Browsing by Author "Damoah, L.N.W."

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AlF3 reactive Al2O3 foam filter for the removal of dissolved impurities from molten aluminum: Preliminary results
(Elsevier, 2011) Damoah, L.N.W.; Zhang, L.
Filters coated with AlF3 can be used to filter molten aluminum to simultaneously remove nonmetallic inclusions and dissolved alkali and alkaline earth metal impurities. Coating experiments were carried out in which anhydrous HF gas was generated from reactions involving NaF or CaF2 and concentrated H2SO4, and used in a reaction with Al2O3 ceramic foam filter to produce a layer of AlF 3 coating on the surface of the Al2O3 filter. Samples from these experiments were studied by X-ray diffraction, scanning electron microscopy and electron probe microanalysis. Preliminary results of the coating experiments showed that it is possible to coat Al2O 3 filters with AlF3 by this method. Increasing the pressure of HF gas increased the yield of AlF3 in the filter. Theoretical evaluation of the removal efficiency of dissolve impurity elements showed that dissolved calcium can be removed up to 99.8% within 30 s of contact time between the filter material and the molten aluminum.
Beneficial and technological analysis for the recycling of solar grade silicon wastes
(2011) Dong, A.; Zhang, L.; Damoah, L.N.W.
In the current paper, different kinds of silicon wastes during the production of SoG-Si were summarized and the beneficial analyses, such as financial value, energy value, CO2 emissions, and efficiency and energy payback time, were briefly discussed for the recycling of SoG-Si wastes. Possible technologies to recycle and purify SoG-Si wastes were reviewed: such as filtration, sedimentation, solidification control, electromagnetic separation, plasma oxidation, centrifugation, and high temperature remelting process, et al.
Current technologies for the removal of iron from aluminum alloys
(John Wiley & Sons, Inc., 2011) Zhang, L.; Damoah, L.N.W.
In the current paper, the Fe-rich phases in and their detrimental effect on aluminum alloys are summarized. The existence of brittle platelet β-Fe-rich phases lowers the mechanical properties of aluminum alloys. The methods to neutralize the detrimental effect of iron are discussed. The use of high cooling rate, solution heat treatment and addition of elements such as Mn, Cr, Be, Co, Mo, Ni, V, W, Cu, Sr, or the rare earth elements Y, Nd, La and Ce are reported to modify the platelet Fe-rich phases in aluminum alloys. The mechanism of the modification is briefly described. Technologies to remove iron from aluminum are extensively reviewed. The precipitation and removal of Fe-rich phases (sludge) are discussed. The dense phases can be removed by methods such as gravitational separation, electromagnetic separation, and centrifuge. Other methods include electrolysis, electro-slag refining, fractional solidification, and fluxing refining. The expensive three-layer cell electrolysis process is the most successful technique to remove iron from aluminum so far.
Development of porous ceramic bodies from kaolin deposits for industrial applications
(2012) Efavi, J.K.; Damoah, L.N.W.; Bensah, D.Y.; Arhin, D.D.; Tetteh, D.
The possibility of fabricating porous ceramic bodies from kaolin using maize, rice, saw-dust, charcoal, millet and Styrofoam as pore formers have been explored in this work after chemical analysis of two kaolin deposits located at Assin Fosu and Saltpond both in the Central Region of Ghana.Batch formulations of the Kaolin samples were formed into greenbodies and fired to 1400°C at a controlled rate. Samples with charcoal, millet, sawdust, maize and rice pore formers showed severe surface cracks and low thermal shock after firing. A control batch process using Styrofoam exhibited uniform surface characteristics with pores, high strength, thermal stability and no surface cracks thereby confirming the viability of the process modules. Apparent porosity as high as 38% has been calculated.
Entrapment of inclusions in continuous casting billet: Industrial observation and modeling
(AIST – Association for Iron and Steel Technology, 2010) Wang, Y.; Zuo, X.; Zhang, L.; Li, S.; Dong, A.; Damoah, L.N.W.
