Method for producing a nanocarbide powder and use thereof

Abstract

The present application discloses a preparation method of nanometer carbide powder and its application. The preparation method uses metal salt and carbon black as raw materials, molten salt reduction medium and magnesium powder as reducing agent. The raw materials are mixed uniformly and then loaded into a graphite crucible with a cover, and then placed in a gas furnace to synthesize nanometer carbide powder at low temperature under flowing inert atmosphere. The method is simple, does not need special equipment, has low synthesis temperature, and the process condition is easy to control. The prepared carbide powder has a particle size of 10-100 nm, an average particle size of 40 nm, a purity of >98%, and a specific surface area of >41 m 2 / g. The prepared carbide powder can be used in powder metallurgy, cutting tools, fine ceramics, chemical vapor deposition, hard and wear-resistant alloy cutting tools, tools, molds and wear-resistant and corrosion-resistant structural component additives, and can improve the toughness of alloy.

Description

Technical Field

[0001] This invention belongs to the field of advanced metal material preparation research, and relates to a method for preparing nano carbide powder and its application. Background Technology

[0002] Carbides have wide applications in many industrial fields, such as catalysts, refractory materials, and electronic devices. Therefore, providing a simple, economical, and efficient method for preparing carbide powders is of great significance. Taking hafnium carbide (HfC) as an example, hafnium carbide crystals have a very high melting point (3890℃), high hardness, high elastic modulus, good electrothermal conductivity, low coefficient of thermal expansion, good impact resistance, good solid-state stability, and resistance to chemical corrosion. It can be used as an additive in cemented carbides and is widely used in cutting tools and molds. It also has important applications in aerospace, high-temperature linings, and electrodes for arc or electrolysis.

[0003] Currently, domestic reports on the preparation of carbide powders mainly use metal powders and oxide powders as metal sources and carbon black as carbon sources. The carbide powders are prepared by high-temperature carbonization or other methods. The synthesis temperature is relatively high, the particle size of the prepared powder is relatively large, and the product still needs to be crushed and ground to obtain carbide powder.

[0004] The molten salt method utilizes the faster diffusion rate of reactants in a molten salt liquid medium. Simultaneously, the molten salt inhibits particle aggregation and limits crystal growth during the reaction, resulting in smaller particle sizes and better dispersibility of the prepared powder. Therefore, the molten salt method not only lowers the synthesis temperature but also facilitates the preparation of non-agglomerated nano-ceramic powders. Summary of the Invention

[0005] This invention discloses a method for preparing nano-carbide powder and its application, in order to solve any of the above-mentioned and other potential problems in the prior art.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0007] The objective of this invention can be achieved through the following technical measures:

[0008] The method for low-temperature synthesis of carbide ceramic powder by molten salt-assisted magnesothermic reduction described in this invention uses metal salts and carbon black as raw materials to synthesize carbide powder at low temperature through magnesothermic reduction in a molten salt medium. The preparation of hafnium carbide is used as an example below, and the reaction equation is as follows:

[0009] HfCl4 + 2Mg + C = HfC + 2MgCl2

[0010] 2Mg + O₂ = 2MgO

[0011] MgO + 2HCl = MgCl2 + H2O

[0012] The method steps described in this invention are as follows:

[0013] S1) Mix the metal salt, Mg powder, and carbon black in a molar ratio of 1:3-6:1.5-2, to obtain mixture A. The metal salt can be HfCl4, ZrCl4, etc., the Mg powder is the reducing agent, and the carbon black is the carbon source.

[0014] S2) Weigh the molten salts NaCl and / or KCl in the specified proportions;

[0015] S3) Weigh the mixture A and molten salt at a mass ratio of 1:2.5 to 4, mix them evenly, and obtain the mixed powder B;

[0016] S4) Place the mixed powder B in a covered graphite crucible, then place the crucible in an atmosphere furnace, and introduce a flowing inert atmosphere as a protective atmosphere. The inert atmosphere can be argon, nitrogen, etc. Heat to 800-1000℃, hold for 3-6 hours, cool to room temperature and take out to obtain the reactant.

[0017] S5) The reactant product 4 is immersed and stirred in an acidic solution to remove the MgO impurities generated in the reaction and the residual unreacted Mg powder. The acidic solution can be a dilute HCl solution with a concentration of 1-3 mol / L. The immersion and stirring should last for more than 4 hours. The solution after acid washing should still be acidic, with a pH of 1-5. Then, the molten salt is repeatedly washed with deionized water. The powder is separated by suction filtration and centrifugation. The clear liquid after deionized water washing is titrated with silver nitrate solution to determine whether it contains Cl. - The carbide nanoparticles are obtained by drying, and their particle size ranges from 10 to 100 nm.

[0018] The metal salt raw materials used in this invention have a purity greater than 99.5%; the carbon black has a purity greater than 99%; and the magnesium powder has a particle size of less than 74 μm and a purity greater than 98.5%.

[0019] The beneficial effects of the invention are as follows:

[0020] 1. The preparation process is simple and does not require complex equipment and processes.

