Detection of magnetite particles in coal by ferromagnetic resonance

Journal Article · Fri Feb 15 00:00:00 EST 1985 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.334525· OSTI ID:5982062

Malhotra, V M; Graham, W R.M.

The techniques of ferromagnetic (FMR) and electron paramagnetic resonance have been applied in studies of Pittsburgh No. 8 bituminous coal. The specimen has been found to be magnetically very heterogeneous, with paramagnetic Mn/sup 2 +/ and Fe/sup 3 +/, free radicals, and at least one ferromagnetic specie which is identified and characterized in the present paper. The temperature dependence of the spectral line shapes indicates the occurrence of a phase transition at 123 K for a finely ground powder sample and at 121 K for a hand-picked fragment; these temperatures are characteristic of the Verwey transition in magnetite, and confirm its presence in both samples. Linewidth data provide an upper limit of 0.07 ..mu..m on the particle size in the powdered sample. The chemical composition of the magnetite in the powdered sample is estimated, on the basis of the observed transition temperature, to be between Fe/sub 2.988/O/sub 4/ and Fe/sub 2.997/O/sub 4/. Spectra of the residue and the glass extract obtained after treatment of the powdered sample with HCl confirm the identification of magnetite, and indicate that it is not embedded in the organic matter in the coal, but should be easily removed either by acid treatment or magnetic separation. The results suggest the potential usefulness in the identification and physical and chemical characterization of ferro- and ferrimagnetic minerals in coals.

• Research Organization: Department of Physics, Texas Christian University, Fort Worth, Texas 76129
• OSTI ID: 5982062
• Journal Information: J. Appl. Phys.; (United States), Vol. 57:4
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BITUMINOUS COAL
QUANTITATIVE CHEMICAL ANALYSIS
IRON COMPOUNDS
ELECTRON SPIN RESONANCE
FERROMAGNETIC RESONANCE
MAGNETITE
CHEMICAL COMPOSITION
MANGANESE COMPOUNDS
RADICALS
FERRIMAGNETIC MATERIALS
FERROMAGNETIC MATERIALS
IRON OXIDES
LINE WIDTHS
PARTICLE SIZE
PHASE TRANSFORMATIONS
TRANSITION TEMPERATURE
BLACK COAL
CARBONACEOUS MATERIALS
CHALCOGENIDES
CHEMICAL ANALYSIS
COAL
ENERGY SOURCES
FOSSIL FUELS
FUELS
IRON ORES
MAGNETIC MATERIALS
MAGNETIC RESONANCE
MATERIALS
MINERALS
ORES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RESONANCE
SIZE
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
010600* - Coal
Lignite
& Peat- Properties & Composition
400104 - Spectral Procedures- (-1987)