High-alumina glass and method of making

Abstract

The application belongs to the technical field of glass manufacturing, and particularly relates to high-aluminum glass and a preparation method. The raw material components include SiO2 60.0-70.0%, Al2O3 10.0-20.0%, Na2O 3.0-6.0%, K2O 2.0-5.0%, Li2O 0.0-4.0%, CaO 1.0-5.0%, MgO 0.5-4.0%, ZrO2 1.0-4.0%, TiO2 0.5-3.0%, Y2O3 1.0-3.0%, and B2O3 0.5-1.0% in terms of mass percentage. The application adjusts the dosages of the components of the high-aluminum glass, so that the high-aluminum glass has excellent mechanical properties, a surface compressive stress (CS value) of greater than or equal to 1000 MPa, a stress layer depth (DOL) of greater than or equal to 100 microns, and excellent properties such as high hardness, high light transmittance, scratch resistance, drop resistance and high stability.

Description

Technical Field

[0001] This invention belongs to the field of glass manufacturing technology, specifically a high-alumina glass and its preparation method. Background Technology

[0002] High-alumina glass, due to its excellent mechanical properties, chemical stability, and optical properties, is widely used in touchscreen covers, display devices, and military applications. Most smartphone screens on the market use high-alumina glass, which offers improved mechanical properties compared to ordinary glass. However, it still cannot meet the high strength and hardness requirements of future mobile terminal development. Ordinary soda-lime glass can no longer meet these performance requirements, and even chemical strengthening makes it difficult to improve its performance. As a protective cover glass, it needs to meet performance requirements such as thickness and transparency when in contact with the outside world, while also satisfying requirements such as high strength, high transmittance, pressure resistance, scratch resistance, impact resistance, and chemical stability.

[0003] The mechanical properties of traditional glass are primarily limited by its composition and surface microcracks. Its relatively low hardness makes it easily scratched by hard objects such as keys and grit during daily use, affecting display clarity and aesthetics. More seriously, when devices are accidentally dropped, the glass cover needs to withstand enormous impact stress; traditional glass, due to its insufficient toughness, is prone to breakage, leading to functional failure. Furthermore, consumers' demands for screen visual effects are increasingly higher, requiring cover glass with extremely high light transmittance to ensure accurate color reproduction and vibrant display. Simultaneously, in daily use, cover glass frequently comes into contact with chemicals such as sweat, cosmetics, and cleaning agents; therefore, excellent chemical stability is also crucial to ensuring its long-term appearance and performance stability.

[0004] Therefore, it is of great significance to develop a high-alumina glass that, through component synergistic design and industrially feasible manufacturing process, simultaneously possesses high strength, high transmittance, high impact resistance, and high stability. Summary of the Invention

[0005] To address the above problems, this invention provides a high-alumina glass and its preparation method, which solves the problem that existing high-alumina glass cannot simultaneously achieve high hardness, high light transmittance, scratch resistance, drop resistance, and high stability.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In one aspect, the present invention provides a high-alumina glass, wherein, by mass percentage, its raw material composition includes 60.0-70.0% SiO2, 10.0-20.0% Al2O3, 3.0-6.0% Na2O, 2.0-5.0% K2O, 0.0-4.0% Li2O, 1.0-5.0% CaO, 0.5-4.0% MgO, 1.0-4.0% ZrO2, 0.5-3.0% TiO2, 1.0-3.0% Y2O3, and 0.5-1.0% B2O3.

[0008] Furthermore, the mass ratio of CaO to MgO is 1:0.8-1.5.

[0009] Furthermore, the mass ratio of Y2O3 to B2O3 is 2-3.

[0010] Furthermore, the thickness of the high-alumina glass is 0.5-2mm.

[0011] The composition of each component in the high-alumina glass provided by the present invention is described below.

[0012] SiO2 is an essential component of the glass framework, improving its strength, chemical stability, and enabling it to achieve a low coefficient of thermal expansion. When the SiO2 content is too low, the glass's bulk network structure is poor, resulting in inferior mechanical properties and reduced weather resistance. Conversely, when the content is too high, it reduces the glass's network connectivity, thereby lowering its viscosity and melting temperature, making effective tempering difficult because its stable structure hinders ion migration and the formation of the required surface pressure layer. Therefore, the SiO2 content is controlled between 60.0% and 70.0%.

