Supercritical fluids as antisolvents and transport media
This thesis contains details of experiments involving the use of supercritical fluids (SCF) and high pressure liquids acting as antisolvents and transport media. The thesis is divided into six Chapters, each detailing different aspects of SCF technology. Chapter 1: Provides the reader with general information concerning the properties of supercritical fluids. Information is given concerning the use of SCFs as solvents and antisolvents. Reviews of the PCA and GAS processes are also provided. Chapter 2: Describes the initial study of the preparation of C60(gas) intercalation compounds. PCA generates compounds of C₂H₄, C₂H₆, C₃H₆ and C₃H₈, which were characterised by JR. A novel GAS technique is used to allow collection of PXD, SEM and MAS ¹³C NMR data of these compounds. Chapter 3: Details a novel supercritical antisolvent technique which allows the generation of macroscopic crystals of intercalate species C60(C₂H₄) and C60(C₂H₆). Crystallographic data on these compounds is presented. Datasets for the intercalates C60(CO₂), C70(C₂H₆) and C70(CO₂) were also collected. Chapter 4 Contains preliminary information on the formation of ‘nanopeapods', that is, carbon nanotubes filled with C60. A new route to the formation of these materials at room temperature is shown. Chapter 5: Describes the impregnation of mesoporous silica with aluminium containing species using SCF as a solvent. Materials display unprecedented stability to steaming with high retention of structural ordering and surface area. Chapter 6: Describes the extraction of template molecules from mesoporous silica. The possibility of complete removal of surfactant using a SCF is shown. The effect of temperature and pressure effects are also measured. Appendices are available at the back of the thesis to describe the equipment, analytical techniques and some safety principles for use of SCF.