MAXWELL MAGETO - Academia.edu (original) (raw)
Papers by MAXWELL MAGETO
![Research paper thumbnail of Structural, Electronic, and Electrochemical Properties of LixCo[Fe(CN)6]0.902.9H2O](https://attachments.academia-assets.com/115312677/thumbnails/1.jpg)
](Japanese Journal of Applied Physics, 2013
Prussian blue analogues with jungle-gym-type structure are promising candidates for cathode mater... more Prussian blue analogues with jungle-gym-type structure are promising candidates for cathode materials of the lithium-ion secondary battery (LIB). Here, we investigated the structural, electronic, and electrochemical properties of cobalt hexacyanoferrate, Li x Co[Fe(CN)6]0.902.9H2O, against Li concentration (x). The capacity (= 139 mAh/g) of the thin-film electrode was close to the ideal value (= 132 mAh/g) for the two-electron reaction. The discharge curve exhibits three plateaus, i.e., plateaus I, II, and III. The material exhibits a first-order phase transition accompanied by significant volume expansion by 7% at the boundary between plateaus II and III. Ex situ X-ray absorption spectroscopy (XAS) indicates that the discharge processes of plateaus I, II, and III are ascribed to the reduction processes of Fe3+, Co3+, and Fe3+, respectively. The rate (r) and cycle (n) dependence of the electrode performance will be discussed in terms of the reduction processes.
Transparent Pb(Zn 1/3 Nb 2/3)O 3-(Pb 1-x La x)(Zr 1-y Ti y)O 3 (PZN-PLZT) ferroelectric ceramics ... more Transparent Pb(Zn 1/3 Nb 2/3)O 3-(Pb 1-x La x)(Zr 1-y Ti y)O 3 (PZN-PLZT) ferroelectric ceramics have successfully been prepared by hot-pressed sintering in oxygen atmosphere. Uniform cylindrical samples with diameter as large as ס 50 mm can readily be obtained. X-ray analysis and scanning electron microscopy experiments showed a pure perovskite phase, thin grain boundaries, and uniform dense microstructures. Very good transparency was reached for wavelength from near ultraviolet to infrared. The dielectric constant was also measured as a function of temperature and frequency. Some novel phenomena such as good piezoelectric and electro-optical properties have been observed.
Physical Science International Journal, 2019
This paper investigates the outdoor performance of a 20 W monocrystalline silicon solar module in... more This paper investigates the outdoor performance of a 20 W monocrystalline silicon solar module in relation to air mass (AM) in Kakamega. Direct measurement of air mass and module output parameters from experimental setup was done in Kakamega at a location 0.28270 N and 34.7519 E. Experimental results showed a decrease in ISC and VOC with increasing AM. The maximum output power produced by the module reduced with an increase in AM. Maximum power was therefore seen to be produced at noon in this region. VOC increased from 19.47 to 20.04 then decreased to 19.49 V while ISC increased from 0.36 to 1.19 then decreased to 0.48A. It was observed that both the FF and of a monocrystalline solar module increase with increase in air mass. The module performed better during the afternoon than morning and evening hours with the peak performance observed close to AM 1.
Physical Science International Journal, 2018
Solar energy can be harnessed as photovoltaic energy or solar thermal. Photovoltaic modules provi... more Solar energy can be harnessed as photovoltaic energy or solar thermal. Photovoltaic modules provide safe, reliable, and maintenance-free, without noise and environmentally friendly source of power This paper evaluates the outdoor performance of a monocrystalline silicon module based on irradiance and temperature in Kakamega region. The outdoor performance characterisation of a 20 W mono-crystalline silicon module was investigated under different values of solar irradiance and module surface temperature in Kakamega, Kenya. Short circuit current of the module increased significantly with increasing irradiance while open circuit voltage was least affected. Both fill factor and efficiency showed a similar trend with irradiance, increasing slightly and then reducing. The response variables; fill factor, efficiency, open circuit voltage and maximum power were found to reduce with increase in surface temperature while short circuit current increased slightly. The average efficiency, fill factor, short circuit current and open circuit voltage for the module was found to be 10.11%, 0.65, 0.65A, and 19.78V respectively. Maximum Voltage, maximum current and maximum power were found to be 16.78V, 0.48A and 8.11W respectively. A good knowledge of the power output of a solar module and how it varies with solar irradiance and temperature would give accurate information which is vital in sizing and design of photovoltaic system.
