A facile synthesis of CuI-graphene nanocomposite by glucose as a green capping agent and reductant

For the first time, CuI-graphene nanocomposite has been successfully prepared via combination of co-precipitation and hydrothermal methods. Copper nitrate and lithium iodide were applied as starting reagents to fabricate CuI-graphene nanocomposite. For preparing nanoparticles (NPs)-graphene composite we chose post-graphenization method. In synthesis of NPs-graphene with post-graphenization method, graphite oxide acts as starting reagent, so graphite oxide was synthesized via Hummer method. The effect of glucose on the particle size of nanoparticles and their distribution on the graphene sheets were investigated. The as-produced nanocomposites were characterized with the aid of XRD, SEM, TEM, EDS and FT-IR.     

Heavy paraffin dehydrogenation and hydrogenation of nitrobenzene to aniline: Effects of operating conditions

Auto-thermal heat exchanger configurations are recognized as a novel concept in process intensification. In the current study, the influence of operating conditions in a novel coupling reactor with radial-flow pattern is investigated for heavy paraffin dehydrogenation process. Catalytic hydrogenation of nitrobenzene to aniline takes place in the exothermic side and supplies the necessary heat for the endothermic dehydrogenation of heavy paraffin reaction. The performance of the reactor is numerically investigated for various key operating variables, such as inlet molar flow rates of exothermic and endothermic streams, number of subsections, and exothermic side angle. The reactor performance is analyzed based on temperature, olefin production rate, and nitrobenzene conversion.     

A variational approach to path planning for hyper-redundant manipulators

Motion planning for hyper-redundant manipulators in a complicated and cluttered workspace is a challenging problem. Many of the path planning algorithms, based on cell decomposition or potential field, fail due to the high dimensionality and complex nature of the C-space. Probabilistic roadmap methods (PRM) which have been proven to be successful in high dimensional C-spaces suffer from the drawback of generating paths which involve a lot of redundant motion. In this paper, we propose a path optimizing method to improve a given path in terms of path length and the safety against the collisions, using a variational approach. The capability of variational calculus to optimize a path is demonstrated on a variety of examples. The approach succeeds in providing a good quality path even in high dimensional C-spaces.     

Synthesis of Co<Subscript>2</Subscript>P/Co nanocomposites using single source precursor by thermal decomposition method

In this article, the synthesis and characterization of Co₂P/Co nanocomposites are reported. Three kinds of precursors are studied: bis(salicylidene)cobalt(II) [Co(sal)₂], bis(salicylate)cobalt(II) [Co(Hsal)₂] and cobalt oxalate [Co(O₄C₂)·4H₂O]. The cobalt(II) acetate tetrahydrate Co(CH₃COO)₂·4H₂O is used as reference. The nanocomposites are prepared by thermal decomposition method using triphenylphosphine as a surfactant solvent and phosphorus precursor. A possible mechanism of the formation of the nanocomposites is put forward to explain the experimental observations. This is the first time that Co₂P/Co nanocomposites are synthesized. To study the crystalline structure, composition, size, morphology and magnetic property of the products, characterization techniques including XRD, SEM, TEM, FT-IR and VSM are employed.     

Direct numerical and large eddy simulation of longitudinal flow along triangular array of rods using the lattice Boltzmann method

Results of direct numerical (DNS) and large eddy simulation (LES) of turbulent longitudinal flow in rod bundles are presented using the lattice Boltzmann method with the Bhatnagar–Gross–Krook collision operator [P.L. Bhatnagar, E.P. Gross, M. Krook, A model for collision processes in gases. I. Small amplitude processes in charged and neutral one-component systems, Phys. Rev. 94 (1954) 511; Y.H. Qian, d’Humiéres, P. Lallemand, Lattice BGK models for Navier-Stokes equation, Europhys. Lett. 17 (1992) 479] as a computational framework. The problem requires the accurate modeling of curved walls, to which the method proposed by Yu et al. [D. Yu, M.R. Luo, W. Shyy, Viscous flow computations with the method of lattice Boltzmann equation, Prog. Aerospace Sci. 39 (2003) 329] has been applied. The computational domain is a regular hexagonal prism around the rod. Opposite sides of the prism are coupled periodically. In the longitudinal direction periodical boundary conditions are applied and the flow is driven by a body force. Simulations were carried out using two three-dimensional lattices. It has been found that the application of the model with 19 velocities (D3Q19) gives qualitatively false result. However, we have found that the application of the model with 27 links (D3Q27) can provide the proper mean axial velocity profile, and it also predicts the secondary flow patterns deduced from measurements [A.C. Trupp, R.S. Azad, The structure of turbulent flow in triangular array rod bundles, Nucl. Eng. Des. 32 (1975) 47]. Flow pulsation phenomenon is also observed in our simulations just like in some recent measurements of Krauss and Meyer [T. Krauss, L. Meyer, Experimental investigation of turbulent transport of momentum and energy in heated rod bundle, Nucl. Eng. Des. 180 (1998) 185].     

