Summary: The mechanical behavior of rock salt is rate‐dependent at different time scales. Using caverns in rock salt formations for renewable energy storage implies that the underground structures are subjected to both short‐term and long‐term loads, increasing robustness and flexibility requirements for numerical simulators used to assess the safety of such structures. So far, explicit time integration with model‐specific heuristics for time‐step size determination dominate in application studies. In this paper, the suitability of error‐controlled adaptive time‐integration schemes of the diagonally implicit Runge‐Kutta type is investigated in comparison with the Backward Euler and Crank‐Nicolson schemes when applied to the integration of typical elasto‐visco‐plastic constitutive models of rock salt. The comparison is made both for monotonic and for cyclic loads as well as taking account of thermo‐mechanical coupling. Analyses of the time‐integration errors and the time step‐size evolution show the suitability of the integration scheme for these material models. The automatic adjustment of the time‐step size was found to be robust across all material models and boundary conditions as well as for non‐isothermal situations for a single algorithmic parameter set.

The present work used hydrothermal synthesis method utilizing glucose as carbon source to obtain homogeneous nano-sized carbon spheres. The holding time and the concentration of glucose have a remarkable effect on the microstructure of nanometer carbon spheres. When synthesized at a constant temperature and kept the same in the productivity, the lower concentration of glucose or the shorter holding time, the easier to acquired homogeneous and tiny nanometer carbon spheres