The European Physical Journal Applied Physics, 2013
ABSTRACT CoxTi1-xO2 films were deposited by spray pyrolysis technique on Si(1 0 0) substrates at ... more ABSTRACT CoxTi1-xO2 films were deposited by spray pyrolysis technique on Si(1 0 0) substrates at 475 °C. A hydro-alcoholic solution containing titanium (iv) isopropoxide and Co(NO3)2 with various Co doping levels from x = 0-0.015 in solution was used as spray solution. Grazing incident angle of X-ray diffraction illustrates that the CoxTi1-xO2 films are single phase and polycrystal with mixed orientations. Study of surface morphology of the films by atomic force microscope reveals that the annealing atmosphere does not significantly affect the grain size and the microstructure of the films. This study provides further insight into the importance of annealing atmosphere on magnetization of the films. Room temperature magneto-optical Kerr measurement was employed in polar mode. A hysteresis loop and a paramagnetic behavior have been recorded for samples annealed in H2 ambient gas and air, respectively. Chemical composition analysis by X-ray photo-electron spectroscopy showed that Co atoms are bounded to oxygen and no metallic clusters are present. Moreover, it indicates the formation of high spin Co2+ for the sample x = 0.008 annealed in H2 ambient gas. The origin of magnetization can be attributed to the contribution of oxygen vacancies in the spin polarization of the structure.
Alloys
Al–Mg–Si alloys are used in aircraft, train, and car manufacturing industries due to their advant... more Al–Mg–Si alloys are used in aircraft, train, and car manufacturing industries due to their advantages, which include non-corrosivity, low density, relatively low cost, high thermal and electrical conductivity, formability, and weldability. This study investigates the bulk mechanical properties of Al–Mg–Si alloys and the influence of the Si/Mg ratio on these properties. The Al cell was used as the starting structure, and then nine structures were modeled with varying percentages of aluminium, magnesium, and silicon. Elastic constant calculations were conducted using the stress–strain method as implemented in the quantum espresso code. This study found that the optimum properties obtained were a density of 2.762 g/cm3, a bulk modulus of 83.3 GPa, a shear modulus of 34.4 GPa, a Vickers hardness of 2.79 GPa, a Poisson’s ratio of 0.413, a Pugh’s ratio of 5.42, and a yield strength of 8.38 GPa. The optimum Si/Mg ratio was found to be 4.5 for most of the mechanical properties. The study su...
HAL (Le Centre pour la Communication Scientifique Directe), Apr 25, 2022
Case Studies in Construction Materials
Energy Procedia, 2016
Electronic structure theory has recently been used to propose hypothetical compounds in presumed ... more Electronic structure theory has recently been used to propose hypothetical compounds in presumed crystal structures, seeking new useful functional materials. The functional materials include transparent conductors needed in solar cell, light emitting diode and flat panel displays, which represent the usually contraindicated functionalities of optical transparency (generally associated with electrical insulators) coexisting with electrical conductivity (generally associated with optically opaque metals). Usually, such hypothetical materials are meta-stable, albeit with technologically useful long lifetimes. Yet, in other cases, suggested hypothetical compounds may be significantly higher in energy than their lowest-energy crystal structures or competing phases, making their synthesis and eventual device-stability questionable. Shifting focus from the previous searches of doping wide-gap metal oxides turns our focus to the newly predicted never before synthesized ABX compounds of TiIrSb, TaIrSn and ZrIrSb called "filled tetrahedral structure" (sometimes called Half-Heusler). We give interest to these compounds because; there stability range is located around X-richest and A/B-poor growth. The 'inverse design' principles are applied to ABX compounds. Then the effect of atomic number in their materials to tolerance of sufficient level of off-stoichiometry in creation of free holes that avoid the ionic sites and thus lead to high hole mobility at room temperature.
