1. Sufficient strength, rigidity, low mass, and light weight are required to ensure minimal inertial force.
2. Good thermal conductivity, resistance to high temperatures, high pressures, and corrosion, with ample heat dissipation capacity and a small heated area.
3. A low coefficient of friction should exist between the piston and the piston wall.
4. Minimal changes in size and shape with temperature variations are required, and minimal clearance must be maintained between the piston and the cylinder wall.
5. Low coefficient of thermal expansion, low specific gravity, and good anti-friction properties and thermal strength.
