A mullite composite brick, its preparation method and application

Abstract

This invention proposes a mullite composite brick, its preparation method, and its applications, belonging to the field of refractory materials technology. MXene is prepared by etching the MAX phase with hydrofluoric acid, and Si / Al oxide intercalated MXene is prepared by sol-gel reaction. After modification with polydopamine, intercalated montmorillonite is obtained by adding it to a sodium-based montmorillonite suspension. This intercalated montmorillonite is then uniformly mixed with a binder, high-alumina bauxite, and silicon carbide powder, machine-pressed, and calcined to obtain the mullite composite brick. The mullite composite brick prepared by this invention has good thermal insulation, heat insulation, refractory, and mechanical properties, excellent alkali resistance, improved bonding strength, and extended service life. It also has excellent thermal insulation effect, reduces heat loss, and thus plays a role in energy saving, showing broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of refractory materials technology, specifically to a mullite composite brick, its preparation method, and its application. Background Technology

[0002] A rotary kiln is a multifunctional high-temperature device that integrates a burner, heat exchanger, reactor, and conveyor. It is widely used in many production industries such as building materials, metallurgy, chemical industry, and environmental protection. With the rapid development of modern industry in my country, rotary kiln calcination technology has become increasingly mature. In order to meet the calcination requirements, the quality requirements for the refractory bricks lining the rotary kiln are becoming increasingly stringent. Currently, the bricks used for the rotary kiln lining are two layers: an inner insulation layer of lightweight clay bricks and an outer refractory layer of heavy wear-resistant bricks. However, with the overall thickness remaining unchanged, the thickness of the heavy refractory brick layer is relatively thin, and it will fall off before reaching its service life. This leads to the rapid damage of the inner insulation layer refractory bricks, causing the overall temperature of the rotary kiln to rise, resulting in the kiln shutting down due to heat conduction redness. Therefore, further improvements are needed to the existing rotary kiln lining refractory bricks.

[0003] Mullite is the only stable binary compound in the Al2O3-SiO2 system, possessing excellent properties such as chemical stability, good erosion resistance, good thermal shock resistance, high melting point (1870℃), and high hardness (Mohs hardness 6-7). Mullite is mostly synthesized artificially through sintering and electrofusion methods. Based on Al2O3 content, sintered mullite is classified into four grades: M75, M70, M60, and M45, while electrofused mullite is classified into two grades: M75 and M70. Refractory materials prepared using sintered and electrofused mullite each have their own characteristics: sintered mullite has finer grains, resulting in mullite bricks with higher strength; its high-temperature flexural strength at 1400℃ is more than twice that of mullite bricks produced using electrofused mullite. Electrofused mullite exhibits better high-temperature volume stability, making refractory materials prepared from it less prone to deformation during long-term use at high temperatures and demonstrating better thermal shock resistance.

[0004] Therefore, composite bricks made with mullite as the main framework can achieve better thermal insulation and refractory effects when used in rotary kilns, which is beneficial to extending their service life. Summary of the Invention

[0005] The purpose of this invention is to propose a mullite composite brick, its preparation method, and its application. It has good thermal insulation, heat insulation, fire resistance, and mechanical properties, excellent alkali resistance, improved bonding strength, extended service life of the prepared mullite composite brick, and has a good thermal insulation effect, reducing heat loss and thus playing an energy-saving role. It has broad application prospects.

[0006] The technical solution of this invention is implemented as follows:

[0007] This invention provides a method for preparing mullite composite bricks. MXene is prepared by etching the MAX phase with hydrofluoric acid, and Si / Al oxide intercalated MXene is prepared by sol-gel reaction. After modification with polydopamine, intercalated montmorillonite is obtained by adding it to a sodium-based montmorillonite suspension. The mixture is then stirred and mixed evenly with binder, high-alumina bauxite, and silicon carbide powder, machine-pressed, and calcined to obtain mullite composite bricks.

[0008] As a further improvement to the present invention, the following steps are included:

[0009] Preparation of S1.MXene: MAX phase powder was added to hydrofluoric acid solution, heated and stirred to react, diluted with water, centrifuged, washed, filtered through a microporous membrane, and dried to obtain MXene;

[0010] S2. Preparation of Si / Al oxide intercalated MXene: Aluminum isopropoxide and tetraethyl orthosilicate were dissolved in ethanol to obtain solution A. Glacial acetic acid and water were added to ethanol to obtain solution B. Solution B was added dropwise to solution A and stirred to obtain a columnarizing agent. The columnarizing agent was added to the suspension of MXene obtained in step S1 and stirred to react. The mixture was filtered through a microporous membrane, washed, dried, and calcined to obtain Si / Al oxide intercalated MXene.

[0011] S3. Modification: The Si / Al oxide intercalated MXene obtained in step S2 is added to water, dopamine hydrochloride and catalyst are added, the mixture is heated and stirred to react, filtered through a microporous membrane, and dried to obtain modified Si / Al oxide intercalated MXene.

[0012] S4. Preparation of intercalated montmorillonite: Sodium-based montmorillonite and water were mixed to prepare a suspension, and the modified Si / Al oxide intercalated MXene obtained in step S3 was added. The mixture was ultrasonically dispersed, centrifuged, washed, and dried to obtain intercalated montmorillonite.

