Progress in the experimental and computational methods of work function evaluation of materials: A review.

The work function, which determines the behaviour of electrons in a material, remains a crucial factor in surface science to understand the corrosion rates and interfacial engineering in making photosensitive and electron-emitting devices. The present article reviews the various experimental methods and theoretical models employed for work function measurement along with their merits and demerits are discussed. Reports from the existing methods of work function measurements that Kelvin probe force microscopy (KPFM) is the most suitable measurement technique over other experimental methods. It has been observed from the literature that the computational methods that are capable of predicting the work functions of different metals have a higher computational cost. However, the stabilized Jellium model (SJM) has the potential to predict the work function of transition metals, simple metals, rare-earth metals and inner transition metals. The metallic plasma model (MPM) can predict polycrystalline metals, while the density functional theory (DFT) is a versatile tool for predicting the lowest and highest work function of the material with higher computational cost. The high-throughput density functional theory and machine learning (HTDFTML) tools are suitable for predicting the lowest and highest work functions of extreme material surfaces with cheaper computational cost. The combined Bayesian machine learning and first principle (CBMLFP) is suitable for predicting the lowest and highest work functions of the materials with a very low computational cost. Conclusively, HTDFTML and CBMLFP should be used to explore the work functions and surface energy in complex materials.

In-situ assessment of natural terrestrial-radioactivity from Uranium-238 (238U), Thorium-232 (232Th) and Potassium-40 (40K) in coastal urban-environment and its possible health implications.

The risk of natural terrestrial radioactivity on human health is often underestimated, and environmental safety awareness is necessary. Hence, this study aims to assess natural sources of gamma radiation emitter in coastal urban-environment using the radiometric technique. The dosage of gamma radiation from a parent radionuclide such as Uranium-238 (238U), Thorium-232 (232Th) and Potassium-40 (40K) and were measured using portable gamma spectroscopy. The result showed that the measured value of 238U activity was between 10.81 [Formula: see text] 0.69 and 46.31 [Formula: see text] 1.43 Bqkg-1. The mean value was estimated to be 35.44 [Formula: see text] 0.97 Bqkg-1 which is slightly higher than the world average. Meanwhile, 232Th activity ranges from 28.42 [Formula: see text] 1.12 to 69.43 [Formula: see text] 1.76 Bqkg-1 with the calculated mean value of 92.57 [Formula: see text] 1.17 Bqkg-1 while 40K activity ranged between 31.30 ± 1.32 and 328.65 ± 2.32 Bqkg-1 with the estimated mean 137.59 [Formula: see text] 2.42 Bqkg-1. Radiological parameters such as radium equivalent (Req), internal hazard (Hint) and external hazard (Hext) assessment were in the range of 66.00 Bqkg-1 to 141.76 Bqkg-1, 0.232 to 0.452 and 0.178 to 0.383, respectively. The measured values of gamma dose-rates ranged between 54.283 ± 0.78 and 117.531 ± 1.14 nGyh-1 with the calculated mean value of 84.770 ± 0.97 nGyh-1.

STATISTICAL ESTIMATION OF RADIOLOGICAL HAZARDS FROM RADIONUCLIDE CONTENTS IN BUILDING MATERIALS.

Thirteen (13) types of building tiles and Sharp sand commonly used for building purposes were collected for their radionuclide contents analysis using gamma ray spectrometry. The average value of the Radium equivalent activity is 208.81 Bq/kg for all samples considered was found to be lower than the recommended safe limit of 370 Bq/kg. Similarly, both external and internal hazard indices (Hex and Hin) were noted to have mean values of 0.57 and 0.73, respectively, which were lower than the recommended safe standard of 1. More so, the average absorbed gamma dose rate was observed to be 94.31 nGy/h, much higher than the recommended safe limit of 59 nGy/h.

Investigation of natural environmental radioactivity concentration in soil of coastaline area of Ado-Odo/Ota Nigeria and its radiological implications.

Natural radioactivity in coastaline area soil of Ado-Odo/Ota has been carried out to ascertain the presence of radionuclides using gamma-ray spectroscopy (HPGe detector). The result showed that U-238, Th-232 and K-40 ranged from 24 ± 7-49 ± 10; 67 ± 6-120 ± 9 and 88 ± 17-139 ± 20 Bqkg-1 respectively. The radium equivalent for the samples ranged from 132.51 to 230.91 Bqkg-1 with mean value of 185.89 Bqkg-1. The mean value for the gamma dose rate for the soil samples was estimated to be 81.32 nGyh-1. The estimated values of annual effective dose equivalent ranged from 0.61 to 1.07 mSv y-1. The estimation of alpha index representative (Iα) ranged from 0.12 to 0.24 with mean value of 0.21 while the gamma representative index ranged between 0.465 and 0.810. The activity utilization index of the soil samples ranged from 1.09 to 1.89 with mean value of 1.53. The radiological implication in the study area has shown that the soil samples with gamma dose rate value of 89.99 nGyh-1, 94.39 nGyh-1, 97.40 nGyh-1 and 101.04 nGyh-1 respectively are higher than the recommended value of 80 nGyh-1 and may pose health implication for long term exposure.

Dataset on noise level measurement in Ota metropolis, Nigeria.

