阅读说明：本技术 一种高纯石墨毡的制备方法及晶硅炉 (Preparation method of high-purity graphite felt and crystal silicon furnace ) 是由 刘军波 杜武侃 谷元超 于 2020-12-22 设计创作，主要内容包括：本发明公开一种高纯石墨毡的制备方法及晶硅炉,所述制备方法包括以下步骤：将石墨芯棒卷入碳毡中得碳毡卷；将碳毡卷置入炉压小于30Pa的烧结炉中,进行分段控温烧结；首先升温至600-800℃,保温100-140min,并同时向烧结炉内通入氩气；再升温至1850-1900℃,保温200-280min；最后将烧结炉降温至100℃以下,取出、展开并冷却,即得高纯石墨毡。所述晶硅炉采用该高纯石墨毡作为隔热保温层。本发明提供的方法烧制出的石墨毡品质稳定,杂质含量低,在单晶热场内(1600℃)使用无挥发物溢出、石墨粉尘最小化、无流油现象,相较于市场上其他石墨毡更洁净且具有更好的保温性能。(The invention discloses a preparation method of a high-purity graphite felt and a crystalline silicon furnace, wherein the preparation method comprises the following steps: rolling the graphite core rod into a carbon felt to obtain a carbon felt roll; placing the carbon felt roll into a sintering furnace with the furnace pressure less than 30Pa, and carrying out segmented temperature-controlled sintering; firstly, heating to 600-; then raising the temperature to 1850 ℃ and 1900 ℃, and keeping the temperature for 200min and 280 min; and finally, cooling the sintering furnace to below 100 ℃, taking out, spreading and cooling to obtain the high-purity graphite felt. The crystal silicon furnace adopts the high-purity graphite felt as a heat insulation layer. The graphite felt fired by the method provided by the invention has stable quality and low impurity content, does not have the phenomena of volatile substance overflow, graphite dust minimization and oil flowing when used in a single crystal thermal field (1600 ℃), and is cleaner and better in heat preservation performance compared with other graphite felts in the market.)

1. The preparation method of the high-purity graphite felt is characterized by comprising the following steps of:

s1, winding the graphite core rod into a carbon felt to obtain a carbon felt roll;

s2, placing the carbon felt roll into a sintering furnace, closing the furnace and vacuumizing until the furnace pressure is less than 30 Pa;

s3, sintering by temperature control in sections

The first stage is as follows: heating the sintering furnace to 800 ℃ at 600-;

and a second stage: heating the sintering furnace to the temperature of 1850-;

and a third stage: and cooling the sintering furnace to below 100 ℃, opening the furnace, taking out the carbon felt roll, unfolding and cooling to obtain the high-purity graphite felt.

2. The method of claim 1, wherein the length of the graphite core rod in S1 is greater than the width of the carbon felt.

3. The manufacturing method according to claim 1, wherein the sintering furnace in S2 comprises a sintering furnace body, a vacuum pump is disposed at the bottom of the sintering furnace body, an argon pipe is disposed on a furnace cover of the sintering furnace body, the argon pipe is used for injecting argon gas into the sintering furnace body to carry volatile impurities in the carbon felt roll, and the vacuum pump is used for vacuumizing the sintering furnace body and discharging the argon gas mixed with the volatile impurities.

4. The production method according to claim 3, wherein a gas distribution ring is connected to an end of the argon pipe, and an exhaust direction of the gas distribution ring is set perpendicular to an evacuation direction of the vacuum pump.

5. The method as claimed in claim 1, wherein the temperature rise rate of the first stage in S3 is 100-; the temperature rise rate of the second stage is 260-.

6. The method according to any one of claims 1 to 5, wherein the furnace temperature in the first stage in S3 is 800 ℃, the temperature rise rate is 133 ℃/h, and the holding time is 2h, and the furnace temperature in the second stage is 1900 ℃, the temperature rise rate is 275 ℃/h, and the holding time is 4 h.

7. The method according to claim 1, wherein the flow rate of the first-stage argon gas in S3 is 45-55ml/min, preferably the flow rate of the first-stage argon gas is 50 ml/min.

