Surface-coated corrosion-resistant and dioxin-resistant silicon carbide wear-resistant powder material

Abstract

The application provides a surface-coated anti-corrosion dioxin-resistant silicon carbide wear-resistant powder material, and relates to the technical field of silicon carbide materials. The material takes cubic crystal type beta-SiC nano powder as a matrix, realizes the combination of high-temperature corrosion resistance, high wear resistance and high-efficiency dioxin prevention by constructing a gradient coating structure of 'Si-O-C transition layer / ZrO2-Al2O3-Y2O3 middle layer / SiO2-rare earth oxide-phosphotungstic acid multifunctional outer layer'. The preparation method of the material comprises key steps of matrix etching, transition layer construction, hydrothermal deposition and atmosphere calcination, and the process is controllable and has good repeatability. The obtained powder has excellent long-term protection performance, good dispersibility and stable structural integrity, and is suitable for fields of wear-resistant coating, composite reinforcement and waste gas treatment in harsh environments.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide materials technology, and in particular to a surface-coated, corrosion-resistant, dioxin-resistant, wear-resistant silicon carbide powder material. Background Technology

[0002] Silicon carbide (SiC), as a high-performance ceramic material, possesses characteristics such as high hardness, high temperature resistance, excellent mechanical strength, and strong chemical stability, and is widely used in fields such as waste incinerator linings, chemical corrosion-resistant equipment, and high-temperature wear-resistant coatings. Among them, cubic β-SiC has become the preferred matrix for preparing high-performance powder materials due to its easily controllable particle size and excellent dispersibility potential. However, in actual service environments, pure β-SiC powder still has significant technical shortcomings: on the one hand, the presence of HCl-containing flue gas and high-temperature oxidizing atmospheres in scenarios such as waste incineration and chemical reactions can lead to the formation of a loose SiO2 oxide layer on the SiC surface. This oxide layer is easily penetrated by corrosive media, causing matrix erosion, powder performance degradation, and seriously affecting the service life of the material; on the other hand, dioxins (PCDD / Fs) generated during waste incineration are highly toxic pollutants, and existing SiC materials lack targeted inhibition and adsorption functions, failing to meet the needs of environmental protection fields for multifunctional material integration.

[0003] To address these issues, the industry often employs surface coating technology to modify SiC powder, enhancing its corrosion resistance and wear resistance by constructing an inorganic coating layer. However, existing coating technologies still have several shortcomings: some solutions only pursue corrosion resistance or wear resistance without achieving multi-functional synergy, making them difficult to adapt to complex service environments; poor interfacial compatibility and mismatched thermal expansion coefficients between the coating layer and the SiC matrix easily lead to cracking and peeling, especially during high-temperature calcination or thermal cycling, where interfacial defects can further expand, resulting in protective failure; a few solutions attempting to introduce dioxin-resistant functions suffer from uneven dispersion of adsorbents and catalysts, easy detachment of functional components, and low dioxin inhibition efficiency, and fail to achieve effective synergy with corrosion resistance and wear resistance. Furthermore, SiC powder itself has a tendency to agglomerate, and existing modification processes lack sufficient control over dispersibility, further affecting the uniformity of the coating layer and the actual application effect of the material.

[0004] Meanwhile, in existing coating processes, the design of the transition layer is often unreasonable, leading to insufficient density and poor structural stability of the coating layer. For example, the lack of an effective interfacial bridging layer results in the inorganic coating layer and the SiC matrix being merely physically attached, with low bonding strength; poor phase control in the coating layer can trigger phase transformation and volume expansion, generating microcracks and providing penetration channels for corrosive media; and uncontrolled loading and distribution of functional components can lead to excessively rapid degradation of dioxin-resistant properties. Therefore, developing a surface-coated SiC powder material that combines a dense and stable corrosion-resistant and wear-resistant coating structure, efficient dioxin-resistant function, and excellent dispersibility is key to overcoming existing technological bottlenecks and is of great significance for expanding the application of SiC materials in high-end fields such as environmental protection and chemical engineering. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a surface-coated, corrosion-resistant, dioxin-resistant silicon carbide wear-resistant powder material.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a surface-coated anti-corrosion and anti-dioxin silicon carbide wear-resistant powder material, comprising the following raw materials in parts by weight: SiC: 100 parts, methyltrimethoxysilane: 8-12 parts, middle coating liquid: 300-450 parts, outer coating liquid: 400-600 parts, and isopropyl triisostearate titanate: 1-3 parts.

[0007] Preferably, the preparation method of the intermediate coating liquid is as follows: Zirconium nitrate, aluminum nitrate, and yttrium oxide were added to deionized water and stirred until dissolved to obtain a middle-layer coating solution.

[0008] Preferably, the outer coating liquid is prepared as follows: Tetraethyl orthosilicate, neodymium nitrate, cerium nitrate and phosphotungstic acid were added to an ethanol / water mixture and stirred until dissolved to obtain the outer coating solution.

[0009] Preferably, in the preparation method of the intermediate coating liquid, the molar ratio of zirconium nitrate, aluminum nitrate and yttrium oxide is 8-12:2-4:1.

[0010] Preferably, the total mass fraction of solute in the intermediate coating solution is 2.5%-3.5%.

[0011] Preferably, in the preparation method of the outer coating liquid, the molar ratio of tetraethyl orthosilicate, neodymium nitrate, cerium nitrate and phosphotungstic acid is 18-22:0.5-1.5:0.8-1.2:0.3-0.7.

[0012] Preferably, the total mass fraction of the solute in the outer coating liquid is 5%-8%.

[0013] Preferably, the volume ratio of ethanol to water in the ethanol / water mixture in the outer coating liquid is 4:1.

[0014] Preferably, the SiC is cubic β-SiC with a particle size of 50-200 nm.

