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Summary The penetration behaviour of isocyanate-based wood resins was evaluated using x-ray microscopy. Aspen wood pieces were bonded together in a controlled manner. These were embedded in a methacrylate-based resinand thin sections were prepared, cut from the transverse face of thewoodcomposite. X-ray images of these sections were prepared at several selected x-ray energies to allow the isocyanate, cellulose, lignin and the embedding agent distributions to be mapped. The isocyanate resin was found to penetrate deeply into the wood. The resin enters large cell lumen, and wicks along the inner cell wall surfaces. The resin accesses connected cells via connecting pits, which become filled with the resin. The affinity of the isocyanate to the inner surfaces of the large cells is probably due to the hydrophobicity of these surfaces. Isocyanate resins do not penetrate into the smaller parenchyma and tracheid cells and indeed do not even wet the inner surfaces of these cells where isocyanate entry has been allowed due to damage of the cell at the macroscopic surface of the wood. If isocyanates penetrate into the wood-cell walls of the large cells, the concentration in the cell walls has been determined to be less than 2%of the bulk concentration. This lower limit is the sensitivity limit imposed by photon statistics in the data.

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Two laboratory scale x-ray microscopes using laser generated plasma sources are being developed at King's College. One system uses dark field imaging while the other is a scanning x-ray microscope and progress with both is described. In particular, preliminary results from an extensive characterisation of the laser plasma source at the Lasers for Science Facility, CLRC Rutherford Appleton Laboratory, are discussed. This characterisation has shown that the source is eminently suitable for x-ray microscopy.

Orthopaedic surgery often involves the insertion of a prosthetic implant. For successful and rapid healing, it is important for the prosthesis to make a close and well integrated bond with the bone tissue. To assist this integration, a number of “biomaterials” are on trial as components in the prosthetic implants. Much work is in progress to determine the phase, composition and density of bone mineral at the bone/biomaterial interface. It is expected that the results of this work can be used to develop synthetic calcium phosphates which can be incorporated in prosthetic implants. The composition of bone and biomaterials has been investigated using techniques such as x-ray diffraction, Infra-red, NMR and EXAFS on homogenized samples. However, these studies do not determine the spatial distribution of the bone mineral, its density, localized mineral phase or cellular integration with biomaterials. Electron microscopy with electron probe microanalysis, light and Infra-red microscopy can indicate the presence of mineral in relation to the tissue morphology, but do not give a spatial measure of the density or chemical phase of the mineral at the sub micron level.