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Abstract: The crystallization of a trimetallic cobalt–molybdenum–sodium metal–organic framework, poly[μ-ben­zene-1,3,5-tri­car­box­yl­ato-tetra-μ-ox­ido-co­balt­mol­yb­de­num­tri­so­dium], UOW-10 or [Na3Co(MoO4)(BTC)]n, is achieved by solvothermal synthesis using benzene-1,3,5-tri­carb­oxy­lic acid (H3BTC, C9H6O6) as a ligand precursor, Na2MoO4·2H2O and Co(NO3)2·2H2O as metal sources, and N,N-di­methyl­formamide (DMF) as the solvent. 3D electron diffraction (3D ED) reveals that the structure crystallizes in the monoclinic space group P21/c, with lattice parameters of a = 9.718 (2), b = 18.250 (3), c = 6.892 (9) Å, α = γ = 90, β = 96.156 (15)°, V = 1214.7 (4) Å3 and Z = 4. The phase purity of the bulk sample was confirmed using syn­chro­tron powder X-ray diffraction. The organic ligands form a 2D layer, where cobalt and molybdenum are found, with sodium cations located between the layers. There are four crystallographically distinct sodium sites: three exhibit a distorted octa­hedral coordination geometry, while the remaining site is seven-coordinate. The cobalt has trigonal bipyramidal coordination geometry and molybdenum exhibits a tetra­hedral coordination geometry. Half the sodium cations in the structure forms 1D column-like motifs via shared oxygen edges along the crystallographic c axis, which are cross-linked in b by the cobalt and molybdenum sites via bridging O atoms, while the other half of the sodium cations form 2D ribbons in the ac plane, propagating along c, linked by sharing oxygen edges and faces. The optical properties of UOW-10 were investigated through the use of UV–Vis spectroscopy, showing a bandgap of 1.8 eV. Deconvolution of the features in the visible-light region reveals that four peaks are present, which can all be ascribed to the d–d transitions from the trigonal bipyramidal cobalt. By means of thermogravimetric analysis (TGA) and variable-tem­per­a­ture powder X-ray diffraction (VT-PXRD), it is demonstrated that the material has thermal stability to 410 °C, after which structure collapse occurs, leading to a mixture of Na2MoO4, CoO and Co3Mo above 900 °C.

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Abstract: Metal–organic framework (MOF) materials share some common features with metalloenzymes including site-isolated metal centers that template dynamic substrate activation within a functionalized cavity or pocket. We report the light-induced reversible binding of CO2 in a cerium-based MOF, Ce-UiO-66-NH2, incorporating an amino functionalized linker, which enables photoreduction of CO2 to CO in H2O without using sacrificial agents. A production rate for CO of 126 μmol·g–1·h–1 with 100% selectivity is observed, outperforming its non-amine analogue (Ce-UiO-66) and benchmark catalysts reported to date. In situ infrared, X-ray absorption, electron paramagnetic resonance and transient absorption spectroscopy reveal that photoexcitation induces a ligand-to-metal charge transfer to generate transient open Ce(III) sites that bind CO2 in a μ-(η1-O)(η1-C) binding mode. This binding is reversible and activates CO2 for subsequent photoreduction to CO. This work will promote the design of photocatalysts capable of synthesizing fuels from CO2.

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Abstract: The use of conventional zirconium alloys at temperatures above 400 °C is limited by high temperature strength and creep resistance. This has prevented the consideration of zirconium alloys for fusion and Generation IV fission plant designs operating at 500 °C–1000 °C. The physical metallurgy of zirconium is similar to titanium which has seen alloying advances allowing application temperatures up to 600 °C. Although the oxidation resistance of zirconium-based alloys is expected to be poor, in a water environment, new Generation-IV and fusion reactors are designed to operate using alternative coolants such as liquid metals and molten salts. Therefore, a new class of zirconium alloys in the Zr-Al-Sn-(Si,Cr,V) system, designed by analogy to near- titanium alloys, were synthesised by arc melting and processed in a sequence of homogenisation, hot/cold rolling, recrystallisation, and ageing treatments. Microscopy and diffraction identified a refined fully lath grain structure reinforced by nanoscale lamellar or discrete coherent Zr3Al precipitates, with morphology and crystal structure differing with ageing times. Additionally alloying with Si, Cr, and V respectively leads to Zr2Si, ZrCr2, and ZrV2 incoherent precipitates. Tensile testing revealed a strengthening effect by Al, but with significant changes to ductility on ageing depending on the evolution of Zr3Al. Creep testing showed creep rates orders of magnitude better than conventional Zircaloy-4 and nuclear ferritic/martensitic steels, approaching near- Ti alloys. The present work offers new insights and perspectives into how high-temperature zirconium alloys might be designed to meet the requirements for fusion and Gen-IV fission.

