Nanostructured mixed transition metal oxides for high performance asymmetric supercapacitors: Facile synthetic strategy

Exceptionally simple and cost-effective solid-state method is reported for the synthesis of different mixed transition metal oxides (MTMOs) including FeCo₂O₄, MnCo₂O₄ and ZnCo₂O₄ with unique nanostructures. The morphological analysis show that MTMOs possess distinct nanostructures such as tetragonal, spherical nanoparticles and hexagonal nanosheets. Furthermore, these MTMOs showed excellent supercapacitive properties with specific capacitances of 660–1263 F/g at current density of 2 A/g. Asymmetric capacitor was fabricated with FeCo₂O₄ as positive and activated carbon as negative electrode which exhibits a specific capacitance of 88 F/g with energy density of 24 Wh/kg (1.1 mWh/cm³) and cycle life (93%) over 5000 cycles.     

Multi-objective virtual network function placement using NSGA-II meta-heuristic approach

The Journal of Supercomputing - Network function virtualization has facilitated network service development through the integration of network functions (NFs) such as firewalls, deep packet...     

Analysis of a fiber-optic deep-etched silicon Fabry–Perot temperature sensor and modeling its fabrication imperfections

Microsystem Technologies - Design and fabrication of an in-plane silicon Fabry–Perot temperature sensor for fiber-optic temperature sensing was reported in our previous work. To fabricate...     

Potency of commercial TiO2‐P25 nanoparticles to form stainless steel protective coating

This research reports for the first time the surface coating of steel samples with commercial nanoparticles of TiO₂. Aiming to improve the substrate corrosion behavior, a stable suspension containing TiO₂‐P25 nanoparticles and polyvinyl alcohol in the water was prepared and the coating was applied on the surface of the substrate via dip‐coating. Heat treatment led to the formation of strong connection between the substrate and the coating film. Scanning electron microscopy and scanning probe microscopy were utilized to scrutinize the samples in terms of topography and microstructure. In addition, the samples corrosion behavior was investigated through Tafel polarization and impedance spectroscopy. The results showed that one‐step of sample dip‐coating in sol or heat treatment at 600°C cannot provide for desirable and appropriate physical circumstances in the thin film. The applied thin film showed the highest corrosion behavior improvement when the sample was coated with two or three films and the heat treatment was carried out at 400°C. In this respect, according to the Tafel curves, the applied coating efficiency was measured to be approximately 90%. The electrochemical impedance spectroscopy results indicated that the reference sample was single‐time constant and the coated sample was double‐time constant. Applying the coating increased impedance, reduced the capacitive element, and diminished the resistance area. All three mentioned factors contributed to the enhancement of corrosion behavior.     

Review on application of nanoparticles for EOR purposes: A critical review of the opportunities and challenges

Nanoparticles have already gained attentions for their countless potential applications in enhanced oil recovery.Nano-sized particles would help to recover trapped oil by several mechanisms including interfacial tension reduction, impulsive emulsion formation and wettability alteration of porous media. The presence of dispersed nanoparticles in injected fluids would enhance the recovery process through their movement towards oil–water interface. This would cause the interfacial tension to be reduced. In this research, the effects of different types of nanoparticles and different nanoparticle concentrations on EOR processes were investigated. Different flooding experiments were investigated to reveal enhancing oil recovery mechanisms. The results showed that nanoparticles have the ability to reduce the IFT as well as contact angle, making the solid surface to more water wet. As nanoparticle concentration increases more trapped oil was produced mainly due to wettability alteration to water wet and IFT reduction. However, pore blockage was also observed due to adsorption of nanoparticles, a phenomenon which caused the injection pressure to increase. Nonetheless, such higher injection pressure could displace some trapped oil in the small pore channels out of the model. The investigated results gave a clear indication that the EOR potential of nanoparticle fluid is significant.     

Does skill retention benefit from retentivity and symbolic rehearsal? – two studies with a simulated process control task

Two experiments were designed to compare two symbolic rehearsal refresher interventions (imaginary practice, a hidden introspective process) and investigate the role of retentivity in skill retention. Retentivity is investigated as the ability to memorise and reproduce information and associations that were learned a short time ago. Both experiments comprised initial training (week 1), a symbolic rehearsal for the experimental group (week 2) and a retention assessment (week 3). In the first study, the experimental group received a symbolic rehearsal, while the control group received no rehearsal. In the second study, the experimental group received the same symbolic rehearsal used in study 1, enhanced with rehearsal tasks addressing human–computer interaction. The results showed that both symbolic rehearsal interventions were equally likely to mitigate skill decay. The retentivity showed medium to high correlations with skill retention in both studies, and the results suggest that subjects high in retentivity benefit more from a symbolic rehearsal refresher intervention.

