Experimental and theoretical studies on static and dynamic pressure-concentration isotherms of MmNi(5-x)Al(x) (x=0, 0.3, 0.5 and 0.8) hydrides

The static and dynamic pressure concentration isotherms (PCIs) of MmNi(5-x)Al(x). (x = 0, 0.3, 0.5 and 0.8) hydrides were measured at different temperatures using volumetric method. The effect of Al substitution on PCI and thermodynamic properties were studied. The plateau pressure and maximum hydrogen storage capacity decreased with Al content whereas reaction enthalpy increased. The plateau pressure, plateau slope and hysteresis effect was observed more for dynamic PCIs compared to static PCIs. Different mathematical models used for metal hydride-based thermodynamic devices simulation are compared to select suitable model for static and dynamic PCI simulation of MmNi(5)-based hydrides. Few important physical coefficients (partial molar volume, reaction enthalpy, reaction entropy, etc.) useful for development of thermodynamic devices were estimated. A relation has been proposed to correlate aluminium content and physical coefficients for the prediction of unknown PCI. The simulated and experimental PCIs were found matching closely for both static and dynamic conditions. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

The effect of Cu addition on the thermoelectric properties of Cu2CdGeSe4

Recently, research in copper based quaternary chalcogenide materials has focused on the study of thermoelectric properties due to the complexity in the crystal structure. In the present work, stoichiometric quaternary chalcogenide compounds Cu2+xCd1-x,GeSe4 (x = 0, 0.025, 0.05, 0.075, 0.1, 0.125) were prepared by solid state synthesis. The powder X-ray diffraction patterns of all the samples showed a tetragonal crystal structure with the space group I-42m of the main phase, whereas the samples with x = 0 and x = 0.025 revealed the presence of an orthorhombic phase in addition to the main phase as confirmed by Rietveld analysis. The elemental composition of all the samples characterized by Electron Probe Micro Analyzer showed a slight deviation from the nominal composition. The transport properties were measured in the temperature range of 300 K-723 K. The electrical conductivity of all the samples increased with increasing Cu content due to the enhancement of the hole concentration caused by the substitution of Cd (divalent) by Cu (monovalent). The positive Seebeck coefficient of all the samples in the entire temperature ranges indicates that holes are the majority carriers. The Seebeck coefficient of all the samples decreased with increasing Cu content and showed a reverse trend to the electrical conductivity. The total thermal conductivity of all the samples decreased with increasing temperature which was dominated by the lattice contribution. The maximum figure of merit ZT = 0.42 at 723 K was obtained for the compound Cu2.1Cd0.9GeSe4. (C) 2014 Elsevier Ltd. All rights reserved.

Colorimetric detection of melamine based on the size effect of AuNPs

A simple colorimetric detection of melamine was studied using 15 nm (AuNPs-I), 30 nm (AuNPs-II), and 40 nm (AuNPs-III) citrate-capped gold nanoparticles (AuNPs). The AuNPs aggregated in aqueous solution in the presence of melamine, showing a visual color change from red to blue. This color change led to a shift in the absorption peak from 527 nm, 526 nm, and 525 nm to 638 nm, 626 nm, and 680 nm for AuNPs-I, AuNPs-II, and AuNPs-III, respectively. For all the three AuNPs, linearity was observed between the melamine concentration in aqueous solution and the absorbance ratios, A(638/527), A(626/525), and A(680/526), respectively. The limit of detection (LOD) for melamine for the AuNPs-II was found to be 2.37 x 10(-8) M (correlation coefficient R-2 = 0.9745), which showed better sensitivity as compared to the LOD of the AuNPs-I and AuNPs-III, which were 3.3 x 10(-8) M and 8.9 x 10(-8) M, respectively. The synthesis of AuNPs-II also involved a lower HAuCl4 concentration compared with the other two types of AuNPs, which may reduce the process cost. The AuNPs-II was selected to analyze melamine in pre-treated milk samples, and the recovery percentage was in the range of 91-106%. Thus, the efficient detection of melamine was possible using AuNPs-II for the on-site detection without the aid of expensive instruments.

Effect of oxygen vacancies on the elastic properties of zinc oxide: A first-principles investigation

The effect of oxygen vacancies on the elastic properties of zinc oxide (ZnO) is examined using first-principles calculations based on density functional theory. Formation energies of vacancies in different types of oxygen deficient structures were analyzed to ascertain their stability. This analysis reveals that the doubly-charged oxygen vacancy under zinc-rich growth conditions is the most stable. Results show considerable degradation of some of the elastic moduli due to the presence of oxygen vacancies, which is in agreement with recent experiments. The decrease observed in elastic constants is more pronounced with increase in vacancy concentration. Further, the charge state of the defect structure was found to influence the shear elastic constants. Evaluation of elastic anisotropy of stoichiometric and oxygen deficient ZnO indicates the significant anisotropy in elastic properties and stiff c-axis orientation. (C) 2014 Elsevier B.V. All rights reserved.

