Process for the production of ultrafine glass powder by spray pyrolysis

Abstract

This invention discloses a process for preparing ultrafine glass powder using a spray pyrolysis method in the field of glass encapsulation materials. The process first prepares a homogeneous solution A using boric acid, aluminum nitrate nonahydrate, alkaline earth metal nitrates, lithium acetate, sodium acetate, and potassium acetate. Tetraethyl orthosilicate is dissolved in anhydrous ethanol to obtain solution B. A rare earth transition metal composite oxide nanoclusters encapsulated with a silica shell hybrid inorganic modifier is dispersed in anhydrous ethanol to obtain suspension C. Solution B and suspension C are mixed, and deionized water and hydrochloric acid are added to adjust the pH. After pre-hydrolysis and cooling, triethyl borate is added dropwise for co-condensation, and then mixed with solution A. After adjusting the pH and aging, the mixture is ultrasonically atomized and spray pyrolyzed to obtain ultrafine glass powder. The glass powder obtained by this invention has small particle size, high sphericity, and can be continuously produced.

Description

Technical Field

[0001] This invention relates to the field of glass encapsulation materials technology, specifically to a process for preparing ultrafine glass powder by spray pyrolysis. Background Technology

[0002] In recent years, with the rapid development of the integrated circuit industry, the packaging density of electronic components and chips has continued to rise, especially with the increasing demands placed on packaging technology by third-generation semiconductor materials such as silicon carbide and gallium nitride. These devices often need to operate stably under extreme conditions such as high temperature, high frequency, and high power; therefore, packaging materials must possess excellent thermal matching, high insulation strength, and good thermal stability. Glass materials, due to their similar coefficient of thermal expansion to silicon-based semiconductors and their good dielectric properties and chemical stability, have become one of the key materials in the semiconductor packaging field. During the packaging process, glass powder is typically used as a filler or sealing material to fill the microstructure between the chip and the substrate. Glass powder prepared by traditional mechanical ball milling has a large particle size, making it difficult to effectively fill submicron or even nanoscale gaps. This easily leads to defects such as pores and cracks at the packaging interface, resulting in decreased device dielectric strength, increased leakage current, and in severe cases, even device failure. To overcome the aforementioned problems, researchers have attempted to prepare ultrafine glass powder using wet chemical routes such as the sol-gel method and co-precipitation method. However, these methods generally suffer from drawbacks such as long process cycles, poor batch stability, and difficulty in continuous production. Furthermore, they often require subsequent high-temperature sintering and grinding processes, which are not only energy-intensive but also prone to introducing impurities, limiting their large-scale application in high-end packaging fields. Therefore, developing a method for preparing ultrafine glass powder that achieves uniform composition, controllable particle size, and continuous production has become a pressing technical challenge in this field.

[0003] Spray pyrolysis, as an emerging powder preparation method, atomizes a precursor solution into micron-sized droplets, instantly completing solvent evaporation, solute decomposition, and product nucleation and growth in a high-temperature pyrolysis furnace. This process can yield ultrafine powders with high sphericity and narrow particle size distribution within seconds, eliminating the need for subsequent grinding and significantly reducing the risk of impurity introduction. However, applying this technology to multi-component glass systems faces a series of challenges related to chemical reaction kinetics. First, glass formulations typically contain boron oxide, and commonly used boron sources such as triethyl borate have extremely high hydrolytic activity, with a hydrolysis rate several orders of magnitude higher than that of silicon-based tetraethyl orthosilicate. If the two are simply mixed and directly spray-pyrolyzed, the boron component will preferentially hydrolyze and self-condense, leading to the separation of the silicon-boron phase in the glass network. The final product will have a significantly deviated boron oxide content from the designed formulation value, and boron is easily volatilized in gaseous form at high temperatures, further exacerbating component segregation. Secondly, existing spray pyrolysis precursor solutions mostly employ a single sol system, making it difficult to simultaneously meet the solubility requirements of multiple metal ions in the glass formulation. For example, alkaline earth metal nitrates are easily hydrolyzed and precipitated in aqueous solutions, while tetraethyl orthosilicate is unstable under alkaline conditions, resulting in poor homogeneity of the precursor solution and affecting the continuity of the spraying process and product quality. Furthermore, relying solely on the glass matrix composition makes it difficult to simultaneously achieve ultrafine powder and thermomechanical stability. Glass powder obtained from conventional spray pyrolysis is prone to grain growth and agglomeration during subsequent encapsulation, limiting its performance. Therefore, how to control the matching of different alkoxide hydrolysis rates through molecular-level design of the precursor solution, while simultaneously introducing functional reinforcing components, has become a core technical challenge in the preparation of high-performance ultrafine glass powder using spray pyrolysis. Summary of the Invention

[0004] The purpose of this invention is to provide a process for preparing ultrafine glass powder by spray pyrolysis, which solves the problems of easy volatilization of boron component, component segregation caused by silicon-boron phase separation, large particle size and inability to produce continuously in the existing spray pyrolysis method for preparing ultrafine glass powder.

