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.

A stainless steel container, filled with 1 g of water and sealed with a copper plug, was repeatedly heated and cooled over an appropriate temperature range (temperature cycles). Negative pressures, although scattered, increased with temperature cycle repetition through two stages. The cavitation history effect persisted for continued temperature cycles after renewal of only the water. The authors found two efficient means of raising the negative pressure by the cavitation history effect: (i) a high repetition rate of the conditioning cycles and (ii) using a sealing metal melted and cast under vacuum. Aided by these means, negative pressure was raised to -87 bar at 49 degrees C after 392 cycles repeated over a period of one week, while the maximum value of -76 bar at 46 degrees C was attained after a total of 850 cycles continued for over a month. The results can be interpreted by the gas-trapping crevice model supplemented with a working assumption that crevices on the metal surface are supplied with gas from sources in the metal bulk. A more recent maximum value of -125 bar at 47 degrees C, the highest value ever reported for water in a metal tube, supports the assumption.

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.

The authors made a stainless steel tube with a copper plug to study the effects of cavitation history on negative pressure for a system of water in a metal Berthelot tube. The water and the copper plug were pre-treated for air purging. The system was alternatively heated and cooled over appropriate temperature ranges many times. In the Berthelot method, the negative pressure generated with failing temperature becomes highest just before cavitation for a single heating and cooling procedure (one temperature cycle). Negative pressures for respective temperature cycles, though scattered, exhibited an increasing trend through two stages, a steep stage for earlier cycles and a gradual stage for later cycles. A similar effect of the cavitation history persisted even in a series of temperature cycles after exchanges of water, so long as the same plug was used for sealing. The negative pressure -76 atm (-7.7 MPa), which is higher than the values ever reported for water in a metal tube, developed at 46 degrees C through two water exchanges after a total of 850 temperature cycles. The two-stage increase was considered to be caused by the successive fading of the weaker cavitation nuclei in the system.