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21.
Investigations are made to get the experimental conditions for obtaining periodic crystallisation of magnesium hydroxide in agar-agar gel. A detailed study is made on the dependence of the velocity constant (K), the spacing coefficient \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {p = \frac{{x_{n + 1} }}{{x_n }}} \right)'$\end{document} the length of the continuous precipitate and the width of the rings on the concentrations of the inner and outer electrolytes. Using SHINOHARA 's revised coagulation theory, the flocculation value F is calculated. F = Γ + C30, where Γ is the characteristic concentration of the outer electrolyte for which the flocculation starts and C30 is the reduced concentration of the reaction product. The value of the concentration of the outer electrolyte for which the flocculation stops (γ) is calculated. The dependence of F on the concentrations of the reactants is also discussed. Observation of a coneshaped precipitation is also reported. 相似文献
22.
Growth and Characterisation of Pure and Nickel-doped Strontium Tartrate Tetrahydrate Single Crystals
F. Jesu Rethinam D. Arivu Oli S. Ramasamy P. Ramasamy 《Crystal Research and Technology》1993,28(6):861-865
Strontium tartrate tetrahydrate single crystals doped with nickel have been grown in silica gel. The grown crystals have been characterized by X-ray, atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), and etching technique. 相似文献
23.
P. Santhanaraghavan K. Sankaranarayanan J. Arokiaraj S. Anbukumar J. Kumar P. Ramasamy 《Crystal Research and Technology》1994,29(2):223-228
This paper discusses the growth of gallium arsenide single crystals using the LEC technique. The Semi-insulating gallium arsenide was studied. The defect investigations were made by DLTS and etching studies. The variation of deep level concentration along the wafer was estimated using DLTS. The fabrication and efficiency of the PEC Solar cells are also reported. 相似文献
24.
K. Balakrishnan B. Vengatesan N. Kanniah P. Ramasamy 《Crystal Research and Technology》1990,25(6):633-636
Single crystals of ternary chalcopyrite semiconductors such as CuInS2, CuInSe2, CuInTe2, and CuInSSe, a pseudo-ternary semiconductor, have been grown by Chemical Vapour Transport (CVT) technique using iodine as the transporting agent. Microstructural analysis was carried out with the help of Scanning Electron Microscope (SEM) and optical microscope for the grown single crystals. 相似文献
25.
A microprocessor-controlled Bridgman system was designed and fabricated for the growth of II-IV-V2 compounds and one of this group of compounds CdGeAs2 has been grown using a two-zone vertical Bridgman systein. The grown crystals have been characterized by X-ray and Hall effect. 相似文献
26.
S. Ramasamy D. J. Smith P. Thangadurai K. Ravichandran T. Prakash K. PAdmaprasad V. Sabarinathan 《Pramana》2005,65(5):881-891
The ultra high vacuum chamber was developed in the Department of Nuclear Physics, University of Madras with the funding from
DST, India. This UHV chamber is used to prepare nanocrystalline materials by inert gas condensation technique (IGCT). Nanocrystalline
materials such as PbF2, Mn2+-doped PbF2, Sn-doped In2O3 (ITO), ZnO, Al2O3, Ag2O, CdO, CuO, ZnSe:ZnO etc., were prepared by this technique and characterized. Results of some of these materials will be
presented in this paper. In solid-state207Pb NMR on PbF2 a separate signal due to the presence of grain boundary has been observed. The structural phase transition pressure during
the phase transformation from the cubic phase to orthorhombic phase under high pressure shows an increase with the decrease
in grain size. Presence of electronic centres in nanocrystalline PbF2 is observed from Raman studies and the same has been confirmed by photoluminescence studies. Al2O3 was prepared and56Fe ions were implanted. After implantation segregation of56Fe ions was examined by SEM. The oxidation properties of ITO were studied by HRTEM. As against the expectation of oxide coating
on individual nanograins of In-Sn alloy, ITO nanograins grew into faceted nanograins on heat treatment in air and O2 atmosphere. The growth of ITO under O2 atmosphere showed pentagon symmetry. The PMN was initially prepared by solid-state reaction. Further, this PMN relaxor material
will be used to convert into nanocrystalline PMN by IGCT with sputtering and will be studied 相似文献
27.
The oxidation of aniline in glacial acetic acid with percarbonate, a dry carrier of hydrogen peroxide, is a second-order reaction conforming to the isokinetic relationship. The hitherto followed method of correlation of the reaction rates in terms of the structure-reactivity relationships is unsatisfactory and erroneous. But the reaction rates of molecular anilines, obtained for the first time, conform to the structure-reactivity relationships. 相似文献
28.
29.
Kandasamy Ramasamy Roland K. Robins Ganapathi R. Revankar 《Journal of heterocyclic chemistry》1987,24(3):863-868
A stereospecific high-yield glycosylation of preformed fully aromatic pyrroles has been accomplished for the first time. Reaction of the sodium salt of pyrrole-2-carbonitrile ( 1a ) and pyrrole-2,4-dicarbonitrile ( 1b ) with 1-chloro-2-deoxy-3,5-di-O-p-toluoyl-α-D-erythro-pentofuranose ( 2 ) gave exclusively the corresponding blocked nucleosides with β-anomeric configuration 3a and 3b , which on deprotection gave 1-(2-deoxy-β-D-erythro-pentofuranosyl) derivatives of 1a ( 3c ) and 1b ( 3d ). Functional group transformation of 3c and 3d provided a number of 2-monosubstituted 4a-c and 2,4-disubstituted 4d-f derivatives of 1-(2-deoxy-β-D-erythro-pentofuranosyl)pyrrole. Similar glycosylation of the sodium salt of 1a and 1b with 1-chloro-2,3,5-tri-O-benzyl-α-D-arabinofuranose ( 5 ) and further functional group transformation of the intermediate blocked nucleosides 6a and 6b provided 1-β-D-arabinofuranosyl derivatives of pyrrole-2-carboxamide ( 7b ) and pyrrole-2,4-dicarboxamide ( 7d ). The synthetic utility of this glycosylation procedure for the preparation of 1-β-D-ribofuranosylpyrrole-2-carbonitrile ( 12 ) has also been demonstrated by reacting the sodium salt of 1a with 1-chloro-2,3-O-isopropylidene-5-O-(t-butyl)dimethylsilyl-α-D-ribofuranose ( 10 ) and subsequent deprotection of the blocked intermediate 11 . This study provided a convenient route to the preparation of aromatic pyrrole nucleosides. 相似文献
30.
P. Thangadurai S. Ramasamy R. Kesavamoorthy 《Journal of Physics and Chemistry of Solids》2005,66(10):1621-1627
Nanocrystalline tin oxide (SnO2) was prepared by chemical precipitation method with different grain sizes. The X-ray diffraction studies showed the structural stability of nanocrystalline SnO2 under high-pressure. Electrical and dielectric properties were studied on these samples using complex impedance spectroscopy under different hydrostatic pressures. Electrical resistivity and dielectric studies showed a transition in nanocrystalline SnO2 when it was subjected to high-pressure. The transition pressures obtained from both the resistivity and dielectric measurements agree with each other. The transition pressures were found to increase considerably with the decrease in grain size. Dielectric constant was found to decrease with the reduction of grain size. In order to find whether the transition with pressure is structure- related or not, Raman spectroscopy was done at normal temperature and pressure (NTP) and as a function of pressure at room temperature. Raman modes at NTP showed lines which correspond to tetragonal rutile structure of SnO2. In situ high-pressure Raman measurements were carried out up to 3.38 GPa. No structural change was found with pressure. 相似文献