Dielectric dispersion in Li2O–MoO3–B2O3 glass system doped with V2O5

Li₂O–MoO₃–B₂O₃ glasses containing different amounts of V₂O₅, ranging from 0 to 1.5 mol%, were prepared. The dielectric properties (viz., constant ′, loss tan δ, AC conductivity σ_ac over a wide range of frequency and temperature) have been studied as a function of the concentration of vanadium ions. The variation of AC conductivity with the concentration of V₂O₅ passes through a maximum at 0.8 mol% V₂O₅. In the high-temperature region, the AC conduction seems to be connected with the mixed conduction, viz., electronic and ionic conduction. The dielectric relaxation effects exhibited by these glasses have been analyzed quantitatively by pseudo Cole–Cole plot method and the spreading of relaxation times has been established. Further analysis of these results has been carried out with the aid of the data on ESR, IR and optical absorption spectra.     

Micro-channel heat sink with slurry of water with micro-encapsulated phase change material: 3D-numerical study

This study investigates the influence of using micro-encapsulated phase change material (MEPCM) on the thermal and hydraulic performance of micro-channel heat sinks used for heat dissipation of high power electronic devices. A three-dimensional, one-phase, laminar flow model of a rectangular channel using water slurry of MEPCM with temperature dependent physical properties was developed. The results showed a significant increase in the heat transfer coefficient under certain conditions for heat flux rates of 100 W/cm² and 500 W/cm² that is mainly dependant on the channel inlet and outlet temperatures and the selected MEPCM melting temperature. Lower and more uniform temperatures across the electronic device can be achieved at less pumping power compared to using water only as the cooling fluid.     

Sustainable charcoal production from biomass

Charcoal products can be produced from biomass sources such as charcoal from wood, woody agricultural products, the biogenic fraction of municipal wastes, nut shells, etc. The liquid and gaseous fractions obtained from biomass are a valuable fuel source; however, the solid fraction (charcoal) has the recovery potential of carbon black or as carbon adsorbent after applying an activation step. Charcoal is produced by slow heating wood (carbonization) in airtight ovens or retorts, in chambers with various gases, or in kilns supplied with limited and controlled amounts of air. Charcoal has the potential to improve soil properties, crop productivity, and carbon sequestration in soil. The most interesting temperature range for the production of the pyrolysis products is between 625 and 775 K. The charcoal yield decreased gradually from 43.5 to 31.0% for the walnut shell and from 38.3 to 25.4% for the spruce wood with an increase of temperature from 550 to 1150 K. The charcoal yield decreases as the temperature increases. The ignition temperature of charcoal increases as the carbonization temperature increases. The charcoal briquettes that are sold on the commercial market are typically made from a binder and a filler.     

Free vibration of composite plates using the finite difference method

The finite difference method was used to solve differential equations of motion of free vibration of composite plates with different boundary conditions. The effects of shear deformation and rotary inertia on the natural frequencies of laminated composite plates are investigated in this paper. Four cases are studied: neglecting both shear deformation and rotary inertia, considering only rotary inertia, considering only shear deformation, and considering both. Solutions were obtained for symmetric and angle-ply laminated plates. The factors that affect natural frequencies of different composite plates, such as span-to-depth ratio, aspect ratio, angle-ply, and lamination sequence were also investigated. Results were found to agree well with exact and approximate solutions reported in literature. Shear deformation showed a considerable effect on the natural frequencies for composite plates, whereas the rotary inertia effect was found to be negligible.     

Effect of fertilizers,irrigation and plant density on groundnut (Arachis hypogaea L)

Experiments were conducted on sandy clay loam soils of Tirupati Campus of Andhra Pradesh Agricultural University for two summer seasons of 1979 and 1980 to study the effect of fertilizers, irrigation and plant density on Spanish groundnut. Three fertilizer schedules (30 kg N, 20 kg P, 50 kg K; 60 kg N, 40 kg P, 10 kg K and 90 kg N, 60 kg P, 150 kg K ha^?1), three schedules of irrigation (irrigation at 25, 50 and 75% depletion of available soil moisture) and three plant densitites (1,000,000; 666,000; and 444,000 plants per ha) were tested in 3³ factorial confounded design with two replications. Groundnut responded to 60 kg N, 40 kg P and 10 kg K ha^?1 due to delayed sowings in 1979. However, response to fertilisers was marginal in 1980, when the sowings were done in optimum time. Pod yield tended to be maximum when irrigations were scheduled at 25% depletion of available soil moisture (DASM) in 1979 and at 50% DASM in 1980. Plant density of 444,000 plants per ha was optimum in both the years. Interaction of fertilizers and plant density, fertilizers and irrigation and plant density and irrigation increased the pod yield of groundnut, only when the sowings were delayed.     

