Difficult carbonaceous materials and their infra-red and Raman spectra. Reassignments for coal spectra

✍ Scribed by R.A. Friedel; G.L. Carlson

• Publisher: Elsevier Science
• Year: 1972
• Tongue: English
• Weight: 627 KB
• Volume: 51
• Category: Article
• ISSN: 0016-2361
• DOI: 10.1016/0016-2361(72)90079-8

✦ Synopsis

Infra-red and Raman spectra of intractable carbonaceous materials are difficult to obtain. For coals, carbon blacks, and some chars infrared spectra have been obtained with relative ease. Only recently have good infra-red transmission spectra of activated carbons been obtained. More difficult materials have now been successfully studied by the transmission infrared method, most notably ground graphite (non-crystalline), through the use of efficient and extensive grinding. Intense infrared bands are observed at about 1590 and 1360 cm-t for ground graphite, carbon blacks, and some activated carbons. Laser-Raman spectra of coals, carbons, and graphites have two lines at about the same frequencies as the infra-red bands. However, the similarity of these laser-Raman spectra indicates in the case of coal that we may be observing the spectrum of carbonized coal rather than of coal, due to degradation of the sample by the laser beam. These new spectral results necessitate reassignment of some bands in the infra-red spectra of coals. Graphitic structures (non-crystalline) are believed to be responsible for the 1600 cm-l band in coals and the broader 1360 cm-l band, which fit closely the broad band contour in the infrared spectra of coals from 1800 to 900 cm-'. The intensities of the 1600 and 1360 cm-l bands in ground graphite are more than sufficient to account for the band intensities observed in the spectra of coals and chars. Diamond-like structures such as quaternary carbon atoms are weak absorbers and cannot be responsible for either of these bands.