Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121-123, 28006, Madrid, Spain.
Phys Chem Chem Phys. 2012 Aug 14;14(30):10595-602. doi: 10.1039/c2cp41597f. Epub 2012 Jul 2.
An investigation of porosity and isothermal crystallization kinetics of amorphous ice produced either by background water vapour deposition (ASW) or by hyperquenching of liquid droplets (HGW) is presented. These two types of ice are relevant for astronomical ice research (Gálvez et al., Astrophys. J., 2010, 724, 539) and are studied here for the first time under comparable experimental conditions. From CH(4) isothermal adsorption experiments at 40 K, surface areas of 280 ± 30 m(2) g(-1) for the ASW deposits and of 40 ± 12 m(2) g(-1) for comparable HGW samples were obtained. The crystallization kinetics was studied at 150 K by following the evolution of the band shape of the OD stretching vibration in HDO doped ASW and HGW samples generated at 14 K, 40 K and 90 K. Comparable rate constants of ∼7 × 10(-4) s(-1) were obtained in all cases. However a significant difference was found between the n Avrami parameter of the samples generated at 14 K (n∼ 1) and that of the rest (n > 2). This result hints at the possible existence of a structurally different form of amorphous ice for very low generation temperatures, already suggested in previous literature works.
本文研究了通过背景水蒸气沉积（ASW）或液滴超快速淬火（HGW）制备的无定形冰的孔隙率和等温结晶动力学。这两种冰对于天文冰研究都很重要（Gálvez 等人，《天体物理学杂志》，2010 年，724 卷，539 页），本研究首次在可比的实验条件下对它们进行了研究。通过在 40 K 下进行 CH(4)等温吸附实验，得到 ASW 沉积物的比表面积为 280 ± 30 m(2) g(-1)，可比的 HGW 样品的比表面积为 40 ± 12 m(2) g(-1)。在 150 K 下通过跟踪 HDO 掺杂的 ASW 和 HGW 样品中 OD 伸缩振动带形的演化，研究了结晶动力学，这些样品是在 14 K、40 K 和 90 K 下生成的。在所有情况下，都得到了类似的约 7×10(-4) s(-1)的速率常数。然而，在 14 K 下生成的样品的 n Avrami 参数（n∼1）与其他样品（n>2）之间存在显著差异。这一结果暗示了在非常低的生成温度下可能存在一种结构上不同的无定形冰，这在之前的文献中已经有所暗示。