[0013] Al₂O₃ is the main component for improving the ion exchange performance of glass. It can reduce the tendency of glass crystallization and is also a major component for improving the chemical stability, mechanical strength, and elastic modulus of glass. In the glass microstructure, alumina is a network intermediate oxide, located between the network generator and the network exogenous body. The volume of the aluminum-oxygen tetrahedra formed by Al₂O₃ in glass is larger than that of the silicon-oxygen tetrahedra, causing the glass volume to expand, thereby reducing the glass density. This provides exchange channels for the glass during the ion exchange process, increases the compressive stress layer depth of the glass, and at the same time, high Al₂O₃ concentration glass has a high strain point temperature, thus enabling the glass to maintain a high compressive stress after ion exchange. Therefore, the Al₂O₃ content is controlled at 10.0%~20.0%.

[0014] As an essential component for ion exchange, Na₂O can provide a large amount of Na₂O when the glass contains sufficient Na₂O. + It can react with K in molten salt +Ion exchange occurs, resulting in high compressive stress on the glass surface. Simultaneously, Na₂O provides a large amount of free oxygen, thereby disrupting the Si-O bonds in the silicon-oxygen network structure, reducing the glass's viscosity and melting temperature. K₂O is a component that promotes ion exchange and, among alkali metal oxides, is highly effective in increasing the thickness of the compressive stress layer. Li₂O is one of the main components involved in ion exchange, effectively reducing glass viscosity and melting temperature. + The ionic radius is very small, so it can fill the voids inside the glass and balance free oxygen. In the mixed molten salt of NaNO3 and KNO3 used in this invention, the Li in the glass... + With Na in molten salt + Ion exchange can rapidly achieve a high compressive stress layer depth, giving the glass excellent compressive strength and impact resistance. K₂O, Na₂O, and Li₂O, all alkali metal oxides, can increase the ion exchange rate and deepen the compressive stress layer, and also act as a mesh disruptor, reducing the glass's viscosity and melting temperature. Therefore, the contents of Na₂O, K₂O, and Li₂O are controlled at 3.0–6.0%, 2.0–5.0%, and 0.0–4.0%, respectively, with a total content of 8.0–12.0%.

[0015] CaO can enhance the chemical stability and mechanical strength of glass. However, excessive amounts can easily cause glass crystallization, reducing stability. At high temperatures, the presence of CaO can reduce glass viscosity, facilitating clarification. MgO, as an external component of the glass network, can lower the glass melting temperature and is a good flux, improving the chemical stability of glass. The synergistic use of CaO and MgO can enhance the stability and mechanical strength of glass, but the ratio of their amounts must be strictly controlled. Therefore, the contents of CaO and MgO are controlled at 1.0–5.0% and 0.5–4.0%, respectively.

[0016] ZrO2 helps reduce grain size during crystallization, thereby improving glass transmittance, chemical stability, and ion exchange properties. It also increases surface hardness, making the glass more scratch-resistant and drop-resistant. However, excessive ZrO2 significantly increases the melting temperature and can introduce defects such as inclusions, negatively impacting production. Therefore, the ZrO2 content is controlled between 1.0% and 4.0%.

[0017] TiO2, as a co-solvent, can increase the transparency, gloss, and tensile strength of glass. 4+When ions enter the glass network, they can break the Si-O-Si or Al-O-Al bonds in the glass and form stronger Ti-O bonds with oxygen ions. This stronger bonding makes the glass network structure less prone to deformation when heated, thus significantly reducing the glass's coefficient of thermal expansion. The introduction of TiO2 enhances the density of the glass network. 4+ Ions can fill the gaps in the glass network, making the glass structure more robust and effectively resisting the corrosion of water, acids, alkalis, and other substances. An appropriate amount of TiO2 can also reduce the high-temperature viscosity of high-alumina glass, making it easier to melt and clarify, thus improving its processing performance to some extent. Therefore, the TiO2 content is controlled at 0.5% to 3.0%.

[0018] B₂O₃ is also a glass-forming oxide. It exists in glass as boron-oxygen trigonal [BO₃] and boron-oxygen tetrahedron [BO₄] structural units. It reduces high-temperature viscosity and density, stabilizes the glass, prevents crystallization, and lowers the liquidus temperature. B₂O₃ also accelerates glass dissolution and clarification. B₂O₃ also works synergistically with Y₂O₃, and their ratio must be strictly controlled. Therefore, the B₂O₃ content is controlled at 0.5–1.0%.