Modification and development of the optical,structural, thermal and electrical characterization of Chitosan incorporated with Au/Bi2O3/Mo NPs fabricated by laser ablation

The molecular structures of pure polymer (chitosan) incorporated with ternary metal nanoparticles (Au/Bi₂O₃/Mo) synthesized by laser ablation have been performed ia FT-IR and XRD. The surface of the synthesized samples has been investigated ia SEM. Thermal, electrical, and dielectric haracterization have been performed to utilized in energy applications. XRD patterns display the amorphous nature of chitosan (Cs), characterized by two hump peaks at 2? =11.34^o and 2? =19.57^o, which disappeared by doped with Au/Bi₂O₃/Mo NPs. FT-IR spectra revealed that thereare complexation between Cs and Au/Bi₂O₃/Mo NPs took place in amorphous regions. SEM displays grains with rectangular shape after adding different filling nanoparticles, and rod-shaped formed on the surface of the samples.TGA curves obtained the enhancement in the thermal stability of samples . The AC conductivity of the samples increased by the addition of Au/Bi₂O₃/Mo NPs. The results confirm that nanocomposite of Cs/metal have excellent thermal and electronic haracterization, which may suggest the utilization of these nanocomposites in energy storage.

     

Microwave synthesis of noncentrosymmetric BaTiO3 truncated nanocubes for charge storage applications

Truncated nanocubes of barium titanate (BT) were synthesized using a rapid, facile microwave-assisted hydrothermal route. Stoichiometric composition of pellets of nanocube BT powders was prepared by two-stage microwave process. Characterization by powder XRD, Rietveld refinement, SEM, TEM, and dielectric and polarization measurements was performed. X-ray diffraction revealed a polymorphic transformation from cubic Pm3?m to tetragonal P4mm after 15 min of microwave irradiation, arising from titanium displacement along the c-axis. Secondary electron images were examined for nanocube BT synthesis and annealed at different timings. Transmission electron microscopy showed a narrow particle size distribution with an average size of 70 ± 9 nm. The remanence and saturation polarization were 15.5 ± 1.6 and 19.3 ± 1.2 μC/cm(2), respectively. A charge storage density of 925 ± 47 nF/cm(2) was obtained; Pt/BT/Pt multilayer ceramic capacitor stack had an average leakage current density of 5.78 ± 0.46 × 10(-8) A/cm(2) at ±2 V. The significance of this study shows an inexpensive and facile processing platform for synthesis of high-k dielectric for charge storage applications.     

Open circuit voltage durability study and model of catalyst coated membranes at different humidification levels

Fuel cell material durability is an area of extensive research today. Chemical degradation of the ionomer membrane is one important degradation mechanism leading to overall failure of fuel cells. This study examined the effects of relative humidity on the chemical degradation of the membrane during open circuit voltage testing. Five Gore™ PRIMEA^® series 5510 catalyst coated membranes were degraded at 100%, 75%, 50%, and 20% RH. Open circuit potential and cumulative fluoride release were monitored over time. Additionally scanning electron microscopy images were taken at end of the test. The results showed that with decreasing RH fluoride release rate increased as did performance degradation. This was attributed to an increase in gas crossover with a decrease in RH. Further, it is also shown that interruptions in testing may heavily influence cumulative fluoride release measurements where frequent stoppages in testing will cause fluoride release to be underestimated. SEM analysis shows that degradation occurred in the ionomer layer close to the cathode catalyst. A chemical degradation model of the ionomer membrane was used to model the results. The model was able to predict fluoride release trends, including the effects of interruptions, showing that changes in gas crossover with RH could explain the experimental results.     

Three-Dimensional Micromechanics-Based Constitutive Framework for Analysis of Pultruded Composite Structures

A new 3D micromechanics-based framework is proposed for the nonlinear analysis of pultruded fiber-reinforced polymeric composites. The proposed 3D modeling framework is a nested multiscale approach that explicitly recognizes the response of the composite systems (layers) within the cross section of the pultruded member. These layers can have reinforcements in the form of roving, continuous filament mat (CFM), and∕or woven fabrics. Different 3D micromechanical models for the layers can be used to recognize the basic response of the fiber and matrix materials. The framework is implemented with both shell and 3D finite elements. The 3D lamination theory is used to generate a homogenized nonlinear effective response for a through-thickness representative stacking sequence. The proposed modeling framework for pultruded composites is used to predict the stiffness and nonlinear stress-strain response of E-glass∕vinylester pultruded materials reinforced with roving and CFM. The roving layer is idealized using a 3D nonlinear micromechanics model for a unidirectional fiber-reinforced material. A simple nonlinear micromechanics model for the CFM layer is also applied. The proposed model shows very good predictive capabilities of the overall effective properties and the nonlinear response of pultruded composites, based on the in situ material properties, and the volume fractions of the constituents. Experimental data from off-axis tests of pultruded plates under uniaxial compression are used to verify the proposed model. The proposed framework can be easily incorporated within displacement-based finite-element models of composite structures.