| 1 | K. Ugwuagbo, C.A. Madu, E.C. Mbamala, & E.C. Mbamala, & | Total Energy calculation of AlAs and InAs binary semiconductors using projector augmented wave method | The total energy of an element is the basic energy value from which other properties of the element can be calculated. Aluminum Arsenide (AlAs) and Indium Arsenide (InAs) are III – Arsenic binary semiconductors with indirect and direct energy band gap respectively. The total energy of each of them was calculated using the Projector Augmented Wave (PAW) method with the PBE-GGA for the exchange- correlation functional. The total energy were calculated and from the results gotten, the lattice constants were found to be 5.722Ǻ and 6.176Ǻ, the bulk modulus are 68.8 GPa and 50.5GPa respectively while the pressure derivative of the bulk modulus are 4.24 and 4.61 respectively, also the unit cell volumes were gotten as 316.100a.u3 and 397.445a.u3. The computed values are in close agreement with experimental values and that from other methods. | IOSR Journal of Applied Physics, 10(4), 49–53; 2018 | |
| 2 | E.C. Mbamala, I.D. Eguzoro,G.A. Alozie & C.E. Akujor (2017) | Solar powered pool heater using black hosepipe as collector. | We have used a coiled black hosepipe in the design and construction of a hybrid solar and electric powered pool heater. The major materials used include a black hosepipe easily formed into a spiral of surface area 0.986m2; a ½ hp (373W) ac water pump; a water container; and a 2mm thick transparent plastic glass. The electric water pump, runs water (initially cold) stored in the container through the coiled hose and back into the container. This cycle is continued at a controlled speed for a period of time until the water heats up to higher temperatures. The main aim of the work is to heat large volumes of water such as swimming pools at lower cost than using the convectional electric heaters. With the collector covering an area of only 0.986m2, the device was tested for three different volumes of water in three different days as follows: 35liters in Day 1; 40liters in Day 2 and 80liters in Day 3. All three tests were carried out in the month of September between 11:00hrs and 18:00hrs each day. The location was Federal University of Technology, Owerri, Imo-State, Nigeria. Our device showed a peak efficiency of 51.3% for the 35liter volume of water at a peak pool temperature of 58oC. We observed that the average peak temperature of the heated water did not drop as one would expect when the volume of water is increased from 35liters (58oC) to 80liters (48oC). This suggests that the surface area of the collector used in this work need not be increased by orders of magnitude for water volumes of typical swimming pools. Our calculations also show that an energy cost saving of at least 50.5% is achieved. | African Journal of Renewable and Alternative Energy, 2(1), 41–50; 2017 | |
| 3 | K. Ugwuagbo, C.A. Madu, E.C. Mbamala, &N.I. Achuko, (2018) | Total Energy calculation of AlAs and InAs binary semiconductors using projector augmented wave method | The total energy of an element is the basic energy value from which other properties of the element can be calculated. Aluminum Arsenide (AlAs) and Indium Arsenide (InAs) are III – Arsenic binary semiconductors with indirect and direct energy band gap respectively. The total energy of each of them was calculated using the Projector Augmented Wave (PAW) method with the PBE-GGA for the exchange- correlation functional. The total energy were calculated and from the results gotten, the lattice constants were found to be 5.722Ǻ and 6.176Ǻ, the bulk modulus are 68.8 GPa and 50.5GPa respectively while the pressure derivative of the bulk modulus are 4.24 and 4.61 respectively, also the unit cell volumes were gotten as 316.100a.u3 and 397.445a.u3. The computed values are in close agreement with experimental values and that from other methods. | IOSR Journal of Applied Physics, 10(4), 49–53; 2018 | |
| 4 | E.C. Mbamala&C.E. Akujor 2018 | Solar water heater: Black versus Transparent hosepipe heat absorbers | We have compared the performances and efficiencies of solar water heatersconstructed using coiled black and coiled transparent hosepipes.The two hosepipes were equivalent in length and diameter measuring about 50 yards (45.7m) and 1 inch (2.5cm) in diameter. Theyconstituted the heat absorbers of the solar collector system in which water was pumped and cycled continuously in the hosepipe by a dc water pump powered by photovoltaic (PV)panels. The 50 yard long hosepipe (black or transparent) wasformedinto a circular flat coil of about 20 turns inside a shallow rectangular box and covered with a transparent glass/plastic sheet.The waterpump draws water from the bottom of a reservoir, runs it through the coiled hose and discharges it back into the reservoir from the top.In this process the sun heats up the hose through solar radiation and the pipe heats up the water through conduction. We investigated whether a black hose is more efficient in heating the water than a transparent hose and found no significant difference.The explanation lies in the factthat when the hose is contained in the glass covered box, the water heating process is dominated more by greenhouse radiation than by direct radiation. Hence it is immaterial whether the hose is black or not.Thisinvestigation was carried out in the month of January and February and the location was Owerri, South East Nigeria | IOSR Journal of Applied Physics, 10(6), 28–34; 2018 | |
| 5 | E.C. Mbamala (2018) | Performance comparative study of cement and wastepaper as binder sources in briquettes produced from sawdust | In this work, we have used physical combustion parameters such as Percentage moisture content, percentage volatile matter, percentage ash content, percentage fixed carbon, gross calorific value and results of water boiling test to compare briquettes produced from sawdust with two different binding sources namely cement and wastepaper. Simple cylindrical and rectangular metal molders were fabricated to make the briquettes. The results obtained showed that based on the physical characterization as listed above, the briquettes produced with both binder sources showed good briquette qualities. However, results from water boiling test revealed that the suitability of these briquettes a fuel wood depends importantly on the ratio of sawdust – binder compositions. | African Journal of Renewable and Alternative Energy, 3(2), 109–116; 2018 | |
