Studies on optical and dielectric properties of Al2O 3 thin films prepared by electron beam evaporation and spray pyrolysis method

Al2O3 thin films find a number of applications in optoelectronics, sensors and tribology. In this paper, we report the preparation and characterization of alumina films prepared by both electron beam evaporation and spray pyrolysis method. The electrical properties of alumina films were determined by measuring (C-V) and (I-V) characteristics in a metal oxide semiconductor (MOS) structure. A relative dielectric constant (εr) of 9.6 for spray pyrolysed films and 8.3 for evaporated films was obtained. The breakdown electric field was found to be around 5 and 1MV/cm, respectively for spray pyrolysed and evaporated films. The refractive index of alumina films by evaporation was found to be 1.71 and 1.61 at 275 and 500 nm, respectively. The optical band gap of spray pyrolysed films deposited at 300 °C was found to be in the range of 5.40-5.55 eV. Structural, elemental analysis and stoichiometry of the films was studied by scanning electron microscope (SEM), energy dispersive X-ray analysis (EDAX), Auger electron spectroscopy (AES) and Rutherford back scattering (RBS) spectra. © 2003 Elsevier B.V. All rights reserved

Characterization of Al2O3 thin films prepared by spray pyrolysis method for humidity sensor

Al2O3 thin films were deposited on silicon, steel and nickel substrates to fabricate MOS and MIM devices. The films were prepared by spray pyrolysis method using a spray solution of Aluminium acetyl acetonate dissolved in dimethyl formamide and this solution was sprayed on to the hot substrates at temperatures of 300 and 350 °C. The films were amorphous in nature as detected by XRD. Capacitance versus voltage (C-V), current versus voltage (I-V) and capacitance versus frequency (C-f) measurements were taken for these films. MOS capacitor was used as a humidity sensor using the home made humidity sensor setup. ac capacitance and parallel resistance of the capacitor as a function of humidity were studied. It was found that the capacitance value increases from 0.537 to 2.073 nf with the increase in relative humidity (RH) from 0 to 90 and the resistance decreases from 153 to 93 kΩ with the increase in relative humidity from 20 to 87. Relative dielectric constant versus temperature measurements were done for the MOS device to check its ferroelectric behavior and its critical temperature was found to be around 66 °C. MIM device was also used as a humidity sensor by measuring capacitance as a function of time by keeping the sensor in a dessicator. The 555 timer circuits were used to check the sensor behavior of the MOS device. Volume resistivity and breakdown electric field of the film deposited on steel were measured and found to be 5 à 1011 Ω cm and 5 MV/cm, respectively. © 2006 Elsevier B.V. All rights reserved

Carboxylesterases from the seeds of an underutilized legume, Mucuna pruriens; Isolation, purification and characterization

Two carboxylesterases (ME-III and ME-IV) have been purified to apparent homogeneity from the seeds of Mucuna pruriens employing ammonium sulfate fractionation, cation exchange chromatography on CM-cellulose, gel-permeation chromatography on Sephadex G-100 and preparative PAGE. The homogeneity of the purified preparations was confirmed by polyacrylamide gel electrophoresis (PAGE), gel-electrofocussing and SDS-PAGE. The molecular weights determined by gel-permeation chromatography on Sephadex G-200 were 20.89 kDa (ME-III) and 31.62 kDa (ME-IV). The molecular weights determined by SDS-PAGE both in the presence and absence of 2-mercaptoethanol were 21 kDa (ME-III) and 30.2 kDa (ME-IV) respectively, suggesting a monomeric structure for both the enzymes. The enzymes were found to have Stokes radius of 2.4 nm (ME-III) and 2.7 nm (ME-IV). The isoelectric pH values of the enzymes, ME-III and ME-IV, were 6.8 and 7.4, respectively. ME-III and ME-IV were classified as carboxylesterases employing PAGE in conjunction with substrate and inhibitor specificity. The K m of ME-III and ME-IV with 1-naphthyl acetate as substrate was 0.1 and 0.166 mM while with 1-naphthyl propionate as substrate the K m was 0.052 and 0.0454 mM, respectively. As the carbon chain length of the acyl group increased, the affinity of the substrate to the enzyme increased indicating hydrophobic nature of the acyl group binding site. The enzymes exhibited an optimum temperature of 45 °C (ME-III) and 37 °C (ME-IV), an optimum pH of 7.0 (ME-III) and 7.5 (ME-IV) and both the enzymes (ME-III and ME-IV) were stable up to 120 min at 35 °C. Both the enzymes were inhibited by organophosphates (dichlorvos and phosphamidon), but resistant towards carbamates (carbaryl and eserine sulfate) and sulphydryl inhibitors (p-chloromercuricbenzoate, PCMB). © 2011 Elsevier Ltd. All rights reserved

Characterization of End of Life Personal Computers for Optimum Resource Recovery

The End of Life Personal Computers (EOL-PCs) generated by Information and Communication Technology (ICT), end up in waste streams and form a part of E-waste. This waste forms a secondary resource for many metals and non metals recovered through recycling processes. The computers have undergone revolutionary change in size, shape, configuration and its material content, particularly from the last two decades. However, the Handy-Harmann data of 1966 related to quality and quantity of the material used in manufacturing of computer has been very old and not updated since 1966. This may result in inefficient resource recovery and partially treated waste containing hazardous substances may end up in unauthorized landfill or water bodies causing permanent damage to the environment. Therefore, an attempt has been made to characterize the EOL-PCs model P-III which form a major part of E-waste even today. The results obtained help assessment of economic viability of recoverable and recyclable quantities of metals viz., Fe, Cu, Al, Au, Ag, Pd, etc., non metals like plastics and glass from P-III model computers. The paper also discusses comparative study of latest characterization of EOL-PCs with Handy-Harmann data of 1996