[0013] S5. Preparation of adhesive: Add phosphoric acid and aluminum hydroxide to water, stir and mix evenly, add ethanol solution of alkyl orthosilicate, stir and mix evenly to obtain adhesive;

[0014] S6. Preparation of fine high-alumina bauxite: High-alumina bauxite is ball-milled and sieved to obtain fine high-alumina bauxite;

[0015] S7. Preparation of mullite composite bricks: Mullite, fine high-alumina bauxite obtained in step S6, silicon carbide powder, intercalated montmorillonite obtained in step S4, and binder obtained in step S5 are mixed evenly, machine-pressed, and calcined to obtain mullite composite bricks.

[0016] As a further improvement of the present invention, the solid-liquid ratio of the MAX phase powder and hydrofluoric acid solution in step S1 is 1:7-10 g / mL, the concentration of the hydrofluoric acid solution is 37-42 wt%, the heating and stirring reaction temperature is 35-45℃, the time is 40-45 h, and the pore size of the microporous filter membrane is 0.22 μm.

[0017] As a further improvement of the present invention, in step S2, the mass ratio of aluminum isopropoxide, tetraethyl orthosilicate, and ethanol is 5-7:10-15:150-200; the mass ratio of glacial acetic acid, water, and ethanol is 3-5:12-15:30-50; the concentration of the MXene suspension is 10-15 wt%; the stirring reaction temperature is 35-45℃ and the time is 1-3 h; the pore size of the microporous filter membrane is 0.22 μm; and the calcination temperature is 400-500℃ and the time is 2-4 h.

[0018] As a further improvement of the present invention, the mass ratio of Si / Al oxide intercalated MXene, dopamine hydrochloride and catalyst in step S3 is 10-12:7-10:0.5-0.7, the catalyst is a Tris-HCl solution with pH=8.5-9, the heating and stirring reaction temperature is 40-50℃, the time is 1-3h, and the pore size of the microporous filter membrane is 0.22μm.

[0019] As a further improvement of the present invention, the mass ratio of sodium-based montmorillonite and modified Si / Al oxide intercalated MXene in step S4 is 20-30:4-7, and the power of the ultrasound is 1500-2000W.

[0020] As a further improvement of the present invention, in step S5, the mass ratio of phosphoric acid, aluminum hydroxide, water, and ethanol solution of alkyl orthosilicate is 55-65:11-13:25-35:30-37, the concentration of alkyl orthosilicate in the ethanol solution is 12-15 wt%, and the alkyl orthosilicate is methyl or ethyl orthosilicate; the stirring temperature is 35-45°C, and the time is 5-7 h; in step S6, the ball milling time is 1 hour. -3h, the sieve mesh size is 300-500 mesh; the mass ratio of mullite, fine high-alumina bauxite, silicon carbide powder, intercalated montmorillonite, and binder in step S7 is 7-10:4-8:0.5-1:2-4:35-55; the stirring and mixing time is 20-40min, the machine pressing pressure is 95-105MPa, the time is 15-25min, and the calcination temperature is 1300-1500℃, the time is 1-3h.

[0021] As a further improvement to the present invention, the specific steps include:

[0022] Preparation of S1.MXene: MAX phase powder was added to a 37-42 wt% hydrofluoric acid solution, the solid-liquid ratio of the MAX phase powder to the 37-42 wt% hydrofluoric acid solution was 1:7-10 g / mL, heated to 35-45℃, stirred for 40-45 h, diluted with an equal volume of water, centrifuged, washed, filtered through a 0.22 μm microporous membrane, and dried to obtain MXene;

[0023] S2. Preparation of Si / Al oxide intercalated MXene: Dissolve 5-7 parts by weight of aluminum isopropoxide and 10-15 parts by weight of tetraethyl orthosilicate in 150-200 parts by weight of ethanol to obtain solution A. Add 3-5 parts by weight of glacial acetic acid and 12-15 parts by weight of water to 30-50 parts by weight of ethanol to obtain solution B. Add solution B dropwise to solution A and stir for 20-30 min to obtain a columnarizing agent. Add the columnarizing agent to a suspension of 10-15 wt% of MXene obtained in step S1 and stir at 35-45℃ for 1-3 h. Filter with a 0.22 μm microporous membrane, wash, dry, and calcine at 400-500℃ for 2-4 h to obtain Si / Al oxide intercalated MXene.

[0024] S3. Modification: 10-12 parts by weight of the Si / Al oxide intercalated MXene obtained in step S2 are added to 100 parts by weight of water, 7-10 parts by weight of dopamine hydrochloride and 0.5-0.7 parts by weight of catalyst are added, heated to 40-50℃, stirred and reacted for 1-3 hours, filtered with a microporous membrane with a pore size of 0.22μm, and dried to obtain modified Si / Al oxide intercalated MXene;

[0025] The catalyst is a Tris-HCl solution with pH = 8.5-9;

[0026] S4. Preparation of intercalated montmorillonite: 20-30 parts by weight of sodium-based montmorillonite and 100 parts by weight of water are mixed to form a suspension, 4-7 parts by weight of the modified Si / Al oxide intercalated MXene obtained in step S3 are added, and the mixture is ultrasonically dispersed at 1500-2000W, centrifuged, washed, and dried to obtain intercalated montmorillonite.

[0027] S5. Preparation of adhesive: Add 55-65 parts by weight of phosphoric acid and 11-13 parts by weight of aluminum hydroxide to 25-35 parts by weight of water, stir and mix evenly, add 30-37 parts by weight of 12-15 wt% alkyl orthosilicate ethanol solution, stir and mix at 35-45℃ for 5-7 h to obtain adhesive.

