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991.
Sónia Simões Filomena Viana Volker Ventzke Mustafa Koçak A. Sofia Ramos M. Teresa Vieira Manuel F. Vieira 《Journal of Materials Science》2010,45(16):4351-4357
With the stimulus of temperature and pressure Ni and Al can quickly react and produce the intermetallic compound NiAl. This
reaction is highly exothermic and high temperatures can be attained in the surroundings. These characteristics make Ni/Al
multilayers very attractive to technological applications as localised heat sources. In this study, Ni/Al multilayer thin
films are used to promote bonding between TiAl intermetallic alloys. Ni and Al alternated nanolayers were deposited by d.c.
magnetron sputtering onto TiAl samples, with periods of 5, 14 and 30 nm. Joining experiments were performed at 900 °C for
60 or 30 min, in a vertical furnace with a vacuum level better than 10−2 Pa. Applied pressures of 5 MPa were tested. The microstructure of the cross-sections of the bond interface was analysed by
energy dispersive X-ray spectroscopy and characterised by scanning electron microscopy. The observation of the microstructure
for 14 and 30 nm period multilayers revealed sound bonding, while for 5 nm period porosity and cracks within the interlayer
thin film were observed. The interface is divided into three distinct zones: one with columnar grains, another with very small
equiaxed grains and the third with larger equiaxed grains. The joining process appears to depend on the diffusion of Ni and
Ti across the interface and is assisted by the nucleation of nanometric grains at the interface. The mechanical strength of
the joints was evaluated by shear tests. The bonds produced at 900 °C/5 MPa/60 min/14 nm exhibited the highest shear strength
of 314 MPa. 相似文献
992.
The article describes a convenient synthesis and Cr(VI) extraction efficiency of a novel p-tert-butylcalix[8]areneoctamide impregnated Amberlite (XAD-4) resin. Using p-tert-butylcalix[8]arene macrocyclic building block, two strategies have been developed; i.e., derivatization of p-tert-butylcalix[8]arene framework with sophisticated ionophoric groups having efficiency to extract oxoanions from aqueous media and, impregnation of p-tert-butylcalix[8]arene derivative onto the polymeric support. Liquid-liquid and solid-liquid extraction experiments have been performed to evaluate the Cr(VI) extraction efficiency of both p-tert-butylcalix[8]arene derivative and the impregnated resin. From the results, it has been deduced that solid-phase extraction method is more convenient and efficient than liquid-liquid extraction process. The impregnated XAD-4 resin has been found regenerable with better extracting efficiency as compared to the simple p-tert-butylcalix[8]areneoctamide ionophore. 相似文献
993.
Mustafa Balat Mehmet Balat Elif Krtay Havva Balat 《Energy Conversion and Management》2009,50(12):3158-3168
Gasification as a thermo-chemical process is defined and limited to combustion and pyrolysis. The gasification of biomass is a thermal treatment, which results in a high production of gaseous products and small quantities of char and ash. The solid phase usually presents a carbon content higher than 76%, which makes it possible to use it directly for industrial purposes. The gaseous products can be burned to generate heat or electricity, or they can potentially be used in the synthesis of liquid transportation fuels, H2, or chemicals. On the other hand, the liquid phase can be used as fuel in boilers, gas turbines or diesel engines, both for heat or electric power generation. However, the main purpose of biomass gasification is the production of low- or medium heating value gas which can be used as fuel gas in an internal combustion engine for power production. In addition to limiting applications and often compounding environmental problems, these technologies are an inefficient source of usable energy. 相似文献
994.
rfan Kurtba Fevzi Gülimen Abdullah Akbulut Diner Buran 《International Communications in Heat and Mass Transfer》2009,36(8):865-871
A novel conical injector type swirl generator (CITSG) is devised in this study. Performances of heat transfer and pressure drop in a pipe with the CITSG are experimentally examined for the CITSGs' angle (α) of 30°, 45° and 60° in Reynolds number (Re) range of 10,000–35,000. Moreover, circular holes with different numbers (N) and cross-section areas (Ah) are drilled on the CITSG. In this way, total areas (At = N · Ah) of the holes on the CITSG are equaled each other. Besides, flow directors having three different angles (β = 30°, 60° and 90°) to radial direction are attached to every one of the holes. This study is a typical example for decaying flow. All experiments were conduced with air accordingly; Prandtl number was approximately fixed at 0.71. The local Nusselt number (Nux), heat transfer enhancement ratio (NuER) and heat transfer performance ratio (NuPR) are calculated and discussed in this paper. It is found that the NuER decreases with increase in Reynolds number, the director angle (β), the director diameter (d), and with decrease in the CITSG angle (α). Likewise, variation of NuPR and NuER is also essentially similar for the same independent parameters. 相似文献
995.
