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排序方式: 共有1581条查询结果,搜索用时 62 毫秒
81.
K.M. Shaju V. Ganesh Kumar S. Rodrigues N. Munichandraiah A.K. Shukla 《Journal of Applied Electrochemistry》2000,30(3):347-357
Electrochemical studies on AB2 type Zr0.5Ti0.5V0.6Cr0.2Ni1.2 metal hydride electrodes with varying particle size suggests that the electrodes with alloy particles of about 60 m yield the optimum performance. The values for diffusion coefficient of hydrogen in the alloy particles > 25 m are found to be nearly invariant. Both a.c. impedance and linear polarization data on electrodes with varying particle size suggest that the charge-transfer resistance depends on state-of-charge of the electrodes. A comparison of scanning electron micrographs of fresh electrodes and subsequent to their prolonged charge-discharge cycling suggests that the metal hydride particles develop stress-induced cracks owing to their inherent expansion and contraction during the hydriding/dehydriding processes. 相似文献
82.
83.
Sathi Rajachandran Nair Ram Dayal Purohit Avesh Kumar Tyagi Pankaj Kumar Sinha Beant Prakash Sharma 《Journal of the American Ceramic Society》2008,91(1):88-91
Ultrafine La(Ca)CrO3 (LCC) powder was prepared through the glycine–nitrate gel combustion process. It was shown for the first time that the use of relatively inexpensive CrO3 as a starting material for chromium has potential for the bulk preparation of sinter-active LCC powder. As-prepared powder, when calcined at 700°C, resulted in LCC along with a small amount of CaCrO4 . The calcined powder was found to be composed of soft agglomerates with a particle size of ≈70–290 nm. The cold pressing and sintering of the calcined powder at 1200°C resulted in the mono-phasic La0.7 Ca0.3 CrO3 with density ≈98% of its theoretical value. This is the lowest sintering temperature ever reported for La0.7 Ca0.3 CrO3 . The conductivity of the sintered La0.7 Ca0.3 CrO3 at 1000°C was found to be ≈57 S/cm in air. The sintering and electrical behavior achieved for La0.7 Ca0.3 CrO3 may find application as an interconnect material for high-temperature solid oxide fuel cells if problems with chemical expansion and poor conductivity in fuel can be overcome. 相似文献
84.
When the water table rises in a granular soil mass, a large additional settlement of footing resting on such a soil mass is commonly expected. Laboratory model tests show that when the water table rises to the footing level, there can be an additional 400 to 500% of the settlements compared to when the soil is dry. To understand the mechanics of the additional settlements of footings resting on the granular soil masses caused by water table rise, an investigation into the change in the Young's modulus of soil was therefore made using oedometer tests. A relation between the saturated and the dry Young's moduli of the granular soils is presented for use in the elastic analysis of footing settlements. The findings of the investigation were then used to predict the additional settlements of a model footing when subjected to a water table rise, using elastic analysis. The theoretical predictions of the additional settlements are lower than the actual additional settlements observed in the settlement tests conducted in the laboratory using model tests. The model tests show that the additional settlements are larger in loose sands than in dense sands. 相似文献
85.
Carrying hydrogen in chemically bounded form as cycloalkanes and recovery of hydrogen via a subsequent dehydrogenation reaction is a potential option for hydrogen transport and delivery. We have earlier reported a novel method for transportation and delivery of hydrogen through liquid organic hydrides (LOH) such as cycloalkanes. The candidate cycloalkanes including cyclohexane, methylcyclohexane, decalin etc. contains 6 to 8 wt% hydrogen with volume basis capacity of hydrogen storage of 60–62 kg/m3. In view of several advantages of the system such as transportation by present infrastructure of lorries, no specific temperature pressure requirement and recyclable reactants/products, the LOH definitely pose for a potential technology for hydrogen delivery. A considerable development is reported in this field regarding various aspects of the catalytic dehydrogenation of the cycloalkanes for activity, selectivity and stability. We have earlier reported an account of development in chemical hydrides. This article reports a state-of-art in LOH as hydrogen carrier related to dehydrogenation catalysts, supports, reactors, kinetics, thermodynamic aspects, potential demand of technology in field, patent literature etc. 相似文献
86.
