Browsing by Author "Talabi, Segun Isaac"

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    Catalytic graphitization of novolac resin for refractory applications
    (Ceramics International, Elsevier, 2018-03) Talabi, Segun Isaac; Luz, Ana Paula; Lucas, Alessandra de Almeida; Pagliosa, Carlos; Pandolfelli, Victor Carlos
    This study investigated how to induce graphite generation from the carbonization process of novolac resins using conditions that can be adopted for carbon-containing refractories (CCRs) production. The effect of boron oxide or boric acid (graphitizing agents), cross-linking additive (hexamethylenetetramine) and some processing parameters (mixing technique, vacuum degassing, heating rate and thermal treatments) on carbon graphitization from a commercial novolac resin were evaluated. The X-ray diffraction (XRD) technique was selected to measure the graphitization level and crystal parameters of the prepared samples. Based on the attained results, adding graphitizing agents prior to the pyrolysis of resin resulted in carbon crystallization. The best graphitization level was obtained when the mixtures containing 6 wt% B2O3 or 10 wt% H3BO3 were fired up to 1000 °C for 5 h using a heating rate of 3 °C/min. Although the reproducibility of the obtained results was ascertained, heterogeneous graphitization could be observed based on the XRD profiles, as well as some discrepancies in the calculated graphitization level values. This phenomenon was attributed to the additives susceptibility to agglomeration, preferential graphitization starting from lower binding energy sites and heat treatment temperature, among others.
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    EFFECT OF HEAT TREATMENT ON HARDNESS AND WEAR RESISTANCE OF A FAILED AUTOMOBILE BRAKE DISC
    (ACTA TEHNICA CORVINIENSIS – Bulletin of Engineering, Faculty of Engineering - Hunedoara, University POLITEHNICA Timisoara, 2014) Odusote, Jamiu Kolawole; Talabi, Segun Isaac; Agodinrin, G
    In an attempt to improve the wear resistance of a failed automobile brake disc, different type of heat treatment operation was carried out on the samples of the disc. The samples were heated to 840°C 860°C and 880°C in a muffle furnace, and quenched in water, palm oil and air, separately. Water and oil quenched samples were later tempered at 200°C. The chemical composition of the failed brake disc was obtained by an optical emission spectrometer (OES), while the hardness value was measured using Brinell hardness testing machine. The highest Brinell hardness value of 331 BHN was obtained from the water-quenched sample heated to 880°C. The hardness values of the oil-quenched samples surpass that of air-quenched samples. The tempered samples displayed lower hardness values compared with the hardened samples, although the sample heat treated at 880°C, water-quenched and tempered still possesses high hardness value. The reduction in hardness of most of the samples after tempering suggests possible increase in ductility and toughness. As a result of the heat treatment and subsequent quenching, the retained austenite in the samples transforms to martensite, while the ferrite, flakes of graphite, and cementite were restructured. This shows that the brake disc could be hardened and tempered to obtain optimum hardness with improved ductility and toughness. This will result in better wear resistance, increase service life, and thus reduce brake failure and other related transportation hazard.
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    EFFECT OF HEAT TREATMENT ON WEAR RESISTANCE OF A GRINDING PLATE
    (African Journal of Science and Technology, 2013) Odusote, Jamiu Kolawole; Talabi, Segun Isaac; Balogun, S
    The effects of heat treatment on the hardness and by extension the wear resistance of locally produced grinding plate of known composition were investigated. Specimens were prepared from the grinding plate and were heat treated at 840°C, 860°C and 880°C and quenched at different rate. Some of the specimens were quenched in water and palm oil, while some of the quenched specimens were tempered at 200°C. The results obtained were corroborated with the microstructure of the specimens examined under an optical microscope. The hardness values of the grinding plate specimens quenched in various media increased with increased heat treatment temperatures, and are higher than that of the as-cast specimen. Water quenched tempered specimens (WT) displayed higher hardness values than the as-cast, whereas oil quenched tempered specimens (OT) possessed lower hardness values. The presence of carbide was evident on the micrographs of the water quenched specimens at all the exposure temperatures, which corroborated the observed increased in the hardness values with increased heat treatment temperatures. However, there was significant reduction in the hardness value of the water quenched tempered specimens compared with the quenched specimens, which indicates a significant improvement in toughness. Thus, water quenched and tempered specimen with relatively high hardness value and improved toughness, will be suitable for use as grinding plate because of its relatively better wear resistance. The hardness of the specimens was found to depend on the formation of carbide precipitates within the matrix structure. There is also possibility of production of structure consisting of graphite embedded in a martensitic matrix through the heat treatment.
