Method for preparing nano high-purity quartz powder

Abstract

The application relates to the technical field of inorganic nonmetallic materials, in particular to a preparation method of nano high-purity quartz powder, which comprises the following steps: removing impurities in quartz ore by three-stage countercurrent acid leaching to reduce metal impurities; carrying out double-acid etching on the quartz ore by using aminosulfonic acid, fluoroboric acid and silicon carbide seeds, and performing three-stage grinding to obtain 80-180 nm slurry; adding a silane coupling agent and graphene quantum dots, and modifying the slurry by high-pressure homogenization; performing gradient magnetic field centrifugation and ceramic membrane filtration grading; and performing vacuum pulse drying and adding a dispersing agent to prepare nano powder with improved purity and reduced dispersity, which meets the high-end demand of semiconductors and the like. The application improves the purity of the quartz powder and reduces the dispersity by double-acid etching and double-amphiphilic modification and the like, and the quartz powder has high stability and a double-functional interface; the process is environmentally friendly and has low energy consumption, and the application promotes the localization of high-end materials.

Description

Technical Field

[0001] This invention relates to the field of inorganic non-metallic materials technology, specifically to a method for preparing nano-high-purity quartz powder. Background Technology

[0002] High-purity nano-quartz powder is a core material in high-end fields such as semiconductors, optical coatings, and aerospace. Its purity and particle size uniformity directly determine the performance of downstream products. Current preparation processes mainly face the following technical bottlenecks:

[0003] Traditional acid leaching processes have limited efficiency in removing metallic impurities such as aluminum, iron, and calcium from quartz sand, especially at lattice defects. For example, the total content of metallic impurities after conventional acid leaching is typically 100-200 ppm, which fails to meet the requirement of ≤10 ppm for semiconductor-grade materials. Furthermore, existing processes lack methods to enhance the acid leaching process, resulting in slow reaction rates, high energy consumption, poor etching selectivity, and a tendency to damage the quartz crystal structure.

[0004] While mechanical grinding (such as ball milling and sand milling) can achieve nano-sized particles, it suffers from drawbacks such as wide particle size distribution and severe crystal damage. In chemical etching, the etching rate of a single acid system (such as aminosulfonic acid) is difficult to control precisely, and the lack of seed guidance during etching easily leads to the formation of irregular particles. Furthermore, the high surface energy of nanoparticles makes it difficult for conventional modification processes (such as simple silane coupling) to effectively suppress agglomeration, resulting in rapid sedimentation rates in aqueous dispersions that cannot meet the stability requirements of high-end applications.

[0005] Current surface modification methods mostly employ single silane coupling agents, which can only impart a single hydrophilic or hydrophobic property to quartz particles, failing to meet the needs of complex applications (such as those requiring both oleophilic and hydrophilic properties). For example, in optical coatings, particles need to possess both good dispersibility and compatibility with organic matrices; traditional modification processes struggle to achieve bifunctional interface matching. Furthermore, the lack of efficient dispersion methods during modification leads to low coating efficiency (typically <85%) and numerous surface defects on the nanoparticles.

[0006] Traditional manufacturing processes often employ intermittent operation with loose connections between stages, resulting in significant material losses (recycling rate <90%) and high energy consumption. Etching wastewater contains large amounts of waste acid and heavy metal ions, and direct discharge easily causes environmental pollution. Existing recycling technologies are complex and costly. For example, the recovery rate of aminosulfonic acid wastewater is less than 70%, and fluoride treatment costs account for more than 20% of the total process cost. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] To address the shortcomings of existing technologies, this invention provides a method for preparing nano-high-purity quartz powder.

[0009] (II) Technical Solution

[0010] A method for preparing nano-high-purity quartz powder includes the following steps:

[0011] S1: Deep impurity removal from raw quartz ore

[0012] Quartz sand was crushed and subjected to a three-stage countercurrent acid leaching process. The first stage of leaching involved a 1:1 volume ratio mixture of hydrofluoric acid and nitric acid, leached in an ultrasonic field for 1 hour. The second stage of leaching involved the addition of disodium ethylenediaminetetraacetate (EDTA-2Na) and continued leaching for 1 hour. The third stage of leaching involved simultaneous introduction of ozone and leaching for 1 hour. After filtration, the sand was washed with deionized water until the conductivity was ≤1μS / cm, and then dried to obtain high-purity quartz sand.

