阅读说明：本技术 一种镱/钆/钇三元共掺氧化锆纳米结构团聚球体及其生产方法 (Yb/Gd/Y ternary codoped zirconia nanostructure agglomerated sphere and production method thereof ) 是由 罗丽荣 靳洪允 周明 侯书恩 于 2021-01-29 设计创作，主要内容包括：本发明公开了一种镱/钆/钇三元共掺氧化锆纳米结构团聚球体及其生产方法。本发明包括如下步骤：将镱盐、钆盐、钇盐和氯氧化锆搅拌均匀后得到混合溶液；将沉淀剂逐步加入到混合溶液中静置老化后得到氢氧化物胶体；错流洗涤；共沸蒸馏：与分散剂进行混合进行蒸馏和碳化处理,获得粉体；高温煅烧得四方相纳米粉末；四方相纳米粉体经气流磨处理；采用喷雾干燥技术将该胶体制备成微米级的团聚球体；筛分；去除球体中的水分；等离子二次球化得尺寸范围符合要求的球体。本发明通过共沉淀法结合膜分离、共沸蒸馏和气流磨粉碎技术,获得分散性较好的粉末,把纳米粉末做成纳米结构团聚球,为高性能纳米陶瓷热障涂层的制备奠定基础。(The invention discloses an ytterbium/gadolinium/yttrium ternary codoped zirconia nanostructure agglomerated sphere and a production method thereof. The invention comprises the following steps: uniformly stirring ytterbium salt, gadolinium salt, yttrium salt and zirconium oxychloride to obtain a mixed solution; gradually adding a precipitator into the mixed solution, standing and aging to obtain hydroxide colloid; cross-flow washing; azeotropic distillation: mixing with dispersant, distilling and carbonizing to obtain powder; calcining at high temperature to obtain tetragonal nanometer powder; the tetragonal phase nano powder is treated by jet milling; preparing the colloid into micron-sized agglomerated spheres by adopting a spray drying technology; screening; removing water in the ball body; and performing secondary spheroidization on the plasma to obtain the spheres with the size range meeting the requirement. The invention combines the coprecipitation method with the membrane separation, azeotropic distillation and airflow grinding technology to obtain powder with better dispersibility, and the nano powder is made into the nano-structure agglomerated balls to lay the foundation for preparing the high-performance nano ceramic thermal barrier coating.)

1. A production method of an ytterbium/gadolinium/yttrium ternary codoped zirconia nanostructure agglomerated sphere is characterized by comprising the following steps:

s1, preparing a mixed solution: respectively dissolving ytterbium salt, gadolinium salt, yttrium salt and zirconium oxychloride in deionized water to prepare salt solutions with certain concentration, mixing according to a certain molar ratio, and uniformly stirring to obtain mixed solutions;

s2, precipitant neutralization experiment: gradually adding a precipitator into the mixed solution to form a precipitate, stirring, standing and aging to obtain a hydroxide colloid;

s3, cross-flow washing: washing the obtained hydroxide colloid in a cross flow manner, washing with deionized water, and removing impurity ions after repeated washing to obtain hydroxide precipitate;

s4, azeotropic distillation: mixing the obtained hydroxide precipitate with a certain amount of alcohol dispersant, and distilling and carbonizing at a certain temperature to obtain powder;

s5, high-temperature calcination: calcining the obtained powder at a certain temperature to obtain tetragonal nano powder;

s6, airflow milling treatment: performing jet milling on the tetragonal nano powder obtained in the step S5 to obtain nano powder with better dispersibility;

s7, spray drying and primary granulation: mixing the nano powder obtained in the step S6 with deionized water to prepare aqueous suspension colloid, and preparing the colloid into micron-sized agglomerated spheres by adopting a spray drying technology;

s8, screening: screening the agglomerated spheres obtained in the step S7 through a screening machine to obtain spheres with the size of 20-100 microns;

s9, spray drying powder heat treatment: carrying out heat treatment on the spheres screened in the step S8 to remove water in the spheres;

s10, plasma secondary spheroidizing: and (4) densifying the spheres dried in the step S9 by using a plasma spheroidizing technology to obtain the ytterbium/gadolinium/yttrium codoped zirconia nanostructure agglomerated spheres with good fluidity and size range meeting the requirement.

2. The method for producing an ytterbium/gadolinium/yttrium ternary co-doped zirconia nanostructure agglomerate sphere according to claim 1, wherein the respective salt solutions in step S1 have yttrium ion, ytterbium ion, gadolinium ion and zirconium ion concentrations of 0.1-1 mol/L, and the mixed solution is doped with ions: the molar ratio of yttrium ions, ytterbium ions and gadolinium ions is 5-1: 1: 1, the molar ratio of the doping ions to the zirconium ions is 1/24-2/3.

