EVOLUTION OF PORE STRUCTURE IN COMPACTS PRODUCED FROM NICKEL CARBONYL POWDERS DURING SINTERING 

Abstract

The influence of the evolution of the characteristics of the pore structure of compacts during sintering of nickel carbonyl powder with an average particle size of 1.4 μm in the temperature range of 200–1000 ºC on local and volumetric shrinkage during sintering was analyzed. The pore structure of the samples was characterized by the values of the maximum and average diameters of the narrowing of the pore channels, determined by the Barus–Bechgold method. In order to minimize local (incoherent) shrinkage during sintering of dispersed nickel powders, a criterion for uniformity of the pore structure of compacts α ≤ 0.03 was selected, determined by the difference in the values of the maximum and average diameters of the narrowing of the pore channels. The influence of the evolution of the characteristics of the pore structure of compacts made of Ni carbonyl powder with an average particle size of 1.4 and 4 μm on local and volumetric shrinkage during sintering has been experimentally confirmed. The reason for the occurrence of local shrinkage is the three-level structure and wide polydispersity of nickel carbonyl powders. A method has been proposed for determining the average diameter of particles (agglomerates) of Ni carbonyl powder using the Kozeny formula, which establishes the relationship between the particle diameter, the maximum diameter of the narrowing of the pore channels and the porosity of the compacts in the range of 0.25–0.45.