Enoch E N Ogunmuyiwa | Botswana International University of Science & Technology (original) (raw)

Papers by Enoch E N Ogunmuyiwa

Materials and Manufacturing Processes, Sep 27, 2016

ABSTRACT Improvement on the densification and fracture toughness of ceramic materials based on bo... more ABSTRACT Improvement on the densification and fracture toughness of ceramic materials based on boron suboxide (B6O) has been of great importance. The mechanical properties of B6O with and without chromium boride addition, hot pressed at a temperature range of 1850–1900°C and pressures of 50–80 MPa for 20 minutes, were investigated. The relative density, phase relationship, microstructures and mechanical properties of the processed ceramics were examined. More than 96% of the theoretical density was obtained for both ceramic systems. A good combination of mechanical properties was obtained with the B6O-CrB2 material (HV = 32.1 GPa, KIC = 4.5 MPa · m0.5) compared to the pure B6O material (HV = 30.5 GPa, KIC = brittle). The addition of 1.7 wt.% CrB2 resulted in a pronounced improvement in both the hardness and fracture toughness values. Crack bridging and deflection are some of the toughening mechanisms liable for the enhanced fracture toughness of the sintered ceramic materials.

CRC Press eBooks, Aug 18, 2022

Advanced Materials Research, 2014

Vanadium carbide is less dense, harder and tougher than tungsten carbide, and nickel is more corr... more Vanadium carbide is less dense, harder and tougher than tungsten carbide, and nickel is more corrosion resistant that cobalt. Replacing the binder with Ni should improve the corrosion resistance. Since there are eutectics with a wide range of compositions in the C-Ni-V system, this system has potential for wear resistant alloys with ~VC as the discrete hard phase and the nickel solid solution as the binder. The aim of this work was to ascertain if eutectic microstructures with vanadium carbides could be beneficial to wear resistance. Phase studies confirmed the wide range of the eutectic alloys, with VC + (Ni), VC + σ′, VC + (V) and graphite + (Ni) and different morphologies. Preliminary wear tests showed results comparable to WC-Co alloys.

Materials Science Forum

This paper is aimed at investigating the mechanical properties of spark plasma sintered alumina (... more This paper is aimed at investigating the mechanical properties of spark plasma sintered alumina (Al2O3) reinforced with tungsten-carbide-cobalt (WC-12wt%Co). Pure Al2O3 and admixed-Al2O3 powders were sintered using spark plasma sintering (SPS) technique at a temperature of 1800°C, heating and cooling rates of 100 °C/min and 200 °C/min, a pressure of 48 MPa in an argon atmosphere. The density, hardness (HV) and indentation fracture toughness (KIC) of the sintered samples were measured and compared. Between 9 and 17% increase was observed in the HV values of the additives, while the KIC value recorded an increase between 17 and 63% for all the additive as compared to pure Al. Phase analysis and identification was carried out with X-ray diffraction and microstructure was taken with scanning electron microscope. The results obtained showed the samples potential for cutting tool applications.

Journal of Tribology

The influence of annealing on the microstructure, mechanical and sliding wear characteristics of ... more The influence of annealing on the microstructure, mechanical and sliding wear characteristics of Ni-based alloys produced by spark plasma sintering (SPS) was investigated. As-sintered alloys had a lamellar-like microstructure consisting of (γ′)-FeNi3 and γ-(NiFe) phases blended together. Lower Co contents (i.e., 30, 35 wt%) led to the formation of poorly bonded coarse γ precipitate islands. Annealed Ni-5Fe-45Co alloy exhibited the most excellent wear performance with the lowest coefficients of friction (0.142 ± 0.05) and wear-rate (0.3 ± 0.02 × 10−4 mm3/Nm). Annealing resulted in alloys with good strength-ductility combinations due to appreciable γ′ precipitation enhancement.

