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1.
In this study, the separation of hydrogen from gas mixtures using a palladium membrane coupled with a vacuum environment on the permeate side was studied experimentally. The gas mixtures composed of H2, N2, and CO2 were used as the feed. Hydrogen permeation fluxes were measured with membrane operating temperature in the range of 320–380 °C, pressures on the retentate side in the range of 2–5 atm, and vacuum pressures on the permeate side in the range of 15–51 kPa. The Taguchi method was used to design the operating conditions for the experiments based on an orthogonal array. Using the measured H2 permeation fluxes from the Taguchi approach, the stepwise regression analysis was also employed for establishing the prediction models of H2 permeation flux, followed by the analysis of variance (ANOVA) to identify the significance and suitability of operating conditions. Based on both the Taguchi approach and ANOVA, the H2 permeation flux was mostly affected by the gas mixture composition, followed by the retentate side pressure, the vacuum degree, and the membrane temperature. The predicted optimal operating conditions were the gas mixture with 75% H2 and 25% N2, the membrane temperature of 320 °C, the retentate side pressure of 5 atm, and the vacuum degree of 51 kPa. Under these conditions, the H2 permeation flux was 0.185 mol s?1 m?2. A second-order normalized regression model with a relative error of less than 7% was obtained based on the measured H2 permeation flux.  相似文献   
2.
Novel Ln-MOF with microrods shape were successfully combined with ZnIn2S4 (ZIS) microsphere and used for photocatalytic hydrogen generation under UV–Vis and visible light. The Ln-MOFs/ZIS system comprises lanthanide-carboxylate coordination networks (Tm and Gd as metal ions, and 1,3,5-benzenetricarboxylic acid (BTC) as the organic linker) deposited on ZnIn2S4 microspheres. Effect of the amount of ((Tm,Gd)-BTC) (1, 5, 10 wt%) on the optical properties and photocatalytic hydrogen evolution performance was investigated. ZIS microsphere shows the marigold flower-like morphology and hexagonal polytopic crystal form. Our results proved that the combination of ZIS microsphere, Ln-MOF and Pt nanoparticles (NPs) caused significant enhancement in hydrogen generation. Amount of formed hydrogen was raised from 196.3 to 7782.1 μmol g?1 for pristine ZIS and ZIS decorated with 1% (Tm, Gd)-BTC/Pt under UV–Vis light, respectively.  相似文献   
3.
Micro-cracks commonly occur on the catalyst layers (CLs) during the manufacturing of catalyst coated membranes (CCMs). However, the crack shape parameters effect on CLs in-plane (IP) electronic conductivity λs is not clear. In this work, the relationship between crack parameters and the λs is obtained based on the two-dimensional (2D) multiple-relaxation time (MRT) lattice Boltzmann method (LBM). The LBM numerical model is validated by the normalized λs experiment applied on three different home-made cracked CLs, and the parameter study focus on crack width, length, quantity and phase angle are carried out. The results show that the decrease of λs has different sensitivity |k| to the parameters above. The crack width has little effect on λs decrease, and the |kw| is 0.038. However, crack arm length and quantity show more significant impact, which |kl| and |kN| are 0.753 and 0.725, respectively. The CLs with different crack propagation directions show significant anisotropy on λs, and a 53.53% decrease in λs is observed between 0° and 90° crack phase angle change. To manufacture a high electronic conductivity CL, crack initiation and migration mitigation are highly encouraged.  相似文献   
4.
