Dielectric Relaxation in CaO–Bi2O3–B2O3 Glasses

Glasses in the system CaO–Bi₂O₃–B₂O₃ (in molar ratio) have been prepared using melt-quenching route. Ion transport characteristics were investigated for this glass using electric modulus, ac conductivity and impedance measurements. The ac conductivity was rationalized using Almond–West power law. Dielectric relaxation has been analyzed based on the behavior of electric modulus behavior. The activation energy associated with the electrical relaxation determined from the electric modulus spectra was found to be 1.76 eV, close to that the activation energy for dc conductivity (1.71 eV) indicating that the same species took part in both the processes. The stretched exponent β (0.5–0.6) is invariant with temperature for the present glasses.     

Dry sliding wear of zirconia-toughened alumina with different metal oxide additives

Tribological behaviour of zirconia-toughened alumina (ZTA) with different metal oxide additives was studied. Solid oxide lubricants (MO_x; M = Cu, Ti, Mg, Zn, Mn) were added in small quantities (∼8–11 wt%) to provide a self-lubrication action and thereby to decrease the coefficient of dry friction. Dry mixed ceramic composites powders were compacted and pressureless sintered at different temperatures. Densification studies show that near full densities (>97%) were obtained for ZTA ceramic containing both TiO₂–CuO and TiO₂–MnO₂ at 1450 °C. Phase and qualitative compositional analysis was done using X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS). Tribological behaviour of the various ZTA composites was tested by dry sliding the different specimens against SiC abrasive grit paper at a load of 50 N. The lowest specific wear rate of 9.2 × 10⁻⁵ mm³/N m and coefficient of friction of 0.35 were observed for the ZTA ceramic composite with TiO₂–MnO₂. The basic wear mechanisms were abrasion and grain pullout as corroborated from scanning electron microscopy (SEM) images.     

Study of Short- and Long-Term Effectiveness of Ammonium Sulfide as Surface Passivation for InAs/GaSb Superlattices Using X-Ray Photoelectron Spectroscopy

The surface quality of as-etched and ammonium sulfide [(NH₄)₂S]-treated samples of an indium arsenide/gallium antimonide (InAs/GaSb) superlattice structure were compared using x-ray photoelectron spectroscopy (XPS). After short exposure to the atmosphere following passivation, treated samples displayed a complete absence or significant reduction of native oxides compared with untreated samples, confirming better quality of surface passivation. However, extensive sulfidization was not observed, and after extended exposure, the native oxides reappeared on the treated surface, establishing the need for a capping layer for long-term passivation stability. The surface study provides definitive confirmation of previous results on electrical properties of photodetectors fabricated on InAs/GaSb superlattices.     

Analysis of uniform structured RF MEMS switch with different uniform and non-uniform meandering techniques

Microsystem Technologies - This paper mainly focuses on the investigation of different meandering techniques for the MEMS RF shunt capacitive switch. It involves three meandering techniques for the...     

Thermal instability-driven multiple solutions in a grooved channel

ABSTRACT

We present rich non-linear characteristics like multiple-stable states, bifurcation, and transition to chaos as a result of thermal instability-driven multiple solutions in a bottom-heated grooved channel undergoing natural convection with Rayleigh number varying from 1 × 10⁵ to 9 × 10⁵. From our analysis, we identify two different routes in which the solution of the system evolves along with the critical Rayleigh numbers associated with such transitions. In one route, the solution transforms from steady symmetric to chaotic solutions, while for the second route it first undergoes pitchfork bifurcation, where steady symmetric solution transforms to steady asymmetric, followed by Hopf bifurcation to periodic solutions. The two distinct solution routes clearly bring out the dependence of system solutions on initial conditions. The route to chaos in the grooved channel system has been successfully identified, which is supported by the results of time-series, power-spectra density and three-dimensional phase plots, apart from the positive values of largest Lyapunov exponent.     

