Strontium-doped lanthanum ferrite / zirconium oxide spraying powder and preparation method thereof

Abstract

The invention provides strontium-doped lanthanum ferrite / zirconium oxide spraying powder and a preparation method thereof, and belongs to the technical field of radar wave-absorbing material spraying powder. After the raw material powder is subjected to wet ball milling, spray granulation is directly performed to obtain the agglomerated powder, so that the raw material powder is prevented from agglomerating in the solid-phase sintering process and the particle size is increased; the preparation method comprises the following steps: agglomerating lanthanum ferrite / zirconium oxide powder, then melting the agglomerated powder into spherical liquid drops in plasma flame flow by adopting induction plasma, further fully diffusing the components in the melting process to form strontium-doped lanthanum ferrite / zirconium oxide, and cooling to obtain the high-sphericity strontium-doped lanthanum ferrite / zirconium oxide spraying powder. The raw material powder is directly subjected to spray granulation after being subjected to ball milling, solid-phase synthesis and high spheroidization of the raw material powder are achieved at the same time through induction plasma, the process is simplified, and the synthesis efficiency is improved.

Description

Technical Field

[0002] This invention relates to the field of radar absorbing material spraying powder technology, and in particular to a strontium-doped lanthanum ferrite / zirconia spraying powder and its preparation method. Background Technology

[0003] High-temperature radar absorbing materials are functional materials that can absorb electromagnetic waves in high-temperature environments. By spraying high-temperature radar absorbing material powder onto high-temperature components such as aerospace engine nozzles and tail nozzles to form a high-temperature radar absorbing coating, the material not only withstands high temperatures but also absorbs and attenuates radar waves, significantly reducing the likelihood of the aircraft being detected by radar and improving battlefield survivability and penetration capabilities.

[0004] Strontium-doped lanthanum ferrite / zirconium oxide (La 1-x Sr x (FeO3) / ZrO2 possesses excellent microwave absorption properties, a high melting point, and high chemical stability, and is often used as a high-temperature radar absorbing material. Currently, the preparation method of strontium-doped lanthanum ferrite / zirconia spray powder mainly involves mixing lanthanum oxide powder, strontium carbonate powder, iron oxide powder, and zirconium oxide (ZrO2) raw material powder, followed by ball milling, solid-state synthesis, ball milling slurry preparation, spray granulation, and re-sieving to obtain oxide ceramic spray powder. This preparation method is cumbersome, inefficient, and the resulting strontium-doped lanthanum ferrite / zirconia powder has a large particle size and its sphericity needs to be improved. Summary of the Invention

[0005] The purpose of this invention is to provide a strontium-doped lanthanum ferrite / zirconia spray powder and its preparation method. The preparation method provided by this invention is simple and efficient, and the strontium-doped lanthanum ferrite / zirconia spray powder obtained has small particle size and high sphericity.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing strontium-doped lanthanum ferrite / zirconium oxide, comprising the following steps: The raw material powder is subjected to wet ball milling to obtain a slurry; the raw material powder includes lanthanum oxide powder, strontium carbonate powder, iron oxide powder and zirconium oxide powder; The slurry is spray-granulated to obtain agglomerated powder; The agglomerated powder was subjected to plasma solid-state synthesis to obtain strontium-doped lanthanum ferrite / zirconia spray powder.

[0007] Preferably, the particle size of the raw material powder is ≤10μm.

[0008] Preferably, the ratio of the total mass of the lanthanum oxide powder, strontium carbonate powder, and iron oxide powder to the mass of the zirconium oxide powder is 1:(0.25~4).

[0009] Preferably, the inlet temperature of the spray granulation is 200~220℃, the outlet temperature of the spray granulation is 105~115℃, and the atomizer speed of the spray granulation is 18000~21000r / min.

[0010] Preferably, the power of the plasma solid-state synthesis is 31~37kW, and the feeding speed of the plasma solid-state synthesis is 20~25g / min.

[0011] Preferably, the rotation speed of the wet ball mill is 350~450 r / min, the time of the wet ball mill is 6~10 h, and the medium of the wet ball mill is water.

[0012] Preferably, the particle size D50 of the agglomerated powder is 30~50μm.

[0013] The present invention also provides strontium-doped lanthanum ferrite / zirconia spray powder prepared by the preparation method described in the above technical solution.

[0014] Preferably, the particle size of the strontium-doped lanthanum ferrite / zirconia spray powder is 30~50 μm (D50).

