Vivid-Colored Electrorheological fluids with simultaneous enhancements in color clarity and Electro-Responsivity

Limited Electron-Dominated Electrorheological Response with TiO2 Buffer Layer

We report porous carbon sphere electrorheological (ER) nanoparticles coated with a titanium dioxide layer (HCs@TiO2). Utilizing the buffering effect of amorphous TiO2, the HCs@TiO2 ER fluid (ERF) shows a yield stress that exceeds that of previous carbon-based ER nanomaterials. The mechanisms of the high ER response are elucidated through the analysis of the dielectric properties, demonstrating that the amorphous TiO2 shell not only restricts the electron-dominated motion but also significantly improves the interfacial polarization. Furthermore, the HCs@TiO2 ERF exhibits superior sedimentation stability and low current density, which is attributed to the formation of a hydrogen bond network. The rheological behavior of HCs@TiO2 ERF is analyzed using the Bingham and Cho-Choi-Jhon model, where the dynamic yield stress as a function of electric field strength is fitted using a generalized yield stress equation. These analyses indicate that local electrostatic accumulation between the hybrid shells benefits the ER response.

Comparative Study of the Electrorheological Properties of Various Halide Perovskites

Although perovskite-structured materials have primarily been widely employed in solar cell applications, limited studies have been conducted in the field of electrorheology (ER). In this study, various halide perovskite materials, including FAPbBr3, FAPbI3, MAPbBr3, MAPbI3, CsPbBr3, and CsPbI3 were synthesized for the first time to evaluate their applicability in ER for the first time. Initially, the morphological and chemical properties of these materials were characterized to confirm the successful formation of the perovskite structures. In addition, the as-synthesized halide perovskite materials were dispersed in silicone oil (3.0 wt %) to evaluate their suitability as dispersants in ER fluids. Among these, the CsPbI3-based ER fluid exhibited the optimal dielectric properties and the greatest dispersion stability of the various systems examined. In ER applications, the CsPbI3-based ER fluid demonstrated the highest ER performance, achieving a shear stress of 99.4 Pa, owing to the synergistic effects of its intrinsic rod-like structure and dielectric properties, which promoted polarization. The aspect ratios of the CsPbI3 rods were further controlled by modifying the synthetic process, resulting in the generation of both shorter and longer rods. Notably, ER fluids based on CsPbI3 synthesized via a hydrothermal method yielded rod-like structures with a high aspect ratio of 20, leading to an enhanced ER activity of 128.0 Pa. These results highlight the potential of halide perovskite materials for use in ER applications.

Designing Novel LiDAR-Detectable Plate-Type Materials: Synthesis, Chemistry, and Practical Application for Autonomous Working Environment

Plate-type hollow black TiO2 (HL/BT) with a high NIR reflectance was fabricated for the first time as a LiDAR-detectable black material. A TiO2 layer was formed on commercial-grade glass by using the sol-gel method to obtain a plate-type structure. The glass template was then etched with hydrofluoric acid to form a hollow structure, and blackness was further achieved through NaBH4 reduction, which altered the oxidation state of TiO2 to black TixO2x-1 or Ti4+ to Ti3+ and Ti2+. The blackness of the HL/BT material was maintained by a novel approach that involved etching prior to reduction. The thickness of the TiO2 layer was controlled to maximize the NIR reflectance when applied as paint. The HL/BT material with a thickness of 140 nm (HL/BT140) showed a blackness (L*) of 13.3 and high NIR reflectance of 23.6% at a wavelength of 905 nm. This is attributed to the effective light reflection at the interface created by the TiO2 layer and the hollow structure. Plate-type HL/BT140 provides excellent spreadability, durability, and thermal stability in practical paint applications compared with sphere-type materials due to the higher contacting area to the applied surface, making it suitable for use as a LiDAR-detectable inorganic black pigment in autonomous environments.