| 6 | E.C. Mbamala (2018) | Hosepipe pool heater aided by solar powered dc water pump | We have carried pool (water) heating using black hosepipe in which water was pumped and cycled in the hosepipe by a dc water pump powered by photovoltaic (PV) panels thereby making the heating device almost purely solar. This has previously been achieved using ac water pump which relies on ac power sources. The major materials used include a 45.7m (50 yards) long black hosepipe formed into a circular coil of surface area 0.986m2; a 100-watt dc water pump; 200-watt photovoltaic solar panel; a 120-liter reservoir contained in a wooden box filled with sawdust to provide thermal insulation to the water inside the reservoir, etc. The water pump runs water (at some initial temperature) stored in the reservoir through the solar exposed coiled hose and back into the reservoir. This cycle is continued at a controlled speed for a period of time until the bulk water heats up to higher temperatures. The device was tested in the month of January. The test location was Owerri, South East Nigeria. On each day, the water pump was operated from 10:00 am to 6:00 pm local time. For a water volume of 100 liters (0.1m3), a peak temperature of 48.0oC from initial water temperature of 28.0oC was recorded (at about 3:30pm) for a particular day. It was however observed that even when the initial water temperature was as high as 41.0oC, there was no significant change in the peak temperature. We show that the thermal insulation provided to the water reservoir ensured that the heated water retained its warmth, long enough to provide for a warm bath the next day. This prototype system described here can provide regular warm bath water for an average household. Larger systems are capable of heating larger volumes of water such as swimming pools at lower cost than the convectional electric water heaters | Advances in Science and Technology, 12(1&2), 20–26; 2018 | |
| 7 | Obi Kingsley Echendu, Francis Birhanu Dejene, Imyhamy Mudiy Dharmadasa and Francis Chukwuemeka Eze | Characteristics of nanocrystalline-CdS produced by low-cost electrochemical technique for thin film photovoltaic application: The influence of deposition voltage | Electrochemical deposition and characterization of nanocrystallite-CdS thin films for thin film solar cell application are reported.The two-electrode system used provides a relatively simple and cost-effective approach for large-scale deposition of semiconductors for solar cell and other optoelectronic device application. Five CdS thin films were deposited for 45 minutes each at different cathodic deposition voltages in order to study their properties. X-ray diffraction study reveals that the as-deposited films contain mixed phases of hexagonal and cubic CdS crystallites with large amounts of internal strain and dislocation density. Postdeposition annealing results in phase transformation which leaves the films with only the hexagonal crystal phase and reduced strain and dislocation density while increasing the crystallite sizes from 21.0–42.0nm to 31.2-63.0 nm. Photoelectrochemical cell study shows that all the CdS films have n-type electrical conductivity. Optical characterization reveals that all samples show similar transmittance and absorbance responses with the transmittance slightly increasing towards higher growth voltages. All the annealed films show energy bandgap of 2.42 eV. Scanning electron microscopy and energy dispersive X-ray analyses show that grains on the surface of the films tend to get cemented together after annealing with prior CdCl2 treatment while all the films are S-rich. | International Journal of Photoenergy | 2017
|
| 8 | Onwuemeka, J. I., Eze, F. C.,Ndukwe, I. C. | The Study of Chemically Deposited ZnO Thin Films for Possible Device Applications | A study on the Deposition and Characterization of ZnO Thin Films by Solution Growth Technique using Ammonia(NH3) as a complexing agent. Zinc oxide thin films were successfully deposited on glass slides under certain deposition condition of 600C – 1000C of 1M solution of NaOH, using solution growth technique. X-ray fluorescence (XRF) and Rutherford Back scattering Spectroscopy (RBS) analyses confirmed that the films were ZnO thin films. The films of ZnO showed optical transmittance of 20.6% - 65.6% in the UV, 70.2% - 79.2% in the visible and 79.5% - 81.6% in the near-infrared regions of electromagnetic spectrum. ZnO films were found to exhibit absorbance of 25.5% - 68.6% in the UV, 10% - 18.3% in the visible region and 8.8% - 9.96% in the near-infrared regions of electromagnetic spectrum. ZnO thin films, exhibit low reflectance, throughout the electromagnetic spectrum (9.6% - 20.3%). Direct band gap values of 3.31eV is obtained for ZnO thin films. The thickness of 0.082μm thickness was obtained for ZnO films by gravimetric method. Other properties investigated were the refractive index, optical conductivity, absorption coefficient and dielectric constants. From the spectral qualities, ZnO thin film may be found useful in heat mirror application. The sample of ZnO thin films are also found interesting as semiconductor materials for electronic applications. | International Journal of Innovation in Science and Mathematics 2017 | Vol. 5, Issue 3, ISSN (Online): 2347-9051
|
| 9 | C. J. AMAKOM, C. E. ORJI, B. C. EKE, C. IROEGBU AND B. A. OJAKOMINOR (2018 ). | GROSS ALPHA AND BETA ACTIVITY CONCENTRATION IN SOIL AND SOME SELECTED NIGERIAN FOOD CROPS, | Gross alpha and beta activity concentrations in soil, cassava and fluted pumpkin (leaf and stem ) were investigated using a gas flow proportional counter. The gross alpha activity concentrations for the fluted pumpkin were between 3.55and 13.95 Bq/Kg and 3.53 and 3.61 Bq/ Kg for the leaves and stems respectively. The gross alpha activity concentrations for cassava and soil samples ranged from 0.07 to 0.60 Bq/Kg and 0.35 to 0.53 Bq/Kg respectively while the gross beta activity concentrations ranged from 0.43 to 0.89 Bq/Kg and 0.46 to 1.04 Bq/Kg for the cassava and soil samples respectively. The gross alpha and beta activity concentrations in cassava, fluted pumpkin and soil samples have been determined using alpha / beta spectroscopy. The result of the study showed that the Iva – valley coal mine area has lower gross alpha and beta activity concentrations compared to other areas of the country This shows that the coal mining activities in the area may not have increased the radiation burden of the area. Key words : Gross, alpha, beta, concentration, activity, food, crop | INTERNATIONAL JOURNAL OF PHYSICAL SCIENCES. | 13 (11), 183 – 186.
