BiVO4 based high k microwave dielectric materials: a review

The BiVO4material has attracted much attention in recent years due to its active photocatalytic properties under visible light, bright yellow color as a nontoxic pigment, and its high relative permittivity (ϵr) and Qf (quality factor, Q × resonant frequency, f) as a potential microwave dielectric ceramic. In this review, we introduce the origin, synthesis, crystal structure and phase transitions of the four polymorphic phases of BiVO4: orthorhombic (pucherite), zircon (dreyerite), scheelite monoclinic (clinobisvanite) and scheelite tetragonal. We then precis recent studies on doped BiVO4ceramics in terms of A site, B site and A/B site complex substitutions. Low sintering temperature (<800 °C) and high ϵrvalues could be obtained in some solid solution ceramics and near zero temperature coefficient of resonant frequency (TCF/τf) values could be achieved in layered or granulated particle composite ceramics. Besides, a series of temperature stable high ϵrmicrowave dielectric ceramics can also be obtained for many co-fired composite ceramics, such as BiVO4-TiO2, and BiVO4-TiO2-Bi2Ti4O11. The high ϵr, high Qf value, low sintering temperature and chemical compatibility with some base metals suggest that BiVO4-based materials are strong candidates for both LTCC and other microwave device applications in current 4G and future 5G technologies

Corrosion of glaze in the marine environment: study on the green-glazed pottery from the Southern Song “Nanhai I” shipwreck (1127–1279 A.D.)

Abstract The “Nanhai I” shipwreck is an important discovery in the underwater archaeology of China, and many ceramics have been unearthed. These ceramics are important material artifacts of China’s “Maritime Silk Road” and have considerable significance for the study of foreign trade in the Southern Song Dynasty (1127–1279 A.D.). However, these ceramics have been buried in a marine environment for approximately 800 years and have all been corroded to varying degrees, with green-glazed pottery being the most severely corroded. In this study, the chemical compositions of five samples of green-glazed pottery and the corrosion morphology and mechanism of a representative sample were analyzed by optical microscopy, scanning electron microscopy-energy dispersive X‐ray spectrometry (SEM–EDS), Raman spectroscopy, and X-ray diffraction (XRD). Results: The green glaze is a low-temperature silica-aluminum oxide-lead oxide (SiO2-Al2O3-PbO) glaze with copper ions (Cu2+) as the main colorant. The corrosion morphology is characterized by alternating silicon (Si)- and lead (Pb)-rich layers, a sharp reaction interface between the Si-rich layer and the pristine glaze, and a relatively high porosity of the Si-rich gel layer, which is formed by the accumulation of spherical hydrated silica colloidal particles. These features suggest that the glaze was corroded through an interface-coupled dissolution–precipitation mechanism and that the properties of the gel pores controlled the reaction kinetics. Fluctuations in the solution properties at the reaction interface produced the complex morphology of the gel layer, whereas changes in the dryness and humidity of the environment are not essential factors. The samples have been corroding in the marine environment for nearly a thousand years, and explorations of the corrosion morphology and mechanism could provide reference information on the corrosion of various ancient ceramics and glasses and a basis for scientific conservation of these objects

Pseudomonas aeruginosa airway infection recruits and modulates neutrophilic myeloid-derived suppressor cells

Pseudomonas aeruginosa is an opportunistic pathogen that causes infections mainly in patients with cystic fibrosis (CF) lung disease. Despite innate and adaptive immune responses upon infection, P. aeruginosa is capable of efficiently escaping host defenses, but the underlying immune mechanisms remain poorly understood. Myeloid-derived suppressor cells (MDSCs) are innate immune cells that are functionally characterized by their potential to suppress T- and natural killer (NK)-cell responses. Here we demonstrate, using an airway in vivo infection model, that P. aeruginosa recruits and activates neutrophilic MDSCs, which functionally suppress T-cell responses. We further show that the CF gene defect (cystic fibrosis transmembrane conductance regulator, CFTR) modulates the functionality, but not the recruitment or generation of neutrophilic MDSCs. Collectively, we define a mechanism by which P. aeruginosa airway infection undermines host immunity by modulating neutrophilic MDSCs in vivo