Thermal diffusivity behaviour of multi-walled carbon nanotube reinforced Ti6Al4V metal matrix composites

Abstract: This study investigated the thermal diffusivity behaviours of spark plasma sintered (SPS) multi-walled carbon nanotubes (MWCNTs) reinforced Ti6Al4V composites containing 0, 1, 2 and 3 wt. % of the reinforcement respectively, over a range of 50 – 300 °C. The MWCNTs were dispersed into the Ti6Al4V matrices by high-energy ball milling (HEBM) technique and the milled composite powders were consolidated by SPS under a vacuum atmosphere. The sintering conditions employed were heating rate (100 °C/min), holding time at temperature (5 min), sintering temperature (850 °C) and applied pressure of 50 MPa. The relative densities of the composite discs were measured according to Archimedes’ principle while the thermal diffusivities of as-sectioned composite samples were measured using the Laser Flash equipment. Relative densities of the synthesized nanocomposites deteriorated with increase in the weight fraction of MWCNTs added to Ti6Al4V. The thermal diffusivities of the composites containing 1 and 2 wt. % MWCNTs improved with increase in temperature and weight fraction of MWCNTs contents. A reverse trend was observed in the composite containing 3 wt. % MWCNTs, as the measured thermal diffusivities continued to drop with increase in temperature. Although this composite exhibited the best thermal diffusivities compared to the other composites up to 200 °C, a significant drop in thermal diffusivity was recorded between 250 and 300 °C respectively with the values lower than that of the unreinforced Ti6Al4V alloy. However, the thermal diffusivities of MWCNTs/Ti6Al4V composites were generally not dependent on their densification as the composites with higher weight fractions of the reinforcement had higher thermal diffusivities in spite of their lower relative densities

Effect of sintering parameters on the densification and hardness of NiAl-CNTs composite

Abstract : Nickel aluminides have attracted considerable interest in the past few decades owing to its unique properties. In this work, nickel aluminide (NiAl) was formed in-situ during spark plasma sintering of admixed powders of nickel, aluminium and carbon nanotubes (CNTs) after ball milling. 1 wt % CNTs was incorporated into the intermetallic matrix and the effect of varying sintering parameters investigated, particularly the sintering temperature and pressure. Results showed that a combination of higher sintering temperature with lower pressure yielded better results than lower sintering temperature and higher pressure. Thus the former parameters yielded better densification and subsequently higher micro hardness values of the NiAl-CNTs composites as compared to the latter

Influence of spark plasma sintering temperature on the densification and micro-hardness behaviour of Ni-Cr-Al alloy

Abstract : Sintering temperature is essential towards attaining desired densification and formation of phases which in turn influences the microstructure and properties of a material. In this study, the densification and microhardness behaviour of Ni-Cr-Al alloy prepared by spark plasma sintering (SPS) at different sintering temperatures were investigated. After sintering operation, the density, hardness, phase analysis, and microstructural evolution were investigated using the Archimede’s principle, hardness tester, X-ray diffraction (XRD), and scanning electron microscopy (SEM) respectively. The nickel based alloy was sintered at temperatures of 600, 750, 950 and 1100 ºC. The results indicated that the densification, microstructure, and hardness values were influenced by changes in the sintering temperature. The relative density increased from 73.89 % at 600 ºC to 99.89 % at 1100 ºC, while the hardness value was enhanced from 131.9 ± 2.8 HV to 404 ± 1.2 HV respectively

A correlation between nano and micro-hardness properties of TiN nanoparticles strengthened SAF 2205

Abstract : This work studied the correlation between Vickers and nano-hardness of SAF 2205 reinforced with TiN nanoparticles for the convenience of assessing its mechanical properties. Spark plasma sintering was used to fabricate the composites. Micro and nanoindentations were performed to determine micro and nanohardness values of the fabricated composite. Optical microscope was used to assess the microstructure. The microstructure revealed that the TiN dominated the ferrite/ferrite, ferrite/austenite and austenite/austenite grain boundaries. The micro and nanohardness at the TiN dominated grain boundaries were higher compared to the grain hardness. Hardness also increased considerably as the TiN nanoparticles increases. This is also owed to the strengthening effect played by TiN at the grain boundaries by disrupting dislocation motion in the composite. The determined Vickers hardness was plotted as a function of the corresponding nanohardness, a good linear relation was found between Vickers hardness and nanohardness. A linear relationship (HV = 215.15 + 15.03Hnano) was established which indicates that there is no difference in behavior for the Vickers hardness and nano- hardness

Comparative study of spark plasma sintering features on the densification of Ni-Cr binary alloys

