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Sustainable hydrogen generation substrates, catalysts and methods : an overview

- Adeniran, J. A., DeKoker, J. J., Akinlabi, Esther Titilayo, Jen, T. C.

  • Authors: Adeniran, J. A. , DeKoker, J. J. , Akinlabi, Esther Titilayo , Jen, T. C.
  • Date: 2017
  • Subjects: Hydrogen generation , Hydrolysis , Ball milling
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/231926 , uj:23640 , Citation: Adeniran, J.A. et al. 2017. Sustainable hydrogen generation substrates, catalysts and methods : an overview.
  • Description: Abstract: Because of the increasing demand for energy, various alternative sources of energy generation are being examined. Interest in hydrogen generation is on the rise due to its potential as a scalable green energy source, its transportability, and other positive factors. While various studies have been conducted on hydrogen generation, this review explores three major factors in hydrogen generation in relation to sustainability: substrates or hydrogen storage media, catalysts for speeding up the rate of hydrogen reaction, and methods employed. The media used to store the hydrogen, such as metal hydrides and complex hydrides, is examined in relationship to hydrogen yield, ease of hydrogen generation or treatment, cost and environmental friendliness. A list of popular catalysts - particularly precious/rare earth metals, strong acids and weak acids - is examined and compared in terms of hydrogen yield, environmental friendliness, and cost. The recent trend in hydrogen generation techniques and material treatment innovations such as hydrolysis, and ball milling of nanocomposites is examined. Innovations in hydrogen storage material selection and techniques will go a long way in lowering hydrogen generation cost, increasing hydrogen yield and ameliorating negative environmental impacts.
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Phase-structural and morphological features, dehydrogenation/re-hydrogenation performance and hydrolysis of nanocomposites prepared by ball milling of MgH2 with germanium

- Adeniran, J. A., Akbarzadeh, R., Lototskyy, M., Nyallang Nyamsi, S., Olorundare, O. F., Akinlabi, Esther Titilayo, Jen, T. C.

Experimental investigation of ceramic substrates in standing wave thermoacoustic refrigerator

- Alcock, A. C., Tartibu, L. K., Jen, T. C.

Experimental investigation of an adjustable thermoacoustically-driven thermoacoustic refrigerator

- Alcock, A. C., Tartibu, L. K., Jen, T. C.

  • Authors: Alcock, A. C. , Tartibu, L. K. , Jen, T. C.
  • Date: 2018
  • Subjects: Thermoacoustic , Refrigeration , TADTAR
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/281227 , uj:30258 , Citation: Alcock, A.C., Tartibu, L.K. & Jen, T.C. 2018. Experimental investigation of an adjustable thermoacoustically-driven thermoacoustic refrigerator.
  • Description: Abstract: An experimental investigation is conducted on a new adjustable thermoacoustically-driven thermoacoustic refrigerator (TADTAR). This refrigerator comprises of a thermoacoustic engine which drives a thermoacoustic refrigerator. This study aims to demonstrate the possibility to alter the TADTAR performance through the adjustment of specific design parameters. An adjustable resonator, which consisted of stacks, spacing couplings and shell-tube heat exchangers was designed and built. Six different honeycomb ceramic stacks were investigated. For each system, three different stack configuration were studied. Measurements of temperature difference across the refrigerator stack and sound pressure levels at steady states were used to determine the performance of the device. Through the adjustment of the length and the insertion of the heat exchanger, the performance of the device with a longer resonator was relatively higher. This study shows that an adjustable resonator successfully alters the frequency output of the thermoacoustic engine to match the frequency required by the thermoacoustic refrigerator and achieve resonance. In addition, this study demonstrates the possibility to change the geometrical configuration of the device and ultimately alter the performance of the TADTAR. Through the adjustment of the length of the resonator, this study shows that a single device could have different operating points. This creates new possibilities to introduce control system able to adjust the geometry of thermoacoustic system while in operation.
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Optimization of laser machining parameters and surface integrity analysis of the fabricated miniature gears

- Anghel, C., Gupta, K., Jen, T. C.

Effect of laser beam cutting parameters on productivity and dimensional accuracy of miniature spur gears of stainless steel

- Anghel, Cristina, Gupta, Kapil, Jen, T. C.

