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This study examines the flexural performance of reinforced concrete (RC) columns strengthened through a seismic jacket technique developed using a prefabricated steel bar unit that forms peripheral closed hoops and supplementary V ties, satisfying the design requirements of the ACI 318-14 seismic provisions. Three RC jacketed columns were prepared with a parameter of axial load levels and tested under a constant concentric axial load and cyclic lateral loads. Analytical approaches were also applied to examine the axial load–moment interaction of the RC jacketed columns when considering the confinement effect provided by the jacket section and to investigate the applicability of the previous performance-based design models proposed for virgin seismic columns. The test results show that the developed jacket technique possesses a good potential in enhancing the flexural stiffness, strength and ductility of deficient columns, even under a high axial load. Reinforced concrete jacketed columns possess a higher ductility than that estimated using the ductility parameter model, regardless of the axial load level. Thus, the jacket section including the seismic details of a transverse reinforcement can be conservatively designed, based on the axial load–moment interaction and ductility parameter model for the moment and ductility enhancements required by deficient columns.

Typically, the stress-strain relationship of confined lightweight aggregate concrete (LWAC) exhibits lower stiffness in the ascending branch and more brittleness in the descending branch compared to counterpart confined normal-weight concrete (NWC). To describe the rational stress-strain relationship of confined LWAC according to these trends, the concept of concrete brittleness number (ξb) was introduced. Specifically, ξb values were determined as constants in the existing size effect equation. The constants were fitted via regression analysis of 164 datasets compiled in extant studies. The models of elastic modulus, strength gain factor, strain at maximum stress, and strain at 85% of the maximum stress in descending branch were proposed, including ξb to describe the lower stiffness and more brittle behavior in confined LWAC when compared to those of counterpart confined NWC. Other existing models showed significant differences when compared with the test results in the descending behavior. These differences were significant in LWAC and counterpart NWC. Conversely, the proposed stress-strain relationship of confined concrete was in excellent agreement with the test results, irrespective of concrete type, compressive strength of concrete, and volumetric transverse reinforcement index.

Hot corrosion behavior was evaluated by gadolinium monosilicate (Gd2SiO5) with volcanic ash for environmental barrier coatings (EBCs). Sintered Gd2SiO5 was prepared by the spark plasma sintering (SPS) method at 1400 °C for 20 min, and high-temperature corrosion resistance against of volcanic ash was evaluated at 1400 °C for 2 h, 12 h, and 48 h. The surface region of sintered Gd2SiO5 was partially dissolved in molten volcanic ash, creating a chemically reacted area. The formation of the elongated morphology of Ca2Gd8(SiO4)6O2 grains observed in the reaction area is thicker with increasing heat-treatment time as the volcanic ash dissolves. In addition, high-temperature X-ray diffraction was carried out to identify the dynamics of phase evaluation in the volcanic ash and Gd2SiO5. According to the results, corrosion occurs due to reaction of the Gd2SiO5 phase and the Ca component of volcanic ash at 1300 °C, and the Ca2Gd8(SiO4)6O2 phase is generated.

To improve the stability and sensitivity of pH sensors based on AlGaN/GaN high electron mobility transistors (HEMTs), we proposed a modified sensing structure by integrating a reference HEMT device. This structural pH sensor exhibits a typical Nernstian behavior with a sensitivity of 54.38 mV/pH, which is higher than the value of 49.43mV/pH derived from the AlGaN/GaN HEMT-based sensor without integrating the reference HEMTs device. Furthermore, the stability of the new structural sensor is enhanced by approximately 19.2% in comparison with that of its traditional counterpart. The improved performances are analyzed using an electrical double-layer model together with an equivalent circuit model, and we find that the new sensor structure has a larger capacitor and exhibits a better rectification effect, hence decreasing the electrical noise and enhancing the stability of the testing signal. Meanwhile, the new sensor structure displays a smaller equivalent resistance and results in a larger available output current, hence exhibiting a higher sensitivity.

