Preparation method of monoclinic zirconia powder and monoclinic zirconia powder

Abstract

The application relates to the technical field of zirconia material preparation, and particularly provides a preparation method of monoclinic zirconia powder and the monoclinic zirconia powder. The preparation method of the monoclinic zirconia powder comprises the following steps: dissolving a water-soluble zirconium salt and a dispersing agent into water to prepare a solution A with a zirconium salt concentration of 0.5-1.5 mol / L; synchronously adding the solution A and a urea solution into a reaction kettle, stirring while adding, and controlling the adding speed of the urea solution so that the pH of a reaction system is 7.5-8.5, and then obtaining a precipitate; washing the precipitate with dilute ammonia water, then washing with water until no chloride ion is detected, heating to 550-750 DEG C, calcining for 2-5 hours, cooling, taking out, crushing and sieving, and then obtaining the monoclinic zirconia powder. The zirconia powder product obtained by the preparation method has high monoclinic zirconia content and high powder yield.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of zirconia material preparation, in particular, to a preparation method of monoclinic zirconia powder and monoclinic zirconia powder. BACKGROUND

[0002] Zirconia has three different crystal phases: monoclinic phase (m-ZrO2), tetragonal phase (t-ZrO2) and cubic phase (c-ZrO2). The three crystal phases can be transformed at different temperatures, and the monoclinic phase is the most stable at room temperature. Zirconia can be used as a catalyst or a catalyst carrier, and is also widely used in ZrO2 toughened composite ceramics (ZTA), oxygen sensors and the like. The preparation methods of ZrO2 powder mainly include solvothermal method, sol-gel method, precipitation method, hydrolysis method and the like. For example, document 1 discloses that an ethanol / water solution with a volume ratio of 4:1 is used as a solvent of zirconium oxychloride, sodium hydroxide is used for precipitation, the precipitate is dried and then calcined, and then the product is subjected to hydrothermal reaction in hydrochloric acid, and then the product is washed by centrifugation with hydrochloric acid and dried, and then the product is obtained. Document 2 discloses that deionized water and anhydrous methanol are respectively used as solvents, urea is added to a ZrO (NO3) 2·2H2O solution, and then hydrothermal reaction and solvothermal reaction are respectively carried out, and then the product is washed and dried, and then the product is calcined at 400°C for 4h. The content of m-ZrO2 in the zirconia obtained by hydrothermal reaction can reach 67%. Document 3 discloses a synthesis method of nano-monoclinic zirconia material, an alkaline aqueous solution is added dropwise to a zirconium salt solution, the precipitate obtained after washing with distilled water is redispersed in water, and then the product is reacted with concentrated acid at a constant temperature of 120-250°C, and then the product is centrifuged, washed and dried, and then the product is obtained.

[0003] Document 1: Preparation and characterization of tetragonal and monoclinic zirconia nanoparticles, Master's thesis of Lanzhou University, 2013.

[0004] Document 2: Solvent effect in synthesis of pure monoclinic and tetragonal zirconia by solvothermal method, Acta Phys.-Chim. Sin., 2008, 24 (12): 2172-2178.

[0005] Document 3: Chinese invention patent publication No. CN101870587A, publication date 2013.05.01. SUMMARY

[0006] However, in the existing preparation method of zirconia powder, hydrothermal reaction needs a high-pressure reaction kettle, and it is difficult to observe the change of the product in the reaction process. In document 1, sodium hydroxide is used as a precipitant, the alkalinity is too strong, the reaction with the zirconium salt is too violent, the purity of the product is reduced, and Na+ is introduced into the product. In document 2, the reaction is carried out in a high-pressure reaction kettle, and the reaction process is not easy to observe. In document 3, the reaction is carried out in a high-pressure reaction kettle, and the reaction process is not easy to observe. +, will further affect the purity of the product. The need for concentrated acid in document 3 will affect the grain size and powder performance of the powder, and is also not good for the environment.

[0007] In the process of preparing ZrO2 powder by precipitation method, the concentration of raw materials, the pH value during precipitation, the washing and drying process of the precipitate, and the calcination temperature are all main factors affecting the performance of ZrO2 powder. In order to solve the above problems, a simpler and more environmentally friendly method for preparing monoclinic zirconia is provided, and a preparation method of monoclinic zirconia powder and monoclinic zirconia powder are provided.

