Preparation method of high-strength, low-density and lightweight silica brick

Abstract

The invention discloses a method for preparing a high-strength, low-density, lightweight silica brick, comprising the following steps: S1, taking a formula amount of a siliceous raw material, a spherical starch, and a composite mineralizer mixture for ball milling to obtain a first mixture; S2, adding a formula amount of polycarbosilane and ferrocene to the first mixture obtained in step S1, ball milling on a ball mill to obtain a second mixture, and mixing them uniformly; S3, pressing the second mixture obtained in step S2 in a mold, and drying it at a temperature of 60-100°C; S4, pre-sintering the dried silica brick within a first sintering temperature range to generate silicon carbide nano whiskers; S5, finally sintering the pre-sintered silica brick within a second sintering temperature range to obtain a high-strength, low-density, lightweight silica brick reinforced with silicon carbide nano whiskers; the invention can prepare a high-porosity and high-strength lightweight silica brick, so that the lightweight silica brick can still maintain strength under the condition of reduced bulk density, and has a lower thermal conductivity.

Description

Technical Field

[0001] The invention relates to the technical field of silica brick preparation, in particular to a method for preparing high-strength, low-density and lightweight silica bricks. Background Art

[0002] Lightweight silica bricks have low bulk density and good thermal insulation properties. They are an important refractory and thermal insulation material and are widely used in various high-temperature industrial furnaces.

[0003] In the prior art, the main methods for preparing lightweight silica bricks are the foam method and the mechanical pressure combustible method. The foam method has the disadvantages of complex process and high cost. Although the mechanical pressure combustible method has a simple process and low cost, the lightweight silica bricks prepared by it are prone to very uneven pore distribution, resulting in uneven structure of lightweight silica bricks. In order to solve the problems of the above two lightweight silica bricks, other preparation methods have been proposed.

[0004] For example, the Chinese invention patent with patent number CN201410052644.5 discloses a method for preparing lightweight silica bricks, firstly, 30-60wt% silica particles, 10-30wt% silica fine powder, 2-6wt% limestone, 5-15wt% silica sol and 10-30wt% coke are mixed, stirred evenly, and vibrated or rammed into shape; then the formed green body is dried at 110°C for 4-24 hours, and then kept at 1200-1400°C for 3-15 hours to obtain lightweight silica bricks. This preparation method is simple in process and uses abundant raw materials. The prepared lightweight silica bricks have the characteristics of uniform microstructure, low bulk density, excellent thermal insulation performance, high load softening temperature, good high temperature volume stability and wide range of applications.

[0005] Another example is the Chinese invention patent with patent number CN202311419784.7, which discloses a method for preparing lightweight silica bricks. By means of the low melting point characteristics of calcium nitrate tetrahydrate, the baked liquid calcium nitrate tetrahydrate is pre-mixed with silica powder and sawdust by wet method, and other steps are coordinated to solve the problem of uneven distribution of combustibles caused by dry mixing when producing lightweight silica bricks by machine-pressed combustible method. In addition, calcium nitrate tetrahydrate also has the functions of mineralizer and pore former. As a mineralizer and pore former, calcium nitrate tetrahydrate can be evenly distributed and gradually decomposed during high-temperature firing, absorbing stress and reducing thermal conductivity without damaging the brick body.

[0006] Silicon carbide whiskers are single crystal fibers with few defects and a certain aspect ratio. They have very good high temperature resistance and high strength, and can enhance the high temperature strength of lightweight silicon bricks. However, the existing methods for preparing lightweight silicon bricks cannot produce silicon carbide whisker structures in the lightweight silicon bricks prepared therefrom. To this end, the applicant proposes a method for preparing high-strength, low-density lightweight silicon bricks, which can produce lightweight silicon bricks with silicon carbide whisker structures, and can effectively enhance the high temperature strength of lightweight silicon bricks. Summary of the invention

[0007] The object of the present invention is to provide a method for preparing a high-strength, low-density, lightweight silica brick, which can produce a lightweight silica brick with a silicon carbide whisker structure and effectively enhance the high-temperature strength of the lightweight silica brick.

[0008] The present invention is achieved by: a method for preparing a high-strength, low-density, lightweight silica brick, comprising the following steps:

[0009] S1, taking a mixture of a formulated amount of siliceous raw material, spherical starch, and a composite mineralizer and ball-milling it to obtain a first mixture;

[0010] S2, adding the formulated amount of polycarbosilane and ferrocene to the first mixed material obtained in step S1, and ball milling on a ball mill to obtain a second mixed material, and mixing them uniformly;

[0011] S3, pressing the second mixed material obtained in step S2 into a mold, and drying it at a temperature of 60-100° C.;

[0012] S4, pre-sintering the dried silicon brick within a first sintering temperature range to generate silicon carbide nano whiskers;

[0013] S5. Final sintering the pre-sintered silicon bricks within a second sintering temperature range to obtain high-strength, low-density, lightweight silicon bricks reinforced with silicon carbide nanowhiskers, wherein the lowest temperature within the second sintering temperature range is greater than the highest temperature within the first sintering temperature range.

