Non-agglomerated Si-coated HfO2 core-shell structure powder and preparation method thereof

Abstract

The invention provides non-agglomerated Si-coated HfO2 core-shell structure powder and a preparation method thereof, and relates to the field of core-shell structure powder preparation and silicon bonding layers for silicon-based composites, and the preparation method comprises the following steps: preparing HfO2 slurry; the HfO2 slurry is sprayed to the surface of Si powder, and an HfO2 shell layer is formed; and then carrying out drying treatment and / or sintering treatment to obtain the non-agglomerated core-shell structure Si-coated HfO2 powder. According to the method, the non-agglomerated Si-coated HfO2 core-shell structure powder with Si as a core and HfO2 as a shell is obtained. Components and position distribution of a Si core and a HfO2 shell are fixed in each core-shell structure composite particle, the core-shell structure composite particle is not a random mixing system of two kinds of independent powder any more, during subsequent spraying, the core-shell structure single particles serve as minimum uniform units, a silicon bonding layer with hafnium oxide distributed uniformly in a layered mode can be obtained, and the service life of the silicon bonding layer is prolonged. And it is ensured that the coating with a special microstructure and excellent performance is prepared.

Description

Technical Field

[0001] This invention belongs to the field of core-shell structured powder preparation technology, specifically relating to a non-agglomerated Si@HfO2 core-shell structured powder and its preparation method. Background Technology

[0002] With the increasing thrust-to-weight ratio of aero-engines, turbine inlet temperatures have exceeded 1500℃. Faced with these extreme service temperatures, thermal / environmental barrier (T / EBC) multifunctional coatings have become a key technology for ensuring the safe and stable long-term service of silicon-based composite hot-end components. This simultaneously reduces the service temperature of the composite substrate and improves its resistance to water vapor corrosion and low-melting-point molten salt (CMAS) corrosion. It is worth noting that a transition layer—a silicon bonding layer—must exist between the T / EBC and the silicon-based composite. This layer improves the thermal expansion compatibility between the surface layer and the substrate and consumes diffused oxygen to enhance the substrate's oxidation resistance. However, the maximum long-term service temperature of traditional pure silicon bonding layers is 1300℃, which is insufficient to meet current service requirements. This is because: firstly, silicon has a relatively low melting point of 1414℃; secondly, the thermally grown oxide (TGO, SiO2) formed after silicon oxidation undergoes a phase transition, and its coefficient of thermal expansion (10.3 × 10⁻⁶) is relatively low. -6 K -1 ) and silicon carbide matrix (3.5~5.5×10 -6 K -1 The mismatch caused the coating to crack and peel off.

[0003] To address the aforementioned challenges, a solution adopted in recent years is to dope hafnium oxide (HfO2) into the silicon binder layer. This involves first preparing Si-HfO2 multiphase powder, then spraying a Si-HfO2 multiphase coating. The HfO2 reacts with the generated TGO (SiO2) to produce HfSiO4 (with a thermal expansion coefficient of 3.11~5.97×10⁻⁶), which matches the thermal expansion coefficient of the silicon carbide substrate. -6 K -1 This increases the service temperature of the adhesive layer and extends its service life.

[0004] Currently, the common method for preparing Si-HfO2 composite powders is to first mix silicon powder and hafnium oxide powder together to prepare a slurry, and then granulate them together. This results in Si-HfO2 composite agglomerates with randomly distributed silicon powder and hafnium oxide powder. However, during the granulation process, due to the silicon powder (2.33 g / cm³),... 3 ) and hafnium oxide powder (9.68 g / cm³) 3 The significant difference in density between the two powders leads to variations in centrifugal force and inertia during granulation of the blended powder slurry, resulting in poor sphericity of the granulated and agglomerated powder (e.g., Figure 5As shown in a), it affects the flowability of the feed powder, and the coating obtained after spraying is a multiphase coating in which HfO2 particles are randomly distributed in the silicon binder layer.

