Heat treatment method for reducing density and area of bubbles in high-purity quartz glass and application of heat treatment method

Abstract

The invention discloses a heat treatment method for reducing the density and area of bubbles in high-purity quartz glass and application of the heat treatment method, and the heat treatment method comprises the following steps: heating the high-purity quartz glass to 1300-1800 DEG C in a protective gas atmosphere of more than 0.1 MPa, and preserving heat to reduce the density and area of the bubbles in the high-purity quartz glass. The quartz glass product is subjected to heat treatment after being prepared and molded, so that the bubble density and area can be remarkably reduced, the internal defects of the quartz glass product are reduced, the material quality and service performance are improved, and the quartz glass product meets the requirements of optical elements.

Description

Technical Field

[0001] The present invention relates to the technical field of heat treatment of quartz glass, and particularly relates to a heat treatment method for reducing the bubble density and area in high-purity quartz glass and its application. Background Art

[0002] High-purity quartz glass has excellent properties such as high purity, high temperature resistance, and low thermal expansion coefficient, and is widely used in fields such as integrated circuits, photovoltaics, and precision optics. High-purity quartz glass is prepared from high-purity quartz sand, and bubbles may appear during the preparation process, which will significantly affect the properties of quartz glass products such as transmittance, thermal stability, and mechanical strength, and affect the service performance and lifespan of the finished products. Therefore, reducing the bubble density and area in quartz glass has very important practical application value.

[0003] At present, most quartz glass patents mainly focus on suppressing the generation of bubbles during the preparation and forming processes of quartz glass products: for example, the Chinese invention patent application with publication number CN106116122A designs a sintering device and system for preparing quartz glass to avoid or reduce the generation of bubbles in the process of preparing quartz glass by the indirect synthesis method, and improve the sintering efficiency of quartz glass and reduce costs; the Chinese invention patent application with publication number CN105502896A designs a production process for quartz glass ingots, and by controlling the gas pressure in the furnace, the generation of bubbles can be effectively avoided to ensure the density requirements of the products. However, for the bubbles that have already generated in the finished quartz glass material, there is no relevant report on how to reduce the bubble density and area.

[0004] On the other hand, the current mainstream quartz glass heat treatment technologies can only reduce the internal stress level and uneven stress distribution in the material (such as CN113754259A, CN108383365A, etc.), and cannot affect the internal bubbles in the material.

[0005] Therefore, realizing a heat treatment method for reducing the bubble density and area in high-purity quartz glass is of great significance for reducing the internal defects of quartz glass products, improving the material quality and service performance. Summary of the Invention

[0006] In view of the above technical problems and the deficiencies existing in the art, the present invention provides a heat treatment method for reducing the bubble density and area in high-purity quartz glass and its application. The present invention can significantly reduce the bubble density and area, reduce the internal defects of quartz glass products, improve the material quality and service performance, and enable quartz glass products to meet the requirements of optical elements.

[0007] The specific technical solutions are as follows: In a first aspect, the present invention provides a heat treatment method for reducing the bubble density and area in high-purity fused silica glass, including: in a protective gas atmosphere with a pressure above 0.1 MPa, heating the high-purity fused silica glass to 1300 - 1800 °C (such as 1350 °C, 1400 °C, 1450 °C, 1500 °C, 1550 °C, 1600 °C, 1650 °C, 1700 °C, 1750 °C, etc.) and holding the temperature to reduce the bubble density and area in the high-purity fused silica glass. When holding the temperature at 1800 °C, the high-purity fused silica glass will soften to a certain extent but will not completely melt.

[0008] For the heat treatment method for reducing the bubble density and area in high-purity fused silica glass, the pressure of the protective gas atmosphere is preferably greater than 0.1 MPa (atmospheric pressure).

[0009] For the heat treatment method for reducing the bubble density and area in high-purity fused silica glass, the pressure of the protective gas atmosphere is preferably 0.1 - 5.0 MPa, and more preferably greater than 0.1 MPa (atmospheric pressure) and not exceeding 5.0 MPa.