|
| 10 | AMAKOM, M. C., ORJI, C., IROEGBU, C., EKE, C. B., NKWOADA, U. A., MADU, D. A., UGOCHUKWU, G. K. AND OFORMA, J. A. ( 2018 ). | RADIONUCLIDE CONCENTRATION : THE COAL ASH EFFECT, | Radionuclide concentrations in coal ash, soil mixed with coal ash and soil were determined using the gamma spectroscopic method. The average activity concentrations of 226Ra, 232Th and 40K in coal ash samples were found as 35.0, 5.8 and 109.4 Bq/Kg respectively. The average activity concentrations of 226Ra, 232Th and 40K in soil mixed with coal ash samples varied from 21.2 to 30.8, 48.6 to 82.7 and 162.5 to 180.1 Bq/Kg respectively for radionuclides 40K 226Ra and 232Th respectively. From the radiological calculations, it was found that the use of coal ash as a soil additive contributed slightly to the radionuclide concentrations of the area under study. Key words : Radionuclude, coal ash, radium equivalent, external and internal hazard index. | INTERNATIONAL JOURNAL OF PHYSICAL SCIENCES. | 13 (15), 230 – 234
|
| 11 | Imyhamy M. Dharmadasa, Mohammad L. Madugu, Olajide I. Olusola, Obi K. Echendu, Fijay Fauzi, Dahiru G. Diso, Ajith R. Weerasinghe, Thad Druffel, Ruvini Dharmadasa, Brandon Lavery, Jacek B. Jasinski, Tatiana A. Krentsel and Gamini Sumanasekera (2017). | Electroplating of CdTe Thin Films from Cadmium Sulphate Precursor and Comparison of Layers Grown by 3-Electrode and 2-Electrode Systems | Electrodeposition of CdTe thin films was carried out from the late 1970s using the cadmium sulphate precursor. The solar energy group at Sheffield Hallam University has carried out a comprehensive study of CdTe thin films electroplated using cadmium sulfate, cadmium nitrate and cadmium chloride precursors, in order to select the best electrolyte. Some of these results have been published elsewhere, and this manuscript presents the summary of the results obtained on CdTe layers grown from cadmium sulphate precursor. In addition, this research program has been exploring the ways of eliminating the reference electrode, since this is a possible source of detrimental impurities, such as K+ and Ag+ for CdS/CdTe solar cells. This paper compares the results obtained from CdTe layers grown by three-electrode (3E) and two-electrode (2E) systems for their material properties and performance in CdS/CdTe devices. Thin films were characterized using a wide range of analytical techniques for their structural, morphological, optical and electrical properties. These layers have also been used in device structures; glass/FTO/CdS/CdTe/Au and CdTe from both methods have produced solar cells to date with efficiencies in the region of 5%–13%. Comprehensive work carried out to date produced comparable and superior devices fabricated from materials grown using 2E system. | Coatings | 2-Jul
|
| 12 | Ibeneme Sabinus Ikechukwu, Ibe Kalu Kalu, Eluwa Ndidiamaka Nchedo, Chinyem Felix Iwebunor, Nwankwo Stephen, Bulus Joseph Azi, Echendu Obi Kingsley (2017). | Electrical Resistivity and River Flow Velocity Studies of Ebonyi River Bridge Sites at Onicha-Oshiri and Idembia Areas, Southeastern Nigeria | Pre-design Geoelectrical and River Velocity studies have been carried out at two bridge locations: Ebonyi River at Onicha-Oshiri road and Ebonyi River at Idembia Ezza. The objectives of the studies are to determine the geoelectrical parameters with respect to structure and rock type at these locations in combination with geology and carry out the analysis of the river velocity at various points. Four Vertical Electrical Sounding (VES) stations and six Velocity profiles were established (two VES stations and three velocity profiles per bridge site). Three geoelectric layers were proposed for Onicha-Oshiri and four to five geoelectric layers for Idembia. These layers comprise of the Top soil with resistivity range of 290-950Ωm, Silty lateritic soil with resistivity range of 140-181Ωm, Hard lateritic soil with resistivity range of 724-860Ωm, Silty sand with resistivity range of 163-494Ωm and Mudstone with resistivity range of 52-100Ωm. Results of Onicha-Oshiri lot show that the velocity values range from 1.28ms-1 to 1.95ms-1. Along profile D, velocity values rise from point 1 to point 3. Along the present bridge profile, the values are nearly the same for points 1 and 2 and rise to 1.37ms-1 at point 3. However along profile F, the velocity value is higher at point 2 (middle of the river). At Idembia site velocity values range from 0.634m s-1 to 0.99m s-1. Apart from profile B where the value is highest at point 3 (edge of the river) values at profiles A and C have higher amounts at the edges and lower amounts at the central portion indicating increased scouring at the edges. The river at Onicha-Oshiri site has higher velocity possibly on the account of this site being at the youthful stage of the river. At Onicha end, the top lateritic matter is interbedded with fresh blue shale which may be offensive to any structure. This must be taken care of during construction by aiming at the hard sandstone below. | Journal of Civil, Construction and Environmental Engineering | 2-Feb
|
