Evolution of Reactivity of Highly Porous Chars from Raman Microscopy
- 1 April 2000
- journal article
- research article
- Published by Taylor & Francis in Combustion Science and Technology
- Vol. 153 (1), 65-82
- https://doi.org/10.1080/00102200008947251
Abstract
The effect of heal treatment on the evolution of reactivity of a highly porous pure synthetic char was studied with the aid of Raman scattering measurements. Two sets of experiments were carried out. A) Samples were oxidized in air at 600°C without heat treatment and Raman spectra were measured as a function of conversion. B) Samples were heat-treated in the range 900-1400 °C, in nitrogen, then characterized by micro-Raman spectroscopy, in the range 800-1800 cm−1, and then oxidized by air at 500 °C and by CO2 at 900 °C in a thermogravimetric balance. In all Raman scattering measurements the G and D bands were dominant and a weak “1180 cm−1” band was apparent. The following conclusions can be drawn from results of experiments A and B respectively: A) Throughout reaction with oxygen the most significant changes in reactivity and Raman features occur in the conversion range 0- 30%. This is consistent with previous measurements of thermal resistivity and intrinsic reaction rate. B) Heal treatment up to 900 °C at time duration up to 300 minutes did not show any effect on reactivity. Decrease in reactivity was apparent at and beyond 1200 °C. The characteristics of each of the three Raman bands showed clear correlation with reactivity changes both in air and CO2. These were attributed to morphological (dimensions and ordering) changes in the rearrangement of the carbon network structure, as previously suggested. Interpretation of these changes and their effect on reactivity is proposed.Keywords
This publication has 18 references indexed in Scilit:
- The Thermal Conductivity and Porous Structure of Char ParticlesCombustion and Flame, 1998
- Role of the Pore Structure in the Fragmentation of Highly Porous Char ParticlesCombustion and Flame, 1998
- Effect of Various Treatments on Carbon Fiber Surfaces Studied by Raman Microprobe SpectrometryApplied Spectroscopy, 1998
- The influence of heat treatment and weathering on the gasification reactivity of Montana ligniteSymposium (International) on Combustion, 1998
- The effect of microstructural transformation on the evolution of thermal conductivity of highly porous chars during oxidationCombustion and Flame, 1997
- Evolution of char chemistry, crystallinity, and ultrafine structure during pulverized-coal combustionCombustion and Flame, 1995
- Raman scattering of laser-deposited amorphous carbonPhysical Review B, 1993
- Raman spectroscopic investigation of ion-beam-irradiated glassy carbonJournal of Applied Physics, 1990
- Modeling studies of amorphous carbonPhysical Review B, 1984
- Lattice-dynamical model for graphitePhysical Review B, 1982