[0010] For the heat treatment method for reducing the bubble density and area in high-purity fused silica glass, the protective gas atmosphere is a gas atmosphere that does not react with the high-purity fused silica glass, and preferably includes at least one of argon and nitrogen.

[0011] For the heat treatment method for reducing the bubble density and area in high-purity fused silica glass, the heating can include two stages: the first stage is to heat to 1000 °C at a rate of 8 - 12 °C / min (such as 10 °C / min, etc.), and the second stage is to heat to 1300 - 1800 °C at a rate of 3 - 8 °C / min (such as 5 °C / min, etc.).

[0012] For the heat treatment method for reducing the bubble density and area in high-purity fused silica glass, the holding time is preferably more than 5 hours, and more preferably 5 - 20 hours, such as 10 hours, etc.

[0013] The heat treatment method for reducing the bubble density and area in high-purity fused silica glass may further include a cooling process after the holding. The cooling process preferably maintains the pressure of the protective gas atmosphere above 0.1 MPa, and more preferably, the cooling process maintains the pressure of the protective gas atmosphere at 0.1 - 5.0 MPa.

[0014] The heat treatment method for reducing the bubble density and area in high-purity quartz glass, the cooling process may include three stages: the first stage is to cool down to 1000 °C at a rate of 2-4 °C / min, the second stage is to cool down to 500-600 °C at a rate of 4-8 °C / min (such as 5 °C / min, etc.), and the third stage is to cool to room temperature. The cooling rate in the third stage of the cooling process may not be particularly controlled, for example, natural cooling is sufficient.

[0015] The heat treatment method for reducing the bubble density and area in high-purity quartz glass preferably creates a protective gas atmosphere of more than 0.1 MPa before heating up. The specific operation may include: placing the high-purity quartz glass in a heat treatment device, performing a vacuum pumping treatment on the heat treatment device, and then filling it with a protective gas to more than 0.1 MPa (preferably 0.1-5.0 MPa). Preferably, the vacuum pumping treatment pumps the pressure inside the heat treatment device to 1-10 Pa. The vacuum pumping treatment-filling with protective gas operation can be carried out 1-3 times to ensure that the original gas inside the heat treatment device is completely exhausted.

[0016] In a second aspect, the present invention provides an application of the heat treatment method described in the first aspect in reducing the bubble density and area in high-purity quartz glass.

[0017] Compared with the prior art, the beneficial effects of the present invention are: The present invention quickly and conveniently reduces the bubble density and area in high-purity quartz glass through heat treatment. The present invention performs heat treatment on the quartz glass product after it is prepared and formed, reducing the bubble density and area. Description of the Drawings

[0018] Figure 1 It is a schematic flow chart of the heat treatment method for reducing the bubble density and area in high-purity quartz glass in the specific embodiment.

[0019] Figure 2 It is a heating and cooling curve graph of the heat treatment method for reducing the bubble density and area in high-purity quartz glass in Example 1. Specific Embodiments

[0020] The present invention will be further described below in conjunction with the drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The operation methods without specific conditions noted in the following embodiments are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0021] See Figure 1 , a heat treatment method for reducing the bubble density and area in high-purity quartz glass, includes: Step 101: Place high-purity quartz glass in a heat treatment device. Conduct three vacuum pumping treatments on the heat treatment device. The vacuum pumping treatment should pump down to 1 - 10 Pa, then introduce a protective gas. Repeat this pumping and filling operation three times to ensure that the original gas inside the heat treatment device is completely exhausted. Subsequently, fill with the protective gas to the target pressure and maintain this pressure throughout the heat treatment process. For example, argon can be used as the protective gas. Further, the target pressure of 0.1 - 5.0 MPa needs to be maintained throughout the heat treatment process. Step 102: After Step 101, raise the temperature. The temperature increase is divided into two stages: In the first stage, raise the temperature at a rate of 8 - 12 °C / min to 1000 °C, and in the second stage, raise the temperature at a rate of 3 - 8 °C / min to 1300 - 1800 °C. Step 103: After Step 102, hold the temperature for 5 - 20 hours. Step 104: After Step 103, lower the temperature. The temperature decrease is divided into three stages: In the first stage, lower the temperature at a rate of 2 - 4 °C / min to 1000 °C, in the second stage, lower the temperature at a rate of 4 - 8 °C / min to 500 - 600 °C, and in the third stage, do not control the cooling rate and let it cool naturally to room temperature to obtain high-purity quartz glass with a significantly reduced bubble density and area.

