Effect of current density on the corrosion protection performance of polyaniline coated AISI 4140 steel

The present work reports on electropolymerisation of aniline onto AISI 4140 steel substrate at room temperature in oxalic acid media by the potentiodynamic electrodeposition method. The effect of coating current density on the morphology of conductive polymer films and their corrosion behaviour has been investigated. The electrolyte solution comprised 0.1 M aniline?+?0.3 M oxalic acid. The effects of deposition current density changes (0.1, 0.2, 0.3, 0.4 and 0.5?mA cm^?2) on the films were investigated. The PANI film was characterised using cyclic voltammetry and optical microscopy; it was covered with a dark green-yellow homopolymer film of strongly adherent homogeneous characteristic. The corrosion behaviour of steel electrodes with and without polyaniline (PANI) film in 3.5 wt-% NaCl solution was investigated through anodic polarisation curves. The results indicated that the PANI coating obtained under 0.2?mA cm^?2 was the most corrosion protective.     

Dynamic analysis of a trickle bed reactor by moment technique

The performance of a trickle bed reactor is investigated by the moment technique. Residence time distributions of SO₂ tracer in both gas (Helium) and liquid (distilled water) effluents are used to predict zero reduced and first absolute moments and these values are compared with the derived theoretical expressions. Correlations are suggested for gas-liquid mass transfer coefficient, liquid hold up, and extent of axial mixing in liquid phase.True adsorption equilibrium constant of the system is estimated as 0.378 from liquid full bed experiments and contacting efficiency of the trickle bed reactor is found as 0.987.Effect of axial dispersion is not significant on gas-liquid mass transfer coefficient since absorption factor is small, but is found to be quite important on the true estimation of adsorption factor.     

MIMO H∞ control of three-axis ship-mounted mobile antenna systems

The need for on-line information in any environment has led to the development of mobile satellite communication terminals. These high data-rate terminals require inertial antenna pointing error tolerance within fractions of a degree. However, the base motion of the antenna platform in mobile applications complicates this pointing problem and must be accounted for. Gimbaled motorised pedestals are used to eliminate the effect of disturbance and maintain uninterrupted communication. In this paper, a three-axis ship-mounted antenna on a pedestal gimbal system is studied. Based on the derived dynamic model of the antenna pedestal multi input-multi output PID and H_∞ linear controllers are designed to stabilise the antenna to keep its orientation unaltered towards the satellite while the sea waves disturb the antenna. Simulation results are presented to show the stabilisation performance of the system with the synthesised controllers. It is shown through performance comparison and analysis that the proposed H_∞ control structure is preferable over PID controlled system in terms of system stability and the disturbance rejection.     

Interaction of Sodium Ions with Feldspar Surfaces and Its Effect on the Selective Separation of Na- and K-Feldspars

K-feldspar and Na-feldspar exhibit similar mineralogical, chemical and surface properties. Froth flotation is known to be the only technique to enable their separation. Our earlier studies revealed a good selectivity in the presence of K⁺ and to a larger extent with Na⁺ ions. In this context, in order to further identify the role of Na⁺ ions in the selective separation of these minerals, ion selective electrodes were employed to determine the released Na and K ions released from albite and microcline into the solution and those adsorbed ions onto the mineral surfaces. Adsorption isotherms in feldspars/inorganic systems were constructed and the regions representing ion exchange and ion adsorption isotherms delineated. The mechanism of selective separation was elaborated on the basis of micro-flotation, solubility, adsorption and zeta potential measurements.     

What is the Effect of Critical Surface Tension of PbSO3 Thin Film?

This study focuses on the critical surface tension of lead sulfite (PbSO₃) crystalline thin film produced with chemical bath deposition on substrates (commercial glass).The PbSO₃ thin films were deposited at room temperature at different deposition times. The structural properties of the films were defined and examined according to X-ray diffraction (XRD) and the XRD results such as dislocation density, average grain size, and no. of crystallites per unit area. Atomic force microscopy was used to measure the film thickness and the surface properties. The critical surface tension of the PbSO₃ thin films was measured with an optical tensiometer instrument and calculated using the Zisman method. The results indicated that the critical surface tension of films changed in accordance with the average grain size and film thickness. The film thickness increased with deposition time and was inversely correlated with surface tension. The average grain size increased according to deposition time and was inversely correlated with surface tension.