A Si@Yb2O3 feed powder with a spherical core-shell structure, a preparation method and application thereof

Abstract

The application provides a Si@Yb2O3 feed powder with a spherical core-shell structure and a preparation method and application thereof. The Si@Yb2O3 feed powder with the spherical core-shell structure comprises a core-shell structure with Si as an inner core and Yb2O3 as an outer shell, and is prepared by spraying Yb2O3 on the outer surface of Si by a slurry spraying method. The Si@Yb2O3 feed powder prepared by the application is a core-shell structure composite powder, and the powder has the advantages of perfect sphericity, uniform, complete and dense coating. The preparation method is simple, feasible, low in cost and wide in application range; in addition to the field of silicon bonding layer, the method is also applicable to the efficient, convenient and low-cost preparation of core-shell structure powders in other fields.

Description

Technical Field

[0001] This invention belongs to the field of feed powder technology for thermal spraying, specifically a spherical core-shell structured Si@Yb2O3 feed powder, its preparation method, and its application. Background Technology

[0002] As is well known, with the continuous improvement of the thrust-to-weight ratio of engines, ceramic matrix composites have become the preferred material for hot-section components of next-generation aero-engines. Meanwhile, environmental barrier coatings or thermal / environmental barrier coatings are key technologies for protecting the composite material matrix, enhancing its corrosion resistance, and improving its service temperature and service life. Currently, rare earth silicates, due to their excellent corrosion and oxidation resistance, have become the most widely studied and applied environmental barrier coating system, with Yb₂Si₂O₇ coatings being particularly prominent.

[0003] However, Yb₂Si₂O₇ ring barrier coatings cannot be used directly. They typically require a Si bonding layer with a thermal expansion coefficient more compatible with the substrate to achieve bonding with the SiC composite matrix, thus ensuring the overall bonding strength of the coating. This silicon bonding layer has advantages such as good chemical compatibility, strong adhesion, and the ability to act as an oxygen absorption layer. However, Si has a low melting point (1414℃), and the maximum service temperature of pure silicon bonding layers is generally 1350℃. Furthermore, in high-temperature, oxygen-rich environments, it is easily oxidized to form SiO₂, accompanied by a 2.2-fold volume expansion, which easily leads to cracking and ultimately coating peeling failure. Therefore, pure silicon bonding layers can no longer meet current requirements, and there is an urgent need to develop new silicon bonding layer materials to improve their service temperature and reliability.

[0004] Yb2O3 has a high melting point (2346℃) and can react with SiO2 to form Yb2Si2O7, thereby consuming a large amount of SiO2 and alleviating coating failure caused by the accumulation of thermally grown oxides (TGO). Therefore, doping pure silicon binder with Yb2O3 is expected to significantly increase its operating temperature and inhibit oxidation, cracking and peeling of the silicon binder.

[0005] The conventional doping method involves blending Si powder and Yb₂O₃ powder to form a slurry, followed by spray granulation to obtain a mixed-phase agglomerated powder. However, this process has the following problems: 1. The density difference between Si (density 2.33 g / cm³) and Yb₂O₃ (density 9.17 g / cm³) powders is significant. During granulation, the different centrifugal forces can easily cause irregular agglomerated powder morphology, affecting the flowability of the feed powder; 2. The melting points of the two powders differ significantly (1414℃ vs. 2346℃), resulting in inconsistent melting states of the randomly blended multiphase powders during spraying; 3. It is difficult to obtain a layered structure coating with superior performance. Summary of the Invention

[0006] To overcome the shortcomings and deficiencies of existing technologies, this invention provides a spherical core-shell structured Si@Yb2O3 feed powder for silicon bonding layers and its preparation method. This method uses Si powder and Yb2O3 powder as raw materials, and prepares a core-shell structured coated powder through a simple and efficient slurry spraying method. The prepared core-shell structured Si@Yb2O3 multiphase powder has the advantages of exhibiting a perfect spherical shape, complete, uniform, and dense coating, and the coating layer thickness is adjustable and controllable.

[0007] The technical solution of the present invention is as follows: This invention provides a spherical core-shell structured Si@Yb2O3 feed powder, which includes a core-shell structure with Si as the core and Yb2O3 as the outer shell, and has a spherical appearance; wherein, the Yb2O3 is formed on the outer surface of the Si by spraying.

[0008] Furthermore, the particle size distribution of the core is 1~180 μm; the thickness of the outer shell is determined as needed, preferably 0.1~40 μm.

