Improved quality a-SiC:H films prepared by photo chemical vapour decomposition of silane and acetylene

Hydrogenated amorphous and microcrystalline silicon carbon alloy films have been grown by photo-CVD using C₂H₂ as a source gas of carbon. The hydrogenated amorphous silicon carbon (a-SiC:H) film with a band gap of ~2.0 eV prepared at a very low hydrogen (LD) concentration exhibits better photo-electronic properties compared to that at high hydrogen dilution (HD) having a similar optical gap. Notwithstanding a high deposition rate, the high photosensitivity ( 10⁶), the low density of the defect states ( 6 × 10¹⁶cm⁻³) and the Urbach energy parameter (72 meV) for the a-SiC:H film prepared at low hydrogen dilution and pressure are impressive. On the other hand, low pressure along with high hydrogen dilution have been found to be conducive to microcrystalline silicon carbon alloy (μc-Si:H) formation. Interestingly, crystallites are of silicon while carbon remains in the amorphous and grain boundary regions.     

Thermoelectric properties of the ceramic system Pb2−x La x Li0·5 Nb1·5 O6+δ

The Seebeck voltage of the ceramic solid solutions of the system Pb_2−x La _x Li_0·5 Nb_1·5 O_6+δ has been studied as a function of temperature and concentration of lanthanum. The thermoelectric power was strongly dependent on the temperature and doping amount of lanthanum.     

High yield one-step synthesis of carbon spheres produced by dissociating individual hydrocarbons at their autogenic pressure at low temperatures

Hydrocarbons containing 5–14 carbon atoms (pentane, cyclohexane, camphorquinone, xylene, mesitylene, camphene, decahydronaphthalene, diphenylmethane, and anthracene) are individually dissociated under their autogenic pressure developed at 700 °C to produce pure carbon moieties from the respective hydrocarbon precursor. From all of the hydrocarbons, more than 99% pure carbon is obtained in spherical, filament- or egg-like microstructures. One of the key peculiarities in the thermal dissociation of various hydrocarbons, followed by solidification under autogenic pressure, is the formation of products in micrometer dimensions. It is in contrast to previous work with organometallic precursors, which yield nanometric products via a similar method. These results are compared with those obtained for the thermal dissociation of the same hydrocarbons under flow conditions. Specific systematic morphological, structural, and compositional analysis is presented for the products obtained from the thermal dissociation of diphenylmethane. A possible formation mechanism for the obtained products is provided.     

Hazardous organic compounds in urban municipal solid waste from a developing country

Fresh and partially decomposed municipal solid waste (MSW) collected from three places in Chennai city, viz., a residential collection point and two dumping grounds (Kodungaiyur and Perungudi) were screened for hazardous organic pollutants. Toxicity Characteristics Leaching Procedure (TCLP) using a Zero Headspace Extractor (ZHE) followed by further extraction by solvent separation using n-hexane containing 15% di-ethyl ether was performed and the organic extract obtained was qualitatively screened by GC-MS. 28 different types of higher alkanes and their derivatives, 7 types of C6-C8 fatty acids and their esters, 7 different phenolic compounds including alkylated phenols and degradation products and 5 phthalate compounds occurred in a majority of the analysed samples. 17 other organic compounds such as carboxylic acids, chloroform, phosphate, pharmaceutical chemicals etc. were also detected. Among these compounds, phenolics and phthalates are highly hazardous in nature and occurred in relatively higher concentrations. Hazardous compounds like p-cresol, di-butyl, mono butyl and di-ethyl pthalates were found in concentrations more than 200mg/kg in MSW.     

A comparative assessment of information value,frequency ratio and analytical hierarchy process models for landslide susceptibility mapping of a Himalayan watershed,India

This research work presents a comparative performance of geographic information system (GIS)-based statistical models for landslide susceptibility mapping (LSM) of the Himalayan watershed in India. A total of 190 landslide locations covering an area of 14.63 km² were identified in the watershed, using high-resolution linear imaging self-scanning (LISS IV) data. The causative factors used for LSM of the study area are slope, aspect, lithology, curvature, lineament density, land cover and drainage buffer. The spatial database has been prepared using remote sensing data along with ancillary data like geological maps. LSMs were prepared using information value (InV), frequency ratio (FR) and analytical hierarchy process (AHP) models. The validation results using the prediction rate curve technique show 89.61%, 87.12% and 88.26% area under curve values for FR, AHP and InV models, respectively. Therefore, the frequency ratio (FR) model could be used for LSM in other parts of this hilly terrain.

