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The corrosion inhibition of mild steel by miconazole nitrate, an antifungal drug has been investigated using potentiodynamic polarization, electrochemical impedance spectroscopy technique, and weight loss methods. The experimental results suggested miconazole nitrate is a good corrosion inhibitor for mild steel in 1 M hydrochloric acid medium. The inhibition efficiency increased with increase in inhibitor concentration. The thermodynamic parameters were determined and discussed. The inhibition was assumed to occur via adsorption of the inhibitor molecule on the surface of mild steel following Langmuir adsorption isotherm

Continuous p-n junction with extremely low leakage current for micro- structured solid-state neutron detector applications

ABSTRACT Considerable progress has been achieved recently to enhance the thermal neutron detection efficiency of solid-state neutron detectors that incorporate neutron sensitive materials such as 10 B and 6 LiF in Si micro-structured p-n junction diode. Here, we describe the design, fabrication process optimization and characterization of an enriched boron filled honeycomb structured neutron detector with a continuous p + -n junction. Boron deposition and diffusion processes were carried out using a low pressure chemical vapor deposition to study the effect of diffusion temperature on current density-voltage characteristics of p + -n diodes. TSUPREM-4 was used to simulate the thickness and surface doping concentration of p + -Si layers. MEDICI was used to simulate the depletion width and the capacitance of the microstructured devices with continuous p + -n junction. Finally, current density-voltage and pulse height distribution of fabricated devices with 2.5×2.5 mm 2 size were studied. A very low leakage current density of ~2×10 -8 A/cm 2 at -1 V (for both planar and honeycomb structured devices) and a bias-independent thermal neutron detection efficiency of ~26% under zero bias voltage were achieved for an enriched boron filled honeycomb structured neutron detector with a continuous p + -n junction

A Comparison of Dry Plasma and Wet Chemical Etching of GaSb Photodiodes

We report on the performance of GaSb pn junction photodiodes fabricated using electron cyclotron resonance plasma etching using Cl 2 /Ar recipe, a mixed gas recipe consisting of Cl 2 /BCl 3 /CH 4 /Ar/H 2 and wet chemical etching. Diodes fabricated using Cl 2 /BCl 3 /CH 4 /Ar/H 2 recipe show an order of magnitude lower leakage current density and lower ideality factor. The highest value of the zero bias dynamic resistance-area product was obtained for Cl 1 GaSb is an attractive choice as a substrate material because its lattice parameter matches various ternary and quaternary III-V compound semiconductors whose band gaps cover a wide spectral range from ϳ0.3 to 1.58 eV, i.e., 0.8-4.3 m. High quantum efficiency photodetectors, 2,3 photovoltaic cells, 4,5 and laser diodes with low threshold current A common choice of plasma chemistries for dry etching of GaSb-based structures consists of chlorine based precursors, such as SiCl 4 , BCl 3 , or Cl 2 because the volatilities of the gallium and antimony chlorides are generally very high. 8 Also, high-density plasma sources, such as electron cyclotron resonance ͑ECR͒, are preferred because of the increased density of low energy ions in the plasma. Pearton et al. 10 Dry etching of GaSb using methane/hydrogen (CH 4 /H 2 ) and ethane/hydrogen (C 2 H 6 /H 2 ) chemistry has also been reported. 12,13 C 2 H 6 -based plasmas show 50% higher etching rates as compared to the CH 4 -based plasmas. 13 Addition of a polymer forming gas such as CH 4 results in the formation of a polymeric thin film on the sidewalls, which minimizes the undercutting and provides passivation. 14,15 Although mixed chlorine and methane etches have been reported for various III-V compound semiconductors, systematic studies of antimonide are very few. 17 The effect of etching conditions on the device performance of GaSb and related materials has not been well addressed in the literature. In this paper, we have compared the performance of pn junction photodiodes fabricated using a Cl 2 /Ar recipe roughly based on the results reported by Pearton et al. 10,18 a mixed gas recipe consisting of Cl 2 /BCl 3 /CH 4 /Ar/H 2 , 17 and wet chemical etching using a NaK tartrate based recipe. Experimental The substrates used in this study were ͑100͒ n-type GaSb ͑Te doped͒ obtained from Galaxy Compound Semiconductor Inc. The carrier concentration was 5 ϫ 10 17 cm Ϫ3 . The substrates were degreased with hot xylene followed by acetone and methanol rinse ͑XAM cleaning͒. Then the samples were etched in hydrochloric acid ͑HCl͒ to remove the native oxide layer. Zinc ͑Zn͒ acts as p-type impurity in GaSb. Zn diffusion was carried out at 500°C for 5 h using the leaky box technique. 19 Solid Zn pellets were used as the source. The samples were next subjected to backside etching using a 2% solution of bromine in methanol for 30 s. Back side contacts were formed by electron beam ͑E-beam͒ evaporation of 200 Å of tin and 1000 Å of gold; followed by rapid thermal annealing ͑RTA͒ at 350°C for 5 s. The front side metal contact consisted of 400 Å titanium followed by 800 Å gold evaporated using E-beam. The final step in the fabrication process was the mesa etching. The front metal contacts were protected using a photoresist and the mesa areas were patterned. The photoresist was cured by baking at 110°C for 10 min. A Plasmatherm Electron Cyclotron Resonance 357 system with a loadlocked chamber was used for the dry etching of GaSb. One sample set was etched using Cl 2 /Ar plasma. The gases were in the ratio of 1:6 at a pressure of 1.5 mTorr. 100 W rf power and 300 W plasma power was used and the temperature was maintained at Ϫ30°C. The etch rate obtained with this process was 135 nm/min. A Cl 2 /BCl 3 /CH 4 /Ar/H 2 gas mixture in the ratio 2:1:2:6:12 was used to etch the second set of samples. A chamber pressure of 1.3 mTorr, rf power of 150 W, and plasma power of 400 W was used. The etching was carried out at room temperature. This recipe gave an etch rate of about 560 nm/min. The details of the surface morphology after etching are presented elsewhere

