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.     

Influence of particle size on protein extractability from soybean and okara

Nitrogen Solubility Index (NSI) of okara was 38 which was only about half of soybean (71). Maximum protein recovery of 97.0% and 93.4% was achieved with soybean and okara flour from their respective fine fractions (<75 μm) in a three-step-sequential extraction. Recovery of protein from unclassified primary ground flour of soy and okara was much lower compared to their corresponding fine fractions (particle size <75 μm). Secondary grinding of coarse fraction improved the overall protein recovery to an extent of 3.3% in okara and to a much larger extent of 6.8% in soybean. Results showed that a two-step sequential extraction with respective solid-to-solvent (w/v) ratios of 1:20 and 1:10 was suitable in terms of protein recovery. Protein recovery from soy granules and okara flakes improved by 30.6% and 6.9%, respectively with the introduction of primary and secondary grinding steps indicating the benefits of the proposed approach for practical applications.     

Log-convexity of rate region in 802.11e WLANs

In this paper we establish the log-convexity of the rate region in 802.11 WLANs. This generalises previous results for Aloha networks and has immediate implications for optimisation based approaches to the analysis and design of 802.11 wireless networks.     

28—SOME STUDIES ON THE REMOVAL OF SEED-COAT FRAGMENTS FROM COTTON TO CONTROL BLEMISHES ON RING-SPUN COTTON YARNS

In an earlier paper, tiny seed-coat fragments were shown to be a major source of blemishes on ring-spun medium-count yarns. In this paper, the capacity of the various cleaning machines to remove the seed-coat fragments is discussed. The problems arising out of the fragmentation of the large seed-coat particles into smaller particles during the cleaning treatment in machines are highlighted. The effects of machine features, such as density of the wire points, the speed of rotation, and the production rate, on the capacity of machines for seed-coat removal are discussed. The superiority of the cleaning action in the cylinder–flat section is established, and a plausible explanation for this is offered.     

Processing high-temperature refractory-metal silicide in-situ composites

High-temperature, refractory-metal, intermetallic, in-situ composites consist of high-strength, niobium-based silicides with a niobium-based metallic toughening phase. A variety of processing schemes have been used to generate these in-situ composites, including solidification and vapor phase processes. Secondary processing, such as forging and extrusion, has also been employed. These composites offer an excellent balance of high-and low-temperature mechanical properties with promising environmental resistance at temperatures above 1,100°C. Authors’ Note: All compositions are given in atom percent. For more information, contact B.P. Bewlay, General Electric Company, Corporate Research and Development, Schenectady, New York 12301; (518) 387-6121; fax (518) 387-5576.     

Influence of nitrogen addition on the microstructure and mechanical properties of duplex stainless steel weld metals

Duplex stainless steels find extensive applications in off‐shore, paper/pulp, refineries and petrochemical industries owing to their excellent combination of properties. Because of the thermal cycle experienced during the manufacturing/processing operations like welding, the weldment developed in this material is generally inferior in properties (mechanical and corrosion) when compared to the base material. The problem is more severe when the welding is done in the autogenous condition. The current work correlates the microstructure and property of UNS 31803 duplex stainless steel (material no. 1.4462) welded by autogenous GTA process with and without nitrogen in the shielding gas. It has been found that the nitrogen addition to the weld metal through the shielding gas mixture not only helps in achieving the proper phase balance but also improves the impact toughness of the resultant weld metal.     

Synthesis,characterization and properties of photoresponsive polymers comprising photocrosslinkable pendant chalcone moieties

New methacrylate monomers, namely 4‐methacryloyloxyphenyl‐4′‐fluorostyryl ketone and 4‐methacryloyloxyphenyl‐4′‐ethylstyryl ketone comprising a free radical polymerizable group and a photocrosslinkable group, were synthesized by reacting the respective hydroxychalcones with methacryloyl chloride in the presence of triethylamine. The monomers were polymerized in the presence of ethyl methyl ketone (EMK) at 70 °C using benzoyl peroxide as the initiator. The chemical structures were characterized using various spectroscopic techniques: ultraviolet, Fourier transform infrared, ¹H NMR and ¹³C NMR. The thermal stability of the polymers was studied using thermogravimetric analysis in nitrogen atmosphere. Differential scanning calorimetry was used to determine the glass transition temperature of the homopolymers. Photocrosslinking of the synthesized homopolymers was investigated in solution. The two homopolymers were crosslinked within 10–15 min. After crosslinking, the homopolymers were insoluble in the same solvent. Copyright © 2006 Society of Chemical Industry     

Effects of prestrain,rate of prestrain,and temperature on the stress-relaxation behavior of eutectic Sn-3.5Ag solder joints

Stress-relaxation studies on eutectic Sn-Ag solder (Sn-3.5Ag in wt.%) joints were carried out at various temperatures after imposing different amounts and rates of simple shear strain. Stress-relaxation parameters were evaluated by subjecting geometrically realistic solder joints with a nominal joint thickness of ∼100 μm and a 1 mm × 1 mm solder-joint area. The peak shear stress during preloading and residual shear stress resulting from stress relaxation were higher at the low-temperature extremes than those at high-temperature extremes. Also, those values increased with increasing simple shear strain and the rate of simple shear strain imposed prior to the stress-relaxation events. The relaxation stress is insensitive to simple shear strain at 150°C, but at lower temperatures, a faster rate of simple shear strain causes a higher relaxed-stress value. The resulting deformation structures observed from the solder-joint side surfaces were also strongly affected by these parameters. At high temperature, grain-boundary sliding effects were commonly observed. At low temperature, intense shear bands dominated, and no grain-boundary sliding effects were observed.     

FABRICATION OF METALLIC-GLASS RIBBON REINFORCED GLASS-CERAMIC MATRIX COMPOSITES

Metallic-glass ribbon reinforced glass-ceramic matrix composites were fabricated by conventional wet pressing and sintering techniques. Some of the important aspects of composite fabrication are discussed. Variables such as binder content, compaction pressure and specimen size, and their interdependency on one another are discussed. The optimum processing conditions required to obtain the best specimens are described. The sintering temperature was also found to be very important. The sintering temperature not only controls the softening characteristics of the parent glass, but also affects the specimen distortion. Proper selection of the sintering temperature can ensure minimum distortion in the specimens, while at the same time retain the ease and efficiency of fabrication.