[0015] This invention provides a method for preparing strontium-doped lanthanum ferrite / zirconia spray coating powder, comprising the following steps: wet ball milling of raw material powder to obtain a slurry; the raw material powder includes lanthanum oxide powder, strontium carbonate powder, iron oxide powder, and zirconia powder; spray granulation of the slurry to obtain agglomerated powder; and plasma solid-state synthesis of the agglomerated powder to obtain strontium-doped lanthanum ferrite / zirconia spray coating powder. This invention avoids the agglomeration and increased particle size of the raw material powder during solid-state sintering by directly spray granulating the slurry after wet ball milling of the raw material powder. Then, induced plasma is used to melt the agglomerated powder into spherical droplets in a plasma flame. During the melting process, the components further diffuse sufficiently to form strontium-doped lanthanum ferrite / zirconia, and after cooling, a high-sphericity strontium-doped lanthanum ferrite / zirconia spray coating powder is obtained. This invention simplifies the process and improves synthesis efficiency by directly spray-granulating the raw material powder after ball milling and simultaneously achieving solid-phase synthesis and high spheroidization of the raw material powder using inductive plasma. The results of the examples show that the strontium-doped lanthanum ferrite / zirconia powder prepared by this invention has a particle size D50 of 41.36 μm and high sphericity. Attached Figure Description

[0016] Figure 1 This is a 100x magnified 3D image of the strontium-doped lanthanum ferrite / zirconia sprayed powder prepared in Example 1 of the present invention; Figure 2 This is a 500x magnified 3D image of the strontium-doped lanthanum ferrite / zirconia sprayed powder prepared in Example 1 of the present invention; Figure 3 This is a 1000x magnified 3D image of the strontium-doped lanthanum ferrite / zirconia sprayed powder prepared in Example 1 of the present invention; Figure 4 This is a 100x magnified 3D image of the strontium-doped lanthanum ferrite / zirconia sprayed powder prepared in Comparative Example 1 of this invention. Figure 5 This is a 500x magnified 3D image of the strontium-doped lanthanum ferrite / zirconia sprayed powder prepared in Comparative Example 1 of this invention, showing a super depth of field. Figure 6 This is a 1000x magnified 3D image of the strontium-doped lanthanum ferrite / zirconia sprayed powder prepared in Comparative Example 1 of this invention, showing a super depth of field. Figure 7 The image shows the XRD pattern of the strontium-doped lanthanum ferrite / zirconia sprayed powder prepared in Example 1 of this invention. Figure 8 This is a particle size distribution diagram of the mixture after wet ball milling in Example 1 of the present invention; Figure 9 This is a particle size distribution diagram of the strontium-doped lanthanum ferrite / zirconia spray powder prepared in Example 1 of the present invention; Figure 10 This is a particle size distribution diagram of the strontium-doped lanthanum ferrite / zirconia spray powder prepared in Comparative Example 1 of this invention. Detailed Implementation

[0017] This invention provides a method for preparing strontium-doped lanthanum ferrite / zirconia spray powder, comprising the following steps: The raw material powder is wet ball-milled to obtain a slurry; The slurry is spray-granulated to obtain agglomerated powder; The agglomerated powder was subjected to plasma solid-state synthesis to obtain strontium-doped lanthanum ferrite / zirconia spray powder.

[0018] In this invention, the raw material powder includes lanthanum oxide powder, strontium carbonate powder, iron oxide powder, and zirconium oxide powder.

[0019] In this invention, the particle size of the raw material powder is preferably ≤10μm. This invention ensures better density of the subsequent strontium-doped lanthanum ferrite / zirconia spray coating powder by limiting the particle size of the raw material powder.

[0020] In this invention, the molar ratio of lanthanum oxide powder, strontium carbonate powder, and iron oxide powder is preferably consistent with the molar ratio of strontium, iron, and lanthanum elements in the desired strontium-doped lanthanum ferrite / zirconia spray powder.

[0021] In this invention, the preferred mass ratio of the sum of the masses of lanthanum oxide powder, strontium carbonate powder, and iron oxide powder to the mass of zirconium oxide powder is 1:(0.25~4). In embodiments of this invention, the specific mass ratio of the total mass of the lanthanum oxide powder, strontium carbonate powder, and iron oxide powder to the mass of zirconium oxide powder can be 1:0.25, 1:0.5, 1:1, 1:2, 1:3, or 1:4. This invention ensures better microwave absorption performance of the prepared doped lanthanum ferrite / zirconia sprayed powder by limiting the mass ratio of the total mass of the lanthanum oxide powder, strontium carbonate powder, and iron oxide powder to the mass of zirconium oxide powder.

