Steer, William Andrew; (2001) Implementation of an X-ray image-plate camera in characterisation and crystallisation studies of iron-based alloys. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Developed in the early 1980s, versatile X-ray storage phosphor screens have opened up new possibilities in diffraction instruments for crystallography. Originally adopted by high-pressure researchers using diamond-anvil cells and very small sample volumes, flat phosphor screens give great advantage because of their high intrinsic sensitivity. But less demanding applications still stand to benefit from increased throughput and enhanced count rates made possible by this technology. With this in mind the Curved Image Plate camera, a large radius (350mm and 185mm) Debye-Scherrer instrument primarily designed for use with capillary-contained powder samples had been devised. As a substantial part of this work, new software to pre-process the data, calibration procedures and modes of operation were developed to enable the full potential of the system to be realised. One particular application of the CIP camera is the comparative study of a large number of samples, for example as a function of heat treatment. Amorphous and derived nanocrystalline magnetic alloys are of increasing applied and fundamental interest at present, and are predominantly produced by the melt-spinning technique, in the form of ribbons. Borohydride reduction of metal-salt solutions has recently also been shown to be capable of producing amorphous alloy, in powder form, with potential for compaction into bulk materials. Amorphous Fe-M-B alloys (M = Ni,Co,Mn,Cr) have been widely reported, and at UCL attempts had been made to synthesise amorphous Fe-Zr-B by a similar approach. An investigation of the structural, compositional and magnetic properties of the product of this synthesis have been carried out in this study. The application of the CIP camera has enabled the thermally-induced crystallisation of such samples to be followed with unprecedented clarity. It is found, contrary to previous thought, that the main product of this synthesis consists of two distinct amorphous phases, iron-boron and zirconium-oxide, mixed on a sub-micron length scale.

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