Study On Preparation Of High Purity Ultrafine SiO₂Powder From Natural Quartz And Its Applications

The high purity and ultrafine SiO₂powder （the content more than99.99%） had been prepared after those process measures includedcrushing, calcinations, water quenching, grinding, acid leaching,washing, drying and so on, which using natural quartz in SichuanGuangyuan as the main raw materials. And the particle size (d₅₀) of thesa mple was approximately300nm. Through the laser particle sizeanalysis, SEM, XRD, ICP-OES etc detection means, mainly studies thewater quenching ore particles after super fine powder preparati o ntechnology and purification process acid leaching process parameters,based on this study the income high purity ultrafine SiO₂powder as rawmaterial to preparation of amorphous spherical SiO₂and the applicationof quartz cera mics.The research results are described as below:（1） When using870℃ofα-quartz will convert to α-scale quartz ashigh as16%of the volume rate, water quenching after quartz grain inpolyurethane ball mill tank for super fine crushing experiments, get thebest experimental parameters（Slurry concentration is30%,500r/min,ball mill6h） can be prepared d₅₀out about290nm of ultrafine siliconmicro powder.（2） Through the single acid orthogonal experiment results hasformulated the mixed acid test program, and ulti mately the8mol/Lhydrochloric acid and seven mol/L sulfuric acid to volume ratio1:1theconfiguration of the mixed acid in50℃condition reaction4h, can getAl content of11PPM, Fe content is5.5PPM of high purity silicapowder. And studied with hydrochloric acid and sulfuric acid theconfiguration of the mixed acid in ultrasonic field best reaction timefor60min; Microwave field the best experi mental paramet ers for800wpower response under40min; But by mixed acid as ball mill dispersantthe best ball mill reaction time is8h.（3） With high purity ultrafine silica powder preparation ofamorphous spherical silicon micro powder of the study show that:Using anhydrous ethanol, a mmonia water, polyethylene glycol-6000 configuration base fluid, the sodiu m silicate join base fluid rapidl yadjust pH value preparat ion out silicon gel, after classics drying at600℃condition calcined half an hour to get d50is about400nm,dispersion good a morphous spherical silicon micro powder, its physicaland che mical indexes is better than the ministry of electronic industryfor electronic grade melting sex silicon micro powder high-classproducts requirements.（4） Use of a high-purity ultrafine silicon micro powder sinteringquartz ceramics research shows that: In the1400℃next sa mple maincrystal phase for cristobalite phase, and1350℃down almost did notappear cristobalite phase, so consider sintering temperature of1350℃.Comprehensive density test and SEM analysis result in the1350℃sintering sa mples appear mor e glass phase and stomatal basic discharge,good density. In the1350℃condition sintering quartz ceramic densityis2.13g/cm³, dielectric constant is about3.8, dielectric loss for7.5×10^-4, the high purity ultrafine silicon micro powder may be can insteadof quartz glass or crystal leftover material as preparation microwaveperformance quartz ceramic raw materials.