[0013] S2: Dual-acid synergistic etching nanofiberization

[0014] High-purity quartz sand is mixed with aminosulfonic acid (NH2SO3H) and fluoroboric acid (HBF4), and deionized water is added to form a slurry. Silicon carbide nanocrystal seeds are then added to react, and the etching reaction formula is as follows:

[0015]

[0016] After the reaction, a planetary ball mill was used for three-stage grinding: the first stage was dry grinding for 1 hour; the second stage was wet grinding with polyethylene glycol (PEG-6000) for 2 hours; and the third stage was wet grinding with sodium polyacrylate (PAAS) for 2 hours to obtain a quartz slurry with a particle size distribution of 80-180nm.

[0017] S3: Amphiphilic Interface Modification

[0018] Silane coupling agent KH-570 and graphene quantum dots (GQDs) were added to the slurry in sequence, and the pH was adjusted to 9.5 with triethanolamine. The mixture was reacted at 80°C under ultrasonic conditions to form a "silane-GQDs-quartz" coated structure. After the reaction, the mixture was subjected to high-pressure homogenization and then processed by a microfluidic homogenizer.

[0019] S4: Magnetic field-assisted fractional purification

[0020] A gradient magnetic field is installed outside the centrifugal classifier to adsorb and separate magnetic impurities from the slurry; particles with a diameter of 100-150nm are collected and cross-flow filtration is performed using a ceramic membrane with a pore size of 50nm, while the zeta potential of the filtrate is monitored and controlled between -35 and -45mV.

[0021] S5: Vacuum Pulsating Drying

[0022] The graded slurry was transferred to a vacuum drying oven and heated by pulse heating. Nitrogen gas that had been deoxygenated was introduced during the drying process. After drying, a compound dispersant of zinc stearate and nano titanium dioxide was added and mixed in a three-dimensional motion mixer.

[0023] Preferably, the liquid-to-solid ratio of the three-stage countercurrent acid leaching process in S1 is 5:1, and after each stage of acid leaching, a high-gravity rotating bed is used for solid-liquid separation with a rotation speed of 2000 rpm and a separation efficiency of ≥99%.

[0024] Preferably, the silicon carbide nanocrystal seeds in S2 are added as follows: the seeds are first dispersed in a fluoroboric acid solution under ultrasonic conditions with a power of 200W for 30 minutes, and then mixed with an aminosulfonic acid solution.

[0025] Preferably, the hydrolysis process of silane coupling agent KH-570 in S3 is as follows: hydrolyze at 60°C for 1 hour in an acetic acid buffer solution with a pH of 4.5, with a degree of hydrolysis ≥90%.

[0026] Preferably, the ceramic membrane filtration in S4 uses a backwash regeneration process with a backwash pressure of 0.5 MPa and a backwash frequency of once every 15 minutes, each lasting 10 seconds.

[0027] Preferably, the moisture removal rate in the drying process of S5 is monitored in real time by a dew point meter and controlled within 0.5-1.0 kg / (m²·h).

[0028] Preferably, the entire preparation process is carried out in a cleanroom with a cleanliness level of ISO 7, where the concentration of airborne particles ≥0.5μm is ≤35200 particles / m³.

[0029] Preferably, the surface energy of the prepared nano-quartz powder is measured by a contact angle meter, with a contact angle of 75°-85° with water and a contact angle of 30°-40° with liquid paraffin.

[0030] Preferably, the prepared nano-quartz powder has a tap density of 0.85-0.95 g / cm³ and a specific surface area of ​​25-35 m² / g.

[0031] Preferably, the pulse heating method used in S5 is as follows: the first stage is a heating rate of 15℃ / min, which is raised to 120℃ and held for 30min; the second stage is a cooling to 80℃ and held for 20min; and the third stage is a heating to 120℃ and held for 30min.

[0032] (iii) Beneficial technical effects

[0033] Compared with existing technologies, the beneficial effects of this invention are:

[0034] 1. A three-stage countercurrent acid leaching process combined with ozone oxidation and EDTA chelation reduces the total content of metallic impurities such as Fe, Al, and Ca to ≤10ppm, meeting semiconductor-grade standards (GB / T 38514-2020), which is lower than traditional processes. The synergistic etching of dual acids and the heterogeneous nucleation of silicon carbide seeds concentrate the particle size distribution in the 80-180nm range with a dispersion of ≤12%. Further refinement to 100-150nm through three-stage grinding meets the particle size requirements of high-end polishing materials.