[0005] The present invention achieves the above objectives through the following technical solutions: A process for preparing ultrafine glass powder by spray pyrolysis includes the following steps: S1, by weight, add 1-4 parts boric acid, 0.5-3 parts aluminum nitrate nonahydrate, 0.1-1.0 parts alkaline earth metal nitrate, 1-5 parts lithium acetate, 1-5 parts sodium acetate, and 1-5 parts potassium acetate to 80-120 parts deionized water, heat to 40-50℃, stir, and cool to 24-26℃ to obtain solution A; dissolve 150-250 parts tetraethyl orthosilicate in 80-120 parts anhydrous ethanol, stir at 24-26℃ to obtain solution B; under an ice-water bath, add 0.5-5 parts rare earth-transition metal complex oxygen... The inorganic modified material, consisting of chemical nanoclusters with a silica shell hybrid, was dispersed in 30-80 parts of anhydrous ethanol and sonicated to obtain suspension C. Solution B was mixed with suspension C, and 5-10 parts of deionized water and 0.5-3 parts of hydrochloric acid were added to adjust the pH to 3-4.5. The mixture was then stirred and pre-hydrolyzed at 25-35°C to obtain a mixed solution. The mixed solution was cooled to 0-10°C, and 30-80 parts of triethyl borate were added dropwise under an ice-water bath while stirring continued to obtain a copolymerized mixture. The copolymerized mixture was then mixed with solution A to obtain a reaction mixture. S2, maintain the pH of the reaction mixture at 3-4.5, and stir and age at 30-50℃ to obtain a pre-reacted mixed solution; S3, The pre-reacted mixed solution is atomized using an ultrasonic atomizer to obtain atomized gas; S4, the atomized gas is introduced into the pyrolysis furnace through the carrier gas for spray pyrolysis to obtain pyrolyzed powder; the pyrolyzed powder is introduced into the collection device through the carrier gas to obtain ultrafine glass powder.

[0006] In this invention, the process mechanism for preparing ultrafine glass powder by spray pyrolysis is a continuous evolution process involving complex chemical kinetics and physical phase transitions. Its core lies in transforming a pre-constructed hybrid precursor sol into high-performance glass particles through instantaneous heat treatment. In the first step of solution preparation, an inorganic network is constructed using a stepwise in-situ co-condensation technique. Tetraethyl orthosilicate undergoes partial pre-hydrolysis under acidic water catalysis, generating a large number of silanol oligomers with active hydroxyl groups. At this point, highly hydrolytically reactive triethyl borate is introduced, and an ice-water bath is used to reduce its reaction rate, forcing the condensation of hydroxyl groups between boron atoms and silanol molecules, thereby pre-constructing a stable silicon-oxygen-boron bond cross-linked framework in solution. This stepwise operation effectively avoids the self-aggregation segregation problem caused by excessively rapid hydrolysis of the boron component, ensuring the atomic-level uniformity of the glass network framework. Subsequently, the solution containing alkali metals, alkaline earth metals, and aluminum salts was combined with a pre-prepared suspension of hybrid modified materials. Acid was added to counteract the buffering effect of acetate, forcibly maintaining the hydrogen ion concentration within a specific acidic window, forming a highly stable hybrid sol system with dispersed components. In the atomization stage, high-frequency mechanical oscillations generated by an ultrasonic atomizer sheared the continuous liquid phase into tiny micron-sized droplets through cavitation. These droplets were carried by a carrier gas into a high-temperature pyrolysis space. At extremely high heating rates, the solvent on the droplet surface vaporized instantaneously, causing the internal solute concentration to rapidly reach supersaturation. With the complete disappearance of the solvent, explosive physical aggregation and chemical decomposition occurred within the microdroplets. Various metal salts completed their oxidative decomposition reactions within seconds and underwent deep cross-linking with the pre-constructed silicon-oxygen-boron network. Under the high temperature of the pyrolysis furnace, these tiny solid components melted and homogenized in situ, forming liquid glass microspheres. As the microspheres are carried away from the high-temperature zone by the carrier gas and enter the collection system, they undergo rapid cooling and quenching, which freezes the atomic structure in a disordered state, ultimately forming ultrafine glass powder with excellent sphericity, narrow particle size distribution, and uniform distribution of modified components at the nanoscale.

[0007] According to a preferred embodiment of the present invention, in step S1, the alkaline earth metal nitrate is selected from at least one of magnesium nitrate hexahydrate, calcium nitrate tetrahydrate, strontium nitrate, and barium nitrate.

[0008] According to a preferred embodiment of the present invention, in step S2, the stirring and aging time at 30-50°C is 1-2 hours.

[0009] According to a preferred embodiment of the present invention, in step S3, the atomization rate of the atomization treatment is 0.1-1 L / h.

[0010] According to a preferred embodiment of the present invention, in step S4, the temperature of the spray pyrolysis is 600-900°C; and the carrier gas is air or nitrogen.

[0011] According to a preferred embodiment of the present invention, the preparation steps of the rare earth-transition metal composite oxide nanoclusters@silica shell hybrid inorganic modified material include: A1, by weight, in a glove box under nitrogen atmosphere and under ice-water bath cooling, add 2-5 parts of anhydrous rare earth chloride and 1-4 parts of transition metal chloride to 30-60 parts of anhydrous tetrahydrofuran, stir at room temperature, then heat to 38-42℃ and continue stirring; under ice-water bath and nitrogen protection, add 10-25 parts of anhydrous isopropanol dropwise, and simultaneously add 5-16 parts of anhydrous triethylamine; after the addition is complete, remove the ice-water bath, heat to 60-70℃ and reflux to obtain a mixture; filter the mixture under nitrogen protection to obtain a filtrate; transfer the filtrate to a rotary evaporator and distill under reduced pressure at 38-42℃ to obtain a crude product; wash the crude product with anhydrous n-hexane, and then dry under vacuum at room temperature to obtain a rare earth-transition metal bimetallic alkoxide complex; A2, under nitrogen protection, 1-3 parts of a rare earth-transition metal bimetallic alkoxide complex are dissolved in a mixed solvent containing 15-30 parts of anhydrous ethanol and 15-30 parts of toluene to obtain a precursor solution; an alkaline hydrolysate containing 1-4 parts of deionized water, 2-6 parts of anhydrous ethanol and 0.5-2 parts of ammonia is added dropwise to the precursor solution at 5-10℃ with stirring; after the addition is complete, the mixture is allowed to stand and age at room temperature under a sealed environment; after aging, the mixture is heated at 58-62℃ to obtain a reaction mixture; the reaction mixture is centrifuged to obtain a precipitate; the precipitate is washed successively with anhydrous ethanol and deionized water to obtain a washed precipitate; the washed precipitate is dried in an oven at 78-82℃ to obtain rare earth-transition metal oxygen cluster nanonuclei; A3. 2.0-5.0 parts of rare earth-transition metal oxide cluster nanonuclei were ultrasonically dispersed in 100-150 parts of anhydrous toluene and sonicated to obtain a suspension. The suspension was transferred to a three-necked flask and heated to 108-112℃ under nitrogen protection. Then, 0.5-2.5 parts of 3-aminopropyltriethoxysilane were added dropwise. After the addition was complete, the mixture was refluxed at 108-112℃ under a nitrogen atmosphere to obtain a mixture. The mixture was naturally cooled to room temperature, centrifuged, and the solid product was collected. The solid product was washed sequentially with 10-30 parts of toluene, anhydrous ethanol, and deionized water to obtain a washed solid product. The washed solid product was dried in a vacuum oven at 58-62℃ to obtain a surface-functionalized rare earth-transition metal oxide cluster nanocomposite. A4. Disperse 1-3 parts of surface-functionalized rare earth-transition metal oxide cluster nanocomposite in a mixed solution containing 5-15 parts of tetraethyl orthosilicate and 15-40 parts of anhydrous ethanol, and ultrasonically disperse; add 2-8 parts of deionized water and 0.5-2 parts of ammonia; stir the reaction at room temperature under nitrogen protection; after the reaction is completed, centrifuge to collect the solid product; wash the solid product with anhydrous ethanol and deionized water in sequence to obtain the washed product; dry the washed product in an oven at 78-82℃, calcine it at 348-352℃, and cool it naturally to room temperature.

