UC San Diego

Nanoporous materials are involved in many industrial processes such as catalysis, filtration, chromatography, etc. Recently, they are applied to absorb or capture the energy associated with blast, collision, and impact attacks. In such applications, the nanoporous materials are immersed in liquids or gels. The inner surfaces of nanopores are usually modified to increase the degree of hydrophobicity. When an external pressure is applied on the system, the liquid phase can be compressed into the nanoporous space. The liquid infiltration behavior in the nanopores becomes significantly different from that of untreated material. The effective interfacial tension and viscosity of the confined liquid are investigated. While the simple superposition principle can be employed for the analysis of interfacial tension, in a nanopore the effective liquid viscosity is no longer a material constant. It is highly dependent on the pore size and the loading rate, much smaller than its bulk counterpart. In addition, the influence of electrolyte concentration as well as its dependence on temperature are analyzed in detail. As the electrolyte concentration varies, the effective interfacial tension changes rapidly. The testing data show that, the pressure-induced infiltration behavior is not only determined by the cations, but also highly dependent on the anion species. The transport behaviors of solvated ions in nanopores can be field responsive, providing a novel method to develop interactive protection systems. As an external electric field is applied, the observed change in effective solid-liquid interfacial tension is contradictory to the prediction of classic electrochemistry theory. To simplify the materials handling, a polypropylene-matrix composite material is produced. When the temperature is relatively low, the matrix dominates the system behavior. When the temperature is relatively high, with a sufficiently large external pressure the polymer phase can be intruded into the nanopores, providing an energy absorption mechanism