A Preparation Method of Al2O3@C Composite Material

Abstract

The present invention belongs to the technical field of refractory materials, and discloses a preparation method of Al2O3@C composite materials. 0.2-2 mol of metallic aluminum powder is stirred and heated in a water bath at 80-100 °C for 0.5-2.5 h to prepare an AlOOH solution; then a polyvinyl alcohol solution with a concentration of 0.04-0.2 g / ml is added to the boehmite solution, and stirring is continued for 0.2-1 h; then flake graphite powder and an additive are successively added and stirring is continued for 0.5-2.5 h; finally, a gelling agent solution with a concentration of 0.05-0.25 g / ml is added to prepare a precursor gel; the precursor gel is calcined at 1100 °C-1500 °C for 1-5 h under a reducing atmosphere condition to obtain the Al2O3@C composite materials; the present invention adopts inexpensive and easily available raw materials, has the characteristics of low cost and simple preparation process, and the prepared Al2O3@C composite materials have excellent wettability.

Description

Technical Field

[0001] The present invention belongs to the technical field of refractory materials, and particularly relates to a preparation method of Al2O3@C composite materials. Background Art

[0002] Flake graphite is a material with high thermal conductivity, non-wettability to metal slag, and low thermal expansion coefficient, which can significantly improve the thermal shock resistance and corrosion resistance of carbon-containing refractories. However, the limiting factors for this application are its weak oxidation resistance and non-wettability. Due to the hydrophobic property of graphite, the uniform distribution of graphite flakes poses a challenge, which reduces the fluidity of the prepared unshaped refractories and requires a large amount of water for laying; therefore, the porosity of the dried product increases significantly, resulting in a decline in its mechanical properties and corrosion resistance.

[0003] Among them, the published text "A Modified Graphite Material and Its Preparation Method and Application" (CN118515267A) discloses a modified graphite material and its preparation method and application. In the modified graphite material, a part of titanium dioxide particles adheres to the carbon coating layer, and another part protrudes from the carbon coating layer. The titanium dioxide and the carbon coating layer act synergistically to achieve excellent high-rate performance. This method requires processes such as heating under nitrogen protection and vacuum drying, and the operation process is complex. At the same time, expensive chemical supplies such as dioxane are used in the reaction, resulting in high costs.

[0004] The published text "Synthesis Method of Boron-Doped Carbon-Coated Graphite" (CN116375018B) discloses a synthesis method of boron-doped carbon-coated graphite. By using the chemical reaction of B2H6 and CO2, it is deposited on the surface of the graphite material in the form of chemical vapor deposition in a chemical vapor deposition furnace to form a boron-doped carbon-coated graphite material. B2H6 reacts with CO2 to generate carbon, B-C bonds, and H2O, forming boron-doped carbon. The graphite substrate is the inner layer, and the outer layer is boron-doped carbon. The boron doping changes the electronic structure state of the carbon layer, improves the charge storage and transfer rate, and optimizes the electrochemical performance. This method requires steps such as vapor deposition and condensation, and uses a chemical vapor deposition furnace, with a long operation time and a complex process.

[0005] The published text "A High-Thermal-Conductivity Spherical Sulfonated Polyether Ether Ketone / Graphite Core-Shell Structure Filler and Its Preparation Method" (CN110684512A) discloses a high-thermal-conductivity spherical sulfonated polyether ether ketone / graphite core-shell structure filler and its preparation method. Sulfonated polyether ether ketone is prepared by nucleophilic substitution reaction after mixing fluoro ketone, sulfonated fluoro ketone and hydroquinone, softened and then dried to remove 40-60% by volume of water, and then the sulfonated polyether ether ketone is cut using a spherical mold to obtain spherical sulfonated polyether ether ketone particles with different particle size dimensions; finally, the spherical sulfonated polyether ether ketone and micron-sized graphite are electrostatically adsorbed to prepare a high-thermal-conductivity spherical sulfonated polyether ether ketone / graphite core-shell structure filler with sulfonated polyether ether ketone as the core and micron-sized graphite as the shell. This method requires chemical reagents such as fluoro ketone, concentrated sulfuric acid, sulfonated fluoro ketone, hydroquinone and potassium carbonate, with high costs and being unfriendly to the environment. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a preparation method of an Al2O3@C composite material. In the present invention, an AlOOH solution is prepared by the boehmite process of metallic aluminum powder; then graphite and an additive are added and stirred, and then a gelling agent is added to prepare a precursor gel, and finally the Al2O3@C composite material is obtained by heat treatment under a reducing atmosphere. The raw materials used in the synthesis are easily available, non-toxic and environmentally friendly; the operation process only includes three steps: water bath, gelling and firing, with a simple operation process, and the prepared Al2O3@C composite material has good wettability.

