Evan Gray

Evan Gray
Griffith University

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34
Publications
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890
Citations

Publications

Publications (34)
Preprint
Full-text available
Realistic prediction of the superconducting transition temperature (Tc) for PdH is a long-standing challenge, because it depends on robust calculations of the electron and phonon band structures to obtain the electron-phonon scattering matrix element. To date, first-principles calculations employing density functional theory (DFT) have been based o...
Article
Accurate prediction of wind power generation is complex due to stochastic component, but can play a significant role in minimizing operating costs, and improving reliability and security of a power system. This paper proposes a hybrid deep learning model to accurately forecast the very-short-term (5-min and 10-min) wind power generation of the Boco...
Article
The partial atomic volume of hydrogen, vH, is a fundamentally important thermodynamic parameter of interstitial metal hydrides in which dissociated H occupies interstices in the metal lattice. Such an important property should be able to be reliably calculated by a suitable theory or model in order to explain and understand its origin. In practice,...
Article
Density functional theory is increasingly used to predict and understand the properties of hydrogen storage materials. Many such calculations have been performed for various real and hypothetical palladium hydrides, yet despite excellent agreement on electron band structures, significant disparities persist in relation to phonon band structures and...
Article
We have studied the complex decomposition mechanism of cubic γ-Mg(BH4)2 (Ia3̅d, a = 15.7858(1) Å) by in-situ synchrotron X-ray diffraction, temperature-programmed desorption, visual observation of the melt, and Fourier transform infrared (FTIR) spectroscopy. The decomposition and release of hydrogen proceeds through eight distinct steps, including...
Article
Isotopic Mg11B2 has been deuterated at 400 °C and 800 bar, with the production of β-Mg(11BD4)2 observed by in situ neutron diffraction. A natural MgB2 sample has been deuterated under similar conditions and studied ex situ by high resolution X-ray synchrotron diffraction. In both cases, quantitative phase analysis (QPA) indicates a ca. 43% yield of...
Article
“Hybrid” hydrogen storage, where hydrogen is stored in both the solid material and as a high pressure gas in the void volume of the tank can improve overall system efficiency by up to 50% compared to either compressed hydrogen or solid materials alone. Thermodynamically, high equilibrium hydrogen pressures in metal–hydrogen systems correspond to lo...
Article
The use of intermittent renewable energy sources for power supply to off-grid electricity consumers depends on energy storage technology to guarantee continuous supply. Potential applications of storage-guaranteed systems range from small installations for remote telecoms, water-pumping and single dwellings, to farms and whole communities for whom...
Article
Magnesium hydride nanoparticles were synthesized within a carbon aerogel (CA) scaffold using a dibutylmagnesium precursor. The synthesis reaction was tracked using small-angle X-ray scattering (SAXS) to analyze the structural evolution during MgH2 formation. The CA/MgH2 composite was also investigated using X-ray diffraction (XRD) and transmission...
Article
Full-text available
This paper describes new sample cells and techniques for in situ powder X-ray diffraction specifically designed for gas absorption studies up to ca 300 bar (1 bar = 100 000 Pa) gas pressure. The cells are for multipurpose use, in particular the study of solid-gas reactions in dosing or flow mode, but can also handle samples involved in solid-liquid...
Article
We investigated the inter-band transition effects in spin generation in semiconductors by measuring the time-resolved differential transmission of the samples. The degree of polarization pumped with the single- photon excitation of electrons was found to decay with a time constant of 210 ps, giving a spin relaxation time of 420 ps, and to be enhanc...
Article
Spin polarization in the presence of an external magnetic field and electric bias in quantum confined semiconductor structures has been studied by time- and polarization-resolved spectrometry. From measurements with angular variations of the magnetic field from the Voigt configuration (VC) it was found that both the frequency (Ω) and decay rate (β)...
Article
We study theoretically the propagation and distribution of electron spin density in semiconductors within the drift–diffusion model in an external electric field. From the solution of the spin drift–diffusion equation, we derive the expressions for spin currents in the down-stream (DS) and up-stream (US) directions. We find that drift and diffusion...
Article
A mechanochemical synthesis process has been used to synthesise aluminium nanoparticles. The aluminium is synthesised via a solid state chemical reaction which is initiated inside a ball mill at room temperature between either lithium (Li) or sodium (Na) metal which act as reducing agents with unreduced aluminium chloride (AlCl3). The reaction prod...
Article
Full-text available
A superparamagnetic nanoparticle (SPN) is a nanometre-sized piece of a material that would, in bulk, be a permanent magnet. In the SPN the individual atomic spins are aligned via Pauli effects into a single giant moment that has easy orientations set by shape or magnetocrystalline anisotropy. Above a size-dependent blocking temperature $T_{b}(V,\ta...
Article
Full-text available
We describe an experiment which investigates the effect of a longitudinal electric field on the spin-polarized carriers generated by a circularly polarized light in semiconductors. Our experiment observes the effect as a Hall voltage resulting from nonequilibrium magnetization induced by the spin-carrier electrons accumulating at the transverse bou...
Article
