Effect of ‘Zn’ substitution on structural,morphological, magnetic and optical properties of Co–Zn ferrite nanoparticles for ferrofluid application

Journal of Materials Science: Materials in Electronics - The Co1?xZnxFe2O4 (Co–Zn) ferrite nanoparticles with x varying from 0.0 to 0.4 have been manufactured by facile chemical...     

Effect of Dy-substitution on structural and magnetic properties of MnZn ferrite nanoparticles

This paper describes the structural and magnetic properties of Dy-substituted Mn-Zn ferrite nanoparticles. Mn-Zn-Dy ferrite nanoparticles of the composition Mn_(0.5)Zn_(0.5)Dy_xFe_(2-x)O_4(x=0.05, 0.1,0.15 and 0.2) were synthesized by a facile chemical co-precipitation method. The samples were characterized through X-ray diffraction(XRD), transmission electron microscopy(TEM), Fourier transform infrared spectroscopy(FTIR), vibrating sample magnetometer(VSM) and Curie temperature. The XRD patterns confirm the synthesis of single crystalline phase of Mn-Zn-Dy ferrite nanoparticles. Lattice parameter increases with increase in Dy-substitution which confirms the replacement of Fe~(3+) ions by Dy~(3+) ions.Crystallite size is of the order of 6-8 nm for all these samples. The particle sizes observed from TEM analysis are in good agreement with the XRD values. The magnetic measurements show superparamagnetic nature of the samples. The saturation magnetization decreases with increase in Dyconcentration and can be correlated to modifications in the A-B exchange interactions as a result of the structural modifications due to Dy-substitution. The Curie temperature for Mn_(0.5)Zn_(0.5)Fe_2 O_4 nanoparticles is 124 ℃ and decreases up to 84 ℃ with the increase in the Dy-concentration. The decrease in Curie temperature can be attributed to the weakening of the superexchange interaction between A-site and B-site as a result of Dy-substitution. The low value of Curie temperature and higher value of thermomagnetic coefficient k_T shown by these samples makes them suitable for the preparation of temperature sensitive ferrofluid for heat transfer applications.     

Cd1-x Zn x Se thin film electrodes: an electrochemical photovoltaic study

The interface between an n?Cd_1?x Zn _x Se semiconductor and an electrolyte redox couple is investigated through the capacitance–voltage, current–voltage and photovoltaic characteristics. A brief discussion is made on the properties of a semiconductor/electrolyte Schottky barrier with reference to the experiments performed. The observed results of the capacitance–voltage measurements in the dark are compared with the photovoltage measurements. The dependence of the dark current on the dark voltage for both forward and reverse bias is examined and explained. It is probable that the current–voltage characteristics are determined by the electrochemical kinetics in addition to the diode rectifier theory. The measurements of photovoltaic properties show a significant improvement in the cell performance after addition of Zn to CdSe (optimum at x = 0.3).     

Design of mixed energy‐integrated batch process networks by Pseudo‐direct approach

In this article, a novel framework for the design of mixed (combined direct and indirect) integration for batch process systems is presented. The framework is based on the concept of pseudo‐direct energy integration (PDEI) which reformulates indirect integration as direct integration using pseudo‐process streams. Two algorithms are presented to achieve energy integration for batch processes operating cyclically (in a campaign mode). The first algorithm targets maximization of energy recovery and overcomes the limitations of some of the existing contributions for design of mixed integrated systems. The second algorithm provides a network reduction methodology to generate a cadre of integrated designs while exploring the trade‐off between capital (number of heat exchangers and storage units) and operating costs (utility consumption). The proposed framework is illustrated using a benchmark example of two hot and two cold streams. © 2017 American Institute of Chemical Engineers AIChE J, 63: 55–67, 2018     

Photovoltaic properties of n-CdS1−xTex thin film/polysulphide photoelectrochemical solar cells prepared by chemical bath deposition

n-CdS_1−xTe_x (0≤x≤1) thin films were deposited by a chemical bath deposition technique on highly conducting, precleaned stainless steel substrates and were used in a photoelectrochemical conversion process. The as-grown films exhibited photoactivity in an aqueous 0.5 M NaOH+0.5 M Na₂S+0.5 M S (pH 12.6) electrolyte. An interface between n-CdS_1−xTe_x semiconductor photoelectrode and an electrolyte redox couple was formed and investigated through the capacitance-voltage, current-voltage and photovoltaic characteristics. A brief discussion is made on the properties of the semiconductor/electrolyte Schottky barrier with reference to the experiments performed and the photoelectrode composition. The observed results on the capacitance-voltage and current-voltage measurements in dark are compared with the photovoltage measurements. The measurements on the characteristic photovoltaic properties showed a significant enhancement in the cell performance after addition of Te in to CdS (x=0.1).     

Studies on photoelectrochemical (PEC) cells: A correlation between electrochemical and material properties

CdS_0.9Te_0.1 thin films of various thicknesses (680–2740 nm) were deposited onto the clean glass and stainless steel substrates using a chemical deposition technique. The as-grown films exhibited photoactivity in an aqueous 0.5 M NaOH+0.5 M Na₂S+0.5 M S (pH=12.6) electrolyte. An interface between n-CdS_0.9Te_0.1 semiconductor photoelectrode and an electrolyte redox couple was formed and investigated through the capacitance–voltage, current–voltage and photovoltaic characteristics. The results on the capacitance–voltage and current–voltage measurements in dark are compared with the photovoltage measurements. The measurement on the characteristic photovoltaic properties showed a significant enhancement in the cell performance at a thickness of 2740 nm (0.658% efficiency).     

Structural, optical and gas sensing properties of spin coated nanocrystalline zinc oxide thin films

Synthesis of nanocrystalline zinc oxide thin films by sol gel spin coating technique and its application as ammonia gas sensor is presented in this paper. The synthesized sample is pure zinc oxide with hexagonal wurtzite structure. The lattice parameters are: a = 3.2568 Å and c = 5.210 Å. Average crystallite size is of the order of 58 nm. SEM studies show that growth of the film takes place with folded structure, increasing the open surface area of the film. Optical study revealed that band gap of ZnO is 3.25 eV with direct band to band transitions. Gas sensing characteristics showed that ZnO film is sensitive as well as fast responding to ammonia gas at 573 K. A high sensitivity for ammonia gas indicates that the ZnO films are selective for this gas. The rise time and recovery time are 25 and 80 s, respectively. The mechanism of gas sensing is explained adequately.