Fly ash and coal mineral matter transformations during heating
A study is reported of surface segregation phenomena for fly ash and aluminosilicates representative of coal mineral matter during heating. The materials studied included a 20-..mu..m average-diameter fly-ash powder, a glass prepared from the fly ash, and Ca- and K-rich aluminosilicate minerals. The samples were heated both in air and under vacuum for extended periods at temperatures up to 1100/sup 0/C. XPS, Auger and SIMS methods were used to obtain relative surface elemental concentrations for major and minor components and depth profiles for some of the samples. Major differences were noted between samples heated in air (oxidizing) and those heated in vacuum (reducing) environments. For the fly-ash glass heated in air Fe, Ti and Mg become enriched on the surfaces while heating in vacuum leads to Si surface segregation. Different trends upon heating were also observed for the Ca- and K-rich aluminosilicates. The results indicate two levels of surface enrichment upon the fly-ash glass; a thin (<500 A) layer and a thicker (1- to 2-..mu..m) layer most evident for heating in air where an Fe-rich layer is formed. The present results indicate that the rates of surface segregation may not be sufficiently fast on the time scale of fly-ash formation to result in equilibrium surface segregation and that condensation processes during fly-ash formation probably play a major role in the observed fly-ash surface enrichments.
- Research Organization:
- Pacific Northwest Lab., Richland, WA (USA)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 5767523
- Report Number(s):
- PNL-SA-10508; ON: DE83015078
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALUMINIUM SILICATES
CHEMICAL ANALYSIS
SURFACE PROPERTIES
TEMPERATURE EFFECTS
FLY ASH
MINERALS
AIR
AUGER ELECTRON SPECTROSCOPY
CALCIUM
CONTROLLED ATMOSPHERES
ION MICROPROBE ANALYSIS
IRON
MASS SPECTROSCOPY
OXIDATION
PHOTOELECTRON SPECTROSCOPY
POTASSIUM
REDUCTION
VACUUM SYSTEMS
VERY HIGH TEMPERATURE
AEROSOL WASTES
ALKALI METALS
ALKALINE EARTH METALS
ALUMINIUM COMPOUNDS
ASHES
ATMOSPHERES
CHEMICAL REACTIONS
ELECTRON SPECTROSCOPY
ELEMENTS
FLUIDS
GASES
METALS
MICROANALYSIS
NONDESTRUCTIVE ANALYSIS
OXYGEN COMPOUNDS
RESIDUES
SILICATES
SILICON COMPOUNDS
SPECTROSCOPY
TRANSITION ELEMENTS
WASTES
010600* - Coal
Lignite
& Peat- Properties & Composition
400104 - Spectral Procedures- (-1987)