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1.
S. B. Rane V. Deshapande T. Seth G. J. Phatak D. P. Amalnerkar B. K. Das 《Powder Metallurgy and Metal Ceramics》2004,43(9-10):437-442
Submicron silver powder was prepared from AgNO3 by a chemical reduction method in the presence of a mixture of caprylic acid and triethanolamine as a surfactant. Hydrazine hydrate (N2H4·H2O) is preferred as a reducing agent. A spherical silver powder with an average particle size of about 150 nm was achieved. Effort was also made to correlate the crystal structure and microstructure evolution of the prepared powders with the resultant thick film characteristics. 相似文献
2.
V
R Choudhary S
A
R Mulla M
Y Pandit S
T Chaudhari V
H Rane 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2000,75(9):828-834
The influence of the catalyst precursors (for Li2O and MgO) used in the preparation of Li‐doped MgO (Li/Mg = 0.1) on its surface properties (viz basicity, CO2 content and surface area) and activity/selectivity in the oxidative coupling of methane (OCM) process at 650–750 °C (CH4/O2 feed ratio = 3.0–8.0 and space velocity = 5140–20550 cm3 g−1 h−1) has been investigated. The surface and catalytic properties are found to be strongly affected by the precursor for Li2O (viz lithium nitrate, lithium ethanoate and lithium carbonate) and MgO (viz magnesium nitrate, magnesium hydroxide prepared by different methods, magnesium carbonate, magnesium oxide and magnesium ethanoate). Among the Li–MgO (Li/MgO = 0.1) catalysts, the Li–MgO catalyst prepared using lithium carbonate and magnesium hydroxide (prepared by the precipitation from magnesium sulfate by ammonia solution) and lithium ethanoate and magnesium acetate shows high surface area and basicity, respectively. The catalysts prepared using lithium ethanoate and magnesium ethanoate, and lithium nitrate and magnesium nitrate have very high and almost no CO2 contents, respectively. The catalysts prepared using lithium ethanoate or carbonate as precursor for Li2O, and magnesium carbonate or ethanoate, as precursor for MgO, showed a good and comparable performance in the OCM process. The performance of the other catalysts was inferior. No direct relationship between the basicity of Li‐doped MgO or surface area and its catalytic activity/selectivity in the OCM process was, however, observed. © 2000 Society of Chemical Industry 相似文献
3.
Chemically beneficiated high silica/alumina iron ore rejects (27–76% Fe2O3) were used to synthesize iron oxides of purity 96–98% with SiO2/Al2O3 ratio reduced to 0.03. The major impurities on chemical beneficiations were Al, Si, and Mn in the range 2–3%. A 99.73% purity
Fe2O3 was also prepared by solvent extraction method using methyl isobutyl ketone (MIBK) from the acid extracts of the ore rejects.
The magnesium ferrite, MgFe2O4, prepared from these synthetic iron oxides showed high resistivity of ∼ 108 ohm cm. All ferrites showed saturation magnetization, 4πMs, in the narrow range of 900–1200 Gauss and the Curie temperature,T,
cof all these fell within a small limit of 670 ± 30 K. All ferrites had low dielectric constants (ε′), 12–15, and low dielectric
loss, tan δ, which decreased with the increase in frequency indicating a normal dielectric dispersion found in ferrites. The
presence of insignificant amount of polarizable Fe2+ ions can be attributed to their high resistances and low dielectric constants. Impurities inherent in the samples had no
marked influence on the electrical properties of the ferrites prepared from the iron ore rejects, suggesting the possibility
of formation of ferrite of constant composition, MgFe2O4, of low magnetic and dielectric losses at lower temperatures of 1000°C by ceramic technique. 相似文献
4.
Gayatri Koyar Rane Udo Welzel Sai Ramudu Meka Eric Jan Mittemeijer 《Acta Materialia》2013,61(12):4524-4533
An anomalous dependence of the lattice parameter on the crystallite size of nanocrystalline ball-milled powders of metals was observed: lattice contraction followed by lattice expansion with decreasing crystallite size. These data were determined by application of detailed X-ray diffraction measurements. To this end the lattice parameters of the metals investigated – nickel, copper, iron and tungsten – were precisely determined by correcting for influences of stacking faults, in the face-centred cubic metals, as well as by correcting for instrument-related aberrations. The non-monotonic variation of the lattice constant was interpreted as the result of two competing mechanisms: interface-stress-induced contraction vs. expansion as a result of the stress field generated at the crystallite boundary due to the increased excess free volume in the crystallite boundary upon decreasing crystallite size. 相似文献
5.
