Number of the futures of tantalum powders passivation

Full text: Number of features of fine tantalum powder interaction with gaseous nitrogen and effect of chemically active surface layers of Tantalum powder Particles have been under investigation in this article. It is known that the surface of a tantalum powder particle is covered oxide layer preventing interaction with the environment. Thickness of such layer depends on the degree of the surface development and can reach value of some nanometers. Rate and temperature of the oxidation reaction are the features of the oxide layer formation. However, natural oxidation (as formation of oxide film) can be replaced with Nitrogen passivation of the powder surface. The work was aimed to determine optimum settings of the interaction between gaseous Nitrogen and surface layers of Tantalum powder particles prior transferred into reaction active condition for the improvement of some physical and electrical properties. Passivation process has been under the investigation using tantalum powders with prior reduced (ultimately low) oxide layer. Prior to gaseous Nitrogen introduction the powders were heat treated in the Argon protective and reduction atmosphere during several hours. Magnesium transferred into steam condition was used as the reducing agent introduced with the Argon current. Reduction conditions were considered as common for such systems. The quantity of Magnesium used for reduction depended on the value of Oxygen contained in the powder according to the chemical analysis results. Powders with different degrees of the surface development granulometric composition, average Fischer grain sizes and different types as fragment and Sodium thermal capacitor grade were used as samples. Nitrogen passivation process was regulated by the factors of N temperature and time of N introduction. Dependence of N and O content in the resulted powder, change of physical and electrical properties have been investigated, comparisons with properties of the original powders have been performed. Screen electronic microscopy was used for finding out the changes in the powder microstructure. During the discussion and mathematical processing of the results border values of the most optimum temperature areas of the passivation with the gaseous Nitrogen were found, time factor influence was expressed, N saturation dependence on the original powdery objects was determined, special importance of the starting passivation temperature and specific surface area was noted. Number of changes in the microstructure of the powders and their ability to agglomeration were described. Results were obtained that allowed to conclude the decrease of the oxide layer and increase of N content in the surface layers of the Tantalum powder particles. It was noted that in certain quantities powders saturated with Nitrogen show the improvement of some physical and electrical properties