  • Authors: Anghel, Cristina , Gupta, Kapil , Jen, T. C.
  • Date: 2020
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/460212 , uj:40945 , Citation: Cristina Anghel et al 2020 IOP Conf. Ser.: Mater. Sci. Eng. 971 022081
  • Description: Abstract: Product quality and process productivity are one of the major indicators to evaluate the performance of any manufacturing process. The quality of any product covers its appearance, geometric and dimensional accuracy, and surface finish and integrity that majorly include microstructure, micro-hardness type of parameters. Whereas, the productivity can be determined using material removal rate. Laser beam cutting is an important advanced machining process and has been scarcely explored for miniature gears. This paper reports, the effect of laser beam cutting parameters on one of the quality parameters i.e. dimensional deviation of miniature spur gears of stainless steel and material removal rate. Box Behnken design of experiments methodology has been adopted to conduct a total of twenty nine experiments where four important laser parameters i.e. power, cutting speed, focal position, and gas pressure have been varied at three levels each. The manufactured external spur gear of stainless steel consists of ten teeth, 0.750 module, 9.04 mm outside diameter, and 4.5 mm face width or thickness. The investigation found that cutting speed significantly affected material removal rate and laser power affected dimensional deviation. Individual effects of laser parameters on both material removal rate and dimensional deviation are discussed in detail in the chapter. The investigation identifies laser beam cutting as a viable substitute of conventional manufacturing processes for fabrication of quality miniature gears with high productivity.
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Performance evaluation of ceramic substrates for cooling applications in thermo-acoustic refrigerators

- Balonji, S., Tartibu, L. K., Jen, T. C.

Parametric optimization route of oil extraction from seed : a review

- Bitire, S. O., Belaid, M., Imoisili, P. E., Jen, T. C.

The potential for a sustainable biodiesel production by modified biobased catalyst : a review

- Bitire, S. O., Jen, T. C., Belaid, M.

Numerical modeling of effect of annealing on nanostructured CuO/TiO2 pn heterojunction solar cells using SCAPS

- Enebe, G. C., Ukoba, K., Jen, T. C.

  • Authors: Enebe, G. C. , Ukoba, K. , Jen, T. C.
  • Date: 2019
  • Subjects: Annealing , CuO/TiO2; , Modeling
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/395825 , uj:32839 , Citation: Enebe, G.C., Ukoba, K. & Jen, T.C. 2019. Numerical modeling of effect of annealing on nanostructured CuO/TiO2 pn heterojunction solar cells using SCAPS.
  • Description: Abstract: The problem of global warming has led to increased research on solar energy and other renewable energy. Solar cells are a building block of solar energy. Different materials for solar cells fabrication exist with silicon-based being commercially viable and common. The bulk of the alternate materials aimed at providing cheap, efficient and sustainable solar cells. Nanostructured Metal oxides solar cells goes a step further to providing a clean, affordable, sustainable solar cells although the efficiency is still low. This study examined the numerical modelling of the annealing effect on the efficiency of nanostructured CuO/TiO2 pn heterojunction using SCAPS. The motivation for the study is to provide a basis for experimental design of affordable, non-toxic and efficient alternate material for silicon solar cells. The modelling was performed using Solar cells capacitance simulator (SCAPS). The input parameters, obtained from literature, include a working point of 300 K for the as-deposited CuO/TiO2 which was compared with air and nitrogen annealed (423.15 K) nanostructured CuO/TiO2 pn heterojunction. Other working condition included simulated sunlight using illumination of AM 1.5G with a 500 W Xenon lamp, silver was used as the electrode/contact. Film thickness of 2000 nm and 200 nm for absorber and buffer respectively. The results gave an optimum efficiency of 0.47 obtained from Nitrogen annealed CuO/TiO2 pn heterojunction. Also, the optimum Fill Factor was obtained to be 64.01% from Nitrogen annealed. The annealed samples performed better than the as- deposited CuO/TiO2 pn heterojunction. This result will help in the experimental fabrication of improved efficiency metal oxide-based solar cells.
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Analysis of sol aging effects on self-cleaning properties of TiO2 thin film

- Lukong, V. T., Ukoba, K. O., Jen, T. C.

