A pyrochlore-structure high-dispersibility lanthanum zirconate nanopowder and a preparation method thereof

Abstract

The application discloses a pyrochlore-structure high-dispersity lanthanum zirconate nanopowder and a preparation method thereof, and belongs to the technical field of lanthanum zirconate nanopowder. The preparation method comprises the following steps: (1) dissolving soluble zirconium salt, tartaric acid and a surfactant in mixed solvent I, adjusting the solution to be neutral to obtain solution A; dissolving soluble lanthanum salt and a surfactant in mixed solvent II to obtain emulsion B; (2) mixing solution A and emulsion B to carry out a mixing reaction, and then washing and filtering to obtain a precursor; and (3) calcining the precursor to obtain the pyrochlore-structure high-dispersity lanthanum zirconate nanopowder. The chemical co-precipitation method is used to synthesize the lanthanum zirconate nanopowder in one step, the synthesized lanthanum zirconate nanopowder is of the pyrochlore structure, has high dispersity and small particle size (50-100 nm). The preparation method is simple and controllable, the required equipment is simple and low in requirement, the reaction temperature is low, the preparation cost is low, and the method is easy to realize large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of lanthanum zirconate nanopowder technology, specifically relating to a highly dispersible lanthanum zirconate nanopowder with a pyrochlore structure and its preparation method. Background Technology

[0002] Lanthanum zirconate (La₂Zr₂O₇, LZO) is an important rare-earth zirconate with a high melting point (2300℃) and low thermal conductivity (1.56 W·m⁻¹ at 1000℃). -1 ·K -1 Lanthanum zirconate (LZO) possesses excellent thermal stability and high tolerance to defects and ultraviolet absorption, making it valuable for applications in curing media materials. In recent years, homogeneous LZO particles with high crystallinity and purity have attracted significant attention and have been used in thermal barrier coatings (TBCs) for engine turbines, as supports for radioactive waste and residual actinides, and as photocatalysts for dye degradation. Among these applications, controllable structure and composition, suitable particle size, and good flowability are prerequisites for obtaining excellent thermal barrier coatings; therefore, researching the powder preparation process is a crucial step in thermal barrier coating preparation.

[0003] Currently, various technologies are used to prepare LZO powder, including traditional solid-state reaction methods, sol-gel methods, hydrothermal methods, self-propagating combustion methods, molten salt methods, and chemical co-precipitation methods. However, these methods all have some drawbacks. For example, CN115536062A provides a method for solid-state synthesis by mixing raw materials through high-energy ball milling. This method requires expensive equipment, consumes a lot of energy, and the synthesis of the product requires high costs. For example, the molten salt method used in CN115010171A and CN110563035A produces powders with irregular morphology and uneven particle size, which does not meet the requirements of high-quality spray coating powders. The sol-gel method requires expensive alkoxides as raw materials, which is costly, and the organic matter released during the powder calcination process pollutes the environment, making it difficult to use for mass production. The chemical precipitation method has a lower reaction temperature, a simpler process, and lower cost, making it suitable for mass production. Moreover, the powder performance has a high reproducibility, which can well meet market needs. However, in existing technologies, such as CN106495692A and CN104843787A, the solidified products or high-viscosity colloids obtained by using glacial acetic acid or ammonia as precipitants do not have ideal dispersion. The precursors need to be treated by salt melting or freeze drying, making it difficult to synthesize in one step.

[0004] Therefore, researching a one-step chemical co-precipitation method to synthesize highly dispersed lanthanum zirconate nanoparticles with uniform particle size below 100 nm using a pyrochlore structure is particularly important for the development of thermal barrier coatings prepared by plasma spraying technology. Summary of the Invention

[0005] In view of the above problems, the application provides a preparation method of pyrochlore structure high dispersibility lanthanum zirconate nano powder, which adopts a chemical coprecipitation method to synthesize the lanthanum zirconate nano powder in one step.

[0006] The application is achieved by the following technical solutions.

