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In this paper, a single-feed microstrip antenna (MA) equipped with a transmission-mode focusing metasurface (MS) is proposed to achieve dual-polarization capabilities and superior high-gain radiation performance. The original-feed MA comprises two distinct layers of coaxial-fed tangential patches, enabling it to emit a circular polarization (CP) wave with a gain of 3.5 dBic at 5.6 GHz and linear polarization (LP) radiation with a gain of 4 dBi at 13.7 GHz. To improve the performance of the single-feed MA, a dual-polarization transmission focusing MS is proposed and numerically substantiated. By positioning the originally designed MA at the focal point of the MS, we create a transmission-mode MS antenna system capable of achieving CP and LP radiations with the significantly higher gains of 12.9 dBic and 14.8 dBi at 5.6 GHz and 13.7 GHz, respectively. Measurements conducted on the fabricated dual-polarization focusing MS antenna closely align with the simulation results, validating the effectiveness of our approach. This work underscores the significant potential of dual-polarization high-speed data systems and offers a practical solution for enhancing antenna gains in contemporary wireless communication systems. [ABSTRACT FROM AUTHOR]

In order to solve the problem of difficult sintering and high brittleness of B4C-based ceramics, B4C@ZrB2-TiB2 composite powder was synthesized by molten salt method, and B4C–(Zr, Ti)B2 composite ceramics were successfully prepared by spark plasma sintering. The effects of different raw material ratios on the composition, microstructure, and mechanical properties of the prepared composite ceramics were characterized by XRD, XPS, SEM, and TEM. The results show that ZrB2 and TiB2 were grown on the surface of B4C by template mechanism to form a dense nanocrystalline coating, and the original surface of B4C was exposed gradually with the decrease of the ratio of metal powder. When the composite powders were sintered at 1700 °C, ZrB2 and TiB2 formed a solid solution, which can refine grains and improve strength. When the raw material ratio is n(B4C): n(Zr): n(Ti) = 12:1:1, the composite ceramics have excellent comprehensive properties, the Vickers hardness reaches 41.2 GPa. [ABSTRACT FROM AUTHOR]

In order to reduce the sintering temperature and improve the mechanical properties of B4C ceramics, ZrB2 was formed in situ using the SPS sintering method with ZrO2 and B4C as raw materials. Thermodynamic calculations revealed that CO pressure affected the formation of ZrB2 at temperatures from 814 °C to 1100 °C. The experimental results showed that the ZrB2 grain size was <5 µm and that the grains were uniformly distributed within the B4C ceramics. With an increase in ZrO2 content, the Vickers hardness and flexural strength of the B4C ceramics first increased and then decreased, while the fracture toughness continuously increased. When the content of ZrO2 was 15 wt%, the Vickers hardness, fracture toughness and flexural strength of B4C ceramics were 35.5 ± 0.63 GPa, 3.6 ± 0.24 MPa·m1/2 and 403 ± 10 MPa, respectively. These results suggest that ZrB2 inhibits B4C grain growth, eliminates crack tip stress, and provides fine grain to strengthen and toughen B4C ceramics. [ABSTRACT FROM AUTHOR]

Si3N4 powders were synthesized with Fe, Co, or Ni as catalysts using Si powder at 1250 °C in a nitrogen atmosphere by liquid-phase-assisted catalytic nitridation synthesis (LPA–CNS). The catalytic effects of the metals on the nitridation of silicon powder were investigated by mixing the powder with 2 wt% by mass of Fe, Co, or Ni in a high-temperature liquid phase in flowing nitrogen. The α-Si3N4 micro-morphology could be effectively changed by adjusting the type of catalyst in the initial reaction mixtures. Fe, Co, and Ni promoted the formation of α-Si3N4 at 1250 °C and controlled the morphology of the α-Si3N4 particles. The hexagonal flakes of α-Si3N4 with a better defined morphology were obtained using Ni as the catalyst, compared to that obtained from the other two catalysts. [ABSTRACT FROM AUTHOR]

