Browsing by Author "Petrik, Leslie Felicia"

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    Effects of film thickness of ALD-deposited Al2O3, ZrO2 and HfO2 nano-layers on the corrosion resistance of Ti(N,O)-coated stainless steel
    (MDPI, 2023) Dinu, Mihaela; Wang, Kaiying; Petrik, Leslie Felicia; Massima, Mouele Emile S
    The goal of this stydy was to explore the potential of the enhanced corrosion resistance of Ti(N,O) cathodic arc evaporation-coated 304L stainless steel using oxide nano-layers deposited by atomic layer deposition (ALD). In this study, we deposited Al2O3, ZrO2, and HfO2 nanolayers of two different thicknesses by ALD onto Ti(N,O)-coated 304L stainless steel surfaces. XRD, EDS, SEM, surface profilometry, and voltammetry investigations of the anticorrosion properties of the coated samples are reported. The amorphous oxide nanolayers homogeneously deposited on the sample surfaces exhibited lower roughness after corrosion attack compared to the Ti(N,O)-coated stainless steel. The best corrosion resistance was obtained for the thickest oxide layers. All samples coated with thicker oxide nanolayers augmented the corrosion resistance of the Ti(N,O)-coated stainless steel in a saline, acidic, and oxidising environment (0.9% NaCl + 6% H2O2, pH = 4), which is of interest for building corrosion-resistant housings for advanced oxidation systems such as cavitation and plasma-related electrochemical dielectric barrier discharge for breaking down persistent organic pollutants in water.
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    Effects of Film Thickness of ALD-Deposited Al2O3, ZrO2 and HfO2 Nano-Layers on the Corrosion Resistance of Ti(N,O)-Coated Stainless Steel
    (MDPI, 2023) Dinu, Mihaela; Wang, Kaiying; Petrik, Leslie Felicia
    The goal of this stydy was to explore the potential of the enhanced corrosion resistance of Ti(N,O) cathodic arc evaporation-coated 304L stainless steel using oxide nano-layers deposited by atomic layer deposition (ALD). In this study, we deposited Al2O3, ZrO2, and HfO2 nanolayers of two different thicknesses by ALD onto Ti(N,O)-coated 304L stainless steel surfaces. XRD, EDS, SEM, surface profilometry, and voltammetry investigations of the anticorrosion properties of the coated samples are reported. The amorphous oxide nanolayers homogeneously deposited on the sample surfaces exhibited lower roughness after corrosion attack compared to the Ti(N,O)-coated stainless steel. The best corrosion resistance was obtained for the thickest oxide layers. All samples coated with thicker oxide nanolayers augmented the corrosion resistance of the Ti(N,O)-coated stainless steel in a saline, acidic, and oxidising environment (0.9% NaCl + 6% H2O2, pH = 4), which is of interest for building corrosion-resistant housings for advanced oxidation systems such as cavitation and plasma-related electrochemical dielectric barrier discharge for breaking down persistent organic pollutants in water.
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    Effects of film thickness of ald-deposited al2o3, zro2 and hfo2 nano-layers on the corrosion resistance of ti(n,o)-coated stainless steel
    (MDPI, 2023) Dinu, Mihaela; Wang, Kaiying; Petrik, Leslie Felicia
    The goal of this stydy was to explore the potential of the enhanced corrosion resistance of Ti(N,O) cathodic arc evaporation-coated 304L stainless steel using oxide nano-layers deposited by atomic layer deposition (ALD). In this study, we deposited Al2O3, ZrO2, and HfO2 nanolayers of two different thicknesses by ALD onto Ti(N,O)-coated 304L stainless steel surfaces. XRD, EDS, SEM, surface profilometry, and voltammetry investigations of the anticorrosion properties of the coated samples are reported. The amorphous oxide nanolayers homogeneously deposited on the sample surfaces exhibited lower roughness after corrosion attack compared to the Ti(N,O)-coated stainless steel. The best corrosion resistance was obtained for the thickest oxide layers. All samples coated with thicker oxide nanolayers augmented the corrosion resistance of the Ti(N,O)-coated stainless steel in a saline, acidic, and oxidising environment (0.9% NaCl + 6% H2O2, pH = 4), which is of interest for building corrosion-resistant housings for advanced oxidation systems such as cavitation and plasma-related electrochemical dielectric barrier discharge for breaking down persistent organic pollutants in water.
