Browsing by Author "Ndiritu, Francis Gichuki"

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    Characterization of rice husk ash prepared by open air burning and furnace calcination
    (Academic Journals, 2020) Kaleli, Mbinda Jonathan; Kamweru, Paul Kuria; Ndiritu, Francis Gichuki
    Rice husk (RH) is an agricultural waste, and easily available in rice growing areas. The husk is mostly burnt as a way of getting rid of it. The ash obtained after burning or calcination may have economic application, mainly dependent on its properties. These properties in turn depend on the calcination method. However, for commercial viability, and for many applications, the calcination method should not only be as simple as possible but also cheap. This study characterized the elemental composition, crystallinity, functional bonds present and morphology of rice husk ash (RHA) obtained in two ways, that is, calcination of rice husks in a muffle furnace (FRHA) at a temperature of 700°C and open air burning (ORHA) at uncontrolled temperatures. The elemental composition done by Atomic Absorption Spectroscopy showed a high percentage of silicon that is 81.01 and 79.12% for ORHA and FRHA, respectively. X-ray fluorescence showed a high percentage of silica (SiO2), 95.45 and 94.85% for ORHA and FRHA, respectively. X-ray diffractograms indicate that the FRHA was crystalline with the highest peak at 21.8°; while ORHA was amorphous in nature. Fourier Transform Infra-Red spectra confirmed the presence of –OH groups and O-Si-O bonds in the two types of ash. Scanning electron microscopy analysis showed agglomerated ORHA, which may be due to the presence of hydrogen bonding between silanol groups on the surface of rice husk ash for FRHA, and presence of –OH groups in ORHA. The study shows that ORHA is as good as FRHA in applications where crystallinity is optional.
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    Characterization of rice husk ash prepared by open air burning and furnace calcination
    (Academic Journals, 2020) Kaleli, Mbinda Jonathan; Kamweru, Paul Kuria; Gichumbi, Joel Mwangi; Ndiritu, Francis Gichuki
    Rice husk (RH) is an agricultural waste, and easily available in rice growing areas. The husk is mostly burnt as a way of getting rid of it. The ash obtained after burning or calcination may have economic application, mainly dependent on its properties. These properties in turn depend on the calcination method. However, for commercial viability, and for many applications, the calcination method should not only be as simple as possible but also cheap. This study characterized the elemental composition, crystallinity, functional bonds present and morphology of rice husk ash (RHA) obtained in two ways, that is, calcination of rice husks in a muffle furnace (FRHA) at a temperature of 700°C and open air burning (ORHA) at uncontrolled temperatures. The elemental composition done by Atomic Absorption Spectroscopy showed a high percentage of silicon that is 81.01 and 79.12% for ORHA and FRHA, respectively. X-ray fluorescence showed a high percentage of silica (SiO2), 95.45 and 94.85% for ORHA and FRHA, respectively. X-ray diffractograms indicate that the FRHA was crystalline with the highest peak at 21.8°; while ORHA was amorphous in nature. Fourier Transform Infra-Red spectra confirmed the presence of –OH groups and O-Si-O bonds in the two types of ash. Scanning electron microscopy analysis showed agglomerated ORHA, which may be due to the presence of hydrogen bonding between silanol groups on the surface of rice husk ash for FRHA, and presence of –OH groups in ORHA. The study shows that ORHA is as good as FRHA in applications where crystallinity is optional.
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    Surface potential, fermi level and band gap energy of copper doped magnesium nickel ferrite nanoparticles
    (Sami Publishing Compan, 2020) Osamong, Gideon; Kamweru, Paul Kuria; Gichumbi, Joel Mwangi; Ndiritu, Francis Gichuki
    Optical, electrical, and electronic properties of materials are essential in the fabrication of electronic devices. These properties can be improved through doping and reduction of the size of a material to nanoscale. In this study, copper doped magnesium-nickel (CuxMg1-xNiFe2O4, for x=0.00, 0.15, 0.30, 0.45, 0.60, 0.75, 1.00) ferrite nanoparticles were synthesized using the citragel auto combustion method. The electronic and optical properties were evaluated using the scanning Kelvin probe microscopy (SKPM) and UVvisible, respectively. The UV-visible studies revealed that, the band gap energy was at the range of 3.600-3.750 eV. The band gap was noted to increase with copper content up to x=0.45 which then started to decrease. The undoped sample displayed the lowest band gap energy in comparison with the doped. SKPM analysis exhibited the surface potential in the range 4.361-5.002 eV for the area scan and 4.251-5.006 eV for the line scans for the samples. The sample with x=0.75 showed a positive work function for both area and line scans, and all the others had a negative work function. The doped ferrite exhibited the properties that could be applied in optical devices, storage devices, and recording devices. © 2021 by SPC (Sami Publishing Company), Asian Journal of Nanoscience and Materials, Reproduction is permitted for noncommercial purposes