Preparation method of quartz plate for spaceflight observation mirror

Abstract

The invention discloses a preparation method of a quartz plate for a spaceflight observation mirror, and relates to the technical field of quartz. Silicon tetrachloride, titanium tetrachloride and aluminum particles are subjected to high-frequency plasma chemical vapor deposition, high-flow oxygen is introduced, so that the silicon tetrachloride, titanium tetrachloride and aluminum particles react with oxygen plasma, and low-expansion doped quartz glass with extremely high optical uniformity is prepared; doped quartz glass is subjected to homogenization treatment, so that tiny bubbles formed in the deposition process are eliminated, hydroxyl tends to be uniform in the physical migration process, a network structure in a base body starts to be reformed and arranged orderly along with separation of the bubbles from the base body and rising of the heat treatment temperature, and finally the doped quartz glass is obtained. The thermal stress of the glass is removed through constant-speed slow annealing, so that the temperature gradients of the glass are eliminated, the structure of the glass is stable, the optical uniformity is improved, and the mechanical property of the glass is improved.

Description

Technical Field

[0001] This invention relates to the field of quartz technology, specifically to a method for preparing quartz plates for aerospace observation mirrors. Background Technology

[0002] Quartz, with the chemical formula SiO2, possesses a highly ordered crystal lattice structure. Quartz glass is an amorphous material made from high-purity quartz sand. Due to the high bond energy of silicon-oxygen bonds, quartz glass exhibits excellent properties such as high light transmittance, low refractive index, high temperature resistance, chemical corrosion resistance, high hardness, high strength, and wear resistance. Therefore, with the rapid advancement of modern technology, quartz glass has found increasingly widespread applications in high-tech industries.

[0003] In the fields of astronomy and aerospace, to ensure that optical components maintain their surface accuracy under temperature fluctuations, reflective optical components need to have a low coefficient of thermal expansion. For example, the viewing windows of spacecraft not only meet the advantages of special metallic materials such as high strength and corrosion resistance, but also satisfy some of the performance requirements of optical glass. Similarly, the lenses of optical telescopes, which have extremely high precision requirements, also require an extremely low coefficient of thermal expansion. Low-expansion quartz glass meets the basic requirement of low expansion while also possessing high resistance to deformation, making it an ideal optical material for aerospace and astronomy, as well as for reflective optics. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing quartz plates for aerospace observation mirrors, so as to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing a quartz plate for aerospace observation mirrors, comprising the following preparation steps:

[0006] (1) Silicon tetrachloride, titanium tetrachloride and nano-aluminum are subjected to high-frequency plasma chemical vapor deposition to obtain doped quartz glass;

[0007] (2) The doped quartz glass was subjected to a tank sedimentation homogenization treatment to obtain intermediate A;

[0008] (3) Anneal the intermediate A to obtain a quartz plate for aerospace observation mirror.

[0009] Furthermore, the process parameters for the high-frequency plasma chemical vapor deposition described in step (1) are: oxygen flow rate of 10~20 Nm³. 3 / h, hydrogen flow rate is 3~8Nm 3 / h, power of 100~150kW, frequency of 2.5~3.8MHz, temperature of 1900~2700℃, time of 50~100s.

[0010] Furthermore, the flow rate of silicon tetrachloride in step (1) is 15~25 L / h.

[0011] Furthermore, the flow rate of titanium tetrachloride in step (1) is 2~6 L / h.

[0012] Furthermore, the flow rate of the nano-aluminum in step (1) is 50~70g / h.

[0013] Furthermore, the tank settling homogenization conditions in step (2) are: vacuum degree of 16~22 Pa and temperature of 1500~1900℃.

[0014] Furthermore, the process parameters for the tank sedimentation homogenization in step (2) are: power of 40~70kW and time of 80~120min.

[0015] Furthermore, the annealing process described in step (3) is divided into annealing and cooling.

[0016] Furthermore, the annealing process parameters are: temperature of 1025~1100℃, heating rate of 7~10℃ / min, and holding time of 300~350h.