[0007] A preparation method of pyrochlore structure high dispersibility lanthanum zirconate nano powder, comprising the following steps:

[0008] (1) Dissolve soluble zirconium salt, tartaric acid and a surfactant in mixed solvent I, dissolve soluble zirconium salt, tartaric acid and a surfactant in mixed solvent I, and after the solution is adjusted to neutral, solution A is obtained; soluble lanthanum salt and a surfactant are dissolved in mixed solvent II to obtain emulsion B;

[0009] (2) Solution A and emulsion B are mixed and reacted, and after washing and filtering, a precursor is obtained;

[0010] (3) The precursor is calcined to obtain pyrochlore structure high dispersibility lanthanum zirconate nano powder.

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

[0012] Further, in step (1), the surfactant is one or more of sodium dodecyl benzene sulfonate, polyvinylpyrrolidone, polyvinyl alcohol and polyethylene glycol.

[0013] Further, 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] Further, in step (1), the mixed solvent I is composed of water, isopropyl alcohol and glycol solvent according to a volume ratio of 1:0.1-0.4:0.01-0.1; and the mixed solvent II is composed of water, ethanol and cis-oleyl primary amine according to a volume ratio of 1:0.1-0.3:0.001-0.05.

[0015] Further, the glycol solvent is one or more of ethylene glycol, propylene glycol and butylene glycol.

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

[0017] Further, in step (3), the calcination temperature is 400-900 DEG C, and the calcination time is 1-8 h.

[0018] A pyrochlore-structured high-dispersibility lanthanum zirconate nanopowder prepared by the preparation method.

[0019] Further, the lanthanum zirconate nanopowder is of pyrochlore structure, high dispersibility, and grain size of 50-100 nm.

[0020] The preparation principle of the pyrochlore-structured high-dispersibility lanthanum zirconate nanopowder of the application is as follows:

[0021] Tartaric acid can efficiently react with lanthanum ions and zirconium ions due to its unique double-carboxyl and double-hydroxyl complex structure; in the microemulsion reaction system, electrostatic repulsion between precursor particles is generated by means of surfactants, which can promote the precipitation of high-dispersibility, uniform and fine precipitated precursors; meanwhile, the solubility of the precipitated precursors in the solution is adjusted by using mixed solvents, so that the precipitated precursors can stably exist and the particle agglomeration phenomenon is effectively avoided; after low-temperature calcination of the high-dispersibility, fine and uniform precipitated precursors, the pyrochlore-structured high-dispersibility lanthanum zirconate nanopowder is finally successfully prepared.

[0022] Compared with the prior art, the application has the following advantages and beneficial effects:

[0023] 1. The lanthanum zirconate nanopowder is synthesized by one-step chemical co-precipitation method, and the synthesized lanthanum zirconate nanopowder is of pyrochlore structure, high dispersibility, small particle size (50-100 nm) and uniform particle size distribution. Compared with the lanthanum zirconate nanopowder (50-200 nm) prepared by traditional methods, the lanthanum zirconate nanopowder of the application has good uniformity of particle size distribution and better dispersibility.

[0024] 2. Tartaric acid has double-carboxyl and double-hydroxyl complex structure in the application, and can react with lanthanum ions and zirconium ions. Tartaric acid can form stable complexes with zirconium salt, stabilize the zirconium salt in neutral solution, and also can be used as a co-precipitation agent of lanthanum and zirconium, so that the precursors of lanthanum and zirconium are uniformly mixed.

[0025] 3. The electrostatic repulsion between precursor particles is generated by means of the cooperation and dosage control (0.1-3wt% of the surfactants in solution A, and 0.1-1wt% of the surfactants in emulsion B) of surfactants such as sodium dodecyl benzene sulfonate and polyvinylpyrrolidone, so that the particle size and dispersibility of the precipitated precursor are controlled.

[0026] 4、The present application respectively prepares solution A containing zirconium and emulsion B containing lanthanum, and then mixes solution A with emulsion B to react, so that the reactants are better dispersed, the contact area between the reactants is increased, and the product has more uniform particle size distribution.

