Thermal shock resistant firebrick and method of making same

Abstract

The application belongs to the technical field of refractory materials, and particularly relates to a heat shock resistance refractory brick and a preparation method thereof. The refractory brick is prepared from the following raw materials in mass percentage: 8-12 wt% of flake graphite, 2-8 wt% of yttrium-doped hafnium-palladium carbide, 1-3 wt% of nano-alumina, 4-8 wt% of a composite binder, and the balance of magnesium oxide. The yttrium-doped hafnium-palladium carbide is prepared by the following process: adding chloropalladium, chlorohafnium, yttrium chloride and phenolic resin into a mixed solution of acetylacetone and n-butanol, heating and stirring, adding ammonia water for continuous stirring, filtering and drying to obtain a precursor; and calcining the precursor and cooling to obtain the yttrium-doped hafnium-palladium carbide. The refractory brick prepared by the application has excellent compressive strength, high-temperature bending strength and heat shock resistance.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically relating to a thermal shock resistant refractory brick and its preparation method. Background Technology

[0002] Refractory bricks are shaped refractory materials commonly used in the construction of industrial furnaces and kilns in metallurgy, glass, cement, and power industries. They must withstand not only high temperatures but also the pressure of materials, the internal stresses generated by kiln rotation and temperature changes. Therefore, refractory bricks not only require high-temperature resistance but also good mechanical strength and thermal shock resistance. Especially with industrial advancements, the upgrading of high-temperature industries, and the increasing size of blast furnaces, the working environment of refractory bricks has become more extreme. They must withstand high temperatures and high pressures, alternating stress fields, vibration loads, thermal fatigue, high-temperature oxidation, and corrosion from mixed combustion gases. To ensure the service life and operational stability of kilns, even higher requirements are placed on the comprehensive performance of refractory bricks.

[0003] Commonly used materials for refractory bricks include oxides such as alumina, magnesia, calcium oxide, and yttrium oxide. While these materials possess high hardness and high melting points, they also exhibit high thermal expansion coefficients, low thermal conductivity and elasticity, and low tensile strength. Consequently, they have poor resistance to thermal stress and low thermal shock resistance, making them prone to spalling, cracking, and overall fracture under the instantaneous or cyclic action of thermal shock. Non-oxide materials such as silicon carbide, aluminum nitride, and boron nitride not only have high melting points and hardness but also high thermal conductivity and low thermal expansion coefficients. Combining these with oxides can improve the thermal shock stability and chemical resistance of refractory materials. However, these materials readily react with reactive elements, leading to contamination of the products in the kiln. Therefore, further research is needed to optimize the ratio of refractory materials to non-oxide materials and improve the preparation process to enhance the overall performance of refractory bricks, including strength, high-temperature stability, and thermal shock resistance. Summary of the Invention

[0004] The primary objective of this invention is to provide a thermal shock refractory brick, which possesses excellent compressive strength, high-temperature flexural strength, and thermal shock resistance.

[0005] The second objective of this invention is to provide a method for preparing the above-mentioned thermal shock resistant refractory bricks.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A thermal shock resistant refractory brick, wherein the refractory brick is composed of the following raw materials in weight percentage: 8-12 wt% flake graphite, 2-8 wt% yttrium-doped tantalum hafnium carbide, 1-3 wt% nano-alumina, 4-8 wt% composite binder, and the balance being magnesium oxide; The yttrium-doped tantalum carbide hafnium is prepared by the following process: (1) Add tantalum chloride, hafnium chloride, yttrium chloride and phenolic resin to a mixed solution of acetylacetone and n-butanol, heat and stir, then add ammonia water and continue stirring, filter and dry to obtain the precursor; (2) The precursor is calcined and cooled to obtain yttrium-doped tantalum carbide hafnium.

