טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentAvraham Moshe
SubjectStructural Stability of LiCl and MgO under Load and
Temperature Conditions
DepartmentDepartment of Materials Science and Engineering
Supervisor Professor Emeritus Menachem Bamberger


Abstract

The electrolyte in a thermal battery is a solid non-conductive inorganic salt at natural ambient temperatures.

One of the key factors of life time in the thermal batteries is the deformation behavior of the electrolyte pellet that is called the separator

The separator is made of 45-55% MgO (the binder) and LiCl- KCL eutectic

This study, deals with the factors that influence the deformation of the separator, while conducting tests and measurements that will help us to understand the mechanism of deformation.

Here are the parameters that have an influence on the deformation:

  1. Manufacturing conditions
  2. ingredients
  3. testing device and conditions

Tests results and analysis:

  • Pressing force:

The deformation increased as the pressing force was bigger- this behavior occurred due to a good heat transfer among the particles that improved as we pressed the pellets in bigger forces.

  • Pellet density :

The deformation increased as the density increased- this behavior occurred due to a good heat transfer among the particles that improved as the density was bigger.

  • Particle size:

In small particles the deformation was bigger

Due to bigger density in pellet that are made from small particles the heat transfer is better.

Small particles melt faster and deforms faster.

  • MgO percent:

In higher MgO percents we measured less deformation than in low percent of MgO.

The pellets that had a larger percent of MgO had high porosity and did not allow good heat transfer the influence the melting of the pellet.

  • Temperature:

In low temperatures we got bigger deformation than in high temperatures.

In temperatures greater than 550°C the pellets expands and a smaller deformation is measured.

  • Testing pressure:

The higher the pressure applied by the die set we got higher deformation.

  • Porosity:

The porosity in the pellets has a strong connection with the amount of MgO in the pellet.

The more MgO the higher the porosity.

The higher the porosity the smaller the deformation in the pellets due to bad heat transfer.

  • Production processes:

The production process that had the bigger influence was a powder production process that combines pressure and temperature.

The mechanism that takes place while pellet deformation, involves porous distraction and melting due to heat transfer.