Spherical yttrium oxide powder for thermal spraying and preparation method thereof

Abstract

The present invention belongs to the field of rare earth thermal spraying technology, and specifically relates to a spherical yttrium oxide powder for thermal spraying and a preparation method thereof. The preparation method comprises: dissolving yttrium oxide raw material with nitric acid to obtain yttrium nitrate solution; reacting part of yttrium nitrate solution with ammonia water in parallel, aging, washing and filtering in sequence to obtain yttrium hydroxide; reacting the remaining yttrium nitrate solution with a mixed precipitant in parallel, aging, washing and filtering in sequence to obtain alkaline mixed yttrium; mixing yttrium hydroxide and alkaline mixed yttrium with water, then adding dispersant and adhesive step by step, stirring and spray granulation to obtain granulated powder; calcining the granulated powder, adding water and ball milling, then adding dispersant and adhesive step by step again for secondary spray granulation to obtain secondary granulated powder; sintering the secondary granulated powder at high temperature and then screening. The spherical yttrium oxide powder obtained by the present invention has high absolute purity, high ball formation rate, good fluidity, high bulk density and low porosity.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth thermal spraying, and in particular relates to spherical yttrium oxide powder for thermal spraying and a preparation method thereof. Background Art

[0002] Yttrium oxide has good resistance to high-energy plasma erosion, high-temperature stability, and heat resistance in harsh environments, and can be used as erosion-resistant coating materials, high-temperature thermal insulation coating materials, etc. In recent years, with the advent of localization of advanced process integrated circuits, the particle contamination problem caused by the bombardment and erosion of aluminum alloys, quartz, ceramics and other parts in contact with plasma has become a key problem that must be solved in the preparation of key parts of etching machines. Because yttrium oxide has good resistance to high-energy plasma erosion, it is currently the most widely used plasma erosion-resistant material. With the successful development of thermal spraying yttrium oxide powder, yttrium oxide powder is widely used in the preparation of plasma erosion-resistant coatings for parts of integrated circuit chip manufacturing equipment. At the same time, because yttrium oxide has good high-temperature stability and heat resistance in harsh environments, it can be used as a high-temperature thermal insulation coating material, such as for the protection of graphite layers in cemented carbide industry.

[0003] The development of mature, stable, low-cost, high-quality spherical yttrium oxide powder preparation technology for thermal spraying is of great significance to the development of my country's chip industry.

[0004] There are two main methods for preparing spherical yttrium oxide powder for thermal spraying: spray granulation and direct precipitation. Among them, spray granulation is dominant. Spray granulation mostly uses centrifugal spray dryers, and pressure granulators are also used when there are special requirements for particle size. In addition to equipment factors, the properties of spherical yttrium oxide powder also affect the properties of raw materials, process routes, additives (dispersers, adhesives), sintering methods, etc. FUJIMI's preparation method is to prepare a mixture of yttrium oxide, metallic yttrium, and yttrium hydroxide into a slurry for spray drying, and then sinter at high temperature in the atmosphere or oxygen environment. This preparation method has high raw material costs, relatively poor sphericity, and high requirements for sintering equipment. Patent (201110100222.7) uses a water-stabilized plasma spray gun to treat yttrium oxide to obtain a nanoscale precursor, and then adds a binder and a dispersant for spray granulation, and the granulated powder is sintered by an atmospheric plasma spray gun. This method also has problems such as high production costs and high equipment requirements. At present, the mainstream method in China is to use ordinary commercially available yttrium oxide (obtained by roasting oxalic acid precipitation products), directly sand-grind to nanometer level, add adhesives and dispersants, and then spray granulate. Although this method has a short process, it has problems such as poor product stability, low ball formation rate, and low density.

[0005] In 2020, the Ministry of Industry and Information Technology issued my country's first industry standard specifically for yttrium oxide in the thermal spraying industry, "Yttrium Oxide Powder for Thermal Spraying" (XB / T 511-2020). This standard clarified for the first time the chemical composition and particle size range of thermal spraying yttrium oxide powder, see Table 1 and Table 2.

