Superfine lanthanum zirconate powder and preparation method thereof

Abstract

The invention provides superfine lanthanum zirconate powder and a preparation method thereof, and belongs to the technical field of powder preparation. The preparation method comprises the following steps: mixing soluble zirconium salt, soluble lanthanum salt and water to obtain a lanthanum-zirconium solution; adding the lanthanum-zirconium solution and a precipitant into a polyacrylic acid solution for precipitation reaction to obtain a precipitate; the precipitate is sequentially washed and fired, the superfine lanthanum zirconate powder is obtained, the pH value of a washing solution used for washing ranges from 8 to 8.5, and the firing temperature ranges from 1000 DEG C to 1200 DEG C. According to the preparation method, PAA is added as a dispersing agent to inhibit grain aggregation, specifically, the lanthanum-zirconium solution and a precipitator are added into a polyacrylic acid solution for a precipitation reaction, the pH value of a washing solution and the temperature of firing are limited, and therefore the superfine nano lanthanum zirconate powder is prepared and is small in particle size and free of aggregation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of powder preparation, and particularly relates to a superfine lanthanum zirconate powder and a preparation method thereof. BACKGROUND

[0002] Lanthanum zirconate (La2Zr2O7) has the advantages of good thermal stability, low thermal conductivity, high radiation resistance and the like, and is mainly applied to the fields of high-temperature insulation, high-temperature resistant catalyst carrier, high-temperature superconducting buffer layer and solid electrolyte. The particle size plays a key role in the application, and the smaller the particle size, the larger the specific surface area, and the physical and chemical activity of the particles is enhanced. At present, the solid phase method and the precipitation method are mainly used in industrial production. The solid phase reaction method needs to be sintered to 1500 DEG C, and a long time of heat preservation is needed to obtain the pyrochlore structure La2Zr2O7. The powder obtained by the method has the problems of uneven micro-mixing, composition segregation, uneven microstructure and serious agglomeration. The precipitation method has a lower reaction temperature and a low implementation cost, and is more suitable for industrial production. However, the precipitation, washing, filtration and drying processes of the precipitate are prone to agglomeration, and the final powder particles are large, with D50 greater than 10 μm. SUMMARY

[0003] Therefore, the present application aims to provide a superfine lanthanum zirconate powder and a preparation method thereof. The superfine lanthanum zirconate powder prepared by the present application has a small particle size and does not agglomerate.

[0004] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions. The present application provides a preparation method of a superfine lanthanum zirconate powder, comprising the following steps: Mixing a soluble zirconium salt, a soluble lanthanum salt and water to obtain a lanthanum-zirconium solution; Adding the lanthanum-zirconium solution and a precipitant into a polyacrylic acid (PAA) solution to perform a precipitation reaction, to obtain a precipitate; Washing and calcining the precipitate in sequence to obtain the superfine lanthanum zirconate powder, wherein the pH value of the washing liquid used in the washing is 8-8.5, and the temperature of the calcining is 1000-1200 DEG C.

[0005] Preferably, the molar ratio of La element to Zr element in the lanthanum-zirconium solution is 1:1.

[0006] Preferably, the concentration of La element in the lanthanum-zirconium solution is not greater than 1 mol / L.

[0007] Preferably, the concentration of the polyacrylic acid solution is 1-10 g / L.

[0008] Preferably, the volume ratio of the polyacrylic acid solution to the lanthanum-zirconium solution is 1-2:1.

[0009] Preferably, the adding rate of the lanthanum-zirconium solution into the polyacrylic acid solution is 200-500 mL / min.

[0010] Preferably, the pH value of the system during the precipitation reaction is 8-12.

[0011] Preferably, the burning time is 2-6 h.

[0012] Preferably, the molar ratio of the precipitant to the La element in the soluble lanthanum salt is preferably 4-10:1.

[0013] The application also provides the superfine lanthanum zirconate powder prepared by the preparation method.

