Epitaxial nucleation model for chiral-selective growth of single-walled carbon nanotubes on bimetallic catalyst surfaces

An epitaxial nucleation model for single-walled carbon nanotube (SWCNT) growth on bimetallic catalysts surfaces is reported in support of experimental observations of chiral enrichment. We model the bimetallic catalyst surfaces as a 2D (1 1 1) surface consisting of Ni or a combination of Ni and Fe atoms, with varying average bond length between nearest neighbor atoms which corresponds to the crystal structure of the alloys. The energies associated with nanotube cap formation on these various surfaces are calculated using density functional theory (DFT). We find that certain cap chiralities, such as (8, 4), are more stably bound to a surface that resembles a Ni_0.27Fe_0.73 bimetallic catalyst, whereas other chiralities, such as (9, 4), are more stable on a pure Ni surface. These results help explain the predominance of certain chiralities on specific bimetallic catalysts and provide a potential route to controlling the chirality of as-grown SWCNTs.     

Synthesis and characterization of solid-phase super acid catalysts and their application for isomerization of n-alkanes

In the present work, first, the reference catalyst super acidic nanostructured sulfated zirconia (SZ) and super acidic nanostructured aluminum chloride impregnated sulfated zirconium oxides in mole ratios of Zr⁴⁺:Al³⁺ as 2:1 (ACSZ-1), 1:1 (ACSZ-2), and 1:2 (ACSZ-3) were synthesized by a simple precipitation method. The catalytic performance of these four catalysts were evaluated during the isomerization of n-hexane, n-heptane, and n-octane to their corresponding branched chain isomers at low temperature and pressure conditions. ACSZ-2 shows high activity toward isomerization of n-hexane, n-heptane, and n-octane into their corresponding branched chain isomers. The reference catalyst SZ was proved to be less effective compare to the other three synthesized ACSZ catalysts. Ammonia-temperature-programmed desorption of these two materials ensures that the super acidity of ACSZ-2 is higher than that of SZ. Atomic force microscopic and scanning electron microscopic pictures predict the nature of the surface of the catalysts. Transmission electron micrographic analysis indicates the presence of particle-bulks having average size 12–20?nm, presenting an amorphous nature and having no definite surface morphology of ACSZ-2. Fourier transform infrared provides an outline regarding different linkages and bond connectivities between atoms and groups in ACSZ-2 and SZ. After catalyst evaluation and characterization a probable reaction mechanism has been proposed theoretically. The reactivity and selectivity of ACSZ-2 and SZ as well as the order and activation energy of the isomerization reactions in presence of ACSZ-2 have been calculated. The use of ACSZ-2 is beneficial from the point of cost efficiency as well as its use is energy saving.     

Template-free synthesis of flower-shaped zero-valent iron nanoparticle: Role of hydroxyl group in controlling morphology and nitrate reduction

Well-dispersed single phasic flower-like zero valent iron nanoparticles have been synthesized under aerobic conditions using a facile approach without the addition of any additives or templates. The role of hydroxyl groups of polyhydroxy alcohols in controlling surface morphology of nanoparticles has been thoroughly investigated. The obtained nanoparticles have been characterized by TEM, FE-SEM, XRD and BET surface area analyzer. Electron microscopy analyses reveal that the solvent plays a pivotal role in determining the morphology of the particles. With increase in viscosity of the solvent, formations of ‘petal-like’ structures, which are joined at the center are formed. The nitrate removal efficiency of the iron nanoparticles synthesized in different solvents has been studied and it is seen that the “flower-like” iron nanoparticles were most active in the removal of nitrate. Experiments have been done by varying (i) nitrate concentrations, (ii) nanoparticle dose, and (iii) type of nanoparticles. The results conclude that highest removal efficiency (～100%) was achieved when the nanoparticle dose was 2.88 g/L, even for high nitrate concentrations up to 400 mg/L. The major highlight of this work is the fact that even though the nanoparticles synthesized in glycerol-water mixture have larger size in comparison to the other nanoparticles, still they remove the nitrates with highest efficiency.”     

Progressive cutting tool wear detection from machined surface images using Voronoi tessellation method

Tool condition monitoring by machine vision approach has been gaining popularity day by day since it is a low cost and flexible method. In this paper, a tool condition monitoring technique by analysing turned surface images has been presented. The aim of this work is to apply an image texture analysis technique on turned surface images for quantitative assessment of cutting tool flank wear, progressively. A novel method by the concept of Voronoi tessellation has been applied in this study to analyse the surface texture of machined surface after the creation of Voronoi diagram. Two texture features, namely, number of polygons with zero cross moment and total void area of Voronoi diagram of machined surface images have been extracted. A correlation study between measured flank wear and extracted texture features has been done for depicting the tool flank wear. It has been found that number of polygons with zero cross moment has better linear relationship with tool flank wear than that of total void area.     

