CaO-mgo-sio2 system microcrystalline ceramic and preparation method thereof

Abstract

The application provides a CaO-MgO-SiO2 system microcrystalline ceramic and a preparation method thereof. The preparation method of the CaO-MgO-SiO2 system microcrystalline ceramic comprises the following steps: pretreating and uniformly mixing chrysotile asbestos tailings, marble tailings and quartz tailings slag to obtain a green body powder; granulating the green body powder to obtain a green body granule; pressing the green body granule to obtain a green body; and drying, glazing, heat treating and post-treating the green body to obtain the CaO-MgO-SiO2 system microcrystalline ceramic. The CaO-MgO-SiO2 system microcrystalline ceramic can be obtained through the above preparation method. The preparation method has the advantages of simple technological process, low energy consumption, green environmental protection, no need to add a bonding agent in the preparation process and low cost. The CaO-MgO-SiO2 system microcrystalline ceramic has excellent performance and can be used as a substitute for natural stone.

Description

TECHNICAL FIELD

[0001] The present application relates to the fields of solid waste resource utilization and microcrystalline ceramic materials, in particular, to a CaO-MgO-SiO2 system microcrystalline ceramic and a preparation method thereof. BACKGROUND

[0002] Wool asbestos tailings are dangerous solid wastes generated in the process of mining and selecting of wool asbestos ore, containing anthophyllite. Generally, about 20-30 tons of wool asbestos tailings are generated for every ton of wool asbestos ore mined, and the amount of tailings is huge with the accumulation of time. The accumulation of wool asbestos tailings not only occupies a large amount of land, resulting in resource waste, but also causes great pollution to the environment and harms human health. The main mineral components of wool asbestos tailings are serpentine, talc, magnetite, etc., and the chemical components are mainly SiO2, MgO, and also contain Fe2O3 and a small amount of Al2O3, CaO, etc. SiO2 and MgO are common silicate components, which will form the basic framework of ceramics in the preparation process of microcrystalline ceramics. The preparation of microcrystalline ceramics from wool asbestos tailings not only effectively consumes a large amount of accumulated tailings, but also the microcrystalline ceramics is an important environmental protection building material.

[0003] Microcrystalline ceramics are polycrystalline solid materials containing a large amount of microcrystalline phase and glass phase, which are prepared by forming crystal nuclei in the glass body through controlled crystallization behavior of the basic glass with specific composition, and then making the crystal nuclei grow through heat treatment. Microcrystalline ceramics can be divided into various types according to the composition system. Among them, CaO-MgO-SiO2 (CMS) system microcrystalline ceramics can precipitate more types of crystal phases, such as diopside, anorthite, and melilite, which have excellent performance. CaO-MgO-SiO2 system microcrystalline ceramics have excellent mechanical properties, acid and alkali corrosion resistance, and wear resistance, and have been widely studied and used as ceramic tiles, industrial floor coverings and wall materials.

[0004] The existing industrial process for preparing CaO-MgO-SiO2 system microcrystalline ceramics mainly includes melting sintering method, bulk crystallization method and melting calendering method. These methods have long production process, high energy consumption, high production cost and complex equipment, and also cause certain industrial pollution, which are not suitable for the secondary utilization of industrial solid waste. Therefore, it is of great significance to provide a CaO-MgO-SiO2 system microcrystalline ceramic and a preparation method thereof, which have simple production process, low energy consumption, green environmental protection and low cost. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to solve one or more problems in the prior art. For example, one of the purposes of the present application is to provide a CaO-MgO-SiO2 system microcrystalline ceramic preparation method which is simple in process flow and green in environmental protection, and the second purpose of the present application is to provide a CaO-MgO-SiO2 system microcrystalline ceramic with excellent performance.

[0006] To achieve the above object, the present application provides a method for preparing CaO-MgO-SiO2 system microcrystalline ceramic in one aspect.

[0007] The method can include the following steps:

[0008] The warm asbestos tailings, marble tailings and quartz-containing tailings slag are pretreated and uniformly mixed to obtain a green body powder; the green body powder is granulated to obtain a green body granule; the green body granule is pressed and formed to obtain a green body; the green body is dried, glazed, heat treated and post-treated to obtain a CaO-MgO-SiO2 system microcrystalline ceramic.

[0009] According to one exemplary embodiment of the present application, the pretreatment can include: crushing the warm asbestos tailings, marble tailings and quartz-containing tailings slag respectively to obtain a powder particle with a particle size of +10 to -20 mm (i.e. above 10 mm sieve and below 20 mm sieve); roasting the warm asbestos tailings powder particle at a temperature of 700-950°C for 60-180 min, and roasting the marble tailings powder particle at a temperature of 870-1000°C for 20-30 min to obtain active powder particles of magnesium silicate and active powder particles of calcium oxide; mixing 67-75 parts of active powder particles of magnesium silicate, 20-28 parts of active powder particles of calcium oxide and 5 parts of quartz-containing tailings slag powder particles by mass fraction, and grinding for 30-60 min after uniform mixing to obtain a green body powder with a particle size of less than 74 μm.

