Preparation of polybutene‐1/multiwall carbon nanotube composite by oxidation and limonene radical grafting and its characterization

In this study, a novel preparation of a polybutene‐1 (PB) and multiwall carbon nanotube (MWNT) composite was achieved by a combination of PB autooxidation and a radical grafting reaction using an Nd₂O₃/dicumyl peroxide (DCP) radical initiator system with limonene. The autooxidation worked as an amplifier to produce more alkyl radical species in the grafting reaction, and the existence of the MWNTs and the limonene suppressed the side reaction. In addition, the existence of the limonene suppressed the oxidation of the MWNT surface. The composite obtained was assessed in comparison with a PB/MWNT composite and a composite of PB/MWNT modified by Nd₂O₃/DCP without limonene using some spectroscopic methods, optical and electron microscopes, a thermal analyzer and tensile testing. The novel preparation produced a well dispersed nanocomposite compared with the other preparations. The modified MWNT surface was tightly linked to the PB matrix, so that the tensile properties of the composite showed a dependence on MWNT content. Copyright © 2011 Society of Chemical Industry     

Strengthening of spot-welded lap joints by new hardened zone

This paper deals with strengthening of spot-welded lap joints by a new hardened zone. Based on the equation to predict the strength proposed by past researchers, the factors necessary for strengthening were extracted. And, based on these factors, the strengthening of spot-welded lap joints was examined. First of all, in order to increase the hardened zone, the vicinity of the nugget edge was heated with a laser. Next, tensile shear tests were conducted by using spot-welded lap joints, which were heated by laser at various distances from the nugget. Finally, the relationship between tensile shear strength and the distance from the nugget centre to the crack was clarified. As a result, by increasing the hardened zone, we found that the fracture position was far away from the nugget edge. And, we found that the tensile shear strength could be improved by 15%.     

Abrasion phenomena of the contact tip in consumable electrode arc welding

ABSTRACT

In GMA welding, presently, fluctuation of the tip of welding wire has been able to restrain precisely, and metal transfer also has been able to regulate periodically, that is stable arc-like TIG welding has been realized. Then at this stage, reduction of contact tip abrasion is the most important subject to maintain arc stability for a long time. In this investigation, many factors are evaluated with abrasion amount, and new material of contact tip is recommended. Results obtained are as follows. Using uncoated welding wire increases contact tip abrasion rapidly as to Cu-coated welding wire. On the contrary, other welding conditions concerning contact point have almost no influence. Under the same current, the abrasion of contact tip is reduced accordingly as welding wire feeding rate becomes higher. Therefore, the abrasion is accelerated violently at the time of arc ignition because of heat accumulation at the contact point by wire stopping and high current which is needed for arc ignition. That is the welding wire which is induced to contact point with room temperature has considerable influence to cool the contact point. As a measure to reduce the abrasion at arc ignition, shortening the period of high current is effective. To cool the contact point positively, thermoelectromotive force was applied. Constantan (Cu-455Ni) has low thermoelectromotive force and high melting point than Fe. So, Cu–Ni alloy (Cu-43.3%Ni-0.92%Mn) was selected and examined as the contact tip material. The abrasion of Cu–Ni alloy contact tip becomes less than about two-tenth of the abrasion of Cu–Cr contact tip. As the conclusion, the best mixed measures which are effective to reduce the contact tip abrasion are using Cu-coated welding wire, wire retract type arc ignition and Cu–Ni alloy contact tip.     

Risk assessment for optimum low‐voltage distribution facilities constructed by using genetic algorithms

The influences of uncertainty of the load growth rate and interest rate on the total cost of low‐voltage distribution facilities was investigated. We assumed that the total cost was composed of the initial construction cost, the improvement cost, and the cost of power loss. We also assumed that the distribution facilities were operated for 30 years. Genetic algorithms were used to determine how to construct cost‐effective distribution facilities that did not compromise power quality. Two investment methods were compared: one in which the utility cut down the initial construction cost and improves the initial facilities along with the load growth, and one in which the utility bears the large initial cost without the improvement cost. It was found that the lower cost method depends on the load growth rate and the interest rate. It was also found that the influence of uncertainty in the load growth rate increases with an increase in the differential between the actual load growth rate and the expected one. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(2): 10–19, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20976     

Recovery of Tungsten Surface with Fiber-Form Nanostructure by Plasmas Exposures

One of the serious concerns for tungsten materials in fusion devices is the radiation defects caused by helium plasma irradiation since helium is a fusion product. The fiber-formed nanostructure is thought to have a possible weakness against the plasma heat flux on the plasma- facing component and also may destroy the reflectivity of optical mirrors. In this paper an inter- esting method for the recovery of such tungsten surfaces is shown. The recovery process depends on the grade and manufacturing process of tungsten materials.     