M. Canino C. Summonte M. Allegrezza Rimpy Shukla I.P. Jain M. Bellettato A. Desalvo F. Mancarella M. Sanmartin A. Terrasi P. Löper M. Schnabel S. Janz 《Materials Science and Engineering: B》2013,178(9):623-629
Silicon carbide and silicon rich carbide (SiC and SRC) thin films were prepared by PECVD and annealed at 1100 °C. Such a treatment, when applied to SiC/SRC multilayers, aimed at the formation of silicon nanocrystals, that have attracted considerable attention as tunable band-gap materials for photovoltaic applications. Optical and structural techniques (X-ray photoelectron spectroscopy, Reflectance and Transmittance, Fourier Transformed Infrared Spectroscopy) were used to evidence the formation, during the annealing treatment in nominally inert atmosphere, of a parasitic ternary SiOxCy surface compound, that consumed part of the originally deposited material and behaved as a preferential conductive path with respect to the nanocrystal layer in horizontal electrical conductivity measurements. The SiOxCy compound was HF-resistant, with composition dependent on the underlying matrix. It gave rise to a Si-O related vibration in FTIR analysis, that may be misinterpreted as due to silicon oxide. The compound, if neglected, can affect the structural and electrical characterization of the material.To overcome this problem, a procedure is analyzed, based on the deposition of a sacrificial capping a-Si:H layer that partially oxidizes, and is removed by tetra methyl ammonium hydroxide (TMAH) after annealing. XPS analysis revealed that the resulting surface is mainly made up of SiC regardless of the composition of the underlying SRC layer. Subsequent SF6:O2 dry etching results in a porous SiC-rich surface layer. The proposed method is effective in controlling the SRC surface configuration, and allows the performance of reliable optical and electrical characterization. 相似文献
87.
Yogesh S. Kashyap Ashish Agrawal P.S. Sarkar Mayank Shukla Tushar Roy Amar Sinha 《NDT & E International》2011,44(1):41-46
We have used the contrast transfer function based X-ray phase retrieval technique for phase retrieval studies on a two-component system. Pyro-carbon coated alumina matrix was chosen as a two-component system for these studies. Simulations as well as experimental results are presented. This paper shows that X-ray phase contrast along with phase retrieval can become an alternative tool for non-destructive characterization of these materials. We have also attempted to retrieve the spatial distribution of the projected thickness map of the two different elements. 相似文献
88.
B. Joshi S. S. Islam H. S. Mavi Vinita Kumari T. Islam A. K. Shukla Harsh 《Bulletin of Materials Science》2009,32(1):31-35
The laser induced etching of semi-insulating GaAs 〈100〉 is carried out to create porous structure under super- and sub-bandgap
photon illumination (h v). The etching mechanism is different for these separate illuminations where defect states play the key role in making distinction
between these two processes. Separate models are proposed for both the cases to explain the etching efficiency. It is observed
that under sub-bandgap photon illumination the etching process starts vigorously through the mediation of intermediate defect
states. The defect states initiate the pits formation and subsequently pore propagation occurs due to asymmetric electric
field in the pore. Formation of GaAs nanostructures is observed using scanning electron (SEM) and atomic force microscopy
(AFM). 相似文献
89.
Polymer electrolyte fuel cells (PEFCs) employ membrane electrolytes for proton transport during the cell reaction. The membrane
forms a key component of the PEFC and its performance is controlled by several physical parameters, viz. water up-take, ion-exchange
capacity, proton conductivity and humidity. The article presents an overview on Nafion membranes highlighting their merits
and demerits with efforts on modified-Nafion membranes.
Energy security refers to various security measures that a given nation, or the global community as a whole, must carryout
to maintain an adequate energy supply 相似文献
90.