Nanometer zirconium carbide ceramic powder and preparation method thereof

Abstract

The application discloses a kind of nano zirconium carbide ceramic powder and preparation method thereof, comprising the following steps: S1.with inorganic zirconium salt as zirconium source, with acetic acid as chelating agent, carry out sol-gel reaction, then filter using anion exchange resin, namely zirconium sol is obtained;S2.soluble saccharide is added to the zirconium sol, after stirring uniformly, aging and drying are carried out, and dry gel precursor is obtained;S3.in inert atmosphere, the dry gel precursor is pyrolyzed, and then cooled, ball milled, and sieved, and pyrolyzed dry gel precursor is obtained;S4.the pyrolyzed dry gel precursor is calcined, and nano zirconium carbide ceramic powder is obtained.The application uses inorganic zirconium salt as zirconium source, synthesizes dry gel precursor by sol-gel method, and then pyrolysis and calcination are sequentially carried out, and nano zirconium carbide ceramic powder is obtained, and the sintering activity of zirconium ceramic powder is improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of ceramic powder preparation, in particular to a nano zirconium carbide ceramic powder and a preparation method thereof. BACKGROUND

[0002] Zirconium carbide (ZrC) ceramic has many excellent properties such as extremely high melting point, high hardness, strong wear resistance, relatively high electrical conductivity and thermal conductivity, excellent radiation resistance, and has wide application in the fields of ultra-high temperature structural materials, high-speed cutting tool materials, electronic component materials and nuclear energy protection. ZrC ceramic is also difficult to sinter due to its strong covalent bond structure, and the sintering temperature is usually as high as 2000 DEG C, and mechanical pressure is necessary, so high-activity and high-purity nano ZrC ceramic powder becomes an important standard for judging the performance of ZrC ceramic products.

[0003] The synthesis technologies of ZrC powder mainly include carbonthermal solid-phase synthesis, self-propagating synthesis, sol-gel method and hydrothermal method. The advantages of the carbonthermal solid-phase synthesis and the self-propagating synthesis are simple synthesis process and low cost, and the two methods are popularized in industry, but the product purity is not high and the particle size distribution is wide; the hydrothermal method can realize ZrC powder with an average particle size of less than 100 nanometers, but the batch processing capacity of the hydrothermal method is small, the efficiency is low and the cost is high, and it is difficult to meet the large-scale engineering application; the sol-gel method not only has the high-quality characteristics of the hydrothermal method, but also has the advantage of large output, so it has been paid more attention in production and research. However, when the sol-gel method is used, different types of zirconium sources and carbon sources will produce precursors with different activities, resulting in differences in the properties of the final powder products. The use of organic zirconium source is high in cost and is not conducive to large-scale production. Sun Ge and others of Wuhan University of Technology reported a sol-gel method for preparing ZrC powder by using zirconium oxychloride as a zirconium source. The prepared product has large hard agglomeration, and it is difficult to discharge the internal gas during sintering, so the sintering activity is not high.

[0004] Therefore, it is necessary to provide a nano ZrC ceramic powder preparation scheme with high sintering activity and economy. SUMMARY

[0005] Therefore, the application provides a nano zirconium carbide ceramic powder with high sintering activity and low cost and a preparation method thereof, which solves the problem of how to improve the sintering activity and economy of ZrC ceramic powder.

[0006] In order to achieve the above technical purpose, the application adopts the following technical scheme:

[0007] In a first aspect, the application provides a preparation method of a nano zirconium carbide ceramic powder, comprising the following steps:

[0008] S1. Using inorganic zirconium salt as a zirconium source and acetic acid as a chelating agent, a sol-gel reaction is carried out, and then an anion exchange resin is used for filtration, so as to obtain a zirconium sol;

[0009] S2. Adding soluble saccharide into the zirconium sol, stirring uniformly, aging and drying to obtain a xerogel precursor;

[0010] S3. Pyrolyzing the xerogel precursor under inert atmosphere, then cooling, ball milling and sieving to obtain a pyrolytic xerogel precursor;

[0011] S4. Calcining the pyrolytic xerogel precursor to obtain a nano zirconium carbide ceramic powder.

[0012] Preferably, in step S1, the inorganic zirconium salt includes one or more of zirconium oxychloride, zirconium oxynitrate, zirconium acetate and zirconium carbonate.

[0013] Preferably, in step S1, the pH value of the sol-gel reaction is 5-6 and the reaction temperature is 35-60℃.

