Thermochemical insights into rapid solid-state reaction synthesis of β-sialon

Alexandra Navrotsky, Subhash H. Risbud, Jian Jie Liang, Valerie J. Leppert

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

Sialons (Si-Al-O-N) are useful as engineering components because they combine the toughness of silicon nitride with phase stability. Competing reactions occur during conventional processing, making it difficult to form single-phase material without high-temperature/long-time heat treatments. Thermochemical insights into sialon formation are complicated by impure samples, glassy phases, and slow reactions. Here we report the first direct thermochemical measurement of the energetics of a specially synthesized (single-phase, glass-free) β-sialon of composition Si3.17Al2.83O2.83N5.17 by dissolution calorimetry in molten (Li,Na)BO2 at 770°C. A remarkable feature of our synthesis by a pulsed electric discharge method is that the unreacted starting powders (aluminum oxide, aluminum nitride, and silicon nitride) were simultaneously reacted and densified to form the single-phase β sialon, all in just 7 min - a hitherto unattained processing record. Thermochemical measurements gave the first direct determination of the standard enthalpy of formation: -67.8 ± 15.5 kJ/mol from the compounds and -2768.3 ± 8.2 kJ/mol from the elements. The thermochemical data suggest new, possibly self-sustaining, reaction paths to refractory nitride materials.

Original languageEnglish (US)
Pages (from-to)9433-9435
Number of pages3
JournalJournal of Physical Chemistry B
Volume101
Issue number46
DOIs
StatePublished - Nov 13 1997
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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