Cuttable composite-phase mica glass and preparation process thereof

Abstract

The application discloses cuttable composite-phase mica microcrystalline glass and a preparation process thereof, and belongs to the technical field of microcrystalline glass. The technical scheme is as follows: the components include the following components in parts by weight: SiO2 37-46 parts, Al2O3 19-21 parts, MgO 11-13 parts, MgF2 7-9 parts, BaO 3-5 parts, CaO 3-5 parts, K2O 3-5 parts, ZnO 3-4 parts, CeO2 3-4 parts, ZrO2 2.5-3.5 parts, TiO2 1-2 parts, V2O5 0.5-1.5 parts and Li2O 0.5-1.5 parts. The glass components are reasonably designed, the glass presents a composite phase, and finally the cuttable composite-phase microcrystalline glass with high transparency, high hardness, high strength, excellent impact resistance and easy mechanical processing is prepared.

Description

Technical Field

[0001] This invention relates to the field of glass-ceramic technology, specifically to a machinable composite phase mica glass-ceramic and its preparation process. Background Technology

[0002] Glass-ceramics, also known as microcrystalline glass, are non-porous composite materials made from suitable glass raw materials through controlled crystallization via heat treatment. They consist of microcrystalline particles and a glassy phase. While their microstructure, properties, and production methods differ from ordinary glass and ceramics, they also combine the advantages of both. Microcrystalline glass possesses many excellent properties, such as superior electrical, mechanical, optical, and thermodynamic properties. It exhibits a wide range of expansion coefficients, high mechanical strength, good chemical and thermal stability, high operating temperature, and is hard and wear-resistant. Therefore, microcrystalline glass is widely used in defense, aerospace, construction, electronics, optics, chemical engineering, machinery, and everyday life as structural, technical, optical, and electrical insulating materials.

[0003] Microcrystalline glass can be classified in different ways depending on the classification criteria. Based on the principle of microcrystallization, it can be divided into photosensitive microcrystalline glass and thermosensitive microcrystalline glass. Based on appearance, it can be divided into transparent microcrystalline glass and opaque microcrystalline glass. Based on performance, it can be divided into various types of microcrystalline glass, such as those with high temperature resistance, thermal shock resistance, high strength, high hardness and wear resistance, easy machining, easy chemical etching, corrosion resistance, low expansion, zero expansion, low dielectric loss, and strong dielectric properties. Based on the characteristics of the oxides it contains, it can be divided into microcrystalline glass containing Li₂O, Na₂O, MgO, B₂O₃, BaO, or PbO, and those without alkali or silica. Based on the composition of the base glass, it can be divided into five major categories: silicate, aluminosilicate, borosilicate, borate, and phosphate microcrystalline glass.

[0004] Machinable glass-ceramics are a new type of glass-ceramic developed in recent years. They refer to glass-ceramics that can be processed using methods or machinery similar to those used for ordinary metals. They not only possess the superior properties of general glass-ceramics but also have excellent machinability, thus expanding the application areas of glass-ceramics.

[0005] With the continuous expansion of the application range of machinable glass-ceramics, the development of modern high-tech industries has put forward more stringent requirements for the performance of machinable glass-ceramics, making the research and development of high-performance machinable glass-ceramics increasingly urgent. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a machinable composite phase mica microcrystalline glass and its preparation process. By rationally designing the glass composition, the composite phase is made to finally prepare a machinable composite phase microcrystalline glass with high transparency, high hardness, high strength, excellent impact resistance and easy machining.

[0007] The technical solution of this invention is as follows:

[0008] This invention provides a machinable composite phase mica microcrystalline glass, comprising the following components in parts by weight: 37-46 parts SiO2, 19-21 parts Al2O3, 11-13 parts MgO, 7-9 parts MgF2, 3-5 parts BaO, 3-5 parts CaO, 3-5 parts K2O, 3-4 parts ZnO, 3-4 parts CeO2, 2.5-3.5 parts ZrO2, 1-2 parts TiO2, 0.5-1.5 parts V2O5, and 0.5-1.5 parts Li2O.

[0009] Preferably, the components include the following parts by weight: 38.5 parts SiO2, 19.5 parts Al2O3, 11 parts MgO, 7 parts MgF2, 4 parts BaO, 3 parts CaO, 4 parts K2O, 3.5 parts ZnO, 3.5 parts CeO2, 2.5 parts ZrO2, 1 part TiO2, 1.5 parts V2O5, and 1 part Li2O.

[0010] SiO2, as a network-forming oxide, is an essential component of the BaMg[Ti2Al2O3Si2O3]F2 machinable composite mica microcrystalline glass of this invention. With a coordination number of 4, each silicon ion exists surrounded by four oxygen ions, forming a silicon-oxygen tetrahedron [SiO4]. SiO2 significantly influences the amount of crystallization, melting temperature, and chemical stability of the glass.

