Nano zirconium carbide ceramic powder and preparation method thereof

Abstract

The invention discloses nano zirconium carbide ceramic powder and a preparation method thereof.The preparation method comprises the following steps that S1, inorganic zirconium salt serves as a zirconium source, acetic acid serves as a chelating agent, a sol-gel reaction is conducted, and then filtration is conducted through anionic exchange resin to obtain zirconium sol; s2, soluble saccharides are added into the zirconium sol, aging and drying are performed after uniform stirring, and a xerogel precursor is obtained; s3, in an inert atmosphere, pyrolyzing the xerogel precursor, and then cooling, ball-milling and sieving to obtain a pyrolyzed xerogel precursor; and S4, calcining the pyrolytic xerogel precursor, so as to obtain the nano zirconium carbide ceramic powder. The inorganic zirconium salt is used as a zirconium source, the xerogel precursor is synthesized through a sol-gel method, then pyrolysis and calcination are sequentially carried out, the nano zirconium carbide ceramic powder is obtained, and the sintering activity of the zirconium ceramic powder is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic powder preparation, and particularly relates to a nano zirconium carbide ceramic powder and a preparation method thereof. Background Art

[0002] Zirconium carbide (ZrC) ceramics have many excellent properties such as extremely high melting point, high hardness, strong wear resistance, relatively high electrical and thermal conductivity, and excellent radiation resistance. It has a wide range of applications in the fields of ultra-high temperature structural materials, high-speed cutting tool materials, electronic component materials, nuclear energy protection, etc. ZrC ceramics are also difficult to sinter due to their strong covalent bond structure. The sintering temperature is usually as high as 2000°C, and mechanical pressure needs to be added when necessary. Therefore, highly active and high-purity nano ZrC ceramic powder has become an important criterion for evaluating the performance of ZrC ceramic products.

[0003] The main ZrC powder synthesis techniques include carbothermal solid-phase synthesis method, self-propagating high-temperature synthesis method, sol-gel method, hydrothermal method, etc. Among them, the advantages of the carbothermal solid-phase synthesis method and the self-propagating high-temperature synthesis method are simple synthesis process and low cost, which have been industrialized. However, the product purity is not high and the particle size distribution is wide. The hydrothermal method can obtain ZrC powder with an average particle size within a few hundred nanometers, but the batch processing capacity of the hydrothermal method is small, the efficiency is low, and the cost is high, making it difficult to meet large-scale engineering applications. The sol-gel method not only has the high-quality characteristics of the hydrothermal method but also has the advantage of large production capacity, so it has received more attention in production and research. However, when using the sol-gel method, different types of zirconium source and carbon source systems will produce precursors with different activities, resulting in differences in the properties of the final powder products. The cost of using organic zirconium sources is high and is not conducive to large-scale production. And Sun Ge et al. from Wuhan University of Technology reported a sol-gel method for preparing ZrC powder using zirconium oxychloride as the zirconium source. The prepared product has large hard agglomerates, and it is difficult for internal gas to escape during sintering, resulting in low sintering activity.

[0004] Therefore, a preparation scheme for nano ZrC ceramic powder with high sintering activity and economy is needed. Summary of the Invention

[0005] In view of this, the present application provides a nano zirconium carbide ceramic powder and a preparation method thereof with high sintering activity and low cost, which are used to solve the problem of how to improve the sintering activity and economy of ZrC ceramic powder.

[0006] To achieve the above technical purpose, the present application adopts the following technical solutions: In the first aspect, the present application provides a preparation method of a nano zirconium carbide ceramic powder, including the following steps: S1. Using an inorganic zirconium salt as the zirconium source and acetic acid as the chelating agent, carrying out a sol-gel reaction, and then filtering with an anionic exchange resin to obtain zirconium sol; S2. Add soluble sugars to zirconium sol, stir evenly, then age and dry to obtain a dry gel precursor. S3. Pyrolyze the dry gel precursor under an inert atmosphere, then cool, ball mill, and screen to obtain the pyrolyzed dry gel precursor. S4. Calcinate the pyrolyzed dry gel precursor to obtain nano zirconium carbide ceramic powder.

[0007] Preferably, in step S1, the inorganic zirconium salt includes one or more of zirconium oxychloride, zirconium oxynitrate, zirconium acetate, and zirconium carbonate.

[0008] Preferably, in step S1, the pH value of the sol-gel reaction is 5 - 6, and the reaction temperature is 35 - 60 °C.

[0009] Preferably, in step S1, the concentration of the inorganic zirconium salt is 0.2 - 1 mol / L.

[0010] Preferably, in step S2, the soluble sugars include one or more of sucrose, maltose, lactose, glucose, and fructose.