To the best of our knowledge, this is the first time to report the preparation of a dotted nanowire arrayed by 5 nm sized palladium and nickel composite nanoparticles (denoted as PdxNiy NPs) via a hydrothermal method using NU and PdO·H2O as the starting materials. The samples prepared at the mass ratio of NU to PdO·H2O 1:1, 1:2 and 2:1 were, respectively, nominated as catalyst c1, c2 and c3. The chemical compositions of all synthesized catalysts were mainly studied by using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), revealing that metallic Ni was one main component of all prepared catalysts. Surprisingly, the main diffraction peaks appearing in the XRD patterns of all prepared catalysts were assigned to the metallic Ni rather than the metallic Pd. Very interestingly, as indicated by the TEM images, a large number of dotted nanowires arrayed by numerous equidistant 5 nm sized nanoparticles were distinctly exhibited in catalyst c1. More importantly, when being used as electrocatalysts for EOR, all prepared catalysts exhibited an evident electrocatalytic activity towards EOR. In the cyclic voltammetry (CV) test, the peak current density of the forward peak of EOR on catalyst c1 measured at 50 mV s?1 was as high as 56.1 mA cm?2, being almost 9 times higher than that of EOR on catalyst c3 (6.3 mA cm?2). Particularly, the polarized current density of EOR on catalyst c1 at 3600 s, as indicated by the chronoamperometry (CA) experiment, was still maintained to be around 1.47 mA cm?2, a value higher than the latest reported data of 1.3 mA cm?2 (measured on the pure Pd/C electrode). Presenting a novel method to prepare dotted nanowires arranged by 5 nm sized nanoparticles and showing the significant eletrocatalytic activities of the newly prepared dotted nanowires towards EOR were the major contributions of this preliminary work.  相似文献   
5.
The spongy nickel oxide (SNO) was synthesized the solution combustion method. The SNO was selected as a promoter to boost the catalytic activity of nanoraspberry-like palladium (NRPd) toward electrooxidation of five light fuels (LFs): methanol, ethanol, formaldehyde, formic acid, and ethylene glycol. The X-ray powder diffraction, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy, and field emission scanning electron microscope techniques were used for the materials characterization. In comparison with nonpromoted Pd, the NRPd-SNO electrocatalyst shown an excellent efficiency in parameters like the electrochemical active surface area and anti-CO poisoning behavior. The turnover data and the parameters, including reaction order, activation energy, and the coefficients of electron transfer and diffusion, were evaluated for the each process of LFs electrooxidation. The outcome for NRPd-SNO activity toward LFs electrooxidation was compared to some reported electrodes. The SNO increases the removal of intermediates created in the oxidation of LFs that can poison the surface of palladium catalyst. This is due to the presence of the lattice oxygens in SNO structure and Ni switching between its high and low valances. The compatibility of the adsorption process of LFs on the surface of the NRPd-SNO catalyst with different isotherms was determined by studying the Tafel polarization and calculating the surface coverage.  相似文献   
6.
《Ceramics International》2022,48(15):21317-21326
1T phase molybdenum disulfide (1T-MoS2) has aroused extensive concern in energy storage devices such as supercapacitors due to its large interlayer spacing, high conductivity and good hydrophilicity. However, it is struggle to synthesize 1T-MoS2 with stable 1T phase with high content. Herein, Ammonium ion intercalation molybdenum disulfide (A-MoS2) with high 1T content and stable 3D microsphere structure was successfully synthesized using a facile hydrothermal method. We explained the feasibility of ammonium ion (NH4+) intercalation through density functional theory (DFT) calculations and proved the successful intercalation of NH4+ by XRD and XPS. Through XPS fitting, the 1T phase content is calculated as high as 83.1%. The as-prepared A-MoS2 presents a stable 3D microsphere structure with the interlayer spacing expanded to 0.93 nm, which provides a wide ion diffusion channel that allows ions to pass through quickly. Moreover, the high 1T content increases the hydrophilicity of MoS2, thereby improving the wettability of the electrode, which contributes to the interaction between the electrolyte and electrode. In 1 M Na2SO4, A-MoS2 electrode material displays high specific capacitance of 228 F g?1 at 5 mV s?1 and retains 127 F g?1 at 80 mV s?1, which proves the good rate capability. Furthermore, the assembled α-MnO2//A-MoS2 asymmetric supercapacitor (ASC) displayed a wide operating voltage of 2.1 V. The assembled ASC displays a high energy density of 35.8 Wh?kg?1 at a power density of 525.0 W kg?1, which indicates excellent energy storage performance.  相似文献   
7.
