Ion beam analysis of molecular diffusion in heterogeneous materials

• Main Author: Jenneson, P. M.
• Published: University of Surrey 1998
• Subjects: 530.41; Solid-state physics
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265784

Scanning ion micro-beam analysis has been used to determine the diffusion of molecules in materials with a combination of high spatial resolution and concentration sensitivity not possible with other analytical techniques. The ion beam analysis apparatus and techniques available at the University of Surrey are described. Methodologies have been devised to determine the scanning micro-beam line scan size and the diameter of the beam spot. Adaptations to the micro-beam line hardware have been proposed with the design of a novel form of none interrupting beam current monitor utilising a transmission Faraday cup and charge collection from the object aperture. Micro-Nuclear Reaction Analysis (NRA) has been used for the first time to resolve the location and concentration of a hydrocarbon molecule in a biological matrix. Deuterated molecules (a surfactant and a hair conditioning agent) were imaged in perm damaged and undamaged hair fibres. Natural deuterium levels were ascertained with reference to a virgin hair fibre. Profiles of chlorine diffusing into cement paste blends have been determined using micro-Particle Induced X-ray Emission (PIXE). The profiles were fitted with a semi-infinite model of Fickian diffusion. The analysis was combined with micro-NRA to simultaneously profile the aqueous carrier (deuterium oxide) with the diffusing chlorine. A combination of micro-PIXE and micro-NRA has been used for the first time to image the ingress of water (deuterium oxide) and subsequent redistribution of drug in a polymeric drug release system. The two dimensional distributions of water, drug, and polymeric matrix are statistically correlated.