Preparation And Characterization Of CeB₆ And AlB₂ Nanomaterials

Research indicates that metal boride nanocomposites have richness, interesting structure and excellent physical ,chemical properties. For example, lanthanum hexaboride(CeB6), with low work function, high melting point, high conductivity, high mechanical strength and good chemical stability, is a potential candidate of electron field emission applications. Aluminum diboride (AlB2) can be used as a high-temperature refractory and wear Al-based composite as filling intensifier because of its high metal conductivity and chemical stability.The growth mechanism of CeB6 and AlB2 nanocomposites, prepared by chemical vapor deposition and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM), was discussed in the following:First of all, CeB6 have been successfully synthesized with self-catalyst method using cerium powder and boron trichloride gas under the mixed gas(30%H2+70%Ar). Secondly, It was indicated that the compound have good structure and morphology through XRD, SEM, TEM. Moreover, the compound was characterized by FE-SEM exhibting high field emission performance, with 1.35V/μm electric field intensity and 1.1×107A/cm2 efficient field emission electricity.Besides, AlB2 nanocomposites have also been successfully prepared via the same method as CeB6. It was supposed that the growth mechanism of AlB2 is a self-catalyst process from the XRD, SEM results, which indicate that the compounds without Impurity AlB12 were composed of thread and flake shape with a range of 50nm-300nm on diameter, several micrometers on length. A growth mechanism based on the self-catalyst process was proposed for the formation of the nanomaterials.At last, metaborate lanthanum (LaB3O6) compound prepared through sol-gel method was also briefly discussed in this dissertation. The XRD, SEM results inferred that the crystallizability and morphology of the product was influenced by the different stoichiometric raw materials and reaction temperatures.