Materials Science Forum Vol. 1008

Abstract: This paper presents, firstly, an overview of results arisen worldwide on semiconductive thin films used in photovoltaic (PV) cells as a function of time and efficiency. Secondly, the paper demonstrates the electrodeposition of silicon and gallium arsenide films suggested for PV cells, with a focus on electrodeposition from ionic liquids. Ionic liquids, due to their wide electrochemical window, are used for the electrodeposition of elements and compounds impossible to be electrodeposited from aqueous solutions. Finally, a new approach, referred to a recent patent by the author, is illustrated to facilitate the practical electrodeposition of semiconductors from ionic liquids that can be suggested for industrial applications.

Abstract: Methylene blue (MB) is one of the commonly used dyes in the textile industry and can be used as a model pollutant for the textile industry wastewater. In this work, the photocatalytic degradation of MB by synthesized nanoparticles of lanthanum vanadate (LaVO₄) was assessed. The effects of pH, initial MB concentration and catalyst dose on the removal performance of MB were investigated and measuring the optimum values of these operational conditions was performed using response surface methodology (RSM). Catalyst dose of 0.43 g/L, initial MB concentration of 5.0 mg/L, and pH of 6.86 were found to be the optimum conditions in reaction time of 60 min. A mathematical model was formed to relate the removal efficiency of MB to the aforementioned operating parameters. The removal efficiency of MB was 91% without any scavengers at a catalyst dose of 0.3 g/L, pH of 7 and initial MB concentration of 10 mg/L. The trapping experiments confirmed the participation of different reactive species in the photo-degradation process. The degradation rates of MB were 91%, 86%, 81%, 77.70% and 72% in five successive runs using LaVO₄.

Abstract: The addition of metal nanoparticles in the Bi-based superconductors has shown the disorder produced by the cations incorporation in the crystal structure affects the TC (Critical temperature) of the system. the addition of new mixture of (Cr2O3: SnO)x on high temperature superconductors HTS Bi1.6Pb0.4 Sr2Ca2Cu3O10+δ (Bi-2223) with ratio 1:1 where x = 0.0, 0.05, 0.10, 0.15 and 0.20 was investigated by solid-state reaction technique was used to prepare superconductor samples. Samples were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FS-EM), Energy Dispersive X-ray (EDX), and electrical resistivity. the results of XRD proved that the structure of 2223 remains the same even with the addition of (Cr2O3: SnO)x nanoparticles. The phase 2223 has the majority even phase Bi-2212 and phase Ca2PbO4 showed a contribution inside structure. As a result of the change physico-chemical properties resistivity of the doped optimized sample x = 0.10 was increasing 2.2 K approximately rather than the undoped one then decreased gradually up to x = 0.20. From resistivity measurement, the TC of 2223 doped with (Cr2O3: SnO)x at x = 0.10 was 113.2 K approximately. The addition of metal oxides in superconductor materials has been considered to be one of the most promising materials for large scale applications in superconducting industry.

Abstract: Polyaniline (PANI) has successfully been prepared by chemical oxidation polymerization of aniline monomer. The prepared polymer was confirmed by XRD. The conducting form of PANI known as emeraldine salt (ES) through different concentrations of formic acid; 0.4 mmol/ L, 2mmol/ L, 6 mmol/ L, 8 mmol/ L, 10 mmol/ L, and 12 mmol/L is prepared from its insulating emeraldine base (EB) by levels of doping. The objective is to establish a correlation between the levels of doping, the zeta potential of the suspension. Positive zeta potential values (24.75, 27, 33.25, 36.75, 40.50, and 42) mV were obtained for the various PANI suspension. This showed the acquisition of positive charges by the PANI after doping. The observation was made that zeta potential values increases as formic acid concentration increased. This was correlated using UV/VIS spectra and electrophoretic coating with the polyaniline suspensions.

Abstract: Duckweed (Lemna Gibba) was successfully used for phytoremediation of wastewater containing 1,4-dioxane, which could also result in biomass with high protein and carbon content. 1,4-dioxane is not easily removed or separated from wastewater by traditional physicochemical processes such as coagulation and activated carbon adsorption because of its high solubility [1]. Three duckweed-pond continual streams (DWs) lab-scale reactors, i.e., one pond (DW1), two ponds (DW2), and three ponds (DW3), were operated at variable hydraulic retention times (HRTs) of 2, 4, and 6 days respectively that are designed to treat wastewater containing 1,4dioxane. The results showed that the removal efficiency of 1,4 dioxane, COD, TOC, and ammonia were quite high in the DW3 which had the highest removal efficiency in 1,4-dioxane and NH4-N. 1,4-Dioxane and NH4-N removal efficiencies using DW3 (i.e., 56.9 ± 25% and 87.2 ± 7.1%, respectively) were slightly higher than that obtained using DW2 (i.e., 44.8 ± 19.6% and 81.9 ± 8.6%, respectively). Further, it was noted that, at DW3, the average effluent pH decreased that range from (8.80) to (7.45, c (TDS) decreased that range from( 921.5 ± 120.6) to (837.6 ± 83.6) mg/L, and Dissolved Oxygen (DO) increased that range from (3.5 ± 1.9) to (7.5 ± 3) mg/L. Eventually, DW removed 1,4dioxane effectively from wastewater, representing an effective, low operation, eco-friendly, and maintenance costs technology.

