Sukhen Das

The effect of Sn(IV) on transformation of co-precipitated hydrated In(III) and Sn(IV) hydroxides to indium tin oxide (ITO) powder

Multicomponent metal oxide (indium tin oxide, ITO) powders were prepared by the hydrolysis of their corresponding metal salts following co-precipitation technique. Indium tin oxide powders with relatively high content of tin were prepared by the treatment of aqueous NH4OH with the mixture of aqueous In(NO3)3 and SnCl4 solution (pH=8.4–8.7) at an ambient temperature. The composition of the powders were 90:10, 70:30 and 50:50 (In/Sn atomic ratio). The air-dried powders were cured at different temperatures and also at different atmospheric conditions [air and H2(5%)–Ar(95%)]. They were characterized by FTIR spectroscopy, thermal analysis and X-ray powder diffraction studies. FTIR spectroscopy and thermal analysis of powders revealed that the air-dried powders existed as hydroxides of In3+ and Sn4+ in the solid state which transformed to ITO via some metastable intermediates after 300 °C. In addition, the formation of Inue5f8Oue5f8In and Snue5f8Oue5f8Sn type of bonding was also predicted by FTIR. Below 200 °C, the powders predominantly existed as corresponding hydrated oxide phases which corresponded to possible formulations, In(OH)3 and SnO3H2 and transformed to ITO phases after 300 °C. The powders containing below 30% Sn showed pure cubic In2O3 phase whereas the casseterite structure of SnO2 phase was observed in the case of relatively high Sn content (Sn>30%). The crystallite size of the powders increased with temperature as well as with increase in Sn content.

Synthesis and densification of magnesium aluminate spinel: effect of MgO reactivity

Stoichiometric magnesium aluminate spinel was synthesized by reaction sintering of alumina with caustic and sintered magnesia. The volume expansion of 5-7% during MgAl2O4 formation was utilized to identify the starting temperature of spinel formation and densification by high temperature dilatometry. The magnesia reactivity was determined by measurement of crystallite size and specific surface area. Caustic magnesia and sintered magnesia behave differently vis-A-vis phase formation and densification of spinel. Densification of stoichiometric Mag-Al spinel was carried out between 1650 and 1750 degreesC. Attempts were made to correlate the MgO reactivity with microstructure and densification of spinel

Al-Si spinel phase formation in diphasic mullite gels

Abstract Diphasic aluminosilicate gels of varying Al 2 O 3 :SiO 2 ratios were synthesized out of TEOS and ANN in basic condition, heated to different temperatures and finally analyzed for phases. All gels precalcined to ∼1000xa0°C were further calcined after mixing with CaCO 3 and analyzed by XRD. XRD intensity of (440) of intermediate spinel phase formed during mullite formation was recorded. It has been shown that the XRD intensity of spinel phase to calcium fluoride is in excess of what is possible if the spinel phase is simply γ-Al 2 O 3 . This substantiates the view of silicon-incorporation in spinel lattice. This view is verified and extended by the further study of phase development on heating spinel-generated samples with CaCO 3 . Gehlenite forms in Si-rich gels up to approximately 3:2 mullite composition whereas in more Al-rich gels additional calcium aluminate phases are formed.

Heat-induced structural changes in merocyanine dyes: X-ray and thermal studies

Abstract Certain merocyanine dyes undergo heat-induced isomerisation, which is responsible for their thermovoltage generation properties. Using these dyes, our studies reveal the correlation between their thermal properties and their crystalline structure. Differential thermal analysis of hexadecyl, decyl and pentyl dyes showed reversible phase transitions at their respective characteristic temperatures (Tc) owing to thermal isomerisation of the dyes. X-Ray diffraction patterns indicated heat-induced changes in the crystal structure of the dyes. This was also supported by the results obtained from polarising microscopy studies and thermogravimetric analysis. Further heating of these dyes caused a permanent deformation in the crystal structure, which ultimately led to total disintegration as recorded in the thermogravimetric studies.

Determination of coupled sway, roll, and yaw motions of a floating body in regular waves

This paper investigates the motion response of a floating body in time domain under the influence of small amplitude regular waves. The governing equations of motion describing the balance of wave-exciting force with the inertial, damping, and restoring forces are transformed into frequency domain by applying Laplace transform technique. Assuming the floating body is initially at rest and the waves act perpendicular to the vessel of lateral symmetry, hydrodynamic coefficients were obtained in terms of integrated sectional added-mass, damping, and restoring coefficients, derived from Franks close-fit curve. A numerical experiment on a vessel of 19190 ton displaced mass was carried out for three different wave frequencies, namely, 0.56 rad/s, 0.74 rad/s, and 1.24 rad/s. The damping parameters (ςi) reveal the system stability criteria, derived from the quartic analysis, corresponding to the undamped frequencies (βi). It is observed that the sway and yaw motions become maximum for frequency 0.56 rad/s, whereas roll motion is maximum for frequency 0.74 rad/s. All three motions show harmonic behavior and attain dynamic equilibrium for time t>100 seconds. The mathematical approach presented here will be useful to determine seaworthiness characteristics of any vessel when wave amplitudes are small and also to validate complex numerical models.

