A Si-HfO2 multiphase feed powder slurry, powder, preparation method and application thereof

Abstract

This invention discloses a slurry, powder, and preparation method for Si-HfO2 multiphase feed powder, as well as its application. Specifically, granulated silicon agglomerates and a hafnium precursor are used as raw materials. The silicon agglomerates are then impregnated in a hafnium precursor solution to obtain a Si-HfO2 multiphase feed powder slurry. After drying and sieving, the slurry undergoes high-temperature heat treatment to prepare Si-HfO2 multiphase feed powder for silicon binder layers. The innovation of this invention lies in the first use of a precursor impregnation method to prepare Si-HfO2 multiphase powder, and the in-situ generated nano-sized hafnium oxide is uniformly distributed on the surface and inside of the silicon agglomerates. This preparation method is simple, low-cost, and widely applicable; besides the silicon binder layer field, it is also suitable for the efficient, convenient, and low-cost preparation of multiphase powders in other fields.

Description

Technical Field

[0001] This invention relates to the field of feed powder preparation, specifically to a slurry, powder, preparation method, and application of Si-HfO2 multiphase feed powder. Background Technology

[0002] With the continuous improvement of engine thrust-to-weight ratio, ceramic matrix composites have become the preferred material for hot-section components (>1500℃) of next-generation aero-engines due to their excellent high-temperature resistance and lightweight properties. Furthermore, environmental barrier coatings are a key technology to ensure the stable service of ceramic matrix composites and enhance their corrosion resistance. Among them, rare-earth silicate coatings, due to their excellent corrosion and oxidation resistance, have become the most widely researched and promising environmental barrier coatings. However, environmental barrier coatings cannot be directly applied to the composite matrix alone; they require a Si bonding layer with a thermal expansion coefficient more compatible with the matrix to achieve effective bonding, thereby ensuring the robustness and reliability of the coating system.

[0003] Si adhesive layers not only possess good chemical compatibility and excellent bonding strength, but also act as oxygen-absorbing layers, providing multiple protective functions. However, the low melting point of Si (1414℃) means that the service temperature of pure silicon adhesive layers is typically below 1350℃. More importantly, during service, Si undergoes an oxidation reaction to generate SiO2, accompanied by a 2.2-fold volume expansion, leading to internal cracks in the coating and causing it to peel off and fail. Therefore, traditional pure silicon adhesive layers have reached a service life bottleneck, making the development of novel Si adhesive layers with superior performance crucial. Summary of the Invention To overcome the shortcomings and deficiencies of existing technologies, this invention provides a slurry, powder, preparation method, and application of Si-HfO2 multiphase feed powder. This method uses spray-granulated Si agglomerated powder and hafnium precursor as raw materials, and prepares Si-HfO2 multiphase feed powder through a simple and efficient precursor impregnation method. The prepared powder has the advantages of good sphericity, uniform distribution of hafnium oxide at the nanoscale, and complete encapsulation.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a slurry for Si-HfO2 multiphase feed powder, the slurry comprising the following raw materials: silicon agglomerate powder and hafnium precursor solution, wherein the hafnium precursor solution is formed by mixing hafnium precursor and solvent; wherein the concentration of the hafnium precursor solution is 5~50 wt%, and the amount of hafnium precursor added is 0.1~35 mol of the molar ratio of silicon agglomerate powder.

[0005] Furthermore, the hafnium precursor includes one or more of Hf(C3H7O)4, Hf(C4H9O)4, HfCl2O, and HfCl4.

[0006] Furthermore, the particle size distribution of the silicon agglomerate powder is 5~180 μm, preferably 10~100 μm.

[0007] This invention also provides a method for preparing the above-mentioned Si-HfO2 multiphase feed powder slurry. The method includes: heat-treating silicon agglomerate powder to obtain debinded silicon agglomerate powder; mixing a hafnium precursor uniformly in a solvent to obtain a hafnium precursor solution; and adding the debinded silicon agglomerate powder to the hafnium precursor solution for mixing and impregnation to obtain the Si-HfO2 multiphase feed powder slurry. The purpose of mixing and impregnation is to ensure uniform mixing of the silicon agglomerate powder and the hafnium precursor solution and to allow the hafnium precursor solution to penetrate into the interior of the silicon agglomerate powder, so that the silicon particles on the surface and inside the silicon agglomerate powder can uniformly contact the hafnium precursor.

[0008] Furthermore, the temperature for heat treatment of the silicon agglomerate powder is 700~1350℃, and the holding time is 0.5~12 h.

