A microcrystalline glass and a production process thereof

Abstract

The application belongs to the technical field of glass-ceramics, and particularly relates to a glass-ceramic and a production process thereof. According to the application, the glass-ceramic comprises the following components in terms of mole percentage: SiO2 55%-68%, Al2O3 12%-20%, Li2O 8%-15%, Na2O 2%-6%, K2O 0.5%-3%, SnO2 1.5%-5%, P2O5 1%-3%, WO3 0.5%-2%, and a clarifying agent 0.1%-1%. In the preparation of the glass-ceramic, a step-by-step crystallization process is adopted, and particularly, an isostatic pressure of 20-60 MPa is applied in the crystallization stage at 720-800 DEG C, so as to induce in-situ generation of a nano-tungsten bronze phase and inhibit grain coarsening. The main crystal phase of the obtained glass-ceramic is a beta-quartz solid solution, and the secondary crystal phase is a tungsten bronze phase. The glass-ceramic has excellent bending resistance, light transmittance, thermal expansion coefficient and dielectric constant.

Description

Technical Field

[0001] This invention belongs to the field of microcrystalline glass manufacturing technology, specifically a microcrystalline glass and its production process. Background Technology

[0002] With the widespread adoption of smartphones, tablets, and other electronic devices, the demand for larger and thinner touchscreen displays is increasingly prominent, placing higher demands on the mechanical properties of protective glass for electronic devices. While high-alumina glass on the market offers improved mechanical properties compared to ordinary glass, it still cannot meet the high strength and hardness requirements of future mobile terminals. Microcrystalline glass is a type of polycrystalline solid material, produced by controlling the crystallization process during heating using a base glass with a specific composition. It contains a large number of uniformly distributed microcrystalline and glassy phases. Due to the ability to precipitate crystals with special functions, microcrystalline glass possesses a variety of unique properties, such as excellent mechanical properties and good optical properties. However, existing technologies for preparing microcrystalline glass involve adding high-valence metal oxides, which reduces transmittance and limits its application; or the radial distribution of microcrystalline glass is uneven, resulting in large fluctuations in the coefficient of thermal expansion; or aluminum ions are used to form four-coordinate or six-coordinate groups, replacing the SiO4 tetrahedra in the silicate lattice to improve the mechanical strength of the microcrystalline glass, but the bending strength and hardness are relatively low; or the dielectric properties of existing microcrystalline glass cannot meet the needs of mobile terminals.

[0003] Therefore, it is particularly important to develop a new type of microcrystalline glass material with stable crystal phase, low coefficient of thermal expansion, low dielectric constant, high strength, and high light transmittance. Summary of the Invention

[0004] To address the above problems, this invention provides a microcrystalline glass and its manufacturing process, which solves the problems existing in the prior art regarding microcrystalline glass.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a microcrystalline glass, wherein, by molar percentage, the microcrystalline glass comprises the following components: SiO2 55% - 68%, Al2O3 12% - 20%, Li2O 8% - 15%, Na2O 2% - 6%, K2O 0.5% - 3%, SnO2 1.5% - 5%, P2O5 1% - 3%, WO3 0.5% - 2%, clarifying agent 0.1% - 1%.

[0006] The main crystalline phase of the microcrystalline glass is β-quartz solid solution, and the secondary crystalline phase is tungsten bronze structure phase.

[0007] Furthermore, the clarifying agent is at least one of antimony trioxide and cerium dioxide.

[0008] Furthermore, the molar ratio of SnO2:P2O5:WO3 is 1~3:1~2:0.5~1. SnO2, P2O5, and WO3 are composite nucleating agents. In the SnO2-P2O5-WO3 ternary composite nucleating agent, SnO2 provides high-temperature stable nucleation sites; P2O5 promotes liquid-liquid phase separation and increases nucleation density; WO3 generates nanoscale tungsten bronze phase in situ during reducing atmosphere or heat treatment. This phase has low electron affinity and moderate lattice mismatch, which can both induce β-quartz precipitation as heterogeneous nuclei and pin grain boundaries to restrict grain growth, thereby improving the bending strength of glass-ceramics.

[0009] Furthermore, the tungsten bronze phase nanocrystals, with a size of 5-15 nm, are uniformly distributed at the grain boundaries, playing a role in "pinning" and refining the β-quartz grains.

[0010] Further, the molar ratio of WO3 to K2O is 0.4~1.2; preferably, the molar ratio of WO3 to K2O is 0.6~1.9. If the molar ratio is too large, WO3 is in excess, and some WO3 cannot be converted into the tungsten bronze phase, possibly existing as isolated WO3 clusters; if the molar ratio is too small, K2O... + Excess, exceeding the requirements for stabilizing the tungsten bronze phase, excess K + It remains free in the glass phase, reducing the efficiency of chemical strengthening.

[0011] Furthermore, the molar ratio of Al2O3 to Li2O is 0.9~1.6; preferably, the molar ratio is 1.1~1.4. When the molar ratio is too large, Al2O3 is in excess, the viscosity of the glass melt increases significantly, nucleation is difficult, the crystallization rate is insufficient, and the strength improvement is limited; when the molar ratio is too small, Li2O is relatively in excess, the non-bridging oxygen in the glass network increases, resulting in decreased chemical stability, and the grains are prone to overgrowth during the crystallization process, leading to a decrease in light transmittance.