Textured ferroelectric SrBi2Nb2O9 phase obtained by melt-quenching the SrBi2B2O7-Nb2O5 system and its anisotropic dielectric and pyroelectric properties

Textured SrBi₂Nb₂O₉ ceramics were obtained by quenching the melts of SrBi₂B₂O₇-Nb₂O₅ in equimolar ratio. The as-quenched samples were crystalline comprising 40% c-oriented grains. The influence of the post heat-treatment temperature on the orientation factor (f) and microstructure was studied using x-ray powder diffraction (XRD) and Scanning electron microscopy (SEM). The orientation factor was found to increase with increasing post heat-treatment temperature and reached a maximum value of 65% for the samples heated at 700°C for 10 h. Relative density and the grain-size of the partially grain oriented ceramics were found to increase with an increase in the heat-treatment temperature. The effect of texturing yielded anisotropy in the dielectric and pyroelectric properties. The dielectric constant ( e_r^￠ ( ^) = 114 ) \left( {\varepsilon_r^{\prime } \left( \bot \right) = 114} \right) and the pyroelectric coefficient (p(┴) = −0.07 nC cm⁻² °C⁻¹) along the direction perpendicular to the melt pressing axis were superior to that of the direction parallel ((e_r^￠ ( ||) = 93 \varepsilon_r^{\prime } \left( \parallel \right) = 93 ) (p(||) = −0.02 nC cm⁻² °C⁻¹)) (c-axis of the grain) to the pressing axis at room temperature.     

Morphological Changes During Annealing of Electrodeposited Ni-Cr Coating on Steel and Their Effect on Corrosion in 3% of NaCl Solution

 Steel containing carbon of 02% was coated with Ni and Cr through electrodeposition, and subsequently annealed at 400 and 600 ℃ for 5 min, 30 min, 1 h and 2 h. During annealing at 400 ℃, the formation and growth of oxides occurred in the form of petals along with voids, cracks and porosities. However, at 600 ℃, the nucleation and growth of chromium oxide whiskers produced a surface almost free from crack, porosity and void for 1 h and 2 h of holding. In accordance with the surface morphology, the bare steel, as-deposited steel, all specimens deposited and annealed at 400 ℃, and specimens deposited and annealed at 600 ℃ for 5 and 30 min exhibited continuous corrosion in 3% of NaCl solution. However, the specimens deposited and annealed at 600 ℃ for 1 and 2 h exhibited an improved corrosion resistance in 3% of NaCl solution with high pitting potential due to presence of a dense passive oxide film almost free from voids at the surface.     

Effect of End-point Temperature and Degree of Doneness on Sensory and Instrumental Flavor Profile of Beefsteaks

ABSTRACT: Beef M. longissimus thoracis et lumborum was used to investigate the effects of 6 end-point temperatures on flavor and texture. Steaks cooked to medium temperature were associated with 4-heptanolide, whereas those cooked to higher temperatures were associated with pyrazines and hexanol. These steaks were also associated with flavor attributes, such as roasted, burnt, and beefy. However, consumers did not find differences in flavor liking of steaks (P > 0.05) cooked to 6 end-point temperatures. Although steaks cooked to lower temperatures were liked for their tenderness and juiciness, overall liking scores were not affected by end-point temperature. Thus both flavor and tenderness play an important role in consumer satisfaction.     

In situ analyses of gallstone inner layers by external PIXE

External proton induced X-ray emission analyses were carried out to study the elemental profile at different points of two mixed gallstones inner layers. It was observed that ten minor/trace elements namely P, S, Ca, Mn, Fe, Cu, Zn, Br, Rb and Sr were present in the mixed gallstone layers. Among the elements detected, Ca shows the highest concentration whereas Br, Rb and Sr were found only at some points in trace level. Concentrations of Ca and P were observed to be the highest in the core of the gallstones. The presence of high amount of Cu and Zn on the surface of the gallstones, as compared to other layers, may be due to contamination with bile.