Coal gangue-based glass ceramic and preparation method thereof

Abstract

The invention belongs to the technical field of coal gangue resource utilization, and particularly relates to coal gangue-based microcrystalline glass and a preparation method thereof. The method comprises the following steps: S1, providing a coal gangue raw material; s2, crushing the coal gangue raw material, and mixing the crushed coal gangue raw material with calcium oxide and titanium dioxide according to a certain mass ratio to obtain a batch; s3, melting the batch, and then carrying out cooling treatment to obtain base glass; s4, carrying out powdering treatment on the base glass to obtain base glass powder; and carrying out compression molding on the basic glass powder, and carrying out gradient heat treatment including nucleation treatment and crystallization to obtain the coal gangue-based glass ceramic. According to the invention, through component design and a gradient heat treatment process, a glass ceramic product with high hardness, high bending strength and high corrosion resistance is successfully prepared under the condition of high coal gangue doping amount, and the performance bottleneck restricting high-valued utilization of coal gangue for a long time is broken through. And meanwhile, the production energy consumption is obviously reduced through the optimized heat treatment system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coal gangue resource utilization, and in particular relates to a coal gangue-based microcrystalline glass and a preparation method thereof. BACKGROUND

[0002] China is the world's major energy producer and consumer, and has long relied on coal resources. Large-scale mining of coal has led to a large accumulation of coal gangue, which not only occupies land, but also poses a serious threat to the ecological environment. Realizing large-scale high-value utilization of coal gangue is a key link in promoting solid waste resource utilization and green upgrading of the industrial structure.

[0003] Coal gangue is rich in SiO2 and Al2O3 and other components, which makes it a potential ideal raw material for preparing high-performance microcrystalline glass. Microcrystalline glass has the homogeneity of glass and the excellent properties of ceramics such as high temperature resistance, high strength, and high toughness, and has a broad application prospect. However, efficient conversion of coal gangue into high-performance microcrystalline glass still faces severe challenges. Currently, the mainstream of anorthite microcrystalline glass preparation generally adopts a constant high temperature one-time crystallization method, and this traditional process has two major bottlenecks: First, the material performance and the amount of solid waste are difficult to balance. The extensive single-stage temperature control leads to an imbalance in crystal nucleus formation and crystal growth kinetics, which easily causes problems such as crystal coarsening, structure not being dense, and glass phase remaining, resulting in a bending strength of the product generally lower than 120 MPa and a hardness limited to 6~7GPa. In order to maintain basic performance stability, the existing process often has to limit the proportion of coal gangue, which is contrary to the original intention of large-scale consumption of solid waste.

[0004] Second, the production energy consumption is high. The long constant temperature holding process leads to high energy consumption, and in addition, impurity components in coal gangue easily cause non-equilibrium reactions at high temperatures, which further increases the risk of crystallization out of control, and further restricts production efficiency and product yield.

[0005] Therefore, the industry urgently needs to significantly increase the consumption of coal gangue without sacrificing material performance, and to simultaneously reduce energy consumption in the production process. Developing a new technology for preparing coal gangue-based microcrystalline glass that can realize the synergy of high-value solid waste, high-performance products, and low-carbon production has become an inevitable demand to break through the current bottleneck of industrial development. SUMMARY

[0006] The present application aims to provide a complete solution of coal gangue-based glass-ceramics and its preparation method to overcome the shortcomings of the prior art. Through innovative component design and gradient fine heat treatment process, the present application successfully prepares a glass-ceramics product with high hardness, high density, high bending strength and high corrosion resistance, aiming to effectively solve the technical problem of difficult to obtain excellent physical and chemical properties under high coal gangue content, while significantly reducing the production energy consumption, opening up a new path for high value-added and green resource utilization of coal gangue.

[0007] In the first aspect, the present application provides a preparation method of coal gangue-based glass-ceramics, wherein the preparation method comprises the following steps: S1, providing coal gangue raw materials; S2, after crushing the coal gangue raw materials, mixing with calcium oxide and titanium dioxide according to a certain mass ratio to obtain a mixture; S3, melting the mixture, and then obtaining a base glass through cooling treatment; S4, powderizing the base glass to obtain a base glass powder; after the base glass powder is pressed into a shape, gradient heat treatment including nucleation treatment and crystallization treatment is carried out to obtain the coal gangue-based glass-ceramics.

[0008] In the preferred technical solution of the above preparation method, in step S4, the gradient heat treatment is specifically: first, heating to 750-850℃ at a certain heating rate, and nucleating for 2-4h; then heating to 1025-1075℃ at the same heating rate, and crystallizing for 2-4h.

[0009] In the preferred technical solution of the above preparation method, in step S4, the heating rate is 5-10℃ / min.

[0010] In the preferred technical solution of the above preparation method, in step S2, based on the total mass of the mixture, the mass percentages of the coal gangue, calcium oxide and titanium dioxide are respectively: Coal gangue 75-80% Calcium oxide 15-22% Titanium dioxide 3-5%.

[0011] In the preferred technical solution of the above preparation method, in step S3, the melting temperature is 1500-1600℃, and the time is 4-6h.

[0012] In the preferred technical solution of the above preparation method, in step S4, the pressing forming is specifically: the base glass powder is pressed into a blank under a pressure of 4-6MPa for 240-300s.

[0013] In the preferred technical solution of the preparation method, in step S1, the coal gangue raw material is a coal gangue as is, and the coal gangue as is mainly contains SiO2, Al2O3 and TiO2, wherein the content of SiO2 is not less than 50%, the content of Al2O3 is not less than 45%, and the content of TiO2 is not less than 1.2%.

