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Final‐stage densification kinetics of direct current–sintered ZrB2

Final‐stage densification kinetics of direct current–sintered ZrB2 Final‐stage sintering was analyzed for nominally phase pure zirconium diboride synthesized by borothermal reduction of high‐purity ZrO2. Analysis was conducted on ZrB2 ceramics with relative densities greater than 90% using the Nabarro–Herring stress–directed vacancy diffusion model. Temperatures of 1900°C or above and an applied uniaxial pressure of 50 MPa were required to fully densify ZrB2 ceramics by direct current sintering. Ram travel data were collected and used to determine the relative density of the specimens during sintering. Specimens sintered between 1900 and 2100°C achieved relative densities greater than 97%, whereas specimens sintered below 1900°C failed to reach the final stage of sintering. The average grain size ranged from 1.0 to 14.7 μm. The activation energy was calculated from the slope of an Arrhenius plot that used the Kalish equation. The activation energy was 162 ± 34 kJ/mol, which is consistent with the activation energy for dislocation movement in ZrB2. The diffusion coefficients for dislocation motion that controls densification were 5.1 × 10−6 cm2/s at 1900°C and 5.1 × 10−5 cm2/s at 2100°C, as calculated from activation energy and average grain sizes. This study provides evidence that the dominant mechanism for final‐stage sintering of ZrB2 ceramics is dislocation motion. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of the American Ceramic Society Wiley

Final‐stage densification kinetics of direct current–sintered ZrB2

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References (11)

Publisher
Wiley
Copyright
© 2023 The American Ceramic Society.
ISSN
0002-7820
eISSN
1551-2916
DOI
10.1111/jace.19212
Publisher site
See Article on Publisher Site

Abstract

Final‐stage sintering was analyzed for nominally phase pure zirconium diboride synthesized by borothermal reduction of high‐purity ZrO2. Analysis was conducted on ZrB2 ceramics with relative densities greater than 90% using the Nabarro–Herring stress–directed vacancy diffusion model. Temperatures of 1900°C or above and an applied uniaxial pressure of 50 MPa were required to fully densify ZrB2 ceramics by direct current sintering. Ram travel data were collected and used to determine the relative density of the specimens during sintering. Specimens sintered between 1900 and 2100°C achieved relative densities greater than 97%, whereas specimens sintered below 1900°C failed to reach the final stage of sintering. The average grain size ranged from 1.0 to 14.7 μm. The activation energy was calculated from the slope of an Arrhenius plot that used the Kalish equation. The activation energy was 162 ± 34 kJ/mol, which is consistent with the activation energy for dislocation movement in ZrB2. The diffusion coefficients for dislocation motion that controls densification were 5.1 × 10−6 cm2/s at 1900°C and 5.1 × 10−5 cm2/s at 2100°C, as calculated from activation energy and average grain sizes. This study provides evidence that the dominant mechanism for final‐stage sintering of ZrB2 ceramics is dislocation motion.

Journal

Journal of the American Ceramic Society – Wiley

Published: Oct 1, 2023

Keywords: activation energy; densification; modeling; sintering; ZrB 2

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