Theses and dissertations (Engineering and Built Environment)
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Item Processing and characterization of nanoclays reinforced metal (aluminium) matrix composites(2018) Mwangi, Festus Maina; Kanny, Krishnan; Machio, Christopher N.Aluminium is currently one of the most versatile and preferred engineering material of our times. It is the world’s most abundant metal and is the third most common element on earth. The worldwide demand for aluminium has been growing steadily at an average rate of 5-7% annually. In fact, the demand has more than doubled up in the last decade. Despite the marked growth for aluminium, its alloys and composites, there is still a dire need to redesign this material’s system if it is to enjoy progressive and diverse economic feasibility and acceptability in various industrial sectors. This study opens up a new line of thought in the challenge of repositioning the material from an economic, industrial, and environmental perspective. It explores the efficacy of integrating a low-cost nanophased reinforcement system in the form of nanoclays into aluminium and/or its alloys. In the study, an experimental approach was adopted. The study called for an understanding of the intrinsic nature of both the aluminium and/or its alloys on one hand and nannoclays on the other. Based on that understanding, potential processing technologies were identified, with powder metallurgy eventually emerging as the most preferred processing route. For the current study, AMB-2712 Al alloy was used as the matrix. Two nanoclays at 1% – 12.5%wt content were experimented with as the reinforcement system, i.e. Nanofil 116 and Cloisite Ca++DEV. A conventional press and sinter approach was used to process the composites. Variables under investigation included the effects of green compaction pressure, sintering temperature profile, sintering atmosphere, and the percentage weight content of nanoclay. Besides physical inspection, hardness and tensile testing were used in comparatively evaluating the composites’ structural integrity. Thermal behaviour was assessed using DSC- TGA. Additionally, thermal conductivity, thermal diffusivity, specific heat capacity, and thermal expansion were examined with thermal-management-applications in mind. Results from the study show that nanoclays can feasibly be integrated into aluminium and/or its family of alloys and composites. Under the processing parameters used in this study, best results were obtained with 1%wt nanoclay addition. For better appreciation, both the load bearing capacity of the reference alloy and its percentage elongation to fracture were increased by more than 150%. Melting temperature was increased by 6.6%. It was also observed that the thermal conductivity, diffusivity, and specific heat capacity were not only significantly improved, but also more stable. While the results for reference sample were deteriorating after 2200C, the composites were observed to be stable at 3000C and still showing signs of potential to progress further. At 3%wt, content, the nanoclays were observed to demonstrate thermal barrier properties. Microstructural analysis portrayed the nanoclays as heat-sinks, thereby ideal for use in thermal management systems in areas such as the automotive engine components. Effects of nanoclays as revealed by microstructural analysis further demonstrated that the successful use of nanoclays as a reinforcement system for aluminium and/or its alloys presents a novel technique of preparing conventional aluminium alloys in a more economical way.