Hydrogen termination of oxidized silicon in hydrofluoric acid results from an etching process that is now well understood and accepted. This surface has become a standard for studies of surface science and an important component in silicon device processing for microelectronics, energy, and sensor applications. The present work shows that HF etching of oxidized silicon carbide (SiC) leads to a very different surface termination, whether the surface is carbon or silicon terminated. Specifically, the silicon carbide surfaces are hydrophilic with hydroxyl termination, resulting from the inability of HF to remove the last oxygen layer at the oxide/SiC interface. The final surface chemistry and stability critically depend on the crystal face and surface stoichiometry. These surface properties affect the ability to chemically functionalize the surface and therefore impact how SiC can be used for biomedical applications.

Fast charging rate and large energy storage are becoming key elements for the development of nextgeneration batteries, targeting high-performance electric vehicles. Developing electrodes with high volumetric and gravimetric capacity that could be operated at a high rate is the most challenging part of this process. Using silicon as the anode material, which exhibits the highest theoretical capacity as a lithium-ion battery anode, we report a binder-free electrode that interconnects carbon-sheathed porous silicon nanowires into a coral-like network and shows fast charging performance coupled to high energy and power densities when integrated into a full cell with a high areal capacity loading. The combination of interconnected nanowires, porous structure, and a highly conformal carbon coating in a single system strongly promotes the reaction kinetics of the electrode. This leads to fast-charging capability while maintaining the integrity of the electrode without structural collapse and, thus, stable cycling performance without using binder and conductive additives. Specifically, this anode shows high specific capacities (over 1200 mAh g −1 ) at an ultrahigh charging rate of 7 C over 500 charge−discharge cycles. When coupled with a commercial LiCoO 2 or LiFePO 4 cathode in a full cell, it delivers a volumetric energy density of 1621 Wh L −1 with a LiCoO 2 cathode and a power density of 7762 W L −1 with a LiFePO 4 cathode.

The paper examines the effect of ownership and governance on firm performance. Tracing the post financial crisis experience, 1998-2002, of the Korean commercial bank industry, the paper investigates whether the involvement of foreign investors in the ownership structure had any significant effect on the banks' performance i.e., return and risk measures. Further, it examines the effects of the presence of outside directors, especially directors from foreign countries, in the corporate board structure impacts banks performance. Evidence indicates that the extent of the foreign ownership level, not the mere existence of foreign ownership, has a significant positive association with the bank return and a significant negative association with the bank risk. The number of outside board of directors does not have any significant affect on performance however the presence of a foreign director on that board is significantly associated with bank return and risk. These findings are relatively robust under the different specifications of performance measures.

The synthesis of a new type of redox‐active covalent triazine framework (rCTF) material, which is promising as an anode for Li‐ion batteries, is reported. After activation, it has a capacity up to ≈1190 mAh g−1 at 0.5C with a current density of 300 mA g−1 and a high cycling stability of over 1000 discharge/charge cycles with a stable Coulombic efficiency in an rCTF/Li half‐cell. This rCTF has a high rate performance, and at a charging rate of 20C with a current density of 12 A g−1 and it functions well for over 1000 discharge/charge cycles with a reversible capacity of over 500 mAh g−1. By electrochemical analysis and theoretical calculations, it is found that its lithium‐storage mechanism involves multi‐electron redox‐reactions at anthraquinone, triazine, and benzene rings by the accommodation of Li. The structural features and progressively increased structural disorder of the rCTF increase the kinetics of infiltration and significantly shortens the activation period, yielding fast‐charging Li‐ion half and full cells even at a high capacity loading.