[0022] The following are specific examples of using the above heat treatment method for reducing the bubble density and area in high-purity quartz glass and some related comparative examples.

[0023] Example 1: As Figure 2 shown, a heat treatment method for reducing the bubble density and area in high-purity quartz glass includes the following steps: (1) Take a clean high-purity quartz glass round plate (diameter 350 mm, height 80 mm), take several optical microscope photos to record the bubble density and area, and then put it into the heat treatment device. (2) Conduct three vacuum pumping treatments on the heat treatment device: Pump down to 1 Pa, then introduce argon. Repeat this pumping and filling operation three times to ensure that the original gas inside the heat treatment device is completely exhausted. Subsequently, fill with argon to normal pressure (0.1 MPa) and maintain this pressure.

[0024] (3) Conduct two temperature increases. The first temperature increase is at a rate of 10 °C / min to 1000 °C, and the second temperature increase is at a rate of 5 °C / min to 1400 °C.

[0025] (4) Hold the temperature at 1400 °C for 10 hours.

[0026] (5) Lower the temperature in three steps: The first temperature decrease is at a rate of 2 °C / min to 1000 °C, the second temperature decrease is at a rate of 5 °C / min to 500 °C, and the third temperature decrease does not control the cooling rate and let it cool naturally to room temperature, then take out the quartz glass.

[0027] (6) Take several optical microscope photos after heat treatment; analyze the bubble density before and after heat treatment (the number of all bubbles in a single photo / the area of a single photo), calculate the percentage change in bubble density (bubble density after heat treatment / bubble density before heat treatment); analyze the area of a specific single bubble before and after heat treatment, calculate the percentage change in the area of this bubble (the area of this bubble after heat treatment / the area of this bubble before heat treatment), select five bubbles, and obtain the average percentage change in bubble area.

[0028] Example 2: Compared with Example 1, shorten the holding time, including the following steps: (1) Take a clean high-purity quartz glass round plate (diameter 350 mm, height 80 mm), take several optical microscope photos to record the bubble density and area, and then put it into the heat treatment device; (2) Conduct three vacuum pumping treatments on the heat treatment device: pump to 1 Pa, and then introduce argon. Repeat this pumping and filling operation three times to ensure that all the original gas inside the heat treatment device is completely exhausted. Subsequently, fill argon to normal pressure (0.1 MPa) and maintain this pressure.

[0029] (3) Conduct two temperature increases. The first temperature increase is to 1000 °C at a rate of 10 °C / min, and the second temperature increase is to 1400 °C at a rate of 5 °C / min.

[0030] (4) Hold at 1400 °C for 5 hours.

[0031] (5) Cool down in three steps: the first cooling is to 1000 °C at a rate of 2 °C / min, the second cooling is to 500 °C at a rate of 5 °C / min, and the third cooling does not control the cooling rate and naturally cools to room temperature, then take out the quartz glass.

[0032] (6) Take several optical microscope photos after heat treatment; analyze the bubble density before and after heat treatment (the number of all bubbles in a single photo / the area of a single photo), calculate the percentage change in bubble density (bubble density after heat treatment / bubble density before heat treatment); analyze the area of a specific single bubble before and after heat treatment, calculate the percentage change in the area of this bubble (the area of this bubble after heat treatment / the area of this bubble before heat treatment), select five bubbles, and obtain the average percentage change in bubble area.

[0033] Example 3: Compared with Example 1, increase the internal pressure of the heat treatment device, including the following steps: (1) Take a clean high-purity quartz glass round plate (diameter 350 mm, height 80 mm), take several optical microscope photos to record the bubble density and area, and then put it into the heat treatment device; (2) Conduct three vacuum pumping treatments on the heat treatment device: pump down to 1 Pa, and then introduce argon. Repeat this pumping and filling operation three times to ensure that all the original gas inside the heat treatment device is completely exhausted. Subsequently, fill argon to 5.0 MPa and maintain this pressure.

