A method for preparing titanium carbide powder surface-modified with hafnium oxide

Abstract

A method for preparing titanium carbide powder surface-modified with hafnium oxide relates to a method for modifying titanium carbide powder. The method aims to address the technical issues of the cumbersome and high-cost preparation process of existing high-temperature resistant powder coatings. The method comprises the following steps: adding TiC powder to a hafnium salt solution, adding concentrated ammonia solution dropwise while stirring, to obtain a mixed slurry; drying the mixed slurry, and then sintering it in a vacuum furnace to obtain titanium carbide powder surface-modified with hafnium oxide. The surface of the TiC powder is coated with rare earth oxide, which improves the high-temperature stability of the TiC powder, inhibits oxidation of the TiC powder at high temperatures, and effectively addresses the problem of TiC powder being easily oxidized at high temperatures. The titanium carbide powder surface-modified with hafnium oxide can be used in the fields of metal ceramics, wear-resistant materials, and high-temperature radiation-resistant materials.

Description

Technical Field

[0001] The invention relates to a method for modifying titanium carbide powder. Background Art

[0002] Titanium carbide ceramics are typical transition metal carbides with a NaCl-type cubic crystal structure and extremely strong covalent bonds between atoms, resulting in metal-like characteristics such as high melting point, high hardness, high Young's modulus, high chemical stability, wear and corrosion resistance, good electrical and thermal conductivity, and other properties. They are commonly used in the field of high-temperature materials. For example, titanium carbide is often added to other materials in the form of a hard phase to prepare metal ceramics, wear-resistant materials, high-temperature radiation-resistant materials, and other composite materials to improve the strength and high-temperature resistance of the materials. In addition, titanium carbide powder can also be used to make crucibles for smelting metals such as tin, lead, cadmium, and zinc.

[0003] However, TiC powder is easily oxidized in high-temperature air environments, accompanied by the release of CO2 gas, which limits its performance in high-temperature environments. More importantly, after TiC powder is oxidized, it produces TiO2, which will significantly reduce the purity of TiC and its content in other materials, thereby causing a serious decline in the high-temperature performance of metal ceramics, wear-resistant materials, high-temperature radiation-resistant materials, and other composite materials. Therefore, how to solve the high-temperature oxidation problem of TiC powder through simple and effective methods to maintain its high-temperature stability is of great significance to the promotion and application of TiC ceramic powder.

[0004] Currently, surface modification of TiC powder is a simple and effective method. Methods include coupling agent modification, plasma spraying, hydrothermal modification, and sol-gel methods. The article "Surface Modification Mechanism of Stearic Acid to Zirconia Powders Induced by Ball Milling for Water-Based Injection Molding," published in the Journal of the American Ceramic Society, Vol. 94, Issue 5, 2011, pp. 1327-1330, proposes using a titanate coupling agent to modify the surface of zirconia powder, successfully suppressing powder agglomeration. Che Jianfei of Nanjing University of Science and Technology, in his paper "Surface Modification and Dispersion Technology of Nano-Oxides and Their Application in Polymer Friction Materials," proposes treating TiO2 powder with a surface modifier, γ-glycidyloxypropyltrimethoxysilane, to improve its dispersibility in organic solvents. The article "Preparation of HfO2 Coatings on Cf / SiC Composites and Their Thermal Shock Resistance" published in the Journal of Equipment and Environmental Engineering, Vol. 13, Issue 3, 2016, pp. 25-30, proposes a method of preparing HfO2 particles using hydrothermal and spray granulation, followed by plasma spraying on the surface of the Cf / SiC composite, significantly improving its high-temperature performance. However, these methods are both complex and costly. Summary of the Invention

[0005] The present invention aims to solve the technical problems of the complicated and high-cost preparation process of existing high-temperature resistant powder coatings, and proposes a method for preparing titanium carbide powder with a hafnium oxide surface modification. The present invention uses a simple process to prepare a low-cost hafnium oxide-modified coating on the surface of TiC powder, effectively inhibiting the high-temperature oxidation behavior of TiC powder, thereby improving the performance of composite materials with TiC as the hard reinforcement phase.

[0006] The preparation method of the hafnium oxide surface-modified titanium carbide powder of the present invention is carried out according to the following steps:

[0007] 1. Preparation of hafnium salt solution: Use deionized water as solvent and prepare hafnium salt solution at a concentration of 0.03-1 mol / L;

[0008] 2. Preparation of mixed slurry: According to the ratio of the mass of TiC powder to the volume of hafnium salt solution of 1g:(10-50)mL, TiC powder is added to the hafnium salt solution, and then the concentrated ammonia solution is added dropwise while stirring at a molar ratio of hafnium salt to concentrated ammonia solution of 1:(1-10). The ammonia solution addition rate is controlled at 0.1-1mL / min. After the ammonia solution is added dropwise, stirring is continued for 3-4h to obtain a mixed slurry;

[0009] 3. Drying the mixed slurry: Dry the mixed slurry obtained in step 2 at a temperature of 50-100° C. for 5-12 hours to obtain a precursor powder;

[0010] 4. Vacuum sintering: Place the precursor powder in a vacuum furnace at a temperature of 400-1000°C and a vacuum degree of 1×10 -5 ~1×10 -3 The powder is sintered at 400 nm and 500 nm under the conditions of Pa for 1 to 3 hours to obtain titanium carbide powder with hafnium oxide surface modification.

