
3.1.2 Certification of Glass Beads  Particle Size Distribution, SRM 1018b
Lisa M. Gill Statistical Engineering Division, ITL
Jim Kelly Ceramics Division, MSEL
This Standard Reference Material is intended primarily for use in evaluating and calibrating particle size measurement instrumentation covering 220 microns to 750 microns range. The SRM consists of a single bottle containing approximately 87 g of solid spherical sodalime glass beads. Typical use is in the evaluation of wirecloth test sieves. The certified cumulative volume (mass) distribution was determined using both calibrated scanning electron microscopy (SEM) and standard sieving procedures on samples chosen using a stratified random sampling selection plan. The sieve analyses of ten bottles were used to determine the heterogeneity properties of the material, as well as for a comparison with the SEM results. The sieving process, which is similar to how the SRM will be employed by the customer, was used to assess the material heterogeneity. An estimate of the material heterogeneity was estimated for each sieve. Since the variability was similar for each of the sieves, a pooled estimate of material variability was included in the overall uncertainty. The certified values were determined from the average of results from SEM analyses on five bottles. Several hundred particles were measured by SEM for each sieve fraction for a total of approximately 3000 beads measured per bottle. Particle size distributions describing the percentage of mass represented by beads with diameters in increments of 5 microns were calculated.
The certified value at each diameter is a mean percentile. The stated uncertainty is based on
a 95% prediction interval. It includes allowances for measurement error (assessed from the
SEM data) and material variability (from the sieving experiment).
Figure 2: Cumulative distribution with 95% prediction bands
Date created: 7/20/2001 