[0015] Furthermore, the present invention also provides a method for preparing a surface-coated corrosion-resistant, dioxin-resistant silicon carbide wear-resistant powder material, comprising the following steps: (1) SiC was added to dilute hydrochloric acid and hydrofluoric acid in sequence, and ultrasonically cleaned for 30-60 min. During this period, the mixture was stirred at 100-200 rpm to assist dispersion. Then, it was vacuum filtered and the filter cake was washed with deionized water until the pH of the filtrate was neutral to obtain purified SiC. The purified SiC was added to hydrofluoric acid / oxalic acid composite etching solution, heated to 35-45℃ and stirred at 200-400 rpm for 1-2 h. Then, it was filtered and washed with deionized water until the pH of the filtrate was neutral. After vacuum drying, the SiC matrix was obtained. The core of this step is to remove metallic impurities and the native oxide layer from the surface of SiC powder, and to construct a porous structure through gentle etching, providing mechanical intercalation sites for the subsequent coating layer. Dilute hydrochloric acid can undergo a displacement reaction with transition metal impurities such as Fe and Cu attached to the SiC surface, with reactions such as Fe + 2HCl → FeCl2 + H2↑ and Zn + 2HCl → ZnCl2 + H2↑. The synergistic effect of ultrasound and stirring enhances the contact efficiency between hydrochloric acid and impurities, improving the purification effect. The subsequent hydrofluoric acid (HF) treatment targets the native SiO2 oxide layer on the SiC surface, reacting with SiO2 + 4HF → SiF4↑ + 2H2O. This etching process removes the oxide layer, exposing the clean SiC substrate surface. In the hydrofluoric acid / oxalic acid composite etching solution, HF gently etches the SiC surface, forming pits, while oxalic acid, as a complexing agent, can react with the trace amounts of Si dissolved during the etching process. 4+ A complexation reaction occurs, forming a stable [Si(C2O4)3] group. 2- Complex ions, avoiding Si 4+ By redepositing and blocking the pores, the resulting porous matrix can significantly improve the mechanical bonding force with subsequent coating layers. (2) Add the SiC matrix to anhydrous ethanol, ultrasonically disperse for 20-40 min, then add methyltrimethoxysilane, stir evenly, adjust the pH of the system to 4-5 with glacial acetic acid, heat to 60-70℃ and stir for 2-4 h, cool to room temperature and filter, wash with deionized water and dry to obtain SiC powder with Si-OC transition layer on the surface. The purpose of this step is to construct a continuous Si-OC transition layer on the surface of a porous matrix through the hydrolysis and condensation of organosilanes, thereby achieving an "organic-inorganic" bridge between the matrix and the subsequent inorganic coating layer and improving interfacial compatibility. Anhydrous ethanol is used as a dispersion medium to ensure uniform suspension of the porous matrix, and ultrasonic dispersion further breaks up powder agglomerates, ensuring full contact between methyltrimethoxysilane (MTMS) and the matrix surface. Glacial acetic acid adjusts the pH of the system to 4-5, providing an acidic catalytic environment for the hydrolysis of MTMS. MTMS undergoes a hydrolysis reaction to generate hydrolysis products containing silanol groups. The silanol groups in the hydrolysis products undergo a dehydration condensation reaction with the hydroxyl groups exposed on the surface of the porous matrix, with the reaction formula SiC-OH + HO-Si-CH3 → SiC-O-Si-CH3 + H2O, ultimately forming a Si-OC transition layer on the SiC surface. (3) Add the SiC powder with the Si-OC transition layer on the surface to the middle coating liquid, disperse it by ultrasonication for 20-40 min, then add ammonia water under stirring to adjust the pH of the system to 9-10, then transfer it to a hydrothermal reactor, seal it and heat it to 170-190℃ for hydrothermal reaction for 8-12 h, cool it to room temperature, filter it, wash the filter cake with deionized water 2-3 times, dry it and place it in a muffle furnace, introduce argon gas, heat it to 700-800℃, keep it at the temperature for calcination for 2-3 h to obtain the middle coated powder; This step involves the hydrothermal deposition and thermal decomposition of a hydroxide precursor to construct a dense intermediate layer, while simultaneously protecting the SiC substrate from oxidation using an argon atmosphere. Zirconium nitrate and aluminum nitrate in the intermediate layer coating solution dissociate into Zr in the aqueous solution. 3+ Al 3+ Yttrium oxide is dispersed in the form of nanoparticles. SiC powder coated with a Si-OC transition layer is ultrasonically dispersed, and the addition of ammonia raises the pH of the system to 9-10. Zr... 3+ Al 3+ Hydrolysis occurs, generating hydroxide precursors. These precursors are adsorbed onto the transition layer surface via hydrogen bonds and van der Waals forces. The hydrothermal reaction is carried out under high temperature and pressure (170-190℃), which promotes the rearrangement and dense deposition of precursor particles, while achieving preliminary crystallization and improving the bonding strength between the precursor layer and the transition layer. Subsequent calcination at 700-800℃ under an argon atmosphere causes thermal decomposition of the hydroxide precursors, generating the target oxides ZrO2 and Al2O3. Furthermore, argon, as an inert gas, isolates oxygen, preventing the SiC matrix from undergoing oxidation at high temperatures (SiC + 2O2 → SiO2 + CO2), thus ensuring the integrity of the matrix structure. During calcination, yttrium oxide dissolves into the ZrO2 lattice, inhibiting the oxidation of ZrO2. 22 The phase transition from the tetragonal phase to the monoclinic phase avoids cracking of the coating layer caused by the volume expansion of the phase transition, and finally forms a wear-resistant ZrO2-Al2O3-Y2O3 intermediate layer. (4) Add the middle layer coated powder to the outer layer coated liquid, ultrasonically disperse for 20-40 min, heat to 60-70℃ and stir for 4-6 h, then vacuum filter, wash the filter cake 2-3 times with anhydrous ethanol, dry and place in a muffle furnace, heat to 600-700℃ in air atmosphere, keep warm and calcine for 3-4 h, cool to room temperature to obtain the outer layer coated powder; The core of this step is to construct a composite layer that combines dioxin adsorption and catalytic inhibition functions. The choice of air atmosphere calcination is based on the dense protective effect of the middle layer and the process requirements of the outer layer components. The ethanol / water mixed solvent in the outer coating solution provides a suitable environment for the hydrolysis of tetraethyl orthosilicate (TEOS). TEOS undergoes a hydrolysis-condensation reaction, forming a three-dimensional SiO2 gel network. Neodymium nitrate, cerium nitrate, and phosphotungstic acid are uniformly dispersed in the gel network. Constant temperature stirring at 60-70℃ promotes the tight bonding between the gel network and the middle layer surface. Vacuum filtration and washing with anhydrous ethanol remove unreacted sol components. Subsequent calcination at 600-700℃ in air atmosphere ensures that the dense structure of the middle ZrO2-Al2O3-Y2O3 layer completely isolates oxygen from the inner SiC matrix, preventing matrix oxidation. Simultaneously, the air atmosphere promotes the thermal decomposition of neodymium nitrate and cerium nitrate, generating rare earth oxides with catalytic inhibition functions. The reaction formula is 2Nd(NO3)3→Nd2O3+ 6NO2↑+3O2↑, 2Ce (NO3)3→Ce2O3+6NO2↑+3O2↑, and this calcination temperature will not destroy the Keggin structure of phosphotungstic acid (PWA). Phosphotungstic acid can be uniformly distributed on the SiO2 gel network, providing sufficient sites for dioxin adsorption, and finally forming a multifunctional outer layer with both adsorption and inhibition functions. (5) Add the outer coating powder to anhydrous ethanol and ultrasonically disperse for 10-30 min. Then add triisostearate titanate isopropyl triisostearate, heat to 60-70℃ and stir for 2-4 h. After the reaction is complete, vacuum filter, wash the filter cake with deionized water 2-3 times, dry it and put it into a planetary ball mill, grind it and pass it through a 300-mesh sieve to obtain a surface-coated anti-corrosion and anti-dioxin silicon carbide wear-resistant powder material. The core of this step is to improve the powder dispersibility through coupling agent modification, while simultaneously breaking up agglomerates through gentle grinding. Anhydrous ethanol is used as the dispersion medium to ensure uniform suspension of the outer coated powder. After ultrasonic dispersion, isopropyl triisostearate titanate is added. The isopropoxy group in its molecular structure can undergo an esterification reaction with the hydroxyl groups on the surface of the outer phosphotungstic acid, with the reaction formula being PWA-OH+(RO)3Ti-OOCR'→PWA-O-Ti. (OR)2-OOCR'+ROH (where PWA represents phosphotungstic acid, R is isopropyl, and R' isostearyl), the ester bond generated by the reaction firmly grafts the coupling agent molecule onto the powder surface, while the long-chain isostearyl group at the other end of the coupling agent molecule extends outward to form a steric hindrance layer, effectively preventing the agglomeration between powder particles. The subsequent planetary ball milling uses agate balls with a combined particle size of 2-3mm and 3-5mm, with a ball-to-powder ratio of 5-10:1 and a rotation speed of 200-400rpm, which is within the range of mild dispersion. The agate balls disperse the micron-sized agglomerates formed after powder coating through rolling friction rather than violent impact, without destroying the gradient coating structure. The ground powder is passed through a 300-mesh sieve, finally obtaining a surface-coated, corrosion-resistant, dioxin-resistant silicon carbide wear-resistant powder material with excellent dispersibility and complete structure.

