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Kinetics of Carbothermal Reduction Synthesis of Boron Carbide
Author(s) -
Weimer Alan W.,
Moore William G.,
Roach Raymond P.,
Hitt James E.,
Dixit Ravindra S.,
Pratsinis Sotiris E.
Publication year - 1992
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.1151-2916.1992.tb05604.x
Subject(s) - carbothermic reaction , boron carbide , nucleation , atmospheric temperature range , boron , kinetics , boron oxide , carbide , carbon fibers , materials science , oxide , activation energy , phase (matter) , chemistry , inorganic chemistry , analytical chemistry (journal) , metallurgy , thermodynamics , organic chemistry , composite material , physics , quantum mechanics , composite number
Carbothermal reduction kinetics to synthesize boron carbide are studied under conditions of high carbon/boron oxide precursor heating rates (> 10 3 K/s) and intermediate temperatures (1803 K < T < 2123 K). For these conditions, fractional carbon conversion, X, can be described by a nucleation–growth rate expression: In (1 – X ) =– ( kt ) 3 , where K o = 3.86 × 10 6 s −1 and E a = 301 ± 55 kJ/mol for the temperature range (1803 < T < 1976 K) and k o = 2 × 10 20 s −1 and E a = 820 ± 89 kJ/mol for the temperature range (1976 < T < 2123 K), respectively. Boron carbide formation is highly dependent upon the phase change of reactant boron oxide from solid to liquid to gaseous boron suboxides and the effect of reaction environment (i.e., heating rate and ultimate temperature) on the rate at which the phase changes occur.