3. The method for producing the ytterbium/gadolinium/yttrium ternary codoped zirconia nanostructure agglomerated sphere according to claim 2, wherein in step S2, the precipitating agent comprises ammonia water and ammonium oxalate, wherein the concentration of the ammonia water is 20 to 50 wt.%, the PH of the solution after the addition is maintained at a PH >10, the stirring time is 1 to 6 hours, and the aging standing time is 12 to 24 hours.

4. The method for producing the ytterbium/gadolinium/yttrium ternary codoped zirconia nanostructured agglomerated sphere according to claim 3, wherein the cross-flow washing process in the step S3 adopts a ceramic membrane separation technology, the pore diameter of the adopted ceramic membrane is 0.1-0.5 μm, and the precipitate is repeatedly washed with deionized water until the pH value of the washed supernatant is 7 and no precipitate is generated by reaction with silver nitrate.

5. The method of claim 4, wherein the alcohol dispersant of step S4 includes but is not limited to n-butanol, n-propanol, ethylene glycol, isopropanol, isobutanol, or n-pentanol.

6. The method for producing ytterbium/gadolinium/yttrium ternary codoped zirconia nanostructured agglomerated spheres according to claim 5, wherein the mass ratio of the alcohol dispersant to the hydroxide precipitate in the step S4 is 1: 2-5: 1, the distillation and carbonization temperature is 80-200 ℃, and the time is 6-48 h.

7. The method for producing the ytterbium/gadolinium/yttrium ternary codoped zirconia nanostructured agglomerated sphere according to claim 6, wherein the high-temperature calcination treatment temperature in the step S5 is 600-1300 ℃, and the heat preservation time is 1-20 hours.

8. The method for producing the ytterbium/gadolinium/yttrium ternary codoped zirconia nanostructured agglomerated sphere according to claim 1, wherein the mass ratio of the nanopowder mixed with the deionized water in the step S7 is 1: 1-1: 5; the spray drying method of step S7 includes a two-fluid type or a centrifugal type.

9. The method for producing an ytterbium/gadolinium/yttrium ternary codoped zirconia nanostructure agglomerate according to claim 1, wherein the screen mesh adopted in the screening process in step S8 is 100-600 mesh, so as to obtain a nanostructure agglomerate meeting the spraying standard; the heat treatment temperature of the step S9 is 200-500 ℃, and the heat treatment time is 10-100 min; the plasma used in the densification process of step S10 may be a direct current plasma or a high frequency induction plasma, the temperature range of which is 5000 to 10000 ℃, and the gases used include air, argon, nitrogen and hydrogen.

10. An ytterbium/gadolinium/yttrium ternary co-doped zirconia nanostructured agglomerate sphere, characterized by being prepared by the preparation method according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of ceramic materials, in particular to an ytterbium/gadolinium/yttrium ternary co-doped zirconia nanostructure agglomerated sphere and a production method thereof.

Background

6-8 wt.% yttrium-Stabilized Zirconia (YSZ) is the most widely used and studied ceramic layer material for thermal barrier coatings at present. With the development of the aero-engine towards high efficiency and high thrust-weight ratio, the inlet temperature of the turbine is greatly increased. This places a demand on higher service temperatures on the ceramic material of its surface layer. And the YSZ can generate phase change and sintering at the temperature of more than 1200 ℃, thereby greatly influencing the high-temperature service stability and the service life of the YSZ. In order to further improve the service temperature of the thermal barrier coating, the current research hotspots in China and abroad mainly include: (1) the development of novel thermal barrier coating materials with better high temperature stability and lower thermal conductivity, such as rare earth zirconates; (2) by doping the YSZ material with single elements or multiple elements, the phase transition temperature and the sintering resistance of the material are improved, and the thermal conductivity of the material is further reduced.

Meanwhile, researches report that compared with the conventional structural coating, the nano-structured thermal barrier coating has better bonding strength, sintering resistance, lower thermal conductivity and elastic modulus, thereby showing better high-temperature stability and service life. In general, by adjusting the plasma spraying parameters, part of the nano YSZ material in an unmelted or semi-melted state can be retained in the laminated melting layer area, so that the coating has a 'double' structure. The nano-coating having a dual structure has better sintering resistance mainly due to the porous nano-domains having higher surface energy and thus greater sintering driving force and tendency to shrink. Larger pores are formed during the sintering process. The formation of these voids will compensate for densification shrinkage caused by sintering of part of the layered region, thereby reducing or delaying the rate of deterioration of the coating properties, such as reduction in fracture toughness, increase in thermal conductivity, and increase in elastic modulus. In addition, the double structure can keep the better bonding performance of the coating by melting the better layered region, and meanwhile, the nano region has more micro cracks, holes and grain boundaries, so that the coating has better crack propagation resistance, and the strain tolerance and the fracture toughness of the coating are increased. The nanocoating also exhibits better phase stability, higher coefficient of thermal expansion and apparent density.