[0014] Furthermore, in step S1, the formula amounts of siliceous raw material, spherical starch and composite mineralizer are: 60-75wt% of siliceous raw material; 20-35wt% of spherical starch; and 1-5wt% of composite mineralizer.

[0015] Furthermore, in step S2, the formula amounts of polycarbosilane and ferrocene are: 1-5wt% of polycarbosilane; 1-3wt% of catalyst ferrocene.

[0016] Furthermore, in step S2, the ball milling time is 10-20 hours.

[0017] Furthermore, in step S3, the drying time is 24-48 hours.

[0018] Furthermore, in step S4, the first sintering temperature ranges from 800 to 1000°C.

[0019] Furthermore, in step S4, the pre-sintering time is 3-6 hours.

[0020] Furthermore, in step S5, the second sintering temperature ranges from 1400 to 1600°C.

[0021] Furthermore, in step S5, the final sintering time is 3-6 hours.

[0022] Furthermore, the siliceous raw material is one or more of siliceous particles, siliceous fine powder, and waste silicon bricks.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention uses siliceous raw materials as main raw materials, spherical starch and polycarbosilane as binders, and ferrocene as a catalyst and mineralizer, which can improve the strength of semi-finished silicon bricks, and uses silicon carbide whiskers generated in situ after high-temperature cracking of polycarbosilane as a reinforcing phase, thereby improving the high-temperature strength of lightweight silicon bricks, and can prepare lightweight silicon bricks with high porosity and high strength, so that the lightweight silicon bricks can still maintain strength under the condition of reduced bulk density, and make the thermal conductivity coefficient lower.

[0025] 2. The lightweight silica bricks prepared by the present invention have spherical voids and have the advantages of high porosity, uniform microstructure, low bulk density, excellent thermal insulation performance, high load softening temperature, good high-temperature volume stability and a wide range of applications. DETAILED DESCRIPTION

[0026] The following is a further description with reference to specific embodiments.

[0027] Example 1

[0028] A method for preparing high-strength, low-density and lightweight silica bricks comprises the following steps:

[0029] S1, taking 60% of siliceous raw material, 35wt% of spherical starch, and 2wt% of composite mineralizer mixture and ball milling to obtain a first mixture. The siliceous raw material is siliceous particles.

[0030] S2. Add 1 wt % polycarbosilane and 2 wt % ferrocene to the first mixture obtained in step S1, and ball-mill the mixture on a ball mill for 10 h to obtain a second mixture, which is then mixed evenly.

[0031] S3. Pressing the second mixed material obtained in step S2 into a mold, and drying it at 60° C. for 48 hours.

[0032] S4. Pre-sinter the dried silicon brick at 800° C. for 6 hours to generate silicon carbide nano whiskers.

[0033] S5. Sinter the pre-sintered silica brick at 1400° C. for 6 hours to obtain a high-strength, low-density, lightweight silica brick reinforced with silicon carbide nanowhiskers.

[0034] Example 2

[0035] A method for preparing high-strength, low-density and lightweight silica bricks comprises the following steps:

[0036] S1, taking 65wt% of siliceous raw material, 25wt% of spherical starch, and 5wt% of composite mineralizer mixture and ball milling to obtain a first mixture. The siliceous raw material is siliceous particles and siliceous fine powder.

[0037] S2. Add 2 wt % of polycarbosilane and 3 wt % of ferrocene to the first mixture obtained in step S1, and ball-mill the mixture on a ball mill for 14 h to obtain a second mixture, which is then mixed evenly.

[0038] S3. Press the second mixed material obtained in step S2 into a mold and dry it at 75° C. for 28 hours.

[0039] S4. Pre-sinter the dried silicon brick at 950° C. for 4.5 h to generate silicon carbide nano whiskers.

[0040] S5. Sinter the pre-sintered silica brick at 1500° C. for 5 h to obtain a high-strength, low-density, lightweight silica brick reinforced with silicon carbide nanowhiskers.

[0041] Example 3

[0042] A method for preparing high-strength, low-density and lightweight silica bricks comprises the following steps:

[0043] S1, take 60wt% of siliceous raw materials, 30wt% of spherical starch, and 3wt% of composite mineralizer mixture and ball mill to obtain a first mixture. The siliceous raw materials are siliceous particles, siliceous fine powder, and waste silica bricks.

[0044] S2. Add 5 wt % of polycarbosilane and 2 wt % of ferrocene to the first mixture obtained in step S1, and ball-mill the mixture on a ball mill for 16.5 h to obtain a second mixture, which is then mixed evenly.

[0045] S3. Pressing the second mixed material obtained in step S2 into a mold, and drying it at 88° C. for 40 hours.

[0046] S4. Pre-sinter the dried silicon brick at 850° C. for 5 hours to generate silicon carbide nano whiskers.

[0047] S5. Sinter the pre-sintered silica brick at 1550° C. for 4 h to obtain a high-strength, low-density, lightweight silica brick reinforced with silicon carbide nanowhiskers.

[0048] Example 4

[0049] A method for preparing high-strength, low-density and lightweight silica bricks comprises the following steps:

[0050] S1, taking 70wt% of siliceous raw materials, 21wt% of spherical starch, and 2wt% of composite mineralizer mixture and ball milling to obtain a first mixture. The siliceous raw materials are siliceous fine powder and waste silica bricks.