[0034] (3) Conduct two temperature increases. The first temperature increase is to 1000 °C at a rate of 10 °C / min, and the second temperature increase is to 1400 °C at a rate of 5 °C / min.

[0035] (4) Hold at 1400 °C for 10 hours.

[0036] (5) Cool down in three steps: the first cooling is to 1000 °C at a rate of 2 °C / min, the second cooling is to 500 °C at a rate of 5 °C / min, and the third cooling does not control the cooling rate and naturally cools to room temperature, then take out the quartz glass.

[0037] (6) Take several optical microscope photos after heat treatment; analyze the bubble density (the number of all bubbles in a single photo / the area of a single photo) before and after heat treatment, calculate the percentage change in bubble density (bubble density after heat treatment / bubble density before heat treatment); analyze the area of a specific single bubble before and after heat treatment, calculate the percentage change in the area of this bubble (the area of this bubble after heat treatment / the area of this bubble before heat treatment), and take five bubbles to obtain the average percentage change in bubble area.

[0038] Comparative Example 1: Compared with Example 1, reduce the internal pressure of the heat treatment device, including the following steps: (1) Take a clean high-purity quartz glass round plate (diameter 350 mm, height 80 mm), take several optical microscope photos to record the bubble density and area, and then put it into the heat treatment device; (2) Conduct three vacuum pumping treatments on the heat treatment device: pump down to 1 Pa, and then introduce argon. Repeat this pumping and filling operation three times to ensure that all the original gas inside the heat treatment device is completely exhausted. Subsequently, fill argon to 2000 Pa and maintain this pressure.

[0039] (3) Conduct two temperature increases. The first temperature increase is to 1000 °C at a rate of 10 °C / min, and the second temperature increase is to 1400 °C at a rate of 5 °C / min.

[0040] (4) Hold at 1400 °C for 10 hours.

[0041] (5) Cool down in three steps: the first cooling is to 1000 °C at a rate of 2 °C / min, the second cooling is to 500 °C at a rate of 5 °C / min, and the third cooling does not control the cooling rate and naturally cools to room temperature, then take out the quartz glass.

[0042] (6) Take several optical microscope photos after heat treatment; analyze the bubble density before and after heat treatment (the number of all bubbles in a single photo / the area of a single photo), calculate the percentage change in bubble density (bubble density after heat treatment / bubble density before heat treatment); analyze the area of a specific single bubble before and after heat treatment, calculate the percentage change in the area of this bubble (the area of this bubble after heat treatment / the area of this bubble before heat treatment), select five bubbles, and obtain the average percentage change in bubble area.

[0043] Comparative Example 2: Compared with Example 1, change the heat treatment holding temperature, including the following steps: (1) Take a clean high-purity quartz glass round plate (diameter 350 mm, height 80 mm), take several optical microscope photos to record the bubble density and area, and then put it into the heat treatment device; (2) Conduct three vacuum pumping treatments on the heat treatment device: pump to 1 Pa, and then introduce argon. Repeat this pumping and filling operation three times to ensure that the original gas inside the heat treatment device is completely exhausted. Subsequently, fill argon to normal pressure (0.1 MPa) and maintain this pressure.

[0044] (3) Conduct two temperature increases. The first temperature increase is to 1000 °C at a rate of 10 °C / min, and the second temperature increase is to 1200 °C at a rate of 5 °C / min.

[0045] (4) Hold at 1200 °C for 10 hours.

[0046] (5) Cool down in three steps: the first cooling is to 1000 °C at a rate of 2 °C / min, the second cooling is to 500 °C at a rate of 5 °C / min, and the third cooling does not control the cooling rate and naturally cools to room temperature, then take out the quartz glass.

