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Stabilization of the Alkylammonium Cations in Halide Perovskite Thin Films by Water-Mediated Proton Transfer
No full textThe development of alkylammonium lead trihalide perovskite (ALHP) photovoltaics has grown rapidly over the past decade. However, there are remaining critical challenges, such as proton defects, which can lead to the material instability of ALHPs. Although specific strategies, including the use of halide additives, have significantly reduced the defects, a fundamental understanding of the defect passivation mechanism remains elusive. Herein, an approach and mechanism for minimizing proton defects in ALHP crystals by adding ionized halides to the perovskite precursor solution are reported. This work clarifies that the ionized halides induced proton transfer from H2O to the alkylammonium cation in the precursor solution, stabilizing the ALHP crystals. The fundamental characteristics of ALHP and its precursors are examined by X-ray diffraction, transmittance electron microscopy, in situ extended X-ray absorption fine structure, Fourier transform NMR spectroscopy, and Fourier transform infrared spectroscopy. The findings from this work will guide the development of highly stable ALHP crystals, enabling efficient and stable optoelectronic ALHP devices
Technological Leadership in Industry 4.0: A Comparison Between Manufacturing and ICT Sectors Among Korean Firms
No full textThis paper examines the technological structures of the manufacturing and the ICT sectors in Korea to examine the potential shift of dominant technological sectors in the era of the Fourth Industrial Revolution (4IR). By using patent data of Korean firms from 1990 to 2021, we find that the manufacturing sector has been the dominant technological leader in Korea in terms of both the number of patents and the diversity of technologies, even in the era of 4IR. Although the ICT sector has shown an increasing focus on Industry 4.0 (I4) technologies after the 2000s, indicating the potential for a shift in dominance in the future, the gap between the two sectors is still significant. The study also reveals that the manufacturing sector tends to diversify technologies, while the ICT sector specializes in several target technologies. Our analysis also suggests that both sectors exhibit path-dependency, with the ICT sector exhibiting stronger characteristics, and firms in both sectors shows the tendency of intensive and extensive margin in their patenting activities, with the manufacturing sector exhibiting the stronger tendency
Long-range ordered porous carbons produced from C-60
No full textCarbon structures with covalent bonds connecting C-60 molecules have been reported(1-3), but their production methods typically result in very small amounts of sample, which restrict the detailed characterization and exploration necessary for potential applications. We report the gram-scale preparation of a new type of carbon, long-range ordered porous carbon (LOPC), from C-60 powder catalysed by alpha-Li3N at ambient pressure. LOPC consists of connected broken C-60 cages that maintain long-range periodicity, and has been characterized by X-ray diffraction, Raman spectroscopy, magic-angle spinning solid-state nuclear magnetic resonance spectroscopy, aberration-corrected transmission electron microscopy and neutron scattering. Numerical simulations based on a neural network show that LOPC is a metastable structure produced during the transformation from fullerene-type to graphene-type carbons. At a lower temperature, shorter annealing time or by using less alpha-Li3N, a well-known polymerized C-60 crystal forms owing to the electron transfer from alpha-Li3N to C-60. The carbon K-edge near-edge X-ray absorption fine structure shows a higher degree of delocalization of electrons in LOPC than in C-60(s). The electrical conductivity is 1.17 x 10(-2) S cm(-1) at room temperature, and conduction at T < 30 K appears to result from a combination of metallic-like transport over short distances punctuated by carrier hopping. The preparation of LOPC enables the discovery of other crystalline carbons starting from C-60(s)
Self-Catalytic Ternary Compounds for Efficient Synthesis of High-Quality Boron Nitride Nanotubes