[0005] In addition, a second method for preparing Si-HfO2 multiphase powder involves granulating silicon powder and hafnium oxide powder separately, followed by mechanical mixing. While this method allows both silicon and hafnium oxide agglomerates to maintain good sphericity, their significant density difference means that during plasma spraying, the difference in inertia prevents them from being uniformly deposited on the substrate surface, even though they are fed simultaneously. This results in uneven distribution of the two powders within the coating, leading to component segregation.

[0006] When applying Si-HfO2 composite powders prepared by the above two methods, uneven distribution of hafnium oxide in the coating can hinder the effective improvement of oxidation resistance and service temperature of the silicon binder layer, and also lead to decreased adhesion to the substrate or surface layer. Furthermore, for these two types of Si-HfO2 multiphase powders, silicon and air are in direct contact, and silicon undergoes oxidation during plasma spraying. This results in a small amount of total silica (TGO) in the prepared silicon binder layer, which is detrimental to the coating's oxidation resistance. Summary of the Invention

[0007] Therefore, this invention provides a non-agglomerated Si@HfO2 core-shell structure powder and its preparation method, which can solve the problem of poor sphericity of composite powders in the prior art. In addition, it can also suppress the oxidation of silicon powder and the formation of TGO during plasma spraying, improve the uniformity of silicon and hafnium oxide distribution in the coating, and improve the service temperature of silicon bonding layer.

[0008] To achieve the above objectives, this invention provides a method for preparing non-agglomerated Si@HfO2 core-shell structured powder, comprising the following steps: Step 1): Prepare HfO2 slurry; Step 2): Spray the HfO2 slurry onto the surface of large-sized Si powder, so that the HfO2 powder adheres to and coats the silicon powder, thus obtaining coated powder; Step 3): The coated powder is dried and / or sintered to obtain non-agglomerated Si@HfO2 core-shell structured powder.

[0009] Furthermore, in step 1), the HfO2 slurry is a suspension of HfO2 powder; The particle size of the HfO2 raw material powder is 1 nm to 30 μm.

[0010] Furthermore, the solid content of the HfO2 slurry is 5-50%.

[0011] Furthermore, the HfO2 slurry is prepared using ball milling or stirring methods; Preferably, the ball milling or stirring time is 20 min to 60 h.

[0012] Furthermore, in step 2), the Si powder is silicon agglomerate powder obtained by spray granulation of relatively large size or silicon powder obtained by melt crushing.

[0013] Furthermore, in step 3), the drying temperature is 45–150°C.

[0014] Furthermore, in step 3), the sintering temperature is 700–1500°C; the holding time for sintering is 0.5–15 h.

[0015] On the other hand, the present invention provides a non-agglomerated Si@HfO2 core-shell structure powder, wherein the non-agglomerated Si@HfO2 core-shell structure powder is obtained by any of the preparation methods described above, and the prepared powder is basically non-agglomerated and exhibits a core-shell structure in morphology.

[0016] Furthermore, in the core-shell structure of the non-agglomerated Si@HfO2 core-shell structure powder, the thickness of the outer shell is 0.1–50 μm.

[0017] Furthermore, in the core-shell structure of the non-agglomerated Si@HfO2 core-shell structure powder, the diameter of the core is 1–200 μm.