[0047] (6) Take several optical microscope photos after heat treatment; analyze the bubble density before and after heat treatment (the number of all bubbles in a single photo / the area of a single photo), calculate the percentage change in bubble density (bubble density after heat treatment / bubble density before heat treatment); analyze the area of a specific single bubble before and after heat treatment, calculate the percentage change in the area of this bubble (the area of this bubble after heat treatment / the area of this bubble before heat treatment), select five bubbles, and obtain the average percentage change in bubble area.

[0048] Table 1 shows the changes in the average bubble area and bubble density in the quartz glass before and after heat treatment for each example and comparative example.

[0049] Table 1

[0050] As can be seen from Table 1, the bubble density and area of the fused silica glass in Example 1 were significantly reduced after heat treatment, which confirmed the effectiveness of the heat treatment method of the present invention in reducing the bubble density and area of the fused silica glass. The bubble density and area in Example 2 also decreased, and the reduction rate was about half of that in Example 1 because the heat preservation time in Example 2 was half of that in Example 1. This indicates that the heat preservation time is roughly proportional to the reduction of the bubble density and area. In Example 3, due to the higher heat treatment pressure, compared with Example 1, the reduction rate of the bubble density and area was greater, which shows that pressurization can effectively improve the heat treatment effect. The bubble density and area of the fused silica glass in Comparative Example 1 showed an upward trend after heat treatment, indicating that a low pressure environment of 2000 Pa would promote bubble nucleation and growth. In Comparative Example 2, the bubble density and area of the fused silica glass remained unchanged after heat treatment, indicating that a suitable temperature is crucial for reducing the bubble density and area.

[0051] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A heat treatment method for reducing the bubble density and area in high-purity fused silica glass, characterized in that, Comprising: In a protective gas atmosphere above 0.1 MPa, heating the high-purity quartz glass to 1300 - 1800 °C and holding the temperature to reduce the bubble density and area in the high-purity quartz glass.

2. The heat treatment method for reducing the bubble density and area in high-purity fused silica according to claim 1, characterized in that, The pressure of the protective gas atmosphere is 0.1 - 5.0 MPa.

3. The heat treatment method for reducing the bubble density and area in high-purity fused silica according to claim 1, characterized in that, The protective gas atmosphere is a gas atmosphere that does not react with the high-purity quartz glass and includes at least one of argon and nitrogen.

4. The heat treatment method for reducing the bubble density and area in high-purity fused silica according to claim 1, wherein The heating includes two stages: the first stage is to heat to 1000 °C at a rate of 8 - 12 °C / min, and the second stage is to heat to 1300 - 1800 °C at a rate of 3 - 8 °C / min.

5. The heat treatment method for reducing the bubble density and area in high-purity fused silica according to claim 1, wherein The holding time is more than 5 hours.

6. The heat treatment method for reducing the bubble density and area in high-purity fused silica glass according to claim 5, wherein, The holding time is 5 - 20 hours.

7. The heat treatment method for reducing the bubble density and area in high-purity fused silica glass according to claim 1, characterized in that, The heat treatment method further includes a cooling process after the holding ends. During the cooling process, the pressure of the protective gas atmosphere is maintained above 0.1 MPa. Preferably, during the cooling process, the pressure of the protective gas atmosphere is maintained at 0.1 - 5.0 MPa.

8. The heat treatment method for reducing the bubble density and area in high-purity fused silica according to claim 7, characterized in that, The cooling process includes three stages: the first stage is to cool to 1000 °C at a rate of 2 - 4 °C / min, the second stage is to cool to 500 - 600 °C at a rate of 4 - 8 °C / min, and the third stage is to cool to room temperature.

9. The heat treatment method for reducing the bubble density and area in high-purity fused silica according to any one of claims 1-8, characterized in that, Before heating, create a protective gas atmosphere above 0.1 MPa. The specific operation includes: placing the high-purity quartz glass in a heat treatment device, performing a vacuum pumping treatment on the heat treatment device, and then filling it with a protective gas to above 0.1 MPa; The vacuum pumping treatment pumps the pressure inside the heat treatment device to 1 - 10 Pa; Perform the vacuum pumping treatment - filling with a protective gas operation 1 - 3 times.

10. Use of the heat treatment method according to any one of claims 1 - 9 in reducing the bubble density and area in high-purity quartz glass.

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