[0028] S6. Preparation of fine high-alumina bauxite: High-alumina bauxite is ball-milled for 1-3 hours and passed through a 300-500 mesh sieve to obtain fine high-alumina bauxite;

[0029] S7. Preparation of mullite composite bricks: 7-10 parts by weight of mullite, 4-8 parts by weight of fine high-alumina bauxite obtained in step S6, 0.5-1 parts by weight of silicon carbide powder, 2-4 parts by weight of intercalated montmorillonite obtained in step S4, and 35-55 parts by weight of binder obtained in step S5 are stirred and mixed for 20-40 minutes, machine-pressed, the machine-pressing pressure is 95-105 MPa, the time is 15-25 minutes, and calcined at 1300-1500℃ for 1-3 hours to obtain mullite composite bricks.

[0030] This invention further protects a mullite composite brick prepared by the above-described preparation method.

[0031] This invention further protects the application of the above-mentioned mullite composite brick in the preparation of refractory bricks for rotary kiln linings.

[0032] The present invention has the following beneficial effects:

[0033] This invention utilizes hydrofluoric acid (HF solution) to selectively etch the Al atomic layers of the layered compound MAX (Ti3AlC2), obtaining a two-dimensional atomic crystal compound MXene (Ti3C2) with a graphene-like structure. This layered two-dimensional crystal structure exhibits good high-temperature resistance, fire resistance, and wear resistance. A columnarizing agent is formed through a sol-gel reaction between aluminum isopropoxide and tetraethyl orthosilicate, intercalated into MXene, followed by calcination to obtain Si / Al oxide intercalated MXene. This significantly improves the material's fire resistance, temperature resistance, thermal insulation, and mechanical properties.

[0034] After the surface of the Si / Al oxide intercalated MXene was modified with polydopamine, the content of polar groups such as hydroxyl, carboxyl, and amino groups on the material surface was increased, which promoted their intercalation distribution in the layered silicate structure of montmorillonite. Moreover, montmorillonite is inexpensive and has a low cost. The intercalated montmorillonite obtained after uniform intercalation has good mechanical properties and heat resistance.

[0035] The particle size of high-alumina bauxite has a direct relationship with the molding performance, moisture porosity, bulk density, and compressive strength of the finished product. Finer particle size can significantly improve molding performance and avoid problems such as easy breakage of brick edges, poor compactness, and reduced strength. Therefore, the high-alumina bauxite with smaller particle size obtained by ball milling in this invention can significantly improve the molding performance of composite bricks and improve mechanical strength and compactness.

[0036] Aluminum phosphate sol, a binder, was prepared by adding phosphoric acid and aluminum hydroxide to water. This sol was then mixed evenly with a silica sol formed from tetraethyl orthosilicate. The addition of intercalated montmorillonite, high-alumina bauxite, and silicon carbide powder improved the thermal insulation, heat insulation, fire resistance, and mechanical properties of the resulting mullite composite brick. It also enhanced alkali resistance, preventing corrosion by alkaline substances such as K₂O, Na₂O, and CaO, which could cause the brick to expand and become porous, leading to decreased mechanical properties and wear. Furthermore, it improved bonding strength and extended the service life of the resulting mullite composite brick. It exhibits excellent thermal insulation, reduces heat loss, and thus contributes to energy conservation, demonstrating broad application prospects. Detailed Implementation

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] M45 mullite, 325 mesh, purchased from Xinmi Zhengyang Foundry Materials Factory; sodium montmorillonite, CEC value 100 mmol / 100g, purchased from Zhejiang Fenghong New Materials Co., Ltd.; high-alumina bauxite, 0-3mm, aluminum content 60-80wt%, purchased from Zhengzhou Kanghui Refractory Materials Co., Ltd.; MAX phase powder purchased from Shanghai Maclean Chemical Industry Co., Ltd.; silicon carbide powder, average particle size 0.5 microns, purchased from Shandong Huaen New Materials Technology Co., Ltd.

[0039] Example 1

[0040] This embodiment provides a method for preparing mullite composite bricks, specifically including the following steps:

[0041] Preparation of S1.MXene: MAX phase powder was added to 37wt% hydrofluoric acid solution, the solid-liquid ratio of MAX phase powder to 37wt% hydrofluoric acid solution was 1:7 g / mL, heated to 35℃, stirred for 40 h, diluted with an equal volume of water and stirred for 10 min, centrifuged, washed, filtered with a 0.22 μm microporous membrane, and dried to obtain MXene;

[0042] S2. Preparation of Si / Al oxide intercalated MXene: 5 parts by weight of aluminum isopropoxide and 10 parts by weight of tetraethyl orthosilicate were dissolved in 150 parts by weight of ethanol to obtain solution A. 3 parts by weight of glacial acetic acid and 12 parts by weight of water were added to 30 parts by weight of ethanol to obtain solution B. Solution B was added dropwise to solution A and stirred for 20 min to obtain a columnarizing agent. The columnarizing agent was added to a suspension of 10 wt% of MXene obtained in step S1 and stirred at 35 °C for 1 h. The mixture was filtered through a 0.22 μm microporous membrane, washed, dried, and calcined at 400 °C for 2 h to obtain Si / Al oxide intercalated MXene.

[0043] S3. Modification: 10 parts by weight of the Si / Al oxide intercalated MXene obtained in step S2 were added to 100 parts by weight of water, 7 parts by weight of dopamine hydrochloride and 0.5 parts by weight of catalyst were added, heated to 40°C, stirred and reacted for 1 hour, filtered with a microporous membrane with a pore size of 0.22 μm, and dried to obtain modified Si / Al oxide intercalated MXene.

