Nonlinear Modulation of Wave Propagation in Spherical Shell Model and Modified Zhang Model Using Free Space Model as a Bench-Mark

This paper presents nonlinear modulation of wave propagation in spherical shell model (SSM) and modified Zhang model (MZM) using free space model (FSM) as a bench-mark. A typical non-linearity is the change in the dielectric constant due to electromagnetic (EM) wave field that propagates through a medium. By modulation, we mean the characteristic departure of EM waves’ propagation in both media as opposed to the free space propagation. Maxwell’s equations were used to derive the basic equation that govern the propagation of electromagnetic waves in nonlinear media. The equations of the models were found to be nonlinear and their solution were obtained numerically using Runge-Kutta scheme implemented in Matlab software. The spatial EM wave profile graphic displays were supplemented by the symmetric spatial Fast Fourier Transform (FFT) analysis. The symmetric implementation of the FFT meant that the actual number of modes present in any solution was half the number of observed spikes. The free space model (FSM) showed periodic propagation for all frequencies ( examined corresponding to a wavenumber per frequency. The result only serves to give some level of confidence that the algorithm performed well. The MZM supports a variety of characteristics. There are amplitude amplifications or wave steeping, lossless or solitary propagation and multiplicity of modes for all frequencies examined. However, at the fundamental frequency , the SSM is capable of exhibiting amplitude amplification without attenuation. The EM wave propagation characteristics of the MZM and SSP showed that materials which could be fabricated according to this model would be very useful as EM wave guides as they could support waves without losses as opposed to the present known commercial optical fibers. Keywords: Nonlinear modulation, Wave propagation, Spatial Electromagnetic wave

Physiochemical properties of mixed twin clay deposits in Awgbu used for pottery and possible structural applications

The practice of mixing Asha clay and Ajagworo clay deposit at Ngene-Agu site in the ratio of 3:1 by Awgbu women for pottery business is investigated. Physical (Atterberg limits) properties, elemental content, compressive strength, water absorption and characterization for individual and mixed clays were carried out. The result obtained shows that between 700 0C and 1100 0C, the compressive strength of Asha clay and Ajagworo clay derived burnt bricks did not individually meet the Nigeria specifications for structural development, while that of the mixed clay derived burnt bricks satisfied the minimum strength requirement of ∙ / at 1000 0C and above. The result also showed that the mixed clay derived burnt bricks has the least values for porosity of ∙ and water absorption at varying temperatures. This has proved that the practice by Awgbu women of mixing Asha and Ajagworo in the ratio of 3:1 raised the compressive strength to ∙ / and lowered the water absorption to a minimum value of ∙ %. This work has shown that the Awgbu mixed clay can be used for structural development in Anambara State and Nigeria.Keywords: Awgbu mixed clay, Compressive strength, Water Absorption, Porosity and Structural developmen

Photoluminescences analysis of CMC-SrAl2O4:Eu3+ nanoparticles at different excitation wavelengths

Photoluminescence characteristics of Sodium Carboxyl Methyl Cellulose (CMC) capped Europium doped Strontium Aluminate nanoparticles at 1000OC using direct chemical combustion techniques is reported. The impact of CMC (-CH2-COOH) as a capping agent on the optical, structural morphology and photoluminescence properties of SrAl2O4:Eu3+ at different excitation wavelength revealed that the obtained structures were monoclinic with the crystal sizes of 39.35nm, and 37.72nm; energy band gap were 4.94eV and 5.02eV for the uncapped and capped phosphor respectively. The Scanning Electron Micrograph shows that the particles were agglomerated and well passivized; Photoluminescence emission broad band was observed with the capped phosphor between 626nm-697nm and uncapped phosphor between 611nm-690nm and visible peak at 694nm (Orange – Red colour). The intensity of the capped phosphor was found to be lower causing luminescence degradation

Effect of substrate temperature on the structural optical and electrical properties of new Cu2Cd0.8Mn0.2SnS4 photo-absorber layer for solar cells

We report for the first time the effect of substrate temperature on the structural, optical, and electrical properties of Cu2Cd0.8Mn0.2SnS4 new photovoltaic absorber layer. Cu2Cd0.8Mn0.2SnS4 thin films were deposited on soda lime glass (SLG) substrates by the spray pyrolysis method at different substrate temperatures. X-ray diffraction measurement revealed the formation of cernyite structure by Cu2Cd0.8Mn0.2SnS4 thin film. Also, an increase in crystal size from 7.23 to 14.35 nm and crystallinity improvement of Cu2Cd0.8Mn0.2SnS4 thin film with an increase in substrate temperature were achieved. The atomic force microscopy indicated an increase in surface roughness with substrate temperature. The elemental composition of the Cu2Cd0.8Mn0.2SnS4 thin films showed Cu-poor, S-poor, and Sn-poor conditions. The optical characterization showed that the absorption coefficient of Cu2Cd0.8Mn0.2SnS4 is in the order of 104 cm−1 and the bandgap decreased from 1.89 to 1.87 eV with an increase in substrate temperature. The refractive index dispersion parameters were discussed in terms of the Wemple-Didomenico and Sellmeier equations. Hall effect measurement indicated that the Cu2Cd0.8Mn0.2SnS4 films exhibit P-type conductivity. High hole mobility and the highest conductivity of 2.77 x104 cm2/Vs and 5.60 (Ω.cm)-1 respectively, were achieved at 400 °C substrate temperature. The Cu2Cd0.8Mn0.2SnS4 deposited at 400 °C is a potential candidate for use as a top absorber layer in the tandem solar cell

Improved liquid phase exfoliation technique for the fabrication of MoS2/graphene heterostructure-based photodetector

2D nanosheets produced using liquid phase exfoliation method offers scalable and cost effective routes to optoelectronics devices. But this technique sometimes yields high defect, low stability, and compromised electronic properties. In this work, we employed an innovative approach that improved the existing liquid phase exfoliation method for fabricating MoS2/graphene heterostructure-based photodetector with enhanced optoelectronic properties. This technique involves hydrothermally treating MoS2 before dispersing it in a carefully chosen and environmentally friendly IPA/water solvent for ultrasonication exfoliation through an optomechanical approach. Thereafter, heterostructure nanosheets of MoS2 and graphene were formed through sequential deposition technique for the fabrication of vertical heterojunctions. Furthermore, we achieved a vertically stacked MoS2/graphene photodetector and a bare MoS2 photodetector. The MoS2/graphene hybrid nanosheets were characterized using spectroscopic and microscopic techniques. The results obtained show the size of the nanosheets is between 350 and 500 nm on average, and their thickness is less than or equal to 5 nm, and high crystallinity in the 2H semiconducting phase. The photocurrent, photoresponsivity, external quantum efficiency (EQE), and specific detectivity of MoS2/graphene heterostructure at 4 V bias voltage and 650 nm illumination wavelength were 3.55 μA, 39.44 mA/W, 7.54 %, and 2.02 × 1010 Jones, respectively, and that of MoS2 photodetector are 0.55 μA, 6.11 mA/W, 1.16 %, and 3.4 × 109 Jones. The results presented indicate that the photoresponse performances of the as-prepared MoS2/graphene were greatly improved (about 7-fold) compared to the photoresponse of the sole MoS2. Again, the MoS2/graphene heterostructure fabricated in this work show better optoelectronic characteristics as compared to the similar heterostructure prepared using the conventional solution processed method. The results provide a modest, inexpensive, and efficient method to fabricate heterojunctions with improved optoelectronic performance