Fabrication, Properties, and Performance of Polymer-Clay Nanocomposites for Organic Dye Removal from Aqueous Media
(Adsorption Science & Technology, 2023) Tsekpo, Y.M.; Appiah, A.N.S.; Damoah, L.N.W.; Amusah, D.; Annan, E.
Methylene blue dye (MB dye) is a harmful contaminant for wastewater streams of industries and is harmful to human and aquatic life. An ecofriendly sugar templating process was used to generate porous bentonite/polydimethylsiloxane (PB) and porous magnetite nanoparticles/bentonite/polydimethylsiloxane (PBNP) composite absorbents to remove MB dye in this study. During the infiltration of PDMS solution into the sugar template in the vacuum chamber, bentonite and magnetite particles were integrated on the surface of the PDMS, and the porous structure was generated during the leaching out of sugar particles in water. The absorbents were characterized using Fourier infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The absence of the methyl bond at 2924 cm-1 and phenol bond at 3325 cm-1 in the FTIR spectra of the formed membrane proves that the food grade sugar was completely removed. The SEM images confirm that porosity was achieved as well as uniform mixing of the in the formation of composite. MB dye was effectively removed from wastewater using the as-prepared composite as absorbent. The removal efficiencies of the composite PBNP and PB were ~91% and ~85%, respectively. The experimental data was applied to pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models as well as the Dubinin-Radushkevich, Harkins-Jura, and Elovich models for the adsorption isotherm. The data was found to fit the pseudosecond-order and Elovich models, respectively. The results show that the presence of magnetite nanoparticles improved MB dye removal significantly.
Flow Improvers and Pipeline Internal Coating Benefits and Limitations with Respect to Pipeline Capacity Enhancement
(Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, 2023) Okyere, M.S.; Damoah, L.N.W.; Nyankson, E.; Konadu, D.B.
This article illustrates the outcome of a theoretical examination of applying internal coating and flow improver to gas and liquid pipeline systems. A test case of a 12-inches, 18-inches, 24-inches, 30-inches, 36-inches, and 42-inches diameter gas and liquid transmission pipelines evaluates hypothetically, synergistic use of pipeline internal coating with flow improver to enhance flow rate of a pipeline and minimize internal friction. The improvements in pipeline hydraulics are recognized and the enhancement of pipeline capacity calculated over a broad range of parameters. The hydraulic benefits are presented as percentage increase in pipeline capacity using flow equations. Analysis shows that internal coating of pipelines plus injection of flow improver is hydraulically and economically viable for both gas and liquid pipelines with a typical capacity increase greater than 116%. Corrosion protection and safety is improved with low operating cost.
Formation of the solid layer on the top of molten aluminum
(TMS, 2010) Damoah, L.N.W.; Zhang, L.; Adegboyega, N.F.
The formation of the top solid layer on the molten aluminum in launders during refining and casting, constituting production loss, were experimentally, thermodynamically and kinetically investigated in the current study. The effects of humidity and composition of the metal on the oxide layer were discussed. The thickness of the top thin oxide layer was only 1 - 5 μm, and the rest of the top layer averaging 350μm were mainly composed of aluminum matrix with MgO clusters, other inclusions and Fe-rich precipitated phases. Two most feasible reactions were determined to be responsible for the formation of the thin oxide layer: (1) the oxidation of molten aluminum by water vapor in humid air and (2) the oxidation of dissolved magnesium by O2. Higher humidity enhanced the oxidation of molten aluminum while lower humidity favored dissolve [Mg] oxidation. Increasing the humidity reduced the thickness of the oxide layer, however, resulted in more hydrogen in the molten metal.
Green Pyrolysis of Used Printed Wiring Board Powders
(John Wiley & Sons, Inc., 2011) Zuo, X.; Damoah, L.N.W.; Zhang, L.; Schuman, T.; Kers, J.