[0044] The catalyst is a Tris-HCl solution with pH = 8.5;

[0045] S4. Preparation of intercalated montmorillonite: 20 parts by weight of sodium-based montmorillonite and 100 parts by weight of water were mixed to prepare a suspension, and 4 parts by weight of the modified Si / Al oxide intercalated MXene obtained in step S3 were added. The mixture was ultrasonically dispersed at 1500W for 20 min, centrifuged, washed, and dried to obtain intercalated montmorillonite.

[0046] S5. Preparation of adhesive: 55 parts by weight of 85 wt% phosphoric acid and 11 parts by weight of aluminum hydroxide were added to 25 parts by weight of water and stirred for 20 min. Then, 30 parts by weight of ethanol solution of 12 wt% tetraethyl orthosilicate were added and stirred at 35°C for 5 h to obtain the adhesive.

[0047] S6. Preparation of fine high-alumina bauxite: High-alumina bauxite was ball-milled for 1 hour and passed through a 300-mesh sieve to obtain fine high-alumina bauxite;

[0048] S7. Preparation of mullite composite bricks: 7 parts by weight of M45 mullite, 4 parts by weight of fine high-alumina bauxite obtained in step S6, 0.5 parts by weight of silicon carbide powder, 2 parts by weight of intercalated montmorillonite obtained in step S4, and 35 parts by weight of binder obtained in step S5 are stirred and mixed for 20 minutes, machine-pressed, the machine-pressing pressure is 95 MPa, the time is 15 minutes, and calcined at 1300℃ for 1 hour to obtain mullite composite bricks.

[0049] Example 2

[0050] This embodiment provides a method for preparing mullite composite bricks, specifically including the following steps:

[0051] Preparation of S1.MXene: MAX phase powder was added to 42wt% hydrofluoric acid solution, the solid-liquid ratio of MAX phase powder to 42wt% hydrofluoric acid solution was 1:10 g / mL, heated to 45℃, stirred for 45h, diluted with an equal volume of water and stirred for 10min, centrifuged, washed, filtered through a 0.22μm microporous membrane, and dried to obtain MXene;

[0052] S2. Preparation of Si / Al oxide intercalated MXene: 7 parts by weight of aluminum isopropoxide and 15 parts by weight of tetraethyl orthosilicate were dissolved in 200 parts by weight of ethanol to obtain solution A. 5 parts by weight of glacial acetic acid and 15 parts by weight of water were added to 50 parts by weight of ethanol to obtain solution B. Solution B was added dropwise to solution A and stirred for 30 min to obtain a columnarizing agent. The columnarizing agent was added to a suspension of 15 wt% MXene obtained in step S1 and stirred at 45 °C for 3 h. The mixture was filtered through a 0.22 μm microporous membrane, washed, dried, and calcined at 500 °C for 4 h to obtain Si / Al oxide intercalated MXene.

[0053] S3. Modification: 12 parts by weight of the Si / Al oxide intercalated MXene obtained in step S2 were added to 100 parts by weight of water, 10 parts by weight of dopamine hydrochloride and 0.7 parts by weight of catalyst were added, heated to 50°C, stirred and reacted for 3 hours, filtered with a microporous membrane with a pore size of 0.22 μm, and dried to obtain modified Si / Al oxide intercalated MXene.

[0054] The catalyst is a Tris-HCl solution with pH = 9;

[0055] S4. Preparation of intercalated montmorillonite: 30 parts by weight of sodium-based montmorillonite and 100 parts by weight of water were mixed to prepare a suspension, and 7 parts by weight of the modified Si / Al oxide intercalated MXene obtained in step S3 were added. The mixture was ultrasonically dispersed at 2000W for 20 min, centrifuged, washed, and dried to obtain intercalated montmorillonite.

[0056] S5. Preparation of adhesive: 65 parts by weight of 85 wt% phosphoric acid and 13 parts by weight of aluminum hydroxide were added to 35 parts by weight of water and stirred for 20 min. Then, 37 parts by weight of ethanol solution of 15 wt% tetraethyl orthosilicate were added and stirred at 45°C for 7 h to obtain the adhesive.

[0057] S6. Preparation of fine high-alumina bauxite: High-alumina bauxite was ball-milled for 3 hours and passed through a 500-mesh sieve to obtain fine high-alumina bauxite;

[0058] S7. Preparation of mullite composite bricks: 10 parts by weight of M45 mullite, 8 parts by weight of fine high-alumina bauxite obtained in step S6, 1 part by weight of silicon carbide powder, 4 parts by weight of intercalated montmorillonite obtained in step S4, and 55 parts by weight of binder obtained in step S5 are stirred and mixed for 40 minutes, machine-pressed, the machine-pressing pressure is 105 MPa, the time is 25 minutes, and calcined at 1500℃ for 3 hours to obtain mullite composite bricks.

[0059] Example 3

[0060] This embodiment provides a method for preparing mullite composite bricks, specifically including the following steps:

[0061] Preparation of S1.MXene: MAX phase powder was added to 40wt% hydrofluoric acid solution, the solid-liquid ratio of MAX phase powder to 40wt% hydrofluoric acid solution was 1:8 g / mL, heated to 40℃, stirred for 42h, diluted with an equal volume of water and stirred for 10min, centrifuged, washed, filtered with a 0.22μm microporous membrane, and dried to obtain MXene;

[0062] S2. Preparation of Si / Al oxide intercalated MXene: 6 parts by weight of aluminum isopropoxide and 12 parts by weight of tetraethyl orthosilicate were dissolved in 170 parts by weight of ethanol to obtain solution A. 4 parts by weight of glacial acetic acid and 13.5 parts by weight of water were added to 40 parts by weight of ethanol to obtain solution B. Solution B was added dropwise to solution A and stirred for 25 min to obtain a columnarizing agent. The columnarizing agent was added to a suspension of 12 wt% of MXene obtained in step S1 and stirred at 40 °C for 2 h. The mixture was filtered through a 0.22 μm microporous membrane, washed, dried, and calcined at 450 °C for 3 h to obtain Si / Al oxide intercalated MXene.

