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Search Results: 1 - 10 of 654261 matches for " J. A. Ajao "
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Preparation and Structural Characterization of Vanadium Doped Ni – B Binary Hard Alloys  [PDF]
J. A. Ajao
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2010, DOI: 10.4236/jmmce.2010.96040
Abstract: The microstructure of a series of binary Ni-B alloys containing various amounts of vanadium additions were investigated by Differential Thermal Analysis (DTA), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Analysis (EDXA). Due to the vanadium addition in the alloys quenched from the liquidus, the formation of the Ni3B phase was enhanced even when the nominal composition was hypoeutectic. The addition of vanadium led to the formation of t (Ni20.4V2.6B6) phase during the present investigation. In addition, the crystallographic orientation relationship of this ternary phase with the nickel matrix was reported. The solid-state eutectoid transformation of the Ni3B phase during cooling was also reported and discussed.
Effect of Solidification Process Parameters on the Microstructure of Some Meltspun Nickel-Based Hardfacing Alloys  [PDF]
J. A. Ajao
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2009, DOI: 10.4236/jmmce.2009.810067
Abstract: The influence of solidification parameters on the morphology of a number of meltspun Nickelbased hard alloys has been investigated by means of scanning electron microscopy (SEM), conventional transmission electron microscopy and energy dispersive X-ray analysis (EDXA). It was established that the wheel velocity played a prominent role in the types of microstructure observed. Very high wheel velocity could lead to the formation of amorphous structure as observed in some of the alloys investigated. No appreciable effect of the ribbon thickness was observed on the microhardness of the alloys. It was also reported that the thermal transfer mode between the ideal and newtonian coolings was observed in all the alloys investigated.
Scanning Electron Microscopy of Some Slowly Cooled Nickel-Based Hardfacing Alloys Containing Iron Additions  [PDF]
J. A. Ajao
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2010, DOI: 10.4236/jmmce.2010.92012
Abstract: The service lifespan of components used at higher temperatures in corrosive and abrasive environments can be prolonged by high-temperature corrosion-resistant coatings. This study is concerned with the microstructural characterization of some slowly cooled Nickel–based hardfacing alloys investigated by differential thermal analysis (DTA), energy dispersive X – ray analysis (EDXA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The alloys were prepared in high frequency induction furnace under controlled atmosphere. Three major primary hard phases (Ni (α), M7C3, and the π phase) were identified during slow cooling in DTA depending on the nominal compositions of the alloys. Large undercoolings as well as intense solid state precipitations were observed in alloys with iron additions. The precipitations formed the basis of the high hardness values and strength of the alloys. It was also reported that the hardness values of the alloys increased as the iron contents increased.
Thermal, Hardness and Microstructural Characterization of Al-Si-SiCp Composites  [PDF]
O. A. Alo, L. E. Umoru, J. A. Ajao, K. M. Oluwasegun
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2012, DOI: 10.4236/jmmce.2012.112013
Abstract: This study investigated the effects of silicon and silicon carbide particles contents on the thermal, hardness and microstructural behaviour of Al-Si-SiCp composites. 16 samples of the composite produced by stir casting technique were of silicon contents of 1, 2, 3 and 4% by weigh, and silicon carbide contents of 0.5, 1, 1.5 and 2% by weight for each composition of silicon. Each of the samples were subjected to homogenizing annealing heat treatment. Differential thermal analysis (DTA), hardness test and microstructural analysis were then performed on the samples from each composition. The results obtained showed that the hardness of the composite increased gradually as the silicon and silicon carbide particles content increased. The micrographs obtained revealed the presence of silicon carbide, silicon precipitates and aluminium carbide (Al4C3) within the metallic matrix. The amounts of these phases varied with the silicon and silicon carbide content. All the samples gave DTA curves with major endothermic peaks between 550 – 570℃ and two sets of exothermic peaks between 580 – 610℃ for the first set and between 565 – 570℃ for the second set. It was inferred from the study that although varied silicon and silicon carbide contents affected the thermal, hardness and microstructural behaviour of the Al-Si-SiCp composites, the variation of the SiCp content had a more pronounced effect on the hardness value of the Al-Si-SiCp composite.
Contributions of Edible Mushroom (A Non-timber Forest Product of Tropical Forest Ecosystem) to Rural Livelihood in Oyo State, Nigeria
V.A.J. Adekunle,V.A.J. Adekunle,K. Ajao
Pakistan Journal of Social Sciences , 2012,
Abstract: The contribution of edible mushrooms to rural livelihood was assessed in this study. Data were collected with well-structured questionnaire administered on 150 randomly selected household heads from ten villages distributed among four Local Government Areas of Oyo State, Nigeria. The result reveals that majority of the respondents (95%) were actively involved in collection, consumption and sales of the commodity. Consumption of mushrooms was not affected by educational status, occupation and social background of the respondents. It was also discovered that the consumption substituted for animal proteins usually absent in rural dwellers’ diet. The respondents have secured gainful employment and income from the sale of this important non-timber forest product as substantial amount of money was being realized from its sales. The seasonal occurrence of this product is discovered as the major setback to its constant availability. For its potentials to be fully realized, cultivation of the product should be embarked upon so as to make it available throughout the year.
