Studies on Young's Moduls of Graphites (I)

Abstract

By means of the flexural vibration method, the temperature dependence of Young's modulus of polycrystalline graphites in the range from room temperature to 1000°C, has been investigated under a variety of conditions; e. g. in vacuum, nitrogen and argon.
The effects of repeated heating and cooling, heating rate and holding time have also been investigated.
In every case, the curves of Young's modulus vs. temperature showed the hysteresis between heating and cooling, and showed a minimum value at about 200-400°C during heating.
In vacuum, the degree of the hysteresis was larger than in gas atmosphere.
In gas atmosphere, a characteristic inflexion was observed in the 1st heating.
Except in the 1st heating cycle in gas atmosphere, the relation between Young's modulus and temperature during heating could be approximately expressed by the formula: E_T/E₅₀=a+bT+cT².
The temperature dependence of Young's modulus was also influenced by the heating rate and holding time.