[0016] Preferably, in step (1), SiC is added to dilute hydrochloric acid and hydrofluoric acid in a mass ratio of 1:5-10.

[0017] Preferably, the concentration of dilute hydrochloric acid in (1) is 3-7 wt%, and the concentration of hydrofluoric acid is 3-5 wt%.

[0018] Preferably, the ultrasonic cleaning parameters in (1) are ultrasonic power of 300-500W and frequency of 28-40kHz.

[0019] Preferably, the purified SiC in (1) is added to the hydrofluoric acid / oxalic acid composite etching solution at a mass ratio of 1:5-10.

[0020] Preferably, in the hydrofluoric acid / oxalic acid composite etching solution in (1), the concentration of hydrofluoric acid is 2-5 wt% and the concentration of oxalic acid is 1-3 wt%.

[0021] Preferably, in step (2), the SiC matrix and anhydrous ethanol are in a weight ratio of 1:15-20.

[0022] Preferably, the ultrasonic dispersion parameters in (2) are ultrasonic power of 300-500W and frequency of 28-40kHz.

[0023] Preferably, the concentration of glacial acetic acid in (2) is 1-5 mol / L.

[0024] Preferably, the ultrasonic dispersion parameters in (3) are ultrasonic power of 300-500W and frequency of 28-40kHz.

[0025] Preferably, the concentration of ammonia in (3) is 25-28 wt%.

[0026] Preferably, the argon gas introduction rate in (3) is 50-100 ml / min.

[0027] Preferably, the heating rate of the muffle furnace in (3) is 3-7℃ / min.

[0028] Preferably, the ultrasonic dispersion parameters in (4) are ultrasonic power of 300-500W and frequency of 28-40kHz.

[0029] Preferably, the heating rate of the muffle furnace in (4) is 2-5℃ / min.

[0030] Preferably, the ultrasonic dispersion parameters in (5) are ultrasonic power of 300-500W and frequency of 28-40kHz.

[0031] Preferably, in step (5), the outer coating powder and anhydrous ethanol are in a weight ratio of 1:10-15.

[0032] Preferably, in the planetary ball mill of (5), agate balls are used as the grinding medium, and the grinding is carried out at a ball-to-material ratio of 5-10:1 and a rotation speed of 200-400 rpm for 30-60 minutes. The agate balls are composed of particles with a particle size of 2-3 mm and 3-5 mm in a weight ratio of 7:3.

[0033] Preferably, the mechanism of action of the surface-coated anti-corrosion and dioxin-resistant silicon carbide wear-resistant powder material of the present invention is explained as follows: This invention uses cubic β-SiC as a matrix, whose nanoscale characteristics of 50-200nm endow the material with excellent mechanical strength and wear resistance. The porous structure formed by HF-oxalic acid composite etching provides sufficient mechanical intercalation sites for subsequent coating layers. The Si-OC transition layer, as an "organic-inorganic" bridging medium between the matrix and the intermediate layer, achieves a firm bond with the matrix through the hydrolysis and condensation reaction of MTMS. The generated silicon-containing hydroxyl hydrolysis products then undergo dehydration condensation with the hydroxyl groups on the surface of the β-SiC matrix to form a dense covalent bonded transition layer. The thermal expansion coefficient of this transition layer is between that of the β-SiC matrix and the ZrO2-Al2O3-Y2O3 intermediate layer, which can effectively alleviate the difference in thermal stress during high-temperature calcination and service, avoid cracking or peeling of the coating layer due to thermal expansion mismatch, and improve the interfacial bonding strength, laying the foundation for the stable adhesion of subsequent functional layers. The intermediate layer, as the core protective layer, derives its corrosion resistance and wear resistance from its dense structure, crystal phase regulation, and synergistic effect with the substrate. During preparation, zirconium nitrate and aluminum nitrate undergo hydrolysis under alkaline conditions. The resulting hydroxide precursor is densely deposited via a hydrothermal reaction, followed by thermal decomposition through high-temperature calcination in an argon atmosphere, forming a ZrO2-Al2O3-Y2O3 intermediate layer. The key role of the argon atmosphere is to isolate oxygen, prevent oxidation of the β-SiC substrate, and ensure the integrity of the substrate structure. Yttrium oxide, in a molar ratio of 8-12:2-4:1, is combined with the Zr and Al components and can dissolve into the ZrO2 lattice, inhibiting the phase transition of ZrO2 from the tetragonal phase to the monoclinic phase (this phase transition is accompanied by approximately 3-5% volume expansion). This prevents microcracks in the coating layer due to the phase transition. The resulting intermediate layer structure is dense and has high hardness, effectively resisting the penetration of corrosive media such as HCl-containing fumes. Its corrosion protection mechanism is manifested in the dense oxide layer blocking Cl... - The contact with the substrate, along with the presence of Al2O3, further enhances the interlayer density, thereby reducing the corrosion rate. The high wear resistance of ZrO2 and the synergistic effect of the crystal phase stabilization of Y2O3 give the middle layer excellent wear resistance. The outer layer is the core of the dioxin-preventing function, blocking the formation and accumulation of dioxins through a dual mechanism of "adsorption-catalytic inhibition." Its effectiveness depends on the synergistic effect and precise ratio of each component. First, positive TEOS undergoes hydrolysis and condensation in an ethanol / water mixed solvent to form a three-dimensional SiO2 gel network. This network provides a uniformly dispersed support for neodymium nitrate, cerium nitrate, and phosphotungstic acid. Upon calcination at 600-700℃ in air, neodymium nitrate and cerium nitrate undergo thermal decomposition, generating rare earth oxides (Nd₂O₃, Ce₂O₃) with unique electronic structures that can block the key catalytic cycle of dioxin formation. This is achieved by adsorbing and stabilizing Cu in the system. 2+ / Cu + The presence of catalytically active ions inhibits the catalytic effect of chloroaromatic dehydrogenation and cyclization reactions, significantly improving the inhibition rate of dioxin resynthesis. Simultaneously, the high efficiency of phosphotungstic acid in adsorbing dioxins and their precursors stems from the synergistic effect of its stable Keggin structure and surface properties. The Keggin structure of phosphotungstic acid ([PW...)...) 12 O 40 ] 3-It has a regular three-dimensional cage-like structure with abundant micropores and mesopores inside, and can be a dioxin molecule (such as PCDD / Fs) and precursor (such as 2,4-dioxins). Dichlorophenol provides ample physical adsorption sites, and the size of its cage-like structure is highly matched to the size of dioxin molecules, enabling it to firmly capture molecules through spatial confinement. Simultaneously, its surface is rich in hydroxyl groups and terminal and bridging oxygen atoms. These groups can form strong hydrogen bonds with polar sites such as chlorine atoms and hydroxyl groups in dioxin molecules, and can also form π-π stacking effects with aromatic rings in the molecule through coordination, thereby enhancing chemisorption. Furthermore, phosphotungstic acid maintains the integrity of its Keggin structure after calcination at 600-700℃ and achieves uniform dispersion through the SiO2 gel network, avoiding adsorption site blockage caused by its own aggregation. Its proton acidity further enhances the adsorption affinity for chlorinated aromatic compounds, ultimately forming a highly efficient adsorption mechanism that combines physical and chemisorption, significantly improving the capture efficiency of dioxins and their precursors. In addition, the tight bonding between the outer and middle layers forms continuous protection, and the density of the SiO2 network prevents functional components from detaching, ensuring long-term dioxin protection performance. The dispersibility of powder directly affects its practical application effect. This invention achieves a balance between powder dispersibility and structural integrity through modification with triisostearate titanate isopropyl triisostearate and a precise grinding process. The core of the coupling agent modification is the esterification reaction: the isopropoxy group in the triisostearate titanate isopropyl triisostearate molecule reacts with the hydroxyl group on the surface of the outer phosphotungstic acid, firmly grafting the coupling agent molecule onto the powder surface through ester bonds. The long-chain isostearyl group extends outward to form a steric hindrance layer, significantly reducing van der Waals forces and hydrogen bonding between powder particles and inhibiting agglomeration. Subsequent planetary ball mill grinding uses a combination of 2-3mm (70%) and 3-5mm (30%) agate balls, with a ball-to-particle ratio of 5-10:1 and a grinding speed of 200-400 rpm for 3 days. From 0 to 60 minutes, this process falls under the category of "mild dispersion": the agate balls are broken up by rolling friction rather than violent impact, resulting in micron-sized agglomerates. Due to the high hardness and density of the middle layer ZrO2-Al2O3-Y2O3, the grinding process does not damage the gradient coating structure. After grinding, the powder is passed through a 300-mesh sieve (particle size ≤48μm) to further ensure uniform particle size and excellent dispersibility, enabling it to be evenly distributed in subsequent applications (such as composite material filling and coating preparation) and fully exert its comprehensive properties of corrosion resistance, wear resistance, and dioxin prevention.