Proceedings of ISES World Congress 2007 (Vol. I – Vol. V), 2008
A simple model developed at Uppsala University was used to estimate the energy balance of uncoate... more A simple model developed at Uppsala University was used to estimate the energy balance of uncoated single and double glazed windows, a low-e double glazed window and a solar control double glazed window using climate data for the city of Hefei, China. The results show that the reduction of heat losses through the window in February can be as much as 87% for a north orientation by using a low-e window, and the reduction of cooling load in August can be 66–68% in all four orientations by using a solar control window. Estimation is also carried out for non-insulated and well-insulated walls. It shows the energy reduction for heating and cooling by using an insulated wall can be of the order of 75% both in February and August, respectively.
American Journal of Materials Science, 2013
F-co-doped Palladiu m Tin Oxide (PTO) thin films were pyrolytically deposited on glass substrate ... more F-co-doped Palladiu m Tin Oxide (PTO) thin films were pyrolytically deposited on glass substrate at 450 0 C using an alcoholic precursor solution consisting of Tin (IV) Chloride (SnCl 4 .5H 2 O), Palladiu m Ch loride (Pd Cl 2) and Ammoniu m Fluoride (NH 4 F). A resistivity of 0.3-6.9×10-2 Ωcm was obtained in F-co-doped PTO films prepared with a Pd content of 3.68at% and F content of 0-23.96at% under optimized conditions. The optical properties were studied in the UV/ VIS/ NIR region. The optical bandgap of the films laid in the range 3.945-4.014 eV. Using dispersion analysis with Drude and Kim terms, optical constants were determined fro m spectro-photometric measurements for films on glass.
Solid State Communications
Physical Science International Journal, 2018
Anaerobic digestion is an effective method for organic pollution reduction and bio-energy product... more Anaerobic digestion is an effective method for organic pollution reduction and bio-energy production and has increasing applications worldwide. Produced biogas consists mainly of 50-70% methane (CH 4) and 30-50% carbon dioxide (CO 2). The most common utilization route of biogas is for electricity production, often combined with utilization of the excess heat. This widens up the opportunities to utilize biogas in distant energy consumption locations. The most common methods for biogas upgrading include water washing, pressure swing adsorption, polyglycol adsorption, and chemical treatment, which are performed outside the anaerobic reactor and require investments in
Thin films of SnO2: Pd have been deposited on glass substrate at 450 0 C using an alcoholic precu... more Thin films of SnO2: Pd have been deposited on glass substrate at 450 0 C using an alcoholic precursor solution consisting of Tin (IV) Chloride (SnCl4.5H2O) and Palladium Chloride (PdCl2). The influence of increasing Pd concentration on the electrical and optical properties has been investigated. The minimum resistivity of Ωcm for 3.68at% Pd film was obtained. The optical properties were studied in the UV/VIS/NIR region. The optical band gap for undoped SnO2 films lies at 3.93 eV and Palladium doped films lay in the range 3.86 - 3.99 eV. Using dispersion analysis with Drude and Kim terms, optical constants were determined from spectro-photometric measurements for films on glass. The film thickness was determined through analysis using the SCOUT software to be in the range 140 - 223 nm. Key wrods:
Thin films of SnO2: Pd have been deposited on glass substrate at 450C using an alcoholic precurso... more Thin films of SnO2: Pd have been deposited on glass substrate at 450C using an alcoholic precursor solution consisting of Tin (IV) Chloride (SnCl4.5H2O) and Palladium Chloride (PdCl2). The influence of increasing Pd concentration on the electrical and optical properties has been investigated. The minimum resistivity of Ωcm for 3.68at% Pd film was obtained. The optical properties were studied in the UV/VIS/NIR region. The optical band gap for undoped SnO2 films lies at 3.93 eV and Palladium doped films lay in the range 3.86 – 3.99 eV. Using dispersion analysis with Drude and Kim terms, optical constants were determined from spectro-photometric measurements for films on glass. The film thickness was determined through analysis using the SCOUT software to be in the range 140 – 223 nm.