Synthesis and thermal characterization of novel poly(tetramethyl-1,3-silphenylenesiloxane) derivative bearing adamantyl moiety

A novel poly(tetramethyl-1,3-silphenylenesiloxane) derivative having adamantyl moiety, i.e., poly(tetramethyl-5-adamantyl-1,3-silphenylenesiloxane) (P1) was synthesized by solution polycondensation of a novel disilanol monomer, i.e., 1-[3,5-(dimethylhydroxysilyl)phenyl]adamantane (M1). M1 was prepared by the Grignard reaction using chlorodimethylsilane and 1-(3,5-dibromophenyl)adamantane, followed by the hydrolysis catalyzed by 5% palladium on charcoal. P1 exhibited the good solubility in common organic solvents, such as tetrahydrofuran (THF), chloroform, dichloromethane, benzene, and toluene at ambient temperature. P1 was also soluble in hot hexane, diethyl ether, and ethyl acetate. The glass transition temperature (T _g) and temperature at 5% weight loss (T _d5) of P1 were 85 and 517 °C, respectively, and much higher than those of poly(tetramethyl-1,3-silphenylenesiloxane), indicating that P1 is a new polysiloxane derivative with good solubility as well as good thermostability.     

Transitional ventilated filling box flow with a line heat source

A ventilated filling box flow in the transitional regime has been investigated over a wide range of Reynolds number, Re, and Prandtl number, Pr, to examine their effects, using direct numerical simulation. It has been shown that the parameter Re²/Pr is an important control parameter, representing a measure of the strength of the plume source. A mapping of parameter-dependent behaviours was obtained, and the instability mechanism has been qualitatively analysed. The balance of kinetic energy equation terms demonstrated that the contribution of the shear production towards the total production reduces and the buoyancy production dominance increases with increasing Pr. Turbulence intensity in the upper buoyant layer was found to become increasingly Pr dependent with reducing Re²/Pr. It has also been observed that with increasing Re²/Pr the Pr dependence of the location of the interface, that forms between lower ambient and upper buoyant fluids, is more predominantly determined by that of the ventilation rate, while with reducing Re²/Pr the Pr dependence of the location of the interface becomes affected also by the Pr dependent variation in the plume volume flux.     

Fused thiophene-split oligothiophenes with high ionization potentials for OTFTs

Fused thiophene-split oligothiophenes were synthesized by Suzuki coupling. The relationship between the structure of these fused thiophene-split oligothiophenes and DH-6T (α,ω-dihexylsexithiophene) and their performance in OTFTs was discussed. The realignment of HTTfTTTH (2,5-bis-(5′-hexyl-[2,2′]bithiophenyl-5-yl)-thieno[3,2-b] thiophene) molecule on the substrate after annealing was revealed by X-ray diffraction and atomic force microscopy. A similar but novel compound, TTfTTT (2,5-bis-[2,2′]bithiophenyl-5-yl-thieno[3,2-b]thiophene), was also prepared and evaluated as an organic transistor material. Air stabilities of these three compounds in OTFT devices were affected mainly by chemical properties, but also by the ionization potentials (I_p) of these materials. Among the three compounds, HTTfTTTH had a higher I_p because the thiophene sequence was split by fused thiophene and the best air stability, due to the end-capping of its active α-positions by hexyl substitution.     

Evolution model of δ³⁴S and δ¹⁸O in dissolved sulfate in volcanic fan aquifers from recharge to coastal zone and through the Jakarta urban area, Indonesia

The sources of sulfate in an aquifer system, and its formation/degradation via biogeochemical reactions, were investigated by determining sulfate isotope ratios (δ³⁴S_SO4 and δ¹⁸O_SO4) in dissolved sulfate in groundwater from the Jakarta Basin. The groundwater flow paths, water ages, and geochemical features are well known from previous studies, providing a framework for the groundwater chemical and isotopic data, which is supplemented with data for spring water, river water, hot spring water, seawater, detergents, and fertilizers within the basin. The sulfate isotope composition of groundwater samples varied widely from − 2.9‰ to + 33.4‰ for δ³⁴S_SO4 and + 4.9‰ to + 17.8‰ for δ¹⁸O_SO4 and changed systematically along its flow direction from the mountains north to the coastal area. The groundwater samples were classified into three groups showing (1) relatively low and narrow δ³⁴S_SO4 (+ 2.3‰ to + 7.6‰) with low and varied δ¹⁸O_SO4 (+ 4.9‰ to + 12.9‰) compositions, (2) high and varied δ³⁴S_SO4 (+ 10.2‰ to + 33.4‰) with high δ¹⁸O_SO4 (+ 12.4‰ to + 17.3‰) compositions, and (3) low δ³⁴S_SO4 (<+6.1‰) with high δ¹⁸O_SO4 (up to + 17.8‰) compositions. These three types of groundwater were observed in the terrestrial unconfined aquifer, the coastal unconfined and confined aquifers, and the terrestrial confined aquifer, respectively. A combination of field measurements, concentrations, and previously determined δ¹⁵N_NO3 data, showed that the observed isotopic heterogeneity was mainly the result of contributions of pollutants from domestic sewage in the rural area, mixing of seawater sulfate that had experienced previous bacterial sulfate reduction in the coastal area, and isotopic fractionation during the formation of sulfate through bacterial disproportionation of elemental sulfur. Our results clearly support the hypothesis that human impacts are important factors in understanding the sulfur cycle in present-day subsurface environments. A general model of sulfate isotopic evolution along with groundwater flow has rarely been proposed, due to the complicated hydrogeological research setting that causes varied isotope ratios, although its understanding has recently received great attention. This pioneer study on a simple volcanic fan aquifer system with a well-understood groundwater flow mechanism provides a useful model for future studies.