Rapid technological innovation has propelled the use of electronic equipment leading to the generation of more and more waste electrical and electronic equipments (WEEE). Printed wiring board (PWB) is a component made of one or more layers of insulating material with electrical conductors. To investigate an environmentally friendly process to recycle PWBs, PWB samples with and without additives were pyrolyzed. Liquid, gas and solid products were achieved with different conversion fraction. Analysis of the exhaust gases from the experiments using GC-MS and MS showed that without CaCO3 additives poisonous gases such as C6H6 and HBr were produced which were adequately controlled if CaCO3 was added.
High frequency electromagnetic purification of silicon
(John Wiley & Sons, Inc., 2012) Damoah, L.N.W.; Zhang, L.
The use of electromagnetic field to remove suspended particles from metals such as aluminum by pushing to the boundary has been well studied. However, the potential of this method is yet to be exploited for the removal of inclusions from silicon. Considering the increasing amount of Top-cut SoG-Si scraps year upon year, mere is the need to harness all the potentials of technologies to recycle this materials to ensure sustainability. This study investigates, and discusses new results on the effect of processing parameters such as composition, coil current, and frequency on the removal of inclusions from silicon under high frequency AC electromagnetic field.
High frequency electromagnetic separation of inclusions from aluminum
(John Wiley & Sons, Inc, 2012) Damoah, L.N.W.; Zhang, L.
Removal of inclusions from aluminum is a critical step during the production of high quality aluminum alloys. Electromagnetic purification method for the removal of inclusions has been proposed to complement the existing methods, and many researchers have devoted a lot of effort to studying the electromagnetic inclusion removal process. It has been widely published that high frequency electromagnetic field is limited in the depth of penetration into the molten metal thereby rendering the separation method ineffective. The contribution of the high circulatory fluid flow associated with such high frequencies has also been reported to be negative. The effect of wall temperature to the electromagnetic inclusion removal process has also not been clearly established. This study presents new results that show that, fluid flow contributes greatly in the presence of lower wall temperature to remove particles during high frequency (63 kHz) EM purification of aluminum, contributing to overcoming skin depth effect in small and large crucibles.
Inclusions in Runner Steel During Ingot Casting
(John Wiley & Sons, Inc., 2011) Zhang, L.; Yang, S.; Damoah, L.N.W.
This paper reported the observation of inclusions in the steel of an ingot runner. Thermodynamic modeling was performed to study the formation mechanism and sources of inclusions. CFD modeling on fluid flow, heat transfer, solidification of molten steel was carried out and the entrapment of inclusions in runner steel was predicted and compared with the measurement. Al2O3-based inclusions were the main ones in the steel samples. MgOˑAl2O3 mainly stemmed from the lining refractory. The high MnO inclusions in the runner steel came from the runner slag. The effect of natural convection was very important for the cooling and solidification of the steel in the runner. Both the observation and the modeling show that > 50μm inclusions more accumulated on the upper area in the runner and < 50μm inclusions dispersed well and more accumulated on the lower area of the runner.
Industrial Applications of Clay Materials from Ghana - A Review
(Oriental Journal of Chemistry, 2018-08) Asamoah, R.B.; Nyankson, E.; Annan, E.; Agyei-Tuffour, B.; Efavi, J.K.; Kan-Dapaah, K.; Apalangya, V.A.; Damoah, L.N.W.; Dodoo-Arhin, D.; Tiburu, E.K.; Kwofie, S.K.; Onwona-Agyeman, B.; Yaya, A.
Clay minerals are phyllosilicate groups naturally found in soils in all parts of the world. They have proven to be among the most essential industrial minerals because of their unique physicochemical properties and versatile applications within a wide range of fields including ceramics, construction, and environmental remediation, biomedical as well as cosmetics. Clay minerals are also primary to the production of other materials such as composite for secondary applications. In Ghana, clay mineral deposits are commonly found in several areas including soil horizons as well as geothermal fields and volcanic deposits, and are formed under certain geological conditions. This review seeks to explore the geographical occurrence and discusses the current uses of various local clay materials in Ghana in order to highlight opportunities for the utilization of these materials for other applications.
