Aerospacial window glass and method for its production

Abstract

The application discloses a window glass for aerospace and a preparation method thereof, and belongs to the glass field. The window glass is prepared from the following raw materials in percentage by mass: SiO2: 72-79%, B2O3: 10-15%, Na2O: 3-7%, K2O: 0.5-2%, MgO: 1-2%, SrO: 0.5-2%, BaO: 0.05-0.3%, PbO: 0.5-2%, ZnO: 0.05-0.5%, ZrO2: 0.4-1%, TiO2: 0.05-0.2%, La2O3: 0.1-0.4% and NaCl: 1-2%. The raw materials are mixed uniformly, melted, clarified and formed into glass blocks, and then annealed to obtain the glass. The application is suitable for the field of aerospace, and has excellent thermal stability and mechanical properties, and certain radiation resistance, and has good adaptability and protection to the extreme environment in the service of aerospace.

Description

Technical Field

[0001] This invention belongs to the field of glass, specifically relating to a window glass for aerospace applications and its preparation method. Background Technology

[0002] With the continuous development of aerospace technology, the application fields of aerospace glass are also constantly expanding. Besides traditional applications such as spacecraft structural components, observation windows, and solar panels, it is also being used in laser weapon systems and space stations. Spacecraft experience extreme temperature changes during flight, requiring aerospace glass to possess a wide range of thermal stability, maintaining good light transmittance and mechanical strength under drastic temperature variations to ensure the normal operation of spacecraft under various temperature conditions. Simultaneously, the high-energy radiation in the space environment poses a hazard to spacecraft, internal equipment, and personnel; therefore, aerospace glass must also possess a certain radiation absorption capacity to effectively shield harmful radiation. Thus, the development of aerospace applications places increasingly stringent requirements on aerospace glass.

[0003] To meet the above operating environment requirements, aerospace glass must possess excellent thermal stability, mechanical properties, and optical protection performance. Quartz glass is the most common aerospace material, but its manufacturing conditions are demanding, production costs are high, its radiation protection is poor, and it is difficult to process into hemispherical domes. These problems greatly limit the application of quartz glass. Summary of the Invention

[0004] To overcome the above-mentioned technical problems, this invention provides a window glass for aerospace applications and its preparation method. By adjusting the glass composition, it can be made to have excellent thermal stability, chemical stability, mechanical properties and optical protection properties, providing key material support for major aerospace projects.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A type of aerospace window glass comprises the following raw materials in the following mass percentages: SiO2: 72-79%, B2O3: 10-15%, Na2O: 3-7%, K2O: 0.5-2%, MgO: 1-2%, SrO: 0.5-2%, BaO: 0.05-0.3%, PbO: 0.5-2%, ZnO: 0.05-0.5%, ZrO2: 0.4%-1%, TiO2: 0.05-0.2%, La2O3: 0.1-0.4%, and NaCl: 1-2%.

[0007] The mass ratios of B2O3 / SiO2 are 0.12–0.19, (Na2O+K2O) / B2O3 are 0.4–0.7, K2O / Na2O are 0.15–0.3, (MgO+SrO+BaO+PbO+ZnO) / (Na2O+K2O) are 0.7–1, and ZnO / PbO are 0.1–0.3.

[0008] Regarding the above components:

[0009] SiO2, as a glass network forger, is a major component constituting the glass network framework. It effectively reduces the coefficient of thermal expansion of glass and improves its thermal shock resistance, heat resistance, and mechanical strength. By controlling the SiO2 content within the scope of this application, the thermal stability and mechanical strength of the glass are improved. Therefore, the SiO2 content is 72–79%, preferably 76–78%.

