From experimental measurements, it is known that the symmetry of the framework changes from monoclinic (space group P21/n.1.1.) toward orthorhombic (space group Pnma) by increasing the temperature above 340 K. The experimentally observed change in the geometry of the zeolite is compared with that...
The extra-framework content, the nature and amount of Si substituents, and the temperature have been proved to influence the real symmetry of the material and reduce the symmetry from orthorhombic Pnma to monoclinic P21/n space group (s.g.) [18], [19]. In addition to the synthetic phases...
While in mutinaite no symmetry change is observed as a function of pressure, a phase transition from monoclinic (P2 _1/n) to orthorhombic (Pnma) symmetry occurs at about 1.0 GPa in the silicalite samples. This phase transition is irreversible upon decompression. The second order bulk moduli ...
Free energy minimisation calculations of the crystal structure of the zeolite MFI are shown to reproduce the observed phase transition from monoclinic to orthorhombic symmetry.doi:10.1039/b208064hGrau-Crespo, RicardoAcuay, EnriqueRuiz-Salvador, A. Rabdel...
The monoclinic lattice symmetry of silicalite-1 changes to orthorhombic on introduction of titanium. The titanium silicalites retain their orthorhombic symmetry even after calcination in air. On progressive incorporation of titanium, (i) the unit cell dimensions and volume (from XRD) increase linearly,...
Molecular dynamics (MD) simulations of an MFI-type zeolite have been performed at various temperatures. Crystal structures and vibrational spectra obtained from the simulations were in good agreement with the experimental data. The temperature induced phase transition between orthorhombic and monoclinic ...
X-ray powder diffraction study of silicalite and mutinaite compressibility. Silicalite is the most compressible zeolite up to now studied. A phase transition from monoclinic to orthorhombic symmetry occurs in silicalite. Among MFI-type zeolites the most rigid material is mutinaite....
Influence of downsizing of zeolite crystals on the orthorhombic monoclinic phase transition in pure silica MFI-typeMFINanosheetsPhase transitionPowder X-ray diffraction29Si MAS NMR•Micro- and nanosized silicalite-1 exhibit orthorhombic ↔ monoclinic phase transition.•Identification of phase transition...
The interaction results in the structural symmetry of MFI zeolite changing from monoclinic to orthorhombic. At 298 K the H atom of the amine group attacks the [Si–O] framework to form O H N bonds. On raising the temperature to 323 K, the signal belonging to Si–N connection appears in...