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    Effect of Manganese Additions and Wear Parameter on the Tribological Behaviour of NFGrey (8) Cast Iron
    (Tribology in Industry, University of Maribor, 2012) AGUNSOYE, Johnson; Ochulor, E. F.; Talabi, Segun Isaac; Olatunji, S.
    The effect of manganese and wear parameter on the abrasive wear behaviour of NFGREY8 cast iron composition under dry lubrication conditions was investigated. The wear parameters studied are sliding speed, applied load, time and percentage of ferro-manganese additions. The experimental data were taken in a controlled way. Scanning electron microscope was used to examine the morphology of the samples. The results from linear regression equation and analysis of variances (ANOVA) shows that manganese additions, load and speed variable are more pronounced on the wear behaviour of the NFGrey (8) cast iron. The result showed that the additions of the 75 % ferro manganese grade decreases the carbon equivalent CE and fortify the matrix with the formation of tough (FeMn)3C inter-metallic leading to increased wear resistance of the examined composition.
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    Effect of Mercerization on the Mechanical and Thermal Response of Hybrid Bagasse Fiber/CaCO3 Reinforced Polypropylene Composites
    (Polymer Testing, Elsevier, 2019-07) Oladele, Isiaka Oluwole; Ibrahim, Ibrahim Oghie; Akeem Damilola, Akinwekomi; Talabi, Segun Isaac
    This study evaluated the effect of sodium hydroxide mercerized bagasse fiber (BF) on the mechanical and thermal properties of polypropylene composites reinforced with hybrid BF/calcium carbonate (CaCO3). Samples were fabricated with a compression molding machine and characterized for tensile, flexural, and thermal properties. Hybrid composites with mercerized BF (HMC) exhibited improved mechanical properties than the unmercerized hybrid composite (UHC), single-component composite (SC) and control sample. Additionally, TGA/DTG analysis revealed that the HMC were more thermally stable in comparison with other samples. Crystallinity index of HMC was about 24% higher than UHC, as indicated by XRD analysis. SEM images showed good interfacial adhesion in the morphology of HMC compared to UHC, which contributed to the improved thermal and mechanical properties exhibited by HMC. These results indicated that mercerization treatment and reinforcement hybridization could be utilized for improving the thermal and mechanical responses of natural fiber reinforced polypropylene composites.
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    Effect of welding variables on mechanical properties of low carbon steel welded joint
    (Advances in Production Engineering & Management, University of Maribor, 2014) Talabi, Segun Isaac; Owolabi, Oluwasegun Biodun; Adebisi, Jeleel Adekunle; Yahaya, Taiwo
    This paper discussed the effect of welding variables on the mechanical prop-erties of welded 10 mm thick low carbon steel plate, welded using the Shield-ed Metal Arc Welding (SMAW) method. Welding current, arc voltage, welding speed and electrode diameter were the investigated welding parameters. The welded samples were cut and machined to standard configurations for tensile, impact toughness, and hardness tests. The results showed that the selected welding parameters had significant effects on the mechanical properties of the welded samples. Increases in the arc voltage and welding current resulted in increased hardness and decrease in yield strength, tensile strength and impact toughness. Increasing the welding speed from 40-66.67 mm/min caused an increase in the hardness characteristic of the welded samples. Initial decrease in tensile and yield strengths were observed which thereafter increased as the welding speed increased. An electrode diameter of 2.5 mm provided the best combination of mechanical properties when compared to the as received samples. This behaviour was attributed to the fact that in-creased current and voltage meant increased heat input which could create room for defect formation, thus the observed reduced mechanical properties.
