Applied Science and Technology Express

The burgeoning of highly effective electromagnetic (EM) wave-absorbing material is of high research interest due to rising electromagnetic interference (EMI) issues. In this study, the electromagnetic scattering parameters of cobalt ferrite (CF) nanoparticles grown in situ on eggshell membranes (ESM) via a hydrothermal method were studied at X band frequency. The chemical composition and phase crystallinity of the composites was studied. The analysis of the electromagnetic scattering parameters revealed that optimum minimum reflection and maximum transmission coefficient can be achieved with CESM@CF and UCESM@CF samples. The CESM@CF sample achieved a minimum reflection coefficient of 0.01119 and a maximum transmission coefficient of 0.99993 was achieved at an optimum thickness of 3.0 mm for CESM@CF. For UCESM@CF, a minimum reflection coefficient of 0.0137 and a maximum transmission coefficient of 0.99981 were achieved at an optimum thickness of 3.0 mm. These results indicate that CESM@CF and UCESM@CF composites can attenuate electromagnetic waves at X-band frequency.

Heavy metal contamination levels in vegetables grown around the Riruwai mining area in Kano State, Nigeria, were investigated. Fifteen (15) vegetable samples, including lettuce (Lacuta sativa), tomato (Solanum lycopersicum), and bean (Phaseolus vulgaris L), and their corresponding soils were collected. The concentrations of arsenic, cadmium, chromium, mercury, manganese, nickel, lead, and zinc in all the samples were determined using Microwave Plasma Atomic Emission Spectrometry, and the measured concentrations were used to compute the bioaccumulation factor (BAF). Heavy metal concentrations in the investigated vegetables and soils were found to be significantly high, with the majority of levels exceeding the WHO/FAO (2007) recommended limit. Pollution levels differed significantly (p ≤ 0.05) for heavy metals and vegetable types. Cadmium had the highest BAF value, with a value significantly greater than one, and lettuce had the highest accumulation of all vegetables studied. The higher concentration of these metals in vegetables, particularly cadmium, necessitates immediate scientific attention and further research to determine the optimum concentration required for human health. Planting of vegetables for human and animal consumption should be stopped until this is accomplished.

Using the non-equilibrium Green’s function and inversion symmetry tight-binding model, we found that in -zigzag borophene nanoribbons (ZBNRs) with different widths, spin polarization for transmitted electrons in the absence of the exchange field is zero and the presence of an exchange field is essential. Our results for ZBNRs with different widths show that for observing spin polarization, the strength of the exchange field must be higher than 0.001 eV. By increasing the exchange field and obtaining high transmission probability, ZBNRs are able to generate a pure spin current which can be exploited in designing spintronic devices.

With the decline in oil discoveries during the last few decades, enhanced oil recovery (EOR) technologies play significant roles to meet the growing energy demand. Foam flooding, commonly known as foam assisted water alternating gas (FAWAG), has been recognized among the effective techniques in EOR. In this study, seeds of Fenugreek plant were used to extract oil through solvent extraction technique. Subsequently, the oil was used to chemically synthesize a surfactant and characterized using FTIR spectroscopy. Dynamic foam stability (t_1/2) was investigated using Ross miles method to establish synergy actions between the surfactant and brine using a response surface methodology tool. Furthermore, a t_1/2 numerical model was developed after establishing the optimized stability condition. At this condition, foam morphology was characterized by microscopic analysis to observe changes in bubble size and distribution in decay profile. The results revealed that by utilizing 25 g of the seed materials, about 7 % of the oil yield was obtained which has resulted to the synthesis of about 13.86 g of surfactant. The surfactant was confirmed by the FTIR analysis due to the appearance of many important characteristic functional groups. The surfactant foam demonstrates appreciable stability (maximum; 152.66 s and optimized; 52.3 s) in relation to its good morphology (bubble size and distribution) observed. The study further established that the t_1/2 is due to synergy between the surfactant and brine in the model. The findings of the paper have provided sufficient preliminary investigations and recommend suitable applications of plant derived surfactants in EOR foam technology.  

The lead position effects on spin-dependent transport through round phosphorene quantum dots (RPQDs) by using Green’s function method in the presence of Rashba spin-orbit interaction (RSOI) have been investigated. According to the results, the symmetry of the structure due to the position of the leads disturbs the quantum transport through RPQDs. It has been obtained that when the input lead is located at the center of RPQDs and the angle between leads is about , the transmission probability is at its maximum value, and the spin polarization is entirely observed. This study can be utilized to create optimized spintronic devices which are based on phosphorene quantum dots.

Hierarchical porous carbon (HPC) chitin derived from carbonized shrimp shells (SS) doped with magnetic species (Nickel and Cobalt) was prepared via an in-situ adsorption mechanism for microwave absorption (MA). The MA performance of the synthesized variants of SS, namely carbonized shrimp shells without any dopants (Neat SS), carbonized shrimp shells doped with cobalt nanoparticles (SS/Co), carbonized shrimp shells doped with nickel nanoparticles (SS/Ni), and carbonized shrimp shells doped with cobalt and nickel nanoparticles (SS/CoNi) were investigated in this study. Regardless of the structural attenuation capability of the hierarchical porous carbon, the addition of magnetic nanoparticles introduces magnetic loss due to impedance matching between the magnetic species and incident electromagnetic wave. In this study, SS/CoNi composite showed the highest MA performance among all the samples, evident from the reflection loss (RL) value of -42.216 dB at 10.84 GHz with a sample thickness of only 1.5 mm. However, at a higher sample thickness of 4.0mm, the minimum RL peak value of -51.14 dB was attained for SS/CoNi at a frequency of 11.28 GHz.