Energetic Characteristics of Hydrophobic Porous Materials as Candidates for Manufacturing of Nanorockets.

A new propulsion mechanism for nano- and microrocket engines is hypothesized. It is based on the instantaneous expulsion from hydrophobic nanopores triggered by irradiation from electromagnetic microwaves, ultrasound, or sudden pressure release. A large energy output is needed for the propulsion of a nanoparticle, and the value can be determined experimentally and by means of atomistic simulations. As such, we measured the heat of intrusion of water into ITQ-29 (LTA) pure silica zeolite with cage structure of pores. The heat effect is exothermic and equal to -7.3 ± 0.8 J/g of zeolite. Similar values were reported for chabazite, ZIF-8, and grafted mesoporous silica EVA. All these materials have cage structures of pores. In contrast, silicalite-1 (MFI) zeolite with a channel structure of pores exhibits endothermic intrusion. Molecular dynamics simulations of pure silica zeolites with LTA, CHA, and MFI topologies at a broad range of water loadings show that water becomes thermodynamically stable in cage-shaped pores while it is unstable in channel-shaped pores. A large energy release is expected during water expulsion from channel-type pores.