Carbon-coated alumina particles, and preparation method and application thereof

Abstract

The application belongs to the technical field of carbon-coated materials, and discloses carbon-coated alumina particles, a preparation method and application thereof, wherein the preparation method comprises the following steps: mixing a glucose solution and hydrochloric acid to obtain a mixed solution; and mixing the mixed solution with alumina and then performing a hydrothermal reaction to obtain carbon-coated alumina particles. The carbon-coated alumina particles are prepared through a low-temperature hydrothermal synthesis reaction, so that the carbon can be better filled between oxide particles, and the carbon content can be regulated by regulating the concentration of the glucose solution; and the application has the advantages of simple operation, short preparation period and low price.

Description

Technical Field

[0001] This invention relates to the field of carbon-coated materials technology, and in particular to a carbon-coated alumina particle, its preparation method, and its application. Background Technology

[0002] Pure alumina particles have poor thermal shock resistance, and studies have shown that adding graphite to alumina particles can improve their thermal shock resistance due to its lubricating and antioxidant properties. However, existing preparation methods cannot meet the requirements for uniform mixing, and phenomena such as local agglomeration and excessive carbon content do not significantly improve thermal shock resistance.

[0003] Therefore, it is of great significance to study and obtain a carbon-coated alumina particle that can uniformly coat alumina with carbon and has good thermal shock resistance, as well as its preparation method and application. Summary of the Invention

[0004] In view of this, the present invention provides carbon-coated alumina particles, their preparation method and application, the purpose of which is to solve the problems of easy agglomeration, excessive carbon content and poor thermal shock resistance of carbon-coated alumina particles prepared by the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a method for preparing carbon-coated alumina particles, comprising the following steps:

[0007] (1) Mix glucose solution with hydrochloric acid to obtain a mixed solution;

[0008] (2) The mixed solution is mixed with alumina and then subjected to a hydrothermal reaction to obtain carbon-coated alumina particles.

[0009] Preferably, the glucose solution has a mass concentration of 20-60%, and the hydrochloric acid has a mass concentration of 37-40%.

[0010] Preferably, the pH value of the mixed solution is 2 to 4.

[0011] Preferably, the mass ratio of alumina to glucose is 1:4 to 7, and the mixture of the solution and alumina is ultrasonically mixed; the particle size of alumina is 1 to 100 μm.

[0012] Preferably, the hydrothermal reaction temperature is 180–220°C, and the hydrothermal reaction time is 4–8 hours.

[0013] Preferably, the hydrothermal reaction is followed by centrifugation and carbonization.

[0014] Preferably, the centrifugation speed is 4800-5200 rpm and the centrifugation time is 8-12 min.

[0015] Preferably, the carbonization time is 1 to 2 hours and the carbonization temperature is 800 to 1200°C.

[0016] The present invention also provides carbon-coated alumina particles prepared by the method for preparing the carbon-coated alumina particles, wherein the thickness of the carbon coating layer in the carbon-coated alumina particles is 100-600 nm.

[0017] The present invention also provides the application of the carbon-coated alumina particles in refractory materials.

[0018] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] This invention prepares carbon-coated alumina particles through a low-temperature hydrothermal synthesis reaction, allowing carbon to better fill the spaces between oxide particles. Furthermore, the carbon content can be controlled by adjusting the concentration of the glucose solution, thereby forming uniformly carbon-coated alumina particles. The preparation method described in this invention has the advantages of simple operation, short preparation cycle, and low cost.

[0020] The carbon-coated alumina particles of the present invention have the ability to absorb and buffer thermal stress, which can reduce the damage of thermal stress to the material structure, significantly improve the thermal shock resistance, and can be applied to improve the actual service life of refractory materials and avoid material failure caused by thermal shock resistance. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0022] Figure 1 Here is a SEM image of the carbon-coated alumina particles obtained in Example 1;

[0023] Figure 2 Here is a SEM image of the carbon-coated alumina particles obtained in Example 1;

[0024] Figure 3 The image shows the XRD pattern of the carbon-coated alumina particles obtained in Example 1. Detailed Implementation

[0025] This invention provides a method for preparing carbon-coated alumina particles, comprising the following steps:

[0026] (1) Mix glucose solution with hydrochloric acid to obtain a mixed solution;

[0027] (2) The mixed solution is mixed with alumina and then subjected to a hydrothermal reaction to obtain carbon-coated alumina particles.

[0028] In this invention, the mass concentration of the glucose solution is preferably 20-60%, more preferably 30-50%, and even more preferably 35-45%, and the mass concentration of the hydrochloric acid is preferably 37-40%, and even more preferably 38-39%.

[0029] In this invention, the glucose solution is preferably prepared by dissolving glucose in deionized water and stirring until the solution is clear and transparent.

