Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

The fate of chemical and radioactive wastes in the environment is related to the ability of natural phases to attenuate and immobilize contaminants through chemical sorption and precipitation processes. Our understanding of these complex processes at the atomic level is provided by a few experimental and analytical methods such as X-ray absorption and NMR spectroscopies. However, due to complexities in the structure and composition of clay and other hydrated minerals, and the inherent uncertainties of the experimental methods, it is important to apply theoretical molecular models for a fundamental atomic-level understanding, interpretation, and prediction of these phenomena. In this effort, we have developed a general force field, CLAYFF, suitable for the simulation of hydrated and multicomponent mineral systems and their interfaces with aqueous solutions. Interatomic potentials were derived from parametrizations incorporating structural and spectroscopic data for a variety of simple hydrated compounds. A...

Molecular Models of Hydroxide, Oxyhydroxide, and Clay Phases and the Development of a General Force Field

A novel high excited state energy transfer pathway to overcome the phonon quenching effect in rare-earth (RE) oxide upconversion (UC) materials is reported. In Er(Tm)-Yb oxide systems, an extraordinary enhancement of UC luminescence efficiency with four orders of magnitude is realized by Mo co-doping. The RE oxides with significant UC efficiency are successfully utilized for temperature sensing and in vivo imaging.

Temperature Sensing and In Vivo Imaging by Molybdenum Sensitized Visible Upconversion Luminescence of Rare‐Earth Oxides

This review examines the detailed chemical insights that have been generated through 150 years of work worldwide on magnesium-based inorganic cements, with a focus on both scientific and patent literature. Magnesium carbonate, phosphate, silicate-hydrate, and oxysalt (both chloride and sulfate) cements are all assessed. Many such cements are ideally suited to specialist applications in precast construction, road repair, and other fields including nuclear waste immobilization. The majority of MgO-based cements are more costly to produce than Portland cement because of the relatively high cost of reactive sources of MgO and do not have a sufficiently high internal pH to passivate mild steel reinforcing bars. This precludes MgO-based cements from providing a large-scale replacement for Portland cement in the production of steel-reinforced concretes for civil engineering applications, despite the potential for CO2 emissions reductions offered by some such systems. Nonetheless, in uses that do not require steel reinforcement, and in locations where the MgO can be sourced at a competitive price, a detailed understanding of these systems enables their specification, design, and selection as advanced engineering materials with a strongly defined chemical basis.

Magnesia-Based Cements: A Journey of 150 Years, and Cements for the Future?

Thermodynamics of rare earth sesquioxides

Diffraction-deformation electron-density (Δp) images for small, naturally faced single crystals of synthetic calcite (CaCO 3 ), magnesite (MgCO 3 ) and mineral rhodochrosite (MnCO 3 ) were measured with focused λ = 0.7 and 0.9 A synchrotron (SR) X-radiation. Mo Kα (λ = 0.71073 A) structure factors were also measured for MnCO 3 . Lattice mode frequencies predicted from eigenvalues of T and L tensors for CO 3 rigid-group motion in these structures are close to spectroscopic values. High approximate Δp symmetry around the cations increases towards 6/mmm in the sequence CaCO 3 , MgCO 3 to MnCO 3 . The Δp topography near the CO 3 groups shows the influence of the cations, and correlates strongly with the refractive indices, as required for a cause and effect relationship between electron density and optical anisotropy. Aspherical electron density around the Mn atom can be attributed to the effect of a non-ideal octahedral crystal field on the 3d electron distribution. The relationship of the Δp topography near the Mn atom with that near the CO 3 group in MnCO 3 is consistent with magnetic interactions. Space group R3c, hexagonal, Z = 6, T= 295K : CaCO 3 , M r = 100.09, a = 4.988(2), c = 17.068(2) A, V = 367.8(3) A 3 , D x = 2.711 Mg m -3 , μ 0.7 = 1.93 mm -1 , F(000) = 300, R = 0.015, wR = 0.012, S = 3.0 for 437 unique reflections ; MgCO 3 , M r = 84.31, a = 4.632(1), c = 15.007 (2) A, V = 278.8 (2) A 3 , D x = 3.013 Mg m -3 , μ 0.9 = 0.99 mm -1 , F(000) = 252, R = 0.015, wR = 0.021, S = 4.34 for 270 unique reflections ; MnCO 3 , M r = 114.95, a = 4.772(3), c = 15.637 (3) A, V = 308.4 (4) A 3 , D x = 3.713 Mg m -3 , p 0.7 = 5.62 m -1 , F(000) = 330, R = 0.015, wR = 0.039, S = 3.38 for 386 unique reflections of the SR data set and a = 4.773 (1), c = 15.642(1) A, V = 308.6 (1) A 3 , D x = 3.711 Mg m -3 , μ(Mo Kα) = 5.86 mm -1 , R = 0.017, wR = 0.024, S = 2.79 for 368 unique Mo Kα reflections.

