In-situ formed mullite reinforced zircon spherical dense aggregate and preparation method thereof

Abstract

The invention belongs to the technical field of zircon refractory aggregates and discloses an in-situ mullite-reinforced zircon spherical dense aggregate and a preparation method thereof. Zircon powder, clay powder and silicon powder are used as raw materials, and the zircon aggregate is directly prepared by a granulation method. The zircon aggregate is vacuum impregnated with aluminum sol and sintered to obtain the in-situ mullite-reinforced zircon spherical dense aggregate. In the invention, the aluminum sol and the zircon generate needle-shaped mullite in situ, and the zirconium oxide phase fills the gaps between the mullite and the zirconium oxide phase and interweaves with the mullite. The mullite generated by the clay reaction forms a gradient structure with the needle-shaped mullite. The mullite is used as a medium to accelerate the migration of aluminum ions from the interior of the zircon spherical aggregate to the outside, thereby forming the mullite gradient structure. The invention has the excellent properties of simple preparation process, high bulk density, good anti-stripping performance, stable high-temperature performance and high strength, and is a preferred material for preparing zircon refractory materials for glass kilns and zircon ceramics.

Description

Technical Field

[0001] The invention belongs to the technical field of zircon refractory aggregates, and particularly relates to an in-situ formed mullite-reinforced zircon spherical dense aggregate and a preparation method thereof. Background Art

[0002] In recent years, my country's glass industry has continued to expand in scale and significantly improved its technological level. The industry has not only achieved quality and efficiency improvements for traditional float glass, but has also made significant breakthroughs in high-end fields such as photovoltaic glass, electronic glass, and energy-saving glass. The rapid development of various new types of glass has also placed higher demands on refractory materials for glass furnaces. Higher smelting temperatures place even higher demands on the high-temperature stability of refractory materials for glass furnaces. At the same time, refractory materials for glass furnaces must maintain high mechanical properties during the molten glass flushing process, thereby increasing service life and reducing contamination of the molten glass. Therefore, the preparation of a refractory material with high high-temperature stability has become a current research focus.

[0003] Therefore, the dense structure of the refractory aggregate in refractory materials requires it to be able to withstand extreme high temperatures and have excellent thermal shock stability, making it less susceptible to cracking under rapid cooling and heating conditions. At the same time, it gives the material excellent compressive and flexural strength, making it able to withstand mechanical shock and high-temperature loads, and has strong resistance to corrosive media, extending the service life of the furnace lining or container. However, the surface of dense aggregate is relatively smooth, making it difficult to form a good aggregate-matrix interface with the refractory matrix during refractory preparation, thus affecting high-temperature performance.

[0004] Currently, dense aggregate is mostly prepared by sintering followed by crushing. The dense zircon aggregate described in the patent "Method for Preparing Zircon Bricks Using Dense Zircon Aggregate (CN107935608B)" is prepared by isostatic pressing followed by crushing, screening, and magnetic separation. The special zircon particles described in the patent "Zircon Product Containing Special Zircon Particles (CN102030546B)" are obtained by crushing, acid-washing, drying, and screening the leftovers from finished dense zircon bricks.

[0005] As can be seen from the existing research results, zircon dense aggregate is mainly produced by pressing and forming, then high-temperature firing, followed by crushing and screening. The research focus is to produce a zircon refractory aggregate with simple processing, rough surface, and high strength. Summary of the Invention

[0006] The present invention aims to overcome the shortcomings of the prior art by providing a simple, energy-efficient, and low-cost in-situ mullite-reinforced zircon spherical dense aggregate and its preparation method. The mullite-reinforced zircon spherical dense aggregate prepared by the present invention exhibits high bulk density, excellent spalling resistance, and high strength.

[0007] To achieve the above object, the technical solution adopted by the present invention is: an in-situ formation of mullite-reinforced zircon spherical dense aggregate, the weight proportions of the raw materials added are: 85-92 parts of zircon powder, 5-10 parts of clay powder, and 2-5 parts of silicon powder.

[0008] The preparation method is:

[0009] Zircon powder, clay powder and silica powder are placed in a barrel of a granulating device, and then water accounting for 3-8% of the total weight of the original material is added. The rotor speed is adjusted to 200-400 revolutions per minute and the device is operated for 5-15 minutes. When all the fine powders are spherical and the particle size is 3-5 mm, the prepared refractory spherical aggregate is taken out. Aluminum sol is used for vacuum impregnation for 3-5 hours, and the device is cured at a temperature of 110-150°C. The device is then baked and heated to 1400-1580°C. The heating rate is 10-20°C / min from 25-500°C, 5-10°C / min from 500-1200°C, and 3-5°C / min after 1200°C. The device is kept warm for 3-6 hours to obtain in-situ mullite-reinforced zircon spherical dense aggregate.