International Journal of E-Entrepreneurship and Innovation, 2018

3D printing, also known as additive manufacturing, is becoming the industry standard for manufact... more 3D printing, also known as additive manufacturing, is becoming the industry standard for manufacturing and prototyping. Although the technology is very old, it gained a huge traction in the past two decades. 3D printing favors unique once-off orders (mass customization) in contrast to mass production. This calls for innovative business models in order to realize economic gains from the technology. Increased product innovations in the global economy also contribute to wide adoption of 3D printing unlike in the old days. A transition in the manufacturing field has brought e-manufacturing and now cloud-based manufacturing. Machines, including 3D printers, in the past were not Internet-enabled but modern designs have the capability of Internet connectivity. Cloud-based 3D printing is a new model of design that has a significant impact on today's entrepreneurs. This article focuses on a business case for a cloud-based approach in consumer product niches. A cloud-based 3D printing bus...

Applied Mechanics and Materials, 2013

The effect of solution and aging temperatures on microstructure and tensile property of Ti-5Al-5M... more The effect of solution and aging temperatures on microstructure and tensile property of Ti-5Al-5Mo-5V-3Cr-1Fe Alloy was investigated. The results showed that the tensile strength lowered, when the solution and aging temperature rose respectively. The alloy with different heat treatments showed better tensile strength totally, i.e. the minimum level of ultimate and yield strength passed 1280 MPa and 1245MPa. The highest ultimate tensile strength could reach 1445 MPa. After (α+β) solution and aging treatment, the microstructure consists of primary α phase and transformed β phase with fine secondary α phase precipitating to improve the tensile strength effectively.

The present research study focuses on the investigation of the influence of sand blasting on form... more The present research study focuses on the investigation of the influence of sand blasting on formed mild steel samples. The investigation involved the examinations on the parent material and a sand blasted material. The results were compared to the mechanically formed materials (sand and non-sand blasted) as well as a laser formed material (sand and non-sand blasted). Each material was characterized for the grain sizes and hardness. The percentage change in the grain sizes was quantified and correlation to the microhardness values was established. The Ultimate Tensile Strength (UTS) of the materials was also quantified using the obtained hardness values. The investigations revealed that the sand blasting causes an increase in the Vickers microhardness values of all the materials which also led to an increase in the UTS. After the forming operation, the microstructure revealed elongated grains as compared to almost equiaxed obtained from the parent non-sand blasted materials.

SSRN Electronic Journal, 2021

Pure B6O powder and B6O powders admixed with 1.5 wt% of MgO, 1.4 wt% of CaO, and 0.7 wt% of CaCO3... more Pure B6O powder and B6O powders admixed with 1.5 wt% of MgO, 1.4 wt% of CaO, and 0.7 wt% of CaCO3, were sintered and the microstructure, phase composition and mechanical properties were investigated. Pure B6O powders were sintered at a temperature of 1900 o C and a load of 50 MPa for 20 minutes in an argon environment, while the B6O-admixed powders were sintered at a temperature of 1850 o C and loads from 50-80 MPa, under the same environment. The addition of the alkaline earth metal oxide additives resulted in the formation of boride and borate phases, depending on the oxide used. More than 96% of theoretical densities were achieved and the result indicates a good combination of hardness (between 31.6-32.1 GPa) and fracture toughness (between 6.1-6.8 MPa.m 0.5) in the B6O-alkaline earth oxide materials. The introduction of the additive enhances the improvement in the fracture toughness of the pure B6Omaterials. The fracture mode observed in the sintered materials is mainly transgranular.

Petroleum and its products are a major source of energy that plays a vital role in society, power... more Petroleum and its products are a major source of energy that plays a vital role in society, powering many essential tools that human life depends on. Supply-chain management is very important in the petroleum industry. Few continents have petroleum reserves, hence there is a need for efficient methods of managing the sourcing, storage and distribution processes across the globe. There have been major improvements in safety management practices, during extraction and processing, in transit, and in situ distribution. Bulk storage of petroleum plays a crucial role across the world as it eases distribution hassles and can act as emergency reserves in the event of disruptions in the supply chain. However, lighter fractions of petroleum have a tendency to evaporate during storage as they are highly volatile. Although there are mechanisms such as floating roofs that have been invented to effectively reduce evaporative losses of light petroleum fractions, the percentage of losses are still ...

