Showing papers by "Shivaji University published in 1998"
TL;DR: In this paper, the theoretical intensities of the polycrystalline CdχCu1-χFe2O4 (χ=0.2, 0.4, 1.8 and 1.0) ferrite system were calculated.
65 citations
TL;DR: In this paper, a single phase formation of polycrystalline Li-Cd ferrites with the general formula Li0.5 − x/2Cdx Fe2.
65 citations
TL;DR: In this article, thin films of Bi 2 Se 3 have been prepared from an aqueous acidic bath at room temperature using selenium dioxide as a source by a simple, inexpensive electrodeposition technique.
54 citations
TL;DR: The thermal variations of remanence ratio R and coercive field H c reveal that the compositions of Ni 0.7 Zn 0.3 Al x /Cr x Fe 2− x O 4 ferrites were prepared by the standard ceramic process using a computer controlled furnace as discussed by the authors.
53 citations
TL;DR: N-n-Octylaniline in xylene is used for the extractive separation of palladium(II) from hydrochloric acid medium and is applicable to the analysis of synthetic mixtures and alloys.
45 citations
TL;DR: In this paper, the molar ratio of TMOS:MeOH:H 2 O constant at 1:12:4 was used to obtain the hydrophobic aerogels, tris(hydroxymethyl)aminomethane (TAM) was added in the sol.
43 citations
TL;DR: N-n-octylaniline in xylene is used for the extractive separation of platinum(IV) from acidic media and is applicable to the analysis of synthetic mixtures and alloys, and is fast, accurate and precise.
41 citations
TL;DR: The experimental results on the influence of molar ratios of precursor, solvent and water on the physical properties of TEOS silica aerogels are reported in this article, where it has been found that the gelation time increases whereas the density decreases with an increase in A values.
40 citations
TL;DR: In this paper, a double sintering ceramic technique was used to extract polycrystalline ferrites, which were characterized by X-ray diffraction and showed a paramagnetic behavior.
39 citations
TL;DR: In this article, the CoFe2O4 ferrite thin films have been prepared by spray pyrolysis technique at different substrate temperatures (Ts) and the XRD patterns reveal a good (111) texture in the film prepared at Ts=325°C.
38 citations
TL;DR: In this article, cobalt oxide thin films were prepared by spray pyrolysis technique on to fluorine doped tin oxide (F.T.O.) coated glass substrates.
TL;DR: In this paper, the chemical deposition process is successfully used to obtain (Cd, Hg) S thin films with varying concentration of both Cd2+ and Hg2+ ions.
TL;DR: In this paper, the density of aqueous solutions of 18-crown-6 in the concentration range of 0.1 m to 4.5 m at 25 C was measured.
TL;DR: In this article, a theoretical model for trivalent substitution of polycrystalline ferrites with general formula Cd x Co 1− x Fe 2− y Cr y O 4 (x = 0, 0.25, 0., 0.15 and 0.30) was proposed.
TL;DR: In this paper, cholesterol-linked polysaccharides were prepared by reacting monocholesterylsuccinate (ChMS) with cellulose acetate [AC; degree of substitution (DS) 1.00, 1.80, and 2.33], and the polymers with a higher DS of ChMS showed a thermotropic liquid crystalline behavior.
Abstract: Cholesterol-linked polysaccharides were prepared by reacting monocholesterylsuccinate (ChMS) with cellulose acetate [AC; degree of substitution (DS) 1.00, 1.80, and 2.33], ethyl cellulose (EC; DS 2.46), starch, and hydroxyethyl starch (HES; molar substitution, 0.05–0.07). The degree of ChMS substitution ranged from 0.27 to 1.29. The polymers were characterized by IR, NMR, DSC, and hot-stage coupled polarizing microscopy. Polymers with a higher DS of ChMS showed a thermotropic liquid crystalline behavior. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 195–201, 1998
TL;DR: A modified diamine 2,5-bis [(4-aminophenyl)4-benzamide]-3,4-diphenyl thiophene (VI) with preformed amide linkages and pendant phenyl substituents was synthesized, characterized by IR, NMR, mass spectroscopy, and a physical constant as discussed by the authors.