[0006]

[0007]

[0008] Judging from the yttrium oxide products currently produced by my country's rare earth industry, their relative purity can meet the requirements of product grades TSY-1~TSY-5, but the non-rare earth impurities such as Mg, Fe, Na, Si, Al, Cl in the raw materials are difficult to meet the requirements of TSY-1 and TSY-2. As for the particle size range, the existing granulation methods make it difficult for all the products to be spherical, with poor fluidity, and there are many particles that are too fine (<10μm) or too coarse (>70μm), and the particle size distribution is wide. In addition, the standard requires that the bulk density should not be less than 1.1g / cm 3 However, the current industry requires the bulk density to be greater than 1.5g / cm 3 Even 2.0g / cm 3 However, it is difficult to achieve using existing methods.

[0009] Therefore, based on this, the technical solution of the present invention is proposed. Summary of the invention

[0010] In order to solve the problems existing in the prior art, the present invention provides a spherical yttrium oxide powder for thermal spraying and a preparation method thereof. The spherical yttrium oxide powder overcomes the common problems of the prior art spherical yttrium oxide powder, such as high impurity content, low sphericity, low bulk density, low ball formation rate, and high porosity, and also has the significant advantage of high production batch stability.

[0011] The solution of the present invention is to provide a method for preparing spherical yttrium oxide powder for thermal spraying, the preparation method comprising the following steps:

[0012] (1) dissolving a yttrium oxide raw material with nitric acid to obtain an yttrium nitrate solution;

[0013] (2) reacting a portion of the yttrium nitrate solution with aqueous ammonia in parallel, aging, washing, and filtering in sequence to obtain yttrium hydroxide;

[0014] (3) reacting the remaining yttrium nitrate solution and the mixed precipitant in parallel, aging, washing and filtering in sequence to obtain alkaline mixed yttrium;

[0015] (4) mixing the yttrium hydroxide and the alkaline mixed yttrium with water, and then adding a dispersant and a binder step by step, stirring, and then spraying and granulating to obtain a granulated powder;

[0016] (5) After calcining the granulated powder, adding water to the granulated powder, and then adding a dispersant and a binder step by step to perform secondary spray granulation to obtain a secondary granulated powder;

[0017] (6) The secondary granulated powder is sintered at high temperature and then sieved to obtain spherical yttrium oxide powder of different particle sizes for thermal spraying.

[0018] Preferably, in step (1), the yttrium oxide raw material is common commercially available industrial yttrium oxide, with a relative purity (Y2O3 / ∑REO)>99.999%;

[0019] And / or, the concentration of the yttrium nitrate solution is 0.5-1.5 mol / L, and the pH is 0.1-4.5.

[0020] It is worth noting that the common commercially available industrial yttrium is obtained by roasting yttrium oxalate precipitated with oxalic acid. The yttrium oxide has coarse grains and the particle size is often above 5 μm. If it is directly sand-milled, on the one hand, impurities will be introduced, and on the other hand, the product will have a low balling rate and low density. In the present invention, the yttrium oxide raw material is dissolved in nitric acid to obtain an yttrium nitrate solution, which can remove the undissolved impurities therein and does not introduce harmful impurities such as chloride ions and sulfates into the solution.

[0021] Preferably, in step (2), the concentration of the ammonia water is 1.5-6 mol / L, and the amount of the ammonia water used is 3-6 times the molar mass of yttrium nitrate;

[0022] And / or, the parallel flow reaction is carried out by continuously adding part of the yttrium nitrate solution and ammonia water into a reactor for reaction; the reactor is one of a stirred reactor, a pipeline mixer, and a high gravity reactor; the temperature of the parallel flow reaction is 50-100° C.;

[0023] And / or, the aging temperature is 50-100° C., and the aging time is 1-12 hours.

[0024] Preferably, in step (3), the mixed precipitant is a mixed solution of ammonia water and ammonium bicarbonate; in the mixed precipitant, the concentration of ammonia water is 0.1-0.9 mol / L, the concentration of ammonium bicarbonate is 2.5-10 times the concentration of ammonia water, the total concentration of ammonia water and ammonium bicarbonate is 1.5-3.5 mol / L, and the total amount of ammonia water and ammonium bicarbonate is 3-6 times the molar mass of yttrium nitrate;

[0025] And / or, the temperature of the parallel flow reaction is 50-100° C.; the temperature of the aging is 50-100° C., and the aging time is 1-12 hours;

[0026] And / or, the alkaline mixed yttrium is one or a mixture of two or more of yttrium carbonate, basic yttrium carbonate, and yttrium hydroxide.

