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The dual-active-site tandem catalyst containing Ru single atoms and Ni nanoparticles boosts CO2 methanation
No full textHydrogenation of CO2 into CH4 is an effective strategy for dealing with CO2-relevant environmental problems. Since the CO2 methanation reaction involves multiple electron transfers and various C-1 intermediates, improving the reaction rate at each step is critical to accelerating the entire reaction. Here, we report a dual-active-site tandem catalyst (Ru1Ni/CeO2) composed of Ru single atoms (Ru-1) and Ni nanoparticles, which can effectively convert CO2 to CH4, showing similar to 90% CO2 conversion and similar to 99% CH4 selectivity at 325 degrees C, much higher than those of the Ru-1/CeO2 and Ni/CeO2 catalysts. Experimental and theoretical calculation results reveal that Ru-1 is extremely active for converting CO2 to CO, while the Ni site is highly efficient for the subsequent sequential CO to CH4 reaction step. The coexistence of the Ru-1 and Ni sites significantly boosts the overall reaction. This work offers a promising strategy for the rational design of efficient multisite tandem catalysts
Digital light processing additive manufacturing of thin dental porcelain veneers
No full textDigital light processing (DLP) 3D printing technology was applied to manufacture thin dental porcelain veneers. The prepared thin dental porcelain veneers showed excellent translucency and appearance. The median and mean particle sizes of the printed glass powders were 10.11 mu m and 12.03 mu m, respectively, with a unimodal distribution. The green glass compacts were printed layer by layer, with an individual layer thickness of 50 mu m. The results showed that, according to the thermal expansion coefficient (TEC) and the thermogravimetry/differential scanning calorimetry (TG/DSC), the debinding procedure of the green glass compacts was annealed at 320 degrees C for 120 min and 570 degrees C for 120 min, respectively. The results of the classical sintering kinetics models and SEM examination demonstrated that the glass compacts were sintered at 790 degrees C for 5 min. The flexural strength and the chemical solubility of the sintered glasses were 132.58 +/- 25.83 MPa and 18 mu m.cm(-2), respectively. Both flexural strength and chemical solubility met ISO 6872 criteria
Computational fluid dynamics simulations of phase separation in dispersed oil-water pipe flows
No full textThe separation of liquid-liquid dispersions in horizontal pipes is common in many industrial sectors. It remains challenging, however, to predict the separation characteristics of the flow evolution due to the complex flow mechanisms. In this work, Computational Fluid Dynamics (CFD) simulations of the silicone oil and water two-phase flow in a horizontal pipe are performed. Several cases are explored with different mixture velocities and oil fractions (15%-60%). OpenFOAM (version 8.0) is used to perform Eulerian-Eulerian simulations coupled with population balance models. The 'blending factor' in the multiphaseEulerFoam solver captures the retardation of the droplet rising and coalescing due to the complex flow behaviour in the dense packed layer (DPL). The blending treatment provides a feasible compensation mechanism for the mesoscale uncertainties of droplet flow and coalescence through the DPL and its adjacent layers. In addition, the influence of the turbulent dispersion force is also investigated, which can improve the prediction of the radial distribution of concentrations but worsen the separation characteristics along the flow direction. Although the simulated concentration distribution and layer heights agree with the experiments only qualitatively, this work demonstrates how improvements in drag and coalescence modelling can be made to enhance the prediction accuracy. (c) 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
Insights into structural and electronic properties of (LiH)n (n=5-25) clusters: Density functional calculations
No full textFirst principles calculations have been performed to analyze the structural and electronic properties of (LiH)n clusters by combining an artificial bee colony algorithm within the framework of Density Functional Theory (DFT). The structural analysis shows that with an increase in cluster size, the structural shape tends to become more amorphous in which the lithium (Li) atom occupies the central position, surrounded by hydrogen (H) atoms at the vertex sites. The bond length between Li and H was found to be 1.77-2.01 angstrom, which is in good agreement with the previous study. Through stability analysis, the calculated formation energy of LiH clusters increase from n = 5 through n = 25. The projected density of states was calculated and analyzed to get deeper insight of the electronic structure. The charge density distribution and results of density derived electrostatic and chemical (DDEC6) analysis revealed ionic bonding characteristics between Li and H atoms, and charge density difference analysis concludes electron transfers from Li to H atoms
Insight into the mechanism of gasification fine slag enhanced flotation with selective dispersion flocculation
No full textCoal gasification fine slag (CGFS) produced in the coal chemical industry has caused severe environmental pollution and resource waste. To realize the utilization of CGFS, we have to efficiently separate unburned carbon (UC) in CGFS. In this work, based on the discovery of the covering between CGFS particles, the selective dispersion flocculation flotation method is proposed to improve the efficient separation of UC from CGFS. The mechanism of selective dispersion flocculation is revealed through adsorption mode, interaction force between particles, and the particle size distribution of floc under different reagent conditions. Results show that a hy-drophilic layer is formed on the surface of ash particles, which hinders the adsorption of PAM and ash particles due to the chemical adsorption of SHMP with ash particles. However, carbon particles are not affected by SHMP and can be directly adsorbed with PAM. This selective adsorption dominates the interaction force of adsorbed particles, and then controls the agglomeration of particles. After selective dispersion flocculation, the original carbon-ash selective agglomeration state is changed to the carbon-carbon selective agglomeration state. D90 of fine carbon particles changed from 110.21 mu m to 356.84 mu m. Compared with the traditional flotation process, the combustible recovery rate of foam products is increased by 10.4 % and loss on ignition (LOI) is increased by approximately 5 %. This work is conducive to fundamentally understanding the mechanism of selective dispersion flocculation. It is helpful to guide the separation of carbon and ash from gasification slag in industry