Effect of electron-beam irradiation followed by annealing on the physical properties of poly(vinyl alcohol)–chitosan blend films at different weight ratios

The aim of this study was to examine the effect of electron-beam irradiation followed by annealing on the physical properties of poly(vinyl alcohol) (PVA)–chitosan (CS) blend films. Solution-cast films containing various ratios of polymers were exposed to irradiation doses of 26, 39, and 52 kGy at room temperature and then annealed at 100 °C. The results show that at all doses, with an increase in the weight ratio of CS, the gel content of the samples decreased, and the water absorption of the samples increased. The irradiation dose ranged from 26 to 39 kGy; this led to an increased gel content and a decreased degree of swelling in the samples. However, at 52 kGy, an increase in the amount of swelling was observed. X-ray diffraction analysis and scanning electronic microscopy images of the samples revealed that the increase in the irradiation dose reduced the crystallinity and increased the surface heterogeneity, respectively. The tensile strength of the blends decreased with decreasing PVA–CS weight ratio. This property of the samples increased with dose from 26 to 39 kGy and decreased at 52 kGy. The elongation at break of the samples decreased with both an increase in the irradiation dose and a decrease in the CS content. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47820.     

Comparative study on the sonophotocatalytic degradation of hazardous waste

The enhanced sonophotocatalytic degradation of Chrome Intra Orange G (C.I. 18745), an azo dye, in aqueous solution under UV light has been carried out using solvothermally sensitized ZnO nanoparticles as catalyst. The effects of sonolysis, sonocatalysis, photocatalysis and sonophotocatalysis have been examined to study the influences on the degradation rates by varying the initial dye concentration, dye solution pH, catalyst morphology and loading to ascertain the synergistic effect on the degradation techniques. ZnO sonophotocatalysis was always faster than the respective individual processes. Ultrasound may modify the rate of photocatalytic degradation by promoting the deaggregation of the catalyst and ultrasound-induced increase of its active surface area, by increasing the amount of reactive radical species through cavitation leading to water splitting and formation of H₂O₂ by both photocatalysis and sonolysis. To further verify the direct relation of the effective surface area offered by ZnO to its reaction rate, sonophotocatalysis experiments were conducted using nanorods of different dimensions and aspect ratios. Higher aspect ratio values correspond to an enhancement of the sonophotocatalytic activity.     

Influences of initiator addition methods in suspension polymerization of vinyl chloride on poly(vinyl chloride) particles properties

Vinyl chloride suspension polymerization was carried out in a pilot‐scale reactor to study the effects of different methods of initiator addition on poly(vinyl chloride) (PVC) resin properties. The experiments used different arrangements for adding the initiator to the reactor, whereas other reaction conditions were the same: (i) initiator was added to the continuous aqueous phase and then monomer was dispersed in it (conventional method); (ii) initiator was predissolved in monomer before dispersing in the continuous aqueous phase; and (iii) suspending agents along with initiator were added to the monomer before polymerization. The PVC resin prepared by method of (i) had a higher monomer conversion and a higher Sauter mean diameter of grains with a narrow particle size distribution comparable to that of PVC resins by other methods. Scanning electron microscopy showed more uniform particles and fused primary particles in the grains, which confirms lower porosity and lower cold plasticizer absorption (CPA) for PVC grains produced by procedure of (ii). The results showed that when the suspending agents were also predispersed in monomer along with initiator (iii), CPA increases dramatically due to internal porosity of the grains. Simultaneously, a marked decrease in Sauter mean diameter was apparent. Scanning electron microscopy micrographs show that primary particles in the interior of PVC grains prepared by the latter method are looser, and there is more free volume between primary particles resulting the high internal porosity and consequently higher CPA. Mercury porosimetry analysis also confirms these results. K value as a molecular weight characteristic for all methods was the same . J. VINYL ADDIT. TECHNOL., 24:116–123, 2018. © 2016 Society of Plastics Engineers     

Numerical Simulation of Non-Darcy Forced Convection through a Channel with Nonuniform Heat Flux in an Open Cavity Using Nanofluid

This article aims to numerically investigate forced convection heat transfer phenomena in a two-dimensional horizontal channel having an open cavity with porous medium. A nonuniform heat flux is considered to be located on the bottom surface of the cavity. Three different heating modes are considered at this wall. The rest of the surfaces are taken to be perfectly adiabatic. The physical domain is filled with water based nanofluid containing TiO₂ naparticles. The fluid enters from left and exits from right with initial velocity U _i and temperature T _i . Governing equations are discretized using the penalty finite element method. The simulation is carried out for a range of Prandtl number Pr(=5.2–12.2) and solid volume fraction φ (=0%–15%). Results are presented in the form of streamlines, isothermal lines, local and average Nusselt number, average temperature of the fluid, horizontal and vertical velocities at mid-height of the channel, and mean velocity field for various Pr and φ. It is found that increasing Pr and φ cause the enhancement of the heat transfer rate.     

