Carbon deposition on transition metal- and uranium-oxides

Advanced gas cooled nuclear reactors (AGRs) contain a range of alloys, selected for their physical and chemical performance in the conditions present. Carbon deposition on boiler and fuel pin heat transfer surfaces affects a reactor's efficiency and may necessitate downrating to maintain safety margins. This is believed to arise from decomposition of some of the coolant gas constituents. Deposition minimisation, while maintaining the structural integrity of the reactor, is technologically and economically important. This study has looked at deposition on a range of transition metal spinels, manganese oxides, uranium oxides and single crystal magnetite samples with a view to furthering knowledge of catalytic reactions that may occur within an AGR. In particular, the effect of mixed valency on deposition rates was studied. The spinels were successfully prepared by solid state reactions between the relevant oxides, oxalates and I or carbonates. A range of elemental and chemical analytical techniques were used to characterise the samples both before and after exposure under controlled gas and radiological conditions. Deposition was induced, to varying extents, on all the samples exposed. No filamentary deposits were observed. The spinels gave quantities of deposition in the order: Manganese spinels gave increasing deposition with increasing manganese content at 650°C, but decreasing deposition at 550°C. Iron-cobalt spinels showed no consistent increase or decrease in carbon deposition with changing composition. Nickel rich spinels were unstable in the reaction gas mixture and generated metallic nickel during exposure. At both temperatures, this gave levels of carbon deposition which increased with increasing nickel content of the original oxide. NiF~04 exposed at 550°C fragmented as it catalysed carbon formation. Manganese oxides converted to MnO during exposure, MnO proving also to be a most effective catalyst. Mn304' an Mn2+ I Mn3+ compound where the manganese ions do not form an electron exchanging octahedrally coordinated pair, did not yield large quantities of deposit. The uranium oxides examined converted to the interacting mixed valence U409' which gave copious carbon deposition. The U4+ I U6+ non interacting mixed valence Ot-U30 S gave the least deposition. Magnetite slices gave laminar carbon deposits, but no filamentary growth. Structured deposit was seen in two cases, including on one face oriented approximately parallel to the [111] plane, the plane previously expected to catalyse deposition most effectively

Catalytic Reductive Degradation of Methyl Orange Using Air Resilient Copper Nanostructures

The study describes the application of oxidation resistant copper nanostructures as an efficient heterogeneous catalyst for the treatment of organic dye containing waste waters. Copper nanostructures were synthesized in an aqueous environment using modified surfactant assisted chemical reduction route. The synthesized nanostructures have been characterized by UV-Vis, Fourier transform infrared spectroscopy FTIR spectroscopy, Atomic force microscopy (AFM), Scanning Electron Microscopy (SEM), and X-ray diffractometry (XRD). These surfactant capped Cu nanostructures have been used as a heterogeneous catalyst for the comparative reductive degradation of methyl orange (MO) in the presence of sodium borohydride (NaBH4) used as a potential reductant. Copper nanoparticles (Cu NPs) were found to be more efficient compared to copper nanorods (Cu NRds) with the degradation reaction obeying pseudofirst order reaction kinetics. Shape dependent catalytic efficiency was further evaluated from activation energy (EA) of reductive degradation reaction. The more efficient Cu NPs were further employed for reductive degradation of real waste water samples containing dyes collected from the drain of different local textile industries situated in Hyderabad region, Pakistan

Transport at work Rollover of lorries transporting paper reels

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Acetylsalicylic acid assisted hydrothermal growth of NiO, CuO and Co3O4 nanostructures and their application in the electro-catalytic determination of nalbuphine hydrochloride

This study describes the hydrothermal synthesis of NiO, CuO and Co3O4 nanostructures using acetylsalicylic acid (ASA) as a growth-controlling/directing agent. The as-synthesised nanostructures were shown to possess unique structural features and distinct morphologies, portraying the efficiency of ASA as a suitable growth modifier. The formed metal oxide nanostructures, when used for electrode modification purposes, exhibited excellent electrocatalytic capabilities against the oxidation of nelbuphine hydrochloride (NAL) in aqueous buffer solution. The modified electrodes exhibited distinct electrochemical characteristics, with CuO-based electrodes exhibiting a superior signal sensitivity and lower over-potential value compared to the NiO and Co3O4 nanostructures. The study further explores the variation in the observed electro-catalytic oxidation signal referenced to the distinct morphologies of the metal oxides nanostructures. The CuO-based electrode was selected for the sensitive quantification of NAL in aqueous solution over the linear range 0.001-2.25 mu M. The electrode demonstrated excellent working linearity, with signal sensitivity achieved down to 1 x 10(-4) mu M. Moreover, the successful quantification of NAL in complex matrices, such as human urine and clinical waste water, further reflected the analytical capability of the proposed sensor

