A composite magnet wire includes, in an exemplary embodiment, a metal wire and a coating applied to an outer surface of the wire. The coating includes a polyimide polymer and a plurality of alumina nano particles dispersed in the polyimide polymer. The alumina nano particles have a surface treatment applied to outer surfaces of the alumina nano particles, where the surface treatment includes a phenyl-silane. The composite magnet wire has a thermal degradation temperature index of at least 300° C. as calculated in accordance with ASTM E1641 or D2307.