[0035] 2. The silane coupling agent KH-570 forms a bifunctional coating layer of "hydrophobic segments-hydrophilic groups" with GQDs, resulting in a contact angle of 75°-85° with water and 30°-40° with liquid paraffin. This provides high dispersibility in both aqueous and oil phases, broadening its application scenarios. High-pressure homogenization (150MPa) and microfluidic (200MPa) treatments improve the coating efficiency of GQDs to ≥95%, a significant improvement over traditional ultrasonic modification, and also enhances stability.

[0036] 3. Etching waste liquid is recycled using ion exchange resin to recover aminosulfonic acid and fluoroboric acid, with a reuse rate of ≥90%, reducing waste acid emissions; the vacuum pulse drying process shortens drying time and reduces energy consumption compared to traditional oven drying, achieving green production. The entire process from acid leaching to drying is intelligently controlled (such as online laser particle size monitoring and real-time Zeta potential feedback), significantly improving batch-to-batch consistency and making it suitable for large-scale industrial production.

[0037] 4. The purity of the prepared quartz powder is improved, with a specific surface area of ​​25-35 m² / g. When used in CMP polishing slurries, it reduces wafer surface roughness and defect density. The particle tap density is 0.85-0.95 g / cm³, resulting in increased filling rate and light transmittance in optical thin films, meeting the requirements of high refractive index coatings. Vacuum pulse drying reduces particle agglomeration, improving dispersion uniformity in ceramic matrix composites. Attached Figure Description

[0038] Figure 1 This is a flowchart of a method for preparing nano-high-purity quartz powder;

[0039] Figure 2 This is a line graph comparing the impurity content of the examples and the comparative examples;

[0040] Figure 3 This is a line graph comparing the key performance improvement factors of Example 1 and the comparative example;

[0041] Figure 4 This is a radar comparison chart created by standardizing the key performance data of Example 1 and the comparative example. Detailed Implementation

[0042] according to Figures 1 to 4 The specific embodiments of the present invention are as follows:

[0043] I. Preparation of Materials and Equipment

[0044] 1. Raw material specifications

[0045] Quartz sand (SiO2 ≥ 99%) from Fengyang, Anhui Province, was selected and coarsely crushed to a particle size ≤ 5 mm using a jaw crusher, followed by further pulverization to a particle size ≤ 50 μm using an air jet mill. Sulfamic acid (AR grade, purity ≥ 99.5%) required recrystallization purification to reduce metal impurity content. Fluoroboric acid was prepared using a 40% aqueous solution (purity ≥ 99%), filtered through a 0.22 μm microporous membrane to remove mechanical impurities before use. Silicon carbide nanocrystals (particle size 50 nm, purity ≥ 99.9%) were prepared by vapor deposition, and their surface hydroxyl content was determined to be 0.8 mmol / g by acid-base titration. Silane coupling agent KH-570 (industrial grade, purity ≥ 98%) required hydrolysis degree testing before use to ensure a hydrolysis degree ≥ 90%. Graphene quantum dots (particle size 5-10 nm, carbon content ≥ 95%) were prepared by concentrated sulfuric acid oxidation, with a fluorescence quantum yield of 28%.

[0046] 2. Main Equipment

[0047] The planetary ball mill (XQM-2L) features a zirconium oxide grinding cylinder with a 5mm thick lining to minimize impurity introduction during grinding. The high-pressure homogenizer (NS1001L2K) employs a three-stage homogenizing valve design for precise pressure control. The microjets homogenizer (M-110P) uses diamond for its interactive chambers, capable of withstanding pressures exceeding 200MPa. The gradient magnetic field device (GMF-100) is equipped with a programmable controller, enabling precise control and gradient changes in magnetic field strength. The ceramic membrane filtration system (CFM-50) utilizes a cross-flow filtration mode, with a multi-channel tubular membrane module providing an effective filtration area of ​​0.5m². The vacuum drying oven (DZF-6050) has an inner wall made of 316L stainless steel and is equipped with high-precision vacuum and temperature sensors, achieving a temperature control accuracy of ±1℃.

[0048] II. Example 1: Preparation using standard process

[0049] Formula (by weight)

[0050] 100 parts quartz sand, 30 parts aminosulfonic acid, 10 parts fluoroboric acid, 0.2 parts silicon carbide nanocrystal seeds, 2 parts silane coupling agent KH-570, 0.5 parts graphene quantum dots, 2 parts polyethylene glycol PEG-6000, and 0.5 parts sodium polyacrylate PAAS.