[0014] In the second aspect, the present application provides a coal gangue-based glass ceramic, wherein the coal gangue-based glass ceramic is prepared by the preparation method of the first aspect.

[0015] In the preferred technical solution of the coal gangue-based glass ceramic, the coal gangue-based glass ceramic at least meets one of the performance parameters i-iv: i, the Vickers hardness is not less than 7.5 GPa; ii, the bending strength is not less than 90.0 MPa; iii, the acid resistance is not less than 95.0%; iv, the alkali resistance is not less than 99.0%.

[0016] In the preferred technical solution of the coal gangue-based glass ceramic, the bulk density of the coal gangue-based glass ceramic is not less than 2.8 g / cm 3 .

[0017] The coal gangue-based glass ceramic and the preparation method have the following technical effects: (1) The present application designs a CaO-Al2O3-SiO2 (CAS) glass ceramic system based on kaolinite-type coal gangue. The system realizes high accommodation of coal gangue, and the doping amount can reach more than 75wt%. Under this high doping amount, through component design and process control, the glass ceramic with required performance can be stably prepared, and the key indicators such as bending strength and Vickers hardness can reach a high level (for example, the bending strength is not less than 90.0 MPa). This provides a high-value utilization path for solving the problem of coal gangue solid waste accumulation. In addition, the preparation method has the advantages of simple batching and simple production process. At the same time, the heat treatment temperature can be effectively controlled at a relatively low level of about 1000℃, which significantly reduces the energy consumption compared with the traditional process.

[0018] (2) The present application successfully prepares a high-performance glass ceramic through the synergistic strategy of "component reconstruction-nucleation control-gradient heat treatment". The test results show that the performance of the sample of the preferred embodiment can reach: hardness of 14.07 GPa, bending strength of 136.7 MPa, and bulk density of 2.88 g / cm 3The acid resistance reaches 97.93%, and the alkali resistance reaches 99.98%. More importantly, the key performance indicators of the products obtained in all embodiments consistently meet the high standards set by this invention (such as flexural strength ≥90.0 MPa, hardness ≥7.5 GPa). In particular, under the preferred process parameters (such as Examples 1 and 11), the flexural strength and other indicators can significantly exceed the existing levels mentioned in the background art (<120 MPa), which verifies that the technical solution of this invention has the potential to significantly improve product performance while achieving high solid waste content (≥75%). Attached Figure Description

[0019] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which: Figure 1 This is a process flow diagram of the preparation method of the coal gangue-based microcrystalline glass of the present invention; Figure 2 These are the XRD test results of the original coal gangue sample used in the embodiments of the present invention; Figure 3 The XRD test results are of the microcrystalline glass prepared by the present invention at different nucleation and crystallization temperatures; Figure 4 The results are SEM and energy dispersive spectroscopy of the microcrystalline glass prepared by this invention at different nucleation and crystallization temperatures. Figure 5 The results are Vickers hardness test results of the microcrystalline glass prepared by this invention at different nucleation and crystallization temperatures; Figure 6 These are the bulk density test results of the microcrystalline glass prepared by the present invention at different nucleation and crystallization temperatures; Figure 7 These are the flexural strength test results of the microcrystalline glass prepared by the present invention at different nucleation and crystallization temperatures; Figure 8 The results are the acid resistance weight loss test results of the microcrystalline glass prepared by the present invention at different nucleation and crystallization temperatures; Figure 9 These are the alkali resistance weight loss test results of the microcrystalline glass prepared by this invention at different nucleation and crystallization temperatures. Detailed Implementation

[0020] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0021] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0022] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0023] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0024] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0025] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0026] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used in the following examples are commercially available unless otherwise specified.

[0028] Based on the common technical challenge identified in the background section regarding the difficulty of achieving excellent physicochemical properties with high coal gangue content in existing processes, this invention proposes a solution through innovative component design and synergistic control of a gradient fine heat treatment process. This solution enables the preparation of microcrystalline glass products with high hardness, high flexural strength, and high corrosion resistance at high coal gangue content (≥75%), providing an effective solution to overcome the performance bottleneck that has long constrained the high-value utilization of coal gangue. Simultaneously, this process significantly reduces production energy consumption through optimized heat treatment regimes, providing a practical and feasible technical path for the green resource utilization and high-value-added utilization of coal gangue.

[0029] Specifically, in its first aspect, the present invention provides a method for preparing coal gangue-based microcrystalline glass. Please refer to [link to relevant documentation]. Figure 1 The preparation method includes the following steps: S1. Provide coal gangue raw materials; S2. After crushing the coal gangue raw material, it is mixed with calcium oxide and titanium dioxide in a certain mass ratio to obtain a batch material; S3. Melt the batch material and then cool it to obtain the base glass; S4. The base glass is pulverized to obtain base glass powder; the base glass powder is pressed into shape and then subjected to gradient heat treatment including nucleation and crystallization to obtain the coal gangue-based microcrystalline glass.

[0030] The preparation method provided by this invention successfully constructs a process route with coal gangue as the main raw material, providing a core technical solution for realizing the large-scale, high-value solid waste utilization of coal gangue.

[0031] In some specific embodiments, in step S4, the gradient heat treatment specifically involves: first, heating to 750–850°C at a certain heating rate and holding at that temperature for 2–4 hours for nucleation treatment; then heating to 1025–1075°C at the same heating rate and holding at that temperature for 2–4 hours for crystallization treatment.