[0010] B₂O₃ plays a unique role in glass, acting as a glass-forming oxide on its own. It improves various glass properties and possesses excellent fluxing properties, making it a good fluxing agent. When B₂O₃ is added to silicate glass, Na₂O and K₂O provide free oxygen, forming boron-oxygen tetrahedra [BO₄]. Since boron-oxygen tetrahedra have a framework structure, they can form a homogeneous glass with the silicon-oxygen tetrahedra [SiO₄] in the glass structure, enhancing the glass's network structure. However, when the amount of boron added exceeds a certain limit, it appears in the glass structure not as boron-oxygen tetrahedra but as boron-oxygen trigonal bodies, causing the boron structure to transform from a framework structure to a layered structure, reducing the glass's network connectivity. Therefore, adjusting the B₂O₃ content helps reduce the viscosity of the molten glass, improves the glass's structural density, and results in the glass of this application exhibiting good clarification and high mechanical strength. Therefore, the content of B2O3 is 10-15%, preferably 11-13%, the mass ratio of B2O3 / SiO2 is 0.12-0.19, and the mass ratio of (Na2O+K2O) / B2O3 is 0.4-0.7.

[0011] Na₂O and K₂O are network oxides of glass. Na₂O and K₂O are + and K +Residing within the voids of the glass structure network, Na₂O and K₂O provide free oxygen, increasing the O / Si ratio in the glass structure and causing bond breakage. This reduces the viscosity of the glass, making it easier to melt, thus acting as a glass flux. However, excessively high Na₂O and K₂O contents reduce the chemical stability, thermal stability, and mechanical strength of the glass. Simultaneously, the Na / K ratio affects the interconnectivity of the glass subnetwork. The thermal expansion coefficient and thermal shock resistance of the aerospace window glass of this invention are determined by the connectivity of the silicate subnetwork. To better balance these properties and obtain a glass material with superior overall performance, the preferred composition is Na₂O: 3–7%, K₂O: 0.5–2%, preferably Na₂O: 4–5%, K₂O: 0.5–1%, with a K₂O / Na₂O mass ratio of 0.15–0.3.

[0012] MgO, SrO, BaO, PbO, and ZnO are all network oxides in glass. In this invention, MgO is used instead of CaO to reduce the tendency to crystallize, improve the glass forming performance, and enhance the chemical stability and mechanical properties of the glass. SrO and BaO have the same effect as MgO, but the addition of SrO and BaO can improve the glass's ability to absorb radiation. The addition of PbO can significantly improve the glass's radiation protection ability, but this invention must ensure the thermal stability and mechanical strength of the glass, so it can only be added in appropriate amounts. ZnO can reduce the coefficient of thermal expansion of glass and improve its chemical and thermal stability. Especially when added to glass containing PbO, it helps to eliminate defects such as glass streaks. By adjusting the contents of MgO, SrO, BaO, PbO, and ZnO within the scope of this application, it is beneficial to improve the chemical and thermal stability of the glass and significantly enhance its radiation protection capability. The preferred contents are: MgO: 1–2%, SrO: 0.5–2%, BaO: 0.05–0.3%, PbO: 0.5–2%, ZnO: 0.05–0.5%, preferably MgO: 1.5–2%, SrO: 1–1.5%, BaO: 0.2–0.3%, PbO: 1–1.5%, ZnO: 0.1–0.3%. The raw material for SrO is a mixture of SrCO3 and Sr(NO3)2, with a mass ratio of SrCO3 / Sr(NO3)2 of 10–15. By adjusting the mass ratio of the SrCO3 to Sr(NO3)2 mixture, the problem of high viscosity and difficulty in clarification of molten glass due to high SiO2 content can be improved. The mass ratio of (MgO+SrO+BaO+PbO+ZnO) / (Na2O+K2O) is 0.7 to 1. By adjusting the mass ratio of (MgO+SrO+BaO+PbO+ZnO) / (Na2O+K2O) in the glass within the scope of this application, it is beneficial to reduce the viscosity of molten glass, thereby facilitating the melting of glass raw materials and the forming of glass blocks. The mass ratio of ZnO / PbO is 0.05 to 0.2. By adjusting the mass ratio of ZnO / PbO in the glass, it is beneficial to eliminate defects such as streaks caused by the addition of PbO to the glass.

