http://hdl.handle.net/10204/456 2013-05-26T05:31:52Z 2013-05-26T05:31:52Z Bhaumik, M Setshedi, K Maity, A Onyango, M.S http://hdl.handle.net/10204/6735 2013-05-21T21:55:14Z 2013-06-07T00:00:00Z

Title: Chromium(VI) removal from water using fixed bed column of polypyrrole/Fe3O4 nanocomposite Authors: Bhaumik, M; Setshedi, K; Maity, A; Onyango, M.S Abstract: The adsorption of Cr(VI) using polypyrrole/Fe3O4nanocomposite adsorbent was investigated in a continuous flow fixed-bed column. The effects of composition of the nanocomposite, adsorbent mass, influent Cr(VI) concentration and flow rate on the adsorption characteristics of adsorbent was explored at pH 2. Experimental results confirmed that the breakthrough curves were dependent on bed mass, initial Cr(VI) concentration and flow rate. Three kinetic models; Yoon–Nelson, Thomas, Bohart–Adams were applied to the experimental data to predict the breakthrough curves using linear regression and to determine the characteristic parameters of the column that are useful for process design. The Yoon–Nelson and Thomas models were found appropriate for description of the whole breakthrough curves, whereas the Bohart– Adams model could only predict the initial part of the breakthrough curves. Using environmental water, the PPy/Fe3O4nanocomposite demonstrated its effectiveness in Cr(VI) removal below acceptable level by processing 5.04 L water with initial 76.59 mg/L Cr(VI) concentration using only 2 g of adsorbent mass. It can be concluded therefore that PPy/Fe3O4media provides alternative solution to ameliorate water contaminated with Cr(VI). Description: Copyright: 2013 Elsevier. This is a ABSTRACT ONLY. The definitive version is published in Separation and Purification Technology, Vol.110, pp11-19

2013-06-07T00:00:00Z Roro, KT Tile, N Mwakikunga, B Yalisi, B Forbes, A http://hdl.handle.net/10204/6711 2013-05-03T21:55:14Z 2012-05-01T00:00:00Z

Title: Solar absorption and thermal emission properties of multiwall carbon nanotube/nickel oxide nanocomposite thin films synthesized by sol-gel process Authors: Roro, KT; Tile, N; Mwakikunga, B; Yalisi, B; Forbes, A Abstract: Multiwall carbon nanotubes (MWCNTs)/nickel oxide (NiO) nanocomposites were successfully prepared by a sol–gel process and coated on an aluminium substrate. The MWCNTs were chemically functionalized and then added into NiO alcogels, and magnetic stirred for homogeneous dispersion into the NiO matrix solution. The morphology of the resulting nanocomposite thin films showed that the MWCNTs were embedded in the NiO nano-particle matrix, while HRTEM confirmed that the MWCNTs were surrounded by the NiO nano-particles. Raman spectra for functionalized MWCNTs displayed a red shift from the pristine MWCNTs suggesting successful purification/functionalization. The spectrum for the MWCNTs/NiO nanocomposite indicated the presence of both the TO and LO phonons of NiO, and the D and G bands of the MWCNTs. Red and blue shifts of the NiO phonons and the MWCNT phonons suggested that the vibrational properties of both materials were changed to form new nanocomposite vibrational properties. Despite unoptimized layer thickness and composition, the solar absorptance of the functionalized MWCNTs/NiO nanocomposite films was 0.84 (for a single layer). The thermal emittance at 100 °C was approximately 0.2. These results suggest that MWCNTs/NiO nanocomposite materials are suitable for solar thermal applications. Description: Copyright: 2012 Elsevier. This is an ABSTRACT ONLY. The definitive version is published in Materials Science and Engineering: B, vol. 177(8), pp 581–587

2012-05-01T00:00:00Z 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