[0007] In order to achieve the above object, the technical solution of the present invention is as follows:

[0008] The preparation method of the Al2O3@C composite material of the present invention is as follows:

[0009] Step 1: Stir and heat 0.4-2 mol of metallic aluminum powder at 80-100 °C under a water bath condition for 0.5-2.5 h to prepare an AlOOH solution (i.e., boehmite solution), and an AlOOH coating layer is formed around the particles;

[0010] Step 2: Add a polyvinyl alcohol solution with a concentration of 0.04-0.2 g / ml to the solution obtained in Step 1, and continue stirring for 0.2-1 h;

[0011] Step 3: Sequentially add flake graphite powder and an additive and continue stirring for 0.5-2.5 h; the addition amount of flake graphite is 0.4-2 mol, which is the same as the addition amount of metallic aluminum powder in Step 1; the addition amount of the additive is 0.05-0.25 mol;

[0012] Step 4: Add a gelling agent solution with a concentration of 0.05-0.25 g / ml to prepare a precursor gel;

[0013] Step 5: Calcinate the precursor gel at 1100°C - 1500°C under a reducing atmosphere for 1 - 5 h to prepare an Al2O3 coating layer on the surface of graphite, thus obtaining the Al2O3@C composite material.

[0014] The purity of the metallic aluminum powder is > 98%, and the particle size is ≤ 1 μm.

[0015] The purity of the flake graphite is > 98%, and the particle size is ≤ 10 μm.

[0016] The additive is one or more of analytical pure iron nitrate, chemical pure iron nitrate, and industrial pure iron nitrate, with a purity > 99.9%.

[0017] The gelling agent is one or more of analytical pure borax, chemical pure borax, and industrial pure borax, with a purity > 99.9%.

[0018] The present invention is applied to the preparation of carbon sources in the field of carbon-containing refractory materials.

[0019] The present invention uses metallic aluminum powder because the boehmite process occurs to metallic aluminum powder under a water bath condition, so that an AlOOH coating layer will be formed around the particles, and then a boehmite solution is formed. With the assistance of a polyvinyl alcohol solution, these particles with an AlOOH coating layer are fixed on the graphite surface through a gelling reaction; meanwhile, under a reducing atmosphere condition, with the decomposition of boehmite and the CO formed during the addition process, a certain CO partial pressure is formed; according to the thermodynamic conditions of the Al - O - C system, the regulation of O2 and CO partial pressures in its environment is helpful for the formation of Al2O3.

[0020] The present invention prepares an Al2O3 coating layer on the graphite surface by using the boehmite process, regulates the reaction activity of Al2O3 by controlling the boehmite process and the addition amount of the additive. The surface of the newly formed particles is in a metastable state and can react with the gases in the environment. The specific surface area of the newly formed particles relatively increases, and the activity is improved, thereby realizing the integrity of the coating layer.

[0021] In addition, in carbon-containing unshaped refractory materials, the poor wettability of graphite will lead to uneven dispersion of graphite therein, resulting in uneven distribution of thermal stress in the product and causing cracks. The wetting angle of the present invention is 10 - 40°; it improves the bonding ability between the graphite interface and water.