[0027] 5、The mixed solvent I of the present application is composed of water, isopropyl alcohol and diol solvent, and the mixed solvent II is composed of water, ethanol and cis-oleyl primary amine, the interaction between the various components in the mixed solvent makes the particles better dispersed in the solvent, avoids the agglomeration and precipitation of the particles, and thus improves the stability of the dispersion system.

[0028] 6、The small particle size and high activity of the precursor of the present application reduces the calcination temperature (400-900℃), and thus reduces the particle size of the product powder and improves the dispersibility. Compared with the calcination temperature (1000-1200℃) of the traditional method, the calcination temperature of the present application is reduced by 300-600℃, the calcination temperature is low, the preparation cost is low, and the energy consumption is low.

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

[0030] Figure 1 The XRD pattern of the lanthanum zirconate nano-powder prepared for Examples 1-5.

[0031] Figure 2 The SEM pattern of the lanthanum zirconate nano-powder prepared for Example 1.

[0032] Figure 3 The SEM pattern of the lanthanum zirconate nano-powder prepared for Example 2.

[0033] Figure 4 The SEM pattern of the lanthanum zirconate nano-powder prepared for Example 3.

[0034] Figure 5 The SEM pattern of the lanthanum zirconate nano-powder prepared for Example 4.

[0035] Figure 6 The SEM pattern of the lanthanum zirconate nano-powder prepared for Example 5.

[0036] Figure 7 The SEM pattern of the lanthanum zirconate nano-powder prepared for Example 1 after granulation. DETAILED DESCRIPTION

[0037] The present application will be further described in detail by the following examples, which are only used to illustrate the present application and do not limit the protection scope of the present application.

[0038] Example 1

[0039] Preparation of pyrochlore-structured lanthanum zirconate nanopowder:

[0040] (1) Zirconium oxychloride, DL-tartaric acid and surfactant polyvinylpyrrolidone were dissolved in mixed solvent I (consisting of water, isopropyl alcohol and propylene glycol in a volume ratio of 1:0.1:0.01), and ammonia water was added to adjust the solution to neutral, to obtain solution A. The mass ratio of tartaric acid to soluble zirconium salt in solution A was 2:1, the molar concentration of zirconium ions was 0.1 mol / L, and the content of polyvinylpyrrolidone was 0.1wt% of the volume of solution A.

[0041] (2) Lanthanum chloride and surfactant sodium dodecylbenzenesulfonate were dissolved in mixed solvent II (consisting of water, ethanol and cis-oleyl primary amine in a volume ratio of 1:0.1:0.001) to obtain emulsion B. The molar concentration of lanthanum ions in emulsion B was 0.1 mol / L, and the content of sodium dodecylbenzenesulfonate was 0.01wt% of the volume of emulsion B.

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

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

[0044] Example 2

[0045] Preparation of pyrochlore-structured lanthanum zirconate nanopowder:

[0046] (1) Zirconium chloride, DL-tartaric acid and surfactant polyvinylpyrrolidone were dissolved in mixed solvent I (consisting of water, isopropyl alcohol and propylene glycol in a volume ratio of 1:0.2:0.05), and ammonia water was added to adjust the solution to neutral, to obtain solution A. The mass ratio of tartaric acid to soluble zirconium salt in solution A was 2:1, the molar concentration of zirconium ions was 0.1 mol / L, and the content of polyvinylpyrrolidone was 0.5wt% of the volume of solution A.

[0047] (2) Lanthanum nitrate and surfactants polyvinyl alcohol and polyethylene glycol were dissolved in mixed solvent II (consisting 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 was 0.1 mol / L, and the content of polyvinyl alcohol and polyethylene glycol was 0.05wt% of the volume of emulsion B.

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

[0049] (4) Calcining the precursor in a box furnace at 900°C for 4h to obtain pyrochlore-structured high-dispersity lanthanum zirconate nanometer powder.