Abstract: A modified new aromatic diamine 2,5-bis[(4-aminophenyl)4-benzamide]-3,4-diphenyl thiophene (VI) with preformed amide linkages and pendant phenyl substituents was synthesized, characterized by IR, NMR, mass spectroscopy, and a physical constant. Novel poly(amide-amide)s were synthesized from VI and aromatic diacid chlorides in N,N-dimethylacetamide by a solution polycondensation technique. The polymers were obtained in 98-100% yields and showed reduced viscosities in the range of 0.80-2.68 dL/g. They were readily soluble in aprotic polar solvents. These poly(amide-amide)s showed glass transition temperatures of 277-280°C as measured by DSC and showed no weight loss below 412°C in a nitrogen atmosphere. The polymers showed moisture regain in the range of 9.52-12.67%.
TL;DR: In this article, the effect of temperature on nucleation and growth of cadmium oxalate single crystals has been investigated and it has been found that the nucleation centres decrease drastically (to as low as two) as the temperature increases.
TL;DR: Thermogravimetry studies reveal that in all the samples, decomposition occurs in two stages, and the lattice parameters show a gradually decreasing trend with increasing Mg/Sup 2+/ content which is attributed to ionic radii of Cu/sup 2-/ and Mg-sup 2+/.
Abstract: We have synthesized Cu-Mg-Zn ferrites by using soft chemistry routes using oxalate precursors. Thermogravimetry (TG) studies have been carried out for selecting decomposition temperatures and weight loss measurements. These studies reveal that in all the samples, decomposition occurs in two stages. The lattice parameters show a gradually decreasing trend with increasing Mg/sup 2+/ content which is attributed to ionic radii of Cu/sup 2+/ and Mg/sup 2+/. The variation in saturation magnetization is attributed to cation migration of Mg/sup 2+/ ions to A-site. The density of samples increases gradually with increasing Mg/sup 2+/ content. This is attributed to the fact that Mg/sup 2+/ ions have less ionic radii. The sample with x=0.25 in Mg/sub x/Cu/sub (0.5-x)/Zn/sub 0.5/Fe/sub 2/O/sub 4/ has the highest permeability (/spl mu//sub i/=2181) which is sufficiently higher than that reported for ETKMG-5 ferrite (/spl mu//sub i/=550).
TL;DR: In this paper, a series of aerogel samples of different molar ratio combinations was optically examined in the UV-visible-NIR range by a spectrophotometer equipped with an integrating sphere.
Abstract: To optimize and produce silica aerogels with high direct transmittance and low diffusive values, systematic and detailed experiments were carried out on the effect of sol-gel processing parameters on optical properties of silica aerogels. A series of aerogel samples of different molar ratio combinations was optically examined in the UV–visible–NIR range by a spectrophotometer equipped with an integrating sphere. The overall transmittance of the aerogels in the visible range varied from 75 to 93% depending upon the molar ratio combination. The most relevant parameter being studied was the direct/hemispherical transmittance ratio (τ). The best value of τ obtained for an aerogel in the present study was about 93% with a molar ratio of 1 TMOS: 12 MeOH:4 H2O:3.5 × 10−3 NH4OH, respectively. Apart from visible transparencies, solar energetic transparencies of some silica aerogels were also measured and reported. These optical data, together with the porosity measurements, allowed us to improve the process of fabrication of low-diffusing aerogel material. The experimental results are discussed considering the percentage of porosity and heterogeneity generated in pore size distributions due to the variation of sol-gel processing parameters.
TL;DR: In this article, the operating conditions for the spectrophotometric determination of bismuth(III) with 1-(4′-bromophenyl)-4,4,6-trimethyl-(1H,4H)-pyrimidine-2-thiol (4′bromo PTPT) as a ligand by a liquid-liquid extraction technique are presented.
