Strength and Densification of Ni/Al₂O₃ Membrane Compacted with Uniaxial Pressing and CIP for Hydrogen Separation: Influence of Pressing Process

In our previous studies, 10-40wt%Ni/Al2O3 membrane was prepared by uniaxial pressing and sintered at 900 to 1400°C for 2 h. It was found that 10wt%Ni/Al2O3 membrane sintered at 1400°C showed the highest physical and mechanical properties. Thus, this work we focused on the effect of different pressing processes on the properties of Ni/Al2O3 membrane with longer soaking time. Firstly, 10-40wt%Ni and Al2O3 powders were mixed by dried ball-milling. Then, the mixture powder was pressed to form a bar shape by two different processes; uniaxially pressing (No CIP) and uniaxially pressing followed by cold isostatic pressing (CIP) at 250 MPa for 5 min. All Ni/Al2O3 specimens from two pressing routes were sintered at 1400°C for 4h under air atmosphere and reduced at 900 °C under H2 (99.99%). From the results, it was found that the densification process affected to physical and mechanical properties of Ni/Al2O3. The CIPed - 10wt%Ni/Al2O3 membrane sintered at 1400°C for 4 h showed the highest relative density and flexural strength of 76% and 106 MPa with the lowest pore size (78 nm) and 17% porosity. The addition of nickel content gradually decreased physical and mechanical properties of Ni/Al2O3.