Lawrence A. Harris

Transmission electron microscope observations of porosity in coal

Abstract Samples of a high-volatile bituminous coal (HVab) were examined by means of transmis sion electron microscopy in a high-voltage electron microscope (1 MeV). The porosity observed within the exinite and inertinite constituents of this coal falls primarily into the mesopore size range (2–50 nm). Small particles (≈25 nm in diameter) were seen in a majority of the exinite pores and are believed to have acted as catalysts in the pore formation.

Microscopic identification of carbonaceous particles in stack ash from pulverized-coal combustion

Abstract Carbonaceous particles were separated from the 21–150 μm mass median aerodynamic diameter particle size fraction of two stack ashes collected from two electric power generation plants fuelled with pulverized coal. Scanning electron and light microscopy were used to examine loose particles and polished particle sections mounted in epoxy resin for morphology and internal structure. Several distinct types of carbonaceous particles were identified, ranging from uncombusted macerals of optically isotopic fusinite, to optically anisotropic coked products derived from vitrinite and exinite. The latter displayed complex porous internal structures containing mineral inclusions. X-ray diffraction spectra demonstrated a graphite carbon composition contaminated with quartz and mullite, which is consistent with the results of energy-dispersive X-ray fluorescence spectra.

Solids formed in a solvent-refined-coal pilot plant

Abstract Optical and X-ray diffraction methods have been used to study microstructures in a carbonaceous plug. The plug, which was obtained from a feedline in a solvent-refined-coal (SRC) pilot plant, was shown to consist primarily of minerals and semi-coke. The semi-coke formed the matrix phase surrounding the minerals, mineral and coke mixtures, and fusinite. These studies revealed that all the pyrite had been transformed to pyrrhotite which in turn formed shell-like structures surrounding both inorganic and organic constituents. In addition, it was observed that the slurry mixture of coal and solvent oil had been converted to semi-coke.

The effects of surface oxidation and segregation on the adhesional wear behavior of aluminum—bronze alloys

The worn surfaces of selected Cu-A1 alloys, resulting from sliding contact with a sapphire right cylinder, along with unworn surfaces and wear debris, were characterized using an appropriate combination of scanning electron microscopy (SEM), optical stereomicroscopy, X-ray diffraction (XRD), and X-ray photoelectmn spectroscopy (XPS). XPS, angle-resolved XPS (ARXPS) and ion sputter profiling techniques were employed to characterize surface compositional changes occurring in the unworn and worn surfaces as a function of increasing aluminum content. The transfer of Cu—A1 alloy to the sapphire counterface (adhesional wear of the Al-bronze) increased with increasing aluminum content, which corresponded to increased wear and damage to the alloy surfaces. XPS and SEM analyses of pure copper and a Cu-1 weight percent (w/o) A1 alloy showed the worn surfaces to consist of a smooth and continuous Cu2O layer. ARXPS analysis of as-polished and worn surfaces of Cu-4 w/o A1 and Cu-6 w/o A1 alloys showed significant surf...

Are alternative coalification paths possible for terrestrial coal

It is generally assumed that the coalification of terrestrial kerogens proceeds along an orderly, progressive path from lignitic to anthracitic coal. However, when information concerning the volatile compounds present in coal (the average volatilization rate (AVR) determined by thermogravimetry) is compared with the hydrogen to carbon (H/C) ratio, some subbituminous coal samples that have relatively low H/C ratios (less than or equal to 0.75) appear to contain insufficient amounts of hydrogen to be transformed into high-volatile bituminous coal. These samples also have relatively high oxygen to carbon (O/C) ratios (> 0.14). The positions of these samples on an AVR vs. H/C plot suggests that their transformation to the high-volatile bituminous rank would not be possible unless hydrogen in some form were added from an external source. The results suggest that all terrestrial coal may not necessarily pass through all preceding ranks. Alternative coalification paths may be possible as a result of differences in the composition of precursor plant material, the conditions prevalent during peatification, and the temperature, pressure, and confining-pressure conditions during coalification.

Transmitted near-infrared microscopy of coal☆

Abstract Thin sections of an eastern Kentucky high-splint coal (high-volatile bituminous) from the Thiessen collection have been studied using transmitted infrared microscopy. Several normally opaque structures in the inertinite maceral group were observed to transmit in the near infrared (700–1200 nm). These same structures were also found to be birefringent, consisting of variably oriented optical domains similar in appearance to a polycrystalline material. This technique may prove valuable in studies of seam profiles and correlations.