[0014] Compared with the prior art, the application has the following beneficial effects: The application adds PAA as a dispersant to inhibit grain agglomeration, and specifically limits the adding of the lanthanum-zirconium solution and the precipitant into the polyacrylic acid solution for the precipitation reaction, the pH value of the washing liquid and the burning temperature, so that the superfine nanometer lanthanum zirconate powder is prepared, the particle size is small, and the superfine nanometer lanthanum zirconate powder is not agglomerated. Meanwhile, the operation is simple, industrial raw materials are used, the cost is low, the burning temperature is 1000-1200 ℃, the application is more energy-saving and environment-friendly, and the application is expected to be used for industrialized production of superfine nanometer lanthanum zirconate.

[0015] The application also provides the superfine lanthanum zirconate powder prepared by the preparation method, the D50 of the superfine lanthanum zirconate powder is 400-600 nm, and the grain size is 20-100 nm. The application improves the problem that a large particle is easily formed in a conventional precipitation method, and makes the product be a superfine nanometer particle. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The SEM image of the superfine lanthanum zirconate powder prepared in Example 1 is shown in FIG. 1. Figure 2 The laser diffraction particle size distribution curve of the superfine lanthanum zirconate powder prepared in Example 1 is shown in FIG. 2. Figure 3 The X-ray diffraction analysis diagram of the superfine lanthanum zirconate powder prepared in Example 1 is shown in FIG. 3. Figure 4 The SEM image of the superfine lanthanum zirconate powder prepared in Example 2 is shown in FIG. 4. Figure 5 The laser diffraction particle size distribution curve of the superfine lanthanum zirconate powder prepared in Example 2 is shown in FIG. 5. Figure 6 The SEM image of the superfine lanthanum zirconate powder prepared in Example 3 is shown in FIG. 6. Figure 7A laser diffraction particle size distribution curve of the ultrafine lanthanum zirconate powder prepared for Example 3; Figure 8 An X-ray diffraction analysis chart of the powder prepared for Comparative Example 1; Figure 9 An SEM chart of the powder prepared for Comparative Example 1; Figure 10 An SEM chart of the powder prepared for Comparative Example 2; Figure 11 An SEM chart of the powder prepared for Comparative Example 3; Figure 12 A laser diffraction particle size distribution curve of the powder prepared for Comparative Example 4; Figure 13 A laser diffraction particle size distribution curve of the powder prepared for Comparative Example 5. DETAILED DESCRIPTION

[0017] The present application provides a preparation method of an ultrafine lanthanum zirconate powder, comprising the following steps: Mixing a soluble zirconium salt, a soluble lanthanum salt and water to obtain a lanthanum-zirconium solution; Adding the lanthanum-zirconium solution and a precipitant into a polyacrylic acid solution to perform a precipitation reaction, to obtain a precipitate; Washing and calcining the precipitate in sequence, to obtain the ultrafine lanthanum zirconate powder, wherein the pH value of the washing liquid used for the washing is 8-8.5, and the temperature of the calcining is 1000-1200℃.

[0018] In the present application, the raw materials used are all commercially available goods in the art, unless otherwise specified.

[0019] The present application mixes a soluble zirconium salt, a soluble lanthanum salt and water to obtain a lanthanum-zirconium solution.

[0020] In the present application, the soluble zirconium salt preferably comprises one or more of zirconium oxychloride, zirconium chloride and zirconium nitrate.

[0021] In the present application, the soluble lanthanum salt preferably comprises lanthanum chloride and / or lanthanum nitrate.

[0022] In the present application, the molar ratio of La element to Zr element in the lanthanum-zirconium solution is preferably 1:1.

[0023] The present application preferably first prepares a soluble lanthanum salt aqueous solution, adds the soluble zirconium salt into the soluble lanthanum salt aqueous solution, and then adds water to obtain the lanthanum-zirconium solution.

