Perhaps you should try some spelling variations:
acoustical materials » acoustic material, optical materials, critical materials
acoustic materials » acoustic metamaterials, plastic materials, elastic materials
ionic materials » basic materials, inorganic materials, photonic materials

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: %((ionic materials) OR (((acoustical materials) OR (acoustic materials))))%22.
• Adding a wildcard symbol may retrieve word variants: %((ionic materials) or (((acoustical materials) or (acoustic materials))))%22*.