Model development and validation: Co-combustion of residual char, gases and volatile fuels in the fast fluidized combustion chamber of a dual fluidized bed biomass gasifier

A one-dimensional steady state model has been developed for the combustion reactor of a dual fluidized bed biomass steam gasification system. The combustion reactor is operated as fast fluidized bed (riser) with staged air introduction (bottom, primary and secondary air). The main fuel i.e., residual biomass char (from the gasifier), is introduced together with the circulating bed material at the bottom of the riser. The riser is divided into two zones: bottom zone (modelled according to modified two phase theory) and upper zone (modelled with core-annulus approach). The model consists of sub-model for bed hydrodynamic, conversion and conservation. Biomass char is assumed to be a homogeneous matrix of C, H and O and is modelled as partially volatile fuel. The exit gas composition and the temperature profile predicted by the model are in good agreement with the measured value.     

Poly(L‐lactide)/polypropylene blends: Evaluation of mechanical,thermal, and morphological characteristics

Poly(L lactide) (PLA) was blended with polypropylene (PP) at various ratios (PLA:PP = 90 : 10, 80 : 20, 70 : 30, and 50 : 50) with a melt‐blending technique in an attempt to improve the melt processability of PLA. Maleic anhydride (MAH)‐grafted PP and glycidyl methacrylate were used as the reactive compatibilizers to induce miscibility in the blend. The PLA/PP blend at a blend ratio of 90 : 10, exhibited optimum mechanical performance. Differential scanning calorimetry and thermogravimetric analysis studies showed that the PLA/PP/MAH‐g‐PP blend had the maximum thermal stability with the support of the heat deflection temperature values. Furthermore, dynamic mechanical analysis findings revealed an increase in the glass‐transition temperature and storage modulus with the addition of MAH‐g‐PP compatibilizer. The interaction between the compatibilizers and constituent polymers was confirmed from Fourier transform infrared spectra, and scanning electron microscopy of impact‐fractured samples showed that the soft PP phase was dispersed within the PLA matrix, and a decrease in the domain size of the dispersed phase was observed with the incorporation of MAH‐g‐PP, which acted as a compatibilizer to improve the compatibility between PLA and PP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal and mechanical properties of nano-titanium dioxide-doped polyvinyl alcohol

Organic polymers exhibit poor thermal stability and inferior mechanical properties. Significant improvement in mechanical and thermal properties of polymers can be achieved by homogeneous distribution of inorganic materials preferably in nano size. In this study, these properties of polyvinyl alcohol were found to improve by addition of nano-titanium dioxide. Microwave irradiation method was used to prepare nano-titanium dioxide and doped in polyvinyl alcohol matrix to formulate the composite film. The spectral and morphological characterizations of the composites were carried out by the conventional techniques. Various mechanical properties were determined by Tinus Oisen universal testing machine. Thermal gravimetric analysis and differential scanning calorimetry were used for studying the thermal properties of the composites. Shift in decomposition temperature of polyvinyl alcohol indicated the enhanced thermal stability of polyvinyl alcohol. The composite also exhibited significant improvement in all the mechanical properties.     

Computational Studies on Nitro-Azaboriridine—A High-Energetic Material

Nitrogen heterocycles and their derivatives are one of the classes of compounds that have been widely used in developing high-energetic materials. The energy content of the heterocycle ring systems can be increased by inclusion of nitro, cyano, and azido groups. In the present study nitro derivatives of small three-membered B-N-C ring compounds, viz. 1-nitro-1,2-azaboriridine, 1,3-dinitro-1,2-azaboriridine, and 1,3,3-trinitro-1,2-azaboriridine, have been considered. Thermodynamic properties and energetics of the above compounds have been taken for detailed computational study using G2, G3, and CBSQB3 compound methods. Studies reveal that these compounds can be considered for use as high-energetic materials. Detonation velocity (D) and detonation pressure (P) of the title compounds have also been evaluated using the Kamlet-Jacobs method based on the theoretical densities and heats of formation calculated at G3 level. Calculation shows that 1,3,3-trinitro-1,2-azaboriridine yields a detonation velocity of 9.14 km/s and a detonation pressure of 40.2 GPa at a loading density of 1.91 g/cm³ that is comparable to powerful commercial explosives such as HMX (9.10 km/s, 1.91 g/cm³, 39.0 GPa) and RDX (8.75 km/s, 1.82 g/cm³, 34.0 GPa).     

Habitat structure influences below ground biocontrol services: A comparison between urban gardens and vacant lots

Urban agriculture offers a framework for local self-reliance by provisioning food security, employment opportunities, and other community benefits. However, urban agriculture must rely on the supporting and regulating services of the soil food web. Hence, we quantified belowground biocontrol activity in urban gardens and vacant lots in two post-industrial cities using an in situ insect baiting technique. Due to the differences in habitat structure, we hypothesized that belowground biocontrol services will differ between gardens and vacant lots and the influence of habitat structure would differ with the type of biocontrol organism. Results revealed that biocontrol activity, as assessed by % mortality of baited insects, varied between 51% and 98% with higher activity often recorded in vacant lots than gardens. Major contributions to bait insect mortality were by ants, followed by microbial pathogens and entomopathogenic nematodes, respectively. Ants showed higher (p < 0.0001) % mortality in vacant lots (60% ± 33.4%) than in urban gardens (33.3% ± 22.2%) whereas microbial pathogens exhibited higher (p < 0.0001) mortality in gardens (27.8% ± 15%) than vacant lots (8.3% ± 16.7%). Ants caused higher (p < 0.0001) mortality when larger-mesh size cages were used compared with the smaller-mesh size cages, but mortality by microbial pathogens did not differ with cage type. The high biocontrol activity indicates the resilience of the soil food web in urban ecosystems and the differential effects of habitat structure on biocontrol activity can help guide landscape planning and vegetation management to enhance urban environments and boost local self-reliance.     

