Lifetime of superheated water in a micrometric synthetic fluid inclusion

International audienceA synthetic pure water fluid inclusion presenting a wide temperature range of metastability (Th - Tn ≈ 50°C; temperature of homogenization Th = 144°C and nucleation temperature of Tn = 89°C) was selected to make a kinetic study of the lifetime of an isolated microvolume of superheated water. The occluded liquid was placed in the metastable field by isochoric cooling and the duration of the metastable state was measured repetitively for 7 fixed temperatures above Tn. Statistically, measured metastability lifetimes for the 7 data sets follow the exponential Reliability distribution, i.e., the probability of non nucleation within time t equals . This enabled us to calculate the half-life periods of metastability Τ for each of the selected temperature, and then to predict Τ at any temperature T > Tn for the considered inclusion, according to the equation Τs , (∃T = T - Tn). Hence we conclude that liquid water in water-filled reservoirs with an average pore size ≈ 104 µm3 can remain superheated over geological timelengths (107s), when placed in the metastable field at 10°C above the average nucleation temperature, which often corresponds to high liquid tensions (≈ -120 -70 MPa)

Lifetime of superheated water in a micrometric synthetic fluid inclusion

A synthetic pure water fluid inclusion presenting a wide temperature range of metastability (Th - Tn ≈ 50°C; temperature of homogenization Th = 144°C and nucleation temperature of Tn = 89°C) was selected to make a kinetic study of the lifetime of an isolated microvolume of superheated water. The occluded liquid was placed in the metastable field by isochoric cooling and the duration of the metastable state was measured repetitively for 7 fixed temperatures above Tn. Statistically, measured metastability lifetimes for the 7 data sets follow the exponential Reliability distribution, i.e., the probability of non nucleation within time t equals . This enabled us to calculate the half-life periods of metastability τ for each of the selected temperature, and then to predict τ at any temperature T > Tn for the considered inclusion, according to the equation τ(s) = 22.1 × e1.046×ΔT , (ΔT = T - Tn). Hence we conclude that liquid water in water-filled reservoirs with an average pore size ≈ 104 µm3 can remain superheated over geological timelengths (1013s), when placed in the metastable field at 24°C above the average nucleation temperature, which often corresponds to high liquid tensions (≈ -50 MPa)

Experimental superheating of water and aqueous solutions

International audienceThe metastable superheated solutions are liquids in transitory thermodynamic equilibrium inside the stability domain of their vapor (whatever the temperature is). Some natural contexts should allow the superheating of natural aqueous solutions, like the soil capillarity (low T superheating), certain continental and submarine geysers (high T superheating), or even the water state in very arid environments like the Mars subsurface (low T) or the deep crustal rocks (high T). The present paper reports experimental measurements on the superheating range of aqueous solutions contained in quartz as fluid inclusions (Synthetic Fluid Inclusion Technique, SFIT) and brought to superheating state by isochoric cooling. About 40 samples were synthetized at 0.75 GPa and 530-700 °C with internally-heated autoclaves. Nine hundred and sixty-seven inclusions were studied by micro-thermometry, including measuring the temperatures of homogenization (Th: L + V → L) and vapor bubbles nucleation (Tn: L → L + V). The Th-Tn difference corresponds to the intensity of superheating that the trapped liquid can undergo and can be translated into liquid pressure (existing just before nucleation occurs at Tn) by an equation of state. Pure water (840-935 kg m−3), dilute NaOH solutions (0.1 and 0.5 mol kg−1), NaCl, CaCl2 and CsCl solutions (1 and 5 mol kg−1) demonstrated a surprising ability to undergo tensile stress. The highest tension ever recorded to the best of our knowledge (−146 MPa, 100 °C) is attained in a 5 m CaCl2 inclusion trapped in quartz matrix, while CsCl solutions qualitatively show still better superheating efficiency. These observations are discussed with regards to the quality of the inner surface of inclusion surfaces (high P-T synthesis conditions) and to the intrinsic cohesion of liquids (thermodynamic and kinetic spinodal). This study demonstrates that natural solutions can reach high levels of superheating, that are accompanied by strong changes of their physico-chemical properties

