Synthesis And Characterization Of Different Condensed Matter Zeolite Materials And Investigation Of Their Growth Mechanism

Microporous zeolite materials are an important industrial catalyst and have also been widely used in many fields such as ion-exchange, adsorption and separation. With the development of the synthesis of the zeolites, many new applications have been emerged such as on the preparation and development of the host materials for optical or optoelectronic molecules which base on the synthesis of the zeolite films and large zeolite crystals materials. However, the application of such functional materials, especially micro-devices, are based on handful morphology, higher quality and orientation membrane, as well as lager size of zeolites crystals, which are very difficult to achieve. Hence, the investigation of the zeolite growth mechanism to synthesis such materials are of specific importance but a big challenge.Therefore our research work focused on the syntheses of zeolite large single crystals and oriented films. First, an ordered zeolite MFI film has been first prepared on the substrate of (001) basal face of high-quality large silicalite-1 crystals by epitaxial growth. Then using the the epitaxial growth method, we investigate the crystal structure, defect structure and growth mechanism of the large zeolite MFI. Employing the seeded monocrystalline silicon slice (SMSS) method, we have successfully synthesized the largest zeolite beta crystals (400μm×200μm×200μm) to date. Through the optic microscopy investigation of the large zeolite beta crystals, we observed the hourglass phenomenon in the zeolite beta crystals for the first time. Large all-silica zeolite beta (LASZB) crystals with spontaneous nucleation and growth in submillimetre size have been successfully synthesized using the"two silica source"technique. The integral crystal structure of the LASZB is described as a shell-core model that is closely related to the hourglass structure firstly reported in the large zeolite beta crystals. It is important for the methodology investigation of the synthesis of large zeolite crystals and provided much more information for the growth mechanism of the zeolite crystal.Zeolite films have been widely synthesized and attracted considerable interest due to their potential applicatin as selective membranes, chemical sensors, and low dielectric constant materials. However, the preparation and application of such functional materials, especially micro-devices, are based on the high oriented zeolite films. Here, we employed the basal face of large silicalite-1 crystals instead of the seed layer to prepare a completely c-oriented MFI film which have not been reported up to now. The XRD pattern and the SEM images suggest that the film is a complete c-orientation zeolite MFI film. There are more advantages of the films prepared by epitaxial growth than the traditional method of secondary growth. The secondary growth method bases on the competed growth mechanism while the method of epitaxial growth is that substrate-generated nuclei with the same lattice structure occur and then the crystals grow along the former orientation of the basal face of the large MFI crystal. More importantly, it provides more information for the investigation on the mechanism of the"secondary growth"method which is an important method to prepare zeolite membranes. Analysis of the growth crystals on the base face of the large zeolite MFI crystals by epitaxial growth, leads to the proposal of a generalized growth mechanism for zeolite MFI including the incorporation of defects within the structure. The growth pattern reveals that the large zeolite MFI crystal consists of two interpenetrating species rotated by 90°round the crystallographic c axis. Here, the growth pattern also reveals that structure of the hourglass also consists of two interpenetrating species rotated by 90°round the crystallographic c axis. Large zeolite crystals can be good hosts for guest molecules, ions, and clusters for optical, electric and magnetic micro-devices and also can enable fundamental studies, such as the investigation of the growth process of zeolite crystal and the'rational synthesis of new materials. Therefore, the synthesis of large zeolite crystals is a significant contribution to a number of scientific disciplines. Employing the seeded monocrystalline silicon slice (SMSS) method, we have successfully synthesized the largest zeolite beta crystals (400μm×200μm×200μm) to date. The X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), the atom force microscope (AFM), thermogravimetric (TG) and differential thermal analysis (DTA) and high-resolution transmission electron microscopy (HRTEM) characterizations were completed. The results of X-ray diffraction illustrated that the large zeolite beta presents a sequence of stacking disorder which is different from what is presented by the zeolite beta synthesized in an the alkali system. Through the optic microscopy investigation of the large zeolite beta crystals, we observed the hourglass phenomenon in the zeolite beta crystals for the first time. The FE-SEM and AFM analyses show that the surface of the large zeolite beta is formed in rugged layers. HRTEM characterization reveals the microstructure details of the large zeolite beta. Moreover, the synthesis mechanism has been discussed as a seeded growth with slowly released nutrition via gradually dissolving MSS and the crystals grow by a layer growth manner.Large all-silica zeolite beta (LASZB) crystals with spontaneous nucleation and growth in submillimetre size have been successfully synthesized using the"two silica source"technique. The integral crystal structure of the LASZB is described as a shell-core model that is closely related to the hourglass structure firstly reported in the large zeolite beta crystals. The shell structure of the LASZB crystal is determined as an intergrowth of three polymorphs A, B and C characterized by HR-TEM and 19F MAS NMR. The existence of hourglass structure has been testified by the etching crystal experiment. In addition, we also found that the hourglass structure also exist in the small zeolite beta crystals through the crystal etching experiment, although it can not observed under the polar microscope.In a word, the syntheses of high-quality large single crystals and oriented films of zeolites have been the most important factors for the preparation of zeolite-type materials, and new functional materials based on the structure of zeolites will be a potential area, especially for the optoelectronic devices and the development of material science.