[0050] Example 3

[0051] Preparation of pyrochlore-structured high-dispersity lanthanum zirconate nanometer powder:

[0052] (1) Dissolve zirconium chloride, DL-tartaric acid and surfactant polyvinyl alcohol in mixed solvent I (consisting of water, isopropyl alcohol and butanediol in a volume ratio of 1:0.3:0.05), and add ammonia water to adjust the solution to neutral, to 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 is 1wt% of the volume of solution A.

[0053] (2) Dissolve lanthanum chloride and surfactant polyethylene glycol in mixed solvent II (consisting 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 the content of polyethylene glycol is 0.1wt% of the volume of emulsion B.

[0054] (3) Mix solution A and emulsion B in a volume ratio of 1:1 by stirring dropwise, and then wash and dry the obtained precipitate to obtain the precursor.

[0055] (4) Calcine the precursor in a box furnace at 900°C for 4h to obtain pyrochlore-structured high-dispersity lanthanum zirconate nanometer powder.

[0056] Example 4

[0057] Preparation of pyrochlore-structured high-dispersity lanthanum zirconate nanometer powder:

[0058] (1) Dissolve zirconium nitrate, zirconium chloride, DL-tartaric acid, and surfactants polyvinylpyrrolidone and polyvinyl alcohol in mixed solvent I (consisting of a mixed solution of water, isopropyl alcohol, propylene glycol and butanediol in a volume ratio of 1:0.3:0.1), and add ammonia water to adjust the solution to neutral, to 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 polyvinylpyrrolidone and polyvinyl alcohol is 2wt% of the volume of solution A.

[0059] (2) Dissolve lanthanum nitrate and lanthanum chloride with surfactant sodium dodecyl benzene sulfonate and polyethylene glycol in mixed solvent II (consisting of water, ethanol, cis-oleyl primary amine mixed 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 the content of sodium dodecyl benzene sulfonate and polyethylene glycol in emulsion B is 0.5wt% of the volume.

[0060] (3) Mix solution A with emulsion B in a volume ratio of 2:1 by stirring dropwise, and then mix them to carry out a reaction. After washing and drying the obtained precipitate, a precursor is obtained.

[0061] (4) Calcine the precursor in a box furnace at 900℃ for 1h to obtain pyrochlore-structured high-dispersity lanthanum zirconate nanometer powder.

[0062] Example 5

[0063] Preparation of pyrochlore-structured high-dispersity lanthanum zirconate nanometer powder:

[0064] (1) Dissolve zirconium chloride and zirconium oxychloride, DL-tartaric acid and surfactant polyvinylpyrrolidone in mixed solvent I (consisting of a mixed solution of water, isopropanol, ethylene glycol and propylene glycol mixed in a volume ratio of 1:0.4:0.1), and then add ammonia water to adjust the solution to neutral. Solution A is obtained. 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 polyvinylpyrrolidone in solution A is 3wt% of the volume.

[0065] (2) Dissolve lanthanum chloride with surfactant sodium dodecyl benzene sulfonate in mixed solvent II (consisting of water, ethanol, cis-oleyl primary amine mixed in a volume ratio of 1:0.3:0.05) to obtain emulsion B. The molar concentration of lanthanum ions in emulsion B is 1 mol / L, and the content of sodium dodecyl benzene sulfonate in emulsion B is 1wt% of the volume.

[0066] (3) Mix solution A with emulsion B in a volume ratio of 3:1 by stirring dropwise, and then mix them to carry out a reaction. After washing and drying the obtained precipitate, a precursor is obtained.

[0067] (4) Calcine the precursor in a box furnace at 900℃ for 1h to obtain pyrochlore-structured high-dispersity lanthanum zirconate nanometer powder.

[0068] Comparative Example 1

[0069] A green preparation method of nanometer lanthanum zirconate powder disclosed in patent CN115010171A is taken as comparative example 1. The patent discloses that after the reactants La2O3, ZrO2 and NaCl-KCl mixed salt are uniformly ball-milled and mixed, sintering is carried out at 1000-1200℃ for 2-5h to obtain nanometer La2Zr2O7 powder with a particle size of 50-200nm.

