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Large Grain Sizes (large + grain_size)
Selected AbstractsHigh-cycle fatigue properties in Ti,5% Al,2.5% Sn ELI alloy with large grain size at cryogenic temperaturesFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2004Y. ONO ABSTRACT High-cycle fatigue properties were investigated for Ti,5% Al,2.5% Sn ELI alloy with a mean , grain size of 80 ,m, which had been used for liquid hydrogen turbo-pumps of Japanese-built launch vehicles. At cryogenic temperatures, the fatigue strength in high-cycle region did not increase in proportion to increments of the ultimate tensile strength and the fatigue strengths at around 106 cycles were about 300 MPa independent of test temperatures. Fatigue cracks initiated in the specimen interior independent of the test temperatures of 4 K, 77 K and 293 K. At 4 K and 77 K, several crystallographic facet-like structures were formed at crack initiation sites. On the other hand, there were no facet-like structures that could be clearly identified at the crack initiation sites at 293 K. Low fatigue strengths in longer-life region at cryogenic temperatures could be attributable to the formation of large sub-surface crack initiation sites, where large facet-like structure are formed. [source] Mechanisms and Mechanics Governing the Indentation of Polycrystalline AluminaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2008Zhensong Wei A constitutive model for the inelastic deformation of polycrystalline alumina that accounts for both microcrack growth and plastic slip is implemented into a commercial finite element code. To establish its applicability, the code is used to simulate the deformation that occurs upon spherical and conical indentation. Inelastic zones and indentation pressures are predicted over a range of grain size and compared with measurements. The model replicates the mechanism transition from plasticity control at small grain sizes to micro-crack-control at large grain sizes. It also predicts an extensive micro-crack-dominated inelastic zone at large grain size that reduces the indentation pressures. [source] Preparation and Memory Performance of a Nanoaggregated Dispersed Red 1-Functionalized Poly (N -vinylcarbazole) Film via Solution-Phase Self-AssemblyADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Xiao-Dong Zhuang Abstract A nanoaggregated dispersed red 1-grafted poly(N -vinylcarbazole) (abbreviated PVDR) is self-assembled via ,,, stacking interactions of the carbazole groups in the polymer system after adding a solution of PVDR in N,N -dimethylformamide to dichloromethane. Upon self-assembly, the nanoaggregated PVDR film displays helical columnar stacks with large grain sizes, whereas a non-aggregated PVDR film exhibits an amorphous morphology with smaller grain size. A write-once read-many-times (WORM) memory device is shown whereby a pre-assembled solution of PVDR is spin-coated as the active layer and is sandwiched between an aluminum electrode and an indium-tin-oxide (ITO) electrode. This device shows very good memory performance, with an ON/OFF current ratio of more than 105 and a low misreading rate through the precise control of the ON and OFF states. The stability of the nanoaggregated PVDR device is much higher than that of the non-nanoaggregated PVDR device. This difference in device stability under constant voltage stress can be mainly attributed to the difference in the film crystallinity and surface morphology. No degradation in current density was observed for the ON- and OFF-states after more than one hundred million (108) continuous read cycles indicating that both states were insensitive to the read cycles. These results render the nanoaggregated PVDR polymer as promising components for high-performance polymer memory devices. [source] Mechanisms and Mechanics Governing the Indentation of Polycrystalline AluminaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2008Zhensong Wei A constitutive model for the inelastic deformation of polycrystalline alumina that accounts for both microcrack growth and plastic slip is implemented into a commercial finite element code. To establish its applicability, the code is used to simulate the deformation that occurs upon spherical and conical indentation. Inelastic zones and indentation pressures are predicted over a range of grain size and compared with measurements. The model replicates the mechanism transition from plasticity control at small grain sizes to micro-crack-control at large grain sizes. It also predicts an extensive micro-crack-dominated inelastic zone at large grain size that reduces the indentation pressures. [source] In situ micro-Raman and X-ray diffraction study of diamonds and petrology of the new ureilite UAE 001 from the United Arab EmiratesMETEORITICS & PLANETARY SCIENCE, Issue 7 2008Dominik C. HEZEL This is the first report of a meteorite in this country. The sample is heavily altered, of medium shock level, and has a total weight of 155 g. Bulk rock, olivine (Fo79.8,81.8) and pyroxene (En73.9,75.2, Fs15.5,16.9, Wo8.8,9.5) compositions are typical of ureilites. Olivine rims are reduced with Fo increasing up to Fo96.1,96.8. Metal in these rims is completely altered to Fehydroxide during terrestrial weathering. We studied diamond and graphite using micro-Raman and in situ synchrotron X-ray diffraction. The main diamond Raman band (LO = TO mode at ,1332 cm,1) is broadened when compared to well-ordered diamond single crystals. Full widths at half maximum (FWHM) values scatter around 7 cm,1. These values resemble FWHM values obtained from chemical vapor deposition (CVD) diamond. In situ XRD measurements show that diamonds have large grain sizes, up to >5 ,m. Some of the graphite measured is compressed graphite. We explore the possibilities of CVD versus impact shock origin of diamonds and conclude that a shock origin is much more plausible. The broadening of the Raman bands might be explained by prolonged shock pressure resulting in a transitional Raman signal between experimentally shock-produced and natural diamonds. [source] | ||||||||||