Mechanical loss spectra (two peaks) observed in ZrO, doped with Y,O, (2-10 mol%), are attributed to oxygen vacancy 0-yttrium (Y) associates (V-Y pairs and V-2Y agglomerates). Both peaks were analysed numerically by applying the coupling model. It has been shown that: i) the activation enthalpy H for both peaks increases with Y20, content, ii) the values of coupling parameter n are about 0.6 0.7...

Subcritical crack growth in fused silica is treated as a stress assisted chemical reaction between water and strained bonds at the crack tip. In this work, the kinetics of the reaction is modeled by assuming the stress reduces the energy barrier of the activated complex by affecting both the activation enthalpy and entropy, where the stress dependence can take different forms. This theory is co...

Calculation of excess quantities of ethylene glycol + water binary fluid systems at seven absolute temperatures (293.15 to 353.15) K from experimentally determined values of density and shear viscosity were presented in previous work. The examination of related functions beside the quality of correlation from several equations on these experimental values has also been reported. Considering...

The activation energy to reaction is a key quantity that controls catalytic activity. Having used ab inito calculations to determine an extensive and broad ranging set of activation energies and enthalpy changes for surface-catalyzed reactions, we show that linear relationships exist between dissociation activation energies and enthalpy changes. Known in the literature as empirical Brønsted-Eva...

the charge-transfer complexation reaction between iodine and dibenzo- 18-crown- 6 (db18c6) has been studied spectrophotometrically in chloroform solution at different temperatures. the resulting donor-acceptor complex was formulated as (db 18c6…i )i . the spectrophotometric results , as well as the conductivity measurements, indicated that the gradual release of tiiodide ion from its contact io...

The heat of vaporization of a pure substance at its normal boiling temperature is a very important property in many chemical processes. In this work, a new empirical method was developed to predict vaporization enthalpy of pure substances. This equation is a function of normal boiling temperature, critical temperature, and critical pressure. The presented model is simple to use and provides an ...

High temperature nanoindentation experiments are conducted to assess the activation enthalpy for deformation of nanocrystalline Ni-W alloys, for grain sizes between 3 and 80 nm. Thermal softening becomes less pronounced at finer grain sizes, and the activation enthalpy has an apparent inflection at a grain size near ~10-20 nm, in the vicinity the Hall-Petch breakdown. This inflection is related...

The charge-transfer complexation reaction between iodine and dibenzo- 18-crown- 6 (DB18C6) has been studied spectrophotometrically in chloroform solution at different temperatures. The resulting donor-acceptor complex was formulated as (DB 18C6…I )I . The spectrophotometric results , as well as the conductivity measurements, indicated that the gradual release of tiiodide ion from its contac...

Enthalpy (fuel mass fraction and/or temperature) fluctuations in the oncoming mixture are known to have important impacts on premixed combustion and in particular on combustion instability. Theoretical modeling has primarily been following an empirical approach. In Part I of the present study, an asymptotically reduced first-principle theory was derived from the reactive Navier-Stokes equations...

The kinetics and thermodynamics of berberine inclusion in cucurbit[7]uril was studied by stopped-flow method, fluorescence titrations, and isothermal calorimetry in neat water. The ~500-fold fluorescence intensity enhancement upon encapsulation was exploited to monitor the complex formation in real time at various temperatures. The increase in the fluorescence intensity could be fitted well by ...