Pyrochlore structure high-dispersity lanthanum zirconate nano-powder and preparation method thereof

Abstract

The invention discloses high-dispersity lanthanum zirconate nano-powder with a pyrochlore structure and a preparation method of the high-dispersity lanthanum zirconate nano-powder, and belongs to the technical field of lanthanum zirconate nano-powder. The preparation method comprises the following steps: (1) dissolving soluble zircon salt, tartaric acid and a surfactant in a mixed solvent I, and adjusting the solution to be neutral to obtain a solution A; dissolving soluble lanthanum salt and a surfactant in a mixed solvent II to obtain an emulsion B; (2) carrying out mixed reaction on the solution A and the emulsion B, washing and filtering to obtain a precursor; and (3) calcining the precursor to obtain the high-dispersity lanthanum zirconate nano-powder with the pyrochlore structure. The lanthanum zirconate nano-powder is synthesized in one step by adopting a chemical coprecipitation method, and the synthesized lanthanum zirconate nano-powder is of a pyrochlore structure and has the characteristics of high dispersity and small particles (50-100nm). The preparation method is simple and controllable in process, simple in required equipment, low in requirement, low in reaction temperature, low in preparation cost and easy for large-scale industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of lanthanum zirconate nanopowders, and specifically relates to a pyrochlore structure highly dispersible lanthanum zirconate nanopowder and a preparation method thereof. Background Art

[0002] Lanthanum zirconate (La 2 Zr 2 O 7 , LZO) is an important rare earth zirconate with high melting point (2300℃), low thermal conductivity (1.56W·m at 1000℃) and -1 ·K -1 ), excellent thermal stability and high tolerance to defects and UV absorption, so it has important application value in curing medium materials. In recent years, homogeneous LZO particles with high crystallinity and high purity have attracted widespread attention and have been used for thermal barrier coatings (TBCs) of engine turbines, carriers of radioactive waste and residual actinides, and photocatalysts for dye degradation. Among them, lanthanum zirconate powder with controllable structural components, suitable particle size and good fluidity is the prerequisite for obtaining excellent thermal barrier coatings, so studying the preparation process of powder is also an important part of the preparation of thermal barrier coatings.

[0003] At present, a variety of technologies have been used to prepare LZO powder, including traditional solid phase reaction method, sol-gel method, hydrothermal method, self-propagating combustion method, molten salt method, chemical coprecipitation method, etc., but these methods all have some disadvantages. For example, CN115536062A provides a method of mixing raw materials by high-energy ball milling and then solid phase synthesis. The equipment required for synthesis in this method is expensive, the energy consumption is high, and the synthesis of the product requires a very high cost; for example, the molten salt method used in CN115010171A and CN110563035A, the synthesized powder has irregular morphology and uneven particle size, which does not meet the requirements of high-quality spray powder; and the sol-gel method requires expensive alcohol salt as raw material, which is costly, and the organic matter released during the roasting process of the powder pollutes the environment, so it is difficult to use for mass production; the chemical precipitation method has a low reaction temperature, a simple process, and a low cost, which is suitable for mass production, and the repetition rate of powder performance is high, which can well meet market needs. However, in the existing technologies, such as the solids or high-viscosity colloids obtained by using glacial acetic acid or ammonia water as precipitants provided in CN106495692A and CN104843787A, the dispersion is not ideal, and the precursor needs to be treated secondary by salt melting or freeze drying, which is difficult to synthesize in one step.

[0004] Therefore, it is particularly important to study the development of plasma spraying technology to prepare thermal barrier coatings by one-step synthesis of lanthanum zirconate nanopowders with high dispersion and uniform particle size below 100 nm by chemical co-precipitation method. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for preparing a pyrochlore structure highly dispersible lanthanum zirconate nanopowder, which uses a chemical coprecipitation method to synthesize the lanthanum zirconate nanopowder in one step. The synthesized lanthanum zirconate nanopowder has a pyrochlore structure, is highly dispersible, has small particles (50 to 100 nm), and has uniform particle size distribution. The preparation method of the present invention is simple, the required equipment is simple, the reaction temperature is low, the preparation cost is low, and it is suitable for large-scale industrial production.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for preparing a pyrochlore structure highly dispersible lanthanum zirconate nanopowder comprises the following steps:

[0008] (1) dissolving a soluble zirconium salt, tartaric acid and a surfactant in a mixed solvent I, adjusting the solution to neutrality to obtain a solution A; dissolving a soluble lanthanum salt and a surfactant in a mixed solvent II to obtain an emulsion B;

[0009] (2) mixing solution A and emulsion B for reaction, washing and filtering to obtain a precursor;

[0010] (3) After calcining the precursor, a pyrochlore structured highly dispersed lanthanum zirconate nanopowder is obtained.

[0011] Furthermore, in step (1), the mass ratio of the soluble zirconium salt and tartaric acid in the solution A is 1:1-5, the molar concentration of zirconium ions is 0.1-1 mol / L, and the surfactant accounts for 0.1-3 wt% of the volume of the solution A; the molar concentration of lanthanum ions in the emulsion B is 0.1-1 mol / L, and the surfactant accounts for 0.1-1 wt% of the volume of the emulsion B.

[0012] Furthermore, in step (1), the surfactant is one or more of sodium dodecylbenzene sulfonate, polyvinyl pyrrolidone, polyvinyl alcohol and polyethylene glycol.

[0013] Furthermore, in step (1), the soluble zirconium salt is one or more of zirconium nitrate, zirconium chloride and zirconium oxychloride; and the soluble lanthanum salt is one or more of lanthanum nitrate and lanthanum chloride.

[0014] Furthermore, in step (1), the mixed solvent I is composed of water, isopropanol and a glycol solvent in a volume ratio of 1:0.1-0.4:0.01-0.1; the mixed solvent II is composed of water, ethanol and cis-oleyl primary amine in a volume ratio of 1:0.1-0.3:0.001-0.05.

[0015] Furthermore, the diol solvent is one or more of ethylene glycol, propylene glycol and butanediol.

[0016] Furthermore, in step (2), the volume ratio of solution A to emulsion B is 1 to 3:1.

[0017] Furthermore, in step (3), the calcination temperature is 400-900° C., and the calcination time is 1-8 hours.

[0018] A pyrochlore structured highly dispersed lanthanum zirconate nano powder prepared by the preparation method as described above.

[0019] Furthermore, the lanthanum zirconate nanopowder has a pyrochlore structure, is highly dispersible, and has a grain size of 50 to 100 nm.

[0020] The preparation principle of the pyrochlore structure highly dispersible lanthanum zirconate nanopowder of the present invention is:

[0021] Tartaric acid, with its unique dicarboxyl and dihydroxyl composite structure, can efficiently react with lanthanum ions and zirconium ions; in the microemulsion reaction system, the electrostatic repulsion between the precursor particles is generated with the help of surfactants, which can promote the precipitation of highly dispersed, uniform and fine precipitation precursors; at the same time, the solubility of the precipitation precursor in the solution is adjusted by using a mixed solvent, so that the precipitation precursor can exist stably, effectively avoiding the occurrence of particle agglomeration; after low-temperature calcination of this highly dispersed, fine and uniform precipitation precursor, a pyrochlore structured highly dispersed lanthanum zirconate nanopowder was finally successfully prepared.

[0022] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0023] 1. The present invention adopts a chemical coprecipitation method to synthesize lanthanum zirconate nanopowder in one step. The synthesized lanthanum zirconate nanopowder has a pyrochlore structure and has the characteristics of high dispersion, small particles (50-100nm), and uniform particle size distribution. Compared with the lanthanum zirconate nanopowder (50-200nm) prepared by the traditional method, the lanthanum zirconate nanopowder of the present invention has good uniformity of particle size distribution and better dispersibility.

[0024] 2. Tartaric acid in the present invention has a double carboxyl and double hydroxyl composite structure, and can react with lanthanum ions and zirconium ions. Tartaric acid can form a stable complex with zirconium salts to stabilize zirconium salts in a neutral solution, and can also serve as a coprecipitant of lanthanum and zirconium, so that the precursors of lanthanum and zirconium are evenly mixed.

