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排序方式: 共有422条查询结果,搜索用时 15 毫秒
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The phase equilibrium relationships in the binary system BaO-CeO2 have been investigated by thermal analysis, metallographic and X-ray diffraction methods. The system is characterised by the existence of only one compound, namely, BaCeO3 which is found to melt incongruently at 1480±5°C with formation of solid CeO2 and a liquid. A eutectic is found to occur between BaO and BaCeO3 at 46±0.5 mol% CeO2 and its melting point was determined as 1440±5°C. A narrow solid solubility range of BaO in BaCeO3 exists but no solid solubility of BaCeO3 in either BaO or CeO2 was detected. 相似文献
54.
Interface effects in YBCO/(Y-Pr)BCO multilayers, and the dimensionality of high-Tc superconductivity
S. Guha M. Z. Cieplak S. Vadlamannati C. H. Nien P. Lindenfeld 《Journal of Superconductivity》1994,7(1):201-204
Measurements on YBCO/(Y-Pr)BCO trilayers show that the depression of the transition temperature in ultrathin YBCO is accompanied by a decrease in the conductance of the layers adjacent to the interfaces. The lowering of the conductance seems to be primarily the result of charge transfer across the interfaces, and perhaps to some extent also of defects. The intrinsic properties of YBCO seem to change little or not at all as the thickness decreases from bulk down to that of a single unit cell. 相似文献
55.
This study was carried out to understand and establish the changes in physicochemical parameters of sago starch after acetylation. Highly substituted starch acetate was prepared by reaction with native sago starch and acetic anhydride in organic solvent. Their formation was confirmed by the titrimetric analysis and FT‐IR. The presence of absorption band in FT‐IR at 1748 cm−1 confirmed the carbonyl group attachment. The thermal behavior of native and acetyl substituted sago starch was investigated using thermo gravimetric analysis (TGA) and DSC. The results reveal that highly substituted starch acetate was more thermally stable as compared to native form. The XRD patterns showed loss of crystalline nature and its transformation into amorphous form. The SEM study suggested that the smooth surfaces of starch granules were changed into fibrous form after acetylation. 相似文献
56.
The adsorption behavior of mercury on Aspergillus versicolor biomass (AVB) has been investigated in aqueous solution to understand the physicochemical process involved and to explore the potentiality of AVB in pollution control management. This biomass has been successfully used for reducing the mercury concentration level in the effluent of chloralkali and battery industries to a permissible limit. The results establish that 75.6 mg of mercury is adsorbed per gram of biomass. The adsorption process is found to be a function of pH of the solution, with the optimum range being pH 5.0-6.0. The process obeys the Langmuir-Freundlich isotherm model. Scanning electron microscopic analysis demonstrates a conspicuous surface morphology change of the mercury-adsorbed biomass. A nearly uniform distribution of metal ions on the mycelial surface excepting a few aggregation points is revealed by X-ray elemental mapping profiles. The results of zeta potential measurement, Fourier transform infrared (FTIR) spectroscopy, and blocking of the functional groups by chemical modification reflect the binding of mercury on the biomass occurs through electrostatic and complexation reactions. The accumulation of mercury on the cell wall associated with negligible diffusion and or transportation into cytoplasm finds support from the results of adsorption kinetics and transmission electron micrographs. Mercury adsorption on biomass also leads to elongation of cells and cytoplasmic aggregation of spheroplast/protoplasts, indicating that the cell wall acts as a permeation barrier against this toxic metal. 相似文献
57.
Madhava Naidu Madineni Sheema Faiza Ragu Sai Surekha Ramasamy Ravi Manisha Guha 《Food science and biotechnology》2012,21(3):747-752
Starch isolated from maranta (Maranta arundinacea) tuber and studied for its various physicochemical characteristics. The amylose content of the starch was 24.8%. SEM showed that the granules were small indented and spherical. Maranta starch granule size has a range of 2.92–6.42 μm, (mean of 4.84 μm), length/degree of 1.20, and roundness of 0.73. Maranta starch has a gelatinization temperature of 74.8°C, peak viscosity of 498 BU, and cold paste viscosity of 669 BU. It also possessed higher freeze-thaw stability. Dynamic rheological properties of maranta starch, measured using parallel plate geometry showed increased storage modulus (G’) values, while loss modulus (G″) values were decreased with increasing frequency values (0–100 Hz). The low gelatinization temperature and high freeze thaw stability of starch indicates its potential for application as a thickener in food industries. 相似文献
58.
Halder D Bhowmick S Biswas A Mandal U Nriagu J Mazumdar DN Chatterjee D Bhattacharya P 《Environmental science & technology》2012,46(7):4142-4148
This study assesses the arsenic (As) accumulation in different varieties of rice grain, that people in rural Bengal mostly prefer for daily consumption, to estimate the potential risk of dietary As exposure through rice intake. The rice samples have been classified according to their average length (L) and L to breadth (B) ratio into four categories, such as short-bold (SB), medium-slender (MS), long-slender (LS), and extra-long slender (ELS). The brown colored rice samples fall into the SB, MS, or LS categories; while all Indian Basmati (white colored) are classified as ELS. The study indicates that the average accumulation of As in rice grain increases with a decrease of grain size (ELS: 0.04; LS: 0.10; MS: 0.16; and SB: 0.33 mg kg(-1)), however people living in the rural villages mostly prefer brown colored SB type of rice because of its lower cost. For the participants consuming SB type of brown rice, the total daily intake of inorganic As (TDI-iAs) in 29% of the cases exceeds the previous WHO recommended provisional tolerable daily intake value (2.1 μg day(-1) kg(-1) BW), and in more than 90% of cases, the As content in the drinking water equivalent to the inorganic As intake from rice consumption (C(W,eqv)) exceeds the WHO drinking water guideline of 10 μg L(-1). This study further demonstrates that participants in age groups 18-30 and 51-65 yrs are the most vulnerable to the potential health threat of dietary As exposure compared to participants of age group 31-50 yrs, because of higher amounts of brown rice consumption patterns and lower BMI. 相似文献
59.
J. P. Guha 《Journal of the American Ceramic Society》1991,74(4):878-880
Ternary compounds in the system BaO—TiO2 —La2 O3 were prepared by the solid-state reaction technique at temperatures between 1300° and 1400°C using precursor oxides as the starting materials. In an alternative processing technique, BaTiO3 was reacted with appropriate proportions of prefabricated lanthanum titanates at 1350°C to obtain the compounds. Two compounds were identified in the TiO2 -rich region of the system. The X-ray powder diffraction pattern of a compound with a chemical composition BaLa2 Ti3 O10 (BaO·La2 O3 ·3TiO2 ) is indexed on the basis of an orthorhombic unit cell with a = 7.665 × 10−1 nm, b = 28.524 × 10−1 nm, and c = 3.876 × 10−1 nm. The other compound, which has a chemical composition Ba4 La8 Ti17 O50 (BaO·La2 O3 ·4.25TiO2 ) occurs in a narrow homogeneity range within the system. The X-ray powder diffraction pattern of the compound is indexed on the basis of an orthorhombic unit cell with a = 12.317 × 10−1 nm, b = 22.394 × 10−1 nm, and c = 3.881 × 10−1 nm. Both the compounds are compatible with BaTiO3 and form pseudobinary joins with BaTiO3 in the system BaO—TiO2 —La2 O3 . 相似文献
60.