[0034] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following: 1. The surface-coated corrosion-resistant and dioxin-resistant silicon carbide wear-resistant powder material of the present invention achieves, for the first time, a unified function of high-temperature corrosion resistance, high wear resistance, and efficient dioxin prevention in a single material system by constructing a gradient coating structure of "Si-OC transition layer / ZrO2-Al2O3-Y2O3 middle layer / SiO2-rare earth oxide-phosphotungstic acid multifunctional outer layer". This structure significantly enhances the interfacial bonding strength between the coating layer and the substrate through a combination of chemical bonding and mechanical interlocking, effectively overcoming the technical bottleneck of traditional coating layers being prone to cracking and peeling, and enabling the material to maintain structural integrity and performance stability even in extreme corrosive environments such as high-temperature chlorine-containing flue gas.

[0035] 2. The surface-coated anti-corrosion and dioxin-resistant silicon carbide wear-resistant powder material of this invention exhibits excellent protective capabilities. Its ZrO2-Al2O3-Y2O3 middle coating layer effectively blocks the penetration of corrosive media, while the rare earth oxides stabilize the crystal phase, preventing microcracks caused by phase transformation volume expansion. The special composite design of the outer layer not only efficiently captures dioxins and their precursors through physicochemical adsorption, but also catalytically inhibits the resynthesis of dioxins, achieving a functional leap from "passive protection" to "active inhibition," significantly enhancing its practical value in complex environments such as waste incineration.

[0036] 3. The surface-coated corrosion-resistant and dioxin-resistant silicon carbide wear-resistant powder material of this invention, while maintaining the intrinsic advantages of high hardness and high strength of the silicon carbide matrix, significantly improves the dispersibility and interfacial compatibility of the powder through surface modification. A unique coupling agent grafting process forms a steric hindrance layer on the powder surface, which, combined with gentle grinding technology, allows the powder to be uniformly dispersed in polymer or metal matrices, preventing agglomeration. This ensures that it can fully exert its reinforcing, wear-resistant, and functionalizing effects in composite materials or coating applications, expanding its application potential in the field of high-end composite materials.

[0037] 4. The preparation process parameters adopted in this invention are well-defined and the process is controllable, combining innovation and practicality. From the porous pretreatment of the matrix to the sequential construction of each functional layer, each step has a clear chemical action mechanism and process window, ensuring the stability and reproducibility of batch production. This technical solution provides a clear and efficient technical path for developing multifunctional ceramic powder materials for harsh service environments, and has significant prospects for industrial application. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0039] Example 1: A specific preparation method of a surface-coated corrosion-resistant, dioxin-resistant silicon carbide wear-resistant powder material, comprising the following steps: (1) 100g of SiC was added to 500g of 3wt% dilute hydrochloric acid and 2wt% hydrofluoric acid in sequence. The mixture was ultrasonically cleaned at 300W power and 28kHz frequency for 30min, with stirring at 100rpm to assist dispersion. Then, the mixture was vacuum filtered and the filter cake was washed with deionized water until the pH of the filtrate was neutral to obtain purified SiC. 100g of purified SiC was added to 500g of hydrofluoric acid / oxalic acid composite etching solution (2wt% hydrofluoric acid and 1wt% oxalic acid). The mixture was heated to 35℃ and stirred at 200rpm for 1h. Then, the mixture was filtered and washed with deionized water until the pH of the filtrate was neutral. After vacuum drying, the SiC matrix was obtained. (2) 100g of SiC matrix was added to 1.5kg of anhydrous ethanol and ultrasonically dispersed at 300W power and 28kHz frequency for 20min. Then 8g of methyltrimethoxysilane was added and stirred evenly. The pH of the system was adjusted to 4-5 with 1mol / L glacial acetic acid. The temperature was raised to 60℃ and stirred for 2h. After cooling to room temperature, the mixture was filtered, washed with deionized water and dried to obtain SiC powder with Si-OC transition layer on the surface. (3) Add zirconium nitrate, aluminum nitrate and yttrium oxide to deionized water in a molar ratio of 8:2:1 and stir until dissolved to obtain a middle layer coating solution with a total mass fraction of 2.5% of solute; add 100g of SiC powder coated with Si-OC transition layer to 300g of middle layer coating solution, and ultrasonically disperse at 300W power and 28kHz frequency for 20min. Then, add 25-28wt% ammonia water under stirring to adjust the pH of the system to 9-10. Then transfer it to a hydrothermal reactor, seal it and heat it to 170℃ for hydrothermal reaction for 8h. Cool it to room temperature, filter it, wash the filter cake with deionized water 2-3 times, dry it and place it in a muffle furnace. Introduce argon gas at a rate of 50ml / min and heat it to 700℃ at a heating rate of 3℃ / min. Keep it at the temperature for 2h to obtain the middle layer coated powder. (4) Tetraethyl orthosilicate, neodymium nitrate, cerium nitrate and phosphotungstic acid were added to an ethanol / water mixed solution (ethanol and water volume ratio of 4:1) in a molar ratio of 18:0.5:0.8:0.3 and stirred until dissolved to obtain an outer coating solution with a total mass fraction of 5% solute; 100g of middle coating powder was added to 400g of outer coating solution and ultrasonically dispersed at a power of 300W and a frequency of 28kHz for 20min, heated to 60℃ and stirred for 4h, then vacuum filtered, the filter cake was washed 2-3 times with anhydrous ethanol, dried and placed in a muffle furnace, heated to 600℃ at a heating rate of 2℃ / min under air atmosphere, kept heated for 3h, cooled to room temperature to obtain outer coating powder; (5) Add 100g of outer coating powder to 1kg of anhydrous ethanol and ultrasonically disperse it for 10min at a power of 300W and a frequency of 28kHz. Then add 1g of triisostearate titanate isopropyl, heat to 60℃ and stir for 2h. After the reaction is completed, vacuum filter, wash the filter cake 2-3 times with deionized water, dry it and put it into a planetary ball mill. Use agate balls as the grinding medium and grind at a ball-to-material ratio of 5:1 and a speed of 200rpm for 30min. The agate balls are composed of particles with a particle size of 2-3mm and 3-5mm in a weight ratio of 7:3. After grinding, pass through a 300-mesh sieve to obtain a surface-coated anti-corrosion and dioxin-resistant silicon carbide wear-resistant powder material.