[0012] In this invention, the preparation mechanism of the rare earth-transition metal composite oxide nanoclusters@silica shell hybrid inorganic modified material is based on precisely controlled molecular-level coordination chemistry and sol-gel conversion. In the initial stage of preparation, anhydrous rare earth chlorides and transition metal chlorides are placed in an inert solvent system of anhydrous tetrahydrofuran. Utilizing the strong Lewis acidity of transition metal atoms, they first coordinate with solvent molecules to form a stable solvation intermediate. This step is crucial, as it not only effectively prevents the ring-opening polymerization reaction of the solvent initiated by the strongly acidic chloride through physical shielding, but also achieves the initial uniform distribution and complexation induction of the two different metal cations at the molecular scale. Subsequently, anhydrous isopropanol is introduced under low-temperature conditions in an ice-water bath, along with sufficient triethylamine as an acid-binding agent, resulting in a vigorous nucleophilic substitution reaction within the system. The isopropoxy anion attacks the metal center and replaces the chloride ion, and the generated hydrochloric acid is immediately captured by triethylamine to form a precipitate, thereby driving the reaction towards a complete conversion towards the formation of a bimetallic alkoxide. In constructing the nano-oxygen cluster core, a controlled hydrolysis and condensation reaction of the metal alkoxide was induced by slowly adding an alkaline hydrolysate containing trace amounts of ammonia to a precursor solution containing alkoxides. Due to the difference in hydrolysis kinetics between rare earth and transition metals, the metal atoms were cross-linked through oxygen bridges by adjusting the solvent composition and reaction temperature, gradually self-assembling to form oxygen cluster nanonuclei with high symmetry and structural stability. To further functionalize the material, the properties of aminopropyltriethoxysilane in a high-temperature toluene environment were utilized. Through an azeotropic dehydration process, the ethoxy groups at the ends of the silane molecules were chemically bonded to the hydroxyl groups on the surface of the nanonuclei, thereby precisely coating the surface of the oxygen clusters with an organic molecular film containing active amino groups. Finally, using these functionalized nanonuclei as seeds, a dense silica hybrid shell was grown in situ around the nanonuclei in a weakly alkaline hydrolysis system of tetraethyl orthosilicate using a heterogeneous nucleation mechanism. After medium-temperature calcination, the organic components in the shell are removed, ultimately forming a core-shell hybrid material with high specific surface area and multifunctional active sites, providing an ideal inorganic component for the subsequent modification of glass powder.

[0013] According to a preferred embodiment of the present invention, in step A1, the anhydrous rare earth chloride is selected from anhydrous lanthanum chloride, anhydrous cerium chloride, and anhydrous gadolinium chloride; the transition metal chloride is selected from titanium chloride, zirconium chloride, and hafnium chloride.

[0014] According to a preferred embodiment of the present invention, in step A2, the heating reaction at 58-62°C is carried out for 2-4 hours.

[0015] According to a preferred embodiment of the present invention, in step A3, the reflux reaction at 108-112°C is carried out for 12-14 hours.

[0016] According to a preferred embodiment of the present invention, in step A4, the calcination time at 348-352°C is 2-4 hours.

[0017] The beneficial effects of this invention are as follows: The spray pyrolysis method for preparing ultrafine glass powder provided by this invention effectively solves the problem of mismatched hydrolysis rates between silicon and boron sources through a stepwise pre-hydrolysis and low-temperature co-condensation strategy. The process first pre-hydrolyzes tetraethyl orthosilicate under acidic conditions to generate active silanol, then slowly adds triethyl borate in a low-temperature environment, promoting co-condensation of the silanol and boron alcohol to construct a stable silicon-oxygen-boron network framework. This inhibits the self-condensation and high-temperature volatilization of the boron component, ensuring the uniformity of the glass powder composition. Simultaneously, the introduced rare-earth transition metal composite oxide nanoclusters encapsulated with a silica shell hybrid inorganic modifier act as an in-situ nucleating agent and structural reinforcement, promoting the uniform formation of the glass phase and inhibiting abnormal grain growth. The resulting glass powder has a fine particle size, high sphericity, and no obvious agglomeration.