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    The Effects of Cocos Nucifera (Coconut Shell) on the Mechanical and Tribological Properties of Recycled Waste Aluminium Can Composites
    (2014) AGUNSOYE, Johnson; Talabi, Segun Isaac; Bello, S. A.; Awe, I. O.
    The dry sliding wear behaviour and mechanical properties of recycled aluminium metal matrix composite reinforced with 5 and 10 % coconut shell particles (CSp) has been investigated. The particle size of Cocosnucifera (coconut shell) that were used ranges from 50-300μm. The wear behaviors of developed samples were investigated under varied loads and speed using pin on disc equipment. The samples were also subjected to tensile, impact and hardness test. The result shows that the additions of coconut shell particles improved the wear resistance of the recycled aluminium can/CSp composites at low Speed (2.36 m/s). However, with increase in Speed (4.72 m/s), an increase in the specific wear rates were observed. Increasing the coconut shell particles additions to the recycled waste aluminium cans (RWAlC) reduced the impact resistance, hence the toughness of the RWAlC/CSp composite samples. However, the impact resistance of the composites increased as the Cocosnucifera particle size increased. The result of the filler size variation shows that decrease in filler particles size improved the tensile strength and yield strength of the developed aluminium metal matrix /CSp composite. The hardness of the composite increased with increased additions of the filler within the matrix.
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    Effects of cow bone filler on the microstructure and mechanical properties of recycled polyethylene/cow bone particulate composites
    (Advanced Engineering Solutions (AES), Montréal, CANADA, 2012) AGUNSOYE, Johnson; Talabi, Segun Isaac; Obe, Adeola; Adamson, Olubukola
    The morphology and mechanical properties of cow bone reinforced polyethylene composite was evaluated to assess the possibility of using it as a new material for engineering applications. Cow bone reinforced matrix composite was prepared from low density polyethylene matrix containing up to 25% cow bone fillers and the effect of the filler on the mechanical properties of the composite was investigated. Scanning electron Microscopy (SEM) of the composites (with 0-25% filler) surfaces indicates good interfacial interaction between the bone fillers and the low density polyethylene matrix. The tensile strength and the hardness of the composite increases with increase in filler content while the impact strength and rigidity of the composite decreases with increase in the filler content.
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    FATIGUE CHARACTERISTIC OF MEDIUM CARBON STEEL WITH DIFFERENT GRAIN STRUCTURES
    (2014) Abdulkareem, Sulaiman; Abdulrahim, A. T.; Talabi, Segun Isaac; Amuda, O. H.
    This paper investigated the effect of heat treatment operations on the fatigue resistance of low carbon steel. Specimens after preparation for fatigue testing were subjected to annealing, normalizing and quenching heat treatment. Results show that the annealed specimen had the largest number of cycles to failure, indicating a high fatigue resistance. The microstructure of the specimens was examined in other to corroborate the obtained property with the microstructure. When compared with the untreated specimen, the annealed specimen (with optimum fatigue resistance) shows a large grains size of pearlite which was distributed across the entire surface of the microstructure. Generally, it was found that the size and distribution of specimens' grains affect the resistance of the low carbon steel to fatigue failure.