[0012] Furthermore, according to molar percentage, the microcrystalline glass comprises the following components: SiO2 58% - 64%, Al2O3 14% - 18%, Li2O 10% - 13%, Na2O 3% - 5%, K2O 1% - 2%, SnO2 2% - 4%, P2O5 1.5% - 2.5%, WO3 0.8% - 1.5%, clarifying agent 0.2% - 0.5%.

[0013] In a second aspect, the present invention provides a manufacturing process for the microcrystalline glass described in the first aspect, comprising the following steps: (1) Weigh each raw material according to the stated molar percentage and mix them evenly to obtain a mixture; (2) Melt the mixture and stir to obtain a uniform glass melt; (3) The uniform molten glass is poured, shaped, annealed, and cooled to obtain the base glass; (4) The base glass is crystallized and then strengthened to obtain the product.

[0014] Furthermore, in step (2), the melting temperature is 1580-1650℃; the melting time is 6-10 hours.

[0015] Furthermore, in step (3), the annealing temperature is 550-620℃ and the annealing time is 1-3 hours.

[0016] Furthermore, in step (4), the crystallization operation consists of three steps: pre-nucleation, high-pressure crystallization, and annealing. Further, in step (4), the crystallization operation is specifically as follows: First step: heat up to 620℃-680℃ at 1-5℃ / min and hold for 2-6 hours; Second step: continue to heat up to 720℃-800℃, while applying isostatic pressure of 20-60MPa and holding for 1-4 hours; Third step: cool down to 550℃-600℃, release the pressure, hold for 0.5-2 hours, and then cool down to room temperature at 0.5-2℃ / min.

[0017] Furthermore, in step (4), the gas pressure medium is nitrogen or argon.

[0018] Furthermore, in step (4), the enhanced operation is ion exchange in KNO3 molten salt at 400℃-480℃ for 2-6 hours.

[0019] The production process of this invention employs pre-nucleation, high-pressure crystallization, and annealing steps in the crystallization stage, which differs from conventional atmospheric pressure crystallization. The preparation process of this invention can suppress the excessively rapid growth of crystals along preferred orientations, promote isotropic development of grains into nanoscale spheres, and reduce light scattering; it also compresses residual bubbles and micropores in the glass matrix, increases bulk density, and simultaneously achieves higher light transmittance than conventional microcrystalline glass, as well as improves the dielectric constant, coefficient of thermal expansion, flexural strength, and other properties of the glass.

[0020] The beneficial effects of this invention are as follows: This invention employs a SnO2-P2O5-WO3 ternary composite nucleating agent. SnO2 provides high-temperature stable nucleation sites; P2O5 promotes liquid-liquid phase separation and increases nucleation density; WO3 generates nanoscale tungsten bronze phases in situ during reducing atmosphere or heat treatment. This phase has low electron affinity and moderate lattice mismatch, serving both as heteronuclei to induce β-quartz precipitation and pinning grain boundaries to limit grain growth. Furthermore, this invention strictly controls the dosage of each component, such as Al2O3 and Li2O, WO3 and K2O, and other components, improving the product's dielectric constant, coefficient of thermal expansion, flexural strength, and other properties.

[0021] The production process of this invention employs distributed crystallization treatment, which can suppress the excessively rapid growth of crystals along the preferred orientation, promote the isotropic development of grains into nanoscale spheres, reduce light scattering, compress residual bubbles and micropores in the glass matrix, improve bulk density, and simultaneously achieve higher light transmittance than conventional microcrystalline glass, as well as improve the overall performance of the product. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solution, the present invention will be described in detail below with reference to embodiments. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0023] Example 1 A microcrystalline glass, prepared from raw materials comprising the following parts by weight: SiO2 60.8%, Al2O3 16%, Li2O 11%, Na2O 4%, K2O 2%, SnO2 2%, P2O5 2.5%, WO3 1.5%, CeO2 0.2%.

[0024] The specific steps are as follows: (1) Weigh each raw material according to the molar percentage, put them into the mixer, and stir at a speed of 500 r / min to make them evenly mixed to obtain a mixture.

[0025] (2) Place the mixture in a platinum-rhodium crucible and melt it at 1600℃ for 8 hours. Stir to obtain a uniform glass melt.

[0026] (3) Pour the uniform glass liquid into a preheated mold to form it, and then transfer it into an annealing furnace. Anneal at 600°C for 2 hours, and then cool it to room temperature with the furnace to obtain the base glass.

[0027] (4) Heat the base glass to 650°C at 5°C / min and hold for 4 hours; continue heating to 750°C and apply isostatic pressure of 30MPa nitrogen gas, and hold for 2 hours; cool to 600°C, release the pressure, hold for 1 hour, and then cool to room temperature at 1°C / min; place the crystallized glass in KNO3 molten salt at 450°C for ion exchange for 4 hours to obtain the final product.

