Construction of macroscopic 3D foams of metastable manganese oxides via a mild templating route: Effects of atmosphere and calcination

Manganese oxides are metastable phases due to oxygen loss at high temperature. Conventional ceramic routes need high temperature and thus are unsuitable for making MnOx foams. A mild templating route at 300-400 °C was developed to construct metastable MnOx foams. Interwoven OMS-2 (cryptomelane) nanofibers with a length-diameter ratio of ca. 3000 over a template may create an OMS-2 foam at 400 °C with an atmosphere of 21% O2 content, a MnO/C foam at 400 °C with an atmosphere of 0% O2 content, OMS-2/Mn3O4 foams at 400 °C with an atmosphere of 1-5% O2 content, or Mn3O4/MnO2 foams at 300-350 °C in an atmosphere of 1% O2 content. Three foam materials are materials with ductility while others belong to brittle materials.