Influence of reaction conditions on the formation of nanotubes/nanoparticles of polyaniline in the presence of 1‐amino‐2‐naphthol‐4‐sulfonic acid and applications as electrostatic charge dissipation material

BACKGROUND: Poly(1‐amino‐2‐naphthol‐4‐sulfonic acid) and its copolymers with aniline are a new class of conducting polymers which can acquire intrinsic protonic doping ability, leading to the formation of highly soluble self‐doped homopolymers and copolymers. Free ? OH and ? NH₂ groups in the polymer chain can combine with other functional groups that could be present in protective paints which can thus be successfully used as antistatic materials. RESULTS: This paper reports the formation of nanotubes of polyaniline on carrying out oxidative polymerization of aniline in the presence of 1‐amino‐2‐naphthol‐4‐sulfonic acid (ANSA) in p‐toluenesulfonic acid (PTSA) as an external dopant. The presence of ? SO₃H groups in the ANSA comonomer allows the copolymer to acquire intrinsic protonic doping ability. The polymerization mechanism was investigated by analysing the ¹H NMR, ¹³C NMR, Fourier transform infrared and X‐ray photoelectron spectra of the copolymers and homopolymers, which revealed the involvement of ? OH/? NH₂ in the reaction mechanism. Scanning and transmission electron microscopy showed how the reaction route and the presence of a dopant can affect the morphology and size of the polymers. Static decay time measurements were also carried out on conducting copolymer films prepared by blending of 1 wt% of copolymers of ANSA and aniline with low‐density polyethylene (LDPE) which showed a static decay time of 0.1 to 0.31 s on dissipating a charge from 5000 to 500 V. CONCLUSION: Copolymers of ANSA with aniline were synthesized in different reaction media, leading to the formation of nanotubes and nanoparticles of copolymer. Blends of 1 wt% of PTSA‐ and self‐doped copolymers of ANSA and aniline with LDPE can be formulated into films with effective antistatic properties. Copyright © 2009 Society of Chemical Industry     

Effect of nitrate ions on the corrosion of stellite in permanganate media

The dissolution behaviour of stellite #3 in two oxidizing agents of equivalent acidity namely, permanganic acid (HMnO₄) and a mixture of nitric acid and potassium permanganate (NP) was evaluated. The presence of nitrate in the permanganate formulation was found to reduce its efficiency for oxidizing stellite. Electrochemical polarization and impedance studies were carried out at 90 °C in NP and HMnO₄. The redox potential of both the oxidizing agents favoured transpassive dissolution of chromium from the alloy. In NP, only the chromium depleted inter-phase boundary was attacked while most of the chromium rich carbide phases were intact. In contrast, in HMnO₄, uniform corrosion of the surface was observed. The impedance response was found to change with duration of exposure. The nitrate ions in permanganate were found to promote the repassivation of the surface. HMnO₄ was found to be a better formulation for dissolving cobalt from the alloy as compared to NP.     

Development of pellets of nifedipine using HPMC K15 M and κ-carrageenan as mucoadhesive sustained delivery system and in vitro evaluation

Polymeric mucoadhesive pellets of nifedipine were designed using computer software and they were prepared by extrusion-spheronization using HPMC K15M and κ-carrageenan with microcrystalline cellulose. A randomized rotatable two factor central composite design was applied for assessment of influence of two independent variables such as concentration of κ-carrageenan and HPMC K15M on dependent variables. Pellets were characterized by FTIR, DSC, SEM, flow properties, particle size, abrasion resistance, sphericity, drug content, percent production yield, in vitro drug release, ex vivo mucoadhesion, stability studies and similarity factor. The optimized formulation was selected based on criteria of sphericity nearest to 1.0 with maximum cumulative drug release percentage. Formulation NF6 exhibited sufficient porous spheres, free flowing and smooth surface mucoadhesion of 91.34 % and drug content 98.22 ± 0.37 %. Kinetic modeling revealed that the formulation followed the Higuchi model and showed the Quassi-Fickian drug release mechanism. The similarity factor, F2 value, was found to be 74 ± 6 and there was no significant change in drug content and ex vivo mucoadhesion after 90 days at 40 ± 2 °C, and 75 ± 5 % RH clearly indicated the optimized batch NF6 was stable. Thus, it can be concluded that use of κ-carrageenan, microcrystalline cellulose and HPMC K15M at the 20:35:10 w/w ratio could provide an effective carrier for enhancement of sphericity and sustained release of matrix pellets.     

