Preparation and electrorheological properties of eggshell-like TiO2 hollow spheres via one step template-free solvothermal method

rGO@TiO2-x Schottky heterojunction for enhanced bidirectional catalysis in polysulfide conversion

The shuttling and sluggish conversion kinetics of lithium polysulfides (LiPSs) lead to poor cycling performance and low energy efficiency in lithium-sulfur batteries (LSBs). In this work, a hierarchically structured nanocomposite, synthesized through a surfactant-directed hydrothermal growth following dopamine-protected pyrolysis, serves as a bidirectional catalyst for LSBs. This nanocomposite comprises N-doped reduced graphene oxide (rGO) nanosheets anchored with uniformly distributed TiO2-x nanoparticles via interfacial N-Ti and C-Ti bonding, resulting in the formation of abundant 2D/0D Schottky heterojunctions (rGO/TiO2-x). Density functional theory (DFT) calculations and in situ Raman characterizations demonstrate that rGO/TiO2-x effectively inhibits the shuttling of LiPSs with enhanced redox kinetics, achieving high utilization of the sulfur cathode and improving the overall reversibility. A high areal capacity is attained at a high sulfur loading and a low electrolyte/sulfur ratio. The initial specific capacity reaches 1010 mA h g-1 at a current density of 0.2C (1C = 1675 mA g-1), and a retention of 86.4 % is attained over 100 cycles. A light-emitting diode (LED) screen using two LSBs with rGO/TiO2-x demonstrates their high potential for practical applications.

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

HYPOTHESIS

Surface modification of dielectric materials changes the dipole-dipole interactions under electric fields, thereby controlling the electrorheological (ER) response. The introduction of metal oxides onto mica templates and further coating of dyes is expected to simultaneously improve the color clarity and ER performance.

EXPERIMENTS

Dye-coated TiO2 platelets on mica are synthesized for high-performance colorful ER fluids. A sol-gel method is utilized to grow TiO2 on mica to prepare precursor light-colored mica/TiO2 materials, which are coated with appropriate dyes to enhance the vividness as determined by the Commission Internationale de clairage L*a*b* color system. The color expression and color clarity improvement are explained via the light interference effect and the presence of chromophores.

FINDINGS

The uniform TiO2 layers can be obtained under low pH conditions with controlled nucleation kinetics. The addition of dyes to TiO2 increases the surface area and porosity of ER materials and introduces heteroatoms that act as positive factors. In practical ER applications, dye-coated TiO2-based ER fluids exhibit higher ER performances compared with the corresponding light-colored TiO2-based ER fluids. The vivid-colored ER fluids could provide an easy selection for a wide range of rheological systems requiring a specific magnitude of stress by confirming the color.

Titanium oxide-coated titanium-loaded metal organic framework (MOF-Ti) nanoparticles show improved electrorheological performance

Uniform small-sized MOF-Ti nanoparticles were prepared by a one-step hydrothermal method, and then a 5-10 nm TiO2 shell was coated onto them by using the sol-gel method, and MOF-Ti/TiO2 with a specific surface area of 50.2 m2 g-1 was successfully prepared. The nanoparticles were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), nitrogen adsorption-desorption isotherms (BET), and X-ray photoelectron spectroscopy (XPS). The above-analyses have elaborated the experimental study of their morphology, elements, and energy of organic functional groups. At the same time, through the use of a high-voltage rotary rheometer to test their rheological properties, the analysis of shear stress, ER efficiency, shear viscosity, etc. was performed and their dielectric constant and dielectric loss were studied by using a broadband dielectric spectrometer. Finally, we found that MOF-Ti/TiO2 is a new core-shell nanocomposite particle with a small particle size and good electrorheological properties.