Corrosion inhibition of aluminium by 2-chloronicotinic acid in HCl medium

228-233The inhibiting effect of 2-chloronicotinic acid on the dissolution of aluminium in various concentrations of HCl has been studied using weight loss and polarization measurements. The inhibition efficiency was found to increase with increasing concentration of the inhibitor. The effect of temperature on corrosion inhibition was investigated. The results indicate the decreased inhibition efficiency for the increase in temperature. The inhibitor was found to be adsorbed on aluminium surface probably following Langmuir adsorption isotherm at higher concentrations of HCl

Inhibition of Al corrosion in 0.5 M HCl solution by Areca flower extract

The corrosion inhibition property of Areca flower extract species on the Al surface in acid (0.5 M HCl) medium was tested by weight loss, Tafel plot, impedance, scanning electron microscopy and atomic force microscopy techniques. The influence of different concentrations of Areca flower extract, 0.5 M HCl solution temperature and aluminum immersion (contact) time was also evaluated. Parameters such as Ea, ΔH∗, ΔS∗, Kads and ΔG°ads were calculated by the gravimetric (weight loss) technique. Results of mass loss technique indicated that, the Areca flower extract molecules are strongly adsorbed at Al- 0.5 M HCl solution interface and follows the law of the Langmuir adsorption model. Tafel curves show that, the Areca flower extract molecules effectively adsorbed on the active Al sites by replacing the H2O molecules and strongly interact with cathodic and anodic sites impeding the dissolution reaction by mixed mode. Hence, Al metal is protected. Electrochemical impedance results indicate that, area of a semicircle (Nyquist plots) in the presence of the Areca flower extract is high compared to the bare system. The variation in the surface topography of aluminum was analyzed through scanning electron microscopy and atomic force microscopy techniques. Further, AFM results show that, surface roughness values in the protected Al system are low compared to the unprotected Al system. Keywords: Aluminum, Areca flower, Hydrochloric acid, Langmuir adsorption model, Surface morpholog

Study on acoustic behaviour of potassium thiocyanate in aqueous and various non-aqueous solvents at 298 - 313K

252-256The results obtained in the acoustic behaviour study, such as ultrasonic velocity (U), adiabatic compressibility (βad), intermolecular free-length(Lf), acoustic impedence (Z), relative association (RA), solvation number (Sn), of potassium thiocyanate in water, methanol, ethanol, dimethylformarnide, and dimethyl sulphoxide at 298, 308 and 313K have been reported. Ultrasonic velocity of potassium thiocyanate has been determined by ultrasonic interferometer, and its density by pyknometer in all the cases and these data have been used to estimate the acoustic parameters. The apparent molar compressibility (ΦK), apparent molar volumue (Φv) and limiting apparent molar compressibility, (Φ), limiting apparent molar volume (Φ) have been computed at 298K for various cases. Masson's equation has been verified and used in the interpretation of ion-ion, and ion-solvent interactions involved in the system under prevailing condition.  Ultrasonic velocity of potassium thiocyanate in solutions is found to vary in the order H2O> DMSO>DMF>EtOH>MeOH whereas computed intermolecular free length is found to increase in the reverse order

Kinetics of Oxidation of Thiocyanate Ion by Iodamine-T in Perchloric Acid Medium

1149-115

Kinetics of Oxidation of Thiosemicarbazide by Iodamine-T, Iodine Monochloride & Iodine in Acid Medium

974-97

Ion-solvation studies of chloramine-T species in water, acetonitrile, DMF and their mixture by conductometry

1052-1055Transport property of the species of chloramine-T has been studied in water, acetonitrile, DMF and varying compositions (v/v) of water-acetonitrile, water-DMF mixtures and the data analysed by different conductivity models to identify the involvement of association process in the system. Limiting molar conductance has been found to be maximum in acetonitrile and minimum in DMF indicating the preferential solvation of cation by DMF. Association constant has been identified at all temperatures and compositions. Thermodynamic parameters have been estimated in all the cases. Viscosity of various solvents and solvent mixtures have been determined and used to compute Walden product from which Stoke's molecular radius is estimated. The ion-solvent and solvent-solvent interactions involved in the system have been qualitatively discussed

Kinetics & Mechanism of Oxidation of Thiocyanate Ion by Chloramine-B & Bromamine- B in Alkaline Medium

215-21