Temperature distribution in the area of the electrical contact surface of graphite

For the first time, the temperature distribution on both sides of the contact plane at an equal distance along the surface of a vertical graphite sample was determined using contactless optical pyrometry. Analysis of the dependence of the temperature distribution on the distance measured from the contact plane showed that in the temperature range of $750$–$1700$ K, the temperature field is symmetrical, which, in accordance with the experiment, is maintained with a successive pressure increase $(49{,}~77{,}~105$ kPa$)$ and with a change in the polarity of the direct electric current. According to Fourier's law, the symmetry of the temperature field means achievement of a symmetrical distribution of the heat flux rate relative to the contact plane. The symmetry of the temperature field and heat flux rate entails the fulfillment of boundary conditions of the fourth kind in the contact plane.