http://hdl.handle.net/10204/922 2013-05-22T23:45:59Z 2013-05-22T23:45:59Z Ochonogora, OF Meacock, C Abdulwahaba, M Pityana, S Popoolaa, API http://hdl.handle.net/10204/6708 2013-04-22T21:55:12Z 2012-12-01T00:00:00Z

Title: Effects of Ti and TiC ceramic powder on laser-cladded Ti-6Al-4V in situ intermetallic composite Authors: Ochonogora, OF; Meacock, C; Abdulwahaba, M; Pityana, S; Popoolaa, API Abstract: Titanium metal matrix composite (MMCs) was developed on titanium alloy (Ti–6Al–4V) substrate with the aim of improving the hardness and wear properties by laser cladding technique using a Rofin Sinar 4 kW Nd: YAG laser. Wear investigations were carried out with the aid of three body abrasion tester. The resultant microstructure show homogeneous distribution of TiC particles free from cracks and pores. Multiple track deposited systems with 50% overlap revealed micro-hardness increase from 357.3 HV0.1for the substrate reaching a peak as high as 922.2 HV0.1 for 60%Ti + 40%TiC and the least 665.3 HV0.1 for 80%Ti + 20%TiC MMCs. The wear resistance of the materials improved significantly, indicating a fifteen-fold wear rate reduction due to the proper distribution of ceramic particles thereby forming interstitial carbides as revealed by the X-ray diffraction spectrum. Description: Copyright: 2012 Elsevier. This is an ABSTRACT ONLY. The definitive version is published in Applied Surface Science, vol. 263, pp 591-596

2012-12-01T00:00:00Z Mabhali, LAB Sacks, N Pityana, S http://hdl.handle.net/10204/6702 2013-04-19T21:55:16Z 2012-03-01T00:00:00Z

Title: Impact toughness of laser surface alloyed Aluminium Authors: Mabhali, LAB; Sacks, N; Pityana, S Abstract: Laser surface alloying of aluminium AA1200 was performed with a 4kW Nd:YAG laser and the impact resistance of the alloys was investigated. The alloying powders were a mixture of Ni, Ti and SiC in different proportions. Surfaces reinforced with intermetallic phases and metal matrix composites were achieved during laser alloying. Brittle fracture of the SiC particles and transgranular cracking of the intermetallic phases was observed for the laser alloyed samples, while ductile fracture was observed for the bulk aluminium. The aluminium metal absorbed more energy during fracture compared to the laser alloyed samples due to its high ductility. Laser alloyed layers with a high Ti content had high absorbed energies which represent a reduction in brittleness, while alloyed layers with a high Ni content had low absorbed energies which indicate a preference for brittle fracture. Description: Copyright: 2012 Elsevier. This is the Pre/post print version of the work. The definitive version is published in Journal of Materials Science & Technology, pp 1-29

2012-03-01T00:00:00Z Mokgalaka, MN Pityana, SL Popoola, API Meacock, C http://hdl.handle.net/10204/6680 2013-04-17T21:55:19Z 2012-10-01T00:00:00Z

Title: Effect of laser power and scanning speed on laser deposited Ti6Al4V/TiB2 matrix composites Authors: Mokgalaka, MN; Pityana, SL; Popoola, API; Meacock, C Abstract: Titanium is an attractive choice for many components in the aerospace, automotive and biomedical industry. It is frequently chosen as one of the preferred alloys for parts and components due to the excellent combination of specific mechanical properties they exhibit. Description: Additive Manufacturing in Industry Conference, Kwa Maritane, Pilanesberg National Park, 31 October-2 November 2012

2012-10-01T00:00:00Z Chetty, AS Vargha, V Maity, A Moolman, FS Rossouw, C Anandjiwala, R Boguslavsky, L Mancama, D Focke, WW http://hdl.handle.net/10204/6677 2013-04-17T21:55:20Z 2013-02-01T00:00:00Z

Title: Development of thermoresponsive poly(propylene-g-N-isopropylacrylamide) non-woven 3D scaffold for smart cell culture using oxyfluorination-assisted graft polymerisation Authors: Chetty, AS; Vargha, V; Maity, A; Moolman, FS; Rossouw, C; Anandjiwala, R; Boguslavsky, L; Mancama, D; Focke, WW Abstract: Growing cells on 3D scaffolds is far superior to the conventional 2D monolayer culture method. In this study, a novel 3D thermoresponsive poly(propylene-g-N-isopropylacrylamide) (PP-g-PNIPAAm) nonwoven fabric (gNWF) was developed for cell culture using oxyfluorination-assisted graft polymerisation (OAGP). New polar functional groups were detected on the oNWF, and PNIPAAm was confirmed in the gNWF by attentuated total-reflectance Fourier transform infrared (ATR-FTIR) and scanning X-ray photoelectron spectroscopy (S-XPS). Scanning electron microscopy (SEM) revealed a rough surface morphology and confinement of the PNIPAAm graft layer to the surface of the fibres in the gNWF. The OAGP method did not affect the crystalline phase of bulk PP, however, twin-melting thermal peaks were detected for the oNWF and gNWF indicating crystal defects. Contact angle studies showed that the surface of the gNWF exhibited a thermoresponsive behaviour. Hepatocyte cells attached onto gNWF disks in a bioreactor at 37 C and remained viable for 10 days in culture. Upon cooling the cell culture media to 20 C, cells were spontaneously released as 3D multi-cellular constructs without requiring destructive enzymes. The development of 3D thermoresponsive scaffolds capable of non-invasive 3D cell culture could provide a more reliable in vitro model for cells. Description: Copyright: 2013 Elsevier. This is an ABSTRACT ONLY. The definitive version is published in Colloids and Surfaces A: Physicochemical and Engineering Aspects, vol. 419, pp 37-45

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