[0010] The zircon powder has a ZrO2 content of ≥64wt% and a SiO2 content of ≤33wt%.

[0011] The particle size of the zircon powder is ≤0.088 mm.

[0012] The clay powder has an Al2O3 content of ≥32wt% and a SiO2 content of ≤55wt%.

[0013] The particle size of the clay powder is ≤0.074 mm.

[0014] The SiO2 content of the silicon micropowder is ≥98wt%.

[0015] The particle size of the silicon micropowder is ≤0.074 mm.

[0016] The Al2O3 content in the aluminum sol is ≥20wt%.

[0017] The particle size of Al2O3 in the aluminum sol is ≤80nm.

[0018] The invention uses zircon powder, clay powder and silicon powder as raw materials, adopts a granulation method to directly prepare zircon aggregate, and obtains the zircon aggregate after vacuum impregnation with aluminum sol and sintering treatment.

[0019] In the present invention, the mullite formed in situ by the aluminum sol and zircon has a needle-like structure, the zirconium oxide phase fills the gaps in the needle-like mullite, and the zirconium oxide phase and the needle-like mullite whiskers are intertwined; the mullite generated by the clay reaction and the needle-like mullite generated by the aluminum sol and zirconium reaction form a gradient structure, and the mullite is used as a medium to accelerate the migration of aluminum ions from the interior to the outside of the zircon spherical aggregate, thereby forming a mullite gradient structure.

[0020] Vacuum impregnation effectively reduces the apparent porosity of zircon spherical aggregate, increasing the material's density while also creating a higher specific surface area and strengthening the aggregate-matrix interface. Regarding the crystalline phase, the introduction of alumina sol partially promotes the decomposition of zircon in contact with the sol, producing zirconium oxide and silicon oxide. The silicon oxide reacts with the alumina sol to form a mullite phase. The resulting mullite phase has a needle-like structure, with zirconium oxide filling the gaps in the acicular mullite. The interweaving of zirconium oxide and acicular mullite whiskers creates a toughening effect, further improving strength, spalling resistance, and erosion resistance.

[0021] The particle size of zircon determines the particle size of the decomposed silica. The lower the particle size, the easier it is to react and form needle-shaped mullite. The particle size of the clay determines its binding properties. The lower the particle size, the better the dispersion, which significantly improves the overall binding properties of the aggregate. Furthermore, during the firing process, a lower particle size of clay also favors the formation of needle-shaped mullite, which creates uniformity with the mullite formed on the surface. The particle size of the silica powder is also designed to form needle-shaped mullite.

[0022] The invention is characterized in that the zircon powder is rapidly dispersed in the granulation equipment by the centripetal force, and gradually sphericalized under the bonding action of clay and water; during the impregnation process of the aluminum sol, the aluminum sol is evenly coated on the surface of the zircon spherical aggregate, forming a better core-shell structure;

[0023] During the sintering process, the clay will react in situ to form the mullite phase. At the same time, the aluminum sol will accelerate the decomposition reaction of the zircon phase in contact with it to form the zirconium oxide phase and the silicon oxide phase. The silicon oxide phase will further react in situ with the aluminum sol to form the needle-shaped mullite phase. The zirconium oxide phase exists alone in the mullite phase to play a toughening effect.

[0024] As we all know, conventional mullite is in block or granular form. Compared to block or granular mullite, acicular mullite has a cross-linked structure and does not slip at high temperatures. Acicular mullite covers the surface of zircon aggregate, which plays a role in toughening and increasing the specific surface area.

[0025] Mullite generated by the reaction of clay inside and needle-shaped mullite generated by the reaction of aluminum sol and zircon will form a gradient structure. Mullite is used as a medium to accelerate the migration of aluminum ions from the inside to the outside of the zircon spherical aggregate, thus forming a mullite gradient structure.

[0026] This is because the amount of aluminum sol on the outside is relatively small, insufficient to fully react with the silica decomposed from the zircon on the aggregate surface. A larger amount of aluminum oxide is required for this reaction to occur. Secondly, the surface contains a large amount of silica, which easily forms a liquid phase. Aluminum has a certain solubility in this liquid phase, and when it is unsaturated, it attracts the internal aluminum ions to migrate outward.

[0027] Therefore, the mullite formed on the surface of zircon spherical aggregate is an interdigitated needle-like structure with a relatively high specific surface area. At the same time, it will not slip at high temperatures and has good high-temperature mechanical properties.

[0028] The mullite surface reinforced zircon spherical dense aggregate prepared by the present invention has a bulk density of 3.9-4.2 g / cm 3 The apparent porosity is 1-4%, the average pore diameter is 0.1-0.3μm, and the thermal shock stability is 70-83% after one water cooling at 1000℃.