[0051] S2. Add 4 wt % of polycarbosilane and 3 wt % of ferrocene to the first mixture obtained in step S1, and ball-mill for 18 h on a ball mill to obtain a second mixture, which is then mixed evenly.

[0052] S3. Pressing the second mixed material obtained in step S2 into a mold, and drying it at 90° C. for 38 hours.

[0053] S4. Pre-sinter the dried silicon brick at 1000° C. for 4 hours to generate silicon carbide nano whiskers.

[0054] S5. Sinter the pre-sintered silica brick at 1600° C. for 5 h to obtain a high-strength, low-density, lightweight silica brick reinforced with silicon carbide nanowhiskers.

[0055] Example 5

[0056] A method for preparing high-strength, low-density and lightweight silica bricks comprises the following steps:

[0057] S1, taking 75wt% of siliceous raw materials, 20wt% of spherical starch, and 1wt% of a composite mineralizer mixture and ball milling to obtain a first mixture. The siliceous raw materials are siliceous particles and waste silicon bricks.

[0058] S2. Add 3 wt % polycarbosilane and 1 wt % ferrocene to the first mixture obtained in step S1, and ball-mill the mixture on a ball mill for 20 h to obtain a second mixture, which is then mixed evenly.

[0059] S3. Pressing the second mixed material obtained in step S2 into a mold, and drying it at 100° C. for 24 hours.

[0060] S4. Pre-sinter the dried silicon brick at 1000° C. for 3 hours to generate silicon carbide nano whiskers.

[0061] S5. Sinter the pre-sintered silica brick at 1600° C. for 3 h to obtain a high-strength, low-density, lightweight silica brick reinforced with silicon carbide nanowhiskers.

[0062] Working principle of the present invention: The present invention uses siliceous raw materials as the main raw materials, spherical starch and polycarbosilane as binders, and ferrocene as a catalyst and mineralizer. It can improve the strength of semi-finished silicon bricks, and use the silicon carbide whiskers generated in situ after high-temperature cracking of polycarbosilane as the reinforcing phase, which improves the high-temperature strength of lightweight silicon bricks. It can prepare lightweight silicon bricks with high porosity and high strength, so that the lightweight silicon bricks can still maintain strength under the condition of reduced bulk density, and make the thermal conductivity coefficient lower. The lightweight silicon bricks prepared by the present invention are spherical voids, and have the advantages of high porosity, uniform microstructure, low bulk density, excellent thermal insulation performance, high load softening temperature, good high-temperature volume stability and a wide range of applications.

[0063] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing high-strength, low-density and lightweight silica bricks, characterized in that: The following steps are involved: S1, taking a mixture of a siliceous raw material, spherical starch, and a composite mineralizer in a formula amount and ball-milling it to obtain a first mixture; the formula amount of the siliceous raw material, spherical starch, and composite mineralizer is: 60-75wt% of siliceous raw material; 20-35wt% of spherical starch; 1-5wt% of composite mineralizer; S2, adding the formulated amount of polycarbosilane and ferrocene to the first mixed material obtained in step S1, and ball-milling the mixture on a ball mill to obtain a second mixed material, and mixing the mixture evenly; the formulated amount of polycarbosilane and ferrocene is: 1-5wt% of polycarbosilane; 1-3wt% of ferrocene as catalyst; S3, pressing the second mixed material obtained in step S2 into a mold, and drying it at a temperature of 60-100° C.; S4, pre-sintering the dried silicon brick within a first sintering temperature range to generate silicon carbide nano whiskers; S5. Final sintering the pre-sintered silicon bricks within a second sintering temperature range to obtain high-strength, low-density, lightweight silicon bricks reinforced with silicon carbide nanowhiskers, wherein the lowest temperature within the second sintering temperature range is greater than the highest temperature within the first sintering temperature range.

2. The method for preparing a high-strength, low-density, lightweight silica brick according to claim 1, characterized in that: In the step S2, the ball milling time is 10-20 hours.

3. The method for preparing a high-strength, low-density, lightweight silica brick according to claim 1, characterized in that: In step S3, the drying time is 24-48 hours.

4. The method for preparing a high-strength, low-density, lightweight silica brick according to claim 1, characterized in that: In the step S4, the first sintering temperature ranges from 800 to 1000°C.

5. The method for preparing a high-strength, low-density, lightweight silica brick according to claim 4, characterized in that: In step S4, the pre-sintering time is 3-6 hours.

6. The method for preparing a high-strength, low-density, lightweight silica brick according to claim 1, characterized in that: In the step S5, the second sintering temperature ranges from 1400 to 1600°C.

7. The method for preparing a high-strength, low-density, lightweight silica brick according to claim 6, characterized in that: In the step S5, the final sintering time is 3-6 hours.

8. A method for preparing a high-strength, low-density, lightweight silica brick according to any one of claims 1 to 7, characterized in that: The siliceous raw material is one or more of siliceous particles, siliceous fine powder and waste silicon bricks.