[0011] Al₂O₃ is an intermediate oxide that can participate in the formation of a glass network, expanding the region for transparent glass formation. However, when its content is too low or too high, it reduces the stability of the glass and makes it prone to devitrification. Aluminum ions and oxygen can form tetracoordinate [AlO₄] and hexacoordinate [AlO₆] groups. In Al₂O₃, [AlO₄] reacts with KMgSi₃O₃. 10 The F2 reaction produces KMg[Al2O3Si2O3]F2, which reduces the glass's crystallization tendency and rate, lowers its coefficient of thermal expansion, and improves its viscosity, surface tension, softening temperature, chemical stability, thermal stability, and mechanical strength, making it the most effective glass stabilizer. Increasing the Al2O3 content raises the glass's melting temperature; further increasing the Al2O3 content also facilitates the precipitation of the BaMg[Ti2Al2O3Si2O3]F2 composite phase, and allows for the acquisition of mica crystals in various morphologies.

[0012] MgO primarily functions as a modifier oxide, but can also act as an intermediate oxide. It can reduce the high-temperature viscosity of glass while improving its mechanical strength and chemical stability. Simultaneously, MgO has a complex effect on glass viscosity: above 900℃, it decreases the viscosity of molten glass; however, between 750-900℃, it tends to increase the viscosity. MgO also significantly influences the crystallization tendency of glass; increasing the crystallization temperature favors MgO. 2+ migration, Mg 2+ The migration of KMgSi3O accelerates the reaction of alkaline earth metal oxides such as BaO, thereby inducing the formation of the BaOAl2O32SiO2 crystal phase. 10 The formation of F2 and BaOAl2O32SiO2 crystalline phases makes the microstructure of the machinable glass-ceramic of the present invention interwoven, thereby improving the machinability of the glass-ceramic.

[0013] In this invention, F in MgF2 - The radius is 0.136 nm, and O 2- The radius is close to 0.140 nm, therefore only two F... - Replace an O 2- Only then can electrical neutralization be achieved, which structurally corresponds to two silicon-fluorine bonds (≡Si-F) replacing one silicon-oxygen bond (≡Si-O-Si≡). The presence of the ≡Si-F group often results in significant phase separation in the glass-ceramic, creating favorable conditions for phase nucleation and growth during the heat treatment process. Because MgF2 is an effective nucleating agent for the composite crystal of this invention, MgF2 preferentially precipitates from the melt during the furnace cooling process of the glass melt. The MgF2 crystal serves as the nucleation center of the glass of this invention, providing nucleation sites for the growth of the BaMg[Ti2Al2O3Si2O3]F2 composite phase crystal.

[0014] K₂O is a network-modifying ion that causes breakage in the continuous glass network structure; K + It fills the pores or gaps in the disordered network structure. Simultaneously, the introduction of K₂O increases the number of cations in the glass, making it easier to form the basic unit [KMgSi₃O] of this invention. 10 [F2] This causes changes in the composite crystalline phase of the material system. Adding an appropriate amount of K2O can increase the oxygen supply and promote overall crystallization. K2O has a very low melting point and acts as a flux, significantly reducing the melting temperature; however, excessive K2O content can affect the overall crystallization of the glass, thus impacting its machinability.

[0015] With K + The introduction of ions leads to an increase in the number of non-bridging oxygen atoms in the melt, Al 3+ Tends to form [AlO 4 / 2 ]- Group, neighboring K + Ions are attracted by the negatively charged aluminum oxide group to form [AlO] 4 / 2 [K] complex. This complex reacts with [SiO] 4 / 2 Tetrahedrons have excellent compatibility. K + The introduction of ions forms [AlO] 4 / 2 K complex, [AlO 4 / 2 ] and [AlO 4 / 2 The mixing of K structural units enters the silicon-rich phase, causing the formation of the mica structural group [AlSiO3].

[0016] Alkaline earth metal oxides like BaO also act as network modifiers in glasses, typically increasing the number of non-bridging oxygen atoms when added to the glass network. Adding a small amount of BaO reduces the number of non-bridging oxygen atoms in the glass network, thus stabilizing the structure. The resulting folkin mica KMgSi3O... 10 BaO is added to F2 to form divalent Ba. 2+ Alternative to fluorinated phlogopite KMgSi3O 10 K between layers in F2 + As a composite network modifier, it promotes the formation of [AlSiO3] groups, laying the foundation for the formation of the mica phase, improving interlayer bonding, and resulting in a compact mica structure. Therefore, fluorinated phlogopite-type barium mica BaMgSi3O 10 F2 is a fluorinated phlogopite (KMgSi3O) 10 F2 has high strength and does not affect the machinability of glass-ceramics.

[0017] On the one hand, CaO can provide free oxygen to the glass, widening the glass-forming range; on the other hand, as a network modifier, CaO can alter the network structure of the glass-ceramic. The glass transition temperature and softening temperature of the glass-ceramic both decrease with increasing CaO content, while the thermal stability of the glass increases. This indicates that the addition of CaO significantly improves the crystallization characteristics of the glass-ceramic, reconciling the contradiction between the initial state of the glass and its crystallization properties. It further reduces the continuity of the glass network structure, thereby altering its crystallization characteristics and ultimately enabling it to meet the performance requirements of machinable glass-ceramics.

