Conversion of MAX phase single crystals in highly porous carbides by high temperature chlorination

We show that combining high temperature chlorination with the chemical sensitivity of the A-atom planes of single crystals of some nano-lamellar MAX phases allows one to synthesize highly porous and electrically conducting carbides. Focusing on the case of porous Cr3C2, we present the dependence of the layer morphology, structure and formation kinetics on processing parameters such as temperature and time. The determination of the Raman signature of Cr3C2 and Cr7C3 allows us to follow the creation and elimination of the various phases as a function of processing time. Electrical resistivity and magnetoresistance data versus temperature and magnetic field are also presented and analyzed.