Bending strength of silica gel with bimodal pores: II. Effect of variations in morphology and porosity

The bending strength of amorphous silica gels with bimodal pore structure was evaluated by changing macropore morphology and porosity, where the macropore morphology was controlled by inducing phase separation during gelation of silicate solution and the porosity was controlled by changing aging conditions and calcination temperature. At the same porosity, the bending strength was decreased for gels with larger macropores. In this preparation of bimodal porous silica gels, however, samples with large macropores also had many small particles in the macropores. Therefore, the decrease in bending strength with increasing macropore size was attributed to the presence of the particles that contributed to increasing bulk density but not bending strength. A power law applies to the bending strength and the bulk density of gels with the same macropore morphology, where the exponent depends on the morphology.