Reinforced thin-film composite nanofiltration membranes: Fabrication,characterization, and performance testing

Hollow-fiber (HF) membranes have the advantage of a higher packing density compared to flat-sheet and spiral-wound configurations. However, the low pressure tolerance of HF membranes limits their applications in nanofiltration (NF). In this study, reinforced thin-film composite (r-TFC) HF NF membranes were fabricated and evaluated in tests with water containing different salts and organic matter. Reinforced polysulfone ultrafiltration membranes were used as a support for a polyamide layer prepared from piperazine and trimesoyl chloride monomers. The interfacial polymerization conditions were optimized via selection of the trimesoyl chloride reaction time that gave the highest membrane performance. A specific permeate flux of 5.1 L m^–2 h^–1 bar^–1, an MgSO₄ rejection of 69%, and an NaCl rejection of 26% at a transmembrane pressure of 6 bars were obtained with the optimized r-TFC membranes. Performance studies with water characterized by synthetic solution demonstrated removals of the total organic carbon, ultraviolet absorbance at 254 nm, and turbidity in excess of 65, 80, and 90%, respectively. The results of this study illustrate the feasibility of manufacturing r-TFC HFs and using them in water-treatment applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48001.     

Donor:Acceptor Janus Nanoparticle-Based Films as Photoactive Layers: Control of Assembly and Impact on Performance of Devices

Water-processable organic semiconductor nanoparticles (NPs) are considered promising materials for the next-generation of optoelectronic applications due to their controlled size, internal structure, and environmentally friendly processing. Reasonably, the controllable assembly of donor:acceptor (D:A) NPs on large areas, quality, and packing density of deposited films, as well as layer morphology, will influence the effectiveness of charge transfer at an interface and the final performance of designed optoelectronic devices.This work represents an easy and effective approach for designing self-assembled monolayers of D:A NPs. In this self-assembly procedure, the NP arrays are prepared on a large scale (2 × 2 cm²) at the air/water interface with controlled packing density and morphology. Due to the unique structure of individual D:A Janus particles and their assembled arrays, the Janus nanoparticle (JNP)-based device exhibits an 80% improvement of electron mobility and more balanced charge extraction compared to the conventional core–shell NP-based device. An outstanding performance of polymer solar cells with over 5% efficiency is achieved after post-annealing treatment of assembled arrays, representing one of the best results for NP-based organic photovoltaics. Ultimately, this work provides a new protocol for processing water-processable organic semiconductor colloids and future optoelectronic fabrication.     

Effect of microstructure on the phase composition and hydrogen absorption-desorption behaviour of melt-spun Mg-20Ni-8Mm alloys

The effect of microstructure on the phase composition and hydrogen absorption-desorption behaviour of Mg-based Mg-20Ni-8Mm (wt.%) (Mm = La-rich Mischmetal) alloys has been studied. Rapid solidification (RS) processing resulted in the formation of the high-temperature cubic modification of Mg₂NiH₄ and the solid solution hydride Mg₂NiH_0.3, in the disappearance of the monoclinic modification of Mg₂NiH₄, as well as in a decrease in the unit cell volumes of the constituent hydride phases. The above-mentioned tendencies became more pronounced in the order “as-cast < Cu-300 < Cu-1000 ≈ Cu-2000” (where the sample names Cu-#### denote the spinning velocity of the copper wheel in rpm), which is explained by an increase in the mechanical stresses in the materials and/or by an increased interfacial energy of the fine grains of the corresponding hydrides. The hydrogen absorption kinetics was improved in the order “Cu-300 < Cu-1000 < Cu-2000”. The temperature range of hydrogen thermal desorption from the hydrogenated alloys shrank in the order “Cu-300 > Cu-1000 >> Cu-2000”, which is explained by increased uniformity of the hydrides grain size in the hydrides with increasing solidification rate. During PCT (pressure composition temperature) tests, the Cu-1000 and Cu-2000 samples displayed the largest pressure hysteresis and the smallest slope of the higher Mg₂NiH₄ plateau, but also the lowest hydrogen storage capacity.     

SAXS investigation of nanoporous structure of thermal-modified carbon materials

The article investigates the effect of thermal modification of porous carbon material (PCM), obtained from plant feedstock, on its morphology and fractal structure by small-angle X-ray scattering (SAXS) method. The analysis of the scattering intensity curves serve the basis for calculating the parameters of the PCM porous structure: the Porod constant, the Porod invariant, average pore radius, specific surface area, and mass and surface fractal dimensions. It has been found out that the PCMs obtained have fractal structure, formed from mass and surface fractals, the sizes of which increase at the growth of temperature and modification time.