[0051] Preparation steps

[0052] Deep impurity removal from raw quartz ore

[0053] Pretreated quartz sand (D50=30μm) was fed into a three-stage countercurrent acid leaching system. In the first-stage leaching tank, a mixture of 5% hydrofluoric acid and 10% nitric acid was added at a liquid-to-solid ratio of 5:1. An ultrasonic generator (300W power, 35kHz frequency) was turned on, and leaching was carried out at 40℃ with stirring for 1 hour. In the second-stage leaching tank, 0.2% (mass fraction) of EDTA-2Na was added, and leaching continued for 1 hour. EDTA-2Na forms a stable complex with metal ions, improving the impurity removal efficiency. In the third-stage leaching tank, ozone (concentration 5mg / L) was introduced to utilize the strong oxidizing properties of ozone to break down the metal oxide film on the quartz surface, and leaching was carried out for 1 hour. After leaching, the slurry was transported to a high-gravity rotating bed (2000rpm) for solid-liquid separation, achieving a separation efficiency of over 99%. The filter cake was repeatedly washed with deionized water (resistivity ≥ 18.2 MΩ·cm) until the conductivity of the washing water dropped to 0.8 μS / cm. Then it was dried at 120℃ for 2 hours to obtain high-purity quartz sand with a total metal impurity content of 48 ppm.

[0054] Dual-acid synergistic etching nanofiber

[0055] High-purity quartz sand, aminosulfonic acid, and fluoroboric acid were added to a reactor at a mass ratio of 1:0.3:0.1, and deionized water was added to prepare a slurry with a solid content of 20%. Silicon carbide nanocrystals were pre-dispersed in a fluoroboric acid solution using ultrasonic dispersion (200W power, 30 minutes) to ensure uniform dispersion. The reaction was carried out at 70℃ and a stirring speed of 800 rpm for 4 hours, with real-time monitoring of pH changes to maintain it between 2.0 and 2.5. After the reaction, the slurry was transferred to a planetary ball mill for three-stage grinding. The first stage involved dry grinding for 1 hour at a ball-to-particle ratio of 8:1 at 400 rpm to initially refine the quartz particles. The second stage involved adding 2% (mass fraction) of PEG-6000 as a dispersant and wet grinding for 2 hours to prevent particle agglomeration. The third stage involved adding 0.5% (mass fraction) of PAAS as a grinding stabilizer to further refine the particles. After grinding, the particle size distribution of the slurry was detected by a laser particle size analyzer. The particle size distribution was D10=85nm, D50=120nm, and D90=175nm, indicating a narrow particle size distribution.

[0056] Amphiphilic interface modification

[0057] Before use, the silane coupling agent KH-570 requires hydrolysis. It is hydrolyzed for 1 hour at 60°C in an acetic acid buffer solution with a pH of 4.5, achieving a degree of hydrolysis of 92%. The hydrolyzed KH-570 is then added to a quartz slurry and stirred thoroughly. Graphene quantum dots are then added, and the pH is adjusted to 9.5 with triethanolamine. The mixture is reacted at 80°C and 400W ultrasonic power for 1.5 hours to ensure thorough coating of the silane coupling agent and graphene quantum dots onto the quartz particle surface. After the reaction, the slurry is homogenized three times using a high-pressure homogenizer (150 MPa), followed by two more homogenizations using a microfluidic homogenizer (200 MPa) to further improve coating efficiency. X-ray photoelectron spectroscopy (XPS) analysis of the coated particles shows a C / Si atomic ratio of 0.92, indicating good coating performance.

[0058] Magnetic field-assisted fractional purification

[0059] The modified slurry was fed into a gradient magnetic field device and centrifuged (8000 rpm) under a magnetic field strength of 0.5-1.2T. Magnetic impurities were adsorbed onto the inner wall of the device under the influence of the magnetic field, thus separating from the quartz particles. The fractionated slurry was then finely filtered through a ceramic membrane filtration system using a cross-flow filtration mode (membrane surface velocity 4 m / s, operating pressure 0.3 MPa). The zeta potential of the filtrate was monitored in real time and controlled to approximately -42 mV to ensure particle dispersion stability. Particles with a diameter between 100-150 nm were collected, with a yield of 82%.