Effect of sputtering parameters on the structure, microstructure and magnetic properties of Tb-Fe films

The effect of sputtering parameters such as gas pressure and power on the structure, microstructure and magnetic properties of sputtered Tb-Fe thin films was investigated. X-ray diffraction and transmission electron microscopy studies showed that all the films were amorphous in nature irrespective of the sputtering parameters. A fine island kind of morphology was observed at low sputtering power whereas large clusters were seen at higher sputtering power. While the composition of Tb-Fe films remained constant with increasing sputtering power, the magnetic behaviour was found to change from superparamagnetic to ferromagnetic. On the other hand, the increase in argon gas pressure was found to deplete the iron concentration in Tb-Fe thin films, which in turn reduced the anisotropy and Curie temperature. Annealing of the films at 773 K did not result in any crystallization and the magnetic properties were also found to remain unchanged. (C) 2015 Elsevier B.V. All rights reserved.

Effect of the nature of a transition metal dopant in BaTiO3 perovskite on the catalytic reduction of nitrobenzene

In the present study, we have synthesized Fe, Co and Ni doped BaTiO3 catalyst by a wet chemical synthesis method using oxalic acid as a chelating agent. The concentration of the metal dopant varies from 0 to 5 mol% in the catalysts. The physical and chemical properties of doped BaTiO3 catalysts were studied using various analytical methods such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), BET surface area and Transmission electron microscopy (TEM). The acidic strength of the catalysts was measured using a n-butylamine potentiometric titration method. The bulk BaTiO3 catalyst exhibits a tetragonal phase with the P4mm space group. A structural transition from tetrahedral to cubic phase was observed for Fe, Co and Ni doped BaTiO3 catalysts with an increase in doped metal concentration from 1 to 5 mol%. The particle sizes of the catalysts were calculated from TEM images and are in the range of 30-80 nm. All the catalysts were tested for the catalytic reduction of nitrobenzene to azoxybenzene. The BaTiO3 catalyst was found to be highly active and less selective compared to the doped catalysts which are active and highly selective towards azoxybenzene. The increase in selectivity towards azoxybenzene is due to an increase in acidic strength and reduction ability of the doped metal. It was also observed that the nature of the metal dopant and their content at the B-site has an impact on the catalytic reduction of nitrobenzene. The Co doped BaTiO3 catalyst showed better activity with only 0.5 mol% doping than Fe and Ni doped BaTiO3 catalysts with maximum nitrobenzene conversion of 91% with 78% selectivity to azoxybenzene. An optimum Fe loading of 2.5 mol% in BaTiO3 is required to achieve 100% conversion with 93% selectivity whereas Ni with 5 mol% showed a conversion of 93% and a azoxybenzene selectivity of 84%.

Synergistic effect of colchicine and iodide ions on the corrosion of mild steel in 0.5 M H2SO4

The inhibition behavior of colchicine (CC) on the corrosion of mild steel in 0.5 M H2SO4 was evaluated by electrochemical methods such as potentiodynamic polarization and electrochemical impedance spectroscopic measurements. The inhibition efficiency increases with increasing concentration of CC. The potentiodynamic polarization results reveal that CC act as a mixed-type inhibitor by retarding both cathodic and anodic corrosion reactions. Additionally, the synergism was carried out between CC and KI to improve the corrosion inhibition behavior of CC on mild steel. The adsorption of both CC alone and the combined inhibitor (CC + KI) on mild steel surface follows Langmuir adsorption isotherm. The synergism parameter (S (theta) ) was calculated to recognize the existence of synergism between CC and iodide ions. Lastly, an adsorption mechanism of CC molecules with iodide ions is discussed.

Effect of H-2/CO Composition on Extinction Strain Rates of Counterflow Syngas Flames

This work presents a detailed experimental and numerical investigation of the effect of H-2/CO composition on extinction characteristics of premixed and nonpremixed syngas flames. Experimental measurements of local and global extinction strain rates in counterflow diffusion flames have been reported at atmospheric pressure for six different compositions of syngas fuel. The concentration of H-2 was varied from 5 to 20% with a 3% increment, and correspondingly, CO was decreased from 35 to 20% in steps of 3%. Particle imaging velocimetry has been used to determine the local extinction strain rates. Local extinction strain rates increased with an increase in the H-2/CO ratio in both nonpremixed and premixed flames. The predicted extinction strain rates for both nonpremixed and premixed counterflow flames using five different mechanisms available in the literature were compared with measurements. The Davis H-2/CO and Ranzi H-2/CO mechanisms predicted extinction strain rates within 10% of experimental values irrespective of the H-2/CO ratio. In the nonpremixed case, the Cl mechanism by Li et al., GRI 3.0, and the Ranzi H-2/CO mechanism predicted extinction strain rates well for low H-2/CO ratios (from 5:35 to 14:26) but deviated from experiments for higher H-2/CO values (17:23 and 20:20). In addition to kinetics, preferential diffusion effects were found to affect the reaction zone significantly and create distinct localized reaction zone structures in nonpremixed flames, which could contribute to discrepancies in extinction predictions.

