CTAB-Assisted Synthesis of FeNi Alloy Nanoparticles: Effective and Stable Electrocatalysts for Urea Oxidation Reactions

Development of highly efficient electrocatalysts for treating urea-rich wastewater is an important problem in environmental management and energy production. In this work, an iron-nickel alloy (Fe-Ni alloy) was synthesized via soft-template cetyltrimethylammonium bromide (CTAB)-assisted precipitation using low-temperature calcination. The as-synthesized nanoalloy was characterized by X-ray diffraction (XRD), which revealed the formation of a face-centered cubic (FCC) structure of the Fe-Ni alloy; field emission-scanning electron microscopic (FE-SEM) analysis revealed the spherical shape of the Fe-Ni alloy; high-resolution transmission electron microscopy (HR-TEM) revealed the average size to be ∼33.09 nm; and X-ray photoelectron spectroscopy (XPS) showed the presence of Fe, Ni, C, and O components and their chemical composition and valence states in the Fe-Ni alloy. The electrochemical urea oxidation reaction (UOR) was investigated by conducting linear sweep voltammetry (LSV) tests on the synthesized electrocatalysts with different Ni/Fe ratios in alkaline electrolytes with urea. The potential required to reach a current density of 10 mA cm-2 is 1.27 V vs RHE, which demonstrates the higher electrochemical activity of the Fe-Ni alloy compared to other individual compounds. This could be due to CTAB which improved the structural stability and synergetic and electronic effects in the nanoscale. This study will further contribute to renewable energy generation technology with long-term energy sustainability and also opens up great potential for reducing water pollution.

Dielectric and Mechanical Properties of CTAB-Modified Natural Rubber Latex-Cement Composites

Cetyl trimethyl ammonium bromide (CTAB)-modified natural rubber latex/Portland cement paste (CTAB + NL/PC) composites were fabricated by varying the NL/cement and CTAB/cement ratios to improve the elastic property of PC. The stability and workability of the CTAB-modified NL particles in the PC matrix were significantly improved. The microstructure and dielectric property analyses of PC, CTAB/PC, NL/PC, and (CTAB + NL)/PC composites were performed to describe the interaction mechanism between the CTAB-modified NL and PC. The portlandite phase in PC was reduced by incorporating CTAB + NL. Although the tensile strength of NL/PC was significantly increased, its compressive strength also greatly decreased by ~40.3%. The tensile and compressive strengths of CTAB/PC were not significantly improved. Notably, the tensile strength of (CTAB + NL)/PC was significantly increased compared to those of PC, CTAB/PC, and NL/PC, while the depreciated compressive strength was only 18.7%. The optimized compressive–tensile performance of (CTAB + NL)/PC was equal to that of PC. The dielectric constants of NL/PC, CTAB/PC, and (CTAB + NL)/PC were reduced due to the low dielectric constant of NL and the ability of CTAB to capture negative charges in the PC matrix, leading to a reduction in the negative surface charges and hence the interfacial polarization. This result was confirmed by the decreased loss tangent in a low-frequency range, which is usually reduced by decreasing the free charges. This work provides a comprehensive guideline for significantly improving the elastic property of PC while retaining a high compressive strength.

Reversible and Irreversible Color Change during Photo and Thermal Degradation of PolyphenyleneSulfide Composite

The effect of the light spectral composition and temperature on the change of color characteristics and reflection spectra during the irradiation of polyphenylene sulfide reinforced by short glass fibers in the SUNTEST apparatus was analyzed. The scales of reversible color change upon successive exposure to total radiation corresponding to the sunlight spectrum and to visible light wereevaluated and the possible mechanisms for the observed effects are discussed. The features of the color change upon visible light irradiation of previously thermally aged samples wereconsidered. Possible causes for deviation from the Arrhenius law during thermal aging of the composite are discussed. It wasdemonstrated that even with a significant change in color, the physicomechanical and electrotechnical characteristics of the composite only changedslightly or remained virtually at the same high level.