[0040] Example 2: A specific preparation method of a surface-coated corrosion-resistant, dioxin-resistant silicon carbide wear-resistant powder material, comprising the following steps: (1) 100g of SiC was added to 800g of 5wt% dilute hydrochloric acid and 3wt% hydrofluoric acid in sequence. The mixture was ultrasonically cleaned at 400W power and 35kHz frequency for 45min, with stirring at 150rpm to assist dispersion. Then, the mixture was vacuum filtered and the filter cake was washed with deionized water until the pH of the filtrate was neutral to obtain purified SiC. 100g of purified SiC was added to 800g of hydrofluoric acid / oxalic acid composite etching solution (hydrofluoric acid concentration of 3wt% and oxalic acid concentration of 2wt%). The mixture was heated to 40℃ and stirred at 300rpm for 1.5h. Then, the mixture was filtered and washed with deionized water until the pH of the filtrate was neutral. After vacuum drying, the SiC matrix was obtained. (2) 100g of SiC matrix was added to 1.8kg of anhydrous ethanol and ultrasonically dispersed at 400W power and 35kHz frequency for 30min. Then 10g of methyltrimethoxysilane was added and stirred evenly. The pH of the system was adjusted to 4-5 with 3mol / L glacial acetic acid. The temperature was raised to 65℃ and stirred for 3h. After cooling to room temperature, the mixture was filtered, washed with deionized water and dried to obtain SiC powder with Si-OC transition layer on the surface. (3) Add zirconium nitrate, aluminum nitrate and yttrium oxide to deionized water in a molar ratio of 10:3:1 and stir until dissolved to obtain a middle layer coating solution with a total mass fraction of 3%; add 100g of SiC powder coated with Si-OC transition layer to 400g of middle layer coating solution, and ultrasonically disperse at 400W power and 35kHz frequency for 30min. Then, add 25-28wt% ammonia water under stirring to adjust the pH of the system to 9-10, and then transfer it to a hydrothermal reactor. After sealing, heat to 180℃ and hydrothermally react for 10h. Cool to room temperature, filter, wash the filter cake with deionized water 2-3 times, dry and place in a muffle furnace. Introduce argon gas at a rate of 80ml / min and heat to 750℃ at a rate of 5℃ / min. Calcine at this temperature for 2.5h to obtain the middle layer coated powder. (4) Tetraethyl orthosilicate, neodymium nitrate, cerium nitrate and phosphotungstic acid were added to an ethanol / water mixed solution (volume ratio of ethanol and water was 4:1) in a molar ratio of 20:1:1:0.5 and stirred until dissolved to obtain an outer coating solution with a total mass fraction of 6% solute; 100g of middle coating powder was added to 500g of outer coating solution and ultrasonically dispersed at a power of 400W and a frequency of 35kHz for 30min, heated to 65℃ and stirred for 5h, then vacuum filtered, the filter cake was washed 2-3 times with anhydrous ethanol, dried and placed in a muffle furnace, heated to 650℃ at a heating rate of 3℃ / min under air atmosphere, kept heated for 3.5h, cooled to room temperature to obtain the outer coating powder; (5) Add 100g of outer coating powder to 1.2kg of anhydrous ethanol and ultrasonically disperse it for 20min at a power of 400W and a frequency of 35kHz. Then add 2g of triisostearate titanate isopropyl, heat to 65℃ and stir for 3h. After the reaction is completed, vacuum filter, wash the filter cake with deionized water 2-3 times, dry it and put it into a planetary ball mill. Use agate balls as the grinding medium and grind at a ball-to-material ratio of 8:1 and a speed of 300rpm for 45min. The agate balls are composed of particles with a particle size of 2-3mm and 3-5mm in a weight ratio of 7:3. After grinding, pass through a 300-mesh sieve to obtain a surface-coated anti-corrosion and dioxin-resistant silicon carbide wear-resistant powder material.