[0063] S3. Modification: 11 parts by weight of the Si / Al oxide intercalated MXene obtained in step S2 were added to 100 parts by weight of water, 8.5 parts by weight of dopamine hydrochloride and 0.6 parts by weight of catalyst were added, heated to 45°C, stirred and reacted for 2 hours, filtered with a microporous membrane with a pore size of 0.22 μm, and dried to obtain modified Si / Al oxide intercalated MXene.

[0064] The catalyst is a Tris-HCl solution with pH = 8.7;

[0065] S4. Preparation of intercalated montmorillonite: 25 parts by weight of sodium-based montmorillonite and 100 parts by weight of water were mixed to prepare a suspension, and 5.5 parts by weight of the modified Si / Al oxide intercalated MXene obtained in step S3 were added. The mixture was ultrasonically dispersed at 1700W for 20 min, centrifuged, washed, and dried to obtain intercalated montmorillonite.

[0066] S5. Preparation of adhesive: 60 parts by weight of 85 wt% phosphoric acid and 12 parts by weight of aluminum hydroxide were added to 30 parts by weight of water and stirred for 20 min. Then, 33 parts by weight of ethanol solution of 13.5 wt% tetraethyl orthosilicate were added and stirred at 40°C for 6 h to obtain the adhesive.

[0067] S6. Preparation of fine high-alumina bauxite: High-alumina bauxite was ball-milled for 2 hours and passed through a 400-mesh sieve to obtain fine high-alumina bauxite;

[0068] S7. Preparation of mullite composite bricks: 8.5 parts by weight of M45 mullite, 6 parts by weight of fine high-alumina bauxite obtained in step S6, 0.7 parts by weight of silicon carbide powder, 3 parts by weight of intercalated montmorillonite obtained in step S4, and 45 parts by weight of binder obtained in step S5 are stirred and mixed for 30 minutes, machine-pressed, the machine-pressing pressure is 100 MPa, the time is 20 minutes, and calcined at 1450℃ for 2 hours to obtain mullite composite bricks.

[0069] Comparative Example 1

[0070] The difference from Example 3 is that aluminum isopropoxide was not added in step S2.

[0071] Specifically as follows:

[0072] Preparation of Si oxide intercalated MXene: 18 parts by weight of tetraethyl orthosilicate were dissolved in 170 parts by weight of ethanol to obtain solution A. 4 parts by weight of glacial acetic acid and 13.5 parts by weight of water were added to 40 parts by weight of ethanol to obtain solution B. Solution B was added dropwise to solution A and stirred for 25 min to obtain a columnarizing agent. The columnarizing agent was added to a suspension of 12 wt% of MXene obtained in step S1 and stirred at 40 °C for 2 h. The mixture was filtered through a 0.22 μm microporous membrane, washed, dried, and calcined at 450 °C for 3 h to obtain Si oxide intercalated MXene.

[0073] Comparative Example 2

[0074] The difference from Example 3 is that tetraethyl orthosilicate was not added in step S2.

[0075] Specifically as follows:

[0076] S2. Preparation of Al oxide intercalated MXene: 18 parts by weight of aluminum isopropoxide were dissolved in 170 parts by weight of ethanol to obtain solution A. 4 parts by weight of glacial acetic acid and 13.5 parts by weight of water were added to 40 parts by weight of ethanol to obtain solution B. Solution B was added dropwise to solution A and stirred for 25 min to obtain a columnarizing agent. The columnarizing agent was added to a suspension of 12 wt% of MXene obtained in step S1 and stirred at 40 °C for 2 h. The mixture was filtered through a 0.22 μm microporous membrane, washed, dried, and calcined at 450 °C for 3 h to obtain Al oxide intercalated MXene.

[0077] Comparative Example 3

[0078] The difference from Example 3 is that step S3 was not performed.

[0079] Specifically as follows:

[0080] Preparation of S1.MXene: MAX phase powder was added to 40wt% hydrofluoric acid solution, the solid-liquid ratio of MAX phase powder to 40wt% hydrofluoric acid solution was 1:8 g / mL, heated to 40℃, stirred for 42h, diluted with an equal volume of water and stirred for 10min, centrifuged, washed, filtered with a 0.22μm microporous membrane, and dried to obtain MXene;

[0081] S2. Preparation of Si / Al oxide intercalated MXene: 6 parts by weight of aluminum isopropoxide and 12 parts by weight of tetraethyl orthosilicate were dissolved in 170 parts by weight of ethanol to obtain solution A. 4 parts by weight of glacial acetic acid and 13.5 parts by weight of water were added to 40 parts by weight of ethanol to obtain solution B. Solution B was added dropwise to solution A and stirred for 25 min to obtain a columnarizing agent. The columnarizing agent was added to a suspension of 12 wt% of MXene obtained in step S1 and stirred at 40 °C for 2 h. The mixture was filtered through a 0.22 μm microporous membrane, washed, dried, and calcined at 450 °C for 3 h to obtain Si / Al oxide intercalated MXene.

