Study On Preparation Of Ultrafine Platinum Powder By Ultrasonic Chemical Liquid Reduction Method

Platinum ultrafine powders have attached growing attention due to their high chemical activities and invaluable applications in microelectronics, biomedicine and catalysis. As one of the precious metals, the shortage of Platinum resources is always a global issue, therefore, to achieve the Platinum ultrafine powder with high dispensability, high specific surface area and high activity should be a common goal for researchers.The preparation of platinum ultrafine powder by traditional chemical liquid phase reduction can be low cost, short processing cycle. However, the platinum ultrafine powders can be so difficult to be cleaned and easy to spontaneous combustion. For all this, we need to explore a new milling technology, by using ultrasound to take place of the dispersant. During the whole reduction process free of any dispersant. High resolution transmission electron microscopy (HRTEM), Scanning Electron Microscopes (SEM), and Ultraviolet-visible spectroscopy (UV-vis) were used to characterization the Pt particles.To prepare the ultrafine platinum powder with optimal parameters of high dispersion, high sphericity and uniformity by designing experiments with different types of the reducing agent and the reaction temperature, the concentration of reducing agent, the concentration of precursor and ultrasonic time. The results show that the ultrasonic frequency of 40kHz, with the pH value of 2, the reaction temperature at 50 ℃ and the concentration of Potassium chloroplatinite with 0.02mol/L, by regulating the concentration of ascorbic acid, the size of the platinum particles can be obtained, and the size of the sphericity of platinum superfine powders are of highly uniform and decentralized. With the ultrasonic wave of 40kHz and the pH value of 2, under the reaction temperature at 50℃, ascorbic acid concentration is O.lmol/L, by regulating the concentration of platinum ions, the quantity and the size of the platinum particles can be marked change. Meanwhile, the crystal structure of these particles are of significantly difference.To explore the role of ultrasound time during the reduction process, this paper would explore the nanometer crystal growth mechanism with the "classical nucleation theory" and "the classical nucleation theory" by choosing the experiment condition with the pH value of 2, the reaction temperature at 50 ℃, the concentration of the platinum acid potassium chloride solution of 0.02 mol/L and the concentration of the ascorbic acid of 0.25 mol/L. The ultrasound may increase the kinetic reaction between reactants and reducing reagent to improve the formation of the metal, as well as distribute the particles more uniformly. Ultrasonic would promote the nucleation of the precursor solution under the condition of low degree of supersaturation. The ultrasonic can also speed up the collision between the particles, which can promote the particles to grow up.