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stoichiometry
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Fabrication of Nuclear Fuel Pellet With a Mixture of Micro and Nano UO2 Powders And Investigation of Its Physical and Mechanical Properties
, M.Sc. Thesis Sharif University of Technology ; Otukesh, Mohammad (Supervisor) ; Taghizade, Mohammad (Supervisor) ; Roshanzamir, Manouchehr (Co-Advisor)
Abstract
Uranium dioxide (UO2) has been widely used as nuclear fuel in water cooled reactors since 1960s. UO¬2 is a refractory oxide with a melting point in excess of 28000C and therefore, requires high sintering temperature around 17000C in a hydrogen atmosphere for several hours. In the conventional method, the sintering is incorporated with indirect heating of green pellets in a refractory-type electrical resistance furnace. This furnace, however, uses a large number of expensive heating elements and refractory materials to achieve and maintain the high temperature for a long time. Moreover, it consumes much electrical energy and time. Since nanocrystalline materials contain a large fraction of...
Synthesis and Characterization of Praseodymium Nickelate for Low Temperature Solid Oxide Fuel Cell Cathode
, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali (Supervisor)
Abstract
Solid oxide fuel cells as high temperature electrochemical devices draw much attention in the last decades due to their fuel flexibility, high efficiency and low pollution. However, lowering operating temperature from about 850°C to around 650°C without significant overpotential loss, in order to lower costs and increase cells life time has remained a challenge. Recently, a new family of mixed ionic and electronic conducting ceramics (MIECs) which are formulated Ln2NiO4+δ (Ln= La,Nd,Pr) and crystallized in Ruddlesden–Popper structure, have been regarded as appropriate cathode materials for the low or intermediate temperature solid oxide fuel cells (IT-SOFC). Amongst these compounds,...
Effect of Doping of La in Pr Site and Cu/Fe in Ni site on Crystal Structure, Oxygen Non-stoichiometry level and Electrical Conductivity of Pr2NiO4 as Intermediate Temperature Solid Oxide Fuel Cell Cathode
, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali (Supervisor)
Abstract
Nowadays, one of the most important research goals is to develop intermediate-temperature solid oxide fuel cells (IT-SOFC) operated at 500–800 °C. However, the large cathode polarization resistance caused by the reduced temperature is a major barrier against such an urgent demand for commercialization. In this regard, it is necessary to select a proper material as a cathode working efficiently at reduced temperatures without losing its desired performance. Various mixed ionic electron conductors (MIECs), especially Ruddlesden–Popper-type oxides, are used to improve the cathode performance at intermediate temperatures. Among these layered oxides, Pr2NiO4 has been reported to possess the...