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Heterojunctioned CuO/Cu 2 O catalyst for highly efficient ozone removal
No full textIn recent years, near surface ozone pollution, has attracted more and more attention, which necessitates the development of high efficient and low cost catalysts. In this work, CuO/Cu 2 O heterojunctioned catalyst is fabricated by heating Cu 2 O at high temperature, and is adopted as ozone decomposition catalyst. The results show that after Cu 2 O is heated at 180 ??C conversion of ozone increases from 75.2% to 89.3% at mass space velocity 1,920,000 cm 3 /(g ??hr) in dry air with 1000 ppmV ozone, which indicates that this heterojunction catalyst is one of the most efficient catalysts reported at present. Catalysts are characterized by electron paramagnetic resonance spectroscopy and ultraviolet photoelectron spectroscopy, which confirmed that the heterojunction promotes the electron transfer in the catalytic process and creates more defects and oxygen vacancies in the CuO/Cu 2 O interfaces. This procedure of manufacturing heterostructures would also be applicable to other metal oxide catalysts, and it is expected to be more widely applied to the synthesis of high-efficiency heterostructured catalysts in the future. ?? 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V
Fabrication of Ti-6Al-4V alloy powder by a novel sintering-deoxygenation process
No full textGiven the high cost of fabricating the Ti-6Al-4V alloy powder by the traditional hydriding-dehydriding and atomization methods, a novel sintering-deoxygenation process was proposed and studied in this research. With the help of the developed deoxygenation treatment, value-added raw materials such as Ti sponge can be substituted by low-cost and low-grade materials with high oxygen content. In addition, sintering in a solid state saves a significant amount of processing energy compared to alloying above the melting point of Ti in the conventional alloy production process. This paper prepared six sintering precursors with different initial compositions and oxygen contents using the low-valued raw materials of crude titanium, crude vanadium, V2O3, Al powder, and Al2O3 powder. These precursors' sintering performances on shrinkage, phase composition, microstructure, and porosity were investigated. The results show that the sintering shrinkage is positively correlated with the sintering temperature and holding time and is also affected by the raw materials. The pellet made by mixed crude titanium and AlV master alloy showed the largest shrinkage and the densest bulk. The various combinations of the raw materials led to the changes in the oxygen contents in the precursors, the alpha-beta phase ratio, and the shift of the diffraction peaks of the alpha-phase. The dissolving of the AlV master alloy and the formation of the Ti3Al intermediate phase took place during sintering due to diffusion. Sintering at 900-1000 degrees C is critical for elemental diffusion and densifi-cation, and sintering at higher temperatures is decisive for microstructure homogenization and further densification. Using the hydrogen-assisted Mg deoxygenation method, all the sintered samples could be treated to an oxygen level of around 0.4 wt% regardless of oxygen content in precursors. The contents of Ti, Al, V, and Fe in the obtained Ti-6Al-4V powders met the requirements of GB/T 34486-2017. This research has demonstrated the feasibility of fabricating Ti-6Al-4V alloy powder by the novel sintering-deoxygenation process.(c) 2022 Elsevier B.V. All rights reserved
Effect of mesoscale structures on solid phase stress in gas-solid flows
No full textSolid phase stress plays an important role in hydrodynamic modeling and simulations of gas-solid flows. However, heterogeneous gas-solid flows are typically regarded as homogeneous systems. Their solid phase stresses are usually calculated by the classical kinetic theory of granular flow (KTGF) without considering mesoscale structures, which is a major source of inaccuracies. This work investigates the effect of mesoscale structures in gas-solid flows via a dilute-dense two-phase partition, and proposes a phase-specific model to predict solid phase stress. Subsequently, the sensitive of threshold for phase partition is discussed, and a specific threshold is utilized in the proposed model to investigate the effect of mesoscale structures on solid phase stress with large-scale particle-resolved direct numerical simulation (PR-DNS) data. Numerical results show that classical KTGF underestimates the solid phase stress due to the ignorance of these structures
Quantum chemistry insight into the interactions of 1,3-diisopropoxycalix[4]arenecrown-6 with alkali metal cations: Structure, selectivity, and solvation
