The acid-base titration,atomic force microscopy(AFM),contact angle technique,energy dispersive X-ray(EDX)and electron probe microanalysis(EPMA)were performed to check the existence of the gel-layer on the chitosan surface after it was dipped in aqueous TPAOH solution as well as in TS-1 synthesis solution.The evolution of TS-1 monolayer and multi-layered film on the chitosan surface was studied using SEM imaging at different stages during hydrothermal reactions.Experimental evidence for the formation mechanism of supported zeolite films and membranes revealed that a gel-layer enriched with TPA cations and TS-1 precursors was first formed on the chitosan surface,followed by the nucleation within the gel-layer especially on the chitosan surface.The nuclei formed on the chitosan surface were further transformed into crystalline particles and TS-1 crystal grains.The nuclei beyond the chitosan surface subsequently grew up,leading to the formation of multi-layered TS-1 film with preferential b-orientation.The result is significant for engineering the microstructure of supported zeolite films and membranes in hydrothermal reactions.
LIU XiuFengWANG XiaoDongNA PingJIANG HaiYangLANG LinZHAO HongSheZHANG BaoQuan
Pure CoAPO-36 crystal grains were synthesized by hydrothermal reaction. Porous α-Al2O3, stainless steel and K2Ti6O13 supported CoAPO-36 films were fabricated using in situ crystallization for the first time. SEM images and XRD measurements demonstrate that a continuous CoAPO-36 film was obtained on the K2Ti6O13 substrate. Diffuse reflectance UV-Vis spectra indicate that Co2+ has been incorporated into the ATS framework. Both CoAPO-36 crystal grains and the K2Ti6O13 supported CoAPO-36 film exhibit satisfactory catalytic activities for the oxidation of cyclohexane.
WANG XiaoHuiLI JianWANG YanJiZHANG BaoQuanLIU XiuFeng
The aligned array and thin film of zeolites and molecular sieves possess a variety of potential applica- tions in membrane separation and catalysis, chemical sensors, and microelectronic devices. There are two main synthesis methods for manufacturing the aligned arrays and thin films of zeolites and mo- lecular sieves, i.e. in situ hydrothermal reaction and self-assembly of crystal grains on substrates. Both of them have attracted much attention in the scientific community worldwide. A series of significant progress has been made in recent years. By the in situ hydrothermal synthesis, the oriented nucleation and growth of zeolite and molecular sieve crystals can be achieved by modifying the surface properties of substrates or by changing the composition of synthesis solutions, leading to the formation of uni- formly oriented multicrystal-aligned arrays or thin films. On the other hand, the crystal grains of zeo- lites and molecular sieves can be assembled onto the substrate surface in required orientation using different bondages, for instance, the microstructure in the array or thin film can be controlled. This review is going to summarize and comment the significant results and progress reported recently in manufacturing highly covered and uniformly aligned arrays or thin films of zeolites and molecular sieves. It involves (1) in situ growth of highly aligned zeolite arrays and thin films via embedding func- tional groups on the substrate surface, modifying the surface microstructure of substrates, as well as varying the composition of synthesis solutions; (2) assembly of zeolite and molecular sieve crystals on various substrates to form aligned arrays and thin films with full coverage by covalent, ionic, and in- termolecular coupling interactions between crystals and substrates; (3) coupling surface assembly with microcontact printing or photoetching technique to produce patterned zeolite arrays and thin films. Finally, the functionality and applications of zeolite arrays and thin films are briefly introduced.