Datasets contained in this article are noise level measurement carried out at 41 different locations in Ota metropolis, Nigeria. The noise readings were measured at a time interval of 30 min for each site considered using a precision grade sound level meter. The analysis was based on the noise descriptors LAeq, L10, L90, LD, TNI and NEI. Results from the study reflects that the highest and lowest equivalent noise levels (LAeq) were recorded at commercial areas (96 dB (A)) and residential areas (52 dB (A)), respectively, the background noise level (L90) has the highest and lowest values at commercial areas (77 dB (A)) and residential areas (44 dB (A)), respectively and the peak value (L10) has the highest value and lowest value at the commercial areas (96 dB (A)) and residential areas (56 dB (A)). Based on the WHO recommendations and standards, only 2 out of the 41 locations considered are under normally acceptable situation while the noise levels of other areas are not acceptable. Noise map developed in this study provides enough information for technical controls and interim legislation against environmental noise pollution in the metropolis. Moreover, considering the noise emission standards, planning and promoting the citizens awareness about the high noise risk could help to mitigate the effect of noise in Ota, Metropolis. The noise data in this study are useful as reference and guideline for future regulations on noise limit to be implemented for urban areas in Nigeria and developing countries at large.

Radionuclides proportion and radiological risk assessment of soil samples collected in Covenant University, Ota, Ogun State Nigeria.

The activity levels of 238U, 232Th and 40K in soil surrounding major office complexes in Covenant University were analyzed for radiological hazards to determine the safety of the residents in such environment. Sixteen (16) soil samples were collected, prepared and sent to Acme laboratory in Canada for analysis with the use of high purity germanium detector. The mean activity concentrations of 238U, 232Th and 40K were found to be 45 ± 10, 135 ± 8 and 195 ± 20 respectively. The concentrations of 238U and 232Th were found to be higher than the world recommended standard of 35 and 30, while the result for 40K was noted to be lower than the world safe limit. The average values of Raeq, D, AED, Iyr, Hex and ELCR in this study were estimated to be 252.33 Bq/kg, 110.15 nGy/h, 0.13 mSv/y, 1.78, 0.68 and 0.47 × 10-3 respectively. It was noticed that none of the measured parameters was higher than the internationally recommended safe limits. 232Th was found to be the major contributor to the environmental radionuclides in the area of study. Therefore, the inhabitants of the office complexes whose environment was assessed are considered not be exposed to any radiological hazards.

Assessment of natural radioactivity in various commercial tiles used for building purposes in Nigeria.

In this study, we evaluated the activity concentration of natural radionuclides (226Ra, 232Th and 40K) for fifteen (15) different brands of tile samples used for building purposes in Nigeria. The tile samples were analyzed using High purity Germanium gamma detector. The mean activity concentrations of 226Ra, 232Th, and 40K were observed to be 61.1 ±â€¯5.5 Bq/kg, 70.2 ±â€¯6.08 Bq/kg and 514.7 ±â€¯59.8 Bq/kg respectively. Various hazard indices such as absorbed dose rate, external and internal hazard index, annual effective dose rate, Gamma activity Index (Iγ) and Alpha Index (Iα) were calculated. The obtained results showed that the mean radium equivalent activity (Raeq), the absorbed dose rate (D), external and internal hazard index, the annual effective dose (AEDR) equivalent, Gamma activity Index (Iγ) and Alpha Index (Iα) were: 204.42 Bq/kg, 177.61 nGyh-1, 0.55, 0.77, 0.96 mSvyr-1, 0.74 and 0.32 respectively. The average value of radium equivalent obtained in this study is less than that of the recommended value of 370 Bq/kg but the average values of the other radiological hazards for some samples are found to be slightly above international recommended values except Hex, Hin and AEDE which are within the international reference value of unity. The measured concentrations of these radioactive materials were correlated with other previous result obtained from similar tile materials used in other countries and found to be in good agreement with the international standard, however, the tiles are recommended for decoration purposes in Nigeria.

Comparative Analysis of Natural Radioactivity Content in Tiles made in Nigeria and Imported Tiles from China.

In this investigation, natural radioactive contents in tiles manufactured in Nigeria and tiles imported from China were measured using gamma ray spectroscopy. High Purity Germanium detector was used to estimate the concentrations of some radioisotopes present in 17 samples of various tiles from Nigeria and China. The average activity concentrations of 226Ra, 232Th, and 40K for the tiles were found to be 68.2 ± 0.5; 173.9 ± 9.2 and 490 ± 15 Bq/kg and 58.2 ± 0.5, 161.5 ± 9.4 and 455.7 ± 15.1 Bq/kg for the tiles from Nigeria and China respectively. Radiological hazard indices such as absorbed dose rate, radium equivalent activity, external Hazard Index (Hex), internal Hazard Index (Hin), Annual Effective Dose (mSv/y), Gamma activity Index (Iγ) and Alpha Index (Iα) were determined for both kind of tiles from Nigeria and China. The mean values obtained were: 354.56 and 317.16 Bq/kg; 169.22 nGyh-1 and 153.92 nGyh-1; 0.95 and 0.87; 1.14 and 1.08; 1.59 mSv/y and 1.52 mSv/y; 1 and 1.15 and; 0.34 and 0.29 respectively. The mean value of radium equivalent obtained in this study is less than that of the international reference value of 370 Bq/kg for the both kind of tiles.