Kinetics of formation of a platelet-reinforced ceramic composite prepared by the directed reaction of zirconium with boron carbide

Journal Article · Sun Sep 01 00:00:00 EDT 1991 · Journal of the American Ceramic Society; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1991.tb08265.x· OSTI ID:5845598

Johnson, W B; Nagelberg, A S; Breval, E ^[1]

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1. Lanxide Corp., Newark, DE (US)

In this paper the kinetics of formation of a new class of ceramic composite material, zirconium diboride platelet-reinforced zirconium carbides, are discussed. These materials are prepared by the directed reaction of molten zirconium with boron carbide to form a ceramic material composed of zirconium diboride platelets approximately uniformly distributed in a zirconium carbide matrix containing a controlled amount of residual zirconium metal. Results from interrupted growth studies, differential thermal analysis, adiabatic reaction temperature calculations, and kinetic measurements have been used to study the kinetics of the process. The reaction is very fast and proceeds parabolically with time with a rate constant between 1.6 {times} 10{sup {minus}2} and 3.9 {times} 10{sup {minus}2} cm{sup 2}/s. The proposed mechanism suggests that when molten zirconium contacts boron carbide, the molten zirconium exothermically reacts with the boron carbide to form a boron-rick liquid. Further reaction is sustained by the continuous dissolution of the boron carbide as the boron-rich liquid is drawn into the boron carbide. The product is a zirconium diboride/zirconium carbide/zirconium composite which homogenizes quickly at the reaction temperature to yield a uniform product microstructure throughout the composite. Two alternative rate-limiting steps are discussed and the implications of each are explored.

• OSTI ID: 5845598
• Journal Information: Journal of the American Ceramic Society; (United States), Vol. 74:9; ISSN 0002-7820
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BORON CARBIDES
CHEMICAL REACTION KINETICS
MICROSTRUCTURE
SUPERCONDUCTING COMPOSITES
FABRICATION
PROCESS CONTROL
ZIRCONIUM CARBIDES
DIFFERENTIAL THERMAL ANALYSIS
REINFORCED MATERIALS
THERMODYNAMICS
BORON COMPOUNDS
CARBIDES
CARBON COMPOUNDS
COMPOSITE MATERIALS
CONTROL
CRYSTAL STRUCTURE
KINETICS
MATERIALS
REACTION KINETICS
THERMAL ANALYSIS
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
665412 - Superconducting Devices- (1992-)
665411 - Basic Superconductivity Studies- (1992-)
661300 - Other Aspects of Physical Science- (1992-)