[0017] Furthermore, the cooling step involves cooling the furnace at a rate of 3-5°C / h to 900-980°C.

[0018] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0019] The quartz plate of the present invention is prepared by high-frequency plasma chemical vapor deposition process, and then subjected to homogenization and annealing treatment to achieve the effects of low expansion coefficient and high optical and mechanical properties.

[0020] First, silicon tetrachloride, titanium tetrachloride, and aluminum particles are decomposed into plasma under the action of a high-frequency electromagnetic field. Through the introduction of a high-flow-rate working gas—oxygen—the molecules move violently in a high-temperature environment with concentrated energy, causing the silicon tetrachloride, titanium tetrachloride, and aluminum particles to react with the oxygen plasma. In this process, all silicon ions are converted into nuclei to form a melt of silicon dioxide, while the formed alumina and titanium dioxide are deposited in the matrix. Some of the tetravalent titanium forms titanium-oxygen tetrahedra and enters the glass structure network, forming a three-dimensional silicon-oxygen-titanium network structure with the silicon-oxygen tetrahedra. Furthermore, titanium dioxide and alumina can act as intermediates to reconnect the broken silicon-oxygen network, enhance the network structure, and reduce the expansion coefficient of the matrix, thereby producing a low-expansion doped quartz glass with extremely high optical uniformity.

[0021] Secondly, the doped quartz glass is homogenized by vacuum pressure bath deposition, and the bubbles in the matrix are compressed and absorbed, thereby eliminating the microbubbles formed during the deposition process and making the hydroxyl groups evenly distributed. With the assistance of high temperature, it is beneficial for the matrix to diffuse from high concentration to low concentration, and the distribution of hydroxyl groups on the horizontal surface tends to be balanced. The flow of glass melt will make the hydroxyl groups tend to be uniform in the physical migration process. After homogenization, the hydroxyl groups distributed on the surface will detach from the matrix as the bubbles detach, and as the heat treatment temperature increases, the ions will occupy the most energy-advantaged equilibrium position. The network structure inside the matrix begins to be reorganized and arranged in an orderly manner. Finally, the thermal stress of the glass is removed by uniform and slow annealing. As the holding time increases, the structural relaxation rate slows down, thereby eliminating the temperature gradients of the glass, making its structure stable, increasing optical uniformity, and improving the mechanical properties of the glass. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] To more clearly illustrate the method provided by the present invention, the following embodiments are provided in detail. The testing methods for various indicators of the quartz plate used in the aerospace observation mirror produced in the following embodiments are as follows:

[0024] Low expansion: Take the same size examples and comparative examples and test their expansion coefficients from 0 to 100°C according to GB / T7962.16.

[0025] Optical performance: Using examples and comparative examples of the same size, the transmittance in the visible light range was tested in accordance with GB / T12997.

[0026] Mechanical properties: The Young's modulus and Knoop hardness of the same size examples and comparative examples were tested according to GB / T7962.6 and GB / T7962.18, respectively.

[0027] Example 1; (1) Silicon tetrachloride, titanium tetrachloride, and nano-aluminum were introduced into the mold at flow rates of 15 L / h, 2 L / h, and 50 g / h, respectively, and high-frequency plasma chemical vapor deposition was performed under hydrogen protection at a flow rate of 3 Nm3 / h. The process parameters were: oxygen flow rate of 10 Nm3 / h. 3 A doped quartz glass was obtained by setting the following parameters: / h, power of 100kW, frequency of 2.5MHz, temperature of 1900℃, and time of 50s.

[0028] (2) The doped quartz glass was subjected to a tank sedimentation homogenization treatment at 1500℃ and a vacuum of 16Pa. The process parameters were: power of 40kW and time of 80min, to obtain intermediate A;

[0029] (3) The intermediate A is heated to 1025℃ at 7℃ / min and kept at that temperature for 300h. Then it is cooled to 900℃ at 3℃ / h and cooled in the furnace to obtain a quartz plate for aerospace observation mirror.

