Ion beam analysis of molecular diffusion in heterogeneous materials.

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

An X-ray micro-tomography system optimised for the low-dose study of living organisms

An X-ray micro-tomography system has been designed that is dedicated to the low-dose imaging of radiation sensitive living organisms and has been used to image the early development of the first few days of plant development immediately after germination. The system is based on third-generation X-ray micro-tomography system and consists of an X-ray tube, two-dimensional X-ray detector and a mechanical sample manipulation stage. The X-ray source is a 50 kVp X-ray tube with a silver target with a filter to centre the X-ray spectrum on 22 keV.A 100 mm diameter X-ray image intensifier (XRII) is used to collect the two-dimensional projection images. The rotation tomography table incorporates a linear translation mechanism to eliminate ring artefact that is commonly associated with third-generation tomography systems' Developing maize seeds (Triticum aestivum) have been imaged using the system with a cubic voxel linear dimension of 100 mum, over a diameter of 25 mm and the root lengths and volumes measured. The X-ray dose to the plants was also assessed and found to have no effect on the plant root development. (C) 2003 Elsevier Science Ltd. All rights reserved

Examining Nanoparticle Assemblies Using High Spatial Resolution X-ray Microtomography

An experimental system has been designed to examine the assembly of nanoparticles in a variety of process engineering applications. These applications include the harvesting from solutions of nanoparticles into green parts, and the subsequent sintering into finished components. The system is based on an x-ray microtomography with a spatial resolution down to 5 mum. The theoretical limitations in x-ray imaging are considered to allow experimental optimization. A standard nondestructive evaluation type apparatus with a small focal-spot x-ray tube, high-resolution complementary metal oxide semiconductor flat-panel pixellated detector, and a mechanical rotational stage is used to image the static systems. Dynamic sintering processes are imaged using the same x-ray source and detector but a custom rotational stage which is contained in an environmental chamber where the temperature, atmospheric pressure, and compaction force can be controlled. Three-dimensional tomographic data sets are presented here for samples from the pharmaceutical, nutraceutical, biotechnology, and nanoparticle handling industries and show the microscopic features and defects which can be resolved with the system.</p

Examining nanoparticle assemblies using high spatial resolution x-ray microtomography

An experimental system has been designed to examine the assembly of nanoparticles in a variety of process engineering applications. These applications include the harvesting from solutions of nanoparticles into green parts, and the subsequent sintering into finished components. The system is based on an x-ray microtomography with a spatial resolution down to 5 m. The theoretical limitations in x-ray imaging are considered to allow experimental optimization. A standard nondestructive evaluation type apparatus with a small focal-spot x-ray tube, high-resolution complementary metal oxide semiconductor flat-panel pixellated detector, and a mechanical rotational stage is used to image the static systems. Dynamic sintering processes are imaged using the same x-ray source and detector but a custom rotational stage which is contained in an environmental chamber where the temperature, atmospheric pressure, and compaction force can be controlled. Three-dimensional tomographic data sets are presented here for samples from the pharmaceutical, nutraceutical, biotechnology, and nanoparticle handling industries and show the microscopic features and defects which can be resolved with the system