Investigating Triaxial Electrical Properties of Ceramic Composites for Electroporcelain Insulators
(Journal of Ceramic Processing Research, 2018-04) Dowuona, A.N.N.; Yaya, A.; Nyankson, E.; Efavi, J.K.; Damoah, L.N.W.; Dodoo-Arhin, D.; Apalangya, V.; Annan, E.; Tiburu, E.K.; Onwona-Agyeman, B.; Tomiczek, B.
Four porcelain composites comprising kaolin (27-37%), beach sand (20-24%), ball clay (13-18%) and feldspar (25-40%), were formulated and characterized using powder XRD, SEM and particle size distribution analysis in order to determine their potential for use as electroporcelain insulators. Chemical, mechanical and electrical properties were also evaluated. Each of the formed samples were compressed at 200 MPa and sintered at 1250 o C for 1 hour. Bending strength results of the porcelain bodies showed increase in bending strength with reduction in particle sizes. An increase in dielectric strength was found for samples with a higher felspar content. The XRD pattern for all the sintered samples showed the presence of quartz and mullite phases in the body at different intensities. Samples with lower particle sizes showed similar electrical and mechanical properties to commercially available electroporcelains albeit at a cheaper cost of production.
Kinetic analysis of the thermal degradation of printed wiring boards
(2011) Luyima, A.; Zhang, L.; Damoah, L.N.W.
The non-isothermal pyrolysis of printed wiring boards (PWBs) was investigated by simultaneous thermogravimetric and differential thermal analysis (TG-DTA) in the temperature range of 300-1200 K. Pyrolysis experiments were carried out on PWBs samples at three different heating rates of 10, 20, and 30°C/min. In this study, the kinetic parameters of PWBs pyrolysis have been estimated using model free and model fitted methods.
Mathematical modeling on the removal of impurity elements from molten aluminum
(2012) Damoah, L.N.W.; Zhang, L.
In order to remove impurity elements from molten aluminum, many processes, such as using inert gas, reactive gas, reactive powders, unreactive powders, slag, or their combinations, have been used during the past 30 years. In the current paper, mathematical models on the removal of impurity elements from molten aluminum for these processes were extensively developed, and validated by industrial measurement from literatures. Special parameters were introduced to express the refining efficiency. Mathematical models for the combined processes like inert gas mixed with reactive gas purging, reactive powders injection with inert gas as carrying gas, were also developed. The removal efficiency of impurity elements for batch reactor and continuous reactor were derived for these processes, either the single method or the combined method. The effects of gas flow rate, impellor rotating speed, fraction of reactive gas, injecting rate of reactive powders, and temperature on the removal of impurity elements were discussed.
Mechanisms of inclusion removal from aluminum through filtration
(TMS, 2008) Zhang, L.; Damoah, L.N.W.; Li, S.; Abebe, W.
Ceramic Foam Filters (CFF) are used to remove inclusions from aluminium in laboratory experiments. Morphology and composition of inclusions in aluminium are identified using before and after filtration using optical microscope, SEM, XRD and EPMA. Qualitative analysis of results form various filtration experiments indicates that CFF filtration is an effective process to remove inclusions from molten aluminium. Interaction between inclusions and filter materials is investigated, which includes the effects of surface energy change before and after attachment, inclusion size, and fluid flow. Mechanisms of inclusion removal through filtration are then proposed. Both uncoated and slurry coated Al2O3 CFFs were found to have very good filtration efficiencies. However, qualitative analysis showed that the uncoated filter has more excellent filtration capabilities than the slurry coated filters.
Non-Metallic Particles in Solar Grade Silicon (SoG-Si)
(IEEE, 2010) Damoah, L.N.W.; Dong, A.; Zhang, L.; Zhu, H.; Wang, C.
