Biomedical subjects

I Brough

Publications and source records attributed to I Brough.

6 recordsLinked to original sources

PubMed2005

The characterization of low-angle boundaries by EBSD.

A method of accurately measuring misorientations by electron backscatter diffraction (EBSD), which is an extension of that proposed by Wilkinson and based on the comparison of diffraction patterns, is described. The method has been applied to linescans, and found to improve the angular resolution by a factor of more than 30. The consequent improvement in determining misorientation axes is also analysed. Small changes of orientation very close to some low-angle boundaries were investigated and found to be artefacts of the analysis. Measurements of the area from which diffraction patterns are generated show this to be much larger than the effective spatial resolution of EBSD, and it is concluded that this may be a limiting factor in the use of EBSD for microstructural characterization.

Journal Article↗

PubMed2002

The application of a hot deformation SEM stage, backscattered electron imaging and EBSD to the study of thermomechanical processing.

The technique of combining in situ hot-deformation and high resolution electron backscattered diffraction (EBSD) has been applied to study the mechanisms operating during the thermomechanical processing of metals. A simple hot tensile-straining stage is installed in a field emission gun scanning electron microscope equipped with an EBSD system and has been used successfully for a number of preliminary investigations. These investigations include substructure formation, dynamic subgrain and grain growth, superplastic deformation in aluminium alloys, and dynamic recrystallization in copper. Despite the surface topography, which inevitably increases during plastic deformation, channelling contrast backscattered electron micrographs have been successfully obtained after strains of up to approximately 50%. Good quality EBSD maps have been obtained after strains of up to 100%. Most observations and measurements from the in situ experiments are consistent with what is known about the mechanisms occurring in the bulk. The microstructures revealed in the centre of the in situ samples after later repolishing are generally similar to those at the surface.

Journal Article↗

PubMed1999

Electron backscatter diffraction of grain and subgrain structures - resolution considerations.

Characterization of microstructures containing small grains or low-angle grain boundaries by electron backscattered diffraction (EBSD) is limited by the spatial and angular resolution limits of the technique. It was found that the best effective spatial resolution (60 nm) for aluminium alloys in a tungsten-filament scanning electron microscope (SEM) was obtained for an intermediate probe current which provided a compromise between pattern quality and specimen interaction volume. The same specimens and EBSD equipment when used with a field-emission gun SEM showed an improvement in spatial resolution by a factor of 2-3. For characterizing low-angle boundary microstructures, the precision of determining relative orientations is a limiting factor. It was found that the orientation noise was directly related to the probe current and this was interpreted in terms of the effect of probe current on the quality of the diffraction patterns.

Journal Article↗

PubMed1999

High resolution electron backscatter diffraction with a field emission gun scanning electron microscope.

A scanning electron microscope with a thermal field emission gun (FEGSEM) is found to offer significant improvements in electron backscatter diffraction performance over a conventional W-filament scanning microscope. The spatial resolution is improved by a factor of approximately 3 in the FEGSEM and is optimized at probe currents of 50-300 nA and at 10-15 keV. The angular accuracy is optimized at probe currents above approximately 150 nA and at 30 keV.

Microscopy, Electron, Scanning↗

PubMed1984

Degradation of the copper-releasing intrauterine contraceptive device and its significance.

Measurements were made of the copper remaining on used Gravigard intrauterine contraceptive devices (IUCDs) that had been in utero for up to 40 months. The topography and composition of the surface deposits were analysed by scanning electron microscopy and energy-dispersive X-ray analysis. The rate of copper loss decreased exponentially from 0.42 mumol d-1 (26.7 micrograms d-1) upon insertion to 0.056 mumol d-1 (3.6 micrograms d-1) after 26 months of use; between 27 and 40 months of use a linear release of 0.32 mumol d-1 (20.3 micrograms d-1) was observed. There was no correlation between this changing rate of copper loss and the pregnancy rate with the device in situ. The changes in the rate of copper loss were probably due to the growth of a surface corrosion product which, due to internal stresses, fractured after about 2 years and exposed fresh copper; this results in a progressive increase in breakage of the copper wire after 3 years. It is recommended that a copper IUCD of this type be replaced after 3 years.

Copper↗

PubMedDate not supplied

An investigation of an ion strengthening paste for dental porcelains.

The effect of a commercial ion exchange paste on the tensile strength of high- and low-expansion dental porcelains was investigated. Strength measurements were correlated with changes in surface chemistry. The paste was found to be more effective for aluminous porcelains than for an inlay ceramic, although only when applied to the surface placed in tension. Surface finish also influenced the effectiveness of the paste. The depth of ion exchange was assessed by energy dispersive x-ray analysis and was found to extend to at least 100 microns, although the most marked change occurred within a 10-microns layer below the surface.

Aluminum Oxide↗