The development of a novel Al matrix composite is described based on a simple displacement reaction when II SiO2 particulate preform is brought into contact with liquid AZ at: temperatures between 1273 and 1373 K. Thi...
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The development of a novel Al matrix composite is described based on a simple displacement reaction when II SiO2 particulate preform is brought into contact with liquid AZ at: temperatures between 1273 and 1373 K. This interaction leads to the wetting of the SiO2 particles by Al and its eventual transformation to a composite with Al2O3/AI particles in an Al matrix. Infiltration of the preform as induced by this reaction takes place with the simultaneous formation of the Al2O3/Al particles in situ. Synthesis of engineered multiphase composites, wherein reinforcements of other materials incorporated into the preform and reacted with liquid Al, is also presented.
Lithium ion batteries have revolutionized the portable electronics market, and they are being intensively pursued now for transportation and stationary storage of renewable energies like solar and wind. The success of...
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Lithium ion batteries have revolutionized the portable electronics market, and they are being intensively pursued now for transportation and stationary storage of renewable energies like solar and wind. The success of lithium ion technology for the latter applications will depend largely on the cost, safety, cycle life, energy, and power, which are in turn controlled by the component materials used. Accordingly, this Perspective focuses on the challenges and prospects associated with the electrode materials. Specifically, the issues associated with high-voltage and high-capacity cathodes as well as high-capacity anodes and the approaches to overcome them are presented.
One of the greatest challenges in surface enhanced Raman scattering (SERS) sensing is to detect biochemicals directly from suspension with ultrasensitivity. In this work, we employed strategically designed longitudina...
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We report a mechanistic understanding of a moisture-driven intermediate-phase transition that improves the quality of perovskite thin films based on a lead-acetate precursor, improving the power-conversion effidency. ...
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We report a mechanistic understanding of a moisture-driven intermediate-phase transition that improves the quality of perovskite thin films based on a lead-acetate precursor, improving the power-conversion effidency. We clarify the composition of the intermediate phase and attribute the transition of this phase to the hygroscopic nature of the organic product, i.e., methylammonium acetate. Thermal annealing aids in the coarsening of the grains. These decoupled processes result in better crystal formation with a lower spatial and energetic distribution of traps. Thermal annealing of the films without exposure to air results in a faster intermediate-phase transition and grain coarsening, which occur simultaneously, leading to disorder in the films and a higher deep trap-state density. Our results indicate the need for a humid environment for the growth of high-quality perovskite films and provide insight into intermediate-phase dissociation and conversion kinetics. Thus, they are useful for the large-scale production of effident solution-processed perovskite solar cells.
The growth of nickel oxide films has attracted much attention over the years, and various diffusion mechanisms have been proposed to model the process. The popular techniques used to study the mass transport mechanism...
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The growth of nickel oxide films has attracted much attention over the years, and various diffusion mechanisms have been proposed to model the process. The popular techniques used to study the mass transport mechanisms have been Auger electron spectroscopy and secondary ion mass spectroscopy (SIMS). Another approach that has been suggested is the study of isotope separation during thin film growth. This type of analysis can give the mechanism of reaction during the film growth and is the technique used in this study. A normal isotope separation implies either grain boundary or lattice diffusion, whereas a reverse separation explicity implies grain boundary diffusion. This study looks at nickel oxides grown on polycrystalline nickel at 400, 600 and 800°C, and which range from 1.5 to 18 μm in thickness. Oxides were grown under atmospheric oxygen partial pressure conditions. X-ray diffraction was used to determine the nature of the oxide, and SIMS, in conjunction with Auger spectroscopy and argon ion sputtering, was used to determine the isotope separation if any. It was found that the oxide grown at 800°C exhibited reverse isotope separation, whereas the oxides grown at lower temperatures showed normal separation. Simplified calculations of the chemical diffusion coefficients of nickel in nickel oxide have also been made at the temperatures of interest, and activation energies ranging from 55.2 to 190.4 kJ mol -1 were obtained.
As the chiral drug market grows, developing efficient separation methods while ensuring quality has become a key focus for the pharmaceutical industries. Chiral column chromatography is effective but often impractical...