No full textDouble-hybrid functional PWPB95-D3 with precise description of dispersion is employed to calculate the thermodynamic properties of complexes with 1,3-Diisopropoxycalix[4]arenecrown-6 (BPC6) and alkali metal cations (Li', Na', K', Rb', and Cs') in the gas phase and solutions (chloroform, methanol, and ace-tonitrile). Moreover, symmetry-adapted perturbation theory (SAPT) and IGM based on Hirshfeld partition of molecular density (IGMH) are for the first time used to reveal the interactions of complexes due to the accuracy energy decomposition and markedly graphical effect, respectively. For the complexes of BPC6 with alkali metal cations in the gas phase, the electrostatic energy takes up nearly 70% of the total energy. The electrostatics energy dominated attractive part of the interaction energy. The dielectric screen of sol-vents leads to the decrease of the absolute value of binding Gibbs free energy (|AG|). The protic solvent provides a further decrease of |AG|. The |AG| of each M'/BPC6 complex in solvents follow the order of | AG|(gas) > |AG|(chloroform) > |AG|(acetonitrile) > |AG|(methanol). In complex Cs'/BPC6, the ratio of dis-persion is as high as 26%. Thus, the dispersion interaction is non-negligible for complexation with large cations in the solvents. Because the AG of complex Cs'/BPC6 is less affected by solvation effect than that of other cations, Cs'/BPC6 is the most stable complex in all the three solvents. The |AG| of complexes with alkali metal cations decreases with the increase of the cationic radii in the gas phase, and increases with that in the solvent solutions. The regulars of |AG| are well match that of the experimental results in literatures.(c) 2022 Elsevier B.V. All rights reserved
Rubber-Composite-Nanoparticle-Modified Epoxy Powder Coatings with Low Curing Temperature and High Toughness
No full textIn this study, a rubber-composite-nanoparticle-modified epoxy powder composite coating with low curing temperature and high toughness was successfully fabricated. The effects of N,N-dimethylhexadecylamine (DMA) carboxy-terminated nitrile rubber (CNBR) composite nanoparticles on the microstructure, curing behavior, and mechanical properties of epoxy-powder coating were systematically investigated. SEM and TEM analysis revealed a uniform dispersion of DMA-CNBR in the epoxy-powder coating, with average diameter of 100 nm. The curing temperature of the epoxy-composite coatings had reduced almost 19.1% with the addition of 1phr DMA-4CNBR into the coating. Impact strength tests confirmed that DMA-CNBR-modified epoxy-composite coatings showed significant improvements compared with the neat EP coating, which was potentially attributed to the nanoscale dispersion of DMA-CNBR particles in epoxy coatings and their role in triggering microcracks. Other mechanical properties, including adhesion and cupping values, were improved in the same manner. In addition, thermal and surface properties were also studied. The prepared epoxy composite powder coating with the combination of low curing temperature and high toughness broadened the application range of the epoxy coatings
High performance BaCO3-CeO2 composite catalyst for solvent-free selective oxidation of cyclohexane with molecular oxygen
No full textBaCO3-CeO2 composite catalysts were prepared by the hydrothermal synthesis method, and the influence of Ba/ Ce on the structural and catalytic performance for selective oxidation of cyclohexane with molecule oxygen was studied. The characterization results exhibited that the doping amount of BaCO3 would influence the morphology, the content of surface Ce3+ and surface oxygen species (O beta), and alkalinity. Meanwhile, the amount of alkali is the key to the decomposition of cyclohexyl hydrogen peroxide (CHHP). 10.5% conversion of cyclohexane and 85.0% selectivity of KA oil were achieved under the reaction conditions of 1.0 MPa O2 and 150 degrees C for 2 h. The excellent catalytic activity was attributed to its high atomic ratios of Ce3+/Cetotal and O beta/Ototal on the surface and optimal redox capacity
Fabrication of MgO-Y2O3 Composite Nanopowders by Combining Hydrothermal and Seeding Methods
No full textIn this study, the combination of hydrothermal technique and seed-doping method was conducted to coordinately control the formation of fine MgO-Y2O3 powders, which are promising mid-infrared materials applied to hypersonic aircraft windows due to their excellent infrared transmissions over wide regions. Y(NO3)(3)center dot 6H(2)O, Mg(NO3)(2)center dot 6H(2)O, Y2O3 seeds and MgO seeds were used as raw materials to prepare the MgO-Y2O3 composite powders (50:50 vol.%), and the influences of the seed contents and hydrothermal treatment temperatures on the final powders and hot-pressed ceramics were investigated by XRD, SEM and TEM techniques. The results show that powders with a seed content of 5% that are hydrothermally synthesized at 190 degrees C can present a better uniformity and dispersion with a particle size of similar to 125 nm. Furthermore, the ceramics prepared with the above powders displayed a homogenous two-phase microstructure, fewer pores and a fine grain size with Y2O3 of similar to 1 mu m and MgO of similar to 620 nm. The present study may open an avenue for developing transparent ceramics based on MgO-Y2O3 nanopowders prepared by hydrothermal technique