5673
Rehab El-Sayed Abd-Alaziz Negida
Investigation and Sintering of
Nano-manganite Ceramic Powders
Prepared Via Different Methods
Perovskite sructure, manganite compounds, sofc, Nano particles
Perovskite-manganite ceramic is an interesting material which plays important role in our lives due to its good physical, magnetic and electrical properties. It can be utilized for various applications like sensors, catalysts, as a cathode material in solid oxide fuel cell (SOFC) and as a potential candidate for magnetic refrigeration applications at room temperature. This work concerned with the studying of: 1) the effect of various cations substitution e.g. Ca and Sr, on phase and microstructural charcteristics of lanthanum manganite (LaMnO3) and 2) the role of these cations on the electrical, physical and magnetic properties of such materials. Two different methods of preparation have been used; namely, hydrothermal method and mechanical activation method. In hydrothermal synthesis, the crystalline powder was prepared in one step from solutions of metal salts at temperature of 230°C for 48 h. On other hand, the mechanical activation method was carried out by the suitable metal oxides from different sources. Manganese oxide was firstly extracted from low-grade manganese ore by using glucose as a reducing agent indilute nitric acid. Then, the perovskite manganites were prepared by mixing and milling of the reactant metal oxides (extracted MnO and La2O3, CaO or SrO as pure chemicals). The following manganite powders, i.e. LaxCa1-xMnO3 and LaxSr1-xMnO3 (x = 0.1, 0.3, 0.5 and 1.00) were prepared by the two aforementioned methods and then sintered at different temperatures ranging from 1100oC to 1450oC. The powder of metaldoped lanthanum manganites was characterized utilizing x-ray diffraction to elucidate the phase transformation, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) to elucidate the size, morphology and crystalline structure of the particles. For the powders prepared by hydrothermal procedures, the results revealed that the maximum sintering temperature for lanthanum calcium manganite (LCMO) was 1400oC while for lanthanum strontium manganite (LSMO) was 1450oC.
2020
Ph.d
Ain Shams
Science