Formation of New Polymorphs of Carbon and Fluid Flow Patterns by Irradiation of Solid Carbons with a CO2 Laser

摘要

Several varieties of solid carbon under a blanket of rare gas near atmospheric pressure were irradiated at power densities up to about kw/sq cm with focused 10.6-micrometer-wavelength radiation from 0.25- to 30-kw continuous CO2-N2-He lasers. Craters or holes were formed that were lined and surrounded with light-reflecting 'white deposits. This material exhibited a high incidence of patterns of chaoite ('white' carbon) when examined by transmission and reflection electron diffraction. When both static and rapidly spinning samples of carbon were exposed to the laser radiation, deposits were formed with shapes that strongly suggested that the laser produced liquid carbon at pressures close to 1 atm. Finally, the production of crystal forms of carbon other than graphite or diamond at atmospheric pressure or below indicates that there are probably serious inconsistencies in the low-pressure region of the currently accepted phase diagram of carbon. (Author)