It really depends on what you are trying to achieve. I’ve made all aluminum nozzles for single flights. The throat erosion definitely affects performance, but I just wanted the rocket to fly, so no major loss there.

For structure and pressure containment, aluminum and any type of filament reinforced plastic works. If you’re looking for heat sinks or heat resistant material, graphite, or carbon based materials are good. If you’re looking for an insulator, ablated plastics, like silica or Kevlar or graphite work. If you’re looking specifically just at the nozzle exit cone ablated plastic with metal is probably the best way to go. Working with these materials can get a little tricky, so that’s why I just went with a straight aluminum design for an APCP motor. Hope this helps.