[0060] Vacuum Pulsating Drying

[0061] The graded slurry was transferred to a vacuum drying oven and evacuated to a pressure of 45 Pa. A pulse heating method was used, first raising the temperature to 120°C at a rate of 15°C / min and holding it at that temperature for 30 minutes; then lowering it to 80°C and holding it at that temperature for 20 minutes; finally, raising it back to 120°C and holding it at that temperature for 30 minutes. During the drying process, deoxygenated nitrogen gas (oxygen content 8 ppm, dew point -72°C) was introduced to prevent particle oxidation. After drying, 0.8% (mass fraction) of zinc stearate and 0.2% (mass fraction) of nano-titanium dioxide were added to the drying oven as a compound dispersant, and the mixture was thoroughly mixed using a three-dimensional motion mixer (20 rpm, mixing time 30 minutes) to obtain a nano-high-purity quartz powder product.

[0062] III. Example 2: High Purity Optimization Process

[0063] Formula (by weight)

[0064] 100 parts quartz sand, 35 parts aminosulfonic acid, 12 parts fluoroboric acid, 0.2 parts silicon carbide nanocrystal seeds, 2 parts silane coupling agent KH-570, 0.5 parts graphene quantum dots, 2 parts polyethylene glycol PEG-6000, and 0.5 parts sodium polyacrylate PAAS.

[0065] Preparation steps

[0066] Deep impurity removal from raw quartz ore

[0067] Pretreated quartz sand (D50=30μm) was added to a three-stage countercurrent acid leaching system. In the first-stage leaching tank, a mixture of 15% nitric acid and 5% hydrofluoric acid was added at a liquid-to-solid ratio of 5:1. An ultrasonic generator (300W, 35kHz) was turned on, and the leaching was carried out at 40°C with stirring for 1 hour to enhance the dissolution of Fe and Al oxides. In the second-stage leaching tank, 0.3% EDTA-2Na was added, and the leaching continued for 1 hour to remove Ca through chelation. 2+ Mg 2+ Plasma leaching; a three-stage leaching tank was leached with 7 mg / L ozone for 1 hour to oxidize and decompose organic impurities. After separation by a high-gravity rotating bed (2000 rpm), the slurry was washed with deionized water (resistivity ≥18.2 MΩ·cm) until the conductivity ≤0.7 μS / cm, and dried at 120℃ for 2 hours to obtain high-purity quartz sand (total metallic impurities 35 ppm, Fe=2.5 ppm, Al=4.2 ppm).

[0068] Dual-acid synergistic etching nanofiber

[0069] High-purity quartz sand was mixed with aminosulfonic acid and fluoroboric acid at a mass ratio of 1:0.35:0.12 to prepare a 20% solids content slurry. Silicon carbide nanocrystals were pre-dispersed in the fluoroboric acid solution (ultrasonic 200W / 30min). The reaction was carried out at 70℃ and 800rpm for 5 hours, with pH monitored in real time and acid added to maintain 2.0-2.5. The slurry was then transferred to a planetary ball mill: the first stage was dry grinding (ball-to-material ratio 8:1, 400rpm, 1 hour) to break up agglomerates; the second stage involved wet grinding with 2% PEG-6000 for 2 hours to prevent agglomeration; and the third stage involved adding 0.5% PAAS to refine the particles. Laser particle size distribution showed D10=90nm, D50=130nm, D90=180nm, and PDI=0.12.

[0070] Amphiphilic interface modification

[0071] KH-570 was hydrolyzed in a pH 4.5 acetate buffer solution at 60°C for 1 hour (92% degree of hydrolysis). Graphene quantum dots were added to the slurry after the hydrolysate was added, and the pH was adjusted to 9.5 with triethanolamine. The reaction was carried out at 80°C and ultrasonically at 400W for 1.5 hours to promote condensation. Soft agglomerates were broken up three times using a high-pressure homogenizer (150MPa), and the coating uniformity was improved by two treatments using a microfluidic homogenizer (200MPa, diamond cavity). XPS analysis showed a C / Si atomic ratio of 0.93 and an O / Si ratio of 1.15.

[0072] Magnetic field-assisted fractional purification

[0073] The slurry was centrifuged and classified at 8000 rpm in a gradient magnetic field device (1.5T), and the magnetic impurity adsorption removal rate was 99.2%. The classified slurry was then subjected to cross-flow filtration through a ceramic membrane (membrane surface flow rate 5 m / s, pressure 0.2 MPa), and the zeta potential was monitored to be -43.5 mV. 100-150 nm particles were collected (yield 78%).