Abstract: The operating conditions for the spectrophotometric determination of bismuth(III) with 1-(4′-bromophenyl)-4,4,6-trimethyl-(1H,4H)-pyrimidine-2-thiol (4′bromo PTPT) as a ligand by a liquid-liquid extraction technique are presented. In acidic conditions bismuth(III) forms a yellow complex with the ligand which can be extracted in chloroform with an absorption maxima at 410 nm. The molar absorptivity is 1.5×104 l mole−1 cm−1 and Sandell's sensitivity is 14.3 ng cm−2. The difference in the absorbance between the chloroform blank and bismuth(III) sample increases linearly in the concentration range 2-14 ppm at 0.3 M hydrochloric acid. The proposed method is extremely sensitive, rapid, reproducible and has been satisfactorily applied to the determination of trace amounts of bismuth(III) in synthetic mixtures, alloys and pharmaceutical formulations and also provides binary separation of bismuth(III) from selenium, tellurium, lead, antimony, copper and gold. The overall process of extraction and determin...
TL;DR: In this article, a sol-to-gel method was used to obtain monolithic carbon carbogels, which were then impregnated by H 2 PtCl 6 to obtain a weight % of metal equal to 0.44.
Abstract: Electrical vehicles (Zero Emission Vehicles) represent a very elegant solution in order to decrease pollution in industrialised cities. To meet the pollution requirements, it is envisaged to replace gasoline engines by light fuell cells. They necessitate good electroconductive carbon monolithic electrodes. Monolithic organic resorcinol-formaldehyde aerogels (carbogels) can easily be made using the sol to gel method accompanied by the supercritical drying process using liquid CO 2 (critical temperature = 31 °C). Thereafter, these copolymer monolithic carbogels are pyrolysed in an atmosphere of N 2 at 1050 °C for 3 hours, in order to obtain monolithic carbon carbogels. The carbon carbogels are impregnated by H 2 PtCl 6 to obtain a weight % of metal equal to 0.44. In this work, the unique solvent used was acetone in each step, - the sol to gel reactions were catalysed by perchloric acid, from the copolymer synthesis up to the final impregnation of the carbon monoliths. The advantages of this new preparation method are compared to the aqueous former one.
TL;DR: In this paper, thin films of CdS have been electrodeposited from an acidic bath using CdSO4, Na2S2O3 and EDTA at pH 5 to 6 on the stainless steel and fluorine-tin oxide (FTO) coated glass substrates.
TL;DR: In this paper, thin films of CdCr2S4 are electrosynthesized from an aqueous acidic both consisting of 0.05 M CdSO4-0.5 M Na2S2O3-2.5M CrO3 onto stainless steel, indium-tin oxide coated glass and titanium substrate.
TL;DR: In this paper, coprecipitated oxalates of Cu 2+, Mg 2+, Zn 2+ and Fe 2+ were coprecimitated from the mixture of respective acetate solutions using 0.6 m oxalic acid solution to form a homogeneous solid solution Mg x Cu (0.5− x ) Zn 0.5
TL;DR: In this article, a spray pyrolysis technique using oxalic acid as a complexing agent was used for the deposition of Bi2S3 thin films, which were characterized for their structural, optical and electrical properties.
TL;DR: In this paper, a series of experiments using hydrolysis and condensation method with tetramethylorthosilicate (TMOS, Si(OCH 3 ) 4 ) as a precursor was conducted to synthesize transparent and monolithic crystalline PbS doped porous silica xerogels.
