To investigate effects of mechanical sealing on negative pressures in water/metal tube Berthelot systems, trends in negative pressure are observed through runs of temperature cycles below 90˚C in two systems made of metals having small amounts of gas inclusions. The first system is a pre-degassed all-stainless-steel tube/plug system. The steel is a special product for vacuum engineering. The second is the same tube sealed with plugs made of silver solidified one-dimensionally in a vacuum furnace. A new type of trend, stagnation for intermediate cycles is found in both systems so long as sealing distortion of each plug is small in amount. The stagnation period for the first system is longer than that for the second one. A metallurgical mechanism of a gas-being-replenished crevice model is proposed: distorted parts of metals undergo heat-treatment during runs of temperature cycles, and the heat-treatment enhances the rates of impurity gas transports to crevices on the metal surface where cavitation occurs, and the transport causes the stagnation for cycles during which the rates are still high.

Trends in negative pressures and cavitation events were investigated for a Berthelot system comprising a water/stainless steel tube (SUS 316)/sealing Ni plug. When the system was repeatedly heated and then cooled over an appropriate temperature range (temperature cycle), negative pressure was usually found to increase with the cycle. A de-gassing pre-treatment for the sealing metal above 350 degrees C provided a retardation in the increasing trend; and, despite this, an eventual higher negative pressure than that attained for a metal which was non-de-gassed. Underwater pre-pressurization for the plug at a few kbar exhausted weak gaseous nuclei efficiently. Heterogeneous nuclei which still crept into the system were exhausted by temperature cycles after closing the system. The pre- and post-treatment conditioning led to a rise in negative pressure to -170 bar for about 1 g of water (the highest value ever recorded in a metal tube) at 59 degrees C after a total of 1500 temperature cycles. The result shows the potential of a metal Berthelot tube with which high static negative pressure can be achieved in useful volumes of liquids.

Trends in negative pressure achieved over a few thousand cavitation events were observed for ethanol, benzene and xylene in a stainless steel Berthelot tube sealed with a pre-de-gassed Ni plug. When the system was repeatedly heated and then cooled alternately over a temperature range between 60 degrees C and 10 degrees C (temperature cycle), negative pressure increased steeply for earlier cycles and levelled off eventually as in a water-metal tube system. Owing to the cavitation history effect, negative pressures of around -200 bar, the highest ever attained for organic liquids in the Berthelot method, were generated at around 15 degrees C in a useful volume ( approximately 1 cm3). It has become feasible to measure thermodynamic properties of organic liquids under negative pressure, since the pressures were up to half of the homogeneous nucleation limits of cavitation.

Two series of trends in negative pressure with cavitation in water were observed by the Berthelot method using single- and poly-crystalline molybdenum tubes sealed with single-crystalline copper plugs by repeating runs of temperature cycles at rates of 70-100 cycles/day between 50 and 98 °C, where a run means successive cycles with the same water. The first series were observed while both tubes and plugs were pre-degassed, and the second after exposure of the both tubes alone to N2 gas. The all-single-crystalline-metal tube in the pre-degassed state yielded a steady increase from -120 to -140 bar (1 bar≃0.1 MPa) in the initial 1250 cycles. After its gas exposure the single-crystalline tube yielded a trend having an initial peak of -160 bar followed by a steady fall to -110 bar in the first run, and recovered the capability of yielding a trend levelling around -165 bar throughout the sixth run after a total of about 5000 cycles. In any run cavitation occurred within about ±12 bar around the current average. In contrast, the poly-crystalline Mo tube in the pre-degassed state yielded widely-scattered negative pressures; the higher envelope increased gradually to -140 bar while lower envelope remained to be about -40 bar in the second run to a total of initial 4000 cycles. After similar gas exposure of the tube alone, the deteriorated capability of the poly-crystalline tube was recovered only to -120 bar after a total of 1.2×104 cycles. The results form qualitative evidence of the crucial effects of impurity gas transport in metal bulks on trends in negative pressures of water in metal tubes. The thermodynamic and metallurgical causes of the time consumption for achieving high negative pressure in liquid/metal Berthelot tube systems are discussed.

Trends in negative pressure over a few thousand cavitation events have been investigated for a Berthelot system comprising water/stainless steel/tube/sealing Ni plug in order to study the effects and extents of surface pre-treatments for the sealing metal, polishing, etching, and electroplating. The polishing and etching pre-treatments separated two kinds of cavitation nuclei on the metal surface; gases trapped within pores (crevices) (i) in the metal surface, and (ii) extending deep into the metal bulk. The latter, although much tougher, influenced negative pressure for a thousand cavitation events at most. The rise in negative pressure after a total of 1800 temperature cycles levelled off at around -115 bar (-11.5 MPa) irrespective of the surface finishes of the plugs. Electroplated plugs gave poor increasing trends owing to the co-deposited hydrogen. Impurity gases in the metal did limit the rise in negative pressure. These results, together with those reported before, have validated the authors extended gas-trapping crevice model, negative pressure is eventually limited by a supply of gas from sources in the metal bulk to surface crevices.