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    Isolation and characterisation of cellulose nanocrystal obtained from sugarcane peel
    (Rasayan Journal, 2020) Petrik, Leslie Felicia; Abiaziem, C. V.; Williams, Akan B.
    This work was aimed at developing efficient and stable cellulose nanocrystal (CNC) from sugarcane peel, which has been of growing concern as a potential for various industrial applications and providing a solution to the problem of indiscriminate disposal of peels of sugarcane, which creates nuisance in the environment. The alkaline treatment with sodium hydroxide and bleaching with acidified sodium chlorite were used to isolate cellulose from sugarcane peel, followed by acid hydrolysis which was done at 45o C for 45 min using 64% sulphuric acid to prepare the CNC. The chemical composition of the samples and their physicochemical properties were studied. The untreated and treated samples were characterised using various techniques, scanning electron microscopy (SEM), x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The CNC exhibited FT-IR spectra identified as cellulose structures. XRD showed that the CNC earmarked the structure of the cellulose nanocrystal with a crystallinity index of 99.2%. The SEM micrograph revealed fiber bundles separated into individualized CNC; the TEM image showed a needle-shaped CNC with a particle size of 20.57 nm and 153.05 nm in diameter and length, respectively. The TGA curve revealed a good thermal stability for the CNC. The results showed an effective synthesis of CNC from sugarcane peel.
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    Silver-coated polyethene terephthalate membrane for detection of pharmaceuticals using surface-enhanced Raman spectroscopy
    (University of the Western Cape, 2017) Ndilowe, George Michael; Petrik, Leslie Felicia
    Surface-enhanced Raman spectroscopy (SERS) has emerged as one of the analytical tools for detection of micro pollutants in the aquatic environment. The SERS technique is touted to have fingerprinting capability, specificity, ease of operation and single-molecule sensitivity. Therefore SERS can be used for detection of trace level organic pollutants in water. Trace level aquatic micro pollutants such as pharmaceuticals, have been detected in effluents from water treatment plants. Pharmaceuticals, due to the intended therapeutic use, may have adverse effects on living organisms, even in trace-level concentrations. Furthermore, the growing interest to reuse wastewater to augment conventional water supplies has resulted in a growing demand to explore sensitive and rapid analytical techniques such as SERS. In addition the use of track-etched polymer membranes in the filtration process has attracted considerable attention due to their flexibility in providing shape, durability and pore size control versatility. In this work, a silver-coated track-etched polyethene terephthalate (PET) membrane was developed as a platform to detect acetaminophen and had its surface-enhance Raman properties evaluated. The silver-coated track-etched PET membrane was fabricated by modifying the surface of the PET membrane with diethylenetriamine (DETA) via solid-liquid interface reaction known as aminolysis. The characterisation techniques used to ascertain the surface modification of track-etched PET membrane are Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS). Silver nanoparticles were immobilised on the amine-modified surface of track-etched polyethene terephthalate membrane by immersing an amine-modified track-etched PET membrane in a 102 mL mixture of 1 mM of silver nitrate and 1% trisodium citrate heated at 90 oC for 30 minutes. The immobilised silver nanoparticles were of varying sizes with an average size of 62 nm and mostly of spherical shape. The successful immobilisation of silver nanoparticles on modified track-etched PET membrane was further characterised by ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).
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    The use of factor analysis and acid base accounting to probe the speciation of toxic metals in gold mine waste
    (Springer Nature, 2020) Abegunde, O. A.; Okujeni, Charles D.; Petrik, Leslie Felicia
    The generation of acidic drainage has become pervasive over the years and toxic elements are released due to exposure to oxidising agents, unforeseen circumstances, and human interactions. Uncontrolled acidic mine drainage release can result in substantial ecological disruption in sensitive and productive receiving waters. This study probes the element mobility of gold tailings with regard to various zones identified, based on possible phenomena such as the natural water medium, or acidic and alkaline media using sequential extraction and multivariate analyses. Factor analysis results, coupled with mineralogy, were corroborated with acid generation potential to identify various relationships that exist and establish the efficacy of the research towards predicting acid mine drainage generation potential. The statistical analysis was able to establish that pH or acidity, Fe ions, Ca2+ and Mg2+ played a major role in the released metals. Out of the four factors (80.8% accounted for) identified in factor analysis results for water fraction (WF), Fe contributed to three factors which showed the presence of Fe ions (assuming Fe2+ and Fe3+) responsible for the increased acidity of the tailings.