[0041] Example 3: A specific preparation method of a surface-coated corrosion-resistant, dioxin-resistant silicon carbide wear-resistant powder material, comprising the following steps: (1) 100g of SiC was added sequentially to 1kg of 7wt% dilute hydrochloric acid and 5wt% hydrofluoric acid, and ultrasonically cleaned at 500W power and 40kHz frequency for 60min, with stirring at 200rpm to assist dispersion. Then, the mixture was vacuum filtered and the filter cake was washed with deionized water until the pH of the filtrate was neutral to obtain purified SiC. 100g of purified SiC was added to 1kg of hydrofluoric acid / oxalic acid composite etching solution (5wt% hydrofluoric acid and 3wt% oxalic acid), heated to 45℃ and stirred at 400rpm for 2h. Then, the mixture was filtered and washed with deionized water until the pH of the filtrate was neutral. After vacuum drying, the SiC matrix was obtained. (2) 100g of SiC matrix was added to 2kg of anhydrous ethanol and ultrasonically dispersed at 500W power and 40kHz frequency for 40min. Then 12g of methyltrimethoxysilane was added and stirred evenly. The pH of the system was adjusted to 4-5 with 5mol / L glacial acetic acid. The temperature was raised to 70℃ and stirred for 4h. After cooling to room temperature, the mixture was filtered, washed with deionized water and dried to obtain SiC powder with Si-OC transition layer on the surface. (3) Add zirconium nitrate, aluminum nitrate and yttrium oxide to deionized water in a molar ratio of 12:4:1 and stir until dissolved to obtain a middle layer coating solution with a total mass fraction of 3.5%; add 100g of SiC powder coated with Si-OC transition layer to 450g of middle layer coating solution, and ultrasonically disperse at 500W power and 40kHz frequency for 40min. Then, add 25-28wt% ammonia water under stirring to adjust the pH of the system to 9-10, and then transfer it to a hydrothermal reactor. After sealing, heat to 190℃ and hydrothermally react for 12h. Cool to room temperature, filter, wash the filter cake 2-3 times with deionized water, dry and place in a muffle furnace. Introduce argon gas at a rate of 100ml / min and heat to 800℃ at a rate of 7℃ / min. Calcinate for 3h to obtain the middle layer coated powder. (4) Tetraethyl orthosilicate, neodymium nitrate, cerium nitrate and phosphotungstic acid were added to an ethanol / water mixed solution (ethanol and water volume ratio of 4:1) in a molar ratio of 22:1.5:1.2:0.7 and stirred until dissolved to obtain an outer coating solution with a total mass fraction of 8% solute; 100g of middle coating powder was added to 600g of outer coating solution and ultrasonically dispersed at a power of 500W and a frequency of 40kHz for 40min. The mixture was heated to 70℃ and stirred for 6h. Then it was vacuum filtered, and the filter cake was washed 2-3 times with anhydrous ethanol. After drying, it was placed in a muffle furnace and heated to 700℃ at a heating rate of 5℃ / min under an air atmosphere. The mixture was kept at the temperature for 4h and then cooled to room temperature to obtain the outer coating powder. (5) Add 100g of outer coating powder to 1.5kg of anhydrous ethanol and ultrasonically disperse it for 30min at a power of 500W and a frequency of 40kHz. Then add 3g of triisostearate titanate isopropyl, heat to 70℃ and stir for 4h. After the reaction is completed, vacuum filter, wash the filter cake 2-3 times with deionized water, dry it and put it into a planetary ball mill. Use agate balls as the grinding medium and grind at a ball-to-material ratio of 10:1 and a speed of 400rpm for 60min. The agate balls are composed of particles with a diameter of 2-3mm and 3-5mm in a weight ratio of 7:3. After grinding, pass through a 300-mesh sieve to obtain a surface-coated anti-corrosion and dioxin-resistant silicon carbide wear-resistant powder material.

[0042] Comparative Example 1: The difference between Comparative Example 1 and Example 3 is that in step (1), the hydrofluoric acid / oxalic acid composite etching solution is replaced with hydrofluoric acid etching solution, and the concentration of hydrofluoric acid is 5wt%. The remaining steps are the same as in Example 3.

[0043] Comparative Example 2: The difference between Comparative Example 2 and Example 3 is that step (2) is omitted, and the SiC matrix obtained in (1) is directly added to the intermediate coating liquid in (3). The remaining steps are the same as in Example 3.

[0044] Comparative Example 3: The difference between Comparative Example 3 and Example 3 is that yttrium oxide is not added in step (3), the total mass fraction of solute in the intermediate coating solution is still 3.5%, and the other steps are the same as in Example 3.

[0045] Comparative Example 4: The difference between Comparative Example 4 and Example 3 is that phosphotungstic acid is not added in step (4), the total mass fraction of solute in the outer coating solution is still 8%, and the other steps are the same as in Example 3.

[0046] Comparative Example 5: The difference between Comparative Example 5 and Example 3 is that neodymium nitrate and cerium nitrate are not added in step (4), the total mass fraction of solute in the outer coating solution is still 8%, and the other steps are the same as in Example 3.

[0047] Comparative Example 6: The difference between Comparative Example 6 and Example 3 is that step (5) is changed to "put 100g of outer coating powder into a planetary ball mill, use agate balls as the grinding medium, grind at a ball-to-material ratio of 10:1, at a speed of 400rpm for 60min, wherein the agate balls are composed of particles with a particle size of 2-3mm and 3-5mm in a weight ratio of 7:3, and after grinding, pass through a 300-mesh sieve to obtain a surface-coated anti-corrosion and dioxin-resistant silicon carbide wear-resistant powder material", and the remaining steps are the same as in Example 3.

[0048] Performance testing: 1. High-Temperature Corrosion Resistance Test: Referring to GB / T 19746-2005 "Corrosion of Metals and Alloys - Peripheral Immersion Test in Salt Solutions", static corrosion tests were conducted in a simulated industrial HCl-containing flue gas corrosion environment. Powder materials from each example and comparative example were cold-pressed into Φ10mm×5mm circular samples (forming pressure 20MPa, no binder) and placed in a high-temperature corrosion test chamber. The test conditions were set as follows: temperature 800℃, simulated flue gas containing 5vol% HCl, 21vol% O2, and 74vol% N2, gas flow rate 50mL / min, continuous corrosion for 1000h. After corrosion, the samples were cooled to room temperature, and the mass of the samples before and after corrosion was measured using an electronic balance with an accuracy of 0.0001g. The corrosion rate was calculated as: corrosion mass loss / (sample surface area × corrosion time). The experimental results are shown in Table 1.

[0049] 2. Wear resistance test: Weigh 5g of powder material from each example and comparative example, place it in a polytetrafluoroethylene mold (inner diameter Φ8mm × height 10mm), and press it under 300MPa pressure for 30min using a cold isostatic press to prepare a dense cylindrical sample; place the sample in an 80℃ vacuum drying oven for 2h to remove residual trace moisture and ensure that the sample structure is stable and free from loosening or cracking; Hardness test: Vickers hardness test was performed using a hardness tester. The loading force was set to 30g and the holding time was 10s. Three sections (upper, middle and lower) were selected for each sample. Ten test points were evenly selected on each section. The hardness value of each point was recorded. The maximum and minimum values ​​were removed and the average value was taken as the average hardness of the powder material. The experimental results are shown in Table 1. Friction and wear test: A friction and wear testing machine was used, and a Φ1mm diamond probe was selected for the wear pair. The test parameters were set as follows: load 0.5N, sliding speed 0.1m / s, sliding distance 500μm, test temperature 25℃, and no lubrication. Three different surface areas of each sample were selected for testing. After the test, the width and depth of the wear marks were measured, and the wear volume was calculated. The experimental results are shown in Table 1. Comprehensive verification of wear resistance: The tested samples were weighed (accuracy 0.0001g), and the wear rate by mass method was calculated as wear mass / (load × sliding distance). The experimental results are shown in Table 1.

[0050] 3. Dioxin protection performance test Dioxin adsorption rate test Using 2,4-dichlorophenol (a key dioxin precursor) as a simulated adsorbate, the static adsorption method was employed. 0.5 g of the powder sample prepared in each example and comparative example was accurately weighed and added to 50 ml of a 100 mg / L aqueous solution of 2,4-dichlorophenol. The solution was placed in a constant temperature water bath shaker and shaken at 25°C and 150 rpm for 24 h to reach adsorption equilibrium. The concentration of the remaining 2,4-dichlorophenol in the solution was then determined using high performance liquid chromatography (HPLC). The adsorption rate was calculated as (initial concentration - equilibrium concentration) / initial concentration × 100%. The experimental results are shown in Table 1.