[0019] Y₂O₃ is a high-performance additive in glass. Introducing Y₂O₃ into the glass network (usually as a network explant oxide) can "strengthen" the glass structure, making it more resistant to corrosion by media such as water, acids, and alkalis. Strong YO bonds increase the difficulty of atomic movement and rearrangement, thereby raising the temperature (Tg) required for the glass to transition from a solid to a supercooled liquid state. This allows the glass to better maintain its shape and properties at high temperatures. Y₂O₃ can broaden the glass formation range and interact with B₂O₃ to influence the structure. Y₂O₃ can act as a modifier for the transformation from "boron-oxygen trigonal [BO₃]" to "boron-oxygen tetrahedral [BO₄]", changing the [BO₃] / [BO₄] ratio, thereby adjusting the coefficient of thermal expansion and chemical stability. As a network explant oxide, Y₂O₃ can also provide free oxygen, promoting the formation of Al₂O₃. 3+ It exists in the form of [AlO4], thereby strengthening the silicon-oxygen network. Meanwhile, Y... 3+ And Al 3+ All of these elements can occupy the gaps in the glass network, acting as "fillers" and "pinches," making the glass structure denser and stronger, synergistically enhancing the glass network, and significantly improving chemical stability and hardness. Therefore, the content of Y2O3 is controlled at 1.0~3.0%.

[0020] A second aspect of the present invention provides a method for preparing high-alumina glass, the method comprising at least the following steps:

[0021] (1) Weigh the raw materials according to the component ratio, put the raw materials into the mixer and mix them evenly to obtain the batching mixture;

[0022] (2) The ingredients mixture is subjected to high-temperature melting treatment, and a medium-intensity magnetic field is introduced in the later stage of the melting treatment;

[0023] (3) The molten mixture is poured into a mold to form a shape and then annealed to obtain a glass sheet;

[0024] (4) The original glass sheet is strengthened to obtain the high-alumina glass product.

[0025] Furthermore, in step (2), the melting temperature is 1500-1600℃ and the melting time is 4-5h.

[0026] Furthermore, the magnetic field treatment lasts for 20-40 minutes, with a magnetic field strength of 3-4T. The magnetic field can suppress thermal convection in the melt, making the flow smoother, thereby reducing erosion of the refractory material and the formation of streaks, and improving homogenization. The magnetic field can also eliminate bubbles; it may alter the tension at the interface between the molten glass and bubbles or the refractory material, facilitating bubble detachment and growth. The magnetic field also affects the diffusion and arrangement of metal ions, thus influencing the glass properties.

[0027] Furthermore, in step (3), the annealing temperature is 600-700℃ and the annealing time is 2-4h.

[0028] Further, the strengthening treatment operation in step (4) is as follows: the strengthening treatment operation is as follows: the strengthening uses a mixed salt of sodium nitrate and potassium nitrate, the mixing ratio is 1:1-2.5; the strengthening temperature is 350-420℃, and the strengthening time is 1-3h.

[0029] Furthermore, the strengthening process is aided by the application of 2-3 GHz microwave treatment. Microwave energy acts directly on the entire glass, heating both the inside and outside simultaneously at an extremely rapid rate. This shortens the processing time, achieves highly uniform overall heating, and avoids microcracks caused by localized overheating. Microwave assistance allows potassium or sodium ions in the molten salt to penetrate more quickly and deeply into the glass, forming a thicker compressive stress layer (DOL). This means the glass can achieve higher impact resistance, bending resistance, and damage resistance.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] The high-alumina glass provided by this invention achieves excellent mechanical properties by adjusting the amount of each component, especially the mass adjustment of Y2O3 and B2O3, CaO and MgO, and the synergistic combination of other components, and by using magnetic field assistance during the preparation process. The surface compressive stress (CS value) is ≥1000MPa, the stress layer depth (DOL) is ≥100μm, and it also has excellent properties such as high hardness, high light transmittance, scratch resistance, drop resistance and high stability. Attached Figure Description

[0032] Figure 1 This is a photograph of the original glass sheet prepared in Example 1;

[0033] Figure 2 This is a photograph of the high-alumina glass prepared in Example 1. Detailed Implementation

[0034] 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.

