Development of silica-coated rare-earth doped strontium aluminate toward superhydrophobic, anti-corrosive and long-persistent photoluminescent epoxy coating

Photoluminescent and photochromic smart window from recycled polyester reinforced with cellulose nanocrystals

Smart windows with long-persistent phosphorescence, UV protection, high transparency, and high rigidity were developed by easily immobilizing varying ratios of lanthanide-activated aluminate phosphor nanoscale particles within a composite of recycled polyester/cellulose nanocrystals (RPET/CNC). Cellulose nanocrystals were prepared from rice straw waste. Cellulose nanocrystals were used at low concentration as both crosslinker and drier to improve both transparency and hardness. The phosphor nanoscale particles must be distributed into the recycled polyester/cellulose nanocrystals composite bulk without agglomeration in order to produce transparent RPET/CNC substrates. Photoluminescence characteristics were also studied by using spectroscopic profiles of excitation/emission and decay/lifetime. The hardness efficiency was also examined. This transparent recycled polyester waste/cellulose nanocrystals nanocomposite smart window has been shown to change color under UV light to strong green and to greenish-yellow when it is dark, as proved by CIE Lab color parameters. It was found that the afterglow RPET/CNC smart window had phosphorescence intensities of 428, 493 and 523 nm upon excitation at 368 nm. There were evidences of improved UV shielding, photostability, and hydrophobic activity. In the presence of low phosphor ratio, the luminescent RPET/CNC substrates showed quick and reversible fluorescent photochromic activity when exposed to UV radiation.

Facile and Eco-Friendly Preparation of Mild Steel Based Superhydrophobic Surfaces without Chemical Modifications

The fabrication of superhydrophobic coatings on mild steel has attracted considerable attention. However, some methods are cumbersome and unsuitable for large-scale preparation, limiting industrial applications. Furthermore, the extensive use of fluorinated compounds to achieve low surface energy is not environmentally friendly. This paper proposed a facile method based on electrodeposition and annealing to prepare mild steel-based superhydrophobic surfaces without chemical modifications. Subsequently, SEM images were analyzed, and it was observed that the plating parameter (current and time) significantly affected surface morphology. At optimum process parameters, a rough surface with a multi-level structure was formed on the plated surface, contributing to superhydrophobic properties. XPS, EDS, and XRD were utilized to analyze surface composition. The results indicated the presence of copper oxides, zinc oxides, and a large number of hydrocarbons on the prepared superhydrophobic surface. These transition metal oxides on the surface adsorbed hydrocarbons in the air during the annealing process, which lowered the surface energy. Combined with the obtained multi-level morphology, a superhydrophobic surface was achieved. Finally, the corrosion behavior was evaluated in 3.5 wt% NaCl solution by AC impedance spectroscopy. Results showed that the obtained superhydrophobic surface, compared with the untreated coating and the steel substrate, showed a substantial improvement in corrosion resistance. A mild steel-based superhydrophobic surface with a contact angle greater than 150 degrees and excellent corrosion resistance was finally obtained. We hope this study will facilitate the industrial preparation of superhydrophobic coatings, especially in marine engineering, since this method does not require complex processes or expensive equipment and does not require fluorinated substances.