Composite materials: Textural characteristics

Evaporation of polar and nonpolar liquids from silica gels and fumed silica

“…1); however, contribution of nanopores at R p < 1 nm is small. Consequently, the errors of developed approach can be significant for the evaporation from (b) Incremental PSD of nanosilica A-300 (SBET = 330 m 2 /g, Vp = 0.734 cm 3 /g) calculated using NLDFT (cylindrical pore model) and self-consistent regularisation (SCR) method with a complex model of slit-shaped and cylindrical pores and voids between spherical particles (SCV) packed in random aggregates [28] for initial dry powder and after suspending (4 ml of water per 1 g of silica and sonication for 5 min) and drying of A-300 (SBET = 297 m 2 /g, Vp = 1.41 cm 3 /g after drying). narrow pores of Si-40.…”

“…The value of R p in Eq. (7) could be calculated as the ratio of the first and zero moments of the distribution function of pore sizes [8,28].…”

“…The NLDFT method (equilibrium cylindrical pore model for silica, Quantachrome software) [27] was used to calculate the pore size distributions (PSD) of silica gels Si-40, Si-60, and Si-100. To characterise fumed silica, a complex model of pores with slit-shaped and cylindrical pores and voids between spherical particles (SCV) packed in random aggregates was applied with an integral adsorption equation solved using a self-consistent regularisation (SCR) [28].…”

“…1a). However, there are several factors affecting a difference in the PSD shapes such as different temperatures (77.4 K for NLDFT) and (360-450 K for TG), some swelling of silica gel beads in water (TG); associative desorption of water (from neighbouring silanols) upon heating in TG contributing the left wing of the PSD (toward smaller R p ), and some features of calculations in the methods based on different phenomena [8,[25][26][27][28][42][43][44]. It is clear from this comparison that the textural characteristics can play an important, determining role in both adsorption of nonpolar nitrogen and desorption of polar water.…”

“…1b). The latter corresponds to voids between spherical nonporous nanoparticles (average diameter 8.3 nm) randomly packed in aggregates (<1 m in size) and agglomerates of aggregates (>1 m) [8,28,[42][43][44]. The average pore radius (determined as the ratio of the first and zero moments of the differential PSD) is 2.1, 4.7, 6.9, and 12.2 nm for Si-40, Si-60, Si-100, and A-300, respectively.…”