Performance Investigations of Quasi-Yagi Loop and Dipole Antennas on Silicon Substrate for 94 GHz Applications

This paper introduces the design and implementation of two high gain Quasi-Yagi printed antennas developed on silicon substrate for 94 GHz imaging applications. The proposed antennas are based on either driven loop or dipole antennas fed by a coplanar waveguide (CPW) feeding structure. For better matching with the driven antennas, a matching section has been added between the CPW feedline and the driven antenna element. To improve the gain of either loop or dipole antennas, a ground reflector and parasitic director elements have been added. Two Quasi-Yagi antenna prototypes based on loop and dipole antenna elements have been fabricated and experimentally tested using W-band probing station (75–110 GHz). The measured results show good agreement with simulated results and confirm that the proposed antennas are working. In addition, a feed and matching configuration is proposed to enable coupling a microbolometer element to the proposed Quasi-Yagi antenna designs for performing radiation pattern measurements

Fabrication and Characterization of a W-Band Cylindrical Dielectric Resonator Antenna-Coupled Niobium Microbolometer

We report on the fabrication and characterization of a novel antenna-coupled detector configuration for detection at 94 GHz, a coplanar waveguide- (CPW-) fed, slot-excited twin dielectric resonator antenna- (DRA-) coupled niobium (Nb) microbolometer. The antenna is based on two low permittivity cylindrical dielectric resonators (CDRs) excited by rectangular slots placed below the CDRs. The antenna resonant currents are fed to an Nb microbolometer by the means of a CPW feed. The ceramic DRA structure is manufactured using a novel fabrication process that enables patterning an SU-8–Alumina (Al2O3) nanopowder composite using conventional photolithography. The detector measured a voltage responsivity of 0.181 V/W at a modulation frequency of 150 Hz. The detector measured a time constant of 1.94 μs. The antenna radiation pattern of the developed detector configuration was measured and shows a good agreement with the simulation

Mesoporous and macroporous Ag-doped Co3O4 nanosheets and their superior photo-catalytic properties under solar light irradiation

An ideal photocatalyst should have a wider absorption capacity, a larger surface area, a narrow optical band gap, a better electronic conductivity, a lower load transfer resistance and a minimum charge recombination probability. Herein, mesoporous and macroporous nanosheets of Ag·Co3O4 have been synthesized via a two-step hydrothermal and post-annealing approach. The catalytic activities of the doped and undoped Co3O4 samples were tested and compared using Methylene Blue dye (MB) as a model pollutant. The specific surface area, optical band gap, electrical conductivity, and charge transfer resistance of the fabricated samples were analyzed using BET, UV/Visible, I–V, and EIS analyses. The Ag·Co3O4 sample showed a higher catalytic aptitude than the pristine Co3O4 sample because it degrades comparatively higher concentration of MB dye at a faster rate under natural sunlight irradiation. Specifically, the Ag·Co3O4 sample eliminated 88.4% MB dye at the rate constant (k) of 2.1 × 10−2 min−1 in only 90 min of solar irradiation. The outstanding removal efficiency and higher rate performance of the Ag·Co3O4 sample is attributed to its novel bimodal-porous structure, higher surface area (258 m2 g-1), narrow bandgap (1.55 eV), good electrical conductivity (1.5 × 105 Sm−1) and smaller charge transfer resistance. The exceptional activity of the Ag·Co3O4 sample under solar irradiation reveal its greatest potential to eliminate toxic and harmful dyes from industrial effluents

Fabrication of CNTs supported binary nanocomposite with multiple strategies to boost electrochemical activities

Electroactive materials with higher surface area, porous structure, higher conductivity, and self-supported design are considered promising candidates for electrochemical applications. The fabrication of an electrode material with a unique design having all the features mentioned above is a major challenge for electrochemical researchers. In this work, pristine CoS2 nanoparticles and CoS2/CNTs nanocomposite have been prepared and decorated directly on nickel foam (NF) using a two-step approach: hydrothermal and post-annealing, for energy storage applications. The CoS2/CNTs@NF electrode shows superior performance as it has a specific capacity (Csp) of 499.8 C g−1 @ 1 A g−1 and excellent cyclic stability of 90.8% after 6000 GCD cycles @ 12 A g−1. The CNTs-supported CoS2 sample displays a minimum capacitance loss of 13.5% by increasing the applied current density from 1 to 12 A g−1, demonstrating its excellent rate-capability. Furthermore, the EIS results show that the value of the charge transfer resistance (RCT) and the mass transfer resistance for CoS2 decreases after its nanocomposite formation with conductive CNTs. The exceptional electrochemical activity of the CoS2/CNTs@NF electrode has been attributed to the synergistic effect of its self-standing design, larger specific surface area, porous-nanostructure, and hybrid composition. The present study provides a new way of designing the electrode material with integrated electrochemical features

The impact of highly paramagnetic Gd\u3csup\u3e3+\u3c/sup\u3e cations on structural, spectral, magnetic and dielectric properties of spinel nickel ferrite nanoparticles