[0025] 3. The present invention generates electrostatic repulsion between precursor particles by combining and regulating the dosage of surfactants such as sodium dodecylbenzene sulfonate and polyvinyl pyrrolidone (the surfactant accounts for 0.1 to 3 wt% of the volume of solution A and 0.1 to 1 wt% of the volume of emulsion B), thereby controlling the particle size and dispersibility of the precipitate precursor.

[0026] 4. The present invention prepares a zirconium-containing solution A and a lanthanum-containing emulsion B respectively, and mixes the solution A and the emulsion B for reaction. The emulsion reaction can better disperse the reactants, increase the contact area between the reactants, and make the product particle size distribution more uniform.

[0027] 5. The mixed solvent I of the present invention is composed of a mixture of water, isopropanol and a glycol solvent, and the mixed solvent II is composed of a mixture of water, ethanol and cis-oleyl primary amine. The interaction between the various components in the mixed solvent enables the particles to be better dispersed in the solvent, avoiding agglomeration and precipitation of the particles, thereby improving the stability of the dispersed system.

[0028] 6. The small particle size and high activity precursor of the present invention reduces the calcination temperature (400-900°C), thereby reducing the particle size of the product powder and improving the dispersibility. At the same time, compared with the calcination temperature (1000-1200°C) of the traditional method, the calcination temperature of the present invention is reduced by 300-600°C, the calcination temperature is low, and the preparation cost is low.

[0029] 7. The preparation method of the present invention has simple and controllable process, simple and low requirements for the equipment required, low reaction temperature, low preparation cost, low energy consumption, high environmental protection, and is easy for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The XRD diagrams of the lanthanum zirconate nanopowders prepared in Examples 1-5 are shown respectively.

[0031] Figure 2 This is the SEM image of the lanthanum zirconate nanopowder prepared in Example 1.

[0032] Figure 3 This is the SEM image of the lanthanum zirconate nanopowder prepared in Example 2.

[0033] Figure 4 This is the SEM image of the lanthanum zirconate nanopowder prepared in Example 3.

[0034] Figure 5 This is the SEM image of the lanthanum zirconate nanopowder prepared in Example 4.

[0035] Figure 6 This is the SEM image of the lanthanum zirconate nanopowder prepared in Example 5.

[0036] Figure 7This is a SEM image of the lanthanum zirconate nanopowder prepared in Example 1 after granulation. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below by way of examples. These examples are only used to illustrate the present invention and do not limit the protection scope of the present invention.

[0038] Example 1

[0039] Preparation of pyrochlore structured highly dispersed lanthanum zirconate nanopowders:

[0040] (1) Dissolve zirconium oxychloride, DL-tartaric acid and surfactant polyvinyl pyrrolidone in a mixed solvent I (composed of water, isopropanol and propylene glycol in a volume ratio of 1:0.1:0.01), add ammonia water to adjust the solution to neutrality, and obtain solution A. The mass ratio of tartaric acid to soluble zirconium salt in solution A is 2:1, the molar concentration of zirconium ions is 0.1 mol / L, and the content of polyvinyl pyrrolidone accounts for 0.1 wt% of the volume of solution A.

[0041] (2) Lanthanum chloride and a surfactant sodium dodecylbenzene sulfonate are dissolved in a mixed solvent II (composed of water, ethanol, and cis-oleyl primary amine in a volume ratio of 1:0.1:0.001) to obtain an emulsion B. The molar concentration of lanthanum ions in the emulsion B is 0.1 mol / L, and the sodium dodecylbenzene sulfonate accounts for 0.01 wt% of the volume of the emulsion B.

[0042] (3) Solution A and emulsion B are mixed and reacted by stirring and dropping in a volume ratio of 1:1, and the resulting precipitate is washed and dried to obtain a precursor.

[0043] (4) The precursor was calcined in a box furnace at 400° C. for 8 h to obtain a pyrochlore structured highly dispersed lanthanum zirconate nanopowder.