8. The method according to claim 1, wherein the cooling time of the third stage in S3 is 55-65min, preferably 60 min.

9. A crystalline silicon furnace, which is characterized by comprising a graphite cylinder, a thermal field arranged in the graphite cylinder and a heat insulation layer coated outside the graphite cylinder, wherein the heat insulation layer is a high-purity graphite felt prepared by the preparation method as claimed in any one of claims 1 to 8.

Technical Field

The invention relates to the technical field of heat preservation parts for silicon crystal growing furnaces, in particular to a preparation method of a high-purity graphite felt and a silicon crystal furnace.

Background

Market data show that the single crystal thermal field has better heat preservation performance, lower heating power and use cost by wrapping the graphite soft felt. However, the single crystal silicon has higher requirement on the cleanliness in the furnace in the drawing process, and the aims of improving the thermal field heat preservation performance and reducing the production cost can be ensured only by using the graphite soft felt with excellent quality and performance under the condition of not influencing the yield of the single crystal, otherwise, the single crystal silicon cannot be compensated.

The main component of the carbon felt is carbon, and the carbon felt can cause internal combustion when being contacted with a small amount of air during high-temperature sintering, and the internal combustion of the carbon felt is easy to cause the reduction of the qualification rate of products due to poor control on the vacuum degree of a furnace body during firing of the carbon felt in the prior calcining process on the market; in addition, the furnace body structure for calcining the carbon felt is unreasonable, the whole calcining process is sealed, the generated volatile impurities are difficult to be completely discharged from the sealed furnace body by pumping through a vacuum pump, the volatile impurities which are not discharged can be remained in the prepared graphite felt, when the graphite felt is wrapped outside the single crystal furnace, the volatile impurities which are not discharged can be volatilized again to enter the single crystal furnace under the high temperature condition, the environment in the single crystal furnace is polluted, the quality of the subsequently produced single crystal is influenced, the quality of the produced graphite felt is extremely unstable and the qualification rate can be caused finally, in addition, the existing calcining process is difficult to completely burn the carbon felt during the firing, therefore, the produced graphite felt has poor heat-conducting property.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, so that the invention provides the preparation method of the high-purity graphite felt and the crystal silicon furnace, the graphite felt fired by the method has stable quality and low impurity content; the crystal silicon furnace adopts the high-purity graphite felt as a heat insulation layer, when a single crystal thermal field is within 1600 ℃, no volatile substance overflows, no oil flowing phenomenon occurs, graphite dust is minimized, and the crystal silicon furnace is cleaner and has better heat insulation performance compared with other graphite felts in the market.

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

a preparation method of a high-purity graphite felt comprises the following steps:

s1, winding the graphite core rod into a carbon felt to obtain a carbon felt roll;

s2, placing the carbon felt roll into a sintering furnace, closing the furnace and vacuumizing until the furnace pressure is less than 30 Pa;

s3, sintering by temperature control in sections

The first stage is as follows: heating the sintering furnace to 800 ℃ at 600-;

and a second stage: heating the sintering furnace to the temperature of 1850-;

and a third stage: and cooling the sintering furnace to below 100 ℃, opening the furnace, taking out the carbon felt roll, unfolding and cooling to obtain the high-purity graphite felt.

As a practical way, the length of the graphite core rod in S1 is greater than the width of the carbon felt.

This application places the graphite plug that highly is higher than carbon felt certain length in the inside of carbon felt when the charge, thereby the high heat conductivity of usable graphite rod makes the inside and outside temperature of carbon felt when high temperature stage reach unanimous carbon felt of burning through, and then improves the thermal insulation performance of graphite felt product.

As an implementation manner, in S2, the sintering furnace includes a sintering furnace body, a vacuum pump is disposed at the bottom of the sintering furnace body, an argon pipe is disposed on a furnace cover of the sintering furnace body, the argon pipe is used for injecting argon gas into the sintering furnace body to carry volatile impurities in the carbon felt roll, and the vacuum pump is used for vacuumizing the sintering furnace body and discharging argon gas mixed with the volatile impurities.

