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991.
992.
Joseph D. Rigney M.S. Preet M. Singh Ph.D. John J. Lewandowski Ph.D. 《JOM Journal of the Minerals, Metals and Materials Society》1992,44(8):36-41
A variety of materials have been toughened via the addition of a ductile phase. Brittle silicide intermetallics such as Nb5Si3 have been significantly toughened by niobium particles incorporated during in-situ processing techniques. In the work described here, toughness tests conducted on Nb5Si3 were monitored in a scanning electron microscope to view the process of toughening provided by the niobium particles. In particular, the behavior of the ductile phase was monitored and related to the toughness obtained. In an attempt to vary the behavior of the ductile phase, the composite materials were exposed to a variety of gaseous environments and subsequently tested in air. The resulting toughness, resistance-curve behavior, and in-situ results highlight the importance of the behavior of the ductile phase on subsequent properties. 相似文献
993.
A symmetrical perylene bisimide (PERI) with tert-butylphenoxy side groups at the 1,7-bay positions of the perylene and acetonaphthopyrazine dicarbonitrile terminal moieties was synthesized and characterized. The long-wave absorption maximum of PERI was at 455 nm with thin film absorption onset at 583 nm corresponding to an optical band gap of 2.13 eV. We have used blend of PERI as electron acceptor with a dithyenylbenzoselenadiazole-based small molecule (Se-SM) as electron donor for the fabrication of bulk heterojunction photovoltaic devices. The power conversion efficiency (PCE) of the ITO/PEDOT:PSS/Se-SM:PERI/Al device using as cast active layer, is about 1.28% which is improved up to 3.88% when a thermally annealed blend is used as active layer. The improvement in the PCE has been associated with the enhanced crystallinity of the blend upon thermal annealing and the increase in hole mobility that results in improved charge transport. 相似文献
994.
Badekai Ramachandra Bhat Dileep Ramakrishna John Kiran Anthony Fabian Rotermund 《Synthetic Metals》2010,160(13-14):1584-1586
The third-order optical nonlinearity of the composite film of coordination complex [CoLPPh3Cl] (L = N-(2-pyridyl)-N′-(salicylidene)hydrazine) and PMMA has been investigated by using Differential Optical Kerr Gate (DOKG) and Z-scan measurements. Large value of the third-order nonlinear optical susceptibility (χ(3)) of the order of 10?10 esu was measured and its nonlinear response time was found to be faster than or comparable to the laser pulse width (90 fs) used. The single beam Z-scan technique was used to investigate the nonlinear absorption property of the composite near 800 nm. The sample exhibit saturable absorption. The nonlinear absorption coefficient of sample is found to be ?32 cm/GW. 相似文献
995.
Chinmaya R. Dandekar Yung C. Shin John Barnes 《International Journal of Machine Tools and Manufacture》2010,50(2):174-182
Titanium alloy (Ti–6Al–4V) is one of the materials extensively used in the aerospace industry due to its excellent properties of high specific strength and corrosion resistance, but it also presents problems wherein it is an extremely difficult material to machine. The cost associated with titanium machining is also high due to lower cutting speeds (<60 m/min) and shorter tool life. Laser-assisted machining (LAM) and consequently hybrid machining is utilized to improve the tool life and the material removal rate. The effectiveness of the two processes is studied by varying the tool material and material removal temperature while measuring the cutting forces, specific cutting energy, surface roughness, microstructure and tool wear. Laser-assisted machining improved the machinability of titanium from low (60 m/min) to medium-high (107 m/min) cutting speeds; while hybrid machining improved the machinability from low to high (150–200 m/min) cutting speeds. The optimum material removal temperature was established as 250 °C. Two to three fold tool life improvement over conventional machining is achieved for hybrid machining up to cutting speeds of 200 m/min with a TiAlN coated carbide cutting tool. Tool wear predictions based on 3-D FEM simulation show good agreement with experimental tool wear measurements. Post-machining microstructure and microhardness profiles showed no change from pre-machining conditions. An economic analysis, based on estimated tooling and labor costs, shows that LAM and the hybrid machining process with a TiAlN coated tool can yield an overall cost savings of ~30% and ~40%, respectively. 相似文献
996.
David Petti John Maki John Hunn Pete Pappano Charles Barnes John Saurwein Scott Nagley Jim Kendall Richard Hobbins 《JOM Journal of the Minerals, Metals and Materials Society》2010,62(9):62-66
The high outlet temperatures and high thermal-energy conversion efficiency of modular high-temperature gas-cooled reactors (HTGRs) enable an efficient and cost-effective integration of the reactor system with non-electricity-generation applications, such as process heat and/or hydrogen production, for the many petrochemical and other industrial processes that require temperatures between 300°C and 900°C. The U.S. Department of Energy (DOE) has selected the HTGR concept for the Next Generation Nuclear Plant (NGNP) Project as a transformative application of nuclear energy that will demonstrate emissions-free nuclear-assisted electricity, process heat, and hydrogen production, thereby reducing greenhouse-gas emissions and enhancing energy security. The objective of the DOE Advanced Gas Reactor (AGR) Fuel Development and Qualification program is to qualify tristructural isotropic (TRISO)-coated particle fuel for use in HTGRs. An overview of the program and recent progress is presented. 相似文献
997.