[0070] Comparative Example 2

[0071] Using a rare earth zirconate nanoparticle and its preparation method and application disclosed in patent CN110563035A as comparative example 2, the patent discloses mixing rare earth oxides, zirconium oxide, molten salt and anhydrous ethanol, and calcining the resulting mixture at 1000-1200℃ for 2-8 hours to obtain rare earth zirconate nanoparticles 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 using X-ray diffraction (XRD). The results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the lanthanum zirconate nanopowders prepared in Examples 1-5 are all pyrochlore structures, and there are no other impurity phases in the powder.

[0075] (II) Scanning Electron Microscopy (SEM) Analysis

[0076] The lanthanum zirconate nanopowders prepared in Examples 1-5 were characterized and analyzed using scanning electron microscopy (SEM), and the results are as follows: Figures 2-6 As shown. By Figures 2-4 It can be seen that the lanthanum zirconate nanoparticles prepared in Examples 1-3 are uniformly distributed, have clearly distinguishable outlines, and a grain size of approximately 50 nm, exhibiting high dispersibility and small particle characteristics. Figure 5 It can be seen that the lanthanum zirconate nanoparticles prepared in Example 4 have uniform particle distribution, clearly distinguishable outlines, and a grain size of approximately 65 nm, exhibiting high dispersibility and small particle characteristics. Figure 6 It can be seen that the lanthanum zirconate nanoparticles prepared in Example 5 have uniform particle distribution, clearly distinguishable outlines, and a grain size of approximately 100 nm, exhibiting high dispersibility and small particle characteristics. Figure 7 It can be seen that the lanthanum zirconate nanoparticles prepared in Example 1 have good sphericity and flowability after granulation, which meets the requirements of high-quality spray coating powder.

[0077] From the above SEM analysis, the particle size of the lanthanum zirconate nanopowder in the examples 1-5 is 50-100 nm, the particle size distribution is uniform, and the calcination temperature required in the preparation process of the lanthanum zirconate nanopowder is 400-900 ℃, while the particle size of the lanthanum zirconate nanopowder in the comparative examples 1 and 2 is 50-200 nm, the particle size distribution is not uniform, and the calcination temperature is 1000-1200 ℃, the calcination temperature is high. Compared with the comparative examples 1 and 2, the particle size of the lanthanum zirconate nanopowder of the present application is below 100 nm, the particle size distribution is uniform, the dispersibility is better, the preparation temperature is lower, and the large-scale industrial production is easier.

[0078] The above merely provides the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a pyrochlore-structured lanthanum zirconate nanopowder having high dispersibility, characterized by, The method comprises the following steps: (1) dissolving a soluble zirconium salt, tartaric acid and a surfactant in mixed solvent I to obtain solution A after adjusting the solution to neutral; dissolving a soluble lanthanum salt and a surfactant in mixed solvent II to obtain emulsion B; the surfactant is one or more of sodium dodecyl benzene sulfonate, polyvinylpyrrolidone, polyvinyl alcohol and polyethylene glycol; the mixed solvent I is composed of water, isopropyl alcohol and glycol solvent according to 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 according to a volume ratio of 1:0.1-0.3:0.001-0.05; (2) mixing solution A and emulsion B to react, washing and filtering to obtain a precursor; (3) calcining the precursor to obtain pyrochlore-structured high-dispersity lanthanum zirconate nano-powder.

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

3. The method for preparing highly dispersed lanthanum zirconate nanoparticles with a pyrochlore structure 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.

4. The method for preparing highly dispersed lanthanum zirconate nanoparticles with a pyrochlore structure according to claim 1, characterized in that, In step (1), the glycol solvent is one or more of ethylene glycol, propylene glycol and butylene glycol.

5. The method for preparing highly dispersed lanthanum zirconate nanoparticles with a pyrochlore structure according to claim 1, characterized in that, In step (2), the volume ratio of solution A to emulsion B is 1-3:

1.

6. The method for preparing highly dispersed lanthanum zirconate nanoparticles with a pyrochlore structure according to claim 1, characterized in that, In step (3), the calcination temperature is 400-900 ℃, and the calcination time is 1-8 h.

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