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    Graphitization of Lignin-Phenol-Formaldehyde Resins
    (Materials Research, Scielo, 2020) Talabi, Segun Isaac; Luz, Ana Paula; Pandolfelli, Victor Carlos; Lima, Vitor Hugo; Lucas, Alessandra de Almeida
    Environmental friendliness and cost demand the development of lignin-modified phenolic (LPF) resins for application as a binder for carbon-containing refractories (CCRs) production. Moreover, the in-situ graphitization of such resins can produce crystalline carbon, which is an essential component of CCRs. Consequently, this study investigated LPF resins graphitization using ferrocene, boron oxide and boric acid. The modified resins were synthesized using thermally treated kraft lignin based on 1.5 formaldehyde to phenol molar ratio and with up to 30 wt.% lignin as phenol replacement. The resins chemical composition and the structural organization and oxidation resistance of carbons derived from the plain resins and those containing the graphitizing additives were determined. The results showed that ferrocene and the boron compounds could induce graphitic carbon generation when carbonizing LPF resins at 1500 °C for 5 hours. The best graphitization level (73%) was achieved when 10 wt.% boric acid was added to the resin produced with 20 wt.% lignin. Regarding the formulations containing ferrocene, the highest amount of graphitic carbon (48%) was generated when 5 wt.% of this additive was added to the resin synthesized with 10 wt.% lignin. The carbons derived from the formulations containing boron oxide presented the best oxidation resistance.
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    Inhibitive Potentials of Bitter Kola Stem (BKS) on Mild Steel in Acidic Media
    (2017) Adediran, Adeolu Adesoji; Olawale, Olamide; Talabi, Segun Isaac; Busari, Yusuf O.
    This paper deals with the inhibitive potentials of bitter kola stem extract (BKS) on the deterioration of mild steel in 1 M HCl and 1 M H2SO4 using gravimetric method. Coupons of dimension 5.0 cm x 4.0 cm were immersed in test solutions of uninhibited acid and also in those containing various amount of BKS (10, 25 and 40 %v/v) at 30 oC and 60 oC respectively. The results showed that the extract addition reduced mild steel corrosion in the acidic media. The inhibitive efficiency of 92.07 % was attained at 40 %v/v in 1 M H2SO4 at 30 oC temperature, while the efficiency of 89.19 % was realized at the same concentration in 1 M HCl at 60 oC temperature. Hence, BKS can be considered as a good and safe inhibitor against mild steel corrosion in both acidic media.
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    Inhibitory action of Vernonia amygdalina extract (VAE) on the corrosion of carbon steel in acidic medium
    (Journal of Electrochemical Science and Engineering, International Association of Physical Chemists, 2017) Olawale, Olamide; Adediran, Adeolu Adesoji; Talabi, Segun Isaac; Nwokocha, Geraldine Chika; Ameh, Alewo Opuada
    This study investigates the inhibition potential of Vernonia amygdalina stem extract (VAE) on the corrosion of mild carbon steel immersed in 1 M HCl solution containing various concentrations of the inhibitor. The corrosion rate and inhibition efficiency were evaluated using mass loss and adsorption techniques. The results revealed that VAE efficiently inhibits the corrosion rate of mild carbon steel immersed in the acidic medium. The concentration of 0.6 g/L provides the highest inhibition efficiency of 78.1 %. The adsorption process was consistent with the physisorption mechanism and obeyed the Langmuir isotherm. The functional groups responsible for inhibition were identified using Fourier Transform Infrared (FTIR) spectra. The surface morphology of the corroded samples examined with Scanning Electron Microscope (SEM) revealed the presence of protective oxide layer. Inhibition efficiency was found depended on the presence of oxalate, phytate, tannins, saponins and flavonoids in the VAE. It has been concluded that VAE is safe, cheap and efficient corrosion inhibitor for mild carbon steel.
