Characterization of vapour plume species and deposition residues resulting from pulsed laser ablation of a graphite/epoxy composite

Abstract

Form Approved REPORT DOCUMENTATION PAGEOMB maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information 14. ABSTRACT A modified time-of-flight mass spectrometer fitted with a special collection stage for carbon-coated transmission electron microscope specimen grids is used to monitor laser-pulse ablation products from graphite/epoxy composite targets. Scanning electron microscopy observations show ablation damage to consist of matrix pyrolysis, fibre fracture and spallation of fragments which include elemental hydrogen, carbon epoxide and acetylene groups. SPONSORING I MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) SPONSORIMONITOR'S REPORT NUMBER(S)Transmission electron microscope examination of specimen grids showed a variety of crystals and polycrystalline hexagonal graphites having a wide range of shapes including spheres and faceted polyhedra and platelets, textured flake structures, microrosettes. These observations lend some credibility to a model for laser-shock and pyrolysis effects which create molecular plume fragments and deposition fragments of hexagonal graphite. A modified time-of-flight mass spectrometer fitted with a special collection stage for carbon-coated transmission electron microscope specimen grids is used to monitor laser-pulse ablation products from graphite/epoxy composite targets. Scanning electron microscopy observations show ablation damage to consist of matrix pyrolysis, fibre fract. and spallation of fragments which include elemental hydrogen, carbon epoxide and acetylene groups. Transmission electron microscope examination of specimen grids showed a variety of crystals and polycrystalline hexagonal graphites having a wide range of shapes including spheres and faceted polyhedra and platelets, textured flake structures, and microrosettes. These observations lend some credibility to a model for laser-shock and pyrolysis effects which create molecular plume fragments and deposition fragments of hexagonal graphite. SUBJECT

Computerization of Spectral Recording and Processing for Laser-Pyrolysis/Time-of-flight Mass Spectrometry

“…Over the past three decades, LP/TOFMS has been utilized to study such diverse topics as rapid heating of coals, 3 characterization of polymers, 4 heat-shield ablation on the surface of space vehicles during re-entry, 5 the mechanism of polymer degradation in polymer combustion and flame retardancy 6,7 and laser blow-off of polymer composites. 8 The recent resurgence of interest in time-of-flight mass spectrometry 9 and the growing requirements for application of high temperature and laser techniques in modern science and technology will offer more opportunities for the application of LP/TOFMS in the future.…”