[0009] This invention also provides a method for preparing the above-mentioned spherical core-shell structured Si@Yb2O3 feed powder, the method comprising: (1) raw material selection: selecting suitable silicon powder as the core; (2) slurry preparation and spraying: preparing a stable and uniform Yb2O3 slurry; spraying the Yb2O3 slurry onto the surface of the silicon powder and drying it, so that the Yb2O3 powder is coated onto the outer surface of the silicon powder, thereby obtaining the spherical core-shell structured Si@Yb2O3 feed powder. It should be understood that in the field of silicon bonding layers: the amount of Yb2O3 added is 0~60 mol% of the molar percentage of silicon powder, preferably 0~30 mol%. The amount added in other fields depends on the needs.

[0010] Furthermore, in step (1), the silicon powder includes molten and crushed silicon powder and / or silicon agglomerate powder prepared by spray drying.

[0011] Furthermore, step (2) specifically includes: the Yb2O3 slurry is prepared by ball milling or mechanical stirring; the solid content of the Yb2O3 slurry is 3%~40%, the particle size of Yb2O3 is 0.01~30 μm; and the drying temperature is 40~160℃.

[0012] Furthermore, the method also includes: (3) post-processing: heat treatment of the spherical core-shell structured Si@Yb2O3 feed powder.

[0013] Furthermore, in step (3), the process parameters of the heat treatment include: a heating rate of 1~20 ℃ / min, a temperature of 600~1450℃, and a holding time of 20~600 min.

[0014] Furthermore, step (3) also includes: sieving the heat-treated spherical core-shell structured Si@Yb2O3 feed powder.

[0015] Furthermore, the particle size of the spherical core-shell structured Si@Yb2O3 feed powder obtained after sieving is 5~200 μm, preferably 20~120 μm.

[0016] The present invention also provides an application of the above-mentioned spherical core-shell structured Si@Yb2O3 feed powder as a binder layer in an environmental barrier coating system or a thermal / environmental barrier coating system.

[0017] Compared with the prior art, the advantages and beneficial effects of the present invention include at least the following: (1) Regular morphology: This invention develops a novel and simple slurry spraying method to prepare core-shell structured powder. By spraying Yb2O3 slurry onto the surface of Si powder, a core-shell structured coated Si@Yb2O3 feed powder is prepared. The resulting feed powder has a perfect spherical shape and the coating layer is very uniform, complete and dense.

[0018] (2) Thickness is adjustable and controllable: The core-shell structure powder prepared by the present invention has an adjustable and controllable shell thickness. The shell thickness can be quantitatively controlled by adjusting the process parameters, which has the advantage of quantitative and controllable preparation.

[0019] (3) Reasonable structural distribution: The present invention uses a high-melting-point Yb2O3 shell to coat a low-melting-point Si core. On the one hand, during the plasma spraying process, the melting sequence of the powder is more reasonable, which can effectively reduce the volatilization loss of silicon; on the other hand, the Yb2O3 shell, which is not easily oxidized, coats the easily oxidized Si, which can suppress the oxidation of Si during plasma spraying and reduce the initial content of silicon oxide in the Si bonding layer.

[0020] (4) Suitable for industrial production: The preparation method provided by the present invention has the advantages of convenient operation, simple process, environmental friendliness and low equipment cost.

[0021] (5) Applicable fields: In addition to the field of feed powder for this binder layer, it also has broad application prospects in other fields such as core-shell structure powder. Attached Figure Description

[0022] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments, and unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0023] Figure 1 The image shows the XRD pattern of the Si@Yb2O3 core-shell structure powder prepared in Example 1. Figure 2 The images show the cross-sectional morphology and EDS spectrum of the Si@Yb2O3 core-shell structured feed powder prepared in Example 2. Figure 3 This is a cross-sectional morphology diagram of the Si@Yb2O3 core-shell structured feed powder prepared in Example 3; Figure 4 The image shows the microstructure of the feed powder prepared in Comparative Example 1, which exhibits uneven, incomplete, non-dense, and agglomerated encapsulation. Figure 4 The 'd' in the figure indicates the presence of powder agglomeration. Figure 5 The flowchart and microstructure diagram of the preparation of common core-shell structure powders in the literature are shown in Comparative Example 2. Detailed Implementation

[0024] To this end, the present invention designs the microstructure of the feed powder to prepare a core-shell structure powder with a high melting point Yb2O3 shell and a low melting point Si core as the feed powder, and uses a simple slurry spraying process to achieve efficient preparation of the core-shell structure powder, ultimately achieving the purpose of increasing the working temperature of the silicon binder layer and extending the service life of the environmental barrier coating.

[0025] The present invention will now be described in detail with reference to specific embodiments.