[0029] Therefore, the invention is simple in industry, low in cost and easy to industrialize and produce; the prepared mullite surface reinforced zircon spherical dense aggregate has high strength and good thermal shock resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the microstructure of the zircon spherical aggregate obtained in Example 1.

[0031] Figure 2 This is the XRD pattern of the internal structure of the zircon spherical aggregate obtained in Example 1. DETAILED DESCRIPTION

[0032] The following examples illustrate the implementation and features of the present invention, but the present invention is not limited to the following examples.

[0033] An embodiment of the present invention provides an in-situ formed mullite reinforced zircon spherical dense aggregate and a preparation method thereof;

[0034] The zircon powder has a ZrO2 content of ≥64wt%, and a SiO2 content of ≤33wt%. The zircon powder has a particle size of ≤0.088mm. The clay powder has an Al2O3 content of ≥32wt%, and a SiO2 content of ≤55wt%. The clay powder has a particle size of ≤0.074mm. The silica micropowder has a SiO2 content of ≥98wt%. The silica micropowder has a particle size of ≤0.074mm. The Al2O3 content in the aluminum sol is ≥20wt%. The Al2O3 particle size in the aluminum sol is ≤80nm.

[0035] Example 1

[0036] A method for preparing in-situ mullite-reinforced zircon spherical dense aggregate comprises the following steps: 85 parts of zircon powder, 10 parts of clay powder, and 5 parts of silicon powder, all in parts by weight, are placed in a barrel of a granulating device, and then 8% of the total weight of the original material is added with water. The rotor speed is adjusted to 200-400 revolutions per minute and the aggregate is run for 5 minutes. When all the fine powder is spherical and the particle size is 3-5 mm, the prepared refractory spherical aggregate is taken out and aluminum solution is used to melt the spherical aggregate. The glue is vacuum impregnated for 5 hours, cured at a temperature of 110-150°C, and then baked, heating to 1400-1580°C, wherein the heating rate from 25-500°C is 10-20°C / min, the heating rate from 500-1200°C is 5-10°C / min, and the heating rate after 1200°C is 3-5°C / min. The mixture is kept warm for 3 hours to obtain in-situ formed mullite reinforced zircon spherical dense aggregate.

[0037] The mullite surface reinforced zircon spherical dense aggregate prepared by the present invention has a bulk density of 4.15 g / cm 3 The apparent porosity is 1.3%, the average pore diameter is 0.14μm, and the thermal shock stability is 80.2% after one water cooling at 1000℃.

[0038] Example 2

[0039] A method for preparing in-situ mullite-reinforced zircon spherical dense aggregate is as follows:

[0040] 92 parts of zircon powder, 5 parts of clay powder, and 3 parts of silicon micropowder, all in parts by weight, are placed in a barrel of a granulating device, and then 3% of water, which accounts for the total weight of the original material, is added. The rotor speed is adjusted to 200-400 revolutions per minute and the device is operated for 15 minutes. When all the fine powders are spherical and the particle size is 3-5 mm, the prepared refractory spherical aggregate is taken out and vacuum impregnated with aluminum sol for 5 hours. The aggregate is cured at a temperature of 110-150° C. and then baked to a temperature of 1400-1580° C., wherein the heating rate is 10-20° C. / min from 25-500° C., 5-10° C. / min from 500-1200° C., and 3-5° C. / min after 1200° C. The aggregate is kept warm for 6 hours to obtain an in-situ formed mullite-reinforced zircon spherical dense aggregate.

[0041] The mullite surface reinforced zircon spherical dense aggregate prepared by the present invention has a bulk density of 3.93 g / cm 3 The apparent porosity is 2.9%, the average pore diameter is 0.22μm, and the thermal shock stability is 78.5% after one water cooling at 1000℃.

[0042] Example 3

[0043] A method for preparing in-situ mullite-reinforced zircon spherical dense aggregate is as follows:

[0044] 90 parts of zircon powder, 6 parts of clay powder, and 4 parts of silicon micropowder, all in parts by weight, are placed in a barrel of a granulating device, and then water accounting for 6% of the total weight of the original material is added. The rotor speed is adjusted to 200-400 revolutions per minute and the device is operated for 10 minutes. When all the fine powders are spherical and the particle size is 3-5 mm, the prepared refractory spherical aggregate is taken out and vacuum impregnated with aluminum sol for 4 hours. The aggregate is cured at a temperature of 110-150° C. and then baked to a temperature of 1400-1580° C., wherein the heating rate is 10-20° C. / min from 25-500° C., 5-10° C. / min from 500-1200° C., and 3-5° C. / min after 1200° C., and the temperature is maintained for 3-6 hours to obtain an in-situ formed mullite-reinforced zircon spherical dense aggregate.