[0011] Preferably, the molar ratio of zirconium to carbon elements in the zirconium source and carbon source is 3 - 3.5:1.

[0012] Preferably, in step S3, the pyrolysis process is: heat up to 400 - 700 °C at a rate of 2 - 10 °C / min, and then react for 2 - 3 h.

[0013] Preferably, in step S3, the particle size of the sieve used for screening is 100 - 120 mesh.

[0014] Preferably, in step S4, the calcination process is: heat up to 1500 - 1700 °C at a rate of 2 - 10 °C / min, and then react for 1 - 2 h.

[0015] In the second aspect, the present application provides a nano zirconium carbide ceramic powder.

[0016] The beneficial effects of the present application are as follows: 1. In this technical solution, inorganic zirconium salt is used as the zirconium source. Inorganic zirconium salts have the significant advantages of low cost and wide sources, which is conducive to the batch production of ultrafine zirconium carbide powder.

[0017] 2. In this technical solution, an anion exchange resin is used to remove harmful impurity anions in the raw materials. Using an anion exchange resin can efficiently remove harmful impurity ions at low temperature, avoiding high-risk pollutants generated by subsequent high-temperature reactions and their pollution to the products, which has environmental protection and economy.

[0018] 3. Based on a low-cost zirconium source, this technical solution optimizes important synthesis parameters such as the carbon-zirconium ratio, and further improves the sintering activity of the nano-ZrC ceramic powder product on the basis of the traditional sol-gel method. Description of the Drawings

[0019] Figure 1 are the morphology diagrams of different products; Figure 2 are the sintered thickness volume densities of different products. Detailed Embodiments

[0020] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further describes the present invention in detail with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0021] In order to further improve the sintering activity of nano-zirconium carbide ceramic powder prepared by the sol-gel method and reduce the cost, the present invention selects a low-cost inorganic zirconium salt as the raw material, and realizes the compatibility of high activity and low cost of nano-zirconium carbide powder by optimizing the raw material composition and process parameters.

[0022] The present application provides a method for preparing nano-zirconium carbide ceramic powder, comprising the following steps: S1. Using an inorganic zirconium salt as the zirconium source and acetic acid as the chelating agent, carrying out a sol-gel reaction, and then filtering with an anionic exchange resin to obtain zirconium sol; S2. Adding soluble sugars to the zirconium sol, stirring evenly, followed by aging and drying to obtain a dry gel precursor; S3. Pyrolyzing the dry gel precursor under an inert atmosphere, followed by cooling, ball milling, and sieving to obtain a pyrolyzed dry gel precursor; S4. Calcining the pyrolyzed dry gel precursor to obtain nano-zirconium carbide ceramic powder.

[0023] The present application uses an inorganic zirconium salt as the zirconium source, acetic acid as the chelating agent, and soluble sugar as the carbon source. After synthesizing a dry gel precursor by the sol-gel method, pyrolysis and calcination are carried out in sequence to obtain nano-zirconium carbide ceramic powder, improving the sintering activity of the zirconium ceramic powder.

[0024] Among them, the purpose of pyrolysis is that the dry gel precursor thermally decomposes to remove water to become elemental carbon and zirconium oxide, avoiding side reactions such as oxidation reactions caused by a large amount of product water in subsequent high-temperature reactions. At the same time, under the action of argon protective gas, the elemental carbon converted from sucrose is spared from oxidation and remains; the purpose of calcination is to generate zirconium carbide powder through high-temperature chemical reactions.

[0025] It is worth noting that in step S1 of the present application, the use of low-cost anion exchange resin to replace harmful anions in the sol can efficiently remove harmful impurity ions at low temperatures, avoiding high-risk pollutants produced by subsequent high-temperature reactions and their contamination of products. Harmful anions inevitably come from different types of selected zirconium sources, such as common chloride ions, sulfate ions, nitrate ions, etc. Different ion indicators can be used to detect the residual ions in the sol to determine the number of times the filtration and replacement are performed, until the raw material sol is basically free of residual harmful ions and subsequent steps can be carried out.

[0026] In some embodiments, in step S1, the inorganic zirconium salt includes one or more of zirconium oxychloride, zirconium oxynitrate, zirconium acetate, and zirconium carbonate.

[0027] In the present application, acetic acid is used as a chelating agent, and the reversible chelation reaction with metal ions can stabilize the zirconium ion concentration in the sol, so that the overall gel reaction rate is stable and controllable; in some embodiments, the ratio of acetic acid concentration to zirconium ion concentration is 2-4:1.

[0028] In some embodiments, in step S1, the pH value of the sol-gel reaction is 5-6, and the reaction temperature is 35-60°C.

