Browsing by Author "Konadu, D.S."
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Item Application of clay ceramics and nanotechnology in water treatment: A review(Cogent Engineering, 2018-07) Annan, E.; Agyei-Tuffour, B.; Bensah, Y.D.; Konadu, D.S.; Yaya, A.; Onwona-Agyeman, B.; Nyankson, E.The increasing demand to provide clean water for drinking has brought to the fore the importance of seeking other materials with the ability or combined effect with other materials to purify water. Clay ceramics are known to be natural and also easily engineered porous-structured materials. Review papers on water filtration over the last decade have been on specific mechanisms or technologies. This review paper presents a single platform which provides information encapsulating all these technologies. This paper highlights water contaminants, and their various treatment technologies. The effectiveness of these technologies are evaluated via scholarly documented peer-reviewed papers. Moreover, the discussions are interspersed with the World Health Organization’s (WHO) standard for various contaminants along with the exploration of the efficiency of clay minerals as potent water filtration material. Finally, current trends in application of nanotechnology in water purification systems are also highlighted. These technologies include adsorption, microbial disinfection, and photocatalysis.Item Comparison of testing of susceptibility to solidification cracking of ferritic stainless steels using two methods(Welding in the World, 2020-04-10) Konadu, D.S.; Pistorius, P.G.H.The susceptibility to solidification cracking of unstabilized and stabilized ferritic stainless steels was investigated using self-restrained Houldcroft and Modified Varestraint-Transvarestraint (MVT) tests. Nine steel grades of unstabilized and stabilized ferritic stainless steels were used in this study. Seven steels comprising an unstabilized, two monostabilized (Ti and Nb) respectively, three dual stabilized (Ti + Nb), and a dual stabilized containing Mo were used for the self-restrained Houldcroft method. A monostabilized Nb and dual stabilized (Ti + Nb) grades (experimental alloys) and commercial grades of an unstabilized and a dual stabilized (Ti + Nb) ferritic stainless steels were employed in the MVT test. Autogenous gas tungsten arc welding at a speed of 6 mm/s, 3 mm/s, and 1 mm/s was done for the Houldcroft test and welding at a speed of 6 mm/s and 3 mm/s for MVT test. The results of the tests were evaluated by measuring the crack length, considering the microstructure and using multiple linear regression analysis of the crack length. The MVT method was successful in demonstrating the deleterious effect of Nb on ferritic stainless steels. Cracking of the Houldcroft samples was dependent on Ti, welding parameters, and the weld bead geometry.Item The corrosion behaviour of WC-VC-Co hardmetals in acidic media(Corrosion Science, 2010-06-01) Konadu, D.S.; van der Merwe, J.; Potgieter, J.H.; Potgieter-Vermaak, S.; Machio, C.N.The effect of increasing vanadium carbide (VC) content on the corrosion behaviour of tungsten carbide – 10 wt% cobalt hardmetals was investigated in 1 M hydrochloric (HCl), and sulphuric (H2SO4) acids solutions. Increasing VC content makes the open circuit potential (OCP) in the test solutions more negative than the base alloy. Specimens exhibited pseudo passivation in all the test solutions. Increasing VC led to decreasing corrosion current density. However, the corrosion current densities during chronoamperometric tests were lower for 0 wt% VC. XRD and Raman spectroscopy showed that hydrated WO3 formed in the surface films of all specimens in hydrochloric acid (HCl), while hydrated vanadyl sulphate also formed for higher VC content specimens in sulphuric acid (H2SO4).Item The effect of decahydronaphthalin on the mechanical properties of montmorillonite reinforced polypropylene nanocomposites(ARPN Journal of Engineering and Applied Sciences, 2012-10) Yaya, A.; Dodoo-Arhin, D.; Efavi, J.K.; Konadu, D.S.The exceptional property exhibited by nanoparticles such as carbon nanotubes and silicate layers has been the major drive for research into advanced nanocomposites. The solution method is used to prepare polypropylene/clay nanocomposites with loadings of 2% and 5%. Decahydronaphthalin was used to disperse the clay and dissolution of the polypropylene matrix. The intercalation of macromolecular chains into the organoclay was evident from XRD and confirmed by SEM studies. Decahydronaphthalin was observed to have a considerable effect on the polymer matrix properties and the tensile moduli of the nanocomposites compared to the pristine polypropylene. Tensile moduli of nanocomposite treated with decahydronaphthalin have been observed to be lower than those of pristine polypropylene. The moduli of both the 2% and 5% PP/clay nanocomposite was 528 MPa and 547 MPa