New Methods And Research On The Preparation Of Transition Metal Oxides Crystallites

Transition metal oxides constitute a well-studied category of materials for their many distinctive properties and numerous applications. The methods of preparing transition metal oxides crystals have received much attention in recent years. Many growth methods have been introduced based on technical requirement, thus causing the diversity of crystals growth methods and the complicacy of the preparation equipments and technique.In this paper, we introduce a simple hydrothermal method without any surfactants to prepare Co3O4 and ZnO nano-crystals as precursors. Hexagonal Co3O4 nanoplatelets with an average diameter of 300 nm and a thickness of 30 nm have been successfully prepared. ZnO nano-particles with an average diameter of 30 nm have also been successfully prepared. Then finally cuspate deltoid CoO crystallites with an average grain size of 3μm and ZnO crystallites with different grain sizes were obtained via developing the precursors under the KCl/NaCl flux atmosphere. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and selected area electron diffraction. The electrochemical properties of the Co3O4 and CoO were investigated by an Electrochemical Workstation device at room temperature. A supercapacitor behavior has been observed, specific capacitances up to 110 F/g for the Co3O4 product and 88 F/g for the CoO product have been achieved, revealing that the as-made Co3O4 and CoO products have excellent capacitive characteristics and might be promising candidate materials for supercapacitor application. As for the ZnO crystallites product, the factors like flux temperature and molten salts categories affecting the crystallites growth have been primarily discussed.Porous crystals of CoFe2O4 were produced using mesoporous silicas, SBA-15 as hard templates and nitrates as precursors. By a new convenient approach, the solid-liquid method, the precursors could be completely incorporated into the channels of SBA-15 templates by a temperature controlled one-step impregnation process. After decomposition of the nitrates precursors at 500℃and dissolution of the templates by using NaOH solution at proper temperature, ordered mesoporous CoFe2O4 material was obtained, which maintains the macroscopic morphology and ordered mesostructures of the SBA-15 templates. Characterization of the materials was performed mainly by using X-ray powder diffraction and transmission electron microscopy. The advantages and disadvantages of this solvent-free method are discussed in comparison with the previously established methods.