Stretchable electronics are considered as next‐generation devices; however, to realize stretchable electronics, it is first necessary to develop a deformable energy device. Of the various components in energy devices, the fabrication of stretchable current collectors is crucial because they must be mechanically robust and have high electrical conductivity under deformation. In this study, the authors present a conductive polymer composite composed of Jabuticaba‐like hybrid carbon fillers containing carbon nanotubes and carbon black in a simple solution process. The hybrid carbon/polymer (HCP) composite is found to effectively retain its electrical conductivity, even when under high strain of ≈200%. To understand the behavior of conductive fillers in the polymer matrix when under mechanical strain, the authors investigate the microstructure of the composite using an in situ small‐angle X‐ray scattering analysis. The authors observe that the HCP produces efficient electrical pathways for filler interconnections upon stretching. The authors develop a stretchable aqueous rechargeable lithium‐ion battery (ARLB) that utilizes this HCP composite as a stretchable current collector. The ARLB exhibits excellent rate capability (≈90 mA h g−1 at a rate of 20 C) and outstanding capacity retention of 93% after 500 cycles. Moreover, the stretchable ARLB is able to efficiently deliver power even when under 100% strain.

Effects of rotary oscillation on unsteady laminar flow past a circular cylinder have been investigated in this study. Numerical simulations are performed for the flow at Re=100 in the range of 0.2⩽Ω⩽2.5 and 0.02⩽Stf⩽0.8, where Ω and Stf are, respectively, the maximum rotational speed and forcing oscillation frequency normalized by the free-stream velocity and cylinder diameter. Results show that the rotary oscillation has significant effects on the flow. The lock-on frequency range becomes wider as the rotational speed increases. In a non lock-on region, modulations in the velocity, lift and drag signals occur and the modulation frequency is expressed as a linear combination of the forcing frequency and vortex-shedding frequency. Also, the mechanism for the modulation phenomenon is presented in terms of the vortex merging process. Finally, it is found that the mean drag and amplitude of the lift fluctuations show local minima near the boundary between the lock-on and non lock-on regions.

We show that a high energy density can be achieved in a practical manner with freestanding electrodes without using conductive carbon, binders, and current collectors. We made and used a folded graphene composite electrode designed for a high areal capacity anode. The traditional thick graphene composite electrode, such as made by filtering graphene oxide to create a thin film and reducing it such as through chemical or thermal methods, has sluggish reaction kinetics. Instead, we have made and tested a thin composite film electrode that was folded several times using a water-assisted method; it provides a continuous electron transport path in the fold regions and introduces more channels between the folded layers, which significantly enhances the electron/ion transport kinetics. A fold electrode consisting of SnO/graphene with high areal loading of 5 mg cm has a high areal capacity of 4.15 mAh cm, well above commercial graphite anodes (2.50-3.50 mAh cm), while the thickness is maintained as low as ∼20 μm. The fold electrode shows stable cycling over 500 cycles at 1.70 mA cm and improved rate capability compared to thick electrodes with the same mass loading but without folds. A full cell of fold electrode coupled with LiCoO cathode was assembled and delivered an areal capacity of 2.84 mAh cm after 300 cycles. This folding strategy can be extended to other electrode materials and rechargeable batteries.

Cesium copper halides (CCHs) show promise for optoelectronic applications, and their syntheses usually involve high-temperatures and hazard solvents. Herein, the synthesis of highly luminescent and phase-pure Cs 3 Cu 2 X 5 (X = Cl, Br, and I) and CsCu 2 I 3 via a solvent-free mechanochemical approach through manual grinding is demonstrated. This costeffective approach can produce CCHs on a scale of tens to hundreds of grams. Rietveld refinement analysis of the X-ray diffraction patterns of the as-synthesized CCHs reveals their structural details. Notably, the emission characteristics of green-emitting, chloride-based CCHs remain stable even at elevated temperaturesmaintaining 80% of initial PL efficiency at 150 °C. Lastly, a postsynthetic reversible transformation between zero-and one-dimensional CCH materials is demonstrated, indicating the labile nature of their crystal structure. The proposed study suggests that mechanochemistry can be an alternative and promising synthetic tool for fabricating high-quality lead-free metal halides.