[0013] ZrO2 can significantly improve the chemical and thermal stability of glass, but its content should not be too high. Glass containing ZrO2 is prone to crystallization and difficult to melt. By adjusting the ZrO2 content within the range of this application, it is beneficial to reduce the coefficient of thermal expansion and improve the thermal shock resistance of the glass. Therefore, ZrO2: 0.4% to 1%, preferably 0.5% to 0.8%.

[0014] TiO2 can improve the refractive index and chemical stability of glass, and its appropriate addition can enhance the glass's ability to shield against radiation. However, TiO2-containing glass is prone to devitrification at low temperatures. Therefore, the TiO2 content is adjusted within the scope of this application, with TiO2 content ranging from 0.05% to 0.2%, preferably from 0.08% to 0.1%.

[0015] La₂O₃ can effectively improve the chemical stability and radiation protection properties of glass. At high temperatures, its thermal decomposition produces oxygen, which, when added together with NaCl, helps clarify the glass. However, excessive La₂O₃ content can reduce glass stability. Therefore, the optimal concentration of La₂O₃ is 0.1–0.4%, preferably 0.2–0.3%.

[0016] As a further aspect of the present invention: the raw material for B2O3 is a mixture of B2O3 and H3BO3, and the mass ratio of B2O3 / H3BO3 is 10 to 12; the raw material for Na2O is a mixture of Na2CO3 and NaNO3, and the mass ratio of Na2CO3 / NaNO3 is 1 to 2.

[0017] As a further aspect of the present invention: the raw material for SrO is a mixture of SrCO3 and Sr(NO3)2, and the mass ratio of SrCO3 / Sr(NO3)2 is 10 to 15.

[0018] The obtained coefficient of thermal expansion for the aerospace window glass is 3.0 × 10⁻⁶. -6 / ℃~3.8×10 -6 / ℃, thermal shock resistance ΔT / ℃≥200, transmittance in the 450~780nm wavelength range≥90%, lead equivalent ≥0.15mmPb.

[0019] Another object of the present invention is to provide a method for manufacturing the aforementioned aerospace window glass, as follows:

[0020] The raw materials are mixed evenly, melted, clarified, and shaped to obtain a glass block, which is then annealed to obtain the aerospace window glass.

[0021] In the above preparation method, the melting temperature is 1650℃~1700℃, the melting holding time is 2h~4h, the furnace working gas pressure during clarification is 0.3~0.7 standard atmospheres, the clarification holding time is 0.5h~2h, and the annealing temperature is 700℃~800℃.

[0022] The beneficial effects of this invention are:

[0023] This invention is applicable to the aerospace field. The glass not only has excellent thermal stability and mechanical properties, but also has a certain degree of radiation protection, and has good adaptability and protection against the extreme environments in aerospace service.

[0024] The raw materials used in this invention do not contain arsenic or antimony, and the preparation method provided has advantages such as simple preparation process and environmental friendliness. Detailed Implementation

[0025] 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.

[0026] The present invention provides the raw material composition (mass percentage ratio) and performance indicators of the glass of Examples 1 to 6 and Comparative Examples 1 to 5 as shown in Table 1:

[0027] The raw materials for SiO2, B2O3, Na2O, K2O, MgO, SrO, BaO, PbO, ZnO, ZrO2, TiO2, La2O3, and NaCl are SiO2, B2O3+H3BO3, Na2CO3+NaNO3, K2CO3, MgO, SrCO3+Sr(NO3)2, BaCO3, PbO·SiO2, ZnO, ZrO2, TiO2, La2O3, and NaCl, respectively. The above raw materials are mixed evenly according to the proportions shown in Table 1, and then put into a furnace for high-temperature melting. The temperature in the high-temperature furnace is raised to 1680°C and held for 3 hours. During clarification, the working gas pressure in the furnace is 0.5 standard atmospheres and the clarification holding time is 1 hour. After melting, the mixture is poured into a mold for shaping to obtain a glass block. The glass block is placed in an annealing furnace for annealing at a temperature of 750°C. Then the annealing furnace is turned off, and the glass block is allowed to cool naturally to room temperature. After annealing, the glass block is cut, ground, and polished to obtain aerospace window glass.

