A facile synthesis of heterojunctional BiVO₄/Bi₅O₇I with enhanced photocatalytic activity for organic dyes degradation

Abstract Photocatalysis technology has risen to effectively degrade the hardly-degraded organic pollutants in recent years and the photocatalysts play an important role in striding the obstacles of the visible light response. Herein, a high-efficiency BiVO₄/Bi₅O₇I heterojunctional photocatalysts have been purposefully designed by controlling the reactant ratios and ultrasonic time of reaction at room temperature. Photocatalytic experimentals confirm that the prepared optimal BiVO₄/Bi₅O₇I composites displayed enhanced photocatalytic ability to degrade rhodamine B and quinoline blue under visible light irradiation. Furthermore, the photocatalysts exhibits high photostability and reusability proved by four consecutive cycling experiments. A possible mechanism of p–n heterojunctional BiVO₄/Bi₅O₇I composites enhanced the photocatalytic performance was discussed in detail on the basis of the reactive species trapping experiments in photocatalytic degradation process

Microstructure and crystallization mechanism of Ti-based bulk metallic glass by electron beam welding

Abstract In this work, we report on the successful welding of the Ti-based bulk metallic glass (BMG) plates via electron beam welding route. Microstructure determination shows that crystalline phases exist both in weld zone (WZ) and heat affected zone (HAZ). The critical cooling rate for glass formation in WZ is depended on the solidification condition. The continuous heating transformation curve (CHT) of glass transition temperature (Tg) and crystallization temperature (Tx) during heating process, time-temperature-transformation diagram (C-curve) during cooling process, and the thermal cycle curves are obtained by Kissinger equation, nucleation theory, and temperature field simulation, respectively. The crystallization mechanism in HAZ was discussed in details during the heating and cooling processes. The intersection between cooling curve and C-curve denotes the crystallization of HAZ during the cooling process

Combining Ce-metal–organic framework with CdS for efficient photocatalytic removals of heavy metal ion and organic pollutant under visible and solar lights

Abstract Among various emerging contaminants in water bodies, heavy metal ions and organic pollutants pose persistent damages that are hardly remediated naturally. In this regard, photocatalysis empowered by high-performance catalytic materials is a perfect fit. Herein, a series of CdS/Ce-MOF heterostructures were successfully synthesized through a facile hydrothermal method and superior photocatalytic abilities to remove Cr(VI) and Crystal violet (CV) from aqueous ambiences were unveiled. Up to 95.6% and 90% removal capabilities were reached for Cr(VI) and CV in 30 and 40 min by using as-prepared CdS/Ce-MOF heterojunctions as catalysts under solar light, and the capabilities retained high in cyclic tests. Following structural, morphological, optical, and electrochemical characterization results, the excellent photoredox ability of CdS/Ce-MOF was identified and attributed to enhanced visible light absorption ability and the improvement of charge separation ability in the heterostructure

Leaf-structure patterning for antireflective and self-cleaning surfaces on Si-based solar cells

Abstract As the naturally evolved sunlight harvester, plant foliage is gifted with dedicated air-leaf interfaces countering light reflections and ambient ruins, yet offering antireflective and self-cleaning prototypes for manmade photovoltaics. In this work, we report on an ecological and bio-inspired coating strategy by replicating leaf structures onto Si-based solar cells. Transparent photopolymer with leaf surface morphologies was tightly cured on Si slabs through a facile double transfer process. After bio-mimicked layer coverages, sunlight reflection drops substantially from more than 35% down to less than 20% once lotus leaf was employed as the master. Consequentially, 10.9% gain of the maximum powers of the photovoltaic is obtained. The leaf replicas inherited their masters’ hydrophobicity which is resistant to acidic and basic conditions. Physically adhered dusts are easily removed by water rolling. Lightwave guidance mechanism among air-polymer-Si interfaces is explicated through optical simulations, while wettability through the morphological impacts on hydrophobic states. Taking advantages of varieties of foliage species and surface structures, the work is hoped to boost large-scale industrial designs and realizations of the bionic antireflective and superhydrophobic coating on future solar cells

Antireflective design of Si-based photovoltaics via biomimicking structures on black butterfly scales

