FORMATION OF NANO-AND ULTRAFINE PALLADIUM POWDERS IN THE PRESENCE OF «RED-OX»SYSTEM«TITANIUM (III) - TITANIUM (IV)»

The results of studies on the processes of obtaining ultra - and nanodispersed palladium powders from sulphate solutions by a combined chemical and electrochemical method in the presence of a "red-ox" system of titanium (III) - titanium (IV) are presented. It has been shown that when a titanium trivalent sulphate solution is added to a solution containing palladium (II) ions, palladium ions are immediately reduced to elemental state to form a nanodispersed powder. The completeness of the above-mentioned oxidizing-reducing reactions is established on the basis of calculating the equilibrium constant (K), which is 1034 and indicates that trivalent titanium ions completely reduce palladium ions to elemental state. Effect of initial concentration of palladium ions on amount of formed palladium powder with addition of equivalent amount of trivalent titanium ions is investigated. According to the authors, upon reduction of palladium ions, elemental palladium is formed in the atomic state, and over time, the atoms begin to combine with each other. Subsequently, atomic particles are combined into colloidal particles. It has been found that in the absence of coagulants, the colloidal palladium solution is stable for 2-3 hours, and in the presence of gelatin, the stability increases and remains for 36 hours. It was shown that in all experiments powders with spherical particles are formed, the average sizes of which range from 0.116-0.240 microns. Based on the results of the presented studies, a new technology for producing ultra - and nano-sized palladium powders is proposed.

Influence of Morphology of the Press Powder Particles and Thermal Annealing on the Structure and Microhardness of Palladium Obtained by Solid-Phase Sintering

The article is devoted to the investigation of the structure of pressed palladium-barium cathodes. These cathodes are made from a polycrystalline palladium matrix with inclusions of the particles of the activator phase Pd5Ba. The high efficiency and durability of pressed palladium-barium cathodes is ensured by the formation of an active-emission BaO layer on the working surface. The active metal Ba comes from the volume to the surface by diffusion of atoms on the defects of the crystal structure of the palladium matrix. When comparing the electrical parameters of the cathodes, the matrices of which were made from the same fractions but different batches of palladium powder, a considerable spread of electrical parameters was established. There were also revealed significant differences in the roughness of the cathode working surface. These differences affect the uniformity and stability of the emission current. This indicates the need for a detailed study of the characteristics of the initial palladium powder and their effect on the structure of the sintered material, and, consequently, on the physicomechanical properties of its surface. In this paper, the morphological features of eight batches of palladium powder in the initial state and after the purification annealing were studied by the method of electron microscopy. Significant differences in the form of particles and agglomerates of powder from different batches have been revealed. A metallographic analysis of microsections of the palladium samples prepared by solid-phase sintering was carried out. The influence of the morphological features of the particles of the initial powder on the grain size and the mechanical properties of the sintered compact is determined. Studies have shown that to obtain a compact palladium with reproducible and predictable properties, stability of the morphological characteristics of the original powder is necessary.

Chaotic variations of electrical conductance in powdered Pd correlating with oscillatory sorption of D2

Periodic thermokinetic oscillations correlate with chaotic fluctuations of electric current passed through palladium powder during sorption of deuterium.

Study on Dissolution Different of Metal Palladium Powder and Place

The chemistry of the dissolution of Palladium in pressure-cyanide has not received considerable attention. At room temperature and pressures, the reaction between sodium cyanide and Palladium does not occur because of poor kinetics. However, at elevated temperatures between 100-160 °C, Palladium can be leached by sodium cyanide like the reaction of gold. A research study has been undertaken to develop the fundamentals of a method for the direct dissolution of Palladium In this work, the dissolution of Palladium powder and place were measured in pressure clear cyanide solution. The cyanide leaching reaction mechanism is also discussed. The data of Palladium powder and place at different cyanide concentrations, different temperature and different oxygen pressure are obtained. The dissolution rate of metal Palladium powder and place were found to be relate to the cyanide and oxygen level.

Study on Pressure-Cyanide Dissolution of Metal Palladium Powder

A research study has been undertaken to develop the fundamentals of a method for the direct dissolution of Metal Palladium. At room temperature and pressures, the reaction between sodium cyanide and platinum group metals (PGMs) does not occur because of poor kinetics. However, at elevated temperatures between 100°C and 180°C, PGMs can be dissolved by sodium cyanide like the reaction of gold. In this work, the dissolution of Palladium was measured in pressure clear cyanide solution. The data at different cyanide concentrations, different temperature and different oxygen pressure are obtained. With increasing cyanide concentration and oxygen pressure, the dissolution first increased to a maximum value and then decreased. With increasing temperature the dissolution is increased. The dissolution was found to have a relation of the cyanide and oxygen level. The dissolution were independent of rotation speed for oxygen-saturated solutions and cyanide concentrations above 5 mol.m-3 and were well below chemical reaction-limited for cyanide and oxygen.