[0030] Example 2; (1) Silicon tetrachloride, titanium tetrachloride, and nano-aluminum were introduced into the mold at flow rates of 20 L / h, 4 L / h, and 60 g / h, respectively, at a flow rate of 5 Nm 3 High-frequency plasma chemical vapor deposition (PVD) is performed under hydrogen protection at a flow rate of 15 Nm³ / h. The process parameters are: oxygen flow rate of 15 Nm³ / h. 3 A doped quartz glass was obtained by operating at a speed of / h, a power of 125kW, a frequency of 3.2MHz, a temperature of 2300℃, and a time of 60s.

[0031] (2) The doped quartz glass was subjected to a tank sedimentation homogenization treatment at 1700℃ and a vacuum of 19Pa. The process parameters were: power of 55kW and time of 100min, to obtain intermediate A;

[0032] (3) The intermediate A was heated to 1070℃ at 8℃ / min and kept at that temperature for 325h. Then it was cooled to 940℃ at 4℃ / h and cooled in the furnace to obtain a quartz plate for aerospace observation mirror.

[0033] Example 3; (1) Silicon tetrachloride, titanium tetrachloride, and nano-aluminum were introduced into the mold at flow rates of 25 L / h, 6 L / h, and 70 g / h, respectively, at a flow rate of 8 Nm 3 High-frequency plasma chemical vapor deposition (PVD) is performed under hydrogen protection at a flow rate of 20 Nm³ / h. The process parameters are: oxygen flow rate of 20 Nm³ / h. 3 A doped quartz glass was obtained by operating at a power of 150kW, a frequency of 3.8MHz, a temperature of 2700℃, and a time of 100s.

[0034] (2) The doped quartz glass was subjected to a tank sedimentation homogenization treatment at 1900℃ and a vacuum of 22Pa. The process parameters were: power of 70kW and time of 120min, to obtain intermediate A;

[0035] (3) The intermediate A is heated to 1100℃ at 10℃ / min and kept at that temperature for 350h. Then it is cooled to 980℃ at 5℃ / h and cooled with the furnace to obtain a quartz plate for aerospace observation mirror.

[0036] Comparative Example 1; The difference between Comparative Example 1 and Example 2 is that step (1) is different. Step (1) is changed to: silicon tetrachloride and nano-aluminum are introduced into the mold at flow rates of 20L / h and 60g / h, respectively, at a flow rate of 5Nm 3 High-frequency plasma chemical vapor deposition (PVD) is performed under hydrogen protection at a flow rate of 15 Nm³ / h. The process parameters are: oxygen flow rate of 15 Nm³ / h. 3 The process involves setting the temperature at 2300℃ and the time at a power of 125kW, a frequency of 3.2MHz, and a time of 60s, to obtain doped quartz glass; the remaining steps are the same as in Example 2.

[0037] Comparative Example 2; The difference between Comparative Example 2 and Example 2 is that step (1) is different. Step (1) is changed to: silicon tetrachloride and titanium tetrachloride are introduced into the mold at flow rates of 20 L / h and 4 L / h, respectively, and the flow rate is 5 Nm 3 High-frequency plasma chemical vapor deposition (PVD) is performed under hydrogen protection at a flow rate of 15 Nm³ / h. The process parameters are: oxygen flow rate of 15 Nm³ / h. 3 The process involves setting the temperature at 2300℃ and the time at a power of 125kW, a frequency of 3.2MHz, and a time of 60s, to obtain doped quartz glass; the remaining steps are the same as in Example 2.

[0038] Comparative Example 3; The difference between Comparative Example 3 and Example 2 is that step (2) is omitted; the remaining steps are the same as in Example 2.

[0039] Comparative Example 4; The difference between Comparative Example 4 and Example 2 is that step (3) is omitted; the remaining steps are the same as in Example 2.

[0040] Comparative Example 5; The difference between Comparative Example 5 and Example 2 is that steps (2) and (3) are omitted; the remaining steps are the same as in Example 2.

[0041] Example of effect

[0042] Table 1 below presents the performance analysis results of the quartz plates for aerospace observation mirrors using Examples 1 to 3 and Comparative Examples 1 to 5 of the present invention.