[0024] In the present application, the concentration of La element in the lanthanum-zirconium solution is preferably not more than 1 mol / L, and specifically can be 0.25, 0.5 or 1 mol / L.

[0025] After obtaining the lanthanum-zirconium solution, the lanthanum-zirconium solution is added into the polyacrylic acid solution with a precipitant to perform a precipitation reaction, so as to obtain a precipitate.

[0026] In the present application, the concentration of the polyacrylic acid solution is preferably 1-10 g / L, and specifically can be 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 g / L.

[0027] In the present application, the volume ratio of the polyacrylic acid solution to the lanthanum-zirconium solution is preferably 1-2:1, and specifically can be 1:1, 20:15 or 2:1.

[0028] In the present application, the adding rate of the lanthanum-zirconium solution into the polyacrylic acid solution is preferably 200-500 mL / min, and specifically can be 200, 300, 400 or 500 mL / min. The polyacrylic acid solution plays a role of dispersing particles, and in combination with adding the lanthanum-zirconium solution into the polyacrylic acid solution, agglomeration into large particles is prevented, and the particle size is reduced.

[0029] In the present application, the lanthanum-zirconium solution and the precipitant are preferably simultaneously added into the polyacrylic acid solution, and then stirring is performed to perform the precipitation reaction.

[0030] In the present application, the stirring speed is preferably 150-250 rpm, and specifically can be 150, 200 or 250 rpm.

[0031] In the present application, the precipitant is preferably ammonia water and / or ammonium bicarbonate solution, and the concentration of the precipitant is preferably 2-3 mol / L.

[0032] In the present application, the molar ratio of the precipitant to La element is preferably 4-10:1, and specifically can be 4:1, 6:1, 8:1, 9.6:1 or 10:1.

[0033] In the present application, the pH value of the system in the process of the precipitation reaction is preferably 8-12, and specifically can be 8, 9, 10, 11 or 12. The present application preferably controls the pH value of the system in the precipitation by adjusting the flow of the precipitant.

[0034] In the present application, the temperature of the precipitation reaction is preferably room temperature, and the time is preferably 30-120 min, and specifically can be 30, 60, 90 or 120 min.

[0035] After the precipitation reaction is completed, the present application preferably removes the mother liquor by filtration to obtain the precipitate.

[0036] After the precipitate is obtained, the precipitate is sequentially washed and calcined to obtain the superfine lanthanum zirconate powder, the pH value of the washing liquid used in the washing is 8-8.5, and specifically can be 8 or 8.5, and the temperature of the calcination is 1000-1200 ℃, and specifically can be 1000, 1100 or 1200 ℃.

[0037] The deionized water is preferably adjusted in pH value by using ammonia water to obtain the washing liquid.

[0038] The specific parameters of the washing are not particularly limited in the present application, and the method well known to those skilled in the art can be used.

[0039] After the washing is completed, the obtained washing material is preferably dried by microwave, and then the calcination is performed. The specific parameters of the microwave drying are not particularly limited in the present application, and the drying can be completed.

[0040] In the present application, the time of the calcination is preferably 2-6 h, and specifically can be 2, 3, 4, 5 or 6 h.

[0041] The present application also provides a superfine lanthanum zirconate powder prepared by the preparation method, and the D50 of the superfine lanthanum zirconate powder is 400-600 nm, and specifically can be 471, 580 or 583 nm, and the grain size is 20-100 nm.