PACS

81.05.Uw; 61.05.cf; 82.47.Aa     

Computational fluid dynamics modeling of the flow in a laboratory membrane filtration cell operated at low recoveries

Scaled-down models of industrial filtration units are often used in laboratory studies of membrane processes. Knowledge of the flow field and shear stresses at the membrane surface is vital for the accurate interpretation of bench scale experiments. In this paper, we present results of computational fluid dynamics modeling of the flow within the SEPA CF flat sheet membrane filtration cell operated at low recoveries. The problem was formulated as the steady-state isothermal laminar flow of incompressible Newtonian fluid. Pressure, velocity, and shear stress distributions were computed with resolution for different average inlet velocities. Flow was found to be unidirectional over most of the channel area with exception of the corners of the channel. Stagnation areas in dead ends of inlet and outlet tubes and in the channel areas behind duct entries as well as local regions of high shear in duct-channel transition areas were observed. The relation between the highest shear rate created in this geometry and the average inlet velocity is given.     

Linear and Nonlinear Development of the <Emphasis Type="Italic">m</Emphasis> = 0 Instability in Z-Pinch Equilibria with Axial Sheared Flows

The effect of sheared flows on the m = 0 instability development in a z-pinch is numerically investigated using a 2D magnetohydrodynamic (MHD) code. The behavior of both internal and free-boundary modes is studied by using two types of initial configurations: a diffuse Bennett equilibrium and a free-boundary parabolic equilibrium. It was found that sheared flows change the m = 0 development by reducing the linear growth rates, decreasing the saturation amplitude, and modifying the instability spectrum. Full stability can be obtained for supersonic plasma flows, but a larger shear is needed to obtain stabilization of free-boundary modes.     

Numerical Modeling of a Magnetic Flux Compression Experiment

A possible plasma target for Magnetized Target Fusion (MTF) is a stable diffuse z-pinch in a toroidal cavity, like that in MAGO experiments. To examine key phenomena of such MTF systems, a magnetic flux compression experiment with this geometry is under design. The experiment is modeled with 3 codes: a slug model, the 1D Lagrangian RAVEN code, and the 1D or 2D Eulerian Magneto-Hydro-Radiative-Dynamics-Research (MHRDR) MHD simulation. Even without injection of plasma, high-Z wall plasma is generated by eddy-current Ohmic heating from MG fields. A significant fraction of the available liner kinetic energy goes into Ohmic heating and compression of liner and central-core material. Despite these losses, efficiency of liner compression, expressed as compressed magnetic energy relative to liner kinetic energy, can be close to 50%. With initial fluctuations (1%) imposed on the liner and central conductor density, 2D modeling manifests liner intrusions, caused by the m = 0 Rayleigh-Taylor instability during liner deceleration, and central conductor distortions, caused by the m = 0 curvature-driven MHD instability. At many locations, these modes reduce the gap between the liner and the central core by about a factor of two, to of order 1 mm, at the time of peak magnetic field.     

Security network interface for alarm systems

Authors suggested the development of a specialized network interface for network of detectors that are part of alarm system. Providing a high level of network security against intruder is achieved using a large number of security elements and their dynamic change in on-line mode network operation. The proposed system uses traditional detectors; each is connected to the network through node based on a microcontroller. This allows connection of traditional detectors into two-wired network with common bus type and to reduce the number of wired lines without loss of system informative channels. An additional advantage is in powering sensors by a server via informational network channel.     

Simulation of thermal state of containers with spent nuclear fuel: multistage approach

The safe thermal conditions of spent nuclear fuel storage are the important component of complex safety of the dry spent nuclear fuel storage facility. The multistage approach for numerical definition of thermal fields in storage containers with spent fuel assemblies is proposed. The approach is based on solving of the series of the conjugate heat transfer problems with different geometrical detailing. The developed approach is used for estimation of thermal state of ventilated containers with spent nuclear fuel of WWER‐1000 reactors of Zaporizhska nuclear power plant. The results of the thermal calculations for single‐placed container on open‐site storage platform were presented. The safety of containers usage in normal and extreme ambient temperatures was proven. Copyright © 2015 John Wiley & Sons, Ltd.