Abstract: Spark plasma sintering (SPS) has been widely regarded as an advanced powder consolidation technique which helps in the development of array of engineering materials. Many have been reported in the literature about sintering parameters such as temperature, pressure, heating rate and holding time. However, little or no reports has been made on some of the intricate features such as process time(s), power SPS (KW), pressing speed (mm/min), and average pressing force (KN) on which sintering parameters are directly related to. This study aims to investigate the behaviour of spark plasma sintered Ni-17Cr binary alloys with emphasis on the densification, hardness value and spark plasma sintering features such as process time (s), power SPS (KW), pressing speed (mm/min), and the average pressing force (KN). Nickel and chromium powders were milled individually using High energy ball milling for durations of 5hr, 10 hr prior to mixing and subsequent sintering. The sintered 5 hr and 10 hr milled Ni-17Cr binary alloys attained relative densities of 98.72 % and 99.1 % respectively. The Microstructural morphology was examined using Scanning electron microscopy (SEM). The sintered 10 hr milled Ni-17Cr binary alloy revealed the higher hardness

Information knowledge and technology for Development in Africa

Information, knowledge, and technology occupy significant space in the information and knowledge society and ongoing debates on development such as sustainable development goals (SDGs) agenda 2030 and the fourth industrial revolution (4IR). Disruptive technologies and cyber-physical systems, obscuring the lines between the physical, digital and biological, escalated by the COVID-19 pandemic, present a ‘new normal’ that profoundly affects the nature and magnitude of responses required to sustain and benefit from the new developments. Africa, known for late adoption of new technologies and innovations, is leapfrogging development stages in several enviable ways. This book, Information knowledge and technology for development in Africa’, written by eminent African scholars, comprises chapters that satisfactorily address information access, artificial intelligence, information ethics, e-learning, library and information science education (LISE) in the 4IR, data literacy and e-scholarship, and knowledge management, which are increasingly essential for information access, services, and LISE in Africa. We expect the book to support research, teaching and learning in African higher education and worldwide for comparative scholarship

Information knowledge and technology for Development in Africa

Information, knowledge, and technology occupy significant space in the information and knowledge society and ongoing debates on development such as sustainable development goals (SDGs) agenda 2030 and the fourth industrial revolution (4IR). Disruptive technologies and cyber-physical systems, obscuring the lines between the physical, digital and biological, escalated by the COVID-19 pandemic, present a ‘new normal’ that profoundly affects the nature and magnitude of responses required to sustain and benefit from the new developments. Africa, known for late adoption of new technologies and innovations, is leapfrogging development stages in several enviable ways. This book, Information knowledge and technology for development in Africa’, written by eminent African scholars, comprises chapters that satisfactorily address information access, artificial intelligence, information ethics, e-learning, library and information science education (LISE) in the 4IR, data literacy and e-scholarship, and knowledge management, which are increasingly essential for information access, services, and LISE in Africa. We expect the book to support research, teaching and learning in African higher education and worldwide for comparative scholarship

Physical, chemical and mechanical properties of corn sheath as pulp and paper raw material

Most papers are made from virgin wood-based pulp of hardwood sources but recently, softwood have received enormous attention as alternative to hard wood because the hardwood takes a significant number of years to mature enough for use in the pulp and paper industry unlike softwood which are majorly annual plants. The annual crop in focus in this work is the yellow open-pollinated variety of corn which generates tons of waste at harvest. A novel attempt is made to ascertain the viability of corn sheaths as raw material for the pulp and paper industry by carrying out a comprehensive analysis on the pulp and paper made from the pulp. The sheaths were dried, shred and cut into pieces suitable for the digester and the pulps obtained were analysed for physicochemical properties. Hand sheets were also made using the generated pulp and its physico-mechanical properties were analysed. Results obtained were compared with pulp from corn husks from other parts of the country, three Nigerian fibre sources – silk cotton, bagasse and rice straw and other foreign non-wood sources and found to be of competitive properties. Pulp properties of Lignin content, ash content, cellulose, hot and cold water solubility of the fibres were 13.72 ± 1.21%, 1.27 ± 0.23%, 53.26 ± 1.11%, 15.20 ± 2.11 and 6.14 ± 2.43 respectively while the mechanical properties of paper from the pulp were Bursting strength (282.163 KPa m2/g), Tear strength (146.119), Tensile strength (257.6N/m) and Tensile Index (3.9Nm/g). It was found that in all properties, the corn sheath was better than the rice straw fibers but not as good as the silk cotton and bagasse fibers. However, the corn sheath has been identified, as a viable raw material for the pulp and paper industry in Nigeria

Improving mechanical and thermal properties of graphite–aluminium composite using Si, SiC and eggshell particles

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Process Parameter Influence on Tensile Property of Friction Stir Processed Al/Ni-Fe Composite

Friction stir processing (FSP) is a solid-state processing technique that has proven to be an efficient surface modification process for producing aluminium matrix composites (AMCs). However, practical challenges still occur during the processing of AMCs even though extensive progress has been made in recent years. In the present study, the influence of FSP process parameters on the tensile property of Al-Ni-Fe composite has been investigated. The process parameters studied were rotational speed and advancing speed. The rotational speed varied between 600 and 1000 rpm while the advancing speed varied between 70 and 210 mm/min. The rotational speed was kept constant at each setting and the advancing speed varied. Other processing parameters were kept constant throughout the experiments. The results were compared with those of the base metal (Al). The results showed that the tensile strength decreased as the advancing speed increased. The highest tensile strength was obtained at a rotational speed of 1000 rpm and an advancing speed of 70 mm/min