Oxidation characteristics of porous-nickel prepared by powder metallurgy and cast-nickel at 1273 K in air for total oxidation time of 100 h.
| Autor: | Mohamed LZ; Mining, Petroleum and Metallurgical Engineering Department, Faculty of Engineering, Cairo University, Egypt., Ghanem WA; Corrosion and Surface Protection, Central Metallurgical Research and Development Institute (CMRDI), Helwan, Egypt., El Kady OA; Powder Technology Division, Central Metallurgical Research and Development Institute (CMRDI), Helwan, Egypt., Lotfy MM; Mining, Petroleum and Metallurgical Engineering Department, Faculty of Engineering, Cairo University, Egypt., Ahmed HA; Mining, Petroleum and Metallurgical Engineering Department, Faculty of Engineering, Cairo University, Egypt., Elrefaie FA; Mining, Petroleum and Metallurgical Engineering Department, Faculty of Engineering, Cairo University, Egypt. |
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| Jazyk: | angličtina |
| Zdroj: | Journal of advanced research [J Adv Res] 2017 Nov; Vol. 8 (6), pp. 717-729. Date of Electronic Publication: 2017 Aug 19. |
| DOI: | 10.1016/j.jare.2017.08.004 |
| Abstrakt: | The oxidation behavior of two types of inhomogeneous nickel was investigated in air at 1273 K for a total oxidation time of 100 h. The two types were porous sintered-nickel and microstructurally inhomogeneous cast-nickel. The porous-nickel samples were fabricated by compacting Ni powder followed by sintering in vacuum at 1473 K for 2 h. The oxidation kinetics of the samples was determined gravimetrically. The topography and the cross-section microstructure of each oxidized sample were observed using optical and scanning electron microscopy. X-ray diffractometry and X-ray energy dispersive analysis were used to determine the nature of the formed oxide phases. The kinetic results revealed that the porous-nickel samples had higher trend for irreproducibility. The average oxidation rate for porous- and cast-nickel samples was initially rapid, and then decreased gradually to become linear. Linear rate constants were 5.5 × 10 -8 g/cm 2 s and 3.4 × 10 -8 g/cm 2 s for the porous- and cast-nickel samples, respectively. Initially a single-porous non-adherent NiO layer was noticed on the porous- and cast-nickel samples. After a longer time of oxidation, a non-adherent duplex NiO scale was formed. The two layers of the duplex scales were different in color. NiO particles were observed in most of the pores of the porous-nickel samples. Finally, the linear oxidation kinetics and the formation of porous non-adherent duplex oxide scales on the inhomogeneous nickel substrates demonstrated that the addition of new layers of NiO occurred at the scale/metal interface due to the thermodynamically possible reaction between Ni and the molecular oxygen migrating inwardly. |
| Databáze: | MEDLINE |
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