Practitioner Summary: Skill decay becomes a problem in situations in which jobs require the correct mastery of non-routine situations. Two experimental studies with simulated process control tasks showed that symbolic rehearsal and retentivity can significantly mitigate skill decay and that subjects higher in retentivity benefit more from refresher interventions.     

A 3D simulation of two-phase flow in an effervescent atomizer for suspension plasma spray

In the suspension spray of nanoparticles, where the attempt is to reach nano-scaled uniform coatings, there is a vital demand to produce a controllable and non-pulsating spray. Effervescent atomizers, in which a gas is bubbled into the bulk of liquid through an aerator, have shown to be a technological alternative to the conventional atomizers when liquid atomization with various concentrations of nano-particles is required. Thus, understanding the behavior of gas and liquid flow through the nozzle is crucial to predict the condition of resultant spray. The two-phase flow inside an effervescent atomizer is numerically investigated. Using an incompressible Eulerian/Eulerian approach, the three-dimensional structure of two-phase flow inside an aerated-liquid injector is modeled. The behaviour of liquid film carrying nano-particles in the discharge passage is studied using different Gas to Liquid mass flow Ratios (GLR), ranging from 0.08% to 1.25%. These numerical results are compared with the experimental data available in literature. The effect of nano-sized solid particles concentration on the liquid film thickness at the exit of the atomizer is studied through the change in liquid bulk density and viscosity. The results show that the atomizing gas-to-liquid mass flow ratio (GLR) does play a key role on the flow behaviour inside the atomizer. At low GLRs of 0.15%, the thickness of the liquid film decreases rapidly and as GLR increases to 1.25% the liquid film thickness dependency on GLR reduces. The results also show that there is no significant effect of particle concentrations, varying within the range of Newtonian fluid, on the liquid film thickness. This feature makes effervescent atomizers a technology choice for controllable suspension thermal spray processes.     

Different behaviors of metallocene and Ziegler–Natta catalysts in ethylene/1,5‐hexadiene copolymerization

The behaviors of three different catalyst systems, TiCl₄/MgCl₂, Cp₂ZrCl₂ and Cp₂HfCl₂, were investigated in ethylene/1,5‐hexadiene copolymerization. In the Fourier transform infrared spectra of the copolymers, cyclization and branching were detected for 1,5‐hexadiene insertion in the metallocene and Ziegler–Natta systems, respectively. DSC and viscometry analyses results revealed that copolymers with lower T_m and crystallinity and higher molecular weight were obtained with metallocene catalysts. The sequence length distribution of the copolymers was investigated by using the successive self‐nucleation and annealing thermal fractionation technique. The continuous melting endotherms obtained from successive self‐nucleation and annealing analysis were employed to get information about short‐chain branching, the branching dispersity index, comonomer content and lamella thickness in the synthesized copolymers. The results established that metallocene catalysts were much more effective than Ziegler–Natta catalysts in the incorporation of 1,5‐hexadiene in the polyethylene structure. Metallocene‐based copolymers had higher short‐chain branching and comonomer content, narrower branching dispersity index and thinner lamellae. Finally, the tendency of the employed catalysts in the 1,5‐hexadiene incorporation and cyclization reaction was explored via molecular simulation. The energy results demonstrated that, in comparison to Ziegler–Natta, metallocene catalysts have a much higher tendency to 1,5‐hexadiene incorporation and cyclization. © 2018 Society of Chemical Industry     

Evolution of shell formation process in PP/PMMA/PS ternary blends: correlation between the melt rheology and phase morphology

Correlation between the melt rheology and phase morphology of PP/PMMA/PS ternary blends during the shell formation process were studied in detail. In this PP-matrix ternary system, theoretical predictions in agreement with the direct SEM observations demonstrated the core-shell morphology with PMMA and PS phases as core and shell phases, respectively. Morphological observations revealed that the complete shell formation takes place at about 12 and 9 wt% of PS minor phase in ternary blends composed of low and high viscosity PMMAs, respectively. In terms of rheological properties, this was corresponding to the maximum value on the storage modulus versus PS content (shell thickness) curves. Encapsulation of high viscosity PMMA core particles at lower PS contents was related to the bigger particles and low interfacial area in this system compared to the system with low viscosity PMMA core particles. At high PS contents, single and multi-core structures were observed for composite droplets of ternary blends containing low and high viscosity PMMAs, respectively. The single core morphology of low viscosity PMMA particles was related to the coalescence of core particles after the coalescence of the corresponding shells, while high viscosity PMMA cores are less likely to coalescence, leading to creation of multi-core morphology in latter system.