International Journal of Engineering Research in Africa, 2021

This work investigated the dry sliding wear behaviour of spark plasma sintered (SPSed) Ti-Ni bina... more This work investigated the dry sliding wear behaviour of spark plasma sintered (SPSed) Ti-Ni binary alloys produced at varying nickel content with alloy steel ball as the counterface material, at room temperature under varied applied normal loads. Finite element modeling was used to investigate the high-velocity impact response of the sintered alloys due to the dimensional constraint associated with SPSed samples. Microstructural analysis results revealed the presence of intermetallic phases of Ti-Ni with increasing nickel content. The best wear resistance ranging from 0.25 x 10-3 mm3/Nm to 0.22 x 10-3 mm3/Nm across all applied loads was obtained in Ti-6Ni alloy. This was attributed to the compaction of the protective triboxide and carbide layers on the surface of the sample. Oxidative and wear by adhesion were observed at low applied normal load while at high loads the prevalent wear mechanism was abrasive with reduced influence of oxidative and adhesive wear. Finite element analys...

Particulate Science and Technology, 2017

Pure boron suboxide (B6O) powder admixed with 1.08 vol% of MgO, CaO, and CaCO3 (corresponding to ... more Pure boron suboxide (B6O) powder admixed with 1.08 vol% of MgO, CaO, and CaCO3 (corresponding to 1.5wt%, 1.4wt% and 0.7wt% respectively), were synthesized by hot-pressing and the mechanical properties evaluated. Pure B6O powders were sintered at a temperature of 1900 o C, while the B6O-alkaline earth metal oxide admixed powders were sintered at a temperature 2 of 1850 o C. All sintering was done under an applied load of 80 MPa in an argon environment. The microstructures and phase analyses were studied by scanning electron microscopy and X-ray diffraction techniques, respectively. The addition of the alkaline earth metal oxide additives resulted in the formation of boride and borate phases, depending on the oxide used. Mechanical properties of the hot-pressed materials were characterized based on their density, hardness and fracture toughness. Between 95 to 98% of theoretical densities were achieved and the result indicate a good combination of hardness (between 31.6-32.1 GPa) and fracture toughness (between 6.1-6.8 MPa.m 0.5) in the B6O-alkaline earth metal oxide materials. The introduction of the additive enhances the fracture toughness of the pure B6O-materials, while the fracture mode observed in the sintered materials is mainly transgranular.

Particulate Science and Technology, 2016

ABSTRACT Boron suboxide (B6O)−based materials have shown good properties which make them good can... more ABSTRACT Boron suboxide (B6O)−based materials have shown good properties which make them good candidates for cutting tool and other applications where abrasive wear resistance is important. The objective of this study was to optimize the production of B6O at ambient pressure by varying reaction temperature and time. B6O powders were produced from the reaction between boric acid and amorphous boron powders at the reaction temperatures between 300°C and 1400°C for 6 h. The powders produced were characterized in terms of particle size, phase analysis and composition, product yield, as well as morphology. Increase in temperature increased both the yield as well as the particle size of the produced powders. X-ray diffraction (XRD) pattern obtained also showed improved crystallinity of the produced powder as the temperature increases. Scanning electron microscopy (SEM) images of the synthesized powder at higher temperature clearly showed improved crystallinity (star-like crystals) as the reaction temperature was increased. The B6O powders synthesized at 1300°C for 6 h had the optimum yield of over 95%.

This study investigated and compared the mechanical properties of boron suboxide (B 6 O) with and... more This study investigated and compared the mechanical properties of boron suboxide (B 6 O) with and without chromium bromide (CrB 2) additive, hot pressed at 1900 o C and 1850 o C and for 20 minutes, with applied pressures of 50 and 80 MPa respectively. The theoretical density attained for these materials was More than 96%. The phase relationship, microstructures and mechanical properties of these materials were examined and good combination of mechanical properties was obtained with the B 6 O-CrB 2 material (HV 32.1 GPa, K IC 4.5 MPa.m 0.5) compared to pure B 6 O material. Mixing with a small amount (1.7 wt.%, equivalent of 0.4 vol.%) of CrB 2 additive resulted in a pronounced improvement in both the hardness and fracture toughness values. The improvement in the fracture toughness was attributed to the introduction of the second phase and the toughening mechanism is presumed to be by crack bridging and deflection due to bimetallic stress.