respectively. The pristine PP had a modulus of 794 MPa and that of the PP dissolved in decahydronaphthalin alone was found to be 639 MPa. © 2006-2012 Asian Research Publishing Network (ARPN).Item Effects of Graphene Oxide and Reduced Graphene Oxide on the Mechanical and Dielectric Properties of Acrylonitrile-Butadiene Rubber and Ethylene-Propylene-Diene-Monomer Blend(International Journal of Polymer Science, 2022) Mensah, B.; Konadu, D.S.; Agyei-Tuffour, B.The composites of properties of ethylene-propylene-diene-monomer (E) and acrylonitrile butadiene-rubber (N) composites of graphene oxide (GO) and reduced graphene oxide (G) were prepared by a combination of solution and open-roll method. They include single matrices (EGO and EG) and blends N/E, 20 part of hundreds of rubber (phr)/80 phr (A), 80 phr/20 phr (B), and 50 phr/50 phr(C) blend containing GO and G. The physico-mechanical properties including vulcanization, tensile, glass transition temperature (Tg), and dielectric spectroscopic properties were evaluated. The N-rich systems reinforced with GO, cured faster than the E-rich systems. Also, N-rich systems obtained the highest dielectric constant ðɛ′Þ, especially when GO and G were incorporated, for example, NG and N-GO obtained 317 and 283% increment in ɛ′ than EG and EGO, respectively. In terms of tensile properties, AGO exhibited the highest strength and elongation at break properties (%). Therefore, solution mixing technique of rubber blends filled with nanoinclusion can be achieved with the tendency of reducing cost without the use of compatibilizer and still maintain the integrity of the physical properties of the final product. The result obtained therefore shows that the current compositions can find various applications in oil/gas sealants, heat-resistant applications, and energy storage materials with minimal losses.Item Graphene-maleic anhydride-grafted-carboxylated acrylonitrile butadiene-rubber nanocomposites(Heliyon, 2022) Mensah, B.; Efavi, J.K.; Konadu, D.S.; Manu, G.P.Ethylene-propylene grafted-maleic anhydride (EPR-g-MA) and a pure maleic anhydride (MA) were separately used to compound carboxylated acrylonitrile butadiene-rubber (XNBR) together with reduced graphene oxide (G) to form nanocomposites, by using melt compounding technique. The G-sheets in the presence of MA (GA samples) or EPR-g-MA (GB samples) generally increased the physico-mechanical properties including; crosslinking density, tensile strength and thermal degradation resistance etc., when compared with sample without MA or EPR-g-MA (GAO) and the virgin matrix. For the thermal degradation resistance measured by the char residue (%), by using thermal gravimetric analysis technique; GA1 (0.1 ph G and 0.5 ph MA) was 106.4% > XNBR and 58% > GAO (0.1 ph G) while that of GB1 (0.1 ph G and 0.5 ph EPR-g-MA) was 60% > XNBR and 22.2% > GAO respectively. Although, homogeneous dispersions of the Gsheets assisted by MA or EPR-g-MA was a factor, but the strong bonding (covalent, hydrogen and physical entanglements) occurring in GA and GB was observed to be the main contributing factor for these property enhancements. Thus, these nanostructured materials have exhibited multifunctional capabilities and could be used for advanced applications including high temperature (heat sinks), flame retardants, and structural applications.Item The influence of Ti and Nb on solidification cracking of ferritic stainless steels, as determined using self-restrained samples(Welding in the World, 2019-06-04) Konadu, D.S.; Pistorius, P.G.H.; Toit, M.D.The susceptibility to solidification cracking of ferritic stainless steels was studied using the self-restrained method. The unstabilised steel was compared with mono and dual stabilised (Ti and/or Nb) steels. Autogenous gas tungsten arc welding at a speed of 6 mm/s, 3 mm/s, and 1 mm/s was done. All the specimens cracked at a welding speed of 6 mm/s. The weld metal of both the unstabilised and the stabilised steels contained a mixture of columnar and equiaxed grains. At a welding speed of 3 mm/s, all the specimens except the unstabilised grade cracked. The weld metal microstructures were mostly columnar, and the dual stabilised grades showed equiaxed grains. At a welding speed of 1 mm/s, the Nb stabilised and the dual stabilised steel containing Mo cracked whilst the other alloys did not crack. At a welding speed of 1 mm/s, the weld metal was dominated by columnar grains. The cracks were interdendritic. The crack surfaces were enriched in Nb, Ti, Mn, Si, Al, Mn, and Mo. The unstabilised ferritic stainless steel was resistant to solidification cracking whilst the stabilised steels were not. Low melting point eutectic phases associated with Ti and Nb might have contributed to solidification cracking.Item Investigation of formation of precipitates and solidification temperatures of ferritic stainless steels using differential scanning