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- ItemOpen AccessEffect of Feldspar and Silica Variation on the Properties of Dental Porcelain(Nigerian Journal of Technology (NIJOTECH), 2023-03) Okoubulu, A. B.; Mgbemere, H. E.; Obidiegwu, E. O.; Nwaeju, C. C.Dental porcelain was produced by mixing feldspar, silica, kaolin and bone ash by varying the contents of feldspar and silica. The processing steps include milling, sieving, pressing/shaping, drying, and sintering while the characterisation techniques were Hardness, Compressive strength, X-ray diffraction, Scanning electron microscopy and Fourier Transform Infrared (FTIR). The mixture was subjected to temperatures of 1100 and 1200 oC in a sintering furnace. The chemical composition was determined using X-ray fluorescence and they confirm that SiO2 and Al2O3 are the two major constituents in feldspar and kaolin while CaO is the major constituent in bone ash. For samples sintered at 1200oC, the X-ray diffraction showed that some glass phase possibly consisting of hedenbergite, ilmenite and silica were formed while crystalline phases namely microcline and sanidine were obtained for samples sintered at 1100°C. The morphology of the grains revealed that samples sintered at 1200oC had some hexagonal silica crystals while flakes of different sizes were obtained for samples sintered at 1100oC. Hardness values between 262 and 536 BHN, compressive modulus values ranging from 219 MPa to 324 MPa and linear shrinkage values between 6.34 and 7.6% were obtained. The batches of different compositions with ranges: quartz (silica) (15-25%), feldspar (70-80%), kaolin (Edda/Bauchi) (4%) and bone ash (1%) were fired at 1100, 1200oC, and the developed properties were tested. The sample with 70 wt.% of feldspar, 25 wt.% silica, 4 wt.% of Bauchi clay, and 1 wt.% bone ash sintered at 1200oC gave the best properties and has the potential to be used in dental restoration.
- ItemOpen AccessMICRO-MACRO MODELLING OF SOLIDIFICATION WITH EXPERIMENTAL VALIDATION IN SELECTED EUTECTIC BINARY ALUMINIUM ALLOYS(Journal of Applied Physical Science International, 2021-03-02) Mgbemere, H. E.; Egole, C. P.; Sobamowo, M. G.; Lawal, G. I.Experimental and numerical studies of solidification phenomena have continued to complement each other in the quest for advanced knowledge during component manufacture. The dynamics of engineering designs coupled with the desire for lightweight and improved materials have sustained the progress achieved in recent decades on the modelling of casting systems. The current study presents the simulation of solidification conditions for different aluminium-based eutectic binary alloys and validation with an experimental investigation. The effect of mould material was analysed for the solidification of Al-4.5% Cu using metallic, sand, quartz and Plaster of Paris (POP) moulds respectively. Simulation of the eutectic alloys was carried out using micro-macro model previously developed by the current authors. The effect of mould size and transient evolution of structure during solidification in static casting process were successfully simulated. The results of the experimental investigation showed that although the cooling curves for the different mould materials are qualitatively similar, they respond differently to the presence of the liquid metal leading to significantly different rates of latent heat evolution. The simulated cooling curves for the four eutectic alloys solidified inside sand mould showed that Al-4.5% Cu and Al-3.0% Si have the fastest transformations while Al-6.0% Mg and Al-3.0% Zn have the slowest rate of cooling. Mould size has significant influence on thermal distribution during solidification as temperature tends to reach steady-state and homogenize faster in smaller moulds than bigger ones. For all the alloys compared, nucleation period is very small relative to the total solidification time. The results showed that transient evolution of volumetric grain density and grain radius varied significantly.
