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- Author or Editor: D. Chen x
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Abstract
By using a simultaneous thermogravimetry (TG) and differential thermal analyzer (DTA), the hydration processes of the pure C3S and with the addition of Ca(NO3)2 was followed. The peak temperature was determined and kinetic analysis on one of the hydration products, calcium hydroxide, was performed. Results show that the use of Ca(NO3)2 increased the activation energy value of calcium hydroxide formed which is one aspect of the accelerating properties of Ca(NO3)2 while there is no sign of hydration for the addition of sucrose which proved its retarding property. It was also shown that the activation energy increased when the hydrated pastes aged.
Alkaline fading of bromophenol blue was chosen for the investigation of the effect of heating rate on the activation energies derived from the dynamic kinetic method. Freeman and Carroll's treatment was adopted to compute the activation energies from experimental data taken with three heating rates: namely 1°, 0.5° and 0.25°/min. It was found that the activation energy increases as the heating rate decreases. This is attributed to the non-equilibrium conditions. By extrapolating to zero heating rate, the activation energy obtained is comparable to that obtained via classical isothermal kinetics.
Abstact
The reduction process of silica supported cobalt catalyst was studied by thermal analysis technique. The reduction of the
catalyst proceeds in two steps:
Blue sticky traps on 3.0 m high poles were used to determine the characteristics of Thrips tabaci and Frankliniella occidentalis migratory flight in Israel from 2003 to 2007. In an open area, both thrips species were caught from March to November. The dominant species was T. tabaci except during the spring. About 70% of the thrips were caught below 1.0 m above ground. Trapping height appears to reflect thrips’ concentration gradient in the air because it was not affected by setting up the poles over a sticky surface. From April to September the westerly sea breezes usually exceed 10 km/h from late morning to twilight time. As a result, about 85% and 10% of the thrips were caught in the morning and at dusk, respectively. When we used similar traps mounted on wind vanes, at 1.0 m above ground 70% of the thrips were caught on the leeward side. Thus, it appears that thrips fly mainly upwind during their migration. Indeed, while most prevailing winds are from the west, most thrips were caught on the eastern side of the poles (40–50%) and the fewest on the western side (10–20%). This information may be used to focus monitoring and control of these thrips in time and space.
Abstract
DSC and TG-DTA techniques were used to investigate micro-sized silver powder particles and the adsorption of ethyl cellulose on these particles in a solution of ethyl acetate. The apparent specific heat of the silver particles was determined, and the kinetics of temperature-programmed desorption (TPD) of these adsorbed silver particles was investigated. Results show that the apparent specific heat and desorption kinetic parameters obtained by thermal analysis techniques could be used to characterize certain physico-chemical properties of such a particulate system.
Testing of some dynamic kinetic equations
Part III. Zero-order reaction
The acid-catalysed iodination of acetone in aqueous solution was used to test three dynamic kinetic equations. The Freeman and Carroll treatment yields the most satisfactory results.
Testing of some dynamic kinetic equations
Part II. Second-order reaction
The conversion of ammonium cyanate into urea in aqueous solution was used to test three dynamic kinetic methods. It is concluded that the Freeman and Carroll method is the most satisfactory.
Abstract
Thermal decomposition of BaC2O40.5H2O in air was studied by a combination of stepwise isothermal analysis (SIA) and non-isothermal thermogravimetry. The results from both techniques show that the crystal water is released in one step and that anhydrous barium oxalate is decomposed in one step, while BaCO3 decomposes in three steps to BaO, forming two intermediate compounds with the formulas of BaCO3(BaO)2 and (BaCO3)0.5(BaO)2.5. Reaction mechanism analyses using the data from SIA measurements show that the controlling mechanism for all the five decomposition steps in isothermal conditions is a two-dimensional phase-boundary controlled process. Kinetic parameters are obtained for the five decomposition steps from the non-isothermal thermogravimetric data.
Abstract
This work discusses thermal behavior of Ni/MH battery with experimental methods. The present work not only provides a new way to get more exactly parameters and thermal model, but also concentrates on thermal behavior in discharging period. With heat generation rate gained by experiments with microcalorimeter, heat transport equations are set up and solved. The solutions are compared with experiment results and used to understand the reactions inside the battery. Experiments with microcalorimeter provide more reliable data to create precise thermal model.