[0009] This invention employs a precursor impregnation method to synthesize Si-HfO2 feed powder in which nano-sized hafnium oxide is uniformly distributed on both the surface and interior of silicon agglomerate powder. It should be noted that the silicon agglomerate powder obtained by spray drying is a commonly used feed powder for silicon bonding. The silicon agglomerate powder formed by particle aggregation contains many gaps, allowing the precursor solution to penetrate. After drying, heat treatment allows the hafnium precursor to undergo in-situ pyrolysis, forming nano-sized hafnium oxide, which is uniformly distributed on both the surface and interior of the silicon granulation powder.

[0010] Furthermore, the impregnation method is stirring, ultrasonication, or vacuum impregnation. When the impregnation method is stirring, the stirring time is 0.1~12 h; when the impregnation method is ultrasonication, the ultrasonication time is 10 s~60 min; when the impregnation method is vacuum impregnation, the vacuum impregnation time is 10 s~6 h.

[0011] The present invention also provides a Si-HfO2 multiphase feed powder, which is prepared from the above-mentioned Si-HfO2 multiphase feed powder slurry.

[0012] The present invention further provides a method for preparing the above-mentioned Si-HfO2 multiphase feed powder, the method comprising: drying, sieving and high-temperature heat treatment of the Si-HfO2 multiphase feed powder with a slurry in sequence to prepare Si-HfO2 multiphase feed powder for silicon bonding layer; wherein, the drying temperature is 50~150℃ and the time is 3~72 h; the high-temperature heat treatment temperature is 600~1400℃ and the holding time is 0.5~24 h.

[0013] Furthermore, the particle size of the sieved multiphase powder is 10~200 μm, preferably 20~110 μm.

[0014] The present invention also provides an application of the above-mentioned Si-HfO2 multiphase feed powder in the field of silicon bonding layer and feed powder for hot end components of aero-engine composite materials.

[0015] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages: (1) Compared with traditional pure silicon agglomerate powder, the present invention adds hafnium oxide, which can effectively increase the service temperature of the adhesive layer, eliminate thermally grown oxides, and improve the reliability and service life of the adhesive layer.

[0016] (2) Compared with other emerging Si-HfO2 multiphase feed powders, the present invention provides a novel precursor impregnation method for preparing multiphase powders, and the feed powder has the characteristics of high sphericity, uniform distribution of hafnium oxide doping at the nanoscale, and comprehensive coating.

[0017] (3) The Si-HfO2 multiphase feed powder prepared in this invention has a reasonable compositional structure distribution—HfO2, which is not easily oxidized, is attached to and coated on the outer surface of the silicon agglomerate powder and impregnated into the gaps between silicon particles inside the agglomerate powder. During atmospheric plasma spraying, the silicon powder coated with hafnium oxide has a lower degree of oxidation, less silicon oxide exists in the silicon binder layer, and the coating has better oxidation resistance.

[0018] (4) This invention is easy to operate, simple in process, and low in equipment cost, making it suitable for industrial production. In addition to the field of feedstock powders, it also has broad application prospects in other fields such as multiphase powders, and the method has wide applicability. Attached Figure Description

[0019] Figure 1 The XRD pattern of the Si-HfO2 multiphase feed powder prepared in Example 1; Figure 2 The images show the surface morphology and EDS spectrum of the Si-HfO2 multiphase feed powder prepared in Example 2. Figure 3 The images show the cross-sectional morphology and EDS spectrum of the Si-HfO2 multiphase feed powder prepared in Example 3. Figure 4 The image shows the morphology and composition of the Si-HfO2 composite powder prepared by the traditional process in Comparative Example 1. Detailed Implementation

[0020] Currently, modified Si-HfO2 multiphase coatings show significant advantages in the development of novel Si binders. Firstly, HfO2 has an extremely high melting point (2758℃), fundamentally improving the heat resistance of the binder. Secondly, at high temperatures, HfO2 can react with SiO2 generated from Si oxidation to form HfSiO4 with a matching coefficient of thermal expansion. This significantly consumes SiO2, effectively mitigating coating failure caused by the accumulation of thermally grown oxides (TGO) and the mismatch in coefficients of thermal expansion. In summary, doping pure silicon binders with HfO2 not only effectively increases the operating temperature of the binder but also significantly inhibits oxidation cracking and peeling, providing strong support for the long-term stable operation of environmental barrier coating systems.

[0021] The inventors discovered that a common doping method involves blending Si and HfO2 solid powders to prepare a slurry of the mixed powder, followed by spray granulation to prepare Si-HfO2 agglomerated powder. However, this process has the following problems: Si (2.33 g / cm³) and HfO2 (9.68 g / cm³)... 3 The powders have significant density differences, leading to inconsistent behavior under centrifugal force during granulation. This results in poor sphericity of the prepared agglomerated powders, and the distribution of the two particle types (Si and Hf elements) at the nanoscale is not uniform. Figure 4 As shown.