CHARACTERIZATION OF ALPHA-AMYLASE FROM THE SEEDS OF Mucuna pruriens

Amylases are hydrolytic enzymes which are widely distributed in nature, animals, plants and microorganisms. Amylases are of great significance in present-day biotechnology. In present study, amylases are isolated from the soaked seeds of Mucuna pruriens under extreme acidic conditions. Conventional protein purification techniques such as salt fractionation, ion exchange chromatography on CM-cellulose and sephadex G-75 was employed for the purification of amylase from the seeds of Mucuna pruriens. The amylase activity was eluted in one peak. The specific activity and yield of the purified amylase was 6.25 and 29.99, respectively. Native PAGE, SDS-PAGE and gel electrofocussing were employed to establish homogeneity of the purified amylase. SDS-PAGE and gel-filtration chromatography on sephadex G-75 was used to determine the molecular weight of the purified amylase. The purified amylase was nearly homogenous and its molecular weight was found to be 78.4 kDa. The optimum pH and temperature of the purified amylase were 7.0 and 50oC, respectively. The isolectric pH of the purified amylase was 7.2 and the activity was linear up to 60 minutes

Electrochemical Pretreatment of Distillery Wastewater Using Aluminum Electrode

Electrochemical (EC) oxidation of distillery wastewater with low (BOD5/COD) ratio was investigated using aluminum plates as electrodes. The effects of operating parameters such as pH, electrolysis duration, and current density on COD removal were studied. At a current density of 0.03 A cm-2 and at pH 3, the COD removal was found to be 72.3%. The BOD5/COD ratio increased from 0.15 to 0.68 for an optimum of 120-min electrolysis duration indicating improvement of biodegradability of wastewater. The maximum anodic efficiency observed was 21.58 kg COD h-1 A-1 m-2, and the minimum energy consumption observed was 0.084 kWh kg-1 COD. The kinetic study results revealed that reaction rate (k) decreased from 0.011 to 0.0063 min-1 with increase in pH from 3 to 9 while the k value increased from 0.0035 to 0.0102 min-1 with increase in current density from 0.01 to 0.03 A cm-2. This study showed that the COD reduction is more influenced by the current density. The linear and the nonlinear regression models reveal that the COD reduction is influenced by the applied current density

Study of the Electrochemical Process for Distillery Wastewater Treatment

In this work the electrochemical (EC) process is used as a pretreatment step for the treatment of distillery wastewater using iron plates as electrodes in a batch EC reactor. The maximum COD removal of 56% was achieved at a current density of 0.10 A cm-2 with 140 min of electrolysis time at wastewater pH of 3. The BOD to COD ratio increased from 0.15 to 0.52 indicating improvement in wastewater biodegradability. The maximum anodic efficiency observed was 2.68 kg COD h-1A-1m-2 with a corresponding energy consumption of 0.71 kWh kg-1 COD

Improvement of Bod5/Cod Ratio Inpre-Treated Distillery Waste Water by Electrochemical Treatment Method

Electrochemical oxidation of low (BOD5/COD) ratio post-methanation distillery wastewater was investigated. The effects of operating parameters like pH, electrolysis duration and current density on COD removal were studied. At a current density of 0.03 Ampere/cm2 and at pH 3 the COD removal was found to be 72%. The BOD5/COD ratio of pretreated distillery wastewater was 0.145 and increased to 0.686 for an optimum of 120 minutes electrolysis duration indicating improvement of biodegradability of wastewater. The TOC reduction is 8.77% at 180 minutes of electrolysis duration. The maximum anodic efficiency observed was 21.58 kg COD h-1A-1m-2 and the minimum energy consumption observed was 84.16 wh kg-1 COD. The kinetic study reveals that reaction rate (k) decreases with increase in pH and increases with increase in current density

Second law analysis of the flow of two immiscible couple stress fluids in four zones

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.This work investigates the entropy generation in a steady flow of two immiscible couple stress fluids in a horizontal channel bounded by two porous beds at the bottom and top. The flow is considered in FOUR zones: zone-IV contains the flow of viscous fluid in the large porous bed with low permeability at the bottom, zone-I and II contain free flow of two immiscible couple stress fluids and zone-III contains the flow of viscous fluid in the thin porous bed with high permeability at the top. The flow is assumed to be governed by Stokes’s couple stress fluid flow equations in the free channel. In zone-IV, Darcy’s law together with the Beavers-Joseph (B-J) slip condition at the interface is used whereas in zone-III Brinkman’s model is used for flow. The plates of the channel are maintained at constant temperatures higher than that of the fluid. The closed form expressions for entropy generation number and Bejan number are derived in dimensionless form by using the expressions of velocity and temperature. The effects of relevant parameters on velocity, temperature, entropy generation number and Bejan number are analyzed and presented through graphs.dc201