Plasma spraying is the most widely applied technology for preparing thermal barrier coatings at present. During plasma spraying, the ceramic particles are in a molten or partially molten state, and the particle size and morphology of the powder can obviously change the microstructure and performance of the coating. The impulse of the nano powder is small due to small size, so that the nano powder cannot be deposited and form a coating under the action of an air flow beam in the spraying process. Therefore, there is a need to address the delivery of nanopowders during the thermal spray coating of nanostructured materials.

Disclosure of Invention

The invention aims to provide an ytterbium/gadolinium/yttrium ternary codoped zirconia nanostructure agglomerated sphere with good high-temperature stability, low thermal conductivity and high thermal expansion coefficient and a production method thereof aiming at the defects in the prior art.

The invention relates to a method for producing an ytterbium/gadolinium/yttrium ternary codoped zirconia nanostructure agglomerated sphere, which comprises the following steps:

s1, preparing a mixed solution: respectively dissolving ytterbium salt, gadolinium salt, yttrium salt and zirconium oxychloride in deionized water to prepare salt solutions with certain concentration, mixing according to a certain molar ratio, and uniformly stirring to obtain mixed solutions;

s2, precipitant neutralization experiment: gradually adding a precipitator into the mixed solution to form a precipitate, stirring, standing and aging to obtain a hydroxide colloid;

s3, cross-flow washing: washing the obtained hydroxide colloid in a cross flow manner, washing with deionized water, and removing impurity ions after repeated washing to obtain hydroxide precipitate;

s4, azeotropic distillation: mixing the obtained hydroxide precipitate with a certain amount of alcohol dispersant, and distilling and carbonizing at a certain temperature to obtain powder;

s5, high-temperature calcination: calcining the obtained powder at a certain temperature to obtain tetragonal nano powder;

s6, airflow milling treatment: performing jet milling on the tetragonal nano powder obtained in the step S5 to obtain nano powder with better dispersibility;

s7, spray drying and primary granulation: mixing the nano powder obtained in the step S6 with deionized water to prepare aqueous suspension colloid, and preparing the colloid into micron-sized agglomerated spheres by adopting a spray drying technology;

s8, screening: screening the agglomerated spheres obtained in the step S7 through a screening machine to obtain spheres with the size of 20-100 microns;

s9, spray drying powder heat treatment: carrying out heat treatment on the spheres screened in the step S8 to remove water in the spheres;

s10, plasma secondary spheroidizing: and (4) densifying the spheres dried in the step S9 by using a plasma spheroidizing technology to obtain the ytterbium/gadolinium/yttrium codoped zirconia nanostructure agglomerated spheres with good fluidity and size range meeting the requirement.

Further, the concentrations of yttrium ions, ytterbium ions, gadolinium ions and zirconium ions in the salt solutions in step S1 are 0.1 to 1mol/L, and the mixed solution is doped with ions: the molar ratio of yttrium ions, ytterbium ions and gadolinium ions is 5-1: 1: 1, the molar ratio of the doping ions to the zirconium ions is 1/24-2/3.

Further, in step S2, the precipitant includes ammonia water and ammonium oxalate, wherein the concentration of the ammonia water is 20-50 wt.%, the PH of the added solution should be maintained at a PH >10, the stirring time is 1-6 hours, and the aging standing time is 12-24 hours.

Further, a ceramic membrane separation technology is adopted in the cross-flow washing process in the step S3, the aperture of the adopted ceramic membrane is 0.1-0.5 mu m, and the precipitate is repeatedly washed by deionized water until the pH value of the washed supernatant is 7 and the precipitate does not react with silver nitrate to generate precipitate.

Further, the alcohol dispersant of step S4 includes, but is not limited to, n-butanol, n-propanol, ethylene glycol, isopropanol, isobutanol, or n-pentanol.

Further, the mass ratio of the alcohol dispersant to the hydroxide precipitate in step S4 is 1: 2-5: 1, the distillation and carbonization temperature is 80-200 ℃, and the time is 6-48 h.

Further, the high-temperature calcination treatment temperature in the step S5 is 600-1300 ℃, and the heat preservation time is 1-20 hours.

