Core-shell structure composite foaming agent and preparation method thereof, as well as granite slag lightweight glazed microcrystalline glass and preparation method thereof

Abstract

The present invention discloses a core-shell structure composite foaming agent and a preparation method thereof, as well as a granite mud lightweight glazed microcrystalline glass and a preparation method thereof. The present invention heat-treats silicon micropowder in a mixed atmosphere of ammonia and argon or methane and argon to obtain a composite foaming agent; the composite foaming agent is mixed with granite mud, and pressure-formed to obtain a blank; low-temperature dense sintering and high-temperature glaze firing and foaming are then performed to obtain a lightweight glazed microcrystalline glass. The present invention can greatly improve the utilization rate and added value of granite mud; in addition, the use of a composite foaming agent and a step-by-step sintering method not only has low energy consumption, but also produces lightweight glazed microcrystalline glass with uniform and controllable pores and excellent performance, and is expected to be used in high-end building decoration materials.

Description

Technical Field

[0001] The invention belongs to the field of porous ceramics, and in particular relates to a preparation method of a core-shell structure composite foaming agent and a lightweight glazed microcrystalline glass. Background Art

[0002] Granite is a kind of rock with abundant resources and widespread distribution, mainly composed of minerals such as quartz and feldspar. Granite is widely used as a building decoration material due to its wide variety, rich styles, high hardness and good durability. A large amount of mud residue is produced during the mining and processing of granite. The long-term accumulation of mud residue is easy to cause dust pollution and affect the surface and groundwater quality around the yard.

[0003] At present, the resource utilization of granite slag is mainly concentrated in the fields of concrete, microcrystalline glass, fine ceramics and recycled minerals (Wang D, Lu J, Zhan J, et al. Recent Advances in the Reutilization of Granite Waste in Various Fields[J]. Journal of Material Science and Technology Research, 2021, 8: 30-40.), but most of it is used as concrete aggregate, with low added value, and the enthusiasm of related industries is not high. Because the slag contains a large amount of colored impurities, its large-scale value-added utilization is restricted. As a porous material, foamed ceramics have excellent properties such as sound insulation and noise reduction, low bulk density and high porosity (Jiang Congcong, et al. Research progress of solid waste-based foamed ceramics based on in-situ foaming process[J / OL]. Journal of the Chinese Ceramic Society: 1-17 [2022-09- 19].). Granite slag contains SiO2 and Al2O3, which can be used as the main raw material of foamed ceramics. The alkaline earth metal oxides contained in it can be used as co-solvents to promote foaming and make the foaming process more convenient. Patent CN106187134A discloses a foamed lightweight wall material based on granite waste residue, which uses granite as an auxiliary material and is mixed with clay and sintered to prepare the foamed material. However, the utilization rate of the granite waste residue is low, the product performance is poor, and it is difficult to promote and apply. Summary of the invention

[0004] The invention adds a composite foaming agent with a core-shell structure to granite mud, adopts a step-by-step sintering technology, first performs low-temperature dense sintering, and then performs high-temperature glaze firing and foaming, so as to prepare granite mud lightweight glazed microcrystalline glass.

[0005] The invention provides a core-shell structure composite foaming agent and a preparation method thereof, as well as a granite mud slag lightweight glazed microcrystalline glass and a preparation method thereof.

[0006] A core-shell structure composite foaming agent, with elemental silicon as the core and silicon nitride or silicon carbide as the shell, the particle size of the composite foaming agent is 1 to 10 The shell thickness is 0.1 to 0.5 .

[0007] A method for preparing a core-shell structure composite foaming agent, wherein the silicon micropowder is heat-treated in a mixed atmosphere of ammonia and argon or methane and argon, the heat treatment temperature range is 800-1000°C, and the heat treatment time is 1-30 min; a core-shell structure composite foaming agent of silicon nitride or silicon carbide coated silicon particles is prepared respectively.

[0008] A method for preparing a granite slag lightweight glazed glass-ceramics comprises the following steps:

[0009] Step 1: mixing the core-shell structure composite foaming agent with granite mud, and pressure molding to obtain a green blank;

[0010] Step 2: sintering the green blank at a constant temperature of 1050-1200° C. for 2 h to perform low-temperature dense sintering;

[0011] Step 3: The densely sintered green body is fired at a constant temperature of 1250-1300° C. for 1-30 min to perform high-temperature glaze firing and foaming to obtain a lightweight glazed microcrystalline glass.

[0012] Preferably, the particle size of the silicon powder is 1 to 10 .

[0013] Preferably, the usage of the core-shell structure composite foaming agent is 0.5-5% of the mass of the granite mud.

[0014] The pore size of granite mud lightweight glazed glass-ceramics is 0.5 to 2.5 mm.

[0015] Granite slag lightweight glazed glass-ceramics can be used in building decoration materials.