TEM investigations of wear mechanism of Al2O3 and Si3N4 compacts with GLPs additions

Extended lifetime of ceramic cutting plates is ever more desired. One way of approaching it entails sintering precursor materials with graphene-like nanoplatelets (GLPs) acting as solid lubricants. Therefore, Al₂O₃ and Si₃N₄ ceramic powders with addition of GLPs of grade 3 (fine) or grade 4 (coarse) were Spark Plasma Sintered. It is found that the 0.15 wt% GLPs addition of both grades allows to keep hardness practically at the same level as GLPs-free compacts (~16 GPa). Only larger GLPs additions (2 wt%) caused its evident decrease (down to 14−15 GPa). The ball-on-disc test revealed that only Al₂O₃+0.15 wt% GLPs(3) shows a 50% reduction in wear rate. The post mechanical test examination by SEM confirmed that Al₂O₃ compacts with small GLPs showed smooth wear track, as opposed to those having a Si₃N₄ matrix with large meandering cavities. TEM observations revealed that the wear damage caused by the ball was restricted to ~2 µm deep sub-surface areas, while, carbon is found to transfer from the GLPs agglomerates into tribo-film. The present experiments showed, that ceramic sinters with small addition of GLPs platelets could exhibit lower wear than GLPs-free ones and therefore show a potential for application as cutting plates.     

Influence of the sol gel synthesis parameters on the photoluminescence properties of ZnO nanoparticles

In this work, ZnO NPs were successfully synthesized by the sol–gel method without any organic additives or post annealing. The effect of the preparation process on the structural and optical properties of the resulting NPs was investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. The structural characterization demonstrated clearly that the NPs crystallize in pure ZnO würtzite structure without any other secondary phases. Furthermore, we show that it is possible to perform the control of the crystalline growth orientation of ZnO NPs, which is a key parameter when seeking to develop ZnO NPs with piezoelectric properties for nano-transducer applications. In fact, TEM observations show that the reduction of the NaOH flow changes the NPs shape from hexagonal NPS to short nanorods grown along the c-axis. The PL spectra of the obtained NPs excited at 280 nm, present an UV emission centered at approximately 380 nm with a slight shift when varying the synthesis temperature and/or the NaOH flow. Moreover, as the visible region (from 400 to 650 nm) is concerned, it was shown that the increasing of the synthesis temperature affects strongly the kind of interstitial defects (O_i, Zn_i and V_oZn_i) formed in ZnO nanostructures. However, the excitation at 320 nm revealed a broad deep-level emission for all the samples that can be deconvoluted into two Gaussian peaks centered at 514 nm (P₁) and 581 nm (P₂). These last results have been discussed in the light of a physical mechanism based on the Schottky barrier.     

Computer Simulated Magnetic Properties of Nd2Fe14B/α-Fe Nanocomposite Magnets

Micromagnetic models of assemblies of randomly oriented, exchanged coupled nanocrystals consisting of magnetically hard Nd₂Fe₁₄B and very soft alpha Fe have been simulated. The modeling of two-dimensional chessboard consisted of 50 vol. % hard and 50 vol.% soft nanocrystals with the size varying from 5, 10, 25, to 50 nm. Hysteresis curves of each model system were obtained by solving the Landau-Lifshitz-Gilbert equation by time integration of the stiff differential equations. The simulation was focused on the effect of domain size and distribution in each nano crystal of fixed size. Eventually the simulated results were compared with magnetic properties obtained from experimental results of NdFeNbB based magnetic alloys showing the identical grain sizes to the simulated model. The present study exhibited the important role of soft phase in terms of volume fraction and arrangement of the phase.     

Lattice structure on some fuzzy algebraic systems

In this paper, we study the lattice structure of some fuzzy algebraic systems such as (G-)fuzzy groups, some fuzzy ordered algebras and fuzzy hyperstructures. We prove that under suitable conditions, these structures form a distributive or modular lattice. This research partially is supported by the “ Fuzzy Systems and its Applications Center of Excelence, Shahid Bahonar University of Kerman, Iran”.     

Thermal and fluorescent properties of optical brighteners and their whitening effect for pelletization of cycloolefin copolymers

The thermal and fluorescent properties of 4,4-bis(5-methyl-2-beazoxoazol)ethylene (Hostalux KS-N), 1,4-bis(benzoxazolyl-2-yl)naphthalene (Hostalux KCB), 2,5-bis-(5-tertbutylbenzoxazole-2-yl) thiophene (Uvitex OB), 2,2′-(4,4′-diphenolvinyl)dibenzoxazol (Uvitex OB-1), and 1,1′-biphenyl-4,4′-bis(2-(methoxyphenyl)ethenyl) (Uvitex 127) have been investigated. All of them exhibit good thermal stability (> 300 °C) and high fluorescent quantum yields (> 0.8). Furthermore, we also have successfully blended these optical brighteners into cycloolefin copolymers with the antioxidant (Irganox HP2921) to improve the discoloration after pelletization based on their whitening effect.