[0032] The nucleation and crystallization processes of this invention employ a gradient thermal treatment regime. The core of this regime lies in precisely separating the overall crystallization process into nucleation and crystallization stages with progressively increasing temperature gradients, and achieving precise control by regulating the heating rate between stages. Specifically, this gradient thermal treatment regime first performs nucleation treatment in a lower temperature range (750–850°C) to promote the uniform formation of crystal nuclei; subsequently, it raises the temperature at a controlled rate (5–10°C / min) to a higher specific temperature range (1025–1075°C) for crystallization treatment, driving the crystal to grow controllably on the formed crystal nuclei. This non-isothermal, staged, and temperature-gradient-controlled heating mode effectively coordinates the crystal nucleation and crystal growth rates kinetically, helping to avoid defects such as coarse grains, uneven distribution, and glass phase residues caused by traditional one-time crystallization, thereby obtaining a dense, high-performance microcrystalline glass.

[0033] In some specific embodiments, in step S4, the heating rate is 5 to 10 °C / min.

[0034] The heating rate range defined by this invention can ensure that the sample is heated evenly and the internal stress is released gradually during the heat treatment process. This is beneficial for obtaining microcrystalline glass products with complete structure, no cracks, and uniform grain size.

[0035] In some preferred embodiments, in step S4, the gradient heat treatment specifically involves: first, heating to 800°C at a heating rate of 10°C / min and holding at that temperature for 2 hours for nucleation treatment; then heating to 1025°C at the same heating rate and holding at that temperature for 2 hours for crystallization treatment.

[0036] This invention innovatively proposes a synergistic control strategy of "component reconstruction – nucleation regulation – gradient heat treatment". This strategy, through precise control of multi-stage temperature changes and matching with crystal growth kinetics, systematically elucidates the precipitation mechanism of anorthite in this coal gangue-based glass system. The temperature of the gradient heat treatment regime has a significant impact on the properties of the sintered glass-ceramic. The nucleation temperature mainly controls the number of crystal nuclei formed. Nucleation at 800℃ results in a greater number of crystal nuclei formed within the glass matrix compared to 750℃ and 850℃, which helps to refine the grains during subsequent crystallization, resulting in a more compact grain arrangement and a denser internal structure of the glass-ceramic. The crystallization temperature mainly controls the size of the precipitated crystals. When the nucleation temperature is 800℃, the glass-ceramic obtained after crystallization at 1025℃ has a smaller grain size, only 40-50 nm, with a dense microstructure, thus exhibiting excellent physicochemical properties. However, the flexural strength and corrosion resistance of the microcrystalline glass obtained after crystallization at 1075℃ decreased compared to that obtained at 1025℃. Scanning electron microscopy revealed coarse grains and localized microcracks in the sample. This is because the sample structure was already sufficiently dense at 1075℃; further increasing the crystallization temperature promoted crystal growth, and excessive grain growth led to stress concentration at grain boundaries, inducing microcracks and thus reducing the physicochemical properties of the microcrystalline glass. Therefore, considering both the physicochemical properties and energy consumption of the finished microcrystalline glass, the selected heat treatment regime was: nucleation temperature: 800℃; nucleation time: 2h; crystallization temperature: 1025℃; crystallization time: 2h.

[0037] In some specific embodiments, in step S2, based on the total mass of the batching material, the mass percentages of the coal gangue, calcium oxide, and titanium dioxide are respectively: Coal gangue 75-80% Calcium oxide 15~22% Titanium dioxide 3~5%.

[0038] This invention achieves "component reconstruction" of the system through this specific raw material ratio, effectively controlling the network structure of the base glass. This not only ensures a high coal gangue content, but also lays the compositional foundation for the precipitation of target crystalline phases (calcium feldspar and wollastonite) during subsequent heat treatment.

[0039] In some specific embodiments, in step S3, the melting temperature is 1500–1600°C, and the time is 4–6 hours. For example, the temperature can be 1500°C, 1530°C, 1550°C, 1580°C, 1600°C, or any value within the range; the time can be 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, or any value within the range.

[0040] The melting temperature and time described above in this invention ensure that raw materials such as coal gangue react fully, melt homogenize, and are efficiently clarified, thereby obtaining a base glass with chemical homogeneity and few bubble defects.

[0041] In one embodiment, in step S3, the batch material is placed in an alumina crucible and melted at a high temperature of 1550°C for 6 hours. During this process, the molten glass is fully homogenized and clarified, forming a high-quality melt. Subsequently, the resulting molten glass is cooled. In a preferred embodiment, the cooling process is specifically water quenching, i.e., the high-temperature molten glass is rapidly poured into cold water at room temperature, causing it to shatter and thus obtain granular base glass.

[0042] In some specific embodiments, step S4, the pressing and molding process specifically involves pressing the base glass powder into a blank under a pressure of 4–6 MPa for 240–300 s. For example, the pressing and molding pressure can be 4 MPa, 5 MPa, 6 MPa, or any number within the range; the pressing and molding time can be 240 s, 260 s, 280 s, 300 s, or any value within the range.

[0043] The pressing and molding parameters used in this invention help to obtain glass powder preforms with high density and good strength, thereby reducing the risk of deformation, cracking and other problems caused by insufficient density or strength of the preforms during subsequent heat treatment.

[0044] In some preferred embodiments, in step S4, the pressing and molding process involves pressing the base glass powder into a blank under a pressure of 5 MPa for 240-300 s.

[0045] In some exemplary embodiments, the blank is a strip shape of 3×4×40 mm.