NiWO4-induced partial oxidation of MXene for photo-electrochemical detection of prostate-specific antigen

MXene-based hybrid composites are gaining substantial attention due to their impressive chemical and electronic characteristics. Herein, an in-situ engineered heterojunction is constructed using partially-oxidised Ti3C2Tx sheets and photo-active NiWO4 nanoparticles (NPs). The NiWO4 NPs were used to induce partial surface oxidation of Ti3C2Tx, resulting in the formation of a Ti3C2Tx-TiO2/NiWO4 hybrid composite (MX-NiWO4). The electrocatalytic and photo-electrochemical (PEC) characteristics of MX-NiWO4 were studied in reference to the reduced graphene oxide-NiWO4 (rGO-NiWO4) and H2O2-treated Ti3C2Tx (MX-H2O2) hybrids. The MX-NiWO4, based on its in-situ driven configuration, constructed an ideal interfacial arrangement for the electrocatalytic mechanism-based PEC immuno-sensing of prostate-specific antigens (PSA). The developed PEC biosensor was capable of detecting PSA, over a wide detection range of 1.2 fg.mL(-1) to 0.18 mg.mL(-1), with a detection limit of 0.15 fg.mL(-1). The synergic integration of Ti3C2Tx with photo-active NiWO4 offers a superior signal response and practical applicability when used for the quantification of PSA from human saliva samples, anticipating the hybrid's promising future in clinical detection

NiWO4-induced partial oxidation of MXene for photo-electrochemical detection of prostate-specific antigen

MXene-based hybrid composites are gaining substantial attention due to their impressive chemical and electronic characteristics. Herein, an in-situ engineered heterojunction is constructed using partially-oxidised Ti3C2Tx sheets and photo-active NiWO4 nanoparticles (NPs). The NiWO4 NPs were used to induce partial surface oxidation of Ti3C2Tx, resulting in the formation of a Ti3C2Tx-TiO2/NiWO4 hybrid composite (MX-NiWO4). The electrocatalytic and photo-electrochemical (PEC) characteristics of MX-NiWO4 were studied in reference to the reduced graphene oxide-NiWO4 (rGO-NiWO4) and H2O2-treated Ti3C2Tx (MX-H2O2) hybrids. The MX-NiWO4, based on its in-situ driven configuration, constructed an ideal interfacial arrangement for the electrocatalytic mechanism-based PEC immuno-sensing of prostate-specific antigens (PSA). The developed PEC biosensor was capable of detecting PSA, over a wide detection range of 1.2 fg.mL(-1) to 0.18 mg.mL(-1), with a detection limit of 0.15 fg.mL(-1). The synergic integration of Ti3C2Tx with photo-active NiWO4 offers a superior signal response and practical applicability when used for the quantification of PSA from human saliva samples, anticipating the hybrid's promising future in clinical detection

Functionalised CuO nanostructures for the detection of organophosphorus pesticides: A non-enzymatic inhibition approach coupled with nano-scale electrode engineering to improve electrode sensitivity

This study explores the potential of a newly-developed indium tin oxide (ITO) based electrode for the development of an electro-catalytic inhibition sensor system for organophosphorus pesticides. The sensor relies on the redox signal inhibition of pralidoxime chloride (PAM) immobilised over the pimelic acid functionalised CuO nanostructures grown in-situ over an ITO substrate. The in-situ growth enabled on-pot modification and functionalisation of ITO electrodes with the formation of uniform nanostructures possessing high surface area and excellent interface contact. The versatility of the proposed electrode was evident from its excellent electrochemical characteristics evaluated in comparison to bare and slurry-driven glassy carbon electrodes (GCEs). The high structural uniformity and greater surface coverage achieved by in-situ growth provided a uniform surface environment for electrode-analyte interaction, leading to good inhibition signal sensitivity and repeatability. The developed sensor was successful in detecting chlorpyrifos, fenthion and methyl parathion within the concentration range of 0.01-0.16 mu M with signal sensitivity reaching down to 1.6 x 10(-9), 2.5 x 10(-9) and 6.7 x 10(-9) M respectively. Moreover, the proposed sensor demonstrated excellent applicability when tested for chlorpyrifos from vegetable extracts using a standard addition method. (c) 2018 Elsevier B.V. All rights reserved