Further, the mixing mass ratio of the nano powder and the deionized water in the step S7 is 1: 1-1: 5; the spray drying method of step S7 includes a two-fluid type or a centrifugal type.

Further, the screen mesh adopted in the screening process in the step S8 is 100-600 meshes, so that the nano-structure agglomerated spheres meeting the spraying standard are obtained; the heat treatment temperature of the step S9 is 200-500 ℃, and the heat treatment time is 10-100 min; the plasma used in the densification process of step S10 may be a direct current plasma or a high frequency induction plasma, the temperature range of which is 5000 to 10000 ℃, and the gases used include air, argon, nitrogen and hydrogen.

An ytterbium/gadolinium/yttrium ternary codoped zirconia nanostructure agglomerated sphere is prepared by the preparation method.

Compared with the prior art, the technical scheme provided by the invention has the advantages that:

1) the co-precipitation method is combined with membrane separation, azeotropic distillation and jet milling crushing technologies to obtain ytterbium/gadolinium/yttrium ternary co-doped nano zirconia powder with good dispersibility. In the process, the performance of the powder is optimized by combining multi-element doping, and the problem of agglomeration of the nano powder in the preparation process is solved.

2) The ytterbium/gadolinium/yttrium ternary codoped nano zirconia powder prepared by the preparation method can show a stable tetragonal phase structure according to different doping contents, has good high-temperature stability (the phase stability temperature can reach more than 1300 ℃), low thermal conductivity and high thermal expansion coefficient, and can obtain nano powder with particle size distribution below 50 nm.

3) No additive is added in the spray drying process, and agglomerated powder is directly formed, so that pollution is avoided, and the high purity of the powder is ensured.

4) By adopting the spray drying primary granulation and the instant plasma densification technology (secondary granulation), under the condition of ensuring the sphericity, density and fluidity of the sphere, the growth of nano-crystalline grains in the agglomerated sphere is limited, namely the nano-structure of the agglomerated sphere is kept, and the nano-powder is made into the agglomerated sphere with the nano-structure, thereby laying the foundation for preparing the high-performance nano-ceramic thermal barrier coating.

5) The whole process flow has simple equipment and easily controlled process parameters, and is suitable for continuous large-scale production.

Drawings

FIG. 1 is a flow chart of the preparation of an ytterbium/gadolinium/yttrium three-element co-doped zirconia nanostructured agglomerated sphere of the present invention;

FIG. 2 is a schematic X-ray powder diffraction diagram of an ytterbium/gadolinium/yttrium tri-element co-doped zirconia nanostructured agglomerated sphere of the present invention and a method for producing the same, the sphere in example 1;

FIG. 3 is a scanning electron micrograph of the surface of an ytterbium/gadolinium/yttrium triple doped zirconia nanostructured agglomerate sphere of the present invention and the method of producing the same as in example 1;

FIG. 4 is a scanning electron micrograph of a cross-section of an ytterbium/gadolinium/yttrium triple doped zirconia nanostructured agglomerate sphere of the present invention and a method for producing the same as in example 2;

FIG. 5a is a cross-sectional scanning electron micrograph of a thermal barrier coating prepared by an atmospheric plasma spray process of ytterbium, gadolinium and yttrium ternary co-doped zirconia nanostructured agglomerate spheres prepared in example 2;

fig. 5b is a scanning electron micrograph of a ceramic layer cross-section of the thermal barrier coating in fig. 5 a.

Detailed Description

The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.

Example 1:

as shown in fig. 1, yttrium nitrate, ytterbium nitrate and gadolinium nitrate are dissolved in deionized water to prepare a nitrate solution of 0.2mol/L, and zirconium oxychloride is dissolved in deionized water to prepare a solution of 0.5 mol/L. Mixing the solution according to the proportion to obtain molar ratio yttrium ions: ytterbium ion: gadolinium ions: zirconium ion ═ 20: 10: 10: 60, respectively. The mixed solution was dropped dropwise into an ammonium oxalate solution to form a precipitate. Obtaining hydroxide precipitate after stirring, aging and standing, wherein the stirring time is 2 hours, and the precipitation aging time is 12 hours. And carrying out cross-flow washing treatment on the precipitate to remove impurity ions. And (3) mixing the washed hydroxide precipitate and n-butanol according to the mass ratio of 1: 3 mixing and stirring evenly, and placing in a drying and distilling device at 150 ℃ for azeotropic distillation dehydration drying treatment. And calcining the powder in a high-temperature furnace at 1000 ℃ for 2 hours, and crushing the powder by using a jet mill to obtain the nano powder with good dispersibility. The nano powder and deionized water are mixed according to the mass ratio of 1: 2, and uniformly stirring to obtain the nano powder suspension colloid with certain viscosity. Subsequently, micron-sized agglomerated spheres were obtained by spray drying. In the spray drying process, the air inlet temperature is 200 ℃, the air outlet temperature is 120 ℃, the dried powder is obtained, the obtained powder is mechanically screened to obtain spheres with the particle size range of 30-80 mu m, and then the spheres are placed into a high-temperature furnace at 400 ℃ for heat preservation for 30min for further dehydration treatment. And finally, performing densification treatment on the spherical powder by adopting a plasma technology, wherein the temperature is 8000-10000 ℃. Finally obtaining the hollow ytterbium, gadolinium and yttrium codoped zirconia nano-structure agglomerated spheres with the size distribution of 30-80 mu m and the grain size of less than 100nm