[0074] Vacuum Pulsating Drying

[0075] The slurry was pulse-heated in a vacuum drying oven (35 Pa): 15℃ / min to 120℃ and held for 30 min → 80℃ and held for 20 min → then back to 120℃ and held for 30 min, with deoxygenated nitrogen gas (oxygen content ≤5ppm) purging throughout. After drying, 0.8% zinc stearate and 0.2% nano titanium dioxide were added, and the mixture was homogenized using a three-dimensional motion mixer (20 rpm / 30 min). The final product purity was ≥99.999%, Fe ≤2ppm, Al ≤5ppm.

[0076] IV. Example 3: High-efficiency mass production process

[0077] Formula (by weight)

[0078] 100 parts quartz sand, 30 parts aminosulfonic acid, 10 parts fluoroboric acid, 0.2 parts silicon carbide nanocrystal seeds, 2 parts KH-570, 0.5 parts graphene quantum dots, 2 parts PEG-6000, and 0.5 parts PAAS.

[0079] Preparation steps

[0080] Deep impurity removal from raw quartz ore

[0081] A continuous three-stage countercurrent acid leaching system (processing capacity 50 kg / h) is employed. The first stage involves adding a 5% HF + 10% HNO3 mixture (liquid-to-solid ratio 5:1) and ultrasonic leaching at 40℃. The second stage continuously adds 0.2% EDTA-2Na. The third stage introduces 5 mg / L ozone. PLC automatically controls temperature, pressure, and stirring (40±0.5℃, 300 rpm). The slurry is continuously discharged via a high-speed gravity separator (2500 rpm), with online conductivity monitoring showing ≤0.8 μS / cm and metallic impurities ≤45 ppm.

[0082] Dual-acid synergistic etching nanofiber

[0083] Etching was performed in a 316L stainless steel pipe reactor (200mm in diameter, 30m in length), with jacketed hot oil circulation for temperature control at 70±2℃, and an online pH monitor maintaining the pH at 2.0-2.5. The flow rate was 0.15m / s, and the residence time was 4 hours. The ball milling procedure was the same as in Example 1, with a slurry D50 of 120nm.

[0084] Amphiphilic interface modification

[0085] After hydrolysis with KH-570, the slurry was added and ultrasonically reacted at 80℃ for 1.5 hours (pH 9.5). A high-pressure homogenizer (150MPa×3 times, 80L / h) and a microfluidic homogenizer (200MPa×2 times, 40L / h) were connected in series, with a processing capacity of 100L / h and a coating efficiency of 96%.

[0086] Magnetic field-assisted fractional purification

[0087] Gradient magnetic field device (0.5-1.2T) with PLC programming control of gradually increasing magnetic field strength; impurity adsorption rate ≥99% after centrifugation and grading. Ceramic membrane filtration (membrane surface flow rate 4m / s, pressure 0.3MPa), Zeta potential -42±1mV, yield 82%.

[0088] Vacuum Pulsating Drying

[0089] A double-cone rotary dryer (500L volume, 15rpm) was used, with a vacuum of 40Pa and jacketed heat transfer oil heating at 120±2℃, and drying was carried out for 2 hours under deoxygenated nitrogen gas (oxygen content ≤8ppm). After drying, 0.8% zinc stearate and 0.2% nano TiO2 were added and mixed thoroughly using a V-type mixer (30rpm / 20min). Production targets: 50kg / h capacity for acid leaching section + 100kg / batch for purification section, D50 fluctuation ≤±5nm, purity fluctuation ≤±0.001%.

[0090] V. Comparative Example: Traditional Craftsmanship

[0091] Formula and process

[0092] Quartz sand from the same source (without deep impurity removal) was used. The nano-sizing process employed a single hydrofluoric acid etching solution (10% concentration) followed by ball milling for 6 hours (300 rpm). Surface modification utilized only a single silane coupling agent, KH-550 (1% dosage), achieved through mechanical stirring. The grading process employed conventional centrifugation (5000 rpm), and drying was performed using standard vacuum drying (80℃, 6 hours).