[0022] To address the aforementioned issues, this invention proposes for the first time a precursor impregnation method for preparing Si-HfO2 multiphase feed powder. Silicon agglomerated powder is impregnated in a hafnium precursor solution. This allows the hafnium precursor to not only coat the surface of all surface Si particles in the silicon agglomerated powder but also to penetrate along the particle gaps into the interior of the spherical agglomerated powder, filling and coating the surface of the internal Si particles. Subsequent heat treatment generates nanoscale HfO2 in situ on the surface of all silicon particles and both on and inside the silicon agglomerated powder. The final product is a Si-HfO2 multiphase powder with HfO2 uniformly and completely coated on the surface and inside of the silicon agglomerated powder, thereby increasing the operating temperature of the silicon binder layer, improving the oxidation resistance of the coating, and extending the service life of the environmental barrier coating.

[0023] The present invention will now be described in detail with reference to specific embodiments.

[0024] Example 1 Weigh 20 g of Hf(C3H7O)4 and add it to 80 mL of n-propanol. Stir to mix the two evenly to obtain a stable precursor solution. Add silica agglomerates with a particle size of 15-120 μm (after degumming heat treatment: 750 ℃ ​​for 10 h) to the precursor solution and stir for another 3 h to obtain the stirred solution, which is the slurry for Si-HfO2 multiphase feed powder. Place the stirred solution in an oven and dry at 85 ℃ for 36 h. After complete drying, sieve to obtain powder with a particle size of 25-95 μm. Then, perform high-temperature heat treatment at a sintering temperature of 1300 ℃ for 1.5 h to obtain Si-HfO2 multiphase feed powder. The XRD diffraction pattern of the powder is shown below. Figure 1 As shown in the figure, the powder contains only two phases, Si and HfO2, which proves that pure-phase Si-HfO2 multiphase feed powder has been prepared.

[0025] Example 2 10 g of HfCl2O·8H2O was weighed and added to 50 mL of deionized water. The mixture was mechanically stirred to ensure homogeneity, yielding a stable hafnium precursor solution. Silicon agglomerates with a particle size of 20–130 μm (after debinding and heat treatment at 1050 ℃ for 5 h) were added to the precursor solution and sonicated for 5 min to obtain the sonicated solution, which is the slurry for Si-HfO2 multiphase feed powder. The sonicated solution was dried in an oven at 140 ℃ for 12 h. After complete drying, the powder with a particle size of 30–100 μm was obtained by sieving. Then, high-temperature heat treatment was performed at 1000 ℃ for 6 h to obtain Si-HfO2 multiphase feed powder. The surface morphology and EDS spectrum of the powder are shown below. Figure 2 As shown in the figure, the prepared multiphase powder has a high sphericity. Furthermore, not only Si elements can be seen on the surface of the spherical silicon agglomerate powder, but Hf elements can also be seen. This indicates that hafnium oxide is relatively uniformly coated on the surface of the silicon agglomerate powder, thus achieving the coating of silicon agglomerate powder by hafnium oxide.

[0026] Example 3 30 g of Hf(C4H9O)4 was weighed and added to 100 mL of n-propanol, and stirred until homogeneous to obtain a stable precursor solution. Silicon agglomerates with a particle size of 10–110 μm (after desizing heat treatment at 1300 ℃ for 1 h) were added to the precursor solution, and then placed in a vacuum defoaming chamber for vacuum impregnation for 0.5 h to obtain the impregnated solution, which is the slurry for Si-HfO2 multiphase feed powder. The impregnated solution was then dried in an oven at 60 ℃ for 50 h. After complete drying, the powder with a particle size of 10–90 μm was obtained by sieving. Then, high-temperature heat treatment was performed at 850 ℃ for 12 h to obtain Si-HfO2 multiphase feed powder. The cross-sectional morphology and EDS energy spectrum of the powder are shown below. Figure 3 As shown in the figure, the sphericity of the prepared multiphase powder is very high, and the interior of the spherical silicon agglomerate powder contains not only Si elements but also Hf elements, and the concentration distribution of both is relatively uniform, indicating that hafnium oxide is also uniformly distributed inside the silicon agglomerate powder.

[0027] It should be understood that the silicon agglomerate powder used can be obtained by spray drying silicon powder using conventional methods, or it can be commercially available.

[0028] Comparative Example 1 This comparative example provides a traditional and commonly used method for preparing Si-HfO2 composite powder, the specific method of which is as follows: First, Si powder and HfO2 powder are ball-milled and stirred together to form a uniform Si-HfO2 slurry. Then, the mixed powder slurry is spray-granulated to prepare Si-HfO2 agglomerated powder with random distribution of hafnium oxide and silicon powder.