Abstract The naturally evolved sunlight harvesters are not limited to foliage. Animals also harvest sunlight for light-heat conversion. A typical antireflective and light-trapping scheme has been well demonstrated on thin butterfly scales where solar energy is converted to heat besides being diffracted for surface coloration. Biomimicking scale structures offers a unique route to enhance light harvesting efficiencies happening on manmade solar cells. Herein, we performed a computational investigation of using microstructures on black butterflies for solar cell efficiency enhancement. Scale microstructures were obtained from nine species of black butterflies and employed as coating structures in numerical models built on Si-slabs. Introducing butterfly wing structures not only reduces the light reflection and transmittance but also increases the light absorption within Si-slabs. Surface reflection was decreased down to 10%, and the short-circuit current was increased by 66% correspondingly. An antireflection design strategy is given and hoped to benefit light harvesting in Si-based solar cells eventually

Leaf-mimicking polymers for hydrophobicity and high transmission haze

Abstract Gifted with unique optical and hydrophobic properties, the plant leaves have been recently considered as micro/nanostructure prototypes for functional surface engineering. Imprinting bio-inspired structures onto surfaces can yield in similar functional properties than in the nature. In this article, we report on a simple and effective method to copy leaf surface structures onto poly-(methyl methacrylate) sheets. The replicated surface structures reduce optical reflectance and enhance optical haze. Besides, the artificial polymer sheets exhibit good hydrophobic properties. Correlation between optical haze and hydrophobicity was studied

Brazing ZrB₂-SiC ceramics to Ti6Al4V alloy with TiCu-based amorphous filler

Abstract In this work, the Ti-6Al-4V alloy and ZrB₂-SiC ultra-high temperature ceramic joint was brazed by TiCuZrNi amorphous filler at 910 °C with varied holding time. The element diffusion, microstructure and precipitation phase of the joints were analyzed in details. Reaction products in the joints were identified as β-Ti, (Ti,Zr)₂(Cu,Ni), TiCu, Ti₂Cu, TiC, Ti₅Si₃, TiB and TiB₂. The formation schemes of reaction products were investigated. The holding time has substantial impacts on interfacial microstructure and shear strength of joints. A maximum shear strength of 345 MPa of the joint was reached under a brazing temperature of 910 °C and holding time of 1200 s. It is also found that the shear strength depends on the amount of eutectic structure and brittle compounds in the joints

Introducing magnetism into 2D nonmagnetic inorganic layered crystals:a brief review from first-principles aspects

Abstract Pioneering explorations of the two-dimensional (2D) inorganic layered crystals (ILCs) in electronics have boosted low-dimensional materials research beyond the prototypical but semi-metallic graphene. Thanks to species variety and compositional richness, ILCs are further activated as hosting matrices to reach intrinsic magnetism due to their semiconductive natures. Herein, we briefly review the latest progresses of manipulation strategies that introduce magnetism into the nonmagnetic 2D and quasi-2D ILCs from the first-principles computational perspectives. The matrices are concerned within naturally occurring species such as MoS², MoSe², WS², BN, and synthetic monolayers such as ZnO and g-C²N. Greater attention is spent on nondestructive routes through magnetic dopant adsorption; defect engineering; and a combination of doping-absorbing methods. Along with structural stability and electric uniqueness from hosts, tailored magnetic properties are successfully introduced to low-dimensional ILCs. Different from the three-dimensional (3D) bulk or zero-dimensional (0D) cluster cases, origins of magnetism in the 2D space move past most conventional physical models. Besides magnetic interactions, geometric symmetry contributes a non-negligible impact on the magnetic properties of ILCs, and surprisingly leads to broken symmetry for magnetism. At the end of the review, we also propose possible combination routes to create 2D ILC magnetic semiconductors, tentative theoretical models based on topology for mechanical interpretations, and next-step first-principles research within the domain

Quantitative assessment of structural and compositional colors induced by femtosecond laser:a case study on 301LN stainless steel surface

Abstract The topic of durable coloration and passivation of metal surfaces using state-of-the-art techniques has gained enormous attention and devotion with unremitting efforts of researchers worldwide. Although femtosecond laser marking has been performed on many metals, the related coloration mechanisms are mainly referred to structural colors produced by the interaction of visible light with periodic surface structures. Yet, general quantitative determination of the resulting colors and their origins remain elusive. In this work, we realized quantitative separations of structural colors and compositional pigmentary colors on 301LN austenitic stainless steel surfaces that were treated by femtosecond laser machining. The overall color information was extracted from surface reflectance, with structural color given by numerical simulations, and oxide compositions by chemical state analysis. It was shown that the laser-induced apparent colors of 301LN steel surfaces were combinations of structural and compositional colorations, with the former dominating the angular response and the latter setting up the brownish bases. In addition to the quantification of colors, the analysis method in this work may be useful for the generation and specification of tailored color palettes for practical coloration on metal surfaces by femtosecond laser marking