[0016] At a lower sintering temperature, the feldspar in the sludge melts to form a liquid glass phase, which promotes the dense sintering of the green body. During the sintering process, the shell silicon nitride or silicon carbide of the core-shell structure composite foaming agent is oxidized, the generated silicon dioxide dissolves into the liquid glass phase, and the generated nitrogen or carbon dioxide forms bubble nuclei in the glass phase. At a higher sintering temperature, the feldspar in the green body continues to melt, the quartz in the sludge gradually dissolves into the glass phase, and a glaze layer is formed on the surface. At this time, the silicon particles in the composite foaming agent slowly oxidize, releasing silicon monoxide gas, which promotes the growth of bubble nuclei in the glass phase, and obtains lightweight glazed microcrystalline glass with uniform pore size and controllable size.

[0017] The core-shell structure composite foaming agent and preparation method thereof, as well as the granite slag lightweight glazed glass-ceramics and preparation method thereof provided by the present invention have the following beneficial effects:

[0018] (1) The present invention uses granite mud as raw material, and no other additives are used except for the composite foaming agent, which greatly improves the utilization rate of granite mud. At the same time, the silicon nitride or silicon carbide in the shell layer and the silicon particles in the core of the core-shell composite foaming agent are used as foaming agents for low-temperature dense sintering and high-temperature glaze firing, respectively, which is conducive to reducing the amount of foaming agent used.

[0019] (2) The present invention adopts the step-by-step sintering and foaming technology to prepare lightweight glazed microcrystalline glass with uniform and controllable pores and excellent performance.

[0020] In summary, this invention can greatly improve the utilization rate and added value of granite mud residue; in addition, the use of composite foaming agent and step-by-step sintering method not only has low energy consumption, but also produces lightweight glazed microcrystalline glass with uniform and controllable pores and excellent performance, which can be used for high-end building decoration materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the preparation process of granite mud lightweight glazed micro-ceramic glass.

[0022] Figure 2 This is a photo of the glazed glass-ceramics prepared in Example 1.

[0023] Figure 3 This is a real photo of the lightweight glazed glass-ceramics prepared in Example 2.

[0024] Figure 4 This is the XRD spectrum of the lightweight glazed glass-ceramics prepared in Example 2.

[0025] Figure 5 This is a SEM photograph of the lightweight glazed glass-ceramics prepared in Example 2.

[0026] Figure 6 This is a real photo of the lightweight glazed glass-ceramics prepared in Example 3. DETAILED DESCRIPTION

[0027] The present invention is further described by the following examples, but the present invention is not limited to the contents involved in the examples.

[0028] The specific process steps of the present invention are as follows Figure 1 As shown, a composite foaming agent is added to the granite mud, the material is mixed and granulated, placed in a mold for pressure molding, and made into a green body, which is densely sintered at a relatively low temperature to form bubble nuclei; the temperature is continued to be raised to a higher temperature for sintering to form a glaze layer, and at the same time, foaming is uniformly performed to obtain a granite mud lightweight glazed microcrystalline glass.

[0029] Embodiment 1:

[0030] 0.1 g of silicon micropowder was weighed and mixed evenly with 5 g of granite mud residue, wherein the particle size of silicon micropowder was 10 μm. The powder was mixed and granulated, placed in a mold, and pressed under a pressure of 50 MPa. The green blank was placed in a sintering furnace, the room temperature was raised to 1200 °C, the temperature was kept constant for 2 hours, and then cooled to room temperature with the furnace to obtain granite mud residue glazed microcrystalline glass. Figure 2 This is a photo of a glazed glass-ceramic using 2% silica powder as a foaming agent. The biscuit is sintered evenly and densely, and the surface glaze has good gloss, indicating that adding silica powder has a great effect on the surface of the glass. No foaming occurs during sintering. The compressive strength of the sintered sample was tested on a ceramic bending tester and was 68.9 MPa. The volume density was tested using the Archimedean drainage method and was 2.15 g / cm 3 .

[0031] Embodiment 2:

[0032] Weigh 0.1 g of silicon powder, the particle size of the powder is 2.5 , heat treated at 1000 ℃ for 15 min in a mixed atmosphere of ammonia and argon to obtain a core-shell structure composite foaming agent of silicon nitride coated silicon micropowder; weigh 5 g of granite mud, add 1% composite foaming agent, mix evenly, granulate, put it in a mold, and press it under a pressure of 50 MPa; place the green body in a sintering furnace, raise the temperature from room temperature to 1100 ℃, and keep it for 2 h; then raise the temperature from 1100 ℃ to 1300 ℃, keep it for 15 min, and cool it to room temperature with the furnace to obtain granite mud lightweight glazed microcrystalline glass. Figure 3 This is a photo of a lightweight glazed glass-ceramic with 1% composite foaming agent added. The sample is uniformly foamed, and the pore size is between 0.5 and 1.5 mm. The crystal structure of the lightweight glazed glass-ceramic is analyzed by powder X-ray diffraction (XRD). Figure 4 As shown in Figure 1, the main crystalline phases of the microcrystalline glass are calcium feldspar and quartz. The crystallinity is 17.4% using Jade software. The microstructure is observed using a scanning electron microscope (SEM). Figure 5 As shown in the figure, the pore walls are dense, indicating that the pores are all closed-cell structures. The compressive strength was measured to be 17.3 MPa on a ceramic bending tester, and the volume density was 1.76 g / cm3 using the Archimedes drainage method. 3 .