Application of fly ash as a catalyst for synthesis of carbon nanotube ribbons

The larger diameter-based carbon nanotube (CNT) ropes and ribbons are currently synthesized by catalytic decomposition of hydrocarbons with transition metal-based catalysts e.g., Co, Ni, Fe and Mo at 1100-1200 °C, using chemical vapour deposition (CVD) and electric arc methods. We produced CNT ribbons by fly ash (FA) catalyzed pyrolysis of a composite film of poly (vinyl alcohol) (PVA) with FA at 500 °C for 10 min under a nitrogen flow of 2 L/min. Different geometrical structures, e.g.; knotted and twisted, U- and spiral-shaped CNT ribbons were observed in the images of scanning and transmission electron microscopy. The widths of the CNT ribbons measured varied in the ranges 18-80 nm. X-ray photoelectron spectroscopy analysis showed five types of carbon binding peaks, C-C/C-H (∼77%), C-O-H (∼9%), -C-O-C (∼5%), CO (∼5%) and -O-CO (∼3%). The ratio of intensities of G and D bands, IG/ID was 1.61 analysed by Raman Spectroscopy. CNT ribbons grown on the surface of FA have potential for the fabrication of high-strength composite materials with polymer and metal.     

Exergy analysis of small DI diesel engine fueled with waste cooking oil biodiesel

ABSTRACT

This study investigates the merits of exergy analysis over energy analysis for small direct injection (DI) diesel engine using the blend of waste cooking oil biodiesel and petroleum diesel. Taguchi’s “L’ 16” orthogonal array has been used for the design of experiment. The engine tested at different engine speeds, load percentages, and blend ratios, using the waste cooking oil biodiesel. Basic performance parameters and fuel input exergy, exergetic efficiency (second law efficiency), exergy associated with heat transfer, exergy associated with the exhaust gas and destruction of exergy are calculated for each blend of waste cooking oil biodiesel and diesel. Results show that the optimum operating conditions for minimum brake-specific fuel consumption (BSFC) and exergy destruction are achieved when engine speed at 1900 rev/min, load percentage is 75%, and the engine is fueled with B40.     

Kinetics and mechanism of corrosion of laboratory hot briquetted iron

While considerable work has been reported in the literature on the corrosion behavior and products of direct reduced iron and sponge iron, very little has been published on hot briquetted iron (HBI). The present article reports the kinetics and mechanism of HBI corrosion. As corrosion is an electrochemical process, measurements using electrochemical techniques have been made and these are compared to data gained by measuring mass changes in the briquettes over time. Similar trends were seen in data from both techniques, and the corrosion extent predicted by electrochemical measurements in saline solution was very close to the mass gain result obtained. Kinetic analysis of the data from mass gain over time trials was conducted. The activation energy for corrosion at temperatures between 25 °C and 80 °C has been calculated. The values of activation energy obtained indicate that corrosion was predominantly controlled by diffusion of oxygen in the liquid state. The internal structure of the briquettes was observed by microscopy both before and after corrosion in distilled water.     

Temperature-Dependent Indentation Behavior of Transformation-Toughened Zirconia-Based Ceramics

Indentation behavior of Ce-TZP, Y-TZP, and Mg-PSZ between room temperature and 1300°C was investigated. Hardness decreased with increasing temperature for all three materials, but indentation cracking increased with increasing temperature. The opposing temperature dependences are discussed in terms of dislocation and transformation plasticity.