单壁碳纳米管中受限水的热容及饱和含水量

Heat Capacity of Confined Water and Maximum Water Content of Single-Walled Carbon Nanotubes

单壁碳纳米管纳米级的管径使其成为一种准一维的容器.用示差扫描量热的方法对受限于单壁碳纳米管中水的热容进行研究,结果显示,受限水的热容-温度曲线在所测量的温度范围内并未出现熔融峰,并且相比于同温度下的本体水,单壁碳纳米管中受限水的热容有反常的降低.红外光谱显示,单壁碳纳米管内水的氢键强度相对本体水变弱.结合红外结果可知,受限水热容反常降低的现象是因为氢键强度的下降,导致构象对热容的贡献减少.通过对溢出部分水的焓值计算可知,单壁碳纳米管内受限水含量质量分数上限为16,%.简化模型预测的单壁碳纳米管理论含水量比实际含水量质量分数高出2%左右.

A single-walled carbon nanotube can be regarded as quasi one-dimension container owing to its nanoscale diameter. The specific heat capacities of water confined in single-walled carbon nanotubes were calculated with differ- ential scanning calorimeter. The results showed that the confined water presented no melting peak in the heat capacity plot, and had an anomalous lower heat capacity than that of bulk water at the same temperature. Fourier transform infrared spectroscopy results showed the hydrogen bonding in confined water was weaker than that of the bulk water. The anomalous lower heat capacity could be ascribed to the weakening of the hydrogen bonding, which induced the decrease of the configurational contribution. An approximate 16% maximum water mass fraction of single-walled carbon nanotubes was obtained through enthalpy calculation. A simplified model predicted a 2% higher maximum water mass fraction of single-walled carbon nanotubes, indicating that the model was successful to a certain extent.