Abstract: In the present study, the combustion characteristics of LPG gaseous fuel diffusion flame at elevated air temperatures were experimentally investigated. An experimental test rig was manufactured to examine a wide range of operating conditions. The investigated parameters are the air temperatures of 300, 350, 400, 450, and 500 K with constant percentage of nitrogen addition in combustion air stream of 5 % to give low oxygen concentration of 18.3 % by mass at constant air swirl number, air to fuel mass ratio, and thermal load of 1.5, 30, and 23 kW, respectively. The gaseous combustion characteristics were represented as axial and radial temperatures distributions, temperatures gradient, visible flame length and species concentrations. The results indicated that as the air temperature increased, the chemical reaction rate increased and flame volume decreased, the combustion time reduced leading to a reduction in flame length. The NO concentration reaches its maximum values near the location of the maximum centerline axial temperature. Increasing the combustion air temperature by 200 K, the NO consequently O₂ concentrations are increased by about % 355 and 20 % respectively, while CO₂ and CO concentrations are decreased by about % 21 and 99 % respectively, at the combustor end.

Abstract: Falling film on horizontal tube evaporators, of both Mechanical Vapor Compression (MVC) and the Multi-Effect Distillation (MED) desalination systems, plays an important role in the heat and mass transfer (evaporation) and accordingly the systems productivity. Falling film thickness is mainly influenced by the intertube space, circumferential angle and the film’s Reynolds number. This paper presents two-dimensional numerical study of falling film thickness around horizontal tube in MVC and MED evaporators. The study is based on computational fluid dynamics (CFD) using volume of fraction (VOF) as a multi-phase technique in ANSYS Fluent. The numerical model is developed in order to study the heat and mass transfer charactristics, the liquid falling film behaviour and thickness distribution around circular horizontal. Four CFD study cases are developed to simulate the falling film behaviour at circumferential angle range from 150 to 1650 with inter-tube spacing of 10 mm, 16 mm, 33 mm and 40 mm and for constant value of flow rate and at the same surrounding conditions. Simulations are conducted using a domain of only two tubes with 20 mm outer diameter.The results from the numerical models are compared with the published experimental correlations, showing a comparatively reasonable agreement. In addition, a parametric study is carried out to illustrate the effect of flow Reyonlds number (Re) and intertube space on the average circumferential film thickness and heat transfer rates.

Abstract: The present study is concerned with the removal rate of Copper ions Cu++ from wastewater by cementation of copper from copper sulfate solution on a horizontal steel sheet placed at the bottom of a square stirred tank reactor and fitted with square steel turbulence promoters. The variables studied were solution concentration, rotation speed, impeller geometry, promoter diameter and distance between promoters. The rate of mass transfer was found to increase with the rotational speed and decreased with the increase of distance between promoters. The data were correlated to develop the relationship Sh α Re x

Abstract: The objective of the present work is to investigate the pyrolysis of sugarcane bagasse in a semi-batch reactor and study the effect of process parameters of pyrolysis on the products yield to determine optimum parameters for maximum bio-oil production. Parameters of the pyrolysis process such as temperature, particle size of sugarcane bagasse and flow rate of nitrogen (N₂) have been varied as 350–600 °C, 0.25–2 mm and 100–500 cm³/min, respectively. According to the various pyrolysis conditions applied in the experimental studies, the obtained oil, char and gas yields ranged between 38 and 45 wt%, 24 and 36 wt%, and 23 and 37 wt%, respectively. The maximum pyrolysis bio-oil yield of 45 wt% was achieved at temperature of 500 °C, particle size of 0.5 -1 mm with nitrogen(N₂) flow rate of 200 cm³/min. Based on the results captured under this study's pyrolysis conditions, temperature is considered to be the most important parameter for product distribution. As the increases of the pyrolysis temperature the bio-char yield decreased and increase of gas yield. The bio-oil yield increases with increasing the temperature, reaches a maximum value at about 500 °C and reduces thereafter at higher temperature is expect due to secondary cracking reactions of the volatiles, which results produce a higher gaseous yield.

Abstract: Owing to the high mixing capacity, the stirred tank reactor is the key class of reactors in the chemical process industry and pharmaceutical industry. The mass transport nature of a batch stirred tank reactor with a fixed copper wall with a cylinder form was studied using copper dissolution in acidified dichromate which is controlled by diffusion. Variables analyzed included the speed of rotation of the impeller, the shape of the impeller and the physical specifications of the solution and the existence of baffles. The data were correlated for the conditions 3667.323 < Re < 34993.18 and 960 < Sc < 1364, for radial flow by the equation: Sh =0.3453 *Sc^1/3*Re^0.66 but for axial flow by the equation: Sh =0.5866 *Sc^1/3*Re^0.59. Through speed of rotation of the impeller increases,it allows the rate of mass transfer from the fixed bed to the solution to rise. The radial-flow turbine is more effective than the axial-flow turbine in increasing the rate of mass transfer. The usage of baffles plays a significant role in rising the rate of mass transfer. Using baffles; the correlation will be Sh =0.0769 *Sc^1/3*Re^0.84 for radial flow and Sh =0.1157 *Sc^1/3*Re^0.78 for axial flow. The purpose of this research is to estimate the rate of mass transport that can be required in corrosive reactions, and also to maximize the mass transfer rate that can be achieved in other processes, such as electroplating in presence of baffles.