The impact of thermodynamic factors on deviation from linearity of diffusion path in the
ternary system Cu-Fe-Ni is analyzed. For that the slope function of the diffusion path for the
diffusion couples 65Ni30Cu5Fe –29.5Ni16.5Cu54Fe, 49.5Ni50.5Fe – 51Ni49Cu and 84Cu16Ni –
50Ni50Fe, annealed at 1000°C for 196h, were calculated by an approximate equation using only
thermodynamic data. Results of the calculation were compared with the values of the slope function
obtained directly from experimental data. It is shown that despite of the fact that the tracer diffusion
coefficients of the components in the system Cu-Fe-Ni are not equal the coincidence between the
calculated and experimental values of the slope function is remarkable. This allows us to conclude
that at least in this case the deviation of the diffusion path from linearity depends mainly on the
thermodynamic properties of the system.
ZrO2 nanopowders derived from zirconium n-propoxide [Zr(OC3H7)4]-acetylacetone-water-isopropanol have been investigated with respect to their tetragonal metastability on heating-cooling processes. The transformation temperature of metastable tetragonal to monoclinic (t′ → m) phase is found to be governed by ultimate firing temperature, time, and atmospheres employed. Crystallite growth is fastened with increase in calcination temperatures over 1000–1400 °C, and the t′ → m transformation temperature is correlated linearly with crystallite size in the studied range of 12–20 nm. Heating in an oxygen environment increases the size of the final crystallites and hence the rate of the t′ → m transformation. It is revealed that the t′ → m transformation temperature depends largely on the heating atmosphere, but only weakly on the cooling one. Based on the findings of this work, surface oxygen deficiencies are attributed to be responsible for low-temperature tetragonal metastability. A crystallite growth model to explain the decline of t′-ZrO2phase is proposed. Kinetic and thermodynamic factors are also discussed in connection with the existing theories of tetragonal metastability.
A series of 5,10,15-triarylcorroles has been prepared, with the meso-aryl rings functionalized with different substituents to investigate their influence on the aryl ring rotation with respect to the corrole plane. The study has been carried out by different NMR techniques, allowing the complete assignment of the 1H NMR spectra and giving insights on the kinetic and thermodynamic factors driving the atropisomerism in triarylcorrole derivatives.