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101.
Excess Molar Volume and Viscosity of Isobutyric Acid + Water Binary Mixtures Near and Far Away from the Critical Temperature 总被引:1,自引:0,他引:1
The excess molar volume VE, shear viscosity deviation Δη and excess Gibbs energy of activation ΔG∗E of viscous flow have been investigated by using density (ρ) and shear viscosity (η) measurements for isobutyric acid + water (IBA+W) mixtures over the entire range of mole fractions at five different temperatures,
both near and close to the critical temperature (2.055K ≤ (T−Tc)≤ 13.055K). The results were also fitted with the Redlich–Kister equation. This system exhibited very large negative values
of VE and very large positive values of Δη due to increased hydrogen bonding interactions and correlation length between unlike molecules in the critical region and
to very large differences between the molar volumes of the pure components at low temperatures. The activation parameters
ΔH∗ and ΔS∗ have been also calculated and show that the critical region has an important effect on the volumetric properties. 相似文献
102.
Functionalization of polymers by grafting monomeric species on to the backbone of molecular chains with the use of γ-radiation
has been used extensively. In this work methacrylic acid was grafted onto a commercial grade of polycaproamide (Nylon 6) by
preirradiating the polymer granules to 15 kGy at a rate of 1.0 kGy per hour and subsequently immersing these in a 10% aqueous
solution of methacrylic acid in the presence of small quantities of FeSO4 as homopolymerization inhibitor. The polymer was subsequently neutralized by mixing it with zinc acetylacetonate in a laboratory
scale melt mixing device. The acid-grafting polymer modification resulted in an increase in glass transition temperature,
while the addition of zinc acetylacetonate gave rise to two transitions: The lower transition corresponds to a miscible mixture
of free polyamide and acid-grafted polymer, both plasticized with undecomposed zinc compound, while the upper transition corresponds
to the zinc salt of the acid grafted polyamide. Through rheological measurements it was shown that both the acid-grafted polymer
and the derived zinc salt have a branched structure, possibly containing also some crosslinked domains. Large improvements
in solvent resistance were observed for both type of polymer modifications.
Received: 13 December 1996 Accepted: 10 February 1997 相似文献
103.
The mathematical evaluation of the activation
energy, E, of non-isothermal degradation
reactions is usually made using the Ozawa/Flynn–Wall isoconversion principle
and involves the numerical resolution of a set of integrals without closed
form solution, which are solved by polynomial approximation or by numeric
integration. In the present work, the isoconversion principle, originally
described and maintained until now as an algebraic problem, was written as
a set of ordinary differential equations (ODEs). The individual ODEs obtained
are integrated by numeric methods and are used to estimate the activation
energy of simulated examples. A least square error (LSE) objective function
using the introduced ODEs was written to deal with multiple heating rate CaCO3
thermal decomposition TG experiments. 相似文献
104.
建立了一种人工神经网络-X射线荧光光谱法测定钢中酸溶铝的方法,用X射线荧光光谱法测定低合金钢中总铝值,应用所建立的ANN-BP网络模型,输入总铝含量直接预测出酸溶铝含量。同时使用改进的BP算法,避免了神经网络学习中可能产生的麻痹现象。该方法用于钢中酸溶铝的测定,结果满意。 相似文献
105.
The results detail a novel methodology for the electrochemical determination of ammonia based on its interaction with hydroquinone in DMF. It has been shown that ammonia reversibly removes protons from the hydroquinone molecules, thus facilitating the oxidative process with the emergence of a new wave at less positive potentials. The analytical utility of the proposed methodology has been examined with a linear range from 10 to 95 ppm and corresponding limit-of-detection of 4.2 ppm achievable. Finally, the response of hydroquinone in the presence of ammonia has been examined in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide, [EMIM][N(Tf)2]. Analogous voltammetric waveshapes to that observed in DMF were obtained, thereby confirming the viability of the method in either DMF or [EMIM][N(Tf)2] as solvent. 相似文献
106.
A Triton X-100-4.0G-D (4.0G-D refers to a 4.0-generation dendrimer) was brought forward as a new phosphorescence labeling reagent. Two types of specific affinity adsorption (AA) reactions (direct method and sandwich method) were carried out between the labeling product of Triton X-100-4:0G-D-Wheat germ agglutinin (WGA) and alkaline phosphatase (ALP), the product of AA reaction preserved the good characteristics of room temperature phosphorescence (RTP) of 4.0G-D and △Ip of the product was proportional to the content of ALP. According to the fact stated above, a new method for the determination of trace ALP by affinity adsorption solid substrate-room temperature phosphorimetry (AA-SS-RTP) was established on the basis of WGA labeled with the Triton X-100-4.0G-D. The detection limits were 0.20 ag·spot^-1 (corresponding concentration: 5.0×10^-16 g·mL^-1, namely 5.0×10^-18 mol·L^-1) for a direct method and 0.14 ag·spot^-1 (corresponding concentration: 3.5×10^-16 g·mL^-1, namely 3.5×10^-18 mol·L^-1) for a sandwich method, respectively. For their high sensitivity, good repeatability and high accuracy, the direct method and sandwich method have been successfully appfied to determine the content of ALP in human serum, and the results were coincided with the clinical detection results of the enzyme-linked immunosorbent assay method by the Zhangzhou Hospital of Traditional Chinese Medicine. Meanwhile, the mechanism for the determination of trace ALP by AA-SS-RTP was discussed. 相似文献
107.
In our former investigations, the phenomenon high temperature corrosion (HTC) was described exemplarily on selected materialcoating combinations for blades of stationary gas turbines, mainly in the temperature region of up to 750° C. To answer the question, in which manner higher gas inlet and/or higher material surface temperature would influence the HTC behaviour, a special analytical technique—the integral layer profile analysis—was introduced to ameliorate concentration profile methods. By examining IN 738 LC specimens with CoCrAlY plasma spray coating, stressed by hot gas at 900° C, the limits of this system are shown by explaining the corrosion mechanism; the method is also used for other systems, e.g. U 520 with NiCrAlY coating at 750° C. 相似文献
108.
Mark T. DeMeuse 《先进技术聚合物》1995,6(2):76-82
A review of work which has been performed on high temperature polymer blends is presented. The discussion is divided into miscible and immiscible blends. It is pointed out that one problem with miscible polymer blends is that of processing in the miscible state. In the case of immiscible blends, particularly ones containing liquid crystal polymers, the issue of adhesion of the two phases is discussed. Finally, the need for better theoretical models for predicting miscibility in polymer blends is highlighted. 相似文献
109.
The SHS route is based on the well-known thermite reaction, in which a strongly exothermic reaction can sustain itself and propagate in the form of a combustion wave until the reactants have been completely consumed. The successful application of the method to the synthesis of superconducting ceramics of stoichiometry RBa2Cu3Oy (R=Y, Er, Yb) is reported. The 123 phase was obtained when pellets of R2O3, BaO2 and Cu metal in the correct proportions were dropped into a heater held at 800°C in an oxygen atmosphere and left there for only 10 minutes. Thermal methods (DSC and DTA) are excellent techniques with which to investigate the dependence of the reaction on heating rate, atmosphere and starting composition. 相似文献
110.