and is low in cost, but the graphite crucible can react with silicon melt and silicon vapor in a silicon melt furnace to generate SiC in the process of smelting polycrystalline silicon at high temperature, so that the crucible and a silicon block are bonded. Therefore, how to improve the graphite material to enable the graphite crucible to be directly used in the production of purifying polycrystalline silicon is an effective way for reducing the production cost of polycrystalline silicon.

Disclosure of Invention

Technical problem to be solved

Aiming at the defects of the prior art, the invention provides a graphite crucible for purifying polycrystalline silicon, which aims to solve the technical problem that in the process of smelting the polycrystalline silicon at high temperature, graphite carbon can react with silicon vapor to generate SiC, so that the crucible is bonded with a silicon block.

(II) technical scheme

In order to achieve the purpose, the invention provides the following technical scheme:

a graphite crucible for purifying polysilicon comprises a graphite crucible substrate, and Si is adhered on the surface of the graphite crucible substrate₃N₄Coating of Si₃N₄The preparation method of the coating comprises the following steps:

the method comprises the following steps: mixing Si₃N₄Adding the powder into a beaker filled with ultrapure water, wherein Si is contained₃N₄The weight ratio of the powder to the ultrapure water is 1: 4, firstly carrying out ultrasonic oscillation and then stirring to ensure that water and Si are mixed₃N₄The powders are fully mixed to obtain Si₃N₄Sizing agent;

step two: placing the graphite crucible matrix in a drying oven, preheating at 45-60 ℃, and then placing the Si obtained in the first step₃N₄The slurry is uniformly coated on the surface of the graphite crucible substrate for the first time, and Si is coated on the surface of the graphite crucible substrate for the first time₃N₄The graphite crucible matrix of the slurry is placed at 45 toDrying in a vacuum drying oven at 60 ℃;

then, the coating is coated with Si₃N₄Coating the graphite crucible matrix with the slurry for the second time, and coating Si for the second time₃N₄Placing the graphite crucible matrix of the slurry in a vacuum drying oven at 45-60 ℃ for drying;

then, the coating is coated with Si₃N₄Coating the graphite crucible matrix with the slurry for the third time, and coating Si for the third time₃N₄Placing the graphite crucible matrix of the slurry in a vacuum drying oven at 45-60 ℃ for drying to obtain the graphite crucible matrix with Si solidified on the surface₃N₄A graphite crucible base of the slurry;

step three: solidifying the surface of the second step with Si₃N₄And (3) moving the graphite crucible substrate of the slurry into a quartz heating furnace cavity, introducing nitrogen, heating to 1050-1200 ℃ within 2 hours, and preserving heat at 1050-1200 ℃ for 3 hours to obtain the graphite crucible.

Further, Si of the first step₃N₄Average particle diameter of powder<2.6um。

Further, the graphite crucible matrix comprises the following raw materials in parts by weight: 100 parts of regenerated graphite powder, 60 parts of white corundum particles, 20 parts of alumina clinker particles, 10 parts of alumina clinker fine powder and 10 parts of alpha-Al₂O₃Micropowder, 15 parts of Si₃N₄Powder, 40 parts of phenolic resin (PF).

Further, the preparation of the graphite crucible matrix comprises the following steps:

the method comprises the following steps: adding white corundum particles and alumina clinker particles into a liquid bonding agent consisting of phenolic resin (PF) and absolute ethyl alcohol, mixing to wet the white corundum particles and the alumina clinker particles, and uniformly attaching the liquid resin to the particles to obtain a first mixing component;

step two: adding the regenerated graphite powder into the mixing component I in the step I, and continuously mixing to ensure that the regenerated graphite powder is completely wetted and well bonded with a bonding agent to obtain a mixing component II;

step three: fine powder of alumina clinker,α-Al₂O₃Fine powder of Si₃N₄Adding the powder into the second mixing component in the second step, continuously mixing to make pug uniform, and then placing to make absolute ethyl alcohol fully volatilize to obtain a third mixing component;