[0045] The mullite surface reinforced zircon spherical dense aggregate prepared by the present invention has a bulk density of 3.98 g / cm 3 The apparent porosity is 3.5%, the average pore diameter is 0.26μm, and the thermal shock stability is 72.5% after one water cooling at 1000℃.

[0046] Example 4

[0047] A method for preparing in-situ mullite-reinforced zircon spherical dense aggregate is as follows:

[0048] 87 parts of zircon powder, 10 parts of clay powder, and 3 parts of silicon micropowder, all in parts by weight, are placed in a barrel of a granulating device, and then 3-8% of water, which accounts for the total weight of the original material, is added. The rotor speed is adjusted to 200-400 revolutions per minute and the device is operated for 8 minutes. When all the fine powders are spherical and the particle size is 3-5 mm, the prepared refractory spherical aggregate is taken out and vacuum impregnated with aluminum sol for 5 hours. The aggregate is cured at a temperature of 110-150° C. and then baked to a temperature of 1400-1580° C., wherein the heating rate is 10-20° C. / min from 25-500° C., 5-10° C. / min from 500-1200° C., and 3-5° C. / min after 1200° C. The aggregate is kept warm for 5 hours to obtain an in-situ formed mullite-reinforced zircon spherical dense aggregate.

[0049] The mullite surface reinforced zircon spherical dense aggregate prepared by the present invention has a bulk density of 4.08 g / cm 3 The apparent porosity is 1.9%, the average pore diameter is 0.17μm, and the thermal shock stability is 79.2% after one water cooling at 1000℃.

[0050] Due to the adoption of the above technical solution, the present invention has the following positive effects compared with the prior art:

[0051] The invention processes zircon fine powder, clay powder and silicon micropowder in a granulating device, then impregnates them with aluminum sol, and sinters them under the condition of 1400-1580°C in an air atmosphere. The operation is simple, the aggregate surface presents a needle-shaped mullite interwoven structure, has high mechanical properties and good thermal shock resistance.

[0052] The zircon aggregate prepared by the present invention is used as a raw material for refractory materials and structural ceramics, and can promote the interface bonding between the aggregate and the matrix, enhance the corrosion resistance, and increase the service life.

[0053] Therefore, the present invention is simple to operate and easy to industrialize. The in-situ formed mullite reinforced zircon spherical dense aggregate prepared by the method has high bulk density, low porosity, small pore diameter and good thermal shock resistance.

Claims

1. An in-situ formed mullite reinforced zircon spherical dense aggregate, characterized by: Zircon aggregate is directly prepared by a granulation method using zircon powder, clay powder and silica powder as raw materials. The zircon aggregate is vacuum impregnated with aluminum sol and sintered to obtain the zircon aggregate. The weight proportions of the raw materials added are: 85-92 parts of zircon powder, 5-10 parts of clay powder and 2-5 parts of silica powder. The mullite formed in situ by the aluminum sol and zircon has a needle-like structure, and the zirconium oxide phase fills the gaps in the needle-like mullite.

2. The in-situ formed mullite reinforced zircon spherical dense aggregate according to claim 1, characterized in that: The ZrO2 content of the zircon powder is ≥64wt%, and the SiO2 content is ≤33wt%; the particle size of the zircon powder is ≤0.088mm.

3. The in-situ formed mullite reinforced zircon spherical dense aggregate according to claim 1, characterized in that: The Al2O3 content of the clay powder is ≥32wt%, and the SiO2 content is ≤55wt%; the particle size of the clay powder is ≤0.074mm.

4. The in-situ formed mullite reinforced zircon spherical dense aggregate according to claim 1, characterized in that: The SiO2 content of the silicon micropowder is ≥98wt%; the particle size of the silicon micropowder is ≤0.074mm.

5. The in-situ formed mullite reinforced zircon spherical dense aggregate according to claim 1, characterized in that: The Al2O3 content in the aluminum sol is ≥20wt%; the Al2O3 particle size in the aluminum sol is ≤80nm.

6. The method for preparing in-situ mullite-reinforced zircon spherical dense aggregate according to claim 1, characterized in that: Zircon powder, clay powder and silica powder are placed in a barrel of a granulating device, and then water accounting for 3-8% of the total weight of the original material is added. The rotor speed is adjusted to 200-400 revolutions per minute and the device is operated for 5-15 minutes. When all the fine powders are spherical and the particle size is 3-5 mm, the prepared refractory spherical aggregate is taken out. Aluminum sol is used for vacuum impregnation for 3-5 hours, and the device is cured at a temperature of 110-150°C. The device is then baked and heated to 1400-1580°C. The heating rate is 10-20°C / min from 25-500°C, 5-10°C / min from 500-1200°C, and 3-5°C / min after 1200°C. The device is kept warm for 3-6 hours to obtain in-situ mullite-reinforced zircon spherical dense aggregate.

Images