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71.
Multiwalled carbon nanotubes were irradiated with ultra-low energy (few eV) nitrogen and hydrogen ions using a microwave discharge. These ultra-low energy plasma-ions remain confined to the nanotube walls, transferring their maximum energy to the carbon atoms, and produce extraordinary structural changes to the carbon nanotube pillars as well as within the carbon nanotubes. Conical shaped emitters and nanotube structures with nano-defects are produced that exhibit remarkable field emission with ultra-low turn-on electric field (∼0.16 V/μm) and a >300-fold increase in the maximum emission current density compared to non-irradiated nanotubes. Doping of nitrogen is also identified due to such irradiation processes. 相似文献
72.
This paper presents a new method for incorporating imperfect FC (fault coverage) into a combinatorial model. Imperfect FC, the probability that a single malicious fault can thwart automatic recovery mechanisms, is important to accurate reliability assessment of fault-tolerant computer systems. Until recently, it was thought that the consideration of this probability necessitated a Markov model rather than the simpler (and usually faster) combinatorial model. SEA, the new approach, separates the modeling of FC failures into two terms that are multiplied to compute the system reliability. The first term, a simple product, represents the probability that no uncovered fault occurs. The second term comes from a combinatorial model which includes the covered faults that can lead to system failure. This second term can be computed from any common approach (e.g. fault tree, block diagram, digraph) which ignores the FC concept by slightly altering the component-failure probabilities. The result of this work is that reliability engineers can use their favorite software package (which ignores the FC concept) for computing reliability, and then adjust the input and output of that program slightly to produce a result which includes FC. This method applies to any system for which: the FC probabilities are constant and state-independent; the hazard rates are state-independent; and an FC failure leads to immediate system failure 相似文献
73.
M Misra A Guest M Tilley 《Surface Coatings International Part B: Coatings Transactions》1998,81(12):594-595
Summary By utilising the Michael addition reaction, a wide range of acrylate functional silane coupling agents have been developed.
These can be used to confer functionality on the surface of nanocomposite colloidal oxides, particularly silica which can
then be incorporated into acrylic UV-curable matrices. Coatings developed from these systems provide greatly enhanced abrasion
resistance, and can approach the performance of thermally-cured silicone hardcoats. The wide range of coupling agents by this
method allows considerable flexibility in the design of coatings suitable for different substrates and a wide range of applications.
Acknowledgements: M Sollberger, T Washer, J Blizzard and J Tonge, Dow Corning Corp. 相似文献
74.
75.
Adel A. Sharif Fuming Chu Amit Misra Terence E. Mitchell John J. Petrovic 《Journal of the American Ceramic Society》2000,83(9):2246-2250
The elastic properties of single-crystalline erbia (Er2 O3 ) at room temperature have been investigated using resonant ultrasound spectroscopy. The three independent stiffness constants of anisotropic Er2 O3 cubic type-C crystals have been measured. The values of the stiffness constants were c 11 = 256.4 GPa, c 12 = 146.8 GPa, and c 44 = 75.2 GPa. From the stiffness constants, the estimated values for dense polycrystalline erbia for Young's modulus, the shear modulus, the bulk modulus, and Poisson's ratio at room temperature were 179 GPa, 67 GPa, 183.3 GPa, and 0.337, respectively. The value of Young's modulus is a minimum along [001] and a maximum along [111]. The value of the shear modulus is independent of the direction in the (001) and (111) planes, whereas it decreases in (11¯0) from 75 GPa along [001] to 55 GPa along [110]. 相似文献
76.
N. Li J. Wang X. Zhang A. Misra 《JOM Journal of the Minerals, Metals and Materials Society》2011,63(9):62-66
Epitaxial thin films of nanotwinned face-centered cubic metals such as Cu possess an unprecedented combination of high hardness
and high electrical conductivity due to the unique structure of nanometer-spaced coherent twin boundaries. Recent studies
of in-situ nanoindentation in a transmission electron microscope have provided new insights on the deformation behavior of
nanotwins that are reviewed here. In particular, two unit processes are highlighted: first, stress-induced migration of Σ3
{112} incoherent twin boundary that leads to de-twinning of nanotwins; second, twinning dislocation can be multiplied at Σ3
{111} coherent twin boundary. 相似文献
77.
Of concern in the paper is the distribution of thermal stresses in the vicinity of a penny-shaped crack in a thick elastic
plate made of a non-isotropic material. The problem pertains to the situation where the crack is opened by a prescribed normal
pressure and a prescribed heat-flux or a prescribed temperature. 相似文献
78.
Dinesh Kumar Misra Sung Woo Sohn Won Tae Kim Do Hyang Kim 《Science and Technology of Advanced Materials》2008,9(4)
The plastic deformation of Ti45Zr16Be20Cu10Ni9 bulk metallic glass has been investigated by nanoindentation performed with loads ranging from 10 to 200 mN in a wide range of loading rates. The plastic flow in the alloy exhibited conspicuous serrations at low loading rates. The serrations, however, became less prominent as the rate of indentation increased. Atomic force microscopy showed a significant pile-up of materials around the indents, indicating that a highly localized plastic deformation occurred under nanoindentation. The possible mechanism governing the plastic deformation in bulk metallic glass specimens is tentatively discussed in terms of strain-induced free volume. 相似文献
79.
Alloy 617 (nickel based austenitic alloy) is a candidate structural material for next generation high temperature nuclear reactor. The secondary phases present in the Alloy 617 has been identified as TiN and M23C6 by optical microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). Surface potentials of these phases have been evaluated by Scanning Kelvin Probe Force Microscope (SKPFM). SKPFM investigation showed higher surface potential of the secondary phases than that of the austenite matrix. The surface potential of the TiN was nobler than that of M23C6 indicating that these precipitates could act as cathodic sites during oxidation reaction. Difference in the local chemistry of these phases results in variation of the chemical potentials, which in turn could lead to enhanced oxidation at localized areas in the vicinity of the secondary phase precipitates that act as cathodic sites. 相似文献
80.
L. Plantarum NCIM 2084 cells are homofermentative, essentially producing lactic acid as the main end product of glucose fermentation. Prolonged use through repeated batch fermentation with the cells of L. plantarum immobilized on chitosan treated polypropylene matrix showed a shift in the metabolic pathway from the homofermentative to heterofermentative, accompanied by morphological changes in immobilized cells from the normal rod shape to the coccoid shape. These changes appear to be related to a shift in the bacterial cell metabolism, resulting in a decrease in lactic acid yields. 相似文献