High pressure torsion of nickel powders obtained by electrodeposition

Abstract

A new synthesis route for the production of bulk nanostructured materials is presented. Fine Ni powder was made by selected appropriate electrolysis conditions. A compact material with an average grain size below 40 nm was obtained by subsequent cold pressing. Then, using the high pressure torsion (HPT) deformation technique dense bulk nanocrystalline Ni was achieved. The detailed structural investigations of the asprepared and HPT deformed Ni powder, including X-ray diffraction (XRD) and transmission electron microscopy (TEM), reveal in both cases the presence of a face centered cubic (FCC) phase without presence of any oxides. Coherently scattering domain size measurements by XRD show a value of 24 nm for the as-deposited powder and an even smaller value of 13.5 nm after HPT deformation. In addition, optical emission spectroscopy was employed to determine the impurity content of the obtained nanostructured material, showing a relatively low content of 0.9 % carbon and oxygen. The microhardness increased after deformation from (1.5 ± 0.08) GPa for the as-deposited Ni powder to (6.6 ± 0.2) GPa for the HPT deformed Ni powder. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20619