Japanese Journal of Applied Physics, 2013
Prussian blue analogues with jungle-gym-type structure are promising candidates for cathode mater... more Prussian blue analogues with jungle-gym-type structure are promising candidates for cathode materials of the lithium-ion secondary battery (LIB). Here, we investigated the structural, electronic, and electrochemical properties of cobalt hexacyanoferrate, Li x Co[Fe(CN)6]0.902.9H2O, against Li concentration (x). The capacity (= 139 mAh/g) of the thin-film electrode was close to the ideal value (= 132 mAh/g) for the two-electron reaction. The discharge curve exhibits three plateaus, i.e., plateaus I, II, and III. The material exhibits a first-order phase transition accompanied by significant volume expansion by 7% at the boundary between plateaus II and III. Ex situ X-ray absorption spectroscopy (XAS) indicates that the discharge processes of plateaus I, II, and III are ascribed to the reduction processes of Fe3+, Co3+, and Fe3+, respectively. The rate (r) and cycle (n) dependence of the electrode performance will be discussed in terms of the reduction processes.
Transparent Pb(Zn 1/3 Nb 2/3)O 3-(Pb 1-x La x)(Zr 1-y Ti y)O 3 (PZN-PLZT) ferroelectric ceramics ... more Transparent Pb(Zn 1/3 Nb 2/3)O 3-(Pb 1-x La x)(Zr 1-y Ti y)O 3 (PZN-PLZT) ferroelectric ceramics have successfully been prepared by hot-pressed sintering in oxygen atmosphere. Uniform cylindrical samples with diameter as large as ס 50 mm can readily be obtained. X-ray analysis and scanning electron microscopy experiments showed a pure perovskite phase, thin grain boundaries, and uniform dense microstructures. Very good transparency was reached for wavelength from near ultraviolet to infrared. The dielectric constant was also measured as a function of temperature and frequency. Some novel phenomena such as good piezoelectric and electro-optical properties have been observed.
Physical Science International Journal, 2019
This paper investigates the outdoor performance of a 20 W monocrystalline silicon solar module in... more This paper investigates the outdoor performance of a 20 W monocrystalline silicon solar module in relation to air mass (AM) in Kakamega. Direct measurement of air mass and module output parameters from experimental setup was done in Kakamega at a location 0.28270 N and 34.7519 E. Experimental results showed a decrease in ISC and VOC with increasing AM. The maximum output power produced by the module reduced with an increase in AM. Maximum power was therefore seen to be produced at noon in this region. VOC increased from 19.47 to 20.04 then decreased to 19.49 V while ISC increased from 0.36 to 1.19 then decreased to 0.48A. It was observed that both the FF and of a monocrystalline solar module increase with increase in air mass. The module performed better during the afternoon than morning and evening hours with the peak performance observed close to AM 1.
Physical Science International Journal, 2018
Solar energy can be harnessed as photovoltaic energy or solar thermal. Photovoltaic modules provi... more Solar energy can be harnessed as photovoltaic energy or solar thermal. Photovoltaic modules provide safe, reliable, and maintenance-free, without noise and environmentally friendly source of power This paper evaluates the outdoor performance of a monocrystalline silicon module based on irradiance and temperature in Kakamega region. The outdoor performance characterisation of a 20 W mono-crystalline silicon module was investigated under different values of solar irradiance and module surface temperature in Kakamega, Kenya. Short circuit current of the module increased significantly with increasing irradiance while open circuit voltage was least affected. Both fill factor and efficiency showed a similar trend with irradiance, increasing slightly and then reducing. The response variables; fill factor, efficiency, open circuit voltage and maximum power were found to reduce with increase in surface temperature while short circuit current increased slightly. The average efficiency, fill factor, short circuit current and open circuit voltage for the module was found to be 10.11%, 0.65, 0.65A, and 19.78V respectively. Maximum Voltage, maximum current and maximum power were found to be 16.78V, 0.48A and 8.11W respectively. A good knowledge of the power output of a solar module and how it varies with solar irradiance and temperature would give accurate information which is vital in sizing and design of photovoltaic system.
