Particle Technology, Inc.(PTI) conducted a project for the International Fine Particle Research Institute(IFPRI) to produce 3 Kg. of spherical transparent powder in the 0.3 to 3 pm size range. Several clear glassy compositions were tried and a Barium Altino Boro Silicate(BABS) composition was chosen because it produced fairly spherical particles, apparently transparent under optical microscope. Three Kg. of this material were produced and size distribution tested at the DuPont Engineering Test Center using a Leeds And Northrup Microtrac instrument. The powder appeared to be in or near the target size range and easily dispersed in water reproducibly as indicated by repeated measurements over several hours duration.
A sample was sent to the AEA Winfrith laboratory and field emission micrographs revealed a gritty composition rather than a homogeneous one, and the particle size distribution as measured by a Malvern instrument was much coarser, however, the dispersion technique used at AEA may be improved to get a better dispersion as indicated by comparison with data from DuPont. The gritty texture continues to be a problem with the BABS powder.
Continued work at PTI indicates that higher processing temperatures and a different starting precursor composition can overcome this problem of the grittines. Several tens of grams of the new powder were prepared and a sample will be sent to AEA for evaluation after completion of our own evaluation.. PTI plans independent scale up of the process and if successful shall make a 3 Kg. sample for inclusion in the Standards Program.