Study of evaporative drying of treated silica gels

Optimization of instantaneous solvent exchange/surface modification process for ambient synthesis of monolithic silica aerogels

“…Dissolved HCl could promote a strong acidic environment around the silica surface while the solvent exchange and silylation steps progressed. It could be considered as a major cause of crack generation and exfoliation on silica surfaces [20,21], as seen in Fig. 6.…”

Silica aerogel; synthesis, properties and characterization

“…One of the important parameters in this step is the apparent diffusion coefficient of the solvent. Bisson et al (2004) studied this phase of evaporating for treated (or silylated) silica gels. They used thrimethylcholorosilane (TMCS) and isopropyl alcohol (IPA) as silylation agent and solvent, respectively.…”

“…Consequences of the surface modification are a reduction of the maximum densification observed during drying, and an increase in the apparent diffusion coefficient. Comparison between untreated and treated samples during the last drying step showed how and when spring-back takes place for the latter (Bisson et al, 2004;Schadl and Mersmann, 1985). Deshpande et al (1992) described a drying method based on the so-called "spring-back effect".…”

SiO2 Aerogels

“…The compressive strength, tensile strength, and elastic modulus of silica aerogels are very low and largely depend on the network connectivity [153] and aerogel density [154]. Indeed, silica aerogels can easily be elastically compressed when the porous texture is studied, for example, by the capillary stresses that they are subjected to during nitrogen adsorption or desorption [155] or by compression during mercury porometry and thermoporometry [83,156]. The magnitude of the contraction can reach~50% by length [157].…”