This study investigated the non-metallic inclusions in Solar 2rade Silicon (SoG-Si), especially the distribution of inclusions in the top 15mm layer of multicrystalline silicon ingot. The SoG-Si ingot produced from directional solidification process usually pushes the impurities to the top and finally cut off and discarded, which leads to material loss. The hard inclusions lead to wire breakages during the cutting of the ingot into wafers. The main kinds of inclusions found in top-cut silicon scraps from two manufacturers have been investigated using acid extraction, automated feature analysis techniques and SEM-EDS and optical Microscope: they are needle-like Si3N4 and lumpy SiC inclusions. Surface observations of the scraps before polishing revealed that, Si3N4 inclusions are usually bigger and in some cases can be about a few millimeters. SiC inclusions are usually smaller, ∼200μm but can be ∼500μm in some cases. F or the directional solidified silicon ingot, it was determined that an approximate distance of ∼10mm is a good enough cutoff thickness.
Photocatalytic degradation of fractionated crude oil: potential application in oil spill remediation
(Cogent Engineering, 2020-04-07) Agyei-Tuffour, B.; Gbogbo, S.; Dodoo-Arhin, D.; Damoah, L.N.W.; Efavi, J.K.; Yaya, A.; Nyankson, E.
The current oil spill remediation strategies are costly and may be toxic to aquatic species and clean-up workers. There is, therefore, the need to look for alternative oil spill remediation strategies that are less costly and non-toxic. This paper presents the potential of TiO2 and its modified form (Fe-TiO2) to remediate crude oil fractions under the irradiation of sunlight (UV-Vis), visible (Vis) and ultraviolet (UV) lights. The TiO2 and Fe-TiO2 were synthesized by mild hydrothermal method and characterized with X-ray diffraction (XRD), Ultra-violet-visible spectroscopy (UV-Vis), Diffusion reflectance spectroscopy (DRS), Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDX). The DRS result of Fe-TiO2 showed an enhanced absorption in the visible light region. The estimated optical band gaps were ~3.12 and ~2.9 eV for TiO2 and Fe-TiO2, respectively. The potential application of TiO2 and Fe-TiO2 in oil spill remediation was investigated through photocatalytic degradation of benzene soluble fraction, n-hexane soluble fraction and 1:1 volume by volume methanol/benzene soluble fraction in crude oil. The degraded crude oil fractions were characterized with UV-vis, Fourier Transform Infrared (FTIR) Spectroscopy and Gas Chromatography-Mass Spectrometer (GC-MS). The FTIR and UV-vis results showed that the Fe-TiO2 was more effective in photodegrading the crude oil fractions under sunlight light irradiation than TiO2. The GCMS results showed excellent photodegradation of the various crude oil fractions with the formation of new intermediate products. The results from the study show the potential application of TiO2 and Fe-TiO2 in crude oil spills remediation.
The physico-mechanical influence of dehydroxylized activated local kaolin: A supplementary cementitious material for construction applications
(Case Studies in Construction Materials, 2019-11-05) Marfo, N.K.; Dodoo-Arhin, D.; Agyei-Tuffou, B.; Nyankson, E.; Obada, D.O.; Damoah, L.N.W.; Annan, E.; Yaya, A.; Onwona-Agyeman, B.; Bediako, M.
This work presents the effect of partially replacing metakaolin with Portland limestone cement to produce mortars for construction. Teleku Bokazo kaolin was explored as a SCM in the production of mortars. The hydration product between Portland limestone and metakaolin was studied. The kaolin was heat treated to form metakaolin and partially used to replace Portland limestone cement (PLC) in mortars to explore the optimum replacement and its mechanical and durability effect. The samples were characterized using X-ray diffraction (XRD) for phases and crystallinity of the kaolin. Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) gave information on the functional groups formed during the hydration and structure and surface morphology respectively. The pastes and mortars produced were subjected to setting time, water absorption, flexure and compression strength test. The mechanical properties were observed to increase with increasing metakaolin replacements. Therefore, from the results obtained, it is suggested that 20 % replacement of Portland limestone cement with Teleku Bokazzo metakaolin can be very suitable for construction applications.