News


Riverside path with obstacles

Riverside path with obstacles

April 2018 - A quick evening stroll from the National Resources Wales car park at Gelli Ddu/Black Covert near Trawsgoed. This is just a flat walk through mixed woodland by the side of the Afon Ystwyth. On this occasion, the path was blocked in several places because windblown trees were scattered throughout the forest. This necessitated a few detours to the edge of the woodlands, with views across farmland in the Ystwyth valley. [more external link]  [other news]

Recent beamtime


GISAXS beamtime on solvent annealing of diblock films at DESY

GISAXS beamtime on solvent annealing of diblock films at DESY

This experiment was our first scattering experiment on polymer films, in particular polystyrene-polymethylmethacrylate films with and without embedded CuInGaS2 nano-particles. We built a sample cell to study the effect of selective solvent atmospheres in situ but had to make some adjustments to it during the experiment to cope and make best use of the microfocus beam at P03. Originally, we had planned to use mica substrates, which work very well for AFM measurements but turned out to rough for microbeam GISAXS because of their tendency to delaminate at the edges. Silicon is clearly better suited here! We were able to see the effect of selective solvent atmospheres on the film structure - films become more ordered within minutes of the injection of THF into the cell, and the layer thickness changes as a result. We have also observed that added nano-particles stabilise horizontal layer morphologies, which are otherwise disrupted when the intense beam evaporates solvent from the film. [more] [beamtimes]

Teaching materials


Fourier transformation

Fourier transformation

These are notes of a Fourier workshop I used to run over three days for our 3rd year MPhys students. This is now covered in other modules, but I've decided to keep the notes online as they may be useful to someone out there. [more] [teaching]

Research papers


Dynamic strain propagation in nanoparticulate zirconia refractory

Dynamic strain propagation in nanoparticulate zirconia refractory

Residual and intrinsic strains in granular materials have been studied extensively. However, understanding the dynamic strains that cause these resultant residual strains is key to developing better strain-resistant materials. This investigation demonstrates a method for characterizing dynamic strain propagation in granular materials. The specimen is a zirconia based refractory composed of sol-gel-derived zirconia nanoparticles in a potassium silicate glass binder. In situ synchrotron X-ray powder diffraction in flat-plate geometry is used to characterize the sample structure on timescales of the order of 1ms. A 125W CO2 laser is used to strain the sample with a 25ms pulse length. To compensate for the poor flux on this timescale, a pump-probe method is repeated 1000 times and the resulting data are subsequently re-binned to improve statistics. A Gaussian weighting function is also used to introduce better contrast between strained and unstrained frames. TOPAS Academic is used for fitting with a Le Bail model in batch mode. Lattice parameters and sample height are refined during fitting, along with a Lorentzian line width for extracting microstrain broadening. Microstrains, epsilon, in the range of 1.01% < epsilon < 1.46% are reported on a 1ms timescale. [request reprint]  [papers]

Walking in Wales


Half the Alltfedw circuit

Half the Alltfedw circuit

Coed Alltfedw from Gelli Ddu/Black Covert NRW car park
National Resources Wales provide a car park by the Afon Ystwyth near Trawsgoed with two waymarked paths. One of them leads onto Alltfedw, a low ridge to the east of Llanilar and ending fairly abruptly at Trawsgoed. It is mostly covered in forest (Coed Alltfedw). Unfortunately, there had been significant storm damage recently, which hasn't been cleared yet. However, the lower part is accessible with care, while I had to turn round near the summit because the toppled trees were piled up or l... [more]
Elenydd  3.4km  120m  1hrs   [more] [walks]

Other diversions


Google orf poepel woh cna type

Google orf poepel woh cna type

Google has become sooo clever these days, it even knows better what I want search for than I do myself. At least it thinks it does. Alas, when seeking for a noodle in a haystack, it's not helpful to find zillions of needles instead. Here's a search box that keeps the pesky spell checker in check. [more] [other diversions]