Synthesis, characterization and gas sensing property of hydroxyapatite ceramic

Hydroxyapatite (HAp) biomaterial ceramic was synthesized by three different processing routes viz. wet chemical process, microwave irradiation process, and hydrothermal technique. The synthesized ceramic powders were characterized by SEM, XRD, FTIR and XPS techniques. The dielectric measurements were carried out as a function of frequency at room temperature and the preliminary study on CO gas sensing property of hydroxyapatite was investigated. The XRD pattern of the hydroxyapatite biomaterial revealed that hydroxyapatite ceramic has hexagonal structure. The average crystallite size was found to be in the range 31–54 nm. Absorption bands corresponding to phosphate and hydroxyl functional groups, which are characteristic of hydroxyapatite, were confirmed by FTIR. The dielectric constant was found to vary in the range 9–13 at room temperature. Hydroxyapatite can be used as CO gas sensor at an optimum temperature near 125°C. X-ray photoelectron spectroscopic studies showed the Ca/P ratio of 1.63 for the HAp sample prepared by chemical process. The microwave irradiation technique yielded calcium rich HAp whereas calcium deficient HAp was obtained by hydrothermal method.     

5th International Symposium on Electrochemical Impedance Spectroscopy Marilleva (Trento), Italy, June 2001

Preface

5th International Symposium on Electrochemical Impedance Spectroscopy Marilleva (Trento), Italy, June 2001     

Electrical properties of MOS capacitors formed by PEALD grown Al2O3 on silicon

In the present work, we have grown 2.83 nm thin Al₂O₃ films directly on pre-cleaned p-Si (100) substrate using precursor Trimethyl Aluminium (TMA) with substrate temperature of 300°C in a Plasma Enhanced Atomic Layer Deposition (PEALD) chamber. The MOS capacitors were fabricated by depositing Pt/Ti metal bilayer through shadow mask on Al₂O₃ high-k by electron beam evaporation system. The MOS devices were characterized to evaluate the electrical properties using a capacitance voltage (CV) set-up. The dielectric constant calculated through the CV analysis is 8.32 for Al₂O₃ resulting in the equivalent oxide thickness (EOT) of 1.32 nm. The flat-band shift of 0.3 V is observed in the CV curve. This slight positive shift in flat-band voltage is due to the presence of some negative trap charges in Pt/Ti/ALD-Al₂O₃/p-Si MOS capacitor. The low leakage current density of 3.08 × 10^?10 A/cm² is observed in the JV curve at 1 V. The Si/Al₂O₃ barrier height Φ _B and the value of J _FN are calculated to be 2.78 eV and 3.4 × 10^?5 A/cm² respectively.     

Fabrication of silicon based glass fibres for optical communication

Silicon based glass fibres are fabricated by conventional fibre drawing process. First, preform fabrication is carried out by means of conventional MCVD technique by using various dopants such as SiCl₄, GeCl₄, POCl₃, and FeCl₃. The chemicals are used in such a way that step index single mode fibre can be drawn. The fibre drawing process consists of various steps such as heating the preform at elevated temperature, diameter monitor, primary and secondary coating, and ultra violet radiation curing. The fibres are then characterized for their geometrical and optical properties. The drawn fibre has diameter of core and cladding to be 8.3 μm and 124.31 μm, respectively whereas non-circularity is found to be 4.17% for core and 0.26% for cladding as seen from phase plot. Mode field diameter is found to be 8.9 μm and 9.2 μm using Peterman II and Gaussian method, respectively. The fabricated fibres showed the signal attenuation of 0.35 dB/km and 0.20 dB/km for 1310 nm and 1550 nm, respectively as measured by the optical time domain reflectometer (OTDR).     

Conducting polyaniline based paints on low carbon steel for corrosion protection

Conducting polyaniline powder was synthesized chemically and paints containing conducting polyaniline powder were applied on low carbon steel samples. The conducting polyaniline powder was characterized by UV-Visible absorption spectroscopy and the morphology of paint coating on low carbon steel was studied by scanning electron microscopy. The corrosion protection performance of the coating was evaluated by using potentiodynamic polarization techniques and electrochemical impedance spectroscopy. It has been found that the 2 wt % polyaniline-hydrochloric acid based paint coating offers maximum corrosion protection to low carbon steel in chloride medium.     