An acid–base junction flow battery (ABJFB) is a new type of energy conversion system using neutralization and water dissociation in the presence of acid and base electrolytes. The bipolar membrane (BPM) is a core component in determining the performance of the ABJFB. In particular, the development of an anion exchange layer (AEL) is essential to improve the performance of the BPM. In the present study, we fabricated a novel BPM composed of aligned ion channels of a quaternary aminated poly (2,6-dimethyl-1,4-phenylene oxide) (QPPO) layer and a pellicle of the cation exchange layer (CEL). The results showed that the through-plane conductivity of the QPPO membrane prepared under an AC electric field improved from 26.78 to 120.83 mS cm−1, owing to the aligned ion channels. The fabricated BPM based on the aligned QPPO membrane showed the remarkably improved performance of water dissociation and neutralization reactions in the presence of acid and base electrolytes without delamination. The ABJFB assembled with the optimized BPM showed a high power density of 3.85 mW cm−2 under a high strength acid/base of 2 N H2SO4 and NaOH solutions. In addition, we first performed a long-term operation of 60 cycles with a high coulombic efficiency of 98.9%, energy efficiency of 55.5%, and voltage efficiency of 56.1% under 2 N H2SO4 and NaOH at a high current density of 4 mA cm−2.

Light-emitting diodes (LEDs) based on metal halide perovskite nanocrystals (MHP NCs) have been rapidly developed to reach external quantum efficiencies of up to 22% with their defect-tolerant nature and extremely high color purity (full width half maxima

Au/TiO2/GaN junctions with a TiO2 interlayer were deposited at various oxygen pressures from 5 mTorr to 80 mTorr, and their surface, microstructural, and electrical properties were investigated. Compared with a single 5 μm-Si-doped GaN film on an (0001) Al2O3 substrate, the 0.2 μm-Si-doped GaN film with an undoped GaN buffer layer demonstrated improved properties for the application to metal/semiconductor junctions. Atomic force microscope and tunneling electron microscope measurements suggested that the TiO2 interlayer deposited at room temperature exhibited a distinctive change above the oxygen deposition pressure of 40 mTorr. In contrast to the small rectification ratio of 101-102 for Au/GaN junctions, the Au/TiO2/GaN junctions with the TiO2 interlayers displayed a large rectification ratio of 106-107 when the oxygen pressure during the deposition of TiO2 interlayer was maintained at 40 mTorr. These results suggest that the leakage current and the rectification behavior in a metal/oxide/semiconductor junction can be effectively controlled using the oxygen deposition pressure for an oxide interlayer.

A ternary hybrid photocatalyst consisting of Au@CeO2 core–shell nanostructures coated with ultralow Pt-functionalized surface contents (Au@CeO2–Pt) was synthesized using a facile hydrothermal method. The Pt-decorated Au@CeO2 core–shell photocatalyst had a large Brunauer–Emmett–Teller (BET) surface area (86.50 m2 g−1) with an abundance of catalytically active sites. The hydrogen production rate over Au@CeO2–Pt under visible light (8.7 μmol mg−1 h−1) was much higher than that observed over binary Au@CeO2 (3.9 μmol mg−1 h−1) and pure CeO2 (0.9 μmol mg−1 h−1) catalysts. Enhancement of the hydrogen evolution reaction (HER) was attributed mainly to the surface plasmon resonance (SPR) effect of the Au cores, which was highly advantageous for light absorption and conversion. In addition, the Pt co-catalyst served as an electron sink that accepted photogenerated electrons migrating from the Au@CeO2 core–shells. This extended the lifetime of the photogenerated charge carriers and resulted in HER activity that was superior to that of the Pt-free photocatalysts. The large BET surface area of the ternary core–shell nanostructure and the presence of many catalytically active sites also enhanced the HER performance.

Fabrication of high-conductivity ion exchange membranes (IEMs) is crucial to improve the performance of non-aqueous vanadium redox flow batteries (NAVRFBs). In the present work, anion exchange membranes with high-conductivity were fabricated by aligning ion channels of the polymer electrolyte impregnated in porous polytetrafluoroethylene (PTFE) under electric fields. It was observed that the ion channels of the polymer electrolyte were uniformly orientated in the atomic-force microscopy image. Its morphological change could minimize detouring of the transport of BF4− ions. The results showed through-plane conductivity was improved from 12.7 to 33.1 mS cm−1. The dimensional properties of the fabricated membranes were also enhanced compared with its cast membrane owing to the reinforcing effect of the substrate. Especially, the NAVRFB assembled with the optimized membrane showed increased capacities, with a 97% coulombic efficiency and 70% energy efficiency at 80 mA cm−2. Furthermore, the optimized membrane made it possible to operate the NAVRFB at 120 mA cm−2. Its operating current density was 120 times higher than that of a frequently used AHA membrane for RFBs.

