Measuring research performance of Iraqi universities using Scopus data

Scientometrics - This study investigates the research performance of the Iraqi public and private universities using the Scopus citation database. The investigation consists of three stages. The...     

Temperature dependence of the dielectric response of BaZrO3 by immittance spectroscopy

Electrical measurements using AC immittance spectroscopic technique over the temperature range of 25-300°C, on sintered compacts of pure BaZrO₃ and those containing 5 wt.% BaSnO₃ sintered in the temperature range of 1600-1700°C for up to 12 h are reported. Data analyses revealed that the capacitance and the derived dielectric constant remained invariant over more than three decades of frequency in the kilo to megahertz regime. Typically, the average dielectric constant was 15 and the TCK values were P3 and P186 ppm/°C for pure and 5 wt.% BaSnO₃-added BaZrO₃, respectively, in the range 25-300°C.     

Synthesis of BaZrO3 by a solid-state reaction technique using nitrate precursors

High phase purity barium metazirconate powders have been synthesized from a modified solid-state reaction. Reactive powders consisting of submicron particles and narrow particle size distribution were obtained by heating a 1:1 molar mixture of barium nitrate and zirconyl nitrate at 800°C up to 8 h. Simultaneous thermal analysis (TG-DTA) assisted in elucidating the probable reaction pathways leading to the formation of the target compound in the BaO-ZrO₂ system. Systematic structural and microstructural characterization on the green powders and the compacts sintered up to 1700°C were carried out. A two-stage sintering schedule consisting of a 6 h soak at 1600°C followed by slow heating up to 1700°C with no dwell, led to highly dense microstructural features.     

Liquid holdup in horizontal two-phase gas—liquid flow

The purpose of this study was to simplify and improve the mechanistic model developed by Taitel and Dukler (1976) for estimating the liquid holdup in horizontal two-phase flow. An experimental study was first conducted to develop a data bank used for evaluation and improvement. The holdup data were obtained using an air-kerosene mixture flowed through a test section consisting of a horizontal pipe 2-in (50.8 mm) in diameter and 118 ft (36 m) long. The liquid holdup ranged from 0.009 to 0.61 and the flow patterns observed were stratified, slug and annular.It was shown that the Taitel-Dukler model, which consists of several equations and requires an iterative method to solve, can be accurately represented by a single explicit equation.Based on the measured data, it was found that Taitel-Dukler model tends to overestimate liquid holdup for stratified wavy, slug and annular flow patterns, whereas it tends to underestimate the liquid holdup for stratified smooth flow. An empirical modification, therefore, is proposed which results in a significant improvement in predictions compared to experimental data.Based on statistical results, it is observed that the proposed model gives excellent results and clearly outperforms the original model and all the existing correlations when tested against the present data (89 points) and against data from the literature (111 points).     

Novel Structural Modulation in Ceramic Sensors Via Redox Processing in Gas Buffers

High selectivity, enhanced sensitivity, short response time, and long shelf-life are some of the key features sought in the solid-state ceramic-based chemical sensors. As the sensing mechanism and catalytic activity are predominantly surface-dominated, benign surface features in terms of small grain size, large surface area, high aspect ratio and, open and connected porosity, are required to realize a successful material. In order to incorporate these morphological features, a technique based on rigorous thermodynamic consideration of the metal/metal oxide coexistence is described. By modulating the oxygen partial pressure across the equilibrium M/MO proximity line, formation and growth of new oxide surface on an atomic/submolecular level under conditions of "oxygen deprivation," with exotic morphological features, has been achieved in potential sensor materials. This paper describes the methodology and discusses the results obtained in the case of potential semiconducting ceramic oxide-based carbon monoxide and hydrogen sensors with enhanced characteristics.     

Characterization of BaSnO3-based ceramics: Part 1. Synthesis, processing and microstructural development

The compound BaSnO₃ together with its Ca- and Sr-analogs, has recently been projected as potential electronic ceramic material (thermally stable capacitor, chemical sensor for humidity, CO and NO_x, etc.). In order to fill the information gaps in the reported research, a vigorous and systematic investigation on these exotic materials has been initiated. A thorough study of BaSnO₃ with respect to its synthesis, processing and microstructural characterization has been made. In order to establish a standard methodology for low-cost mass-manufacturing with identical and beneficial microstructure and reproducible electrical characteristics, different synthesis routes (solid-state and self-heat-sustained) were adopted. Evolution of microstructure which is intimately related to the envisaged properties in the ceramics, was closely and systematically followed in terms of sintering over a wide range of temperatures and soak time. This communication forms the first of two parts in a series of investigations on MSnO₃ systems, where results on the synthesis and processing of “phase pure” barium stannate (BaSnO₃) and development of interesting microstructure are presented.     

Overview of energy storage systems for storing electricity from renewable energy sources in Saudi Arabia

Renewable power (photovoltaic, solar thermal or wind) is inherently intermittent and fluctuating. If renewable power has to become a major source of base-load dispatchable power, electricity storage systems of multi-MW capacity and multi-hours duration are indispensable. An overview of the advanced energy storage systems to store electrical energy generated by renewable energy sources is presented along with climatic conditions and supply demand situation of power in Saudi Arabia. Based on the review, battery features needed for the storage of electricity generated from renewable energy sources are: low cost, high efficiency, long cycle life, mature technology, withstand high ambient temperatures, large power and energy capacities and environmentally benign. Although there are various commercially available electrical energy storage systems (EESS), no single storage system meets all the requirements for an ideal EESS. Each EESS has a suitable application range.     

Critical temperature of the lead-bismuth eutectic (LBE) alloy

Liquid metals such as Bi and Pb and Pb-Bi eutectic alloy are serious contenders for use as coolant in LMFBRs in lieu of sodium due to a number of attractive characteristics (high density, low moderation, low neutron absorption and activation, high boiling point and poor interaction with water and air, etc.). Analysis of hypothetical accidents is of relevance to predict the catastrophe involving loss of coolant accident (LOCA) in LMFBRs. One key parameter to take into account is the critical temperature data of the liquid metals for reactor safety analysis. This communication reports the application of a theoretical model called internal pressure approach to predict the critical temperature (T_c) of the LBE alloy for the first time.     

Facile Synthesis and Characterization of Fe/FeS Nanoparticles for Environmental Applications

Multicomponent nanoparticles containing two or more different types of functionalities show unique physical and chemical properties, leading to significantly enhanced performance. In this study, we have developed a new one-pot method to prepare Fe/FeS nanoparticles using dithionite at room temperature. The FeS precipitates on the Fe surface are formed by the interaction between dissolved iron species and hydrogen sulfide, one of the decomposition products of dithionite in solution. The resulting Fe/FeS nanoparticles have high surface area, good electrical conductivity, and strong magnetic responsivity. In addition, the Fe/FeS shows a much higher reactivity toward contaminants than the pure Fe nanoparticles. The above synthesized nanoparticles are successfully applied for the rapid removal of trichloroethylene (TCE) from water. The study reveals that Fe/FeS nanoparticles are a promising candidate for the efficient removal of pollutants.