Synthesis of bulk nanostructured aluminum alloy component through vacuum plasma spray technique

The benefits of large-size engineering components with nanocrystalline structure (providing improved strength) are yet to be realized due to processing difficulties and associated grain growth problems. In this work, a free-standing bulk nanocrystalline structure of hypereutectic aluminum alloy (Al–21wt.%Si) has been fabricated through the vacuum plasma spray (VPS) forming technique using micron-size powder feedstock. Optical microscopy, scanning electron microscopy and transmission electron microscopy have been used to investigate the evolution of multi-scale microstructure as the result of rapid solidification in VPS forming process. The characterization implies the presence of nanosized eutectic Al–Si grains (25–100 nm) with uniformly distributed ultrafine primary silicon particles of submicron size. The effect of microstructural evolution on mechanical properties has been studied by tensile testing and microhardness measurement. A considerable improvement in ultimate tensile strength and hardness of the sprayed deposit has been observed in comparison with conventionally cast hypereutectic Al–17wt.%Si alloys.     

Wear Behavior of Plasma-Sprayed Carbon Nanotube-Reinforced Aluminum Oxide Coating in Marine and High-Temperature Environments

Wear behavior of plasma-sprayed carbon nanotube (CNT)-reinforced aluminum oxide (Al₂O₃) composite coatings are investigated at room temperature (298 K), elevated temperature (873 K), and in sea water. Lowest wear volume loss was observed in the sea water as compared to dry sliding at 298 and 873 K. Relative improvement in the wear resistance of Al₂O₃-8 wt.% CNT coating compared to Al₂O₃ was 72% at 298 K, 76% at 873 K, and 66% in sea water. The improvement in the wear resistance of Al₂O₃-CNT coatings is attributed to (i) larger area coverage by protective film on the wear surface at room temperature and in sea water, (ii) higher fracture toughness of Al₂O₃-CNT coatings due to CNT bridging between splats, and (iii) anti-friction effect of sea water. The average coefficient of friction (COF) was the lowest (0.55) in sea water and the highest (0.83) at 873 K for Al₂O₃-8 wt.% CNT coating.     

Conduction behavior in ionic liquids assisted electrodeposited polypyrrole layers

The electropolymerization of pyrrole in ionic liquid media was carried out to produce an adherent, uniform, and durable polypyrrole (PPy) films with enhanced electrical properties. A threefold increase in the conductivity value can be attained with the selective choice of polymerizing media and ambient temperature dc conductivity value of 43, 15, and 13 S cm^?1 for films grown in 1‐ethyl‐3‐methylimidazolium bis(perfluoroethanesulfonyl)imide, 1‐ethyl‐3‐methylimidazolium triflate and in lithium triflate in acetonitrile respectively. The corresponding localization lengths were found to be 17, 33, and 48 nm indicate that carriers are strongly localized. At low temperature, all three types of PPy films show metallic type behavior. Though transition is observed above 200 K for all the three films, the charge transport mechanism remains unaltered at higher temperatures for the films grown in ionic liquids, while the film grown in lithium triflate in acetonitrile assumes a three‐dimensional variable range hopping conduction behavior. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Chromium removal by combining the magnetic properties of iron oxide with adsorption properties of carbon nanotubes

The adsorption features of multiwall carbon nanotubes (MWCNTs) with the magnetic properties of iron oxides have been combined in a composite to produce a magnetic adsorbent. Composites of MWCNT/nano-iron oxide were prepared, and were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and Fourier transform infrared spectroscopy (FTIR). XRD suggests that the magnetic phase formed is maghemite and/or magnetite. FESEM image shows nano-iron oxides attached to a network of MWCNTs. The adsorption capability of the composites was tested in batch and fixed bed modes. The composites have demonstrated a superior adsorption capability to that of activated carbon. The results also show that the adsorptions of Cr(III) on the composites is strongly dependent on contact time, agitation speed and pH, in the batch mode; and on flow rate and the bed thickness in the fixed bed mode. Along with the high surface area of the MWCNTs, the advantage of the magnetic composite is that it can be used as adsorbent for contaminants in water and can be subsequently controlled and removed from the medium by a simple magnetic process.     

Crosstalk analysis of simultaneously switching interconnects

This article focusses on the waveform analysis and crosstalk peak estimation at far-end of victim line for simultaneously switching inputs with resistive drivers. A low loss coupled transmission line-model of interconnect is used for analytical purpose. Noise peaks are estimated for the conditions when inputs to two coupled interconnects are switching in-phase and out-of-phase. Waveforms are analysed in general with homogeneous and non-homogeneous drivers for unipolar inputs. The driver is modelled as linear resistance. Comparison of the analytical results with simulation programme with integrated circuit emphasis (SPICE)-extracted results shows that the error involved is less than 2% and 5% for in-phase and out-of-phase switching, respectively. The comparisons of analytically obtained results with SPICE simulations show that the proposed model captures noise peaks, their timings and waveform shape for all switching conditions with an average error of less than 4%.     