[0044] Example 2

[0045] Preparation of pyrochlore structured highly dispersed lanthanum zirconate nanopowders:

[0046] (1) Dissolve zirconium chloride, DL-tartaric acid and surfactant polyvinyl pyrrolidone in a mixed solvent I (composed of water, isopropanol and ethylene glycol in a volume ratio of 1:0.2:0.05), add ammonia water to adjust the solution to neutrality, and obtain solution A. The mass ratio of tartaric acid to soluble zirconium salt in solution A is 2:1, the molar concentration of zirconium ions is 0.1 mol / L, and the content of polyvinyl pyrrolidone accounts for 0.5 wt% of the volume of solution A.

[0047] (2) Lanthanum nitrate and surfactants polyvinyl alcohol and polyethylene glycol are dissolved in a mixed solvent II (composed of water, ethanol, and cis-oleyl primary amine in a volume ratio of 1:0.2:0.01) to obtain emulsion B. The molar concentration of lanthanum ions in emulsion B is 0.1 mol / L, and polyvinyl alcohol and polyethylene glycol account for 0.05 wt% of the volume of emulsion B.

[0048] (3) Solution A and emulsion B are mixed and reacted by stirring and dropping in a volume ratio of 1:1, and the resulting precipitate is washed and dried to obtain a precursor.

[0049] (4) The precursor was calcined in a box furnace at 900° C. for 4 h to obtain a pyrochlore structured highly dispersed lanthanum zirconate nanopowder.

[0050] Example 3

[0051] Preparation of pyrochlore structured highly dispersed lanthanum zirconate nanopowders:

[0052] (1) Dissolve zirconium chloride, DL-tartaric acid and surfactant polyvinyl alcohol in a mixed solvent I (composed of water, isopropanol and butanediol in a volume ratio of 1:0.3:0.05), add ammonia water to adjust the solution to neutrality, and obtain solution A. The mass ratio of tartaric acid to soluble zirconium salt in solution A is 3:1, the molar concentration of zirconium ions is 0.1 mol / L, and the content of polyvinyl alcohol accounts for 1 wt% of the volume of solution A.

[0053] (2) Lanthanum chloride and surfactant polyethylene glycol are dissolved in a mixed solvent II (composed of water, ethanol, and cis-oleyl primary amine in a volume ratio of 1:0.2:0.02) to obtain emulsion B. The molar concentration of lanthanum ions in emulsion B is 0.1 mol / L, and polyethylene glycol accounts for 0.1 wt% of the volume of emulsion B.

[0054] (3) Solution A and emulsion B are mixed and reacted by stirring and dropping in a volume ratio of 1:1, and the resulting precipitate is washed and dried to obtain a precursor.

[0055] (4) The precursor was calcined in a box furnace at 900° C. for 4 h to obtain a pyrochlore structured highly dispersed lanthanum zirconate nanopowder.

[0056] Example 4

[0057] Preparation of pyrochlore structured highly dispersed lanthanum zirconate nanopowders:

[0058] (1) Dissolve zirconium nitrate, zirconium chloride, DL-tartaric acid, and surfactants polyvinyl pyrrolidone and polyvinyl alcohol in a mixed solvent I (composed of a mixed solution of water, isopropanol, propylene glycol, and butanediol in a volume ratio of 1:0.3:0.1), add ammonia water to adjust the solution to neutrality, and obtain solution A. The mass ratio of tartaric acid to soluble zirconium salt in solution A is 1:1, the molar concentration of zirconium ions is 1 mol / L, and the content of polyvinyl pyrrolidone and polyvinyl alcohol accounts for 2 wt% of the volume of solution A.

[0059] (2) Lanthanum nitrate and lanthanum chloride, and surfactants sodium dodecylbenzene sulfonate and polyethylene glycol are dissolved in a mixed solvent II (composed of water, ethanol, and cis-oleyl primary amine in a volume ratio of 1:0.3:0.03) to obtain emulsion B. The molar concentration of lanthanum ions in emulsion B is 1 mol / L, and sodium dodecylbenzene sulfonate and polyethylene glycol account for 0.5 wt% of the volume of emulsion B.

