Investigation on gradient dielectric characteristics of bamboo (Dentroclamus strictus)

Dependence of dielectric constant (ε′) and dielectric dissipation factor (tan δ) on distance from outermost skin to the center of bamboo has been determined. Dielectric measurements have been done in the temperature range of 24–120°C and in the frequency range, 4–100 kHz. Gradient behavior in ε′ and tan δ has been found in bamboo. It has also been observed that ε′ and tan δ increase with increasing temperature and decrease with increasing frequency. Relaxation times have been calculated for the four samples at 80, 90, and 100°C temperatures, which show that relaxation time decreases with the increase of temperature because of the increased molecular mobility. A continuous increase in the hardness from center (48) to outer surface (70) and density from 0.45 to 0.80 g/cc has been observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 380–386, 2006     

Room temperature chemical synthesis of highly oriented PbSe nanotubes based on negative free energy of formation

The sacrificial template free chemical synthesis of PbSe nanotubes at room temperature has been performed by lead hydroxination from cadmium hydroxide nanowires. This process was based on the ion exchange reaction to replace Cd²⁺ with Pb²⁺ ions from hydroxyl group followed by replacement of hydroxyl group with selenium ions. The reaction kinetics was accomplished due to more negative free energy of formation and thus the difference in the solubility products. The formed nanotubes were inclusive of Pb and Se with proper inter-chemical bonds with preferred orientations having diameter in tens of nanometer. These nanotubes can have future applications in electronic, optoelectronics and photovoltaic's as well.     

Charge transport and microstructure in PFO:MEH-PPV polymer blend thin films

Current density–voltage characteristics of poly(9,9′-dihexyl fluorenyl-2,7-diyl) (PFO) thin films (～120 nm) have been studied in hole only device configuration at different temperatures (100–290 K) in pure form and with blending (～0.25–50 wt%) of poly(2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene) (MEH-PPV). It has been found that in the case of pure PFO the charge transport at low fields show an ohmic region which is followed by space charge limited conduction region. Blending of PFO with MEH-PPV at low ratio (up to 2 wt%) increases the current density. As the ratio is increased further, the current density decreases. Analysis show that there is a change in conduction mechanism up to 6 V from SCLC to thermally activated ohmic conduction upon blending indicating the creation of new energy level near the transport states of PFO. Morphology of the polymer blended thin films was obtained by atomic force microscopy (AFM) technique. It has been found that the surface roughness of the investigated films is significantly increased upon blending indicating aggregation as well as phase separation at high blending ratios. The decrease in conductivity at high blending ratio can be related to the change in morphology of the films.     

Physicochemical,Pasting, and Functional Properties of Amaranth Seed Flours: Effects of Lipids Removal

The present work was carried out to evaluate physicochemical (composition, hunter color, and sodium dodecyl sulfate–polyacrylamide gel electrophoresis [SDS‐PAGE]), pasting, and functional properties (foaming, emulsification, water, and fat absorption capacity) of amaranth full‐fat flours from 6 lines/cultivars (AFs), and to see the effects of lipid removal/defatting on these properties. Protein, ash, and lipid content of AFs ranged between 12.5% to 15.2%, 3.0% to 3.5%, and 7.1% to 8.0%, respectively. The flours showed a number of bands between 97 and 7 kDa, with main subunits of approximately 58, 37, 33, 31, 23, and 16 kDa in the SDS‐PAGE profiles. The protein content and L* value increased, while b* values decreased following defatting for most of the lines/cultivars. The defatted flours (DAFs) had higher final viscosity and stability (lower breakdown viscosity) as compared to counterpart AFs. The protein profiling of the flours was not affected with the lipid removal/defatting. However, water absorption capacity and foam stability of the flours improved upon defatting. Principal component analysis revealed that pasting temperature was positively related to lipid content, while breakdown viscosity was negatively related to protein content. Foaming properties (capacity and stability) showed negative relationship with lipid content, and positive with protein content, ash content, water, and fat absorption capacity.     