[0008] The technical scheme adopted by the present application is as follows:

[0009] A preparation method of monoclinic zirconia powder, comprising the following steps:

[0010] S1, dissolving water-soluble zirconium salt and dispersant into water to prepare a solution A with a zirconium salt concentration of 0.5-1.5 mol / L;

[0011] S2, dissolving urea or ammonium carbonate in water to prepare a solution B with a concentration of 7-15wt%;

[0012] S3, synchronously adding the solution A of step S1 and the solution B of step S2 into a reaction kettle, stirring while adding, and controlling the dropping speed of the solution B so that the pH of the reaction system is 7.5-8.5, to obtain a precipitate;

[0013] S4, washing the precipitate of step S3 with ammonia water, then washing with water until no chloride ion is detected, heating to 550-750℃ and calcining for 2-5 hours, cooling, taking out, crushing and sieving, to obtain the product.

[0014] Preferably, the water-soluble zirconium salt of step S1 is selected from one or a combination of zirconium oxychloride, zirconium nitrate, zirconium acetate, zirconium sulfate and zirconium chloride.

[0015] Preferably, the dispersant of step S1 is selected from one or a combination of high molecular dispersant and non-ionic surfactant.

[0016] More preferably, the dispersant is selected from a combination of high molecular dispersant and non-ionic surfactant in a weight ratio of 1:0.3-4:1.

[0017] Preferably, the weight ratio of the water-soluble zirconium salt and the dispersant of step S1 is 100:0.5-3.5.

[0018] Preferably, the dropping speed of the solution A of step S3 is 1ml-50000ml / min.

[0019] Preferably, the concentration of the ammonia water of step S4 is 0.05-0.2wt%.

[0020] Preferably, the chloride ion detection in step S4 is performed by using a 0.1wt% silver nitrate solution.

[0021] Preferably, the heating rate in step S4 is 2-10℃ / min.

[0022] A monoclinic zirconia powder is prepared by the preparation method in any of the above technical solutions.

[0023] In summary, the present application has the following beneficial effects:

[0024] 1. The present application uses a simple method to mix zirconium salt aqueous solution and urea aqueous solution under the action of dispersant, and controls the pH of the reaction system by adjusting the dropping speed of urea or ammonium carbonate aqueous solution. The obtained precipitate is washed with dilute ammonia water and water, and then calcined at high temperature, so that a monoclinic zirconia powder with high powder yield and high purity can be obtained. The purity can reach 99.5% or above, and the powder yield can reach 95% or above.

[0025] 2. The present application uses a relatively simple precipitation method to prepare monoclinic ZrO2 powder, which does not require a high-pressure container like hydrothermal method, nor a long reaction time and low efficiency like sol-gel method. The preparation method of the present application is simple, efficient, and can observe the changes in the reaction process in real time. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described in detail below.

[0027] Throughout this specification, unless otherwise specifically indicated, the terms used herein are understood to have the meanings as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present application belongs. If there is a contradiction, the present specification takes priority.

[0028] In one aspect, the present application provides a preparation method of monoclinic zirconia powder, comprising the following steps:

[0029] S1. Dissolve water-soluble zirconium salt and dispersant in water to prepare solution A with a zirconium salt concentration of 0.5-1.5mol / L;

[0030] S2. Dissolve urea or ammonium carbonate in water to prepare solution B with a concentration of 7-15wt%;

[0031] S3, synchronously adding the solution A of step S1 and the solution B of step S2 into a reactor, stirring while adding, and controlling the dropping speed of solution B so that the pH of the reaction system is 7.5-8.5, to obtain a precipitate;

[0032] S4, washing the precipitate of step S3 with ammonia water, then washing with water until no chloride ion is detected, calcining at 550-750℃ for 2-5 hours, cooling, taking out, crushing and sieving, to obtain the product.

[0033] In the present application, the above steps S1 and S2 have no specific order of operation steps, and can be operated first in step S1, or first in step S2, or simultaneously in steps S1 and S2.

[0034] The present application uses a simple precipitation method to prepare monoclinic zirconia powder, and by controlling the selection of alkaline precipitant, i.e. urea or ammonium carbonate, and the adding speed, monoclinic zirconia powder with high yield can be obtained.

[0035] In a preferred embodiment of the present application, the water-soluble zirconium salt in step S1 is selected from one or a combination of zirconium oxychloride, zirconium nitrate, zirconium acetate, zirconium sulfate and zirconium chloride. Specifically, the concentration of zirconium salt in solution A can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, etc.