[0018] Ca 2+ Mg 2+ and K 2+ In this invention, ions act as network modifiers, primarily existing in the interstices of the glass network, inducing the formation of non-bridging oxygen. This can break the continuous glass network, weakening the Si-O bonds within the network, increasing the glass's immiscibility, facilitating phase separation, and resulting in superior mechanical properties.

[0019] CeO2 decomposes at high temperatures, releasing oxygen. This oxygen enters the bubbles within the molten glass, lowering the partial pressure of the gas in the bubbles and causing them to continue absorbing gas. This increases the volume of the small bubbles in the glass, allowing them to escape from the surface. Therefore, CeO2 plays a certain role in clarifying and homogenizing during the glass melting process. The relevant chemical reaction equations are as follows:

[0020] 2CeO2→Ce2O3+[O]↑

[0021] 2Ce₂O₃ + O₂ → 4CeO₂

[0022] The nucleation and crystallization effects of ZrO2 are very significant; its addition can effectively promote [KMgSi3O] 10 Precipitation of F2] crystals, [KMgSi3O 10 [F2] The ZrO2 content is the basic crystalline phase of machinable glass-ceramics. The higher the ZrO2 content, the more significant the promoting effect on mica crystal precipitation. With the increase of ZrO2 content, the density of the glass-ceramics also increases, mainly because the addition of ZrO2 effectively promotes the densification process of the glass-ceramics, refining the grain size and thus increasing the density. ZrO2 can also improve the mechanical properties of glass-ceramics, which can be attributed to two aspects: first, it inhibits the further growth of precipitated crystals, as smaller grains generally result in higher strength; second, due to the phase transformation toughening effect of ZrO2 itself, when the material is subjected to external force, the tensile stress generated near the crack tip weakens the matrix's binding of tetragonal zirconia, causing it to transform into a monoclinic phase. The resulting volume expansion further reduces the stress at the crack tip, thus requiring a higher stress for the crack to propagate until fracture, thereby improving the fracture toughness of the glass-ceramics.

[0023] TiO2 is an intermediate oxide; at high temperatures, Ti... 4+ and O 2- It readily forms [TiO4] tetrahedra and exhibits good compatibility with the glass framework structure of [SiO4] tetrahedra, thus allowing it to exist stably within the glass network. Fluorophytic barium mica (BaMgSi3O) 10 The extra Ba in F2 2+ O in the [TiO4] tetrahedron 2- A coordination reaction occurs, producing

[0024] The BaMg[Ti2Al2O3Si2O3]F2 composite crystalline phase forms a titanium-rich composite phase. The addition of TiO2 results in a relatively low viscosity of the molten glass and a lower atomic diffusion activation energy, making atoms more prone to migration and promoting nucleation and crystallization. CeO2 alone cannot act as a nucleating agent, but together with TiO2, it can promote crystallization.

[0025] V₂O₅, as a network-forming oxide, has a low melting point. V₂O₅ can significantly reduce the surface tension of glass, achieving a suitable viscosity for nucleation at lower temperatures, thus enabling the production of numerous crystal nuclei. Furthermore, due to the V₂O₅... 5+ The small ionic radius has minimal impact on the migration rates of other ions, allowing the crystal to grow at nucleation sites even at slightly higher temperatures, thus promoting overall crystallization. When V₂O 5、 When TiO2 and ZrO2 are used as composite nucleating agents, they increase the solubility in glass, which facilitates the precipitation of the crystalline phase in glass-ceramics. After crystallization, the flexural strength of the machinable composite phase glass-ceramics containing BaMg[Ti2Al2O3Si2O3]F2 is significantly improved.

[0026] Li₂O is primarily used to suppress the precipitation of Li₂SiO₃ crystals, allowing the glass to form as much of the BaMg[Ti₂Al₂O₃Si₂O₃]F₂ composite phase crystal as possible. Without Li₂O, the glass crystallizes naturally, containing the process byproduct Li₂SiO₃ crystals, which affects the formation of the composite crystal. When the Li₂O content exceeds 1%, it may also inhibit the precipitation of other crystalline phases, affecting the mechanical strength of the glass. Overall, adding an appropriate amount of Li₂O is beneficial for improving the fracture toughness of glass-ceramics.

[0027] The forming principle of float glass is to suspend molten glass, which has been melted at high temperature, on a molten metal with a higher density. Gravity and surface tension give the glass a smooth and flat surface without polishing. Then, through a cooling and hardening process, glass with a surface close to that of a polished glass is obtained.

[0028] The preparation process of the machinable composite phase mica microcrystalline glass of the present invention includes the following steps: batching, melting, clarification and homogenization, annealing, rapid cooling, nucleation, and crystallization. The float glass forming process for microcrystalline glass is not significantly different from that for ordinary glass, both being formed on molten tin. During the forming process, a drawing machine is typically used to apply a certain traction force to the glass strip to control its thickness and width, thereby obtaining glass products with different widths and thicknesses. Compared with other processes, the float glass process can achieve glass forming through horizontal drawing and can produce glass products with better polishing effects.

