Department of Physics & Materials Science: Recent submissions
Now showing items 61-80 of 164
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Evaluating the effect of the substrate on the electrocatalytic performance of Cu2ZnSnS4 and Cu2ZnSnSe4 counter electrodes in dye-sensitized solar cells
(Elsevier, 2022)The colloidal synthesis of Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) nanoparticles and their application as counter electrodes in dye-sensitized solar cells (DSSCs). In particular, the effect of three substrates namely; ... -
Microstructural and elastic properties of stable aluminium-rich TiAl and TiAl2 formed phase Intermetallics
(North-Holland, 2021)We studied aluminium-rich Ti-Al (Ti32Al68 and Ti40Al60) binary alloys that were composed of TiAl and TiAl2 lamellar microstructures. The law of mixtures was employed in calculating the theoretical Young’s moduli. The ... -
Optical properties and Raman studies of amorphous se-bi thin films
(The African Review of Physics, 2014)Flash evaporated amorphous Se Bi (x = 0, 1, 2, 3, and 4 at. %) thin films of 350 ± 10 thickness have been investigated in the wavelength range of 200nm − 3000nm. It is found that the effect of increasing bismuth content ... -
Investigation of the effect of film thickness on the optical properties of amorphous Se85-xte15sbx thin films
(Africa Journal of Physical Sciences, 2014)Amorphous thin films of Se85-xTe15Sbx (x = 0.0, 0.5, 2.5, and 5.0 at. %) deposited by flash evaporation technique, have been investigated in the wavelength range of 500nm-3000nm. It is found that the effect of increasing ... -
Compositional and Thickness Effects on the Optical Properties of Zinc– Doped Selenium–Antimony Thin Films
(AJOL, 2018)Chalcogenide system of antimony (Sb)-selenium (Se)-zinc (Zn) system is a promising semiconductor for phase change memory devices due to its thermal stability and low power consumption. The study investigated the effect ... -
Investigation of long acoustic waveguides for the very low frequency characterization of monolayer and stratified air-saturated poroelastic materials
(Elsevier, 2021)When sound propagates in a porous medium, it is attenuated via several energy loss mechanisms which are switched on or off as the excitation frequency varies. The classical way of measuring acoustic energy loss in porous ... -
Microstructural and Elastic Properties of Stable Aluminium-rich TiAl and TiAl2 Formed Phase Intermetallics
(North-Holland, 2021)We studied aluminium-rich Ti-Al (Ti32Al68 and Ti40Al60) binary alloys that were composed of TiAl and TiAl2 lamellar microstructures. The law of mixtures was employed in calculating the theoretical Young’s moduli. The lattice ... -
Kenya’s response to the COVID-19 pandemic: a balance between minimising morbidity and adverse economic impact
(African Academy of Sciences, 2021)Coronavirus disease 2019 (COVID-19) has ravaged the world’s socioeconomic systems forcing many governments across the globe to implement unprecedented stringent mitigation measures to restrain its rapid spread and adverse ... -
Kenya-Ethiopia Relations: a Study of the Significance of Economic and Political Factors Contributing to Co-operation, 1963-1991
(Nairobi university, 2005)This thesis analyses and explains the nature of inter-state relations between Kenya and Ethiopia. An analysis of the two countries' relations shows that despite change of leadership in both Kenya and Ethiopia and despite ... -
Analysis of Loss Ratios Using a Mixed Linear Model
(University of Nairobi, 2008)Loss ratios have been employed by a broad range of users for diverse purposes. Insurance companies, regulators, investors, rating agencies, investment analysts, lenders and others have used the loss ratio for their particular ... -
Quiet Time Geomagnetic Field Variations in the Equatorial East African Region During the Inclining Phase of Solar Cycle 24
(Science Publishing Group, 2014)In the present paper, geomagnetic field data obtained from magnetometer measurements at two ground based stations have been used to study solar activity dependence of the solar quiet variations. The study has focused on ... -
A study of the Equatorial Ionosphere over Nairobi During selected magnetically disturbed and quiet times for the year 2009 Using co-located instruments
(IJARPS, 2014)Investigation of the behavior of the Equatorial Ionosphere over Nairobi-Kenya within the East Africa region is done using co-located instruments, that is, SCINDA-GPS system and a Magnetometer ( MAGDAS). This was done for ... -
Quiet Time Correlation Between Geomagnetic Field Variations and the Dynamics of the East African Equatorial Ionosphere
(Science Publishing Group, 2017)The equatorial ionosphere is highly dynamic and consequently poses serious threats to communication and navigation systems. As a result, proper understanding of ionospheric dynamics is important. The present paper presents ... -
Total electron content and scintillations over Maseno, Kenya, during high solar activity year
(Springer International Publishing, 2019)Proper characterization of total electron content (TEC) and scintillation is very important to global positioning system (GPS) users in communication, navigation, ionospheric or atmospheric studies. Quiet time variation ... -
Variability of VTEC Gradient and TEC Rate Index Over Kisumu, Kenya During Selected Quiet and Storm Days of 2013 and 2014
(Science Publishing Group, 2019)Vertical Total electron content (VTEC) gradient or rate of change of TEC (ROT) and total electron content (TEC) rate index or rate of change of TEC index (ROTI) can directly be estimated from receiver independent exchange ... -
: Spray Pyrolysis Technique (SPT) was used to deposit thin films (TFs) of cadmium stannate, doped with iron (Fe) for the first time. The precursor solutions that were used wereprepared at a concentration of 0.1M, doped with Feand then sprayed onto the pre-heated glass slides immediately at deposition temperatures of 350 ± 7°C, 400 ± 7°C and 450 ± 7°C. The optical properties of the deposited Fe-doped TFs were studied in the wavelength range of 300-1100nm. The X-Ray diffraction (XRD) studies showed that the TFs were orthorhombic with growth orientation along the (2 0 0) direction. Film thickness of 85 ± 10 nm was obtained. It was found out that anincrease in the deposition temperature increased transmittance and band gap, but decreased absorption coefficient, extinction coefficient and refractive index, which was attributed to the improvement in crystallinity of the deposited TFs. Doping reduced transmittance and band gap, but increased refractive index, absorption coefficient and extinction coefficient, which was attributed to the increase in free carriers. KEYWORDS:cadmium stannate, deposition temperature, iron-doped, optical properties of cadmium stannate
(Elsevier, 2020)The elastic properties of the orthorhombic cadmium stannate (Cd2SnO4) were investigated using density functional theory, applying both energy-strain relationship (which is found in the literature) and stress-strain ... -
Effect Of Deposition Temperature On The optical Properties Of Iron-Doped Cadmium Stannate Thin Films Deposited By Spray Pyrolysis
(IJSTRE, 2019): Spray Pyrolysis Technique (SPT) was used to deposit thin films (TFs) of cadmium stannate, doped with iron (Fe) for the first time. The precursor solutions that were used wereprepared at a concentration of 0.1M, doped ... -
Ab initio study of the structural, vibrational and thermal properties of Ge2Sb2Te5
(Imperial College Press, 2015-06-12)The structural, vibrational and thermal properties of hexagonal as well as cubic Ge2Sb2Te5 (GST) have been calculated from first principles. The relative stability of the possible stacking sequences of hexagonal GST has ... -
Nitrogen Doping of Hexagonal and Cubic Ge2Sb2Te5Nanocrystals: An Ab Initio Study
(World Scientific Publishing Company, 2018-12-17)The effect of nitrogen doping on the structural, electronic and optical properties of hexagonal and cubic Ge2Sb2Te5 (GST) has been investigated from first principles. The nitrogen content was set to 10 at.% and 25 at.%, ...