step four: pressing the mixing component III in the step III into a crucible blank by using a mould, wherein the forming pressure is 30MPa, and the specification of a formed sample is 10 multiplied by 12 multiplied by 40 mm;

then, drying the crucible blank at the temperature of 100 ℃ for 1h, and then carrying out curing reaction on the crucible blank at the temperature of 200 ℃ for 6 h;

step five: and D, firing the crucible blank solidified and formed in the step four in a reducing atmosphere by adopting a carbon-buried firing process, wherein the firing temperature is 1450 ℃, the firing heat preservation time is 5 hours, and then naturally cooling to room temperature to obtain the graphite crucible matrix.

(III) advantageous technical effects

Compared with the prior art, the invention has the following beneficial technical effects:

the invention is characterized in that Si is coated on the graphite crucible substrate₃N₄Coating of Si₃N₄The coating is quickly solidified on the preheated graphite crucible substrate and is roasted at high temperature to prepare the graphite crucible used for purifying the polysilicon, and the graphite crucible is heated at 1540 ℃ and the vacuum degree of 3.08 multiplied by 10^-2The results of the silicon melt test at Pa are: the silicon blocks realize smooth demoulding, do not have the adhesion with the crucible, and are Si after the silicon blocks are stripped₃N₄The surface of the coating is kept flat and has no obvious damage phenomenon;

therefore, the technical problem that in the process of smelting polycrystalline silicon at high temperature in the conventional graphite crucible, graphite carbon can react with silicon vapor to generate SiC, so that the crucible is bonded with a silicon block is solved.

Detailed Description

The following raw materials were used:

crushing waste materials generated in the production process of graphite products, namely regenerated graphite, by a crusher, and then screening to obtain regenerated graphite powder with the average particle size of less than 150 um;

white corundum grains, average grain size<250um，Al₂O₃≥98％；

Alumina clinker particles with average particle size of 160-250 um and Al₂O₃>88％；

Fine powder of alumina clinker having an average particle diameter<38um，Al₂O₃>88％；

α-Al₂O₃Fine powder of average particle diameter<38um，Al₂O₃>98％；

Si₃N₄Powder, average particle diameter<2.6um，Si₃N₄≥99.9％；

Phenolic resin (PF) with solid content not less than 75%, carbon residue not less than 45%, free aldehyde not more than 7%, and heat treatment temperature of 200 deg.C;

the preparation of the graphite crucible matrix comprises the following steps:

the method comprises the following steps: adding 60g of white corundum particles with the average particle size of less than 250um and 20g of alumina clinker particles with the average particle size of 160-250 um into a liquid bonding agent consisting of 40g of phenolic resin (PF) and 30g of absolute ethyl alcohol, mixing to wet all the white corundum particles and the alumina clinker particles, and uniformly attaching the liquid resin to the particles to obtain a first mixing component;

step two: adding 100g of regenerated graphite powder with the average particle size of less than 150um into the mixing component I in the step I, and continuously mixing to ensure that the regenerated graphite powder is completely wetted and well bonded with a bonding agent to obtain a mixing component II;

step three: average particle diameter of 10g<Fine 38um bauxite clinker powder, 10g of average particle size<38um alpha-Al₂O₃Fine powder, average particle diameter of 15g<2.6um Si₃N₄Adding the powder into the second mixing component in the second step, continuously mixing to make pug uniform, and then placing to make absolute ethyl alcohol fully volatilize to obtain a third mixing component;

step four: pressing the mixing component III in the step III into a crucible blank by using a mould, wherein the forming pressure is 30MPa, and the specification of a formed sample is 10 multiplied by 12 multiplied by 40 mm;

then, drying the crucible blank at the temperature of 100 ℃ for 1h, and then carrying out curing reaction on the crucible blank at the temperature of 200 ℃ for 6 h;

step five: and D, firing the crucible blank solidified and formed in the step four in a reducing atmosphere by adopting a carbon-buried firing process, wherein the firing temperature is 1450 ℃, the firing heat preservation time is 5 hours, and then naturally cooling to room temperature to prepare the graphite crucible substrate.