No full textThe large-scale synthesis of high-quality boron nitride nanotubes (BNNTs) has attracted considerable interests due to their applications in nanocomposites, thermal management, and so on. Despite decades of development, efficient preparation of high-quality BNNTs, which relies on the effective design of precursors and catalysts and deep insights into the catalytic mechanisms, is still urgently needed. Here, a self-catalytic process is designed to grow high-quality BNNTs using ternary W-B-Li compounds. W-B-Li compounds provide boron source and catalyst for BNNTs growth. High-quality BNNTs are successfully obtained via this approach. Density functional theory-based molecular dynamics (DFT-MD) simulations demonstrate that the Li intercalation into the lattice of W2B5 promotes the formation of W-B-Li liquid and facilitates the compound evaporation for efficient BNNTs growth. This work demonstrates a high-efficient self-catalytic growth of high-quality BNNTs via ternary W-B-Li compounds, providing a new understanding of high-quality BNNTs growth
Reelin and APP Cooperatively Modulate Dendritic Spine Formation In Vitro and In Vivo
No full textAmyloid precursor protein (APP) plays an important role in the pathogenesis of Alzheimer???s disease (AD), but the normal function of APP at synapses is poorly understood. We and others have found that APP interacts with Reelin and that each protein is individually important for dendritic spine formation, which is associated with learning and memory, in vitro. However, whether Reelin acts through APP to modulate dendritic spine formation or synaptic function remains unknown. In the present study, we found that Reelin treatment significantly increased dendritic spine density and PSD-95 puncta number in primary hippocampal neurons. An examination of the molecular mechanisms by which Reelin regulates dendritic spinogenesis revealed that Reelin enhanced hippocampal dendritic spine formation in a Ras/ERK/CREB signaling-dependent manner. Interestingly, Reelin did not increase dendritic spine number in primary hippocampal neurons when APP expression was reduced or in vivo in APP knockout (KO) mice. Taken together, our data are the first to demonstrate that Reelin acts cooperatively with APP to modulate dendritic spine formation and suggest that normal APP function is critical for Reelin-mediated dendritic spinogenesis at synapses
Sulfur-Rich N-Doped Co9S8 Catalyst for Highly Efficient and Durable Overall Water Electrolysis Application
No full textFacile template-free controllable growth of freestanding polyhedron-like CoS onto microporous Ni foam with three-dimensional architecture via a mild hydrothermal technique is reported. The as-obtained CoS catalyst phase was first tailored to N-Co9S8 (nitrogen doped Co9S8), and its inherent reaction kinetics and conductivity were then enhanced through sulfur incorporation via a hydrothermal process. The electrochemical performance of the pristine CoS and a sulfur-enriched N-Co9S8 (S, N-Co9S8) electrode in alkaline 1.0 M KOH was examined. The optimized polyhedral S, N-Co9S8 structured catalyst exhibits significantly enhanced electrocatalytic activity for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). As a result, low overpotentials of 244 and -92 mV is required to achieve the current density of 10 mA cm(-2) for the OER and HER, respectively. Furthermore, when the polyhedral S, N-Co9S8 catalyst was employed as a bifunctional catalyst in a two-electrode electrolyzer cell exhibiting a cell voltage of 1.549 V at 10 mA cm(-2) and demonstrates excellent long-term (50 hrs.) chronopotentiometric electrolysis at various current rate, reveals excellent bifunctional OER and HER activities at different applied current densities. The superior OER and HER activities of the S, N-Co9S8 catalyst is result of the improved electronic conductivity and enhanced intrinsic reaction kinetics, which led to the enhanced electrocatalytically active sites after the incorporation of heteroatoms in the catalyst structure
The Atomic Drill Bit: Precision Controlled Atomic Fabrication of 2D Materials
No full textThe ability to deterministically fabricate nanoscale architectures with atomic precision is the central goal of nanotechnology, whereby highly localized changes in the atomic structure can be exploited to control device properties at their fundamental physical limit. Here, an automated, feedback-controlled atomic fabrication method is reported and the formation of 1D-2D heterostructures in MoS2 is demonstrated through selective transformations along specific crystallographic orientations. The atomic-scale probe of an aberration-corrected scanning transmission electron microscope (STEM) is used, and the shape and symmetry of the scan pathway relative to the sample orientation are controlled. The focused and shaped electron beam is used to reliably create Mo6S6 nanowire (MoS-NW) terminated metallic-semiconductor 1D-2D edge structures within a pristine MoS2 monolayer with atomic precision. From these results, it is found that a triangular beam path aligned along the zig-zag sulfur terminated (ZZS) direction forms stable MoS-NW edge structures with the highest degree of fidelity without resulting in disordering of the surrounding MoS2 monolayer. Density functional theory (DFT) calculations and ab initio molecular dynamic simulations (AIMD) are used to calculate the energetic barriers for the most stable atomic edge structures and atomic transformation pathways. These discoveries provide an automated method to improve understanding of atomic-scale transformations while opening a pathway toward more precise atomic-scale engineering of materials