[0028] Table 1

[0029]

[0030]

[0031] As shown in Examples 1 to 6 of Table 1, within the scope of the application components, the thermal expansion coefficient of the aerospace window glass provided by this invention is 3.0 × 10⁻⁶. -6 / ℃~3.8×10 -6 The aerospace window glass and its preparation method provided by this invention not only have excellent thermal shock resistance, but also excellent radiation resistance. The thermal shock resistance ΔT / ℃ is ≥200, the transmittance in the wavelength range of 450~780nm is ≥90%, the lead equivalent is ≥0.15mmPb, and the bubble degree grade is A0.

[0032] Compared to Comparative Examples 1 to 5, as shown in Table 1, the addition of PbO and BaO in Comparative Example 1 improves the radiation protection of the glass. In Comparative Example 2, the excessive change in the B2O3 / SiO2 ratio reduces the network structure of the glass, leading to a decrease in its thermal stability. In Comparative Example 3, the excessive change in Na2O reduces the amount of free oxygen available in the glass, resulting in fewer boron-oxygen tetrahedra and the appearance of boron-oxygen trigonal bodies in the glass structure. This causes the boron structure to change from a framework structure to a layered structure, reducing the network connectivity of the glass, thus reversing the property. In Comparative Example 4, the reduction of NaCl affects the clarification effect of the glass, leading to an increase in the number of bubbles per unit volume. In Comparative Example 5, increasing the amount of PbO significantly improves the radiation resistance of the glass, but PbO content exceeding the application scope causes changes in the structure and system of the glass, thereby altering the density of the glass network structure, and changing the glass's thermal stability and optical properties.

[0033] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A type of window glass for aerospace applications, characterized in that, The raw materials include the following mass percentages: SiO2: 72-79%, B2O3: 10-15%, Na2O: 3-7%, K2O: 0.5-2%, MgO: 1-2%, SrO: 0.5-2%, BaO: 0.05-0.3%, PbO: 0.5-2%, ZnO: 0.05-0.5%, ZrO2: 0.4%-1%, TiO2: 0.05-0.2%, La2O3: 0.1-0.4%, NaCl: 1-2%; The mass ratios of B2O3 / SiO2 are 0.12–0.19, (Na2O+K2O) / B2O3 are 0.4–0.7, K2O / Na2O are 0.15–0.3, (MgO+SrO+BaO+PbO+ZnO) / (Na2O+K2O) are 0.7–1, and ZnO / PbO are 0.1–0.

3.

2. The aerospace window glass according to claim 1, characterized in that, The raw material for B2O3 is a mixture of B2O3 and H3BO3, with a mass ratio of B2O3 / H3BO3 of 10 to 12.

3. The aerospace window glass according to claim 1, characterized in that, The raw material for Na2O is a mixture of Na2CO3 and NaNO3, with a mass ratio of Na2CO3 / NaNO3 of 1 to 2.

4. The aerospace window glass according to claim 1, characterized in that, The raw material for SrO is a mixture of SrCO3 and Sr(NO3)2, with a mass ratio of SrCO3 / Sr(NO3)2 of 10 to 15.

5. The aerospace window glass according to claim 1, characterized in that, The thermal expansion coefficient of the aerospace window glass is 3.0 × 10⁻⁶. -6 / ℃~3.8×10 -6 / ℃, thermal shock resistance ΔT / ℃≥200, transmittance in the 450~780nm wavelength range≥90%, lead equivalent ≥0.15mmPb.

6. The method for preparing aerospace window glass according to any one of claims 1-5, characterized in that, Specifically as follows: The raw materials are mixed evenly, melted, clarified, and shaped to obtain a glass block, which is then annealed to obtain the aerospace window glass.

7. The method for preparing aerospace window glass according to claim 6, characterized in that, The melting temperature is 1650℃~1700℃, the melting holding time is 2h~4h, the furnace working gas pressure during clarification is 0.3~0.7 standard atmospheres, the clarification holding time is 0.5h~2h, and the annealing temperature is 700℃~800℃.

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