We report molecular simulation studies on the interaction forces between silica nanoparticles in supercritical carbon dioxide at 318 K. Our goal is to find a better understanding of the interparticle solvation forces during rapid expansion of supercritical solutions. The parameters for interatomic potentials of fluid-fluid and solid-fluid interactions are obtained by fitting our simulations to (i) experimental bulk C O2 phase diagram at a given temperature and pressure and (ii) C O2 sorption isotherms on silica at normal boiling and critical temperatures. Our simulations show that the interaction forces between particles and supercritical C O2 at near-critical pressure of p=69 atm (i.e., slightly below critical condition) reaches a minimum at distances of 0.5-0.8 nm between the outer surfaces of the particles and practically vanishes at distances of approximately 3 nm. The attraction is most prominent for densely hydroxylated particle surfaces that interact strongly with C O2 via hydrogen bonds. The effective attraction between silica and C O2 is significantly weaker for dehydroxylated particles. We also compared fluid sorption and interparticle forces between supercritical C O2 and subcritical nitrogen vapor, and our results showed qualitative similarities, suggesting that the C O2 configuration between the particles resembles a liquidlike junction.