Evidence for two stage mullite formation during thermal decomposition of kaolinite

Abstract Structural changes on heat treatment of English kaolinite have been studied by a standard X-ray technique. Changes in the lattice parameters, strain values, and crystal sizes of mullite and cristobalite have been calculated using a computer based Rietveld program. The results show two separate stages of mullite formation during the reaction of kaolinite. Changes in the composition of mullite during the course of its formation are discussed.

Heat-induced voltage generation in hexadecyl merocyanine dye-probed planar lipid membranes

Abstract A hexadecyl merocyanine dye was used as a heat driven proton gate, by incorporating it in a planar lipid membrane which is a good model for biological membranes. Being hydrophobic in nature, it prevents charge recombination, and transmembrane voltages of high magnitude (∼310 mV) were obtained upon heating. The process was reversible and the whole cycle took about 20 h, suggesting that the system could be used as a heat driven storage cell. Comparison of the X-ray diffraction patterns of the thin films of the dye at 30°C showed a heat-induced conformational change in the crystalline structure of the dye. From differential thermal analysis three reversible phase transitions were observed, at 39·2°C, 53·7°C and 62·1°C, and the associated enthalpy changes were calculated. The results indicate that the heat-induced conformational change of the dye molecule is responsible for the observed thermovoltage generation.

ANALYTICAL MODEL TO DETERMINE RESPONSE AMPLITUDE OPERATOR OF A FLOATING BODY FOR COUPLED ROLL AND YAW MOTIONS AND FREQUENCY-BASED ANALYSIS

The paper deals with the mathematical modeling of response amplitude operator (RAO) and frequency-based analysis for coupled roll and yaw motions in regular waves. Prior to obtaining the RAO expressions for linearly coupled conditions, hydrodynamic coefficients are computed by using the strip theory formulation. We consider sinusoidal wave with frequency (ω) varying between 0.3 rad/s and 1.2 rad/s acts on beam to the floating body for zero forward speed. Two limiting cases corresponding to ω → 0 and ω → ∞ are considered and general expressions of RAO for intermediate frequencies are derived. Analytical result shows that the norm of RAO is maximum when ω ≈ ωn ≈ 0.74 for coupled roll and yaw motions. The asymptotic convergence of real part, imaginary part and norm of uncoupled yaw transfer functions are noticed with the increase of wave frequency. Using the normalization procedure and frequency based analysis; group based equations are formulated for each case. To understand the relative importance of the hydrodynamic coefficients, analytical solutions are obtained. The sensitivity analysis with respect to the initial conditions is investigated for roll and yaw motions. This study could be useful to model the floating body dynamics and corresponding wave loads in the design stage.

Photoinduced changes in structure and function of hexadecyl merocyanine dyes incorporated into lipid membranes

Abstract In the purple membrane of Halobacterium halobium, bacteriorhodopsin (BR) acts as a proton pump leading to a transmembrane potential difference. A biomimetic system can be formed using merocyanine derivative dye which, when incorporated into a bilayer lipid membrane, creates a potential difference across the membrane. In this system, the dye molecules in combination with the lipid molecules act as a proton transport pump due to a light-induced conformational change of the dye. In this paper, we report the photovoltaic properties and crystal structure of hexadecyl merocyanine dye, together with the change in peak intensity in the X-ray diffraction pattern of the dye and dye-lipid system after illumination. We show that, at room temperature (σ300 K), merocyanine dyes exhibit a crystalline form with a long-chain, fibre-like structure (diameter, 2.89 nm). However, on interaction with light, the crystalline form of the dye changes but the diameter remains the same.

Simulation of Return Flow in Restricted Navigation Channel for Barge-tow Movements

Simulations of barge-tow movement in the sub-critical range along the Illinois River near Kampsville are performed to determine the return flow (RF) characteristics for upstream and downstream bound barge-tows. Simulations are carried out using the OpenFOAM® based CFD software for six barge-tow configurations considering two-dimensional shallow water equation. The RF velocities are simulated for 0s to 100s at an interval of 10s at nine different locations, taken across the river from vessel to bank for upstream and downstream bound barge-tows. The computed RF velocities at these points between the bow and the bank are analyzed and compared with the observed field data for identical conditions. The simulated RF velocity agrees well with the computed RF velocity of Hochestein and Adams, and Maynord and Siemsen, except closer to the barge-tow. Model simulation shows that the RF profiles (lateral velocity distributions transverse to vessel movement) vary with time and the length of the vessel. To understand the associated phenomena, drawdown and squat are computed using empirical formulations given by earlier researchers. The simulated result clearly indicates the location of the zero velocity point for downstream bound barge-tows. The present study would be helpful to hydraulic engineers, planners and biologists to predict RF hydrodynamic in a restricted channel.