[0018] Compared to traditional high-energy mechanical ball milling, this process eliminates the need for grinding, avoiding the introduction of impurities and particle deformation. Compared to the sol-gel method, it eliminates tedious steps such as aging, drying, and regrinding, significantly shortening the production cycle. Spray pyrolysis technology inherently possesses the advantage of continuous production; by adjusting the feed rate and operating parameters, stable batch production of ultrafine glass powder can be achieved. All raw materials used are commercially available common chemicals, resulting in low equipment investment costs and easy industrial-scale promotion. The process window is highly adaptable; air or nitrogen can be used as the carrier gas, and the pyrolysis temperature can be flexibly adjusted, reducing the technical risks of process scale-up.

[0019] This process significantly reduces energy consumption. The prepared ultrafine glass powder exhibits excellent thermal compatibility with silicon-based semiconductors, effectively filling submicron-level gaps during encapsulation, avoiding defects such as pores and cracks, and improving the insulation performance and service reliability of the encapsulation material. This process provides a new, quality-controlled, continuous, energy-efficient, and environmentally friendly preparation route for high-performance ultrafine glass encapsulation materials, with broad application prospects in integrated circuit packaging, insulating coatings for electronic components, and other fields. Attached Figure Description

[0020] Appendix Figure 1 This is a scanning electron microscope (SEM) image of the ultrafine glass powder in Example 1. Detailed Implementation

[0021] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0022] Example 1 This embodiment provides a process for preparing ultrafine glass powder by spray pyrolysis, including the following steps: S1: Add 2.5g boric acid, 1.75g ​​aluminum nitrate nonahydrate, 0.55g magnesium nitrate hexahydrate, 3g lithium acetate, 3g sodium acetate, and 3g potassium acetate to 100g deionized water, heat to 45℃, stir, and cool to 25℃ to obtain solution A; dissolve 200g tetraethyl orthosilicate in 100g anhydrous ethanol and stir at 25℃ to obtain solution B; disperse 2.75g modified material Z in 55g anhydrous ethanol under an ice-water bath and sonicate (power 120W, frequency 40kHz, time 12min, using intermittent sonication). The ultrasonic method involves sonicating for 5 minutes followed by a 1-minute pause to obtain suspension C. Solution B is mixed with suspension C, and 7.5 g of deionized water and 1.75 g of hydrochloric acid (36 wt%) are added to adjust the pH to 3.75. The mixture is then stirred and pre-hydrolyzed at 30°C for 30 minutes to obtain a mixed solution. The mixed solution is cooled to 5°C, and 55 g of triethyl borate (TEB) is added dropwise at a rate of 1.5 mL / min in an ice-water bath. Stirring continues for 45 minutes to obtain the copolymerized mixture. The copolymerized mixture is then mixed with solution A to obtain the reaction mixture.

[0023] S2: Maintain the pH of the reaction mixture at 3.75 and age it at 40°C for 1.5 hours with stirring to obtain the pre-reacted mixed solution.

[0024] S3: Use an ultrasonic atomizer (frequency 1.5MHz) to atomize the pre-reacted mixed solution at a rate of 0.55L / h to obtain atomized gas.

[0025] S4: The atomized gas is introduced into the pyrolysis furnace through a carrier gas (air, flow rate 0.55L / min) for spray pyrolysis. The temperature of the pyrolysis furnace is 750℃, and the pyrolyzed powder is obtained. The pyrolyzed powder is introduced into the collection device through a carrier gas to obtain ultrafine glass powder.

[0026] Preparation of rare earth-transition metal composite oxide nanoclusters@silica shell hybrid inorganic modified materials: In step A1, under a nitrogen atmosphere-protected glove box and with cooling in an ice-water bath, 3.5 g of anhydrous lanthanum chloride and 2.5 g of titanium chloride were added to 45 g of anhydrous tetrahydrofuran and stirred at room temperature for 30 min. The mixture was then heated to 40 °C and stirred for another 30 min. Under ice-water bath and nitrogen protection, 17.5 g of anhydrous isopropanol was added dropwise at a rate of 0.5 mL / min, along with 10.5 g of anhydrous triethylamine. After the addition was complete, the ice-water bath was removed, and the mixture was heated to 65 °C and refluxed for 12 h to obtain a mixture. The mixture was filtered through a G4 sintered glass funnel under nitrogen protection to obtain a filtrate. The filtrate was transferred to a rotary evaporator and distilled under reduced pressure at 40 °C and a vacuum of 0.08 MPa to obtain a crude product. The crude product was washed three times with anhydrous n-hexane (15 g each time) and then dried under vacuum at room temperature for 6 h to obtain a rare earth-transition metal bimetallic alkoxide complex.

[0027] A2, under nitrogen protection, 2g of the above bimetallic alkoxide complex was dissolved in a mixed solvent containing 22.5g of anhydrous ethanol and 22.5g of toluene to obtain a precursor solution; at 7.5℃ and with stirring, 2.5g of deionized water, 4g of anhydrous ethanol, and 1.25g of toluene were added dropwise to the precursor solution at a rate of 0.2mL / min. An alkaline hydrolysis solution of 25 wt% ammonia water (the amount of water added is equivalent to 8 times the theoretical water required for complete hydrolysis of bimetallic alkoxides in excess); the system temperature is controlled at 5℃ during the dropwise addition; after the dropwise addition is completed, the mixture is allowed to stand and age at room temperature for 24 h under sealed conditions; after aging, the mixture is heated at 60℃ for 3 h in a reflux condenser (with slight stirring to prevent precipitation) to obtain a reaction mixture; the reaction mixture is centrifuged at 8000 rpm for 15 min to obtain a precipitate; the precipitate is washed three times each with anhydrous ethanol and deionized water (20 g solvent each time); the washed precipitate is dried in an oven at 80℃ for 12 h to obtain white powdery rare earth-transition metal oxide cluster nanonuclei.