[0007] Further, in step (1), the ratio of tantalum chloride, hafnium chloride, yttrium chloride, phenolic resin, acetylacetone, n-butanol and ammonia is 1 g: (0.2-0.8) g: (0.1-0.15) g: (0.2-0.4) g: (5-10) mL: (40-60) mL: (5-10) mL; and the mass concentration of the ammonia is 25-28%.

[0008] Further, the heating and stirring temperature in step (1) is 60-80 ℃ and the time is 1-2 h; the stirring time is 0.5-1 h.

[0009] Furthermore, the calcination temperature in step (2) is 1450-1550 ℃ and the time is 2-4 h.

[0010] Furthermore, the composite adhesive is prepared by the following process: Silane coupling agent and magnesium boride are added to water and ultrasonically treated at 50-70 °C for 2-5 h. After filtration, washing and drying, modified magnesium boride is obtained. The modified magnesium boride is then mixed with phenolic resin to obtain a composite binder.

[0011] Furthermore, the mass ratio of magnesium boride to silane coupling agent is 1:(0.15-0.25); the silane coupling agent is vinyltrimethoxysilane.

[0012] Furthermore, the mass ratio of the modified magnesium boride to the phenolic resin is 1:(3-5).

[0013] The above-mentioned method for preparing thermal shock resistant refractory bricks includes the following steps: The raw materials are mixed evenly, placed into a mold and pressed to obtain a brick blank; the brick blank is then sintered in a gradient and cooled to obtain a refractory brick.

[0014] Furthermore, the pressure held is 220-280 MPa for 3-5 minutes.

[0015] Furthermore, the gradient sintering process is as follows: first, sinter at 200-300 ℃ for 5-10 h, then raise the temperature to 800-900 ℃ for 4-8 h, and then raise the temperature to 1400-1500 ℃ for 2-3 h.

[0016] The beneficial technical effects of this invention are as follows: 1. This invention adds yttrium-doped tantalum hafnium carbide to refractory bricks, which can effectively improve the strength and thermal shock resistance of the refractory bricks. Tantalum hafnium carbide has high hardness, high-temperature strength, and good thermal conductivity. As an additive, it can improve the strength and high-temperature resistance of refractory bricks, and timely disperse thermal stress, reduce internal cracks caused by temperature gradients, thus improving thermal shock resistance. Doping rare earth yttrium into tantalum hafnium carbide can improve its interfacial bonding performance with the matrix, reduce internal stress caused by differences in thermal expansion coefficients, further inhibit crack propagation, and improve the thermal shock resistance of refractory bricks.

[0017] 2. This invention employs a composite binder of magnesium boride and phenolic resin, combined with a segmented sintering process, to promote sintering densification and enhance the strength of the refractory bricks. The phenolic resin cures at low temperatures, forming a stable cross-linked network; magnesium boride forms a liquid phase at medium temperatures, promoting crystal structure rearrangement and increasing sintering strength; the two react at high temperatures to generate a dense phase, preventing oxygen from entering and resulting in tighter sintering of all components, leading to superior overall performance of the refractory bricks. Furthermore, magnesium boride has good thermal conductivity, which can disperse thermal stress, reduce crack formation, and improve the thermal shock resistance of the refractory bricks. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of yttrium-doped tantalum carbide hafnium prepared in Example 1 of the present invention. Detailed Implementation

[0019] The following is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all reagents or instruments used are conventional products obtained through commercial channels.

[0020] (I) Implementation Examples Example

[0021] Example 1 provides a thermal shock refractory brick composed of the following raw materials by mass percentage: 10 wt% flake graphite, 6 wt% yttrium-doped tantalum hafnium carbide, 2 wt% nano alumina, 6 wt% composite binder, and the balance being magnesium oxide; The yttrium-doped tantalum carbide hafnium is prepared by the following process: (1) Tantalum chloride, hafnium chloride, yttrium chloride, phenolic resin, acetylacetone, n-butanol and ammonia were added to a mixed solution of acetylacetone and n-butanol according to the ratio of 1 g: 0.5 g: 0.12 g: 0.3 g: 8 mL: 50 mL: 8 mL. The mixture was stirred at 70 °C for 1 h, and then ammonia was added dropwise and stirring was continued for 0.8 h. The solid substance was filtered out and dried to obtain the precursor. (2) The precursor was calcined at 1500 °C for 3 h and cooled to room temperature to obtain yttrium-doped tantalum carbide hafnium; the scanning electron microscope image of the yttrium-doped tantalum carbide hafnium prepared in this embodiment is shown in the figure. Figure 1 As shown.

