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91.
Ecaterina Stela Dragan Marcela Mihai Anton Airinei 《Journal of polymer science. Part A, Polymer chemistry》2006,44(20):5898-5908
The thermochemical transformation of electrostatically formed complexes of methyl orange (MO) with polycations containing primary amine groups such as ammonium salts afforded new polymers with a high concentration of covalently bound 4‐N,N‐dimethylaminoazobenzene groups in the side chain. Poly(allylamine hydrochloride) and poly(β‐aminoethylene acrylamide hydrochloride) were employed as support polycations for MO. The transformation of sulfonate–ammonium ion pairs into sulfonamide bonds, via heating at an elevated temperature, was supported by the polymer properties before and after the thermal treatment. The polymer structure changes were monitored with elemental analysis, Fourier transform infrared, 1H NMR, and ultraviolet–visible absorption spectroscopy, and thermogravimetric analysis. The spacer length between the backbone and azobenzene structures used as side chains strongly influenced the polymer properties before and after the heat‐induced reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5898–5908, 2006 相似文献
92.
绕圆柱体自由表面磁流体流动和传热的研究 总被引:1,自引:0,他引:1
本文对在不同雷诺数下,绕圆柱体的磁流体自由表面流动及传热进行了模拟,分析了磁场对绕流圆柱尾迹和涡分离的影响,获得了两种雷诺数下的电磁力密度、流场和温度场分布。结果表明,磁场不仅影响了流动的形态,而且对湍流有抑制作用,降低了自由表面的更新机制,从而减少了传热能力;在相同的Hartmann数下,相比低雷诺数下的流动换热情况,高雷诺数下的湍流不能被完全抑制,自由表面与尾迹的相互作用也较强,因而自由表面换热也较强。 相似文献
93.
It is conceptually proposed that the total entropy of polymer solution is contributed from two distinct parts: the positional and the oomformational. The former can be represented analytically, while the latter can be simulated with the random self-avoiding walk model on the simple cubic lattice for multichain systems. The obtained results indicated that both the conformational entropy and the mixing heat are consistent with the scaling laws wry well. 相似文献
94.
WU Xiu-Lan WANG Fen REN Qiang 《结构化学》2007,26(6):732-736
Homogeneous cordierite has been synthesized at low cost by talc-magnesite and coal gangue as the main raw materials. The mechanism of synthesizing cordierite under such a com- posing system of raw materials, and the effect of temperature on the crystal cell parameters and microstructure and thermal expansion coefficient of cordierite crystal have been studied via testing methods of XRD, SEM, etc. The result shows that the homogeneous cordierite can be synthesized by the systematic composing materials of “talc-magnesite—coal gangue—talc” with heat pre- servation at 1350 ℃ for 1 h; as the keeping time is prolonged, Al3+ and Mg2+ in cordierite crystal are replaced by a few impurity ions such as Fe3+, Fe2+, etc., and the crystal cell parameters of cordierite present an increase trend; as the high-temperature heat preservation is prolonged, the content of glassy phase in the sample is increased, its density is improved, and its thermal expansion coeffi- cient presents an increase trend. 相似文献
95.
Polyazido high-nitrogen compounds: hydrazo- and azo-1,3,5-triazine 总被引:13,自引:0,他引:13
Huynh MH Hiskey MA Hartline EL Montoya DP Gilardi R 《Angewandte Chemie (International ed. in English)》2004,43(37):4924-4928
96.
Enthalpies of solution have been measured from 5 to 85°C for aqueous tetraethyl- and tetrapropylammonium bromides, and the integral heat method is employed to evaluate
for these electrolytes over a wide temperature range. Data taken from the literature have been used to evaluate
for aqueous Bu4NBr over a similar temperature range. These data, along with similar data for Me4NBr, previously reported, have been used to evaluate absolute ionic heat capacities. While the absolute values agree only qualitatively with two other methods of division, the temperature dependences of the three methods essentially agree up to 65°C. Heat capacities due to structural effects on the solvent, obtained by subtracting the inherent heat capacities of the ions, are extraordinarily positive for all four tetraalkylammonium ions and have negative temperature coefficients, indicating that all four ions, including the tetramethylammonium ion, are structure-making ions. 相似文献
97.
Summary A method for the gas chromatographic trace analysis of underivatized nitrophenols in ground-water is presented. Using a highly
de-activated separation system a satisfactory precision for their quantitative GC analysis could be achieved by avoiding condensation
of the solvent and by fast injection of the sample. The reproducibility of the peak areas of eleven nitrophenols in ethylacetate
was <5 % RSD. Using a nitrogen-phosphorus detector detection limits were in a range from 10 to 30 pg. Within the concentration
range from 0.1 to 10 ng μl−1 the calibrations were linear with correlation coefficients >0.992.
The approach described was applied to the analysis of nitrophenols in ground-water near a former ammunition plant, after preconcentration
by continuous liquid/liquid extraction with ethylacetate. Using a GC-MS technique and retention times various nitrophenols
were identified and then quantified in the μg/L-range by applying NPD. 相似文献
98.
The geometries,heats of formation and electronic structures of 15 azido-derivatives of 1,2,3-TNB (Ⅰ),1,2,4-TNB (Ⅱ) and 1,3,5-TNB (Ⅲ) have been studied using quantum chemical AMI method at HF level.The effect of azido substitution on the structures and properties of TNBs has been discussed and the relative stability of the title compounds has been established.The processes of the decomposition of the title compounds by breaking C-NO2,C-N3 and CN-N2 bonds are investigated at UHF-AM1 level.It is shown that the decomposition of the title compounds may be initiated by the cleavage of both C-NO2 and N-N2 bonds. 相似文献
99.
Laurence E. Strong Christopher L. Brummel Robert Ryther John R. Radford Alan D. Pethybridge 《Journal of solution chemistry》1988,17(12):1145-1167
Precision molar conductances of benzoic, o-toluic, 2,6-dimethylbenzoic, 2,3,6-trimethylbenzoic, and, o-fluorobenzoic acids have been determined in aqueous solution as a function of temperature and of concentration up to near saturation (<0.035 M). At the higher concentrations molar conductances are found to be less than anticipated for the simple dissociation of a 1-1 electrolyte. Although the deviations are only 1% or less they have been interpreted to show that these acids are dimerized in solution. The interpretation includes an assumption that the dimer ionizes to produce a triple ion. Increasing numbers of methyl groups lead to increasing dimerization. For those acids with two ortho groups the dimerization increases with increasing temperature while the other three show decreasing dimerization with increasing temperature. Temperature functions have been determined for the dimerization constants and from these functions standard changes in enthalpy, entropy, and heat capacity have been determined. Comparisons are made with dimerization studies in non-aqueous solvents. From these as well as the behavior of benzene in water it is concluded that a major factor driving the dimerization is hydrophobic interaction. To provide a limiting conductance of the triple ion needed in the dimerization calculations a conductance study was also made for o-Phenylbenzoic acid on the assumption that its anion provides an approximate model of the triple ion. 相似文献
100.
A
DSC investigation has been performed on a Mg–RE–Y–Zr (RE=rare earth) technical alloy WE43. Hardness trend
during isothermal treatments has been correlated to the calorimetric traces
evolution and to the forming β phases with its precursors. Oversaturation
of solute elements occurs at temperatures higher than 150±C, on cooling
at room temperature after the anneals. Activation energies, found under non-isothermal
conditions on artificially aged samples, suggest a slow transformation velocity,
while the hardness response is relatively fast. 相似文献