| 13 | O. K. Echendu, B. F. Dejene and I. M. Dharmadasa (2017). | Fluorine-induced improvement of structural and optical properties of CdTe thin films for solar cell efficiency enhancement | CdTe thin films of different thicknesses were electrodeposited and annealed in air after different chemical treatments to study the effects of thickness and the different chemical treatments on these films for photovoltaic applications. The thicknesses of the samples range from 1.1 to 2.1 μm and the annealing process was carried out after prior CdCl2 treatment and CdCl2 + CdF2 treatment as well as without any chemical treatment. Detailed optical and structural characterisation of the as-deposited and annealed CdTe thin films using UV–Vis spectrophotometry and X-ray diffraction reveal that incorporating fluorine in the well-known CdCl2 treatment of CdTe produces remarkable improvement in the optical and structural properties of the materials. This CdCl2 + CdF2 treatment produced solar cell with efficiency of 8.3% compared to CdCl2 treatment, with efficiency of 3.3%. The results reveal an alternative method of post-deposition chemical treatment of CdTe which can lead to the production of CdTe-based solar cells with enhanced photovoltaic conversion efficiencies compared to the use of only CdCl2. | Journal of Materials Science: Materials in Electronics | 28
|
| 14 | O. K. Echendu, F. B. Dejene and I. M. Dharmadasa (2017) | An investigation of the influence of different transparent conducting oxide substrates/front contacts on the performance of CdS/CdTe thin-film solar cells | CdS/CdTe/Au thin film solar cells have been fabricated on different transparent conducting oxide (TCO) substrates/front contacts to study the influence of these different TCOs on the performance of the devices. The TCOs used were ZnO, ZnO:Al and SnO2:F. Under dark condition,all three device structures of the type glass/TCO/n-CdS/n-CdTe/Au n–n heterojunction + Schottky barrier, show interesting rectifying behaviors with rectification factors (RF) in the range (102.5—105.0), Schottky barrier heights (ΦB) greater than (0.69–0.81) eV, diode ideality factors (n) in the range (1.85–2.12), reverse saturation current densities (J0) in the range (3.18 × 10−6–3.18 × 10−8) A cm−2, series resistances (Rs) in the range (507–1114) Ω and shunt resistances (Rsh) in the range (0.84–271) MΩ. The device structures glass/SnO2:F/n-CdS/n-CdTe/Au and glass/FTO/ZnO:Al/n- CdS/n-CdTe/Au show the best performance with equal J0 of 3.18 × 10−8 A cm−2, equal ΦB > 0.81 eV, RF of 104.9 and 105.0, n value of 2.01 and 2.12, Rs of 615 Ω and 507 Ω and Rsh of 197 and 271 MΩ respectively. The device structure with ZnO shows the least performance. Under AM1.5 illumination, the device structure glass/SnO2:F/n-CdS/n-CdTe/Au shows the best solar cell performance with open-circuit voltage of 630 mV, short-circuit current density of 23.5 mAcm−2, fill factor of 0.44 and conversion efficiency of 6.5%, and is followed by the device structure with ZnO:Al showing a conversion efficiency of 6.0%. Suggested energy band diagrams of the devices as well as possible reasons for the observed trends in performance are presented and discussed. | Journal of Materials Science: Materials in Electronics | 28/24
|
| 15 | Obi Kingsley Echendu, Francis Birhanu Dejene, Imyhamy Mudiy Dharmadasa and Francis Chukwuemeka Eze (2017) | Characteristics of nanocrystalline-CdS produced by low-cost electrochemical technique for thin film photovoltaic application: The influence of deposition voltage | Electrochemical deposition and characterization of nanocrystallite-CdS thin films for thin film solar cell application are reported.The two-electrode system used provides a relatively simple and cost-effective approach for large-scale deposition of semiconductors for solar cell and other optoelectronic device application. Five CdS thin films were deposited for 45 minutes each at different cathodic deposition voltages in order to study their properties. X-ray diffraction study reveals that the as-deposited films contain mixed phases of hexagonal and cubic CdS crystallites with large amounts of internal strain and dislocation density. Postdeposition annealing results in phase transformation which leaves the films with only the hexagonal crystal phase and reduced strain and dislocation density while increasing the crystallite sizes from 21.0–42.0nm to 31.2-63.0 nm. Photoelectrochemical cell study shows that all the CdS films have n-type electrical conductivity. Optical characterization reveals that all samples show similar transmittance and absorbance responses with the transmittance slightly increasing towards higher growth voltages. All the annealed films show energy bandgap of 2.42 eV. Scanning electron microscopy and energy dispersive X-ray analyses show that grains on the surface of the films tend to get cemented together after annealing with prior CdCl2 treatment while all the films are S-rich. | International Journal of Photoenergy | |
| 16 | O. K. Echendu, B. F. Dejene and I. M. Dharmadasa (2018) | The effects of anode material type on the optoelectronic properties of electroplated CdTe thin films and the implications for photovoltaic application | The effects of the type of anode material on the properties of electrodeposited CdTe thin films for photovoltaic application have been studied. Cathodic electrodeposition of two sets of CdTe thin films on glass/fluorine-doped tin oxide (FTO) was carried out in two-electrode configuration using graphite and platinum anodes. Optical absorption spectra of films grown with graphite anode displayed significant spread across the deposition potentials compared to those grown with platinum anode. Photoelectrochemical cell result shows that the CdTe grown with graphite anode became p-type after post-deposition annealing with prior CdCl2 treatment, as a result of carbon incorporation into the films, while those grown with platinum anode remained n-type after annealing. A review of recent photoluminescence characterization of some of these CdTe films reveals the persistence of a defect level at (0.97–0.99) eV below the conduction band in the bandgap of CdTe grown with graphite anode after annealing while films grown with platinum anode showed the absence of this defect level. This confirms the impact of carbon incorporation into CdTe. Solar cell made with CdTe grown with platinum anode produced better conversion efficiency compared to that made with CdTe grown using graphite anode, underlining the impact of anode type in electrodeposition. | Journal of Physics and Chemistry of Solids | 114