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Al matrix composites reinforced with micro-composite Al2O3/Al particles were synthesized by reactive infiltration of molten Al into preforms of particulate SiO2 or Mg + SiO2 mixtures at 1075 degrees C. Displacement re...
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Al matrix composites reinforced with micro-composite Al2O3/Al particles were synthesized by reactive infiltration of molten Al into preforms of particulate SiO2 or Mg + SiO2 mixtures at 1075 degrees C. Displacement reactions between silica and magnesium containing oxides lead to in-situ formation of the reinforcements and also aid the infiltration of the melt. In the presence of Mg, it was found that the consistency of infiltration was better and that the transformation of silica to alumina involved intermediate displacement reactions unlike the single step reaction without Mg in the preform. It was observed that the morphology and size scale of the micro-composite Al2O3/Al particles were affected by the presence of Mg. Without Mg a finer scale Al2O3/Al microstructure with a tendency to be elongated in the growth direction formed, while a coarser morphology with interconnectivity in both phases developed from Mg + SiO2 preforms. Potential for such microstructural variations of the reinforcements permits control of the overall mechanical properties of the composite. (C) 1997 Acta Metallurgica Inc.
Ammonia is a key feedstock of fertilizers for farming and convenient hydrogen carrier as an emerging clean fuel,but industrial ammonium production process,Haber-Bosch reaction,is an energy-intensive process,consuming...
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Ammonia is a key feedstock of fertilizers for farming and convenient hydrogen carrier as an emerging clean fuel,but industrial ammonium production process,Haber-Bosch reaction,is an energy-intensive process,consuming 1%–2%of global energy and producing 3%global *** nitrogen reduction reaction(NRR)is one of the most promising routes to realize highly efficient NH3 production under ambient ***,up to now,few precious-metal-free electrocatalysts with desirable catalytic performance have been *** this work,Mo2C nanodots anchored on three-dimensional ultrathin macroporous carbon(Mo2C@3DUM-C)framework is developed toward significantly enhanced nitrogen reduction *** to the special structural design of 3D ultrathin macroporous carbon and highly active and stable Mo2C toward N2 electrochemical reduction,the Mo2C@3DUM-C framework exhibits a high Faradaic efficiency of 9.5%for NH3 production at−0.20 V and the yield rate reaches 30.4µg h−1 mgMo2C−*** electrochemical characterizations reveal the enhanced electron transfer and increased electrochemical surface area in the 3D macroporous carbon ***,the Mo2C@3DUM-C electrocatalysts hold high catalytic stability after long-term NRR *** temperature-dependent yield rate of NH3 demonstrates that the activation energy of nitrogen reduction on the employed catalyst was calculated to be 28.1 kJ mol−*** proposed earth-abundant Mo2C@3DUM-C demonstrates an alternative insight into developing efficient and stable nitrogen fixation catalysts in acids as alternatives to noble metal catalysts.
Rechargeable Li-ion batteries were first commercialized in 1991 by Sony company,and the current portable electronic devices and electric vehicles powered by rechargeable batteries have significantly accelerated the de...
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Rechargeable Li-ion batteries were first commercialized in 1991 by Sony company,and the current portable electronic devices and electric vehicles powered by rechargeable batteries have significantly accelerated the development of social *** Nobel Prize in Chemistry 2019 was also awarded jointly to John ***,*** Whittingham,and Akira Yoshino for their outstanding contribution to rechargeable Li-ion batteries.
Recent advances in the field of two-dimensional(2D)materials have led to new electronic and photonic devices enabled by their unique properties at atomic *** 2D materials into desired patterns on substrates is often a...
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Recent advances in the field of two-dimensional(2D)materials have led to new electronic and photonic devices enabled by their unique properties at atomic *** 2D materials into desired patterns on substrates is often an essential and foremost step for the optimum performance of the functional *** this regard,optical patterning of 2D materials has received enormous interest due to its advantages of high-throughput,site-specific,and on-demand *** years have witnessed scientific reports of a variety of optical techniques applicable to patterning 2D *** this minireview,we present the state-of-the-art optical patterning of 2D materials,including laser thinning,doping,phase transition,oxidation,and *** applications based on optically patterned 2D materials will be discussed as *** further developments,optical patterning is expected to hold the key in pushing the frontiers of manufacturing and applications of 2D materials.
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