[0022] The composite adhesive is prepared by the following process: Magnesium boride, vinyltrimethoxysilane, and water were added to water at a mass ratio of 1:0.2:10, and the mixture was ultrasonically treated at 60 °C for 3 h. After filtration, washing, and drying, modified magnesium boride was obtained. The modified magnesium boride and phenolic resin were mixed evenly at a mass ratio of 1:4 to obtain a composite binder.

[0023] This embodiment also provides a method for preparing the above-mentioned thermal shock resistant refractory bricks, the specific steps of which are as follows: Weigh out all the raw materials for the above-mentioned thermal shock refractory bricks and mix them evenly. After loading them into the mold, pressurize them at 260 MPa for 4 minutes to obtain the brick blank. Sinter the brick blank at 250 ℃ for 8 h, then raise the temperature to 850 ℃ for 6 h, and then raise the temperature to 1450 ℃ for 2 h. After cooling, the refractory brick is obtained. Example

[0024] Example 2 provides a thermal shock refractory brick composed of the following raw materials by mass percentage: 8 wt% flake graphite, 2 wt% yttrium-doped tantalum hafnium carbide, 1 wt% nano alumina, 4 wt% composite binder, and the balance being magnesium oxide; The yttrium-doped tantalum carbide hafnium is prepared by the following process: (1) Tantalum chloride, hafnium chloride, yttrium chloride, phenolic resin, acetylacetone, n-butanol and ammonia were added to a mixed solution of acetylacetone and n-butanol according to the ratio of 1 g: 0.2 g: 0.1 g: 0.2 g: 5 mL: 40 mL: 5 mL. The mixture was stirred at 60 °C for 1 h, and then ammonia was added dropwise and stirring was continued for 0.5 h. The solid substance was filtered out and dried to obtain the precursor. (2) The precursor was calcined at 1450 °C for 2 h and cooled to room temperature to obtain yttrium-doped tantalum carbide hafnium.

[0025] The composite adhesive is prepared by the following process: Magnesium boride, vinyltrimethoxysilane, and water were added to water at a mass ratio of 1:0.15:8, and the mixture was ultrasonically treated at 50 °C for 2 h. After filtration, washing, and drying, modified magnesium boride was obtained. The modified magnesium boride and phenolic resin were mixed evenly at a mass ratio of 1:3 to obtain a composite binder.

[0026] This embodiment also provides a method for preparing the above-mentioned thermal shock resistant refractory bricks, the specific steps of which are as follows: Weigh out all the raw materials for the above-mentioned thermal shock refractory bricks and mix them evenly. After loading them into the mold, pressurize them at 220 MPa for 3 minutes to obtain the brick blank. Sinter the brick blank at 200 ℃ for 5 h, then raise the temperature to 800 ℃ for 4 h, and then raise the temperature to 1400 ℃ for 2 h. After cooling, the refractory brick is obtained. Example

[0027] Example 3 provides a thermal shock refractory brick composed of the following raw materials by mass percentage: 12 wt% flake graphite, 8 wt% yttrium-doped tantalum hafnium carbide, 3 wt% nano alumina, 8 wt% composite binder, and the balance being magnesium oxide; The yttrium-doped tantalum carbide hafnium is prepared by the following process: (1) Tantalum chloride, hafnium chloride, yttrium chloride, phenolic resin, acetylacetone, n-butanol and ammonia were added to a mixed solution of acetylacetone and n-butanol according to the ratio of 1 g: 0.8 g: 0.15 g: 0.4 g: 10 mL: 60 mL: 10 mL. The mixture was stirred at 80 °C for 2 h, and then ammonia was added dropwise and stirred for another 1 h. The solid substance was filtered out and dried to obtain the precursor. (2) The precursor was calcined at 1550 °C for 4 h and cooled to room temperature to obtain yttrium-doped tantalum carbide hafnium.