The vacuum pump is used for vacuumizing the sintering furnace body, the furnace pressure is controlled below 30Pa in the whole sintering process, the vacuum degree of the sintering furnace is standardized, the internal combustion probability of the carbon felt can be effectively reduced through the standardized control, and the product percent of pass is improved; the argon pipe can fill argon into the sintering furnace body in the carbon felt impurity removing stage, and the high-efficiency guide impurity removal is realized by matching with the vacuum pump, so that the impurity removal of the product is more thorough and the quality is higher.

In one embodiment, an end of the argon pipe is connected to a gas distribution ring, and an exhaust direction of the gas distribution ring is perpendicular to an evacuation direction of the vacuum pump.

The gas distributing ring used for introducing argon gas is arranged in the sintering furnace body, the gas distributing ring is installed to distribute the argon gas to the top of the carbon felt roll, and due to the fact that the exhaust direction of the argon gas in the gas distributing ring is perpendicular to the air exhaust direction of the vacuum pump at the bottom of the sintering furnace body, formed air flow can be discharged to the limit of volatile impurities when guiding and impurity discharging, and therefore the cleanliness of products is improved.

As a practical way, the temperature rising rate of the first stage in S3 is 100-; the temperature rise rate of the second stage is 260-.

In S3, the furnace temperature in the first stage is 800 ℃, the temperature-rising rate is 133 ℃/h, the heat-preserving time is 2h, the furnace temperature in the second stage is 1900 ℃, the temperature-rising rate is 275 ℃/h, and the heat-preserving time is 4 h.

The furnace temperature of the first stage is controlled to be 600-800-; and when the furnace is opened, the temperature of the furnace is reduced to be below 100 ℃, so that the phenomenon of internal combustion is prevented, and the qualification rate of products is ensured.

In a practical manner, the flow rate of the first-stage argon in S3 is 45-55ml/min, and preferably, the flow rate of the first-stage argon is 50 ml/min.

The flow rate of the argon is controlled to be 45-55ml/min, so that the influence on the furnace temperature is avoided, and meanwhile, the gas flow is enough to carry volatile impurities.

In an implementation manner, the cooling time of the third stage in S3 is 55-65min, and preferably, the cooling time of the third stage is 60 min.

The crystalline silicon furnace comprises a graphite cylinder, a thermal field arranged in the graphite cylinder and a heat insulation layer coated outside the graphite cylinder, wherein the heat insulation layer is a high-purity graphite felt, and the high-purity graphite felt is prepared by the preparation method.

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

the preparation method of the high-purity graphite felt provided by the invention has the advantages that the graphite core rod is placed when the carbon felt is placed in the furnace, so that the internal and external temperatures of the carbon felt at a high temperature stage can be consistent and can be completely burnt, the heat preservation performance of a finished product is greatly improved, the sintering of the carbon felt is carried out at a high vacuum degree, the internal combustion probability of the carbon felt can be effectively reduced from the source, the qualification rate of the product is improved, in addition, the sintering temperature is controlled in a step mode, the furnace temperature of 600-800 ℃ is arranged at the first stage, the furnace temperature is most favorable for volatilizing impurities in the carbon felt, argon is introduced at the step, the efficient impurity removal effect can be realized, the high-temperature sintering temperature of 1850-1900 ℃ is arranged at the second stage, and the temperature is kept for 200-280min, so that the prepared graphite felt can not volatilize impurities in the process of preparing single crystals, the yield of the single crystals is not influenced, and the furnace temperature is controlled to be reduced to be below 100 ℃ in the third stage when the furnace is opened, so that the internal combustion phenomenon can be further prevented, and the qualification rate of the product is ensured. Under the control of the standard complete preparation process, the fired graphite felt has more excellent and stable quality, and volatile impurities of the graphite felt manufactured by the sintering process can be thoroughly removed, so that no volatile substance overflows, graphite dust is minimized, no oil flow phenomenon is generated when the graphite felt is used in a single crystal thermal field at 1600 ℃, and the graphite felt is cleaner and has better heat preservation performance compared with other graphite felts in the market.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly described below.