[0030] In this invention, the pH value of the mixed solution is preferably 2 to 4, and more preferably 3.

[0031] In this invention, the mass ratio of alumina to glucose is preferably 1:4 to 7, more preferably 1:5 to 6, and the mixing of the mixed solution with alumina is preferably ultrasonic mixing; the particle size of alumina is preferably 1 to 100 μm, more preferably 30 to 70 μm, and more preferably 40 to 60 μm.

[0032] In this invention, the ultrasonic mixing power is preferably 220-250W, more preferably 230-245W, and even more preferably 235-240W; the ultrasonic mixing time is preferably 25-35min, more preferably 28-32min, and even more preferably 30min; the ultrasonic mixing can make the alumina particles uniformly dispersed in the glucose solution.

[0033] In this invention, the temperature of the hydrothermal reaction is preferably 180-220°C, more preferably 190-210°C, and even more preferably 195-205°C. The time of the hydrothermal reaction is preferably 4-8 hours, more preferably 5-7 hours, and even more preferably 6 hours.

[0034] In this invention, centrifugation and carbonization are preferably performed sequentially after the hydrothermal reaction.

[0035] In this invention, the hydrothermal reaction product is preferably sieved before centrifugation, preferably sieved 3 times, and the particle size of the sieved particles is preferably greater than or equal to 3 μm, more preferably greater than or equal to 4 μm, and more preferably greater than or equal to 30 μm.

[0036] In this invention, the centrifugation speed is preferably 4800-5200 rpm, more preferably 4900-5100 rpm, and even more preferably 4950-5050 rpm, and the centrifugation time is preferably 8-12 min, more preferably 9-11 min, and even more preferably 10 min.

[0037] In this invention, the carbonization time is preferably 1 to 2 hours, more preferably 1.2 to 1.8 hours, and even more preferably 1.4 to 1.6 hours. The carbonization temperature is preferably 800 to 1200°C, more preferably 900 to 1100°C, and even more preferably 950 to 1050°C.

[0038] In this invention, centrifugation is used to remove residual carbon from the hydrothermal reaction products.

[0039] In this invention, carbonization refers to the removal of impurity elements from the carbon shell of carbon-coated alumina particles.

[0040] The present invention also provides carbon-coated alumina particles prepared by the method for preparing the carbon-coated alumina particles, wherein the thickness of the carbon coating layer in the carbon-coated alumina particles is preferably 100-600 nm, more preferably 200-500 nm, and even more preferably 300-400 nm.

[0041] The present invention also provides the application of the carbon-coated alumina particles in refractory materials.

[0042] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0043] Example 1

[0044] Dissolve glucose in deionized water to prepare a 60% glucose solution; add 37% hydrochloric acid to the glucose solution until the pH value of the glucose solution is 3 to obtain a mixed solution.

[0045] Alumina particles with a particle size of 84 μm (the mass ratio of alumina particles to glucose is 1:5) were added to the mixed solution, and the mixture was ultrasonically stirred at 240 W for 30 min. Then, it was hydrothermally reacted at 180 °C for 6 h and sieved 3 times to obtain carbon-coated alumina particles with impurities and a particle size greater than 4 μm.

[0046] The carbon-coated alumina particles containing impurities were centrifuged at 5000 rpm for 10 min to remove residual carbon, and then carbonized at 1000℃ for 1 h to remove impurity elements in the carbon shell, resulting in carbon-coated alumina particles with a carbon shell thickness of 570 nm.

[0047] In the carbon-coated alumina particles obtained in this embodiment, the alumina particles are uniformly coated with a carbon shell.

[0048] Example 2

[0049] Dissolve glucose in deionized water to prepare a 40% glucose solution; add 37% hydrochloric acid to the glucose solution until the pH value of the glucose solution is 4 to obtain a mixed solution.

[0050] Alumina particles with a particle size of 30 μm (the mass ratio of alumina particles to glucose is 1:6) were added to the mixed solution, and the mixture was ultrasonically stirred at 245 W for 28 min. After hydrothermal reaction at 200 °C for 5 h, the mixture was sieved 3 times to obtain carbon-coated alumina particles with impurities and a particle size greater than 84 μm.

[0051] The carbon-coated alumina particles containing impurities were centrifuged at 5200 rpm for 8 min to remove residual carbon, and then carbonized at 800℃ for 1.5 h to remove impurity elements in the carbon shell, resulting in carbon-coated alumina particles with a carbon shell thickness of 460 nm.

[0052] In the carbon-coated alumina particles obtained in this embodiment, the alumina particles are uniformly coated with a carbon shell.