We have applied X-ray and neutron small-angle scattering techniques (SAXS, SANS, and USANS) to study the interaction between fluids and porous media in the particular case of subcritical CO2 sorption in coal. These techniques are demonstrated to give unique, pore-size-specific insights into the kinetics of CO2 sorption in a wide range of coal pores...
Article
Time- and position-resolved synchrotron small angle X-ray scattering data were acquired from samples of two Australian coal seams: Bulli seam (Bulli 4, Ro = 1.42%, Sydney Basin), which naturally contains CO2 and Baralaba seam (Ro = 0.67%, Bowen Basin), a potential candidate for sequestering CO2. This experimental approach has provided unique, pore-...
Article
An experimental and theoretical study on the optically stimulated spin transport in zinc-blende semiconductors is presented. The first part of the paper describes an experiment which investigates the effect of a longitudinal electric field on the spin-polarized carriers induced by a circularly polarized light. Since the photo-generated hole spins r...
Article
Full-text available
Layered and nanotubular systems that are metallic or graphitic are known to exhibit unusual dispersive van der Waals (vdW) power laws under some circumstances. In this letter we investigate the vdW power laws of bulk and finite layered systems and their interactions with other layered systems and atoms in the electromagnetically non-retarded case....
Article
The long-standing controversy over the occupation by hydrogen of tetrahedral interstices in palladium has been addressed experimentally and theoretically. Using the highest resolution neutron powder diffractometer available, diffraction profiles were recorded from single-phase samples obtained by loading Pd with deuterium in situ at 310 °C, at D2 p...
Article
A pressure cell designed for high-energy X-ray diffraction in transmission mode is described. The cell is intended for use at temperatures up to 573 K with samples that are large enough to permit the real-time determination of the amount of absorbed gas by measuring the gas pressure. The design is driven by the need to ensure that the sample temper...
Article
We consider a semiconductor device similar to the subject of recent experiments on the spin-dependent Hall effect and analyse electric field effects in spin transport. A drift-diffusion equation for spin density is derived, and drift and diffusion contributions to the spin current are examined, which importantly suggests a possible way for the enha...
Article
The longitudinal current in Si-doped gallium arsenide was spin-polarized using circularly polarized light. The spin current was detected by the extraordinary Hall effect. An enhancement of Hall conductivity with increasing moderately Si-doping was found, indicating that the introduction of dopants increases the electronic spin polarization. This fi...
Article
Accurate determination of the quantity of hydrogen absorbed by a potential hydrogen storage material is crucial to progress in the field. The most common techniques for measuring hydrogen uptake from the gas phase by a solid host, the Sieverts technique and gravimetry, both become susceptible to systematic errors as the density of the host material...
Article
The time-of-flight diffraction techniques that are normally practiced at pulsed neutron sources afford opportunities that are not readily available at continuous fixed-wavelength sources. The present work concerns the increasing trend in materials science to study samples in complex non-ambient environments, such as high gas pressure. Taking the ex...
Article
More than three decades of research have not solved the problem of storing hydrogen on board for transport fuel. Hydrogen storage therefore constitutes a major technological barrier to the hydrogen economy. The present paper considers why the problem is so tough and assesses the prospects for the two most popular storage concepts, pressurised gas s...
Article
Full-text available
Atomic short-range order is commonly observed in _CuMn alloys via a diffuse (1 ½ 0) peak in neutron diffraction patterns. There has been speculation for many years on the existence and nature of any corresponding long-range order. A sample of Cu80Mn20 has been irradiated in a high fast-neutron flux to produce a large number of crystal defects at ar...
Article
In this article, we describe a high-pressure gas-handling cell at high temperatures developed for neutron scattering studies. The cell has been developed from a pre-existing autoclave design, that was developed for high-pressure high-temperature synthesis of ternary alkali-metal-transition-metal hydrides. Yes Yes
Article
Full-text available
The crystallography of the Pd-Dx system has been studied by in situ neutron powder diffraction at 309 °C, in the supercritical region, and, after quenching in the pure β phase to 50 °C, in the two-phase region at 50 °C. Rietveld profile analysis of the supercritical diffraction patterns showed that 14% of D interstitials were occupying tetrahedral...
Article
There have been many neutron-scattering studiesof short-range order in Cu_Mn alloys which show a diffuse (1½ 0) peak. It has been suggested that this may be a precursor of long-range order in the alloys. Atomic short-range order in Cu_Mn alloys is strongly associated with effects on the magnetic properties of the samples. Irradiating a sample of Mn...
Article
In situ synchrotron powder diffraction data for the LaNi5–H system were collected and the dislocation structures formed during the hydrogen activation cycle were studied by Rietveld refinement analysis in which anisotropic line broadening was modeled by dislocation scattering. Marginal line broadening was observed in the α phase formed by the very...
Article
During the first few hydrogenation–dehydrogenation cycles of virgin LaNi5, the absorption plateau pressure drops sharply, accompanied by powdering of the starting intermetallic. We looked for an explanation of this phenomenon in the microstructural features of the metal that can be studied via diffraction. Five complete absorption–desorption cycles...

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