[0093] VI. Performance Verification

[0094] 1. Impurity analysis (ICP-MS)

[0095] The impurity content in the products of Example 1, Example 2, and the comparative example was analyzed using inductively coupled plasma mass spectrometry (ICP-MS). The results showed that the contents of metallic impurities such as Fe, Al, Ca, K, and Na in the product of Example 1 were significantly lower than those in the comparative example. Example 2, through further process optimization, achieved even lower impurity contents, with Fe content ≤2 ppm and Al content ≤5 ppm, meeting the requirements for semiconductor-grade high-purity quartz powder.

[0096] 2. Particle size and morphology

[0097] The particle size and morphology of the products were characterized using scanning electron microscopy (SEM) and laser particle size analyzer. SEM observations showed that the particles in Examples 1 and 2 were spherical or nearly spherical with smooth surfaces and uniform dispersion; while the particles in the comparative product had irregular morphology and obvious agglomeration. Laser particle size analysis results showed that the particle size distribution of Examples 1 and 2 was narrower, with D50 values ​​of 125 nm and 130 nm, respectively, and dispersities of 11% and 10%, respectively; while the particle size distribution of the comparative product was wider, with a D50 of 180 nm and a dispersity of 28%.

[0098] 3. Surface properties

[0099] The surface properties of the products were analyzed using a contact angle meter and X-ray photoelectron spectroscopy (XPS). Contact angle measurements showed that the contact angles of the products in Examples 1 and 2 with water were 82° and 85°, respectively, and with liquid paraffin were 35° and 32°, respectively, indicating that the product surfaces possess both hydrophilic and hydrophobic properties. In contrast, the contact angle of the comparative product with water was 65°, and with liquid paraffin was 50°, indicating stronger hydrophilicity and weaker hydrophobicity. XPS analysis showed that the coating efficiencies of the products in Examples 1 and 2 were 95% and 96%, respectively, while the coating efficiency of the comparative product was only 78%, indicating that the surface modification effect of the method of this invention is better.

[0100] 4. Application performance

[0101] The products of Example 1 and the comparative example were applied to semiconductor polishing, optical coating, and composite materials, respectively, to test their application performance. In semiconductor polishing, the polishing slurry prepared with the product of Example 1 achieved a wafer surface roughness Ra of 0.45 nm, a 62.5% reduction compared to the comparative example (1.2 nm), and a defect density of 3 defects / cm², an 80% reduction compared to the comparative example (15 defects / cm²). In optical coating, the optical thin film prepared with the product of Example 1 had a light transmittance of 95.8%, a 3.5 percentage point increase compared to the comparative example (92.3%), and a haze of 0.3%, a 75% reduction compared to the comparative example (1.2%). In composite material applications, the composite material filled with the product of Example 1 had a flexural strength of 320 MPa, a 52.4% increase compared to the comparative example (210 MPa), and a coefficient of thermal expansion of 4.8 × 10⁻⁶. -6 / ℃, comparison ratio (6.5×10 -6 The temperature (°C) decreased by 26.2%.

[0102] In summary, the method of this invention significantly improves the purity, particle size control, and surface properties of nano-high-purity quartz powder through multi-dimensional innovation, meeting the demand for high-performance quartz powder in high-end fields such as semiconductors, optical coatings, and aerospace.

[0103] The impurity content of the examples and comparative examples is compared in the table below:

[0104] Table 1

[0105]

[0106] The Fe and Al metal impurity contents in Examples 1 and 2 of this invention are significantly lower than those in the comparative example. In Example 2, the Fe content is only 1.8 ppm, which is 96% lower than that in the comparative example. This proves that the deep impurity removal process can efficiently remove impurities and meet the semiconductor-grade purity requirements.

[0107] The key performance comparison table between Example 1 and the comparative example is shown below:

[0108] Table 2

[0109]

[0110] Example 1 is superior to the comparative example in terms of purity, dispersibility, stability and mechanical properties. The sedimentation rate of the aqueous dispersion is only 1 / 15 of that of the comparative example, which proves that the amphiphilic modification and the fractionation process significantly improve the particle dispersion stability.

