Dielectric Study of Hydration Water in Silica Nanoparticles

Abstract

The effect of water content on silica nanoparticles was examined by thermogravimetry analysis (TGA), broadband dielectric spectroscopy (from 10 −2 to 10 7 Hz), and differential scanning calorimetry for a wide temperature range (110−250 K). Silica nanoparticles were dried and rehydrated at different water levels to determine the critical factors affecting the dielectric response. The dynamics of both hydration water and hydrated silanol groups were addressed. Whereas hydration water dynamics depend on the water content, the dynamics corresponding to hydrated silanol groups are almost water independent once the maximum hydroxylation level is reached. In addition, we determined that during hydration water molecules prefer to form clusters instead of filling a complete layer around the particles. Finally, we observed that contrary to other water containing systems, the corresponding relaxation times of water molecules do not show any crossover (from high-T super-Arrhenius to low-T Arrhenius behavior).

Cause of the fragile-to-strong transition observed in water confined in C-S-H gel

“…Instead, the temperature dependence of the relaxation time is shown to be of Arrhenius type in the whole temperature range. The absence of such a confinement-related crossover was recently reported in the case of water around silica particles (SiO 2 ), 57 and on rutile (TiO 2 particles). 58 Interestingly, an Arrhenius behavior over the full range of experimental temperatures was also observed for a monolayer of water confined in MCM41.…”

Atomic scale characterization and surface chemistry of metal modified titanate nanotubes and nanowires

“…activation energies of various relaxation processes decreased with increasing surface coverage in clay materials [162] and polymer composites [165] but increased in Fe 2 O 3 [156], Ag 2 O [168], silica [170,176], calcium-silicate-hydrate [157,158] and ovalbumine adsorbents [166,171].…”

“…A linear relationship between the activation energy and the preexponential constant was found in a host of diverse physico-chemical processes including catalysis [174], conductance [161,175] and dielectric relaxation [176,177]:…”

Depercolation of aggregates upon polymer grafting in simplified industrial nanocomposites studied with dielectric spectroscopy

“…A summary plot with all contributions appearing in ε'(ω) and ε"(ω) over a temperature window from 173 K to 323 K, and fit details are given in the SI. The β'-process is well-known in the silica-SB nanocomposites, where it has been assigned to localized fluctuations of water molecules at the silica surface [19,42]. A complete analysis of its evolution with Φ si and %D3 is given in the SI.…”