Fig 1.
Schematic illustration of the scanning cryomacroscope setup and peripheral instrumentation [11]; the modified experimentation stage for thermal conductivity measurements is displayed with more detail in Fig 2.
Fig 2.
Schematic illustration of (a) the cryomacroscope experimentation stage (the red arrow represents the direction of view), and (b) the hot wire sensor setup in the cuvette (sample container).
Fig 3.
Typical thermal history during thermal conductivity measurements of 7.05M DMSO, where TC1 measures the chamber temperature, TC2 measures the wall inner surface at the center of one of the faces, and TC3 measures the temperature of the outer surface of the wall.
Fig 4.
Temperature measurements during thermal conductivity experiments: (a) temperature results of three consecutive thermal experiments, where the change in the bulk sample temperature is best-fitted with a 2nd order polynomial; (b) a higher magnification of an experimental dataset; and (c) a temperature dataset used to calculate the thermal conductivity after the subtraction of the bulk sample rewarming curve, where the slope of the best-fitted curve on a semi-log plot is used to calculate the thermal conductivity (shown as a solid line in figure).
Fig 5.
Cryomacroscope images of samples in various states: (a) a vitrified 7.05M DMSO sample at a temperature of -147°C; (b) a 2M DMSO sample undergoing crystallization in the form of dendrites at temperature of -10°C; (c) a partially crystallized 6M DMSO sample at a temperature of -58°C; and (d) a completely crystallized 6M DMSO solution at a temperature of -65°C.
Fig 6.
Thermal conductivity measurements of pure water ice and glycerol in the current study, compared with literature data, where the curve by Rabin (2000) [7] represents compilation of earlier literature data.
Fig 7.
Thermal conductivity measurements of DMSO and pure water ice.
The Cahill-Pohl model for thermal conductivity of amorphous solids is calculated with Eq (8) for 10 M DMSO. Based on cryomacroscope observations, DMSO concentrations of 6M or less underwent crystallization while concentrations of 7.05M and above vitrified.
Table 1.
Best-fit polynomial approximation data for the thermal conductivity curves displayed in Fig 7.
Fig 8.
Solid fraction during solidification of a water-DMSO mixture, extracted from a phase diagram [13].
Table 2.
The temperature of melting completion based on experimental results, Tm, observed during thermal conductivity measurements in comparison with the liquidus temperature, Tl, from a water-DMSO phase diagram [9].
Fig 9.
Thermal conductivity as a function of solid fraction for DMSO at various concentrations, where the Bruggeman model is calculated with Eq (7) for 6M DMSO.
Table 3.
The liquidus temperature, Tl, and the solidus temperature, Ts, of solution concentrations observed to vitrify in this study, from a water-DMSO phase diagram [9].