Bio-inspired self-similar hierarchical honeycombs are multifunctional cellular topologies used for resisting various loadings. However, the crushing behavior under large plastic deformation is still unknown. This paper investigates the in-plane compressive response of selective laser melting (SLM) fabricated hierarchical honeycombs. The effects of hierarchical order, relative density as well as constituent material are evaluated. The results show that at small deformation, the AlSi10Mg alloy hierarchical honeycombs show great advantages over the elastic modulus and compressive strength than 316L steel hierarchical honeycombs. As the relative density and hierarchical order increase, the failure mechanism of AlSi10Mg alloy honeycombs gradually changes from a bending-dominated mode to a fracture-dominated mode; whereas all the 316L steel honeycombs fail due to the distortion of original unit cells. At large deformation, the AlSi10Mg alloy honeycombs behave with brittle responses, while the 316L steel honeycombs exhibit ductile responses, showing a negative Poisson's ratio behavior and gradient deformation of hierarchical unit cells. The addition of unit cell refinements improves the elastic modulus of AlSi10Mg alloy honeycombs and advances the densification of 316L steel honeycombs. In addition, the effect of constituent material on the compressive response of hierarchical honeycombs has been discussed. This study facilitates the development and future potential application of multifunctional ultra-light sandwich structures. [ABSTRACT FROM AUTHOR]

A novel nano-β-FeOOH/Fe3O4/biochar composite with enhanced photocatalytic performance and superparamagnetism was successfully fabricated via an environmentally friendly one-step method. The structural properties of the prepared composite were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and a vibrating sample magnetometer. The XPS spectrum of the as-prepared composites confirmed the presence of Fe-O-C bonds between β-FeOOH and biochar, which could be conducive to transfer photo-generated electrons. UV-vis spectroscopy confirmed the existence of an electron–hole connection between β-FeOOH and biochar, which promoted the rapid interface transfer of photogenerated electrons from β-FeOOH to biochar. These novel structures could enhance the response of biochar to accelerate the photoelectrons under visible light for more free radicals. Electron spin resonance analysis and free radical quenching experiments showed that •OH was the primary active species in the photodegradation process of methyl orange by nano-β-FeOOH/Fe3O4/biochar. In the synergistic photocatalytic system, β-FeOOH/Fe3O4/biochar exhibited excellent catalytic activity for the degradation of azo dye (methyl orange), which is 2.03 times higher than that of the original biochar, while the surface area decreased from 1424.82 to 790.66 m2·g−1. Furthermore, β-FeOOH/Fe3O4/biochar maintained a stable structure and at least 98% catalytic activity after reuse, and it was easy to separate due to its superparamagnetism. This work highlights the enhanced photocatalytic performance of β-FeOOH/Fe3O4/biochar material, which can be used in azo dye wastewater treatment. [ABSTRACT FROM AUTHOR]

The "HOPE-I" type high-current pulsed electron beam (HCPEB) equipment was used to irradiate the pure aluminum material with Zr coating preset by ball milling to realize the alloying of a Zr–Al coating surface. The microstructure and phase analysis were conducted by XRD, SEM, and TEM. The experimental results show that after Zr alloying on the Al surface by HCPEB, a layer of 15 μm was formed on the surface of the sample, which was mainly composed of Zr and Al–Zr intermetallic compounds. A large number of Al3Zr (Ll2) particles was uniformly distributed in the alloyed layer, and the Al grains were obviously refined. In addition, the surface hardness and corrosion resistance of the samples were improved significantly after HCPEB irradiation. [ABSTRACT FROM AUTHOR]

