Studies On Preparation Of CoS₂, NiS₂ Powders Obtained By Hydrothermal/Solvent-thermal Method

We recite the development of nano-materials and the chief preparation method of them briefly. Besides, we present the superiority and principle of hydrothermal/solvent-thermal method on the preparation of nano-materials. In addition, we introduce the characteristic and some preparation method of the sulfides and list several samples on the preparation of metal sulfides which are synthesized by hydrothermal/solvent-thermal method.Hydrothermal method, which is known as a solution-based chemical method, might provide an effective and convenient route to generate nanoscale materials of transition metal sulfides. Solvent-thermal method is similar to hydrothermal method, except that organic solvent was substituted for water. In our experiment, we used the hydrothermal method and solvent-thermal method to prepareâ…¡-â…¥group transition metal disulfides CoS₂ and NiS₂. This method is not only simple but also can be easily controlled. CoS₂ powder was synthesized by EDTA-assisted hydrothermal method under alkali conditions, adding NiSe2 as seeds. In the process, the free Co²⁺ ions continuous release from Co(â…¡)-EDTA compound, then combine S₂^2-in the solution form CoS₂. We have studied the influence of reaction condition and the quantity of seed on the formation of CoS₂ and refine the final product to get the detailed crystal structure. In the preparation of nanocrystal NiS₂, we choose pyridine as solvent and the diameter of final product is 50 nm. The crystal growth process of NiS₂ nanocrystalline was discussed with a simplified mathematics model and divided into two steps. The first step is a nucleation and growth of small grain process while the second step is a process during which big grain merges small grain and grows to larger size. The crystal growth activation energy was obtained respectively. The crystallization process could be described by Avrami equation and the value of the Avrami exponent n was measured about 1.56.At the end of the study, a summary and expectation were made and some notion was...