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© 2019 This neutron diffraction study of deuterated tripalmitin has provided further insight into a forensic observation of the crystallisation of lipids under high-shear conditions. To achieve this, an experimental set up was designed to enable simultaneous rheological data from a Couette cell to be recorded with neutron powder diffraction, enabling the influence of shear on the polymorph transformation on cooling to be monitored in real time. Tripalmitin was observed to directly transform from a liquid phase to a β polymorph under the influence of shear. Although the liquid to β transition was not observed to be influenced by shear rate, the degree of crystallinity, qualitatively denoted by an increase in the sharpness of the diffraction peaks, was observed at higher shear rates. Evidence is also presented that the rate of cooling influences the ordering in the β-polymorph produced in zero shear conditions.

QUOKKA is a 40 m pinhole small-angle neutron scattering instrument in routine user operation at the OPAL research reactor at the Australian Nuclear Science and Technology Organisation. Operating with a neutron velocity selector enabling variable wavelength, QUOKKA has an adjustable collimation system providing source–sample distances of up to 20 m. Following the large-area sample position, a two-dimensional 1 m2 position-sensitive detector measures neutrons scattered from the sample over a secondary flight path of up to 20 m. Also offering incident beam polarization and analysis capability as well as lens focusing optics, QUOKKA has been designed as a general purpose SANS instrument to conduct research across a broad range of scientific disciplines, from structural biology to magnetism. As it has recently generated its first 100 publications through serving the needs of the domestic and international user communities, it is timely to detail a description of its as-built design, performance and operation as well as its scientific highlights. Scientific examples presented here reflect the Australian context, as do the industrial applications, many combined with innovative and unique sample environments.

The Earth's polar regions are experiencing a greater frequency of freeze-thaw events throughout the polar summer, contributing to atmospheric methane and destabilising clay-rich sediments. Clays in soils tightly bind pore water and thus substantially modify freeze-thaw events. While temperatures of phase transitions for confined pore water may be precisely assessed using calorimetric or thermal analyses to −30 or −40 °C, neutron scattering directly probes how pores in clay minerals control ice formation and melting to lower temperatures. We apply elastic neutron scattering to accurately quantify the unfrozen water content of clay gels and unambiguously identify different pore-water environments by their freezing temperatures. Using this approach, we conclude that cryosuction controls water mobility in frozen soils in the absence of soluble salts to much lower temperatures than observed by other techniques. Dyanmics determined from neutron scattering indicates that water in clay gel pores thaws at much lower temperatures than currently considered, and thus pose potential risks for contaminant migration at sub freezing temperatures. The general poor strength of wet clays can significantly impact infrastructure in cold regions undergoing an increased frequency of freeze-thaw events.

Knowledge of the surface composition of planetary bodies comes from a number of sources; such as landers, remote sensing and meteorites. However, the bulk mapping of the composition of planetary surfaces has been undertaken by analysis of reflected sunlight and these data—principally collected in the near-infra-red (IR) region—are notoriously broad and ambiguous. Hence, if laboratory spectra could be tied to physical properties measurements, such as diffraction, this would substantially aid our understanding of processes occurring in these extra-terrestrial environments. This contribution presents the capability of collecting near-IR data at the same time as neutron and synchrotron X-ray diffraction in a range of conditions (low temperature, vacuum, and humidity variations) and highlights two examples where this capability could enhance our understanding of planetary surfaces.

We present a high-resolution neutron powder diffraction study of the triclinic β form of tripalmitin as well as in situ crystallisation experiments, monitored with neutron diffraction, conducted over three different cooling rates. We use the results from the high-resolution study to anticipate if neutron diffraction could be beneficial in differentiating the polymorphism in triacylglycerol systems. We extend on this to present analysis of a diffraction pattern of cocoa butter, to establish the potential for neutron diffraction to study the (hydrogenous) forms of triacylglycerols used in food production.

Neutron diffraction experiments of ice VII at pressures up to 6.2 GPa and 10.2 kV/mm were conducted to investigate the potential ferroelectrically ordered structure of ice VII induced by a high electric field. To accomplish this, we developed a high-pressure cell assembly to allow for powder neutron diffraction to be conducted under both high-pressure and high-electric field conditions. However, the subsequent observed diffraction patterns taken in situ at these conditions do not show sufficient evidence of the proposed ferroelectrically ordered structure of ice VII. We estimate the degree of the hydrogen ordering in ice VII under the applied conditions from high-pressure $P\ensuremath{-}E$ loop measurements, and discuss the future possibilities of detecting the ferroelectrically ordered structure.

The nature of providing sample environment equipment and support is constantly evolving, as new technologies and experimental techniques are developed. To remain at the cutting edge of neutron scat...

A system for positioning powder samples in top-loading cryofurnaces during neutron scattering experiments, while facilitating the successive delivery of gas doses at set temperatures to the sample, has been designed and tested. The positioning system is compatible with a Hiden Isochema IMI instrument as a gas-dosing platform, enabling gases to be delivered to the sample through a centrally located and thermally stabilized capillary line and valve. The positioning system separates into an upper and a lower section, with the lower section enabling the sample to be isolated and inserted into a glove box. This work describes the system using example neutron powder diffraction results obtained with this system in closed-cycle cryofurnaces.