[0027] It is worth noting that the present invention adopts a parallel flow method to react yttrium nitrate with ammonia water, and yttrium nitrate with a mixed solution of ammonia water and ammonium bicarbonate, in order to achieve uniform nucleation and rapid precipitation to ensure uniform particle size.

[0028] It is further worth noting that the process parameters set in step (2) and step (3) of the present invention can obtain nano-scale products while also having the effect of removing impurities and purifying the products, thereby preventing trace amounts of impurities such as silicon, calcium, magnesium, chlorine, and sulfate from being precipitated into the products, thereby ensuring the high purity of the final spherical yttrium oxide powder.

[0029] It is worth noting that no surfactant, dispersant or other reagent is added in step (2) and step (3) of the present invention, which simplifies the operation, reduces the cost, avoids adding other impurities to the product, and further ensures the high purity of the final spherical yttrium oxide powder.

[0030] Preferably, in step (4), the mass ratio of the yttrium hydroxide to the alkaline mixed yttrium is 0.1:1 to 1:1;

[0031] And / or, the amount of water added is 0.5 to 1.5 times the total mass of the yttrium hydroxide and the alkaline mixed yttrium;

[0032] And / or, the dispersant is one or a mixture of polyethylene glycol, polyvinyl pyrrolidone, ethanol or propylene glycol, and the amount of the dispersant is 0.1-1.0% of the total mass of the yttrium hydroxide and the alkaline mixed yttrium;

[0033] And / or, the adhesive is one or a combination of polyvinyl alcohol and polyvinyl pyrrolidone, and the amount of the adhesive is 0.3-3.0% of the total mass of the yttrium hydroxide and the alkaline mixed yttrium;

[0034] And / or; the spray granulation adopts a centrifugal spray dryer, the inlet temperature of the centrifugal spray dryer is 150~300℃, and the outlet temperature is 80~220℃.

[0035] It is worth noting that the present invention uses a mixture of two yttrium compounds in a certain ratio for spraying, which can improve the sphericity of the granulated powder, especially the density of the final product.

[0036] Preferably, in step (5), the calcination temperature is 600-1300° C. and the calcination time is 1-6 hours;

[0037] and / or, the amount of water added during ball milling is 0.5 to 1.0 times the mass of the granulated powder;

[0038] And / or, the ball milling particle size is 0.5~5μm.

[0039] Preferably, in step (6), the high temperature sintering is carried out at a temperature of 1500-1700° C. and for a time of 1-6 hours.

[0040] It is worth noting that the present invention adopts a two-step granulation and two-step calcination method, which is the innovation of the present invention. Its significant significance is that the two-step granulation reduces the requirements for the type, quantity and purity of the dispersant and the adhesive, reduces the cost of reagent use, and more significantly, the two-step granulation can make the final spherical yttrium oxide have extremely high sphericity and extremely high yield, without the generation of waste and defective products, avoiding the loss of raw materials, and more significantly reducing the cost. The two-step calcination makes the process more stable, and the final product obtained has higher density and strength.

[0041] Based on the same technical concept, another embodiment of the present invention is to provide a spherical yttrium oxide powder for thermal spraying obtained by the above preparation method.

[0042] The beneficial effects of the present invention are:

[0043] (1) The present invention uses common industrial commercially available yttrium oxide as raw material, dissolves it with nitric acid, and adopts two precipitation methods to obtain yttrium compound raw materials. While being able to obtain nano-scale products, the present invention also has the function of removing impurities and purifying the products, and can prevent trace amounts of silicon, calcium, magnesium, chlorine, sulfate and other impurities in the original materials from precipitating into the products, thereby ensuring the high purity of the final spherical yttrium oxide powder. The sphericity of the granulated powder, especially the density of the final product, can be improved.

[0044] (2) The present invention adopts an innovative two-step granulation method, which reduces the requirements for the type, quantity and purity of dispersants and adhesives, and reduces the cost of reagent use. More significantly, the two-step granulation method can make the final spherical yttrium oxide have extremely high sphericity and extremely high yield, without the generation of waste and defective products, avoiding the loss of raw materials, and more significantly reducing costs.

[0045] (3) The present invention adopts a two-step sintering method, which makes the process more stable and the final product has higher density and strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 This is a particle size distribution diagram of the yttrium oxide raw material used in Example 1.