[0018] The present invention provides a non-agglomerated Si@HfO2 core-shell structured powder and its preparation method, which has the following beneficial effects: 1. On one hand, the present invention provides a method for preparing non-agglomerated Si@HfO2 core-shell structured powder, comprising the following steps: preparing HfO2 slurry; spraying the HfO2 slurry onto the surface of large-sized Si powder, so that the HfO2 powder adheres to and coats the silicon powder, thereby obtaining a coated powder; and then subjecting the coated powder to drying and / or sintering treatment to obtain non-agglomerated Si@HfO2 core-shell structured powder. It should be noted that, based on the above method, by spraying a slurry of small-sized HfO2 powder onto the surface of large-sized Si powder, similar to spraying paint, the HfO2 powder will coat the silicon powder. Continuous spraying accumulates and thickens the coating, thereby forming a hafnium oxide coating layer of a certain thickness, ultimately obtaining a non-agglomerated Si@HfO2 core-shell structured powder with Si as the core and HfO2 as the shell. Each core-shell composite particle has a fixed composition and positional distribution of Si core + HfO2 shell, and is no longer a random mixture of two independent powders. In subsequent spraying, these core-shell single particles serve as the smallest uniform units, which helps to obtain a silicon bonding layer with hafnium oxide exhibiting a layered and uniform distribution, ensuring the preparation of a coating with special microstructure and excellent performance.

[0019] 2. Furthermore, high-melting-point (2758℃) HfO2 powder is used to encapsulate low-melting-point (1414℃) silicon powder. This ensures that both powders with different melting points reach a reasonable melting state during plasma spraying, avoiding the excessive volatilization of silicon powder caused by conventionally randomly distributed Si-HfO2 multiphase particles during spraying to ensure sufficient melting of hafnium oxide. This is because the boiling point of silicon powder (2355℃) is lower than the melting point of hafnium oxide, and silicon is more prone to volatilization under the same conditions. Secondly, the core-shell structured powder uses oxidation-resistant HfO2 powder to encapsulate oxidation-sensitive silicon powder. This reduces silicon powder oxidation during plasma spraying, resulting in a lower silicon oxide content in the prepared binder layer, which helps improve the oxidation resistance of the silicon binder layer.

[0020] 3. On the other hand, the present invention provides a non-agglomerated Si@HfO2 core-shell structured powder, which is obtained by any of the preparation methods described above, wherein the thickness of the outer shell is 0.1–50 μm and the diameter of the core is 1–200 μm. Furthermore, the thickness of the outer shell coating layer is adjustable and controllable. The coating layer of the prepared core-shell structured powder is uniform, complete, and dense, effectively solving the problems of uneven and incomplete coating in conventional processes.

[0021] 4. Traditional preparation processes for core-shell structured powders include sol-gel methods, chemical plating, co-precipitation, ion exchange, and hydrothermal methods. These wet chemical solution methods easily lead to agglomeration of core-shell structured powders (including other non-core-shell structured powders) during drying. This is because, towards the end of the drying process, numerous capillaries form between the powder particles in the slurry or suspension. The surface tension or capillary force of the liquid causes the powder to compress, shrink, and agglomerate, sometimes forming fragmented, cake-like, or blocky hard polymers. To solve the powder agglomeration problem and prepare non-agglomerated, independently dispersed coated powders, this invention employs a scientific strategy and method of synergistically controlling the spraying rate and powder drying rate. This ensures that the coated powder is essentially in a dry powder preparation state. As long as there is no large amount of continuous liquid phase between large-sized silicon powder particles, the silicon powder will not agglomerate, thus ultimately forming a non-agglomerated Si@HfO2 multiphase powder with a core-shell structure. Furthermore, traditional methods suffer from cumbersome processes, long preparation cycles, and high costs. This work has invented a novel slurry spraying method that enables the simple, efficient, and convenient preparation of core-shell structured powders, with low cost and easy industrial production.