[0022] The beneficial effects of the present invention are as follows: In the present invention, the boehmite process is carried out on metallic aluminum powder under the condition of a water bath, and then graphite, polyvinyl alcohol solution and additives are added and stirred, and a precursor is prepared through a gelling agent; the precursor is heat-treated under a reducing atmosphere condition to obtain an Al2O3@C composite material; the raw materials used in the present invention are easily available, non-toxic, environmentally friendly, and the operation process only includes three steps: water bath, gelling and firing, the operation process is simple, and the prepared Al2O3@C composite material has good wettability. Brief Description of the Drawings

[0023] Figure 1 SEM photograph of the Al2O3@C composite material prepared in Example 1. Detailed Description of the Embodiments

[0024] The present invention will be further described in detail below in conjunction with specific embodiments. An Al2O3@C composite material and a preparation method thereof provided by an embodiment of the present invention, wherein the purity of the metallic aluminum powder > 98%, and the particle size ≤ 1 μm; the purity of the flake graphite > 98%, and the particle size ≤ 10 μm; 0.4 - 2 mol of metallic aluminum powder is stirred and heated for 0.5 - 2.5 h under the condition of an 80 - 100 °C water bath to prepare an AlOOH solution; then a polyvinyl alcohol solution with a concentration of 0.04 - 0.2 g / ml is added to the boehmite solution, and stirring continues for 0.2 - 1 h; then flake graphite powder and an additive are added in sequence and stirring continues for 0.5 - 2.5 h; finally, a gelling agent solution with a concentration of 0.05 - 0.25 g / ml is added to prepare a precursor gel, and the precursor gel is calcined at 1100 °C - 1500 °C for 1 - 5 h under a reducing atmosphere condition to obtain the Al2O3@C composite material.

[0025] Example 1:

[0026] Step 1: 0.4 mol of metallic aluminum powder is stirred and heated for 0.5 h under the condition of an 80 °C water bath to prepare an AlOOH solution (i.e., a boehmite solution);

[0027] Step 2: A polyvinyl alcohol solution with a concentration of 0.04 g / ml is added to the solution obtained in Step 1, and stirring continues for 0.2 h;

[0028] Step 3: Flake graphite powder and analytical pure ferric nitrate are added in sequence and stirring continues for 0.5 h; the addition amount of flake graphite is 0.4 mol; the addition amount of analytical pure ferric nitrate is 0.05 mol;

[0029] Step 4: A chemical pure borax solution with a concentration of 0.05 g / ml is added to prepare a precursor gel;

[0030] Step 5: Calcinate the precursor gel at 1100 °C for 1 h under a reducing atmosphere to prepare an Al2O3 coating layer on the graphite surface, thereby obtaining the Al2O3@C composite material; its wetting angle is: 25° - 40°.

[0031] Example 2:

[0032] Step 1: Stir and heat 1 mol of metallic aluminum powder in a water bath at 85 °C for 1 h to prepare an AlOOH solution (i.e., a boehmite solution);

[0033] Step 2: Add a polyvinyl alcohol solution with a concentration of 0.1 g / ml to the solution obtained in Step 1 and continue stirring for 0.5 h;

[0034] Step 3: Sequentially add flake graphite powder and analytical pure ferric nitrate and continue stirring for 1 h; the addition amount of flake graphite is 1 mol; the addition amount of analytical pure ferric nitrate is 0.1 mol;

[0035] Step 4: Add an analytical pure borax solution with a concentration of 0.1 g / ml to prepare a precursor gel;

[0036] Step 5: Calcinate the precursor gel at 1200 °C for 3 h under a reducing atmosphere to prepare an Al2O3 coating layer on the graphite surface, thereby obtaining the Al2O3@C composite material; its wetting angle is: 20° - 35°.