Computational approach to photonic drilling of silicon carbide

The ability of lasers to carry out drilling processes in silicon carbide ceramic was investigated in this study. A JK 701 pulsed Nd:YAG laser was used for drilling through the entire depth of silicon carbide plates of different thicknesses. The laser parameters were varied in different combinations for a well-controlled drilling through the entire thickness of the SiC plates. A drilling model incorporating effects of various physical phenomena such as decomposition, evaporation-induced recoil pressure, and surface tension was developed. Such comprehensive model was capable of advance prediction of the energy and time required for drilling a hole through any desired depth of material.     

Superprotonic Conductivity of MOFs and Other Crystalline Platforms Beyond 10−1 S cm−1

The proton-exchange membrane (PEM) is a fundamental module of proton-exchange membrane fuel cells (PEMFCs), permitting proton passage and thus governing the overall performance of PEMFCs. Till now, Nafion has been the extensively used marketable PEM material due to its high protonic conductivity of 10⁻²–10⁻¹ S cm⁻¹ under high relative humidity and 80–85 °C. On the other hand, crystalline materials such as metal-organic frameworks (MOFs), coordination polymers (CPs), covalent organic frameworks (COFs), hydrogen-bonded organic framework (HOFs), metalo hydrogen-bonded organic framework (MHOFs), and polyoxometalates (POMs) are emerging as potential PEM materials, where crystallinity has paved the way to study the conduction pathway and associated mechanisms to understand structure-function relationships. However, to date, ultrahigh superprotonic conductivity to the level of 10⁻¹ S cm⁻¹, close to Nafion, is relatively scarce for the crystalline proton conductors. In this review, the discussion is focused on materials that demonstrate a conductivity order of 10⁻¹ S cm⁻¹ and higher for those individual crystalline platforms (to be on the equal footing and superior to nafion, respectively) based on their synthesis approach while highlighting the design norms and key features for attaining such ultrahigh conductivity. While a critical analysis is made, the key issues and future prospects are also addressed.     

ESKI-IBE: Efficient and secure key issuing identity-based encryption with cloud privacy centers

Multimedia Tools and Applications - Digital certificate validation associated with traditional public key cryptosystems make it impractical in real-world environments due to their storage cost. The...     

Electrical,optical and hole transport mechanism in thin films of poly(3-octylthiophene-co-3-hexylthiophene): Synthesis and characterization

The present study demonstrates the designing of copolymer poly(3-octylthiophene-co-3-hexylthiophene) (P3OT-HT) and study of the hole transport mechanism in it. Detailed structural, optical and thermal studies of P3OT-HT discuss its synthesis aspects. Current density–voltage characteristics have been studied at different temperatures (290–110 K) to understand the mechanism of hole transport in P3OT-HT. It has been established that current density in P3OT-HT thin films is governed by space charge limited conduction with traps distributed exponentially in energy and space. Hole mobility is both temperature and electric field dependent arising due to substituent functional groups attached the polymer backbone.     

Forming-free bipolar resistive switching in nonstoichiometric ceria films

The mechanism of forming-free bipolar resistive switching in a Zr/CeO _x /Pt device was investigated. High-resolution transmission electron microscopy and energy-dispersive spectroscopy analysis indicated the formation of a ZrO _y layer at the Zr/CeO _x interface. X-ray diffraction studies of CeO _x films revealed that they consist of nano-polycrystals embedded in a disordered lattice. The observed resistive switching was suggested to be linked with the formation and rupture of conductive filaments constituted by oxygen vacancies in the CeO _x film and in the nonstoichiometric ZrO _y interfacial layer. X-ray photoelectron spectroscopy study confirmed the presence of oxygen vacancies in both of the said regions. In the low-resistance ON state, the electrical conduction was found to be of ohmic nature, while the high-resistance OFF state was governed by trap-controlled space charge-limited mechanism. The stable resistive switching behavior and long retention times with an acceptable resistance ratio enable the device for its application in future nonvolatile resistive random access memory (RRAM).