[0046] In some specific embodiments, in step S1, the coal gangue raw material is the original coal gangue, which contains, by mass percentage: SiO2 content not less than 50%, Al2O3 content not less than 45%, and TiO2 content not less than 1.2%.

[0047] This invention limits the lower limit of the content of beneficial components in raw coal gangue samples, thereby ensuring that it can be used as a qualified raw material to prepare high-performance microcrystalline glass.

[0048] For example, in some exemplary embodiments, in step S1, the original coal gangue sample contains, by mass percentage: 50.64% SiO2, 45.97% Al2O3, 1.50% TiO2, 0.60% Fe2O3, 0.14% CaO, 0.19% Na2O, 0.13% K2O, and 0.83% other components.

[0049] It should be noted that in step S4, the base glass is pulverized to obtain glass powder suitable for pressing and molding. This pulverization process can be achieved using any equipment and method known in the art capable of breaking glass into powder, such as, but not limited to, mechanical crushing, ball milling, vibratory milling, air jet milling, and grinding. The powder particle size can be adjusted according to molding requirements.

[0050] In this invention, after performing the gradient heat treatment in step S4, the method further includes cooling the coal gangue-based microcrystalline glass to room temperature.

[0051] Furthermore, it also includes a step of surface processing of the obtained coal gangue-based microcrystalline glass.

[0052] In some specific embodiments, the surface processing includes grinding and / or polishing.

[0053] Furthermore, in a second aspect, the present invention provides a coal gangue-based microcrystalline glass, wherein the coal gangue-based microcrystalline glass is prepared by the preparation method described in the first aspect above.

[0054] The microcrystalline glass products prepared by the method have a specific microstructure formed inside, which is determined by the unique process, resulting in the material exhibiting excellent and reliable mechanical properties.

[0055] In some specific embodiments, the chemical composition of the coal gangue-based microcrystalline glass, based on the mass percentage of oxides, includes: 35-45% SiO2, 30-40% Al2O3, 15-25% CaO, 3-6% TiO2, 0-1% Fe2O3, with the balance being impurities.

[0056] The microcrystalline glass products of this invention have a specific range of chemical compositions, which is the inherent reason for their high hardness, high strength and excellent corrosion resistance.

[0057] In some specific embodiments, the coal gangue-based glass-ceramic satisfies at least one of the i-iv performance parameters: i. Vickers hardness is not less than 7.5 GPa; ii. Bending strength not less than 90.0 MPa; iii. Acid resistance not less than 95.0%; iv. Alkali resistance not less than 99.0%.

[0058] In some preferred embodiments, the coal gangue-based microcrystalline glass also satisfies a bulk density of not less than 2.8 g / cm³. 3 .

[0059] The microcrystalline glass products described in this invention exhibit excellent performance in key performance indicators and can achieve high performance standards (such as hardness not less than 7.5 GPa, bending strength not less than 90.0 MPa, etc.). In particular, the products prepared by the optimized process have comprehensive performance that is significantly better than the general levels mentioned in the background art.

[0060] The following detailed embodiments illustrate the coal gangue-based microcrystalline glass and its preparation method of the present invention.

[0061] In the following embodiments, a BCF13 / 12 muffle furnace was used, with a temperature range from room temperature to 1600°C; X-ray diffraction tests were performed using a Rigaku Dmax-2500PC fully automated powder X-ray diffractometer (Japan); the morphology of the minerals was observed using a Hitachi SU8020 field emission scanning electron microscope (Japan). The hardness of the glass-ceramic was tested using an HV-1000 Vickers hardness tester. The bulk density of the glass-ceramic was tested using an AccuPyc II 1340 fully automated true density meter (USA). The flexural strength of the glass-ceramic was tested using a universal testing machine with a three-point bending method.

[0062] In the following embodiments, the XRD patterns of the selected original coal gangue samples are as follows: Figure 2 As shown.

[0063] Example 1 The preparation method of coal gangue-based microcrystalline glass in this embodiment includes the following steps: S1. Raw coal gangue (50.64wt% SiO2, 45.97wt% Al2O3, 1.50wt% TiO2, 0.60wt% Fe2O3, 0.14wt% CaO, 0.19wt% Na2O, 0.13wt% K2O, 0.83wt% other) was selected as raw material; S2. The selected coal gangue is crushed to a particle size of less than 200 mesh, then mixed with calcium oxide and titanium dioxide at a mass ratio of 20:5:1 and ball-milled at 500 r / min for 30 min to obtain a batch with a particle size of less than 200 mesh. The theoretical chemical composition of the batch is calculated to be: SiO2: 38.91%, Al2O3: 35.32%, CaO: 19.31%, TiO2: 5.10%, Fe2O3: 0.46%, Na2O: 0.15%, K2O: 0.10%, and others: 0.65%. S3. Place the batch material in a muffle furnace and melt it at 1550℃ for 6 hours. After homogenization and clarification, quench it with water to obtain the base glass. S4. The base glass is ground and pressed under a pressure of 5 MPa for 300 s to form a strip shape of 3×4×40 mm. Then, a gradient heat treatment is performed, including nucleation and crystallization: first, the temperature is increased to 800℃ at a heating rate of 10℃ / min and held for 2 h for nucleation; then, the temperature is increased to 1025℃ at the same heating rate and held for 2 h for crystallization. After gradient heat treatment, the glass is cooled to room temperature in the furnace to obtain coal gangue-based microcrystalline glass. It is then ground, polished, and subjected to subsequent performance tests.

