Preparation And Catalytic Properties Of Ordered Nano Composite Materials

Nowadays it is well-known that design and preparation of materials at nanoscale is one of the most forward fields of science and technology. This scale of the materials possesses novel physical and chemical properties because of their peculiar and fascinating properties, such as quantum size effect, small bulk effect, surface effect and macroscopic quantum tunneling effect. However, there are two key problems in this field, namely "spontaneous reunion" and "random distribution ", making the nano-material is difficult to obtain remakeble nano-effect, limiting the application of nano materials in a great degree.In this paper, considering these bottleneck problems described above, the nano-antidot array materials are chosen as the study object. It can obviously restrain "spontaneous reunion" and solve the problem of “random distribution” via the design, assembly and controlled preparation of nano-materials. That synthesized according to the design intention of microstructure controllable has excellent catalytic performance for its significant nano-effect. The main research contents and results are as follows:(1) Highly monodisperse polystyrene(PS) microspheres in the range of 0.8~5.0 μm were synthesized by a improvement dispersion polymerization which named dropwise monomer feeding metnod by our recheach group. Moreover, the effects of proportion of monomer/dispersion medium and alcohol water ratio on the diameter and monodisperse of PS microspheres were studied, respectively. The results indicated that the solubility of polymer chain had a significant effect on the size of PS microspheres in process of dispersion polymerization. With the increase of proportion of monomer/dispersion medium, the solubility of the polymer chain is increased, which could help to promote PS microspheres growing up. Furthermore, the poor dispersion of PS microspheres mainly came from the "second nucleation" phenomenon. With the increase of proportion of alcohol/water in the mixed system, the solubility parameter and polarity would be reduced. Thus, it resulted in a large number of "second nucleation" phenomenon, which is responsible for the poor dispersion. In addition, highly ordered and controllable colloidal crystal were assembled by centrifugal sedimentation method through the PS microspheres preparaed above.(2) Continuously adjustable nano-antidot arrays with feature size(aperture 0.48~1.65μm, wall thickness 50~150 nm) constructed by colloidal crystal templating technology, and the influence of precursor concentration and calcination temperature on microstructure were studied with in detail. The experimental results showed that the concentration of precursor was the main influential factor for the defects of microstructure, such as local fracture, hole wall discontinuous, and wall thickness nonuniform, and so on. Meanwhile, the calcining temperature was fundamental reason for the defects of pore blockage and wall collapse of the macropores. Thus, highly ordered nano-antidot arrays were obtained at large area through adjusting the parameters of precursor concentration to 0.5~0.8 mol/L and calcination temperature of 530~550℃ precisely in this paper.(3)Au@Al2O3 ordered nanocomposite with different aperture and wall thickness prepared by colloidal gold deposition method. The internal connection on microstructure and catalytic performance were studied. Results showed that microstructure has a significant influence on the catalytic properties of ordered nanocomposite materials. Moreover, owing to that the pore size and wall thickness are the fundamental reason for effective active area and channel transmission. Thus, with the increase of pore diameters, the catalytic performance increased rapidly then decreased gradually, and reached highest at the pore size of 1.27 μm. Consequently, the excellent catalytic properties could acquire via adjusting the microstructure of Au@Al2O3 ordered nanocomposites, which is better than that of commercial vehicle catalyst. In addition, with the change of the microstructure, that effective active area and channel transmission efficiency also varied. And ultimately, the highest catalytic performance gained when that competition between of effective active area and channel transmission efficiency achieve to a delicate balance at a particular size. Furthermore, the feature size of Au@Al2O3 ordered nanocomposite could adjustable with accurately and continuously in nanoscale, that were considered as the main reasons for much higher than the commercial vehicle catalyst. Thus, the ordered nanocomposite materials fabricated in this thesis, have a wide of application prospect in many fields,such as petrochemical industry, industrial catalysis, atomic energy, photocatalysis, and photonic crystal.