Apparatus for processing of samples at high pressures and high temperatures in a fast quenching-rate regime and synthesis of polyacetylene by pulsed laser heating of confined carbon thin films

Abstract

The pulsed laser heating of confined samples followed by ultrafast cooling constitutes an interesting route to explore the production of new phases and compounds. Indeed, in some cases the ultrafast cooling allows retaining at ambient conditions species that were produced under extreme conditions. The experimental setup described in this work allows the heating of thin film samples to temperatures ranging from 1400 to 5500 K, in a controlled and measurable way, with estimated cooling rates in excess of 1011 K s -1. In this paper, we show that the pulsed laser heating of thin amorphous carbon films deposited on copper substrates leads to the formation of polyacetylene in peak temperatures ranging from 1400 to 2600 K and static pressures between 0.8 and 1.1 GPa. The probable source of hydrogen was tracked to the small amount of water physically adsorbed at the carbon film/copper gasket interface. Because of the fast heating and cooling rate in these experiments, the hydrogen formed by water dissociation at high temperatures does not have enough time to diffuse out of the reaction cell. The results here reported strongly suggest that the evolution and stability of carbon-rich species produced by pulsed-laser heating at high pressure and high temperature critically depends on the capability of hydrogen retention in the reactional system.