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.