[0037] Example 3:

[0038] Step 1: Stir and heat 1.5 mol of metallic aluminum powder in a water bath at 90 °C for 1.5 h to prepare an AlOOH solution (i.e., a boehmite solution);

[0039] Step 2: Add a polyvinyl alcohol solution with a concentration of 0.15 g / ml to the solution obtained in Step 1 and continue stirring for 0.8 h;

[0040] Step 3: Sequentially add flake graphite powder and industrial pure ferric nitrate and continue stirring for 1.5 h; the addition amount of flake graphite is 1.5 mol; the addition amount of industrial pure ferric nitrate is 0.2 mol;

[0041] Step 4: Add an industrial pure borax solution with a concentration of 0.15 g / ml to prepare a precursor gel;

[0042] Step 5: Calcinate the precursor gel at 1300 °C for 4 h under a reducing atmosphere to prepare an Al2O3 coating layer on the graphite surface, thereby obtaining the Al2O3@C composite material; its wetting angle is: 15° - 30°.

[0043] Example 4:

[0044] Step 1: Stir and heat 2 mol of metallic aluminum powder in a water bath at 100 °C for 2.5 h to prepare an AlOOH solution (i.e., boehmite solution).

[0045] Step 2: Add a polyvinyl alcohol solution with a concentration of 0.2 g / ml to the solution obtained in Step 1, and continue stirring for 1 h.

[0046] Step 3: Sequentially add flake graphite powder and chemically pure ferric nitrate, and continue stirring for 2.5 h; the addition amount of flake graphite is 2 mol; the addition amount of chemically pure ferric nitrate is 0.25 mol.

[0047] Step 4: Add a chemically pure borax solution with a concentration of 0.25 g / ml to prepare a precursor gel.

[0048] Step 5: Calcinate the precursor gel at 1500 °C for 5 h under a reducing atmosphere to prepare an Al2O3 coating layer on the graphite surface, thereby obtaining an Al2O3@C composite material; its wetting angle is: 10° - 25°.

[0049] This preparation method has the following advantages: the raw materials are non-toxic, harmless, and easy to obtain, and the production cost is relatively low; this preparation process only requires water bath, gelatinization, and heat treatment processes, and the process is simple.

[0050] The parts not detailed in the present invention are prior arts. The above embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. Without departing from the scope of the present invention defined by the appended claims, various changes in form, details, or equivalents made using the present invention book are within the protection scope of the present invention.

Claims

1. A method for preparing an Al2O3@C composite material, characterized in that: The prepared Al2O3@C composite material is used in carbon-containing amorphous refractory materials. Step 1: Stir and heat 0.4~2 mol of metal aluminum powder in a water bath at 80~100°C for 0.5~2.5 hours to prepare a boehmite solution; the purity of the metal aluminum powder is >98%, and the particle size is ≤1μm; Step 2: Add a polyvinyl alcohol solution with a concentration of 0.04~0.2g / ml to the solution obtained in Step 1, and continue stirring for 0.2~1h; Step 3: Add flake graphite powder and additives in sequence and continue stirring for 0.5~2.5h; the amount of flake graphite added is 0.4~2 mol, which is consistent with the amount of metal aluminum powder added in Step 1; the amount of additive added is 0.05~0.25 mol; the additive is analytical pure ferric nitrate, chemical pure ferric nitrate, and industrial pure ferric nitrate. one or more of the above, with a purity of >99.9%; step 4, adding a gelling agent solution with a concentration of 0.05-0.25 g / ml to prepare a precursor gel; the gelling agent is one or more of analytical pure borax, chemical pure borax, and industrial pure borax, with a purity of >99.9%; step 5, calcining the precursor gel at 1100°C-1500°C under reducing atmosphere for 1-5 hours to prepare an Al2O3 coating layer on the graphite surface, i.e., obtaining an Al2O3@C composite material with a wetting angle of 10-40°; the reaction activity of Al2O3 is regulated by regulating the boehmite process and the amount of additives added, the surface of the newly formed particles is in a metastable state, and can react with the gas in the environment, the specific surface area of ​​the newly formed particles is relatively increased, and the activity is improved, thereby achieving the integrity of the coating layer.

2. The method for preparing an Al2O3@C composite material according to claim 1, characterized in that: The purity of flake graphite is >98% and the particle size is ≤10μm.

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