[0021] 2. This invention utilizes the advantages of the molten salt method, using metal salt as the metal source and Mg powder as the reducing agent, so that metal ions are synthesized into carbides in the molten salt in an ionic state. This not only reduces the synthesis temperature, but also produces carbide powder with a small particle size distribution range of 10-100 nm, which is narrow.

[0022] 3. The preparation temperature is low and the powder purity is high, with the mass percentage of carbide phase in the prepared powder being greater than 95%.

[0023] 4. The carbide powder prepared by this invention can be used to prepare ultra-high temperature ceramic structural components, wear-resistant and corrosion-resistant structural component additives, and C / C composite material modifiers. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating a method for preparing nano-carbide powder according to the present invention.

[0025] Figure 2 The image shows a SEM image of the nano-zirconium carbide powder obtained in Example 1 using the preparation method of the present invention.

[0026] Figure 3 This is a TEM image of the nano-hafnium carbide powder obtained in Example 2 using the preparation method of the present invention. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0028] like Figure 1 As shown, the present invention discloses a method for preparing nano-carbide ceramic powder, which specifically includes the following steps:

[0029] S1) Mix the metal salt, reducing agent, and carbon source in a certain proportion to obtain mixture A:

[0030] The molar ratio of the metal salt, reducing agent, and carbon source is 1:1.5-2.2:3-4.

[0031] S2) Then mix the mixture A obtained in S1) with molten salt in a certain proportion to obtain mixture B; the mass ratio between mixture A and molten salt is 1:2.5 to 4.

[0032] S3) The mixture B is heated in an inert atmosphere to obtain the reactants;

[0033] S4) After washing the reactants obtained in S3), a certain amount of acidic solution is added to the precipitate, and the mixture is soaked for a certain period of time to remove the molten salt. The powder is then separated by suction filtration and centrifugation, and dried to obtain nano-carbide ceramic powder. The nano-carbide ceramic powder has a particle size of 10–100 nm, an average particle size of 40 nm, a purity >98%, and a specific surface area >41 m². 2 / g.

[0034] In addition to the aspects and any possible implementations described above, a further implementation is provided in which the metal salt has a purity greater than 99.5%, and the metal salt is a metal chloride or a chlorine oxide;

[0035] In addition to the aspects and any possible implementations described above, a further implementation is provided in which the reducing agent is magnesium powder with a purity greater than 98.5% and a particle size less than 100 μm;

[0036] In addition to the aspects and any possible implementations described above, an implementation is further provided in which the carbon source is one of carbon black, glucose, or glycine with a purity greater than 99%.

[0037] In addition to the aspects and any possible implementations described above, a further implementation is provided in which the molten salt is NaCl, or a mixture of NaCl and KCl in a certain proportion.

[0038] In addition to the aspects and any possible implementations described above, a further implementation is provided in which the heat treatment temperature in S3) is 800–1100°C and the holding time is 1–9 h; the inert atmosphere is argon or helium.

[0039] In addition to the aspects described above and any possible implementation, a further implementation is provided in which the acidic solution in S4) is dilute HCl or dilute nitric acid with a concentration of 1 to 5 mol / L; and the soaking time is 4 hours.

[0040] The application of nano-carbide ceramic powder prepared by the above preparation method in the preparation of ultra-high temperature ceramic structural components, wear-resistant and corrosion-resistant structural component additives, and C / C composite material modifiers.

[0041] A nano-carbide powder, wherein the nano-carbide ceramic powder is prepared by the above method.

[0042] Example 1:

[0043] Mix HfCl4 powder, Mg powder, and carbon black in a molar ratio of 1:4:2 to obtain mixture 1. Weigh molten salts NaCl and KCl in a molar ratio of 1:1 and mix them evenly to obtain salt mixture 2. Weigh mixture 1 and salt mixture 2 in a mass ratio of 1:3 and mix them evenly to obtain mixed powder 3. Place mixed powder 3 in a covered graphite crucible, then place the crucible in an atmosphere furnace, heat it to 900℃ in a flowing argon atmosphere, hold it at that temperature for 6 hours, and then cool it to room temperature. Place the product in a solution containing 1 mol / L hydrochloric acid and stir magnetically for 6 hours. Then wash it repeatedly with deionized water to remove the molten salt. Separate the hafnium carbide powder from the solution using a vacuum filter and dry it at 60℃ for 1 hour to obtain hafnium carbide powder with a particle size of less than 100 nm.

[0044] Example 2:

[0045] Mixture 1 is prepared by mixing ZrCl4 powder, Mg powder, and carbon black in a molar ratio of 1:4:1.5. Molten salts NaCl and KCl are weighed in a molar ratio of 1:0 and mixed evenly to obtain salt mixture 2. Mixture 1 and salt mixture 2 are weighed in a mass ratio of 1:3 and mixed evenly to obtain mixed powder 3. Mixed powder 3 is placed in a covered graphite crucible, and then the crucible is placed in an atmosphere furnace. The temperature is raised to 900℃ in a flowing argon atmosphere and held for 6 hours. After cooling to room temperature, product 4 is obtained. Product 4 is placed in a solution containing 1 mol / L hydrochloric acid and magnetically stirred for 6 hours. Then, it is repeatedly washed with deionized water to remove the molten salt. Zirconium carbide powder is separated from the solution using a vacuum filter and dried at 60℃ for 1 hour to obtain zirconium carbide powder with a particle size of less than 100 nm.

