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961.
Hamideh Sharifi Noghabi Gholam Hossein Rounaghi Mohammad Hossein ArbabZavar Javad Ebrahimi 《Russian Journal of General Chemistry》2014,84(7):1429-1433
We report on conductometric study of complexation between benzylbisthiosemicarbazone [(2E,2′E)-2,2′-(1,2-diphenylethane-1,2-diylidene)bis(hydrazine-1-carbothioamide)] with Zn2+, Cr3+, Co2+, and Ni2+ cations at different temperatures in acetonitrile-dimethylformamide binary solvents of varied composition. The equilibrium constant and standard thermodynamic parameters (Δc H 0 and Δc S 0) of the complexes formation have been determined and found to be dependent on the binary solvent composition, the metal ion nature, and temperature. 相似文献
962.
Mohammad Hayatifar Luca Bernazzani Anna Maria Raspolli Galletti 《Journal of Thermal Analysis and Calorimetry》2014,115(2):1711-1718
Random ethylene/1-hexene copolymers with the 1-hexene content in the range from 2 to 28 mol% were produced with a novel post-metallocene catalyst and analyzed by three techniques, FTIR, 13C NMR, and DSC. The 1-hexene content and the sequence distribution in the copolymers were determined by means of FTIR-M and 13C NMR. The crystallization behavior of the copolymers was studied by DSC under dynamic and isothermal conditions; the Avrami model was used to analyze the crystallization kinetics. It was found that both the 1-hexene content and the crystallization temperature affect the relative crystallinity. The bulk crystallization rate decreases with the 1-hexene content and reduces exponentially with an increase of T c. The melting behavior of isothermally crystallized samples was also investigated and it was found that the melting temperatures of the copolymers under equilibrium conditions were related to the composition. 相似文献
963.
Narges Zohari Mohammad Hossein Keshavarz Seyed Abolfazl Seyedsadjadi 《Journal of Thermal Analysis and Calorimetry》2014,115(1):93-100
This study presents a novel relationship between electric spark sensitivity of nitroaromatic energetic compounds and their activation energies of thermal decomposition. The new correlation can help to elucidate the mechanism of initiation of energetic materials by electric spark. It can be used to predict the magnitude of electric spark sensitivity of new nitroaromatics, which is difficult to measure. The methodology assumes that electric spark sensitivity of a nitroaromatic energetic compound with general formula CaHbNcOd can be expressed as a function of its activation energy of thermal decomposition as well as optimized elemental composition and the contribution of specific molecular structural parameters. The new correlation has the root mean square and the average deviations of 1.43 and 1.17 J, respectively, for 22 nitroaromatic energetic compounds with different molecular structures. The proposed new method is also tested for eight nitroaromatic energetic compounds, which have complex molecular structures, e.g., 1,3,7,9-tetranitrophenoxazine, 2,4,6-tris(2,4,6-trinitrophenyl)-1,3,5-triazine, and 1-(2,4,6-trinitrophenyl)-5,7-dinitrobenzotriazole. 相似文献
964.
Saied Ahmadjo Hassan Arabi Gholamhossien Zohuri Mehdi Nekoomanesh Gholamreza Nejabat Seyed Mohammad Mahdi Mortazavi 《Journal of Thermal Analysis and Calorimetry》2014,116(1):417-426
(2-RInd)2ZrCl2 (R:Ph,H) catalyst was supported on MCM-41 and ethylene copolymerization behavior as well as microstructure of copolymers were studied. A steady rate–time profile behavior was observed for homo and copolymerization of ethylene using supported catalysts. It was noticed that increasing the comonomer content can result in lower physical properties. The obtained results indicated that (2-PhInd)2ZrCl2/MCM-41 had higher ability of comonomer incorporation than the non-substituted supported catalysts. The CCC, CCE, and ECC (C: comonomer, E: ethylene) triad sequence distribution in backbone of copolymers were negligible, that means no evidence could be detected for comonomer blocks. The polymer characterization revealed that utilizing 1-octene instead of 1-hexene as the comonomer leads to more heterogeneous distribution of chemical composition. The heterogeneity of the chemical composition distribution and the physical properties were influenced by the type of comonomer and catalyst. (2-PhInd)2ZrCl2/MCM-41 produced copolymers containing narrower distribution of lamellae (0.3–1 nm) than the copolymer produce using Ind2ZrCl2/MCM-41 (0.3–1.6 nm). 相似文献
965.