- ItemOpen AccessA Simulation and Experimental Investigation of the Thermal Characteristics of Refractory Bricks Produced Using Fireclay and Agroforestry Wastes(Journal of Casting & Materials Engineering, 2022-05-28) Obidiegwu, E. O.; Esezobor, D. E.; Mgbemere, H. E.; Odili, C. C.Manufacturing and processing industries usually consume large quantities of materials and energy in the course of their opera tions. The energy supplied for high-temperature processes are used partially for the actual technical process and between 30 to 40% of the energy escapes through the walls of the reactor into the atmosphere, leading to a high degree of thermal inefficiency and fuel consumption. This paper studies the thermal behaviour of insulating refractory bricks produced from a blend of fireclay and agroforestry wastes. The fireclays used were obtained from Ukpor deposit in Anambra State (Latitude 5.95°N, Longitude 6.92°E), Osiele deposit in Abeokuta, Ogun State (Latitude 7.18°N, Longitude 3.45°E) and Kankara Katsina State (Latitude 11.93°N, Longitude 7.41°E), all of which are in Nigeria. Samples were prepared with various weight percentages (60–100 wt.%) clays and (0–40 wt.%) of agroforestry waste, with grain sizes between 212 and 600 µm. Raw materials and the developed refractory bricks were characterised using appropriate standard techniques. The chemical, mineralogical constituents and phases present in the microstructure were examined. Physical and thermo-mechanical properties were investigated. The insulating refractory bricks developed have porosity of 78.83% , cold crushing strength (CCS) 3.144 kN/m2 and thermal conductivity 0.04–0.046 W/(m∙K) that compare favourably with imported bricks 75–85%, 2.756 kN/m2 and 0.049 W/(m∙K) in both physical, mechanical and thermal properties respectively. The reason is that the agroforestry waste used (coconut shell), served to create the pores that improve insulation after burning. Also the ash that remains serves as reinforcement to improve the mechanical properties. The thermal behaviour of the bricks was studied using Finite Element Method and shows a strong correlation with the experimental findings. This indicates that the produced insulating bricks have the thermal properties required for insulation of furnaces.
- ItemOpen AccessEffect of Varying Silicon Carbide Particulate On The Mechanical Properties Of Aluminium Based Alloy Automobile Brake Disc Component(Iran University of Science and Technology, 2019-06-01) Ogbonna, V. E.; Olayiwola, P. S.; Mgbemere, H. E.In the current study, effect of varying Silicon Carbide particulate on the mechanical properties of Aluminium based alloy automobile brake disc component was investigated. The result of experimental investigation on mechanical properties of Silicon Carbide particle reinforced Aluminium Matrix was achieved for composite brake disc using universal tensile test machine, Rockwell hardness testing machine and numerical/theoretical model. The influence of reinforced ratio of 5, 10, 15 20, and 25 weight percentage of Silicon Carbide particles on mechanical properties was examined. Aluminium Metal Matrix Composites containing, 5, 10, 15, 20, and 25 weight percentages of reinforcement Particles was obtained using Stir-Casting method. The result obtained showed that highest Yield Strength (350.64MPa), Modulus of Rigidity (6137.4MPa), and Hardness (76.5Kg/mm2 ) was obtained on 25wt%SiC (190μm) particle reinforcements.
- ItemOpen AccessEffects of Velocity of Impact on Mechanical Properties and Microstructure of Medium Carbon Steel during Quenching Operations(Scientific Research Publishing Inc. (Engineering), 2015-07-17) Agboola, J.B.; Abubakre, O.K.; Mudiare, E.; Adeyemi, M.BTheoretical analysis of the effects of the velocity of impact using suitable heat transfer equations expressed in forms of finite difference method was developed and used to determine their effects on the characteristic cooling parameters during the quenching process. Various velocities of impact obtained by varying the heights of specimen drops were also used to experimentally determine their effects on characteristic cooling parameters and mechanical properties of medium carbon steel using water as the quenching medium. At a height of drops of 0.5 m, 1.0 m, 1.5 m, and 2.0 m, the tensile strength of the material is 410.4, 496.12, 530.56, and 560.40 N/mm2 respectively. The corresponding hardness values are 42.4, 45.2, 46.2, 50.5 HRC respectively. It is found that as the velocity of impact increases, the maximum cooling rate increases. Hardness and ultimate tensile strength also increase. There are good agreements between theoretical and experimentally determined values of critical cooling parameters of water during quenching operations.