High Dielectric Constant ZrO<Subscript>2</Subscript> Films by Atomic Layer Deposition Technique on Germanium Substrates

Germanium has been reconsidered as a potential substitute channel material for high-performance MOSFETs due to its intrinsic high mobilities for both electrons (3900 cm² s^-1V^-1) and holes (1900 cm² s^-1V^-1). In the present work we have fabricated Pt/Ti metal bilayered ALD-ZrO ₂/n-Ge based MOS capacitors. The ZrO₂ thin film was deposited on n-Ge (100) substrates by using ZrEMA and oxygen precursors at 300 ^°C in a PEALD system. The Pt/Ti bilayer metallization was carried out using e-beam evaporation and PMA using a RTA system at 350 ^°C in the forming gas. The thickness of the ZrO₂ gate stack was measured to be 3.61 nm using an ellipsometer. The electrical study was done by analyzing capacitance voltage and current voltage measurements. The flat-band shift was found to be 0.22 V, Q_eff was 3.55×10¹² cm^-2 and D_it was 8.53×10¹² cm^-2 eV^-1. Current voltage characteristics have been analyzed to know the conduction mechanism in fabricated MOS devices.     

Bio-Inspired Multilevel Security Protocol for Data Aggregation and Routing in IoT WSNs

Mobile Networks and Applications - The resource limitation and unreliability of IoT WSN makes the sensors susceptible to a lot of malicious attacks. In this research work, we propose ANT Particle...     

Radial basis function neural network for pulse radar detection

A new approach using a radial basis function network (RBFN) for pulse compression is proposed. In the study, networks using 13-element Barker code, 35-element Barker code and 21-bit optimal sequences have been implemented. In training these networks, the RBFN-based learning algorithm was used. Simulation results show that RBFN approach has significant improvement in error convergence speed (very low training error), superior signal-to-sidelobe ratios, good noise rejection performance, improved misalignment performance, good range resolution ability and improved Doppler shift performance compared to other neural network approaches such as back-propagation, extended Kalman filter and autocorrelation function based learning algorithms. The proposed neural network approach provides a robust mean for pulse radar tracking     

Dehydration of glycerin/water mixtures by pervaporation using homo and copolymer membranes

Separation characteristics of glycerol/water mixtures were studied using hydrophilic poly(acrylonitrile-comethacrylic acid) (PANMAC), poly(acrylonitrile-co-hydroxyethyl methacrylate) (PANHEMA), Poly(vinyl alcohol) GFT-1001, and poly(vinyl alcohol) (PVA) crosslinked with maleic anhydride (PVAManh) membranes. All membranes were found to be highly water selective. PVAManh membrane yielded the highest permeation flux for water over the entire range of water concentration studied. Homopolymers (PVAManh and GFT-1001) gave better permeation rates than copolymer membranes (PANHEMA and PANMAC). But the swelling of homopolymers is nuch greater than that of copolymers, which is why PVA membranes have poor longevity. No effect on selectivity of the membrane was observed with a change in operating parameters. No decomposition/polymerization of glycerin was observed, as there was no involvement of high temperatures as there is with distillation. A comparison of pervaporation with vapor-liquid equilibrium data showed that pervaporation of glycerin/water mixtures yielded better selectivity than vapor-liquid equilibrium, particularly for glycerol concentrations above 90 wt%.     

Zinc ion-imprinted polymer based on silica particles modified carbon paste electrodes for highly selective electrochemical determination of zinc ions

ABSTRACT

In this study, Zn(II) ion-imprinted polymer was prepared on the surface of vinyl silica particles and applied for detection of Zn(II) ions using differential pulse voltametry. The ion- imprinted polymer particles were prepared by free radical polymerization. The prepared particles were characterized by different morphological and elemental techniques. The ion-imprinted particles were used to fabricate the carbon paste electrode as a zinc ions sensor. The modified zinc sensor showed linear response in the concentration range 6.12 × 10^?9 to 4.59 × 10^?8 mol L^?1. The limit of detection and limit of quantification of the electrode were 1.351 × 10^?8 and 4.094 × 10^?8 mol L^?1, respectively.