[0010] According to one exemplary embodiment of the present application, the granulation can include: placing the green body powder in a granulation device to spray industrial water for granulation, the ratio of the industrial water to the green body powder being 0.05-0.08:1, and obtaining a green body granule with a particle size of +0.15 to -0.85 mm after screening.

[0011] According to one exemplary embodiment of the present application, the pressing and forming can include: uniformly laying the green body granule in a mold, and obtaining a green body after demolding under a pressure of 20-50 MPa for 10-20 s.

[0012] According to one exemplary embodiment of the present application, the drying can include baking, and the baking can include baking the green body at 150-200°C for 3-15 min.

[0013] According to an example embodiment of the aspect of the present application, the heat treatment can include sintering and cooling, the sintering can include: heating the green body to 1210-1240℃ at a heating rate of 5-10℃ / min, and holding for 60-120min; and the cooling can include: naturally cooling or slow cooling first and then fast cooling to room temperature, the slow cooling first and then fast cooling can include: slow cooling to below 300℃ at a cooling rate of 5-20℃ / min, and then fast cooling to room temperature at a cooling rate of 20-50℃ / min.

[0014] According to an example embodiment of the aspect of the present application, the post-processing can include trimming and / or polishing the sintered body; the waste produced by the post-processing can be crushed to make green powder particles, the mass fraction of the waste in the green powder can be 0-2%; and the cooling water produced by the post-processing can be reused after precipitation.

[0015] According to an example embodiment of the aspect of the present application, the chrysotile asbestos tailings can include chemical components of 30-50% SiO2, 30-45% MgO, 5-12% Fe2O3, 0.1-5% CaO, 1.5-5% Al2O3, and the balance can be loss on ignition or other trace elements; the marble tailings can include chemical components of 56-60% CaO, 1.5-2% SiO2, 1-2% Al2O3, 0.2-0.4% Fe2O3, and 0.1-0.2% MgO, and the balance can be loss on ignition or other trace elements; and the quartz-containing tailings can include one or more of quartz sand tailings, silica tailings, gold-containing quartz vein waste and tailings thereof, and the SiO2 content of the quartz-containing tailings can be greater than 75%.

[0016] Another aspect of the present application provides a CaO-MgO-SiO2 system microcrystalline ceramic, which can be a product prepared by the above-mentioned method for preparing a CaO-MgO-SiO2 system microcrystalline ceramic.

[0017] According to an example embodiment of the aspect of the present application, the chemical composition of the CaO-MgO-SiO2 system microcrystalline ceramic can include chemical components of 34-38% SiO2, 21-25% MgO, 11-17% CaO, 4-9% Al2O3, 5-6% Fe2O3, 0.28-0.29% Na2O, and 0.32-0.33% K2O; the main crystal phase of the CaO-MgO-SiO2 system microcrystalline ceramic can be diopside and hedenbergite, the secondary crystal phase can be forsterite, and the amorphous phase can be a small amount of glass phase.

[0018] Compared with the prior art, the present application can have at least one of the following beneficial effects:

[0019] (1) The CaO-MgO-SiO2 system microcrystalline ceramic preparation method provided by the application selects the currently large amount of accumulated and difficult to utilize chrysotile asbestos tailings and marble tailings as main raw materials, and tailings containing quartz slag as auxiliary materials to prepare microcrystalline ceramics, which can solve the environmental problems caused by the large amount of accumulation of chrysotile asbestos tailings and marble tailings, and can replace natural mineral resources as a cheap mineral raw material for preparing microcrystalline ceramics.

[0020] (2) The CaO-MgO-SiO2 system microcrystalline ceramic preparation method provided by the application has a simple process flow, and has greater technical advantages compared with the melting sintering method, the whole crystallization method and the melting calendering method, low energy consumption, green environmental protection, and is conducive to industrial promotion, and does not need to add a bonding agent in the preparation process, and has low cost.

[0021] (3) The CaO-MgO-SiO2 system microcrystalline ceramic preparation method provided by the application realizes the whole utilization of chrysotile asbestos tailings, marble tailings and tailings containing quartz slag, and the waste of the product can also be recycled in the polishing and edge cutting process, and there is no solid waste discharge.

[0022] (4) The CaO-MgO-SiO2 system microcrystalline ceramic provided by the application has excellent performance, and the various indexes thereof can be comparable to natural mineral materials such as marble and granite, and can be used as a substitute for natural stone materials, and can be used for high-grade building decoration materials, process carving and functional microcrystalline ceramic materials and the like. BRIEF DESCRIPTION OF DRAWINGS

[0023] The above and other objects and features of the present application will become more apparent from the following description made with reference to the accompanying drawings, in which:

[0024] Figure 1 A flowchart of the CaO-MgO-SiO2 system microcrystalline ceramic preparation method of one exemplary embodiment of the present application is shown;

[0025] Figure 2A An SEM image of the surface of a CaO-MgO-SiO2 system microcrystalline ceramic sample of one exemplary embodiment of the present application is shown;

[0026] Figure 2B An SEM image of the surface of a CaO-MgO-SiO2 system microcrystalline ceramic sample of one exemplary embodiment of the present application is shown;

[0027] Figure 3 An SEM image of the cross section of a CaO-MgO-SiO2 system microcrystalline ceramic sample of one exemplary embodiment of the present application is shown;

[0028] Figure 4The XRD pattern of the CaO-MgO-SiO2 system microcrystalline ceramic sample of Example 1 of the present invention is shown. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention.