[0036] The dispersant can play a role in dispersing and protecting the formed precipitate particles, avoiding the aggregation of the formed precipitate, and affecting the grain size and purity. In a preferred embodiment of the present application, the dispersant in step S1 can be selected from one or a combination of high molecular dispersants and non-ionic surfactants. For example, the high molecular dispersant refers to a dispersant with an average molecular weight of more than 1000, which can be polyacrylic acid PAA, polyvinyl alcohol PVA, polyvinylpyrrolidone PVP, etc.; the non-ionic surfactant is a surfactant with a molecular weight of less than 500, which can be fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, sorbitan monooleate polyoxyethylene ether, etc., for example, AEO-3, AEO-6, AEO-9, AEO-12, OP-4, OP-7, OP-10, OP-15, OP-20, tween-20, tween-40, tween-60, tween-65, tween-80, etc.

[0037] More preferably, the dispersant is selected from the group consisting of a high molecular dispersant and a non-ionic surfactant in a weight ratio of 1:0.3-4:1. For example, the weight ratio of the high molecular dispersant and the non-ionic surfactant can be 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1.2:1, 1.5:1, 1.7:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.7:1, 2.8:1, 3:1, 3.1:1, 3.3:1, 3.5:1, 3.7:1, 3.8:1, 4:1, etc. The inventors have found that the use of a combination of a high molecular dispersant and a non-ionic surfactant is more conducive to dispersing and protecting the formed precipitated particles, avoiding the aggregation and growth of the precipitated particles, and also avoiding the presence of too many impurities in the precipitate and affecting the purity.

[0038] In a preferred embodiment of the present application, the weight ratio of the water-soluble zirconium salt to the dispersant in step S1 is 100:0.5-3.5. When the weight ratio of the water-soluble zirconium salt to the dispersant is within the above range, a precipitated powder with good stability can be obtained. For example, the weight ratio of the water-soluble zirconium salt to the dispersant can be 100:0.5, 100:0.8, 100:1, 100:1.2, 100:1.3, 100:1.5, 100:1.6, 100:1.8, 100:2, 100:2.2, 100:2.5, 100:2.7, 100:3, 100:3.2, 100:3.5, etc.

[0039] In a preferred embodiment of the present application, the dropping speed of the A solution in step S3 is not particularly limited and can be adjusted according to the volume of the A solution and the B solution. The dropping speed of the A solution can be 1-50000 ml / min. Generally, the larger the volume of the A solution, the faster the dropping speed of the A solution. For example, when the volume of the A solution is 10 L, the dropping speed of the A solution can be 1-1000 ml / min, or further, the dropping speed of the A solution can be 10-100 mL / min. When the volume of the A solution is 100 L, the dropping speed of the A solution can be 100-1000 mL / min. When the volume of the A solution is higher, the dropping speed can be correspondingly increased.

[0040] In the existing preparation of zirconia powder technology, the role of ammonia is as a precipitant for the precipitation of zirconium hydroxide powder. In the prior art, ethanol or acetone is generally used to wash the precipitate to avoid the grain agglomeration and growth caused by washing with water. However, the present inventors have found that washing the formed precipitate with dilute ammonia can quickly wash away the chloride ions in the precipitate, reduce the number of water washing times, avoid the growth of precipitate grains, and further promote the stability of the precipitate particle structure and the improvement of the powder yield. In a preferred embodiment, the concentration of ammonia in step S4 is 0.05-0.2wt%. For example, the concentration of ammonia can be 0.05wt%, 0.07wt%, 0.08wt%, 0.09wt%, 0.1wt%, 0.11wt%, 0.12wt%, 0.13wt%, 0.15wt%, 0.17wt%, 0.18wt%, 0.2wt%. In this application, the operation of ammonia washing can be: put 5-50 times the weight of the collected precipitate into the precipitate, stir, filter, and collect the solid. In this application, after ammonia washing, the chloride ions in the precipitate can be completely removed by washing with water for 2-3 times. If ethanol or acetone is used for cleaning, organic solvent pollution will be produced. If deionized water is used for cleaning without ammonia, more than 5 times of washing is needed, which will cause process extension and waste of water resources.

[0041] In a preferred embodiment of the present application, no chloride ions are detected in step S4 by using a 0.1wt% silver nitrate solution for chloride ion detection, which can effectively detect the chloride ion concentration in the water after washing. The chloride ion detection can be as low as 1ppm.

[0042] In a preferred embodiment of the present application, the rate of temperature rise in step S4 is 2-10℃ / min. The temperature rise rate in the above range can better control the temperature rise process. For example, the temperature rise rate can be 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, etc.