Mustafa Anik Hakan Gasan Selda Topcu Işın Akay Nedret Aydinbeyli 《International Journal of Hydrogen Energy》2009
Mg1.5Al0.5−xZrxNi (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) type alloys were synthesized by mechanical alloying and their electrochemical hydrogen storage characteristics were investigated. X-ray diffraction studies showed that Zr facilitated the amorphization of Mg2Ni phase, while Al retarded the amorphization of this phase. The increase in the Zr content was observed to bring about significant improvement in the discharge capacities at all the ball milling durations. The stepwise replacement of Al with Zr, however, caused considerable reduction in the initial discharge capacities of the alloys. Despite the adverse effect of Al on the initial discharge capacity, it prevented the rapid degradation of Mg2Ni phase with the charge/discharge cycles. When the beneficial effects of Zr and Al were combined by designing Mg1.5Al0.5−xZrxNi type alloys, Mg1.5Al0.2Zr0.3Ni alloy was found to have the highest discharge capacity at almost all the charge/discharge cycle steps. Among the obtained capacity retaining rates, Mg1.5Al0.4Zr0.1Ni alloy had the best performance. This alloy has kept at least 50% of its initial discharge capacity at 20th cycle. The analysis by the electrochemical impedance spectroscopy revealed that the charge transfer resistances of Al-rich alloys were low at high depth of discharges. This observation was attributed to the formation of the porous unstable Mg(OH)2 layer due to the intercalation of Al2O3 layers, which have the high rate of solubility in strongly basic solutions, and thus the exposition of the underlying electrocatalytically active Ni sites. 相似文献
996.
The purpose of this study is to assess the political, economic and environmental impacts of producing hydrogen from biomass. Hydrogen is a promising renewable fuel for transportation and domestic applications. Hydrogen is a secondary form of energy that has to be manufactured like electricity. The promise of hydrogen as an energy carrier that can provide pollution-free, carbon-free power and fuels for buildings, industry, and transport makes it a potentially critical player in our energy future. Currently, most hydrogen is derived from non-renewable resources by steam reforming in which fossil fuels, primarily natural gas, but could in principle be generated from renewable resources such as biomass by gasification. Hydrogen production from fossil fuels is not renewable and produces at least the same amount of CO2 as the direct combustion of the fossil fuel. The production of hydrogen from biomass has several advantages compared to that of fossil fuels. The major problem in utilization of hydrogen gas as a fuel is its unavailability in nature and the need for inexpensive production methods. Hydrogen production using steam reforming methane is the most economical method among the current commercial processes. These processes use non-renewable energy sources to produce hydrogen and are not sustainable. It is believed that in the future biomass can become an important sustainable source of hydrogen. Several studies have shown that the cost of producing hydrogen from biomass is strongly dependent on the cost of the feedstock. Biomass, in particular, could be a low-cost option for some countries. Therefore, a cost-effective energy-production process could be achieved in which agricultural wastes and various other biomasses are recycled to produce hydrogen economically. Policy interest in moving towards a hydrogen-based economy is rising, largely because converting hydrogen into useable energy can be more efficient than fossil fuels and has the virtue of only producing water as the by-product of the process. Achieving large-scale changes to develop a sustained hydrogen economy requires a large amount of planning and cooperation at national and international alike levels. 相似文献
997.
Celal Kocatepe Aslan nan Oktay Arkan Recep Yumurtac Bedri Kekezolu Mustafa Baysal Altu Bozkurt Yener Akkaya 《Renewable & Sustainable Energy Reviews》2009,13(9):2553-2561
This paper presents measurement system and detailed analysis of power quality at the substation of two different wind farm sites which are of low and high power rate. Measurement system has been designed using a data acquisition board (DAQ), Labview software, Matlab programming and a portable PC. The system has been installed at medium voltage level at substation of both wind farms. The real measurement results at substations are compared to current regulations in Turkey. 相似文献
998.
Halogenated volatile organic compounds from the use of chlorine-bleach-containing household products
Odabasi M 《Environmental science & technology》2008,42(5):1445-1451
Sodium hypochlorite (NaOCl) and many organic chemicals contained in household cleaning products may react to generate halogenated volatile organic compounds (VOCs). Halogenated VOC emissions from eight different chlorine bleach containing household products (pure and diluted) were investigated by headspace experiments. Chloroform and carbon tetrachloride were the leading compounds along with several halogenated compounds in the headspace of chlorine bleach products. One of the most surprising results was the presence of carbon tetrachloride (a probable human carcinogen and a powerful greenhouse gas that was banned for household use by the U.S. Food and Drug Administration) in very high concentrations (up to 101 mg m(-3)). By mixing surfactants or soap with NaOCl, it was shown that the formation of carbon tetrachloride and several other halogenated VOCs is possible. In addition to quantitatively determined halogenated VOCs (n = 15), several nitrogen-containing (n = 4), chlorinated (n = 10), oxygenated compounds (n = 22), and hydrocarbons (n = 14) were identified in the headspace of bleach products. Among these, 1,1-dichlorobutane and 2-chloro-2-nitropropane were the most abundant chlorinated VOCs, whereas trichloronitromethane and hexachloroethane were the most frequently detected ones. Indoor air halogenated VOC concentrations resulting from the use of four selected household products were also measured before, during, and 30 min after bathroom, kitchen, and floor cleaning applications. Chloroform (2.9-24.6 microg m(-3)) and carbon tetrachloride (0.25-459 microg m(-3)) concentrations significantly increased during the use of bleach containing products. During/ before concentration ratios ranged between 8 and 52 (25 +/- 14, average +/- SD) for chloroform and 1-1170 (146 +/- 367, average +/- SD) for carbon tetrachloride, respectively. These results indicated that the bleach use can be important in terms of inhalation exposure to carbon tetrachloride, chloroform and several other halogenated VOCs. 相似文献
999.
1000.