Optical properties of carbonaceous dust analogues
1998; EDP Sciences; Volume: 332; Issue: 1 Linguagem: Inglês
ISSN
1432-0746
AutoresC. Jäger, H. Mutschke, Th. Henning,
Tópico(s)Carbon Nanotubes in Composites
ResumoStructurally different carbon materials with an in- creasing sp 2 /sp 3 ratio were synthesized by pyrolizing cellulose materials at 400, 600, 800 and 1000 o C. The hybridization ra- tiosandtheinternalstructuresinthesesamplesweredetermined by using High Resolution Transmission Electron Microscopy, Electron Energy Loss Spectroscopy, Raman spectroscopy, IR spectroscopyandelementalcombustionanalysis.Thepyrolized carbon samples were embedded in an epoxide resin and the sur- face was grinded and polished. The reflectance of the samples could be measured in the range between 200 nm and 500 m, coveringmostofthespectralrangerelevantforradiativetransfer calculations. Using the Lorentz-oszillator t method we were able to determine the optical constants n and k. A big change in the optical behaviour could be seen between 600 and 800 o C, which is caused by the presence of free charge carriers in the samples pyrolized at 800 and 1000 o C. In these samples the graphiticareashavebeengrowntoabout1.5 nminsize.Theab- sorption behaviours of small spheres in the Rayleigh limit and a continous distribution of ellipsoids (CDE) were calculated. The spectral index in the FIR region (100 m) increases from 1.2 for the very disordered still aliphatic-dominated carbon ma- terial pyrolized at 400 o C to 2.2 for the more ordered graphitic sample carbonized at 1000 o C in case of spherical particles. In the more graphitic samples pyrolized at 800 and 1000 o C, the spectral index is strongly dependent on the shape of the particles.
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