Effect of Annealing Temperature on Physical Properties of Xerogel Structures Prepared by Cryogenic Compression Technique

Abstract

In this work, xerogel materials were synthesized by the cryogenic compression technique and the effects of annealing temperature in the range of 100-1000°C on their physical properties were introduced and studied. Results showed that the porosity continuously decreases from its maximum at 85% to its minimum at <15% with increasing temperature due to the merging, sintering, and collapse of porous structure. An inverse relationship between porosity and relative hardness was observed as the hardness at 1000°C increased by 8 times than its value at 100°C. The optical transparency of the synthesized xerogels showed a nonlinear behavior as it increased from <5% to 85% at 400°C and then sharply decreased to <15% at high temperatures (800-1000°C) due to the collapse of pores and formation of crystalline phases and defects within the structure. These results present an important understanding for the relationship between heat treatment (annealing) and xerogel characteristics, which assists in the preparation of xerogel materials for specific applications such as insulation or catalysis.