Energetic Performances of Pure-Silica DDR Zeolite by High-Pressure Intrusion-Extrusion of Electrolyte Aqueous Solutions: A Shock-Absorber with Huge Absorbed Energy

Pure-silica DDR-type zeolite (zeosil) displays a porosity composed of two kinds of small cages (pore opening of 4-6 MR) and of a large nonadecahedron cage with pore windows of 8 MR. In order to study the energetic performances of this hydrophobic material by high-pressure intrusion-extrusion experiments, water and 10 and 20 M LiCl aqueous solutions were chosen as nonwetting liquids. The intrusion pressure increases from 60 to 357 MPa when using water and 20 M LiCl aqueous solution, respectively. The latter pressure is the highest ever found for a zeosil-based system. It is associated with a large intruded volume of 0.26 mL/g, which is close to the total theoretical porosity of the DDR structure. The corresponding "DDR-20 M LiCl aqueous solution" system demonstrates mainly shock-absorber behavior, and both features (high intrusion pressure and large intruded volume) lead to the highest amount of absorbed mechanical energy for such systems: 93 and 61 J/g for the first and the following intrusion cycles, respectively. After-intrusion extrusion of LiCl aqueous solutions and depending on the concentration of the solution or the number of the intrusion-extrusion cycles, slight distortions of the DDR unit cell are clearly evidenced by XRD and Si-29 MAS NMR analyses. Two possible explanations are advanced to explain such distortions.