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Pressureless Sintering of Boron Carbide
Author(s) -
Lee Hyukjae,
Speyer Robert F.
Publication year - 2003
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2003.tb03498.x
Subject(s) - materials science , sintering , dilatometer , eutectic system , graphite , boron carbide , volatilisation , atmospheric temperature range , carbon fibers , evaporation , metallurgy , carbide , particle (ecology) , boron oxide , oxide , chemical engineering , composite material , microstructure , composite number , chemistry , thermal expansion , physics , oceanography , organic chemistry , meteorology , thermodynamics , geology , engineering
B 4 C powder compacts were sintered using a graphite dilatometer in flowing He under constant heating rates. Densification started at 1800°C. The rate of densification increased rapidly in the range 1870°–2010°C, which was attributed to direct B 4 C–B 4 C contact between particles permitted via volatilization of B 2 O 3 particle coatings. Limited particle coarsening, attributed to the presence or evolution of the oxide coatings, occurred in the range 1870°–1950°C. In the temperature range 2010°–2140°C, densification continued at a slower rate while particles simultaneously coarsened by evaporation–condensation of B 4 C. Above 2140°C, rapid densification ensued, which was interpreted to be the result of the formation of a eutectic grain boundary liquid, or activated sintering facilitated by nonstoichiometric volatilization of B 4 C, leaving carbon behind. Rapid heating through temperature ranges in which coarsening occurred fostered increased densities. Carbon doping (3 wt%) in the form of phenolic resin resulted in more dense sintered compacts. Carbon reacted with B 2 O 3 to form B 4 C and CO gas, thereby extracting the B 2 O 3 coatings, permitting sintering to start at ∼1350°C.