Investigation on the friction coefficient between graphene-coated silicon and glass using barrel compression test

Graphene-coating on silicon wafer can prevent adhesion between silicon and glass in precision glass compression molding. The main goal of this research is to evaluate the graphene/glass interface friction coefficient, which dictates the flow behavior of glass and the durability of the silicon mold. In this research, barrel compression tests using BK7 glass were conducted at different molding temperatures. The purpose of the tests was to obtain the glass cylinder's axial displacement history and the final dimensions after pressing, both of which were decided by the friction coefficient. First, the friction coefficients were estimated by the empirical equations. Then, finite element analysis was implemented to simulate the friction behavior in the pressing stage. The roles of friction coefficient, molding temperature, and applied force were discussed separately. By comparing the experimental and numerical simulation results, both the axial displacement history plots and friction calibration curves show that the best matching friction coefficient is between 0.20 and 0.25 in the temperature range of 660-700°C. Furthermore, the specific friction coefficient values in the same temperature range were calculated using linear interpolation of the friction calibration curves, and showed good agreement with the results from the empirical equation. This study also demonstrated that the friction in the graphene/glass interface has no direct correlation with test temperature. In summary, this study revealed graphene coating's extraordinary low and stable friction behavior at high molding temperatures.