The Preparation,Characterization And Application Of Inorganic Ultrafine Powders

Ultrafine powder is one of the most important materials with itsstructural features in the range of I O~ to 1 O~ m. Owing to the extremely smalldimensions, naonometer materials are structurally characterized by a largevolume fraction of grain boundaries or interphase boundaries, which exhibitsome unique structural characteristics and novel properties with respect to theconventional coarse-grained polycrystalline materials. As a part of newtnaterials, nanostructured materials will play an important role in the nextinformation field, manufacturing, biotechnology and agriculture etc. Thispaper has developed several new methods for synthesis of ultrafrne cobaltpowders, Co304 nanocrystals and samarium oxide nanoparticles, respectively.The main content consists of four parts:PART I. ReviewChapter 1. Materials with nanometer-sized dimensions namednanocrystalline materials, can be formed by several methods. A scientificunderstanding of the unique structural characteristics and the novelproperties of the nanostructured materials have been partially achieved. Thetendency of development of this special interdisciplinary area of science hasan obvious impact on our potential ability to produce new materials. In thispart, many kinds of techniques and recent progress in preparing nanometerpowders including the principles, varieties and characteristics of solid-phase,liquid-phase and gas-phase methods have been reviewed scientifically. ThePostgraduate:Zhao Yanchun. Speciality: Analytical ChemistrySupervisors:Prof. Gao Jinzhang, Yang Wu and Kang iiagwanZhao Yanchun: The Preparation, Characterization and Application of inorganic Ultrajine Powderstendency of development of the techniques for preparing nanoparticles andapplications of this new class of materials were also outlooked in this paper.Chapter 2. The recent research progress in synthesis of nanostructuredmaterials including powders, thin films of cobalt, cobalt oxide and theircomposites have been reviewed from 1970 to the early 2001 throughrepresentative examples. The characteristic and application of these materialshave also been pointed out in this paper. 156 references are cited.PART II. Nanocrystalline cobalt powders have been prepared fromaqueous solution by reducing their corresponding metal salts under suitableconditions. The experimental conditions including the types andconcentration of protective agents and reducing agents, and the pH of thesolution that influence the average particle size and the yield of ultrafinecobalt powders have been studied in detail. The result shows the optimumcondition is to use a pH 9?10 NaHCO3-Na2CO3 buffer, and to keep themolar ratio of CoCl2 to sodium citrate is 1:1 at 75 ? 85 ~`C . Higherconcentration of surfactant and relative lower concentration of Co2~ weresuitable selections to form nanoscale cobalt powders. X-ray powderdiffraction patterns show that the cobalt powder consists of hexagonalcrystallite. And XPS results reveal a continuous 1.8 nm thick absorptionlayer and CoO at the interface. The average particle size of the ultrafinecobalt powders is S5nm.PART III. A new citrate acid-hydrazine sd-gel route for preparationof Co304 nanoparticles has been developed. Different particle-sizes andmorphologies of Co304 nanoparticles were prepared at different heatPostgraduate: Zhao Yanchun, Speciality: Analytical Chemistry2Supervisors:Prof. Gao Jinzhang. Yang Wu and Kang JingwanZhao Yanchun: The Preparation, Characterization and Application of inorganic (Jltrafine Powderstreatment temperatures and the pure cubic nanocrystals of Co304 wereobtained at 600 0C . The synthesis results were monitored by Infraredspectroscopy (IR), Thermal gravimetric and differential thermal analysis(TG-DTA). The...