Spherical silica sintering

Sanchez has shown no ditferential x—y shrinkage during sintering for tape casts of monodisperse spherical silica powders [38],... 

Steven J. MBne, Mohammed Patel, and Eric Dickinson Experimental studies of particle packing and sintering behaviour of monosize and bimodal spherical silica powders, J. Eur. Ceram. Soc., 11 (1) (1993) 1 7... 

Zorbax PSM particles are made from small (80-2000 A), extremely uniform colloidal silica sol beads. In a patented polymerization process, these beads are agglutinated to form spherical particles. The size of the Zorbax PSM particles is controlled by the polymerization process, and the pore size is determined by the size of the silica sol beads. After polymerization, the silica is heated to remove the organic polymer and sinter the particles. The result is a spherical, porous, mechanically stable, pure silica particle that provides excellent chromatographic performance (Pig. 3.1). 

Leaching of Sintered Granules. The initial studies in this work(J3) were done in granules consisting of 80% PW-4b spray-calcined simulated waste, 10% silica, and 10% borosilicate glass frit sintered at 1100 C. The granules were about 0.6 cm in diameter and weighed about 370 mg each. The surface area, based on the assumption of an impervious hard") spherical shape,... 

Pellicular or controlled surface porosity particles were introduced in the late 1960s these have a solid inert impervious spherical core with a thin outer layer of interactive stationary phase, 1-2 pm thick [13]. Originally, the inner sphere was a glass bead, 35-50 pm i.d., with a thin active polymer film or a layer of sintered modified silica particles on its surface. Such particles were not very stable, had very low sample load capacities because of low surface areas and are not used any more. Nowadays, this type of material is available as micropellicular silica or polymer-based particles of size 1.5 to 2.5 pm [14]. Micropellicular particles are usually packed in short columns and because of fast mass-transfer kinetics have outstanding efficiency for the separation of macromolecules. Because the solutes are eluted as very sharp narrow peaks, such columns require a chromatograph designed to minimise the extra-column contributions to band broadening. 

ADDITIONAL SILICA DEPOSITION AND OSTWALD RIPENING AT THE NECKS FORMED BETWEEN THE 1-2nm PARTICLES RESULT IN DENSE, ROUGHLY SPHERICAL PARTICLES. THIS PROCESS IS NOT UNLIKE SINTERING IN POWDERED METALS... 

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