Covalent 0D–2D Heterostructuring of Co9S8–MoS2 for Enhanced Hydrogen Evolution in All pH Electrolytes

Ultrasmall Co₉S₈ nanoparticles are introduced on the basal plane of MoS₂ to fabricate a covalent 0D–2D heterostructure that enhances the hydrogen evolution reaction (HER) activity of electrochemical water splitting. In the heterostructure, separate phases of Co₉S₈ and MoS₂ are formed, but they are connected by Co–S–Mo type covalent bonds. The charge redistribution from Co to Mo occurring at the interface enhances the electron‐doped characteristics of MoS₂ to generate electron‐rich Mo atoms. Besides, reductive annealing during the synthesis forms S defects that activates adjacent Mo atoms for further enhanced HER activity as elucidated by the density functional theory (DFT) calculation. Eventually, the covalent Co₉S₈–MoS₂ heterostructure shows amplified HER activity as well as stability in all pH electrolytes. The synergistic effect is pronounced when the heterostructure is coupled with a porous Ni foam (NF) support to form Co₉S₈–MoS₂/NF that displays superior performance to those of the state‐of‐the‐art non‐noble metal electrocatalysts, and even outperforms a commercial Pt/C catalyst in a practically meaningful, high current density region in alkaline (>170 mA cm^?2) and neutral (>60 mA cm^?2) media. The high HER performance and stability of Co₉S₈–MoS₂ heterostructure make it a promising pH universal alternative to expensive Pt‐based electrocatalysts for practical water electrolyzers.     

A high capacity tunable retransmission type frequency coded chipless radio frequency identification system

This article presents a 12‐bit frequency coded chipless RFID system in the frequency range of 3 to 6 GHz. The system consists of a fully printable chipless tag and a pair of high‐gain reader antennas. The tag also incorporates its own antennas to improve the read range. Information is encoded into frequency spectrum using a multi‐resonant circuit. The circuit consists of multiple microstrip U and L‐shaped open stub resonators patterned in a unique configuration. The proposed configuration aids in capturing more data in a reduced space as well as tunable frequency operation. Tag and reader antennas utilize techniques such as stepped impedance feeding line, defective partial ground plane, and stair‐step patch structure to achieve wide‐band impedance bandwidth in miniature size. The results of the wireless measurements in the non‐anechoic environment show that the proposed system has a reading range of more than 20 cm. The presented system possesses great potential for low‐cost short‐range inventory tracking.     

Efficient Hydrogen Evolution Reaction Catalysis in Alkaline Media by All‐in‐One MoS2 with Multifunctional Active Sites

MoS₂ becomes an efficient and durable nonprecious‐metal electrocatalyst for the hydrogen evolution reaction (HER) when it contains multifunctional active sites for water splitting derived from 1T‐phase, defects, S vacancies, exposed Mo edges with expanded interlayer spacings. In contrast to previously reported MoS₂‐based catalysts targeting only a single or few of these characteristics, the all‐in‐one MoS₂ catalyst prepared herein features all of the above active site types. During synthesis, the intercalation of in situ generated NH₃ molecules into MoS₂ sheets affords ammoniated MoS₂ (A‐MoS₂) that predominantly comprises 1T‐MoS₂ and exhibits an expanded interlayer spacing. The subsequent reduction of A‐MoS₂ results in the removal of intercalated NH₃ and H₂S to form an all‐in‐one MoS₂ with multifunctional active sites mentioned above (R‐MoS₂) that exhibits electrocatalytic HER performance in alkaline media superior to those of all previously reported MoS₂‐based electrocatalysts. In particular, a hybrid MoS₂/nickel foam catalyst outperforms commercial Pt/C in the practically meaningful high‐current region (>25 mA cm^?2), demonstrating that R‐MoS₂‐based materials can potentially replace Pt catalysts in practical alkaline HER systems.     

Grain boundary precipitation in Inconel 718 and ATI 718Plus

Grain boundary precipitates in Inconel 718 and ATI 718Plus are important to control during hot working processes, since they can control the grain size. Precipitating excessive or insufficient amounts can be detrimental to the final component. Therefore, it is important for manufacturers to understand the formation and kinetics of grain boundary precipitation and the effect this has on mechanical properties. This review considers the background of grain boundary precipitation, including the effect of the thermal stability of γ′ and γ^″ phases. In addition, the effect of stress on the grain boundary phases and their precipitation kinetics in different conditions are also included. Also, the impact of grain boundary precipitation on the mechanical properties is explored.

This review was submitted as part of the 2017 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged     

Harnessing Photochemical Shrinkage in Direct Laser Writing for Shape Morphing of Polymer Sheets

Structures that change their shape in response to external stimuli unfold possibilities for more efficient and versatile production of 3D objects. Direct laser writing (DLW) is a technique based on two‐photon polymerization that allows the fabrication of microstructures with complex 3D geometries. Here, it is shown that polymerization shrinkage in DLW can be utilized to create structures with locally controllable residual stresses that enable programmable, self‐bending behavior. To demonstrate this concept, planar and 3D‐structured sheets are preprogrammed to evolve into bio‐inspired shapes (lotus flowers and shark skins). The fundamental mechanisms that control the self‐bending behavior are identified and tested with microscale experiments. Based on the findings, an analytical model is introduced to quantitatively predict bending curvatures of the fabricated sheets. The proposed method enables simple fabrication of objects with complex geometries and precisely controllable shape morphing potential, while drastically reducing the required fabrication times for producing 3D, hierarchical microstructures over large areas in the order of square centimeters.     

Identification of the main mixing process in the synthesis of alloy nanoparticles by laser ablation of compacted micropowder mixtures

Journal of Materials Science - Alloy nanoparticles offer the possibility to tune functional properties of nanoscale structures. Prominent examples of tuned properties are the local surface...     

A passive technique for detecting copy-move forgeries by image feature matching

Multimedia Tools and Applications - Due to the recent evolutions in the technologies various digital devices and image processing tools are available in the market. Consequently, crime rates are...