[0048] Figure 2 This is a scanning electron microscope image of the yttrium oxide raw material used in Example 1.

[0049] Figure 3 This is a scanning electron microscope image of the single-spray granulated powder obtained in step (4) of Example 1.

[0050] Figure 4 This is a scanning electron microscope image of the secondary spray granulation powder obtained in step (5) of Example 1.

[0051] Figure 5 This is a scanning electron microscope image of the secondary spray granulation powder obtained in step (5) of Example 2.

[0052] Figure 6 This is a scanning electron microscope image of the secondary spray granulation powder obtained in step (5) of Example 3.

[0053] Figure 7 This is a scanning electron microscope image of the secondary spray granulation powder obtained in step (5) of Example 4.

[0054] Figure 8 This is a scanning electron microscope image of the secondary spray granulation powder obtained in step (5) of Example 5. DETAILED DESCRIPTION

[0055] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0056] Example 1

[0057] This embodiment provides a method for preparing spherical yttrium oxide powder for thermal spraying, the preparation method comprising the following steps:

[0058] (1) Weigh 32 kg of yttrium oxide raw material and dissolve it in 16 mol / L nitric acid to obtain an yttrium nitrate solution with a concentration of 1.15 mol / L;

[0059] (2) 41 L of the above yttrium nitrate solution was taken and 71 L of 3 mol / L ammonia water was prepared. The two solutions were continuously added to the supergravity reactor in parallel. The reaction temperature was controlled at 70°C. After the reaction was completed, the mixture was aged for 6 hours, and then filtered and washed to obtain 16.5 kg of yttrium hydroxide precipitate;

[0060] (3) 82 L of the above yttrium nitrate solution was taken and a mixed precipitant with a volume of 133 L and a concentration of 3.2 mol / L was prepared, wherein the concentration of ammonia water was 0.5 mol / L and the concentration of ammonium bicarbonate was 4 mol / L. The two solutions were continuously and concurrently added to a supergravity reactor. The reaction temperature was controlled at 70° C. After the reaction was completed, the mixture was aged for 6 hours, and then filtered and washed to obtain 30.65 kg of yttrium carbonate precipitate;

[0061] (4) The two precipitates obtained in the above steps were mixed with 47 L of water to prepare a solution with a solid-liquid ratio of 1:1, 141.5 g of polyethylene glycol was added, and after stirring and dispersion, 141.5 g of polyvinyl alcohol was added and stirred, and then spray granulation was performed; a centrifugal spray granulator was used for granulation, wherein the atomizer speed was 10000 rpm, the inlet air temperature was set to 220°C, and the exhaust air temperature was set to 90°C;

[0062] (5) The obtained granulated powder was calcined at 900°C for 4 hours, and then ball-milled with 23.5 L of water for a second time after calcination. After ball-milling, the conditions were the same as those of the first granulation, and a second granulation was performed;

[0063] (6) The obtained secondary granulated powder is sintered at a high temperature of 1600° C. and sieved after sintering to obtain a spherical yttrium oxide powder product for thermal spraying with a particle size of 40 μm.

[0064] like Figure 1 and Figure 2 As shown in Table 3, they are the original particle size distribution diagram and microscopic morphology diagram of the raw material used in Example 1. As shown in Table 3, they are the non-rare earth impurity contents in the raw material, the primary granulated powder, and the secondary granulated powder. Although the relative purity of the raw material is 99.999%, the non-rare earth impurity content therein only meets the TSY-4 standard in the national standard for granulated powder, while the granulated powder obtained after treatment in this example can meet the TSY-2 standard. Figure 3 and Figure 4 Shown is the morphology of the powder after the first granulation and the second granulation in Example 1.

