Browsing by Author "Thomas, PS"

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    Rheo-ND: temperature and shear induced crystal transformation of a model triglyceride observed using neutron diffraction
    (Australian Institute of Nuclear Science and Engineering (AINSE), 2018-11-19) Maynard-Casely, HE; Stuart, BH; Booth, N; Thomas, PS
    Rheo-SANS (rheology and small angle neutron diffraction) is now a well-established technique to probe the shape and size of particles under different shear and temperature regimes [1]. Recent work on WOMBAT [2], the high intensity neutron diffraction instrument at the Australian Centre for Neutron Scattering, has successfully combined rheology and neutron diffraction. This was used to follow the crystalline phase transformations in a model (deuterated) triglyceride. The initial impetus for this work was part of a forensic investigation [3] linking the crystallisation of triglycerides under high shear rates that are encountered in motor vehicle accidents. However now the technique has been demonstrated it may be of interest to investigate crystallization due to shear in other organic systems. Figure 1 - Diffraction data collected from the shear cell during cooling and shearing at 1000 s-1, colours give the intensity of the diffraction pattern (left axis) and the black squares chart the measured viscosity (right axis). This demonstrates the ability to track crystallisation in situ under high shear rates. The high neutron flux and detector efficiency available at WOMBAT is instrumental in allowing diffraction patterns to be collected from the small sample volumes available in the Couette cell geometry. The Couette cell used has a sample gap of 1mm and was mounted tangentially to the neutron beam. The shear rate applied to the sample can be varied over a range of 10-2500 s-1 and the temperature can be controlled using an external water jacket from between -10 and 80 ⁰C. We invite other researchers who are interested in this capacity to contact us about possible experiments. © The Authors.
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    Three impossible things before lunch - the task of a sample environment specialist
    (IOS Press, 2017-11-16) Booth, N; Davidson, G; Imperia, P; Lee, S; Stuart, BH; Thomas, PS; Komatsu, K; Yamane, R; Prescott, SW; Maynard-Casely, HE; Nelson, A; Rule, KC
    In the course of their day, sample environment professionals can be confronted by numerous technical challenges applicable to a range of scientific questions. This paper presents three successful outcomes from user-posed sample environment challenges for in situ neutron scattering experiments undertaken at the Australian Centre for Neutron Scattering (formerly the Bragg Institute). The sample environments presented here have nothing in common other than their novelty. They may not be the best solution but have been constrained by time, resources and ability. The questions the users posed were: Can we mount a cylinder in cylinder (CIC) rheometer, more regularly used on a small angle scattering instrument, on a diffraction instrument and obtain usable data? Can we supply high-voltage (up to 10 kV) across a sample within the Paris–Edinburgh press while mounted on a powder diffraction instrument? And finally can a Lakeshore 340 and an in-house built liquid conductivity cell do the job of a commercial liquid conductivity meter? This paper presents the engineering and equipment solutions that were used to answer these questions, and in each case the scientific users left with useful, intriguing and, hopefully, publishable data. © 2017 IOS Press