[0029] The float glass microcrystalline process also has many advantages: the float glass production line is shorter than other processes, and its length is adjustable, allowing for the production of microcrystalline glass of different sizes, even large sizes; it has a high level of mechanization and automation, with a long continuous working cycle and stable production; the transverse temperature of the glass is more uniform, and crystallization is uniform and stable during crystallization in the tin bath, resulting in good product quality; it has a large output, high production efficiency, many varieties, low cost, and low equipment maintenance costs; in the float glass process, the glass float polishing process is achieved on the molten tin, and under the action of the molten tin, its surface is flat and smooth, achieving the effect of mechanical polishing.

[0030] Preferably, the preparation method of the machinable composite phase mica microcrystalline glass of the present invention specifically includes the following steps: each component is prepared into a batch, mixed evenly and poured into a glass melting furnace, the molten glass is clarified and homogenized and then flows into a tin bath filled with protective gas (N2), under the combined action of surface tension and its own gravity, it is spread and polished on the tin surface to become a glass ribbon with a flat surface and uniform thickness, then annealed in an annealing furnace and then rapidly cooled, followed by nucleation and crystallization.

[0031] Preferably, the nucleation temperature is 650-700℃ and the crystallization temperature is 850-950℃.

[0032] Preferably, in the glass furnace, the melting temperature is 1250-1450℃ and the clarification and homogenization temperature is 1500-1650℃.

[0033] Preferably, the annealing temperature in the annealing furnace is 550-600℃.

[0034] Microcrystalline glass, by adjusting its composition, alters the thermodynamic and kinetic conditions of the glass, causing the nucleation and crystal growth kinetic curves to partially overlap, such as... Figure 15 The image shows a one-step glass heat treatment process. This one-step process allows nucleation and crystal growth to occur simultaneously within a specific temperature range. In this process, the melting temperature is 1250-1650℃, the annealing temperature is 550-600℃, and after annealing, the glass is rapidly cooled. Subsequently, the temperature is increased to 1000-1100℃ at a rate of 3-5℃ / min for crystallization. After cooling, the glass is cut to obtain the finished product.

[0035] The nucleation and crystal growth of glass-ceramics each have their own kinetic curves. For typical glass-ceramics, the nucleation rate is highest at a certain temperature above Tg (the glass transition point; crystallization occurs in a supercooled state above Tg). Afterward, as the temperature rises, the nucleation rate decreases sharply, gradually reaching a maximum crystal growth rate, which is much higher than the temperature at which the nucleation rate reaches its maximum. The crystal growth temperature is generally about 100-200°C higher than the nucleation temperature. Therefore, during heat treatment crystallization, this invention first nucleates at a lower temperature and then raises the temperature to allow the nuclei to grow, i.e., a two-step heat treatment process (e.g., ...). Figure 14 (As shown). The two-step heat treatment process results in faster crystal nucleation, more crystal nuclei, and no formation of impurity phases. The more crystal nuclei there are, the more favorable it is for the formation of the BaMg[Ti2Al2O3Si2O3]F2 crystal phase, and the better the machinability of the glass-ceramic.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] 1. This invention, through the rational design of the glass composition, enables it to exhibit a BaMg[Ti2Al2O3Si2O3]F2 composite phase, utilizing MgF2 crystals as nucleation centers to provide nucleation sites for the growth of the BaMg[Ti2Al2O3Si2O3]F2 composite phase crystals; V2O 5、 TiO2 and ZrO2 act as composite nucleating agents, increasing the solubility in the glass and promoting the precipitation of the microcrystalline phase. Ultimately, this results in a machinable composite microcrystalline glass with high transparency, high hardness, high strength, excellent impact resistance, and easy machining.

[0038] 2. The crystallization process of glass is generally divided into two stages: the formation of crystal nuclei (nucleation) and the growth of crystals (crystallization). The nucleation of glass has little effect on the crystalline phase, while crystallization determines the crystalline phase of the glass. Therefore, this invention adopts a two-step method (nucleation first, then crystallization) to perform heat treatment on the parent glass. Compared with the one-step method, separating the nucleation and crystallization processes makes the control of crystallization temperature and time more precise and is not conducive to the formation of impurity phases, thereby preparing a high-performance machinable composite phase microcrystalline glass. Attached Figure Description

[0039] Figure 1 This is the XRD pattern of the glass prepared in Example 1 of the present invention.

[0040] Figure 2 This is the XRD pattern of the glass prepared in Example 2 of the present invention.

[0041] Figure 3 This is the XRD pattern of the glass prepared in Example 3 of the present invention.

[0042] Figure 4 This is the XRD pattern of the glass prepared in Example 4 of the present invention.

[0043] Figure 5 This is the XRD pattern of the glass prepared in Example 5 of the present invention.

[0044] Figure 6 This is the XRD pattern of the glass prepared in Comparative Example 1 of the present invention.

[0045] Figure 7 This is the XRD pattern of the glass prepared in Comparative Example 2 of the present invention.

[0046] Figure 8 This is the XRD pattern of the glass prepared in Comparative Example 3 of the present invention.

[0047] Figure 9 This is the XRD pattern of the glass prepared in Comparative Example 4 of the present invention.

[0048] Figure 10 This is the XRD pattern of the glass prepared in Comparative Example 5 of the present invention.