Numerical evaluation of the cryogenic cooling effect on compacted graphite iron during end-milling
No full textCompacted graphite iron (CGI) is a metal that exhibits remarkable mechanical properties based on the adhesion of graphite and iron particles. CGI has attracted considerable attention from the automobile industry and has been used as a substitute for gray iron. However, CGI is hard to machine because of high strength and toughness. In this study, a cryogenic machining process was applied to CGI, and numerical studies were performed. Cryogenic machining uses liquid nitrogen (LN2) as a coolant, as this improves machinability. In the numerical study, cutting force and temperature were simulated, and machining characteristics were analyzed according to the cutting condition during cryogenic end-milling. The cutting force was predicted using a model of material plastic behavior, and the tool geometry and machining conditions were the input parameters. The contact mechanism between LN2 and the work material was studied, and the cutting temperature was simulated according to the rotation angle of the cutting tool. The numerical modeling was experimentally validated. The simulation and experimental machining data were in good agreement; the maximum and minimum errors were 31.5% and 2.6% for the cutting force and 17.6% and 10.3% for the temperature, respectively. The effects of cryogenic cooling were further studied experimentally. The sprayed LN2 increased the cutting force and decreased the temperature and tool surface friction. The friction decreased slightly with the insignificant influence on cutting force
Recent Trends in Continuum Modeling of Liquid Crystal Networks: A Mini Review
No full textThis work aims to provide a comprehensive review of the continuum models of the phase behaviors of liquid crystal networks (LCNs), novel materials with various engineering applications thanks to their unique composition of polymer and liquid crystal. Two distinct behaviors are primarily considered: soft elasticity and spontaneous deformation found in the material. First, we revisit these characteristic phase behaviors, followed by an introduction of various constitutive models with diverse techniques and fidelities in describing the phase behaviors. We also present finite element models that predict these behaviors, emphasizing the importance of such models in predicting the material's behavior. By disseminating various models essential to understanding the underlying physics of the behavior, we hope to help researchers and engineers harness the material's full potential. Finally, we discuss future research directions necessary to advance our understanding of LCNs further and enable more sophisticated and precise control of their properties. Overall, this review provides a comprehensive understanding of the state-of-the-art techniques and models used to analyze the behavior of LCNs and their potential for various engineering applications
Development of immobilized novel fungal consortium for the efficient remediation of cyanide-contaminated wastewaters
No full textFree cyanide is a hazardous pollutant released from steel industries. Environmentally-safe remediation of cyanide-contaminated wastewater is required. In this work, Pseudomonas stutzeri (ASNBRI_B12), Trichoderma longibrachiatum (ASNBRI_F9), Trichoderma saturnisporum (ASNBRI_F10) and Trichoderma citrinoviride (ASN-BRI_F14) were isolated from blast-furnace wastewater and activated-sludge by enrichment culture. Elevated microbial growth, rhodanese activity (82 %) and GSSG (128 %) were observed with 20 mg-CN L-1. Cyanide degradation > 99 % on 3rd d as evaluated through ion chromatography, followed by first-order kinetics (r2 = 0.94-0.99). Cyanide degradation in wastewater (20 mg-CN L-1, pH 6.5) was studied in ASNBRI_F10 and ASN-BRI_F14 which displayed increased biomass to 49.7 % and 21.6 % respectively. Maximum cyanide degradation of 99.9 % in 48 h was shown by an immobilized consortium of ASNBRI_F10 and ASNBRI_F14. FTIR analysis revealed that cyanide treatment alters functional groups on microbial cell walls. The novel consortium of T. saturnisporum-T. citrinoviride in the form of immobilized culture can be employed to treat cyanide -contaminated wastewater