Authors

Yuan XueFollow

Date of Completion

1-28-2011

Embargo Period

1-28-2011

Open Access

Campus Access

Abstract

Solid-oxide fuel cells (SOFC) are electrochemical conversion devices to convert electricity directly from oxidizing a fuel with high efficiency and low emission. . The triple-phase-boundaries (TPBs), where cathode and electrolyte make contact with gas phase, are considered to be the active sites for oxygen reduction reactions. The microstructure and chemical properties of TPBs appear to play a significant role in the long-term stability and efficiency of SOFCs. Strontium doped lanthanum (LSM) is one of the most popular materials used as a high temperature cathode in SOFCs due to its good chemical and good stability with YSZ electrolyte at high temperature. Barium cerate (BaCeO3) is a candidate material for proton conducting electrode in SOFC and other solid-state ionic devices.

In this thesis, the crystalline BaCeO3 has been successfully synthesized using hydrothermal route by hexamethylenetetramine (HMTA). The crystal structure, surface and grain morphologies and microstructural defects of both as-synthesized and heat-treated nanoparticles of BaCeO3 are presented. Two-phase model microstructures of LSM-CeO2 and LSM-YSZ are developed to simulate the triple phase boundaries, and the composite microstructures are characterized by X-ray diffraction (XRD), atomic-force microscopy (AFM), focused ion beam (FIB) milling, field-emission scanning electron microscopy (FESEM), X-ray energy dispersive spectroscopy (XEDS) and transmission electron microscopy (TEM). Last, the La0.8Sr0.2MnO3 powders are synthesized by HMTA. The crystal structure and surface morphologies were investigated using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The mechanical properties including hardness, elastic modulus and fracture toughness of LSM as a function of sintering temperature are presented and discussed.

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