[0049] Figure 11 This is the XRD pattern of the glass prepared in Comparative Example 6 of the present invention.

[0050] Figure 12 This is the XRD pattern of the glass prepared in Comparative Example 7 of the present invention.

[0051] Figure 13 This is the XRD pattern of the glass prepared in Comparative Example 8 of the present invention.

[0052] Figure 14 This is a temperature-time diagram illustrating the nucleation and crystal growth of the two-step heat treatment process of this invention.

[0053] Figure 15 This is a temperature-time diagram illustrating the nucleation and crystal growth process in a one-step heat treatment process. Detailed Implementation

[0054] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention.

[0055] Examples 1-5 and Comparative Examples 1-8

[0056] The formulations of the 3 mm thick machinable composite phase mica microcrystalline glass prepared in Examples 1-5 and Comparative Examples 1-8 are shown in Table 1-2:

[0057] Table 1

[0058] Components Example 1 Example 2 Example 3 Example 4 Example 5 <![CDATA[Parts of SiO2]]> 38.5 39 39.5 37 37.5 <![CDATA[Al2O3 / parts]]> 19.5 20.5 19 21 20 MgO 11 11.5 12 12 11.5 <![CDATA[MgF2 / part]]> 7 7.5 7 8 8.5 BaO / serving 4 4.5 3.5 3.5 3 CaO / serving 3 3 4.5 3 3.5 <![CDATA[K2O / part]]> 4 3 3 3.5 3.5 ZnO / serving 3.5 2.5 3.5 2.5 2 <![CDATA[CeO2 / part]]> 3.5 3 3 3.5 4 <![CDATA[ZrO2 / part]]> 2.5 2.5 2.5 3 3 <![CDATA[TiO2 / parts]]> 1 1.5 1 2 1.5 <![CDATA[V2O5 / parts]]> 1.5 1 0.5 0.5 1.5 <![CDATA[Li2O / parts]]> 1 0.5 1 0.5 0.5

[0059] Table 2

[0060]

[0061] The preparation process of the machinable composite phase mica microcrystalline glass in Examples 1-5 is as follows: Each component is prepared into a batch, mixed evenly, and then poured into a glass melting furnace. The molten glass is clarified and homogenized before flowing into a tin bath filled with a protective gas (N2). Under the combined action of surface tension and its own gravity, the glass is spread and polished on the tin surface to form a smooth, uniformly thick glass strip. It is then annealed in an annealing furnace, held at a certain temperature, and rapidly cooled to room temperature, followed by nucleation and crystallization. After cooling, it is cut to obtain the finished glass. The parameter settings for each process are shown in Table 3. The parameter settings for Comparative Examples 1-7 are the same as in Example 1.

[0062] Table 3

[0063]

[0064] Comparative Example 8 employs a one-step heat treatment process. The specific preparation process is as follows: each component is prepared into a batch, mixed evenly, and then poured into a glass melting furnace. The glass is melted at 1500℃ into molten glass. After homogenization, the molten glass flows into a tin bath filled with protective gas (N2). Under the combined action of surface tension and its own gravity, the glass is spread and polished on the tin surface to become a glass strip with a flat surface and uniform thickness. Then, it is annealed in an annealing furnace at 550℃, held for 120 minutes, and then cooled to room temperature. At a heating rate of 5℃ / min and a cooling rate of 5℃ / min, the crystallization temperature is 1000℃, and the holding time is 250 minutes. After cooling, the finished glass is cut to obtain the finished glass.

[0065] The densities of the glasses prepared in Examples 1-5 and Comparative Examples 1-8 were measured using the Archimedes method with an analytical balance. The samples were placed in deionized water for 10 minutes. The glass density was calculated using the following formula. Each sample was measured 5 times and the average value was taken.

[0066] p = p0m2 / (m2-m1)

[0067] The flexural strength of the glasses prepared in Examples 1-5 and Comparative Examples 1-8 was tested using the three-point bending method. The fired microcrystalline glass was smoothed with sandpaper ranging from coarse to fine, and then polished with diamond abrasive paste to form standard specimens of 3mm x 4mm x 36mm. The flexural strength was measured on a Shimadzu TG-10TA tensile testing machine with a range of 200-5000N and a loading speed of 0.5mm / min. The flexural strength of the glass could be calculated using the following formula. Ten measurements were taken for each sample, and the average value was recorded.

[0068]

[0069] In the formula: denoted as σb, where P is the load at fracture (N), L is the span (30 mm), b is the specimen width (mm), and h is the specimen height (mm).

[0070] The hardness of the glasses prepared in Examples 1-5 and Comparative Examples 1-8 was measured using the Vickers hardness test. The sample was a 14mm × 1.5mm glass sheet, tested with a TUKON 2100 micro / Vickers hardness tester. A load of 100g was applied and held for 20 seconds before the load was removed, leaving an indentation on the sample surface. The length of the indentation diagonal was measured, and the surface area of ​​the indentation was calculated to determine the load stress per unit area. Substituting this into the following formula, the Vickers hardness value Hv of the glass could be calculated. Each sample was measured five times, and the average value was taken.

