High-hardness high-crystallinity transparent glass-ceramics and method for preparing the same

Abstract

The application discloses a kind of high-hardness high-crystallinity transparent glass ceramics and preparation method thereof.Glass powder raw materials are weighed, after grinding, melt in platinum rhodium crucible, obtain glass liquid;Wherein the glass powder raw materials are composed of the following mass percentage components:ZnO 0~12wt%, MgO 6~18wt%, Al2O3 22~35wt%, SiO2 40~50wt%, Sb2O3 1~3wt%, nucleating agent 0.5~9wt%;Glass liquid is poured in preheated copper mould, and transparent glass block is obtained;Annealing, cutting and polishing, and the precursor glass with a thickness of 2mm is obtained;The precursor glass is placed between electrode sheets, first nucleation temperature at 700~900℃ is kept for 1~10h, then crystallization temperature at 900~1150℃ is kept for 2~8h, and transparent glass ceramic is prepared.The application realizes controllable crystallization by controlling crystallization time and temperature, and the crystallinity of glass ceramic is greater than or equal to 85%, and it has good optical quality and transmittance, and the transmittance of glass ceramic with a thickness of 1.5mm at 800nm is greater than or equal to 86.5%.

Description

Technical Field

[0001] This invention relates to the field of glass-ceramic preparation technology, specifically to a high-hardness, high-crystallinity transparent glass-ceramic and its preparation method. Background Technology

[0002] Glass-ceramics, as important materials, possess excellent mechanical properties, high heat resistance, good chemical stability, good optical properties, and flexible design. Among them, spinel-based glass-ceramics are a class of materials with excellent optical and mechanical properties, showing broad application prospects in flat panel displays, photovoltaic substrates, high-temperature optical windows, lasers, and medical fields. The uneven size, large refractive index differences, and morphology of precipitated crystals in glass-ceramics all affect the transmittance of glass-ceramics. Therefore, adjusting the raw material formulation and ratio, improving the sintering process and regime, and using appropriate dopants to promote uniform grain size and distribution can enhance the transparency and mechanical properties of glass-ceramics.

[0003] Numerous studies have investigated spinel-based glass ceramics with the aim of controlling the luminescence of fluorescent ceramics. One such study (ZnO-Al2O3-SiO2 glass ceramics: Influence of composition on crystal phases, crystallite size and appearance, 2021, 120481) achieved nanoscale grain sizes. However, other phases such as Zn2SiO4 and Zn2Ti3O8 may appear, resulting in significant differences in refractive index between these phases. This leads to the opacity of the fabricated glass ceramics, and the hardness of these glass ceramics has not been explored. The literature (Crystallization behavior and properties of ZnO-MgO-Al2O3-SiO2 transparent glass-ceramics with SnO2 and ZrO2 asnucleating agents, 2024, 23150-23056) prepared transparent ZnO-MgO-Al2O3-SiO2 (ZMAS) microcrystalline glass using ZrO2 and SnO2 as nucleating agents through melting and two-step heat treatment. SnO2 promoted the formation of ZrO2 nanocrystals, providing nucleation sites for subsequent crystallization, and the Vickers hardness was 8.28 MPa. However, with the increase of crystallization temperature, the transparency of the glass-ceramics decreased, and it was impossible to obtain highly crystalline transparent glass-ceramics. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing high-hardness, high-crystallinity, transparent glass-ceramics.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing high-hardness, high-crystallinity transparent glass-ceramics, comprising the following steps:

[0006] (1) Weigh the glass powder raw material, grind the glass powder for 0.5 to 2 hours, add it to a platinum-rhodium crucible, and melt it at 1500 to 1750°C for 2 to 4 hours to obtain glass liquid; wherein the glass powder raw material is composed of the following components in mass percentage: ZnO 0 to 12 wt%, MgO 6 to 18 wt%, Al2O3 22 to 35 wt%, SiO2 40 to 50 wt%, Sb2O3 1 to 3 wt%, nucleating agent 0.5 to 9 wt%;

[0007] (2) Pour the molten glass into a preheated copper mold to obtain a transparent glass block;

[0008] (3) Anneal the glass block to obtain the precursor glass, and cut and polish the precursor glass. The glass thickness is 2mm.