[0022] 5. This invention can be used not only to prepare non-agglomerated core-shell structured Si@HfO2 multiphase powders for silicon binder layers in the aero-engine field, but also to prepare most other core-shell structured powders in the industrial field, demonstrating wide applicability and broad application prospects. The most prominent advancement and advantage of this invention is that the thickness of the outer shell coating layer is adjustable and controllable, which is usually difficult to achieve with traditional coating processes. Attached Figure Description

[0023] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0024] Figure 1 The images show the surface and cross-sectional scanning electron microscope (SEM) images of the non-agglomerated Si@HfO2 core-shell structured powder prepared in Example 1. Figure 2 This is a cross-sectional energy spectrum of the non-agglomerated Si@HfO2 core-shell structured powder prepared in Example 2; Figure 3 This is a cross-sectional scanning electron microscope image of the non-agglomerated Si@HfO2 core-shell structured powder prepared in Example 3; Figure 4 The X-ray diffraction pattern of the non-agglomerated Si@HfO2 core-shell structured powder prepared in Example 4; Figure 5 The morphology and composition diagram of the Si-HfO2 composite powder prepared in Comparative Example 1 are shown. Figure 6 The image shows the cross-sectional morphology of the Si-HfO2 composite powder prepared in Comparative Example 2. Detailed Implementation

[0025] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0026] This invention provides a method for preparing non-agglomerated Si@HfO2 core-shell structured powder, comprising the following steps: Step 1): Prepare HfO2 slurry using ball milling or slurry stirring method; The HfO2 slurry is a suspension of HfO2 powder; the particle size of the HfO2 powder is 1 nm to 30 μm; the solid content of the HfO2 slurry is 5% to 50%; and the ball milling or stirring time is 20 min to 60 h.

[0027] Step 2): Spray HfO2 slurry onto the surface of relatively large-sized Si powder, so that HfO2 powder adheres to and coats the silicon powder, thereby forming an HfO2 powder shell layer with a certain thickness, and obtaining coated powder; The Si powder is either silicon agglomerates obtained by spray granulation of relatively large size or silicon powder obtained by melt crushing.

[0028] Step 3): The coated powder is dried and / or sintered to obtain non-agglomerated Si@HfO2 powder; wherein the non-agglomerated Si@HfO2 powder has a core-shell structure with Si as the core and HfO2 as the shell.

[0029] The drying temperature is 45–150℃; the sintering temperature is 700–1500℃; and the holding time for sintering is 0.5–15 h.

[0030] Based on the above method, by spraying a slurry of small-sized HfO2 powder onto the surface of relatively large-sized Si powder, the HfO2 powder adheres to and coats the silicon powder, resulting in a non-agglomerated Si@HfO2 core-shell structure powder with Si as the core and HfO2 as the shell. Each core-shell composite particle has a fixed composition and positional distribution of the Si core and HfO2 shell, no longer a random mixture of two independent powders. During subsequent spraying, these core-shell single particles serve as the smallest uniform units, helping to obtain a silicon bonding layer with a layered and uniformly distributed hafnium oxide, ensuring the preparation of a coating with a special microstructure and excellent performance.

[0031] Furthermore, using high-melting-point (2758℃) HfO2 powder to encapsulate low-melting-point (1414℃) silicon powder ensures that both powders with different melting points reach a reasonable melting state during plasma spraying. This avoids the phenomenon where conventional randomly distributed Si-HfO2 multiphase particles fail to fully melt hafnium oxide (2758℃) during spraying, leading to excessive volatilization of silicon powder due to its low boiling point (2355℃). Secondly, the core-shell structure powder uses oxidation-resistant HfO2 powder to encapsulate oxidation-sensitive silicon powder. This reduces silicon powder oxidation during plasma spraying, resulting in a lower silicon oxide content in the prepared binder layer, which helps improve the oxidation resistance of the silicon binder layer.

[0032] On the other hand, the present invention provides a non-agglomerated Si@HfO2 core-shell structure powder, which is obtained by any of the above preparation methods; in the core-shell structure, the thickness of the outer shell is 0.1 to 50 μm; and the diameter of the core is 1 to 200 μm.

[0033] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0034] Example 1 This embodiment provides a method for preparing non-agglomerated Si@HfO2 core-shell structured powder, including the following steps: Step 1): Weigh 30 grams of HfO2 powder with a silicon powder molar percentage of 5 mol% and a particle size of 10 nm to 5 μm. Prepare 600 grams of suspension with a solid content of 5% by slurry stirring method. The stirring time is 2 h.

