Thermal and calorimetric investigations of titania–silica composites

Abstract

The paper presents the studies of effects of TiO 2 amount differentiation on the structural and thermal properties of titania-silica complex oxides prepared by chemical vapor deposition of TiCL 4 onto the Si-40, Si-60, and Si-100 silica gels. The mesoporous materials, characterized by a varied pore structure with highly developed surface and large pore volume, were obtained. The porous structure of materials under investigations was characterized by the low-temperature nitrogen adsorption-desorption method as well as by power spectral density calculated from the calorimetric investigations of water confined in the pores. Moreover, the thermodesorption of water using the quasi-isothermal thermogravimetry was used to characterize their thermal and surface properties. The adsorbed water layers and the concentration of weakly and strongly bound water as well as the surface free energy on the adsorbent-water interfaces were calculated. It was stated that the increase of titania content causes a gradual decrease of specific surface area and has a significant effect on the porous structure formation. The water thermodesorption from the surface proceeds in few stages because of the porosity created by TiO 2 . The decrease in the total surface free energy (ÁG AE ) can be observed with the increasing TiO 2 content. The largest ÁG AE value at the adsorbent/strongly bound water interface is exhibited by the adsorbents of Si-100 series. The lowering of the freezing/melting points of water contained in the pores of the studied materials is strongly connected with their porous structure.

Characterization of Multimodal Silicas Using TG/DTG/DTA, Q-TG, and DSC Methods

“…The differential f S (R) functions were used to estimate the deviation (∆w) of the pore shape [21]. The f V (R) functions were also used to calculate the contribution of micropores (V micro , S micro for R p < 1 nm), mesopores (V meso , S meso for 1 nm < R p < 25 nm), and macropores (V macro , S macro for R p > 25 nm) [10,22,23]. The obtained results are summarized in Table 1.…”

Structural and photocatalytic properties of Ni-TiO₂ photocatalysts prepared by mechanochemical synthesis assisted with calcination

“…The differential function was transformed into the incremental pore size distribution (dV/dR = f(R), IPSDV) based on the procedure presented by Gun'ko and Mikhalovsky (2004). The volume as well as the surface area for the mesopores (Vmeso, Smeso) and the micropores (Vmicro, Smicro,) and the pore shape deviation (Δw) were calculated using the differential function (Table 1) (Charmas et al, 2017;Gun'ko and Do, 2001).…”