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Chandrakant Parlikar Md Zafir Alam Dipak K. Das 《Transactions of the Indian Institute of Metals》2014,67(2):203-208
The effect of prior oxidation, for various durations up to 2,000 h in air at 650 °C, on the room temperature tensile properties of uncoated and Al3Ti diffusion aluminide coated near α Ti alloy, Titan 29A, has been evaluated. The tensile properties of the uncoated alloy deteriorated with oxidation. Oxidation for just 100 h caused 11–13 % decrease in yield strength (YS) and ultimate tensile strength (UTS) of the alloy. The uncoated alloy exhibited brittle fracture within the elastic regime at significantly lower stress after oxidation for 2,000 h. On the other hand, the strength of the coated alloy remained unaffected even after 2,000 h of oxidation and the YS and UTS was similar to that of the un-oxidized alloy. The ductility of the coated alloy, however, decreased with the increase in oxidation duration. Such differences in the tensile behavior of the uncoated and coated alloy can be ascribed to the beneficial effect of the Al3Ti diffusion aluminide coating in preventing surface embrittlement in the alloy during oxidation. 相似文献
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D Massel 《Canadian Metallurgical Quarterly》1997,133(6):713-714
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Md Zafir Alam B. Srivathsa S. V. Kamat V. Jayaram D. K. Das 《Transactions of the Indian Institute of Metals》2011,64(1-2):57-61
The Brittle-to-ductile-transition-temperature (BDTT) of free-standing Pt-aluminide (PtAl) coating specimens, i.e. stand-alone coating specimens without any substrate, was determined by micro-tensile testing technique. The effect of Pt content, expressed in terms of the thickness of initial electro-deposited Pt layer, on the BDTT of the coating has been evaluated and an empirical correlation drawn. Increase in the electrodeposited Pt layer thickness from nil to 10 μm was found to cause an increase in the BDTT of the coating by about 100°C. 相似文献
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Bahareh Khezri Filip Novotný James Guo Sheng Moo Muhammad Zafir Mohamad Nasir Martin Pumera 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(27)
Self‐propelled autonomous nano/microswimmers are at the forefront of materials science. These swimmers are expected to operate in highly confined environments, such as between the grains of soil or in the capillaries of the human organism. To date, little attention is paid to the problem that in such a confined environment the fuel powering catalytic nano/microswimmers can be exhausted quickly and the space can be polluted with the product of the catalytic reaction. In addition, the motion of the nano/microswimmers may be influenced by the confinement. These issues are addressed here, showing the influence of the size of the capillary and length of the micromotor on the motion and the influence of the depletion of the fuel and excess of the exhaust products. Theoretical modeling is provided as well to bring further insight into the observations. This article shows challenges that these systems face and stimulates research to overcome them. 相似文献
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Sodium caseinate (NaCas)-stabilized oil-in-water emulsions were added to skim milk and the rennet-induced aggregation was observed in situ using light scattering and dynamic oscillatory rheology. The gelation of the recombined milk was greatly inhibited by the addition of the oil droplets, at volume fractions >0.025. The development of the turbidity parameter, 1/l*, and the apparent hydrodynamic radius during renneting were determined using diffusing wave spectroscopy. Although the recombined milk samples contained two scattering particles, namely, casein micelles and fat globules, the latter overwhelmingly contributed to the overall light-scattering signal. This made possible to follow the behaviour of NaCas-stabilized fat globules during the gelation process. The enzymatic reaction associated with the hydrolysis of micellar κ-casein was not significantly affected by the presence of the NaCas-stabilized fat globules. However, the emulsion droplets impeded the aggregation of rennet-altered casein micelles preventing the formation of a gel network. The inability of renneted casein micelles to develop a gel network can be attributed in part to an altered equilibrium between soluble and micellar calcium phosphate, caused by the association of soluble Ca2+ with casein molecules, but mostly can be attributed to the effect of non-adsorbed caseins on the surface of the casein micelles. 相似文献
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Md. Zafir Alam D. Chatterjee K. Muraleedharan T. K. Nandy S. V. Kamat V. Jayaram D. K. Das 《Metallurgical and Materials Transactions A》2011,42(6):1431-1434
The ductile-to-brittle transition temperature (DBTT) of a free-standing Pt-aluminide (PtAl) bondcoat was determined using
the microtensile testing method and the effect of strain rate variation, in the range 10−5 to 10−1 s−1, on the DBTT studied. The DBTT increased appreciably with the increase in strain rate. The activation energy determined for
brittle-to-ductile transition, suggested that such transition is most likely associated with vacancy diffusion. Climb of 〈100〉
dislocations observed in analysis of dislocation structure using a transmission electron microscope (TEM) supported the preceding
mechanism. 相似文献
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A finite element method (FEM)-based study has been carried out for the design of flat microtensile samples to evaluate tensile properties of Pt-aluminide (PtAl) bond coats. The critical dimensions of the sample have been determined using a two-dimensional elastic stress analysis. In the present testing scheme, the ratio of the dimensions of the holding length to the fillet radius of the sample was found important to achieve failure within the gage length. The effect of gage length and grip head length also has been examined. The simulation predictions have been experimentally verified by conducting microtensile test of an actual PtAl bond coat at room temperature. The sample design and testing scheme suggested in this study have also been found suitable for evaluation of tensile properties at high temperature. 相似文献