Reactive Formation of Zircon Inclusion Pigments by Deposition and Subsequent Annealing of a Zirconia and Silica Double Shell

A novel general method for coating particles with a complex oxide was described. Zirconia precursor and silica layers with careful control of film thickness were coated separately onto hematite particles in corresponding solutions. A zircon shell was subsequently obtained by heat treatment at 800 °C for 3 h using LiF as a mineralizer. The as-prepared zircon-occluded hematite pigment gave a pink color to the glazed sample after annealing at 1120 °C. The current research suggests that various chromophoric particles can be encapsulated with zircon to prepare ceramic pigments for high-temperature use

Enantioselective 1,3-Dipolar (5+3) Cycloadditions of Oxidopyrylium Ylides and Vinylcyclopropanes toward 9‑Oxabicyclononanes

We have developed an efficient and mild enantioselective palladium-catalyzed (5+3) cycloaddition of vinylcyclopropanes and oxidopyrylium ylides generated in situ from benzopyranones, in the presence of a chiral PHOX ligand. These reactions afford various highly functionalized bridged oxa-[3.3.1]­carbocycles with three stereogenic centers that are challenging to synthesize, in moderate to good yields and enantioselectivities

Controlled Preparation and Mechanism Study of Zirconia-Coated Hematite Particles by Hydrolysis of Zirconium Sulfates

Zirconia-precursor-coated hematite particles were prepared by hydrolysis of zirconium sulfate in aqueous solution. The as-prepared zirconia-precursor shell was amorphous with a thickness of about several ∼30 nm that can be controllably achieved by varying the processing parameters and had a composition of Zr2(OH)6SO4, which crystallized to tetragonal ZrO2 after annealing at 700 °C. The focus of this work is to investigate in detail the process and to understand the key issues for surface coating in solution. The thermodynamic analysis on hydrolysis of zirconium sulfate was conducted, and a “surface-deposition region” for zirconia coating was suggested in this work. Furthermore, the kinetic study of the process was also described. The hydrolysis could be considered as a pseudo-second-order reaction at 50 °C, and the rate constant was calculated to be 0.61 L mol−1 s−1. The hydrolysis mechanism of zirconium salt was also interpreted from the viewpoint of structural chemistry. The influence of the surfactants on the coating process was also discussed

Tuning the Metal–Insulator Transition in TiO₂/VO₂ Superlattices by Modifying the Layer Thickness or Inducing Defects

Vanadium dioxide (VO2) is a thermochromic material that can be used in advanced applications such as smart energy-saving windows and other smart optical/electronic devices. However, obtaining a comfortable metal–insulator transition temperature while improving solar utilization in VO2 remains an unresolved question at both the fundamental and application levels of research. Although studies on designing TiO2/VO2 multilayers to address the above issues have been widely reported, the nature of the metal–insulator transition and how thickness and defects affect phase transition behaviors are still subjects of ongoing debate. Herein, by varying the VO2 or TiO2 layer thicknesses or inducing defects such as oxygen vacancies and interstitial Ti/V atoms, the metal–insulator behavior including the atomic and electronic structures of TiO2/VO2 superlattices was systematically investigated. Our results show that the V–V distances in (m + n)­TiO2/VO2(001) superlattices exhibit discontinuous dimerization characteristic and the superlattices exhibit alternating metal–insulator transition characteristics as the layer thickness m increases from 0 to 10. When 0 m = n < 10, the band gaps for (m + n)­TiO2/VO2(001) superlattices exhibit a downward-opening parabola. However, when 0 m m + n = 10, the band gaps fluctuate around 0.4 eV. Additionally, defects such as oxygen vacancies or cationic interstitial Ti/V atoms have a great impact on the metal–insulator transition in (m + n)­TiO2/VO2(001) superlattices. Oxygen vacancies are preferentially located in the VO2 layer. When oxygen vacancies are present in the TiO2 layer, they migrate across the interface into the VO2 layers, indicating that there is considerable interdiffusion of V/Ti interstitial atoms across the interface. The interstitial V atoms diffuse more easily into the VO2 layer than interstitial Ti atoms. The current findings may be useful in understanding the metal–insulator behavior of VO2/TiO2 superlattices by varying the layer thickness or inducing defects, thereby providing a new approach for designing VO2-based heterostructures for smart energy-saving windows or other smart optical/electronic devices

Bioinspired Ant-Nest-Like Hierarchical Porous Material Using CaCl₂ as Additive for Smart Indoor Humidity Control

Inspired by the functional microstructure of the ant nest, a humidity control material was prepared by the sintering of modified low-grade sepiolite. A hierarchical porous structure accelerates the diffusion of water vapor. Meanwhile, CaCl2 was applied subtly to enhance absorption/desorption of water vapor in response to the change of air relative humidity. The water vapor adsorption–desorption content reaches 550 g·m–2 with a steady performance after 10 cycles. The flexural strength of the specimen is excessive, 10 MPa. Furthermore, two model houses were used to evaluate the performance of the material in a real environment. The result indicated that it could narrow indoor humidity fluctuation by more than 10% RH spontaneously and mainly maintained the humidity within a healthy range (RH 40–70%) without energy consumption. This invention makes it possible for large-scale fabrication of this material in terms of wall bricks for smart indoor humidity control