Preparation and characterization of polyphenylene sulfide/graphene nanoplatelets composite fibers with enhanced oxidation resistance

Composite masterbatches of polyphenylene sulfide (PPS) with functionalized graphene nanoplatelets (GNPs) were prepared by melt blending via a twin-screw extruder. The structure and morphology of composite masterbatches were characterized by scanning electron microscopy and X-ray diffraction analysis. The PPS/functionalized GNPs composite fibers were then manufactured by a self-made spinning equipment via melt spinning. The oxidation resistance and other properties of PPS composite fibers were also examined. The results showed that the pure PPS fibers exhibited smooth surface, whereas the surface of PPS/functionalized GNPs composite fibers was rough. The addition of functionalized GNPs could be acted as heterogeneous nucleating agents to improve the crystallization and increase the degree of crystallinity. The retention rate of breaking strength of PPS/functionalized GNPs composite fibers could maintain up to 85% after the oxidation treatment. The improvement in the oxidation resistance of PPS/functionalized GNPs composite fibers is the results of comprehensive effects characterized by the X-ray photoelectron spectroscopy analyses. The addition of functionalized GNPs could limit the damage of the C–S group and retard the generation of sulfuryl groups (–SO–) during the oxidation treatment. The chemical combination of the elements sulfur (S) and oxygen (O) could also be restricted, thus weakening the oxidation activity.

Improvement of graphene oxide/epoxy resin adhesive properties through interface modification

The heat-conducting, dielectric, and bonding properties of a composite adhesive have been enhanced using toluene diisocyanate (TDI) to chemically modify the interface between graphene oxide (GO) and epoxy resin (EP), which was characterized using Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The thermal conductivity of TDI10-GO0.5/EP was 0.624 W·m−1·K−1 (166% of EP and 117% of GO0.5/EP), with its TDI10-GO0.5/EP interfacial thermal resistance being reduced by a factor of 36 times GO0.5/EP. The insulating properties of the adhesive in small resistors and capacitors were improved by the inclusion of GO, with the dielectric strength of the adhesive shown to be 25.96 kV·mm−1 and its volume resistivity found to be 1.50 × 1014 Ω·m.

Nonisothermal crystallization kinetics, morphology, and tensile properties of polyphenylene sulfide/functionalized graphite nanoplatelets composites

Polyphenylene sulfide (PPS)/graphite nanoplates (GNPs) nanocomposites were manufactured by simple melt compounding. The GNPs were first functionalized using synthesized benzimidazolium salt to improve the compatibility with PPS matrix. The functionalized GNPs showed an exfoliated dispersion in PPS matrix, which also could significantly improve the tensile properties of composites. Differential scanning calorimetry was used to investigate the nonisothermal crystallization kinetics of PPS/functionalized GNPs composites. The results showed that the PPS/functionalized GNPs composites always had a higher crystallization peak temperature ( Tc) than pure PPS resin at different cooling rates due to the addition of GNPs. The GNPs could also play the role of heterogeneous nucleating agents to accelerate the crystallization; however, at high content, they could also limit the mobility of PPS macromolecular chains and hinder the crystallization. The Mo equation could be used to analyze the nonisothermal crystallization kinetics, whereas the Ozawa equation was not suitable for the nonisothermal crystallization process. Consistent with a previous analysis, the results also showed that the addition of GNPs could also decrease the crystallization activation energy ( Ec) of PPS resin at low content while increasing the Ec at high content.

Enhanced Oxidation Resistance of Polyphenylene Sulfide Composites Based on Montmorillonite Modified by Benzimidazolium Salt

Organic montmorillonite (MMT) modified by 1,3-dihexadecyl-3H-benzimidazolium bromide (Bz) was used to prepare polyphenylene sulfide (PPS)/MMT composites by melting intercalation. The PPS/MMT composites showed mixed morphology, being comprised of exfoliated and intercalated structures with slight agglomerates. The tensile property of PPS/MMT composites was significantly improved due to the good dispersion of the MMT nanolayers. The test results showed that the tensile strength retention of PPS/MMT composites was higher than that of pure PPS after the oxidation treatment. Moreover, FTIR and XPS analyses were also used to evaluate the oxidation resistance of PPS composites. The FTIR analysis confirmed that adding MMT could better limit the damage of the C⁻S group and retard the generation of sulfuryl groups (⁻SO₂⁻) during the oxidation treatment compared to pure PPS. The XPS analysis also suggested that the addition of MMT could reduce the chemical combination of the elements sulfur (S) and oxygen (O) during oxidation treatment. Furthermore, the MMT nanolayers could also promote the transfer of S from a C⁻S bond into an ⁻SO₂⁻ group.