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Browsing by Author "Jafta, CJ"

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Electrocatalytic oxidation of ethylene glycol at palladium-bimetallic nanocatalysts (PdSn and PdNi) supported on sulfonate-functionalised multi-walled carbon nanotubes

Author: Ramulifho, T ; Ozoemena, KI ; Modibedi, Remegia M ; Jafta, CJ ; Mathe, Mahlanyane K Date: Apr 2013 Electrocatalytic oxidation of ethylene glycol (EG) in alkaline medium using nano-scaled palladium-based bimetallic catalysts (PdM, where M = Ni and Sn) supported on sulfonated multi-walled carbon nanotubes (SF-MWCNTs) is compared. The bimetallic ... Read more
Electrochromic and electrochemical capacitive properties of tungsten oxide and its polyaniline nanocomposite films obtained by chemical bath deposition method

Author: Nwanya, AC ; Jafta, CJ ; Ejikeme, PM ; Ugwuoke, PE ; Reddy, MV ; Osuji, RU ; Ozoemena, KI ; Ezema, FI Date: May 2014 Polyanine and its nanocomposite WO3/PANI films were deposited on fluorine doped tin oxide (FTO) glassslides by simple chemical bath deposition method. The morphology structure of the composite film wasstudied using atomic force microscopy ... Read more
Fast microwave-assisted solvothermal synthesis of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated MWCNTs: Pd-based bimetallic catalysts for ethanol oxidation in alkaline medium

Author: Ramulifho, T ; Ozoemena, KI ; Modibedi, Remegia M ; Jafta, CJ ; Mathe, Mahlanyane K Date: Jan 2012 The preparation of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated multi-walled carbon nanotubes (SF-MWCNTs) using a very rapid microwave-assisted solvothermal strategy has been described. Electrocatalytic behaviour of the SF-MWCNT-Pd ... Read more
High-performance aqueous asymmetric electrochemical capacitor based on graphene oxide/cobalt(II)-tetrapyrazinoporphyrazine hybrids

Author: Lekitima, JN ; Ozoemena, KI ; Jafta, CJ ; Kobayashi, N ; Song, Y ; Tong, D ; Chen, S ; Oyama, M Date: 2013 A novel asymmetric electrochemical capacitor (AEC) with high energy and power densities has been developed using a graphene oxide/cobalt(II)tetrapyrazinoporphyrazine composite (GO/CoTPyzPz) as the positive electrode and graphene oxide/carbon ... Read more
A high-rate aqueous symmetric pseudocapacitor based on highly graphitized onion-like carbon/birnessite-type manganese oxide nanohybrids

Author: Makgopa, K ; Ejikeme, PM ; Jafta, CJ ; Raju, Kumar ; Zeiger, M ; Presser, V ; Ozoemena, KI Date: Jan 2015 We present a study on the pseudocapacitive properties of birnessite-type MnO(sub2) grafted on highly graphitized onion-like carbon (OLC/MnO(sub2)). In a three-electrode setup, we evaluated two different substrates, namely a platinum disc and ... Read more
In situ engineering of urchin-like reduced graphene oxide–Mn2O3–Mn3O4 nanostructures for supercapacitors

Author: Chidembo, AT ; Aboutalebi, SH ; Konstantinov, K ; Jafta, CJ ; Liu, H ; Ozoemena, KI Date: Jan 2014 We report the use of spray pyrolysis method to synthesize high surface area (BET surface area of 139 m2g-1) self–organized, micron sized urchin-like composites made up of reduced graphene oxide and needle-shaped manganese oxide (rGO-Mn2O3/Mn3O4). ... Read more
Magnetism variations and susceptibility hysteresis at the metal-insulator phase transition temperature of VO2 in a composite film containing vanadium and tungsten oxides

Author: Akande, AA ; Rammutla, KE ; Moyo, T ; Osman, NSE ; Nkosi, SS ; Jafta, CJ ; Mwakikunga, Bonex W Date: Feb 2015 We report on the magnetic property of 0.67–WO3+0.33–VOx mixture film deposit on the corning glass substrate using the chemical sol–gel and atmospheric pressure chemical vapour deposition (APCVD) methods. The XRD and Raman spectroscopy confirm ... Read more
Manganese oxide/graphene oxide composites for high-energyaqueous asymmetric electrochemical capacitors

Author: Jafta, CJ ; Nkosi, F ; Le Roux, Lukas J ; Mathe, Mahlanyane K ; Kebede, Mesfin A ; Makgopa, K ; Song, Y ; Tong, D ; Oyama, M ; Manyala, N ; Chen, S ; Ozoemena, KI Date: Nov 2013 A high-energy aqueous asymmetric electrochemical capacitor was developed using manganese diox-ide ( -MnO2)/graphene oxide (GO) nanocomposites. The nanostructured -MnO2was prepared frommicron-sized commercial electrolytic manganese dioxide ... Read more
Microwave irradiation controls the manganese oxidation states of nanostructured (Li[Li0.2Mn0.52Ni0.13Co0.13Al0.02]O2) layered cathode materials for high-performance lithium ion batteries

