LAUSR

Abstract In this work, syntheses of crystalline DDR powder and DDR membranes were studied with regard to memory effects happening to the repetitively used synthesis vessel. It was found that promoted nucleation and growth towards DDR framework structures occur during a certain number of synthesis sequences. X-ray diffraction (XRD), scanning electronic microscopy (SEM), thermogravimetry (TG) and differential scanning calorimetry (DSC) and single-gas permeation tests were partially used to characterize obtained DDR crystals, as-synthesized DDR membranes as well as detemplated DDR membranes. The results implied that intermediate residues remain as traces on or within the re-used synthesis liner wall and act as seeds in the subsequent synthesis approaches. The obtained crystals derived from the different synthesis sequences were used as seed materials for DDR membrane growth. It could be shown that thin films of pure DDR phase start to form onto alumina supports within 18 h secondary growth and a defect-free DDR membrane can be achieved after 24 h of synthesis.