A New Hybrid Algorithm for Numerical Simulation of VOC Emissions Using Single-Layer and Multilayer Approaches

A new hybrid algorithm based on the lattice Boltzmann method (LBM) and the finite-volume method (FVM) is proposed for numerically calculating the emissions of volatile organic compounds (VOCs) from building materials and predicting their space distribution. Most building envelopes are comprised of single as well as multilayer materials, with some of them being porous and others nonporous. First, only the LBM is used to calculate the VOC concentration in airtight and ventilated chambers with constant as well as variable ventilation. For multilayer materials, including both porous and nonporous, half-lattice division methodology in the LBM is used, which ensures flux continuity at the interfaces. Good agreement is found between computed results and experimental data available in the literature. The effect of variable ventilation is also studied for both types of sequences of porous/nonporous layers. Then the LBM coupled with the FVM is used to investigate the VOC concentration distribution in the room emitted from styrene-butadiene rubber (SBR) plate, and good agreement is found between obtained results and those already published. The hybrid algorithm with multilayer approach is also used to conduct a detailed study of the effect of different ventilation organizations on the concentration in the room air, and the best one is found by the simulation.     

Graphene oxides nanosheets mediation of poly(vinyl alcohol) films in tuning their structural and opto-mechanical attributes

Herein, we report successful incorporation of graphene oxide (GO) nanosheets into poly(vinyl alcohol) (PVA) matrix by employing solution casting method. The effect of GO loadings on structural, optical and mechanical properties of PVA films was investigated. Most of the optical properties of such films are reported for the first time in the present study. On incorporating GO nanosheets into PVA matrix, the properties of nanocomposites were changed entirely. The tensile strength and Young’s modulus of nanocomposites were enhanced. Alongside, a variation in absorption edge, direct/indirect band gap, Urbach energy, refractive index, optical dielectric constant, optical conductivity and dispersion parameters were noticed. The band gap and dispersion parameters were calculated using Tauc’s and Wemple–DiDomenico models, respectively. Helpin–Tsai and mixture rule models were employed to calculate Young’s modulus. The applied models reinforced the experimental results in the present study. Advanced analytical techniques were employed to characterize the nanocomposites films. The prepared nanocomposites might be used in designing the opto-electronic devices.     

Analysis of junction properties of gold–zinc oxide nanorods-based Schottky diode by means of frequency dependent electrical characterization on textile

Present work is an effort to reveal the junction properties of gold/zinc oxide (ZnO) nanorods-based Schottky diode by using the frequency dependent electrical properties. The most important electrical parameters such as conductance, resistance, capacitance, and impedance were studied as function of frequency across the series of AC voltages. Moreover, current density–voltage (J–V) was measured to know the performance of present Schottky diode. The effect of native defects was also studied by using cathodoluminescence spectroscopy measured at different accelerating voltage. The textile substrate was used for the growth of ZnO nanorods by using the aqueous chemical growth method and Schottky diode fabrication. Diode fabrication on textile fabric is a step forward toward the fabrication of electronic devices on nonconventional, economical, soft, light weight, flexible, wearable, washable, recyclable, reproducible, and nontoxic substrate.     

Structure and charge transport mechanism in hydrothermally synthesized (La<Subscript>0.5</Subscript>Ba<Subscript>0.5</Subscript>MnO<Subscript>3</Subscript>) cubic perovskite manganite

Perovskite manganites with chemical formula La_0.5Ba_0.5MnO₃ (LBMO) samples were synthesized though the hydrothermal process by heating suitable reactants at 270?°C in an autoclave for 25 h. After washing with de-ionized water several times, the as prepared samples were then calcined at different temperatures, ranging from 120 to 1000?°C to remove the impurities. Final sintering of the sample was carried out at 1350?°C for 24 h. Subsequent X-ray diffraction (XRD) measurements were also carried out. Rietveld refinement of XRD data for the sample sintered at 1350?°C confirmed single phase cubic structure with lattice parameter a?=?3.9057? and space group P m ?3 m. The dc electrical measurements were performed in a broad range of temperatures from 77 to 870 K on this sample. The focal point of this study was to obtain microscopic parameters and characteristic length in order to discuss the relationship between magnetic, electric and phonon excitations. The electrical resistivity measurements revealed a metallic/ferromagnetic to semiconductor/paramagnetic phase transition (T_C) at 339 K. In the metallic region the experimental data best fitted the resistivity equation \(\uprho (\text{T})={\uprho _{o}}+{\uprho _2}{\text{T}^2}+{\uprho _{2.5}}{\text{T}^{2.5}}+{\uprho _{4.5}}{\text{T}^{4.5}}\) showing that the resistivity effect arises due to residual impurities, grain boundaries, electron–electron (e–e), electron–magnon (e–mag) and electron–phonon (e–ph) scattering. The analysis of the resistivity data above T_C has shown a transformation in conduction mechanism from Mott’s variable range hopping (MVRH) to small polaron hopping (SPH), around 585 K. Hopping of carriers to larger distances with multiplying values of activation energies are analyzed through MVRH below 585 K. Above 585 K, the carriers were found to be trapped by several scattering centers through small polaron, this behavior having been interpreted in the light of SPH model.     

Medium effect on electrochemical behaviour of anodized aluminium

The effect of some anions on the growth of the oxide film on aluminium was studied in acid and neutral media, as well as the effect of pH in presence of the same anion. In all the cases studied an inner barrier layer is formed adjacent to the metal and is covered on top with a porous layer. This latter outer layer differentiates into two regions, the one adjacent to the solution being characterized by a more open structure and a higher degree of anion incorporation as compared to the region embedded between it and the inner barrier layer. The rate of dissolution of the barrier layer is not affected by pH or anion type prevailing in the formation medium, since this layer is formed of pure alumina. The dissolution of the outer porous layer, on the other hand, is affected by both pH and anion type.     

The fabrication of white light-emitting diodes using the n-ZnO/NiO/p-GaN heterojunction with enhanced luminescence

Cheap and efficient white light-emitting diodes (LEDs) are of great interest due to the energy crisis all over the world. Herein, we have developed heterojunction LEDs based on the well-aligned ZnO nanorods and nanotubes on the p-type GaN with the insertion of the NiO buffer layer that showed enhancement in the light emission. Scanning electron microscopy have well demonstrated the arrays of the ZnO nanorods and the proper etching into the nanotubes. X-ray diffraction study describes the wurtzite crystal structure array of ZnO nanorods with the involvement of GaN at the (002) peak. The cathodoluminescence spectra represent strong and broad visible emission peaks compared to the UV emission and a weak peak at 425 nm which is originated from GaN. Electroluminescence study has shown highly improved luminescence response for the LEDs fabricated with NiO buffer layer compared to that without NiO layer. Introducing a sandwich-thin layer of NiO between the n-type ZnO and the p-type GaN will possibly block the injection of electrons from the ZnO to the GaN. Moreover, the presence of NiO buffer layer might create the confinement effect.