INFLUENCE OF POROSITY ON THE ELECTRICAL SENSING ZONE AND LASER DIFFRACTION SIZING OF SILICAS - A COLLABORATIVE STUDY

The objective of a continuing study by the Belgian Particle Technology Group involves difficulties in practical size determinations. This pa rt describes the behaviour of silicas with different porosities during sizing by electrical sensing zone and laser diffraction methods. Anis otropy and porosity were identified to be important particle character istics in understanding the differences between the two methods. Espec ially large pore diameters and pore volumes were found to be responsib le for shifts in size distribution of 50 to 100%. The use of optical v alues and optical models was shown to influence these shifts considera bly. In the case of spherical silica particles with moderate porosity, no significant differences could be found between the two sizing meth ods.