The first embodiment is as follows:

the graphite crucible used for purifying polycrystalline silicon comprises a graphite crucible base body, and Si is adhered to the surface of the graphite crucible base body₃N₄Coating of Si₃N₄The preparation method of the coating comprises the following steps:

the method comprises the following steps: average particle diameter<2.6um Si₃N₄Adding the powder into a beaker filled with ultrapure water, wherein Si is contained₃N₄The weight ratio of the powder to the ultrapure water is 1: 4;

then, the beaker is placed in an ultrasonic cleaning instrument for ultrasonic oscillation for 30min, and is stirred by a glass rod to reduce Si₃N₄Agglomerating the powder to make Si₃N₄Uniformly dispersing the particles in ultrapure water to form stable suspension, and stirring the suspension for 30min after ultrasonic oscillation to allow water and Si to be dissolved₃N₄The powders are fully mixed to obtain Si₃N₄Sizing agent;

step two: placing the graphite crucible matrix in a drying oven, preheating for 20min at 45 ℃, and then placing Si obtained in the first step₃N₄The slurry is uniformly coated on the surface of the graphite crucible substrate for the first time, the coating thickness is 100 mu m, and Si is coated for the first time₃N₄Placing the graphite crucible matrix of the slurry in a vacuum drying oven at 60 ℃ for drying for 20 min;

then, the coating is coated with Si₃N₄Coating the graphite crucible matrix with the slurry for the second time, wherein the coating thickness is 50 mu m, and coating Si for the second time₃N₄Placing the graphite crucible matrix of the slurry in a vacuum drying oven at 60 ℃ for drying for 20 min;

then, the coating is coated with Si₃N₄Coating the graphite crucible matrix with the slurry for the third time, wherein the coating thickness is 50 mu m, and coating Si for the third time₃N₄Placing the graphite crucible matrix of the slurry in a vacuum drying oven at 60 ℃ for drying for 20min to obtain the graphite crucible matrix with the surface solidified with Si₃N₄A graphite crucible base of the slurry;

step three: solidifying the surface of the second step with Si₃N₄And (3) moving the graphite crucible matrix of the slurry into a quartz heating furnace cavity, introducing nitrogen for 30min, heating to 1100 ℃ within 2h, preserving the heat at 1100 ℃ for 3h, and naturally cooling to room temperature to obtain the graphite crucible for purifying the polycrystalline silicon.

Example two:

the graphite crucible used for purifying polycrystalline silicon comprises a graphite crucible base body, and Si is adhered to the surface of the graphite crucible base body₃N₄Coating of Si₃N₄The preparation method of the coating comprises the following steps:

the method comprises the following steps: average particle diameter<2.6um Si₃N₄Adding the powder into a beaker filled with ultrapure water, wherein Si is contained₃N₄The weight ratio of the powder to the ultrapure water is 1: 5;

then, the beaker is placed in an ultrasonic cleaning instrument for ultrasonic oscillation for 20min, and is stirred by a glass rod to reduce Si₃N₄Agglomerating the powder to make Si₃N₄Uniformly dispersing the particles in ultrapure water to form stable suspension, and stirring the suspension for 20min after ultrasonic oscillation to allow water and Si to be dissolved₃N₄The powders are fully mixed to obtain Si₃N₄Sizing agent;

step two: placing the graphite crucible matrix in a drying oven, preheating for 20min at 50 ℃, and then placing Si obtained in the first step₃N₄The slurry is uniformly coated on the surface of the graphite crucible substrate for the first time, the coating thickness is 100 mu m, and Si is coated for the first time₃N₄Placing the graphite crucible matrix of the slurry in a vacuum drying oven at 50 ℃ for drying for 20 min;

then, the coating is coated with Si₃N₄Coating the graphite crucible matrix with the slurry for the second timeThe thickness is 100um, and the second time of coating is carried out on Si₃N₄Placing the graphite crucible matrix of the slurry in a vacuum drying oven at 50 ℃ for drying for 20 min;

