Umar Aliyu | UPM - Universiti Putra Malaysia (original) (raw)

Papers by Umar Aliyu

Materials Chemistry and Physics, Dec 1, 2022

Polymers, Aug 26, 2020

This article describes attenuation and absorption measurements using the microstrip transmission ... more This article describes attenuation and absorption measurements using the microstrip transmission line technique connected with a microwave vector network analyzer (Agilent 8750B). The magnitudes of the reflection (S 11) and transmission (S 21) coefficients obtained from the microstrip transmission line were used to determine the attenuation and absorption of oil palm empty fruit bunch/polylactic acid (OPEFB/PLA) composites in a frequency range between 0.20 GHz and 12 GHz at room temperature. The main structure of semi-flexible substrates (OPEFF/PLA) was fabricated using different fiber loading content extracted from oil palm empty fruit bunch (OPEFB) trees hosted in polylactic acid (PLA) using the Brabender blending machine, which ensured mixture homogeneity. The commercial software package, Computer Simulation Technology Microwave Studio (CSTMWS), was used to investigate the microstrip line technique performance by simulating and determine the S 11 and S 21 for microwave substrate materials. Results showed that the materials' transmission, reflection, attenuation, and absorption properties could be controlled by changing the percentage of OPEFB filler in the composites. The highest absorption loss was calculated for the highest percentage of filler (70%) OPEFB at 12 GHz to be 0.763 dB, while the lowest absorption loss was calculated for the lowest percentage of filler 30% OPEFB at 12 GHz to be 0.407 dB. Finally, the simulated and measured results were in excellent agreement, but the environmental conditions slightly altered the results. From the results it is observed that the value of the dielectric constant (ε r) and loss factor (ε r) is higher for the OPEFB/PLA composites with a higher content of OPEFB filler. The dielectric constant increased from 2.746 dB to 3.486 dB, while the loss factor increased from 0.090 dB to 0.5941 dB at the highest percentage of 70% OPEFB filler. The dielectric properties obtained from the open-ended coaxial probe were required as input to FEM to calculate the S 11 and S 21 of the samples.

Materials Chemistry and Physics

Journal of the Nigerian Society of Physical Sciences

The analysis of the field strength variability using the meteorological parameters (temperature, ... more The analysis of the field strength variability using the meteorological parameters (temperature, pressure and relative humidity) retrieved from the archive of National Aeronautical and Space Administration (NASA) was conducted for 61 locations between 2016 and 2020 to check for the spatial and seasonal variation. The result shows a seasonal variation with higher field strength variability during the dry season and lower field strength variability during the wet season. The spatial variation shows a significant difference between stations in the drier locations up north and those in the coastal areas. This could be attributed to the moisture contents of the atmosphere. Further analysis of the Inter-Tropical Discontinuity (ITD) position during the study period has confirmed this assertion where we discovered the northward movement of the ITD brings along with it more moisture and consequently a weak field strength. The variation in the high grounds is not manifesting because of the fa...

$Research paper thumbnail of Spatial and Seasonal Estimation of Tropospheric Radio Refractivity in Nigeria$

African Scientific Reports

The spatial and seasonal variation of tropospheric radio refractivity of Nigeria has been studied... more The spatial and seasonal variation of tropospheric radio refractivity of Nigeria has been studied using meteorological variables (temperature, relative humidity and pressure) retrieved from the archive of the United States’ National Aeronautics for Space Administration (NASA). This work established a seasonal variation. The results also revealed an increase in radio refractivity from minimum of about 270N-units at Abadam to maximum of about 415N-units at Warri. The variation of radio refractivity is synchronous with rainfall in most of the stations especially those in the Guinea Savannah, Tropical Rainforest and Coastal areas where the effects of august break manifest vividly on the curves. Intense refractivity was measured mostly in the tropical rainforest and coastal areas. This could be attributed to the intensity of rain and the length of the wet season in those locations. The Sahel, Sudan and Guinea savannah which experience less rain with short period of wet season recorded re...

Journal of Materials Science: Materials in Electronics

ASEANA, Mar 15, 2021

Locally mined salts that are sourced from rock and soils constitutes natural radionuclides of ura... more Locally mined salts that are sourced from rock and soils constitutes natural radionuclides of uranium (238U) and thorium (232Th) series, and the potassium (40K) radioactive isotope at a varying amounts. A total of 10 soil samples from different site of locally mined salt were collected and analysed using gamma ray spectrometer in order to determine the activity concentrations of the natural radionuclides. The mean activity concentrations determined for K-40, U -238, Th-232 were 1324.27 ± 68.91 Bq/kg, 147.43 ± 17.21 Bq/kg, 60.03 ± 3.56 Bq/kg which is above the worldwide weighted mean of 420 Bq/kg, 45 Bq/kg and 33 Bq/kg respectively, with the mean radium equivalent activity of 335.23 ± 27.61 Bq/kg which is below the upper limit of 370 Bq/kg, the external hazard index, the internal hazard index, the absorbed dose rate and the effective dose rate, Activity utilization index and Representative level index in the salt soil were evaluated. The results showed high gamma radiation absorbed dose and radiation hazard index, which does not present a better indications for human health in the study area.