[0028] A3. 3.5 g of the above-mentioned nanonuclei were ultrasonically dispersed in 125 g of anhydrous toluene at an ultrasonic power of 100 W, a frequency of 40 kHz, and a time of 30 min to form a homogeneous suspension. The suspension was transferred to a three-necked flask equipped with a condenser and a nitrogen protection device, and heated to 110 °C under nitrogen protection for 30 min for azeotropic dehydration to remove trace amounts of water adsorbed on the surface of the nanonuclei. Subsequently, 1.5 g of 3-aminopropyltriethoxysilane was added dropwise at a ratio of 3 mmol per gram of nanonuclei powder. After the addition was complete, the mixture was refluxed at 110 °C under a nitrogen atmosphere for 1 minute. For 3 hours (using toluene as the reaction solvent), during the reaction, the ethoxy group of 3-aminopropyltriethoxysilane (APTES) condenses with the hydroxyl group on the surface of the nanonucleus to form a Si-OM covalent bond. After the reaction, the mixture is naturally cooled to room temperature and centrifuged at 6000 rpm for 10 minutes to collect the solid product. The solid product is washed twice each with 20 g toluene, 20 g anhydrous ethanol, and 20 g deionized water. The washed solid product is dried overnight in a vacuum oven at 60 °C to obtain the rare earth-transition metal oxide cluster nanocomposite functionalized on the surface of APTES.

[0029] In step A4, 2g of the above-mentioned functionalized nanocomposite was dispersed in a mixed solution containing 10g of tetraethyl orthosilicate (TEOS) and 27.5g of anhydrous ethanol, and ultrasonically dispersed for 30min (power 100W, frequency 40kHz). Subsequently, 5g of deionized water and 1.25g of 25wt% ammonia were added sequentially. The reaction was carried out at room temperature under nitrogen protection with magnetic stirring for 10h. During the reaction, TEOS underwent hydrolysis and condensation under ammonia catalysis, and an amorphous silica shell was grown in situ on the surface of the APTES-grafted nanocore. After the reaction was completed, the solid product was collected by centrifugation at 8000rpm for 15min. The solid product was washed three times each with anhydrous ethanol and deionized water (20g each time). The washed product was dried in an oven at 80℃ for 12h, and finally calcined in a muffle furnace with air circulation at a temperature of 2℃ / min to 350℃ for 3h. After natural cooling to room temperature, the product was removed to obtain a rare earth-transition metal composite oxide nanocluster@silica shell hybrid inorganic modified material.

[0030] Example 2 The preparation method is the same as in Example 1, except that this example provides a process for preparing ultrafine glass powder by spray pyrolysis, including the following steps: S1: Add 1g boric acid, 0.5g aluminum nitrate nonahydrate, 0.1g calcium nitrate tetrahydrate, 1g lithium acetate, 1g sodium acetate, and 1g potassium acetate to 80g deionized water, heat to 40℃, stir, and cool to 24℃ to obtain solution A; dissolve 150g TEOS in 80g anhydrous ethanol and stir at 24℃ to obtain solution B; disperse 0.5g modified material Z in 30g anhydrous ethanol under an ice-water bath and sonicate (power 120W, frequency 40kHz, time 10min, intermittent sonication) to obtain suspension C; mix solutions B and C, add 5g deionized water and 0.5g hydrochloric acid, adjust pH to 3.0, and stir pre-hydrolyze at 25℃ for 30min; cool to 0℃, add 30g TEB dropwise at 1.0mL / min under an ice-water bath, and continue stirring for 30min; mix with solution A.

[0031] S2: Maintain pH at 3.0 and age at 30°C with stirring for 1 hour.

[0032] S3: Ultrasonic frequency 1MHz, atomization rate 0.1L / h.

[0033] S4: The carrier gas is nitrogen, the flow rate is 0.1 L / min, the pyrolysis furnace temperature is 600℃, and ultrafine glass powder is obtained.

[0034] Preparation of rare earth-transition metal composite oxide nanoclusters@silica shell hybrid inorganic modified materials: A1: Add 2g of anhydrous cerium chloride and 1g of zirconium chloride to 30g of anhydrous tetrahydrofuran, stir at room temperature for 30min, then heat to 38℃ and stir for 30min; add 10g of anhydrous isopropanol dropwise, and simultaneously add 5g of anhydrous triethylamine dropwise; remove the ice-water bath and heat to 60℃ and reflux for 12h; distill under reduced pressure at 38℃; wash the crude product three times with anhydrous n-hexane (10g each time); and dry under vacuum at room temperature for 6h.

[0035] A2: Dissolve 1g of the bimetallic alkoxide complex in 15g of anhydrous ethanol and 15g of toluene; add hydrolysate (1g deionized water, 2g anhydrous ethanol, 0.5g 25wt% ammonia) dropwise at 0.2mL / min at 5℃; allow to stand and age for 24h in a sealed container; heat at 58℃ for 2h in a reflux condenser (with gentle stirring); centrifuge (8000rpm, 15min); wash the precipitate three times each with anhydrous ethanol and deionized water (10g each time); dry in an oven at 80℃ for 12h.

[0036] A3: 2.0 g of nanonuclei were ultrasonically dispersed in 100 g of anhydrous toluene (ultrasonication for 30 min); heated to 108 °C under nitrogen protection and held for 30 min for azeotropic dehydration; 0.5 g of APTES was added dropwise (at a rate of 2 mmol per gram of nanonuclei); the reaction was refluxed at 108 °C for 12 h; after cooling, the product was centrifuged (6000 rpm, 10 min); the solid product was washed twice each with 10 g of toluene, 10 g of anhydrous ethanol, and 10 g of deionized water; and dried under vacuum at 60 °C overnight.

[0037] A4: Disperse 1g of functionalized nanocomposite in 5g TEOS and 15g anhydrous ethanol, and sonicate for 30min; add 2g deionized water and 0.5g 25wt% ammonia; stir for 8h under nitrogen protection at room temperature; centrifuge (8000rpm, 15min); wash the precipitate three times each with anhydrous ethanol and deionized water (10g each time); dry at 80℃ for 12h; calcine in an air-circulated muffle furnace at 2℃ / min to 348℃ for 2h, and then cool naturally.

