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排序方式: 共有129条查询结果,搜索用时 208 毫秒
1.
Animesh Chakravorty 《Israel journal of chemistry》1985,25(2):99-105
Model complexes of nickel(III) and nickel(IV) are furnished by hexadentate and tridentate oxime-imine-amine ligands derived by the condensation of biacetyl monoxime with amines. The synthesis, characterisation, structure, redox equilibria and reactivity of these complexes are critically reviewed. Correlations and generalisations pertaining to oxidation state stability, electroprotic equilibria and reaction mechanisms are examined. The possible significance of the present complexes in the context of the nickel-containing methanogenic enzymes is noted. 相似文献
2.
C R Chakravorty 《Bulletin of Materials Science》1994,17(6):733-745
Magnesium-lithium alloys are among the lowest density metallic materials. Addition of lithium, with a relative density of
0·53, in magnesium reduces the density of the alloy significantly. Furthermore, addition of nearly 11 wt.% lithium converts
hexagonal close packed structure of pure magnesium to a body centered cubic lattice, markedly improving formability of the
alloy. The development of these alloys, however, had been hampered due to the high reactivity of lithium and magnesium in
the molten state and also, due to poor creep resistance and instability of mechanical properties at room temperature. In an
attempt to indigenize these ultra light alloys for possible applications in Indian satellite programme, detailed research
work was initiated in DMRL. The difficulties associated with producing sound cast ingots have been overcome by controlling
melting and casting parameters of these alloys. Extensive work has been done on structure-property correlation of alloys with
varying lithium content and minor alloying additions. Based on these work, advanced magnesium-lithium alloys have been developed
with improved tensile properties, room temperature stability and creep resistance. Wrought products (plates/sheets) of magnesium-lithium
alloy have been supplied to ISAC, Bangalore and are being used in their INSAT-2 programme. This paper describes the systematic
studies carried out in the laboratory to indigenize these ultra light alloys. 相似文献
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Isothermal sections of the Ni-Cr-Al-W system have been investigated at 75 at % Ni and temperatures of 1523 and 1273 K, by means of phase compositional analysis, X-ray diffraction and microscopical examination. The alloys studied lay in the range 2.5 to 10 at % Cr, 12.5 to 20 at% Al, 2.5 to 6.25 at % W, The phases formed were, and the bcc solid solution based on tungsten (designated
2). The maximum extent of the region was found to be 3 at % each of chromium and tungsten. Preferential partitioning of tungsten to occurred. Study of an Ni-10Cr-12.5Al-2.5W alloy aged at 1273 and 1073 K, after quenching from 1573 K, showed that changes in and compositions and lattice parameters occur as a function of ageing time. 相似文献
7.
The constitution of the Ni-Al-Ru system has been investigated in the range 0 to 50 at% Al. Isothermal sections at 1523 and 1273 K have been determined using microstructural observations, electron probe microanalysis and X-ray diffraction. The phases present were: nickel-based solid solution (); (based on Ni3Al); solid solutions based on NiAl and RuAl, respectively (designated 1 and 2), and ruthenium-based solid solution (Ru). The maximum solubility of Ru in was 5 at%. 1, and 2 show extensive range of solubilities, namely up to 20at% Ru in 1 and up to 25 to 35 at% Ni in 2. Three-phase equilibrium between , 2 and (Ru) existed at 1523 and 1273 K. Also at 1523 K, three-phase equilibria existed between , and 1 and ,1 and 2, while at 1273 K, the equilibria were between , 1,2 and , , 2 indicating the occurrence of a reaction +1, +2 at a temperature between 1523 and 1273 K. Liquidus features have been deduced from data on as-solidified structures. Lattice parameter data and hardnesses are also reported. 相似文献
8.
An investigation is reported of the 75 at% nickel section of the Ni-Cr-Al-Ru system at 1523 and 1273 K. Constitutional data obtained by electron probe microanalysis, X-ray diffraction and microscopical examination are presented as partial isothermal sections. At 1523 K, the major part of the section consists of phase, while the aluminium-rich region contains a and+ region; the extent of the solid solution of chromium and ruthenium in totals ~ 4 at%. The ruthenium-rich corner of the section shows a two-phase region consisting of + ruthenium-rich solid solution. At 1273 K the,+ and + ruthenium regions increase in extent. The/ mismatch values in the equilibrated alloys studied lie in the range ~ –0.08 to –0.39%. Constitutional features of as-cast alloys are also reported. 相似文献
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An oxalate route for the production of BaTiO3 has been modified to incorporate Mn (upto 2%) as a dopant and the reaction sequence has been studied. The resulting Mn-doped
BaTiO3 exhibits a dielectric constant with an increasing insensitivity to temperature and applied a.c. field as the Mn content is
increased. These samples possess a high electrical resistivity even after treatment in hydrogen at 1100°C and are therefore
suitable as dielectric for multilayer capacitors with base metal electrodes. 相似文献