calorimetry and Thermo-Calc simulation(Indian Academy of Sciences, 2021) Konadu, D.S.; Pistorius, P.G.H.The phase transformations in unstabilized and stabilized ferritic stainless steels during solidification were studied using Thermo-Calc and differential scanning calorimetry (DSC). The solidus and liquidus temperatures of the Thermo-Calc simulations were compared to the liquidus and solidus temperatures measured with DSC. Thermo-Calc software revealed the precipitates of the ferritic stainless steels to be MnS, TiN, Ti4C2S2, NbC, and Ti(C,N). Given the low volume fraction of precipitates, DSC could not be used to reveal the onset of precipitation. There was reasonable correlation between the liquidus and the solidus temperature, as calculated using Thermo-Calc and as measured using DSC. Generally, a higher niobium content resulted in a higher solidification temperature rangeItem Nanostructured TiO2 and their energy applications-a review(ARPN Journal of Engineering and Applied Sciences, 2013-10) Nyankson, E.; Agyei-Tuffour, B.; Asare, J.; Annan, E.; Rwenyagila, E.R.; Konadu, D.S.; Yaya, A.; Dodoo-Arhin, D.Environmental sustainability and reliable energy sources are major challenges facing the world in the 21st century. Ironically, the solution to these taunting problems may lie in something small. Nanomaterials with attractive chemical and physical properties are being explored for potential uses in energy and environmental applications. Nanostructured Titanium dioxide (TiO2) has gained considerable attention in the energy and environment sectors due to their brilliant prospects in photo catalysis, solar cells, environmental pollution treatment and its use in solar water splitting for the production of H2. There are many processing techniques such as; the Sol gel (SG), the hydro-thermal (HT), the solvothermal (ST) and chemical vapor deposition (CVD) which are used in the production of nanostructured TiO2 for the applications stated above. This review aims at examining the general characteristics of nanostructured TiO2 and its application in dye sensitized solar cells, photocatalytic splitting of water and solid state hydrogen storage devices. The analysis is meant to demystify the anxiety associated with the application of nanomaterials in solving everyday challenges in the energy and environmental sectors. © 2006-2013 Asian Research Publishing Network (ARPN).Item Physico-mechanical properties of bauxite residue-clay bricks(ARPN Journal of Engineering and Applied Sciences, 2012-12) Annan, E.; Agyei-Tuffour, B.; Damoah, L.N.W.; Konadu, D.S.; Mensah, B.This study is focused on consolidating knowledge on the application of Bauxite residue in the building industry. X-Ray fluorescence (XRF) reports of the bauxite and bauxite residue are given. Physico-mechanical properties of red mud (RM)-Clay (AC) bricks are also presented. The RM-AC bricks have compositions; 90%-10%, 80%-20%, 70%-30%, 60%- 40%, 50%-50%, 40%-60% prepared and fired at sintering temperatures 800°C, 900°C and 1100°C. The experimental results obtained showed that ateach of the three stated sintering temperatures, bulk density increases as apparent porosity and water of absorption reduces. Bulk densities computed were within the range (1.3-1.8)g/cm3 at 11000°C sintering temperature. Maximum flexural strength was found to be associated with 50%-50% (Red mud-clay) composition at 1100°C. And the compressive strength (3.2-12.5) MPa range found for all batches at 1100°C sintering temperature. Generally, flexural and compressive strengths were increased with higher sintering temperature. The results obtained for various characterization analysis compares well with literature and hold potential in bauxite residue eco-friendly application as fired brick ©2006-2012 Asian Research Publishing Network (ARPN).Item Potential Application of Dioctyl Sodium Sulfosuccinate Salt (DOSS)–Saponin Binary Dispersant in Oil Spill Remediation: Synergistic Interaction Between DOSS and Saponin(Water, Air, & Soil Pollution, 2020-02-03) Nyankson, E.; Agyei-Tuffour, B.; Efavi, J.K.; Yaya, A.; Onwona-Agyeman, B.; Konadu, D.S.; Amedalor, R.; Frimpong, B.K.The interfacial activity of dispersants can be enhanced by combining two or more surfactants to formulate the dispersant. This paper examines the effects of Bio-Saponin (BS), a phytogenic surfactant on the interfacial activity of synthetic dioctyl sulfosuccinate sodium salt (DOSS) usually adopted as a suitable surface-active agent in dispersants used in dealing with large-scale oil spills. The o/w emulsion created with the binary DOSS-BS was very stable and recorded the least average droplet size compared with that of DOSS only and BS only. Lower surface and interfacial tension values were also obtained from the DOSS-BS binary formulation. The dispersion effectiveness was also higher compared with that of DOSS and BS. However, they were dependent on the