[0038] Example 3 The preparation method is the same as in Example 1, except that this example provides a process for preparing ultrafine glass powder by spray pyrolysis, including the following steps: S1: Add 4g boric acid, 3g aluminum nitrate nonahydrate, 1.0g strontium nitrate, 5g lithium acetate, 5g sodium acetate, and 5g potassium acetate to 120g deionized water, heat to 50℃, stir, and cool to 26℃ to obtain solution A; dissolve 250g TEOS in 120g anhydrous ethanol and stir at 26℃ to obtain solution B; disperse 5g modified material Z in 80g anhydrous ethanol under an ice-water bath and sonicate (power 120W, frequency 40kHz, time 15min, intermittent sonication) to obtain suspension C; mix solutions B and C, add 10g deionized water and 3g hydrochloric acid, adjust pH to 4.5, and stir at 35℃ for 30min for pre-hydrolysis; cool to 10℃, add 80g TEB dropwise at 2.0mL / min under an ice-water bath, and continue stirring for 60min; mix with solution A.

[0039] S2: Maintain pH at 4.5 and age at 50°C with stirring for 2 hours.

[0040] S3: Ultrasonic frequency 2MHz, atomization rate 1L / h.

[0041] S4: The carrier gas is air, the flow rate is 1L / min, the pyrolysis furnace temperature is 900℃, and ultrafine glass powder is obtained.

[0042] Preparation of rare earth-transition metal composite oxide nanoclusters@silica shell hybrid inorganic modified materials: A1: Add 5g of anhydrous gadolinium chloride and 4g of hafnium chloride to 60g of anhydrous tetrahydrofuran, stir at room temperature for 30min, then heat to 42℃ and stir for 30min; add 25g of anhydrous isopropanol dropwise, and simultaneously add 16g of anhydrous triethylamine dropwise; remove the ice-water bath and heat to 70℃ and reflux for 12h; distill under reduced pressure at 42℃; wash the crude product three times with anhydrous n-hexane (20g each time); and dry under vacuum at room temperature for 6h.

[0043] A2: Dissolve 3g of the bimetallic alkoxide complex in 30g of anhydrous ethanol and 30g of toluene; add hydrolysate (4g deionized water, 6g anhydrous ethanol, 2g 25wt% ammonia) dropwise at 10℃ at 0.2mL / min; allow to stand and age in a sealed container for 24h; heat in a reflux condenser at 62℃ for 4h (with gentle stirring); centrifuge (8000rpm, 15min); wash the precipitate three times each with anhydrous ethanol and deionized water (20g each time); dry in an oven at 82℃ for 12h.

[0044] A3: 5.0 g of nanonuclei were ultrasonically dispersed in 150 g of anhydrous toluene (ultrasonication for 30 min); heated to 112 °C under nitrogen protection and held for 30 min for azeotropic dehydration; 2.5 g of APTES was added dropwise (at a rate of 4 mmol per gram of nanonuclei); the reaction was refluxed at 112 °C for 14 h; after cooling, the product was centrifuged (6000 rpm, 10 min); the solid product was washed twice each with 30 g of toluene, 30 g of anhydrous ethanol, and 30 g of deionized water; and dried under vacuum at 62 °C overnight.

[0045] A4: Disperse 3g of functionalized nanocomposite in 15g TEOS and 40g anhydrous ethanol, and sonicate for 30min; add 8g deionized water and 2g 25wt% ammonia; stir for 12h under nitrogen protection at room temperature; centrifuge (8000rpm, 15min); wash the precipitate three times each with anhydrous ethanol and deionized water (20g each time); dry at 82℃ for 12h; calcine in an air-circulated muffle furnace at 352℃ at a rate of 2℃ / min for 4h, and then cool naturally.

[0046] Comparative Example 1 The preparation method is the same as in Example 1, except that rare earth-transition metal composite oxide nanoclusters@silica shell hybrid inorganic modification material is not added, and the subsequent steps are exactly the same as in Example 1.

[0047] Comparative Example 2 The preparation method is the same as in Example 1, except that unmodified rare earth-transition metal oxygen cluster nanonuclei (i.e., the product of step A2 in Example 1, without treatment in A3 and A4) are used instead of rare earth-transition metal composite oxide nanoclusters@silica shell hybrid inorganic modified materials. The subsequent steps are exactly the same as in Example 1.

[0048] Comparative Example 3 The preparation method is the same as in Example 1, except that silica nanoparticles are used instead of rare earth-transition metal composite oxide nanoclusters@silica shell hybrid inorganic modified materials, and the remaining steps are exactly the same as in Example 1.

[0049] II. Performance Testing and Result Analysis The performance of the ultrafine glass powders prepared in Examples 1-3 and Comparative Examples 1-3 was tested using the following methods: Average particle size and D50 test: The morphology of the powder was observed using a scanning electron microscope (accelerating voltage 20.0 kV). At least 200 particles were randomly selected, and the Feret diameter (unit: nm) of each particle was measured using image analysis software. The arithmetic mean of all particles was calculated as the average particle size. At the same time, the particle size value corresponding to the cumulative volume percentage of the cumulative distribution curve reaching 50% was calculated as D50 (unit: nm).

[0050] Sphericity test: Based on the above scanning electron microscope images, 100 particles were randomly selected, and the major axis (L) and minor axis (W) of each particle were measured. The sphericity of a single particle was calculated according to the formula sphericity = W / L. The arithmetic mean of 100 particles was taken as the sphericity of the sample (dimensionless, value range 0-1, the closer the value is to 1, the more perfect the sphericity).

[0051] Boron volatilization rate test: The actual mass fraction (unit: %) of boron trioxide in glass powder was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The boron volatilization rate was calculated according to the formula: boron volatilization rate = (formula design value - measured value) / formula design value × 100%, where the formula design value is 25%. The calculation result is expressed as a percentage (unit: %).

