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Öğe Agro-waste shaped porous Al2O3/Ni composites: Corrosion resistance performance and artificial neural network modelling(Elsevier Science Inc, 2018) Dele-Afolabi, T. T.; Hanim, M. A. Azmah; Norkhairunnisa, M.; Sobri, S.; Calin, R.; Ismarrubie, Z. N.In the present study, an analysis on the combined effect of nickel (Ni) reinforcement and pore former type in characterizing the corrosion behavior of composite porous alumina ceramics was performed. In order to showcase the potential of the new porous ceramics, pore-forming agents (PFAs) from rice husk (RH) and sugarcane bagasse (SCB) were used in shaping the plain and composite porous alumina samples having sample formulation of Al2O3-xNi-PFA; x = 0, 2, 4, 6 and 8 wt%. Results showed that the emergence of a highly stable Ni3Al2SiO8 spinelloid phase in the RH-graded composites enhanced their chemical stability in the corrosive mediums (10 wt% NaOH and 20 wt% H2SO4) relative to the plain and the corresponding SCB-graded counterparts. An artificial neural network (ANN) model has been developed for predicting the corrosion behavior of the plain and composite porous alumina ceramics based on the experimental data. The developed ANN model satisfactorily predicted the percent mass losses of the porous ceramics in strong alkali and strong acid solutions with coefficient of determination (R-2) of approximately 0.99.Öğe Investigating the effect of porosity level and pore former type on the mechanical and corrosion resistance properties of agro-waste shaped porous alumina ceramics(Elsevier Sci Ltd, 2017) Dele-Afolabi, T. T.; Hanim, M. A. Azmah; Norkhairunnisa, M.; Sobri, S.; Calin, R.The strength integrity and chemical stability of porous alumina ceramics operating under extreme service conditions are of major importance in understanding their service behavior if they are to stand the test of time. In the present study, the effect of porosity and different pore former type on the mechanical strength and corrosion resistance properties of porous alumina ceramics have been studied. Given the potential of agricultural wastes as pore-forming agents (PFAs), a series of porous alumina ceramics (Al2O3-xPFA; x=5, 10, 15 and 20 wt%) were successfully prepared from rice husk (RH) and sugarcane bagasse (SCB) through the powder metallurgy technique. Experimental results showed that the porosity (44-67%) and the pore size (70-178 mu m) of porous alumina samples maintained a linear relationship with the PFA loading. Comprehensive mechanical strength characterization of the porous alumina samples was conducted not just as a function of porosity but also as a function of the different PFA type used. Overall, the mechanical properties showed an inverse relationship with the porosity as the developed porous alumina samples exhibited tensile and compressive strengths of 20.4-1.5 MPa and 179.5-10.9 MPa respectively. Moreover, higher strengths were observed in the SCB shaped samples up to the 15 wt% PFA mark, while beyond this point, the silica peak observed in the XRD pattern of the RH shaped samples favored their relatively high strength. The corrosion resistance characterization of the porous alumina samples in hot 10 wt% NaOH and 20 wt% H2SO4 solutions was also investigated by considering sample formulations with 5-15 wt% PFA addition. With increasing porosity, the mass loss range in RH and SCB shaped samples after corrosion in NaOH solution for 8 h were 1.25-3.6% and 0.44-2.9% respectively; on the other hand, after corrosion in H2SO4 solution for 8 h, the mass loss range in RH and SCB shaped samples were 0.62-1.5% and 0.68-3.3% respectively.Öğe Research trend in the development of macroporous ceramic components by pore forming additives from natural organic matters: A short review(Elsevier Sci Ltd, 2017) Dele-Afolabi, T. T.; Hanim, M. A. Azmah; Norkhairunnisa, M.; Sobri, S.; Calin, R.Macroporous ceramics with tailored porosity offer a great deal of advantage in wide-ranging industrial applications including fluid filtration, thermal insulation and lately, waste water treatment. To a large extent, attempts by researchers in enhancing the development of ample homogenous porous ceramics through the exploitation of state of the art processing technologies have thus far been successful. However, these