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Mechanisms and Kinetics of Reaction‐Bonded Aluminum Oxide Ceramics
Author(s) -
Wu Suxing,
Holz Dietmar,
Claussen Nils
Publication year - 1993
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.1151-2916.1993.tb05321.x
Subject(s) - activation energy , kinetics , microstructure , ceramic , materials science , reaction rate , chemical kinetics , atmospheric temperature range , order of reaction , particle size , aluminium , melting point , oxide , chemical engineering , metallurgy , mineralogy , chemistry , thermodynamics , composite material , catalysis , reaction rate constant , organic chemistry , physics , quantum mechanics , engineering
Reaction‐bonded Al 2 O 3 (RBAO) ceramics were fabricated starting from mechanically alloyed Al 2 O 3 /Al, Al 2 O 3 / Al/ZrO 2 , and Al 2 O 3 /Al/ZrO 2 /Zr mixtures. Isopressed compacts were heat‐treated in air up to 1550°C. Reaction‐bonding mechanisms, kinetics, and the influence of ZrO 2 and Zr additions are investigated. Independent of additive, oxidation of Al proceeds both as solid/gas and liquid/gas reaction, and the reaction kinetics follow a parabolic rate law. The reaction rate depends strongly on the particle size of Al. The activation energy of the reaction depends essentially on green density. Below the melting temperature of Al, in samples containing 45 vol% Al and 55 vol% Al 2 O 3 , it is 112 and 152 kJ/mol at ∼64% and ∼74% TD, respectively, while above the melting temperature, it lies in the range ∼ 26–33 kJ/mol. Zr additions reduce the activation energy to some extent. Samples with only ZrO 2 additions exhibit nearly the same activation energies as ZrO 2 ‐free samples, though ZrO 2 has a very positive effect on the microstructural development in RBAO ceramics. Microstructure evolution and some strength data of RBAO bodies are also reported.