K. S. Rane V. M. S. Verenkar R. M. Pednekar P. Y. Sawant 《Journal of Materials Science: Materials in Electronics》1999,10(2):121-132
Direct current electrical conductivity () measurements as a function of temperature have been carried out on -Fe2O3 prepared from precursors, iron (II) carboxylatohydrazinates, -FeOOH and hydrazinated -FeOOH. The conductivity variation obeys an Arrhenius equation, I = \oe- E / kT and the plots of log versus 1/T of the as prepared -Fe2O3, which are in general linear, during the very first heating up to 350°C and cooling to room temperature (RT) do not overlap. This indicates a hysteresis behavior of conductivity, thereby suggesting involvement of two different conductivity mechanisms. When the heat treated sample was equilibrated in a known partial pressure of moisture at 200°C and then conductivity measured from RT, the log plots during heating and cooling did not overlap and a hysteresis behavior similar to the as prepared -Fe2O3 is observed again in the conductivity. Water is considered to be crucial during the synthesis of -Fe2O3 through magnetite, Fe3O4. Protons, H+, are thought to be introduced in the spinel Fe3O4 making it defective and the oxidation product of this is -Fe2O3 which retains few protons in its spinel structure. From the structural similarity of such proton incorporated -Fe2O3 and lithium ferrite, LiFe5O8, (Fe3+)8 [Fe3+
12 Li1+
4]O32, a formula HFe5O8, (Fe3+)8 [Fe3+12H1+4]O32 is suggested. A hydrogen iron oxide of formula H1-xFe5+x3O8, where x 0.1 is probably formed as a maximum limit. Protons are removed during the very first heating of the as prepared sample in the present studies and hence the conductivity of proton free -Fe2O3 is different and therefore a hysteresis behavior is observed. Moisture equilibration reintroduces the protons. The lithiated samples in the present studies were found to substitute for protons in -Fe2O3 and no hysteresis behavior is observed in such samples even after moisture equilibration. 相似文献
6.
Dhananjay S. Rane Man M. Sharma 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,59(3):271-277
Some new strategies, such as the use of hydrotropes, surfactants, co-solvent, etc., were applied to the Hofmann reaction of fatty amides to obtain isocyanates, amines and carbamates. Additionally, some industrially important aromatic amines were synthesised. 相似文献
7.
Recirculating fluidized bed (RCFB) is a spouted bed with a draft tube at the center. This is used for a variety of operations such as incineration, coal and heavy crude oil gasification, grain drying, blending and mixing, etc. Solid circulation rate is an important parameter for any circulation system, and it describes the efficiency of operation. Mathematical models do not always predict the circulation rates accurately. Hence, there is a need to measure the circulation rates directly. Most of the methods (for direct measurement) reported are either costly, involving high expertise and sophisticated equipment, or time consuming. A butterfly valve arrangement can measure the solid circulation rate accurately and quickly. It is sturdy, and the cost/expertise involvement is the bare minimum. Solid circulation rates measured directly using the butterfly valve arrangement are compared with the solid circulation rates computed based on the particle velocity and the operating voidage in the downcomer bed. Solid circulation rates measured directly are in close comparison (mostly within a deviation of 10%) with the computed circulation rates. 相似文献
8.
Incineration, in spite of being a costly option, is widely used for the treatment and disposal of solid, liquid, and gaseous wastes. Use of fluidized beds paved the way for less polluting incinerators. Circulating fluidized bed systems can burn low-heat-content watery wastes without (or with minimum) auxiliary fuel. Equations of heat transfer and heat balance for different zones of a recirculating fluidized bed (RCFB) incineration system are presented along with a computational procedure to predict the performance details of the system. The method presented is applied to compute the performance of an RCFB incineration system burning distillery spent wash. Results show that RCFB incinerators are capable of burning a spent wash of solids content considerably lower than 60%. The incineration units in operation at present concentrate spent wash to about 60% solids content in external evaporators for autogenous burning. This costly and difficult operation can be minimized by the use of RCFB for incineration. 相似文献
9.
Vilas H Rane Sopan T Chaudhari Vasant R Choudhary 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2006,81(2):208-215
Rare earth (viz. La, Ce, Sm, Nd and Yb) promoted CaO catalysts have been investigated, comparing their surface properties (viz. surface area and basicity/base strength distribution) and catalytic activity/selectivity in the oxidative coupling of methane at different reaction conditions (temperatures, 650–800 °C, CH4/O2 ratios, 2.0–8.0 and space velocity, 51 360 cm3 g?1 h?1). The surface properties and catalytic activity/selectivity are strongly influenced by the rare earth promoter and its concentration. Apart from the Sm‐promoted CaO catalyst, both the total and strong basic sites (measured in terms of CO2 chemisorbed at 50° and 500 °C respectively) are decreased due to the promotion of CaO by rare earth metals (viz. La, Ce, Nd and Yb). The catalytic activity/selectivity is strongly influenced by the temperature, particularly below ?700 °C, whereas at higher temperature no further effect is seen. The La2O3? CaO, Nd2O3? CaO and Yb2O3? CaO catalysts showed high activity and selectivity, and also their results are comparable. Among the catalysts, Nd‐promoted CaO (with Nd/Ca = 0.05) showed the best performance (19.5% CH4 conversion with 70.8% C2+ selectivity) in the oxidative coupling of methane. A close relationship between the surface density of total and strong basic sites (measured in terms of CO2 chemisorbed at 50° and 500 °C respectively) and the C2+ selectivity and/or C2+ yield has been observed. Copyright © 2005 Society of Chemical Industry 相似文献
10.
The solid solution of pyrochlore oxides, Nd2ZrxTi2−xO7 (x = 0.2, 0.4, 0.6, 0.8 and 1.0) was synthesized by citrate gel method and the conventional ceramic method. The results indicate that the citrate gel method gives pyrochlore phase formation at a much lower temperature and better morphology of the product oxides as compared with the ceramic method. The dc conductivity study was carried out on some samples to understand the defects, if any, in the lattice of the solid solution Nd2TixZr2−xO7 (x = 0.2, 0.4, 0.6, 0.8 and 1.0) on substitution of Zr by Ti. The formation of defects in the lattice on substitution of Zr by Ti, was explained on the basis of XPS studies. 相似文献