In this work, fabrication of Gd3+ substituted nickel spinel ferrite (NiGdxFe2-xO4) nanoparticles was carried out via co-precipitation route. X-ray powder diffraction (XRD) confirmed the spinel cubic structure of NiGdxFe2-xO4 nanoparticles. XRD data also facilitated to determine the divalent and trivalent metal cations distribution at both A and B sites of the ferrite lattice. Site radii, hopping and bond lengths were also calculated from XRD data. The spectral studies elucidated the formation of cubic spinel ferrite structure as well as stretching vibrations of M–O (metal–oxygen) bond at A and B sites of ferrites, represented by two major bands υ1 and υ2 respectively. FESEM analysis confirmed the irregular morphology of NiGdxFe2-xO4 nanoparticles. EDX spectrographs estimated the elemental compositions. The dielectric attributes were explained on the basis of the Debye-relaxation theory and Koop\u27s phenomenological model. At higher applied frequencies (AC) no prominent dielectric loss was observed. Magnetic parameter variations can be attributed to the substitution of the rare earth cations having larger ionic radii as compared to the radii of Fe3+ ions. Moreover, spin canting, magneto-crystalline anisotropy and exchange energy of electrons also helped in magnetic evaluation. Due to small coercivity values NiGdxFe2-xO4 nanoparticles can be employed significantly in high-frequency data storage devices

Hydrothermal synthesis of CuS nanochips and their nanohybrids with CNTs for electrochemical energy storage applications

The nanostructured carbonaceous materials (CNTs, graphene, and activated carbon) possess excellent conductivity, larger surface area, good chemical stability, and unique structure. Therefore, these materials have great potential to boost the electrochemical performance of the transition metals based pseudocapacitive materials. In this study, the hydrothermal method was used to prepare copper sulfide nanochips. The electrical conductivity and capacitive properties of the fabricated sample were improved by forming their nanohybrid with conductive as well as capacitive CNTs. The morphological, structural, compositional, and electrical behavior of materials was investigated by conducting various analyses. The calculated electrical conductivity value of the nanohybrid sample (2.34 × 102 Sm−1) was considerably higher than the bare sample (1.85 × 10−4 Sm−1), which ensured the existence of a positive association between cobalt sulfide nanochips and one-dimensional CNTs. During electrochemical testing, the nanohybrid sample showed a much better capacitive ability than the pristine cobalt sulfide sample due to its tuned electrical properties, hybrid composition, and constructive interaction between its supplements. More precisely, the nanohybrid sample displayed a good gravimetric capacitance (Cg) (677 Fg-1) at 1 Ag-1 and excellent capacitance retention (81.9%) at 5 Ag-1. Moreover, the nanohybrid sample showed superior cyclic-aptitude as it lost only 17.7% capacity, whereas the pristine metal sulfide sample lost nearly 36% of its initial capacity after 1000 cyclic discharge experiments. The electrochemical results showed that our synthesized sample offer excellent potential for practical application in next-generation electrochemical equipments

Visible light irradiated photocatalytic activity of copper substituted CoMn2O4 nanoparticles

In the current investigation, copper substituted cobalt manganese spinel oxide (Cux Co1–x Mn2 O4) photocatalyst was prepared via the co-precipitation method. The synthesized nanoparticles were characterized by X-ray diffraction, field emission scanning electron microscopy, and Fourier-transform infrared spectroscopy. The prepared Cu0.2 Co1–0.2 Mn2 O4 nanoparticle exhibited excellent photocatalytic activity for degradation of typical organic-based dye Methylene blue (MB). Furthermore, the comparative study of pure CoMn2 O4 and Cu-substituted CoMn2 O4 nanoparticles (NPs) towards the photocatalytic performance was also conducted. As compared to the CoMn2 O4 nanoparticles, the Cux Co1–x Mn2 O4 nanoparticles exhibited excellent photocatalytic capability for the degradation of MB dye. After 80 min of visible light irradiation, the decomposition of MB by Cux Co1–x Mn2 O4 nanoparticles was higher as compared to degradation MB dye in the presence of copper substituted CoMn2 O4 NPs. Copper substituted cobalt manganese oxide nano-photocatalyst was also used for comparative study. The Cu0.2 Co(1–0.2) Mn2 O4 showed excellent (~86%) photocatalytic performance in contrast with Cu0 CoMn(1–0) O4 (22%), Cu0.5 Co(1–0.5) Mn2 O4 (57), Cu0.1 Co(1–0.1) Mn2 O4 (60%), Cu0.15 Co(1–0.15) Mn2 O4 (73%) for the degradation of MB in visible light irradiation. The enhanced photocatalytic activity is mainly attributed to the optimized bandgap, which might have developed by the inclusion of copper ions into the CoMn2 O4 spinel oxide. The copper substitution not only contributed to the inhibition of photo-induced electron–hole pairs but also assisted a great redox capability. Cux Co1–x Mn2 O4 photocatalyst holds great potential for massive pollutant treatment due to the superb photocatalytic performance for organic pollutants