A mesh-type dimensionally stable anode (DSA) consisting of ruthenium and iridium with low catalyst loading was prepared as an oxygen evolution reaction catalyst in acidic and alkaline media. The electrodeposition (ED) conditions, i.e., applied current density and total cycle number, and ED solutions with different precursor ratios of ruthenium to iridium are examined to fabricate various DSAs with a uniform thickness, and the effect of the iridium content on the catalytic activity is investigated. Among various DSA electrodes, the DSA electrode without iridium exhibits the highest activity and stability in the acidic medium owing to the high ratio of ruthenium. Conversely, the DSA electrode obtained using the ED solution with the ratio of 8:2 exhibits the highest performance in the alkaline medium. This is because the DSA electrode without iridium showed low stability, which is attributed to the dissolution of ruthenium oxide in the alkaline medium. In addition, two large-scale DSA electrodes optimized in the acidic and alkaline electrolytes show excellent performance, indicating the feasibility of the application of this electrode in practical electrolysis.

Formic acid is a chemical with a simple molecular structure containing hydrogen. This liquid at room temperature is easy to handle and has a low toxicity, and is thus in the spotlight as a fuel. In particular, formic acid is an excellent fuel candidate because it can be operated at low temperatures when applied as a fuel in fuel cells with a high theoretical open-circuit voltage (1.48 V). However, it has a drawback in that the electrode catalyst is deactivated due to the generation of CO intermediates when formic acid is oxidized during cell operation. Therefore, to prevent this, an irreversibly adsorbed Bi on Pt catalyst is applied to a direct formic acid fuel cell (DFAFC) anode because it is easy to synthesize and economical. Physical analyses such as transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were conducted, and electrochemical evaluations were performed through half-cell and single-cell level tests. The results revealed that the formic acid oxidation reaction activity of the Bi-modified Pt/C was 13 times higher than that of the conventional catalyst at 0.58 V. Further, a DFAFC stack was fabricated using the Bi-modified Pt/C, which yielded a power of 300 W. These results suggest that a simple synthesis method can be applied to fabricating industrially available DFAFC stacks.

Titanium alloy is a highly specific strength material, having excellent mechanical characteristics such as high stiffness, fracture resistance, and hardness at high temperature, so it is applied to various fields such as automotive, aerospace and bio-industry. Yet, the excellent characteristics of titanium alloy generate high cutting heat in cutting process, stimulating tool wear and degrading process accuracy. This study looked into turning characteristics of Ti–6Al–4V alloy using super light, coated carbide and cermet tool and applied Taguchi method to identify factors affecting turning process. In the process of titanium alloy, the major cause of tool wear was adhesion of the chip by cutting heat at a high temperature, and to enhance tool life, cutting speed control is necessary. Factors affecting tool life were in the order of tool material, cutting speed and feed rate.

In this study, we developed high-performance anion-exchange membrane water electrolysis (AEMWE) by investigating various parameters. To enhance AEMWE performance, the effects of the membrane-electrode assembly (MEA) fabrication method, operating conditions, and MEA parameters were examined. As a result of the optimization and the use of FAA-3-50 and FAA-3-Br as the AEM and anion-exchange ionomer, respectively, AEMWE showed the highest performance reported thus far. Single-cell tests and electrochemical impedance spectroscopy results indicate that optimized AEMWE minimized the ohmic, charge-transfer, and mass transport resistances. Overall, by examining the AEMWE parameters, we were able to improve the electrochemical reactions, namely, the oxygen evolution reaction and hydrogen evolution reaction, and achieved outstanding performance.

The A182 steel is used in the steam pressure regulator of power plant valves. Since the part is operated under high temperature and high pressure conditions, it is necessary to study the machining characteristics. In this study, EDS analysis of the tool wear shape according to the cutting condition of A182 steel was performed. The A182 steel is identified as a steel belonging to the hardest cutting material and will be used to derive the optimum cutting condition.

AlGaN/GaN heterostructures were successfully grown with the AlIn(Ga)N back barrier at 900 °C. However, the atomic composition of the AlIn(Ga)N layer was strongly dependent on the growth pressure, which resulted in a different lattice constant of the layer. The AlIn(Ga)N back barrier grown at 400 torr was almost lattice-matched to GaN layer. The AlGaN/GaN heterostructures with 10 and 15 nm-thick AlIn(Ga)N back barrier exhibited improved 2-DEG properties, compared to those of the conventional AlGaN/GaN heterostructure without the back barrier. The high electron mobility transistors (HEMTs) fabricated on the AlGaN/GaN heterostructure with a 15 nm-thick AlIn(Ga)N back barrier exhibited a very low off-state leakage current of ∼2 × 10−7 A/mm which is about 1 order lower in magnitude than the value of the device without the back barrier. The AlIn(Ga)N back barrier is a promising candidate as an alternative to conventional AlGaN and InGaN back barrier.

