UC San Diego

For many decades, people have been actively investigating high-performance energy absorption materials, so as to develop lightweight and small-sized protective and damping devices, such as blast mitigation helmets, vehicle armors, etc. Recently, the high energy absorption efficiency of nanoporous materials functionalized (NMF) liquids has drawn considerable attention. A NMF liquid is usually a liquid suspension of nanoporous particles with large nanopore surface areas (100 - 2,000 m²/g). The inner surfaces of nanopores mush be non-wettable to the liquid phase. The liquid can enter the nanopores only when a sufficiently high external pressure is applied. During the pressure induced infiltration, mechanical work is converted to solid-liquid interfacial energy. At the equilibrium state, E = Äã·A, where Äã = rPin/2, Äã is the effective solid-liquid interfacial tension, A is the nanopore surface area, r is the effective pore radius, and Pin is the infiltration pressure. In order to understand the energy absorption behaviors of NMF liquid, we investigate nanofluidic behaviors in hydrophobic nanoenvironments, which is different from continuum fluids in terms of structures, length scale, time scale geometry surface properties, electrolyte, effective flow rate, profile, etc. The current research on NMF liquids is focused on 1) the anion effects on the ion transport pressure, 2) the inner surface group length effects, 3) electrically responsive energy absorption behaviors, 4) the relation between the functional surface group density and the energy absorption behaviors, 5) primary particle size effects, 6) the repeatability of the energy absorption behaviors, and 7) simple, cost-efficient synthetic methods of a nanoporous silica