[0071] Hv = P / S = 1.8544P / d 2

[0072] In the formula: Hv is the Vickers hardness value of the glass, P is the load (N), S is the surface area of ​​the indentation (mm), and d is the average length of the diagonal of the indentation (mm).

[0073] The fracture toughness of the glasses prepared in Examples 1-5 and Comparative Examples 1-8 was tested by indentation method. The length of the crack generated by the indentation and its four corners was calculated by the following formula while the Vickers microhardness was measured. Each sample was measured 10 times and the average value was taken.

[0074] K = 0.016(E / Hv) 1 / 2 (P / C 3 / 2 )

[0075] In the formula: K is the fracture toughness of the glass, E is the elastic modulus (GPa), Hv is the Vickers hardness (GPa), P is the load (N), and C is the crack length (mm).

[0076] The performance test results of the 3 mm thick machinable composite phase mica microcrystalline glass prepared in Examples 1-5 and Comparative Examples 1-8 are shown in Tables 4-5:

[0077] Table 4

[0078]

[0079]

[0080] Table 5

[0081]

[0082] As can be seen from the data comparison in Table 4-5, the microhardness of the glass prepared in Comparative Example 1 is reduced compared with Example 1. This is mainly because MgF2 is structurally equivalent to two silicon-fluorine bonds (≡Si-F) replacing one silicon-oxygen bond (≡Si-O-Si≡). The presence of the ≡Si-F group often results in a large number of phase separation phenomena in the glass-ceramic, affecting the structure and causing a decrease in microhardness.

[0083] Compared to Example 1, the mechanical properties of the glass prepared in Comparative Example 2 decreased. This is because the CaO content in CaO decreased. 2+ In this invention, it acts as a network modifier, mainly existing in the gaps of the glass network. It induces the formation of non-bridging oxygen, which can break the continuous network of the glass, weaken the Si-O bonds in the glass network, increase the glass's immiscibility, facilitate phase separation, and make the glass have excellent mechanical properties.

[0084] Compared with Example 1, the density of the glass prepared in Comparative Example 3 was reduced, mainly because the addition of ZrO2 can effectively promote the densification process of glass-ceramics, refine the glass-ceramic particles, and thus increase the density of glass-ceramics.

[0085] Compared to Example 1, the flexural strength of the glass prepared in Comparative Example 4 decreased, mainly due to the reduction in TiO2 strength at high temperatures. 4+ and O 2- It readily forms [TiO4] tetrahedra and has good compatibility with the glass framework structure [SiO4] tetrahedra, thus it can stably exist in the glass network to enhance the glass's bending strength.

[0086] Compared with Example 1, the bending strength of the glass prepared in Comparative Example 5 is reduced, mainly because V2O5 has a low melting point, which can greatly reduce the surface tension of the glass and improve its bending strength.

[0087] Compared with Example 1, the Vickers hardness and microhardness of the glass prepared in Comparative Example 6 decreased. This is because when Li2O is not added, the glass will crystallize naturally, which will contain the process product Li2SiO3 crystals, affecting the formation of composite crystals and the mechanical strength of the glass.

[0088] Compared with Example 1, the bending strength of the glass prepared in Comparative Example 7 is reduced because V2O5, TiO2 and ZrO2, when used as composite nucleating agents, can increase the solubility of the glass, which helps the precipitation of the crystalline phase and increases the bending strength of the glass.

[0089] Compared with Example 1, the mechanical properties of the glass prepared in Comparative Example 8 were reduced because the one-step process could not precisely control the temperature of the heat treatment, resulting in non-uniform growth of crystal nuclei during the nucleation and crystallization process, which led to a decrease in the microhardness and fracture toughness of the glass.

[0090] XRD was used to qualitatively or semi-quantitatively analyze the phase composition of the machinable composite mica microcrystalline glass prepared in Examples 1-5 and Comparative Examples 1-8. By analyzing the position, relative intensity, and number of peaks in the diffraction patterns, the substances contained in the sample could be determined. The specific procedure was as follows: the glass sample was crushed, ground for 1 hour, and then sieved through a 200-mesh sieve. The obtained powder sample was then subjected to XRD analysis. The instrument used was a Rigaku Electric Corporation D / MAX-II rotating target X-ray diffractometer. The experimental conditions were: 20 kV, 110 mA, CuKα, and a scanning speed of 0.03 °C / s. The XRD patterns of the 3 mm thick machinable composite mica microcrystalline glass prepared in Examples 1-5 and Comparative Examples 1-8 are shown below. Figure 1-13 As shown.

[0091] XRD patterns revealed a certain similarity in the spectral lines of the BaMg[Ti2Al2O3Si2O3]F2 composite phases from Examples 1-5, with an increase in the intensity of the main absorption bands, indicating a continuous improvement in the crystallinity of the samples. 2+It has a strong effect on accumulating charge, and the phase separation tendency increases with increasing MgO content. Ca 2+ Mg 2+ and K + The ions are in equilibrium [AlO4]. - The tetrahedral charge facilitates the formation of [AlO4]2Ca, [AlO4]2Mg, and [AlO4]K complexes within the glass network structure. These complexes exhibit good compatibility with [SiO4] tetrahedra, thus promoting the formation of the mica basic unit [AlSiO3] groups. The spectra show that the glass structure prepared in this invention contains a short-range ordered composite phase similar to the structural units of Folkink, exhibiting machinability.