FIG. 1 is a schematic structural view of a sintering furnace according to an embodiment of the present invention;

fig. 2 is a schematic structural view of a gas distribution ring according to an embodiment of the present invention.

Description of reference numerals:

1. a sintering furnace body; 2. a vacuum pump; 3. an argon pipe; 4. a gas distribution ring; 5. a roll of carbon felt.

Detailed Description

The technical scheme of the invention is clearly and completely described in the following with reference to the accompanying drawings.

Example 1

The preparation method of the high-purity graphite felt is carried out in a sintering furnace, please refer to fig. 1, the sintering furnace mainly comprises a sintering furnace 1, a vacuum pump 2 and an argon pipe 3, wherein the vacuum pump 2 is arranged below the sintering furnace 1, the argon pipe 3 is arranged above the sintering furnace 1, for example, on a furnace cover of the sintering furnace 1, the vacuum pump 2 is mainly used for controlling the vacuum degree in the sintering furnace 1, so that the sintering of the carbon felt roll 5 is carried out under the high vacuum degree, the internal combustion probability of the carbon felt is effectively reduced from the source, in addition, the vacuum pump 2 also has the function of guiding airflow, when the argon pipe 3 introduces argon into the sintering furnace 1, the argon is discharged by the vacuum pump together with volatile impurities in the carbon felt roll 5 under the action of the vacuum pump 2, of course, in order to have a better impurity discharge effect, the embodiment optimizes the exhaust direction of the argon and the suction direction of the vacuum pump, firstly, in view of the production efficiency of graphite felt, a plurality of carbon felt rolls 5 are usually arranged in a sintering furnace for sintering, so that in order to uniformly spray argon gas to each carbon felt roll 5 to carry volatile impurities (see fig. 2, and the arrow in fig. 2 shows the gas flow direction of the argon gas), a gas distribution ring 4 is arranged at the outlet end of an argon gas pipe 3, the gas distribution ring 4 can spray the injected argon gas circumferentially to the upper part of each carbon felt roll 5, and secondly, referring to fig. 1 (the arrow in fig. 1 shows the gas flow direction of the argon gas), the exhaust direction of the argon gas on the gas distribution ring 4 is perpendicular to the suction direction of a vacuum pump 2, for example, the gas distribution ring 4 is arranged on a furnace cover, and the argon gas is sprayed from top to bottom, the carbon felt rolls 5 are arranged below the gas distribution ring 4, and the vacuum pump 2 is arranged below the side wall of the sintering furnace body 1, so as to exhaust the volatile impurities, the cleanliness of the product is improved. Of course, a plurality of vacuum pumps 2 may be provided along the side wall of the sintering furnace body 1 as required, but when a plurality of vacuum pumps 2 are used simultaneously, the furnace pressure of the sintering furnace should be kept not more than 30 Pa.

The sintering furnaces used in the following examples are provided by the present implementation and will not be described in detail below.

Example 2

The embodiment provides a preparation method of a high-purity graphite felt, which comprises the following steps:

the graphite core rod with the height higher than that of the carbon felt is placed in the center of the whole roll of the carbon felt for heat conduction, the height difference between the graphite core rod and the carbon felt roll is based on actual needs, the height is not required to be too high, the cost of the graphite core rod is increased, but the height is better than that of the carbon felt roll 5, so that the whole roll of the carbon felt can be uniformly conducted with heat conduction, and if the height of the graphite core rod is lower than that of the carbon felt roll 5, the heat conduction effect is improved to a certain extent compared with the carbon felt roll 5 which is directly fired without the graphite core rod, but the effect is not as good as the arrangement mode that the height of the graphite core rod is larger than that of the carbon felt; taking two to three rolls of carbon felt rolls 5 and placing the rolls in a sintering furnace as given in example 1, closing the furnace, starting a vacuum pump 2, pumping the furnace pressure of the sintering furnace to be below 30Pa, and heating the sintering furnace;

