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The oxidation of austenitic fine-grained steel TP347HFG exposed to supercritical water at 550 °C and 25 MPa with the dissolved oxygen concentration of 100 ppb, 300 ppb and 2000 ppb was investigated. The results indicated weight gain increased with the dissolved oxygen increasing. The herpes-shaped oxides were formed on the sample surface. The oxide layer was a typical dual-layered structure with a Fe-rich outer layer and a Fe-Cr-Ni-rich inner layer. The influences of the dissolved oxygen concentration and grain size on oxidation behavior were discussed finally.

In order to investigate the effect of isothermal annealing on the powder morphology, Bi3NbTiO9 powders were first synthesized by molten salt method and then calcinated at different temperatures for different dwelling time. The microstructure observation revealed that the crystal morphology of Bi3NbTiO9 powder changed greatly with the prolonged dwelling time. The powders started to change from cube to sphere in shape with the dwelling time prolonged to 240min and then became cube again as the dwelling time was prolonged beyond 360min at 850oC. In addition to a time-dependent particle evolution study, we explored primarily the original drive force of morphology transform from the viewpoint of dynamics.

Lu2Ti2O7octahedrons were synthesized by molten salt synthesis (MSS) through selecting appropriate source materials and controlling proper external conditions. The phase constituents and microstructure morphologies of as-product were characterized by X-ray powder diffraction, Energy Dispersive Spectrometer, Field Emission Scanning Electron Microscopy and High-resolution Transmission Electron Microscopy. According to the experimental results, the detailed microstructure and growth mechanism of Lu2Ti2O7octahedron have been analyzed. The presented results in this paper may benefit to a deeper understanding of the fundamental physical and chemical processes of MSS methods.

Lu2Ti2O7 powders have been prepared using TiO2 and Lu2O3 oxides as precursors based on molten salt technique and the effects of salt-oxide ratio on the phase transformation is studied. A significant influence of salt-oxide ratio on phase transformation has been observed and the salt-oxide molar ratio of 3:1 is preferred for improved synthesis reaction efficiency. Such an experimental trend is analyzed with the assistant of JMA equation and the possible correlations between salt amount and the nucleation rate is given. After confirming linearly increasing of the crystal size with time, which is an indicative of interface controlled crystal growth kinetics, the investigations on the curves resulting from the logarithm of phase transformation fraction (ln[-ln(1-α)]) plots versus both the annealing time (lnt) and calcinations temperatures ( ) under isothermal and non-isothermal conditions respectively suggest that the enhanced crystallization is derived from the modification of salt amount to the nucleation rate.