Journal of the Nigerian Society of Physical Sciences, 2022

Elastic moduli of {[(TeO2)0.7 (B2O3)0.3]0.8 (SiO2)0.2}1-y (Er2O3 NPs)y glasses with y = 0.01, 0.... more Elastic moduli of {[(TeO2)0.7 (B2O3)0.3]0.8 (SiO2)0.2}1-y (Er2O3 NPs)y glasses with y = 0.01, 0.02, 0.03, 0.04, 0.05 were studied in this work using the theoretical elastic models. The Makishima & Mackenzie, Rocherulle and bond compression models were employed for the study. In the Makishima and Mackenzie model, the packing density was calculated from the bulk glass molar weight and the bulk glass density whereas in Rocherulle model it is determined as the individual oxides. Young, shear and bulk moduli as well as the Poisson ratio were calculated for the glasses in the Makishima and Rocherulle models, while longitudinal, was calculated in addition to young, bulk and shear moduli using the bond compression model. Bond per unit volume number (nb), bulk modulus, bulk modulus ratio (Kbc/Ke), atomic ring size (?) and stretching force constant were also calculated and presented. The values of the Young, bulk and shear moduli obtained from Makishima model increased from 52.854 to 55.335 ...

Journal of Science and Mathematics Letters, 2018

From the agricultural waste of rice (rice husk), high purity SiO2 with about 98.548 % purity was ... more From the agricultural waste of rice (rice husk), high purity SiO2 with about 98.548 % purity was extracted using a very simple room temperature leaching method. Using the rice husk extracted silicate, a system of silicate borotellurite glasses was fabricated with composition equation [(TeO2)0.7 (B2O3)0.3]1-x (SiO2)x with x= 0.0, 0.1, 0.2, 0.3 and 0.4. The density and molar volume were measured, and Fourier transform infrared (FTIR), X-ray diffraction (XRD) and UV-Vis analyses were performed on the glasses. Both the density and molar volume decreased and the XRD pattern confirmed the glasses' amorphous nature. The FTIR showed the presence of TeO3, TeO4, BO3, BO2O, SiO4, and H3BO3 structural units in the glasses. The concentrations of TeO3, TeO4, BO3 and BO2O structures were determined by the deconvolution of the FTIR spectra using an Origin software. The optical energy band gap, index of refraction, oxygen packing density (OPD), molar refractive index, metallization criterion and polaron radius were determined for the glasses. Based on the glass transparency, high refractive index value (2.3026 and 2.2937) and metallization criterion (0.4109 and 0.4132) of the glasses with x= 0.1 and 0.2 have potential for fiber and optical non-linear applications.

Solid State Phenomena, 2021

Borotellurite glass had been widely applied in the field of optical communications and devices. I... more Borotellurite glass had been widely applied in the field of optical communications and devices. In this work, holmium oxides doped borotellurite glass had been successfully fabricated via conventional melt-quenched technique. The structural properties of holmium doped tellurite glass were found using x-ray diffraction (XRD) method. The nonexistence of sharp peaks in XRD pattern shows that the inclusion of holmium tellurite glass leads to the formation long range of disorderness. The optical properties of the glass system such as refractive index and optical band gap energy are investigated using UV-Vis spectrophotometer. The value of refractive index is found in nonlinear trend along with holmium oxides concentration. It is found that the refractive index is more than 2 at 0.01, 0.03 and 0.04 of holmium concentrations. The optical band gap energy was found in similar trend with refractive index which is in nonlinear pattern.

