Tonkushina, M. O.Belozerova, K. A.Gagarin, I. D.Adamova, L., V...
7页
查看更多>>摘要：The thermodynamics of the interaction between the nanocluster iron-molybdenum Keplerate-type polyoxometalate {Mo72Fe30} and thiamine hydrochloride (vitamin B-1) was studied. This system is considered as a model for new types of targeted drug delivery systems. We evaluated the thermodynamic characteristics of the interaction between {Mo72Fe30} and B-1 using experimentally measured sorption parameters for methanol vapour and the enthalpy of the interaction with liquid methanol for the initial compounds ({Mo72Fe30}, B1) and the {Mo72Fe30}+B-1 conjugate. It was determined that the energetically unfavourable interaction of the components is due to entropy's predominant contribution to the Gibbs energy. Using X-ray analysis, it was shown that the increase in entropy is associated with one of the components (thiamine hydrochloride) losing its crystal structure.
查看更多>>摘要：A dynamic self-cooling inhomogeneous temperature gradient field was applied instead of steady-state temper-ature at the mold cavity surface to study the effect of different cooling rates on the crystallization progress after the melt flow. The results showed that both the crystallinity and the beta phase content increased with the gradient of the inhomogeneous mold temperature. When the mold temperature gradient of the high-temperature and the low-temperature sides increased from 0 to 40 degrees C, the size of the shish-kebab in the shear layer and the amount of small beta phase spherulites in the transition layer increased. During the melt flows, a cavity temperature gradient higher than 30 degrees C was required to increase the stability of beta phase in the transition layer. The yield stress and the elongation at break increased with the temperature gradient, but decreased at the temperature gradient of 45 degrees C.
查看更多>>摘要：The suitability of thermogravimetric analysis (TGA) and rheology for predicting analytical composition of flour was verified. The percentage weight loss of flour samples in different temperature ranges and their analytical composition determined following the American Association of Cereal Chemists (AACC) approved methods were correlated. The moisture content determined by AACC method showed a strong correlation with the weight loss of dried samples in the temperature range 30 - 125 degrees C. Similarly, the weight loss of fully swollen samples, determined by TGA in the temperature range of 30 - 125 degrees C, perfectly correlated with the water-Solvent Retention Capacity (w-SRC) determined by standard method (AACC). The weight loss in the range 200 - 400 degrees C revealed a good correlation with the starch content, while the weight loss in the range 400 - 600 degrees C correlated with the gluten content. Finally, the so-called residue at 600 degrees C (usually attributable to mineral content) correlated with the ash content (AACC standard method). The rheological parameters (G', G '' and tan delta) also showed a strong correlation with the analytical composition of analyzed flours. A perfect correlation was observed between the mineral content and the elastic modulus, as well as between both G' and G '' and the starch content. As the resilience of dough samples strongly depends on the relative amount of gliadins and glutenins, a strong correlation between the Gli/Glu ratio and tan delta was also found.
查看更多>>摘要：This study investigates the homopolymerization of a diglycidyl ether of Bisphenol A resin using 1-Methylimidazole as an initiator and provides a new perspective on volume changes and cross-linking reactions via "Tem-perature Modulated Optical Refractometry" (TMOR) under isothermal conditions. It is shown that the chemical reaction process is divided into an initiation regime, a homopolymerization regime and the chemically induced glassy state. The simultaneous access to the chemically induced volume changes and thermal expansion via TMOR allows to clearly distinct between the three different stages of polymerization and easily determine the region of the (dynamic) glass transition. Also, insights into the statistcial variety of the polymer network formation are provided.
查看更多>>摘要：Phase change materials (PCM) can store and release thermal energy mostly through a transition from solid to liquid and vice versa. This transition and its related parameters such as melting point, enthalpy and heat capacity were most often studied from a thermodynamic point aspect. Investigating the phase transition from a rheological point of view can provide us with important information such as viscosity change during the transition and in the melt. Considering the importance of natural convection during the melting of a PCM, the rheological knowledge can improve the estimations resulting from the numerical analysis of a phase change transition. However, there are a few studies on rheological behavior of PCMs. Here, the rheological behavior of an organic PCM, adipic acid, is studied. This PCM melts at 150 degrees C which corresponds to a medium temperature range for application in industrial waste heat recovery. Rotational and oscillatory tests under thermal insulation have been performed using a controlled stress rheometer and a plate geometry. Finally, the heat flow measured by Differential Scanning Calorimetry (DSC) is compared to the rheological oscillatory test results to provide a detailed information of phase transition range. To the authors best knowledge, this study is the first study in the rheology of a PCM at medium to high temperature (150 degrees C).
