This study is devoted to the confinement effects on freezing and melting in electrochemical systems containing nanomaterial electrodes and liquid electrolytes. The melting of nanoparticles formed upon freezing of liquids confined in pores of disordered nanostructured n-type silicon has been studied by low-temperature differential scanning calorimetry. Experimental results obtained for deionized water, an aqueous solution of potassium sulfate, and n-decane are presented. A model is proposed for predicting the melting point of nanoparticles formed during freezing of liquids inside the pores of a disordered nanostructured material. The model is based on the classical thermodynamic concept of the phase transition temperature dependence on the particle size. It takes into account the issues arising when a liquid is dispersed in a matrix of another material: the effect of mechanical stress resulted from the difference in the thermal linear expansion coefficients at a temperature gradient, the effect of the volumetric liquid content in the matrix, the presence of a nonfreezing liquid layer inside the pores, and the effect of wettability of the matrix with the liquid. Model calculations for water and n-decane confined in nanostructured silicon matrix have been carried out considering the volumetric liquid content. The results obtained have been compared with the differential scanning calorimetry data.
Keywords: bulk density of strain energy; differential scanning calorimetry; electrode; electrolyte; melting point depression; modeling; nanostructured silicon.