Preparation And Catalysis Studies Of LDH Grafted On Carbon Nanotubes And Electrospinning Study Of PVP/LDH Composite Fibers

In this thesis, nickel aluminum and magnesium aluminum layered double hydroxides (NiAl-CO₃-LDH and MgAl-CO₃ LDH) were grafted on the surface of multi-walled carbon nanotubes (MWNTs) through the hydroxyl groups, respectively. Powder X-ray diffraction (XRD), Energy Dispersive Analysis of X-rays (EDAX), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and X-ray Photoelectron Spectroscopy (XPS) were used to investigate the crystalline structure, chemical composition and grafting mechanism of the composites. Moreover, the catalytic properties of NiAl-CO₃-LDH/ MWNTs for the reaction of phenyl aldehyde oxidation have also been investigated.NiAl-CO₃-LDH nanoparticles were grafted onto the surface of MWNTs induced by the hydroxyl groups by the hydrothermal method. The structure, composition as well as grafting mechanism of NiAl-CO₃-LDH nanoparticles have been thoroughly studied by XRD, EDAX, SEM, TEM and XPS. Furthermore, the catalytic properties of the grafted NiAl-LDH for the oxidation reaction of phenyl aldehyde have been investigated. The results showed that the grafted LDH can be used as a catalyst in the oxidation reaction of phenyl aldehyde, which exhibits higher activity compared with that of pristine LDH as a reference sample. This is possibly related to the large specific surface area of MWNTs as well as the high dispersion of LDH on the surface of MWNTs.MgAl-CO₃-LDH grafted on MWNTs has been synthesized by hydrothermal method. XRD, EDAX, SEM, TEM and XPS were used to investigate its crystalline structure, chemical composition and grafting mechanism. The influence of aging temperature on the crystal structure and particle size of LDH has been studied. It was found that well-defined LDH with high crystallinity and large particle size can be obtained upon increasing aging temperature.The second part of this thesis focuses on the fabrication of poly vinyl pyrrolidone (PVP)/LDH composite nanofibers based on the electrospinning technique. Firstly, MgAl-LDH particles were prepared by coprecipitation and nonaqueous hydrothermal method, respectively. Secondly, the LDH particles were dispersed in the PVP solution thoroughly and then PVP/LDH nanofibers were fabricated by electrospinning. The products were characterized by XRD and SEM. The results showed that compared with the coprecipitation method, the LDH particles synthesized by nonaqueous hydrothermal method exhibit more uniform morphology and thus better compatibility with PVP, and the optimal addition of LDH is 5%. Furthermore, the combustion temperature of the PVP/LDH nanofibers increased by some 50℃compared with the pristine PVP nanofibers.Therefore, this work opens new opportunities for further research into the LDHs-based composite materials and their prospective applications in the fields of catalysts and polymer additives.