[0011] Furthermore, the hafnium salt in step 1 is one or more of hafnium dichloride octahydrate, hafnium chloride, hafnium chloride hydrate and hafnium sulfate.

[0012] Furthermore, the concentrated ammonia water in step 2 is ammonia water with a mass percentage concentration of 25% to 28%.

[0013] Furthermore, the stirring in step 2 is performed on a magnetic stirrer, and the rotation speed of the magnetic stirrer is 500-800 r / min.

[0014] Furthermore, the average particle size of the TiC powder in step 2 is 50 nm to 5 μm.

[0015] The rare earth surface-modified titanium carbide powder of the present invention is titanium carbide ceramic particles coated with hafnium oxide (HfO2), wherein the hafnium oxide serving as the coating layer has a melting point of 2758°C. Due to the high melting point and good high-temperature stability of the oxide coated on the surface, the coating is uniform. Therefore, the high-temperature stability of the TiC powder can be improved without affecting the original properties of the TiC powder, and oxidation of the TiC powder at high temperatures can be suppressed, effectively solving the problem of the TiC powder being easily oxidized at high temperatures.

[0016] The rare earth surface-modified titanium carbide powder of the present invention is simple to prepare, has a short preparation cycle, and is low in cost. The rare earth surface-modified titanium carbide powder of the present invention can be used as a reinforcement in metal-based composite materials. The small amount of rare earth coated on the powder surface can improve the uniformity of the structure and properties of the metal-based composite material, stabilize the phase structure of the ceramic material, and increase the density of the ceramic material. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1This is a scanning electron microscope photograph of the hafnium oxide surface-modified titanium carbide powder obtained in step 4 of Example 1.

[0018] Figure 2 This is an energy dispersive spectrometer photograph of the hafnium oxide surface-modified titanium carbide powder obtained in step 4 of Example 1.

[0019] Figure 3 The XRD spectrum of the hafnium oxide surface-modified titanium carbide powder obtained in step 4 of Example 1 is

[0020] Figure 4 1 is the XRD spectrum of the unmodified TiC powder and the titanium carbide powder surface-modified with hafnium oxide prepared in Example 1 after oxidation. DETAILED DESCRIPTION

[0021] Use the following examples to verify the beneficial effects of the present invention:

[0022] Example 1: The preparation method of hafnium oxide surface-modified titanium carbide powder of this embodiment is carried out according to the following steps:

[0023] 1. Preparation of hafnium salt solution: using deionized water as solvent, prepare hafnium oxychloride solution according to the concentration of hafnium oxychloride octahydrate of 2.5 mol / L;

[0024] 2. Preparation of a mixed slurry: According to the ratio of the mass of TiC powder to the volume of hafnium oxychloride solution of 1g:10mL, TiC powder with a mean particle size of 1μm is added to the hafnium oxychloride solution prepared in step 1, the liquid is kept at a constant temperature of 25°C, and then concentrated ammonia water with a mass percentage concentration of 26% is added dropwise under magnetic stirring at a molar ratio of hafnium oxychloride to ammonia water of 1:5. The ammonia water dropwise addition speed is controlled at 0.5mL / min. After the ammonia water is added dropwise, stirring is continued for 3.5h to obtain a mixed slurry; wherein the stirring speed of the magnetic stirring is 750r / min;

[0025] 3. Drying the mixed slurry: Dry the mixed slurry obtained in step 2 at 90°C for 6 hours to obtain a precursor powder;

[0026] 4. Vacuum sintering: The precursor powder obtained in step 3 is placed in a vacuum tube furnace at a temperature of 600°C and a vacuum degree of 1×10 -3 Pa for 1 h to obtain titanium carbide powder surface modified with hafnium oxide.

[0027] The scanning electron microscope photograph of the titanium carbide powder surface modified with hafnium oxide obtained in this example is as follows: Figure 1 As shown, Figure 2 is the corresponding energy spectrum analysis diagram, from Figure 1 and Figure 2It can be seen that Hf and O elements are evenly distributed on the surface of TiC powder.

[0028] The XRD spectrum of the hafnium oxide surface modified titanium carbide powder obtained in this example is as follows: Figure 3 As shown, from Figure 3 It can be seen that the hafnium oxide on the surface of titanium carbide powder is HfO2. Figure 1 、 2 and Figure 3 This shows that the HfO2 coating was successfully prepared on the surface of TiC powder.