[0035] Step 2): Spray the HfO2 powder slurry onto 95 mol% silicon agglomerate powder using a spray bottle or spray gun. The slurry spraying rate is 15~16 g / min, so that the HfO2 spray droplets adhere to the surface of the silicon agglomerate powder and accumulate until they completely coat the silicon powder, thus obtaining coated powder. Step 3): Dry the above-mentioned coated powder at 135°C, continuously stir the silicon powder to dry the sprayed HfO2 powder slurry as soon as possible, and after all the powder slurry has been sprayed, sinter the above powder at 1400°C for 0.5h, so that the outer shell layer is firmly coated on the surface of the core silicon powder, and obtain non-agglomerated Si@HfO2 core-shell structure powder.

[0036] The surface and cross-sectional micromorphology of the non-agglomerated Si@HfO2 core-shell structured powder prepared in this embodiment are as follows: Figure 1 As shown in the left figure, the powder exhibits high sphericity, and the hafnium oxide powder adheres firmly to the surface of the silicon agglomerate powder. The right figure shows a distinct core-shell structure in its microstructure, with an average HfO2 coating thickness of approximately 1.2 μm and a silicon agglomerate powder particle size of 101 μm. Furthermore, the prepared core-shell structured powder consists of individual powder particles, without any powder agglomeration.

[0037] Example 2 This embodiment provides a method for preparing non-agglomerated Si@HfO2 core-shell structured powder, including the following steps: Step 1): Weigh 50 grams of HfO2 powder with a silicon powder molar percentage of 10 mol% and a particle size of 100 nm to 15 μm. Use a ball mill to prepare a suspension with a solid content of 15% of 333.3 grams. The ball milling time is 12 h.

[0038] Step 2): Spray the HfO2 powder slurry onto 90 mol% silicon agglomerate powder using a spray bottle or spray gun. The slurry spraying rate is 9~10 g / min, so that the HfO2 spray droplets adhere to the surface of the silicon agglomerate powder and accumulate until they completely coat the silicon powder, thus obtaining coated powder. Step 3): Dry the above-mentioned coated powder at 110°C, continuously stir the silicon powder to dry the sprayed HfO2 powder slurry as soon as possible, and after all the powder slurry has been sprayed, sinter the above-mentioned powder at 1300°C for 2 hours, so that the outer shell layer is firmly coated on the surface of the core silicon powder, and obtain non-agglomerated Si@HfO2 core-shell structure powder.

[0039] The cross-sectional morphology and energy dispersive spectroscopy (EDS) images of the non-agglomerated Si@HfO2 core-shell structured powder prepared in this embodiment are shown below. Figure 2 As shown in the figure, the powder exhibits high sphericity and a distinct core-shell structure in its cross-sectional morphology. Hafnium oxide powder is firmly coated around the silicon agglomerates, with the core being silicon powder and the outer shell being HfO2. It can also be seen that the average thickness of the HfO2 coating layer is approximately 6.7 μm, and the particle size of the silicon agglomerates is around 110 μm. In particular, the outer shell coating layer is very uniform in thickness, resulting in a complete and dense coating effect, achieving an ideal coating effect. Furthermore, the prepared core-shell structured powder consists of individual powder particles, without any powder agglomeration.

[0040] Example 3 This embodiment provides a method for preparing non-agglomerated Si@HfO2 core-shell structured powder, including the following steps: Step 1): Weigh 90 grams of HfO2 powder with a silicon powder molar percentage of 35 mol% and a particle size of 500 nm to 25 μm. Use a ball mill to prepare a suspension with a solid content of 40% of 225 grams. The ball milling time is 50 h.

