Study On Preparation And Application Of ZnO-based Nanocomposites

Zinc Oxide（ZnO）nanoparticles have excellent chemical and physical properties,such as good ultraviolet ray（UV）absorption,high electron mobility,large exciton binding energy,wide band gap,high thermostability and mechanical stability,etc.It has great application prospects in the fields of functional composites and photocatalysis.However,how to avoid the agglomeration problem caused by its high surface energy in the application process,so as to realize the nano-scale dispersion of ZnO nanoparticles with small size and uniform particle distribution in the application system,which is the key scientific problem for its wider application.In this work,ZnO/polythene（PE）and ZnO/g-C₃N₄ nanocomposites were prepared by“liquid-solid masterbatch”method and in-situ loading method based on high-gravity technology,which completely solved the dispersion problem of ZnO nanoparticles in the substrate.The work focus on the effects of preparation conditions on the morphology,size and dispersion of ZnO nanoparticles.In addition,the mechanical properties of ZnO/PE nanocomposites and the photocatalytic properties of ZnO/g-C₃N₄ nanocomposites were studied.The main research contents and conclusions are as follows.Monodispersed ZnO nanoparticles were prepared by high-gravity method combined with in-situ surface modification technology.The effects of different preparation and modification conditions on the size distribution and dispersion of ZnO nanoparticles were explored.The suitable technological conditions are as follows:the speed of the rotating bed is 2500 rpm,the dosage of tetraethyl orthosilicate is 15 wt%and the reaction temperature is 70℃.Two silane coupling agents are used with a weight ratio of 0.4:1,the modification time is 45 min,the amount of modifiers is 75 wt%.Compared with the conventional reactor method,ZnO nanoparticles prepared by the high-gravity technology have smaller size and narrower particle size distribution,with an average particle size of about 6 nm.It can be monodispersed in toluene to form transparent ZnO nanodispersions.ZnO/PE nanocomposites were prepared by“liquid-solid masterbatch” method with ZnO nanodispersions mentioned above.The results show that ZnO nanoparticles can be monodispersed in PE matrix,and the ZnO/PE nanocomposites have excellent mechanical properties,UV-aging resistance,etc.Compared with pure PE,the tensile strength and impact strength of the nanocomposites are increased by 35.8%and 99.3%when the addition amount of ZnO is 1 wt%,it shows that the strength and toughness of composites are improved simultaneously.After 240 h of UV enhanced irradiation,there is no obvious yellowing,and the tensile strength,impact strength and elongation at break of the nanocomposites decreased by 8.3%,11.8%and 8.2%,which are obviously lower than that of pure PE.In addition,ZnO nanoparticles significantly improves the thermal stability of the composites.The g-C₃N₄ nanosheets were prepared using urea as precursor.ZnO/g- C₃N₄ nanocomposites with typeⅡheterojunction were prepared by high-gravity technology combined with in-situ loading method.ZnO nanoparticles with a small particle size of about 7 nm are uniformly loaded on the g-C₃N₄ nanosheets.The g-C₃N₄ nanosheets are so tiny and thin due to high-gravity technology,so the composites have a large specific surface area and a large number of catalytic active sites.DRS,PL,transient photocurrent response and EIS results show that ZnO/g-C₃N₄ nanocomposites have excellent visible light absorption and photogenic electron/hole pair separation efficiency.The active species capture experiment and ESR results show that·O₂^-and h⁺are the main active species in the photocatalytic process,while·OH is the secondary active species.Moreover,the concentration of active species produced under light is high,which is conducive to the degradation of pollutants.The photocatalytic degradation of amoxicillin is the best when ZnO loading is 45 wt%,and the degradation rate reaches 86.7%within 3 h.Meanwhile,ZnO/g-C₃N₄ have good catalytic stability.