Ionic Conduction Mechanisms in Nanocomposite Electrolyte and Their Relationship toMicrostructural Features
Materials Science and Engineering, PhD Dissertation, 2014
Prof. Dr. Mehmet Ali Gülgün (Thesis Supervisor), Assoc. Prof. Cleva Ow Yang (Thesis Co-Supervisor), Prof. Dr. Yuda Yürüm, Assoc. Prof. Melih Papila, Assoc. Prof. Ebru Alkoy
Date & Time: January, 6th, 2014 – 10 AM
Place: SUNUM G111
Keywords : Nano-composite Electrolyte, Interface, Impedance Spectroscopy, SDC, SOFC
A unique feature of nano-composite electrolyte is the nano-scale interfacial area, associated surface charge and percolation of the oxide-matrix interface. Higher interfacial area helps to facilitates enhanced ionic conduction behavior of nano-composites. The objective of the thesis is to address how interface characteristic can affect ionic transport mechanisms and under which circumstances improve particularly ionic conduction properties of two phase nano-composite.
The hypothesis is that incorporation of Na2CO3 into the oxide with ionic transportation prosperity and has high surface area results in significant improvements in the ionic conductivity. The impedance spectroscopy tests demonstrate significant increase in the ionic transportation response. Under the consideration of fixed oxide to Na2CO3 amount, the enhancement is attributed to the combined effect of the two factors: the interface and the surface charge of the oxide leading to dissociate Na2CO3/NaHCO3 matrix. Oxides embedded into amorphous Na2CO3 network during the composite heat treatment process to improve composite density without high temperature. Consecutively, this thesis traces the effect of the Na2CO3 percolation with temperature via impedance spectroscopy investigation. Multi-scale electron microscopic investigation including SEM and TEM are employed to address the interface property at nano-scale in nano-composites. Coupled with series of experimental study on the interface, we proposed model helps to elucidate the physical mechanisms.
Overall, the idea of specific design of interface in composites with Na2CO3 matrix is significantly effective. The experimental results show that the given the knowledge of the matrix system, proper choice of oxide skeleton provides higher interfacial region and improved ionic transportation properties.