Morphology and dynamics of ice crystals and the effect of proteins

• Main Author: Cascajo Castresana, María
• Other Authors: Bittner, Alexander M., Cerveny, Silvina, CIC nanoGUNE, Diputación Foral de Guipúzcoa
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universidad del País Vasco 2017
• Subjects: Antarc*; Antarctica
• Online Access: http://hdl.handle.net/10261/180233

This PhD thesis has been performed at, Self-Assemblu Group: CIC nanoGUNE, Polymers and Soft Matter Group Materials Physics Center (CFM) and Institute for Atmospheric and Climate Science ETH Zürich. [EN]: The thesis "Morphology and dynamics of ice crystals and the effect of proteins" is based on a wide range of themes, from the basics of ice structure (such as ice surface and ice morphology), over the interaction of proteins with ice, to environmental science (which encompasses cloud formation and glacier dynamics). The focus is on interfaces, namely ice/vapour and ice/water. By extending environmental scanning electron microscopy (ESEM) to unusually low temperatures, areas in the pressure-temperature landscape of ice morphologies were accessed in-situ. This means recording real time ESEM images and movies under full humidity control in a dynamic ice-vapour equilibrium. Besides reproducing known morphologies of single crystalline and of polycrystalline ice, the high time resolution (frame rate <=1 Hz) gives access to dynamic growth and sublimation events. During these processes, well-known forms of ice crystallites and polycrystalline ice were found. The time-resolved growth of ice is generally rather difficult to control, especially on the microscale. However, difficulties with the method for studying the growth of ice crystals, such as the effect of the electron beam-gas ionization and charging effects, the problem of facilitating repeated and localized ice growth are discussed and successfully overcome. Sublimation events at small undersaturation of water vapour are better accessible. The sublimation rates fit to natural phenomena on ice fields, e.g. in the Antarctica or on Mars. The dynamically evolving shapes are complex: From hexagonal single crystal columns, but also from smooth polycrystalline surfaces, sharp sub-microscale ridges develop, and finally dominate the overall structure. A new geometry are the so-called "pools", circular features of some μm diameter, into which grain boundaries on ...