[0092] Furthermore, compared with the XRD pattern of the glass prepared in Example 1, the intensity of the crystal phase diffraction peak in the XRD pattern of the glass prepared in Comparative Example 1 is very small. This is because MgF2 crystal is the nucleation center of the glass of the present invention. No MgF2 was added in Comparative Example 1, so no BaMg[Ti2Al2O3Si2O3]F2 composite phase crystal was formed in the glass.

[0093] Compared with the XRD pattern of the glass prepared in Example 1, the XRD pattern of the glass prepared in Comparative Example 2 shows not only high-intensity diffraction peaks of the composite crystalline phase, but also the presence of a heterocrystalline phase, which affects the machinability of the glass.

[0094] Compared with the XRD pattern of the glass prepared in Example 1, the XRD pattern of the glass prepared in Comparative Example 3 shows a higher intensity of the diffraction peaks of the crystalline phase, but it also shows a greater number of impurity phases, which affect the machinability of the basic crystalline phase [KMgSi3O]. 10 The formation of [F2] is due to the fact that ZrO2 can promote nucleation and crystallization, and its addition can effectively promote the formation of [KMgSi3O]. 10 The precipitation of F2 crystals.

[0095] Compared with the XRD pattern of the glass prepared in Example 1, the XRD pattern of the glass prepared in Comparative Example 4 shows that the time for the formation of the composite crystalline phase is longer than that in Example 1. This is because TiO2 makes the glass melt viscosity relatively low, the atomic diffusion activation energy is low, which makes it easier for atoms to migrate, thus promoting nucleation and crystallization.

[0096] Compared with the XRD pattern of the glass prepared in Example 1, the XRD pattern of the glass prepared in Comparative Example 5 shows that the precipitation of the crystalline phase is slow and there is the formation of the impurity phase. This is because when V2O5, TiO2 and ZrO2 are used as composite nucleating agents, the solubility in the glass increases, which helps the precipitation of the microcrystalline phase.

[0097] Compared to the XRD pattern of the glass prepared in Example 1, the XRD pattern of the glass prepared in Comparative Example 6 shows a higher intensity of crystalline phase diffraction peaks, but also an excessive amount of impurity phases, resulting in the formation of the Li2SiO3 crystalline phase, which is detrimental to the glass's properties. This is because Li2O is mainly used to suppress the precipitation of Li2SiO3 crystals, allowing the glass to form as much BaMg[Ti2Al2O3Si2O3]F2 composite phase crystal as possible. When no Li2O is added to Comparative Example 6, the glass crystallizes naturally, containing the process product Li2SiO3 crystals, which affects the formation of the composite crystal.

[0098] Compared with the XRD pattern of the glass prepared in Example 1, the XRD pattern of the glass prepared in Comparative Example 7 shows that the diffraction peak intensity of the early crystalline phase is too large, and the crystalline phase of the glass precipitates first. However, there are more than 10 kinds of impurity phases generated, which affects the formation of the glass composite phase and its performance.

[0099] Compared with the XRD pattern of the glass prepared in Example 1, the diffraction peaks of the crystalline phase in the XRD pattern of the glass prepared in Comparative Example 8 are relatively reduced. The present invention separates the nucleation and crystallization processes, which makes the control of crystallization temperature and time more precise and is not conducive to the formation of impurity phases. Compared with the one-step method, it can prepare high-performance machinable composite phase microcrystalline glass.

[0100] The machinability test method for the glasses prepared in Examples 1-5 and Comparative Examples 1-8 is as follows: A drilling method was used, specifically measuring the depth of hole drilled per unit time. The samples were 50mm × 20mm cylindrical specimens with a drill bit diameter of 2.3mm. The machinability of the microcrystalline glass was represented by the drilling depth in 30 seconds. The processing equipment was a bench drill press with a constant axial force of 392N and a rotation speed of 800r / min. Each sample used a new drill bit, and each sample was measured 5 times, with the average value taken.

[0101] The machinability test results of the 3 mm thick machinable composite mica microcrystalline glass prepared in Examples 1-5 and Comparative Examples 1-8 are shown in Table 6-7:

[0102] Table 6

[0103] project Example 1 Example 2 Example 3 Example 4 Example 5 Drilling depth / mm 10.5 9.9 10.1 8.9 9.3

[0104] Table 7

[0105]

[0106] As can be seen from Tables 6-7, the machinability of the glass prepared in Comparative Example 1 is reduced compared to Example 1. This is because MgF2 is an effective nucleating agent for the composite crystal and serves as the nucleation center for the glass, providing nucleation sites for the growth of the BaMg[Ti2Al2O3Si2O3]F2 composite phase crystal. Therefore, the glass prepared in Comparative Example 1 without the addition of MgF2 no longer has machinability.