Electron density and optical anisotropy in rhombohedral carbonates. III. Synchrotron X-ray studies of CaCO3, MgCO3 and MnCO3

Structure factors for synthetic haematite, α-Fe 2 O 3 , have been measured for two small crystals using focused λ=0.7 A synchrotron radiation. The structure factors from the two data sets are consistent. Approximate symmetry in the concordant densities, related more closely to the Fe-Fe geometry than to the nearest-neighbour Fe-O interactions, is similar to that in the corundum α-Al 2 O 3 structure. Deformation density maxima are located at the midpoint of the Fe-Fe vector along the c axis, on a common face for O-octahedra, perpendicular to c. Maxima also occur at the midpoint of the Fe-Fe vector bisecting the edges of the O-octahedra. These results are in accordance with theoretical predictions for metal-metal bonding

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Synchrotron X-ray study of the electron density in α-Al2O3

Synchrotron X-ray study of the electron density in a-Al2O3

The structural geometry, vibrations and deformation density Ap for lithium niobate, LiNbO3, and lithium tantalate, LiTaO3, are derived from synchrotron radiation diffraction measurements. Electron density is transferred from the Nb (Ta) atom towards the large 03 triangle near the Li atom. Spontaneous polarizations of 0.43 (LiNbO3) and 0.33 cm -2 (LiTaO3), calculated with Hirshfeld charges, agree qualitatively with experimental values of 0.71 and 0.50 cm -2, respectively. Both strong Li...Nb (Ta) interactions in the structure are markedly shorter than all Li...Li, Nb...Nb or Ta..-Ta vectors, as expected if the Li and Nb (Ta) cations carry charges of opposite sign. The Li atom's negative charge plays a pivotal role in the polarization responsible for ferroelectricity. LiNbO3, space group R3c, rhombohedral, Mr = 147.8, a = 5.493 (2)/~, o~ = 55.89 (3) °, V= 106.02 (4)/~3, Z = 2, Dx = 4.629 Mg m -3, F(000) = 136, lz(0.7/~) = 5.01 mm -l, Ymin = 0.27, T = 293 K, R = 0.015, wR = 0.015, S = 3.276 (84) for 773 unique reflections. LiTaO3, R3c, rhombohedral, Mr = 235.9, a = 5.471 (2)/~, c~ = 56.16(3) °, V= 105.51 (4)/~,3, Z = 2, Dx = 7.412 Mg m -3, F(000) = 200, #(0.7/~) = 50.03 mm -~ , Ymin = 0.32, T = 293 K, R = 0.016, wR = 0.022, S = 1.372(35) for 773 unique reflections.

E.N. Maslen

Papers

Electron density and optical anisotropy in rhombohedral carbonates. III. Synchrotron X-ray studies of CaCO3, MgCO3 and MnCO3

Synchrotron X-ray study of the electron density in α-Al2O3

Synchrotron X-ray study of the electron density in a-Al2O3

Electron density and optical anisotropy in rhombohedral carbonates. III. Synchrotron X-ray studies of CaCO3, MgCO3 and MnCO3

Synchrotron X-ray Studies of LiNbO3 and LiTaO3