[0028] The composite adhesive is prepared by the following process: Magnesium boride, vinyltrimethoxysilane, and water were added to water at a mass ratio of 1:0.25:12, and the mixture was ultrasonically treated at 70 °C for 5 h. After filtration, washing, and drying, modified magnesium boride was obtained. The modified magnesium boride and phenolic resin were mixed evenly at a mass ratio of 1:5 to obtain a composite binder.

[0029] This embodiment also provides a method for preparing the above-mentioned thermal shock resistant refractory bricks, the specific steps of which are as follows: Weigh out all the raw materials for the above-mentioned thermal shock refractory bricks and mix them evenly. After loading them into the mold, pressurize them at 280 MPa for 5 minutes to obtain the brick blank. Sinter the brick blank at 300 ℃ for 10 h, then raise the temperature to 900 ℃ for 8 h, and then raise the temperature to 1500 ℃ for 3 h. After cooling, the refractory brick is obtained.

[0030] (ii) Comparative Example Comparative Example 1 Comparative Example 1 is basically the same as Example 1, except that yttrium-doped tantalum carbide hafnium is omitted.

[0031] Comparative Example 2 Comparative Example 2 is basically the same as Example 1, except that yttrium-doped tantalum carbide hafnium is replaced with a mixture of tantalum carbide hafnium and yttrium oxide.

[0032] Comparative Example 3 Comparative Example 3 is basically the same as Example 1, except that the composite adhesive is replaced with phenolic resin.

[0033] (III) Test Examples The refractory bricks prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to the following performance tests.

[0034] Room temperature compressive strength test: The compressive strength of the refractory bricks in Examples 1-3 and Comparative Examples 1-3 was tested according to GB / T 5072-2023 "Test method for room temperature compressive strength of refractory materials". The results are shown in Table 1.

[0035] High-temperature flexural strength test: The high-temperature flexural strength of the refractory bricks in Examples 1-3 and Comparative Examples 1-3 was tested according to GB / T 3002-2017 "Test Method for High-Temperature Flexural Strength of Refractory Materials". The test conditions were 1400℃×0.5 h. The results are shown in Table 1.

[0036] Thermal shock resistance test: The thermal shock resistance of the refractory bricks in Examples 1-3 and Comparative Examples 1-3 was tested according to GB / T 30873-2014 "Test method for thermal shock resistance of refractory materials". The test method was water quenching method. The results are shown in Table 1.

[0037] Table 1. Test results of thermal shock refractory bricks for compressive strength, high-temperature flexural strength, and thermal shock resistance.

[0038] As shown in Table 1, the thermal shock refractory bricks prepared in Examples 1-3 of the present invention have excellent compressive strength, high-temperature flexural strength and thermal shock resistance.

[0039] Compared to Example 1, Comparative Example 1 omitted yttrium-doped tantalum carbide hafnium, while Comparative Example 2 replaced yttrium-doped tantalum carbide hafnium with a mixture of tantalum carbide hafnium and yttrium oxide. Both thermal shock resistance and strength decreased in Comparative Example 2, indicating that adding yttrium-doped tantalum carbide hafnium to refractory bricks can effectively improve their strength and thermal shock resistance. Specific analysis shows that tantalum carbide hafnium possesses high hardness, high-temperature strength, and good thermal conductivity. As an additive, it can improve the strength and high-temperature resistance of refractory bricks, promptly disperse thermal stress, and reduce internal cracks caused by temperature gradients, thus improving thermal shock resistance. Doping tantalum carbide hafnium with rare earth yttrium can improve its interfacial bonding with the matrix, reduce internal stress caused by differences in thermal expansion coefficients, further inhibit crack propagation, and enhance the thermal shock resistance of refractory bricks.

