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Gd-doped Ba1-xGdxCo2Fe16O27 (BGxCF) x = (0.00, 0.05, 0.10, 0.15, 0.20, and 0.25) wt.% W-type hexaferrite ceramic pellets were synthesized by ball milling solid-state reaction technique. XRD patterns of the prepared samples verify the single-phase polycrystalline nature without any impurity phase. The doping of Gd ions in the samples impacted the lattice parameters, unit cell volume and bulk density increases. Morphological results analysis using SEM shows the hexagonal plate-like structure of the BGxCF particles. The increase of Gd contents in the samples created multi-domain structure and grain growth occurred. FT-IR analysis confirmed the existence of the octahedral and tetrahedral vibration of Fe–O, with Gd substitution bond strength between the atom decreases. Raman analysis verifies the existence of A1g, E1g and E2g Raman modes, with Gd wt.% increases there is a red shift of the vibration modes. Magnetic results reveal that with Gd substitution in the BGxCF samples, the magnetization saturation (Ms) increased for x = 0.05, and 0.10 samples due to strain magnetization, while, for x = 0.15 and 0.20 samples, Ms decreased due to the spinning by Gd ions, and but it is increased for x = 0.25 samples. Moreover, with increases of Gd wt.% in the samples, there is a decrease in the coercive field due to the increase of particle size and a decrease of magnetocrystalline anisotropy. In addition, the dielectric properties revealed increases in both permittivity and dielectric loss with the Gd contents in BGxCF samples. Permeability studies show the existence of spin resonance phenomena in the samples. The magnetic losses in the Gd-doped samples are higher than the undoped sample due to the decreases of magnetocrystalline anisotropy. The highest values of both dielectric and magnetic losses of the Gd-doped BGxCF samples make these materials enhance its performance in microwave potential devices applications. [ABSTRACT FROM AUTHOR]

In the current study, the effect of rGO ratio on the N-dopped TiO2 has been synthesized through sol–gel method. The prepared N-doped TiO2/rGO composites were examined for humidity sensing applications. The relationship between optical properties and the humidity sensing properties was studied. The structure, morphology, and bonding interaction have been examined using XRD, FT-IR, PL and HRTEM respectively. The average particle size as estimated from XRD and HRTEM was found to be about 9 nm. The optical properties have been studied using UV/ Vis. Spectroscopy. Further, optical parameters including refractive index and optical band gap energy have been estimated. The humidity sensing behavior of the resultant composites were evaluated in a wide range of humidity (7%–97% RH) at different testing frequencies. The optical band gap was found to be decreased as the amount of rGO increase. Among all prepared samples, both the optical parameters and humidity sensing experiments confirmed that the 0.5% rGO@N-dopped TiO2 sample is the best candidate for the humidity sensing applications. The best optimum testing frequency was demonstrated to be 50 Hz. The sensor demonstrates a fast response and recovery times of 13 s and 33 s with low hysteresis and large sensitivity. The humidity sensing mechanism was studied using complex impedance spectroscopy at different RH levels under testing frequency range from 50 Hz to 5 MHz and testing voltage of 1 VAC. The produced structure demonstrated a promising material for humidity measuring devices. [ABSTRACT FROM AUTHOR]

One useful technique for increasing the efficiency of organic dye-sensitized solar cells (DSSCs) is to extend the π-conjugated bridges between the donor (D) and the acceptor (A) units. The present study used the DFT and TD–DFT techniques to investigate the effect of lengthening the polyene bridge between the donor N, N-dimethyl-anilino and the acceptor dicyanovinyl. The results of the calculated key properties were not all in line with expectations. Planar structure was associated with increasing the π-conjugation linker, implying efficient electron transfer from the donor to the acceptor. A smaller energy gap, greater oscillator strength values, and red-shifted electronic absorption were also observed when the number of polyene units was increased. However, some results indicated that the potential of the stated dyes to operate as effective dye-sensitized solar cells is limited when the polyene bridge is extended. Increasing the polyene units causes the HOMO level to rise until it exceeds the redox potential of the electrolyte, which delays regeneration and impedes the electron transport cycle from being completed. As the number of conjugated units increases, the terminal lobes of HOMO and LUMO continue to shrink, which affects the ease of intramolecular charge transfer within the dyes. Smaller polyene chain lengths yielded the most favorable results when evaluating the efficiency of electron injection and regeneration. This means that the charge transfer mechanism between the conduction band of the semiconductor and the electrolyte is not improved by extending the polyene bridge. The open circuit voltage (VOC) was reduced from 1.23 to 0.70 V. Similarly, the excited-state duration (τ) decreased from 1.71 to 1.23 ns as the number of polyene units increased from n = 1 to n = 10. These findings are incompatible with the power conversion efficiency requirements of DSSCs. Therefore, the elongation of the polyene bridge in such D-π-A configurations rules out its application in solar cell devices. [ABSTRACT FROM AUTHOR]

In this study, copper matrix composites were prepared using the cold and hot pressing technique and then investigated to select the suitable one for the self-lubricating applications. A hybrid of alumina and molybdenum disulfide with a 1:1 ratio by the mechanical milling for 40 h was proceeded to peel the molybdenum disulfide and cover the alumina particles with their layers. Three different samples like Cu, Cu/10 Al2O3, and Cu/hybrid 20(Al2O3–MoS2) were mixed for 15 h. The ball-to-powder ratio in the two mentioned steps was 10:1. The X-ray analysis, HRTEM, Raman spectra, and scanning electron miscopy were used to study the crystal structure, chemical composition, and morphology of the new hybrid and prepared samples. The density was evaluated by the Archimedes method. Mechanical properties, including hardness, wear rate, and coefficient of friction, were investigated. The mixing for 15 h improves the exfoliation of MoS2 flakes inside the copper matrix. A clear hardness improvement was achieved by adding alumina and the mixture of (Al2O3–MoS2). The copper sample reinforced with the hybrid of alumina/MoS2 gave the lowest mechanical wear rate and the lowest average friction coefficient of 0.17. [ABSTRACT FROM AUTHOR]