A5012932024- High-pressure geophysics and materials
- Geological and Geochemical Analysis
- earthquake and tectonic studies
- Rare-earth and actinide compounds
- Geology and Paleoclimatology Research
- Diamond and Carbon-based Materials Research
- X-ray Diffraction in Crystallography
- Astro and Planetary Science
- Methane Hydrates and Related Phenomena
- Metallurgical Processes and Thermodynamics
- Crystal Structures and Properties
- nanoparticles nucleation surface interactions
- Marine Biology and Ecology Research
- Hydrogen Storage and Materials
- Metallurgy and Cultural Artifacts
- Microstructure and Mechanical Properties of Steels
- Paleontology and Stratigraphy of Fossils
- Mineralogy and Gemology Studies
- Planetary Science and Exploration
- Semiconductor materials and interfaces
- Metallurgical and Alloy Processes
- Intermetallics and Advanced Alloy Properties
- Nuclear Materials and Properties
- Additive Manufacturing Materials and Processes
- Material Dynamics and Properties
University of Bristol
2016-2025
University College London
2011-2014
We performed laser-heated diamond anvil cell experiments on bulk compositions in the systems MgO–SiO2–H2O (MSH) and MgO–Al2O3–SiO2–H2O (MASH) that constrain stability of hydrous phases Earth's lower mantle. Phase identification by synchrotron powder diffraction reveals a consistent set relations for high-pressure, dense silicate D H. In MSH system phase is stable to ~ 50 GPa, independent temperature from 1300 1700 K. H becomes between 35 40 out reaction occurs at 55 GPa 1600 K with negative...
High-temperature superconductivity has been observed in binary hydrides such as <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi>LaH</a:mi><a:mn>10</a:mn></a:msub></a:math> at pressures close to <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mn>180</b:mn><b:mspace width="0.16em"/><b:mi mathvariant="normal">G</b:mi><b:mi>Pa</b:mi></b:mrow></b:math>, whereby hydrogen cagelike structures have identified a common motif beneficial for high critical temperatures...
We present detailed studies of the superconductivity in high-pressure ${\mathrm{H}}_{3}\mathrm{S}$. X-ray diffraction measurements show that cubic $Im\overline{3}m {\mathrm{H}}_{3}\mathrm{S}$ was synthesized from elemental sulfur and hydrogen donor ammonia borane (${\mathrm{NH}}_{3}{\mathrm{BH}}_{3}$). Our electrical transport confirm with a transition temperature ${T}_{c}=197\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ at $153\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$. From analysis both...
The melting curve of FeSi has been determined to 150 GPa in the laser‐heated diamond anvil cell (LH‐DAC) on basis discontinuities power versus temperature function. A multianvil experimental cross‐check at 12 using textural criteria as a proxy for is good agreement with our LH‐DAC results. point reaches ∼4000 K core mantle boundary and an extrapolated value 4900 inner‐core (ICB). We also present by Lindemann law; this agrees well 70 then diverges higher temperatures, reaching 6200 ICB. These...
[1] Wüstite, Fe1-xO, is an important component in the mineralogy of Earth's lower mantle and may also be a core. Therefore its high pressure-temperature behavior, including electronic structure, essential to understanding nature evolution deep interior. We performed X-ray diffraction radiometric measurements on wüstite laser-heated diamond anvil cell, finding insulator-metal transition at pressures temperatures. Our data show negative slope for this apparently isostructural phase boundary,...
We report ab initio atomistic simulations of hydrous silicate melts under deep upper mantle to shallow lower conditions and use them parameterise density viscosity across the ternary system MgO-SiO2-H2O (MSH). On basis phase relations in MSH system, primary partial have 40-50 mol% H2O. Our results show that these will be positively buoyant at boundaries transition zone except very iron-rich compositions, where ≳ 75% Mg is substituted by Fe. Hydrous also highly inviscid. indicate if melting...
The melting curve of Sn initially rises steeply as a function pressure but exhibits decrease in slope ($d{T}_{m}/dP$) above 40 GPa to become nearly flat 50 GPa. Previous studies have argued that body-centered tetragonal (bct) cubic (bcc) phase transition occurs this range at room temperature. However, our investigations shown the behavior is more complex region with orthorhombic (bco) splitting reflections occurring x-ray diffraction pattern 32 and coexisting signatures bco bcc structures...