《Ceramics International》2022,48(24):36860-36870
For the advantages of high-temperature resistance, corrosion resistance and ultra-high hardness, SiCf/SiC composite is becoming a preferred material for manufacturing aero-engine parts. However, the anisotropy and heterogeneity bring great challenges to the processing technology. In this study, a nanosecond pulsed laser is applied to process SiCf/SiC composite, where the influence of the scanning speed and laser scanning direction to the SiC fibers on the morphology of ablated grooves is investigated. The surface characteristics after ablation and the involved chemical reaction of SiCf/SiC are explored. The results show that the increased laser scanning speed, accompanied by the decreasing spot overlap rate, leads to the less accumulation of energy on the material surface, so the ablation effect drops. In addition, for the anisotropy of the SiCf/SiC material, the obtained surface characteristics are closely dependent on the laser scanning direction to the SiC fibers, resulting in different groove morphology. The element composition and phase analysis of the machined surface indicate that the main deposited product is SiO2 and the carbon substance. The results can provide preliminary technical support for controlling the machining quality of ceramic matrix composites.  相似文献   
8.
A appropriate size with three-dimension(3 D) channels for lithium diffusion plays an important role in constructing highperforming LiNi_(0.5)Mn_(1.5)O_4(LNMO) cathode materials, as it can not only reduce the transport path of lithium ions and electrons, but also reduce the side effects and withstand the structural strain in the process of repetitive Li~+ intercalation/deintercalation. In this work, an e fficient method for designing the hollow LNMO microsphere with 3 D channels structure by using polyethylene oxide(PEO) as soft template agent assisted solvothermal method is proposed. Experimental results indicate that PEO can make the reagents mingle evenly and nucleate slowly in the solvothermal process, thus obtaining a homogeneous distribution of carbonate precursors. In the final LNMO products, the hollow 3 D channels structure obtained by the decomposition of PEO and carbonate precursor in the calcination can provide abundant electroactive zones and electron/ion transport paths during the charge/discharge process, which benefits to improve the cycling performance and rate capability. The LNMO prepared by adding 1 g PEO possesses the most outstanding electrochemical performance, which presented an excellent discharge capacity of 143.1 mAh g~(-1) at 0.1 C and with a capacity retention of 92.2% after 100 cycles at 1 C. The superior performance attributed to the 3 D channels structure of hollow microspheres, which provide uninterrupted conductive systems and therefore achieve the stable transfer for electron/ion.  相似文献   
9.
A digital light processing (DLP) technology has been developed for 3D printing lead-free barium titanate (BTO) piezoelectric ceramics. By comparing the curing and rheological properties of slurries with different photosensitive monomer, a high refractive index monomer acryloyl morpholine (ACMO) was chosen, and a design and preparation method of BTO slurry with high solid content, low viscosity and high curing ability was proposed. By further selecting the printing parameters, the single-layer exposure time was reduced and the forming efficiency has been greatly improved. Sintered specimens were obtained after a nitrogen-air double-step debinding and furnace sintering process, and the BTO ceramics fabricated with 80 wt% slurry shows the highest relative density (95.32 %) and piezoelectric constant (168.1 pC/N). Furthermore, complex-structured BTO ceramics were prepared, impregnated by epoxy resin and finally assembly made into hydrophones, which has significance for the future design and manufacture of piezoelectric ceramic-based composites that used in functional devices.  相似文献   
10.
Hook and claw pumps are used for recirculation of excess hydrogen in fuel cells. Optimization of the pump design is essential. Computational Fluid Dynamic (CFD) is an effective method for performance optimization. However, it is difficult to conduct CFD simulation because of the sharp cusp of the rotor profile. Cut cell Cartesian mesh could be the solution to handle this complex and moving geometries. The aim of this paper is to evaluate ANSYS Forte for hook and claw pumps. Firstly, the conservation accuracy of the cut cell cartesian mesh is verified using an adiabatic piston cylinder case. Then, simulation results of hook and claw type pump are compared with experimental data. Finally, simulation results of air and hydrogen are compared. The results show that the CFD simulation of hook and claw pumps using cut cell cartesian mesh could provide an efficient and effective approach for the optimization of the system.  相似文献   
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