Abstract
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Carbonaceous materials including cokes, chars, and pyrolyzed coals were annealed at temperatures
ranging from 973 K to 1773 K (700 C to 1500 C) in an inert atmosphere. Macro and
microstrengths of original and annealed carbonaceous materials were characterized by the
tensile strength and fracture toughness. Fracture toughness was determined for inert maceralderived
component (IMDC) and reactive maceral-derived component (RMDC) using ultramicro
indentation. Experimental data obtained by tensile tests were processed using the Weibull
statistical method to find ‘‘inherent’’ strength. Tensile strength of chars and coals was significantly
increased by annealing at temperatures ranging from 973 K to 1373 K (700 C to
1100 C); further increase in annealing temperature to 1773 K (1500 C) increased their tensile
strength only slightly. Tensile strength of cokes decreased with the increasing annealing temperature;
the major effect was observed in the temperature range from 1573 K to
1773 K (1300 C to 1500 C). Fracture toughness of chars and coals was enhanced significantly
by heat treatment at temperatures ranging from 973 K to 1373 K (700 C to 1100 C) as a result
of pyrolysis, while that of cokes increased slightly by heat treatment. Fracture toughness of
IMDC was higher than RMDC.Macrostrength of carbonaceous materials was strongly affected
by their porosity and microstrength. The effect of pore geometry on macrostrength was marginal.
Decreasing the porosity was more effective compared with increasing the microstrength in
improving the macrostrength of carbonaceous materials.