[0051] Dioxin resynthesis inhibition rate test A small fixed-bed reactor was used to simulate the flue gas environment of waste incineration, with a reaction temperature of 300℃ (the peak temperature for dioxin synthesis). 2g of the powder samples prepared in each example and comparative example were packed into the reactor, and an atmosphere containing 100μg / m³ of [unspecified substance] was introduced. 3 2,4-Dichlorophenol, 50 mg / m 3 The simulated flue gas consisted of CuCl2 (catalyzed dioxin synthesis), 10 vol% O2, 8 vol% H2O, and 82 vol% N2, with a gas flow rate of 100 ml / min and a reaction time of 2 h. After the reaction products were adsorbed and enriched by XAD-2 resin, the total amount of dioxins (PCDD / Fs) generated was determined by gas chromatography-mass spectrometry (GC-MS). Using the dioxin generation in the blank reactor (without powder sample) as a baseline, the resynthesis inhibition rate was calculated as (generated amount in the blank group - generated amount in the sample group) / generated amount in the blank group × 100%. The experimental results are shown in Table 1.

[0052] 4. Powder dispersibility test: Accurately weigh 0.1g of the powder samples prepared in each example and comparative example, add 100ml of anhydrous ethanol, place in an ultrasonic cleaner (400W, 35kHz) and ultrasonically disperse for 30min. After forming a suspension, immediately pour it into a 100ml graduated cylinder and record the initial absorbance of the suspension (measured using a UV-Vis spectrophotometer). After standing for 12h, measure the absorbance of the supernatant. Calculate the absorbance retention rate = absorbance after standing / initial absorbance × 100%. The experimental results are shown in Table 1.

[0053] Table 1 Performance Test Results Performance Analysis: Based on the performance test data in Table 1, the silicon carbide wear-resistant powder material prepared by the technical solution of the present invention in the examples is significantly better than the comparative examples in terms of core properties such as high temperature corrosion resistance, wear resistance, dioxin prevention and powder dispersibility. Among them, Example 3 has the best overall performance.

[0054] Example 3 exhibits excellent high-temperature corrosion resistance, likely due to its continuous, dense gradient coating structure and stable interfacial bonding. After high-concentration hydrofluoric acid / oxalic acid composite etching, the SiC substrate forms a porous surface, providing ample mechanical intercalation sites for the Si-OC transition layer. The transition layer, through the complete hydrolysis and condensation of methyltrimethoxysilane, forms a strong covalent bond with the substrate, effectively mitigating thermal stress differences. The ZrO2-Al2O3-Y2O3 intermediate layer forms a highly dense ceramic layer under high-temperature hydrothermal reaction and high-temperature calcination. Yttrium oxide dissolves into the ZrO2 lattice, suppressing the tetragonal-to-monoclinic phase transition and preventing coating layer cracking. The dense oxide structure completely blocks Cl... - The corrosive medium penetrates into the substrate. Compared to Example 3, Comparative Example 1, due to the use of single hydrofluoric acid etching, lacks the effect of oxalic acid on Si. 4+ The complexation of the Si-OC layer leads to the blockage of the pores on the SiC surface, and the irregular bonding between the transition layer and the substrate makes it easy for corrosive media to penetrate from the defects. In Comparative Example 2, the Si-OC transition layer was omitted, and there was no chemical bridging between the middle layer and the SiC substrate. Under high-temperature corrosion environment, the coating layer was easy to fall off, and the SiC substrate reacted directly with the HCl-containing flue gas, resulting in a significant increase in the corrosion rate. In Comparative Example 3, due to the lack of yttrium oxide in the middle layer, the phase transformation of ZrO2 caused microcracks to form in the coating layer, forming corrosion channels and accelerating the diffusion of corrosive media into the substrate.

[0055] The outstanding wear resistance of Example 3 is mainly due to its high hardness, dense intermediate layer structure, and good interfacial bonding strength. After the solute in the intermediate coating solution undergoes a long-term hydrothermal reaction at 190°C, the hydroxide precursor particles are fully rearranged and densely deposited. Then, after high-temperature calcination at 800°C, a high-hardness ZrO2-Al2O3-Y2O3 composite ceramic layer is formed, which forms a strong bond with the Si-OC transition layer. This results in the highest average hardness of the powder compact, with only slight abrasive wear occurring during the wear process. Comparative Example 1, due to poor etching, had a slightly weaker bond strength between the transition layer and the substrate, and a slightly lower density in the intermediate layer, resulting in slightly inferior hardness and wear resistance compared to Example 3. Comparative Example 2 lacked a transition layer, and the bond between the intermediate layer and the substrate was loose. During wear, the coating layer was easily detached, and the substrate directly participated in friction, leading to a significant decrease in hardness and a substantial increase in wear volume and mass wear rate. Comparative Example 3, due to the absence of yttrium oxide's crystal phase stabilizing effect, experienced a decrease in intermediate layer density and hardness after the ZrO2 phase transformation. During wear, crack propagation led to the peeling off of the intermediate layer, resulting in a significant reduction in wear resistance. The other comparative examples did not affect the core structure and composition of the intermediate layer, and their wear resistance was similar to that of Example 3, with only minor differences due to the randomness of the testing.

[0056] Example 3 exhibits the best dioxin-preventing performance, thanks to the highly efficient synergistic effect of the "adsorption-catalytic inhibition" dual mechanism. In the outer coating solution, tetraethyl orthosilicate undergoes complete hydrolysis and condensation to form a three-dimensional SiO2 gel network, providing a uniformly dispersed support for neodymium nitrate, cerium nitrate, and phosphotungstic acid. After high-temperature calcination, the rare earth oxides generated from the complete decomposition of neodymium nitrate and cerium nitrate are uniformly distributed within the gel network. Their unique electronic structure can efficiently adsorb and stabilize Cu in the system. 2+ / Cu + The catalytically active ions block the key catalytic cycle of dioxin formation. The Keggin structure of phosphotungstic acid remains stable at this calcination temperature, forming sufficient adsorption sites based on the SiO2 network, which can efficiently capture dioxins and their precursors. Compared with Example 3, Comparative Example 4, due to the lack of phosphotungstic acid in the outer layer, has a significantly reduced adsorption capacity for dioxin precursors. Comparative Example 5, due to the lack of neodymium nitrate and cerium nitrate, has no rare earth oxides participating in catalytic inhibition, and the dioxin resynthesis process is not hindered, resulting in a sharp drop in inhibition rate to a low level. Other comparative examples did not change the core "adsorption-catalytic inhibition" system of the outer layer, and their dioxin prevention performance was basically the same as that of Example 3 only due to slight differences in the density or dispersibility of the coating layer.

[0057] The powder dispersibility of Example 3 was optimal, primarily due to the synergistic effect of sufficient coupling agent modification and gentle grinding process. Sufficient amounts of triisostearate titanate underwent a complete esterification reaction with the hydroxyl groups on the outer phosphotungstic acid surface, forming a complete steric hindrance layer on the powder surface, significantly reducing van der Waals forces and hydrogen bonding between particles. The subsequent planetary ball mill used agate balls of 2-3 mm and 3-5 mm in a 7:3 weight ratio. Under suitable ball-to-powder ratio and rotation speed, rolling friction gently dispersed the micron-sized agglomerates without disrupting the gradient coating structure, ensuring powder uniformity. Compared to Example 3, Comparative Example 6 omitted the coupling agent modification step, resulting in a lack of steric hindrance protection on the powder surface, making particle agglomeration more likely. After standing, the particles settled rapidly, and the absorbance retention rate decreased significantly. Other comparative examples all employed the complete coupling agent modification process; only due to minor differences in etching effect and coating layer bonding state, their dispersibility was slightly lower than Example 3, but overall, they maintained good dispersion stability.