Size Effect in Metastable Water

International audienceWe experimentally determined the maximum tension in synthetic fluid inclusions from the differ ence between the temperatures of homogenization (Th) and spontaneous vapor nucleation (Tn). At temper atures of 100-200°C, liquid water may exist at negative pressures of up to 100-150 MPa. Owing to an increase in surface tension, the effect is even more significant in salt solutions and occurs at higher tempera tures. A decrease in the linear dimension of fluid phase by an order of magnitude and, correspondingly, a three orders of magnitude decrease in volume (which is proportional to R3) increase the maximum tension by ~25MPa. Tension in the liquid phase of water-salt systems may be higher than ~200 MPa without cavitation. Metastability of water and salt solutions in small sized vacuoles generates stresses in the fluid-mineral system resulting in high solubilities of solid phases. An increase in volume due to coalescence of small inclusions or vanishing of metastability results in an abrupt decrease in supersaturation

Vapour nucleation in metastable water and solutions by synthetic fluid inclusion method.

Experimental data for temperatures of homogenization (Th, L+V->L) and vapour phase nucleation (Tn, L

Experimental superheating and cavitation of water and solutions at spinodal-like negative pressures

International audienceThe superheated liquids are metastable with respect to their vapour, what means they can exist under arid conditions whatever the temperature: capillary liquid extracted from arid soils (desert shrubs, Mars sub-surface, ...), solutions in the deep Earth crust, or water involved in rapid disequilibrium events (terrestrial or submarine geysers). The superheating state changes the solvent properties of liquids, and so modifies phase transitions (solid-liquid, liquid-vapor) P-T-X conditions. The synthetic fluid inclusion (SFI) enables to fabricate micro-volumes of hand-made liquid dispersed inside quartz, which readily superheat. Volumes of SFI are intermediate between macro-systems, in which superheating is restricted to around -30-35 MPa with very short lifetime, and nanosystems, wherein confinement effects predominate and in which the host size is similar to the one of the critical nucleus of vapour phase (huge nucleation barrier). This volume-to-metastability relationship is still to be defined quantitatively, and we are targeting to combine thermometric classical measurements with spectrometric characterizations, enabling to establish the threshold between micro- and nano-systems precisely. Meanwhile, the experiments performed so far illustrate the diversity of contexts and situations that could be impacted by superheating issues

Superheating water to model soil " immobile " water

International audienceSuperheating The superheated liquids are less stable than their vapour, while their criteria of internal stability are met. They can be produced when an increasing T or a decreasing internal P (including negative pressure, or liquid tension) beyond the stable values is produced in liquid in such conditions that vapor does not nucleate. This nucleation suppression can be reached in nature either during a short time by a very rapid P or/and T variation (phreatomagmatism, for instance), or by decreasing the air humidity at a liquid-air interface located in infra-micronic container (soil capillarity, for instance). The method of choice to experimentally probe superheating is the micro-thermometry of fluid inclusions [1], that can be designed in terms of composition and density of occluded liquids (in quartz). Their volumes are intermediate between macro-systems, in which superheating is restricted to low tensions with very short lifetime, and nanosystems, wherein the host matches the size of the critical vapor nucleus. Properties and behaviours of interes