B 6 O powders were produced from the reaction between boric acid and amorphous boron powders at t... more B 6 O powders were produced from the reaction between boric acid and amorphous boron powders at the reaction temperatures between 300 and 1400 o C for 6 hours. The powders produced were characterized in terms of particle size, phase analysis and composition, product yield as well as morphology. Increase in temperature increases both the yield as well as the particle size of the produced powders. XRD pattern obtained also showed improved crystallinity of the produced powder as the temperature increases. SEM image obtained at higher temperature clearly showed improved crystallinity (star-like crystals) as the reaction temperature was increased. The B 6 O powders synthesised at 1300 o C for 6 hours had the optimum yield of over 95%.

Abstract— Although B6O materials have shown excellent potentials for wear resistant and cutting t... more Abstract— Although B6O materials have shown excellent potentials for wear resistant and cutting tool applications, the problem of low fracture toughness and the difficulties to densify has delayed the application of B6O materials in the industry. In this work, efforts have been directed towards improving the fracture toughness and densification of these materials by incorporating suitable secondary phases and tailoring the microstructure to the desired properties. Synthesized B6O was hot pressed at 1850oC and 80 MPa in an argon environment, with nickel compounds (nickel (Ni) and nickel oxide (NiO)). The addition of 1.10 vol.% of additives improved the densification of the B6O powders in comparison to the pure B6O material. The fracture mode observed in the sintered materials is mainly transgranular.

Application of lean manufacturing tools in abattoirs promise great process improvements, despite ... more Application of lean manufacturing tools in abattoirs promise great process improvements, despite limited sources and literature specific to abattoirs. Due to the inadequacy of research papers in application of lean manufacturing tools in abattoir; audits, process efficiency measurements, document analyzing, identification of value adding and non-value adding activities, site visits, plant tours, conducting trainings and awareness, motion study, work and method study, plant tour and observation were used. Data collection, recommendations and improvements were made on the basis of authors’ knowledge, observations, audits results, change management responses, feedbacks, process measurements, and abattoir staff advice. Lean manufacturing tools, practices and philosophies that succeeded in carrying out the research in abattoirs are takt, standardization, 5S and waste elimination, value stream mapping. These lean manufacturing tools improved business processes, work methods and productivi...

Journal of Alloys and Compounds, 2020

Abstract Ti–Ni–TiCN composites with varying TiCN contents (5, 10 and 15 wt%) were consolidated us... more Abstract Ti–Ni–TiCN composites with varying TiCN contents (5, 10 and 15 wt%) were consolidated using the novel spark plasma sintering technique at a sintering temperature of 1100 °C, for 10 min holding time under a vacuum condition of lower than 4 Pa, 100 °C/min heating rate and applied pressure of 50 MPa. The effects of Ni additive and TiCN nanoceramic reinforcement content on densification, microstructure and mechanical properties of the developed composites were investigated. Scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscope (EDS) and X-ray diffraction (XRD) techniques were employed to study the morphology and phases present in the developed composites. SEM results revealed the presence of undissolved particles and lamella arrangements of phases within the matrix of the sintered composites which were confirmed by the EDS and XRD results as undissolved TiCN particles, in-situ formed TiN and Ti2Ni intermetallic phases. The relative density of the sintered compacts decreased from 99.3% to 98.23% with increase in the reinforcement content. The hardness of the sintered composites was found to increase with increasing reinforcement content. Compressive test results indicated that Ti–Ni–TiCN composites displayed improved compressive strength than the pure Ti samples. The optimum properties were obtained in Ti–6Ni–10TiCN composite with Vickers hardness of 398 HV1.0, compressive yield and ultimate strengths of about 998 MPa and 1156 MPa respectively.

Materials, 2020

Plastics have remained the material of choice, and after serving their intended purpose, a large ... more Plastics have remained the material of choice, and after serving their intended purpose, a large proportion ends up in the environment where they persist for centuries. The packaging industry is the largest and growing consumer of synthetic plastics derived from fossil fuels. Food packaging plastics account for the bulk of plastic waste that are polluting the environment. Additionally, given the fact that petroleum reserves are finite and facing depletion, there is a need for the development of alternative materials that can serve the same purpose as conventional plastics. This paper reviews the function of packaging materials and highlights the future potential of the adoption of green materials. Biopolymers have emerged as promising green materials although they still have very low market uptake. Polylactic acid (PLA) has emerged as the most favoured bioplastic. However, it is limited by its high cost and some performance drawbacks. Blending with agricultural waste and natural fil...