Electric-field-induced self-assembled one-dimensional nanostructures in CdX and HgX (X=Se, Te) thin films

Self-assembling due to the presence of electric field during deposition in the spray deposited nanocrystalline CdX and HgX (X=Se and Te) thin films is reported. The films are deposited using solvothermally synthesized nanoparticles dispersed in 1-butanol and sprayed on the glass substrates at 200 °C without any voltage as well as by applying a voltage to the nozzle. The electron microscopy studies reveal the formation of nanorods for the films deposited with the voltage. The X-ray diffractograms of CdSe films deposited without voltage and with voltage show hexagonal crystal structure. On the other hand, CdTe films deposited without voltage show cubic crystal structure and the films deposited with voltage show hexagonal crystal structure. HgX films deposited without and with voltage show cubic crystal structure and there is no nanorod formation below 700 V. HRTEM studies show the growth direction of the CdX nanostructures. In view of the self-assembly observed under voltage, the induced dipole moment and the resultant electrostatic interaction are expected to be the driving force for the growth of nanorods. Blueshift in the band gap is observed for all the films deposited without and with voltages, and it is attributed to the quantum confinement effect due to the formation self-assembled one-dimensional nanostructures.     

Large Eddy Simulation of Turbulent Slot Jet Impingement Heat Transfer at Small Nozzle-to-Plate Spacing

We present fluid flow and heat transfer of a slot jet impingement heat transfer at a small value of the nozzle-to-plate spacing at which a secondary peak in the Nusselt number is observed. Large eddy simulation has been performed with a finite-volume-based computational fluid dynamics code and using a dynamic Smagorinsky model. The optimum domain size and grid for large eddy simulation (LES) have been produced based on LES computations on a coarse mesh and Reynolds-averaged Navier–Stokes-based computations. Two inflow conditions, namely, using the vortex method and no perturbations, were compared. The present LES results, using the vortex method, capture the secondary peak in the Nusselt number better as compared to the case with no perturbations. Results show that mean velocity profile in the stagnation region deviates from the standard law of the wall. Further, large-scale vortical structures were observed near the location of the secondary Nusselt number peak. Increases in both the streamwise and wall normal turbulence fluctuations are observed near the secondary peak in the Nusselt number. The secondary peak in Nusselt number is found to be associated with the combined effect of flow acceleration and an increase in the turbulence kinetic energy.     

A semantic geo-catalogue for a local administration

The enhancement of the search capabilities of geo-spatial tools occupies one of the highest positions in the agenda of the INSPIRE initiative. This can be done by equipping applications with tools able to understand user terminology. However, this is in contrast with current approaches, which tend to fix in advance the terminology with a consequent rigidity in the way users interact with the system. In this paper we present the work we have done with the Semantic Geo-Catalogue (SGC) project in providing a semantic extension to the geo-catalogue of the Autonomous Province of Trento (PAT) in Italy. This was done through the adoption of a semantic matching tool and a faceted ontology that codifies knowledge about the geography of the PAT and that was created by reorganizing data extracted from the local geographical dataset. Thanks to the semantic extension, queries to the geo-catalogue are expanded with domain specific terms taken from the ontology thus obtaining a higher number of relevant documents in output. We also complied with the Open Government Data (OGD) initiative by publishing in RDF and by linking to relevant dictionaries some useful data taken from the local repository.     

Exploring the Influence of Methylene Diphenyl Diisocyanate as a Modifier for Ethylene Vinyl Acetate/Thermoplastic Polyurethane Blends

Ethylene vinyl acetate (EVA)/thermoplastic polyurethane (TPU) blend at various blend ratios has been modified via reactive processing with 4,4′-methylene diphenyl diisocyanate (MDI). Modification of the blends with even small amount of MDI shows significant improvement in physico-mechanical properties for EVA/TPU 50/50 and 30/70 blends, and it is also supported by the superior melt rheological behavior and dramatic improvement in oil resistance property. After the treatment of electron beam (dose range: 50–150?kGy), radiation crosslinked EVA/TPU (30:70) blend reveals further improvement in various properties. This particular material can find potential application as cable sheathing component.     

Low-Temperature Processing of PZT Thick Film by Seeding and High-Energy Ball Milling and Studies on Electrical Properties

Lead zirconate titanate thick film with molecular formula PbZr_0.52Ti_0.42O₃ (PZT) was prepared by a modified conventional sol–gel method through seeding and high-energy ball milling, resulting in perovskite phase formation at lower temperatures. The ball-milling time was optimized by keeping the seed particle loading (5 wt.%) constant in the sol–gel solution. This methodology helped in reduction of the crystalline phase formation temperature to 300°C, which is much lower than that reported in the literature (450°C). The well-established perovskite phase was confirmed by x-ray diffraction (XRD) analysis. Scanning electron microscopy (SEM) of PZT films revealed uniform and crystalline microstructure. Film prepared by this methodology showed higher spontaneous polarization (2.22 μC/cm²), higher capacitance (1.17 nF), and low leakage current density (18 μA/cm²). The results obtained from ferroelectric characterization showed a strong correlation with the XRD and SEM results.     

Design of efficient fir digital differentiators of second and higher degrees by using universal weights

We propose in this paper an efficient design of FIR digital differentiators of degree k, k= 1, 2, 3,…, and their implementation in a novel structure which allows the order to be varied without having to alter the weights used in it. More precisely, we show that by using these ‘universal weights’ in a structure of order N_max, the order can be varied from N= 3 to N_max while keeping the weights fixed and retaining the optimality of performance. Mathematical formulae have been derived for these ‘universal weights’ for differentiators performing in the low- or midband-frequency ranges.