Sintering of the Metallic Nickel Hollow Fibers into High-Performance Membranes for H2 Permeation

The sintering process is a crucial step for fabricating nickel hollow fiber membranes (NHFMs), which significantly affects hydrogen permeability of the membrane and the qualified rate of membrane manufacturing. Optimizing sintering conditions will accelerate the industrial applications of nickel hollow fiber membranes. In this work, the effects of the sintering conditions (temperatures, duration, and the atmosphere) on the membrane microstructure and hydrogen permeation performance of the resultant NHFMs are extensively investigated. Results show that small metal grain size results in large grain boundary density, leading to enhanced hydrogen permeability and decreased activation energy for hydrogen permeation. Sintering temperatures significantly affect the metal grain size, thereby affecting hydrogen permeation and activation energy. When the sintering temperature decreases from 1400 to 1100 degrees C, the hydrogen flux remarkably increases by a factor of 2 and the activation energy decreases from 57.47 to 48.89 kJ mol-1. On the other hand, increasing the sintering time and hydrogen concentration in the sintering atmosphere only slightly affects the grain size and thus results in a minor change in hydrogen permeation. However, short sintering time and low hydrogen concentration in the sintering atmosphere may cause defects on the membrane and increase the difficulties on full removal of carbon residues in the membrane, which leads to the decrease in the qualified rate of produced membranes.