[0029] The unmodified TiC powder and the hafnium oxide surface-modified titanium carbide powder prepared in this embodiment were placed in a high-temperature furnace at a temperature of 400°C for oxidation for 0.5 h to conduct an oxidation test. After the oxidation was completed, an XRD spectrum test was performed. The results are as follows: Figure 4 As shown. Figure 4 It can be seen that the unmodified TiC powder oxidized to generate TiO2, while the hafnium oxide surface-modified titanium carbide powder prepared in this example did not oxidize, indicating that the HfO2 layer on the titanium carbide surface protects TiC, prevents TiC from high-temperature oxidation, and improves TiC's resistance to high-temperature oxidation.

[0030] Example 2: The preparation method of the hafnium oxide surface-modified titanium carbide powder of this embodiment is carried out according to the following steps:

[0031] 1. Preparation of hafnium salt solution: using deionized water as solvent and hafnium chloride concentration of 0.05 mol / L, prepare hafnium chloride solution;

[0032] 2. Preparation of a mixed slurry: According to the ratio of the mass of TiC powder to the volume of hafnium chloride solution of 1g:10mL, TiC powder with a mean particle size of 500nm was added to the hafnium chloride solution prepared in step 1, and the liquid was kept at a constant temperature of 25°C. Then, concentrated ammonia water with a mass percentage concentration of 26% was added dropwise under magnetic stirring at a molar ratio of hafnium chloride to ammonia water of 1:5. The ammonia water addition rate was controlled at 0.5mL / min. After the ammonia water was added dropwise, stirring was continued for 3.5h to obtain a mixed slurry; wherein the stirring speed of the magnetic stirring was 750r / min;

[0033] 3. Drying the mixed slurry: Dry the mixed slurry obtained in step 2 at 90°C for 10 hours to obtain a precursor powder;

[0034] 4. Vacuum sintering: The precursor powder obtained in step 3 is placed in a vacuum tube furnace at a temperature of 900°C and a vacuum degree of 1×10 -5 Pa for 1 h to obtain titanium carbide powder surface modified with hafnium oxide.

[0035] After surface modification of TiC powder using the method of this example, the HfO2 coating was uniformly coated on the surface of the TiC powder. Oxidation tests were conducted on the unmodified TiC powder by subjecting it to a high-temperature treatment at 400°C for 30 minutes, and the oxidized powder was analyzed by XRD. The results showed that the unmodified TiC powder underwent significant oxidation at 400°C, with a TiO2 oxidation peak appearing in the XRD curve. However, the TiC powder surface-modified with HfO2 showed no oxidation at 400°C, with only a TiC diffraction peak in the XRD curve. This demonstrates that the HfO2-modified layer can inhibit oxidation of TiC particles at high temperatures.

Claims

1. A method for preparing titanium carbide powder surface-modified with hafnium oxide, characterized in that The method proceeds as follows:

1. Preparation of hafnium salt solution: Use deionized water as solvent and prepare hafnium salt solution at a concentration of 0.03-1 mol / L; 2. Preparation of mixed slurry: TiC powder is added to the hafnium salt solution according to the ratio of the mass of TiC powder to the volume of hafnium salt solution of 1g:(10-50)mL, and then concentrated ammonia water is added dropwise while stirring according to the molar ratio of hafnium salt to concentrated ammonia water of 1:(1-10). The ammonia water addition rate is controlled at 0.1-1mL / min. After the ammonia water is added, continue stirring for 3-4h to obtain a mixed slurry; 3. Drying the mixed slurry: Dry the mixed slurry obtained in step 2 at a temperature of 50-100° C. for 5-12 hours to obtain a precursor powder; 4. Vacuum sintering: Place the precursor powder in a vacuum furnace at a temperature of 400-1000°C and a vacuum degree of 1×10 -5 ~1×10 -3 The titanium carbide powder with hafnium oxide surface modified is sintered for 1 to 3 hours under the conditions of Pa.

2. The method for preparing hafnium oxide surface-modified titanium carbide powder according to claim 1, characterized in that: The hafnium salt described in step 1 is one or more of hafnium dichloride octahydrate, hafnium chloride, hafnium chloride hydrate and hafnium sulfate.

3. The method for preparing hafnium oxide surface-modified titanium carbide powder according to claim 1 or 2, characterized in that: The concentrated ammonia water described in step 2 is ammonia water with a mass percentage concentration of 25% to 28%.

4. The method for preparing hafnium oxide surface-modified titanium carbide powder according to claim 1 or 2, characterized in that: The stirring in step 2 is carried out on a magnetic stirrer, and the rotation speed of the magnetic stirrer is 500-800 r / min.

5. The method for preparing hafnium oxide surface-modified titanium carbide powder according to claim 1 or 2, characterized in that: The average particle size of the TiC powder described in step 2 is 50 nm to 5 μm.

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