| Tensile strength
and liquids do not seem to combine easily. They do however. Liquids can
exist in metastable states if there is an energy barrier to the formation
of droplets of a second phase in a homogeneous metastable parent phase.
The nucleation of the phase transition is assumed to be accomplished by
the thermal activation of incipient droplets of the second phase over
top the top of this barrier. One avenue to increase the probability to
overcome the barrier is to heat (superheat) the liquid. Such rapid superheatings
were published in Physical Review B for liquid
helium-3. |
| The tensile strength
of water has been subject to measurement for over 150 years. Not unexpectedly,
it turns out that it has an important consequence in nature: the height
of trees is determined by the fact that water can sustain a tensile strength.
Was this not the case, trees would not exceed about 10 m in height. The
tensile strength also plays a role in dispersal of spores of certain ferns. |
| The first measurement
of the tensile strength of liquid helium was measured in this laboratory
after many fruitless attempts by many other researchers. The obstacle
to overcome is heterogeneous nucleation of the vapor phase. Many causes
contribute to the heterogeneous nucleation, such as: formation of the
vapor phase at a surface, nucleation induced by cosmic rays, and nucleation
due to the presence of foreign gases dissolved in the liquid. |
| The approach developed
by us determined the tensile strength of a liquid was as follows. The
cavitation limit was reached by focusing a short burst of ultrasound into
a small volume of helium and detecting the onset of cavitation by the
scattering of laser light. The first presentation was at the Cryogenic
Engineering Conference in 1987 and published in the proceedings. |
| Subsequent papers
were published in Physical Review B and J.
Applied Physics. In another paper, the tensile strength of nitrogen
was measured. |
| |
| A cute review without
the reference to the truly first, pioneering, original, and correct experiment
at negative pressures in liquids and liquid helium in particular is: http://www.aip.org/pt/feb00/maris.htm |