[0035] Example 1

[0036] This embodiment discloses a method for preparing high-alumina glass, including the following steps:

[0037] (1) Weigh the raw materials according to the component ratio, put the raw materials into the mixer and mix them evenly to obtain the batching mixture;

[0038] (2) The ingredients mixture is melted at 1600℃ for 4 hours, and a 3T magnetic field is introduced for 30 minutes in the later stage of the melt treatment;

[0039] (3) The molten mixture is poured into a mold and shaped at 900°C, and then annealed at 700°C for 3 hours to obtain the glass sheet;

[0040] (4) The glass substrate was placed in a mixed salt bath of sodium nitrate and potassium nitrate (mass ratio of sodium nitrate to potassium nitrate is 1:1) at 400°C for 1.5 h; microwave assisted treatment at 2 GHz was used during the strengthening process.

[0041] Actual image of the original glass sheet Figure 1 As shown in the image, a physical picture of high-alumina glass (strengthened glass) is as follows. Figure 2 As shown.

[0042] Examples 2-5

[0043] Adjust the dosage of each component, otherwise remain the same as in Example 1. The dosage of each component in Examples 1-5 is shown in Table 1.

[0044] Table 1. Dosage of each component

[0045]

[0046] Comparative Example 1

[0047] Compared to Example 1, the difference is that the strengthening process does not use microwave assistance.

[0048] Comparative Example 2

[0049] Compared to Example 1, the difference is that no magnetic field treatment is used in the later stage of the melt treatment.

[0050] Comparative Example 3

[0051] Compared to Example 1, the difference is that only a mixed salt of sodium nitrate and potassium nitrate was used for strengthening for 3.5 hours.

[0052] Comparative Example 4

[0053] The difference compared to Example 1 is that the Y2O3 content is 1.8%. ， The content of B2O3 is 1.2%, and the mass ratio of Y2O3 to B2O3 is 1.5.

[0054] Comparative Example 5

[0055] The difference compared to Example 1 is that the Y2O3 content is 2.3%. ， B2O3 0.7%.

[0056] Comparative Example 6

[0057] Compared to Example 1, Y2O3 was not used, and SiO2 content was 67%.

[0058] Comparative Example 7

[0059] Compared to Example 1, B2O3 was not used, and SiO2 content was 66%.

[0060] Comparative Example 8

[0061] Compared to Example 1, TiO2 was not used, and SiO2 content was 66%.

[0062] Comparative Example 9

[0063] Compared to Example 1, CaO was not used, and MgO was 3%.

[0064] Comparative Example 10

[0065] Compared to Example 1, MgO is not used, and CaO is 3%.

[0066] Comparative Example 11

[0067] Compared to Example 1, the CaO content was 2% and the MgO content was 1%.

[0068] Comparative Example 12

[0069] Compared to Example 1, the CaO content was 1% and the MgO content was 2%.

[0070] The performance test results of Examples 1-5 and Comparative Examples 1-12 are shown in Table 2-4.

[0071] Table 2 Performance parameter test values ​​of Examples 1-5

[0072]

[0073]

[0074]

[0075] 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 high-alumina glass, characterized in that, The raw materials, by mass percentage, consist of the following components: SiO2 65%, Al2O3 15%, Na2O 4%, K2O 4%, Li2O 4%, CaO 1.5%, MgO 1.5%, ZrO2 1%, TiO2 1%, Y2O3 2%, B2O3 1%. The method for preparing the high-alumina glass includes the following steps: (1) Weigh the raw materials according to the component ratio, put the raw materials into the mixer and mix them evenly to obtain the batching mixture; (2) The ingredients mixture is subjected to high-temperature melting treatment, and a medium-intensity magnetic field is introduced for treatment in the later stage of melting treatment; (3) The molten mixture is poured into a mold to form a shape and then annealed to obtain a glass sheet; (4) The original glass sheet is strengthened to obtain the high-alumina glass product; The magnetic field treatment lasted for 30 minutes, with a magnetic field strength of 3T. The enhancement process is assisted by the application of 2GHz microwave processing; The enhancement treatment in step (4) is as follows: a mixed salt of sodium nitrate and potassium nitrate is used, with a mass ratio of sodium nitrate to potassium nitrate of 1:1; the enhancement temperature is 400℃ and the enhancement time is 1.5h.

2. The high-alumina glass according to claim 1, characterized in that, In step (2), the melting temperature is 1600℃ and the melting time is 4h.

3. The high-alumina glass according to claim 1, characterized in that, In step (3), the annealing temperature is 700℃ and the annealing time is 3h.

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