Optical Materials, 2021

Abstract Er2O3 doped silica borotellurite glasses were synthesized using the melt-quenching techn... more Abstract Er2O3 doped silica borotellurite glasses were synthesized using the melt-quenching technique with a chemical compositional formula (1 – x){(SiO2)0.2 [(B2O3)0.3 (TeO2)0.7]0.8} (Er2O3)x. Using the XRD, FTIR, UV–Vis, and photoluminescence spectroscopies, the structural, optical and spectroscopic properties of the glasses were studied. The absorption spectra and the refractive index, penetration depth, extinction coefficient, absorption coefficient, dielectric constant, optical conductivity for the glasses were presented. The absorption and emission cross-sections, cross-sectional gain, effective bandwidth, and bandwidth quality factor were also calculated using the UV–Vis data. Photoluminescence and the upconversion luminescence of the glasses were presented for pump wavelengths of 350 nm and 540 nm respectively. The studied glasses presented a high refractive index with values between 2.452 and 2.5153. The emission cross-section, effective bandwidth, bandwidth quality factor increased respectively from 3.53 × 10–22 to 1.3637 × 10–20 cm2, 66.3–103 nm, and 3.636 × 1028–91.095 × 1028 cm3 with increase in the Er3+ ions concentration in the glass system. The synthesized glasses exhibits a high-quality up-conversion emissions around 397.5 nm, 426 nm, and 475 nm from an excitation due to a pump of 540 nm wavelength. Furthermore, a high-quality luminescence emission around 543 nm, 500 nm, 475 nm and 425 nm from an excitation due to a pump of 350 nm wavelength was observed. Considering the values of the glasses refractive index, dielectric behaviour, absorption and emission cross-sections, effective bandwidths and other parameters presented, the synthesized glasses possess great potential for optoelectronic, laser and Erbium dope fibre amplifier (EDFA) applications.

The International Journal of Science & Technoledge, 2019

Soil is a composite system which consists of organic and inorganic matter that directly or indire... more Soil is a composite system which consists of organic and inorganic matter that directly or indirectly supports plant and animal life and is a crucial component of our rural and urban environments (Emanuel, 2015). Trace elements are natural constituents of soil which come from rocks and soils through the processes of erosion, transport and deposition. They can also be derived from anthropogenic sources in which case they are incorporated into sediments as artificial pollutants from industrial or urban releases and wastes (Bermea et al., 2002). Their low Igeo index are usually safe, but increased in Igeo index of these elements in the environment can be significantly destructive to plants and animal life (Macfarlane & Burchett, 2000). As such soil is feasibly the most endangered component of our environment which is open to potential contamination by a variety of different pollutants arising from majorly human activities such as nuclear,

Journal of Applied Physics, 2020

The density of nanofluids is an important thermophysical property whose value is required to eval... more The density of nanofluids is an important thermophysical property whose value is required to evaluate various heat-transfer parameters such as the Reynolds number, the Nusselt number, pressure loss, and the Darcy friction factor. The determination of these parameters is central to the design of many heat-transfer applications. Notably, the density of nanofluids has received relatively little research attention compared with other thermophysical properties. The present study thus focuses on the development of a support vector regression model to estimate the densities of aluminum nitride, titanium nitride, and silicon nitride nanoparticles dispersed in ethylene glycol solution. As inputs, the proposed model uses the mass fraction, temperature, nanoparticle size, and the molecular weight of the nanoparticles. The proposed model predicts the nanofluid densities with high accuracy, as determined by a correlation coefficient of 99.87% and an absolute average relative deviation of 0.0701....

Polymers, 2020

This paper presents the electromagnetic interference properties of multi-walled carbon nanotubes ... more This paper presents the electromagnetic interference properties of multi-walled carbon nanotubes (MWCNTs) as a novel nano-reinforcement filler in poly (lactic acid) (PLA)/poly (ethylene glycol) (PEG) polymer matrix that was prepared via melt blending mode. Plasticization of PLA was first carried out by PEG, which overcomes its brittleness problem, in order to enhance its flexibility. A waveguide adapter technique was used to measure the dielectric properties ε r , and S-parameters reflection (S11) and transmission (S21) coefficients. The dielectric properties, microwave attenuation performances, and electromagnetic interference shielding effectiveness (EMISE) for all the material under test have been calculated over the full X-Band (8–12 GHz) due to its importance for military and commercial applications. The prepared samples were studied while using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transforms infrared spectroscopy (FTIR), mechan...

Polymers, 2019

In this study, a nanocomposite of reduced graphene oxide (RGO) nanofiller-reinforcement poly(lact... more In this study, a nanocomposite of reduced graphene oxide (RGO) nanofiller-reinforcement poly(lactic acid) (PLA)/poly(ethylene glycol) (PEG) matrix was prepared via the melt blending method. The flexibility of PLA was improved by blending the polymer with a PEG plasticizer as a second polymer. To enhance the electromagnetic interference shielding properties of the nanocomposite, different RGO wt % were combined with the PLA/PEG blend. Using Fourier-transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM) and X-ray diffraction, the structural, microstructure, and morphological properties of the polymer and the RGO/PLA/PEG nanocomposites were examined. These studies showed that the RGO addition did not considerably affect the crystallinity of the resulting nanomaterials. Thermal analysis (TGA) reveals that the addition of RGO highly improved the thermal stability of PLA/PEG nanocomposites. The dielectric properties and electromagnetic interference s...