[0042] The technical solutions in the present application will be clearly and completely described below by combining with the embodiments in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0043] Embodiment 1 3.75 mol of zirconium oxychloride is dissolved in a lanthanum chloride solution (wherein the amount of substance of the lanthanum chloride is 3.75 mol), deionized water is added to make up to 15 L, the concentration of Zr element is 0.25 mol / L, the lanthanum zirconium solution is added to a 20 L, 3 g / L PAA solution at a speed of 500 mL / min, 3 mol / L ammonia water is added at the same time, the flow rate (average speed is 400 mL / min) of the ammonia water is adjusted to control the pH value of the system to be maintained at 8-8.5, the total volume of the added ammonia water is 12 L, the precipitation time is 30 min, the stirring speed during the precipitation process is 250 rpm, after the precipitation reaction is completed, the mother liquor is immediately filtered, washed with weakly alkaline water (deionized water is adjusted in pH value by using ammonia water to obtain the weakly alkaline water) with a pH value of 8, dried by microwave, and then calcined at 1000 ℃ for 6 h to obtain a superfine lanthanum zirconate powder, Figure 1The SEM image of the superfine lanthanum zirconate powder prepared in Example 1 shows that the crystal grains are 20-100 nm, Figure 2 The laser diffraction particle size distribution curve of the superfine lanthanum zirconate powder prepared in Example 1 shows that the D50 is 0.583 µm, Figure 3 The X-ray diffraction analysis chart of the superfine lanthanum zirconate powder prepared in Example 1 shows that the phase is lanthanum zirconate La2Zr2O7.

[0044] Example 2 7.5 mol of zirconium chloride was dissolved in a lanthanum chloride solution (wherein the amount of substance of the lanthanum chloride was 7.5 mol), deionized water was added to make up to 15 L, the concentration of Zr element was 0.5 mol / L, the lanthanum-zirconium solution was added to a 20 L, 5 g / L PAA solution at a speed of 250 mL / min, while 2 mol / L of ammonium bicarbonate solution was added, the flow rate of the ammonium bicarbonate solution was adjusted (the average speed was 250 mL / min) to control the pH value of the system to be maintained at 8-8.5 at all times, the total volume of the ammonium bicarbonate solution was 15 L, the precipitation time was 60 min, the stirring speed during the precipitation process was 250 rpm, the mother liquor was immediately filtered after the completion of the precipitation reaction, washed with weakly alkaline water (deionized water was adjusted to weakly alkaline water by using ammonia water to adjust the pH value), and then dried by microwave, and then calcined at 1000°C for 4 h to obtain a superfine lanthanum zirconate powder, Figure 4 The SEM image of the superfine lanthanum zirconate powder prepared in Example 2 shows that the crystal grains are 20-100 nm, Figure 5 The laser diffraction particle size distribution curve of the superfine lanthanum zirconate powder prepared in Example 2 shows that the D50 is 0.580 µm, and the X-ray diffraction analysis of the superfine lanthanum zirconate powder prepared in Example 2 shows that the phase is lanthanum zirconate La2Zr2O7.

[0045] Example 3 24 mol of zirconium oxychloride was dissolved in a lanthanum nitrate solution (wherein the amount of substance of the lanthanum nitrate was 24 mol), deionized water was added to make up to 24 L, the concentration of Zr element was 1 mol / L, the lanthanum-zirconium solution was added to a 20 L, 10 g / L PAA solution at a speed of 200 mL / min, while a mixed solution composed of 24 L of 3 mol / L ammonium bicarbonate solution and 24 L of 1 mol / L ammonia water was added, the flow rate of the mixed solution was adjusted (the average flow rate was 480 mL / min) to control the pH value of the system to be maintained at 8-8.5 at all times, the precipitation time was 120 min, the stirring speed during the precipitation process was 250 rpm, the mother liquor was immediately filtered after the completion of the precipitation reaction, washed with weakly alkaline water (deionized water was adjusted to weakly alkaline water by using ammonia water to adjust the pH value), and then dried by microwave, and then calcined at 1200°C for 4 h to obtain a superfine lanthanum zirconate powder, Figure 6 The SEM image of the superfine lanthanum zirconate powder prepared in Example 3 shows that the crystal grains are 20-100 nm,Figure 7 The laser diffraction particle size distribution curve of the superfine lanthanum zirconate powder prepared in Example 3 shows that the D50 is 0.471 µm. The X-ray diffraction analysis of the superfine lanthanum zirconate powder prepared in Example 3 shows that the phase is lanthanum zirconate La2Zr2O7.

