Abstract
The «sessile drop» method for determining the surface energy of solids – γ is considered. For graphite and graphene, this method yielded average values of γ2 = 53.6 ± 2.1 and γ1 = 44.8 ± 14.7 mJ/m2. Using the crystal cleavage method for graphite, the average value of γ2 = 3250 mJ/m2 was obtained, which is 60 times higher than the value of γ2 obtained by the "sessile drop" method. Analysis of both methods showed that the "sessile drop" method for determining the surface energy of solids cannot be used without modification. We propose new methods for determining the surface energy of solids: 1) through the melting point of a solid; 2) through the size dependence of a physical property on the thickness of the deposited coating; 3) through the measured value of the contact potential difference. The following values were obtained for graphene: γ1 = 947.1; γ1 = 974; γ1 = 960 mJ/m2, which is an order of magnitude higher than in the sessile drop method. The values of γ1 must be multiplied by 3 and we obtain the values for graphite – γ2 = 2841; γ2 = 2922, γ2 = 2880 mJ/m2, which differs slightly from the crystal splitting method.