[0033] Embodiment 3:

[0034] Weigh 0.1 g of silicon powder, the particle size of the powder is 2.5 , heat treated at 900 ℃ for 15 min in a mixed atmosphere of methane and argon to obtain a core-shell structure composite foaming agent of silicon carbide coated silicon micropowder; weigh 5 g of granite mud, add 1% composite foaming agent, mix evenly, granulate, put it in a mold, and press it under a pressure of 50 MPa; place the green body in a sintering furnace, raise the temperature from room temperature to 1100 ℃, and keep it for 2 h; then raise the temperature from 1100 ℃ to 1300 ℃, keep it for 15 min, and cool it to room temperature with the furnace to obtain granite mud lightweight glazed microcrystalline glass. Figure 6 This is a photo of a lightweight glazed glass-ceramic with 1% composite foaming agent added. The sample is uniformly foamed, the surface has good glaze gloss, and the pore size is 1.0~2.0 mm. The compressive strength is 7.2 MPa measured on a ceramic bending tester, and the volume density is 1.29 g / cm tested using the Archimedes drainage method. 3 .

[0035] Embodiment 4:

[0036] Weigh 0.1 g of silicon powder, the particle size of the powder is 1.0 , heat treated at 1000 ℃ for 1 min in a mixed atmosphere of methane and argon to obtain a core-shell structure composite foaming agent of silicon carbide coated silicon micropowder; weigh 5 g of granite mud, add 2% composite foaming agent, mix evenly, granulate, place in a mold, and press under 50 MPa pressure to form; place the green blank in a sintering furnace, heat from room temperature to 1150 ℃, keep warm for 2 h; then heat from 1150 ℃ to 1300 ℃, keep warm for 5 min, cool to room temperature with the furnace, and obtain granite mud lightweight glazed microcrystalline glass. The lightweight glazed microcrystalline glass is uniformly foamed, the surface has good glaze gloss, and the pore size is 2.0~2.5 mm. Its compressive strength is 5.8 MPa measured on a ceramic bending tester, and its volume density is 1.23 g / cm tested by the Archimedes drainage method. 3 .

[0037] In summary, this invention can greatly improve the utilization rate and added value of granite mud residue; in addition, the use of composite foaming agent and step-by-step sintering method not only has low energy consumption, but also produces lightweight glazed microcrystalline glass with uniform and controllable pores and excellent performance, which can be used for high-end building decoration materials.

Claims

1. A core-shell structure composite foaming agent, characterized in that: The single substance silicon is used as the core, silicon nitride or silicon carbide is used as the shell layer, the particle size of the composite foaming agent is 1 to 10 μm, and the thickness of the shell layer is 0.1 to 0.5 μm.

2. A method for preparing a core-shell structure composite foaming agent as claimed in claim 1, characterized in that: Silicon micropowder is heat treated in a mixed atmosphere of ammonia and argon or methane and argon at a temperature range of 800-1000°C for a time of 1-30 minutes to prepare core-shell composite foaming agents of silicon nitride or silicon carbide coated silicon particles.

3. A method for preparing light glazed glass-ceramics made of granite mud, characterized in that: The steps include: Step 1: Mixing the core-shell structure composite foaming agent as claimed in claim 1 with granite mud, and pressure molding to obtain a green blank; the core-shell structure composite foaming agent has elemental silicon as a core and silicon nitride or silicon carbide as a shell; Step 2: sintering the green blank at a constant temperature of 1050-1200° C. for 2 hours to perform low-temperature dense sintering; Step 3: The densely sintered green body is fired at a constant temperature of 1250-1300° C. for 1-30 min to perform high-temperature glaze firing and foaming to obtain a granite mud lightweight glazed microcrystalline glass.

4. The method according to claim 3, characterized in that The usage of the core-shell structure composite foaming agent is 0.5-5% of the mass of the granite mud residue.

5. The granite mud lightweight glazed glass-ceramics obtained by the method according to claim 3 is characterized in that: The pore size of the granite mud lightweight glazed glass-ceramics is 0.5 to 2.5 mm.

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