[0028] Example 2 A microcrystalline glass, prepared from raw materials comprising the following parts by weight: SiO2 62%, Al2O3 14.5%, Li2O 13%, Na2O 2.8%, K2O 1.25%, SnO2 2%, P2O5 2.5%, WO31.5%, CeO2 0.45%.

[0029] The steps are the same as in Example 1.

[0030] Comparative Example 1 Compared with Example 1, the difference is that WO3 is not used in the raw materials, and the corresponding SiO2 increases to 62.3%.

[0031] Comparative Example 2 Compared with Example 1, the difference is that P2O5 is not used in the raw materials, and the corresponding SiO2 increases to 63.3%.

[0032] Comparative Example 3 Compared with Example 1, the difference is that SnO2 is not used in the raw materials, and the corresponding SiO2 content is increased to 62.8%.

[0033] Comparative Example 4 Compared with Example 1, the difference is that Al2O3 is 12% and Li2O is 15%, while the rest are the same as in Example 1.

[0034] Comparative Example 5 Compared with Example 1, the difference is that Al2O3 is 17% and Li2O is 10%, while the rest are the same as in Example 1.

[0035] Comparative Example 6 Compared with Example 1, the difference lies in WO3 0.8% and K2O 2.7%, while the rest are the same as in Example 1.

[0036] Comparative Example 7 Compared with Example 1, the difference lies in WO3 2.05% and K2O 1.45%, while the rest are the same as in Example 1.

[0037] Comparative Example 8 Compared with Example 1, the difference is that in step (4), the isostatic pressure of 30 MPa nitrogen is not applied at the same time.

[0038] Comparative Example 9 Compared with Example 1, the difference lies in SnO2 2%, P2O5 1.5%, WO3 2.5%, and the rest are the same as in Example 1.

[0039] The performance test results of Examples 1-2 and Comparative Examples 1-9 are shown in Table 1.

[0040]

[0041] It should be noted that, in this document, the terms "comprising," "including," and any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Specific examples have been used in this document to illustrate the principles and implementation methods of the present invention. These examples are merely for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be pointed out that, due to the limitations of written expression and the objective existence of infinite specific structures, those skilled in the art can make several improvements, modifications, or variations without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, variations, or combinations, or the direct application of the concept and technical solution of the present invention to other situations without modification, should all be considered within the scope of protection of the present invention.

Claims

1. A microcrystalline glass, characterized in that, According to a molar percentage, the microcrystalline glass comprises the following components: SiO2 55% - 68%, Al2O3 12% - 20%, Li2O 8% - 15%, Na2O 2% - 6%, K2O 0.5% - 3%, SnO2 1.5% - 5%, P2O5 1% - 3%, WO3 0.5% - 2%, clarifying agent 0.1% - 1%; The main crystalline phase of the microcrystalline glass is β-quartz solid solution, and the secondary crystalline phase is tungsten bronze structure phase.

2. The microcrystalline glass according to claim 1, characterized in that, The clarifying agent is at least one of antimony trioxide and cerium dioxide.

3. The microcrystalline glass according to claim 1, characterized in that, The molar ratio of SnO2:P2O5:WO3 is 1~3:1~2:0.5~1.

4. The microcrystalline glass according to claim 1, characterized in that, The nanocrystal size of tungsten bronze phase is 5-15 nm.

5. The microcrystalline glass according to claim 1, characterized in that, The molar ratio of WO3 to K2O is 0.4 to 1.2; preferably, the molar ratio of WO3 to K2O is 0.6 to 1.

9.

6. The microcrystalline glass according to claim 1, characterized in that, The molar ratio of Al2O3 to Li2O is 0.9 to 1.6; preferably, the molar ratio is 1.1 to 1.

4.

7. The method for preparing the microcrystalline glass according to claim 1, characterized in that, Includes the following steps: (1) Weigh each raw material according to the stated molar percentage and mix them evenly to obtain a mixture; (2) Melt the mixture and stir to obtain a uniform glass melt; (3) The uniform molten glass is poured, shaped, annealed, and cooled to obtain the base glass; (4) The base glass is crystallized and then strengthened to obtain the desired product; The crystallization operation is specifically as follows: First step: Heat to 620℃-680℃ at 1-5℃ / min and hold for 2-6 hours; Step 2: Continue heating to 720℃-800℃, while applying isostatic pressure of 20-60MPa, and maintain the temperature and pressure for 1-4 hours; Step 3: Cool to 550℃-600℃, release the pressure, maintain the temperature for 0.5-2 hours, and then cool to room temperature at a rate of 0.5-2℃ / min.

8. The preparation method according to claim 7, characterized in that, In step (2), the melting temperature is 1580-1650℃; the melting time is 6-10 hours.

9. The preparation method according to claim 7, characterized in that, In step (3), the annealing temperature is 550-620℃ and the annealing time is 1-3 hours.

10. The preparation method according to claim 7, characterized in that, In step (4), the enhancement operation is ion exchange in KNO3 molten salt at 400℃-480℃ for 2-6 hours.

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