[0065] Table 3

[0066]

[0067] Example 2

[0068] This embodiment provides a method for preparing spherical yttrium oxide powder for thermal spraying, the preparation method comprising the following steps:

[0069] (1) Weigh 26 kg of yttrium oxide raw material and dissolve it in 16 mol / L nitric acid to obtain an yttrium nitrate solution with a concentration of 0.8 mol / L;

[0070] (2) 48 L of the above yttrium nitrate solution was taken and 38.4 L of 5 mol / L ammonia water was prepared. The two solutions were continuously added to the supergravity reactor in parallel. The reaction temperature was controlled at 70° C. After the reaction was completed, the mixture was aged for 8 hours, and then filtered and washed to obtain 13.6 kg of yttrium hydroxide precipitate;

[0071] (3) 96 L of the above yttrium nitrate solution was taken and a mixed precipitant with a volume of 120 L and a concentration of 3.2 mol / L was prepared, wherein the concentration of ammonia water was 0.5 mol / L and the concentration of ammonium bicarbonate was 4 mol / L. The two solutions were continuously and concurrently added to a supergravity reactor. The reaction temperature was controlled at 70° C. After the reaction was completed, the mixture was aged for 8 hours, and then filtered and washed to obtain 24.1 kg of yttrium carbonate precipitate;

[0072] (4) The two precipitates obtained in the above steps were mixed with 37.7 L of water to prepare a solution with a solid-liquid ratio of 1:1, 188.5 g of polyethylene glycol was added, and after stirring and dispersion, 188.5 g of polyvinyl alcohol was added and stirred, and then spray granulation was performed; a centrifugal spray granulator was used for granulation, wherein the atomizer speed was 6000 rpm, the inlet air temperature was set to 180°C, and the exhaust air temperature was set to 80°C;

[0073] (5) The obtained granulated powder was calcined at 1000°C for 4 h, and then ball-milled with 18.85 L of water for a second time. After ball-milling, the conditions were the same as those of the first granulation, and a second granulation was performed;

[0074] (6) The obtained secondary granulated powder is sintered at a high temperature of 1600° C. and sieved after sintering to obtain a spherical yttrium oxide powder product for thermal spraying with a particle size of 60 μm.

[0075] Example 3

[0076] (1) Weigh 26 kg of yttrium oxide raw material and dissolve it in 16 mol / L nitric acid to obtain an yttrium nitrate solution with a concentration of 1 mol / L;

[0077] (2) 15 L of the above yttrium nitrate solution was taken and 30 L of 3 mol / L ammonia water was prepared. The two solutions were continuously added to the supergravity reactor in parallel. The reaction temperature was controlled at 60° C. After the reaction was completed, the mixture was aged for 5 hours, and then filtered and washed to obtain 5.2 kg of yttrium hydroxide precipitate;

[0078] (3) 100 L of the above yttrium nitrate solution was taken to prepare a 300 L mixed precipitant with a concentration of 2 mol / L, wherein the concentration of ammonia water was 0.8 mol / L and the concentration of ammonium bicarbonate was 2.5 mol / L. The two solutions were continuously and concurrently added to a supergravity reactor. The reaction temperature was controlled at 60° C. After the reaction was completed, the mixture was aged for 5 hours, and then filtered and washed to obtain 32.8 kg of a precipitate of basic yttrium carbonate;

[0079] (4) The two precipitates obtained in the above steps were mixed with 64 L of water to prepare a solution with a solid-liquid ratio of 0.6:1, 38.5 g of polyethylene glycol was added, and after stirring and dispersion, 38.5 g of polyvinyl alcohol was added and stirred, and then spray granulation was performed; a centrifugal spray granulator was used for granulation, wherein the atomizer speed was 15000 rpm, the inlet air temperature was set to 220°C, and the exhaust air temperature was set to 90°C;

[0080] (5) The obtained granulated powder was calcined at 900°C for 4 hours, and then ball-milled with 21L of water for a second time. After ball-milling, the second granulation was performed under the same conditions as the first granulation;

[0081] (6) The obtained secondary granulated powder is sintered at a high temperature of 1600° C. and sieved after sintering to obtain a spherical yttrium oxide powder product for thermal spraying with a particle size of 25 μm.

[0082] Example 4

[0083] (1) Weigh 26 kg of yttrium oxide raw material and dissolve it in 16 mol / L nitric acid to obtain an yttrium nitrate solution with a concentration of 1 mol / L;

[0084] (2) 57.5 L of the above yttrium nitrate solution was taken and 95.8 L of 3 mol / L ammonia water was prepared. The two solutions were continuously added to the supergravity reactor in parallel. The reaction temperature was controlled at 70°C. After the reaction was completed, the mixture was aged for 6 hours, and then filtered and washed to obtain 21.8 kg of yttrium hydroxide precipitate;