[0082] S3. Modification: 11 parts by weight of the Si / Al oxide intercalated MXene obtained in step S2 were added to 100 parts by weight of water, 8.5 parts by weight of dopamine hydrochloride and 0.6 parts by weight of catalyst were added, heated to 45°C, stirred and reacted for 2 hours, filtered with a microporous membrane with a pore size of 0.22 μm, and dried to obtain modified Si / Al oxide intercalated MXene.

[0083] The catalyst is a Tris-HCl solution with pH = 8.7;

[0084] S4. Preparation of intercalated montmorillonite: 25 parts by weight of sodium-based montmorillonite and 100 parts by weight of water were mixed to prepare a suspension, and 5.5 parts by weight of the modified Si / Al oxide intercalated MXene obtained in step S3 were added. The mixture was ultrasonically dispersed at 1700W for 20 min, centrifuged, washed, and dried to obtain intercalated montmorillonite.

[0085] S5. Preparation of adhesive: 60 parts by weight of 85 wt% phosphoric acid and 12 parts by weight of aluminum hydroxide were added to 30 parts by weight of water and stirred for 20 min. Then, 33 parts by weight of ethanol solution of 13.5 wt% tetraethyl orthosilicate were added and stirred at 40°C for 6 h to obtain the adhesive.

[0086] S6. Preparation of fine high-alumina bauxite: High-alumina bauxite was ball-milled for 2 hours and passed through a 400-mesh sieve to obtain fine high-alumina bauxite;

[0087] S7. Preparation of mullite composite bricks: 8.5 parts by weight of M45 mullite, 6 parts by weight of fine high-alumina bauxite obtained in step S6, 0.7 parts by weight of silicon carbide powder, 3 parts by weight of intercalated montmorillonite obtained in step S4, and 45 parts by weight of binder obtained in step S5 are stirred and mixed for 30 minutes, machine-pressed, the machine-pressing pressure is 100 MPa, the time is 20 minutes, and calcined at 1450℃ for 2 hours to obtain mullite composite bricks.

[0088] Comparative Example 4

[0089] The difference from Example 3 is that no ethanol solution of tetraethyl orthosilicate was added in step S5.

[0090] Specifically as follows:

[0091] S5. Preparation of adhesive: 60 parts by weight of 85 wt% phosphoric acid and 12 parts by weight of aluminum hydroxide were added to 30 parts by weight of water, stirred and mixed for 20 min, and then stirred and mixed at 40°C for 6 h to obtain the adhesive.

[0092] Comparative Example 5

[0093] The difference from Example 3 is that step S6 was not performed.

[0094] Specifically as follows:

[0095] Preparation of S1.MXene: MAX phase powder was added to 40wt% hydrofluoric acid solution, the solid-liquid ratio of MAX phase powder to 40wt% hydrofluoric acid solution was 1:8 g / mL, heated to 40℃, stirred for 42h, diluted with an equal volume of water and stirred for 10min, centrifuged, washed, filtered with a 0.22μm microporous membrane, and dried to obtain MXene;

[0096] S2. Preparation of Si / Al oxide intercalated MXene: 6 parts by weight of aluminum isopropoxide and 12 parts by weight of tetraethyl orthosilicate were dissolved in 170 parts by weight of ethanol to obtain solution A. 4 parts by weight of glacial acetic acid and 13.5 parts by weight of water were added to 40 parts by weight of ethanol to obtain solution B. Solution B was added dropwise to solution A and stirred for 25 min to obtain a columnarizing agent. The columnarizing agent was added to a suspension of 12 wt% of MXene obtained in step S1 and stirred at 40 °C for 2 h. The mixture was filtered through a 0.22 μm microporous membrane, washed, dried, and calcined at 450 °C for 3 h to obtain Si / Al oxide intercalated MXene.

[0097] S3. Modification: 11 parts by weight of the Si / Al oxide intercalated MXene obtained in step S2 were added to 100 parts by weight of water, 8.5 parts by weight of dopamine hydrochloride and 0.6 parts by weight of catalyst were added, heated to 45°C, stirred and reacted for 2 hours, filtered with a microporous membrane with a pore size of 0.22 μm, and dried to obtain modified Si / Al oxide intercalated MXene.

[0098] The catalyst is a Tris-HCl solution with pH = 8.7;

[0099] S4. Preparation of intercalated montmorillonite: 25 parts by weight of sodium-based montmorillonite and 100 parts by weight of water were mixed to prepare a suspension, and 5.5 parts by weight of the modified Si / Al oxide intercalated MXene obtained in step S3 were added. The mixture was ultrasonically dispersed at 1700W for 20 min, centrifuged, washed, and dried to obtain intercalated montmorillonite.

[0100] S5. Preparation of adhesive: 60 parts by weight of 85 wt% phosphoric acid and 12 parts by weight of aluminum hydroxide were added to 30 parts by weight of water and stirred for 20 min. Then, 33 parts by weight of ethanol solution of 13.5 wt% tetraethyl orthosilicate were added and stirred at 40°C for 6 h to obtain the adhesive.

[0101] S6. Preparation of mullite composite bricks: 8.5 parts by weight of M45 mullite, 6 parts by weight of high-alumina bauxite, 0.7 parts by weight of silicon carbide powder, 3 parts by weight of intercalated montmorillonite obtained in step S4, and 45 parts by weight of binder obtained in step S5 are stirred and mixed for 30 minutes, machine-pressed, the machine-pressed pressure is 100 MPa, the time is 20 minutes, and calcined at 1450℃ for 2 hours to obtain mullite composite bricks.

[0102] Comparative Example 6

[0103] The difference from Example 3 is that in step S7, the intercalated montmorillonite is replaced by an equal amount of sodium-based montmorillonite.

