Dispersion characteristics of carbon nanotubes in metallic alloys and metal oxides
- Authors: Lesufi, Miltia
- Date: 2019
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/398277 , uj:33147
- Description: Abstract : There has been a great consideration in the research and development of carbon nanotubes and its composites due to both their physical and chemical properties which make them desirable for wide uses in the engineering fields such as in catalysts, supercapacitors, nanoelectronic devices, solar energy, aerospace, etc. However, there are still some challenges during the homogenous dispersion of carbon nanotubes (CNTs) in metal and metal oxides without breaking/damaging the nanotube structure. This research focused on the study of dispersion characteristics of multi-walled CNTs (MWCNTs) in Ti-6Al-4V and TiO2 matrix composites, using two methods namely; planetary ball milling and sonication-freeze drying. Efforts were made to understand the relationship between the processing parameters and effect of MWCNTs on the dispersion of MWCNTs in Ti-6Al-4V and TiO2 by studying the microstructures and phases of reinforced Ti-6Al-4V and TiO2 composite powders and sintered composites. Furthermore, the 1 vol. % and 2 vol. % of MWCNTs were dispersed in Ti-6Al-4V and TiO2 respectively by adapted planetary ball milling (in dry condition under vacuum and with no addition of process control agent) and sonication freeze drying. Subsequently, the unreinforced Ti-6Al-4V, TiO2 and mixed composite powders were consolidated by spark plasma sintering (SPS) under vacuum at 850 °C and 1000 °C. Different characterization technique such as scanning electron microscopy and X ray diffraction were used to quantitively analyse the microstructure and nanostructural evolution of the crystalline phases in the MWCNTs/Ti-6Al-4V and MWCNTs/TiO2 powder mixtures after planetary ball milling and of the sintered bulk materials. The density and microhardness of the sintered bulk materials were also measured. The results obtained from this study showed that during planetary ball milling, especially at prolonged milling time (5 hrs) results in better dispersion of MWCNTs in the matrix composite powders than the sonication freeze drying technique. In addition, it was observed that it is difficult to effectively disperse MWCNTs of higher volume fraction in metal matrices. It was also observed that the relative densities of the consolidated MWCNTs/Ti-6Al-4V and MWCNTs/TiO2 composites improved at higher sintering temperature (1000 °C) but decreased with increased volume fraction of MWCNTs. The use of planetary ball milling and SPS technique showed better dispersion of MWCNTs in Ti-6Al-4V and TiO2 no sign of interfacial reactions in the composites. , M.Tech. (Metallurgy)
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Evaluation of microstructural and nanomechanical performance of spark plasma sintered TiFe-SiC reinforced aluminium matrix composites
- Authors: Akinwamide, Samuel Olukayode , Lesufi, Miltia , Akinribide, Ojo Jeremiah , Mpolo, Peggy , Olubam, Peter Apata
- Date: 2020
- Subjects: Spark plasma sintering , Aluminium , Silicon carbide
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/444284 , uj:38831 , Citation: Akinwamide, S.O. et al. 2020. Evaluation of microstructural and nanomechanical performance of spark plasma sintered TiFe-SiC reinforced aluminium matrix composites.
- Description: Abstract: tDue to the increasing demand for lighter materials with enhanced properties, the upgrade oftechniques to improve the production of high-performance composite materials is of greatinterest in modern technology. The microstructural and mechanical properties of sparkplasma sintered aluminium based composites with ferrotitanium (TiFe) and silicon carbide(SiC) reinforcements were investigated. High energy ball milling technique was adopted toeffectively disperse the particles SiC and TiFe reinforcements into the matrix of aluminium,and the admixed powders were compacted using spark plasma sintering technique. Thespecimens sectioned from the sintered compacts were analysed using an X-ray diffractome-ter (XRD), optical microscope (OM), and field emission scanning electron microscope (FESEM)to understand the microstructural features and phase evolution of the sintered compos-ites. The mechanical properties of the composites were also investigated through hardness,nanomechanical and tribology tests. Results from the microstructural examinations con-ducted shows that the reinforcement particles were evenly dispersed within the aluminiummatrix, as a result of the milling process. Furthermore, all the sintered composites hadtheir microstructural features enhanced, but properties such as hardness, frictional coeffi-cient, and elastic modulus were more enhanced in specimen reinforced with 2%SiC+2%TiFeparticles. The reduced crystallite size recorded by the sintered specimens confirmed theeffectiveness of the milling process, and powder metallurgy route adopted for fabrication.
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