A triangular-to-square lattice transition of topological magnetic particles (skyrmions) was observed in a chiral magnet MnSi., Magnetic skyrmions exhibit particle-like properties owing to the topology of their swirling spin texture, providing opportunities to study crystallization of topological particles. However, they mostly end up with a triangular lattice, and thus, the packing degree of freedom in the skyrmion particles has been overlooked so far. We report a structural transition of the skyrmion lattice in MnSi. By use of small-angle neutron scattering, we explore a metastable skyrmion state spreading over a wide temperature and magnetic field region, after thermal quenching. The quenched skyrmions undergo a triangular-to-square lattice transition with decreasing magnetic field at low temperatures. Our study suggests that various skyrmion lattices can emerge at low temperatures, where the skyrmions exhibit distinct topological nature and high sensitivity to the local magnetic anisotropy arising from the underlying chemical lattice.

The melanins are a class of pigmentary bio-macromolecules ubiquitous in the biosphere. They possess an intriguing set of physico-chemical properties and have been shown to exhibit hybrid protonic-electronic electrical conductivity, a feature derived from a process termed chemical self-doping driven by the sorption of water. Although the mechanism underlying the electrical conduction has been established, how the sorbed water interacts with the melanin structure at the physical level has not. Herein we use neutron reflectometry to study changes in the structure of synthetic melanin thin films as a function of H2O and D2O vapour pressure. Water is found to be taken up evenly throughout the films, and by employing the contrast effect, the existence of labile protons through reversible deuterium exchange is demonstrated. Finally, we determine a sorption isotherm to enable quantification of the melanin-water interactions.

Small angle neutron scattering measurements have been performed to study the thermodynamic stability of skyrmion-lattice phases in Cu$_2$OSeO$_3$. We found that the two distinct skyrmion-lattice phases [SkX(1) and SkX(2) phases] can be stabilized through different thermal histories; by cooling from the paramagnetic phase under finite magnetic field, the SkX(2) phase is selected. On the other hand, the 30$^{\circ}$-rotated SkX(1) phase becomes dominant by heating the sample from the ordered conical phase under finite field. This difference in stabilization is surprisingly similar to the irreversibility observed in spin glasses. The zero-field cooling results in the co-existence of the two phases. It is further found that once one of the skyrmion-lattice phases is formed, it is hardly destabilized. This indicates unusual thermal stability of the two skyrmion-lattice phases originating from an unexpectedly large energy barrier between them., 9 pages, 10 figures

PurposeThe emerging new influencer community is wielding significant power over the perceptions of brands and companies, largely driven by the rapid expansion of social media channels through which influencers communicate. The “nobodies” of the past are now the new “somebodies” demanding the attention of communication professionals who seek continuous engagement with targeted consumers throughout the various channels of the social web. The purpose of this paper is to present a means of identifying these new “somebodies”.Design/methodology/approachThis paper reviews a customizable valuation algorithm created to identify the “new somebodies” who are the influencers creating a revitalized level of brand awareness for companies. The index valuation algorithm measures a cross‐section of variables that numerically rate influencers in the social media conversation about a particular company, product or service.FindingsThis information helps us understand how these “somebodies” influence traditional target audiences, and help communications professionals establish effective outreach strategies. Integrating the influencer index data into a holistic social media strategy provides a comprehensive social media approach for optimizing brand equity.Originality/valueThe index identifies the “conversation points” that should guide engagement with each individual influencer, determining aspects such as subject and tone, and identifies these influencers.

An enhanced nucleation heat treatment process was employed to refine the grain structure of 7075Al/ 7wt.% SiCp metal matrix composite material. The grain structure of the metal matrix composite was investigated. The resulting microstructures were compared. It was found that a fine grained microstructure developed after the rapid heat treatment process. An increase in hardness was achieved, with hardness increasing from 129 HV in the cold extruded state to 137 – 153 HV after the heat treatment process.

There have been growing demands of high performance metal matrix composites in advanced engineering applications in virtue of their high specific strengths. This paper is to report an assessment of the mechanical properties of LC4/SiCp metal matrix composites using an innovative testing technique, small punch test. The composite materials of this study were produced by stir casting method with particulate reinforcements of 7wt.% and 14wt.% of SiC respectively. Small punch testing was performed on the LC4 base alloy and the two composites materials. The small punch test is a relatively new mechanical testing technique capable of utilizing small disk-shaped samples to determine the mechanical properties of the test materials. In this study, the equivalent fracture strain, εqf of the LC4/SiCp MMCs was characterised and compared with the base alloy. The fracture mechanism of the test samples was examined using scanning electron microscopy.

This study investigates the effect of specimen volume on the compressive strength of open cell brittle ceramics. A series of unconfined compression tests were carried out on specimens ranging in volume. The crushing strength and apparent stiffness were measured and these results are correlated with the volume of material stressed. It was found that as the volume of material tested decreased the strength decreased. © 2008 Trans Tech Publications.