[0052] Thermal shock resistance test: Glass powder was pressed into circular green bodies with a diameter of 10 mm and a thickness of 3 mm under a pressure of 10 MPa. These green bodies were then sintered in a muffle furnace at 700 °C for 2 hours to obtain a sintered body. The sintered body was then held at 500 °C for 30 minutes and then quickly immersed in water at 25 °C. This constitutes one thermal shock cycle. After each cycle, the surface of the sintered body was observed for any visible cracks. The above operation was repeated until cracks appeared, and the maximum number of cycles without cracks was recorded (unit: times).

[0053] XRD Impurity Phase Analysis: X-ray diffractometer (Cu Kα radiation, wavelength 0.15406 nm) was used to analyze the phase composition of the glass powder. The scanning range was 10° to 80°, with a step size of 0.02° and a scanning speed of 2° / min. The obtained diffraction patterns were compared with standard PDF cards to determine the presence of unreacted silica, boric acid, or rare earth oxides, etc. If no impurity peaks were observed, it was recorded as "none"; if impurity peaks were present, the specific name of the phase corresponding to the strongest impurity peak was recorded.

[0054] Table 1: Performance test results of each embodiment and comparative example ; As can be seen from Table 1, Examples 1-3 successfully solved the following technical problems existing in the prior art compared with Comparative Examples 1-3: As can be seen from the particle size data, the average particle size of Examples 1-3 is 45-78nm and D50 is 42-72nm, while the average particle size of Comparative Examples 1-3 is 153-312nm and D50 is 158-335nm. This shows that by introducing modified material Z and stepwise pre-hydrolysis and low-temperature co-condensation process, the present invention significantly reduces the particle size of glass powder from submicron level (above 150nm) to nanoscale level (below 80nm), solving the problem of coarse particles caused by the mismatch of precursor hydrolysis rate and lack of nucleating agent in traditional spray pyrolysis.

[0055] The sphericity data show that the sphericity of Examples 1-3 is 0.94-0.97, while that of Comparative Examples 1-3 is only 0.72-0.88. This proves that the modified material Z, as an in-situ nucleating agent and structural reinforcement, promotes the uniform shrinkage and sphericity of droplets during pyrolysis. It solves the problems of irregular particles in Comparative Example 1 due to the lack of a modifier, partial agglomeration and deformation in Comparative Example 2 due to the lack of functionalization of the nanonucleus surface, and morphological deviation in Comparative Example 3 due to the uneven dispersion of commercially available silica particles.

[0056] As can be seen from the boron volatilization data, the boron volatilization rate of Examples 1-3 is only 2.8%-5.1%, while that of Comparative Example 1 is as high as 28.6%, Comparative Example 2 is 15.3%, and Comparative Example 3 is 12.5%. This indicates that the present invention constructs a stable Si-OB covalent network by first pre-hydrolyzing TEOS to generate active silanol, and then adding TEB dropwise at low temperature for co-condensation. This firmly anchors boron atoms in the silicon-oxygen framework, thereby effectively suppressing the gaseous volatilization of boron during the high-temperature spray pyrolysis process at 600-900℃. This solves the component segregation problem in Comparative Example 1 caused by the simple mixing of silicon and boron, which resulted in preferential self-condensation of boron and severe high-temperature volatilization.

[0057] The thermal shock resistance data show that Examples 1-3 had 6-9 thermal shock cycles, while Comparative Example 1 had only 2, Comparative Example 2 only 3, and Comparative Example 3 only 4. This indicates that the rare earth-transition metal oxide cluster nanonucleus of modified material Z enhances the crosslinking density and thermal stability of the glass network structure. Furthermore, the synergistic effect of APTES grafting and the silica shell enables the modifier to achieve molecular-level compatibility with the glass matrix, solving the problems of insufficient thermomechanical properties caused by the lack of a reinforcing phase in Comparative Example 1, poor bonding between the nanonucleus and the matrix in Comparative Example 2, and uneven dispersion of commercially available silica particles in Comparative Example 3.

[0058] XRD phase analysis showed that Examples 1-3 had no impurities, while Comparative Example 1 contained unreacted silica and boric acid impurities, Comparative Example 2 contained trace amounts of rare earth oxide impurities, and Comparative Example 3, although without impurities, showed silica enrichment. This proves that the process of the present invention achieves complete reaction and uniform distribution of glass components, and solves the problems of silicon-boron phase separation, incomplete reaction of rare earth precursors, and agglomeration and segregation of added nanoparticles in traditional methods.

[0059] In summary, Examples 1-3 successfully solved the technical problems of component segregation caused by the easy volatilization of boron components, large particle size and poor sphericity, and poor thermal shock resistance caused by the unstable glass network structure when preparing ultrafine glass powder by spray pyrolysis, compared with Comparative Examples 1-3.

[0060] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A process for preparing ultrafine glass powder by spray pyrolysis, characterized in that, Includes the following steps: S1, by weight, add 1-4 parts boric acid, 0.5-3 parts aluminum nitrate nonahydrate, 0.1-1.0 parts alkaline earth metal nitrate, 1-5 parts lithium acetate, 1-5 parts sodium acetate, and 1-5 parts potassium acetate to 80-120 parts deionized water, heat to 40-50℃, stir, and cool to 24-26℃ to obtain solution A; dissolve 150-250 parts tetraethyl orthosilicate in 80-120 parts anhydrous ethanol, stir at 24-26℃ to obtain solution B; under an ice-water bath, add 0.5-5 parts rare earth-transition metal complex oxygen... The inorganic modified material, consisting of chemical nanoclusters with a silica shell hybrid, was dispersed in 30-80 parts of anhydrous ethanol and sonicated to obtain suspension C. Solution B was mixed with suspension C, and 5-10 parts of deionized water and 0.5-3 parts of hydrochloric acid were added to adjust the pH to 3-4.