[0009] (4) Place the precursor glass between the electrode sheets, first keep it at a nucleation temperature of 700-900℃ for 1-10h, then keep it at a crystallization temperature of 900-1150℃ for 2-8h, and take it out after cooling to room temperature to prepare transparent glass ceramic.

[0010] Preferably, in step (1), the heating rate of the lifting furnace is 5 to 20 °C / min.

[0011] Preferably, the nucleating agent in step (1) is selected from one or more of P2O5, ZrO2, TiO2, Eu2O3, and CeO2.

[0012] Preferably, in step (2), the preheating temperature of the preheated copper mold is 300-600℃.

[0013] Preferably, in step (4), the glass is air-annealed at 500-800°C for 4-10 hours.

[0014] Preferably, in step (4), the glass is placed between the anode and cathode of the electrode sheet, and the electric field strength is 300-1000V / cm. When the temperature inside the furnace rises to the crystallization temperature, the power is turned on and maintained at the target electric field strength until the crystallization time ends.

[0015] Preferably, step (4) further includes milling and polishing the crystallized glass ceramic, the glass ceramic having a thickness of 1.5 mm.

[0016] Residual glass in glass-ceramics can act as a grain connector. Properly controlling the content of residual glass can improve the hardness of glass-ceramics. Simultaneously, during crystallization, as the crystallization rate increases, the content of alkaline earth metal ions in the residual glass decreases, thereby increasing the viscosity of the residual glass, enhancing the connection between grains, and improving the hardness of the glass-ceramic. Adding an appropriate amount of nucleating agent promotes uniform crystal nucleus formation, thus improving grain uniformity. Applying an electric field to both ends of the glass during crystallization helps refine the grains, thereby improving the transmittance of the glass-ceramic.

[0017] On the other hand, the present invention also provides a high-hardness, high-crystallinity transparent glass-ceramic prepared by the above-described preparation method. The glass-ceramic mainly comprises zinc-aluminum spinel and magnesium-aluminum spinel, as well as a residual glass phase that serves as a bonding element.

[0018] The glass-ceramic particles have a size of 20–100 nm, forming a dense structure between crystalline phases. The addition of nucleating agents effectively lowers the melting and crystallization temperatures of the glass, facilitating crystalline phase formation and improving glass stability. It is transparent in the visible light range; a 1.5 mm thick glass-ceramic exhibits a transmittance of ≥86.5% at 800 nm. The nucleating agents provide additional nucleation sites, making it easier for crystal nuclei to form during the cooling process of the glass melt, and also allowing control over the grain size and distribution in the final glass-ceramic.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The transparent glass-ceramic prepared by this invention achieves controllable crystallization through a two-step crystallization process by controlling the crystallization time and temperature. The nucleating agent provides additional nucleation sites, and the grain size and uniformity can be controlled by adjusting the crystallization conditions, thereby enhancing the mechanical properties of the material. The crystallinity of the glass-ceramic is ≥85%.

[0021] (2) During the crystallization process, an electric field is applied to the glass provided by this invention, which is beneficial to the formation of the spinel phase. The resulting grains are small and uniform, thus the glass-ceramic exhibits good optical quality and transmittance. A 1.5mm thick glass-ceramic has a transmittance ≥86.5% at 800nm. The remaining glass phase contains Zn... 2+ Mg 2+ Reducing the viscosity of the glass increases the viscosity of the residual glass, which is beneficial to improving the mechanical properties of glass ceramics.

[0022] (3) Based on mature glass forming technology, transparent glass ceramics can be obtained by heat treatment of precursor glass. The process is simple, efficient and has high crystallinity. Large-size transparent glass ceramics can also be prepared by this method. Attached Figure Description

[0023] Figure 1Transmittance diagrams of the transparent glass ceramics prepared in Examples 1-4 of this invention;

[0024] Figure 2 SEM image of the transparent glass-ceramic prepared in Example 1 after hydrofluoric acid etching;

[0025] Figure 3 The XRD pattern of the transparent glass-ceramic prepared in Example 1;

[0026] Figure 4 Vickers hardness diagrams of the transparent glass-ceramics prepared in Examples 1-4. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0028] The raw material powders used in the following examples are all commercially available products with a purity greater than 99.9%.