Results in Physics, 2018

Tellurite glass systems in the form of [ZnO] x [(TeO 2) 0.7-(PbO) 0.3 ] 1-x with x = 0.15, 0.17, ... more Tellurite glass systems in the form of [ZnO] x [(TeO 2) 0.7-(PbO) 0.3 ] 1-x with x = 0.15, 0.17, 0.20, 0.22 and 0.25 mol % were prepared using the melt quenching technique. XRD of the prepared samples have been measured for all samples. Both FTIR (280-4000 cm −1) and UV-Vis (200-800 nm) spectra have been measured. Optical band gap and refractive index were calculated for every glass sample. Density of glass, molar volume and oxygen packing density (OPD) were obtained. Values of the direct, indirect band gap ranged were found in the range 3.41-3.94 eV and 2.40-2.63 eV with increasing of ZnO concentration. Refractive index 2.58 and dielectric constant 6.66 were heigh at 17 ZnO mol% concentration. Molar polarizability, metallization criterion, polaron radius have been calculated for every glass composition.

Journal of Applied Polymer Science, 2018

ABSTRACTFabrication of hybrid composite of nickel oxide (NiO) combined with oil palm empty fruit ... more ABSTRACTFabrication of hybrid composite of nickel oxide (NiO) combined with oil palm empty fruit bunch (OPEFB) reinforced with polycaprolactone (PCL) has been done by using thermal Haake blending machine, which ensured mixture homogeneity. All hybrid composites' characterizations were carried out using X‐ray diffraction (XRD), Fourier transform infrared spectrometry, differential thermogravimetry, thermogravimetric analysis, and scanning electron microscopy. The results showed that the XRD profile patterns of the composites clearly changed as the filler loading amount was increased. Fourier transform infrared spectra illustrated a slight change in the frequencies and positions of the peaks after adding NiO, indicating that some interactions occurred between C=O and O–H or among the fiber, NiO, and PCL. The microwave electromagnetic properties, such as reflection loss (dB), relative complex permittivity (εr =–j), and permeability (−j) were calculated at various microwave frequenc...

A radioactivity measurement was carried out in sediments of Zobe Dam. Samples of sediments from Z... more A radioactivity measurement was carried out in sediments of Zobe Dam. Samples of sediments from Zobe Dam were collected, prepared and analyzed using NaI(Tl) gamma ray spectrometer for the activity concentrations of the primordial Ra, Th and K. The results obtained show average activity concentrations of 49.67±3.07 (35.89-75.75), 127.29±4.42 (47.21-112.91) and 443.43±9.51 (338.88-638.40) in Bq/kg for Ra, Th and K respectively. To assess the radiological hazard of Dam sediments, the radiological hazard indices such as absorbed dose rate, annual effective dose equivalent (AEDE), hazard indices (Hex and Hin) were calculated and found to be comparable with the world average values. The mean absorbed dose rate obtained is124.52 nGy/ h, and is higher than the world average of 55 nGy/h. The measured average annual effective dose rate 0.152mSv/y is lower than the world average value of 1 mSv/y [7]. The measured average values of external and internal hazard index is 0.717 and 0.851 and are l...

Journal of Science and Mathematics Letters, 2019

The data for this research contains the in-situ measured activity concentration of radionuclides ... more The data for this research contains the in-situ measured activity concentration of radionuclides and gamma-radiation dose rate obtained from the radiometric survey in Azara development area of Awe Local Government, Nasarawa State, Nigeria. The data were manually collected in eight (8) locations with 20 data taken from each point using a portable hand held Thermo Scientific Interceptor and a radionuclide IdentiFINDER. The descriptive statistical analysis of the data was equally explored for possible statistical relationships. The result obtained is made available publicly for further extended analyses that can provide insights into the safety status of the study area from radiological health concerns. The data could also serve as a significant baseline radiometric data for future researches and monitoring initiative in Azara and its environs. The data for this research contains the in-situ measured activity concentration of radionuclides and gamma-radiation dose rate obtained from th...

Advances in Materials Science and Engineering, 2017

The aim of this work is to determine the effect of neodymium nanoparticles concentration on the e... more The aim of this work is to determine the effect of neodymium nanoparticles concentration on the elastic properties of zinc-tellurite glass. A series of neodymium nanoparticles doped zinc-tellurite glass systems (NdNPsZT) of composition [(TeO2)0.70(ZnO)0.30]1-x(Nd2O3 NPs)(x), x=0.01, 0.02, 0.03, 0.04, and 0.05, were synthesized by using conventional melt-quenching method. The amorphous nature of the glass system was confirmed by using XRD analysis. The density of the glass system was determined by Archimedes method. The elastic properties were calculated from the measured density and ultrasonic velocity at 5 MHz frequency. The experimental results showed that the elastic properties rely upon the composition of the glass systems and the impact of neodymium nanoparticles (Nd2O3 NPs) within the glass network. The increase in ultrasonic velocities is due to the increase in rigidity and change in structural units of the glass system. The softening temperature and the microhardness increas...