There are over 100 conducting polymers which have been synthesised by chemists with a wide range of specific electrical conductivities. Many of these polymers are suitable for elec tronic device fabrication. Semi-conducting and conducting polymers have potential for application in several areas. In this paper electronic and microwave properties are explored. Fabrication of elec tronic and microwave devices can be achieved with these special polymers which are not possible with say silicon or gallium arsenide. Wide area flexible electronic junctions can be fabricated. Polymers have low density, hence conductivity to weight ratio can be higher than metals. Optical transparency together with electrical conduction has been achieved. This article presents an overview of the results of investigations undertaken within the Centre for Materials Technology (CMT) in this area over the past 4 years. This includes work on monomer and polymer synthesis, molecular structure-property relationships, electromagnetic shielding, thermal, optical and junction properties.

Samples of polypyrrole were synthesised under galvanostatic conditions to produce films possessing a range of electrical conductivity from 10−3 to 10 S cm−1. The electrical and thermal conductivity of these films has been determined between 280 and 335 K. The electrical conductivity was measured using a four probe technique calibrated against ASTM D4496-87. Thermal conductivity was determined from measurements of thermal diffusivity, specific heat and density. Thermal diffusivity was determined using a modified a.c. calorimetry technique, while differential scanning calorimetry (DSC) was used to determine specific heat. The polymer's density was measured using Archimedes' principle. The results were used to calculate the Lorenz number of polypyrrole. A comparison of the predicted behaviour and experimental results was made. Thermal conductivity is found to be large compared to that predicted from the electrical conductivity measurements on low conductivity films. Molecular vibration effects are found to be non-trivial and experimental means for measuring their contribution are mentioned. While polypyrrole has been regarded as a “synthetic metal” the thermal conductivity results show this classification is wrong.

Before conducting polymers can be employed in many applications, some of the intrinsic properties of these materials need to be better understood. An overview of the research and development of conducting polymers being undertaken at UTS is presented. Because conducting polymers are difficult to process once fabricated, an understanding of synthesis parameters and the use of synthesis techniques to pro duce conducting polymer films with desired properties is of the upmost importance. Descriptions of the galvanostatic and potentiostatic techniques employed to produce polyheterocyclics are presented. Thermal properties such as thermal diffusivity, ther mal conductivity and specific heat are being investigated. Preliminary results reveal that the thermal diffusivity of polypyrrole is higher than that achieved with traditional polymers. The nature of contacts and junctions with polypyrrole and poly(3-methyl thiophene) are discussed. High work function metals form ohmic junctions with polypyr role while aluminium forms a Schottky barrier with poly(3-methylthiophene). Micro wave studies on polypyrrole films reveal that the microwave transmission and reflection are dependent upon the doping level of the film. Applications of the conducting polymers in data security modules and for light weight electrically conducting wires are also il lustrated.

gsl 1⁄4 polymers by mixing these most different materials at the nanometer level, and strongly rely on interface stabilization. In particular the mechanical incorporation of nanoparticles into engineering thermoplastics (e.g., by melt blending techniques) has offered a continuous challenge to materials science as thermodynamic and kinetic barriers inhibit the dispersal of inorganic nanoparticles with generally high surface energies within hydrophobic polymer matrices. The physical reason for the dispersion difficulties are strong adhesion forces that act between particles with high surface energy, whilst the polymer has a lower surface energy (see Table 1 for a representative overview). The adhesion forces depend on the particle’s material properties and the polymer. The free energy of adhesion Wa per area between two surfaces of the same material acting in a liquid medium is given by

For almost 30 years, at synchrotron facilities, it has been possible to perform small-angle x-ray scattering experiments whilst simultaneously measuring differential scanning calorimetry (DSC). However, a range of challenges exist to enable the collection of simultaneous small-angle neutron scattering (SANS) and DSC data associated not only with intrinsic flux limitations but also scattering geometry and thermal control. The development of a DSC (temperature range ca. −150 °C to 500 °C) suitable for SANS is detailed here and its successful use is illustrated with combined measurements on a binary blend of normal alkanes in which one component has been deuterium labelled.

The preparation of a new polyaniline-based PVC composite is described. The composite is made by surface treatment of the PVC, followed by coating of the PVC particles with a m-cresol solution of polyaniline doped with camphor sulfonic acid. The composite possesses a low percolation threshold (less than 0.125% weight fraction) and significant conductivity at low loadings. The microwave properties of the composite have been studied and results indicate the material has potential as an EMI shielding material and in the construction of novel microwave devices.

The kiln was first brought to the notice of the Archaeological Research Committee by Mr. F. W. Brookes, who had observed wasters and kiln debris in the rabbit scrapes. The excavation was included in the Committee's first year's programme as it was felt that the pottery would provide a useful dating guide for the upper levels of the Roman city and at the same time give excellent training to the small but enthusiastic band of volunteers at that time being brought together.