Preparation And Electron Microscopy Analysis Of Aluminum-Oxide Compounds And Their Nanoheterostructures

Low-dimensional nanomaterials play an important role in constructing nanoelectronics and optical devices due to their diverse structure and morphology,exhibit a series of novel mechanical,optical,electrical,and thermal properties.Using transmission electron microscopy to characterize the microstructure and morphology of nanomaterials is an indispensable part of nanomaterials research.In this paper,nanomaterials were prepared by chemical vapor deposition.Different products were obtained on the surface of raw materials and the substrates,and the corresponding products were observed in electron microscopy.The results are as follows:On the one hand,the nanomaterials on the surface of aluminum powders were characterized.The products mainly include:?1?trigonal-structure ?-Al₂O₃ nanotubes.Nanotubes are well-crystallized single crystals and it is the first report of the use of CVD methods.?2?orthorhombic-structure 8-Al₂O₃ ultrathin nanosheets with a thickness of 20-30 nm.It is a common metastable phase during the phase transformation of alumina.?3?Al₂O₃/Mg-Al-O heterostructure nanowires.The results show that the nanowires contain two orthogonal Al₂O₃ domain structures and two monoclinic MgAlxOy domain structures,it is found that incorporating the orthorhombic-structure Al₂O₃ can effectively modulate the occurrence of monoclinic domains.Furthermore,the rationality of domain structures is proved theoretically by group theory analysis.We have deepened our understanding of the microstructure of aluminum-oxide compounds and played a certain role in the optimization of material properties and practical applications.On the other hand,a large number of ultra-long nanowires were also obtained on the silicon substrate.Transmission electron microscopy characterizes the products are amorphous SiO₂ and Si3N4/SiO₂ core-shell nanowires.Further HAADF-STEM experiments directly observed the arrangement of Si atom in the a-Si₃N₄[0001]axis.