Surface Characteristics of Sodium (β-Alumina Electrolytes

Surfaces of sodium β/β"-alumina ceramics were characterized via techniques such as scanning electron microscopy, secondary ion mass spectroscopy, and electron spectroscopy for chemical analysis to determine the nature of the resistive surface film that leads to the phenomenon of asymmetric polarization in a sodium-sulfur cell. The results indicated that the resistive surface film is soda rich, has submicrometer thickness, and is removable by a surface treatment. A mechanism consistent with these observations is proposed for the formation of the resistive surface film on sodium β/β"-alumina during the sintering process.     

NATURAL AND APPLIED WAX COATINGS ON ORANGES

Scanning electron microscopy was used to examine the wax coating on oranges. The natural wax platelets are irregular in shape and size, have a rough surface and increase in numbers as the orange matures. Most natural platelets can be removed by dipping the orange in a chloroform-methanol solution and rubbing the surface. Store-bought oranges have natural wax platelets 1–2 microns thick covered with a 2–5 micron layer of commercial wax. Wax applied over platelets may be ineffective if the platelets break off in handling and expose the orange's surface. Removal of natural wax platelets prior to commercial waxing allows uniform wax application and consequently better storage life. Drying with air at 2.5 m/s produced uneven wax thickness while 14 m/s air produced a complete, uniform wax layer.     

Nutritional Quality of Vegetable Pigeonpeas [Cajanus cajan (L.) Mill sp.]: Mineral and Trace Elements

Mineral and trace elements of green and mature seed of pigeonpea genotypes were determined. Among the genotypes tested a considerable variation was observed in phosphorus, potassium and calcium of both green and mature seeds whereas the variation was small for magnesium. When consumed, green seeds are a richer source of iron, copper and zinc on a dry matter basis than the mature seed whereas there was a reverse trend for manganese. The calcium content of mature seed was significantly higher than green seed and this was attributed to the seed coat content of the mature seed.     

In vitro Digestibility of Whey Protein/K-Casein Complexes Isolated from Heated Concentrated Milk

The disulfide-linked complex of _K-casein and whey proteins that forms when concentrated milk is heated was isolated by centrifugation and column chromatography on Sephacryl S-1000. The rate of hydrolysis of β-lactoglobulin and _K-casein in the complex and the reduced and carboxymethylated components of the complex were measured by polyacrylamide gel electrophoresis. The rates of hydrolysis at pH 2.0 (pepsin) and pH 8.0 (trypsin and chymotrypsin) were similar for _k-casein in the complex and its reduced form. β-Lactoglobulin hydrolysis was faster for the reduced complex than for the complex which was much faster than for the native protein for all three enzymes. The results suggest that heating milk increases the digestibility of whey proteins, despite the formation of large protein complexes between the whey proteins and _K-casein.     

Characterization of silicides in high-temperature titanium alloys

Different types of silicides precipitate in high-temperature titanium alloys depending upon the composition and heat treatment of the alloys. However, there are inconsistencies and lacunae with respect to the chemical and crystallographic characteristics of the silicides and these are pointed out here. Hexagonal silicides s1 (a=0.7804 nm; c=0.5447 nm) and s2 (a=0.701 nm; c=0.368 nm) coexist in the ternary alloy Ti–5Zr–Si; however, only the s2 silicide exists when the addition of stabilizing element is made. In addition, there is no common agreement about the space group of s2 silicide while the space group of s1 silicide was found to be P63/mcm (hP16). The (TiZr)6Si3 stoichiometry of s2 silicide is based on the experimental findings; however, the (TiZr)5Si3 stoichiometry of s1 silicide is simply deduced. Also the orientation relationships of silicides with and phases of the matrix are discussed.     

Continuum limit of discrete Sommerfeld problems on square lattice

A low-frequency approximation of the discrete Sommerfeld diffraction problems, involving the scattering of a time harmonic lattice wave incident on square lattice by a discrete Dirichlet or a discrete Neumann half-plane, is investigated. It is established that the exact solution of the discrete model converges to the solution of the continuum model, i.e., the continuous Sommerfeld problem, in the discrete Sobolev space defined by Hackbusch. A proof of convergence has been provided for both types of boundary conditions when the imaginary part of incident wavenumber is positive.     

