MXene Free Standing Films: Unlocking the Impact of Flake Sizes in Microwave Resonant Structures in Humid Environments

Microwave communication devices necessitate elements with high electrical conductivity, a property which was traditionally found in metals (e.g., copper). However, in applications such as satellite communications, metals prevent the payload from achieving lightweight and flexible characteristics. Here, we demonstrate the development of MXene film microwave resonators, leveraging MXene's high electrical conductivity and unique mechanical properties. To investigate resonant performance in humid conditions and study the effects of MXene's processing and treatment, MXene films with different flake sizes are prepared and exposed to cyclic humidity. For the large- and small-flake Ti₃C₂ MXene films in cyclic humidity, the large-flake film demonstrates higher electrical conductivity, higher resonance quality factor (150 and 35 as unloaded, and loaded), and less fluctuation of performance (≈1.7% total shift in resonance frequency). Further, by implementing MXene films of two different diameters, the correlation between film size and resonant frequency is demonstrated. By introducing an active resonant configuration, the effect of MXene degradation and microwave losses can be compensated. This active feedback loop demonstrates a ≈300 times increase in the quality factor of MXene resonators. As a building block for terrestrial and satellite communication modules, MXene resonators potentiate the replacement of metals in achieving unique electrical and mechanical properties.     

Thermodynamic and economic evaluation and optimization of the applicability of integrating an innovative multi-heat recovery with a dual-flash binary geothermal power plant

Clean Technologies and Environmental Policy - Generally, a stand-alone flash-binary geothermal power plant loses most of its input energy, so its efficiency declines accordingly. Its overall...     

The post-annealing effect on tribological and corrosion behaviors of CrN/AlCrN multilayered coating applied by CAE-PVD

The present study investigated the wear and electrochemical behaviors of CrN/AlCrN multilayered coatings post-annealed at 300, 450, and 600°C temperatures. The cathodic arc evaporation technique has been utilized to deposit the coatings. Scanning electron microscope, field emission SEM, energy-dispersive X-ray, grazing incidence X-ray diffraction, and Rockwell-C indenter methods were used to characterize the coatings and to investigate the interdiffusion between the multilayered CrN/AlCrN and the H13 base metal. The results showed that the sharp interface of the CrN and AlCrN layers was blurred by the annealing process supporting the interdiffusion of the layers. The reciprocating wear test and the microhardness tester were used to evaluate the coatings’ mechanical behavior. The hardness and roughness of the coatings were increased by increasing the post-annealing temperature. The smallest wear rates were observed for the samples treated at 300 and 450°C, which were approximately 17 times and 12 times smaller than the wear rate of the sample annealed at 600°C. Electrochemical testing was used to study the corrosion behavior of the coatings. The results showed that by increasing annealing temperature, corrosion resistances of the coatings are improved. As a result, the corrosion current density of the 600°C annealed coating was approximately 434 times smaller than as-deposited coatings.     

Investigation of mixing performance in a semi-active T-micromixer actuated by magnetic nanoparticles: Characterization via Villermaux–Dushman reaction

A semi-active T-type micromixer is designed to intensify micromixing by actuating magnetic nanoparticles (MNPs). Five permanent magnets in a zig-zag arrangement are located next to the mixing channel of the micromixer to apply the magnetic field to the fluid flow. Micromixing performance is considered in terms of the segregation index (X_S) by the Villermaux/Dushman reaction test. The effects of magnetic flux intensity (B = 380–500 mT), the concentration of MNPs (φ = 0.002–0.01 [w/v]), and flow rate ratios on X_S and pressure drop are investigated. By increasing MNPs concentration from φ = 0.002–0.008 (w/v), X_S decreased and the rise in φ up to 0.008 (w/v) has not been significant on X_S. Maximum mixing efficiency (i.e., minimum X_S = 0.0088) is achieved for B = 500 mT and φ = 0.01 (w/v). By applying the magnetic field, the mixing performance increased due to the motion of MNPs, but its negative effect is an increase in the pressure drop along the micromixer reactor. Generally, with the formation of MNPs barriers inside the mixing channel, the main fluid flows through these layers and creates the sinusoidal flow paths compared to no magnetic field conditions, and thus, a superior mixing efficiency could be attained.     

Large-scale precipitation synthesis of α-alumina with poly aluminum chloride: Optimization of synthesis parameters

α-Alumina production has been industrialized since many years ago. Nevertheless, there are still challenges in the efficient synthesis of α-alumina with subtle specifications for high-tech applications, specifically on large scales. So, here, we investigated the large-scale synthesis of α-alumina by the precipitation method and with industrial grade poly aluminum chloride (PAC) as the aluminum precursor, for the first time. The synthesis procedure was optimized in terms of synthesis yield and facilitation of α-alumina formation by adjusting the concentration of the precursor (PAC) and precipitant (NaOH) solutions. The samples were characterized by conducting several analyses, including X-ray diffraction, X-ray fluorescence, field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, dynamic light scattering, and gas adsorption. The results indicated the significant effects of PAC and NaOH concentrations on the synthesis yield and facilitation of the α-alumina formation. According to the results and process considerations, working at higher levels of PAC (.75 g/ml) and NaOH (1.0 M) concentrations was found to be the optimum synthesis conditions. Moreover, the potential of the optimized sample as the abrasive material and the catalyst support was evaluated. The results confirmed the high potential of the optimized sample in these applications. This study therefore introduces a promising and cost-effective method for the large-scale synthesis of versatile α-alumina.     

Studying the Role of Gelation Agents in Gelcasting Non-porous Si3N4 Bodies by Pressureless Sintering

Silicon - The monomer content in the gelcasting process affects the kinetics of cross-linking reactions which determines the quality of the gel network structure and the final properties of the...     

Fabrication and Properties of a Gel-Cast Dense Silicon Carbide Body

Silicon - In this research, the effect of different parameters on the behavior of suspension rheology, as well as the physical and mechanical properties of green and sintered SiC bodies, were...     

Keys to improve the efficiency of nanoparticle-stabilized foam injection based on influential mechanisms

The effect of the existence of nanoparticles on foam stability, foamability, and the oil recovery factor (RF) has been studied experimentally, and influential phenomena and mechanisms have been examined. A sequence of experiments, including, ‘foam bulk-static experiments’, ‘surface tension (ST) measurements,’ and ‘micromodel foam flood,’ were designed and then implemented to study the foam behaviour in two foam systems: (1) anionic-nanoparticles + cationic-surfactant and (2) anionic-nanoparticles + anionic-surfactant. This study provides a comprehensive insight into the mechanisms affecting the stability of nanoparticle-stabilized foam. Also, despite previous studies, the effect of Marangoni flow on nanoparticle-stabilized foam has been discussed briefly. Results show that the interactions of effective mechanisms work differently in the two series. In the like-charge system, surfactant molecules accumulate in the interface of lamellas due to repulsive forces; therefore, stability and foamability improve as surface tension and molecular diffusion reduce. Additionally, Marangoni flow restitutes the negative impact of gravity drainage. In the unlike-charge system, observations illustrate that nanoparticles reach the interface. The presence of nanoparticles at the interface increases detachment energy significantly, and as a result, the stability is boosted. The accumulation of nanoparticles in the interface changes it to a solid-like surface with limited diffusibility and viscosity. Although Marangoni flow is lost, reducing molecular diffusion improves foam stability. Flooding tests show that foam stability increment improves sweep efficiency at near-wellbore areas even when foamability is weak. Finally, it can be claimed that in the unlike-charge system, the sweep efficiency and foam stability increase to a greater extent.