Indian Institute of Technology Kharagpur

About: Indian Institute of Technology Kharagpur is a education organization based out in Kharagpur, India. It is known for research contribution in the topics: Computer science & Dielectric. The organization has 16887 authors who have published 38658 publications receiving 714526 citations.

Effective Coefficients of Piezoelectric Fiber-Reinforced Composites

Abstract: The effective coefe cients of piezoelectric e ber-reinforced composites (PFRC) have been determined through micromechanical analyzes. The method of cells (MOC) and the strength of materials (SM) approach have been employed to predict the coefe cients. A constant electric e eld is considered in the direction transverse to the e ber direction and is assumed to be the same both in the e ber and the matrix. MOC and SM predictions for the effective piezoelectric coefe cient of the PFRC assessing the actuating capability in the e ber direction are in excellent agreement. It has been found for the piezoelectric e bers considered that, when the e ber volume fraction exceeds a critical e ber volume fraction, this effective piezoelectric coefe cient becomes signie cantly larger than the corresponding coefe cient of the piezoelectric material of the e ber. The methods also show the excellent matching of the predictions of the effective elastic constants and the dielectric constant of the PFRC in the useful range of e ber volume fraction.

Lanthanum biosorption by a Pseudomonas sp.: equilibrium studies and chemical characterization.

Abstract: Lanthanum biosorption by a Pseudomonas sp. was characterized in terms of equilibrium metal loading, model fitting, kinetics, effect of solution pH, lanthanum-bacteria interaction mechanism and recovery of sorbed metal. Lanthanum sorption by the bacterium was rapid and optimum at pH 5.0 with equilibrium metal loading as high as 950 mg g(-1) biomass dry wt. Scatchard model and potentiometric titration suggested the presence of at least two types of metal-binding sites, corresponding to a strong and a weak binding affinity. The chemical nature of metal-microbe interaction has been elucidated employing FTIR spectroscopy, energy dispersive X-ray analysis (EDX) and X-ray diffraction analysis (XRD). FTIR spectroscopy and XRD analysis revealed strong involvement of cellular carboxyl and phosphate groups in lanthanum binding by the bacterial biomass. EDX and the elemental analysis of the sorption solution ascertained the binding of lanthanum with the bacterial biomass via displacement of cellular potassium and calcium. Transmission electron microscopy exhibited La accumulation throughout the bacterial cell with some granular deposits in cell periphery and in cytoplasm. XRD confirmed the presence of LaPO4 crystals onto the bacterial biomass after La accumulation for a long period. A combined ion-exchange-complexation-microprecipitation mechanism could be involved in lanthanum accumulation by the biomass. Almost 98% of biomass-bound La could be recovered using CaCO3 as the desorbing agent.