A hard carbon film-coated substrate is disclosed which has between a substrate and a hard carbon film an interlayer principally comprised of at least one selected from the group consisting of Al, Cr, Sn, Co and B, oxides, nitrides and carbides thereof. The panels are preferably fiber cement. The invention further relates to methods of producing tapentadol in a solid, non-crystalline form and to pharmaceutical formulations containing solid, non-crystalline tapentadol.