[0030] This invention addresses the problems of chrysotile asbestos tailings and marble tailings accumulation, which are currently difficult to utilize, as well as the complex processes, high energy consumption, high production costs, and significant industrial pollution associated with existing technologies. It proposes a CaO-MgO-SiO2 system of microcrystalline ceramics and its preparation method.

[0031] Exemplary Example 1

[0032] Figure 1 A schematic flowchart of a method for preparing CaO-MgO-SiO2 system microcrystalline ceramics, an exemplary embodiment of the present invention, is shown.

[0033] This exemplary embodiment provides a method for preparing CaO-MgO-SiO2 system microcrystalline ceramics. For example... Figure 1 As shown, the method for preparing CaO-MgO-SiO2 system microcrystalline ceramics mainly includes: using chrysotile asbestos tailings and marble tailings as main raw materials, and quartz-containing tailings slag as auxiliary materials, crushing and calcining the main raw materials and crushing the auxiliary materials to obtain raw and auxiliary material powders; weighing and grinding the raw and auxiliary material powders to obtain green body powder; granulating the green body powder by spraying industrial water to obtain green body granules; pressing the green body granules to obtain microcrystalline ceramic green body; drying, glazing, and high-temperature firing the green body, and cooling to obtain microcrystalline ceramic rough sample; trimming and / or polishing the obtained microcrystalline ceramic rough sample to finally obtain microcrystalline ceramic. Meanwhile, the waste generated during trimming and / or polishing can be crushed and returned to the raw and auxiliary material powders.

[0034] Specifically, the method for preparing CaO-MgO-SiO2 system microcrystalline ceramics according to the present invention mainly includes the following steps:

[0035] S1. The chrysotile asbestos tailings, marble tailings and quartz-containing tailings slag are crushed separately to obtain chrysotile asbestos tailings, marble tailings and quartz-containing tailings granules.

[0036] S2. The chrysotile asbestos tailings and marble tailings powder particles are roasted separately to obtain active powder particles of magnesium silicate and calcium oxide with a particle size of +10 to -20 mm.

[0037] S3. The magnesium silicate active powder, calcium oxide active powder, and quartz tailings slag powder are weighed and ground in proportion to obtain raw green powder with a particle size of less than 74μm.

[0038] S4, the green body powder is placed in a granulating device and sprayed with industrial water for granulation, and the green body granules with a particle size of +0.15 to -0.85 mm are obtained through screening.

[0039] S5, the green body granules are placed in a molding press for pressing molding to obtain green body.

[0040] S6, the green body is dried, glazed, sintered, cooled and post-processed to obtain CaO-MgO-SiO2 system microcrystalline ceramic.

[0041] In the present exemplary embodiment, in step S1, the chrysotile asbestos tailings and marble tailings are used as main raw materials, and the quartz tailings slag is used as auxiliary material. The main and auxiliary materials are crushed to obtain main and auxiliary material powder particles. Here, the purpose of crushing is to make the particle size of the main and auxiliary materials reach a suitable particle size to promote the completion of sintering.

[0042] In the present exemplary embodiment, in step S2, the chrysotile asbestos tailings and marble tailings powder particles are respectively calcined to obtain active powder particles of magnesium silicate and calcium oxide with a particle size of +10 to -20 mm. Here, the purpose of calcination is to decompose and destroy the fiber structure in the asbestos tailings, obtain active SiO2 and MgO, decompose and activate the calcium carbonate in the marble tailings to obtain active CaO, which is beneficial to the subsequent sintering process, the generation of calcium-magnesium melilite and diopside crystal phase, and the removal of volatile components in the raw materials to prevent the sample from producing gas inside during sintering, causing the performance of the microcrystalline ceramic product to be reduced and foaming.

[0043] Further, the calcination can heat the chrysotile asbestos tailings powder particles to 700-950°C, for example, 705°C, 725°C, 755°C, 785°C, 805°C, 911°C, 923°C, 937°C or 948°C, at a heating rate of 5-10°C / min. Keep warm for 60-180 min, for example, 65 min, 72 min, 88 min, 99 min, 109 min, 112 min or 119 min. The marble tailings powder particles are heated to 870-1000°C, for example, 875°C, 930°C, 980°C or 998°C, at a heating rate of 5-10°C / min. Keep warm for 20-30 min, for example, 21 min, 24 min, 27 min or 29 min, to promote the calcination of the chrysotile asbestos tailings and marble tailings.

