Silicon nitride/zirconium oxide hot‐pressed materials contain ZrO 2 ‐ 2 x N 4 x /3 (0.25≤ x ≤0.43), which readily oxidizes at ≥ 500°C to monoclinic ZrO 2 . The molar volume increase (∼4 to 5%) of this reaction was used to develop compressive surface stresses. The development of these useful surface stresses was demonstrated with an indentation technique used to measure the apparent critical stress intensity factor ( K a ) on the surfaces of materials fabricated with 5 to 30 vol% ZrO 2 and subsequently oxidized at 600° to 800°C. The increase in K a was directly related to the oxidation kinetics and the initial volume content of the unstable phase.
No takes yet. Share an insight, caveat, or question.
F. F. Lange (1980) studied this question.