Liquid-liquid phase transition and dynamic properties of low-temperature water under pressure, and chemical-pressurization effects on water

用量热法测定了含不同第二组分的二氧化硅纳米孔内稀水溶液的热容。在纯水条件下，热容最大值出现在233k左右，当掺杂羟胺（HA）时热容峰值清晰，而当掺杂甲醇等时热容峰值消失。峰呈现一阶转变特征，转变温度随HA组分x的增加而升高，随加压而降低。同时，在5wt % HA溶液的热分析中，过渡峰面积随着加压而减小。基于这些结果，我们提出了一种新的p-T-x相图模型，其中HA掺杂对水产生负压效应，并在负压范围内存在液-液相变线和作为线端的临界点。

Heat capacities of the dilute aqueous solutions, with different second components, confined within silica nanopores were measured by calorimetry. The heat capacity maximum, which appeared around 233 K in pure water, developed to a clear peak with doping hydroxylamine(HA) while it disappeared with doping methanol and so on. The peak revealed characters of first-order transitions, and the transition temperature increased with increase in the HA composition x and decreased with pressurization. Simultaneously the transition peak area in the thermal analysis of a 5 wt% HA solution decreased with pressurization. Based on these results, we proposed a new model of p-T-x phase diagram in which HA doping provides an effect of negative pressurization on water and a liquid-liquid phase transition line and a critical point as the line terminal exist in a negative pressure range.