Abstract The density and structure of liquid Fe‐C alloys have been measured up to 58 GPa 3,200 K by in situ X‐ray diffraction using a Paris‐Edinburgh press laser‐heated diamond anvil cell. Study the pressure evolution local inferred measurements is important understand compression mechanism liquid. Obtained data show that degree greater for first coordination sphere than second third spheres. extrapolation suggests carbon cannot be only light element alloyed iron Earth's core, as 8–16 at % C...
We report on laser-heated diamond anvil cell (LHDAC) experiments in the FeO–MgO–SiO2–CO2 (FMSC) and CaO–MgO–SiO2–CO2 (CMSC) systems at lower mantle pressures designed to test for decarbonation forming reactions. Sub-solidus phase relations based synthesis are reported pressure range of ∼35 90 GPa temperatures ∼1600 2200 K. Ternary bulk compositions comprised mixtures carbonate silica constructed such that reactions produce non-ternary phases (e.g. bridgmanite, Ca-perovskite, diamond, CO2–V),...
Experiments at 20–97 GPa and 2000 K in the system CaO–MgO–TiO2–SiO2 constrain phase relations involving Mg-rich Ca-rich perovskite solid solutions conditions relevant to Earth's deep Transition Zone lower mantle. Bulk compositions were investigated with molar Ti/(Ti + Si) up 0·5 within quasi-ternary 'perovskite plane', which is defined by a reciprocal solution among components MgSiO3, MgTiO3, CaSiO3, CaTiO3. Multi-anvil experiments 20 on bulk plane produce akimotoite coexisting...
Gilsocarbon graphite, as a neutron moderator and load-bearing component in the core of UK fleet Advanced Gas-Cooled Reactors, possesses complex microstructural features including defects/pores over range length-scales from nanometres to millimetres size. As consequence, this material exhibits different characteristics when specimens length-scale are deformed. In work, deformation fracture have been characterised using situ methods for micrometre size (meso-scale) results then compared with...
Recent studies present compelling evidence that a free aqueous fluid phase exists within the upper mantle. Fluid may be at depths as great transition zone (410–660 km) and possibly beyond. The chemical reactivity of such deep fluids can predicted from Born model solvation. To use model, we need to know dielectric constant water under mantle conditions. We have used ab initio molecular dynamics simulations determine up pressure 30 GPa temperature 3000 K. Increased lowers decreases ion...
Fe 2 O 3 produced in a deep magma ocean equilibrium with core-destined alloy sets the early redox budget and atmospheric composition of terrestrial planets. Previous experiments (≤28 gigapascals) first-principles calculations indicate that produces appreciable 3+ but predict /ΣFe ratios conflict by an order magnitude. We present glasses quenched from melts equilibrated at 38 to 71 gigapascals, 3600 4400 kelvin, analyzed synchrotron Mössbauer spectroscopy. These 0.056 0.112 mean...
Abstract Seismic and magnetotelluric studies suggest hydrous silicate melts atop the 410 km discontinuity form 30–100 thick layers. Importantly, in some regions, two layers are observed. These stagnant related to their comparable density surrounding mantle, but formation mechanisms detailed structures remain unclear. Here we report a large decrease of melt viscosity at ~14 GPa, from 96(5) 11.7(6) mPa⋅s, as water content increases 15.5 31.8 mol% H₂O. Such low viscosities facilitate rapid...
Pressure-temperature melting curves in two carbonate-bearing systems of relevance to Earth's mantle have been determined using the laser-heated diamond-anvil cell (LH-DAC). The solidus along MgSiO3-MgCO3 join MgO-SiO2-CO2 system (MS-CO2) was defined from 15 80 GPa situ criteria, reaching a maximum temperature ~2340 K at GPa. occurrence has confirmed with ex-situ textural and chemical analysis recovered samples. curve negative dT/dP slope pressures between ~15 23 resulting subsolidus phase...
The atomic-scale structure, melting curve, and equation of state liquid gallium has been measured to high pressure (p) temperature (T) up 26 GPa 900 K by in situ synchrotron x-ray diffraction. Ab initio molecular dynamics simulations 33.4 1000 are excellent agreement with the experimental measurements, providing detailed insight at level pair distribution functions. results reveal an absence dimeric bonding a continuous increase average coordination number n[over ¯]_{Ga}^{Ga} from 10.4(2)...