[0022] In this invention, the preferred rotational speed of the wet ball mill is 350-450 r / min. In embodiments of this invention, the rotational speed can specifically be 350 r / min, 400 r / min, or 450 r / min. In this invention, the preferred wet ball milling time is 6-10 hours. In embodiments of this invention, the preferred wet ball milling time can specifically be 6, 7, 8, 9, or 10 hours. In this invention, the medium used in the wet ball milling is water. In this invention, the preferred mass ratio of the raw material powder to water is (45-55):100. In this invention, the mass ratio of the raw material powder to water can specifically be 45:100, 50:100, or 55:100. This invention ensures more thorough mixing of the raw material powder by limiting the parameters of the wet ball milling.

[0023] After wet ball milling, the present invention preferably mixes the wet-milled mixture with water to obtain a slurry. In the present invention, the solid content of the slurry is preferably 38-42%. In embodiments of the present invention, the solid content of the slurry can specifically be 38%, 39%, 40%, 41%, or 42%. The present invention limits the solid content of the slurry to ensure that the agglomerated powder obtained by subsequent spray granulation has high bulk density and good flowability.

[0024] In this invention, the particle size of the mixture after wet ball milling is preferably D50≤1.0μm and D90≤1.8μm.

[0025] After obtaining the slurry, the present invention performs spray granulation on the slurry to obtain agglomerated powder.

[0026] In this invention, the slurry is preferably mixed with a dispersant before spray granulation.

[0027] In this invention, the dispersant is preferably polyethylene or polycarboxylate.

[0028] In this invention, the amount of dispersant added is preferably 0.5 to 1% of the mass of the raw material powder.

[0029] In this invention, the inlet temperature of the spray granulation is preferably 200~220℃. In embodiments of this invention, the inlet temperature of the spray granulation can specifically be 200℃, 210℃, or 220℃. In this invention, the outlet temperature of the spray granulation is preferably 105~115℃. In embodiments of this invention, the outlet temperature of the spray granulation can specifically be 105℃, 110℃, or 115℃. In this invention, the atomizer speed of the spray granulation is preferably 18000~21000 r / min. In embodiments of this invention, the atomizer speed of the spray granulation can specifically be 18000 r / min, 19000 r / min, 20000 r / min, or 21000 r / min. This invention ensures that agglomerated powder with good density and high strength can be obtained by limiting the parameters of spray granulation.

[0030] In this invention, the particle size D50 of the agglomerated powder is preferably 30-50 μm. In embodiments of this invention, the particle size D50 of the agglomerated powder can specifically be 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm. This invention ensures a smaller particle size of the final prepared strontium-doped lanthanum ferrite / zirconia spray powder by limiting the particle size D50 of the agglomerated powder.

[0031] After obtaining the agglomerated powder, the present invention performs plasma solid-phase synthesis on the agglomerated powder to obtain strontium-doped lanthanum ferrite / zirconia spray powder.

[0032] In this invention, the plasma melts agglomerated powder into spherical droplets in a plasma flame. During the melting process, the components diffuse sufficiently to form strontium-doped lanthanum ferrite / zirconia, and after cooling, highly spherical strontium-doped lanthanum ferrite / zirconia is obtained. In this invention, the power of the plasma solid-state synthesis is preferably 31-37 kW. In embodiments of this invention, the power of the plasma solid-state synthesis can specifically be 31 kW, 33 kW, 34 kW, 35 kW, or 37 kW. In this invention, the feed rate of the plasma solid-state synthesis is preferably 20-25 g / min. In embodiments of this invention, the feed rate of the plasma solid-state synthesis can specifically be 20 g / min, 22 g / min, 24 g / min, or 25 g / min. In this invention, the carrier gas for the plasma solid-state synthesis is preferably argon and hydrogen. In this invention, the argon flow rate is preferably 33-37 L / min. In this invention, the hydrogen flow rate is preferably 7.4-7.6 L / min. This invention limits the parameters of plasma solid-phase synthesis to ensure that the components diffuse sufficiently to form strontium-doped lanthanum ferrite / zirconia, and further obtains strontium-doped lanthanum ferrite / zirconia spray powder with high sphericity after cooling.

[0033] This invention involves wet ball milling of raw material powder followed by direct spray granulation to obtain agglomerated powder, avoiding the agglomeration and increased particle size that occurs during solid-state sintering. Then, inductively coupled plasma is used to melt the agglomerated powder into spherical droplets in a plasma flame. During melting, the components further diffuse to form strontium-doped lanthanum ferrite / zirconia, and after cooling, a highly spherical strontium-doped lanthanum ferrite / zirconia spray-coated powder is obtained. This invention simplifies the process and improves synthesis efficiency by simultaneously achieving solid-state synthesis and high sphericity of the raw material powder through direct spray granulation after ball milling and the use of inductively coupled plasma.

