Liquids with High Compressibility

Abstract

Compressibility is a fundamental property of all materials. For fluids, that is,gases and liquids, compressibility forms the basis of technologies such aspneumatics and hydraulics and determines basic phenomena such as thepropagation of sound and shock waves. In contrast to gases, liquids arealmost incompressible. If the compressibility of liquids could be increasedand controlled, new applications in hydraulics and shock absorption couldresult. Here, it is shown that dispersing hydrophobic porous particles intowater gives aqueous suspensions with much greater compressibilities thanany normal liquids such as water (specifically, up to 20 times greater overcertain pressure ranges). The increased compressibility results from watermolecules being forced into the hydrophobic pores of the particles underapplied pressure. The degree of compression can be controlled by varying theamount of porous particles added. Also, the pressure range of compressioncan be reduced by adding methanol or increased by adding salt. In all cases,the liquids expand back to their original volume when the applied pressure isreleased. The approach shown here is simple and economical and couldpotentially be scaled up to give large amounts of highly compressible liquids.