[0014] Preferably, in step S1, the concentration of the inorganic zirconium salt is 0.2-1 mol / L.

[0015] Preferably, in step S2, the soluble saccharide includes one or more of sucrose, maltose, lactose, glucose and fructose.

[0016] Preferably, the molar ratio of zirconium to carbon in the zirconium source and the carbon source is 3-3.5:1.

[0017] Preferably, in step S3, the pyrolysis process is: heating at a rate of 2-10℃ / min to 400-700℃ and then reacting for 2-3h.

[0018] Preferably, in step S3, the mesh size of the sieve used for sieving is 100-120 mesh.

[0019] Preferably, in step S4, the calcination process is: heating at a rate of 2-10℃ / min to 1500-1700℃ and then reacting for 1-2h.

[0020] In a second aspect, the present application provides a nano zirconium carbide ceramic powder.

[0021] The beneficial effects of the present application are as follows:

[0022] 1. In the technical solution, inorganic zirconium salt is used as the zirconium source, which has the advantages of low cost and wide source, and is conducive to the batch production of ultra-fine zirconium carbide powder.

[0023] 2. In the technical solution, anion exchange resin is used to remove harmful impurity anions in the raw material. The use of anion exchange resin can efficiently remove harmful impurity ions at low temperature, avoid the generation of high-risk pollutants at high temperature and their pollution to the product, and has environmental protection and economic benefits.

[0024] 3. The technical solution optimizes important synthesis parameters such as the carbon-zirconium ratio on the basis of a low-cost zirconium source, and further improves the sintering activity of the nano ZrC ceramic powder product on the basis of the traditional sol-gel method. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 are the morphology diagrams of different products;

[0026] Figure 2 are the sintering thickness and volume density of different products. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present application more clear and explicit, the present application is further described in detail below in combination with examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0028] In order to further improve the sintering activity of the nano ZrC ceramic powder prepared by the sol-gel method and reduce the cost, the present application selects a low-cost inorganic zirconium salt as a raw material, and realizes the compatibility of high activity and low cost of the nano ZrC powder by optimizing the raw material composition and process parameters.

[0029] The present application provides a preparation method of a nano ZrC ceramic powder, comprising the following steps:

[0030] 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 an anion exchange resin is used for filtration, so as to obtain a zirconium sol;

[0031] S2. A soluble sugar is added to the zirconium sol, and after stirring uniformly, aging and drying are carried out, so as to obtain a dry gel precursor;

[0032] S3. The dry gel precursor is pyrolyzed under an inert atmosphere, and then cooled, ball milled and sieved, so as to obtain a pyrolyzed dry gel precursor;

[0033] S4. The pyrolyzed dry gel precursor is calcined, so as to obtain a nano ZrC ceramic powder.

[0034] The present application uses an inorganic zirconium salt as a zirconium source, acetic acid as a chelating agent and a soluble sugar as a carbon source, and after synthesizing a dry gel precursor by a sol-gel method, pyrolysis and calcination are sequentially carried out, so as to obtain a nano ZrC ceramic powder, and the sintering activity of the zirconium ceramic powder is improved.

[0035] The pyrolysis aims to pyrolyze the dried gel precursor to remove water to become elemental carbon and zirconium oxide, avoid the side reactions caused by a large amount of product water in the subsequent high-temperature reaction, and under the action of the argon protective gas, the elemental carbon converted from sucrose is prevented from being oxidized and retained.

[0036] It is worth noting that in step S1 of the present application, the harmful anions in the sol are replaced by the low-cost anion exchange resin, which can efficiently remove the harmful impurity ions at low temperature, and avoid the high-risk pollutants generated in the subsequent high-temperature reaction and the pollution to the product. The harmful anions inevitably come from different zirconium sources selected, such as common chloride ions, sulfate ions, nitrate ions, etc. Different ion indicators can be used to detect the residual ion situation of the sol to determine the execution times of the filtration and replacement, until the raw material sol is basically free of residual harmful ions and the subsequent steps can be performed.

[0037] In some embodiments, in step S1, the inorganic zirconium salt includes one or more of zirconium oxychloride, zirconium oxynitrate, zirconium acetate, and zirconium carbonate.

[0038] In the present application, acetic acid as a chelating agent can stabilize the concentration of zirconium ions in the sol through the reversible chelation reaction with metal ions, so that the overall gel reaction speed is stable and controllable; in some embodiments, the concentration ratio of acetic acid to zirconium ion concentration is 2-4:1.