[0044] In the present exemplary embodiment, in step S3, the resultant main and auxiliary material powder particles are proportioned, weighed and ground to obtain a green body powder with a particle size of less than 74 μm. Here, the grinding refers to uniformly mixing and grinding the main and auxiliary material powder particles for 30-60 min. The raw material proportions are in parts by mass, and the chrysotile asbestos tailings 67-75 parts, marble tailings 20-28 parts and quartz-containing tailings slag 5 parts are used as the formula, i.e. 67-75 parts of active powder particles of magnesium silicate, 20-28 parts of active powder particles of calcium oxide and 5 parts of quartz-containing tailings slag powder particles are used as the formula. The mass proportion of chrysotile asbestos tailings in the raw material is more than 67%, and the mass proportion of the comprehensive tailings slag in the raw material is 100%, which can meet the demand for high utilization of chrysotile asbestos tailings, marble tailings and quartz-containing tailings slag. The smaller the particle size of the green body powder, the better the performance indicators of the microcrystalline ceramic prepared therefrom. If the particle size is too large, such as greater than 74 μm, the performance of the microcrystalline ceramic prepared therefrom will be poor, for example, the volume density, water absorption, bending strength, acid resistance and alkali resistance will be poor. This is because a particle size that is too large can cause uneven mixing of the raw materials, or insufficient contact reaction of the raw materials during sintering, resulting in poor performance. However, a particle size that is too small can increase energy consumption. Here, the particle size of the green body powder can be +20 μm to -74 μm, for example, 25 μm, 30 μm, 50 μm, 66 μm or 73 μm. Here, the sum of the mass of SiO2, MgO and CaO in the proportioned raw material can be 72-74%, which is the main component of the microcrystalline phase, and the content of Fe2O3 of 5-6% can be used as a good nucleating agent and crystal nucleus agent, which can effectively reduce the sintering activation energy and reduce the sintering cost. The quartz-containing tailings slag can include one or more of quartz sand tailings, silica tailings, gold-containing quartz vein waste rock and tailings thereof, and the main component of the quartz-containing tailings slag is SiO2, of which SiO2 is more than 75%, which can supplement the Si source in the system, promote the formation of diopside, calcium-magnesium melilite phase crystals and liquid phase at high temperature, and improve the mechanical properties of the microcrystalline ceramic.

[0045] In the present exemplary embodiment, in step S4, the obtained green body powder is placed in a granulating device, and granulation can be performed by spraying industrial water, to obtain green body granules having a particle size of +0.15 to -0.85 mm, for example, 0.2 mm, 0.3 mm, 0.44 mm, 0.56 mm, 0.67 mm, 0.78 mm, or 0.84 mm. Here, the amount of industrial water added is 5 to 8% of the mass of the raw material, that is, the ratio of industrial water to green body powder is 0.05 to 0.08:1. When the amount of industrial water is too large, the water content in the green body powder during the molding process will be too high, and the molding process will squeeze out the water in the industrial water. If the mold is not a corrosion-resistant mold, or is not a stainless steel mold, the squeezed-out water will cause great damage to the mold, and the mold will easily rust. From the perspective of the appearance of the microcrystalline ceramic, too much industrial water added will cause the surface of the microcrystalline ceramic sample to crack or the glaze to bulge during the sintering process. When the amount of industrial water added is less than 5% of the mass of the raw material, although it can also be applicable, the microcrystalline ceramic green body formed by the pressing process will not have good forming effects, and cracks are likely to occur during the demolding process. In addition, the green body has low strength and is likely to break during transportation.

[0046] In the present exemplary embodiment, in step S5, the obtained green body granules are pressed to form a microcrystalline ceramic green body. The step of pressing can include uniformly laying the green body powder particles in a mold, maintaining a pressure of 20 to 50 MPa for 10 to 20 s, and demolding to obtain a microcrystalline ceramic green body. For example, the pressure can be maintained at 20 MPa for 20 s, at 35 MPa for 15 s, or at 47 MPa for 10 s. If the molding pressure is small and the pressure maintaining time is short during the pressing process, the product is not easy to form, the sintered product has too many internal pores, the bulk density is relatively small, the corresponding bending strength is small, and the water absorption rate is large. If the molding pressure and the pressure maintaining time are increased, the performance of the sample will improve, but the degree of improvement is not obvious. For example, under the condition that the pressure is greater than 40 MPa and the pressure maintaining time is 20 s, the performance of the product does not increase significantly, and a high pressure will increase energy consumption, and a long pressure maintaining time will reduce production efficiency.

[0047] Further, during the pressing process, the environment for forming the green body can be a room temperature environment, or an environment at a temperature higher than room temperature, for example, 22°C, 28°C, 33°C, 37°C, or 39°C.