Combustion characteristics and flame-kernel development of a laser ignited hydrogen–air mixture in a constant volume combustion chamber

Laser ignition of hydrogen–air mixture was carried out in a constant volume combustion chamber (CVCC) at 10 bar initial chamber filling pressure and 373 K chamber temperature. A Q-switched Nd:YAG laser at 1064 nm with a pulse duration of 6–9 ns was used for plasma generation and ignition of combustible hydrogen–air mixture. Pressure–time history of different hydrogen–air mixtures was measured in the CVCC and flammability limits of hydrogen–air mixture were measured. Flame kernel development was investigated for different air–fuel mixtures using Shawdowgraphy and flame propagation distances were calculated. Minimum ignition energy was measured for hydrogen–air mixtures of different air–fuel ratios and effect laser pulse energy on pressure–time history in the CVCC was experimentally measured. Upon increasing the laser pulse energy, time taken to attain peak cylinder pressure reduced which resulted in faster combustion in hydrogen–air mixtures however the peak cylinder pressure remained similar.     

Scratch-Induced Deformation Behavior of Cold-Sprayed Aluminum Amorphous/Nanocrystalline Coatings at Multiple Load Scales

Scratch-induced deformation behavior of cold-sprayed Al amorphous/nanocrystalline alloy coatings at multiple load scales is reported. Micro-scratch tests are carried out at several loads (1000-4000 μN) in constant and ramp loading conditions. Macro/high load scratch tests are carried out at 5 N load in ramp loading conditions. The deformation of as-sprayed and heat-treated coatings is analyzed in terms of scratch morphology, and friction. A lower coefficient of friction (COF) is obtained for as-sprayed coatings. Despite lower COF, as-sprayed coatings show a higher wear volume loss (4 times in micro-scratch and 1.4 times in macro-scratch) as compared to heat-treated coatings. Fluctuations were observed in COF along the scratch length of as-sprayed coatings in micro-scratch tests, which are correlated to the shear band formation. Higher scratch wear resistance is observed in the heat-treated coatings as compared to as-sprayed coatings due to denser microstructure with embedded intermetallic phases. Scratch-induced deformation behavior changed from the shear band dominated brittle mode in as-sprayed to plowing type in the heat-treated coatings.     

Chemometric study of graft copolymerization of guar‐g‐(acrylamide‐co‐diallyl dimethylammonium chloride)

Chemometrics was employed to study the effect of various reaction conditions on the graft copolymerization of acrylamide (AM) and diallyl dimethylammonium chloride (DADMAC) onto guar gum using the cerous sulfate and potassium persulfate complex initiation system. A two level full factorial design was used to study the effect of reaction parameters on percentage grafting (%G) and monomer conversion (%MC). Synthesized polymers were characterized using Fourier transform infrared spectroscopy (FTIR), ¹H‐NMR (nuclear magnetic resonance spectroscopy), and ¹³C‐NMR and also were analyzed for differences in intrinsic viscosity and charge incurred with changing reaction conditions. The concentration of AM was observed to have the greater effect on %grafting. Interaction effects between the reaction temperature and concentration of AM were also found to be important. Under the reaction condition studied, the highest grafting (%G) was obtained for polymer 1 (0.7M AM concentration, 60°C reaction temperature, and 1M acid concentration). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Essential Oils from Exotic Eucalyptus: Leaf Oils of Eucalyptus Youmonii,Eucalyptus Macrorhyncha,Eucalyptus Macarthuri,and Eucalyptus Cinera from Northwest Himalays (India)

Analyses of oils obtained by hydrodistillation of foliage of E. youmonii, E. macrorhyncha, and E. macarthuri from India revealed that the three oils are chemically alike, but for the quantitative differences of the main components. The eudesmol (α- and β-) content in E. macrorhyncha and E. macarthuri is rather similar (15.38% and 18.91% respectively), but much higher in E. youmonii (50.04%). The 1,8-cineol content in E. youmonii (30.70%) and E. macrorhyncha (29.83%) are alike while geranyl acetate (23.84%) content in E. macarthuri is highest amongst the three. E. cinerea oil contains cineol (64.65%), α-terpineol (11.56%) and limonene (12.51%) as the major components. On the whole E. macrorhyncha, E. macarthuri and E. cinerea oils are rich in monoterpenoids (71.16%, 71.90% and 94.55%) whereas that of E. youmonii is rich in sesquiterpenoids (53.37%).     

FT–Raman Investigation of Milled-Wood Lignins: Softwood,Hardwood, and Chemically Modified Black Spruce Lignins

Abstract

Raman spectroscopy is being increasingly applied to study wood and other lignin-containing biomass/biomaterials. Lignin's contribution to the Raman spectra of such materials needs to be understood in the context of various lignin structures, substructures, and functional groups so that lignin-specific features could be identified and the spectral information could be interpreted usefully. Additionally, to enhance the utility of Raman as a characterization tool, an understanding of chemical-treatment-induced changes to the lignin spectrum is important. In the present work, Raman spectra of four milled-wood lignins (MWLs)—black spruce, loblolly pine, aspen, and sweetgum—were compared, and using black spruce MWL, spectral changes brought about by alkaline hydrogen peroxide bleaching, hydrogenation, acetylation, and methylation reactions were analyzed. The band intensity changes depended upon the nature of the chemical treatments.