[0039] 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.

[0040] In the present application, in the sol-gel reaction, too high pH value is easy to form a precipitate, and too low pH value leads to too long gel time, or even no gel; too high reaction temperature makes the gel reaction speed too fast, which is difficult to ensure product quality, but too low reaction temperature leads to too long gel time and reduces the synthesis efficiency.

[0041] In some embodiments, in step S1, the concentration of the inorganic zirconium salt is 0.2-1 mol / L in terms of the concentration of zirconium ions.

[0042] In the present application, too low inorganic zirconium salt concentration is not conducive to the industrialization synthesis efficiency, and too high inorganic zirconium salt concentration leads to insufficient dissolution, resulting in insufficient sol-gel reaction.

[0043] In some embodiments, the Zr:C molar ratio of the inorganic zirconium salt to the carbon source is 3-3.5:1.

[0044] In the present application, the raw material zirconium source and carbon source are converted into zirconia and carbon element after pyrolysis process, and carbon and zirconia will react completely in a molar ratio of 3:1. Considering the loss of carbon source during preparation, the content of carbon source is appropriately increased. However, the content of carbon source cannot be too high, otherwise it is easy to cause more residual carbon in the product.

[0045] In some embodiments, in step S3, the pyrolysis process is as follows: heating at a rate of 2-10℃ / min to 400-700℃, and then reacting for 2-3h.

[0046] In some embodiments, in step S3, the particle size of the sieve used for sieving is 100-120 mesh.

[0047] In some embodiments, in step S4, the calcination process is as follows: heating at a rate of 2-10℃ / min to 1500-1700℃, and then reacting for 1-2h.

[0048] The present application provides a kind of nano carbon zirconium ceramic powder.

[0049] The present application is further described below by specific examples.

[0050] Example 1

[0051] A preparation method of a nano carbon zirconium ceramic powder comprises the following steps:

[0052] S1. Prepare a zirconium oxychloride solution with a zirconium ion concentration of 0.5 mol / L, add a chelating agent acetic acid to maintain its concentration at 1.6 mol / L, then add appropriate amount of ammonia water to control the pH to 5, control the solution temperature at 50℃, and filter through an anion exchange resin until no chloride ions are detected in the washing liquid by silver nitrate solution to obtain pure zirconium sol;

[0053] S2. Add 0.125 mol / L sucrose (zirconium-carbon molar ratio of 3.0:1) to the zirconium sol, stir uniformly, and then transfer into a 50℃ drying oven for aging until the sol loses fluidity, continue to increase the temperature to 100℃ for drying for 6h, and collect the dry gel precursor after cooling to room temperature;

[0054] S3. Pyrolysis treatment of the dry gel precursor under argon atmosphere protection, wherein the heating rate is 2℃ / min, the holding temperature is 600℃, and the holding time is 2h, and after cooling, the pyrolysis dry gel precursor is obtained by ball milling and crushing to 100 mesh;

[0055] S4. High temperature calcination of the pyrolyzed dry gel precursor, wherein the heating rate is 2℃ / min, the holding temperature is 1700℃, and the holding time is 1h, and after cooling, the nano carbon zirconium ceramic powder is collected; the particle size of the product is 200-300nm, and the electron microscope picture of the powder is as shown in Figure 1 .

[0056] Example 2

[0057] A method for preparing a nano-zirconium carbide ceramic powder comprises the following steps:

[0058] S1. A zirconium oxychloride solution with a zirconium ion concentration of 0.5 mol / L is prepared, a chelating agent acetic acid is added to maintain a concentration of 1.6 mol / L, an appropriate amount of ammonia water is added to control the pH to 5, the solution temperature is controlled at 50°C, and the solution is filtered through an anion exchange resin until no chloride ions are detected in the washing liquid by silver nitrate solution, to obtain a pure zirconium sol;

[0059] S2. 0.146 mol / L sucrose (zirconium-carbon molar ratio of 3.5:1) is added to the zirconium sol, which is stirred uniformly and then transferred into a 50°C drying oven for aging until the sol loses fluidity, and then the temperature is continuously increased to 100°C for drying for 6 h, and the dry gel precursor is collected after cooling to room temperature;

[0060] S3. The dry gel precursor is pyrolyzed under the protection of an argon atmosphere, wherein the temperature increasing rate is 2°C / min, the holding temperature is 600°C, and the holding time is 2 h, and after cooling, the pyrolyzed dry gel precursor is obtained by ball milling and sieving to 100 mesh;

[0061] S4. The pyrolyzed dry gel precursor is calcined at a high temperature, wherein the temperature increasing rate is 2°C / min, the holding temperature is 1700°C, and the holding time is 1 h, and the nano-zirconium carbide ceramic powder is collected after cooling; the product particle size is 150-250 nm, and the powder electron microscope image is shown in Figure 1 .