salinity and type of crude oil. These observations were attributed to the moderation of the interaction between the anionic head group of DOSS by the polysaccharide hydrophilic group of BS. The results revealed the potential application of DOSS-BS binary dispersant in oil spill remediation and in other processes that would require an effective emulsifier.Item Solidification cracking susceptibility of ferritic stainless steels using Modified Varestraint Transvarestraint (MVT) method(Sadhana, 2019-08-19) Konadu, D.S.; Pistorius, P.G.H.; Toit, M.D.; Griesche, A.The Modified Varestraint Transvarestraint (MVT) test was used to investigate the solidification cracking susceptibility of an unstabilised, a Nb-stabilised and two (Ti + Nb) dual-stabilised ferritic stainless steels. Two different welding speeds of 6 and 3 mm/s using autogenous gas tungsten arc welding were employed. At the welding speed of 6 mm/s, the high-content (Ti + Nb) steel was resistant and the Nb-stabilised steel was marginally susceptible to solidification cracking. At the welding speed of 3 mm/s, the Nb and the high (Ti + Nb) steels were found to be marginally susceptible to solidification cracking while the unstabilised and low-content (Ti + Nb) grades were resistant to solidification cracking. The weld metal microstructures transverse to the welding direction revealed columnar grains in all the samples for both welding speeds. The ferritic stainless steels were generally resistant to solidification cracking, except the Nb-stabilised steel, which was marginally susceptible to solidification cracking.Item Synthesis and Characterization of Hydroxyapatite- (HAP-) Clay Composites and Adsorption Studies on Methylene Blue for Water Treatment(Hindawi, 2021) Annan, E.; Arkorful, G.K.; Konadu, D.S.; Asimeng, B.; Dodoo-Arhin, D.; Egblewogbe, M.Dyes used by the textile, tannery, and food industries tend to pollute water bodies and must be removed to get clean water. Hydroxyapatite (HAP) was synthesized from eggshells using the wet precipitation process. 'e as-synthesized HAP was characterized using Fourier Transform Infrared (FTIR) and X-ray powder diffraction (XRD). 'e synthesized HAP was mixed with three different clays: halloysite (HNT), kaolinite (KAO), and bentonite (BENT). 'e removal efficiency values of methylene blue (MB) from the data showed that HAP-BENT adsorbents had higher values, followed by HAP-HNT and then HAP-KAO adsorbents. 'e combined masses of 24 mg, 34.5 mg, and 33 mg (representing 20%, 15%, and 10% of HAP-BENT mass) had average adsorption capacity values of 20.7 mg/g, 17.2 mg/g, and 17.9 mg/g, respectively. For each mass percentage, the adsorption capacity values were found to decrease with adsorbent dosage. 'e HAP-BENT composites had removal efficiency values of 98.4, 91.9%, and 91.9%, respectively. Adsorption data for the HAP-BENT adsorbents were found to be well described by the Langmuir isotherm model and pseudo-second-order kinetic model. 'e effect of temperature on adsorption capacity was evaluated and thermodynamical modeling was undertaken. 'e thermodynamical modeling predicts that based on the value of the change in enthalpy and Gibbs free energy the process was exothermic and spontaneous. 'is work confirms the potential of HAP-clay composites in removing MB from water.Item The Use of Recycled Polyethylene in Water-Oil Emulsion for Lightweight Concrete(International Journal of Polymer Science, 2024) Nangor, E.; Annan, E.; Konadu, D.S.; Damoah, L.N.W.; et al.This study was to determine the suitability of recycled waste polyethylene (WPE) processed into water-oil emulsion for lightweight concrete applications. The processed WPE in the form of polyethylene emulsion (PE-e) is to promote physical interaction between the polymeric material and the cementitious matrix. The PE-e used was also to partially replace concrete mix composition by PE-e_1, PE-e_2.5, PE-e_5, and PE-e_10 percents for reference concrete and to introduce plasticity into the mechanical behaviour of the concrete. The PE was processed into PE-e to promote affinity for water, and this hydrophilicity was prominent in PE-e_1 and PE-e_2.5 percent concretes. Concretes with PE-e_1 and PE-e_2.5 percent formed good miscibility with the cementitious matrix. The density of the PE-e concrete decreased to 13.68% with 10% PE-e at 28 days. The replacement of mix constituents of PE-e_1, PE-e_2.5, and PE-e_5 percent induced elastic to plastic behaviour in the concrete coupled with low water absorption. The FTIR data showed characteristic peaks of 3378 cm-1, 1740 cm-1, and 1148 cm-1 in the PE-e. Using optical microscopy, it was shown that the PE particles were homogenously dispersed in the concrete matrix. The study shows the feasibility of using PE-e_1 percent to produce structural lightweight concrete and up to PE-e_10 percent for nonstructural applications mainly for light, non-load-bearing partitions