Numerical simulation and optimization of p-NiO/n-TiO2 solar cell system using SCAPS

- Mouchou, R. T., Jen, T. C., Laseinde, O. T., Ukoba, K. O.

  • Authors: Mouchou, R. T. , Jen, T. C. , Laseinde, O. T. , Ukoba, K. O.
  • Date: 2020
  • Subjects: Nanostructure , Science , Numerical Simulation
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/481054 , uj:43574 , Citation: Mouchou, R.T., Jen, T.C., Laseinde, O.T. and Ukoba, K.O. 2020. Numerical simulation and optimization of p-NiO/n-TiO2 solar cell system using SCAPS.
  • Description: Abstract: This study illustrates a numerical simulation and optimization of NiO/TiO2 metal oxide thin film for solar cell applications. Metal oxide-based solar cells have now become a new and low-cost alternative for sunlight harvesting and solar power generation. Different material properties like thickness, temperature, and density of states for conduction and valence band were varied using the SCAPS 1D template. The study examined various window layer material with varied range of 300 K –400 K temperature. Therefore, the thickness are also varied between 2 to 0.05 mm and the interface state 1018 to 1021 for absorber and buffer respectively. The objective of this study is to show the numerical annealing effect on the efficiency of nanostructured p-NiO/n-TiO2 heterojunction solar cells using Solar Cells Capacitance Simulator (SCAPS). As the p-NiO layer reduced at high thickness the electrons and holes have more time to recombine whereby the increase in thickness also presented more than 100% increase in fill factor (FF) with the efficiency that was varied from 0.03 to 0.05. The analyzed result indicates that the thickness increase in Jsc, FF, density, and efficiency is due to more electron holes pairs generated.
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A study on Titanium Dioxide Nanoparticles synthesized from Titanium Isopropoxide under Silar-Induced Gel Method : transition from Anatase to Rutile structure

- Nkele, Agnes C., Chime, Ugochi K., Asogwa, Leonard, Nwanya, Assumpta C., Nwankwo, Uba, Ukoba, K., Jen, T. C., Maaza, M., Ezema, Fabian I.

  • Authors: Nkele, Agnes C. , Chime, Ugochi K. , Asogwa, Leonard , Nwanya, Assumpta C. , Nwankwo, Uba , Ukoba, K. , Jen, T. C. , Maaza, M. , Ezema, Fabian I.
  • Date: 2019
  • Subjects: SILAR , Titanium dioxide , Nanoparticles
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/404406 , uj:33913 , Citation: Nkele, A.C. et al. 2019. A study on Titanium Dioxide Nanoparticles synthesized from Titanium Isopropoxide under Silar-Induced Gel Method : transition from Anatase to Rutile structure.
  • Description: Abstract: Successive ionic layer adsorption and reaction (SILAR) method was adopted in synthesizing titanium dioxide nanoparticles at various temperatures so as to investigate their morphological, structural, elemental, optical, chemical bond and photoluminescence properties. The as-prepared nanoparticles were characterized with scanning electron microscopy (SEM), X-ray diffractometry (XRD), transmission electron microscopy (TEM), selected area electron diffractometer (SAED), energy dispersive x-ray spectroscopy (EDX), UV-Visible spectrophotometry (UV-Vis), photoluminescence (PL) spectra and fourier transform infrared spectroscopy (FTIR). Nanospherical balls revealing anatase and rutile crystal structures at (101) and (110) planes respectively were observed. Agglomerations of chain-like small particles manifested in Debye-Scherrer’s rings were evident from the TEM and SAED patterns. EDX spectra confirmed the deposition of the major elements: Ti and O. High transmittance of about 80% with a band gap energy range of 3.41-3.60 eV was obtained from the optical properties. Emission peaks arising from the PL spectra gave information on the charge transport and recombination rates occurring at the TiO2 nanoparticles while FTIR studies revealed the chemical vibrational bonds of the deposited TiO2 NPs. The obtained results show the deposited nanoparticles are suitable for solar cell applications.
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Investigation on laser beam machining of miniature gears

- Popa, C., Gupta, K., Mashamba, A., Jen, T. C.