[0085] (3) 57.5 L of the above yttrium nitrate solution was taken and a mixed precipitant with a volume of 95.8 L and a concentration of 3 mol / L was prepared, wherein the concentration of ammonia water was 0.5 mol / L and the concentration of ammonium bicarbonate was 3.2 mol / L. The two solutions were continuously and concurrently added to a supergravity reactor. The reaction temperature was controlled at 70° C. After the reaction was completed, the mixture was aged for 6 hours, and then filtered and washed to obtain 18.5 kg of yttrium carbonate precipitate;

[0086] (4) Add 40.3 L of water to the two precipitates obtained in the above steps to prepare a solution with a solid-liquid ratio of 1:1, add 77 g of polyethylene glycol, stir and disperse, then add 77 g of polyvinyl alcohol and stir, and then spray granulate; use a centrifugal spray granulator for granulation, wherein the atomizer speed is 12000 rpm, the inlet air temperature is set to 220°C, and the exhaust air temperature is set to 90°C;

[0087] (5) The obtained granulated powder was calcined at 900°C for 4 hours, and then ball-milled with 25 L of water for a second time. After ball-milling, the conditions were the same as those of the first granulation, and a second granulation was performed;

[0088] (6) The obtained secondary granulated powder is sintered at a high temperature of 1600° C. and sieved after sintering to obtain a spherical yttrium oxide powder product for thermal spraying with a particle size of 33 μm.

[0089] Example 5

[0090] (1) Weigh 32 kg of yttrium oxide raw material and dissolve it in 16 mol / L nitric acid to obtain an yttrium nitrate solution with a concentration of 1.3 mol / L;

[0091] (2) 36 L of the above yttrium nitrate solution was taken and 42.12 L of 5 mol / L ammonia water was prepared. The two solutions were continuously added to the supergravity reactor in parallel. The reaction temperature was controlled at 60°C. After the reaction was completed, the mixture was aged for 2 hours, and then filtered and washed to obtain 16.79 kg of yttrium hydroxide precipitate;

[0092] (3) 72 L of the above yttrium nitrate solution was taken and a mixed precipitant with a volume of 120 L and a concentration of 3.5 mol / L was prepared, wherein the concentration of ammonia water was 0.9 mol / L and the concentration of ammonium bicarbonate was 3.8 mol / L. The two solutions were continuously and concurrently added to a supergravity reactor. The reaction temperature was controlled at 60° C. After the reaction was completed, the mixture was aged for 2 hours, and then filtered and washed to obtain 29.8 kg of a precipitate of basic yttrium carbonate;

[0093] (4) The two precipitates obtained in the above steps were mixed with 58.2 L of water to prepare a solution with a solid-liquid ratio of 0.8:1, 465 g of polyethylene glycol was added, and after stirring and dispersion, 465 g of polyvinyl alcohol was added and stirred, and then spray granulation was performed; a centrifugal spray granulator was used for granulation, wherein the atomizer speed was 8000 rpm, the inlet air temperature was set to 200°C, and the exhaust air temperature was set to 110°C;

[0094] (5) The obtained granulated powder was calcined at 800°C for 4 h, and then ball-milled with 46.6 L of water for a second time. After ball-milling, the conditions were the same as those of the first granulation, and a second granulation was performed;

[0095] (6) The obtained secondary granulated powder is sintered at a high temperature of 1600° C. and sieved after sintering to obtain a spherical yttrium oxide powder product for thermal spraying with a particle size of 50 μm.

[0096] Furthermore, the spherical yttrium oxide powder (secondary granulated powder) obtained in Examples 2 to 5 was subjected to characterization tests, and the results are shown in Table 4.

[0097] Table 4

[0098]

[0099] As can be seen from the foregoing and Table 4, the five embodiments of the present invention solve the problem of sphericity of granulated powder by the method of secondary granulation, and realize yttrium oxide products. Its innovation lies in the two-step granulation, and the key implementation process is that the raw material yttrium oxide has a higher purity after being dissolved and removed by nitric acid, and the mixed precipitate obtained by precipitation by the mixed precipitant is more easily aggregated from nano-sized particles into micron-sized spheres during the spray drying process. In addition, yttrium oxide products of different specifications can be customized by changing the granulation conditions.