|
| 17 | F. G. Hone, F. B. Dejene and O. K. Echendu (2018) | Band gap tailoring of chemically synthesized lead sulfide thin films by in situ Sn doping | In the present report, undoped and tin (Sn)‐doped lead sulfide thin films were synthesized via chemical bath deposition method. The effects of Sn molar concentration on the optical, structural, and morphological properties were systematically studied. The concentration of Sn in the chemical bath was characterized by the ratio of [Sn+2]/[Pb+2] and varied from 0 to 15 at.%. Both doped and undoped thin films were polycrystalline in nature with a face‐centered cubic crystal structure; however, the preferred orientations of the crystallites were varied along the (111) and (200) planes with Sn‐doping concentration. The X‐ray powder diffraction results also showed that peak intensities and the crystalline size were decreased with increasing Sn concentration. The lattice constant varied with Sn concentration and found in the range of 6.020 to 5.944 Å. The variation of Sn concentration in PbS:Sn thin films were confirmed by energy dispersive X‐ray analyses study. The scanning electron microscope and atomic force microscopy studies revealed that Sn doping had a critical role on the surface roughness and morphology of the PbS:Sn thin films. The optical band gap study showed that the band gap of PbS:Sn thin films were engineered from 0.676 to 1.345 eV because of incorporation of Sn+2 ions via cost‐effective chemical route. Room temperature photoluminescence spectra showed a well‐defined peak at 427 nm and shoulders at 405 and 462 nm for all Sn‐doped and undoped PbS samples. | Surf Interface Analysis | 50/6
|
| 18 | O. K. Echendu, S. Z. Werta, F. B. Dejene and V. Craciun (2018) | Electrochemical deposition and characterization of ZnOS thin films for photovoltaic and photocatalysis applications | Electrochemical deposition of zinc oxysulphide (ZnOS) thin films for possible photovoltaic and photocatalysis applications has been carried out using zinc acetate and sodium thiosulphate precursors in a simple two-electrode deposition set-up. The deposited films were characterized for their structural, optical, morphological and compositional properties using glancing incidence X-ray diffraction (GIXRD), UVeVis spectrophotometry, scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy respectively. The detailed characterization results show that the ZnOS materials grown at different cathodic potentials of 1450 mV, 1500 mV and 1550 mV display desirable properties for the intended applications. Structural analysis shows that the films were formed by a combination of hexagonal ZnS and ZnO crystal phases. The energy bandgap estimated for the films across the explored potentials is in the range (2.68-3.26) eV for as-deposited films and (2.90-3.10) eV after annealing. These values and the transmittance were also shown to be increased significantly by reducing the deposition duration. SEM images show very compact and densely packed grains in the films while EDX results show Zn/S values of approximately unity and Zn/O values of approximately 0.1 across the deposition potentials explored, in both as-deposited and annealed conditions. | Journal of Alloys and Compounds | 769 |
| 19 | S. Z. Werta, O. K. Echendu, F. B. Dejene, Z. N. Urgessa and J. R. Botha (2018) | Temperature-dependent properties of electrochemically grown CdS thin films from acetate precursor | Cadmium sulphide (CdS) thin films have been successfully deposited on glass/fluorine-doped tin oxide (glass/FTO) from an aqueous electrolyte solution containing cadmium acetate Cd(CH3COO)2 and sodium thiosulphate ( Na2S2O3) using electrodeposition technique. The deposition electrolytic bath temperature was varied at 45, 65 and 85 °C. Two electrode system was applied and the corresponding structural, optical, morphological and compositional properties of these thin films have been characterized using X-ray diffraction, UV–Vis spectrophotometry, scanning electron spectroscopy, scanning probe microscopy and energy dispersive X-ray spectroscopy, respectively. The effect of post growth annealing on the structural, optical and morphological quality of the thin films is also reported. The results show that, growth temperature has significant influence on structural and optical properties of the film properties. Increasing the electrolytic solution temperature resulted in slight improvement in crystallinity of CdS thin films in both as deposited and annealed conditions. Due to increase in bath temperature from 45 to 85 °C the energy band gap narrows down from 2.45 to 2.38 eV for as deposited films and 2.42–2.22 eV for annealed films. The increase in deposition temperature improves the atomic ratio of Cd to S. Similarly, the grain sizes of the films increase with increase in growth temperature. | Applied Physics A: Materials Science and Processing | 124/576
|