[0043] Table 1

[0044]

[0045] A comparison of the experimental data from the examples and comparative examples in Table 1 reveals that high-frequency plasma chemical vapor deposition (PCVD) yields low-expansion doped quartz glass with extremely high optical uniformity. By introducing a high-flow-rate working gas—oxygen—the silicon tetrachloride, titanium tetrachloride, and aluminum particles react with the oxygen plasma. During this reaction, all silicon ions are converted into nuclei, and the resulting alumina and titanium dioxide are deposited within the molten silicon dioxide. Some of the tetravalent titanium dioxide forms titanium-oxygen tetrahedra, which enter the glass structure network, forming a three-dimensional silicon-oxygen-titanium network structure with the silicon-oxygen tetrahedra. Furthermore, titanium dioxide and alumina act as intermediates to reconnect broken silicon-oxygen networks, strengthening the network structure and reducing... The low coefficient of thermal expansion of the matrix; the homogenization treatment of doped quartz glass by vacuum pressure tank deposition eliminates microbubbles formed during the deposition process and makes the hydroxyl groups evenly distributed. With the assistance of high temperature, it is conducive to the diffusion of the matrix from high concentration to low concentration. The flow of glass melt will make the hydroxyl groups tend to be uniform in the physical migration process. After homogenization, the hydroxyl groups distributed on the surface will detach from the matrix as the bubbles detach. As the heat treatment temperature increases, the network structure inside the matrix begins to be reorganized and arranged in an orderly manner. Finally, the thermal stress of the glass is removed by uniform and slow annealing. As the holding time increases, the structural relaxation rate slows down, thereby eliminating the temperature gradients of the glass, making its structure stable, increasing optical uniformity, and improving the mechanical properties of the glass.

[0046] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing a quartz plate for aerospace observation mirrors, characterized in that, The preparation steps include the following: (1) Silicon tetrachloride, titanium tetrachloride and nano-aluminum are subjected to high-frequency plasma chemical vapor deposition to obtain doped quartz glass; (2) The doped quartz glass was subjected to a tank sedimentation homogenization treatment to obtain intermediate A; (3) Anneal the intermediate A to obtain a quartz plate for aerospace observation mirror.

2. The method for preparing the quartz plate for aerospace observation mirror according to claim 1, characterized in that, The process parameters for high-frequency plasma chemical vapor deposition in step (1) are: oxygen flow rate of 10~20 Nm³. 3 / h, hydrogen flow rate is 3~8Nm 3 / h, power of 100~150kW, frequency of 2.5~3.8MHz, temperature of 1900~2700℃, time of 50~100s.

3. The method for preparing the quartz plate for aerospace observation mirror according to claim 1, characterized in that, The flow rate of silicon tetrachloride in step (1) is 15~25L / h.

4. The method for preparing the quartz plate for aerospace observation mirror according to claim 1, characterized in that, The flow rate of titanium tetrachloride in step (1) is 2~6 L / h.

5. The method for preparing a quartz plate for aerospace observation mirror according to claim 1, characterized in that, The flow rate of the nano-aluminum in step (1) is 50~70g / h.

6. The method for preparing a quartz plate for aerospace observation mirror according to claim 1, characterized in that, The conditions for tank settling homogenization in step (2) are: vacuum degree of 16~22 Pa and temperature of 1500~1900℃.

7. The method for preparing a quartz plate for aerospace observation mirror according to claim 1, characterized in that, The process parameters for the tank settling homogenization in step (2) are: power of 40~70kW and time of 80~120min.

8. The method for preparing a quartz plate for aerospace observation mirror according to claim 1, characterized in that, The annealing process described in step (3) consists of annealing and cooling.

9. The method for preparing a quartz plate for aerospace observation mirror according to claim 8, characterized in that, The annealing process parameters are: temperature 1025~1100℃, heating rate 7~10℃ / min, and holding time 300~350h.

10. The method for preparing a quartz plate for aerospace observation mirror according to claim 8, characterized in that, The cooling step involves cooling the furnace at a rate of 3-5°C / h to 900-980°C.

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