[0041] Step 2): Spray the HfO2 powder slurry onto 65 mol% silicon agglomerate powder using a spray bottle or spray gun. The slurry spraying rate is 3~5 g / min, so that the HfO2 spray droplets adhere to the surface of the silicon agglomerate powder and accumulate until they completely coat the silicon powder, thus obtaining coated powder. Step 3): Dry the above-mentioned coated powder at 65°C, continuously stir the silicon powder to dry the sprayed powder slurry as soon as possible, and after all the powder slurry has been sprayed, sinter the above-mentioned powder at 1000°C for 5 hours, so that the outer shell layer is firmly coated on the surface of the core, and obtain non-agglomerated Si@HfO2 core-shell structure powder. The cross-sectional microstructure of the non-agglomerated Si@HfO2 core-shell structured powder prepared in this embodiment is as follows: Figure 3As shown in the figure, all powders exhibit a distinct core-shell structure in their cross-sectional morphology, with a relatively uniform outer shell coating thickness, and all powders show complete and dense coating. It can also be seen that the average thickness of the HfO2 coating layer is approximately 3.0-7.5 μm, and the particle size of the silicon agglomerates is approximately 20-45 μm, achieving an ideal coating effect. Furthermore, the prepared core-shell structured powders are independent powders, with no agglomeration among them.

[0042] Example 4 This embodiment provides a method for preparing non-agglomerated Si@HfO2 core-shell structured powder, including the following steps: Step 1): Weigh 60 grams of HfO2 powder with a silicon powder molar percentage of 20 mol% and a particle size of 300 nm to 20 μm. Use a ball mill to prepare a suspension with a solid content of 25% of 240 grams. The ball milling time is 30 h.

[0043] Step 2): Spray the HfO2 powder slurry onto 80 mol% molten and crushed silicon powder using a spray bottle or spray gun. The slurry spraying rate is 7~9 g / min, so that the HfO2 spray droplets adhere to the surface of the silicon agglomerate powder and accumulate until they completely coat the silicon powder, thus obtaining coated powder. Step 3): Dry the above-mentioned coated powder at 90°C, continuously stir the silicon powder to dry the sprayed powder slurry as soon as possible, and after all the powder slurry has been sprayed, sinter the above-mentioned powder at 800°C for 10 hours, so that the outer shell layer is firmly coated on the surface of the core, and obtain non-agglomerated Si@HfO2 core-shell structure powder. The X-ray diffraction pattern of the non-agglomerated Si@HfO2 core-shell structured powder prepared in this embodiment is as follows: Figure 4 As shown in the figure, the core-shell structured powder contains only two phases: Si and HfO2, with no other impurity phases present. This indicates that the multiphase powder is a pure phase powder, and the core-shell structured powder prepared by this invention has the advantage of high purity.

[0044] Comparative Example 1 This comparative example provides a method for preparing Si-HfO2 composite powder, including the following steps: Si powder and HfO2 powder are ball-milled and stirred together to form a uniform powder slurry. The slurry of mixed powders is then spray-granulated to obtain granulated and agglomerated powder with hafnium oxide and silicon powder randomly distributed.

[0045] Due to the significant density difference between silicon powder and hafnium oxide powder, the centrifugal granulation process results in an irregular liquid shape, and the prepared powder is typically not a regular spherical powder. Specifically, for example... Figure 5 As shown. From Figure 5As can be seen in (a), the morphology of the powders varies greatly and they are not regular spheres; although it is a mixture of powders granulated, there are individual granular silicon powders, see... Figure 5 (b); from Figure 5 As can be seen in (d), the silicon powder and hafnium oxide powder are randomly distributed inside the Si-HfO2 multiphase powder, which is significantly different from the microstructure of the core-shell structure powder in this patent.

[0046] Comparative Example 2 This comparative example provides a method for preparing Si@HfO2 core-shell structured powder, including the following steps: Step 1): Weigh 50 grams of HfO2 powder with a silicon powder molar percentage of 15 mol% and a particle size of 200 nm to 15 μm. Use a ball mill to prepare a suspension with a solid content of 30% of 166.7 grams. The ball milling time is 15 min.