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    Properties optimization of Hadfield austenitic manganese steel casting
    (Annals of Faculty of Engineering Hunedoara-International Journal of Engineering, Faculty of Engineering Hunedoara, University Politehnica of Timisoara, 2015) AGUNSOYE, Johnson; Talabi, Segun Isaac
    The properties of Austenitic Manganese Steel (AMnS), used for rock drilling, was optimized as a highly cost efficient and preferment material for the mining industry. To achieve this, inter-critical annealing and homogenization heat treatments operations were employed. Subsequently, relationships were established between various process parameters, mechanical properties, microstructure and alloying elements. Emphasis was given to the control of grain size and phases, most particularly secondary carbides. Hardness, impact and microscopy investigations were carried out on the heat treated samples. The results show an improvement in hardness and impact characteristic of the AMnS. The microstructures of the heat treated samples show substantial grain refinement and a uniform dispersion of secondary carbides along grain boundaries.
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    Review on Oxide Formation and Aluminum Recovery Mechanism during Secondary Smelting
    (Journal of Castings and Materials Engineering, 2018) Osoba, Lawrence Opeyemi; Owolabi, Oluwasegun Biodun; Talabi, Segun Isaac; Adeosun, Samson Oluropo
    The remelting, refining, and casting process of aluminum alloys often generate aluminum dross containing primarily oxides and nitrides of aluminum and entrapped metallic aluminum at the surface of the molten metal as a result of reactions within the furnace atmosphere at elevated temperatures. The handling of dross is an expensive but necessary activity during aluminum smelting. Furthermore, the amorphous Al2O3 oxide film formed on the pure molten aluminum surface due to the liquid metal randomly distributed atoms is impermeable to the diffusion of aluminum metal and oxygen. In amorphous materials, there is a low mobility of the charge carriers and an absence of preferred diffusion paths. This film can transform to crystalline Al2O3 by nucleation and grows with time and opportunity. This review discusses the mechanism of oxide formation and the aluminum metal recovery processes.
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    REVIEWING ENGINEERING CURRICULA TO MEET INDUSTRIAL AND SOCIETAL NEEDS
    (Proceedings of 2014 International Conference on Interactive Collaborative Learning (ICL), IEEE, 2014-12) Talabi, Segun Isaac; Odusote, Jamiu Kolawole; Alabi, Abdulganiyu Funsho; Olorunmaiye, John Adesiji
    The present state of engineering practices in our country has called for review of engineering curricula to make it more proactive and relevant to the industrial and societal needs. It is imperative that students be shown the difference between studying engineering and becoming an engineer. There is need for strong industrial interaction in our education for the students to know the types of problems engineers face, the concepts, processes, and tools they use to solve those problems, and the personal and professional attributes essential to be a team player in solving engineering problems. An attempt was made to evaluate all these variables in this paper.
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    Stress Corrosion Cracking of Austenitic Stainless Steel in Chloride Environment
    (Faculty of Engineering, Ahmadu Bello University Zaria, 2015) Ahmed, Ismaila Idowu; Alabi, Abdul Ganiyu Funsho; Odusote, Jamiu Kolawole; Aremu, Ishaq Na'Allah; Adebisi, Jeleel Adekunle; Yahaya, Taiwo; Talabi, Segun Isaac; Yahya, Raheem Abolore; Lyon, Stuart B.
    This study was carried out to assess the effect of applied potentials on stress corrosion cracking of Austenitic Stainless Steels (ASS), Type 304L in a potentiostatically controlled chloride environment at ambient temperature. The stress corrosion cracking tests were carried out on annealed ASS using a Slow Strain Rate Test (SSRT) technique in sodium chloride solution acidified with hydrochloric acid at ambient temperature. Post-mortem analyses of failed specimens were carried using optical microscopy. The study showed that plastic elongation, ultimate tensile strength and time to failure decrease as the applied potential increases during the slow strain rate test. The study showed that immunity of ASS to chloride SCC was improved when the electrochemical potential was maintained in the primary passive potential range. Post-mortem analysis of failed samples showed evidences of SCC and ductile failure on the fracture surface.
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    Stress corrosion cracking of austenitic stainless steel in chloride environment
    (Nigerian Journal of Engineering, Faculty of Engineering, Ahmadu Bello University, 2015-03) Ahmed, Ismaila Idowu; Alabi, Abdulganiyu; Odusote, Jamiu Kolawole; Aremu, Ishaq; Adebisi, Jeleel Adekunle; Yahaya, Taiwo; Talabi, Segun Isaac; Yahya, Raheem; Lyon, S. B.