[0048] In the present exemplary embodiment, the green body obtained in step S6 is dried and glazed, and then heated to 1210-1240°C, for example, 1215°C, 1220°C, 1230°C or 1235°C, for sintering, and then cooled after sintering is completed, to obtain the microcrystalline ceramic. Here, the drying can be performed by baking, and the baking step includes baking the green body at 150-200°C for 3-15 min. For example, the baking temperature can be 155°C, 164°C, 178°C, 187°C or 197°C, and the time can be 4 min, 7 min, 11 min or 14 min. The baking temperature cannot be lower than 150°C, otherwise the water in the green body is not evaporated, and the green body has low strength, and cracking or breaking of the green body in the roller kiln can occur during sintering; the baking temperature also cannot be too high, otherwise the water in the green body is rapidly evaporated, and the green body cracks. The sintering temperature cannot be lower than 1210°C, otherwise the sample is not sintered completely, and the sample has poor compactness, small bulk density, high porosity and poor flexural strength; the sintering temperature also cannot be too high, otherwise over-sintering occurs, and the sample has pores on the surface, bubbles in the interior and uneven surface, which affect the performance of the sample and its practical application, and the high temperature also increases energy consumption, which is not in line with the green and low-energy requirements from the environmental protection point of view, and also increases the cost from the economic point of view.

[0049] Further, in step S6, the green body obtained is heated to 1210-1240°C at a rate of 5-10°C / min, for example, 6°C / min, 8°C / min or 9°C / min. Here, using a suitable heating rate can sinter the green body and obtain a microcrystalline ceramic with good sintering compactness and excellent performance. The heating rate cannot be too high, otherwise the sample cracks due to large temperature difference and violent shrinkage during sintering of the green body; the heating rate also cannot be too low, otherwise the sintering compactness of the sample is not improved significantly, and from the green and environmental protection point of view, a low heating rate increases the sintering energy consumption, which is not conducive to green and environmental protection, and from the economic point of view, a low heating rate increases fuel consumption and reduces the sintering efficiency, which is not in line with the green economy. Preferably, in consideration of the green economy and product quality, the heating rate can be selected as a larger value in the above range, which is conducive to ensuring the quality of the product and achieving the effect of energy saving.

[0050] In the present exemplary embodiment, in step S6, the obtained green body is heated to 1210-1240°C and kept for 60-120 min to promote sintering, so as to obtain a qualified product. For example, the keeping time can be 60 min, 80 min, 96 min, 103 min or 119 min. Here, if the keeping time is too low, the sintering of the sample is incomplete, and the product has poor performance; if the keeping time is too long, although the sintering is promoted, the promoting effect is not obvious, and from the perspective of green environmental protection, the keeping time is too long, which increases the sintering energy consumption, is not conducive to green environmental protection, and from the economic perspective, the keeping time is too long, which increases the fuel consumption and reduces the production efficiency, which is not in line with green economy.

[0051] In the present exemplary embodiment, in step S6, after sintering is completed, cooling can be performed, and the cooling step can include: first slow cooling to room temperature, for example, cooling with furnace temperature. The slow cooling step can include: slow cooling to below 300°C, and then rapid cooling, for example, first cooling to 210°C, 240°C or 260°C with furnace temperature, and then cooling outside the furnace. Here, the slow cooling rate can be controlled at 5-20°C / min, for example, 10°C / min, 13°C / min, 17°C / min or 19°C / min. The rapid cooling rate can be controlled at 20-50°C / min, for example, 34°C / min, 37°C / min, 43°C / min or 46°C / min.

[0052] In the present exemplary embodiment, in step S6, the heat treatment process (i.e. the sintering process) can be performed in a roller kiln. Here, the heat treatment process can be performed in an oxygen-containing gas, for example, air or oxygen-enriched gas.

[0053] In the present exemplary embodiment, in step S6, the post-processing can include: cutting and / or polishing the obtained microcrystalline ceramic rough sample, and returning the obtained waste as one of the raw materials. Here, the cooling water generated by cutting and / or polishing can be reused after precipitation. The mass fraction of the waste generated by cutting and / or polishing in the raw material can be 0-2%, for example, 0.1%, 0.3%, 0.5%, 0.7% or 0.9%.

[0054] In the present exemplary embodiment, the chemical composition of the chrysotile asbestos tailings can include, by mass fraction, 30-50% Si02, 30-45% MgO, 5-12% Fe203, 0.1-5% CaO, and 1.5-5% Al203, with the balance being loss on ignition or other trace elements. For example, the chrysotile asbestos tailings can include 44±1% Si02, 32±0.5% MgO, 7±0.5% Fe203, 2±0.5% Al203, 0.5±0.1% CaO, 0.34±0.01% Cr203, 0.35±0.01% NiO, 0.2±0.1% Na20, and 0.15±0.05% K20.

[0055] In the present exemplary embodiment, the chemical composition of the marble tailings can include, by mass fraction, 56-60% CaO, 1.5-2% Si02, 1-2% Al203, 0.2-0.4% Fe203, and 0.1-0.2% MgO, with the balance being loss on ignition or other trace elements. For example, the marble tailings can include 56.34±1% CaO, 1.85±0.1% Si02, 1.5±0.1% Al203, 0.34±0.05% Fe203, 0.11±0.01% K20, and 0.05±0.01% Na20.

