(598g) Stability Limit of Water at Negative Pressure

Pure liquid water can reach and sustain negative pressure, as large as P~ -190 MPa at room temperature [1]. A number of different thermodynamic paths have been explored to reach negative pressure in liquid water [1]. However, only the isochoric cooling of mineral inclusion method [2] has shown to reach the large negative pressure close to theoretically predicted homogeneous nucleation limit. All the other methods, including acoustic cavitation [3], centrifugation [4], and metastable vapor-liquid equilibrium (MVLE) [5], [6] showed 5 folds or greater reduction in tension that they measured.

In this study, we use the MVLE method previously introduced by Wheeler and Stroock [5], [6] in order to generate large tension in liquid water. In MVLE method, a bulk volume of liquid water is separated from water vapor phase by nanoporous membrane, and is allowed to equilibrate with sub-saturated water vapor through the membrane. The equilibrium with sub-saturated vapor lowers the pressure of liquid below its saturation value, as described by Kelvin-Young-Laplace equation [7]. Using poly-hydroxyethyl methacrylate hydrogel (pHEMA) as the membrane [6], the cavitation pressure of P~-22 MPa was obtained, and the origins to the failure to reach the homogeneous nucleation limit in MVLE method remain inconclusive [6]. In this study, we replace the pHEMA membrane with nanoporous silicon membrane, and find the average cavitation pressure at P~-40MPa, with some samples holding tension as large as P~-88MPa, near the kinetic homogeneous nucleation limit at room temperature. We discuss our investigation of possible nucleation mechanisms in our system and the conjecture for thermodynamic path-dependent cavitation limit of liquid water. 

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[5] Wheeler T D and Stroock A D, Nature, 455, 208 (2008)

[6] Wheeler T D and Stroock A D, Langmuir, 25, 7609 (2009)

[7] Rowlinson J S and Widom B, Molecular Theory of Capillarity; Clarendon Press: Oxford, (1982)

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