[0034] The present invention also provides strontium-doped lanthanum ferrite / zirconia prepared by the preparation method described in the above technical solution.

[0035] In this invention, the strontium-doped lanthanum ferrite in the strontium-doped lanthanum ferrite / zirconia is: La 1-x Sr x FeO3. In this invention, x is preferably 0.3 to 0.7. In this invention, x can specifically be 0.3, 0.4, 0.5, 0.6, or 0.7.

[0036] In this invention, the particle size D50 of the strontium-doped lanthanum ferrite / zirconia is preferably 30-50 μm. In embodiments of this invention, the particle size D50 of the strontium-doped lanthanum ferrite / zirconia can specifically be 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm. This invention ensures good spraying effect and a more uniform coating by limiting the particle size of the strontium-doped lanthanum ferrite / zirconia.

[0037] The strontium-doped lanthanum ferrite / zirconia spray powder prepared by this invention has small particle size and high sphericity.

[0038] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0039] Example 1 A strontium-doped lanthanum ferrite / zirconia spray powder (La 0.3 Sr 0.7 The preparation method of FeO3 / ZrO2 is as follows: The raw material powder was wet-ball-milled and then mixed with water and SN-5040 sodium polycarboxylate dispersant to obtain a slurry; the particle size D50 of the wet-ball-milled mixture was 0.896 μm; the amount of dispersant added was 1% of the mass of the raw material powder. The slurry was spray-granulated to obtain agglomerated powder with a particle size D50 of 46.62 μm; The agglomerated powder was subjected to plasma solid-state synthesis to obtain 0.3 (La) powder with a particle size D50 of 44.04 μm. 0.3 Sr 0.7 FeO3) / 0.7ZrO2 spray powder; The raw material powders are lanthanum oxide powder, strontium carbonate powder, iron oxide powder, and zirconium oxide powder; the particle size of the raw material powders is ≤10μm; the molar ratio of lanthanum oxide powder, strontium carbonate powder, and iron oxide powder is 0.3:0.7:1; the mass ratio of the total mass of lanthanum oxide powder, strontium carbonate powder, and iron oxide powder to the mass of zirconium oxide powder is 1:1.5; the wet ball milling speed is 400 r / min; the wet ball milling time is 6.5 h; the medium for the wet ball milling is water; the mass ratio of the raw material powder to water is 1:1; the solid content of the slurry is 42%; the spraying... The inlet temperature of the granulation is 220℃; the outlet temperature of the spray granulation is 115℃; the atomizer speed of the spray granulation is preferably 18000 r / min; the particle size D50 of the agglomerated powder is 44.04 μm; the power of the plasma solid-phase synthesis is 34 kW kW; in this invention, the carrier gas of the plasma solid-phase synthesis is argon and hydrogen; the argon flow rate is preferably 35 L / min; the hydrogen flow rate is preferably 7.5 L / min; and the feeding speed of the inductive plasma solid-phase synthesis is 25 g / min.

[0040] Comparative Example 1 A strontium-doped lanthanum ferrite / zirconia spray powder (La 0.3 Sr 0.7 The preparation method of FeO3 / ZrO2 is as follows: Lanthanum oxide powder, strontium carbonate powder, and iron oxide powder are subjected to a first wet ball milling process to obtain a first slurry; The slurry is mixed with zirconium oxide powder and then subjected to a second wet ball milling process to obtain a second slurry. The second slurry was mixed with water and SN-5040 sodium polycarboxylate dispersant, and then sequentially spray-granulated, solid-phase sintered, and re-sieved to obtain 0.3 (La) particles with a particle size D50 of 53.20 μm. 0.3 Sr 0.7 FeO3) / 0.7ZrO2 spray powder; The amount of dispersant added is 1% of the mass of the raw material powder; The raw material powders are lanthanum oxide powder, strontium carbonate powder, iron oxide powder, and zirconium oxide powder; the particle size of the raw material powders is ≤10μm; the molar ratio of lanthanum oxide powder, strontium carbonate powder, and iron oxide powder is 0.3:0.7:1; the mass ratio of the total mass of lanthanum oxide powder, strontium carbonate powder, and iron oxide powder to the mass of zirconium oxide powder is 1:1.5; the solid-state sintering temperature is 1310℃; the solid-state sintering time is 4h; the rotation speed of the first wet ball mill is 400r / min; the first wet ball milling time is 6.5h; the medium for the first wet ball milling is pure water; the parameters of the second wet ball milling are the same as those of the first wet ball milling; the parameters of the spray granulation are the same as those of Example 1.