The European Physical Journal Applied Physics, 2013
ABSTRACT CoxTi1-xO2 films were deposited by spray pyrolysis technique on Si(1 0 0) substrates at ... more ABSTRACT CoxTi1-xO2 films were deposited by spray pyrolysis technique on Si(1 0 0) substrates at 475 °C. A hydro-alcoholic solution containing titanium (iv) isopropoxide and Co(NO3)2 with various Co doping levels from x = 0-0.015 in solution was used as spray solution. Grazing incident angle of X-ray diffraction illustrates that the CoxTi1-xO2 films are single phase and polycrystal with mixed orientations. Study of surface morphology of the films by atomic force microscope reveals that the annealing atmosphere does not significantly affect the grain size and the microstructure of the films. This study provides further insight into the importance of annealing atmosphere on magnetization of the films. Room temperature magneto-optical Kerr measurement was employed in polar mode. A hysteresis loop and a paramagnetic behavior have been recorded for samples annealed in H2 ambient gas and air, respectively. Chemical composition analysis by X-ray photo-electron spectroscopy showed that Co atoms are bounded to oxygen and no metallic clusters are present. Moreover, it indicates the formation of high spin Co2+ for the sample x = 0.008 annealed in H2 ambient gas. The origin of magnetization can be attributed to the contribution of oxygen vacancies in the spin polarization of the structure.
Alloys
Al–Mg–Si alloys are used in aircraft, train, and car manufacturing industries due to their advant... more Al–Mg–Si alloys are used in aircraft, train, and car manufacturing industries due to their advantages, which include non-corrosivity, low density, relatively low cost, high thermal and electrical conductivity, formability, and weldability. This study investigates the bulk mechanical properties of Al–Mg–Si alloys and the influence of the Si/Mg ratio on these properties. The Al cell was used as the starting structure, and then nine structures were modeled with varying percentages of aluminium, magnesium, and silicon. Elastic constant calculations were conducted using the stress–strain method as implemented in the quantum espresso code. This study found that the optimum properties obtained were a density of 2.762 g/cm3, a bulk modulus of 83.3 GPa, a shear modulus of 34.4 GPa, a Vickers hardness of 2.79 GPa, a Poisson’s ratio of 0.413, a Pugh’s ratio of 5.42, and a yield strength of 8.38 GPa. The optimum Si/Mg ratio was found to be 4.5 for most of the mechanical properties. The study su...
HAL (Le Centre pour la Communication Scientifique Directe), Apr 25, 2022
Case Studies in Construction Materials
Energy Procedia, 2016
Electronic structure theory has recently been used to propose hypothetical compounds in presumed ... more Electronic structure theory has recently been used to propose hypothetical compounds in presumed crystal structures, seeking new useful functional materials. The functional materials include transparent conductors needed in solar cell, light emitting diode and flat panel displays, which represent the usually contraindicated functionalities of optical transparency (generally associated with electrical insulators) coexisting with electrical conductivity (generally associated with optically opaque metals). Usually, such hypothetical materials are meta-stable, albeit with technologically useful long lifetimes. Yet, in other cases, suggested hypothetical compounds may be significantly higher in energy than their lowest-energy crystal structures or competing phases, making their synthesis and eventual device-stability questionable. Shifting focus from the previous searches of doping wide-gap metal oxides turns our focus to the newly predicted never before synthesized ABX compounds of TiIrSb, TaIrSn and ZrIrSb called "filled tetrahedral structure" (sometimes called Half-Heusler). We give interest to these compounds because; there stability range is located around X-richest and A/B-poor growth. The 'inverse design' principles are applied to ABX compounds. Then the effect of atomic number in their materials to tolerance of sufficient level of off-stoichiometry in creation of free holes that avoid the ionic sites and thus lead to high hole mobility at room temperature.
