Date of Award
Master of Science (MS)
School of Materials Science and Engineering
The mineral mayenite (12CaO•7Al2O3, C12A7), possesses a unique cage structure which allows the entrapment of anions due to the positive charge of the cage. The most abundant form of this mineral is C12A7:O2- which exhibits high oxygen conductivity. However, the oxygen can be removed from the cage by reduction and other anions such as OH-, H-, Cl-, and even e- can be substituted in the cage. When electrons act as the anion in the cage, the material is classified as an electride. Mayenite electride shows promising properties such as metallic-like conduction and is a room temperature stable inorganic electride. The cages don’t necessarily need to be occupied by just one anion. It is possible to have a mixture of anions of different species in the cages of mayenite. Through mixed anions present in the cages, mixed conductivity becomes possible. With H- ions and electrons inhabiting the cages of mayenite, it is theoretically possible to have hydrogen permeate through the cages. This allows the material mayenite to be used as a hydrogen permeable membrane. Other applications of mayenite include catalysts for ammonia formation, as well as an energy material for the cathode and electrolyte of a solid oxide fuel cell. To have a hydrogen permeable membrane, the membrane should be fully dense with as many charge carriers as possible to manifest high permeability without allowing molecules to diffuse or permeate through the membrane. This work focuses on the synthesis of mayenite with mixed conductivity to act as a hydrogen permeable membrane. Different dopants were tested such as doping a thin membrane with iron to allow the membrane to be fully dense. Silicon was also investigated as a dopant to replace aluminum sites as to create cages with higher positive charges with a goal of creating a doped mayenite with higher electron densities. Characterization was completed to show that the structure remained when doping, and that doping with silicon did indeed increase the electron density. Work was done to investigate the permeability of hydrogen through a thin membrane of mayenite.
Phaneuf, Vincent Nicholas, "Synthesis, Characterization and Application of Mayenite" (2021). All Theses. 3487.