[0064] The physical and chemical properties of the microcrystalline glass prepared in this embodiment are shown in Table 3.

[0065] Example 2 The preparation method of coal gangue-based microcrystalline glass in this embodiment includes the following steps: S1. Raw coal gangue (50.64wt% SiO2, 45.97wt% Al2O3, 1.50wt% TiO2, 0.60wt% Fe2O3, 0.14wt% CaO, 0.19wt% Na2O, 0.13wt% K2O, 0.83wt% other) was selected as raw material; S2. The selected coal gangue is crushed to a particle size of less than 200 mesh, then mixed with calcium oxide and titanium dioxide at a mass ratio of 20:5:1 and ball-milled at 500 r / min for 30 min to obtain a batch with a particle size of less than 200 mesh. The theoretical chemical composition of the batch is calculated to be: SiO2: 38.91%, Al2O3: 35.32%, CaO: 19.31%, TiO2: 5.10%, Fe2O3: 0.46%, Na2O: 0.15%, K2O: 0.10%, and others: 0.65%. S3. Place the batch material in a muffle furnace and melt it at 1550℃ for 6 hours. After homogenization and clarification, quench it with water to obtain the base glass. S4. The base glass is ground and pressed under a pressure of 5 MPa for 300 seconds to form a strip shape of 3×4×40 mm. Then, a gradient heat treatment is performed, including nucleation and crystallization: first, the temperature is increased to 800℃ at a rate of 10℃ / min and held for 2 hours for nucleation; then, the temperature is increased to 1075℃ at the same rate and held for 2 hours for crystallization. After gradient heat treatment, the glass is cooled to room temperature in the furnace to obtain coal gangue-based microcrystalline glass. It is then ground, polished, and subjected to subsequent performance tests.

[0066] The physical and chemical properties of the microcrystalline glass prepared in this embodiment are shown in Table 3.

[0067] Example 3 The preparation method of coal gangue-based microcrystalline glass in this embodiment includes the following steps: S1. Raw coal gangue (50.64wt% SiO2, 45.97wt% Al2O3, 1.50wt% TiO2, 0.60wt% Fe2O3, 0.14wt% CaO, 0.19wt% Na2O, 0.13wt% K2O, 0.83wt% other) was selected as raw material; S2. The selected coal gangue is crushed to a particle size of less than 200 mesh, then mixed with calcium oxide and titanium dioxide at a mass ratio of 20:5:1 and ball-milled at 500 r / min for 30 min to obtain a batch with a particle size of less than 200 mesh. The theoretical chemical composition of the batch is calculated to be: SiO2: 38.91%, Al2O3: 35.32%, CaO: 19.31%, TiO2: 5.10%, Fe2O3: 0.46%, Na2O: 0.15%, K2O: 0.10%, and others: 0.65%.

[0068] S3. Place the batch material in a muffle furnace and melt it at 1550℃ for 6 hours. After homogenization and clarification, water quench to obtain the base glass.

[0069] S4. The base glass is ground and pressed under a pressure of 5 MPa for 300 seconds to form a strip shape of 3×4×40 mm. Then, a gradient heat treatment is performed, including nucleation and crystallization: first, the temperature is increased to 750℃ at a rate of 10℃ / min and held for 2 hours for nucleation; then, the temperature is increased to 1025℃ at the same rate and held for 2 hours for crystallization. After gradient heat treatment, the glass is cooled to room temperature in the furnace to obtain coal gangue-based microcrystalline glass. It is then ground, polished, and subjected to subsequent performance tests.

[0070] The physical and chemical properties of the microcrystalline glass prepared in this embodiment are shown in Table 3.

[0071] Example 4 The preparation method of coal gangue-based microcrystalline glass in this embodiment includes the following steps: S1. Raw coal gangue (50.64wt% SiO2, 45.97wt% Al2O3, 1.50wt% TiO2, 0.60wt% Fe2O3, 0.14wt% CaO, 0.19wt% Na2O, 0.13wt% K2O, 0.83wt% other) was selected as raw material; S2. The selected coal gangue is crushed to a particle size of less than 200 mesh, then mixed with calcium oxide and titanium dioxide at a mass ratio of 20:5:1 and ball-milled at 500 r / min for 30 min to obtain a batch with a particle size of less than 200 mesh. The theoretical chemical composition of the batch is calculated to be: SiO2: 38.91%, Al2O3: 35.32%, CaO: 19.31%, TiO2: 5.10%, Fe2O3: 0.46%, Na2O: 0.15%, K2O: 0.10%, and others: 0.65%.

[0072] S3. Place the batch material in a muffle furnace and melt it at 1550℃ for 6 hours. After homogenization and clarification, water quench to obtain the base glass.

[0073] S4. The base glass is ground and pressed under a pressure of 5 MPa for 300 seconds to form a strip shape of 3×4×40 mm. Then, a gradient heat treatment is performed, including nucleation and crystallization: first, the temperature is increased to 750℃ at a rate of 10℃ / min and held for 2 hours for nucleation; then, the temperature is increased to 1075℃ at the same rate and held for 2 hours for crystallization. After gradient heat treatment, the glass is cooled to room temperature in the furnace to obtain coal gangue-based microcrystalline glass. It is then ground, polished, and subjected to subsequent performance tests.

[0074] The physical and chemical properties of the microcrystalline glass prepared in this embodiment are shown in Table 3.