[0058] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A surface-coated, corrosion-resistant, dioxin-resistant, wear-resistant silicon carbide powder material, characterized in that, The raw materials include the following parts by weight: SiC: 100 parts, methyltrimethoxysilane: 8-12 parts, middle coating solution: 300-450 parts, outer coating solution: 400-600 parts, and isopropyl triisostearate titanate: 1-3 parts. The preparation method of the intermediate coating liquid is as follows: Zirconium nitrate, aluminum nitrate, and yttrium oxide were added to deionized water and stirred until dissolved to obtain a middle-layer coating solution. The preparation method of the outer coating liquid is as follows: Tetraethyl orthosilicate, neodymium nitrate, cerium nitrate and phosphotungstic acid were added to an ethanol / water mixture and stirred until dissolved to obtain an outer coating solution; In the preparation method of the intermediate coating solution, the molar ratio of zirconium nitrate, aluminum nitrate and yttrium oxide is 8-12:2-4:1, and the total mass fraction of solute in the intermediate coating solution is 2.5%-3.5%. In the preparation method of the outer coating solution, the molar ratio of tetraethyl orthosilicate, neodymium nitrate, cerium nitrate, and phosphotungstic acid is 18-22:0.5-1.5:0.8-1.2:0.3-0.7, and the total mass fraction of solute in the outer coating solution is 5%-8%. The volume ratio of ethanol to water in the ethanol / water mixture of the outer coating solution is 4:

1.

2. The surface-coated corrosion-resistant, dioxin-resistant silicon carbide wear-resistant powder material according to claim 1, characterized in that, The SiC is cubic β-SiC with a particle size of 50-200 nm.

3. The method for preparing surface-coated corrosion-resistant, dioxin-resistant silicon carbide wear-resistant powder material according to any one of claims 1-2, characterized in that, Includes the following steps: (1) SiC was added to dilute hydrochloric acid and hydrofluoric acid in sequence, and ultrasonically cleaned for 30-60 min. During this period, the mixture was stirred at 100-200 rpm to assist dispersion. Then, it was vacuum filtered and the filter cake was washed with deionized water until the pH of the filtrate was neutral to obtain purified SiC. The purified SiC was added to hydrofluoric acid / oxalic acid composite etching solution, heated to 35-45℃ and stirred at 200-400 rpm for 1-2 h. Then, it was filtered and washed with deionized water until the pH of the filtrate was neutral. After vacuum drying, the SiC matrix was obtained. (2) Add the SiC matrix to anhydrous ethanol, ultrasonically disperse for 20-40 min, then add methyltrimethoxysilane, stir evenly, adjust the pH of the system to 4-5 with glacial acetic acid, heat to 60-70℃ and stir for 2-4 h, cool to room temperature and filter, wash with deionized water and dry to obtain SiC powder with Si-OC transition layer on the surface. (3) Add the SiC powder with the Si-OC transition layer on the surface to the middle coating liquid, disperse it by ultrasonication for 20-40 min, then add ammonia water under stirring to adjust the pH of the system to 9-10, then transfer it to a hydrothermal reactor, seal it and heat it to 170-190℃ for hydrothermal reaction for 8-12 h, cool it to room temperature, filter it, wash the filter cake with deionized water 2-3 times, dry it and place it in a muffle furnace, introduce argon gas, heat it to 700-800℃, keep it at the temperature for calcination for 2-3 h to obtain the middle coated powder; (4) Add the middle layer coated powder to the outer layer coated liquid, ultrasonically disperse for 20-40 min, heat to 60-70℃ and stir for 4-6 h, then vacuum filter, wash the filter cake 2-3 times with anhydrous ethanol, dry and place in a muffle furnace, heat to 600-700℃ in air atmosphere, keep warm and calcine for 3-4 h, cool to room temperature to obtain the outer layer coated powder; (5) Add the outer coating powder to anhydrous ethanol and ultrasonically disperse for 10-30 min. Then add triisostearate titanate isopropyl triisostearate, heat to 60-70℃ and stir for 2-4 h. After the reaction is complete, vacuum filter, wash the filter cake with deionized water 2-3 times, dry it and put it into a planetary ball mill, grind it and pass it through a 300-mesh sieve to obtain a surface-coated anti-corrosion and anti-dioxin silicon carbide wear-resistant powder material.

4. The preparation method of the surface-coated corrosion-resistant, dioxin-resistant silicon carbide wear-resistant powder material according to claim 3, characterized in that, In step (1), SiC is added to dilute hydrochloric acid and hydrofluoric acid in a mass ratio of 1:5-10; the concentration of dilute hydrochloric acid is 3-7wt% and the concentration of hydrofluoric acid is 3-5wt%; the ultrasonic cleaning parameters are ultrasonic power of 300-500W and frequency of 28-40kHz.

5. The preparation method of the surface-coated corrosion-resistant, dioxin-resistant silicon carbide wear-resistant powder material according to claim 3, characterized in that, The purified SiC in (1) is added to the hydrofluoric acid / oxalic acid composite etching solution at a mass ratio of 1:5-10; the concentration of hydrofluoric acid in the hydrofluoric acid / oxalic acid composite etching solution is 2-5wt%, and the concentration of oxalic acid is 1-3wt%.

6. The preparation method of the surface-coated corrosion-resistant, dioxin-resistant silicon carbide wear-resistant powder material according to claim 3, characterized in that, In (2), the SiC matrix and anhydrous ethanol are in a weight ratio of 1:15-20; the ultrasonic dispersion parameters are an ultrasonic power of 300-500W and a frequency of 28-40kHz; and the concentration of glacial acetic acid is 1-5mol / L.

7. The preparation method of the surface-coated corrosion-resistant, dioxin-resistant silicon carbide wear-resistant powder material according to claim 3, characterized in that, The parameters for ultrasonic dispersion in (3) are: ultrasonic power of 300-500W, frequency of 28-40kHz, and ammonia concentration of 25-28wt%.

8. The preparation method of the surface-coated corrosion-resistant, dioxin-resistant silicon carbide wear-resistant powder material according to claim 3, characterized in that, The argon gas introduction rate in (3) is 50-100 ml / min; the heating rate of the muffle furnace is 3-7 °C / min.

9. The preparation method of the surface-coated corrosion-resistant, dioxin-resistant silicon carbide wear-resistant powder material according to claim 3, characterized in that, The parameters for ultrasonic dispersion in (4) are: ultrasonic power of 300-500W and frequency of 28-40kHz; and heating rate of muffle furnace of 2-5℃ / min.

10. The preparation method of the surface-coated corrosion-resistant, dioxin-resistant silicon carbide wear-resistant powder material according to claim 3, characterized in that, The parameters for ultrasonic dispersion in (5) are: ultrasonic power of 300-500W and frequency of 28-40kHz; the outer coating powder and anhydrous ethanol are in a weight ratio of 1:10-15; the planetary ball mill uses agate balls as the grinding medium, and grinds at a ball-to-material ratio of 5-10:1 and a speed of 200-400rpm for 30-60min, wherein the agate balls are composed of particles with a diameter of 2-3mm and 3-5mm in a weight ratio of 7:3.

Images