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Item Green chemistry in action: Towards sustainable production of gold nanoparticles.(De Gruyter, 2014-08-17)This study reports the synthesis of gold nanoparticles from a gold precursor salt (HAuCl4·3H2O) using Moringa oleifera bark broth, a cheap renewable material, without adding external surfactant, capping agent or template. Biomolecules responsible for reducing Au3+ to Au0 and stabilization of the resulting nanoparticles were extracted from the bark, and the synthesis was monitored for precursor concentration, percentage broth, pH of reaction media and reaction time. The biosynthesized nanoparticles were characterized using spectroscopic (FTIR and UV-Vis) techniques, advanced microscopic imaging (HRTEM, SEM/EDS), and Zeta potential measurements. Distinct color change from yellow to wine red was observed, indicative of the formation of gold particles at nanoscale. The SPR band was found at around 550 nm, in agreement with conventional synthetic protocols. The particles were stable with a net negative surface charge (–20 mV), a contribution associated with the protein nature of the broth. Addition of Pb2+ to the polydisperse nanoparticle suspension resulted in a color shift, to a faint blue color, coupled with a corresponding SPR shift to higher wavelengths, depending on the concentration of Pb2+ added. This color change is attributed to the aggregation of the colloidal particles due to complexation effects of the metal ions with the biomolecules on the surface of the nanoparticles.Item Analysing the value chain for African leafy vegetables in Limpopo Province, South Africa.(Taylor and Francis, 2018-08-03)The aim of this study has been to analyse the value chain of African leafy vegetables in the Limpopo Province of South Africa. This was done by identifying the prominent value chain actors, institutions governing the chain, the infrastructural endowments, key factors and challenges affecting the success or failure of the value chains for African leafy vegetables. Relationships among the value chain actors were weak, with transactions based mostly on spot markets. While smallholder farmers attain high gross margins, their intention to take part in the mainstream markets are prevented by lack of technical advice on production, lack of packaging and processing services, poor infrastructure, deficiency of contractual agreements between actors, and lack of access to finance. Although producers currently attain relatively higher gross margins, more benefits might be realized if government services (such as training, seed production and distribution) could either be decentralized or privatized. Future policy interventions should focus on promoting value addition along the African leafy vegetable chain, provision of cold storage facilities by municipalities closer to smallholder farmers in the rural areas and this will stabilize farm gate prices to encourage continuation of production.Item Factors influencing the adoption of climate-smart irrigation technologies for sustainable crop productivity by smallholder farmers in arid areas of South Africa.(MDPI, 2021-12-03)The adoption of climate-smart irrigation technologies amongst smallholder farmers generally remains low beside their role in combating food and nutrition security in a society and in climate change adaptation strategies. This study identified the factors influencing smallholder farmers’ decision to adopt Climate Smart Irrigation Technologies (CSIT) in the Limpopo Province of South Africa. Data were collected through the completion of a face-to-face structured questionnaire by 100 smallholder farmers selected through convenience and purposive sampling. A probit regression and OLS model were used to identify factors that influence the smallholder farmer’s decision to adopt CSIT and the level of adoption. The results indicated that only 46% of the smallholder farmers adopted climate-smart irrigation technologies and suggested that adoption is influenced positively by factors such as gender, age, district, farm size, staple food production and knowledge on CSIT. There is an urgent need for related stakeholders to transform the smallholder farmer subsector through improved extension services, training, adopting resilient crop varieties, promoting underutilized and nutrient-dense crops adapted to harsh local conditions, and other interventions. This should be done by promoting awareness to smallholder farmers regarding these interventions and new technologies that have the potential to improve rural livelihoods and enhance resilience and adaptation.Item Synthesis and characterization of al–siC composite coatings on 316L stainless steel fabricated via laser cladding technique.(Springer, 2021-08-26)Al–SiC composite coatings were successfully fabricated on 316L stainless steel substrate using laser cladding technique. The microstructure of the coatings was characterized by Scanning electron microscope (SEM) together with energy-dispersive spectrometer (EDS), while the phases that formed were identified using x-ray diffractometer (XRD) equipment. The microhardness properties of the cladded samples were measured using Vickers hardness tester machine. Electrochemical behavior of the fabricated alloy was analyzed using Autolab potentiostat equipped with nova software. The results revealed that the coatings exhibited a dendritic microstructure with SiC particles segregated along the grain boundaries. Refinement of the microstructure was achieved at high laser scan speeds and coatings synthesized under these conditions also exhibited improved hardness, corrosion and wear resistance.Item Synthesis of ti-al-xNb ternary alloys via laser-engineered net shaping for biomedical application: Densification, electrochemical and mechanical properties studies.(MDPI, 2022-01-12)The lives of many people around the world are impaired and shortened mostly by cardiovascular diseases (CVD). Despite the fact that medical interventions and surgical heart transplants may improve the lives of patients suffering from cardiovascular disease, the cost of treatments and securing a perfect donor are aspects that compel patients to consider cheaper and less invasive therapies. The use of synthetic biomaterials such as titanium-based implants are an alternative for cardiac repair and regeneration. In this work, an in-situ development of Ti-Al-xNb alloys were synthesized via laser additive manufacturing for biomedical application. The effect of Nb composition on Ti-Al was investigated. The microstructural evolution was characterized using a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). A potentiodynamic polarization technique was utilized to investigate the corrosion behavior of TiAl-Nb in 3.5% NaCl. The microhardness and corrosion behaviour of the synthesized Ti-Al-Nb alloys were found to be dependent on laser-processing parameters. The microhardness performance of the samples increased with an increase in the Nb feed rate to the Ti-Al alloy system. Maximum microhardness of 699.8 HVN was evident at 0.061 g/min while at 0.041 g/min the microhardness was 515.8 HVN at Nb gas carrier of 1L/min, respectively.
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