[0026] Example 1 20 g of Yb₂O₃ was weighed and added to a beaker to prepare a slurry with a solid content of 10%. The particle size of the Yb₂O₃ was approximately 0.01–6 μm. A stable and uniform Yb₂O₃ slurry was then obtained by mechanical stirring. Next, 20 g of molten and crushed Si powder with a particle size distribution of 10–120 μm was weighed and sprayed onto the surface of the Si powder. The powder was then dried at 150 °C. The coated powder was then subjected to high-temperature sintering at a heating rate of 10 °C / min, a sintering temperature of 1300 °C, and a holding time of 50 min. After sintering, the powder was sieved to obtain Si@Yb₂O₃ core-shell structured powder with a particle size distribution of 20–135 μm. The XRD diffraction pattern of the powder is shown below. Figure 1 As shown in the figure, the main phases of the prepared core-shell structured powder are Si and Yb2O3 phases.

[0027] Example 2 25g of Yb₂O₃ was weighed and added to a ball mill jar to prepare a slurry with a solid content of 35%. The particle size of Yb₂O₃ was approximately 0.5–30 μm. A stable and uniform Yb₂O₃ slurry was then obtained by ball milling. Next, 35g of Si agglomerated powder with a particle size distribution of 25–110 μm was weighed and sprayed onto the surface of the Si powder. The powder was then dried at 100℃. The coated powder was then subjected to high-temperature sintering at a heating rate of 20℃ / min, a sintering temperature of 1000℃, and a holding time of 300 min. After sintering, the powder was sieved to obtain Si@Yb₂O₃ core-shell structured powder with a particle size distribution of approximately 35–130 μm. The cross-sectional morphology and EDS energy spectrum of the powder are shown below. Figure 2 As shown in the figure, the Yb2O3 shell is wrapped around the surface of the Si agglomerated powder. The particle size of the core Si powder is about 89.5 μm, and the thickness of the Yb2O3 coating layer is about 3.1~6.7 μm with an average thickness of 4.7 μm. This proves that the core-shell structured powder was successfully prepared and the coating is uniform, complete and dense.

[0028] Example 3 30 g of Yb₂O₃ was weighed and added to a ball mill jar to prepare a slurry with a solid content of 20%. The particle size of Yb₂O₃ was approximately 0.3–20 μm. The slurry was then ball-milled to obtain a stable and uniform Yb₂O₃ slurry. Next, 20 g of Si agglomerated powder with a particle size distribution of 30–140 μm was weighed and sprayed onto the surface of the Si powder. The powder was then dried at 60 °C. The coated powder was then subjected to high-temperature sintering at a heating rate of 5 °C / min, a sintering temperature of 800 °C, and a holding time of 500 min. After sintering and sieving, Si@Yb₂O₃ core-shell structured powder was obtained, with the cross-sectional morphology as shown in the figure. Figure 3 As shown in the figure, the particle size distribution of the prepared powder is approximately 52.9~152.1 μm, the thickness of the powder coating layer is approximately 2.1~15.6 μm, the average thickness of the coating layer is approximately 7.3 μm, and the average thickness of the coating layer of more than 90% of the powder is between 3.9~10.1 μm. The outer shell coating layer thickness distribution is uniform, and the prepared core-shell structure powder has no agglomeration phenomenon and good dispersibility, making it an excellent powder for spraying feed.

[0029] Comparative Example 1 25 g of Yb₂O₃ was weighed and added to a ball mill jar to prepare a slurry with a solid content of 45%. The particle size of Yb₂O₃ was approximately 1–40 μm. The slurry was then obtained by ball milling. Next, 20 g of Si agglomerated powder with a particle size distribution of 20–145 μm was weighed and sprayed onto the surface of the Si powder. The powder was then dried at 35 °C. The morphology of the prepared Si@Yb₂O₃ core-shell structured powder is shown below. Figure 4As shown in the figure, it can be seen that the prepared powder is not completely coated and the thickness distribution of the outer shell coating is uneven. Figure 4 As shown in (ab); the coating layer exhibits cracking, and the coating is not dense and is relatively loose, as... Figure 4 As shown in (c), the prepared powder exhibits severe agglomeration and poor dispersibility, making it difficult to meet the requirements for spray feed powder.

[0030] The reasons for the above problems are as follows: 1. The solid content of the spraying slurry is too high, which is not within the range of key process parameters protected by this invention, resulting in uneven spraying and incomplete coating; 2. The particle size distribution of the raw material ytterbium oxide is too large. When the ball milling process is not well controlled, it is difficult to obtain uniform and fine ytterbium oxide particles, which will also cause uneven coating or even gun clogging; 3. The drying temperature is too low, and the evaporation rate of the slurry after spraying is slow, resulting in agglomeration.

[0031] As can be seen from Comparative Example 1, the preparation process parameters protected by this invention are very important. Powders prepared outside the scope of protection of this invention are prone to uneven, incomplete, and non-dense coatings, as well as agglomeration. This also demonstrates the criticality and importance of the preparation process protected by this invention, which is essential to obtaining core-shell structured feed powders with uniform, complete, dense, non-agglomerated, well-dispersed, controllable thickness, and excellent sphericity.