| 20 | O. K. Echendu, B. F. Dejene and F. G. Hone (2018) | Comparative performance of CdS/CdTe thin film solar cells fabricated with electrochemically deposited CdTe from 2-electrode and 3-electrode set-ups | A comparative study of the performance of glass/FTO/CdS/CdTe/Au thin film solar cells was carried out for solar cells fabricated with CdTe electrochemically grown using 2-electrode and 3-electrode set-ups. Structural, optical and morphological characterization of the CdTe films prior to solar cell fabrication show that both electrode set-ups produce CdTe with similar X-ray diffraction patterns, optical absorption properties and surface morphologies. Current density-voltage characterization of resulting solar cells also shows that CdTe from both electrode systems produced solar cells with comparable conversion efficiencies. The open-circuit voltage, shortcircuit current density and fill factor of cells from both systems were in the ranges of (410–630) mV, (15.2–33.0) mAcm−2 and (0.32–0.49), respectively. These results indicate that the 2-electrode set-up can go a long way in reducing production cost by eliminating the reference electrode, which is also a potential impurity source, as well as ensuring a simplified deposition system. | Materials Science & Engineering B | 232–235
|
| 21 | E.C. Mbamala, I.D. Eguzoro, G.A. Alozie & C.E. Akujor (2017) | Solar powered pool heater using black hosepipe as collector. | We have used a coiled black hosepipe in the design and construction of a hybrid solar and electric powered pool heater. The major materials used include a black hosepipe easily formed into a spiral of surface area 0.986m2; a ½ hp (373W) ac water pump; a water container; and a 2mm thick transparent plastic glass. The electric water pump, runs water (initially cold) stored in the container through the coiled hose and back into the container. This cycle is continued at a controlled speed for a period of time until the water heats up to higher temperatures. The main aim of the work is to heat large volumes of water such as swimming pools at lower cost than using the convectional electric heaters. With the collector covering an area of only 0.986m2, the device was tested for three different volumes of water in three different days as follows: 35liters in Day 1; 40liters in Day 2 and 80liters in Day 3. All three tests were carried out in the month of September between 11:00hrs and 18:00hrs each day. The location was Federal University of Technology, Owerri, Imo-State, Nigeria. Our device showed a peak efficiency of 51.3% for the 35liter volume of water at a peak pool temperature of 58oC. We observed that the average peak temperature of the heated water did not drop as one would expect when the volume of water is increased from 35liters (58oC) to 80liters (48oC). This suggests that the surface area of the collector used in this work need not be increased by orders of magnitude for water volumes of typical swimming pools. Our calculations also show that an energy cost saving of at least 50.5% is achieved. | African Journal of Renewable and Alternative Energy, 2(1), 41–50; 2017 | |
| 22 | Onwuemeka, J. I., Eze, F. C.,Ndukwe, I. C. | The Study of Chemically Deposited ZnO Thin Films for Possible Device Applications | A study on the Deposition and Characterization of ZnO Thin Films by Solution Growth Technique using Ammonia(NH3) as a complexing agent. Zinc oxide thin films were successfully deposited on glass slides under certain deposition condition of 600C – 1000C of 1M solution of NaOH, using solution growth technique. X-ray fluorescence (XRF) and Rutherford Back scattering Spectroscopy (RBS) analyses confirmed that the films were ZnO thin films. The films of ZnO showed optical transmittance of 20.6% - 65.6% in the UV, 70.2% - 79.2% in the visible and 79.5% - 81.6% in the near-infrared regions of electromagnetic spectrum. ZnO films were found to exhibit absorbance of 25.5% - 68.6% in the UV, 10% - 18.3% in the visible region and 8.8% - 9.96% in the near-infrared regions of electromagnetic spectrum. ZnO thin films, exhibit low reflectance, throughout the electromagnetic spectrum (9.6% - 20.3%). Direct band gap values of 3.31eV is obtained for ZnO thin films. The thickness of 0.082μm thickness was obtained for ZnO films by gravimetric method. Other properties investigated were the refractive index, optical conductivity, absorption coefficient and dielectric constants. From the spectral qualities, ZnO thin film may be found useful in heat mirror application. The sample of ZnO thin films are also found interesting as semiconductor materials for electronic applications. | International Journal of Innovation in Science and Mathematics | Vol. 5, Issue 3, ISSN (Online): 2347-9051
|
| 23 | Amakom, C.M; Orji E.C; Iroegbu C; Eke, B.C; Nkwoada, A.U; Madu, D.A; Ugochukwu G.K; and Oforma, J.T. (2018) | Radionuclide concentration: The Coal Ash Effect | Radionuclide concentrations in coal ash, soil mixed with coal ash and soil were determined using the gamma spectroscopic method. The average activity concentrations of 226Ra, 232Th, and 40K in coal ash samples were found as 35.0, 5.8, and 109.4 Bq/kg, respectively. The average activity concentrations of 226Ra, 232Th and 40K in soil mixed with coal ash samples varied from 21.2 to 30.8, 48.6 to 82.7, and 162.5 to 180.1 Bq/kg, respectively. The activity concentrations of radionuclides from the non-mixed soil area, which serves as a control to this study ranged from 123.95 to 128.82, 16.33 to 18.38, and 46.63 to 50.30 Bq/kg, respectively for radionuclides 40K, 226Ra, and 232Th, respectively. From the radiological calculations, it was found that the use of coal ash as a soil additive contributed slightly to the radionuclide concentrations of the area under study | International Journal of Physical Science | Vol. 13 (15) pp 230-234
|