[0041] The morphology of the strontium-doped lanthanum ferrite / zirconia sprayed powders prepared in Example 1 and Comparative Example 1 was characterized by three-dimensional ultra-depth-of-field microscopy at magnifications of 100x, 500x, and 1000x, respectively. The results are as follows: Figures 1-3 As shown in Figures 4-6. From the figures, we can see that: Figure 1 The strontium-doped lanthanum ferrite / zirconia sprayed powder prepared in Example 1 has high sphericity and uniform particle size distribution; Figures 2-3 The strontium-doped lanthanum ferrite / zirconia sprayed powder prepared in Example 1 has high surface smoothness and good integrity; Figure 4 The strontium-doped lanthanum ferrite / zirconia spray powder prepared in Comparative Example 1 had no impurity peaks, high phase purity, and a complete solid-phase synthesis reaction. Figures 5-6 The strontium-doped lanthanum ferrite / zirconia spray powder prepared in Comparative Example 1 has a larger particle size and a lower surface finish compared to Example 1.

[0042] The phase composition of the strontium-doped lanthanum ferrite / zirconia sprayed powder prepared in Example 1 was characterized by X-ray diffraction, and the results are as follows: Figure 7 As shown in the figure, the strontium-doped lanthanum ferrite / zirconia spray powder prepared in Example 1 has a stable phase and is free of impurities.

[0043] The particle size distribution of the strontium-doped lanthanum ferrite / zirconia sprayed powders prepared in Example 1 and Comparative Example 1 was characterized using a powder particle size analyzer. The results are as follows: Figure 8 , 9 As shown in Figure 10. From the figure, we can see that: Figure 8 In Example 1, the particle size D50 of the mixture after wet ball milling was 0.86 μm, which increased the contact area of ​​the raw material powder. Figure 9 The strontium-doped lanthanum ferrite / zirconia spray powder prepared in Example 1 has a small particle size, uniform distribution, and good uniformity; while Figure 10 The strontium-doped lanthanum ferrite / zirconia spray powder prepared in Comparative Example 1 has a large particle size and uneven distribution.

[0044] In summary, the preparation method provided by this invention is simple and efficient, and the prepared strontium-doped lanthanum ferrite / zirconia spray powder has small particle size and high sphericity.

[0045] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing strontium-doped lanthanum ferrite / zirconia spray coating powder, comprising the following steps: The raw material powder is subjected to wet ball milling to obtain a slurry; the raw material powder includes lanthanum oxide powder, strontium carbonate powder, iron oxide powder and zirconium oxide powder; The slurry is spray-granulated to obtain agglomerated powder; The agglomerated powder was subjected to plasma solid-state synthesis to obtain strontium-doped lanthanum ferrite / zirconia spray powder.

2. The preparation method according to claim 1, characterized in that, The particle size of the raw material powder is ≤10μm.

3. The preparation method according to claim 1, characterized in that, The ratio of the total mass of lanthanum oxide powder, strontium carbonate powder, and iron oxide powder to the mass of zirconium oxide powder is 1:(0.25~4).

4. The preparation method according to claim 1, characterized in that, The inlet temperature of the spray granulation is 200~220℃, the outlet temperature of the spray granulation is 105~115℃, and the atomizer speed of the spray granulation is 18000~21000r / min.

5. The preparation method according to claim 1, characterized in that, The power of the plasma solid-state synthesis is 31~37kW, and the feeding speed of the plasma solid-state synthesis is 20~25g / min.

6. The preparation method according to claim 1, characterized in that, The wet ball milling speed is 350~450 r / min, the wet ball milling time is 6~10 h, and the medium for the wet ball milling is water.

7. The preparation method according to claim 1, characterized in that, The particle size D50 of the agglomerated powder is 30~50μm.

8. The preparation method according to claim 7, characterized in that, The particle size D50 of the agglomerated powder is 35~40μm.

9. Strontium-doped lanthanum ferrite / zirconia spray powder prepared by the preparation method according to any one of claims 1 to 8.

10. The strontium-doped lanthanum ferrite / zirconia spray powder according to claim 9, characterized in that, The particle size D50 of the strontium-doped lanthanum ferrite / zirconia spray powder is 30~50μm.

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