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    Effect of nickel addition on the microstructure and corrosion resistance properties of porous alumina composites shaped with sugarcane bagasse pore-forming agent
    (Iop Publishing Ltd, 2019) Dele-Afolabi, T. T.; Hanim, M. A. Azmah; Norkhairunnisa, M.; S Sobri; Calin, R.; Ojo-Kupoluyi, O. J.
    In this study, the effect of nickel (Ni) addition on the microstructure and corrosion resistance properties of porous alumina (Al2O3) composites shaped with sugarcane bagasse pore-forming agent were evaluated. Plain and Ni-reinforced porous alumina sampels (Al2O3-xNi-RH; x = 2, 4, 6 and 8wt%) were prepared using the powder metallurgy method. Experimental results showed that the porosity (50.4-57.1vol%) and the pore size (62-109 mu m) of the porous alumina composites increased with rising content of Ni reinforcement. The XRD results showed that the Al2O3 matrix and Ni reinforcement reacted during the heat treatment process to produce nickel aluminate (NiAl2O4) spinel. Corrosion resistance results showed that the porous alumina composites exhibited better chemical stability in strong alkali solution as compared with strong acid solution.
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    Impact of different isothermal aging conditions on the IMC layer growth and shear strength of MWCNT-reinforced Sn-5Sb solder composites on Cu substrate
    (Elsevier Science Sa, 2019) Dele-Afolabi, T. T.; Hanim, M. A. Azmah; Ojo-Kupoluyi, O. J.; Calin, R.
    In this study, the effect of multi-walled carbon nanotubes (MWCNTs) reinforcement on the intermetallic compound (IMC) layer growth and shear strength of Sn-5Sb-xCNT/Cu composite solder joints subjected to different isothermal aging conditions has been investigated. A series of plain and composite lead-free solder systems (Sn-5Sb-xCNT; x = 0, 0.01, 0.05 and 0.1 wt%) was successfully developed through the powder metallurgy method. Isothermal aging process was performed on the solder/Cu joints at 120 degrees C, 150 degrees C and 170 degrees C temperatures in order to investigate the evolution of the interfacial IMC layers and the shear strength property. Experimental results showed that the thickness of the total IMC layer increased with rising aging temperature. While the Cu3Sn IMC maintained a layer-type morphology for all aging conditions, morphology of the Cu6Sn5 IMC transformed from a scallop-type to a layer-type after aging at intermediate (150 degrees C) and high (170 degrees C) temperatures. Given the potential of MWCNTs as a reinforcement material, significant suppression in IMC layer growth was demonstrated by the composite solder joints relative to the plain counterpart. Comprehensive investigation on the growth kinetics showed that the presence of MWCNTs in the composite solder joints was effective in slowing down the diffusion mechanism responsible for IMC growth. Overall, the Sn-5Sb-0.05CNT composite solder joint exhibited the lowest diffusion coefficient within the range of 0.09 x 10(-14)-1.03 x 10(-14) cm(2)/s and 0.95 x 10(-14)-9.8 x 10(-14) cm(2)/s for Cu6Sn5 and Cu3Sn IMC layers respectively. Moreover, the strengthening effect of the MWCNTs reinforcement was well marked in the composite solder joints as the maximum shear strength within a range of 24.2-15.2 MPa was exhibited by the Sn-0.01CNT/Cu composite solder joint subjected to reflow soldering and isothermal aging conditions. (C) 2019 Elsevier B.V. All rights reserved.
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    Tailored pore structures and mechanical properties of porous alumina ceramics prepared with corn cob pore-forming agent
    (WILEY, 2021) Dele-Afolabi, T. T.; Hanim, M. A. Azmah; Ojo-Kupoluyi, O. J.; Calin, R.; Zuhri, M. Y. M.
    In this work, the effects of porosity and different particle sizes of pore-forming agent on the mechanical properties of porous alumina ceramics have been reported. Different grades of porous alumina ceramics were developed using corn cob (CC) of different weight contents (5, 10, 15, and 20 wt%) and particle sizes (<63 mu m, 63-125 mu m and 125-250 mu m) as the pore-forming agent. Experimental results showed that total porosity and pore cavity size of the porous alumina ceramics increased with rising addition of CC pore former. Total porosity increased with increasing particle size of CC with the Al2O3-(<63)CC(5)sample exhibiting the lowest total porosity of 41.3 vol% while the highest total porosity of 68.1 vol% was exhibited by the Al2O3-125-250CC20. The particle size effect of CC on the mechanical properties revealed that diametral tensile strength and hardness of the porous alumina ceramics deteriorated with increasing particle size of CC pore former. The Al2O3-(<63)CC(5)sample exhibited the highest diametral tensile strength and hardness of 25.1 MPa and 768.2 HV, respectively, while Al2O3-(125-250)CC(20)exhibited the lowest values of 1.1 MPa and 35.9 HV. Overall, porous alumina ceramics with the smallest pore sizes under each particle size category exhibited superior mechanical properties in their respective categories.