[0043] On the other hand, the present application proposes a preparation method of monoclinic zirconia powder, which is prepared by the preparation method described in any of the technical solutions.

[0044] The technical solutions of the present application will be described in detail below in combination with examples and comparative examples.

[0045] Example 1

[0046] The weight ratio of zirconium oxychloride and PVA 1792 is 100:2.

[0047] Dissolve PVA 1792 into hot water at 90℃, cool to room temperature, add zirconium oxychloride and the rest of water, stir and dissolve to prepare solution A with zirconium salt concentration of 0.8 mol / L;

[0048] Add urea into water, stir and dissolve to prepare solution B with concentration of 10wt%;

[0049] Take 1L of solution A, add solution A and solution B into the reactor simultaneously, the dropping speed of solution A is 50mL / min, stir while dropping, the stirring speed is 300rpm, control the dropping speed of solution B so that the pH of the reaction system is maintained at 7.5-8, after dropping solution A and solution B, obtain the precipitate;

[0050] Centrifugal collect the above precipitate, add 0.1wt% ammonia water with 20 times the volume of the precipitate, stir for 45min, centrifugal collect the solid, wash the solid with deionized water for 2 times, the washing liquid is detected with 0.1wt% silver nitrate solution, no chloride ion is detected. Put the washed solid into an alumina crucible, put it into the kiln, heat to 620℃ at a heating rate of 5℃ / min, calcine for 3 hours, cool, take out, crush, pass through a 60 mesh sieve, obtain zirconium oxide powder.

[0051] Example 2

[0052] The difference between Example 2 and Example 1 is that in Example 1, PVA 1792 is replaced by equal weight of non-ionic surfactant AEO-9. The rest of the steps remain unchanged.

[0053] Example 3

[0054] The difference between Example 3 and Example 1 is that in Example 1, PVA 1792 is replaced by equal weight of a combination of PVA 1792 and non-ionic surfactant AEO-9 in a weight ratio of 2:1. The rest of the steps remain unchanged.

[0055] Example 4

[0056] The difference between Example 4 and Example 1 is that in Example 1, PVA 1792 is replaced by equal weight of a combination of PVA 1792 and non-ionic surfactant AEO-9 in a weight ratio of 1:2. The rest of the steps remain unchanged.

[0057] Example 5

[0058] The difference between Example 5 and Example 1 is that in Example 1, the dropping speed of solution B is controlled so that the pH of the reaction system is maintained at 8-8.5. The rest of the steps remain unchanged.

[0059] Comparative Example 1

[0060] The difference between Comparative Example 1 and Example 1 is that in Example 1, the dropping speed of solution B is controlled so that the pH of the reaction system is maintained at 6.5-7. The remaining steps remain unchanged.

[0061] Comparative Example 2

[0062] The difference between Comparative Example 2 and Example 1 is that in Example 1, the dropping speed of solution B is controlled so that the pH of the reaction system is maintained at 9-9.5. The remaining steps remain unchanged.

[0063] Comparative Example 3

[0064] The difference between Comparative Example 3 and Example 1 is that in Example 1, the step of “adding 20 times the volume of precipitate of 0.1wt% ammonia water, stirring for 45 min, and collecting the solid by centrifugation” is omitted. The remaining steps remain unchanged.

[0065] Comparative Example 4

[0066] The difference between Comparative Example 4 and Example 1 is that in Example 1, solution B is replaced with a 5wt% NaOH solution. The remaining steps remain unchanged.

[0067] Comparative Example 5

[0068] The difference between Comparative Example 4 and Example 1 is that in Example 1, solution B is replaced with a 5wt% NaOH solution, and the dropping speed of solution B is controlled so that the pH of the reaction system is maintained at 9-9.5. The remaining steps remain unchanged.

[0069] Example 6

[0070] The weight ratio of zirconium chloride, PVP K30 and AEO-6 is 100:1.5:1.

[0071] Dissolve PVP K30 in part of the water, add zirconium chloride, AEO-6 and the remaining water, continue to stir and dissolve to prepare solution A with a zirconium salt concentration of 1.1 mol / L;

[0072] Add urea to water, stir and dissolve to prepare solution B with a concentration of 12wt%;

[0073] Take 1L of solution A, and simultaneously drop solution A and solution B into the reaction kettle, the dropping speed of solution A is 40mL / min, and the stirring speed is 250rpm. The dropping speed of solution B is controlled so that the pH of the reaction system is maintained at 8-8.5. After dropping solution A and solution B, a precipitate is obtained.