| 24 | Amakom, M. Chijioke, Orji, E. Chikwenduet al., | Radiation levels around some x-ray diagnostic centres in Owerri, Imo state, Nigeria | Radiation levels were measured around eight diagnostic centres in Owerri, Imo State Nigeria using a portable Geiger Muller counter model GCA-04. The measuremnts were taken when the radiation sources (x-ray machines) were operational and non-operational. When the machines were non-operational, the background radiation ranged from 0.63 to 1.48 mSv/yr. When the machines were operational, the radiation levels ranged from 0.82 to 24.28 mSv/yr; this adds between 0.19 to 23.14 mSv/yr to the existing background radiation. The diagnostic centres used in this work have background radiation level below the world average dose limit of 2.16 mSv/yr for natural background radiation. Seven centres had annual dose rates that were below the 1.25mSv/yr dose limit for the public when the radiation source is not on and only one centre had a value still below the dose limit for the public when the radiation source was on. The other centres had higher values of annual dose rate when the safety of the general public is considered both for the cases when the radiation source was operational and non-operational. | International Journal of Research and Reviews in Applied Sciences | Vol 35(3), pp. 6-9
|
| 25 | Chijioke M. Amakom, Chikwendu E. Orji, Benedict C. Eke, Chinedu Iroegbu and Bridget A. Ojakominor | Gross alpha and beta activity concentrations in soil and some selected Nigerian food crops | Gross alpha and beta activity concentrations in soil, cassava and Fluted pumpkin (leaf and stem) were investigated using a gas flow proportional counter. The gross alpha activity concentrations for the Fluted pumpkin were between 3.55—13.95 Bq/Kg and 3.53—3.61 Bq/Kg for the leaves and stems respectively. The gross alpha activity concentrations for cassava and soil samples ranged from 0.07-0.60 Bq/Kg and 0.35-0.53 Bq/Kg respectively while the gross beta activity concentrations ranged from 0.43-0.89 Bq/Kg and 0.46-1.04 Bq/Kg for the cassava and soil samples respectively. The gross alpha and beta activity concentrations in cassava, fluted pumpkin and soils samples have been determined using alpha/beta spectroscopy. The result of our study showed that the Iva-valley coal mine area has lower gross alpha and beta activity concentrations compared to other areas of the country. This shows that the coal mining activities in the area may not have increased the radiation burden of the area. | International Journal of Physical Sciences | Vol. 13(11), pp. 183-186
|
| 26 | U. Nkwoada, C. O. Alisa, C. M. Amakom and C. K. Enenebeaku | Establishing Risk Assessment from Reclaimed Nekede Mechanic Village Owerri, Nigeria | The current resettlement of Nekede Auto-Mechanic village by Imo State government of Nigeria created a sparse piece of land awaiting government utilization. Risk assessment was carried out on the land using existing boreholes and soil to determine land utilization potential. Analysis of the physicochemical water parameters showed that there was no contamination of boreholes. The high value of COD correlated with the high levels of Fe in soil and water samples. Heavy metals concentrations showed that Fe was very much present in the soil while Pb, Cd and Cu had reduced concentrations. Risk assessment for the soil samples showed that Fe had the highest mean and median value. The highest mean value for water was Cu metal. Highest variance value was Cu in the soil while Pb had the lowest value in water. Hazard quotient of water samples showed that hazards existed for Cd, Cu and Pb but at a moderate level for Fe. Estimated daily/weekly water intake values were all below WHO/FAO standards. The soil enrichment factor showed no enrichment for Pb, minimal enrichment for Cd, moderate enrichment for Cu and significant contamination for Fe. Ecological risk assessments for the heavy metals were at low ecological risk. Potential ecological | Asian Journal of Environment & Ecology | Vol. 7(2): 1-13, Article no.AJEE.43281
|
| 27 | Nkwoada A.U; Alisa C.O&Amakom C.M | Pollution In Nigerian Auto-Mechanic Villages: A Review | The increasing number of malfunctioning automobiles with subsequent increase in emission levels and waste handling is an environmental concern in Nigeria. The spills from lubricants, gasoline, diesel and by-products of used and spent engine oil constitute the major pollutants in auto mechanic villages in Nigeria. Its environmental pollution has been predominant through soil and groundwater contamination and also poses a major anthropogenic threat. The studied heavy metals on contaminated soil showed that studies had focused on common metals of Cu, Cd, Pb and Zn in the east and west regions, while trace metals were studied in the south and radioactive elements in the north. The statistical evaluation showed high occurrences of Cu, Cd, Pb and Zn in the four geopolitical zones of Nigeria. The detrimental effects of auto-mechanic village activities were on humans and also disrupted growth and flowering of arable plants. The remediation application showed that soil type and contaminant characteristics play a major role in determining the type of remediation procedure to be applied. Hence, Nigeria should provide standard repairs and services to automobiles in-line with emerging technology and best environmental practices. | Journal of Environmental Science, Toxicology and Food Technology | Volume 12, Issue 7 Ver. I PP 43-54
|
