Nisil is an austenitic nickel-silicon alloy (NiSi alloy) used for the negative leg of thermocouples type N. It offers higher thermoelectric stability in air above 1000°C (1830°F) and better oxidation resistance than type E, J and K thermocouples.
Nisil alloy can not be exposed to sulphur-containing gases. This thermocouple alloy is the most recent one among the different types covered by the international standards.