Ultralow-Permittivity and Temperature-Stable Ba1-xCaxMg2Al6Si9O30 Dielectric Ceramics for C-Band Patch Antenna Applications.

Ca-substituted Ba1-xCaxMg2Al6Si9O30 ceramics were prepared to explore the relationships among their crystal structural parameters, phase compositions, dielectric properties, and coefficients of thermal expansion and applications in C-band antenna. The maximum solubility of Ba1-xCaxMg2Al6Si9O30 was located at x = 0.25, and Ba1-xCaxMg2Al6Si9O30 ceramics (0 ≤ x ≤ 0.25) crystallized in the space group P6/mcc. In Ba1-xCaxMg2Al6Si9O30 single-phase ceramics, εr was dominated by ionic polarizability and "rattling effects" of Ba2+ and Al(2)3+; Q × f was controlled by the roundness of [Si4Al2O18] inner rings and total lattice energy; and τf was affected by the bond valence of Si/Al(1)-O(1). Notably, the low average coefficients of thermal expansion (2.668 ppm/°C) at -150 °C ≤ T ≤ 850 °C and near-zero coefficients of thermal expansion (1.254 ppm/°C) at -150 °C ≤ T ≤ 260 °C were achieved for the Ba1-xCaxMg2Al6Si9O30 (x = 0.1) ceramic. Optimum microwave and terahertz dielectric properties were obtained for the Ba1-xCaxMg2Al6Si9O30 (x = 0.1) ceramic with εr = 5.80, Q × f = 31,174 at 13.99 GHz, τf = -7.10 ppm/°C, and εr = 5.71-5.85 at 0.2 THz ≤ f ≤ 1.0 THz. Also, the Ba1-xCaxMg2Al6Si9O30 (x = 0.1) ceramic substrate had been designed as a C-band patch antenna with a high simulated radiation efficiency (87.76%) and gain (6.30 dBi) at 7.70 GHz (|S11| = -38.41 dB).

Polygonal shaping and multi-singularity manipulation of optical vortices via high-order cross-phase.

Increasing demand for practical applications is forcing more in-depth research into optical vortices (OVs): from the generation and measurement to the shaping and multi-singularity manipulation of OVs. Herein, we propose a new type of phase structure called the high-order cross-phase (HOCP), which can be employed to modulate OVs to implement polygonal shaping and multi-singularity manipulation simultaneously at far-field. Theoretically, we investigate the propagation characteristics of OVs modulated by a HOCP. In experiments, we achieve the polygonal shaping and multi-singularity manipulation of OVs via HOCPs. On this basis, we discuss the relationship between shapes and the orders of HOCPs, where we find that the order of a HOCP is exactly equal to the number of sides of polygonal OVs. This work provides a novel method to achieve polygonal shaping and multi-singularity manipulation simultaneously, which facilitate applications in optical micro-manipulation and optical communication.

Synergistic Effects between Doped Nitrogen and Phosphorus in Metal-Free Cathode for Zinc-Air Battery from Covalent Organic Frameworks Coated CNT.

A covalent organic framework that is composed of hexachlorocyclotriphosphazene and dicyanamide has been coated on CNT to prepare metal-free oxygen reduction reaction catalyst through thermal polymerization of the Zn-air battery cathode. The N,P-codoped nanohybrids have highly porous structure and active synergistic effect between graphitic-N and -P, which promoted the electrocatalytic performance. The electrocatalysts exhibits remarkable half-wave potential (-0.162 V), high current density (6.1 mA/cm-2), good stability (83%), and excellent methanol tolerance for ORR in alkaline solution. Furthermore, the N,P-codoped nanohybrids were used as an air electrode for fabrication of a high performance Zn-air battery. The battery achieves a high open-circuit potential (1.53 V) and peak power density (0.255 W cm-2). Moreover, the effect of N,P codoping on the conjugate carbon system and the synergistic effect between graphitic-N and P have been calculated through density functional theory calculations, which are essentially in agreement with experimental data.