We made precipitated nano-ceria (∼5 nm) on the surface of the catalyst by heat treatment of Ce-supersaturated amorphous CeTiOx to improve the oxygen storage properties of CeO2. The catalysts were prepared by sol-gel methods and TiO2 nanoparticles were preferentially generated as a core material to form selective Ce-supersaturated structure on the catalyst surface. Reaction temperature and amount of doping element are optimized to induce selective crystallization of CeO2. Ce Ce (2nd shell) bond around 0.38 nm of Ce L3-edge extended X-ray absorption fine structure is reduced and nanostructure of precipitated ceria on the surface is observed by HREM. The catalyst is present as amorphous with precipitated nano-CeO2 on the surface. The de-NOx efficiency of the catalyst, which has precipitated CeO2, improves by ∼50% owing to the simultaneous reactions of the nano CeO2 and the amorphous CeTiOx.

One of the recent advances in nanotechnology within the medical field is the development of a nanoformulation of anticancer drugs or photosensitizers. Cancer cell-specific drug delivery and upregulation of the endogenous level of reactive oxygen species (ROS) are important in precision anticancer treatment. Within our article, we report a new therapeutic nanoformulation of cancer cell targeting using endogenous ROS self-generation without an external initiator and a switch-on drug release (ROS-induced cascade nanoparticle degradation and anticancer drug generation). We found a substantial cellular ROS generation by treating an isothiocyanate-containing chemical and functionalizing it onto the surface of porous silicon nanoparticles (pSiNPs) that are biodegradable and ROS-responsive nanocarriers. Simultaneously, we loaded an ROS-responsive prodrug (JS-11) that could be converted to the original anticancer drug, SN-38, and conducted further surface functionalization with a cancer-targeting peptide, CGKRK. We demonstrated the feasibility as a cancer-targeting and self-activating therapeutic nanoparticle in a pancreatic cancer xenograft mouse model, and it showed a superior therapeutic efficacy through ROS-induced therapy and drug-induced cell death. The work presented is a new concept of a nanotherapeutic and provides a more feasible clinical translational pathway.

Three-dimensional (3D) printing shows potential for use as an advanced technology for forming biomimetic tissue and other complex structures. However, there are limits and restrictions on selection of conventional bioinks. Here we report the first 3D-printable platelet lysate (PLMA)-based hydrogel, which consists of platelet lysate from whole blood of humans that can simulate the 3D structure of tissues and can be formed into a crosslinked hydrogel layer-by-layer to build cell-laden hydrogel constructs through methacrylated photo-polymerization. Furthermore, it can be customized for use with various tissues by controlling the physical properties according to irradiation time and concentration. In particular, different cells can be mixed and printed, and the integrity of the 3D printed structure can maintain its shape after crosslinking. The bio-ink exhibits excellent cell diffusion and proliferation at low concentrations, which improves moldability and biocompatibility. The 3D-printable PLMA bioinks may constitute a new strategy to create customized microenvironments for the repair of various tissues in vivo using materials derived from the human body.

Electroluminescence efficiencies of metal halide perovskite nanocrystals (PNCs) are limited by a lack of material strategies that can both suppress the formation of defects and enhance the charge carrier confinement. Here we report a one-dopant alloying strategy that generates smaller, monodisperse colloidal particles (confining electrons and holes, and boosting radiative recombination) with fewer surface defects (reducing non-radiative recombination). Doping of guanidinium into formamidinium lead bromide PNCs yields limited bulk solubility while creating an entropy-stabilized phase in the PNCs and leading to smaller PNCs with more carrier confinement. The extra guanidinium segregates to the surface and stabilizes the undercoordinated sites. Furthermore, a surface-stabilizing 1,3,5-tris(bromomethyl)-2,4,6-triethylbenzene was applied as a bromide vacancy healing agent. The result is highly efficient PNC-based light-emitting diodes that have current efficiency of 108 cd A−1 (external quantum efficiency of 23.4%), which rises to 205 cd A−1 (external quantum efficiency of 45.5%) with a hemispherical lens. Guanidinium doping is shown to enhance the operation of perovskite nanocrystal light-emitting diodes.