[0032] After comparing Example 3 and Comparative Example 1, namely Figure 3 and Figure 4 The comparison clearly demonstrates the significant advantages of the core-shell structured powder prepared by this invention: uniform, complete, dense coating, and no agglomeration. The technology is significantly innovative, and its superior effects are very evident.

[0033] Comparative Example 2 The characteristics of core-shell structured powders commonly found in the literature are mostly: irregular morphology; although they possess a core-shell structure, the coating layer thickness is mostly in the nanometer range; the outer shell coating layer thickness cannot be quantitatively controlled, making it difficult to customize the outer shell layer thickness, especially achieving a micrometer-level controllable outer shell layer thickness. Specifically, for example... Figure 5 As shown, these are core-shell structured α-Fe2O3@CeO2 and CeO2@α-Fe2O3 powders synthesized by hydrothermal method. As can be seen from the figure, although the outer shell of conventional core-shell structured powders encapsulates the core powder, the overall morphology of the coated powder is irregular, and the thickness of the coating layer is usually thin, at the nanometer level, and the thickness cannot be quantitatively controlled.

[0034] By comparing the proportions, it can be clearly seen that the preparation technology of the present invention has made significant progress, specifically in the following aspects: (1) the appearance presents a perfectly regular spherical shape, (2) the outer shell layer is uniformly and completely wrapped on the surface of the core powder, and (3) the thickness of the coating layer is adjustable and controllable, and the thickness adjustment range is large: from submicron to micron level.

[0035] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of the present invention. Any person skilled in the art can make their own modifications and alterations without departing from the spirit and scope of the present invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A spherical core-shell structured Si@Yb2O3 feed powder, characterized in that, The powder comprises a core-shell structure with Si as the core and Yb2O3 as the outer shell, and has a spherical appearance. The core-shell structure has a complete, uniform, and dense coating. The Yb2O3 is formed on the outer surface of the Si by spraying. The Yb2O3 coating of Si is used to suppress the oxidation of Si during plasma spraying, thereby reducing the initial content of silicon oxide in the Si binder layer.

2. The spherical core-shell structured Si@Yb2O3 feed powder according to claim 1, characterized in that, The particle size distribution of the core is 1~180 μm; the thickness of the outer shell is determined as needed.

3. The spherical core-shell structured Si@Yb2O3 feed powder according to claim 2, characterized in that, The thickness of the outer shell is 0.1~40 μm.

4. A method for preparing Si@Yb2O3 feed powder with a spherical core-shell structure according to any one of claims 1 to 3, characterized in that, The method includes: spraying Yb2O3 slurry onto the surface of silicon powder and sequentially performing drying and heat treatment to obtain the spherical core-shell structured Si@Yb2O3 feed powder.

5. The method for preparing Si@Yb2O3 feed powder with a spherical core-shell structure according to claim 4, characterized in that, The method specifically includes: (1) Selection of raw materials: Select suitable silicon powder as the core; (2) Preparation and spraying of slurry: Prepare a stable and uniform Yb2O3 slurry; spray the Yb2O3 slurry onto the surface of the silicon powder and dry it so that the Yb2O3 powder is coated on the outer surface of the silicon powder; (3) Post-processing: The product obtained in step (2) is subjected to heat treatment to obtain the spherical core-shell structured Si@Yb2O3 feed powder.

6. The method for preparing Si@Yb2O3 feed powder with a spherical core-shell structure according to claim 5, characterized in that, In step (1), the silicon powder includes molten and crushed silicon powder and / or silicon agglomerate powder prepared by spray drying.

7. The method for preparing Si@Yb2O3 feed powder with a spherical core-shell structure according to claim 5, characterized in that, Step (2) specifically includes: the Yb2O3 slurry is prepared by ball milling or mechanical stirring; the solid content of the Yb2O3 slurry is 3%~40%, the particle size of Yb2O3 is 0.01~30 μm; and the drying temperature is 40~160℃.

8. The method for preparing Si@Yb2O3 feed powder with a spherical core-shell structure according to claim 5, characterized in that, In step (3), the process parameters of the heat treatment include: heating rate of 1~20 ℃ / min, temperature of 600~1450℃, and holding time of 20~600 min.

9. The method for preparing Si@Yb2O3 feed powder with a spherical core-shell structure according to claim 7, characterized in that, Step (3) further includes: sieving the product after heat treatment.

10. The method for preparing Si@Yb2O3 feed powder with a spherical core-shell structure according to claim 9, characterized in that, The particle size of the spherical core-shell structured Si@Yb2O3 feed powder obtained after sieving is 5~200 μm.

11. The application of a spherical core-shell structured Si@Yb2O3 feed powder as a silicon binder layer in an environmental barrier coating system or a thermal / environmental barrier coating system according to any one of claims 1 to 3.

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