[0100] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing spherical yttrium oxide powder for thermal spraying, characterized in that: The preparation method comprises the following steps: (1) dissolving a yttrium oxide raw material with nitric acid to obtain an yttrium nitrate solution; (2) reacting a portion of the yttrium nitrate solution with aqueous ammonia in parallel, aging, washing, and filtering in sequence to obtain yttrium hydroxide; (3) reacting the remaining yttrium nitrate solution and the mixed precipitant in parallel, aging, washing and filtering in sequence to obtain alkaline mixed yttrium; (4) mixing the yttrium hydroxide and the alkaline mixed yttrium with water, and then adding a dispersant and a binder step by step, stirring, and then spraying and granulating to obtain a granulated powder; (5) After calcining the granulated powder, adding water to the granulated powder, and then adding a dispersant and a binder step by step to perform secondary spray granulation to obtain a secondary granulated powder; (6) The secondary granulated powder is sintered at high temperature and then sieved to obtain spherical yttrium oxide powder of different particle sizes for thermal spraying.

2. The method for preparing spherical yttrium oxide powder for thermal spraying according to claim 1, characterized in that: In step (1), the purity of the yttrium oxide raw material is greater than 99.999%; And / or, the concentration of the yttrium nitrate solution is 0.5-1.5 mol / L, and the pH is 0.1-4.

5.

3. The method for preparing spherical yttrium oxide powder for thermal spraying according to claim 1, characterized in that: In step (2), the concentration of the ammonia water is 1.5-6 mol / L, and the amount of ammonia water used is 3-6 times the molar amount of yttrium nitrate; And / or, the parallel flow reaction is carried out by continuously adding part of the yttrium nitrate solution and ammonia water into a reactor for reaction; the reactor is one of a stirred reactor, a pipeline mixer, and a high gravity reactor; the temperature of the parallel flow reaction is 50-100° C.; And / or, the aging temperature is 50-100° C., and the aging time is 1-12 hours.

4. The method for preparing spherical yttrium oxide powder for thermal spraying according to claim 1, characterized in that: In step (3), the mixed precipitant is a mixed solution of ammonia water and ammonium bicarbonate; in the mixed precipitant, the concentration of ammonia water is 0.1-0.9 mol / L, the concentration of ammonium bicarbonate is 2.5-10 times the concentration of ammonia water, the total concentration of ammonia water and ammonium bicarbonate is 1.5-3.5 mol / L, and the total amount of ammonia water and ammonium bicarbonate is 3-6 times the molar amount of yttrium nitrate; And / or, the temperature of the parallel flow reaction is 50-100° C.; the temperature of the aging is 50-100° C., and the aging time is 1-12 hours; And / or, the alkaline mixed yttrium is one or a mixture of two or more of yttrium carbonate, basic yttrium carbonate, and yttrium hydroxide.

5. The method for preparing spherical yttrium oxide powder for thermal spraying according to claim 1, characterized in that: In step (4), the mass ratio of the yttrium hydroxide to the alkaline mixed yttrium is 0.1:1 to 1:1; And / or, the amount of water added is 0.5 to 1.5 times the total mass of the yttrium hydroxide and the alkaline mixed yttrium; And / or, the dispersant is a mixture of one or more of polyethylene glycol, polyvinyl pyrrolidone, ethanol or propylene glycol, and the amount of the dispersant is 0.1-1.0% of the total mass of the yttrium hydroxide and the alkaline mixed yttrium; And / or, the adhesive is one or a combination of polyvinyl alcohol and polyvinyl pyrrolidone, and the amount of the adhesive is 0.3-3.0% of the total mass of the yttrium hydroxide and the alkaline mixed yttrium; And / or; the spray granulation adopts a centrifugal spray dryer, the inlet temperature of the centrifugal spray dryer is 150~300℃, and the outlet temperature is 80~220℃.

6. The method for preparing spherical yttrium oxide powder for thermal spraying according to claim 1, characterized in that: In step (5), the calcination temperature is 600-1300°C and the calcination time is 1-6 hours; and / or, the amount of water added during ball milling is 0.5 to 1.0 times the mass of the granulated powder; And / or, the ball milling particle size is 0.5~5μm.

7. The method for preparing spherical yttrium oxide powder for thermal spraying according to claim 1, characterized in that: In step (6), the high temperature sintering temperature is 1500-1700° C., and the time is 1-6 hours.

8. Spherical yttrium oxide powder for thermal spraying obtained by the preparation method according to any one of claims 1 to 7.

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