2015-Sustainable Industrial Processing Summit
SIPS 2015 Volume 7: Ionic Liquids & Energy Production
| Editors: | Kongoli F, Gaune-Escard M, Mauntz M, Rubinstein J, Dodds H.L. |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2015 |
| Pages: | 310 pages |
| ISBN: | 978-1-987820-30-0 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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CO2 - Laser as a Heating Source for Preparing Materials for Raman Structural Studies of : Glasses, Melts and Graphene / SiC
George Papatheodorou1;1INSTITUTE OF CHEMICAL ENGINEERING SCIENCES- FORTH, Patras, Greece;
Type of Paper: Regular
Id Paper: 268
Topic: 13
Abstract:
This presentation concerns with the use of CO2 - lasers (10.6 µm) as heating source in order to prepare a variety of materials and study their structural properties using Raman spectroscopy.
a) Container-less levitation techniques and CO2-laser heating were used to prepare series of difficult-to-make glasses alkaline earth silicate glasses along the compositional join (1-x) MO-xSiO2 with M=Mg, Ca and x ranging between 0.60 and 0.27; thus reaching compositions beyond the orthosilicate limit (X=0.33). Polarized and depolarized Raman spectra measured at ambient conditions for all these glasses show systematic and smooth band intensity changes with composition indicating the presence of a variety of silicate species. Beyond the x=0.33 limit, the glass structures are characterized by isolated negatively charged 'tetrahedral' SiO44- and O2- anions with M2+ (M =Mg, Ca) as counter cations, held together by pure Coulombic (ionic) interactions
b) Aerodynamic levitation and CO2 - laser melting have been used to synthesize glasses, the yttrium aluminum garnets (YAG) and aluminosilicates of the type zY2O3-yAl2O3-xSiO2. Micro-Raman spectra were used to identify the two polyamorphic LDA (low density) and HDA (high density) phases in these systems. The stability of the LDA phase against crystallization appears to be lower than that of the HDA phase.
c) Self-support melting with CO2-laser techniques were used to obtain in situ quantitative Raman spectra of vitreous and molten silica from 77K to 2200K. The relative intensities of the two 'defect peaks' D1 and D2 associated with the corresponding four- and three-membered ring structures were measured and found to be invariant to temperature. The data show that the vitreous/liquid structure and the ring populations associated with a fictive temperature in the quenching experiments do not reflect by any means the 'equilibrium' structure at that temperature.
d) A novel method for the fast, single-step epitaxial growth of large-area homogeneous graphene film on the surface of SiC(0001) using an infrared CO2 - laser as the heating source is described. Uniform, low-strain graphene film is demonstrated by scanning electron microscopy, X-ray photoelectron spectroscopy, secondary ion-mass spectroscopy, and micro-Raman spectroscopy.