     

An Ellipsometric,XPS and Electrochemical Study of the Passivity of Zircaloy-2

The electrochemical behaviour of zircaloy-2 in the annealed and quenched conditions was determined in 0.5 M H₂SO₄ by the potentiodynamic polarization method Passive films on zircaloy-2 obtained in air as well as in sulphuric acid under open circuit conditions, were characterised and their refractive index and thickness determined. It was seen that the beta quenched alloy showed a nobler potential (-270 mV against standard Calomel electrode) compared with the annealed alloy (-320 mV). It also showed a passive current density about one order less than the annealed material. Ellipsometry showed that the films formed on the quenched alloy were thinner than those on the annealed alloy. After exposure to 0.5 M H₂SO₄ zircaloy developed films which were thicker with power refractive index than both the heat treated conditions. XPS analysis of the films has confirmed incorporation of sulphate into the film which probably leads to a defective and hence a thicker film in acid.     

Characterization of reactive graphene oxide synthesized from ball – milled graphite: its enhanced reinforcing effects on cement nanocomposites

In this study, commercial graphite powder (GP) of particle size 100 micron was subjected to high energy ball-milling (HEBM) to produce ball-milled graphite powder (BMGP) of particle size 780 nm. Both GP and BMGP were converted to respective graphene oxides (GOs) (labeled as GO1 and GO2) using Hummer’s method, which were then characterized using techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X- ray diffraction (XRD). GO1 and GO2 were then investigated for their effects on compressive strength of cement mortar matrix at different curing times of 7, 14, and 28 days. Effect of variation of concentration (ranging between 0.125 and 1.00 wt% of cement) of GO1 and GO2 on the strength of matrix was examined. Microstructures of GO1-cement mortar nanocomposite and GO2-cement mortar nanocomposite were studied after 28 days of curing using SEM. Obtained results show that addition of 1.00 wt% GO1 and GO2 showed best performance by increasing the strength to 63 and 78%, respectively, in comparison to the unreinforced control sample. Improved performance of GO2 was attributed to more number of reactive sites of GO nanosheets induced by ball-milling treatment of graphite precursor.     

Poly(alkylene oxide) copolymers for nucleic acid delivery

The advancement of gene-based therapeutics to the clinic is limited by the ability to deliver physiologically relevant doses of nucleic acids to target tissues safely and effectively. Over the last couple of decades, researchers have successfully employed polymer and lipid based nanoassemblies to deliver nucleic acids for the treatment of a variety of diseases. Results of phase I/II clinical studies to evaluate the efficacy and biosafety of these gene delivery vehicles have been encouraging, which has promoted the design of more efficient and biocompatible systems. Research has focused on designing carriers to achieve biocompatibility, stability in the circulatory system, biodistribution to target the disease site, and intracellular delivery, all of which enhance the resulting therapeutic effect. The family of poly(alkylene oxide) (PAO) polymers includes random, block, and branched structures, among which the ABA type triblocks copolymers of ethylene oxide (EO) and propylene oxide (PO) (commercially known as Pluronic) have received the greatest consideration. In this Account, we highlight examples of polycation-PAO conjugates, liposome-PAO formulations, and PAO micelles for nucleic acid delivery. Among the various polymer design considerations, which include molecular weight of polymer, molecular weight of blocks, and length of blocks, the overall hydrophobic-lipophilic balance (HLB) is a critical parameter in defining the behavior of the polymer conjugates for gene delivery. We discuss the effects of varying this parameter in the context of improving gene delivery processes, such as serum stability and association with cell membranes. Other innovative macromolecular modifications discussed in this category include our work to enhance the serum stability and efficiency of lipoplexes using PAO graft copolymers, the development of a PAO gel-based carrier for sustained and stimuli responsive delivery, and the development of biodegradable PAO-based amphiphilic block copolymers.     

Rapid extraction of Cu(II) heavy metal from industrial waste water by using silver nanoparticles anchored with novel Schiff base

A new Schiff base named N-(4-hydroxy-3-methoxy benzylidine)-biphenyl-4-amine was synthesized from refluxing of equimolar quantity of vanillin and biphenyl-4-amine in alcoholic medium. Its composition, properties, and morphology were characterized by elemental analysis, FTIR (Fourier-transform infrared spectroscopy), UV–vis (ultraviolet visible spectroscopy), nuclear magnetic resonance spectroscopy, and mass spectral studies. Then, silver nanoparticles were synthesized by chemical reduction method and characterized by scanning electron microscope, UV–vis, FTIR, and mass spectra. The silver nanoparticles are then trapped with Schiff base by suitable method. The metal ion was analyzed by atomic absorption spectroscopy. Sugarcane bagasse (SCB) was used as solid phase for the removal of heavy metal from industrial waste water. Activation of solid phase was done with the base and acid, respectively. The Ag nano@Schiff base was adsorbed on the SCB. The effects of several parameters that affect the adsorption of Cu(II) metal ion including initial metal ion concentration, contact time, Schiff base weight, and pH were analyzed.