technologies are capital intensive hence making room for more exploration in finding affordable alternatives. With the growing recognition of low cost sacrificial fugitives processing route for developing porous ceramic materials, pore forming agents from natural organic matters have been one of the most sought after materials for imbuing pores within ceramic matrices. This review intends to document the progress made thus far in the development of porous ceramic systems with natural organic matter inclusion. The article covers critical evaluation and comprehensive comparison of the fabrication routes and the physical properties of porous ceramics processed with varying natural organic matters.Öğe Significant effect of rice husk and sugarcane bagasse pore formers on the microstructure and mechanical properties of porous Al2O3/Ni composites(Elsevier Science Sa, 2018) Dele-Afolabi, T. T.; Hanim, M. A. Azmah; Norkhairunnisa, M.; Sobri, S.; Calin, R.; Ismarrubie, Z. N.Porous alumina systems are suitable for application in wide-ranging industrial processes that require extreme service conditions such as high temperatures and corrosive mediums due to their remarkable thermal and chemical stability. Given the inherent brittleness of ceramics and their high sensitivity to thermo-mechanical loading, large-scale production of porous alumina components is constrained. In this study, the reinforcement of porous alumina ceramics with nickel (Ni) particles has been reported. Plain and Ni-reinforced porous alumina ceramics were developed through the powder metallurgy method with agro-waste materials from rice husk (RH) and sugarcane bagasse (SCB) as the pore-forming agents (PFAs). Experimental results showed that the formation of a stable Ni3Al2SiO8 spinelloid phase in the RH-graded composites actuated the emergence of a relatively refined microstructure while on the other hand, microstructural defects such as dislocated grains and localized voids were observed for the SCB-graded counterparts due to the presence of poorly crystallized NiAl2O4 spinel phase. Generally from the mechanical strength characterization, an inverse relationship was established between the mechanical properties and Ni reinforcement which agrees well with the Griffith's model. Moreover, the strengthening effect of the Ni3Al2SiO8 spinelloid phase was well marked in the RH-graded composites as maximum hardness, tensile and compressive strengths of 167.3HV, 12.6 MPa and 55.3 MPa respectively were achieved for the composite reinforced with 2 wt% Ni. (c) 2018 Elsevier B.V. All rights reserved.Öğe Tensile strength and corrosion resistance properties of porous Al2O3/Ni composites prepared with rice husk pore-forming agent(Elsevier Sci Ltd, 2018) Dele-Afolabi, T. T.; Hanim, M. A. Azmah; Norkhairunnisa, M.; Sobri, S.; Calin, R.; Ismarrubie, Z. N.The mechanical performance and chemical stability of porous alumina materials operating under harsh service conditions are of utmost importance in understanding their operational behavior if they are to stand the test of time. In the present study, the joint effect of nickel (Ni) reinforcement and rice husk (RH) pore-forming agent (PFA) on the tensile strength and the corrosion resistance properties of composite porous alumina ceramics was studied. To exploit the potential of this new porous alumina system, plain and Ni-reinforced porous alumina samples (Al2O3-xNi-RH; x = 2, 4, 6 and 8 wt%) were developed through the powder metallurgy technique. Comprehensive investigation on the tensile strength properties of the developed porous alumina ceramics showed that relative to the plain sample (tensile strength and elastic modulus; 6.1 MPa and 1201 MPa), the presence of highly stable Ni3Al2SiO8 spinelloid promoted the tensile strength enhancement (12.6-6.4 MPa) and the elastic modulus decline (897-627 MPa) of the composite samples. Similarly, corrosion resistance test was performed on the composite porous alumina samples in both 10wt% NaOH and 20wt% H2SO4 hot aqueous solutions. Overall, the composite samples demonstrated superior chemical stability in NaOH solution as compared with the plain sample. On the other hand, the composites were more prone to attack in H2SO4 solution, except for the Al2O3-2Ni-10RH composite sample which maintained its superiority over the plain counterpart.
