Analysis of Gas-Phase Clusters Made from Laser-Vaporized Icosahedral Al−Pd−Mn
An icosahedral Al-Pd-Mn quasicrystal sample is laser vaporized to form metal clusters by gas aggregation. The clusters are subsequently laser ionized and mass analyzed in a time-of-flight mass spectrometer. The mass spectra show cluster compositions which are qualitatively similar to that of the sample. This is consistent with a kinetically controlled cluster growth process. Cluster thermodynamic stability is probed by multiphoton ionization/fragmentation, which induces primarily Al and Mn loss. The resulting spectra are composed of a series of Pd-rich Al-Pd clusters. The average cluster composition is 60 (′1)% Pd. This composition is close to a known eutectic in the Al-Pd system. When manganese is seen on these clusters, it is always in units of Mn 3 . These results are discussed in terms of relative binding strengths in the Al-Pd-Mn alloy system.
Ultrashort pulsed laser vaporisation of icosahedral Al Pd Mn
Abstract In this work, Al 70 Pd 20 Mn 10 quasicrystalline targets were evaporated by a doubled Nd:glass laser with a pulse duration of 250 fs. The produced plasma has been analysed by time of flight mass spectrometry, optical emission spectroscopy and fast imaging. The results indicate that the plume is more complex as compared to other quasicrystalline systems with the presence of quite large clusters and with a higher ionisation degree. The analyses on the deposited films indicate that the vaporisation is not congruent.
High-temperature straining stage for in situ experiments in the high-voltage electron microscope
Abstract A new double-tilting straining stage for in situ deformation in the high-voltage electron microscope at temperatures above 1000°C has been designed to directly investigate plasticity and fracture of ceramics. The deformation equipment is mounted in a tilted cone of a top entry tilting stage. The load train consists of both a fixed and a moveable lever. The deformation is driven by the thermal extension of a stainless steel rod. The specimen grips are heated by electron bombardment via filaments in a notch of each grip. The heat is led away by water cooling in the levers as well as in the tilted cone. The force acting on the specimen can be measured by a bridge of four semiconducting strain gauges. First experiments have been performed on silicon between 530°C and 780°C and on silicon nitride ceramics and cubic and t'-zirconia single crystals at about 1150°C.