Lightweight aluminum honeycomb is a buffering and energy-absorbed structure against dynamic impact and explosion. Direct and indirect explosions with different equivalent explosive masses are applied to investigate the in-plane deformation characteristics and energy-absorbing distribution of aluminum honeycombs. Two finite element models of honeycombs, i.e., rigid plate-honeycomb-rigid plate (RP-H-RP) and honeycomb-rigid plate (H-RP) are created. The models indicate that there are three deformation modes in the X1 direction for the RP-H-RP, which are the overall response mode at low equivalent explosive masses, transitional response mode at medium equivalent explosive masses, and local response mode at large equivalent explosive masses, respectively. Meanwhile, the honeycombs exhibit two deformation modes in the X2 direction, i.e., the expansion mode at low equivalent explosive masses and local inner concave mode at large equivalent explosive masses, respectively. Interestingly, a counter-intuitive phenomenon is observed on the loaded boundary of the H-RP. Besides, the energy distribution and buffering capacity of different parts on the honeycomb models are discussed. In a unit cell, most of the energy is absorbed by the edges with an edge thickness of 0.04 mm while little energy is absorbed by the other bilateral edges. For the buffering capacity, the honeycomb in the X1 direction behaves better than that in the X2 direction. [ABSTRACT FROM AUTHOR]

The effect of colloidal silica (CS) on the hydrate phases and microstructure evolution of calcium aluminate cement (CAC) was investigated. Samples hydrated with CS were obtained and characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared spectroscopy (FT-IR), hydration heat measurement and Nuclear Magnetic Resonance (NMR). The results revealed that SiO2 nanoparticles may affect the hydrates crystallization process. There was a compact structure in the CAC paste with CS, while petal-shaped hydrates with a porous structure were formed in the pure CAC paste. The maximum value of electrical conductivity for CAC paste with CS suggested that the early stage of hydration for CAC was accelerated. However, the hydration heat curves revealed that the late stage of the CAC hydration process was inhibited, and the hydration degree was reduced, this result was in accordance with Thermogravimetry-Differential scanning calorimetry(TG-DSC) curves. The fitting results of hydration heat curves further showed that the hydration degree at NG (nucleation and crystal growth) process stage was promoted, while it was limited at the phase boundaries stage, and the diffusion stage in the hydration reaction was brought forward due to the addition of CS. According to these results and analyses, the differences in the hydration process for CAC with and without CS can be attributed to the distribution and nucleation effect of SiO2 nanoparticles. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction of NOx with NH3 is one of the most widely used technologies in denitration. Vanadium-based catalysts have been extensively studied for the deNOx process. V2O5/WO3(MoO3)TiO2 as a commercial catalyst has excellent catalytic activity in the medium temperature range. However, it has usually faced several problems in practical industrial applications, including narrow windows of operation temperatures, and the deactivation of catalysts. The modification of vanadium-based catalysts will be the focus in future research. In this paper, the chemical composition of vanadium-based catalysts, catalytic mechanism, the broadening of the temperature range, and the improvement of erosion resistance are reviewed. Furthermore, the effects of four major systems of copper, iron, cerium and manganese on the modification of vanadium-based catalysts are introduced and analyzed. It is worth noting that the addition of modified elements as promoters has greatly improved the catalytic performance. They can enhance the surface acidity, which leads to the increasing adsorption capacity of NH3. Surface defects and oxygen vacancies have also been increased, resulting in more active sites. Finally, the future development of vanadium-based catalysts for denitration is prospected. It is indicated that the main purpose for the research of vanadium-based modification will help to obtain safe, environmentally friendly, efficient, and economical catalysts. [ABSTRACT FROM AUTHOR]

This study simulated the bulk structure and surface energy of Al₂O₃ based on the density of states (DOS) and studied the synthesis and microstructure of one-dimensional Al₂O₃ whiskers. The simulation results indicate that the (001) surface has a higher surface energy than the others. The growth mechanism of Al₂O₃ whiskers follows vapor-solid (VS) growth. For the (001) surface with the higher surface energy, the driving force of crystal growth would be more intense in the (001) plane, and the alumina crystal would tend to grow preferentially along the direction of the (001) plane from the tip of the crystal. The Al₂O₃ grows to the shape of whisker with [001] orientation, which is proved both through modeling and experimentation., Competing Interests: The authors declare no conflict of interest.