Mamdouh S. Masoud Alaa E. Ali Marwa Y. Abd El-Kaway 《Journal of Thermal Analysis and Calorimetry》2014,116(1):183-194
Six solid Pd(II) and Hg(II) complexes of some purines and pyrimidines have been prepared and characterized by elemental analyses, IR, UV–Vis spectra, magnetic measurements, and thermal analyses. The data suggest tetrahedral and square planar geometries for mercury and palladium complexes, respectively. The thermal behavior of the complexes has been studied applying TG, DTA, and DSC techniques, and the thermodynamic parameters and mechanisms of the decompositions were evaluated. The ?S* values of the decomposition steps of the metal complexes indicated that the activated fragments have more ordered structure than the undecomposed complexes, and/or the decomposition reactions are slow. The thermal processes proceeded in complicated mechanisms where the bond between the central metal ion and the ligands dissociates after losing small molecules such as H2O, HCl or C=O. The palladium adenine complex is ended with the metal as a final product. However, the thermal reactions of the other five palladium and mercury pyrimidines complexes are ended with metal bonded to O, N, or S of the pyrimidine ring. 相似文献
966.
Xuan Thang Cao Ali Md Showkat Chan Park Yeong Soon Gal 《Molecular Crystals and Liquid Crystals》2015,618(1):103-110
Poly(?-caprolactone) grafted poly(2-hydroxyethyl methacrylate) functionalized hydroxyapatite (HAP@PHEMA-g-PCL) nanocomposites were synthesized by the combination of reversible addition fragmentation chain transfer (RAFT) polymerization and ring-opening polymerization (ROP). The RAFT agent was anchored on the surface of hydroxyapatite nanocrystals (HAPs) through the silane condensation process of 3-chloropropyltrimethoxysilane followed by reaction with potassium xanthogenate. Poly(2-hydroxyethyl methacrylate) (PHEMA) was covalently functionalized on the surface of HAPs by RAFT polymerization. Then, poly(?-caprolactone) (PCL) was grafted on HAPs by ROP based on the hydroxyl groups of PHEMA to afford HAP@PHEMA-g-PCL. The structure and composition of HAP@PHEMA-g-PCL nanocomposites were characterized by FT-IR, XRD, and TGA analyses. The morphology and formation of the polymer encapsulating HAPs were demonstrated from SEM and TEM images, while the 1H MNR analysis of the cleaved PHEMA-g-PCL confirmed the grafting. 相似文献
967.
M. S. Gaur Pramod Kumar Singh Asif Ali Rekha Singh 《Journal of Thermal Analysis and Calorimetry》2014,117(3):1407-1417
β-phase polyvinylidene fluoride (PVDF)–BaTiO3 nanocomposite samples have been prepared by solution mixing method. XRD data represent that the crystallinity of PVDF decreases with increase in loading level of BaTiO3 nanoparticles. DSC curve represents that the melting point of PVDF is lightly affected by loading concentration of BaTiO3. The morphology and microstructure of PVDF and PVDF embedded by BaTiO3 nanofillers were investigated by using inverted contrast microscopy (ICM) and scanning electron microscopy (SEM). FTIR interferrometry is proven that PVDF and BaTiO3 are not chemically interacting; therefore, interaction of BaTiO3 is van der Waals type of interaction. The thermally stimulated discharge current (TSDC) of PVDF and PVDF–BaTiO3 nanocomposites sample was characterized by single peak. The observed TSDC peak is discussed on the basis of dipolar and interfacial polarization. 相似文献
968.