[0040] Compared to Example 1, Comparative Example 3, which replaced the composite binder with phenolic resin, showed a significant decline in both room-temperature compressive strength and high-temperature flexural strength, as well as a decrease in thermal shock resistance. This indicates that using a composite binder of magnesium boride and phenolic resin can improve the strength and thermal shock resistance of refractory bricks. Specific analysis reveals that phenolic resin cures at low temperatures, forming a stable cross-linked network; magnesium boride forms a liquid phase at medium temperatures, promoting crystal structure rearrangement and improving sintering strength; and the two react at high temperatures to form a dense phase, preventing oxygen from entering and resulting in tighter sintering of the components, leading to superior overall performance of the refractory bricks. Furthermore, magnesium boride has good thermal conductivity, which can disperse thermal stress, reduce crack formation, and improve the thermal shock resistance of the refractory bricks.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A thermal shock resistant refractory brick, characterized in that, The refractory brick is composed of the following raw materials in the following mass percentages: 8-12 wt% flake graphite, 2-8 wt% yttrium-doped tantalum hafnium carbide, 1-3 wt% nano alumina, 4-8 wt% composite binder, and the balance being magnesium oxide; The yttrium-doped tantalum carbide hafnium is prepared by the following process: (1) Add tantalum chloride, hafnium chloride, yttrium chloride and phenolic resin to a mixed solution of acetylacetone and n-butanol, heat and stir, then add ammonia water and continue stirring, filter and dry to obtain the precursor; (2) The precursor is calcined and cooled to obtain yttrium-doped tantalum carbide hafnium; In step (1), the ratio of tantalum chloride, hafnium chloride, yttrium chloride, phenolic resin, acetylacetone, n-butanol, and ammonia is 1 g : (0.2-0.8) g : (0.1-0.15) g : (0.2-0.4) g : (5-10) mL : (40-60) mL : (5-10) mL; the mass concentration of the ammonia is 25-28%. The composite adhesive is prepared by the following process: Silane coupling agent and magnesium boride are added to water and ultrasonically treated at 50-70 °C for 2-5 h. After filtration, washing and drying, modified magnesium boride is obtained. The modified magnesium boride is then mixed with phenolic resin to obtain a composite binder.

2. The thermal shock refractory brick according to claim 1, characterized in that, The heating and stirring temperature in step (1) is 60-80 ℃ and the time is 1-2 h; the stirring time is 0.5-1 h.

3. The thermal shock resistant refractory brick according to claim 1, characterized in that, The calcination temperature in step (2) is 1450-1550 ℃ and the time is 2-4 h.

4. The thermal shock refractory brick according to claim 1, characterized in that, The mass ratio of magnesium boride to silane coupling agent is 1:(0.15-0.25); the silane coupling agent is vinyltrimethoxysilane.

5. The thermal shock refractory brick according to claim 1, characterized in that, The mass ratio of the modified magnesium boride to phenolic resin is 1:(3-5).

6. A method for preparing a thermal shock resistant refractory brick according to any one of claims 1-5, characterized in that, Includes the following steps: The raw materials are mixed evenly, placed into a mold and pressed to obtain a brick blank; the brick blank is then sintered in a gradient and cooled to obtain a refractory brick.

7. The method for preparing thermal shock resistant refractory bricks according to claim 6, characterized in that, The pressure held is 220-280 MPa for 3-5 minutes.

8. The method for preparing thermal shock resistant refractory bricks according to claim 6, characterized in that, The gradient sintering process is as follows: first, sinter at 200-300 ℃ for 5-10 h, then raise the temperature to 800-900 ℃ for 4-8 h, and then raise the temperature to 1400-1500 ℃ for 2-3 h.

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