The article aims at developing an efficient and stable catalysts for simultaneous hydrogenation of o-chloronitrobenzene to o-chloroaniline and 1,4-butanediol dehydrogenation to γ-butyrolactone. A series of CoO-Cu-MgO catalysts, composed of 10 wt% of copper, various amount of cobalt loadings (1, 5 and 10 wt%) and remaining of MgO were developed by co-precipitation followed by thermal treatment. o-Chloroaniline and γ-butyrolactone were the main products with high yield of 85% and 90%, respectively. The advantage of the coupling process is that the hydrogenation reaction was conducted without external hydrogen, demonstrating minimize the hydrogen consumption known as hydrogen economy route. From N2O characterization results, the high activity of 5CoO-10Cu-MgO was found that it has high amount of Cu species (Cu0/Cu+1) which govern the stable activity and selectivity on time on stream study in presence of cobalt in Cu-MgO.
Based on first-principles methods, the authors of this paper investigate spin thermoelectric effects of one-dimensional spin-based devices consisting of zigzag-edged graphene nanoribbons (ZGNRs), carbon chains and graphene nanoflake. It is found that the spin-down transmission function is suppressed to zero, while the spin-up transmission function is about 0.25. Therefore, an ideal half-metallic property is achieved. In addition, the phonon thermal conductance is obviously smaller than the electronic thermal conductance. Meantime, the spin Seebeck effects are obviously enhanced at the low-temperature regime (about 80K), resulting in the fact that spin thermoelectric figure of merit can reach about 40. Moreover, the spin thermoelectric figure of merit is always larger than the corresponding charge thermoelectric figure of merit. Therefore, the study shows that they can be used to prepare the ideal thermospin devices.
The porous carbon/Ni nanoparticle composite was prepared by a freeze-drying method using NaCl as the template. It was applied in the effect of the concentration, adsorption time, and temperature of adsorption on the adsorption behavior. The kinetic model and the adsorption isothermic fitting results show that the adsorption behavior fits with the pseudo-secondary dynamics and the Langmuir isothermal model, indicating that the adsorption process is monolayer adsorption. Thermodynamic results indicate that the adsorption process is spontaneous physicochemical adsorption. The fitting showed that the porous carbon/Ni nanoparticle composites reach 217.17 mg·g-1, at 313 K indicates good adsorption for Congo red.
In recent years, nanoporous alloys have presented the advantages of a large specific surface area, low density, and simple operation, and they have been widely used in the fields of catalysis, magnetism, and medicine. Nanoporous Pt-Si alloy was prepared by melt-spun and chemical dealloying, and was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope, and transmission electron microscopy. Pt-Si alloys possess a three-dimensional bicontinuous structure and an average size of 5 nanometers. Compared with commercial Pt/C catalysts, nanoporous Pt-Si alloys exhibit excellent electrocatalytic activity and stability in ethanol-catalyzed oxidation reactions. It is taken into consideration to be a promising catalyst in direct ethanol fuel cells.
Ce4+-doped nanometer ZnO powder was synthesized by so-l gel method. The microstructures and properties of the samples were characterized through XRD, UV-Vis and FTIR. The results indicated that the Ce4+ was successfully incorporated into ZnO, and the diameter of the nanometer was about 10.7nm. It induced the redshifting in the UV-Vis spectra. The photocatalytic activity of the samples was investigated using methylene blue (MB) as the model reaction under irradiation with ultraviolet light. The results showed that the doping of Ce4+ could increase the photocatalytic activities of ZnO nanopowders and that the best molar ratio of Ce4+ was n(Ce)/n(Zn) = 0.05, that the surfactant was sodium dodecyl sulfate, and that the nanometer ZnO was calcinated at 550 ℃ for 3 hours. Meanwhile, it inspected the effect of photocatalytic efficiency through the pH of MB, the amount of catalyst, and illumination time. The experimental results revealed that the initial mass concentration of MB was 10 mg/L, that the pH value was 7-8, that the dosage of Ce4+/ZnO photo-catalyst was 5 g/L, that the UV-irradiation time was 2 h, and that the removal rate of MB reached above 85%. Under the optimized conditions, the degradation rate of real dye wastewater was up to 87.67% and the removal efficiency of COD was 63.5%.
We studied Zeta potentials of nanoparticles titanium dioxides (nTiO2) in different concentration of NaNO3 and phosphate (P) solutions. In addition, the effect of flow rate on the transport of nTiO2 in P was investigated at pH=6.5. Experimental results show that the Zeta potential of nTiO2 is compressed with the increasing ion concentration (IC) of NaNO3 at pH=6.5. The negative charge increases with the augment of P. Therefore, the high P and low NaNO3 induce the stabilization of nTiO2 aggregates. The transport experiments suggest that the rapid flow rate is favorable for the transportability of nTiO2 and soluble phosphate. The breakthrough transport curves (BTCs) of nTiO2 in sand columns can be fitted well with two-site kinetic attachment model. The modeling results suggest that the values of first-order attachment rate coefficients (k2) and detachment rate coefficients (k2d) on site 2 and first-order attachment rate coefficients (k1) on site 1 are responsible to the attaching efficiency of nTiO2 on sands and their transportability.
Magnetic graphene oxide nanocomposites (M-GO) were successfully synthesized by partial reduction co-precipitation method and used for removal of Sr(II) and Cs(I) ions from aqueous solutions. The structures and properties of the M-GO was investigated by X-ray diffraction, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, vibrating sample magnetometer (VSM) and N2-BET measurements. It is found that M-GO has 2.103 mg/g and 142.070 mg/g adsorption capacities for Sr(II) and Cs(I) ions, respectively. The adsorption isotherm matches well with the Freundlich for Sr(II) and Dubinin–Radushkevich model for Cs(I) and kinetic analysis suggests that the adsorption process is pseudo-second-ordered.
Heat removal has become an increasingly crucial issue for microelectronic chips due to increasingly high speed and high performance. One solution is to increase the thermal conductivity of the corresponding dielectrics. However, traditional approach to adding solid heat conductive nanoparticles to polymer dielectrics led to a significant weight increase. Here we propose a dielectric polymer filled with heat conductive hollow nanoparticles to mitigate the weight gain. Our mesoscale simulation of heat conduction through this dielectric polymer composite microstructure using the phase-field spectral iterative perturbation method demonstrates the simultaneous achievement of enhanced effective thermal conductivity and the low density. It is shown that additional heat conductivity enhancement can be achieved by wrapping the hollow nanoparticles with graphene layers. The underlying mesoscale mechanism of such a microstructure design and the quantitative effect of interfacial thermal resistance will be discussed. This work is expected to stimulate future efforts to develop light-weight thermal conductive polymer nanocomposites.
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