[0056] In the present exemplary embodiment, the chemical composition of the quartz sand tailings can include, by mass fraction, 75-90% Si02, 0.2-0.5% Fe203, 0.25-0.5% CaO, 7-10% Al203, 3-5% K20, and 1.5-2.5% Na20, with the balance being loss on ignition or other trace elements. For example, the quartz sand tailings can include 84.93±1% Si02, 8.73±1% Al203, 0.31±0.1% Fe203, 0.38±0.1% CaO, 3.59±0.5% K20, and 1.64±0.1% Na20.

[0057] The CaO-MgO-Si02system microcrystalline ceramic prepared according to the method for preparing a CaO-MgO-Si02system microcrystalline ceramic can be tested for bulk density, water absorption, bending strength, and linear shrinkage, and the various test methods are as follows:

[0058] Bulk density test: The bulk density of the CaO-MgO-Si02system microcrystalline ceramic sample prepared according to the method for preparing a CaO-MgO-Si02system microcrystalline ceramic sample is calculated according to the Archimedes principle, and the formula is:

[0059]

[0060] Wherein, m1 is the sample dry weight, unit is g; m2 is the sample suspension weight, unit is g; m3 is the sample wet weight, unit is g; p is the sample volume density, unit is g / cm 3 .

[0061] Water absorption test: according to the Archimedes principle, the calculation formula of the water absorption of the CaO-MgO-SiO2 system microcrystalline ceramic sample is:

[0062]

[0063] Wherein, W1 is the sample dry weight, unit is g; W2 is the sample suspension weight, unit is g; The water absorption of the sample is the water absorption of the sample, unit is %.

[0064] Flexural strength test: under the condition of span of 40mm and loading speed of 0.5mm / min, the three-point bending method (GB / T4741-1999) is used for testing, and the calculation formula is:

[0065]

[0066] Wherein, F is the maximum load force, unit is N; L is the support span, unit is mm; b is the sample center width, unit is mm; d is the sample center thickness, unit mm; and sigma is the flexural strength, unit is MPa.

[0067] Linear shrinkage test: the comparison method is used for testing, and the calculation formula is:

[0068]

[0069] Wherein, L1 is the diameter of the microcrystalline ceramic blank, unit is mm; L2 is the diameter of the microcrystalline ceramic after firing, unit is mm; LS is the linear shrinkage of the microcrystalline ceramic, unit is %.

[0070] Example 2

[0071] Figures 2A-2B The SEM diagram of the surface of the CaO-MgO-SiO2 system microcrystalline ceramic sample of one example embodiment of the application is shown; Figure 3 The SEM diagram of the section of the CaO-MgO-SiO2 system microcrystalline ceramic sample of one example embodiment of the application is shown; Figure 4 The XRD diagram of the CaO-MgO-SiO2 system microcrystalline ceramic sample of example 1 of the application is shown.

[0072] The example embodiment provides a CaO-MgO-SiO2 system microcrystalline ceramic.

[0073] The CaO-MgO-SiO2system microcrystalline ceramic can include a product prepared by the preparation method of the CaO-MgO-SiO2system microcrystalline ceramic described in the above exemplary embodiment 1.

[0074] In the present exemplary embodiment, the CaO-MgO-SiO2system microcrystalline ceramic has diopside and calcium-magnesium melilite as main crystal phases, the diopside phase has stable chemical properties, the higher the content of the diopside phase, the stronger the chemical corrosion resistance (acid and alkali resistance) of the microcrystalline ceramic, and thus the microcrystalline ceramic product having the phase has excellent performance. The CaO-MgO-SiO2system microcrystalline ceramic also contains a small amount of glass phase, the glass phase wraps the crystal phase, and the different types of crystal grains interweave with each other to form a relatively dense accumulation body, and a small amount of voids exist in the interweaving of the crystal grains.

[0075] In the present exemplary embodiment, the bulk density of the CaO-MgO-SiO2system microcrystalline ceramic can be 1.79-2.71 g / cm 3 , the water absorption can be 0.21-13.87%, the flexural strength can be 22.73-61.06 MPa, the linear shrinkage can be 1.01-10.63%, the acid resistance can be greater than 92.32%, and the alkali resistance can be greater than 99.53%.

[0076] Figure 2A and Figure 2B The SEM image of the surface of the CaO-MgO-SiO2system microcrystalline ceramic sample is shown, which shows that the surface of the microcrystalline ceramic is well sintered and has no obvious pores, which can ensure that the water absorption is below 14%, the internal porosity of the microcrystalline ceramic product is 8-23%, and the porosity of the microcrystalline ceramic can be calculated by the "Imagine Pro-Plus 6.0" software. Figure 2A and Figure 2B The porosity of the microcrystalline ceramic is low, the pore size distribution is uniform, and the sintering effect is good. The number of pores in the microcrystalline ceramic product is small, the pore size distribution is uniform, the internal pore size can be less than 60 μm, for example, between 20-50 μm, which can ensure that the density of the microcrystalline ceramic is reduced on the basis of the mechanical properties, and the self-weight of the microcrystalline ceramic as a building decoration is reduced. If the internal porosity is too large, the mechanical properties (compressive strength and flexural strength) of the microcrystalline ceramic sample will be reduced.

