Fabrication Of Magnetic NiO Nanorings And Hierarchical Ruptured Mechanism Of Bubbles

Nanoring-structures are potential building blocks for nanoscale devices in photonics, optoeletronics, eletronics, bio-detection, information storage, etc. To research the property of nanorings, scientists solve the problem how to prepear them widespread and low-cost first, nowadays the methods of nanorings preparation are focused on colloid template, liquid phase method, and MBE. These methods have their own disadvantages. In this thesis, we demonstrate a simple and low-cost method for fabricating NiO nanorings. Bubble-bursting cascade as template takes an important role in the method.The process of fabrication of NiO nanorings: nickel nitrate was dissolved in the SiO₂ sol first; subsequently the mixed sol was dipcoated onto a substraet to form Ni(NO₃)₂/SiO₂ film, then followed by heat-treatment. Via SEM , we get the information that the NiO nanorings have an outer diameter of 100¹50 nm, and a wall thickness of 10-20 nm, not only integrated structure, but evenly distributed existence. Via XRD, the NiO nanorings are face-centered cubic crystal structure. In additon, we research the factors which influence the experiment. The magnetic property of NiO nanorings at room temperature is investigated. The hysteresis loop at 300K shows a weak ferromagnetic behavior with a coercive force and remanent magnetization are 670 Oe and 8.1×10^-4 emu/cm² respectively.According to intermediate products of the process, namely the droplets and bubbles, the mechanism is proposed of nanorings by hierarchical ruptured bubble template. The molten Ni(NO₃)₂ droplet disperse in the porous SiO₂ films first, then penetrate to surface of the film; during the process of heat-treament, the droplets change into bubbles with gaseous production and the bubbles divide into smaller bubbles constantly to the end of reaction. Because of instability, the bubbles rupture and change into nanorings at last.