<p>In transformers used in
the electrical industry, a coating, such as magnesium oxide or magnesia (MgO),
is needed to coat the magnetic ferrite core, such as silicon steel. The coating
is to provide electrical insulation of the layers of the ferrite core material,
in order to reduce its heat dissipation loss. The coating also separate the
layers of the coiled materials to prevent their sticking or welding during high
temperature uses. </p>
<p> </p>
<p>The goal of this thesis is
to perform a modeling study to understand the mechanical, thermodynamic, magnetic
and thermal properties of pure and M-doped (M stands for Mn, Co, or Ni) magnesia,
thus providing a theoretical understanding of the application of this group of
coating materials for transformer applications. </p>
<p> </p>
<p>The study has the
following sections. The first section is focused on the mechanical properties
of pure magnesia. Using density functional theory (DFT) based calculations, the
computed Young’s modulus, Poisson’s ratio, bulk modulus, and compressibility
are 228.80 GPa, 0.2397, 146.52 GPa, and 0.00682, respectively, which are in
good agreement with the literature data. Using molecular dynamics (MD)
simulations, the computed Young’s modulus is 229 GPa. Using discrete element
model (DEM) approach, the bending deformation of magnesia is simulated.
Finally, using finite element model (FEM), micro-hardness indentation of
magnesia is simulated, and the computed Brinell hardness is 16.1 HB, and
Vickers hardness is 16 GPa.</p>
<p> </p>
<p>The second section is on
the thermodynamic and physical properties of pure and doped magnesia. Using DFT
based simulations, the temperature-dependent thermodynamic properties, such as
free energy, enthalpy, entropy, heat capacity at constant volume, and Debye
temperature of magnesia, are computed. The X-ray powder diffraction (XRD)
spectra of M-doped magnesia are simulated, at the doping level of 1.5%, 3%, 6%
and 12%, respectively. The simulated XRD data show that peaks shift to higher
angles as the doping level increases. </p>
<p> </p>
<p>The third section is on
the magnetic properties of pure and doped magnesia. Using DFT based
simulations, the calculated magnetic moments increase with the doping level,
with Mn as the highest, followed by Co and Ni. This is due to the fact that Mn
has more unpaired electrons than Co and Ni. </p>
<p> </p>
The
fourth section is on the thermal properties of the pure magnesia. Using the Reverse
Non-Equilibrium Molecular Dynamics (RNEMD) method, the computed thermal conductivity of magnesia is 34.63 W/m/K, which is in
agreement with the literature data of 33.0 W/m/K at 400 K.
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/11105189 |
| Date | 04 December 2019 |
| Creators | Asimiyu Ajileye Tiamiyu (8035247) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/SIMULATION_OF_MECHANICAL_THERMODYNAMIC_AND_MAGNETIC_PROPERTIES_OF_MAGNESIA_WITH_SUBSTITUTIONAL_ELEMENTS_FOR_IMPROVED_MAGNETIC_CORE_COATING_APPLICATIONS/11105189 |
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