Investigation of the inhibition effect of ibuprofen triazole against mild steel corrosion in an acidic environment

The inhibition performance of ibuprofen triazole (IT) on mild steel (MS) corrosion in 1.0 M HCl and 0.5 M H2SO4 has been investigated by using electrochemical (potentiodynamic polarization and electrochemical impedance spectroscopy), gravimetric, and quantum chemical studies. Electrochemical investigation indicates that IT hampers MS corrosion via adsorption through a mixed inhibition mechanism. The protection ability of IT increases with an increasing concentration of inhibitor and decreases with increasing temperature. The adsorption of IT molecules on MS surface follows the Langmuir adsorption isotherm. Certain quantum chemical parameters were calculated to ascertain the correlation between inhibitive effect and molecular structure of IT.

Unconjugated Bilirubin exerts Pro-Apoptotic Effect on Platelets via p38-MAPK activation

Thrombocytopenia is one of the most frequently observed secondary complications in many pathological conditions including liver diseases, where hyperbilirubinemia is very common. The present study sought to find the cause of thrombocytopenia in unconjugated hyperbilirubinemic conditions. Unconjugated bilirubin (UCB), an end-product of heme catabolism, is known to have pro-oxidative and cytotoxic effects at high serum concentration. We investigated the molecular mechanism underlying the pro-apoptotic effect of UCB on human platelets in vitro, and followed it up with studies in phenylhydrazine-induced hyperbilirubinemic rat model and hyperbilirubinemic human subjects. UCB is indeed found to significantly induce platelet apoptotic events including elevated endogenous reactive oxygen species generation, mitochondrial membrane depolarization, increased intracellular calcium levels, cardiolipin peroxidation and phosphatidylserine externalization (p < 0.001) as evident by FACS analysis. The immunoblots show the elevated levels of cytosolic cytochrome c and caspase activation in UCB-treated platelets. Further, UCB is found to induce mitochondrial ROS generation leading to p38 activation, followed by downstream activation of p53, ultimately resulting in altered expression of Bcl-2 and Bax proteins as evident from immunoblotting. All these parameters conclude that elevated unconjugated bilirubin causes thrombocytopenia by stimulating platelet apoptosis via mitochondrial ROS-induced p38 and p53 activation.

Effect of Sm3+-Gd3+ on structural, electrical and magnetic properties of Mn-Zn ferrites synthesized via combustion route

Nanocrystalline Mn0.4Zn0.6SmxGdyFe2-(x+y)O4 (x = y = 0.01, 0.02, 0.03, 0.04 and 0.05) were synthesized by combustion route. The detailed structural studies were carried out through X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM). The results confirms the formation of mixed spine phase with cubic structure due to the distortion created with co-dopants substitution at Fe site in Mn-Zn ferrite lattice. Further, the crystallite size increases with an increase of Sm3+-Gd3+ ions concentration while lattice parameter and lattice strain decreases. Furthermore, the effect of Sm-Gd co-doping in Mn-Zn ferrite on the room temperature electrical (dielectric studies) studies were carried out in the wide frequency range 1 GHz-5 GHz. The magnetic studies were carried out using vibrating sample magnetometer (VSM) under applied magnetic field of 1.5T and also room temperature electron paramagnetic resonance (EPR) spectra's were recorded. From the results of dielectric studies, it shows that the real and imaginary part of permittivities are increasing with variation of Gd3+ and Sm3+ concentration. The magnetic studies reveal the decrease of remnant, saturation magnetization and coercivity with increasing of Sm3+-Gd3+ ion concentration. The g-value, peak-to-peak line width and spin concentration evaluated from EPR spectra correlated with cations occupancy. The electromagnetic properties clearly indicate that these materials are the good candidates which are useful at L and C band frequency. (C) 2015 Elsevier B.V. All rights reserved.

