Preparation And Kinetics Of Magnesium Oxide Nanorods

Magnesium oxide of 1D nanomaterials is a new type of high functional fine inorganic material.Because of its special properties,magnesium oxide of 1D nanomaterials is widely used in the fields of high-quality ceramics,electron optical devices,superconductor additives, etc.Up to now,the preparation of magnesium oxide 1D nanomaterials is mainly based on two methods,which are gas phase chemical synthesis and precursor thermal decomposition.In this paper,basic magnesium chloride nanorods are prepared by liquid phase method with light magnesium oxide and magnesium chloride hexahydrate as raw materials.Then,using converting precipitation method,magnesium hydroxide nanorods are synthesized with basic magnesium chloride nanorods as precursor.After calcining the magnesium hydroxide, magnesium oxide nanorods are produced.Preparation factors are systematically investigated, including heating rate,calcination time and temperature,etc.The products are characterized by XRD,SEM,TEM,TG and SAED in order to determine better synthesis conditions and also the kinetic mechanism of magnesium hydroxide nanorods decomposition.The lattice distortion and grain growth kineetics of magnesium oxide nanorods are also made.Magnesium oxide single-crystal nanorods with diameters of 150～250nm and lengths of 6μm-10μm are successfully synthesized by calcining magnesium hydroxide nanorods at the temperature of 400℃for 60min under a low heating rate of 3℃/min.The kinetics of the thermal decomposition of magnesium hydroxide nanorods is investigated using both isothermal and non-isothermal methods of kinetic analysis.It is found that the kinetics mechanism of thermal decomposition is changeful at different temperature by isothermal kinetic analysis.The rate-controlling mechanism of the reaction is nucleation and development(F₁)at 300℃,contracting cylinder(R₂)at 325℃,three dimensional diffusion (D₃)at 350℃,respectively by isothermal methods.And the apparent activation energy is about 194 kJ/mol.The integral mechanism function for the decomposition of magnesium hydroxide nanorods is obtained by analyzing the thermal decomposition of magnesium hydroxide nanorods using thermal gravimeteric data under non-isothermal conditions which is: G(α)=-In(1-α).And the apparent activation energy is 171～197kJ/mol. The crystallization of magnesium oxide nanorods is investigated by XRD at different preparation factor.The results show that with the increase of calcination time and temperature the lattice constant decreases and grain diameter increases.Grain growth exponent and kinetic equation of magnesium oxide nanorods are also determined:n=9, G⁹= 2.094×10³⁰t exp(-186210/RT)...