[0047] Step 2): Spray the HfO2 powder slurry onto 85 mol% silicon agglomerate powder using a spray bottle or spray gun. The slurry spraying rate is 15~16 g / min, so that the HfO2 spray droplets adhere to the surface of the silicon agglomerate powder and accumulate until they completely coat the silicon powder, thus obtaining coated powder. Step 3): Dry the above-mentioned coated powder at 40°C, continuously stir the silicon powder to dry the sprayed powder slurry, and after all the powder slurry has been sprayed, sinter the above-mentioned powder at 1300°C for 1 hour, so that the outer shell layer is firmly coated on the surface of the core to obtain Si@HfO2 core-shell structure powder. The cross-sectional morphology of the Si@HfO2 core-shell structured powder prepared in this comparative example is as follows: Figure 6 As shown in the figure, the powder exhibits incomplete coating, uneven outer shell thickness, relatively loose outer shell, and powder agglomeration. This is because the ball milling mixing time is too short, resulting in larger and less uniform particle size of the powder in the HfO2 slurry, leading to uneven coating thickness; and the low drying temperature results in slow drying efficiency, causing powder agglomeration.

[0048] It will be readily understood by those skilled in the art that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. For example, the spraying rate depends on the total amount of powder prepared. For mass-produced powder, the spraying rate needs to be optimized and increased; that is, the slurry spraying rate of the powder can be designed to be adjustable and controllable according to the production capacity. The above description is merely 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 technical principles 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 non-agglomerated Si@HfO2 core-shell structured powder, characterized in that, Includes the following steps: Step 1): Prepare HfO2 slurry; Step 2): Spray the HfO2 slurry onto the surface of the Si powder to coat the silicon powder with HfO2 powder, thus obtaining coated powder; Step 3): The coated powder is dried and / or sintered to obtain non-agglomerated Si@HfO2 core-shell structured powder.

2. The method for preparing non-agglomerated Si@HfO2 core-shell structured powder according to claim 1, characterized in that, In step 1), the HfO2 slurry is a suspension of HfO2 powder; The particle size of the HfO2 raw material powder is 1 nm to 30 μm.

3. The method for preparing non-agglomerated Si@HfO2 core-shell structured powder according to claim 1, characterized in that, The solid content of the HfO2 slurry is 5-50%.

4. The method for preparing non-agglomerated Si@HfO2 core-shell structured powder according to claim 1, characterized in that, The HfO2 slurry was prepared by ball milling or stirring. Preferably, the ball milling or stirring time is 20 min to 60 h.

5. The method for preparing non-agglomerated Si@HfO2 core-shell structured powder according to claim 1, characterized in that, In step 2), the Si powder is silicon agglomerated powder obtained by spray granulation or silicon powder obtained by melt crushing.

6. The method for preparing non-agglomerated Si@HfO2 core-shell structured powder according to claim 1, characterized in that, In step 3), the drying temperature is 45–150°C.

7. The method for preparing non-agglomerated Si@HfO2 core-shell structured powder according to claim 1, characterized in that, In step 3), the sintering temperature is 700–1500°C; the holding time for sintering is 0.5–15 h.

8. A non-agglomerated Si@HfO2 core-shell structured powder, characterized in that, The non-agglomerated Si@HfO2 core-shell structured powder is obtained by the preparation method described in any one of claims 1 to 7.

9. The non-agglomerated Si@HfO2 core-shell structured powder according to claim 8, characterized in that, In the non-agglomerated Si@HfO2 core-shell structured powder, the thickness of the outer shell is 0.1–50 μm.

10. The non-agglomerated Si@HfO2 core-shell structured powder according to claim 8 or 9, characterized in that, In the non-agglomerated Si@HfO2 core-shell structure powder, the diameter of the core is 1–200 μm.

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