| Ultrafine powders which consist of dispersed nanosize particles of less than 100nm diameter are currently receiving significant attention for their novel physical and chemical properties. Such powders can exhibit properties that substantially differ from those of bulk materials as a result of particle dimension, surface area, quantum confinement, the microstructure, the arrangement of the atoms (the atomic structure) and the size of a solid in one, two or three dimensions. In other words, changing one or several of these parameters, the properties of a solid vary at the same time. Owing to the extremely small dimensions, nanometer materials are structurally characterized by a large volume fraction of grain boundaries or interphase boundaries, which exhibit some unique structural characteristics and novel properties with respect to the conventional coarse-grained polycrystalline materials. As a part of new materials, nanostructured materials are playing an important role in many fields, such as information, manufacturing, biotechnology and agriculture etc. In this paper, we have employed solution SHS method for preparation of NiFe2O4, CoFe2O4 and (Ni0.6Co0.4)Fe2O4 nanopowders, and their structures have been characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). At last, we have also studied their application in electrochmestry.The main content consists of three parts and six chapters:PART I. ReviewChapter 1.In this chapter, we mainly describe some basic and specific properties of nanoparticles, such as quantum-size effect, surface effect, small-size effect, macro-quantum tunnel effect, opitical, magnetic and catalytic properties , hydrogen storage properties and so on. In addition, three main types of nanosized materials have been briefly classified.Chapter 2.Self-propagating high-temperature synthesis(SHS) , also called combustion synthesis(CS), is a new method to synthesize materials. It is an important processing method with wide application. In the SHS process, heat generated by exothermic reactions is been used to synthesize high-temperature inorganic ceramic materials. Here, we will emphasisly introduce the development history, fundamental theory and application of SHStechnology. And solution SHS method is also described. PART II. ExperimentsThe solution SHS process is employed to preparare ultrofine oxide powders from aqueous solution. The starting materials are the metal nitrate acting as oxidizer and a variety of organics such as urea, carbohydrazide, etc., serving as a fuel. The mixture of the two components is made into a pasty mass by dissolving in a minimum quantity of water. The SHS reaction is occurred by igniting the paste. Various exothermic redox reactions ,associated with the decomposition of nitrates and the oxidation of fuel, raise the temperature of the products to >1873K and the products foam and swell up in the container because of the large volume of gases produced. The whole reaction is completed within 5min, typical of SHS reactions. The product mass is highly friable and yields homogeneous and fine-grained particles with an average particle size of approximately 8-20nm. Clearly the distinctive advantages of the process are its simplicity, and the excellent means it provides for incorporating and uniformly distributing any desired dopants in the product oxide. In addition, the process is also safe and instantaneous. We have synthesized NiFe2O4, CoFe2O4, (Ni0.6Co0.4)Fe2O4 and CuFe2O4 nanoparticles. Differential thermal analysis-thermogravimetry (DTA-TG) was used to study the decomposition of their precursors. The structure of the nanosized powders were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). This part consists of the following threecharpters:Chapter3, Chapter4, Chapters.PART HI. ApplicationChapter 6.In this chapter, we have preparared nanometer composite oxide modified carbon paste electrode and have studied the electrochemical B-Z oscillating behavior.
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