Papers by Keyword: Cell Parameter

Abstract: Negative thermal expansion (NTE) material Sc₂Mo₃O₁₂ was prepared by solid-state method. The phase structure, morphology and the thermal stability of the obtained products were examined by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric-differential thermal analysis (TG-DSC), respectively. To study its negative thermal expansion property, two methods were utilized. One is based on the in-situ XRD results and the thermal expansion coefficient (CTE) was calculated by the cell parameters obtained at different temperatures. Another is based on the thermo-mechanical analysis (TMA) and the CTE was calculated by the length of Sc₂Mo₃O₁₂ bar at different temperatures. The differences between these two methods were also discussed.

Abstract: The calcination process of titanium silicalite zeolite TS-1, which was prepared by hydrothermal method, was investigated using TG-DTA, XRD, FT-IR and SEM. With TG-DTA analysis, it has been observed that the crystal form was not changed after calcination under 1073K and the amount of template removal from zeolite channels was not affected by heating rate. The photographs of SEM showed that calcined TS-1 crystal morphology was integrated under 823K, but ruptured at 923K. Analyzing FT-IR with XRD results, the calcination process changed the cell parameter and unit cell volume, and increased the crystallinity of zeolite TS-1.

Abstract: We elaborated two carbide-free bainitic steels with different microstructures through specific heat treatments and alloy design. EBSD analysis was used to point out major differences in these microstructures. In-situ characterizations of the bainitic transformation were performed by high energy synchrotron diffraction to go further into the study of each phase characteristics. The elaborated microstructures exhibited various phase fractions of bainitic ferrite, retained austenite and blocks of martensite and retained austenite. Moreover, the volume fraction of retained austenite increased with higher austempering temperatures. On the other hand, the austempering temperatures showed a strong influence on the kinetics of the bainitic transformation. Isothermal transformation under Ms showed a two stage transformation which led first to the formation of self-tempered martensite and then to bainitic ferrite. Furthermore, the evolution of the austenitic cell parameter showed enrichment in carbon ruled by diffusional mechanisms.