Thermal conductivity modeling of MgO/EG nanofluids using experimental data and artificial neural network 总被引:1,自引:0,他引:1
Mohammad Hemmat Esfe Seyfolah Saedodin Mehdi Bahiraei Davood Toghraie Omid Mahian Somchai Wongwises 《Journal of Thermal Analysis and Calorimetry》2014,118(1):287-294
The application of nanofluids in energy systems is developing day by day. Before using a nanofluid in an energy system, it is necessary to measure the properties of nanofluids. In this paper, first the results of experiments on the thermal conductivity of MgO/ethylene glycol (EG) nanofluids in a temperature range of 25–55 °C and volume concentrations up to 5 % are presented. Different sizes of MgO nanoparticles are selected to disperse in EG, including 20, 40, 50, and 60 nm. Based on the results, an empirical correlation is presented as a function of temperature, volume fraction, and nanoparticle size. Next, the model of thermal conductivity enhancement in terms of volume fraction, particle size, and temperature was developed via neural network based on the measured data. It is observed that neural network can be used as a powerful tool to predict the thermal conductivity of nanofluids. 相似文献
969.
Mohammad Taghi Taghizadeh Nazanin Yeganeh Mostafa Rezaei 《Journal of Thermal Analysis and Calorimetry》2014,118(3):1733-1746
A peak deconvolution procedure used for the analysis of data corresponding to simultaneous overlapping processes begins with separation of individual processes using functions such as Gaussian, Lorentzian, Weibull, and Fraser–Suzuki (FS) followed by application of kinetic analysis methods to the separated peaks. We propose a coupled peak deconvolution procedure to link the parameters of the FS functions of similar peaks in two DTG curves obtained at different linear heating rates, so that the coordinates of each peak can be obtained in a constrained manner. The proposed technique is a kinetic deconvolution method rather than a pure mathematical deconvolution technique. To analyze individual peaks in our study, the non-parametric kinetic and Freidman’s isoconversional methods have been applied to determine kinetic triplet of each process. This technique has been tested with both simulated and experimental data. Using this technique, the effects of molecular weight and degree of hydrolysis of polyvinyl alcohol (PVA) samples on reaction mechanism and activation energy of thermal degradation were studied. The presence of acetate group in the PVA samples causes thermal stability, decreases the rate of main reactions, and increases the activation energy. The results of this study may help tailor heat-resistant materials with proper choice of polymer characteristics. 相似文献
970.
Thermodynamics and kinetics of nicotinamide adenine dinucleotide (NAD+) adsorption on a glassy carbon (GC) electrode surface was investigated at various electrode potentials and NAD+ concentrations using differential capacitance (DC) and attenuated total reflection Fourier transform infrared (ATR-FTIR) techniques. Equilibrium adsorption measurements confirmed that NAD+ spontaneously and strongly adsorbs on the GC electrode surface. The affinity of NAD+ towards adsorption on the GC electrode surface was found to increase with an increase in electrode potential (charge) to more positive values; the corresponding apparent Gibbs free energy of adsorption was ?32.80?±?0.25, ?35.61?±?0.86, and ?38.02?±?0.40 kJ mol?1 on negatively, neutral, and positively charged electrode surfaces, respectively. The kinetics of NAD+ adsorption is also found to be highly dependent on the electrode surface potential (charge), and it increases with an increase in electrode potential (charge) to positive values. The adsorption process was modeled using a two-step kinetic model, in which the adsorption process involves the formation of two forms of NAD+ on the surface: the thermodynamically unstable (NAD+ ads,rev) and stable (NAD+ ads,stable) forms. ATR-FTIR further confirmed that NAD+, indeed, adsorbed on the GC electrode surface. 相似文献