  • Authors: Popa, C. , Gupta, K. , Mashamba, A. , Jen, T. C.
  • Date: 2018
  • Subjects: Laser , Miniature gear , Precision
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/279304 , uj:29994 , Citation: Popa, C. et al. 2018. Investigation on laser beam machining of miniature gears.
  • Description: Abstract: Micro‐machining has become a fast growing field in the global manufacturing sector due to increasing demand of miniature machines and devices. The trend involves the fabrication of precision miniature parts that have widespread applications in many areas such as, electronics, biomedical, aerospace, robotics, automobiles and consumer products. Miniature gears are essential components of miniaturised devices such as miniature motors and pumps, scientific instruments, medical equipment, timing devices, and robots etc. These gears are generally fine‐pitched gears running at very high speed, mainly used for transmission of motion and/or torque. Therefore, minimum running noise, accurate motion transfer and long service life are the required qualities of these gears. Considering that a laser beam is capable of cutting complex shapes with great precision and little waste, motivates its use to machine small sized parts including miniature gears. This article reports on the fabrication of stainless steel miniature gears by laser beam machining (LBM) process. A total of twenty experiments have been conducted following one factor at a time design of experiment strategy on CO2 laser machine. The fabricated gears have 9 mm pitch diameter, 10 teeth, and 4.5 mm thickness. The effects of laser machining parameters on surface roughness (mainly average roughness ‘Ra’ and mean roughness depth ‘Rz’) of gears have been analysed. The best quality miniature gear fabricated by LBM possesses 1.04 μm average roughness and 5.797 μm mean roughness depth at par with that obtained by conventional and other advanced processes of miniature gear manufacturing. Investigation reveals that LBM is capable to produce miniature gears of good surface finish and integrity ensuring their high functional performance and long service life. The outputs of this preliminary work encourage further exploration of LBM to establish it as an alternative process for fabrication of precision miniature gears.
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Cutting tool temperatures in contour turning : transient analysis and experimental verification

- Stephenson, D. A., Jen, T. C., Lavine, A. S.

  • Authors: Stephenson, D. A. , Jen, T. C. , Lavine, A. S.
  • Date: 1997
  • Subjects: Contour turning , Transient analysis , Cutting tools , Cutting temperatures
  • Type: Article
  • Identifier: uj:5245 , ISSN 1087-1357 , http://hdl.handle.net/10210/14851
  • Description: This paper describes a model for predicting cutting tool temperatures under transient conditions. It is applicable to processes such as contour turning, in which the cutting speed, feed rate, and depth of cut may vary continuously with time. The model is intended for use in process development and trouble shooting. Therefore, emphasis is given in the model development to enable rapid computation and to avoid the need to specify parameters such as thermal contact resistances and convection coefficients which are not known in practice. Experiments were conducted to validate the predictive model. The model predictions with two different boundary conditions bound the experimental results. An example is presented which shows the utility of the model for process planning.
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Review of atomic layer deposition of nanostructured solar cells

- Ukoba, O. K., Jen, T. C.

  • Authors: Ukoba, O. K. , Jen, T. C.
  • Date: 2019
  • Subjects: Atomic layer deposition , Solar cells , Review
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/404849 , uj:33970 , Citation: Ukoba, O.K., Jen, T.C. : 2019 : Review of atomic layer deposition of nanostructured solar cells.
  • Description: Abstract : This study reviews atomic layer deposition technique with a special interest on solar cells applications. Atomic layer deposition is a vapour phase deposition technique used for producing thin films for several applications. This review focuses on the chemistry of Atomic Layer Deposition of solar cells, merits and demerits of ALD on thin film solar cells. Solar cells have attracted a lot of interest due to their potential for affordable, clean and sustainable energy. Solar cells can be deposited using different deposition techniques but Atomic layer deposition currently attracts attention owing to the merits. ALD has functional merit to bulk materials, great processing flexibility and affordability. The review examined the merits of ALD and solar cells and areas for future study. It offers affordability, ease of control of film growth, conformal and improvement on the deposition of solar cells. Despite few demerits, ALD is poised to be the deposition technique of choice for modifying interfaces of the film for improved performance.
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