[0029] Example 1

[0030] (1) Weigh the glass powder raw materials according to the following mass percentages: ZnO 10wt%, MgO 15wt%, Al2O3 25wt%, SiO2 45wt%, Sb2O3 1wt%, nucleating agent P2O5 2wt%, nucleating agent Eu2O3 2wt%. Grind the glass powder for 1.5h and mix it evenly. Add it to a platinum-rhodium crucible and place it in a lifting furnace. The heating rate is 10℃ / min. Melt it at 1650℃ for 2h to obtain glass liquid.

[0031] (2) Pour the molten glass into a copper mold preheated to 450°C to form a transparent glass block;

[0032] (3) The glass block was annealed at 700℃ for 4 hours to obtain the precursor glass, and the precursor glass was cut and polished with a thickness of 2mm.

[0033] (4) The precursor glass was placed between the electrode plates with an electric field strength of 400V / cm. It was first kept at a nucleation temperature of 780℃ for 4h, and then kept at a crystallization temperature of 980℃ for 1.5h. After cooling to room temperature, it was taken out and the glass ceramic surface was milled and polished to a thickness of 1.5mm to obtain transparent glass ceramic with a crystallinity of 86%.

[0034] Figure 1The transmittance curve for the transparent glass-ceramic prepared in this embodiment shows that the ceramic has a transmittance of 86.5% at 800 nm, indicating high transmittance. The sample without a nucleating agent exhibits uneven grain size, leading to abnormal grain growth during crystallization and resulting in a lower transmittance of 67.4%. Due to the lack of additional nucleating sites provided by the nucleating agent, the glass crystallinity is also low, at 72.4%.

[0035] Figure 2 The image shows a SEM image of the transparent glass-ceramic prepared in this embodiment after hydrofluoric acid etching. The grain size is uniform, ranging from 20 to 40 nm.

[0036] Figure 3 The XRD pattern of the transparent glass-ceramic prepared in this embodiment shows that the main generated crystalline phases are magnesium aluminum spinel and zinc aluminum spinel, and there is also a residual glass phase that plays a connecting role.

[0037] Figure 4 The Vickers hardness of the transparent glass-ceramic prepared in this embodiment reaches 9.1 GPa.

[0038] Example 2

[0039] (1) Weigh the glass powder raw materials according to the following mass percentages: ZnO 8wt%, MgO 16wt%, Al2O3 30wt%, SiO2 40wt%, Sb2O3 1wt%, nucleating agent TiO2 5wt%. Grind the glass powder for 2 hours and mix it evenly. Add it to a platinum-rhodium crucible and place it in a lifting furnace. The heating rate is 5℃ / min. Melt it at 1600℃ for 3 hours to obtain glass liquid.

[0040] (2) Pour the molten glass into a copper mold preheated to 500°C to form a transparent glass block;

[0041] (3) The glass block was annealed at 750℃ for 6 hours to obtain the precursor glass. The precursor glass was then cut and polished to a thickness of 2mm.

[0042] (4) The precursor glass was placed between the electrode plates with an electric field strength of 600 V / cm. It was first kept at a nucleation temperature of 790℃ for 6 hours, and then kept at a crystallization temperature of 950℃ for 2 hours. After cooling to room temperature, it was taken out and the glass ceramic surface was milled and polished to a thickness of 1.5 mm to obtain transparent glass ceramic with a crystallization rate of 88%.

[0043] The transmittance curve and SEM of the transparent glass-ceramic prepared in this embodiment are similar to those in Example 1. The grain size is 25-45 nm and the Vickers hardness reaches 11.0 GPa.

[0044] Example 3

[0045] (1) Weigh the glass powder raw materials according to the following mass percentages: ZnO 12wt%, MgO 12wt%, Al2O3 26wt%, SiO2 42wt%, Sb2O3 2wt%, nucleating agent TiO2 2wt%, nucleating agent ZrO2 2wt%, nucleating agent Eu2O3 1wt%, nucleating agent CeO2 1wt%. Grind the glass powder for 3 hours and mix it evenly. Add it to a platinum-rhodium crucible and place it in a lifting furnace. The heating rate is 15℃ / min. Melt it at 1680℃ for 2 hours to obtain glass liquid.

[0046] (2) Pour the molten glass into a copper mold preheated to 550°C to form a transparent glass block;

[0047] (3) The glass block was annealed at 780℃ for 5 hours to obtain the precursor glass. The precursor glass was then cut and polished to a thickness of 2mm.