| 28 | Amarachi U. Nkwoada, Chijioke M. Amakom and Emeka E. Oguzie | The Role and Economics of Nano-Graphene Functionalization in Oil Industry Improvement | The toxic pollutants released from oil and gas activities typically takes years of clean-up and reclamation. Hence, creating the need for new nano-materials that can function as adsorbents, filter membranes, and coating materials, which offer a molecular level of control in separating relevant pollutant mixtures. The advances in graphene-family and its derivatives has proven its effectiveness to gradually replace conventional filter membranes, coatings, adsorbents, sensors for nanomaterials applications in the oilfield. The functionalization of graphene and graphene oxide has enabled such nano-graphene-composite materials to be tailored to meet the new development of coatings, adsorbents, filter membranes and sensors for oil and gas applications with high scalability potentials. | Asian Journal of Physical and Chemical Sciences | Vol. 5(2): 1-19
|
| 29 | Chijioke M. Amakom, Chikwendu E. Orji, Benedict C. Eke, Uchenna A. Okoli and Chidiebere S. Ndudi, 2017 | The Influence of Selected Soil Physicochemical Properties on Radionuclide Transfer in Cassava Crops | Radionuclide contamination through the food chain is a major pathway for radiotoxicity to man. The radionuclides of natural origin are absorbed from the soil just like every other nutrient the plants needs for their survival. A study on the effects of some soil physicochemical parameters on the radionuclide transfer factors from soil to plant was carried out. The soil physicochemical properties obtained from the study suggest that the soil in this study fell within the sand category with a pH range of 5.06 – 6.08. Radionuclide activity concentrations for the soil samples ranged from 9.73±0.92 – 56.38±3.29, 35.91±1.71 – 147.26±4.06 and 137.09±4.20 – 247.33±3.42 Bq/Kg for the radionuclides 226Ra, 232Th and 40K respectively. For the cassava samples, the activity concentrations ranged from 19.28±5.29 – 89.22±5.09, 70.46±1.59 – 203.48±1.56 and 39.34±5.59 – 442.45±6.99 for 226Ra, 232Th and 40K respectively. From the correlation statistics, the soil pH and silt content made the most significant contribution in the radionuclide transfer factors. | International Journal of Plant and Soil Science | Vol. 14(1):1-7 IJPSS.30913
|
| 30 | B.Olofinjana, U. S.Mbamara, O.Ajayi, C.Lorenzo-Martin, E.I. Obiajuuwa, E. O. B. Ajayi. (2017). | Tribological behavior of N-doped ZnO thin films by metal-organic chemical vapour deposition under lubricated contacts. | N‐doped ZnO thin films were deposited on 304L stainless steel through the pyrolysis of zinc acetate and ammonium acetate in different ratios at a temperature of 420 °C using metal-organic chemical vapour deposition. Compositional and structural analyzes of the films were performed by using Rutherford backscattering spectroscopy and X‐ray diffraction. The frictional behaviour of the thin films and 304L stainless steel substrate was evaluated using a ball‐on‐flat configuration with reciprocating sliding under marginally lubricated and fully flooded conditions. Al alloy (2017) was used as ball counterface, while basestock synthetic polyalfaolefinoil (PAO10) without additives was used as a lubricant. The flat and ball counterface surfaces were examined toassess the wear dimension and failure mechanism. Under the marginally lubricated condition, N‐doped ZnO thin-films provided a significant reduction in friction, whereas the films have minimal or no effect in friction under fully flooded condition. N‐doped ZnO thin films showed a significant effect in protecting the ball counterface as wear volume was reduced compared with that of the substrate under the marginally lubricated condition. Under the fully flooded condition, with the exception of one of the films, the wear volume of the N‐doped ZnO thin films ball reduced compared with that of the substrate. In all the ball counterfaces for N‐doped ZnO thin films under both conditions, wear occurred through the abrasive mechanism of various degrees or mild polishing. Thus, superfluous lubrication of N‐doped ZnO thin films is not necessary to reduce friction and wear. Keywords: ZnO film; metal-organic chemical vapour deposition; friction; wear; optical microscopy. | Friction-Tsinghua Journals. (Springer). | 0(0): 1-12. ISSN 2223-7690; DOI 10.1007/s40544-017-0154-x; CN 10-1237/TH
|
| 31 | C.I. Onah, U.S. Mbamara, P.M. Favour (2017) | Design and Construction of a Three-Level Clearance Security System | We designed a three-level clearance system using key card access, hardware keypad password authentication and biometrics fingerprint scanner based framework that will provide user authentication and authorization. Authentication means that a principal can prove his identity. This is done by means of secrets, usually cryptographic keys. This standard security mechanism will enhance more consistent security policies. The hardware peripherals are directly interfaced with computer software which coordinated and analyzed all the verification processes and execution of other hardware peripheral controls like the opening of an electronic door, granting access to a restricted file in the computer, automatic triggering of alarm on the bridge of security, simultaneous multi-user verification etc. The security system will also afford expansion when the need arises. If input password is correct, after analyzing it and comparing it with those in the database; access will be granted by activating the third level security for final verification using the personnel's fingerprint biometrics. This stage cannot be bridged even if the first and second levels were successful accessed illegally. On final verification, unrestricted access will be granted to the personnel. Keywords: Security system, keycard access, password, fingerprint biometrics | Journal of Instrumentation Technology and Innovations. | 7(1): 7-19. ISSN: 2249-4731.
|