[0062] Comparative Example 1

[0063] A method for preparing a nano-zirconium carbide ceramic powder comprises the following steps:

[0064] S1. A zirconium oxychloride solution with a zirconium ion concentration of 0.5 mol / L is prepared, a chelating agent acetic acid is added to maintain a concentration of 1.6 mol / L, an appropriate amount of ammonia water is added to control the pH to 5, the solution temperature is controlled at 50°C, and the solution is filtered through an anion exchange resin until no chloride ions are detected in the washing liquid by silver nitrate solution, to obtain a pure zirconium sol;

[0065] S2. 0.167 mol / L sucrose (zirconium-carbon molar ratio of 4.0:1) is added to the zirconium sol, which is stirred uniformly and then transferred into a 50°C drying oven for aging until the sol loses fluidity, and then the temperature is continuously increased to 100°C for drying for 6 h, and the dry gel precursor is collected after cooling to room temperature;

[0066] S3. pyrolysis treatment of the dry gel precursor under the protection of argon atmosphere, wherein the heating rate is 2℃ / min, the holding temperature is 600℃, the holding time is 2 h, and the pyrolysis dry gel precursor is obtained by ball milling and sieving to 100 mesh after cooling;

[0067] S4. high-temperature calcination of the pyrolyzed dry gel precursor, wherein the heating rate is 2℃ / min, the holding temperature is 1700℃, the holding time is 1 h, and the nano zirconium carbide ceramic powder is obtained by collection after cooling; the particle size of the product is 150-250 nm, and the electron microscope picture of the powder is shown in Figure 1

[0068] Test and evaluation

[0069] The nano zirconium carbide ceramic powders obtained in Examples 1-2 and Comparative Example 1 are subjected to electron microscope test, and the results are shown in Figure 1 Figure 1 a corresponds to Example 1 (the product particle size is 200-300 nm), wherein Figure 1 b corresponds to Example 2 (the product particle size is 150-250 nm), wherein Figure 1 c corresponds to Comparative Example 1 (the average product particle size is 150 nm), wherein Figure 1 It can be seen that the powder obtained in Comparative Example 1 is wrapped by a gel-like substance and has serious agglomeration, while the powders obtained in Examples 1 and 2 have good dispersibility.

[0070] The nano zirconium carbide ceramic powders obtained in different examples and comparative examples are subjected to spark plasma sintering (SPS) at 1700℃ for 10 min, and the bulk density of the obtained product is shown in Figure 2

[0071] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.​​​

Claims

1. A method for producing a nano-crystalline zirconium carbide ceramic powder, characterized by, The method comprises the following steps: S1. A sol-gel reaction is carried out by using zirconium oxychloride as a zirconium source and acetic acid as a chelating agent, and then an anion exchange resin is used for filtration to obtain a zirconium sol; S2. Sucrose is added to the zirconium sol, and after stirring, aging and drying, a dry gel precursor is obtained; S3. The dry gel precursor is pyrolyzed under an inert atmosphere, and then cooled, ball-milled and sieved to obtain a pyrolyzed dry gel precursor; S4. The pyrolyzed dry gel precursor is calcined to obtain a nano carbonized zirconia ceramic powder; the carbon:zirconium molar ratio of the zirconium oxychloride to sucrose is 3-3.5:1; The pyrolysis process is as follows: the temperature is raised to 400-700℃ at a rate of 2-10℃ / min, and then the reaction is carried out for 2-3h; the calcination process is as follows: the temperature is raised to 1500-1700℃ at a rate of 2-10℃ / min, and then the reaction is carried out for 1-2h; in step S1, the pH value of the sol-gel reaction is 5-6, and the reaction temperature is 35-60℃.

2. The method of claim 1, wherein the carbon nanoceramics zirconium carbide powder is prepared by the steps of: The particle size of the sieve used for sieving is 100-120 mesh. ​

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