Abstract: Transparent and monolithic crystalline PbS doped porous silica xerogels are synthesised in a series of experiments using hydrolysis and condensation method with tetramethylorthosilicate (TMOS, Si(OCH 3 ) 4 ) as a precursor. The PbS crystallites are formed by passing H 2 S gas at high temperatures (50–350°C) over the Pb 2+ ions incorporated silica xerogels. The H 2 S pressure rate was varied from 0.25 to 2 bar/h by keeping the temperature of the xerogel at 250°C with each molar ratio of Pb/SiO 2 varying from 0.8 × 10 −4 to 4 × 10 −2 and found that the minimum pressure rates of 0.625–1 bar/h, respectively are required for the complete formation of the PbS crystallites throughout the xerogel network. The temperature of the xerogel samples was varied from 50°C to 350°C for each molar ratio of Pb/SiO 2 by keeping the H 2 S pressure rate constant at 1 bar/h. A minimum temperature of 250°C is required for the complete reaction between Pb 2+ ions and H 2 S gas. The colour of the xerogels changed with temperature to 250°C and did not change from 250°C to 350°C. Infrared spectra (IR) and X-ray diffraction (XRD) were used to determine some of the properties of the PbS crystallites in the xerogels for various temperatures and PbS/SiO 2 molar ratios. The observation of a shift in the threshold edge towards the smaller wavelengths in the ultraviolet–visible spectra, with the decrease of PbS/SiO 2 molar ratio from 2 × 10 −2 to 1 × 10 −4 indicated the formation of PbS crystallites leading to the quantum confinement phenomena at PbS/SiO 2 molar ratio −2 . The PbS crystallite structure was found to be cubic from X-ray diffraction of the samples. From the X-ray diffraction and tight binding calculations the PbS crystallite sizes were found to be in the range between 3.5 and 16 nm with the variation of PbS/SiO 2 molar ratio from 1 × 10 −4 to ⩽2 × 10 −2 , respectively. The vibration of PbS bonds was observed in the infrared spectra. The surface area, pore volume and pore sizes of the xerogels, measured from BET analysis and porosimetry, were found to decrease by doping with PbS crystallites.
TL;DR: In this article, the cerium(IV) oxidation of isobutanol, isoamyl alcohol isopropyl alcohol, and secondary butanol catalysed by chromium(III) was studied in sulphuric and perchloric acid mixture at 30 °C.
TL;DR: In this paper, the effect of concentration of the complexing agents on the properties of precipitated powders is studied, and it is observed that the crystallinity goes on decreasing as the concentration of complexing agent increases.
TL;DR: In this article, the porosity present in these ferrite compositions was attributed to porosity in these compositions and the saturation magnetization (Ms) versus temperature curves revealed the curve to be of type Q.
Abstract: The ferrite compositions of Cu(0.5-x)MgxZn0.5Fe2O4 were synthesized by thermal decomposition of the solid solution of oxalate complexes obtained by the coprecipitation technique using oxalate precursors. X-ray diffraction (XRD) patterns of all the samples showed a single spinel phase with no detectable impurity phases. The magnetization values were measured by the superconducting quantum interference device (SQUID) technique and the observed variation in magnetization values is attributed to porosity present in these ferrite compositions. The saturation magnetization (Ms) versus temperature curves revealed the curve to be of type Q. The variation of saturation magnetization (Ms) with temperature (T) for composition x=0.25 and x=0.40 exhibited a type Q-curve at a higher field of 1000 G. The monotonic increase in Hc with grain diameter for ferrite compositions under investigation leads to Hc∝D-1. Saturation magnetization (Ms) values of end ferrites sintered at 1000 °C are higher than those of oxalate complexes decomposed at 600 °C. © 1998 Kluwer Academic Publishers
TL;DR: A column chromatographic method has been developed for the separation of thorium from associated elements using poly-(dibenzo-18-crown-6) as mentioned in this paper, which is carried out from sodium nitrate medium.
Abstract: A simple column chromatographic method has been developed for the separation of thorium from associated elements using poly-(dibenzo-18-crown-6). The separations are carried out from sodium nitrate medium. The adsorption of thorium was quantitative from 0.1-0.5M sodium nitrate. Amongst the various eluents tested, 1.0-8.0M HCl, HBr, H2SO4 and 3.0-8.0M HClO4 were found to be particularly efficient for e elution of thorium. The capacity of poly-(dibenzo-18-crown-6) for thorium was found to be 1.034 mmole/g of crown polymer. Thorium was arated from number of elements in binary mixtures in which most of the elements showed a very high tolerance limit. It was possible to separate tium from a number of elements in multicomponent mixtures. The method was extended to the determination of thorium in monazite sand and ga: artles. The method is very simple, rapid, selective and has good reproducibility (approximately±2%).