[0075] Example 5 The preparation method of coal gangue-based microcrystalline glass in this embodiment includes the following steps: S1. Raw coal gangue (50.64wt% SiO2, 45.97wt% Al2O3, 1.50wt% TiO2, 0.60wt% Fe2O3, 0.14wt% CaO, 0.19wt% Na2O, 0.13wt% K2O, 0.83wt% other) was selected as raw material; S2. The selected coal gangue is crushed to a particle size of less than 200 mesh, then mixed with calcium oxide and titanium dioxide at a mass ratio of 20:5:1 and ball-milled at 500 r / min for 30 min to obtain a batch with a particle size of less than 200 mesh. The theoretical chemical composition of the batch is calculated to be: SiO2: 38.91%, Al2O3: 35.32%, CaO: 19.31%, TiO2: 5.10%, Fe2O3: 0.46%, Na2O: 0.15%, K2O: 0.10%, and others: 0.65%.

[0076] S3. Place the batch material in a muffle furnace and melt it at 1550℃ for 6 hours. After homogenization and clarification, water quench to obtain the base glass.

[0077] S4. The base glass is ground and pressed under a pressure of 5 MPa for 300 seconds to form a strip shape of 3×4×40 mm. Then, a gradient heat treatment is performed, including nucleation and crystallization: first, the temperature is increased to 850℃ at a rate of 10℃ / min and held for 2 hours for nucleation; then, the temperature is increased to 1025℃ at the same rate and held for 2 hours for crystallization. After gradient heat treatment, the glass is cooled to room temperature in the furnace to obtain coal gangue-based microcrystalline glass. It is then ground, polished, and subjected to subsequent performance tests.

[0078] The physical and chemical properties of the microcrystalline glass prepared in this embodiment are shown in Table 3.

[0079] Example 6 The preparation method of coal gangue-based microcrystalline glass in this embodiment includes the following steps: S1. Raw coal gangue (50.64wt% SiO2, 45.97wt% Al2O3, 1.50wt% TiO2, 0.60wt% Fe2O3, 0.14wt% CaO, 0.19wt% Na2O, 0.13wt% K2O, 0.83wt% other) was selected as raw material; S2. The selected coal gangue is crushed to a particle size of less than 200 mesh, then mixed with calcium oxide and titanium dioxide at a mass ratio of 20:5:1 and ball-milled at 500 r / min for 30 min to obtain a batch with a particle size of less than 200 mesh. The theoretical chemical composition of the batch is calculated to be: SiO2: 38.91%, Al2O3: 35.32%, CaO: 19.31%, TiO2: 5.10%, Fe2O3: 0.46%, Na2O: 0.15%, K2O: 0.10%, and others: 0.65%.

[0080] S3. Place the batch material in a muffle furnace and melt it at 1550℃ for 6 hours. After homogenization and clarification, water quench to obtain the base glass.

[0081] S4. The base glass is ground and pressed under a pressure of 5 MPa for 300 seconds to form a strip shape of 3×4×40 mm. Then, a gradient heat treatment is performed, including nucleation and crystallization: first, the temperature is increased to 850℃ at a rate of 10℃ / min and held for 2 hours for nucleation; then, the temperature is increased to 1075℃ at the same rate and held for 2 hours for crystallization. After gradient heat treatment, the glass is cooled to room temperature in the furnace to obtain coal gangue-based microcrystalline glass. It is then ground, polished, and subjected to subsequent performance tests.

[0082] The physical and chemical properties of the microcrystalline glass prepared in this embodiment are shown in Table 3.

[0083] Example 7 The specific steps are the same as in Example 1. The difference from Example 1 is that in step S2, the crushed coal gangue, calcium oxide, and titanium dioxide are mixed in a mass percentage of 75%:22%:3% based on the total mass of the batch.

[0084] The physical and chemical properties of the microcrystalline glass prepared in this embodiment are shown in Table 3.

[0085] Example 8 The specific steps are the same as in Example 1. The difference from Example 1 is that in step S2, the crushed coal gangue, calcium oxide, and titanium dioxide are mixed in a mass percentage of 80%:15%:5% based on the total mass of the batch.

[0086] The physical and chemical properties of the microcrystalline glass prepared in this embodiment are shown in Table 3.

[0087] Example 9 The specific steps are the same as in Example 1. The difference from Example 1 is that in step S4, the gradient heat treatment is as follows: first, the temperature is raised to 800°C at a heating rate of 10°C / min and held for 4 hours for nucleation treatment; then, the temperature is raised to 1025°C at the same heating rate and held for 4 hours for crystallization treatment.

[0088] The physical and chemical properties of the microcrystalline glass prepared in this embodiment are shown in Table 3.

[0089] Example 10 The specific steps are the same as in Example 1. The difference from Example 1 is that in step S4, the gradient heat treatment is as follows: first, the temperature is raised to 850°C at a heating rate of 10°C / min and held for 4 hours for nucleation treatment; then, the temperature is raised to 1075°C at the same heating rate and held for 4 hours for crystallization treatment.

[0090] The physical and chemical properties of the microcrystalline glass prepared in this embodiment are shown in Table 3.

[0091] Example 11 The specific steps are the same as in Example 1. The difference from Example 1 is that in step S4, the gradient heat treatment is as follows: first, the temperature is raised to 800°C at a heating rate of 5°C / min and held for 2 hours for nucleation treatment; then, the temperature is raised to 1025°C at the same heating rate and held for 2 hours for crystallization treatment.

[0092] The physical and chemical properties of the microcrystalline glass prepared in this embodiment are shown in Table 3.

