Abstract
The performance of attractive Ni-based composites can be affected by changing their microstructures, e.g., introducing pores. Here, we report a novel, relatively low-cost process to fabricate Ni/Al2O3 composites with open porosity modified by the size of Al2O3 particles. The mixture of powders was subjected to thermal oxidation twice in air after a maximal temperature of 800 °C was reached in a stepwise manner and maintained for 120 min. The oxidation kinetics were determined thermogravimetrically. The open porosity was evaluated by an Archimedes’ principle-based method. Localization and quantification of NiO, newly formed on the Ni particle surface and acting as a mechanical bonding agent, were explored by scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffractometry. Larger ceramic particles prevented merging of NiO layers on adjacent Ni particles more efficiently; therefore, the open porosity increased from 21% to 24.2% when the Al2O3 particle diameter was increased from 5–20 µm to 32–45 µm. Because both Ni/Al2O3 composites exhibited similar flexural strength, the composite with larger Al2O3 particles and the higher open porosity could be a better candidate for infiltration by molten metal, or it can be directly used in a variety of filtration applications.
Highlights
Ni-based composites are indispensable material in various industries given their attractive mechanical and physical properties are required for applications in high-temperature and corrosive environments [1]
Ni matrix composites reinforced with Al2 O3 particles have drawn a significant interest because Ni/Al2 O3 composites demonstrate various combinations of remarkable thermal, chemical, and mechanical properties of Al2 O3 on the one hand and superior tensile strength and toughness of Ni on the other [2,3,4]
Ni/Al2 O3 composites are usually prepared by various traditional methods such as sol-gel processing, pressureless sintering, or hot pressing [15,16,17,18,19,20,21]
Summary
Ni-based composites are indispensable material in various industries given their attractive mechanical and physical properties are required for applications in high-temperature and corrosive environments [1]. Ni matrix composites reinforced with Al2 O3 particles have drawn a significant interest because Ni/Al2 O3 composites demonstrate various combinations of remarkable thermal, chemical, and mechanical properties of Al2 O3 on the one hand and superior tensile strength and toughness of Ni on the other [2,3,4] These properties make Ni/Al2 O3 composites exceptionally useful; Ni/Al2 O3 composites are used in advanced protective coatings against corrosion and abrasion, becoming an attractive alternative to chromium [5,6,7]. Ni/Al2 O3 composites are usually prepared by various traditional methods such as sol-gel processing, pressureless sintering, or hot pressing [15,16,17,18,19,20,21] These approaches are, not optimal for the fabrication of open-porous products because of matrix deformation resulting in a blockage of a substantial portion of pores. The size effect of Al2 O3 particles on the open porosity, internal microstructure, and flexural strength was evaluated
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