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Abstract: Nuclear fusion power is the promise of clean energy generation to meet the demands of the new century. However, containing a plasma with a core temperature ten times hotter than that of the sun is no easy task. The confinement vessel must be constructed from resilient materials that can withstand both the heat and the bombardment of the plasma species. ITER is the first proof-of-concept reactor in constructed. This thesis aims to assist in ITER's goals of understanding the complex fundamental plasma-material interactions and developing materials resilient to the harsh reactor conditions in the global push for nuclear fusion energy. The first goal of the thesis aims to investigate the thermodynamic properties of helium (He) bubbles to contribute to the existing understanding and models of He PMI expected in ITER. Bulk W samples were exposed to a low-energy (25 eV) He plasma at 573 K (LT) and 1050 K (HT). After plasma exposure, these samples were subject to TDS, ERDA, SEM, and in-situ TEM annealing. Structures comprised of a network of bubbles were stable up to 998 K during in-situ TEM annealing of the LT sample. He desorption from the LT sample was inferred to stem from interstitial He rather than these bubbles. Bubbles in the HT sample were found to be thermally active up to 998 K, resulting in an increase in the average bubble size and a loss of number density. GISAXS analysis on the effects of annealing on bubble radius distribution produces results consistent with the TEM. An "Ostwald ripening-like" model was proposed to explain the differences in annealing behaviours of the LT and HT samples. In-situ TEM annealing of a HT bulk W sample at 1073 K showed a reconfiguration of lattice atoms to reduce the surface area of large voids left behind after plasma exposure. It is suggested that lattice effects also contribute to the formation of fuzz and require more investigation. The results provided a deeper understanding of the bubble formation mechanism and subsequent thermodynamics based on the plasma exposure temperature. The differences in behaviour observed from these experiments can be used to help explain temperature-dependent effects such as recrystallisation suppression and form a wide set of consistent experiments for computational models to be compared to. The second goal of the thesis is to characterise the He-PMI of three alloys for possible use as a divertor material in future fusion reactors. Four sputter-deposited materials: sputtered pure W (WS), W-5%(wt)Ta, W-3%(wt)Cr, and W-5%(wt)Ta-3%(wt)Cr were exposed to 25 eV He plasma at LT and HT. After plasma exposure, these materials were subject to TDS, ERDA, SEM and TEM. The addition of Ta to Ws and WCr has been shown to inhibit the formation of He bubbles. This may be a case of increasing the fluence threshold for fuzz rather than the complete prevention of fuzz. Additionally, the addition of Ta slows grain growth of both Ws and WCr. This property is intrinsic to Ta rather than from an emergent W-Ta interaction and could potentially be used to delay the undesired but inevitable onset of recrystallisation. The electrical resistivities of the four sputtered films were measured as a surrogate for its thermal conductivity to characterise how this property changes with alloying and He exposure. The alloying of Ta significantly increases the resistivity of W, much more than that of Cr. As expected, He plasma exposure degrades the resistivity regardless of the material. WTaCr has the largest electrical resistivity and suffers the largest increase after He plasma exposure likely due to the presence of both alloying impurities deforming the lattice and serving as trapping sites. Both effects increase probability of electron scattering. The reduction in thermal conductivity from both alloying and He plasma irradiation, especially for alloys with more elements, will have to be considered alongside its other benefits when determining its viability for fusion reactors.

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Abstract: Vacuum-based deposition is a scalable, solvent-free industrial method ideal for uniform coatings on complex substrates. However, all-vacuum-deposited perovskite solar cells fabricated by thermal evaporation trail solution-processed counterparts in efficiency and stability due to film quality challenges, necessitating advancement and improved understanding. Here, we report a co-evaporation route for 1.67-eV wide-bandgap perovskites by introducing a PbCl2 co-source to optimize film quality. We promote perovskite formation with pronounced (100) ‘face-up’ orientation and deliver a certified all-vacuum-deposited solar cell with 18.35% efficiency (19.3% in the laboratory) for 0.25-cm2 devices (18.5% for 1-cm2 cells). These cells retain 80% of peak efficiency after 1,080 h under the ISOS-L-2 protocol. Leveraging operando hyperspectral imaging, we provide spatiotemporal spectral insight into halide segregation and trap-mediated recombination, correlating microscopic luminescence features with macroscopic device performance while distinguishing radiative from non-ideal recombination channels. We further demonstrate 27.2%-efficient 1-cm2 evaporated perovskite-on-silicon tandem cells and outdoor stability of all-vacuum-deposited tandems in Italy, retaining ~80% initial performance after eight months.