Pressureless Densification of Zirconium Diboride with Boron Carbide Additions

Abstract

Zirconium diboride (ZrB2) was densified ( > 98% relative density) at temperatures as low as 1850⁰C by pressureless sintering. Sintering was activated by removing oxide impurities (B2O3 and ZrO2) from particle surfaces. Boron oxide had a high vapor pressure and was removed during heating under a mild vacuum (~150 mTorr). Zirconia was more persistent and had to be removed by chemical reaction. Both WC and B4C were evaluated as additives to facilitate the removal of ZrO2. Reactions were proposed based on thermodynamic analysis and then confirmed by X-ray diffraction analysis of reacted powder mixtures. After the preliminary powder studies, densification was studied using either as-received ZrB2 (surface area ~1 m 2/g) or attritionmilled ZrB2 (surface area ~ 7.5 m 2/g) with WC and/or B4C as a sintering aid. ZrB2 containing only WC could be sintered to ~95% relative density in 4 h at 2050⁰C under vacuum. In contrast, the addition of B4C allowed for sintering to > 98% relative density in 1 h at 1850⁰C under vacuum.

Department(s)

Materials Science and Engineering

Keywords and Phrases

Pressureless sintering; Thermodynamic analysis; Zirconium diboride; Boron carbide; Densification; Sintering; Thermodynamics; Vacuum applications; Zirconium compounds; Borides

International Standard Serial Number (ISSN)

0002-7820; 1551-2916

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2006 Wiley-Blackwell, All rights reserved.

Publication Date

01 May 2006

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