Influences of Physical Parameters on Mixed Convection in a Horizontal Lid-Driven Cavity with an Undulating Base Surface

The problem of steady, laminar, and incompressible mixed convection flow in a horizontal lid-driven cavity is studied. In this investigation, two vertical walls of the cavity are perfectly insulated and the wavy bottom wall is considered at an identical temperature higher than the top lid. The enclosure is assumed to be filled with a Bousinessq fluid. The study includes computations for different physical parameters, such as cavity aspect ratio (AR) from 0.5 to 2, amplitude of undulating wall (A) from 0 to 0.075, and number of undulations (λ) from 0 to 3. The pressure-velocity form of Navier-Stokes and energy equations are used to represent the mass, momentum, and energy conservations of the fluid medium in the cavity. The governing equations and boundary conditions are converted to dimensionless form and solved numerically by the penalty finite element method with discretization by triangular mesh elements. Flow and heat transfer characteristics are presented in terms of streamlines, isotherms, average Nusselt number (Nu), and maximum temperature (θ _max ) of the fluid. Results show that the wavy lid-driven cavity can be considered an effective heat transfer mechanism at larger wavy surface amplitude, as well as the number of waves and cavity aspect ratio.     

Modeling of double diffusive buoyant flow in a solar collector with water‐CuO nanofluid

The behavior of a prism‐shaped solar collector with a right triangular cross sectional area is investigated numerically. The water‐CuO nanofluid is taken as the functioning liquid through the solar collector. The leading differential equations with boundary conditions are solved by the penalty finite element method using Galerkin's weighted residual scheme. The performance of parameters in terms of temperature, mass, velocity distributions, radiative, convective heat and mass transfer, mean temperature and concentration of nanofluid, mid height horizontal‐vertical velocities, and sub‐domain average velocity field are investigated systematically. These parameters include the Rayleigh number Ra and the solid volume fraction φ. The outcome explains that the performance of the solar collector can be enhanced with the largest Ra and φ. The code validation shows excellent concurrence with the hypothetical outcome obtainable in the literature. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21039     

Non‐Darcy assisted flow along a channel with an open cavity filled with water–TiO2 nanofluid

Numerical investigation on forced (assisted) convection heat transfer in a two‐dimensional horizontal porous channel with an open cavity is studied in this article. A non‐uniform heat flux is considered to be located on the bottom surface of the cavity. The rest of the surfaces are taken to be perfectly insulated. The physical domain is filled with a water‐based nanofluid containing TiO₂ nanoparticles. The fluid enters from the left and exits from the right with initial velocity U_i and temperature T_i. Governing equations are discretized using the penalty finite element method. The simulation is carried out for a wide range of Reynolds number Re (= 10–500) and Darcy number Da (= 10^?5–∞). Results are presented in the form of streamlines, isothermal lines, local and average Nusselt numbers, average temperatures of the fluid, horizontal and vertical velocities at mid‐height of the channel and mean velocity fields for various Re and Da. The enhancement of heat transfer rate is caused by the increasing Re and falling Da. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21046     

Comprehensive review of solar radiation modeling based on artificial intelligence and optimization techniques: future concerns and considerations

Clean Technologies and Environmental Policy - An alternative energy source such as solar is one of the most important renewable resources. A reliable solar radiation prediction is essential for...     

CdS and CdTeS quantum dot decorated TiO2 nanowires. Synthesis and photoefficiency

An easy process was developed to synthesize TiO(2) nanowires sensitized with CdS and CdTeS quantum dots (QDs) requiring no pretreatment of the TiO(2) nanowires prior to nanoparticle generation. CdS and CdTeS nanoparticles were firstly grown by an in situ colloidal method directly onto the TiO(2) surface, hence not requiring subsequent functionalization of the QDs. The resulting nanostructure assembly and composition was confirmed by transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Successful decoration of the TiO(2) nanowires by the QDs was observed by TEM, while XPS spectra provided clear evidence for the coexistence of CdS and CdTeS QDs and TiO(2) nanowires. The electronic structure of the TiO(2) nanowires was preserved as indicated by Raman spectroscopy. Preliminary photocurrent measurements showed that inclusion of Te in CdS QDs improved the photocurrent efficiency. Compared to bare TiO(2) nanowires, CdS/TiO(2) nanoassemblies showed an enhancement in photocurrent efficiency of 300% while CdTeS/TiO(2) presented an improvement of 350%. This study indicates that the generation of strongly anchored CdS and CdTeS QDs on a TiO(2) nanowire surface is achievable without introduction of a linker molecule, whose presence is known to decrease the electron injection efficiency.     

Determination of lisinopril using β-cyclodextrin/graphene oxide-SO3H modified glassy carbon electrode

An electrochemical method has been successfully demonstrated for sensitive determination of lisinopril with β-cyclodextrin-graphene oxide-SO₃H composite modified glassy carbon electrode (β-CD/GO-SO₃H/GCE). Cyclic voltammetry, differential pulse voltammetry, and chronocoulometry were used to investigate the electrochemical behavior of lisinopril at β-CD/GO-SO₃H/GCE. The cyclic voltammetric results indicate that β-CD/GO-SO₃H/GCE can remarkably enhance electroactivity toward the oxidation of lisinopril in buffer solutions. The electrochemical behavior was further exploited as a sensitive detection scheme for the lisinopril determination by differential-pulse voltammetry. Under optimized conditions, the concentration range and detection limit were 0.21–190.4 and 0.11 µM (S/N = 3), respectively. The method was successfully applied to assay the drug in human serum.