[0077] Figure 3The SEM image of the cross section of the CaO-MgO-SiO2 system microcrystalline ceramic sample is shown, and it can be seen that the morphology of the diopside phase is tetrahedron, the morphology of the gehlenite is short column, and the morphology of the forsterite phase is hexagon or irregular sphere. The diameter of the granular diopside phase can be 1-4 μm, the short columnar gehlenite interweaves, and the granular diopside and forsterite inlaid in the amorphous glass and gehlenite phase can increase the bending strength of the microcrystalline ceramic and improve the mechanical properties. The more compact the internal structure is, the better the bending strength is.

[0078] The CaO-MgO-SiO2 system microcrystalline ceramic prepared by the above CaO-MgO-SiO2 system microcrystalline ceramic preparation method can include the following components according to mass percentage: 34-38% SiO2, 21-25% MgO, 11-17% CaO, 4-9% Al2O3, 5-6% Fe2O3, 0.28-0.29% Na2O and 0.32-0.33% K2O.

[0079] In order to better understand the example 2 of the present application, it is further described below in combination with specific examples.

[0080] Example 1

[0081] (1) The chrysotile asbestos tailings and marble tailings in Sichuan are heated to 800℃ at a heating rate of 5℃ / min, and the temperature is kept for 120 min to remove the volatile components and unburned carbon in the raw materials.

[0082] (2) The calcined chrysotile asbestos tailings and marble tailings are used as the main raw materials, and the quartz sand tailings are used as the auxiliary materials. The chrysotile asbestos tailings, marble tailings and quartz sand tailings are weighed according to the ratio of 71:24:5, and then placed in a ball mill tank. The raw materials and balls are mixed in the ball mill tank at a ratio of 1:1 at 400 rpm for 1 h, and the sample is sieved with a sieve (200 mesh). The undersize sample is taken to obtain the green body powder with a particle size of less than 74 μm.

[0083] (3) The undersize raw materials are mixed uniformly with industrial water to obtain the green body granules. The green body granules are laid flat in the forming mold, and the green body forming pressure is 20 MPa. The pressure is kept for 10 s to prepare the microcrystalline ceramic green body with a size of Ф25 mm and a thickness of 3 mm.

[0084] (4) The green body is dried and glazed, and then placed in a roller hearth kiln. The temperature is raised from room temperature to 1230℃ at a rate of 5℃ / min, and the temperature is kept for 1 h at 1230℃. The sample is taken out after the furnace is cooled down, and polished and edged to obtain the microcrystalline ceramic.

[0085] The performance of the product is tested, and the bulk density of the microcrystalline ceramic product of example 1 is 2.71 g / cm 3The water absorption is 0.35%, the bending strength is 61.06 MPa, the linear shrinkage is 10.56%, the acid resistance is 93.39%, and the alkali resistance is 99.98%. Figure 4 The XRD diagram of the CaO-MgO-SiO2 system microcrystalline ceramic sample obtained in the example is shown, and it is shown that the main crystal phase of the CaO-MgO-SiO2 system microcrystalline ceramic is diopside and calcium-magnesium melilite, and the secondary crystal phase is forsterite.

[0086] In summary, the advantages of the present application can include at least one of the following:

[0087] (1) The CaO-MgO-SiO2 system microcrystalline ceramic preparation method provided by the present application can achieve 100% utilization of solid waste, and no solid waste is discharged during production, which can realize low-cost, high-usage and high-value utilization of tailings waste. At the same time, it can effectively improve the harm to human health and ecological environment caused by the large accumulation of chrysotile asbestos tailings.

[0088] (2) The CaO-MgO-SiO2 system microcrystalline ceramic preparation method provided by the present application solves the problem of difficult utilization of chrysotile asbestos tailings, marble tailings and quartz-containing tailings, wherein the utilization of chrysotile asbestos tailings is 67-75%, the utilization of marble tailings is 20-28%, and the utilization of quartz-containing tailings is 5%.

[0089] (3) The CaO-MgO-SiO2 system microcrystalline ceramic provided by the present application has excellent performance in bending strength, bulk density and water absorption, etc., meets market demand, is conducive to industrial promotion, and the prepared microcrystalline ceramic can be used as a decorative material for floors, floors and hall counter tops, etc., and can also be used as a building brick, a ventilated outer wall for interior wall decoration, etc.

[0090] Although the CaO-MgO-SiO2 system microcrystalline ceramic and the preparation method thereof of the present application have been described above by combining exemplary embodiments, it should be clear to those skilled in the art that various modifications and changes can be made to the exemplary embodiments of the present application without departing from the spirit and scope defined by the claims.

