Sintering Mechanisms and Kinetics for Reaction Hot-Pressed ZrB₂

Abstract

Sintering mechanisms and kinetics were investigated for ZrB2 ceramics produced using reaction hot pressing. Specimens were sintered at temperatures ranging from 1800-C to 2100-C for times up to 120 min. ZrB2 was the primary phase, although trace amounts of ZrO2 and C were also detected. Below 2000⁰C, the densification mechanism was grain-boundary diffusion with an activation energy of 241 ± 41 kJ/mol. At higher temperatures, the densification mechanism was lattice diffusion with an activation energy of 695 ± 62 kJ/mol. Grain growth exponents were determined to be ~4.5, which indicated that a grain pinning mechanism was active in both temperature regimes. The diffusion coefficients for grain growth were 1.5 x 10-16 cm4/s at 1900⁰C and 2.1 x 10-15 cm4/s at 2100⁰C. This study revealed that dense ZrB2 ceramics can be produced by reactive hot pressing in shorter times and at lower temperatures than conventional hot pressing of commercial powders.

Department(s)

Materials Science and Engineering

Keywords and Phrases

Activation energy; Ceramic materials; Chemical activation; Diffusion; Grain boundaries; Hot pressing; Reaction kinetics; Sintering; Commercial powders; Densification mechanisms; Grain growth exponent; Grain-boundary diffusion; Lower temperatures; Reactive hot pressing; Sintering mechanism; Temperature regimes

International Standard Serial Number (ISSN)

0002-7820; 1551-2916

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2015 Blackwell Publishing Inc., All rights reserved.

Publication Date

01 Aug 2015

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