Physicochemical properties of ambient pressure dried surface modified silica aerogels: effect of pH variation

Abstract

This work demonstrates the synthesis of hydrophobic silica aerogels from silicic acid with pH variations by using a costeffective and safe ambient pressure drying process. The work aims to evaluate the effect of pH variation on physicochemical properties of silica aerogels by standard techniques. In the present investigation, we have selected hexane as the solvent and trimethylchlorosilane/hexane was used to perform the surface modification of wet gel in order to elude the contraction and disintegration of gel association subsequent to a drying process. The effect pH on gelation in the form hydrolysis and condensation as well as on amorphous structure, physical properties such as density, thermal stability, surface area, pore-volume, pore radius, optical transmittance were investigated. FTIR spectroscopy was used to confirm the silylation (surface modification) of the prepared silica aerogel samples. Water contact angles were measured to verify the hydrphobic behaviour of all the samples. Among the prepared pH varied samples, the sample having pH ~ 5 shows better results such as high optical transmittance, thermal stability, hydrophobicity and high surface area.

Synthesis of Hierarchical Porous Silica by Sol‐Gel of Sodium Silicate and Nanoemulsion Templating: Effective Combination Conditions

“…Figure 8(a) represents the FTIR of HPS and the transmission peaks at 460 cm −1 , 800 cm −1 , 970 cm −1 , and 1,080 cm −1 are attributable to the bending vibration of the Si−O bond, the Si−O−Si asymmetric stretching vibration, the Si−OH symmetric stretching vibration, and the Si−O−Si symmetric stretching vibration, respectively [21] . The Si−O−Si peaks confirm the silica network formation which helps the three‐dimensional linking of Si−O−Si [15,22] . The TEM image (Figure 8(b)) reveals a disordered wormhole‐like porous structure, which is the result of the clustering of SiO 2 nanoparticles [23] .…”

“…prepared silica gel through the addition of SS to a very acidified water so that the sodium silicate (pH=13) is neutralized to form silicic acid [14] . It was reported that the pH of SS does not only affect the gel formation but also the physico‐mechanical properties of the silica gel [15] . SS is extensively used to prepare silica aerogel [16] .…”

Surface Functionalized Superparamagnetic Zn‐Mg Ferrite Nanoparticles for Magnetic Hyperthermia Application Towards Noninvasive Cancer Treatment

“…It is a well‐known fact that the water contact angle >90° and <90° implies hydrophobic and hydrophilic nature of the sample. [ 24 ] The average contact angle of the surface modified Zn 0.25 Mg 0.75 Fe 2 O 4 nanoferrites calculated from Figure 4 was found to be 25.9°. The lower value of water contact angle signifies the hydrophilic nature of the surface modified Zn 0.25 Mg 0.75 Fe 2 O 4 nanoferrites.…”

Valorization of Starch to Biobased Materials: A Review

“…Their result revealed that all of the samples of the aerogels produced were hydrophobic. However, the sample with a pH of 5 had better outcomes in terms of optical transmittance, thermal stability, hydrophobicity, and surface area when compared to the other pH varied samples [ 220 ]. Figure 5 illustrates the laboratory process for the manufacturing of aerogels.…”