Author: Jafta, CJ ; Raju, Kumar ; Mathe, Mahlanyane K ; Manyala, N ; Ozoemena, KI Date: Feb 2015 A hybrid synthesis procedure, combining microwave irradiation and conventional annealing process, is described for the preparation of lithium-rich manganese-rich cathode materials, Li[Li0.2Mn0.54Ni0.13Co0.13]O2 (LMNC) and its aluminum-doped ... Read more
Microwave-assisted optimization of the manganese redox states for enhanced capacity and capacity retention of LiAl(subx)Mn(sub2-x)O(sub4) (x = 0 and 0.3) spinel materials

Author: Nkosi, FP ; Jafta, CJ ; Kebede, Mesfin A ; Le Roux, Lukas J ; Mathe, Mahlanyane K ; Ozoemena, KI Date: Mar 2015 Microwave irradiation at the pre- and post-annealing steps of the synthesis of LiAl(subx)Mn(sub2-x)O(sub4) (x = 0 and 0.3) spinel cathode materials for rechargeable lithium ion battery is a useful strategy to optimize the average manganese ... Read more
Microwave-assisted synthesis of high-voltage nanostructured LiMn1.5Ni0.5O4 spinel: tuning the Mn3+ content and electrochemical performance

Author: Jafta, CJ ; Mathe, Mahlanyane K ; Manyala, N ; Roos, WD ; Ozoemena, KI Date: Aug 2013 The LiMn1.5Ni0.5O4 spinel is an important lithium ion battery cathode material that has continued to receive major research attention because of its high operating voltage (∼4.8 V). This study interrogates the impact of microwave irradiation ... Read more
Modification to an Auger Electron Spectroscopy system for measuring segregation in a bi-crystal

Author: Jafta, CJ ; Roos, WD ; Terblans, JJ Date: Mar 2013 It is reported that different crystal surface orientations yield different segregation fluxes. Although there were a few attempts to confirm these predictions experimentally, it is very difficult to compare data without making a few assumptions. ... Read more
Novel iron-cobalt derivatised lithium iron phosphate nanocomposite for lithium ion battery cathode

Author: Ikpo, CO ; Jafta, CJ ; Ozoemena, KI ; West, N ; Njomo, N ; Jahed, N ; Baker, PG ; Iwuoha, EI Date: Jan 2013 Described herein is the electrochemical study conducted on lithium ion battery cathode material consisting of composite of lithium iron phosphate (LiFePO(sub4), iron-cobalt derivatised carbon nanotubes (FeCo-CNT) and polyaniline (PA) nanomaterials ... Read more
Recent in situ/operando characterization of lithium-sulfur batteries

Author: Yang, Y ; Zhu, Y ; Raju, Kumar ; Jafta, CJ Date: Feb 2019 To address the ever-increasing energy demand due to the increase in the population and at the same time depleting fossil fuel reserves, new energy storage systems, such as batteries, are being developed. Among various battery systems, Li-S ... Read more
Solution-combustion synthesized nickel-substituted spinel cathode materials (LiNixMn2-xO4; 0≤x≤0.2) for lithium ion battery: enhancing energy storage, capacity retention, and lithium ion transport

Author: Kebede, Mesfin A ; Kunjuzwa, N ; Jafta, CJ ; Mathe, Mahlanyane K ; Ozoemena, KI Date: 2014 Spherically shaped Ni-substituted LiNi(subx)Mn(sub2-x)O(sub4) (x=0, 0.1, 0.2) spinel cathode materials for lithium ion battery with high first cycle discharge capacity and remarkable cycling performance were synthesized using the solution-combustion ... Read more
Studies on bare and Mg-doped LiCoO2 as a cathode material for lithium ion batteries

Author: Reddy, MV ; Wei Jie, T ; Jafta, CJ ; Ozoemena, KI ; Mathe, Mahlanyane K ; Sree Kumaran Nair, A ; Soon Peng, S ; Sobri Idris, M ; Balakrishna, G ; Ezema, FI ; Chowdari, BVR Date: May 2014 In this paper, we report on the preparation of bare and Mg-doped Li(Mg(subx(Co(sub1-x)O(sub2) (x = 0, 0.03, 0.05) phases by a molten salt method and their electrochemical properties. They were prepared at 800 C for 6 h in air. Rietveld refined ... Read more
The surface orientation dependence of the pre-exponential factors extracted from the segregation profiles of a Cu(111/110) bi-crystal

Author: Jafta, CJ ; Roos, WD ; Terblans, JJ ; Asante, JKO ; Ozoemena, KI Date: Jul 2011 Previous experimental investigations have only shown, without explanation, that the pre-exponential factor (D0), in the diffusion coefficient of Sb segregating in Cu, is dependent on the surface orientation of a crystal. In this study, the ... Read more
Synthesis, characterisation and electrochemical intercalation kinetics of nanostructured aluminium-doped Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode material for lithium ion battery

Author: Jafta, CJ ; Ozoemena, KI ; Mathe, Mahlanyane K ; Roos, WD Date: Aug 2012 The electrochemistry and intercalation kinetics of nanostructured Li[Li0.2Mn0.54Ni0.13Co0.13]O2 (LMNC) and its aluminium-doped counterpart Li[Li0.2Mn0.52Ni0.13Co0.13Al0.02]O2 (LMNCA) are reported. FESEM and AFM images showed the LMNCA to be ... Read more

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