[0060] (3) Solution A and emulsion B are mixed and reacted by stirring and dropping in a volume ratio of 2:1, and the resulting precipitate is washed and dried to obtain a precursor.

[0061] (4) The precursor was calcined in a box furnace at 900° C. for 1 h to obtain pyrochlore structured highly dispersed lanthanum zirconate nanopowder.

[0062] Example 5

[0063] Preparation of pyrochlore structured highly dispersed lanthanum zirconate nanopowders:

[0064] (1) Dissolve zirconium chloride and zirconium oxychloride, DL-tartaric acid and a surfactant polyvinyl pyrrolidone in a mixed solvent I (composed of a mixed solution of water, isopropanol, ethylene glycol and propylene glycol in a volume ratio of 1:0.4:0.1), add ammonia water to adjust the solution to neutrality, and obtain a solution A. The mass ratio of tartaric acid to soluble zirconium salt in solution A is 1:1, the molar concentration of zirconium ions is 1 mol / L, and the content of polyvinyl pyrrolidone accounts for 3 wt% of the volume of solution A.

[0065] (2) Lanthanum chloride and a surfactant sodium dodecylbenzene sulfonate are dissolved in a mixed solvent II (composed of water, ethanol, and cis-oleyl primary amine in a volume ratio of 1:0.3:0.05) to obtain an emulsion B. The molar concentration of lanthanum ions in the emulsion B is 1 mol / L, and the sodium dodecylbenzene sulfonate accounts for 1 wt% of the volume of the emulsion B.

[0066] (3) Solution A and emulsion B are mixed and reacted by stirring and dropping in a volume ratio of 3:1, and the resulting precipitate is washed and dried to obtain a precursor.

[0067] (4) The precursor was calcined in a box furnace at 900° C. for 1 h to obtain pyrochlore structured highly dispersed lanthanum zirconate nanopowder.

[0068] Comparative Example 1

[0069] A green preparation method of nano-lanthanum zirconate powder disclosed in patent CN115010171A is used as comparative example 1. The patent discloses that the reactant La 2 O 3 、ZrO 2 After being evenly mixed with NaCl-KCl mixed salt by ball milling, the mixture was sintered at 1000-1200℃ for 2-5h to obtain nano-La with a particle size of 50-200nm. 2 Zr 2 O 7 powder.

[0070] Comparative Example 2

[0071] A rare earth zirconate nanopowder and its preparation method and application disclosed in patent CN110563035A are used as comparative example 2. The patent discloses mixing rare earth oxide, zirconium oxide, molten salt and anhydrous ethanol, calcining the resulting mixture at 1000-1200°C for 2-8h to obtain a rare earth zirconate nanopowder with a particle size of 50-200nm.

[0072] Material Characterization Analysis

[0073] (I) X-ray diffraction (XRD) analysis

[0074] The lanthanum zirconate nanopowders prepared in Examples 1-5 were characterized and analyzed by X-ray diffractometer (XRD). Figure 1 As shown. Figure 1 It can be seen that the lanthanum zirconate nanopowders prepared in Examples 1-5 are all of pyrochlore structure, and there are no other impurities in the powders.

[0075] (ii) Scanning electron microscopy (SEM) analysis

[0076] The lanthanum zirconate nanopowders prepared in Examples 1-5 were characterized and analyzed using a scanning electron microscope (SEM). Figure 2-6 As shown. Figure 2-4 It can be seen that the lanthanum zirconate nanopowders prepared in Examples 1-3 have uniform particle distribution, clear and discernible outlines, and a grain size of about 50 nm, showing high dispersibility and small particle characteristics. Figure 5 It can be seen that the lanthanum zirconate nanopowder prepared in Example 4 has uniform particle distribution, clear and discernible outline, and a grain size of about 65 nm, showing high dispersibility and small particle characteristics. Figure 6It can be seen that the lanthanum zirconate nanopowder prepared in Example 5 has uniform particle distribution, clear and discernible outline, and a grain size of about 100 nm, showing high dispersibility and small particle characteristics. Figure 7 It can be seen that the lanthanum zirconate nanopowder prepared in Example 1 has good sphericity and fluidity after granulation, and meets the requirements of high-quality spray powder.