[0029] Due to Si (2.33 g / cm³) 3 ) and HfO2 (9.68 g / cm) 3 The powders have significant density differences, which leads to irregular shapes of the liquid ejected during centrifugal granulation. The resulting powders are typically not regular shapes. (See...) Figure 4 .from Figure 4 As can be seen in (a), the morphology of the prepared Si-HfO2 powder varies greatly and is not a regular sphere; although the powder is mixed and granulated, there are still individual granular silicon powder particles, such as... Figure 4 As shown in (b); Figure 4 (c) indicates that hafnium oxide powder is present at positions 2 and 4 in the figure. Figure 4 (e) is a magnified photograph of hafnium oxide particles on the surface of the multiphase agglomerated powder; from Figure 4As can be seen in (d), within the Si-HfO2 multiphase powder, silicon powder and hafnium oxide powder are randomly distributed, and the sizes of the two types of particles differ significantly. In summary, whether in terms of microstructure, uniformity of distribution at the nanoscale, or sphericity, it shows significant differences from the powder prepared by this invention, and correspondingly demonstrates the advancement of the powder and its preparation method provided by this invention.

[0030] As can be seen from Examples 2 and 3 and Comparative Example 1, both the silicon particles on the surface and inside the agglomerated powder are relatively completely coated with in-situ generated hafnium oxide; at the same time, hafnium oxide is uniformly coated on both the surface and inside of the spherical silicon agglomerated powder. The Si-HfO2 multiphase feed powder prepared by this invention has the following advantages: 1. First, it has the advantage of high purity; 2. At the same time, it can achieve relatively uniform coating of hafnium oxide on the surface of silicon particles, both on the surface and inside, and obtain uniform mixing of hafnium oxide and silicon particles at the nanoscale, achieving more comprehensive protection for silicon agglomerated powder; 3. It can further ensure a more uniform distribution of hafnium oxide in the coating; 4. It has a high degree of sphericity.

[0031] 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 slurry for Si-HfO2 multiphase feed powder, characterized in that, The slurry comprises the following raw materials: silicon agglomerate powder and hafnium precursor solution, wherein the hafnium precursor solution is formed by mixing hafnium precursor and solvent; and the silicon agglomerate powder is obtained by spray drying. The concentration of the hafnium precursor solution is 5-50 wt%, and the amount of hafnium precursor added is 0.1-35 mol of the molar ratio of silicon agglomerate powder.

2. The Si-HfO2 multiphase feed powder slurry according to claim 1, characterized in that, The hafnium precursor includes one or more of Hf(C3H7O)4, Hf(C4H9O)4, HfCl2O, and HfCl4.

3. The Si-HfO2 multiphase feed powder slurry according to claim 1, characterized in that, The particle size distribution of the silicon agglomerate powder is 5~180 μm.

4. A method for preparing a slurry for Si-HfO2 multiphase feed powder according to any one of claims 1 to 3, characterized in that, The preparation method includes: The silicon agglomerate powder was heat-treated to obtain de-gelled silicon agglomerate powder; The hafnium precursor was placed in a solvent and mixed evenly to obtain a hafnium precursor solution; The degummed silicon agglomerate powder is added to a hafnium precursor solution for mixing and impregnation to obtain the Si-HfO2 multiphase feed powder slurry.

5. The method for preparing Si-HfO2 multiphase feed powder slurry according to claim 4, characterized in that, The temperature for heat treatment of the silicon agglomerate powder is 700~1350℃, and the holding time is 0.5~12 h.

6. The method for preparing Si-HfO2 multiphase feed powder slurry according to claim 5, characterized in that, The impregnation method is stirring, ultrasonic impregnation, or vacuum impregnation. When the mixing and impregnation method is stirring, the stirring time is 0.1~12 h; When the impregnation method is ultrasonic, the ultrasonic duration is 10 s to 60 min. When the impregnation method is vacuum impregnation, the vacuum impregnation time is 10 s to 6 h.

7. A Si-HfO2 multiphase feed powder, characterized in that, The Si-HfO2 multiphase feed powder is prepared from the Si-HfO2 multiphase feed powder slurry according to any one of claims 1 to 3.

8. A method for preparing Si-HfO2 multiphase feed powder according to claim 7, characterized in that, The preparation method includes: The Si-HfO2 multiphase feed powder is dried, sieved, and subjected to high-temperature heat treatment in sequence to prepare Si-HfO2 multiphase feed powder for silicon bonding layer; wherein the drying temperature is 50~150℃ and the time is 3~72 h; the high-temperature heat treatment temperature is 600~1400℃ and the holding time is 0.5~24 h.

9. The method for preparing Si-HfO2 multiphase feed powder according to claim 8, characterized in that, The particle size of the multiphase powder after sieving is 10~200 μm.

10. The application of the Si-HfO2 multiphase feed powder according to claim 7 in the field of silicon bonding layer for hot-end components of aero-engine composites.

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