Study On Synthesis Of Ordered Lamellar/mesoporous Crystalline Zirconia Via Template Method

The ordered lamellar/mesoporous crystalline zirconia was synthesized by a novel reflux-hydrothermal hybrid method with zirconium oxychloride as zirconium source, sodium hydroxide as precipitating agent, sodium dodecyl sulfonate (SDS) and ethanol as template agent. The'reflux-hydrothermal'hybrid method benefits the formation, reinforcement, pretection of the ordered nanostructure and crystallization of zirconia. It also plays a key role in promoting the zirconia good thermostability and synthesizing the ordered lamellar/mesoporous crystalline zirconia. Moreover, the ethanol template with the'reflux-hydrothermal'hybrid method is reported for the first time. The ordered lamellar/mesoporous crystalline zirconia was characterized by XRD, FTIR, N₂ adsorption-desorption, FE-SEM and TEM. In this paper, the syntheses of the ordered lamellar/mesoporous crystalline zirconia are discussed in the SDS-water, ethanol-water, and SDS-ethanol-water systems. The template mechanisms of SDS, ethanol and SDS-ethanol are proposed, respectively. The zirconias as-synthesized in the three systems have good thermostability at 500°C.In the first place, the ordered lamellar/mesoporous crystalline zirconia was synthesized in the SDS-water system with the SDS as the template. The as-synthesized zirconias are composed of tetragonal and monoclinic phases and assembled a flowers-liked porous morphology (50-500 nm) by 10-nm thick curved multi-sheet petals which possess ordered lamellar (1.16 nm) and mesoporous (1.5⁵ nm) structures, Several of 1.5-nm pores merged together and formed a larger mesopore. Therefore, the zirconias are of hierarchically porous structure.In ethanol-water system, another ordered lamellar/mesoporous crystalline zirconia was synthesized. In this system, there is no traditional template, and the small-molecule ethanol serves as template, directs the ordered lamellar and mesoporous structure. Rarely has the templating role of ethanol been reported. The zirconias synthesized in this system are composed of tetragonal and monoclinic phases and spherical morphology (100 nm), possess ordered lamellar (1.16 nm) and exist three mesoporous distributions, centered at about 3.5 nm, 7.2 nm, 15 nm, respectively.Finally, combined the above two systems, a similar ordered lamellar/mesoporous crystalline zirconia was synthesized in the SDS-ethanol-water systems. The zirconias possess ordered lamellar (1.16 nm) and exist two mesoporous distributions, centered at about 3.5 nm, 7 nm, respectively. In the SDS-ethanol-water systems, SDS-ethanol cooperative-competition template plays the template role. The ordered nanostructure and crystallization of zirconia were affected by the hydrothermal temperature, SDS amount and the ratio of ethanol/water, etc.