Hydrothermal Synthesis of Ytterbium Silicate Nanoparticles

A simple, low-cost hydrothermal method was developed to synthesize 20-nm-diameter single-crystalline ytterbium silicate (Yb2Si2O7 and Yb2SiO5) nanoparticles at 200 °C. This is nearly 1000 °C lower than that for the typical sol−gel route to ytterbium silicate powders. Obtained powders showed very low thermal conductivity, a suitable thermal expansion coefficient, and excellent thermal/structural stability, suggesting a potential application to environmental and thermal barrier coatings. Special focus was placed on assessing the hydrothermal reaction mechanism for particle formation

Supplemental Material, sj-pdf-1-arx-10.1177_17298814211044934 - Parameters optimization of central pattern generators for hexapod robot based on multi-objective genetic algorithm

Supplemental Material, sj-pdf-1-arx-10.1177_17298814211044934 for Parameters optimization of central pattern generators for hexapod robot based on multi-objective genetic algorithm by Binrui Wang, Xiaohong Cui, Jianbo Sun and Yanfeng Gao in International Journal of Advanced Robotic Systems</p

Colorful Wall-Bricks with Superhydrophobic Surfaces for Enhanced Smart Indoor Humidity Control

Humidity-control materials have attracted increasing attention because of energy savings and smart regulation of indoor comforts. The current research is a successive work to face challenges, such as poor performance, limitations for large-scale production, and surface contamination. Here, we report a smart humidity-control wall-brick manufactured from sepiolite using CaCl2 as an additive. Low-temperature sintering generated a super hygroscopic interior structure, and further silane modification produced bricks with superhydrophobic surfaces. These superhydrophobic surfaces can promote the moisture storage and prevent the CaCl2 solution from leaking even after the surface is wiped 100 times. Meanwhile, the superhydrophobic surfaces make the wall-bricks easy to clean; also, these materials possess antifouling and antifungal properties. The 24 h and saturated moisture adsorption–desorption contents reached 630 and 1700 g·m–2, respectively. Furthermore, a test was performed using model houses in a real environment, which indicates that the wall-bricks can narrow the daily indoor humidity fluctuations by more than 20% in both wet and dry seasons. The white wall-brick can also be dyed with different colors and thus shows promise for applications in interior decorations of houses

Colorful Wall-Bricks with Superhydrophobic Surfaces for Enhanced Smart Indoor Humidity Control

Humidity-control materials have attracted increasing attention because of energy savings and smart regulation of indoor comforts. The current research is a successive work to face challenges, such as poor performance, limitations for large-scale production, and surface contamination. Here, we report a smart humidity-control wall-brick manufactured from sepiolite using CaCl2 as an additive. Low-temperature sintering generated a super hygroscopic interior structure, and further silane modification produced bricks with superhydrophobic surfaces. These superhydrophobic surfaces can promote the moisture storage and prevent the CaCl2 solution from leaking even after the surface is wiped 100 times. Meanwhile, the superhydrophobic surfaces make the wall-bricks easy to clean; also, these materials possess antifouling and antifungal properties. The 24 h and saturated moisture adsorption–desorption contents reached 630 and 1700 g·m–2, respectively. Furthermore, a test was performed using model houses in a real environment, which indicates that the wall-bricks can narrow the daily indoor humidity fluctuations by more than 20% in both wet and dry seasons. The white wall-brick can also be dyed with different colors and thus shows promise for applications in interior decorations of houses

Calculation Evidence of Staged Mott and Peierls Transitions in VO₂ Revealed by Mapping Reduced-Dimension Potential Energy Surface

Unraveling the metal–insulator transition (MIT) mechanism of VO₂ becomes tremendously important for understanding strongly correlated character and developing switching applications of VO₂. First-principles calculations were employed in this work to map the reduced-dimension potential energy surface of the MIT of VO₂. In the beginning stage of MIT, a significant orbital switching between σ-type d_<i>z</i>² and π-type d_{<i>x</i>²–<i>y</i>²}/d_<i>yz</i> accompanied by a large V–V dimerization and a slight twisting angle change opens a band gap of ∼0.2 eV, which can be attributed to the electron-correlation-driven Mott transition. After that, the twisting angle of one chain quickly increases, which is accompanied by the appearance of a larger change in band gap from 0.2 to 0.8 eV, even though orbital occupancy is maintained. This finding can be ascribed to the structure-driven Peierls transition. The present study reveals that a staged electron-correlation-driven Mott transition and structure-driven Peierls transition are involved in MIT of VO₂