[0077] From the above SEM analysis, it can be seen that the particle size of the lanthanum zirconate nanopowder in Examples 1-5 of the present invention is 50-100nm, the particle size distribution is uniform, and the calcination temperature required in the preparation process of the lanthanum zirconate nanopowder is 400-900°C, while the particle size of the lanthanum zirconate nanopowder in Comparative Examples 1 and 2 is 50-200nm, the particle size distribution is uneven, and the calcination temperature is 1000-1200°C, which is high. Compared with Comparative Examples 1 and 2, the particle size of the lanthanum zirconate nanopowder of the present invention is below 100nm, the particle size distribution is uniform, the dispersibility is better, the preparation temperature is lower, and it is easier to mass industrialize.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a pyrochlore structured highly dispersible lanthanum zirconate nanopowder, characterized in that: The following steps are involved: (1) dissolving a soluble zirconium salt, tartaric acid and a surfactant in a mixed solvent I, and adjusting the solution to neutrality to obtain a solution A; dissolving a soluble lanthanum salt and a surfactant in a mixed solvent II to obtain an emulsion B; (2) mixing solution A and emulsion B for reaction, washing and filtering to obtain a precursor; (3) After calcining the precursor, a pyrochlore structured highly dispersed lanthanum zirconate nanopowder is obtained.

2. The method for preparing pyrochlore structure highly dispersible lanthanum zirconate nanopowder according to claim 1, characterized in that: In step (1), the mass ratio of the soluble zirconium salt and tartaric acid in the solution A is 1:1-5, the molar concentration of zirconium ions is 0.1-1 mol / L, and the surfactant accounts for 0.1-3 wt% of the volume of the solution A; the molar concentration of lanthanum ions in the emulsion B is 0.1-1 mol / L, and the surfactant accounts for 0.1-1 wt% of the volume of the emulsion B.

3. The method for preparing pyrochlore structure highly dispersible lanthanum zirconate nanopowder according to claim 1, characterized in that: In step (1), the surfactant is one or more of sodium dodecylbenzene sulfonate, polyvinyl pyrrolidone, polyvinyl alcohol and polyethylene glycol.

4. The method for preparing pyrochlore structure highly dispersible lanthanum zirconate nanopowder according to claim 1, characterized in that: In step (1), the soluble zirconium salt is one or more of zirconium nitrate, zirconium chloride and zirconium oxychloride; the soluble lanthanum salt is one or more of lanthanum nitrate and lanthanum chloride.

5. The method for preparing pyrochlore structure highly dispersible lanthanum zirconate nanopowder according to claim 1, characterized in that: In step (1), the mixed solvent I is composed of water, isopropanol and glycol solvent in a volume ratio of 1:0.1-0.4:0.01-0.1; the mixed solvent II is composed of water, ethanol and cis-oleyl primary amine in a volume ratio of 1:0.1-0.3:0.001-0.

05.

6. The method for preparing pyrochlore structure highly dispersible lanthanum zirconate nanopowder according to claim 5, characterized in that: The glycol solvent is one or more of ethylene glycol, propylene glycol and butylene glycol.

7. The method for preparing pyrochlore structure highly dispersible lanthanum zirconate nanopowder according to claim 1, characterized in that: In step (2), the volume ratio of solution A to emulsion B is 1 to 3:

1.

8. The method for preparing pyrochlore structure highly dispersible lanthanum zirconate nanopowder according to claim 1, characterized in that: In step (3), the calcination temperature is 400-900° C., and the calcination time is 1-8 hours.

9. A pyrochlore structured highly dispersed lanthanum zirconate nanopowder obtained by the preparation method according to any one of claims 1 to 8.

10. The pyrochlore structure highly dispersible lanthanum zirconate nanopowder according to claim 9, characterized in that: The lanthanum zirconate nano powder is of pyrochlore structure, highly dispersible, and has a grain size of 50 to 100 nm.

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