Claims

1. A method for producing a CaO-MgO-SiO2 system microcrystalline ceramic, characterized by, The preparation method comprises the following steps: The chrysotile asbestos tailings, marble tailings and quartz-containing tailings slag are pretreated and uniformly mixed to obtain a green body powder; The green body powder is granulated to obtain a green body granule; The green body granule is pressed and formed to obtain a green body; The green body is dried, glazed, heat treated and post-treated to obtain a CaO-MgO-SiO2 system microcrystalline ceramic; the heat treatment comprises sintering, and the sintering comprises: heating the green body to 1210-1240 DEG C at a heating rate of 5-10 DEG C / min and keeping the temperature for 60-120 min; The chemical composition of the CaO-MgO-SiO2 system microcrystalline ceramic comprises, by mass percentage, chemical components: 34-38% SiO2, 21-25% MgO, 11-17% CaO, 4-9% Al2O3, 5-6% Fe2O3, 0.28-0.29% Na2O and 0.32-0.33% K2O; the main crystal phase of the CaO-MgO-SiO2 system microcrystalline ceramic is diopside and calcium-magnesium melilite, the secondary crystal phase is forsterite, and the amorphous phase is a small amount of glass phase.

2. The method for producing CaO-MgO-SiO2 system microcrystalline ceramic according to claim 1, characterized by, The pretreatment comprises: The chrysotile asbestos tailings, marble tailings and quartz-containing tailings slag are respectively crushed to obtain powder particles with a particle size of 10-20 mm; The chrysotile asbestos tailings powder particles are calcined at a temperature of 700-950 DEG C for 60-180 min, and the marble tailings powder particles are calcined at a temperature of 870-1000 DEG C for 20-30 min to obtain active powder particles of magnesium silicate and active powder particles of calcium oxide; The active powder particles of magnesium silicate, the active powder particles of calcium oxide and the quartz-containing tailings slag powder particles are mixed in a mass ratio of 67-75:20-28:5, and then ground for 30-60 min to obtain a green body powder with a particle size of less than 74 μm.

3. The method for producing CaO-MgO-SiO2 system microcrystalline ceramic according to claim 1, characterized by, The granulation comprises: the green body powder is placed in a granulation device to spray industrial water for granulation, the mass ratio of the industrial water to the green body powder is 0.05-0.08:1, and the green body granule with a particle size of 0.15-0.85 mm is obtained after screening.

4. The method for producing CaO-MgO-SiO2 system microcrystalline ceramic according to claim 1, characterized by, The pressing and forming comprises: the green body granule is uniformly laid in a mold, and the green body is obtained after the mold is demolded under a pressure of 20-50 MPa for 10-20 s.

5. The method for producing CaO-MgO-SiO2 system microcrystalline ceramic according to claim 1, characterized by, The drying comprises baking, and the baking comprises baking the green body at 150-200 DEG C for 3-15 min.

6. The method for producing CaO-MgO-SiO2 system microcrystalline ceramic according to claim 1, characterized by, The heat treatment comprises cooling, and the cooling comprises: natural cooling or slow cooling first and then rapid cooling to room temperature to cool the body, and the slow cooling first and then rapid cooling comprises: slow cooling to below 300 DEG C at a cooling rate of 5-20 DEG C / min, and then rapid cooling to room temperature at a cooling rate of 20-50 DEG C / min.

7. The method for producing CaO-MgO-SiO2 system microcrystalline ceramic according to claim 1, characterized by, The post-treatment comprises edge cutting and / or polishing of the sintered body; the waste generated by the post-treatment can be crushed to make a green body powder, the mass fraction of the waste in the green body powder is 0-2%, and the cooling water generated by the post-treatment can be reused after precipitation.

8. The method for producing CaO-MgO-SiO2 system microcrystalline ceramic according to claim 1, characterized by, The chrysotile asbestos tailings include chemical components in percentage of mass: 30-50% SiO2, 30-45% MgO, 5-12% Fe2O3, 0.1-5% CaO, 1.5-5% Al2O3, and the balance is loss on ignition or other trace elements; the marble tailings include chemical components: 56-60% CaO, 1.5-2% SiO2, 1-2% Al2O3, 0.2-0.4% Fe2O3 and 0.1-0.2% MgO, and the balance is loss on ignition or other trace elements; the quartz-containing tailings slag includes one or more of quartz sand tailings, silica tailings, gold-containing quartz vein waste rock and tailings thereof, and the SiO2 content of the quartz-containing tailings slag is greater than 75%.

9. A CaO-MgO-SiO2 system microcrystalline ceramic, characterized by, The CaO-MgO-SiO2 system microcrystalline ceramic includes a product prepared by the preparation method of the CaO-MgO-SiO2 system microcrystalline ceramic according to any one of claims 1 to 8; and the water absorption of the CaO-MgO-SiO2 system microcrystalline ceramic is less than 14%.

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