[0074] The precipitate was collected by centrifugation, 0.15wt% ammonia water was added to the precipitate in an amount of 20 times the volume of the precipitate, and stirring was performed for 60 minutes. The solid was collected by centrifugation, and the solid was washed with deionized water twice. The washing liquid was detected with a 0.1wt% silver nitrate solution, and no chloride ions were detected. The washed solid was loaded into an alumina crucible and placed in a kiln. The temperature was raised to 650°C at a rate of 3°C / min and calcined for 2.5 hours. After cooling, the solid was removed, crushed, and sieved through a 60-mesh sieve to obtain a zirconium oxide powder.

[0075] Example 7

[0076] Example 7 differs from Example 6 in that the weight ratio of zirconium chloride, PVP K30, and AEO-6 in Example 6 is adjusted from 100:1.5:1 to 100:1:0.5. The remaining steps remain unchanged.

[0077] Example 8

[0078] Example 8 differs from Example 6 in that the weight ratio of zirconium chloride, PVP K30, and AEO-6 in Example 6 is adjusted from 100:1.5:1 to 100:1.5:1.5. The remaining steps remain unchanged.

[0079] Example 9

[0080] Example 9 differs from Example 6 in that the concentration of ammonia water in Example 6 is adjusted from 0.1wt% to 0.07wt%. The remaining steps remain unchanged.

[0081] Comparative Example 6

[0082] Comparative Example 6 differs from Example 6 in that the step "0.15wt% ammonia water was added to the precipitate in an amount of 20 times the volume of the precipitate, and stirring was performed for 60 minutes" in Example 6 is omitted. The remaining steps remain unchanged.

[0083] Performance and Result Testing

[0084] The crystal form of the zirconium dioxide powder product of Examples 1-9 and Comparative Examples 1-6 was tested by XRD. The content of monoclinic zirconium dioxide in the zirconium dioxide powder product, i.e., the purity of the zirconium dioxide powder product, was tested by the Rietveld full spectrum fitting method.

[0085] The monoclinic ZrO2 powder yield rate = weight of monoclinic ZrO2 in the product / weight of ZrO2 in the raw zirconium source x 100%.

[0086] The results are shown in Table 1 below.

[0087] Table 1 Performance Test Results

[0088]

[0089] From the data results of Table 1, it can be seen that the monoclinic zirconium dioxide content of the zirconium dioxide powder product obtained by the preparation method of the application reaches 99.5%, and the powder yield is high, which can reach more than 95%. By comparing the various comparative examples, it can be seen that when the pH during precipitation deviates from 7.5-8.5, whether it is acidic or alkaline, it is not conducive to obtaining high-purity monoclinic zirconium dioxide powder, and the powder yield of the powder product is also affected. When the precipitate is not treated with ammonia water, the purity and powder yield of monoclinic zirconium dioxide in the product are reduced. When the precipitant ammonia water solution is replaced with sodium hydroxide solution, even if the pH during precipitation is adjusted, the purity and powder yield of monoclinic zirconium dioxide in the product are both low.

[0090] The specific embodiments are only an explanation of the application, and are not a limitation of the application. Those skilled in the art can make modifications to the embodiments according to the needs after reading the specification, and the modifications do not contribute to the creativity, but are protected by the patent law as long as they are within the scope of the claims of the application.

Claims

1. A method for preparing monoclinic zirconia powder, characterized in that the steps include... include: S1. Dissolve the water-soluble zirconium salt and dispersant in water to prepare a solution A with a zirconium salt concentration of 1.1 mol / L; The water-soluble zirconium salt is selected from zirconium chloride; the dispersant is selected from PVP K30 and AEO-6, and the weight ratio of zirconium chloride, PVP K30 and AEO-6 is 100:1.5:1; S2. Dissolve urea in water to prepare a 12wt% solution B; S3. Simultaneously add solution A from step S1 and solution B from step S2 to the reaction vessel while stirring. The dropping rate of solution A is 40 ml / min, and the dropping rate of solution B is controlled to keep the pH of the reaction system at 8-8.5 to obtain a precipitate. S4. The precipitate described in step S3 is washed with 20 times the volume concentration of 0.15wt% ammonia water and then washed with water until no chloride ions are detected. The precipitate is then heated to 650℃ at a heating rate of 3℃ / min and calcined for 2.5 hours. After cooling, the precipitate is removed, crushed, and sieved to obtain the final product. The absence of chloride ions is achieved by using a 0.1 wt% silver nitrate solution for chloride ion detection.

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