[0093] Example 12 The specific steps are the same as in Example 1. The difference from Example 1 is that in step S4, the gradient heat treatment is as follows: first, the temperature is raised to 850°C at a heating rate of 5°C / min and held for 2 hours for nucleation treatment; then, the temperature is raised to 1075°C at the same heating rate and held for 2 hours for crystallization treatment.

[0094] The physical and chemical properties of the microcrystalline glass prepared in this embodiment are shown in Table 3.

[0095] Comparative Example 1 The process is basically the same as in Example 1, except that in step S2, the crushed coal gangue, calcium oxide and titanium dioxide are mixed in a mass percentage of 70%:25%:5% based on the total mass of the batch.

[0096] The physicochemical properties of the microcrystalline glass prepared in this comparative example are shown in Table 3.

[0097] Comparative Example 2 The process is basically the same as in Example 1, except that in step S4, the nucleation and crystallization two-stage treatment is cancelled. The pressed blank is directly heated to 1025°C at a heating rate of 10°C / min and kept at this temperature for 4 hours, and then cooled in the furnace.

[0098] The physicochemical properties of the microcrystalline glass prepared in this comparative example are shown in Table 3.

[0099] Test Example 1 This experiment aims to investigate the effects of different combinations of nucleation and crystallization temperatures on the properties of glass-ceramics.

[0100] 1. Sample preparation Using raw coal gangue (50.64wt% SiO2, 45.97wt% Al2O3, 1.50wt% TiO2, 0.60wt% Fe2O3, 0.14wt% CaO, 0.19wt% Na2O, 0.13wt% K2O, 0.83wt% other components) as raw material, the raw coal gangue, calcium oxide, and titanium dioxide were weighed according to a certain ratio of 20:5:1 and mixed to obtain a mixture. The mixture was ball-milled in a ball mill at 500 r / min for 30 min to obtain a batch material with a particle size of less than 200 mesh. Subsequently, the batch material was placed in a high-temperature furnace and melted at 1550℃ for 6 h. After homogenization and clarification, it was water-quenched to obtain the base glass. The base glass was ground into powder and pressed into long strips of 3×4×40 mm under a pressure of 5 MPa for 300 s.

[0101] The billets were divided into 9 groups and placed under different heat treatment regimes for nucleation and crystallization treatments. The specific process parameters are shown in Table 1.

[0102] Table 1

[0103] All heat treatment processes employed a heating rate of 10℃ / min, with a holding time of 2 hours during both nucleation and crystallization processes. After treatment, the samples were cooled in the furnace, then ground and polished before performance tests were conducted. X-ray diffraction tests were performed on each group of samples, and the results are as follows: Figure 3 As shown.

[0104] Figure 3 In the figures, a) shows the XRD results of the glass-ceramic prepared by nucleation at 750℃, 800℃, and 850℃ for 2 hours, followed by crystallization at 925℃ for 2 hours; b) shows the XRD results of the glass-ceramic prepared by nucleation at 750℃, 800℃, and 850℃ for 2 hours, followed by crystallization at 975℃ for 2 hours; c) shows the XRD results of the glass-ceramic prepared by nucleation at 750℃, 800℃, and 850℃ for 2 hours, followed by crystallization at 1025℃ for 2 hours; d) shows the XRD results of the glass-ceramic prepared by nucleation at 750℃, 800℃, and 850℃ for 2 hours, followed by crystallization at 1075℃ for 2 hours.

[0105] from Figure 3 It can be seen that no crystals precipitated in the glass matrix during crystallization at 925℃, indicating that this temperature is not suitable for the growth of anorthite crystals. However, crystal precipitation was evident in the glass matrix during crystallization at 975℃, 1025℃, and 1075℃, although the number of crystals generated at 975℃ was less than at 1025℃ and 1075℃. When nucleation was performed at 800℃, the number of crystal nuclei formed in the glass matrix was greater than at 750℃ and 850℃, which helps to refine the grains during subsequent crystallization, resulting in a more compact grain arrangement and a denser internal structure of the glass-ceramic. The above XRD analysis results confirm the effectiveness of the crystallization temperature range (1025–1075℃) selected in this invention. Below this range, it is difficult to achieve sufficient crystallization, while within this range, controllable growth of the target crystals can be achieved.

[0106] This experiment further used 800℃ as the nucleation temperature and crystallized at 925℃, 975℃, 1025℃, and 1075℃, observing the morphology of various samples. The results are as follows: Figure 4 As shown.

[0107] Figure 4In the figures, a) shows the SEM results of the glass-ceramic prepared by nucleation at 800℃ for 2 hours and crystallization at 925℃ for 2 hours; b) shows the SEM results of the glass-ceramic prepared by nucleation at 800℃ for 2 hours and crystallization at 975℃ for 2 hours; c) shows the SEM and energy dispersive spectroscopy (EDS) results of the glass-ceramic prepared by nucleation at 800℃ for 2 hours and crystallization at 1025℃ for 2 hours; d) shows the SEM results of the glass-ceramic prepared by nucleation at 800℃ for 2 hours and crystallization at 1075℃ for 2 hours.

[0108] from Figure 4 It can be seen that nucleation at 800℃ and crystallization at 1025℃ and 1075℃ resulted in grains with dense microstructures.