[0046] Comparative Example 1 The same as Example 1, the only difference is that the pH value is 7.5 when precipitating, and the calcination temperature is 850℃. The X-ray diffraction analysis of the prepared powder is shown in Figure 8 , which shows that the phase is LaOCl, ZrO2 and La2Zr2O7, Figure 9 The SEM image of the powder of Comparative Example 1 shows that the prepared powder is micron-level particles.

[0047] Comparative Example 2 The same as Example 1, the only difference is that the PAA solution is replaced by deionized water during the precipitation reaction, and deionized water is used for washing, Figure 10 The SEM image of the powder prepared in Comparative Example 2 shows that the prepared powder is micron-level particles.

[0048] Comparative Example 3 The same as Example 1, the only difference is that ammonia is added to the lanthanum zirconium solution, and the precipitation reaction is carried out at a system pH value of 8.5 for 5 min, Figure 11 The SEM image of the powder prepared in Comparative Example 3 shows that the prepared powder is micron-level particles.

[0049] Comparative Example 4 The same as Example 1, the only difference is that deionized water and alcohol are used for washing, and a forced air drying oven is used for drying at 120℃. The prepared powder is detected by a laser particle size instrument to detect the median diameter D50, Figure 12 The laser diffraction particle size distribution curve of the powder prepared in Comparative Example 4 shows that the D50 is 48.48 µm.

[0050] Comparative Example 5 The same as Example 1, the only difference is that the lanthanum zirconium solution is added to the ammonia water, the system pH value is 8.5, the dropping time is 0.5 h, and the stirring is continued for 1 h after the dropping is completed. Deionized water and alcohol are used for washing, and the prepared powder is detected by a laser particle size instrument to detect the median diameter D50, Figure 13 The laser diffraction particle size distribution curve of the powder prepared in Comparative Example 5 shows that the D50 is 15.24 µm.

[0051] The above only describes the preferred embodiments of the present application, and does not limit the present application in any form. It should be noted that for ordinary skilled persons in the art, some improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing ultrafine lanthanum zirconate powder, characterized in that, Includes the following steps: A lanthanum-zirconium solution is obtained by mixing a soluble zirconium salt, a soluble lanthanum salt, and water. The lanthanum-zirconium solution and the precipitant were added to a polyacrylic acid solution to carry out a precipitation reaction, and a precipitate was obtained. The precipitate was washed and calcined sequentially to obtain the ultrafine lanthanum zirconate powder. The washing solution used for washing had a pH of 8 to 8.5, and the calcination temperature was 1000 to 1200°C.

2. The preparation method according to claim 1, characterized in that, The molar ratio of La to Zr in the lanthanum-zirconium solution is 1:

1.

3. The preparation method according to claim 1 or 2, characterized in that, The concentration of La in the lanthanum-zirconium solution is no greater than 1 mol / L.

4. The preparation method according to claim 1, characterized in that, The concentration of the polyacrylic acid solution is 1~10 g / L.

5. The preparation method according to claim 1 or 4, characterized in that, The volume ratio of the polyacrylic acid solution to the lanthanum zirconium solution is 1~2:

1.

6. The preparation method according to claim 1, characterized in that, The lanthanum-zirconium solution is added to the polyacrylic acid solution at a rate of 200-500 mL / min.

7. The preparation method according to claim 1 or 6, characterized in that, The pH value of the system during the precipitation reaction is 8~12.

8. The preparation method according to claim 1, characterized in that, The burning time is 2 to 6 hours.

9. The preparation method according to claim 1, characterized in that, The molar ratio of the precipitant to the La element in the soluble lanthanum salt is 4~10:

1.

10. The ultrafine lanthanum zirconate powder prepared by the preparation method according to any one of claims 1 to 9, characterized in that, The ultrafine lanthanum zirconate powder has a D50 of 400~600nm and a grain size of 20~100nm.

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