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排序方式: 共有275条查询结果,搜索用时 10 毫秒
1.
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U V Varadaraju G V Subba Rao K D Chandrasekaran A Baradarajan K Krishnaiah Mukesh Agarwala V S Achutharaman P Venugopal K A Padmanabhan L S Vaidyanathan G Rangarajan 《Bulletin of Materials Science》1989,12(1):63-80
The oxygen-deficient phase of the highT
c superconductor, YBa2Cu3O7, was oxygen-enriched using the fluidization technique to give good superconducting properties. The normal method of oxygen
treatment at 900°C for 24 h and at 600°C for 24 h has been reduced to just one treatment at 600°C for 12 h by the fluidization
technique to achieve almost the same strength of superconducting signal for the YBa2Cu3O7 powder, which establishes the attractiveness of the latter route for the large-scale preparation of superconducting material.
The particle sizes were in the range 0–90, 90–180 and 180–420 μm. The fluidized particles were crystalline with orthorhombic
distortion.T
c
onset
, estimated using the a.c. magnetic susceptibility method, was 91·3 K. The volume fraction of superconducting material in
the product was 83·7–85·3%, one of the highest values reported so far for YBa2Cu3O7. 相似文献
3.
4.
K.K. Padmanabhan 《Tribology International》1992,25(5)
Metallic mating surfaces in structural joints offer a good source of frictional energy dissipation resulting in a damped dynamic structural response. This paper reports the results of experiments where the energy dissipation per cycle occurring at a preloaded flat metallic annular interface subjected to cyclic tangential forces is measured. The effects of certain pertinent joint variables on this frictional energy dissipation are investigated by the application of Response Surface Methodology. A central composite rotatable design was utilized for developing empirical expressions for energy loss. The methodology presented suggests a useful technique for tribological research. 相似文献
5.
M. Sharan Chandran K. Padmanabhan D. K. Dipin Raj Yashasvi Chebiyyam 《Journal of Adhesion Science and Technology》2020,34(5):511-530
AbstractInterfacial adhesion of composite materials plays an important role in their mechanical properties and performance. In the present investigation, analysis of the interfacial properties of self-reinforced polyamide composites by using microbond multiple fibre pull-out test is emphasised. Microbond specimens prepared through thermal processing are tested for their interfacial properties by multiple fibre bundle pull-out tests and compared with that of traditional single fibre pull-out test specimens. Multiple fibre pull-out addresses the volume fraction as well as eliminates the possibility of fibre breakage before matrix shear. Higher scatter in the data in the samples is addressed in the present studies. FTIR and Fractographic studies are carried out for deep understanding of the post pull-out interfacial adhesion. 相似文献
6.
T. Sampath Kumar ;S. Balasivanandha Prabu ;Geetha Manivasagam ;K.A. Padmanabhan 《北京科技大学学报(英文版)》2014,(8):796-805
Monolayer and bilayer coatings of TiAlN, AlCrN, and AlCrN/TiAlN were deposited onto tungsten carbide inserts using the plasma enhanced physical vapor deposition process. The microstructures of the coatings were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SEM micrographs revealed that the AlrN and AlCrN/TiAlN coatings were uniform and highly dense and contained only a limited number of microvoids. The TiAIN coating was non-uniform and highly porous and contained more micro droplets. The hardness and scratch resistance of the specimens were measured using a nanoindentation tester and scratch tester, respectively. Different phases formed in the coatings were analyzed by X-ray diffraction (XRD). The AlCrN/TiAlN coating exhibited a higher hardness (32.75 GPa), a higher Young's modulus (561.97 GPa), and superior scratch resistance (LcN = 46 N) compared to conventional coatings such as TiAlN, A1CrN, and TiN. 相似文献
7.
Using the method of drilling holes, the residual stress distributions were determined in two titanium alloys, IMI-685 and IMI-318, in the machined, polished, shot-peened and cyclically stressed (MPSC) as well as the heat-treated and quenched (HTQ) conditions. In IMI-318, the effect of shot-peening pressure on the residual stress distribution was also studied. Tensile cyclic stressing relaxed the shot-peen induced residual stresses in the longitudinal direction and the extent of relaxation depended on the degree of cyclic softening present in the material. In both alloys, in the post- heat-treated and quenched condition, the residual stresses were tensile in nature. In IMI-318, a decrease in the shot-peening pressure led to residual stresses of lower magnitudes. The peak residual stress was present closer to the surface when the shot-peening pressure was increased. 相似文献
8.