[0053] Example 3

[0054] Dissolve glucose in deionized water to prepare a 30% glucose solution; add 37% hydrochloric acid to the glucose solution until the pH value of the glucose solution is 4 to obtain a mixed solution.

[0055] Alumina particles with a particle size of 30 μm (the mass ratio of alumina particles to glucose is 1:4) were added to the mixed solution, and the mixture was ultrasonically stirred at 235 W for 32 min. Then, it was hydrothermally reacted at 220 °C for 4 h and sieved 3 times to obtain alumina particles with impurities and carbon coating with a particle size greater than 30 μm.

[0056] The carbon-coated alumina particles containing impurities were centrifuged at 5200 rpm for 8 min to remove residual carbon, and then carbonized at 1200℃ for 2 h to remove impurity elements in the carbon shell, resulting in carbon-coated alumina particles with a carbon shell thickness of 320 nm.

[0057] In the carbon-coated alumina particles obtained in this embodiment, the alumina particles are uniformly coated with a carbon shell.

[0058] Comparative Example 1

[0059] Dissolve glucose in deionized water to prepare a 10% glucose solution; add 37% hydrochloric acid to the glucose solution until the pH value of the glucose solution is 4 to obtain a mixed solution.

[0060] Alumina particles with a particle size of 84 μm (the mass ratio of alumina particles to glucose is 1:6) were added to the mixed solution, and the mixture was ultrasonically stirred at 240 W for 30 min. Then, it was hydrothermally reacted at 200 °C for 5 h and sieved 3 times to obtain carbon-coated alumina particles with impurities and a particle size greater than 84 μm.

[0061] The carbon-coated alumina particles containing impurities were centrifuged at 5200 rpm for 8 min to remove residual carbon, and then carbonized at 800℃ for 1.5 h to remove impurity elements in the carbon shell, resulting in carbon-coated alumina particles with a carbon shell thickness of 270 nm.

[0062] In the carbon-coated alumina particles obtained in this comparative example, only a small number of alumina particles were uniformly coated by the carbon shell.

[0063] Preparation methods of refractory materials:

[0064] Carbon-coated alumina particles with a mass ratio of 95:5 and phenolic resin aqueous solution (concentration of 50wt%) were mixed in a mixer at a speed of 200rpm for 30min. The mixture was then pressed into a green body of 25×25×160mm. The green body was placed in a high-temperature furnace, carbon was embedded, and the temperature was raised to 1500℃ at a heating rate of 5℃ / min and held for 30min. The mixture was then naturally cooled to room temperature to obtain the refractory material.

[0065] The carbon-coated alumina particles obtained in Example 1 and Comparative Example 1 were used to prepare refractory materials using the above-described refractory material preparation method. The obtained refractory materials were water-cooled at 1000℃, and the water-cooled products were subjected to thermal shock tests according to the national standard GB / T30873-2014. The results showed that the residual strength of the refractory material obtained in Example 1 was more than 20% higher than that of the refractory material obtained in Comparative Example 1.

[0066] The XRD pattern of the carbon-coated alumina particles obtained in Example 1 is as follows: Figure 3 As shown. By Figure 3 As can be seen from the XRD pattern, the carbon-coated alumina particles obtained in Example 1 contain hexagonal close-packed α-Al2O3 and amorphous carbon.

[0067] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing carbon-coated alumina particles for refractory materials, characterized in that, Includes the following steps: (1) Mix glucose solution with hydrochloric acid to obtain a mixed solution; (2) The mixed solution is mixed with alumina and then subjected to a hydrothermal reaction. After the hydrothermal reaction, the mixture is centrifuged and carbonized in sequence to obtain carbon-coated alumina particles. The particle size of alumina is 1~100μm; The mass ratio of aluminum oxide to glucose is 1:4~7; The glucose solution has a mass concentration of 20-60%, and the hydrochloric acid has a mass concentration of 37-40%; the pH value of the mixed solution is 2-4. The hydrothermal reaction temperature is 180~220℃, and the hydrothermal reaction time is 4~8h; The carbonization time is 1-2 hours, and the carbonization temperature is 800-1200℃.

2. The method for preparing carbon-coated alumina particles for refractory materials according to claim 1, characterized in that, The mixture of the solution and alumina is ultrasonically mixed.

3. The method for preparing carbon-coated alumina particles for refractory materials according to claim 1, characterized in that, The centrifuge speed is 4800~5200 rpm, and the centrifugation time is 8~12 min.

4. The carbon-coated alumina particles prepared by the method for preparing carbon-coated alumina particles for refractory materials according to any one of claims 1 to 3, characterized in that, The carbon coating thickness of the carbon-coated alumina particles is 100~600nm.

5. The application of the carbon-coated alumina particles as described in claim 4 in refractory materials.

Images