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Pore lattice strain versus temperature for the sample with 4.4 nm pore diameter. The black circles are from the empty sample (filling fraction f = 0). The blue (triangles down) and red (triangles up) curves stem from the water filled sample (f = 0.99) for the cooling and heating cycles, respectively. Freezing (Tf ) and melting (Tm ) temperatures of the confined pore water are indicated, and the vertical dashed line is at 273 K. The inset sketches the four temperature regions I–IV.
Lattice strain versus temperature for the sample with 3.9 nm pore diameter during heating for four different nominal pore filling fractions. f = 0.1 (black/circle), f = 0.6 (green/ diamond), f = 0.99 (red/triangle up), and f > 1 (magenta/ squares). The melting temperature of water within the pores (233 K)17,18 and the bulk melting temperature of water (273 K) are indicated by vertical lines.
Schematic view of the analogy between the vapor-liquid (upper part) and the solid-liquid (lower part) phase transition mechanism in cylindrical nanopores, leading to the observed deformation behavior of the pore lattice in regions II and III (middle part). The silica walls (dark grey) are in contact with the (wetting) liquid water phase (blue/light grey) and with the water vapor (upper part) or the solid ice phase (lower part) in white.
Pore load modulus obtained from the freezing/melting of confined water. The influence of the empty sample was corrected, and the values used to calculate MPL with Eq. (3) were Hm = 6.01 kJ/mol, Vm = 1.8 10−5 m3/mol, and T 0 = 273 K.17 The modulus values are compared with those obtained from the evaporation of n-pentane (C5H12) using Eq. (2) within the same samples.7
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