    This study was carried out to assess the effect of applied potentials on stress corrosion cracking (SCC) of Austenitic Stainless Steel (ASS). Type 304L in a potentiostatically controlled chloride environment at ambient temperature. The stress corrosion cracking tests were carried out on annealed ASS using a Slow Strain Rate Test (SSRT) technique in sodium chloride solution acidified with hydrochloric acid at ambient temperature. Analyses of failed specimens were carried out using optical microscope. The study showed that plastic elongation, ultimate tensile strength and time to failure decrease as the applied potential increases during the slow strain rate test. The study showed that immunity of ASS to chloride SCC was improved when the electrochemical potential was maintained in the primary passive potential range. Analysis of failed samples showed evidences of SCC.
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    Structural evolution during the catalytic graphitization of a thermosetting refractory binder and oxidation resistance of the derived carbons
    (Materials Chemistry and Physics, Elsevier, 2018-06) Talabi, Segun Isaac; Luz, Ana Paula; Pandolfelli, Victor Carlos; Lucas, Alessandra de Almeida
    Carbon-containing refractories' (CCRs) thermomechanical properties depend on the presence of carbonaceous phase with a structure and features similar to those of graphite. Based on this, boron oxide and boric acid were used to induce graphite generation during the pyrolysis of novolac resin (binder for CCRs) to provide an additional source of crystalline carbons. In this study, the structural evolution leading to crystallization of the derived carbons was studied via Fourier Transform Infrared (FTIR) spectroscopy. The results showed that the carbons graphitization was as a result of the formation and cleavage of the Bsingle bondOsingle bondC bond during heat treatment. The lower binding energy of this bond compared to plain Csingle bondC bond permits carbon atoms rotation and restructuring necessary for graphite generation during the pyrolysis operation. Furthermore, the research investigated the oxidation resistance of the derived carbon samples with the aid of thermogravimetric (TGA) and differential scanning calorimetry (DSC) equipment. The influence of different mixing routes at the preparation stage and hexamethylenetetramine (HMTA) addition to the resin formulations on the carbons' oxidation resistance was also examined. The analysis provides insight on the parameters that control the oxidizing behavior of the different samples obtained based on these variations. Several factors including graphitization, composition and atoms bond strength were observed to influence their performance when the carbons were exposed to the non-reducing environment at high temperatures up to 1000 °C.
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    Wear characteristics of heat-treated Hadfield austenitic manganese steel for engineering application
    (Advances in Production Engineering & Management, University of Maribor, 2015) AGUNSOYE, Johnson; Talabi, Segun Isaac; Bello, O
    The wear behaviour was investigated of heat treated Hadfield austenitic man-ganese steel (HAMnS). The wear test was carried out using spin on disc appa-ratus under different loading loads and speed conditions. A scanning electron microscopy (SEM), an X-ray diffractometer and micro-hardness testing ma-chines were used for examining the morphology, compositions and to meas-ure the hardness of the manganese steel, respectively. The results of the wear test showed that the sliding speed-time interactions effect gave the most significant effect on the austenitic manganese steel. The solution heat treat-ment programme increased the wear resistance of the alloy steel under in-creasing load, speed and time. The as-cast microstructure was characterized by heterogeneously dispersed chromium carbides second phase particle, and was responsible for the observed non-uniform wear rate. In regard to the solution heat treated HAMnS, the segregated carbides were dissolved at 1050 °C and uniformly dispersed within the matrix of its microstructure after rapid water quenching to room temperature. This later development was responsible for the uniform and improved wear resistance of the manganese steel casting. This work demonstrated significantly that there is a direct rela-tionship between the second phase carbides, their distribution and the wear rate pattern of HAMnS casting.