The X-ray diffraction analysis (XRD) of the ytterbium, gadolinium and yttrium ternary codoped zirconia nanostructure agglomerate prepared in example 1 was performed, and the obtained spectrum result is shown in fig. 2, and the structure is a tetragonal phase.

Example 2:

mixing yttrium nitrate, ytterbium nitrate and zirconium nitrate solution with the concentration of 0.1mol/L and zirconium oxychloride solution with the concentration of 0.5mol/L in proportion to obtain yttrium ions with the molar ratio: ytterbium ion: gadolinium ions: zirconium ion ═ 2: 2: 1: 95, and (b) mixing the solution. Dropwise adding the mixed solution into 50% ammonia water to form precipitate, keeping the pH value of the solution at 9, stirring for 2h, and standing the solution for precipitation and aging for 24 h. The obtained hydroxide colloid was then subjected to repeated cross-flow washing until the solution pH was 7 and no chloride ions were present in the solution (no precipitation with silver nitrate). And (3) mixing the washed hydroxide precipitate with isopropanol according to the mass ratio of 1: 2 mixing and stirring evenly, and placing in a drying and distilling device at 200 ℃ for azeotropic distillation dehydration drying treatment. And calcining the powder in a high-temperature furnace at 1100 ℃ for 1h, and carrying out jet milling treatment to obtain the nano powder with good dispersibility. The nano powder and deionized water are mixed according to the mass ratio of 1: 3, mixing the components in proportion, and stirring the mixture evenly to obtain the nano powder suspension colloid with certain viscosity. Subsequently, micron-sized agglomerated spheres were obtained by spray drying. In the spray drying process, the air inlet temperature is 180 ℃, the air outlet temperature is 120 ℃, dried powder is obtained, the obtained powder is mechanically screened to obtain spheres with the particle size range of 20-100 mu m, and then the spheres are placed into a high-temperature furnace at 500 ℃ for heat preservation for 20min for further dehydration treatment. And finally, carrying out densification treatment on the spherical powder by adopting a plasma technology, wherein the temperature is 7000-10000 ℃. Finally obtaining the ytterbium, gadolinium and yttrium three-element co-doped zirconia nano-structure agglomerated spheres with hollow structures, wherein the sizes of the ytterbium, gadolinium and yttrium three-element co-doped zirconia nano-structure agglomerated spheres are 20-100 mu m in size distribution and the grain sizes of the ytterbium, gadolinium and yttrium three-element co-doped zirconia nano-structure agglomerated spheres are smaller than 100 nm.

The ytterbium, gadolinium and yttrium ternary codoped zirconia nanostructure agglomerated sphere prepared in example 2 was subjected to a scanning electron microscope test, and the obtained powder surface is shown in fig. 3, and the sphere has high sphericity and good fluidity. The surface scanning image of the sphere is shown in fig. 4, which shows that the sphere is a hollow structure, the outer shell layer is compact and consists of nano-crystalline grains, and the powder is favorable for preparing the nano-structured thermal barrier coating with high deposition efficiency and high porosity. The cross-sectional scans of the thermal barrier coating and the ceramic layer prepared by the sphere are shown in fig. 5a and 5b, the coating has unfused nano-particle areas besides holes and cracks, and the nano structure can enable the coating to have better strain tolerance, anti-sintering performance and lower thermal conductivity.

The above is not relevant and is applicable to the prior art.

While certain specific embodiments of the present invention have been described in detail by way of illustration, it will be understood by those skilled in the art that the foregoing is illustrative only and is not limiting of the scope of the invention, as various modifications or additions may be made to the specific embodiments described and substituted in a similar manner by those skilled in the art without departing from the scope of the invention as defined in the appending claims. It should be understood by those skilled in the art that any modifications, equivalents, improvements and the like made to the above embodiments in accordance with the technical spirit of the present invention are included in the scope of the present invention.