Kinetics of carbothermal reduction snythesis of boron carbide

This paper reports that carbothermal reduction kinetics to synthesize boron carbide are studied under conditions of high carbon/boron oxide precursor heating rates ([gt] 10[sup 3] K/s) and intermediate temperatures (1803 K [lt] T [lt] 2123 K). For these conditions, fractional carbon conversion, X, c...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 1992-09, Vol.75:9
Main Authors: Pratsinis, S.E., Weimer, A.W., Moore, W.G., Roach, R.P., Hitt, J.E., Dixit, R.S.
Format: Article
Language:English
Subjects:
360202 - Ceramics, Cermets, & Refractories- Structure & Phase Studies
360204 - Ceramics, Cermets, & Refractories- Physical Properties
400201 - Chemical & Physicochemical Properties
BORON CARBIDES
BORON COMPOUNDS
BORON OXIDES
CARBIDES
CARBON
CARBON COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
ELEMENTS
FLUIDS
GASES
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
KINETICS
LIQUIDS
MATERIALS SCIENCE
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
PRECURSOR
REACTION KINETICS
REDOX REACTIONS
SOLIDS
SYNTHESIS
TEMPERATURE RANGE
TEMPERATURE RANGE 1000-4000 K
THERMODYNAMIC PROPERTIES
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Summary:This paper reports that carbothermal reduction kinetics to synthesize boron carbide are studied under conditions of high carbon/boron oxide precursor heating rates ([gt] 10[sup 3] K/s) and intermediate temperatures (1803 K [lt] T [lt] 2123 K). For these conditions, fractional carbon conversion, X, can be described by a nucleation---growth rate expression: ln (1 [minus] X) = [minus](kt)[sup 3], where k[sub 0] = 3.86 [times] 10[sub 6] s[sup [minus]1] and E[sub a] = 301 [plus minus] 55 kJ/mol for the temperature range (1803 [lt] T [lt] 1976 K) and k[sub 0] =-2 [times] 10[sup 20] s[sup [minus]1] and E[sub a] = 820 [plus minus] 89 kJ/mol for the temperature range (1976 [lt] T [lt] 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.
ISSN:0002-7820
1551-2916