[0029] In the present application, in the sol-gel reaction, a too high pH value will easily form a precipitate, while a too low pH value will result in a too long gel time or even no gel; a too high reaction temperature will cause the gel reaction speed to be too fast, making it difficult to ensure product quality, but a too low reaction temperature will result in a too long gel time, reducing the synthesis efficiency.

[0030] In some embodiments, in step S1, the concentration of the inorganic zirconium salt is 0.2-1 mol / L in terms of zirconium ion concentration.

[0031] In the present application, too low a concentration of the inorganic zirconium salt is not conducive to the industrial synthesis efficiency, while too high a concentration of the inorganic zirconium salt leads to insufficient dissolution, resulting in insufficient sol-gel reaction.

[0032] In some embodiments, the Zr:C molar ratio of the inorganic zirconium salt to the carbon source is 3-3.5:1.

[0033] In the present application, the raw zirconium source and carbon source will be transformed into zirconium oxide and carbon after the pyrolysis process, and the carbon and zirconium oxide will react completely at a molar ratio of 3:1. Considering that the carbon source is easily lost during the preparation process, the carbon source content is appropriately increased. However, the carbon source content cannot be too high, otherwise it is easy to cause more residual carbon in the product.

[0034] In some embodiments, in step S3, the pyrolysis process is: heating to 400-700°C at a rate of 2-10°C / min and reacting for 2-3h.

[0035] In some embodiments, in step S3, the particle size of the sieve used for sieving is 100 - 120 mesh.

[0036] In some embodiments, in step S4, the calcination process is as follows: After heating up to 1500 - 1700 °C at a rate of 2 - 10 °C / min, react for 1 - 2 h.

[0037] This application provides a nano - zirconium carbide ceramic powder.

[0038] The following further illustrates this solution through specific embodiments.

[0039] Example 1 A preparation method of a nano - zirconium carbide ceramic powder includes the following steps: S1. Prepare a zirconium oxychloride solution with a zirconium ion concentration of 0.5 mol / L, add the chelating agent acetic acid to maintain its concentration at 1.6 mol / L, then add an appropriate amount of ammonia water to control the pH to 5, control the solution temperature at 50 °C, and filter through an anionic exchange resin until the silver nitrate solution can no longer detect chloride ions in the washing liquid to obtain a pure zirconium sol; S2. Add 0.125 mol / L sucrose to the zirconium sol (the zirconium - carbon molar ratio is 3.0:1), stir evenly, then transfer it to a 50 °C drying oven for aging until the sol loses fluidity, continue to raise the temperature to 100 °C for drying for 6 h, and collect the dry - gel precursor after cooling to room temperature; S3. Pyrolyze the dry - gel precursor under the protection of an argon atmosphere, where the heating rate is 2 °C / min, the holding temperature is 600 °C, and the holding time is 2 h. After cooling, take it out, ball - mill and crush it to pass through a 100 - mesh sieve to obtain a pyrolyzed dry - gel precursor; S4. High - temperature calcine the pyrolyzed dry - gel precursor, where the heating rate is 2 °C / min, the holding temperature is 1700 °C, and the holding time is 1 h. After cooling, collect the nano - zirconium carbide ceramic powder; the particle size of the obtained product is 200 - 300 nm, and the electron microscope image of the powder is as Figure 1 shown.

[0040] Example 2 A preparation method of a nano - zirconium carbide ceramic powder includes the following steps: S1. Prepare a zirconium oxychloride solution with a zirconium ion concentration of 0.5 mol / L, add the chelating agent acetic acid to maintain its concentration at 1.6 mol / L, then add an appropriate amount of ammonia water to control the pH to 5, control the solution temperature at 50 °C, and filter through an anionic exchange resin until the silver nitrate solution can no longer detect chloride ions in the washing liquid to obtain a pure zirconium sol; S2. Add 0.146 mol / L sucrose to the zirconium sol (the molar ratio of zirconium to carbon is 3.5:1). After stirring evenly, transfer it to a drying oven at 50 °C for aging until the sol loses fluidity. Then continue to raise the temperature to 100 °C for drying for 6 h. After cooling to room temperature, collect the xerogel precursor; S3. Pyrolyze the xerogel precursor under the protection of an argon atmosphere. The heating rate is 2 °C / min, the holding temperature is 600 °C, and the holding time is 2 h. After cooling, take it out and grind it to pass through a 100-mesh sieve to obtain the pyrolyzed xerogel precursor; S4. Calcinate the pyrolyzed xerogel precursor at high temperature. The heating rate is 2 °C / min, the holding temperature is 1700 °C, and the holding time is 1 h. After cooling, collect the nano-zirconium carbide ceramic powder; the product particle size is 150 - 250 nm, and the electron microscope image of the powder is as Figure 1 shown.