A detailed Monte Carlo investigation of the structural changes of the framework of sodium zirconium phosphate, [Zr2P3O12]−,—NASICON (acronym for Na-SuperIonic CONductor)—accommodating alkali ions of varying sizes (Li+, Na+, K+, Rb+ and Cs+) is carried out over a range of temperatures. Simulation results are critically compared with the structural models proposed
earlier and available experimental results. Anisotropic changes of the rhombohedral cell parameters—a contracts while c expands with the size of the alkali ion substituted—is observed in good agreement with previous experimental results. The
mechanism of anisotropic variation of lattice parameters involves dominantly, coupled rotations of the polyhedra as proposed
by Alamo and co-workers. It is, however, observed that the distortions of the PO4 tetrahedra and ZrO6 octahedra are significant, and accounts for nearly one-third of the total change in a and c—parameters as the size of the alkali ion increases. This suggests that ‘rigid’ polyhedral models, permitting only angular
distortions of the polyhedra, are of limited quantitative applicability in these solids. The same mechanism is found to be
responsible for the low/anisotropic thermal expansion of these solids. Evidence that the polyhedral rotations are dynamic,
opposed to a static-frozen-in disorder, is provided. 相似文献
9.
Abd Elnaby Kabeel Yazan Taamneh Ravishankar Sathyamurthy Padmanabhan Naveen Kumar Athikesavan Muthu Manokar Thirugnanasambantham Arunkumar 《亚洲传热研究》2019,48(1):100-114
This study primarily focuses on comparative experimental analysis on standalone conventional solar still (CSS), inclined solar still (ISS), and integrated conventional and inclined solar still (CSS‐ISS) for different parameters that affect the freshwater yield. For enhancing the freshwater yield only a few studies are available on still‐still integration. The present novel study provides a greater improvement in improving the freshwater yield by integrating ISS with CSS. This experimental work mainly concentrates on the importance of water depth (d w) and mass flow rate of water ( m w) in the solar still. Water depth inside the conventional still varied from 0.02 to 0.06 m whereas, water is constantly flown with a mass flow rate of 8.33 kg/hour in an ISS with baffles. The experimental result shows that the accumulated freshwater yield from CSS‐ISS, ISS, and CSS were 6.2, 5.04, and 4.24 kg, respectively. CSS‐ISS and ISS produced 46.23% and 18.87% higher productivity than the CSS. From the experimental investigation, it is also identified that the water temperature is significantly improved by 20% using integration as compared with CSS without integration under the same water depth of d w = 0.02 m. The overall improvement in yield was higher in the case of CSS‐ISS. The deviations between experimental and theoretical values of yield from the conventional and modified solar still were in the range of ±7%. 相似文献
10.
Phenolic‐epoxy matrix curable by click chemistry—synthesis,curing, and syntactic foam composite properties 下载免费PDF全文
Alkyne functional phenolic resin was cured by azide functional epoxy resins making use of alkyne‐azide click reaction. For this, propargylated novolac (PN) was reacted with bisphenol A bisazide (BABA) and azido hydroxy propyloxy novolac (AHPN) leading to triazole‐linked phenolic‐epoxy networks. The click cure reaction was initiated at 40–65°C in presence of Cu2I2. Glass transition temperature (Tg) of the cured networks varied from 70°C to 75°C in the case of BABA‐PN and 75°C to 80°C in the case of AHPN‐PN. DSC and rheological studies revealed a single stage curing pattern for both the systems. The cured BABA‐PN and AHPN‐PN blends showed mass loss above 300°C because of decomposition of the triazole rings and the novolac backbone. Silica fiber‐reinforced syntactic foam composites derived from these resins possessed comparable mechanical properties and superior impact resistance vis‐a‐vis their phenolic resin analogues. The mechanical properties could be tuned by regulating the reactant stoichiometry. These low temperature addition curable resins are suited for light weight polymer composite for related applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41254. 相似文献