[0107] Compared with Example 1, the machinability of the glass prepared in Comparative Example 2 was reduced. This is because CaO, as a network modifier, can change the network structure of the glass-ceramic. The addition of CaO significantly improved the crystallization characteristics of the glass-ceramic, reconciled the contradiction between the initial state of the glass and its crystallization characteristics, and further reduced the continuity of the glass network structure, thereby changing its crystallization characteristics and thus enabling it to meet the requirements of glass machinability.

[0108] Compared to Example 1, the machinability of the glass prepared in Comparative Example 3 was reduced. This is because ZrO2 has a very significant nucleation and crystallization effect on the glass, and its addition can effectively promote [KMgSi3O] 10 Precipitation of F2] crystals, [KMgSi3O 10 F2] is the basic crystal phase of the machinable microcrystalline glass of this invention.

[0109] Compared with Example 1, the machinability of the glasses prepared in Comparative Examples 4 and 5 was reduced. This is because when V2O5 and TiO2 are used as composite nucleating agents, the solubility in the glass increases, accelerating the precipitation of the BaMg[Ti2Al2O3Si2O3]F2 crystal phase, thereby enhancing the machinability.

[0110] Compared with Example 1, the machinability of the glass prepared in Comparative Example 6 is reduced. This is because Li2O can suppress the precipitation of Li2SiO3 crystals, allowing the glass to form as much BaMg[Ti2Al2O3Si2O3]F2 composite phase crystal as possible.

[0111] Compared with Example 1, the machinability of the glass prepared in Comparative Example 7 is reduced. This is because V2O5 and ZrO2 can greatly reduce the surface tension of the glass, and the appropriate viscosity for crystal nucleation can be achieved at a lower temperature, thus obtaining a large number of crystal nuclei and promoting overall crystallization.

[0112] Compared with Example 1, the machinability of the glass prepared in Comparative Example 8 was reduced. This is because the one-step heat treatment method could not accurately control the nucleation and crystallization time and temperature, which slowed down the formation rate of BaMg[Ti2Al2O3Si2O3]F2 composite phase crystals and generated impurity phases, thus affecting the machinability of the glass.

[0113] The above experiments demonstrate that the machinable composite-phase mica microcrystalline glass of this invention possesses superior performance, outperforming similar glasses in terms of mechanical strength, hardness, and wear resistance. It can withstand harsh operating environments and, compared to metals with similar mechanical properties, has a lower density but a more compact texture. In addition to the generally excellent properties of microcrystalline glass, it also exhibits unique machinability, allowing for machining using tools typically found in metalworking processes. This means it can be machined using conventional methods such as turning, milling, planing, grinding, sawing, drilling, and tapping to produce components with precise dimensions, fits, and complex shapes—features not found in other microcrystalline glass materials. Furthermore, the machinable composite-phase mica microcrystalline glass of this invention offers excellent designability. The proportions of each component can be adjusted according to actual needs, along with controllable heat treatment processes and the types and quantities of crystals, thereby effectively controlling the performance of the microcrystalline glass and achieving unique mechanical and machinability properties, demonstrating promising application prospects.

Claims

1. A machinable composite phase mica microcrystalline glass, characterized in that, It is composed of the following components in parts by weight: SiO2 37-46 parts, Al2O3 19-21 parts, MgO 11-13 parts, MgF2 7-9 parts, BaO 3-5 parts, CaO 3-5 parts, K2O 3-5 parts, ZnO 3-4 parts, CeO2 3-4 parts, ZrO2 2.5-3.5 parts, TiO2 1-2 parts, V2O5 0.5-1.5 parts, Li2O 0.5-1.5 parts; the composite phase is BaMg[Ti2Al2O3Si2O3]F2; The preparation process of the machinable composite phase mica microcrystalline glass includes the following steps: batching, melting, clarification and homogenization, annealing, rapid cooling, nucleation and crystallization; the nucleation temperature is 650-700℃, and the crystallization temperature is 850-950℃.

2. The machinable composite phase mica microcrystalline glass as described in claim 1, characterized in that, It is composed of the following components in parts by weight: SiO2 38.5 parts, Al2O3 19.5 parts, MgO 11 parts, MgF2 7 parts, BaO 4 parts, CaO 3 parts, K2O 4 parts, ZnO 3.5 parts, CeO2 3.5 parts, ZrO2 2.5 parts, TiO2 1 part, V2O5 1.5 parts, and Li2O 1 part.

3. The machinable composite phase mica microcrystalline glass as described in claim 1, characterized in that, The preparation process specifically includes the following steps: each component is prepared into a batch, mixed evenly and poured into a glass melting furnace. After the molten glass is clarified and homogenized, it flows into a tin bath filled with protective gas. Under the combined action of surface tension and its own gravity, it is spread and polished on the tin surface to become a glass ribbon. Then it is annealed in an annealing furnace and then rapidly cooled, followed by nucleation and crystallization.

4. The machinable composite phase mica microcrystalline glass as described in claim 3, characterized in that, In the glass furnace, the melting temperature is 1250-1450℃, and the clarification and homogenization temperature is 1500-1650℃.

5. The machinable composite phase mica microcrystalline glass as described in claim 3, characterized in that, In the annealing furnace, the annealing temperature is 550-600℃.

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