[0048] (4) The precursor glass is placed between the electrode sheets with an electric field strength of 800V / cm. It is first kept at a nucleation temperature of 800℃ for 2h, and then kept at a crystallization temperature of 940℃ for 2h. After cooling to room temperature, it is taken out and the glass ceramic surface is milled and polished to a thickness of 1.5mm to obtain transparent glass ceramic with a crystallinity of 90%.

[0049] The transmittance curve and SEM of the transparent glass-ceramic prepared in this embodiment are similar to those in Example 1. The grain size is 30-50 nm and the Vickers hardness reaches 10.0 GPa.

[0050] Example 4

[0051] (1) Weigh the glass powder raw materials according to the following mass percentages: ZnO 12wt%, MgO 12wt%, Al2O3 24wt%, SiO2 44wt%, Sb2O3 2wt%, nucleating agent TiO2 2wt%, nucleating agent ZrO2 2wt%, nucleating agent P2O5 2wt%. Grind the glass powder for 3 hours and mix it evenly. Add it to a platinum-rhodium crucible and place it in a lifting furnace. The heating rate is 10℃ / min. Melt it at 1680℃ for 4 hours to obtain glass liquid.

[0052] (2) Pour the molten glass into a copper mold preheated to 500°C to form a transparent glass block;

[0053] (3) The glass block was annealed at 780℃ for 10 hours to obtain the precursor glass. The precursor glass was then cut and polished to a thickness of 2mm.

[0054] (4) The precursor glass was placed between the electrode plates with an electric field strength of 700V / cm. It was first kept at a nucleation temperature of 820℃ for 2 hours, and then kept at a crystallization temperature of 960℃ for 2 hours. After cooling to room temperature, it was taken out and the glass ceramic surface was milled and polished to a thickness of 1.5mm to obtain transparent glass ceramic with a crystallinity of 89%.

[0055] The transmittance curve and SEM of the transparent glass-ceramic prepared in this embodiment are similar to those in Example 1. The grain size is 30-70 nm and the Vickers hardness reaches 9.5 GPa.

[0056] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-hardness, high-crystallinity transparent glass-ceramic, characterized in that, The glass-ceramic mainly comprises zinc aluminum spinel and magnesium aluminum spinel, as well as a residual glass phase that serves as a bonding agent; the glass-ceramic is prepared through the following steps: (1) Weigh the glass powder raw material, grind the glass powder for 0.5-2 hours, add it to a platinum-rhodium crucible, place it in a lifting furnace, and melt it at 1500-1750℃ for 2-4 hours to obtain glass liquid; wherein the glass powder raw material is composed of the following components in mass percentage: ZnO 8-12wt%, MgO 12-18wt%, Al2O3 22-35wt%, SiO2 40-45wt%, Sb2O3 1-3wt%, nucleating agent 4-9wt%; the nucleating agent is selected from one or more of P2O5, ZrO2, TiO2, Eu2O3, and CeO2; (2) Pour the molten glass into a preheated copper mold to obtain a transparent glass block; (3) Anneal the glass block to obtain the precursor glass, and cut and polish the precursor glass. The glass thickness is 2mm. (4) Place the precursor glass between the anode and cathode of the electrode sheet, first keep it at a nucleation temperature of 700-900℃ for 1-10h, then keep it at a crystallization temperature of 900-1150℃ for 2-8h. When the temperature rises to the crystallization temperature, turn on the power supply and maintain it at the target electric field strength of 300-1000 V / cm until the crystallization time ends. After cooling to room temperature, take it out to prepare transparent glass ceramic.

2. The high-hardness, high-crystallinity transparent glass-ceramic according to claim 1, characterized in that, In step (1), the heating rate of the lifting furnace is 5 to 20 °C / min.

3. The high-hardness, high-crystallinity transparent glass-ceramic according to claim 1, characterized in that, In step (2), the preheating temperature of the copper mold is 300-600℃.

4. The high-hardness, high-crystallinity transparent glass-ceramic according to claim 1, characterized in that, In step (3), the glass block is annealed in air at 500-800°C for 4-10 hours.

5. The high-hardness, high-crystallinity transparent glass-ceramic according to claim 1, characterized in that, Step (4) also includes milling and polishing the crystallized glass ceramic, which has a thickness of 1.5 mm.

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