[0104] Specifically as follows:

[0105] S7. Preparation of mullite composite bricks: 8.5 parts by weight of M45 mullite, 6 parts by weight of fine high-alumina bauxite obtained in step S6, 0.7 parts by weight of silicon carbide powder, 3 parts by weight of sodium-based montmorillonite, and 45 parts by weight of binder obtained in step S5 are stirred and mixed for 30 minutes, machine-pressed, the machine-pressed pressure is 100 MPa, the time is 20 minutes, and calcined at 1450℃ for 2 hours to obtain mullite composite bricks.

[0106] Comparative Example 7

[0107] The difference from Example 3 is that montmorillonite was not added in step S7.

[0108] Specifically as follows:

[0109] S7. Preparation of mullite composite bricks: 8.5 parts by weight of M45 mullite, 6 parts by weight of fine high-alumina bauxite obtained in step S6, 0.7 parts by weight of silicon carbide powder, and 45 parts by weight of binder obtained in step S5 are stirred and mixed for 30 minutes, machine-pressed, the machine-pressed pressure is 100 MPa, the time is 20 minutes, and calcined at 1450℃ for 2 hours to obtain mullite composite bricks.

[0110] Test Example 1

[0111] The performance of the mullite composite bricks prepared in Examples 1-3 and Comparative Examples 1-7 was tested, and the results are shown in Table 1.

[0112] Table 1

[0113]

[0114]

[0115] As can be seen from the table above, the mullite composite bricks prepared in Examples 1-3 of this invention have better overall performance, are more heat-insulating and fire-resistant, and have better mechanical properties.

[0116] Test Example 2

[0117] The alkali resistance of the mullite composite bricks prepared in Examples 1-3 and Comparative Examples 1-7 was tested, and the results are shown in Table 2. The alkali resistance was determined using the molten alkali crucible method. Three holes (Φ22mm×25mm) were drilled in the mullite composite bricks. Equal molar amounts of K₂CO₃, Na₂CO₃, and Na₂S were added sequentially to the three holes of the same product. A 50mm×50mm×6mm lid was then placed on top, and the temperature was uniformly raised to 1100℃, held for 5 hours, and allowed to cool naturally before evaluating its alkali resistance.

[0118] Table 2 Evaluation of Alkali Resistance

[0119] Group <![CDATA[K2CO3]]> <![CDATA[Na2CO3]]> <![CDATA[Na2S]]> Example 1 No cracks No cracks No cracks Example 2 No cracks No cracks No cracks Example 3 No cracks No cracks No cracks Comparative Example 1 No cracks No cracks No cracks Comparative Example 2 Minor cracks No cracks No cracks Comparative Example 3 Minor cracks Minor cracks Minor cracks Comparative Example 4 Partial cracks Minor cracks Minor cracks Comparative Example 5 No cracks No cracks No cracks Comparative Example 6 Minor cracks Minor cracks Minor cracks Comparative Example 7 Partial cracks Partial cracks Minor cracks

[0120] As can be seen from the table above, the mullite composite bricks prepared in Examples 1-3 of this invention have better alkali resistance.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing mullite composite bricks, characterized in that, The preparation method of the mullite composite brick includes the following steps: S1. Preparation of MXene: MAX phase powder was added to hydrofluoric acid solution, heated and stirred to react, diluted with water, centrifuged, washed, filtered through a microporous membrane, and dried to obtain MXene; S2. Preparation of Si / Al oxide intercalated MXene: Aluminum isopropoxide and tetraethyl orthosilicate were dissolved in ethanol to obtain solution A. Glacial acetic acid and water were added to ethanol to obtain solution B. Solution B was added dropwise to solution A and stirred to obtain a columnarizing agent. The columnarizing agent was added to the suspension of MXene obtained in step S1 and stirred to react. The mixture was filtered through a microporous membrane, washed, dried, and calcined to obtain Si / Al oxide intercalated MXene. S3. Modification: The Si / Al oxide intercalated MXene obtained in step S2 is added to water, dopamine hydrochloride and catalyst are added, the mixture is heated and stirred to react, filtered through a microporous membrane, and dried to obtain modified Si / Al oxide intercalated MXene. S4. Preparation of intercalated montmorillonite: Sodium-based montmorillonite and water were mixed to form a suspension, and the modified Si / Al oxide intercalated MXene obtained in step S3 was added. The mixture was ultrasonically dispersed, centrifuged, washed, and dried to obtain intercalated montmorillonite. S5. Preparation of adhesive: Add phosphoric acid and aluminum hydroxide to water, stir and mix evenly, add ethanol solution of alkyl orthosilicate, stir and mix evenly to obtain adhesive; S6. Preparation of fine high-alumina bauxite: High-alumina bauxite is ball-milled and sieved to obtain fine high-alumina bauxite; S7. Preparation of mullite composite bricks: Mullite, fine high-alumina bauxite obtained in step S6, silicon carbide powder, intercalated montmorillonite obtained in step S4, and binder obtained in step S5 are mixed evenly, machine-pressed, and calcined to obtain mullite composite bricks. In step S7, the mass ratio of mullite, fine high-alumina bauxite, silicon carbide powder, intercalated montmorillonite, and binder is 7-10:4-8:0.5-1:2-4:35-55, and the calcination temperature is 1300-1500℃.

2. The preparation method according to claim 1, characterized in that, In step S1, the solid-liquid ratio of the MAX phase powder and the hydrofluoric acid solution is 1:7-10 g / mL, the concentration of the hydrofluoric acid solution is 37-42 wt%, the heating and stirring reaction temperature is 35-45℃, the time is 40-45 h, and the pore size of the microporous filter membrane is 0.22 μm.

