Synthesis and characterization of a novel Y-Fe phase via kinetic neutron diffraction

Kinetic in situ neutron diffraction has been used to study the crystallization of amorphous Y67Fe33. The results show that partial crystallization first occurs close to 300 ◦C where the Y phase is formed. The entire sample crystallizes at 390 ◦C and new Bragg peaks appear, signifying the formation of a novel Y–Fe phase. This new phase coexists with Y to 450 ◦C when the Bragg peaks associated with this phase rapidly decrease in intensity and YFe2 also coexisting with Y, emerges as the final crystallization product. Rietveld refinement shows that the new phase crystallizes into a hexagonal structure, space group P63/mmc, with a = 12.8893(7) Å, c = 11.7006(9) Å and γ = 120◦

Kinetic neutron diffraction as an aid to processing

The development of high intensity neutron sources coupled with improvements in instrumentation has made it possible to collect high quality diffraction patterns extremely rapidly, and studies of the kinetics of solid-state processes in real time are now feasible. As a consequence, it is now possible to monitor and optimise production processes in the neutron beam using kinetic neutron diffraction. To illustrate the power of the technique three studies of processing routes are described, one in magnet technology and two in biomaterials science

Determination of hyperfine field distributions in amorphous magnets

We present an overview of two leading methods of determining probability distributions from M¨ossbauer spectra, using the model amorphous magnet Fe80B20. A comparison is made between the maximum-entropy method, which permits analysis using truly arbitrary parameter probability distributions, and a Voigtian-based analysis, which uses a sum of Gaussian components to create parameter distributions of pseudo-arbitrary shape. Our results indicate that, in Fe80B20, a Gaussian distribution of magnetic hyperfine fields is a very good approximation, although small deviations from a Gaussian shape are evident. We find that the apparent existence of correlations between the isomer shift and magnetic hyperfine field parameters, as found using Voigt-based analyses, may be an artefact of imposing a Gaussian shape on the parameter distributions. We conclude that maximum entropy and Voigtian analyses together provide a very powerful means of characterizing magnetic materials with M¨ossbauer spectroscopy

Electron transfer in dextran probed by longitudinal field muon spin relaxation

Electron-transfer processes play a crucial role in bio-nanobattery design, the electron transfer rate through the organic material being a key parameter in determining the resistance, maximum current, power density, discharge rate and duty cycle of the cell. The labelled electron method using positive muons allows such transfer processes in macromolecules, such as polymers and proteins, to be probed on a microscopic level. Here we present the results of an experiment using the labelled electron method with longitudinal field muon spin relaxation (LF-μSR) to investigate electron-transfer processes in dextran. The data are well described using the Risch–Kehr model and the results suggest intra-chain diffusion is the dominant transport process in this systembetween 15 and 250 K. Intra-chain diffusion rates of 1013 s−1 have been determined