Xiaochuan Lu John P. Lemmon Vincent Sprenkle Zhenguo Yang 《JOM Journal of the Minerals, Metals and Materials Society》2010,62(9):31-36
This paper provides a review of materials and designs for sodium-beta alumina battery technology and discusses the challenges ahead for further technology improvement. Sodium-beta alumina batteries have been extensively developed in recent years and encouraging progress in performance and cycle life has been achieved. The battery is composed of an anode, typically molten sodium, and a cathode that can be molten sulfur (Na-S battery) or a transition metal halide incorporated with a liquid phase secondary electrolyte (e.g., ZEBRA battery). In most cases the electrolyte is a dense solid β″-Al2O3 sodium ion-conducting membrane. The issues prohibiting widespread commercialization of sodium-beta alumina technology are related to the materials and methods of manufacturing that impact cost, safety, and performance characteristics. 相似文献
998.
John M. Tartaglia 《Journal of Materials Engineering and Performance》2010,19(4):572-584
Three martensite contents (approximately 35, 50, and 100%) were obtained in a SAE8822 steel by altering the quenching media
and section size. Another variation in martensite content (approximately 80 versus 97%) was achieved by quenching a SAE8622
steel in the same section size. The impact toughness and fatigue properties were determined after tempering to various levels
of monotonic strength. Toughness and strength-toughness combinations improved with increased as-quenched martensite contents
at all levels of as-tempered ultimate tensile strength (UTS). Even at higher levels of yield strength (YS), increased martensite
contents produced higher impact energies and lower fracture appearance transition temperatures. The cyclic YS was independent
of martensite content (at the same level of UTS), even though the monotonic YS increased with martensite content. When fatigue
test results were compared at a tensile strength of 1240 MPa (180 ksi), actual and predicted fatigue lives in the high cycle
regime increased with martensite content, but low cycle fatigue resistance was relatively unaffected. Fatigue strength and
UTS were directly related, and all the quenched and tempered steels exhibited cyclic softening. 相似文献
999.
利用两种等通道角挤压(ECAP)方法(普通单步ECAP和两步ECAP)制备细晶ZK60合金。采用金相显微镜、扫描电镜、透射电镜和X射线衍射仪对合金的组织和织构进行观察,通过拉伸试验研究不同ECAP方法对合金力学性能的影响。结果表明:与单步ECAP变形相比,两步ECAP变形,由于降低了变形温度,晶粒细化效果更好;经过(240℃,4道次)+(180℃,4道次)两步ECAP变形后,合金晶粒细化至约0.8μm;合金的力学性能与材料的织构密切相关,由于存在织构软化效应,与挤压态相比,经单步ECAP变形后合金的强度有所降低,而伸长率明显提高;但经两步ECAP变形后,由于细晶强化和亚结构强化的作用,合金的强度得到提高。 相似文献
1000.
Three-dimensional microstructural changes in the Ni–YSZ solid oxide fuel cell anode during operation
George J. Nelson Kyle N. Grew John R. Izzo Jeffrey J. Lombardo William M. Harris Antonin Faes Aïcha Hessler-Wyser Jan Van herle Steve Wang Yong S. Chu Anil V. Virkar Wilson K.S. Chiu 《Acta Materialia》2012,60(8):3491-3500
Microstructural evolution in solid oxide fuel cell (SOFC) cermet anodes has been investigated using X-ray nanotomography along with differential absorption imaging. SOFC anode supports composed of Ni and yttria-stabilized zirconia (YSZ) were subjected to extended operation and selected regions were imaged using a transmission X-ray microscope. X-ray nanotomography provides unique insight into microstructure changes of all three phases (Ni, YSZ, pore) in three spatial dimensions, and its relation to performance degradation. Statistically significant 3D microstructural changes were observed in the anode Ni phase over a range of operational times, including phase size growth and changes in connectivity, interfacial contact area and contiguous triple-phase boundary length. These observations support microstructural evolution correlated to SOFC performance. We find that Ni coarsening is driven by particle curvature as indicated by the dihedral angles between the Ni, YSZ and pore phases, and hypothesize that growth occurs primarily by means of diffusion and particle agglomeration constrained by a pinning mechanism related to the YSZ phase. The decrease in Ni phase size after extended periods of time may be the result of a second process connected to a mobility-induced decrease in the YSZ phase size or non-uniform curvature resulting in a net decrease in Ni phase size. 相似文献