3. The preparation method according to claim 1, characterized in that, In step S2, the mass ratio of aluminum isopropoxide, tetraethyl orthosilicate, and ethanol is 5-7:10-15:150-200; the mass ratio of glacial acetic acid, water, and ethanol is 3-5:12-15:30-50; the concentration of the MXene suspension is 10-15 wt%; the stirring reaction temperature is 35-45℃ and the time is 1-3 h; the pore size of the microporous filter membrane is 0.22 μm; and the calcination temperature is 400-500℃ and the time is 2-4 h.

4. The preparation method according to claim 1, characterized in that, In step S3, the mass ratio of Si / Al oxide intercalated MXene, dopamine hydrochloride, and catalyst is 10-12:7-10:0.5-0.

7. The catalyst is a Tris-HCl solution with pH=8.5-9. The heating and stirring reaction is carried out at a temperature of 40-50℃ for 1-3 hours. The microporous filter membrane has a pore size of 0.22μm.

5. The preparation method according to claim 1, characterized in that, In step S4, the mass ratio of sodium-based montmorillonite to modified Si / Al oxide intercalated MXene is 20-30:4-7, and the ultrasonic power is 1500-2000W.

6. The preparation method according to claim 1, characterized in that, In step S5, the mass ratio of phosphoric acid, aluminum hydroxide, water, and alkyl orthosilicate in ethanol solution is 55-65:11-13:25-35:30-37, the concentration of alkyl orthosilicate in the ethanol solution is 12-15 wt%, and the alkyl orthosilicate is methyl or ethyl orthosilicate. The stirring temperature is 35-45℃, and the time is 5-7 h. In step S6, the ball milling time is 1-3 h, the sieve mesh size is 300-500 mesh, the stirring time is 20-40 min, the machine pressing pressure is 95-105 MPa, the time is 15-25 min, and the calcination time is 1-3 h.

7. The preparation method according to claim 1, characterized in that, Specifically, the following steps are included: S1. Preparation of MXene: MAX phase powder was added to a 37-42 wt% hydrofluoric acid solution, wherein the solid-liquid ratio of the MAX phase powder to the 37-42 wt% hydrofluoric acid solution was 1:7-10 g / mL. The mixture was heated to 35-45℃ and stirred for 40-45 h. An equal volume of water was added for dilution, followed by centrifugation, washing, filtration through a 0.22 μm microporous membrane, and drying to obtain MXene. S2. Preparation of Si / Al oxide intercalated MXene: Dissolve 5-7 parts by weight of aluminum isopropoxide and 10-15 parts by weight of tetraethyl orthosilicate in 150-200 parts by weight of ethanol to obtain solution A. Add 3-5 parts by weight of glacial acetic acid and 12-15 parts by weight of water to 30-50 parts by weight of ethanol to obtain solution B. Add solution B dropwise to solution A and stir for 20-30 min to obtain a columnarizing agent. Add the columnarizing agent to a suspension of 10-15 wt% of MXene obtained in step S1 and stir at 35-45℃ for 1-3 h. Filter with a 0.22 μm microporous membrane, wash, dry, and calcine at 400-500℃ for 2-4 h to obtain Si / Al oxide intercalated MXene. S3. Modification: Add 10-12 parts by weight of the Si / Al oxide intercalated MXene obtained in step S2 to 100 parts by weight of water, add 7-10 parts by weight of dopamine hydrochloride and 0.5-0.7 parts by weight of catalyst, heat to 40-50℃, stir and react for 1-3 hours, filter with a microporous membrane with a pore size of 0.22μm, and dry to obtain modified Si / Al oxide intercalated MXene; The catalyst is a Tris-HCl solution with a pH of 8.5-9; S4. Preparation of intercalated montmorillonite: 20-30 parts by weight of sodium-based montmorillonite and 100 parts by weight of water are mixed to form a suspension, 4-7 parts by weight of the modified Si / Al oxide intercalated MXene obtained in step S3 are added, and the mixture is ultrasonically dispersed at 1500-2000W, centrifuged, washed, and dried to obtain intercalated montmorillonite. S5. Preparation of adhesive: Add 55-65 parts by weight of phosphoric acid and 11-13 parts by weight of aluminum hydroxide to 25-35 parts by weight of water, stir and mix evenly, add 30-37 parts by weight of 12-15 wt% alkyl orthosilicate ethanol solution, stir and mix at 35-45℃ for 5-7 h to obtain adhesive. S6. Preparation of fine high-alumina bauxite: High-alumina bauxite is ball-milled for 1-3 hours and passed through a 300-500 mesh sieve to obtain fine high-alumina bauxite; S7. Preparation of mullite composite bricks: 7-10 parts by weight of mullite, 4-8 parts by weight of fine high-alumina bauxite obtained in step S6, 0.5-1 parts by weight of silicon carbide powder, 2-4 parts by weight of intercalated montmorillonite obtained in step S4, and 35-55 parts by weight of binder obtained in step S5 are stirred and mixed for 20-40 minutes, machine-pressed, the machine-pressing pressure is 95-105 MPa, the time is 15-25 minutes, and calcined at 1300-1500℃ for 1-3 hours to obtain mullite composite bricks.

8. A mullite composite brick prepared by the preparation method according to any one of claims 1-7.

9. The application of the mullite composite brick as described in claim 8 in the preparation of refractory bricks for rotary kiln linings.

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