[0046] Example 3:

[0047] Mix ZrOCl2 powder, Mg powder, and carbon black in a molar ratio of 1:4:1.5 to obtain mixture 1. Weigh molten salts NaCl and KCl in a molar ratio of 1:1 and mix them evenly to obtain salt mixture 2. Weigh mixture 1 and salt mixture 2 in a mass ratio of 1:3 and mix them evenly to obtain mixed powder 3. Place mixed powder 3 in a covered graphite crucible, then place the crucible in an atmosphere furnace, heat it to 900℃ in a flowing argon atmosphere, hold it at that temperature for 6 hours, and then cool it to room temperature to obtain product 4. Place product 4 in a solution containing 1 mol / L hydrochloric acid and stir magnetically for 6 hours. Then wash it repeatedly with deionized water to remove the molten salt. Separate the zirconium carbide powder from the solution using a vacuum filter and dry it at 60℃ for 1 hour to obtain zirconium carbide powder with a particle size of less than 100 nm.

[0048] Example 4:

[0049] Mixture 1 is prepared by mixing TaCl5 powder, Mg powder, and carbon black in a molar ratio of 1:5:2. Molten salts NaCl and KCl are weighed in a molar ratio of 1:1 and mixed evenly to obtain a mixed molten salt. Mixture A and the mixed molten salt are weighed in a mass ratio of 1:3 and mixed evenly to obtain mixture B. Mixture B is placed in a covered graphite crucible, which is then placed in an atmosphere furnace and heated to 900°C in a flowing argon atmosphere. The temperature is maintained for 6 hours, and after cooling to room temperature, product 4 is obtained. Product 4 is placed in a solution containing 1 mol / L hydrochloric acid and magnetically stirred for 6 hours. Then, it is repeatedly washed with deionized water to remove the molten salt. Zirconium carbide powder is separated from the solution using a vacuum filter and dried at 60°C for 1 hour to obtain tantalum carbide powder with a particle size of less than 100 nm.

[0050] In view of this, the purpose of this invention is to provide a method for low-temperature synthesis of nano-carbide ceramic powder by molten salt-assisted magnesium thermal reduction, which has the characteristics of simple equipment, simple process, small powder particle size, energy saving and easy large-scale production.

[0051] The preparation method of nano-carbide powder and its application provided in the embodiments of this application have been described in detail above. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this application; at the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this application. Therefore, the content of this specification should not be construed as a limitation of this application.

[0052] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising / including but not limited to". "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of illustrating the general principles of this application and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0053] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0054] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0055] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. A method for preparing nano-carbide ceramic powder, characterized in that, The preparation method specifically includes the following steps: S1) Mix the metal salt, reducing agent, and carbon source in a certain proportion to obtain mixture A: S2) Then mix the mixture A obtained in S1) with molten salt in a certain proportion to obtain mixture B; S3) The mixture B is heated in an inert atmosphere to obtain the reactants; S4) After washing the reactants obtained in S3), a certain amount of acidic solution is added to the precipitate, and the precipitate is soaked for a certain time. The molten salt is washed away, and the powder is separated by suction filtration and centrifugation. After drying, nano-carbide ceramic powder is obtained. In S1), the molar ratio of the metal salt, reducing agent, and carbon source is 1:3-6:1.5-2. The metal salt is zirconium chloride or hafnium chloride; The heat treatment temperature in S3) is 800~900℃, and the holding time is 1~9h; the inert atmosphere is argon or helium.

2. The method according to claim 1, characterized in that, The purity of the metal salt is greater than 99.5%; The reducing agent is magnesium powder with a purity greater than 98.5% and a particle size less than 100μm; The carbon source is one of carbon black, glucose, or glycine with a purity greater than 99%.

3. The method according to claim 1, characterized in that, The mass ratio of mixture A to molten salt in S2) is 1:2.5 to 4.

4. The method according to claim 1, characterized in that, The molten salt is NaCl, or a mixture of NaCl and KCl in a 1:1 ratio.

5. The method according to claim 1, characterized in that, The acidic solution in S4) is dilute HCl or dilute nitric acid with a concentration of 1~5 mol / L; the soaking time is 4 hours.

6. The method according to claim 1, characterized in that, The nano-carbide ceramic powder prepared by the method has a particle size of 10-100 nm, an average particle size of 40 nm, a purity >98%, and a specific surface area >41 m². 2 / g.

7. The application of nano-carbide ceramic powder prepared by any one of claims 1-6 in the preparation of ultra-high temperature ceramic structural components, wear-resistant and corrosion-resistant structural component additives, and C / C composite material modifiers.

8. A nano-carbide powder, characterized in that, The nano-carbide ceramic powder is prepared by the method described in any one of claims 1 to 6.

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