Wenheng Jing

Crystallization of CaCO3 in the presence of sulfate and additives: experimental and molecular dynamics simulation studies.

The effects of sulfate and BHTPMP (Bis (hexamethylene) triaminepentakis (methylene phosphonic acid)) on the crystallization rate, phase composition and morphology of calcium carbonate have been studied. It was observed that sulfate reduces the nucleation rate and favors the formation of aragonite form in the calcium carbonate precipitate. Moreover, in the presence of sulfate the rhombohedral morphology of the calcite crystals is modified, and during the formation of calcite, the development of {104} faces are more significantly prohibited than {110} faces. In the presence of sulfate together with BHTPMP, the crystallization process is inhibited and the modified morphology and the dominant calcite form are observed in the solid. The results from molecular dynamics simulations show the more strong combination of sulfate with calcite surface, in particular the {104} face, in comparison with the aragonite surface. The strong interaction of BHTPMP with sulfate and the aragonite surface favors the formation of the dominant calcite phase in the precipitate.

Preparation of meso–macroporous TiO2 ceramic based on membrane jet-flow emulsification—Influences of triblock copolymers on the processes

Meso-macroporous TiO(2) ceramics were obtained based on a two-stage ceramic membrane jet-flow emulsification and the influences of the triblock copolymers on the process are discussed in this study. The two alpha-Al(2)O(3) ceramic membranes with average pore sizes of 0.5 and 1.6 microm were used to control the structure of nonaqueous emulsions. Polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide (PEO) with relative molecular masses of 5800 and 2900 were used as emulsifiers. Monodispersed emulsions with the same average droplet size of 2.6 microm were prepared using the two emulsifiers. However, ordered macroporous structures could only be obtained when the PEO-PPO-PEO of 5800 was used as emulsifier because the lower interfacial tension leans to produce the more stable nonaqueous emulsion. Moreover, the mesoporous structures of 5.4 nm and 7.1 nm could be obtained by the self-assembling block copolymers.

Preparation of Macroporous TiO2 Ceramic Based on Membrane Jet-flow Emulsification

Abstract A novel method to prepare macroporous TiO 2 ceramic, based on membrane emulsification was reported. To solve the paradox between the instability of nonaqueous emulsion and long emulsification time required by the membrane emulsification, a two-stage ceramic membrane jet-flow emulsification was proposed. Discussion was conducted on the evolution of droplet size with time, which followed the Ostwald ripening theory. And a monodispersed nonaqueous emulsion with an average droplet size of 1.6μm could be prepared. Using the emulsion as a template, TiO 2 ceramics with an average pore size of 1.1μ.m were obtained. The material could be prospectively used for preparation of catalysts, adsorbents, and membranes.