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991.
M. Sikorska-Iwan R. Mrozek Z. Rzączyńska 《Journal of Thermal Analysis and Calorimetry》2000,60(1):139-144
The thermal decomposition reactions of manganese(II) complexes with L-proline and 4-hydroxy- L-proline were studied. The Mn(II) proline complex loses the water molecule at 40–95°C and then, heated above 250°C it decomposes
in several steps to manganese oxide. The most appropriate kinetic equations for dehydration process are the geometrical R2
or R3 ones. They give a value of activation energy, E of about 95 kJmol–1. The Mn(II) hydroxyproline complex loses the water molecules in two stages (70–110 and 110–230°C) and next it decomposes
to manganese oxide in several steps. The R3 or D3 (three-dimensional diffusion) models are the most appropriate for the first
stage of dehydration (E is about 155 kJ mol–1). The second step of dehydration is limited by D3 mechanism (E=52 kJ mol–1).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
992.
The separation of potassium and sodium ions from their mixture was performed by electrodialyzing a mixed solution of potassium
chloride and sodium chloride in the presence of 18-crown-6 using a commercial cation-exchange membrane. After 18-crown-6 had
been impregnated in the membrane, the mixed solution containing 18-crown-6 was electrodialyzed as the desalting-side solution.
The permeation of potassium ions through the membrane decreased remarkably and the electrical resistance of the membrane increased
during electrodialysis with increasing concentration of 18-crown-6 in the solution. Because potassium ions form a more stable
complex with 18-crown-6 than sodium ions and because the complex permeated through the membrane with difficulty, sodium ions
are thought to selectively permeate through the membrane. The current efficiency in electrodialysis was greater than 97.0%.
Received: 1 June 1999/Accepted in revised form: 13 August 1999 相似文献
993.
A. A. Gorman I. Hamblett T. A. King M. D. Rahn 《Journal of photochemistry and photobiology. A, Chemistry》2000,130(2-3):127-132
The triplet state of pyrromethene 567, a molecule with potential as a solid state laser dye, has been characterized in benzene by pulse radiolysis in terms of its absorption spectrum, lifetime, self-quenching, electronic excitation energy, triplet–triplet extinction coefficient and oxygen quenching rate constant. The use of laser flash photolysis has then allowed determination of the triplet quantum yield, efficiency of formation of singlet oxygen (1Δg), and the rate constant for reaction of the latter species with the ground state. The affects of oxygen on the fluorescence and triplet yields demonstrate that oxygen-induced intersystem crossing is important, the sum of these parameters being unity within experimental error. The mechanism of reaction of P-567 with 1Δg in benzene is predominantly physical in character with only a small (6%) contribution from chemical reaction. 相似文献
994.
The synthesis of filled skutterudite compounds (Ce or Y)_y(Fe)_x(Co)_(4x)(Sb)_(12), through a solidstate reaction using chloride of Ce or Y,high purity powder of Co, Fe, and Sb as starting materials,was investigated. (Ce or Y)_y(Fe)_x(Co)_(4x)(Sb)_(12) (x=0--1.0, y=0--0.15) compounds were obtained at850--1 123 K. The results of Rietveld analysis demonstrate that (Ce or Y)_y(Fe)_x(Co)_(4x)(Sb)_12synthesized by a solid state reaction possesses a filled skutterudite structure. The filling fraction ofCe or Y obtained by Rietveld analysis agrees well with the composition obtained by chemicalanalysis. The lattice constant of (Ce)_y(Fe)_x(Co)_(4x)(Sb)_(12) increases with increasing substitution of Fe at Cosites, and with an increasing Ce filling fraction in the Sb-dodecahedron voids. The lattice thermalconductivity of (Ce or Y)_y(Fe)_x(Co)_(4x)(Sb)_(12) decreases significantly with an increasing Ce or Y fillingfraction in the voids and with substitution of Fe at Co sites. 相似文献
995.
原子吸收光谱法间接测煤中形态硫 总被引:4,自引:1,他引:4
利用 SO2 -4 在 Ba Cr O4溶液中 ,可定量置换出 Cr O2 -4 ,进行原子吸收光谱法测铬 ,间接测定煤中形态硫的研究。方法较现行使用的重量法简便、快速 ,干扰少 ,硫含量在 1× 1 0 - 4 ~ 3× 1 0 - 3mg·ml- 1 呈良好线性关系。用于样品分析 ,结果满意。 相似文献
996.
997.
Matthias Bruch Dietmar Mder Florian Bauers Ton Loontjens Rolf Mülhaupt 《Journal of polymer science. Part A, Polymer chemistry》2000,38(8):1222-1231
Various copolyesteramides were prepared by melt compounding at 220 °C involving reaction of poly(styrene‐co‐maleic anhydride), SMA, with 6, 17, and 28 wt % maleic anhydride content, and 1‐dodecanol, C12OH, in the presence of 2‐undecyl‐1,3‐oxazoline, C11OXA. Copolymer architectures were examined by means of 1H NMR, FTIR, DSC, and TGA using model compounds prepared via solution reactions. While conversion of anhydride with alcohol was poor due to the thermodynamically favored anhydride ring formation, very high conversions were achieved when stoichiometric amounts of C11OXA were added. According to spectroscopic studies esteramide groups resulted from reaction of oxazoline with carboxylic acid intermediate. In the absence of alcohol, C11OXA reacted with anhydride to produce esterimides. Effective attachment of flexible n‐alkyl side chains via simultaneous reaction of C12OH and C11OXA resulted in lower glass‐transition temperatures of copolyesteramides. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1222–1231, 2000 相似文献
998.
Summary. Parameters of the formalism [1–6] describing spin crossover in the solid state have been defined via molecular potentials in model systems of neutral and ionic complexes. In the first instance Lennard-Jones and electric dipole–dipole potentials have been used whereas in ionic systems Lennard-Jones and electric point-charge potentials have been used. Electric dipole–dipole interaction of neutral complexes brings about
a positive excess energy controlled by the difference of electric dipole moments of HS and LS molecules. Differences of the
order of Δμ = 1–2 D cause an abrupt spin crossover in systems with T1/2 = 100–150 K. Magnetic coupling contributes both to the excess energy and excess entropy, however the overall effect is equivalent
to a modest positive excess energy. Ionic systems in the absence of specific interactions are characterised by very small
excess energies corresponding to practically linear van’t Hoff plots. Detectable positive and negative excess energies in these systems may arise from interactions of ligands belonging
to neighbouring complexes. The HOMO–LUMO overlap in HS–LS pairs can bring about a nontrivial variation of the shape of transition
curves. Examples of regression analysis of experimental transition curves in terms of molecular potentials are given. 相似文献
999.
1000.
The gaseous PVTx properties of ethyl fluoride (HFC-161) + 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) mixtures were measured at temperatures from 318.180 to 403.205 K and corresponding pressures from 961.3 to 3129.8 kPa using the isochoric method. The uncertainties in the present measurements were estimated to be ±1.5 kPa for pressure and ±6 mK for temperature. On the basis of the experimental PVTx property data, a truncated virial equation of state was developed for the binary HFC-161/227ea system. This equation reproduced the experimental data in the gas phase within ±0.164% in pressure and within ±0.178% in density. 相似文献