[0041] Comparative Example 1 A method for preparing nano-zirconium carbide ceramic powder, comprising the following steps: S1. Prepare a zirconyl chloride solution with a zirconium ion concentration of 0.5 mol / L, add the chelating agent acetic acid to maintain its concentration at 1.6 mol / L, then add an appropriate amount of ammonia water to control the pH to 5, control the solution temperature at 50 °C, and filter through an anionic exchange resin until the silver nitrate solution detects no chloride ions in the washing liquid to obtain a pure zirconium sol; S2. Add 0.167 mol / L sucrose to the zirconium sol (the molar ratio of zirconium to carbon is 4.0:1). After stirring evenly, transfer it to a drying oven at 50 °C for aging until the sol loses fluidity. Then continue to raise the temperature to 100 °C for drying for 6 h. After cooling to room temperature, collect the xerogel precursor; S3. Pyrolyze the xerogel precursor under the protection of an argon atmosphere. The heating rate is 2 °C / min, the holding temperature is 600 °C, and the holding time is 2 h. After cooling, take it out and grind it to pass through a 100-mesh sieve to obtain the pyrolyzed xerogel precursor; S4. Calcinate the pyrolyzed xerogel precursor at high temperature. The heating rate is 2 °C / min, the holding temperature is 1700 °C, and the holding time is 1 h. After cooling, collect the nano-zirconium carbide ceramic powder; the obtained product particle size is 150 - 250 nm, and the electron microscope image of the powder is as Figure 1 shown.

[0042] Testing and Evaluation Perform electron microscope tests on the nano-zirconium carbide ceramic powders obtained in Examples 1 - 2 and Comparative Example 1. The results are as Figure 1 shown, where Figure 1 a corresponds to Example 1 (the product particle size is 200 - 300 nm), where Figure 1b corresponds to Example 2 (product particle size is 150 - 250 nm), where Figure 1 c corresponds to Comparative Example 1 (average product particle size is 150 nm), which is composed of Figure 1 It can be seen that the powder obtained in Comparative Example 1 is wrapped by a gel-like substance and has relatively severe agglomeration, while the powders obtained in Examples 1 and 2 have good dispersibility.

[0043] The nano-zirconium carbide ceramic powders obtained from different examples and comparative examples were sintered for 10 min by spark plasma sintering (SPS) at 1700 °C, and the bulk density of the obtained products is as Figure 2 shown. The sintered body density is the ultimate proof of the powder activity. It can be clearly seen that the density of the powder of the product in the comparative example after sintering is much lower than that of Example 1 and Example 2.

[0044] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing nano zirconium carbide ceramic powder, characterized in that: The following steps are involved: S1. Using an inorganic zirconium salt as a zirconium source and acetic acid as a chelating agent, a sol-gel reaction is carried out, and then filtered using an anion exchange resin to obtain a zirconium sol; S2. adding a soluble sugar to the zirconium sol, stirring evenly, aging and drying to obtain a dry gel precursor; S3. Under an inert atmosphere, pyrolyzing the dry gel precursor, and then cooling, ball milling, and sieving to obtain a pyrolyzed dry gel precursor; S4. calcining the pyrolyzed dry gel precursor to obtain nano zirconium carbide ceramic powder.

2. The method for preparing nano zirconium carbide ceramic powder according to claim 1, characterized in that: In step S1, the inorganic zirconium salt includes one or more of zirconium oxychloride, zirconium oxynitrate, zirconium acetate, and zirconium carbonate.

3. The method for preparing nano zirconium carbide ceramic powder according to claim 1, characterized in that: In step S1, the pH value of the sol-gel reaction is 5-6, and the reaction temperature is 35-60°C.

4. The method for preparing nano zirconium carbide ceramic powder according to claim 1, characterized in that: The molar ratio of the inorganic zirconium salt to the carbon source is 3-3.5:

1.

5. The method for preparing nano zirconium carbide ceramic powder according to claim 1, characterized in that: In step S1, the concentration of the inorganic zirconium salt is 0.2-1 mol / L.

6. The method for preparing nano zirconium carbide ceramic powder according to claim 1, characterized in that: The pyrolysis process is: heating to 400-700°C at a rate of 2-10°C / min and reacting for 2-3h.

7. The method for preparing nano zirconium carbide ceramic powder according to claim 1, characterized in that: The particle size of the sieve used for sieving is 100-120 meshes.

8. The method for preparing nano zirconium carbide ceramic powder according to claim 1, characterized in that: The calcination process is: heating to 1500-1700° C. at a rate of 2-10° C. / min, and reacting for 1-2 hours.

9. A nano-zirconium carbide ceramic powder obtained by the preparation method according to any one of claims 1 to 8.

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