5. The mixture was then stirred and pre-hydrolyzed at 25-35°C to obtain a mixed solution. The mixed solution was cooled to 0-10°C, and 30-80 parts of triethyl borate were added dropwise under an ice-water bath while stirring continued to obtain a copolymerized mixture. The copolymerized mixture was then mixed with solution A to obtain a reaction mixture. S2, maintain the pH of the reaction mixture at 3-4.5, and stir and age at 30-50℃ to obtain a pre-reacted mixed solution; S3, The pre-reacted mixed solution is atomized using an ultrasonic atomizer to obtain atomized gas; S4, the atomized gas is introduced into the pyrolysis furnace through the carrier gas for spray pyrolysis to obtain the pyrolyzed powder; The pyrolyzed powder is introduced into a collection device via a carrier gas to obtain ultrafine glass powder.

2. The process for preparing ultrafine glass powder by spray pyrolysis according to claim 1, characterized in that, In step S1, the alkaline earth metal nitrate is selected from at least one of magnesium nitrate hexahydrate, calcium nitrate tetrahydrate, strontium nitrate, and barium nitrate.

3. The process for preparing ultrafine glass powder by spray pyrolysis according to claim 1, characterized in that, In step S2, the stirring and aging time at 30-50℃ is 1-2 hours.

4. The process for preparing ultrafine glass powder by spray pyrolysis according to claim 1, characterized in that, In step S3, the atomization rate of the atomization treatment is 0.1-1 L / h.

5. The process for preparing ultrafine glass powder by spray pyrolysis according to claim 1, characterized in that, In step S4, the temperature of the spray pyrolysis is 600-900℃; the carrier gas is air or nitrogen.

6. The process for preparing ultrafine glass powder by spray pyrolysis according to any one of claims 1-5, characterized in that, The preparation steps of the rare earth-transition metal composite oxide nanoclusters@silica shell hybrid inorganic modified material include: A1, by weight, in a glove box under nitrogen atmosphere and under ice-water bath cooling, add 2-5 parts of anhydrous rare earth chloride and 1-4 parts of transition metal chloride to 30-60 parts of anhydrous tetrahydrofuran, stir at room temperature, then heat to 38-42℃ and continue stirring; under ice-water bath and nitrogen protection, add 10-25 parts of anhydrous isopropanol dropwise, and simultaneously add 5-16 parts of anhydrous triethylamine; after the addition is complete, remove the ice-water bath, heat to 60-70℃ and reflux to obtain a mixture; filter the mixture under nitrogen protection to obtain a filtrate; transfer the filtrate to a rotary evaporator and distill under reduced pressure at 38-42℃ to obtain a crude product; wash the crude product with anhydrous n-hexane, and then dry under vacuum at room temperature to obtain a rare earth-transition metal bimetallic alkoxide complex; A2, under nitrogen protection, 1-3 parts of a rare earth-transition metal bimetallic alkoxide complex are dissolved in a mixed solvent containing 15-30 parts of anhydrous ethanol and 15-30 parts of toluene to obtain a precursor solution; an alkaline hydrolysate containing 1-4 parts of deionized water, 2-6 parts of anhydrous ethanol and 0.5-2 parts of ammonia is added dropwise to the precursor solution at 5-10℃ with stirring; after the addition is complete, the mixture is allowed to stand and age at room temperature under a sealed environment; after aging, the mixture is heated at 58-62℃ to obtain a reaction mixture; the reaction mixture is centrifuged to obtain a precipitate; the precipitate is washed successively with anhydrous ethanol and deionized water to obtain a washed precipitate; the washed precipitate is dried in an oven at 78-82℃ to obtain rare earth-transition metal oxygen cluster nanonuclei; A3. 2.0-5.0 parts of rare earth-transition metal oxide cluster nanonuclei were ultrasonically dispersed in 100-150 parts of anhydrous toluene and sonicated to obtain a suspension. The suspension was transferred to a three-necked flask and heated to 108-112℃ under nitrogen protection. Then, 0.5-2.5 parts of 3-aminopropyltriethoxysilane were added dropwise. After the addition was complete, the mixture was refluxed at 108-112℃ under a nitrogen atmosphere to obtain a mixture. The mixture was naturally cooled to room temperature, centrifuged, and the solid product was collected. The solid product was washed sequentially with 10-30 parts of toluene, anhydrous ethanol, and deionized water to obtain a washed solid product. The washed solid product was dried in a vacuum oven at 58-62℃ to obtain a surface-functionalized rare earth-transition metal oxide cluster nanocomposite. A4. Disperse 1-3 parts of surface-functionalized rare earth-transition metal oxide cluster nanocomposite in a mixed solution containing 5-15 parts of tetraethyl orthosilicate and 15-40 parts of anhydrous ethanol, and ultrasonically disperse; add 2-8 parts of deionized water and 0.5-2 parts of ammonia; stir the reaction at room temperature under nitrogen protection; after the reaction is completed, centrifuge to collect the solid product; wash the solid product with anhydrous ethanol and deionized water in sequence to obtain the washed product; dry the washed product in an oven at 78-82℃, calcine it at 348-352℃, and cool it naturally to room temperature.

7. The process for preparing ultrafine glass powder by spray pyrolysis according to claim 6, characterized in that, In step A1, the anhydrous rare earth chloride is selected from one of anhydrous lanthanum chloride, anhydrous cerium chloride, and anhydrous gadolinium chloride; the transition metal chloride is selected from one of titanium chloride, zirconium chloride, and hafnium chloride.

8. The process for preparing ultrafine glass powder by spray pyrolysis according to claim 6, characterized in that, In step A2, the reaction is carried out at 58-62℃ for 2-4 hours.

9. The process for preparing ultrafine glass powder by spray pyrolysis according to claim 6, characterized in that, In step A3, the reflux reaction at 108-112℃ is carried out for 12-14 hours.

10. The process for preparing ultrafine glass powder by spray pyrolysis according to claim 6, characterized in that, In step A4, the calcination time at 348-352℃ is 2-4 hours.

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