Assessment of mechanical and three-body abrasive wear peculiarity of TiO<Subscript>2</Subscript>- and ZnO-filled bi-directional E-glass fibre-based polyester composites

This paper is about the development of bi-directional E-glass fibre-based polyester composites filled with zinc oxide (ZnO) and titanium dioxide (TiO₂) fillers, respectively. The mechanical characterization of these composites is performed. The three-body abrasive wear characteristic of fabricated composites has been assessed under different operating conditions. For this, the three-body abrasion test is done on dry abrasion test rig (TR-50) and analysed using Taguchi’s experimental design scheme and analysis of variance. The results obtained from these experiments are also validated against existing microscopic models of Ratner–Lancaster and Wang. A good linear relationship is obtained between specific wear rate and the reciprocal of ultimate strength and strain at tensile fracture of these composites. It indicates that the experimentally obtained results are in good agreement with these existing models. It is found that the tensile strength decreases with filler loading, while hardness, flexural strength, inter-laminar shear strength and impact strength are increased. TiO₂-filled composites were observed to perform better than ZnO-filled composites under abrasive wear situations. The wear mechanism is studied in correlation with the SEM micrograph of the worn-out surface of composites. Performance optimization of composites is done by using VIKOR method.     

Hybrid filler composition optimization for tensile strength of jute fibre-reinforced polymer composite

In present research work, pultrusion process is used to develop jute fibre-reinforced polyester (GFRP) composite and experiments have been performed on an indigenously developed pultrusion experimental setup. The developed composite consists of natural jute fibre as reinforcement and unsaturated polyester resin as matrix with hybrid filler containing bagasse fibre, carbon black and calcium carbonate (CaCO₃). The effect of weight content of bagasse fibre, carbon black and calcium carbonate on tensile strength of pultruded GFRP composite is evaluated and the optimum hybrid filler composition for maximizing the tensile strength is determined. Different compositions of hybrid filler are prepared by mixing three fillers using Taguchi L₉ orthogonal array. Fifteen percent of hybrid filler of different composition by weight was mixed in the unsaturated polyester resin matrix. Taguchi L ₉ orthogonal array (OA) has been used to plan the experiments and ANOVA is used for analysing tensile strength. A regression model has also been proposed to evaluate the tensile strength of the composite within 7% error by varying the above fillers weight. A confirmation experiment was performed which gives 73.14 MPa tensile strength of pultruded jute fibre polymer composite at the optimum composition of hybrid filler.     

Imine-linked receptors decorated ZnO-based dye-sensitized solar cells

This study reports the synthesis, characterization and photophysical properties of imine-linked receptors decorated ZnO nanoparticles using wet precipitation method. Initially, polymer dye 3 was synthesized using condensation reaction between 2-furancarboxaldehyde 1 and polyethylenimine 2. The decoration of imine-linked receptors on ZnO nanoparticles (sample A) was characterized and investigated by X-ray diffraction, scanning electron microscope and dynamic light scattering spectroscopic studies. Further, polymer dye 3 was added to ruthenium chloride (RuCl₃) to form a polymer–ruthenium-based composite dye-capped ZnO nanoparticles (sample B). The optical properties of sample A were evaluated by fluorescence and UV–Vis spectroscopy. The samples A and B were further processed to dye-sensitized solar cells using wet precipitation method. The results of observations revealed that the addition of ruthenium–polymer dye molecules increased the light harvesting capacity of ZnO-based DSSCs. A maximum solar power to electricity conversion efficiency (η) of 3.83% was recorded for sample B-based DSSCs with ruthenium–metal complex dye as a good photosensitizer. The recorded photovoltaic efficiency of sample B-based DSSCs was enhanced by 1.36% compared to sample A-based DSSCs.

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Structure and properties of silver-doped calcium phosphate nanopowders

Stable and antimicrobial silver-doped calcium phosphate nanopowders were synthesized using sol–gel route by setting the atomic ratio of Ag/(Ag+Ca) at 3% and (Ca+ Ag)/P at 1.67. Prior to synthesis of nanopowders, influence of time of hydrolyzation on pH and density of precursors were comprehensively studied. Hydrolyzation time was found to have profound influence on pH of constituent precursors. Sufficient hydrolysis resulted in early maturation of sol. Scanning electron microscopy (SEM) showed the heterogeneous and agglomerated state of particles with average size of 3.9± 1.9 μm. Energy dispersive X-ray spectroscopy (EDX) presented uniform distribution of O, Ag, Ca and P elements in nanopowder. Fourier transform infrared spectroscopy (FTIR) confirmed the formation of apatitic structure, whereas X-ray diffraction (XRD) revealed the multiphase constitution of nanopowders primarily composed of β-TCP, Ag and other hybrid phases. Crystallite size and lattice parameters of β-TCP and Ag phases were increased with the rise in calcination temperature. Thermogravimetric analysis (TGA) showed three regions of weight change and indicated the high thermal stability of nanopowders. Disk diffusion method was used to test the antimicrobial resistance of nanopowders against Escherichia coli and Staphylococcus aureus bacterial strains. All nanopowders exhibited antimicrobial resistance against both E. coli and S. aureus bacteria.