Photovoltaic performance of dye-sensitized solar cells fabricated with polyvinylidene fluoride–polyacrylonitrile–silicondioxide hybrid composite membrane

Electrospun fibrous membranes of hybrid composites of polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN) and silicon dioxide (SiO₂) (PVdF–PAN–SiO₂) are prepared with different proportions of SiO₂ (3, 5 and 7% w/w). The field emission scanning electron microscopy (FE-SEM) reveals that these membranes have three-dimensional, fully interconnected network structures, which are combined with micropores of fine SiO₂ distribution. The surface roughness of the membranes increases with increasing the SiO₂ content. It is found that 7 wt% SiO₂/PVdF–PAN electrolyte membrane has the highest ionic conductivity (6.96 × 10⁻² S cm⁻¹) due to the large liquid electrolyte uptake (about 570%). As the concentration of SiO₂ nanoparticles increase, the contact angle value also increases, ranging from 135.70° to 140.60° which indicates that the membrane has higher hydrophobicity. The dye sensitized solar cells (DSSCs) are fabricated using the hybrid composite membrane with PVdF–PAN with 7 wt % SiO₂. Its photovoltaic performance exhibits an open circuit voltage (V_oc) of 0.79 V and a short circuit current 11.6 mA cm⁻² at an incident light intensity of 100 mW cm⁻², producing an efficiency of 5.61%. DSSC, using the hybrid composite electrospun membrane which shows more stable photovoltaic performance than other assembled DSSCs.     

Intramolecular Locked Dithioalkylbithiophene‐Based Semiconductors for High‐Performance Organic Field‐Effect Transistors

New 3,3′‐dithioalkyl‐2,2′‐bithiophene ( SBT )‐based small molecular and polymeric semiconductors are synthesized by end‐capping or copolymerization with dithienothiophen‐2‐yl units. Single‐crystal, molecular orbital computations, and optical/electrochemical data indicate that the SBT core is completely planar, likely via S(alkyl)?S(thiophene) intramolecular locks. Therefore, compared to semiconductors based on the conventional 3,3′‐dialkyl‐2,2′‐bithiophene, the resulting SBT systems are planar (torsional angle <1°) and highly π‐conjugated. Charge transport is investigated for solution‐sheared films in field‐effect transistors demonstrating that SBT can enable good semiconducting materials with hole mobilities ranging from ≈0.03 to 1.7 cm² V^?1 s^?1. Transport difference within this family is rationalized by film morphology, as accessed by grazing incidence X‐ray diffraction experiments.     

Enhancement of electrical properties and blue emission due to nanostructuring of BaZr0.05Ti0.95O3 ferroelectric ceramics

Nano-structuring of various ferroic materials has tailored the existing properties in their bulk counterpart. Keeping this fact in view, nano-crystalline barium zirconate titanate (BaZr_0.05Ti_0.95O₃) ferroelectric ceramics were prepared by mechanical activation process using high-energy planetary ball milling followed by the sintering process. In the present work, effect of milling duration (15, 30 and 45 h) on structural and microstructural properties has been observed with the help of X-ray diffraction, scanning electron microscopy and transmission electron microscopy (for optimized milling duration). The crystallite size of the milled specimen decreases to 14.17 nm on increasing the milling duration from 15 to 45 h. A comparison with its bulk counterpart showed significant enhancement in di-, ferro-, piezo- and pyro-electric properties with strong blue emission in UV light (265 nm). The blue emission in UV light makes it a potential candidate for LEDs and optical devices.     

Dielectric relaxation in Ba(Y1/2Nb1/2)O3–BaTiO3 ceramics

Lead-free (1 ? x)Ba(Y_1/2Nb_1/2)O₃–xBaTiO₃; (0 ≤ x ≤ 1) ceramics have been synthesized using solid-state reaction method and characterized by X-ray diffraction, scanning electron microscopy, dielectric and impedance studies. The crystal-structure of the compounds is found to be cubic with the space group Pm3m(221) except for BaTiO₃ for which it is tetragonal (P4/mmm). Complex impedance spectroscopy analysis indicated the presence of non-Debye type dielectric relaxation in Ba(Y_1/2Nb_1/2)O₃–BaTiO₃ system. Compound 0.25Ba(Y_1/2Nb_1/2)O₃–0.75BaTiO₃ exhibited a low value of temperature coefficient of capacitance (<±8 %) in the working temperature range (up to +100 °C), room temperature dielectric constant equal to 295 and low loss tangent (0.039) which meets the specifications for “Z5F” of Class I dielectrics of Electronic Industries Association. Hence, this composition might be a suitable candidate for capacitor applications. Ac conductivity and electric modulus studies supported the hopping type of conduction in the system and frequency dependent ac conductivity data obeyed Jonscher’s power law.