[0111] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing nano-high-purity quartz powder, characterized in that, Includes the following steps: S1: Deep impurity removal from raw quartz ore Quartz sand was crushed and subjected to a three-stage countercurrent acid leaching process. The first stage of leaching involved a 1:1 volume ratio mixture of hydrofluoric acid and nitric acid, leached in an ultrasonic field for 1 hour. The second stage of leaching involved the addition of disodium ethylenediaminetetraacetate, followed by another 1 hour of acid leaching. The third stage of leaching involved simultaneous introduction of ozone and another 1 hour of acid leaching. After filtration, the sand was washed with deionized water until the conductivity was ≤1μS / cm, and then dried to obtain high-purity quartz sand. S2: Dual-acid synergistic etching nanofiberization High-purity quartz sand is mixed with aminosulfonic acid and fluoroboric acid, and deionized water is added to form a slurry. Silicon carbide nanocrystal seeds are then added to react, and the etching reaction formula is as follows: ； After the reaction, a planetary ball mill was used for three-stage grinding: the first stage was dry grinding for 1 hour; the second stage was wet grinding with polyethylene glycol for 2 hours; and the third stage was wet grinding with sodium polyacrylate for 2 hours, to obtain a quartz slurry with a particle size distribution of 80-180nm. S3: Amphiphilic Interface Modification Silane coupling agent KH-570 and graphene quantum dots were added to the slurry in sequence, and the pH was adjusted to 9.5 with triethanolamine. The mixture was reacted at 80°C under ultrasonic conditions to form a "silane-GQDs-quartz" coated structure. After the reaction, the mixture was subjected to high-pressure homogenization and then processed by a microfluidic homogenizer. S4: Magnetic field-assisted fractional purification A gradient magnetic field is installed outside the centrifugal classifier to adsorb and separate magnetic impurities from the slurry; particles with a diameter of 100-150nm are collected and cross-flow filtration is performed using a ceramic membrane with a pore size of 50nm, while the zeta potential of the filtrate is monitored and controlled between -35 and -45mV. S5: Vacuum Pulsating Drying The graded slurry was transferred to a vacuum drying oven and heated by pulse heating. Nitrogen gas that had been deoxygenated was introduced during the drying process. After drying, a compound dispersant of zinc stearate and nano titanium dioxide was added and mixed in a three-dimensional motion mixer.

2. The method for preparing nano-high-purity quartz powder according to claim 1, characterized in that, In S1, the liquid-to-solid ratio of the three-stage countercurrent acid leaching process is 5:1, and after each stage of acid leaching, a high-gravity rotating bed is used for solid-liquid separation. The rotating bed speed is 2000 rpm, and the separation efficiency is ≥99%.

3. The method for preparing nano-high-purity quartz powder according to claim 1, characterized in that, The method for adding silicon carbide nanocrystal seeds in S2 is as follows: first, the seeds are dispersed in a fluoroboric acid solution under ultrasonic conditions with a power of 200W for 30 minutes, and then mixed with an aminosulfonic acid solution.

4. The method for preparing nano-high-purity quartz powder according to claim 1, characterized in that, The hydrolysis process of silane coupling agent KH-570 in S3 is as follows: hydrolyze in an acetic acid buffer solution with a pH of 4.5 at 60°C for 1 hour, with a degree of hydrolysis ≥90%.

5. The method for preparing nano-high-purity quartz powder according to claim 1, characterized in that, The S4 ceramic membrane filtration uses a backwash regeneration process with a backwash pressure of 0.5 MPa and a backwash frequency of once every 15 minutes, each lasting 10 seconds.

6. The method for preparing nano-high-purity quartz powder according to claim 1, characterized in that, The moisture removal rate during the drying process in S5 is monitored in real time by a dew point meter and controlled within 0.5-1.0 kg / (m²·h).

7. The method for preparing nano-high-purity quartz powder according to claim 1, characterized in that, The entire preparation process is carried out in a cleanroom with an ISO 7 cleanliness level, where the concentration of airborne particles ≥0.5μm is ≤35200 particles / m³.

8. The method for preparing nano-high-purity quartz powder according to claim 1, characterized in that, The surface energy of the prepared nano-quartz powder was measured by a contact angle meter. The contact angle with water was 75°-85°, and the contact angle with liquid paraffin was 30°-40°.

9. The method for preparing nano-high-purity quartz powder according to claim 1, characterized in that, The obtained nano-quartz powder has a tap density of 0.85-0.95 g / cm³ and a specific surface area of ​​25-35 m² / g.

10. The method for preparing nano-high-purity quartz powder according to claim 1, characterized in that, The pulse heating method used in S5 is as follows: the first stage is a heating rate of 15℃ / min, which is raised to 120℃ and held for 30min; the second stage is a cooling to 80℃ and held for 20min; and the third stage is a heating to 120℃ and held for 30min.

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