then, the coating is coated with Si₃N₄Coating the graphite crucible matrix with the slurry for the third time, wherein the coating thickness is 100 mu m, and coating Si for the third time₃N₄Placing the graphite crucible matrix of the slurry in a vacuum drying oven at 50 ℃ for drying for 20min to obtain the graphite crucible matrix with Si solidified on the surface₃N₄A graphite crucible base of the slurry;

step three: solidifying the surface of the second step with Si₃N₄And (3) moving the graphite crucible matrix of the slurry into a quartz heating furnace cavity, introducing nitrogen for 30min, heating to 1200 ℃ within 2h, preserving the heat at 1200 ℃ for 3h, and naturally cooling to room temperature to obtain the graphite crucible for purifying the polycrystalline silicon.

Example three:

the graphite crucible used for purifying polycrystalline silicon comprises a graphite crucible base body, and Si is adhered to the surface of the graphite crucible base body₃N₄Coating of Si₃N₄The preparation method of the coating comprises the following steps:

the method comprises the following steps: average particle diameter<2.6um Si₃N₄Adding the powder into a beaker filled with ultrapure water, wherein Si is contained₃N₄The weight ratio of the powder to the ultrapure water is 1: 3;

then, the beaker is placed in an ultrasonic cleaning instrument for ultrasonic oscillation for 60min, and is stirred by a glass rod to reduce Si₃N₄Agglomerating the powder to make Si₃N₄Uniformly dispersing the particles in ultrapure water to form stable suspension, and stirring the suspension for 60min after ultrasonic oscillation to allow water and Si to be dissolved₃N₄The powders are fully mixed to obtain Si₃N₄Sizing agent;

step two: placing the graphite crucible matrix in a drying oven, preheating for 20min at 60 ℃, and then placing Si obtained in the first step₃N₄The slurry is uniformly coated on the surface of the graphite crucible substrate for the first time, the coating thickness is 50 mu m, and Si is coated for the first time₃N₄Graphite of the slurryPlacing the crucible matrix in a vacuum drying oven at 60 ℃ for drying for 20 min;

then, the coating is coated with Si₃N₄Coating the graphite crucible matrix with the slurry for the second time, wherein the coating thickness is 50 mu m, and coating Si for the second time₃N₄Placing the graphite crucible matrix of the slurry in a vacuum drying oven at 60 ℃ for drying for 20 min;

then, the coating is coated with Si₃N₄Coating the graphite crucible matrix with the slurry for the third time, wherein the coating thickness is 50 mu m, and coating Si for the third time₃N₄Placing the graphite crucible matrix of the slurry in a vacuum drying oven at 60 ℃ for drying for 20min to obtain the graphite crucible matrix with the surface solidified with Si₃N₄A graphite crucible base of the slurry;

step three: solidifying the surface of the second step with Si₃N₄And (3) moving the graphite crucible matrix of the slurry into a quartz heating furnace cavity, introducing nitrogen for 30min, heating to 1050 ℃ within 2h, preserving the heat at 1050 ℃ for 3h, and naturally cooling to room temperature to obtain the graphite crucible for purifying the polycrystalline silicon.

Comparative example: the graphite crucible used for purifying polycrystalline silicon comprises a graphite crucible base body, on the surface of which Si is not attached₃N₄And (4) coating.

And (3) performance testing:

silicon industrial silicon powder is placed in the graphite crucibles prepared in the above examples and comparative examples, and a silicon melting test is carried out according to the vacuum purification standard of polycrystalline silicon, wherein the maximum temperature is 1540 ℃, and the vacuum degree is 3.08 multiplied by 10^-2Pa, melting industrial silicon powder into liquid silicon in the silicon melting process, spreading the liquid silicon on the central position of the graphite crucible, cooling and solidifying, taking out the graphite crucible to investigate the demolding effect of the silicon block and Si after the silicon block falls off₃N₄The results of the coating changes are shown in Table 1 below.

TABLE 1