Preparation and Size Determination of Monodisperse Silica Microspheres for Particle Size Standard Reference Materials

摘要

Five samples of momonodisperse SiO2 microspheres used for reference materials of particle size were synthesized by the use of a seed-growth method through hydrolysis and condensation of tetroethylorthosilicate in a mixture of methanol and water using amoniua as catalyst. Their nominal diameters were 0.15μm, 0.3μm, 0.5μm, 1μm, and 2μm. The accurate average diameters of these microspheres were determinated by SEM array-sizing method, and those of microspheres with 1μm and 2μm nominal diameters were determined through both SEM array-sizing method and optical array-sizing method, while the particle size distribution of these spheres was determined by SEM. The measurement errors for each sample were quantitatively assessed. The SEM magnification was calibrated with a SEM calibration standard traceable to CNIM (China National Institute of metrology), while the optical microscopy magnification was calibrated with a NIST stage micrometer (SRM 2800). The average diameters determined by SEM and optical microscopy are identical to each other. For comparison, the average diameter of these microspheres was also measured with other indenpend techniques-ligh scatting and photo-correlation method, the obtained data agreed well with the array sizing method.