Efficient Near Infrared to Visible and Near‐Infrared Upconversion Emissions in Transparent (Tm3+, Er3+)‐α‐Sialon Ceramics

Intense visible and near‐infrared frequency upconversion and a frequency downconversion photoluminescence have been reported for the first time in Tm³⁺ and Er³⁺ co‐doped transparent α‐Sialon ceramics under 980 nm excitation. The α‐Sialon ceramics were prepared by hot‐press sintering technique. Intense upconversion bands at 554, 678, 803 nm, and a downconversion band at 1530 nm were observed as a result of the efficient energy transfer between Er³⁺ and Tm³⁺ ions. The quadratic dependence of upconversion intensities on the excitation power indicates that the upconversion process is governed by two‐photon absorption process. The sintered samples of thickness 0.20 mm have transparency above 80% in the range of 2000 to 4200 nm and it reaches as high as 82% at 3350 nm. Moderately low phonon energy was found with the highest frequency band at 828 cm^?1. These novel properties manifest the potential applications of transparent α‐Sialon ceramics as a multifunctional material.     

Photoelectrochemical performance of surfactant (polyvinyl alcohol) assisted PbS thin films grown by chemical route

Polyvinyl alcohol is used as a surfactant in the chemical bath deposition of PbS thin films, which causes compact, pinhole free and uniform PbS thin films. Influence of deposition time on the structural, optical, morphological, compositional, electro-chemical and photo-electrochemical (PEC) properties of the PbS thin films are studied. The charge transfer resistance is analysed using electrochemical impedance spectroscopy. The best PEC device fabricated using optimized deposition time (3 h) showed short circuit current density (J_sc) of 1.68 mA. After annealing the optimised P₆₃ sample at 75?°C for 1.5 h the composition changed from Pb rich to near stoichiometric. For typical PA sample J_sc improves to 2.13 mA and photo conversion efficiency advances from 0.045 to 0.072%.     

Investigations on premixed charge compression ignition engine with external mixture formation and exhaust gas recirculation technique

Journal of Mechanical Science and Technology - In present scenario it is need for automobile sector to develop clean technology which will result in less fuel consumption and green house gas. The...     

A tool supported approach for brightness preserving contrast enhancement and mass segmentation of mammogram images using histogram modified grey relational analysis

Multidimensional Systems and Signal Processing - Mammography is a tool that uses X-rays to create mammograms. This tool is mainly used to find early signs of breast cancer. Usually, mammogram image...     

Experimental investigations on flame stabilization behavior in a diverging micro channel with premixed methane–air mixtures

In the present paper, experimental investigations on the characterization of flame stabilization behavior in a 2.0 mm wide diverging channel are carried out with premixed methane–air mixtures. The effect of mixture equivalence ratio (Ф) and flow rate on flame shape, position, stability and emissions are reported in this work. The diverging portion of channel is preheated from the bottom side with a sintered metal burner to provide a positive temperature gradient along the direction of fluid flow which helps in stabilizing a flame in the channel. For a range of velocities and equivalence ratios, different types of stable and partially stable flame propagation modes were observed. Flames obtained for rich mixtures exhibited more stable nature as compared to lean mixtures. The flame stability limits were observed to vary between 0.2 m/s and 1.9 m/s for a range of mixture equivalence ratios.     

Synthesis and characterization of polyaniline–ZnO composite and its dielectric behavior

Films of polyaniline (PANI) and PANI–zinc oxide (ZnO) composites have been synthesized by solution cast and spin coating technique. The ZnO powder of particle size 100–200 nm was synthesized by sol–gel technique and the polyaniline was synthesized by chemical oxidative polymerization of aniline. The composite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infra red (FTIR) and the results were compared with polyaniline films. Dielectric properties of PANI and PANI–ZnO composite films have been investigated between frequency ranges of 8.5 and 13.0 GHz. The ‘a’ lattice parameter of ZnO was found to increase and the ‘c’ lattice parameter was found to decrease after ZnO–PANI composite formed. The characteristic FTIR peaks of PANI were found to shift to higher wave number in ZnO–PANI composite. These observed effects have been attributed to interaction of ZnO particles with PANI molecular chains. Dielectric constant of PANI–ZnO composite film was found to be smaller than the PANI film. The decrease of dielectric constant in PANI–ZnO films as compared to PANI was attributed to the interfaces formed between ZnO particles and PANI.     

A study on the effect of surface orientation on erosion wear of flat specimens moving in a solid-liquid suspension

Wear characteristics of a ductile material, namely, brass have been investigated by orienting the flat specimens at different orientations relative to the velocity direction in a pot tester containing a solid-liquid suspension. The erosion behavior has been studied at various orientation angles, defined as the angle between the tangent to the plane surface and its velocity. Results at different orientation angles show that the wear at any orientation angle increases with increase in velocity and particle size but decreases with increase in solid concentration. It is also seen that the wear at various operating conditions increases with increase in the orientation angle till 30° attaining the maximum value and then decreases up to 90°. It is further observed that the maximum wear is around 3-4.5 times higher than the surface wear measured at 90° orientation angle.     

Oxygen Nonstoichiometry and Thermodynamic Quantities of La2Ni0.95Al0.05O4.025 + δ

The oxygen nonstoichiometry of La₂Ni_0.95Al_0.05O_4.025 + δ (LNAO) is measured as a function of oxygen partial pressure (pO₂) and temperature by coulometric titration method and thermogravimetric analysis (TGA) in 800°C–1000°C temperature range and 10^?16‐1 atm pO₂ range. The partial molar quantities for mixing of oxygen were calculated and results were compared with the literature results on La₂NiO_4 + δ (LNO). The variation in activity coefficient of holes versus oxygen nonstoichiometry illustrated an early positive deviation of the activity coefficient of holes from unity, leading to  ≈  7 at δ  ≈  0.08, which was lower than the literature value of  ≈  14 for La₂NiO_{4  +  δ} at δ  ≈  0.08, indicating lesser deviation of LNAO from ideal solution behavior. The effective mass of holes () was 1.02–1.21 times the rest mass (m_o), which indicated the band‐like conduction and allowed the effect of the small degree of polaron hopping to be ignored. The comparison of oxygen nonstoichiometry and partial molar quantities showed that incorporation of interstitial oxygen is less favorable in LNAO in comparison to LNO.     

CORROSION INHIBITION OF MILD STEEL IN 1 N HCL SOLUTION BY MERCAPTO-QUINOLINE SCHIFF BASE

Corrosion inhibition of mild steel in 1 N HCl solutions was investigated in the absence and presence of different concentrations of some mercapto-quinoline derivatives namely, 3-((phenylimino)methyl)quinoline-2-thiol (PMQ) and 3-((5-methylthiazol-2-ylimino)methyl)quinoline-2-thiol (MMQT) by using conventional weight loss, potentiodynamic polarization, linear polarization, electrochemical impedance spectroscopy, and scanning electron microscopic studies. By EIS and weight loss measurements, it was found that PMQ and MMQT were effective inhibitors and their inhibition efficiency was significantly increased with increasing concentrations of inhibitors. Polarization curves showed that the evaluated PMQ and MMQT both act as mixed inhibitions. The adsorptions of these inhibitors on the mild steel were found to follow the Langmuir adsorption isotherm. Results show that the rate of corrosion of mild steel increased with increasing temperature over the range 25°–45°C both in the presence of inhibitors and in their absence. Activation energies in the presence and absence of PMQ and MMQT were obtained.