Proceedings of ISES World Congress 2007 (Vol. I – Vol. V), 2008
A simple model developed at Uppsala University was used to estimate the energy balance of uncoate... more A simple model developed at Uppsala University was used to estimate the energy balance of uncoated single and double glazed windows, a low-e double glazed window and a solar control double glazed window using climate data for the city of Hefei, China. The results show that the reduction of heat losses through the window in February can be as much as 87% for a north orientation by using a low-e window, and the reduction of cooling load in August can be 66–68% in all four orientations by using a solar control window. Estimation is also carried out for non-insulated and well-insulated walls. It shows the energy reduction for heating and cooling by using an insulated wall can be of the order of 75% both in February and August, respectively.
American Journal of Materials Science, 2013
F-co-doped Palladiu m Tin Oxide (PTO) thin films were pyrolytically deposited on glass substrate ... more F-co-doped Palladiu m Tin Oxide (PTO) thin films were pyrolytically deposited on glass substrate at 450 0 C using an alcoholic precursor solution consisting of Tin (IV) Chloride (SnCl 4 .5H 2 O), Palladiu m Ch loride (Pd Cl 2) and Ammoniu m Fluoride (NH 4 F). A resistivity of 0.3-6.9×10-2 Ωcm was obtained in F-co-doped PTO films prepared with a Pd content of 3.68at% and F content of 0-23.96at% under optimized conditions. The optical properties were studied in the UV/ VIS/ NIR region. The optical bandgap of the films laid in the range 3.945-4.014 eV. Using dispersion analysis with Drude and Kim terms, optical constants were determined fro m spectro-photometric measurements for films on glass.
Solid State Communications
Physical Science International Journal, 2018
Anaerobic digestion is an effective method for organic pollution reduction and bio-energy product... more Anaerobic digestion is an effective method for organic pollution reduction and bio-energy production and has increasing applications worldwide. Produced biogas consists mainly of 50-70% methane (CH 4) and 30-50% carbon dioxide (CO 2). The most common utilization route of biogas is for electricity production, often combined with utilization of the excess heat. This widens up the opportunities to utilize biogas in distant energy consumption locations. The most common methods for biogas upgrading include water washing, pressure swing adsorption, polyglycol adsorption, and chemical treatment, which are performed outside the anaerobic reactor and require investments in
Thin films of SnO2: Pd have been deposited on glass substrate at 450 0 C using an alcoholic precu... more Thin films of SnO2: Pd have been deposited on glass substrate at 450 0 C using an alcoholic precursor solution consisting of Tin (IV) Chloride (SnCl4.5H2O) and Palladium Chloride (PdCl2). The influence of increasing Pd concentration on the electrical and optical properties has been investigated. The minimum resistivity of Ωcm for 3.68at% Pd film was obtained. The optical properties were studied in the UV/VIS/NIR region. The optical band gap for undoped SnO2 films lies at 3.93 eV and Palladium doped films lay in the range 3.86 - 3.99 eV. Using dispersion analysis with Drude and Kim terms, optical constants were determined from spectro-photometric measurements for films on glass. The film thickness was determined through analysis using the SCOUT software to be in the range 140 - 223 nm. Key wrods:
Thin films of SnO2: Pd have been deposited on glass substrate at 450C using an alcoholic precurso... more Thin films of SnO2: Pd have been deposited on glass substrate at 450C using an alcoholic precursor solution consisting of Tin (IV) Chloride (SnCl4.5H2O) and Palladium Chloride (PdCl2). The influence of increasing Pd concentration on the electrical and optical properties has been investigated. The minimum resistivity of Ωcm for 3.68at% Pd film was obtained. The optical properties were studied in the UV/VIS/NIR region. The optical band gap for undoped SnO2 films lies at 3.93 eV and Palladium doped films lay in the range 3.86 – 3.99 eV. Using dispersion analysis with Drude and Kim terms, optical constants were determined from spectro-photometric measurements for films on glass. The film thickness was determined through analysis using the SCOUT software to be in the range 140 – 223 nm.