In-situ study of microscale fracture of diffusion aluminide bond coats: Effect of platinum

The influence of Pt layer thickness on the fracture behavior of PtNiAl bond coats was studied in situ using clamped micro-beam bend tests inside a scanning electron microscope (SEM). Clamped beam bending is a fairly well established micro-scale fracture test geometry that has been previously used in determination of fracture toughness of Si and PtNiAl bond coats. The increasing amount of Pt in the bond coat matrix was accompanied by several other microstructural changes such as an increase in the volume fraction of alpha-Cr precipitate particles in the coating as well as a marginal decrease in the grain size of the matrix. In addition, Pt alters the defect chemistry of the B2-NiAl structure, directly affecting its elastic properties. A strong correlation was found between the fracture toughness and the initial Pt layer thickness associated with the bond coat. As the Pt layer thickness was increased from 0 to 5 mu m, resulting in increasing Pt concentration from 0 to 14.2 at.% in the B2-NiAl matrix and changing alpha-Cr precipitate fraction, the initiation fracture toughness (K-IC) was seen to rise from 6.4 to 8.5 MPa.m(1/2). R-curve behavior was observed in these coatings, with K-IC doubling for a crack propagation length of 2.5 mu m. The reasons for the toughening are analyzed to be a combination of material's microstructure (crack kinking and bridging due to the precipitates) as well as size effects, as the crack approaches closer to the free surface in a micro-scale sample.

Effect of RF power on the structural, optical and gas sensing properties of RF-sputtered Al doped ZnO thin films

The effect of Radio Frequency (RF) power on the properties of magnetron sputtered Al doped ZnO thin films and the related sensor properties are investigated. A series of 2 wt% Al doped ZnO; Zn0.98Al0.02O (AZO) thin films prepared with magnetron sputtering at different RF powers, are examined. The structural results reveal a good adhesive nature of thin films with quartz substrates as well as increasing thickness of the films with increasing RF power. Besides, the increasing RF power is found to improve the crystallinity and grain growth as confirmed by X-ray diffraction. On the other hand, the optical transmittance is significantly influenced by the RF power, where the transparency values achieved are higher than 82% for all the AZO thin films and the estimated optical band gap energy is found to decrease with RF power due to an increase in the crystallite size as well as the film thickness. In addition, the defect induced luminescence at low temperature (77 K) and room temperature (300 K) was studied through photoluminescence spectroscopy, it is found that the defect density of electronic states of the Al3+ ion increases with an increase of RF power due to the increase in the thickness of the film and the crystallite size. The gas sensing behavior of AZO films was studied for NO2 at 350 degrees C. The AZO film shows a good response towards NO2 gas and also a good relationship between the response and the NO2 concentration, which is modeled using an empirical formula. The sensing mechanism of NO2 is discussed.

Effect of potassium present in stratum corneum during non-invasive measurement of potassium in human subjects using reverse iontophoresis

Purpose: Reverse iontophoresis (RI) is one of the potential techniques used to monitor the concentration of various analytes in body fluids non -invasively. Transdermal extraction of potassium is investigated using RI. In the present work, the effect of potassium on stratum corneum (SC) during RI, feasibility of RI for continuous monitoring of potassium, and use of potassium as internal standard in RI, are investigated. Methods: Tape stripping experiment is carried out to find potassium concentration in SC. RI is carried out continuously for 180 min without passive diffusion and after passive diffusion for 60 min. Skin impedance measurements are done at 20 Hz and 20 kHz. Results: Potassium is found to be in the range 300-650 nmol/cm(2) on SC by tape stripping experiment. Correlation coefficient between blood potassium and extracted potassium through RI after passive diffusion (R-2 = 0.5870) is more than without passive diffusion (R-2 = 0.5117). The skin impedance measurement shows that RI has more effect on SC than superficial layer of SC during RI. Conclusion: The present investigations conclude that it is possible to monitor potassium continuously through RI and using potassium as internal standard in RI.

Effect of RF power on the structural, optical and gas sensing properties of RF-sputtered Al doped ZnO thin films

The effect of Radio Frequency (RF) power on the properties of magnetron sputtered Al doped ZnO thin films and the related sensor properties are investigated. A series of 2 wt% Al doped ZnO; Zn0.98Al0.02O (AZO) thin films prepared with magnetron sputtering at different RF powers, are examined. The structural results reveal a good adhesive nature of thin films with quartz substrates as well as increasing thickness of the films with increasing RF power. Besides, the increasing RF power is found to improve the crystallinity and grain growth as confirmed by X-ray diffraction. On the other hand, the optical transmittance is significantly influenced by the RF power, where the transparency values achieved are higher than 82% for all the AZO thin films and the estimated optical band gap energy is found to decrease with RF power due to an increase in the crystallite size as well as the film thickness. In addition, the defect induced luminescence at low temperature (77 K) and room temperature (300 K) was studied through photoluminescence spectroscopy, it is found that the defect density of electronic states of the Al3+ ion increases with an increase of RF power due to the increase in the thickness of the film and the crystallite size. The gas sensing behavior of AZO films was studied for NO2 at 350 degrees C. The AZO film shows a good response towards NO2 gas and also a good relationship between the response and the NO2 concentration, which is modeled using an empirical formula. The sensing mechanism of NO2 is discussed.