Nutrient levels in Guinea current large marine ecosystem (GC-LME) waters
O.A Nubi, E.A Ajao, E.O Oyewo, J.P Unyimadu
Science World Journal , 2008,
Abstract: As part of the UNIDO/GEF/GCLME capacity development programme in the GC-LME countries, water and sediment samples were collected at some stations off Lagos Bar and off the Niger Delta. The nutrient levels were determined spectrophotometrically after appropriate color development following standard methods. Phosphate levels were relatively higher in the sediments. Phosphate and Nitrate levels in the water samples were higher than natural background levels. However, the phosphate and Nitrate levels obtained were similar to those obtained in previous studies on selected wetlands in Ghana. Nitrate levels were relatively higher in water samples while nitrite levels were generally lower than Nitrate levels.
Technical Efficiency of Poultry Egg Producers in Oyo State of Nigeria
S.O. Binuomote,J.O. Ajetomobi,A.O. Ajao
International Journal of Poultry Science , 2008,
Abstract: The study analyzed the Technical Efficiency (TE) of poultry egg producers in Oyo state of Nigeria using a Cobb-Douglas stochastic production frontier function. The data for the study were collected using structured questionnaire administered on random samples of 51 poultry egg producers. The results showed that, the TE of farmers varied between 0.10 and 0.99 with a mean of 0.823. About 90% of the farmers surveyed had technical efficiency score of >0.70. The analysis showed that stock of birds is the most important determinant of poultry egg production while years of experience, management system, educational level and family size are the socioeconomic characteristic influencing the farmers’ technical efficiency. The findings show that further productivity gains linked to the improvement in TE may still be realized in poultry egg production in Nigeria.
Remediation of Polluted Water Using Natural Zeolitic Aluminosilicates/Lateritic Clay Ceramic Matrix Membrane
E. Ajenifuja,O. O. Akinwunmi,M. K. Bakare,J. A. Ajao
ISRN Ceramics , 2012, DOI: 10.5402/2012/672601
Elemental Studies of Soil and Food Flour for Risk Assessment of Highway Pollution Using Particle-Induced X-Ray Emission (PIXE) Spectrometry
O. I. Asubiojo,F. M. Adebiyi,E. I. Obiajunwa,J. A. Ajao
ISRN Analytical Chemistry , 2012, DOI: 10.5402/2012/594598
Elemental Studies of Soil and Food Flour for Risk Assessment of Highway Pollution Using Particle-Induced X-Ray Emission (PIXE) Spectrometry
O. I. Asubiojo,F. M. Adebiyi,E. I. Obiajunwa,J. A. Ajao
ISRN Analytical Chemistry , 2012, DOI: 10.5402/2012/594598
Abstract: The study investigated potential toxic elements in soils and food flours for highway pollution using PIXE spectrometry. The contaminated soils and cassava food flours contained higher levels of the elements than their control samples, while comparison with their standard permissible limits followed similar trend which was attributable to anthropogenic influences. These were corroborated by their elevated Enrichment factor, Pollution index and Geoaccumulation index values for the elements, suggesting significant anthropogenically—derived contaminations of the soils. T-test value (0.038) for the elemental composition of the contaminated soils & cassava flours was significant due to considerable higher concentrations of the elements in the soils than the cassava flours. Cross plot analysis result for the contaminated soils and cassava fours showed moderate positive correlation (R2 = 0.426), indicating inter-element relationship between them. Cluster analysis results for the analyzed elements in the contaminated soil samples indicated that Mn, Fe, V, Cr, Zn, Cl, Ti and S showed closest inter-element clustering and was corroborated by the results of Pearson correlation matrices, while inter-element clustering in the food flour followed the same trend and was also supported by their results of Pearson correlation matrices, validating that the soils and cassava flours were contaminated via similar sources. 1. Introduction Contamination of soil and subsequent food contamination by toxic elements is a major environmental problem that the scientific public is encountering nowadays. The contamination arises via both natural and anthropogenic activities. They are usually established in the soils by forming complexes with organic moieties thereby making their removal very tedious and they persist in the soil until taken up by plants and become part of food chain. Due to the fact that some of the elements, namely, heavy metals are nonbiodegradable, their contamination is difficult to take care of [1]. The occurrence of potential toxic elements above the natural concentrations in highway soils and urban soils is a universal phenomenon [2–8]. In Nigeria, similar studies have been conducted; for instance, in the study carried out by Olajire et al. [9], their report showed the presence of some heavy metals in some soils in an industrial city of southern Nigeria at elevated levels. Study on the contamination of roadside soil and Grass with heavy metals conducted by Olajire and Ayodele [10] revealed that the environmental matrices were contaminated with some heavy metals.
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