查看更多>>摘要：Al-Mg based alloys are widely used in industrial applications and grain refining is used for structural refinement to achieve high strength and ductility. The aim of this work is to investigate the effects of two grain refiners of Al-5Ti-1B and Zr on the solidification transformations of Al-6Mg alloy and dendrite coherency point (DCP) using two thermocouple cooling curve thermal analyses (CCTA). The microstructure and intermetallic phases were studied through scanning electron microscopy (SEM), EDS, and X-ray mapping. Microstructural evaluations showed the main secondary phases of Al-6Mg alloy are Al3Fe, Al8Mg5, and Mg2Si. The CCTA results indicated that the addition of Al-5Ti-B and Zr causes an increment of nucleation temperature, T-N,T-alpha,(from 622.4 to 628.4 and 625.7 degrees C, respectively). The grain refining potential is an inherent property that depends on the growth restriction factor (GRF) and mostly relates to solute concentration and liquidus line slope. The refining power of Al-5Ti-1B for Al-6Mg is more effective because of its larger growth restriction factor (GRF) in comparison with Zr. Therefore, the grain size of the alloy used Al-5Ti-1B or Zr grain refiner was 105 mu m and 185 mu m, respectively. This phenomenon has been proved when recalescence undercooling (Delta T-R,T-alpha) was calculated. It has been shown that Delta T-R,T-alpha reaches zero when Al-5Ti-1B master alloy is added to Al-6Mg alloy. Zr caused the decrement in the first derivative peak intensity of eutectic phases which may be eventuated from extending the solid solubility by the addition of Zr. These grain refiners also affected the dendrite coherency point (DCP). Although Zr changed the T-N-T-DCP and fs(DCP), Al-5Ti-1B increased the T-N-T-DCP interval by about 14.8 degrees C and delayed up the coherency solid fraction by about 89.7 pct which can decrease the casting defects.
查看更多>>摘要：In this study, the influence of iron-based waste catalyst (IWC) from F-T synthesis as a cheap additive on the gasification reaction characteristics of petroleum coke (PC) with CO2 at 1000-1300 degrees C was investigated by thermogravimetric analyzer. The gasification kinetics of PC was analyzed by free model method. The surface complexes of PC were determined through temperature-programmed desorption (TPD) methods to reveal the mechanism of IWC catalytic PC gasification. The results show that IWC is an efficient PC gasification catalyst and can reduce the activation energy of PC CO2 gasification. The induction of iron in IWC makes the surface of PC have more activated carbon sites, thereby forming more oxygen-containing intermediates, and the cyclic redox reaction of iron can act as an oxygen carrier to accelerate the reaction of CO2 and carbon, both of these may be the essential reasons for the CO2 gasification of PC catalyzed by IWC.
查看更多>>摘要：The heat capacity, C-p, measured on heating a glass in adiabatic and scanning calorimetry experiments generally shows an overshoot peak before the liquid state is reached. We argue that when estimates of S-liq, the entropy of a liquid, inadvertently include part of the C-p on the high temperature side of this peak, the decrease of S-liq with T is greater than the true decrease, and the downward curvature of the S-liq-T plot is, as an artefact, greater. This affects the super-linear extrapolation of Sliq to T below the glass to liquid transition temperature, which is basis of the theory for thermodynamic origin of glass formation. The artefact may be avoided by, (i) using the heat capacity of a liquid, C-p,C-liq, measured during cooling in a scanning calorimetry experiment and (ii) by directly determining the ratio, (C-p,C-liq /T) = (partial derivative S-liq / partial derivative T)(P). As examples, we analyze the C-p,C-liq data of two polymers measured during cooling of the melt and heating of the glass, the latter on the same time scale as used in adiabatic calorimetry, and compare the results against those obtained from dynamic measurements. We similarly analyze the C-p of an orientationally-disordered crystal. F. Simon (Z. Anorg. Allg. Chem. 203 (1931) 219-227) had provided a sigmoid shape extrapolation of C-p and sublinear extrapolation of S-exc (= S-liq - S-cryst) of glycerol down to T = 60 K. We discuss it in terms of (C-p,C-exc /T) = (partial derivative S-exc / partial derivative T)(P). Features of the (C-p,C-exc /T) against T plot agree with Simon's Sexc against T plot within experimental and analytical errors.
Rakipov, Ilnaz T.Semenov, Konstantin N.Petrov, Artem A.Akhmadiyarov, Aydar A....
5页
查看更多>>摘要：In present work an enthalpies of solution at infinite dilution and solvation of ethers (diethyl ether, diglyme, 1,4dioxane, 12-crown-4 and 15-crown-5) in aliphatic alcohols at 298.15 K and enthalpies of aliphatic alcohols, alkanes in ethers were determined. The enthalpies of hydrogen bonding for these systems were calculated using experimental data. The hydrogen bond enthalpies of ethers in alcohols are significantly lower by absolute values than the enthalpies of hydrogen bonding in the complexes 1:1 of alcohols in ethers solution due to reorganization effects of aliphatic alcohols as a solvent (breaking of solvent-solvent hydrogen bonds). The cooperative effects in multi-particle complexes of alcohols with ethers were evaluated taking into account reorganization effect.
NSTL
Elsevier