Porous Glasses as a Source of Information on Structural Changes in Sodium Borosilicate Glasses Undergoing Phase Separation

Жданов, С. П.; Koromal’di, E. V.

doi:10.1007/978-1-4757-0157-9_17

Cited by 1 publication

(1 citation statement)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The abbreviations MIP and MAP mean, respectively, "microporous" glass and "macroporous" glass according to the terminology of Zhdanov. 34 By the IUPAC classification, 35,36 the studied glasses belong to mesoporous materials. Sodium borosilicate glass with composition (according to synthesis, mol %): 8Na 2 O, 22B 2 O 3 , 70SiO 2 , subjected to heat treatment at 550 °C for 144 h to form a two-phase structure, was used to manufacture porous glasses.…”

Section: Synthesis Of the Porousmentioning

confidence: 99%

The Nature of the Low-Temperature Crossover of Water in Hard Confinement

et al. 2023

View full text Add to dashboard Cite

The dynamics of water confined in mesoporous MIP (2–3 nm pores in size) with silica gel (secondary silica; further, the abbreviation SG will be used) and MAP (10–35 nm pores in size) without SG borosilicate glasses have been studied by broadband dielectric spectroscopy (BDS), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC). MIP samples contain secondary silica inside the pores and provide a confinement size of about 2–3 nm, whereas MAP samples are free of secondary silica and provide a confinement size of about 10–35 nm. It is shown by BDS and NMR techniques that water exhibits a dynamic crossover of around 180 K when it is confined in MIP samples. By contrast, water confined in larger pores (MAP) does not exhibit any changes in its relaxation behavior. It is also shown that the crossover temperature depends on the hydration level (the higher the hydration level, the lower the crossover temperature). Below the crossover temperature, we find that water reorientation is isotropic (NMR) and that the temperature-dependent dielectric relaxation strength (BDS) follows the tendency expected for a solid-like material. In contrast, water reorientation is related to long-range diffusion above the crossover temperature, and the dielectric relaxation strength follows the tendency expected for a liquid-like material. Furthermore, the calorimetric results are compatible with crossing a glass transition near 180 K. Finally, the results are discussed within the Gibbs–Thomson model. In this framework, the crossover could be related to ice crystals melting.

show abstract

Section: Synthesis Of the Porousmentioning

confidence: 99%