Low temperature exothermic effects on cooling of homoionic clays

Publication year: 2011
Source: Cold Regions Science and Technology, In Press, Accepted Manuscript, Available online 13 June 2011

Tomasz, Kozlowski

Results of differential scanning calorimetry (DSC) experiments on homoionic montmorillonites (Ca2+, Mg2+, Na+, K+) and Na-kaolinite are reported. The low temperature exothermic peaks were observed on cooling down to −90°C after the initial peak corresponding to the breakdown of supercooling of water in macro- and mezopores. In some experiments, the samples were then warmed to −10°C or −5°C and cooled again to −90°C. According to expectations, the non-equilibrium exothermic peaks were absent in this case, being replaced by a wide peak analogical to that obtained on warming. However, the low temperature exothermic peaks were still observed, but their fields were…

 Highlights: ► Homoionic montmorillonites and Na-kaolinite were investigated by use of DSC. ► Low temperature exothermic peaks were observed on cooling between −33 and −47°C. ► Fields of the peak were cut proportionally to the extent of the previous warming. ► Stochastic deconvolution was applied to the endothermic peaks obtained on warming. ► Water, solidifying at the peaks, on warming melts in a wide temperature range.