Analytical approximate solution of competitive facilitated transport of acid gases through liquid membranes

An analytical approximate solution for the competitive facilitation factor of components A and E across a liquid membrane is developed in the case of instantaneous reactions inside the liquid membranes. This analytical solution solves the dimensionless, nonlinear diffusion-reaction transport problem governing the competitive facilitated transport of two gaseous components through liquid membranes. Prediction of the facilitation factors has been obtained for the equilibrium chemical reaction regime, considering the unequal complexes diffusivities and cases of zero and nonzero permeate side solute concentrations. This mathematical solution leads to analytical expressions for the concentration profiles of the species across the liquid membrane. In comparison with the present numerical solution and also numerical calculations and experimental data from the open literature, the difference between the analytical predictions and those obtained from the numerical solution were found to be in well agreement.     

Synthesis and spectroscopic studies of new adducts of organotin(IV) chlorides with a polydentate N,S ligand

The reaction of a polydentate N,S ligand, 1′-amino-1′-cyclohexyl 2-cyclohexylideneamino-1-cyclohexene-1-dithiocarboxylate (ACCCD), with Ph₂SnCl_2, Ph₃SnCl and Me₂SnCl₂ was investigated. The new adducts have been characterized by UV–Vis, ¹H NMR, IR, mass spectroscopy and elemental analysis. These data are consistent with 1:1 adducts. The ligand behaves as a bidentate and shows both nitrogen and sulfur coordination. There is also evidence that the ligand ACCCD exhibits some interest in forming possible inter-/intra-molecular hydrogen bonds through ClH₂N interactions in Me₂SnCl₂ and Ph₂SnCl₂ adducts. The UV–Vis spectra indicate that the compounds partially dissociate in chloroform.     

Water and mercaptan adsorption on 13X zeolite in natural gas purification process

The aim of this work is to model the adsorption process used for mercaptan and water removal from natural gas. Three fixed beds containing Zeolite molecular sieve type 13X, are used in this plant. In this operation, two beds are in process for adsorption purposes and the other one is regenerated simultaneously. This system is also operated under isothermal condition. In modeling of this process, rate of adsorption is approximated by linear driving force (LDF) expression, and the extended Langmuir isotherm is used to describe adsorption equilibrium. The set of partial differential equations of dynamic model is solved by Crank-Nicolson method. The effect of equations of state is also studied and the best equation fitting the industrial data is selected. Also, concentration profile is presented versus bed length at various times. The influences of pressure, inlet concentration and bed height on the breakthrough time are also investigated.     

Supported liquid membrane separation of propylene-propane mixtures using a metal ion carrier

Experimental results for the separation of propylene from a propylene/propane mixture using facilitated transport membrane system with silver nitrate as carrier are presented. The equilibrium constant of the reaction between propylene and silver ion (Ag⁺) at different operating conditions was determined, experimentally. For a 50:50 (vol.%) propylene-propane mixture, at feed pressure of 50-120 kPa, the separation performance of a facilitated transport membrane system was evaluated. It was observed that increasing carrier concentration and trans-membrane pressure, separation factor was increased. At feed pressure of 120 kPa and the carrier concentration of 20 wt.%, a separation factor of 270 was obtained.     

Effects of humic acid and electrolytes on photocatalytic reactivity and transport of carbon nanoparticle aggregates in water

The effects of naturally occurring macromolecules such as humic acid (HA) and electrolytes on four fullerene nanoparticle suspensions (i.e., C₆₀, C₆₀(OH)₂₄, single- and multiwall carbon nanotubes) were explored with respect to: (1) characteristics of nanoparticle aggregates, (2) transport of the aggregates through a silica porous media, and (3) production of reactive oxygen species (ROS) from the photosensitized fullerene aggregates. The presence of HA and salts increased the size of aggregates and relative hydrophobicity associated with transport through silica beads, while decreasing ROS production. These data illustrate the importance that transformation of engineered nanomaterials (ENMs) through interactions with aquatic solutes may have in altering the environmental behavior of nanomaterials.     

Terahertz graphene optics

The magnitude of the optical sheet conductance of single-layer graphene is universal, and equal to e ²/4? (where 2??? = h (the Planck constant)). As the optical frequency decreases, the conductivity decreases. However, at some frequency in the THz range, the conductivity increases again, eventually reaching the DC value, where the magnitude of the DC sheet conductance generally displays a sample- and doping-dependent value between ??e ²/h and 100 e ²/h. Thus, the THz range is predicted to be a non-trivial region of the spectrum for electron transport in graphene, and may have interesting technological applications. In this paper, we present the first frequency domain measurements of the absolute value of multilayer graphene (MLG) and single-layer graphene (SLG) sheet conductivity and transparency from DC to 1 THz, and establish a firm foundation for future THz applications of graphene.      

The effect of tube dimensions on optimized pressure and force loading paths in tube hydroforming process

The precise control of internal pressure and axial force loading paths significantly affects the final product quality. In this study, the effect of tube dimensions on the pressure and force loading paths in tube hydroforming process is investigated by using simulated annealing optimization method linked to a commercial finite element code. The optimized loading paths, obtained for different tube geometries with a constant expansion ratio, are then compared. The effects of initial diameter and wall thickness on shape conformation, optimal internal pressure and axial force (or feed) are discussed on the basis of optimal loading paths. Several guidelines in prediction and determination of tube hydroforming parameters are obtained by optimization analysis.     

Novel thermal interface materials: boron nitride nanofiber and indium composites for electronics heat dissipation applications

With increased power density and continued miniaturization, effective thermal dissipation is of significant importance for operational lifetime and reliability of electronic system. Advanced thermal interface materials (TIMs) with excellent thermal performance need to be designed and developed. Here we report novel TIMs consisted of boron nitride (BN) nanofibers and pure indium (In) solder for heat dissipation applications. The BN nanofibers are fabricated by electrospinning process and nitridation treatment. After surface metallization by sputtering, the porous BN film is infiltrated with liquid indium by squeeze casting to form the final solid composites. The new composites show the in-plane and through-plane thermal conductivity respectively of 60 and 20 W/m K. The direction dependence thermal properties of the TIM are due to the anisotropic thermal performance of BN nanofibers in the composite. A low thermal contact resistance of 0.2 K mm²/W is also achieved at the interface between this new composite and copper substrate. These competent thermal properties demonstrate the great potential of the BN–In TIMs in thermal management for electronic system.