[0109] This embodiment further uses 1025℃ and 1075℃ as crystallization temperatures, and nucleates at 750℃, 800℃, and 850℃. Vickers hardness is tested for each sample according to national standard GB / T 4340.1, flexural strength is measured according to GB / T 6569, and acid and alkali resistance are measured according to GB / T1970. The test results are as follows: Figures 5-9 As shown: Table 2

[0110] As shown in Table 2, nucleation temperature and crystallization temperature have a significant impact on the properties of glass-ceramics. When the nucleation temperature is 800℃ and the crystallization temperature is 1025℃ (Group 1), the prepared microcrystalline glass has the best comprehensive performance, especially its highest bending strength (136.7 MPa) and the best corrosion resistance, which fully demonstrates the advantages of the gradient heat treatment system described in this invention.

[0111] When the nucleation temperature is 850℃ and the crystallization temperature is 1075℃ (Group 6), the hardness of the prepared microcrystalline glass reaches its peak (14.07 GPa), but the bending strength and alkali resistance are sacrificed.

[0112] Comparing groups 1 and 2, 3 and 4, and 5 and 6, it can be seen that, at the same nucleation temperature, increasing the crystallization temperature helps to improve hardness, but leads to a decrease in flexural strength and corrosion resistance.

[0113] Comparing Groups 1, 3, and 5, it can be seen that, at a crystallization temperature of 1025℃, the sample prepared by nucleation at 800℃ is superior to the samples nucleated at 750℃ and 850℃ in terms of both strength and corrosion resistance. Considering the overall physicochemical properties and energy consumption, this indicates that 800℃ is a better nucleation temperature choice under the aforementioned component system.

[0114] Test Example 2 This test example demonstrates the performance of the microcrystalline glass prepared in the various embodiments and comparative examples of the present invention.

[0115] The results are shown in Table 3: Table 3

[0116] The results in Table 3 show that the coal gangue-based microcrystalline glass prepared in all examples meets or exceeds the lower limit indicators set by this invention (e.g., hardness ≥ 7.5 GPa, flexural strength ≥ 90.0 MPa). Among them, Examples 1 and 11 show particularly outstanding performance in terms of high flexural strength (>136 MPa) and high corrosion resistance (acid resistance > 97.9%, alkali resistance > 99.9%). This fully demonstrates that the component design and gradient heat treatment process provided by this invention can stably prepare high-performance microcrystalline glass products with a coal gangue content as high as 75-80%, achieving a synergy of high solid waste content, excellent material properties, and relatively low production energy consumption.

[0117] As can be seen from Comparative Example 1, when the raw material ratio (70:25:5) is outside the scope of this invention, all the key performance indicators of the obtained microcrystalline glass do not meet the basic requirements of this invention. This indicates that the ratio range described in this invention is beneficial to achieving the performance of materials with high solid waste content.

[0118] As can be seen from Comparative Example 2, the performance of the product obtained using the traditional one-time high-temperature crystallization process is lower than that of the embodiment of the present invention. This indicates that the gradient heat treatment of the present invention helps to avoid defects such as coarse grains, uneven distribution, and glass phase residue caused by traditional one-time crystallization, thereby obtaining a microcrystalline glass with a dense structure and excellent performance.

[0119] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a coal gangue-based glass-ceramics, characterized in that, The preparation method comprises the following steps: S1, providing a coal gangue raw material; S2, crushing the coal gangue raw material, and mixing the crushed coal gangue raw material with calcium oxide and titanium dioxide at a certain mass ratio to obtain a batch material; S3, melting the batch material, and then performing cooling treatment to obtain a base glass; S4, performing powderization treatment on the base glass to obtain a base glass powder; and performing gradient heat treatment including nucleation treatment and crystallization treatment on the base glass powder after the base glass powder is formed by compression molding, to obtain the coal gangue-based glass-ceramic.

2. The production method according to claim 1, characterized by, In step S4, the gradient heat treatment specifically comprises: first, increasing the temperature to 750-850℃ at a certain temperature increasing rate, and performing nucleation treatment for 2-4h; and then increasing the temperature to 1025-1075℃ at the same temperature increasing rate, and performing crystallization treatment for 2-4h.

3. The preparation method according to claim 2, characterized in that, In step S4, the temperature increasing rate is 5-10℃ / min.

4. The method of claim 1, wherein, In step S2, the mass percentages of the coal gangue, calcium oxide and titanium dioxide in the total mass of the batch material are as follows: Coal gangue: 75-80% Calcium oxide: 15-22% Titanium dioxide: 3-5%.

5. The preparation method according to claim 1, characterized in that, In step S3, the melting temperature is 1500-1600℃, and the melting time is 4-6h.

6. The method of claim 1, wherein, In step S4, the compression molding specifically comprises: pressing the base glass powder into a green body under a pressure of 4-6MPa for 240-300s.

7. The preparation method according to claim 1, characterized in that, In step S1, the coal gangue raw material is a coal gangue sample, and the coal gangue sample mainly comprises SiO2, Al2O3 and TiO2, wherein the content of SiO2 is not less than 50%, the content of Al2O3 is not less than 45%, and the content of TiO2 is not less than 1.2%.

8. A coal gangue-based glass-ceramic, characterized in that, The coal gangue-based glass-ceramic is prepared by the preparation method of any one of claims 1-7.

9. The coal gangue-based glass-ceramic according to claim 8, characterized in that, The coal gangue-based glass-ceramic at least meets one of the performance parameters i-iv: i, the Vickers hardness is not less than 7.5 GPa; ii, the bending strength is not less than 90.0 MPa; iii, the acid resistance is not less than 95.0%; iv, the alkali resistance is not less than 99.0%.

10. The coal gangue-based glass-ceramic according to claim 8 or 9, characterized in that, The bulk density of the coal gangue-based microcrystalline glass is not less than 2.8 g / cm 3 .

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