the heating process is carried out in three stages, firstly, the first stage is an impurity removing stage, the temperature of a sintering furnace at normal temperature is raised to 600 ℃ within six hours, the temperature is kept for two hours, the temperature is kept from 600 ℃ to a heat preservation stage, the peak period of the volatilization of impurities of the carbon felt is the peak period, so that argon can be introduced into the sintering furnace body 1 from 600 ℃ through a gas distributing ring, the flow of the argon is set to be 50ml/min for airflow guide impurity removal, the introduction of the argon is stopped after the heat preservation of the first stage is finished, the temperature of the furnace is raised to 1900 ℃, the heating and the temperature reduction are stopped after the heat preservation is finished for 4 hours, when the temperature is reduced to 100 ℃, the obtained product cannot be combusted, the product is opened, then the product is spread horizontally, and is dried for 1 hour, and then the product is detected and put in a warehouse, and the high-.

Example 3

The difference from the embodiment 2 is the process of the step-by-step temperature controlled sintering, in this embodiment, firstly, the normal temperature sintering furnace is heated to 800 ℃ at a heating rate of 135 ℃/h, the temperature is maintained for 100min, argon is introduced into the sintering furnace body 1 through the gas distribution ring when the furnace temperature reaches 800 ℃, the flow rate of the argon is set to 55ml/min for gas flow guiding and impurity removal, the introduction of the argon is stopped after the first stage heat preservation is finished, the furnace temperature is heated to 1900 ℃, the heating and temperature reduction are stopped after the heat preservation is finished for 280min, when the temperature is reduced to 90 ℃, the product is taken out after the furnace is opened, and then the product is spread, and is detected and put in storage after the temperature is reduced to 90 ℃, so that the high purity graphite felt with the carbon content of 99.85.

Example 4

The difference from the embodiment 2 is the process of the step-by-step temperature controlled sintering, in this embodiment, firstly, the normal temperature sintering furnace is heated to 700 ℃ at a heating rate of 100 ℃/h, and the temperature is maintained for 140min, argon is introduced into the sintering furnace body 1 through the gas distribution ring when the furnace temperature reaches 700 ℃, the flow rate of argon is set to 45ml/min for gas flow guiding and impurity removal, the introduction of argon is stopped after the first stage heat preservation is finished, the furnace temperature is increased to 1850 ℃, the heating and temperature reduction are stopped after the heat preservation is finished for 200min, when the temperature is reduced to 90 ℃, the product is taken out after the furnace is opened, and then the product is laid open, and is detected and warehoused after being cooled for 55min, so that the high purity graphite felt with the carbon content of 99.8 wt% can.

Example 5

The embodiment provides a crystalline silicon furnace, which comprises a graphite cylinder, wherein a thermal field is arranged in the graphite cylinder, a heat insulation layer is wrapped on the outer side of the graphite cylinder and made of a high-purity graphite felt, the high-purity graphite felt is prepared by the method in the embodiment 2-4, the crystalline silicon furnace in the embodiment adopts the high-purity graphite felt, the heat insulation performance is greatly improved, when the temperature in the single crystal thermal field reaches 1600 ℃, volatile matters do not overflow from the high-purity graphite felt, little graphite dust exists, no oil flow phenomenon occurs, and the cleanliness is higher compared with other graphite felts in the market.

The performance of the viscose-based graphite felt obtained in examples 2 to 4 was measured by the following measurement indexes including thermal conductivity (W/m.k), carbon content (wt%), ash content (ppm), and bulk density (g/cm)³) Tensile strength (Mpa), the detection means refers to national standards, and the detection results are shown in the following table:

the detection results show that: the viscose-based graphite felt obtained in examples 2 to 4 had a thermal conductivity of 0.08 to 0.13W/m.k, a carbon content of not less than 99.8 wt%, an ash content of not more than 400ppm, and a bulk density of not more than 0.1g/cm³The tensile strength is more than or equal to 0.12Mpa, so that the graphite felt obtained after the processing by the process has the advantages of low heat conductivity coefficient, high carbon content, low ash content and the like, and has excellent heat preservation performance and obviously reduced heating power in use.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.