Rétroactions Porosité - Réactivité

International audienceLa structure des milieux poreux est de première importance lorsqu’on étudie les propriétés de transport, avec un intérêt dirigé versla taille des pores et la topologie 3d. Les propriétés réactives ont également des liens très forts avec la structure, et même la micro-structure, notamment la géométrie et la composition locales, les états de surface, des phases dissoutes et solides. Dans cette contribution, nous nous intéressons aux relations spécifiquement entre taille et réactivité, pour déterminer quelle est l’échelle dimensionnelle où les propriétésde l’eau porale changent. Trois situations contrastées sont étudiées : (1) l’eau est abritée dans un pore de grande taille (plusieurs dizaines de microns) ; (2) l’eau liquide est confinée entre deux surfaces de silice ; (3) une épaisseur d’eau entre 0.5 et quelques micromètres est déposée sur une surface. Deux types d’échantillons abritent ces situations : une inclusion fluide de quartz, c’est -à-dire une vacuole fermée au cœur même du solide, contenant soit seulement de l’eau liquide, soit un mélange biphasique eau-air; des canaux de nano-fluidique, à base de silicium monocristallin, dont la hauteur varie entre 5 et 100 nm. Des mesures infra-rouges ont été menées sur cette eau piégée, et les signaux enregistrés sont examinés en fonction de la hauteur de canaux ou de l’éloignement à l’interface.Ces mesures sont ensuite converties en propriétés thermodynamiques en champ moyen et les prédictions en termes de transitions de phase calculées par simulation thermodynamique

Chemo-mechanical coupling at the one-pore scale: fracturing quartz hostby increasing tension in water inclusion

International audienceWater-bearing porous media allow the infilling liquid to become superheated much easily than anyother system. Superheating liquids make them prone to develop a tensile state, that is to say an internalnegative liquid pressure or tension. In this sense, superheated liquid is a close analogue to capillarywater retained in many not-saturated porous media (unsaturated zone of soils, gas/oil-depletedaquifers, CO2-storing aquifers). In granular physics, the role of capillary water tension to rigidify thegranular assemblage is studied for long (sand–castles physics) but little attention has been turned tothe same effect in compacted/continuous systems (rock fissures, fluid inclusions, intra-mineralcavities, etc.).Using synthetic fluid inclusions trapped in quartz, we were able to put the occluded liquid (aqueoussolution, CsCl 12m) at very high tension by isochoric cooling of the samples. Starting with aliquid-vapour assemblage, we heat the sample up to a special temperature at which the vapour bubbledisappears (temperature of homogeneization, Th), and then turn to a cooling procedure that decreasesthe internal pressure of the occluded liquid at constant volume, as long as the bubble does notre-appear again (relaxing the tensile state of the liquid). At a given tension state, we mapped theRaman spectra at the two quartz bands frequencies, in the quartz matrix all around the inclusion undertension. Using frequency-pressure calibration of the literature, it turned out that the quartz host wassubmitted to a small compressive stress in response to the perpendicular traction from the liquid.In a second step, one sample was submitted during one month to repetitive cycles ofsuperheating-relaxation processes, after which the volume of the inclusion changed brutally. This wasrecorded by a change of the liquid density measured through a significant Th shift. In the meantime,another sample was submitted to a constant tension which, after a while, provoked the visiblefracturation of the quartz matrix.These observations and measurements demonstrate that the tension of water occluded in pores, orchannels, or any type of cavities in solids, organics or living cells, is able to exert a stress onto the hostsolid, quantitatively weak. However, it appears that the recurrence of such effect and/or itspreservation through time, create a fatigue in the host that is ultimately able to break out its cohesion,certainly owing to pre-existing matrix defaults. Consequences in terms of chemo-mechanical couplingin hydrosystems or materials submitted to wetting-drying cycles will be eventually highlighted

Water-solid interactions at the pore scale

International audienceWater and aqueous solution confined in restricted volumes (pore, channels, intra-solid cavities, etc) are largely encountered everywhere in nature, and their thermochemical properties define the possible driving forces of their interactions with any phase(s) of interest locally present. At given (T,Ptotal) pairs, liquids are considered to be bulk materials, except when the confinement reaches the nanometric scale. Despite this very usual choice, a growing number of evidences points to the existence of an intermediate-sized domain (1 μm - 50 nm) in which the interaction behaviors seems to change, most probably due to thermodynamic driving forces. This contribution reports on dedicated recent experiments, the measurements of which can be interpreted assuming modified reactive properties in the system