Goal
The advance in knowledge in ceramic matrix composites with 2D nanomaterial fillers is essential to address their future use in technological applications such as high-temperature electrochemical devices. Thus, a deep understanding of the basis of their new functionalities and optimized performance is needed.
This proposal outlines a systematic study of composites with 8 mol% yttria-stabilized zirconia matrix, a well-known ionic conductor, incorporating two different 2D laminar nanomaterials -graphene or boron nitride nanosheets- as fillers, intended for use in solid oxide fuel cells, with the aim to deepen in the understanding of the mechanisms that control their thermal, mechanical and electrical behavior.
To begin with, a processing study will be carried out in order to obtain composites with an optimized microstructure, always pursuing a homogeneous distribution of the 2D nanomaterial throughout the ceramic matrix and a high density. In a first step, the powder processing routine will be optimized in order to enhance the dispersion of the 2D nanostructure in the composite powder. In a second step, a sintering study with different temperatures and pressures will be carried out with the aim of obtaining fully- dense composites. The effect of the 2D nanostructure incorporation on the ceramic composite microstructure will be analyzed in terms of the crystalline phases and distribution, size and structural integrity of the 2D nanomaterials.
Thermal diffusivity and conductivity measurements will be conducted on the sintered composites, as a function of temperature and under different atmospheres to analyze heat dissipation and the effect of the filler dispersion and orientation in the thermal response. These thermal properties are essential since operation of the solid oxide fuel cell takes place at high temperature.
To ensure structural stability of the composites during operation, high-temperature deformation test will be performed controlling stress, temperature, and working atmosphere conditions. The identification of the microscopic mechanisms responsible of the creep behavior as well as the comprehension of the fracture mechanisms and plasticity of the composites will be pursued to allow for prediction and control of their structural response in service.
The electrical conductivity measurements fundamental for this application will be carried out on the composites as a function of temperature in order to assess the effect of the incorporation of the different 2D nanostructures. The conduction type -ionic, mixed or electronic- for the composites with different graphene nanosheets contents will be identified.