How does molybdenum disilicide resist oxidation at high temperatures?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

conductive ceramics Figure 1: Schematic diagram of a zirconia oxygen sensor used to monitor automobile exhaust gases. The sensor, approximately the size of a spark plug, is fitted into the exhaust manifold of an automobile engine. The thimble-shaped zirconia sensor, sandwiched between thin layers of porous platinum, is exposed on its interior to outside air and on its exterior to exhaust gas passing through slits in the sensor shield. The two platinum surfaces serve as electrodes, conducting a voltage across the zirconia that varies according to the difference in oxygen content between the exhaust gas and the outside air.

Molybdenum disilicide (MoSi $_{2}$ ) resists oxidation at high temperatures by forming a protective silica-glass surface layer when exposed to oxidizing atmospheres. This layer acts as a barrier, preventing further oxidation of the underlying material.1

Because of this property, MoSi $_{2}$ is highly effective as a conductive ceramic for heating elements in environments where traditional metal alloys would fail, maintaining stability at temperatures up to 1,800 °C (3,270 °F).1