An interior permanent magnet synchronous motor generally injects adhesive like a bond into the magnet tolerance to prevent vibration between the permanent magnet and the magnet tolerance. In this case, there is a disadvantage that magnet tolerance does not contribute to performance. In this paper, a method to improve the torque density by inserting ferrofluid to utilize magnet tolerance was proposed. When inserting ferrofluid into magnet tolerance, it is important to fix the magnet because it does not use an existing adhesive, and it is important that ferrofluid does not act as a leakage path in the insertion space. In this study, a new rotor configuration using injection plastic that satisfies these considerations was introduced. The analysis was conducted through finite element analysis, and the analysis results and experimental results were compared through dynamo test to verify this study. It was confirmed that no-load back electromotive force increased in the final model through ferrofluid injection.

In this work, threshold voltage modulation realized by adjusting fin width and dielectric layer were investigated through MIS-FinFETs. As fin width decreases from 120 to 30 nm, threshold voltage shifts toward positive direction and finally becomes positive value while maintaining SS smaller than 60 mV/dec. The phenomenon of achieving sub-60 mV/dec characteristics were illustrated by simulation and the concept of effective channel length. As for dielectric layer, by 20 nm-thick SiO 2 dielectric layer, device with fin width of 90 nm exhibits a threshold voltage of −0.5 V with SS as small as 50 mV/dec. Even when fin width is 30 nm, drain leakage is still not small enough when VG = 0, which indicates that the gate is not able to totally deplete the fin structure. In order to further increase threshold voltage and enhance the gate controllability, by 10 nm-thick Al 2 O 3 dielectric layer, a threshold voltage of 2 V is achieved when fin width is 40 nm with SS as small as 52 mV/dec due to the higher dielectric constant and thinner thickness of Al 2 O 3 compared with SiO 2 . Therefore, by the modulation of fin width, dielectric layer type, and dielectric thickness, threshold voltage can be carefully designed according to the application requirements while maintaining SS below 60 mV/dec.

The formation of highly dispersed Pt nanoclusters supported on zeolite-templated carbon (PtNC/ZTC) by a facile electrochemical method as an electrocatalyst for the oxygen reduction reaction (ORR) is reported. The uniform micropores of ZTC serve as nanocages to stabilize the PtNCs with a sharp size distribution of 0.8–1.5 nm. The resultant PtNC/ZTC exhibits excellent catalytic activity for the ORR due to the small size of the Pt clusters and high accessibility of the active sites through the abundant micropores in ZTC.

We report herein a simple ligand-assisted reprecipitation method at room temperature to synthesize mixed-cation hybrid organic–inorganic perovskite nanocrystals with low structural dimensionality., We report herein a simple ligand-assisted reprecipitation method at room temperature to synthesize mixed-cation hybrid organic–inorganic perovskite nanocrystals with low structural dimensionality. The emission wavelength of iodide-based perovskites is thus tuned from the near-infrared to the red part of the visible spectrum. While this is mostly achieved in the literature by addition of bromide, we demonstrate here a controllable blueshift of the band gap by varying the chain length of the alkylammonium ligands. Furthermore, an antisolvent washing step was found to be crucial to purify the samples and obtain single-peak photoluminescence with a narrow linewidth. The so-formed nanocrystals exhibit high and stable photoluminescence quantum yields exceeding 90% over 500 hours, making these materials ideal for light-emitting applications.

Existing gels are mostly polar, whose nature limits their role in soft devices. The intermolecular interactions of nonpolar polymer-liquid system are typically weak, which makes the gel brittle. Here we report highly soft and transparent nonpolar organogels. Even though their elements are only carbon and hydrogen, their elastic modulus, transparency, and stretchability are comparable to common soft hydrogels. A key strategy is introducing aromatic interaction into the polymer-solvent system, resulting in a high swelling ratio that enables efficient plasticization of the polymer networks. As a proof of applicability, soft perovskite nanocomposites are synthesized, where the nonpolar environment of organogels enables stable formation and preservation of highly concentrated perovskite nanocrystals, showing high photoluminescence efficiency (~99.8%) after water-exposure and environmental stabilities against air, water, acid, base, heat, light, and mechanical deformation. Their superb properties enable the demonstration of soft electroluminescent devices that stably emit bright and pure green light under diverse deformations., Perovskite nanocrystals are promising emitters but suffer from environmental instabilities. Here, Park et al. introduce aromatic nonpolar organogels as a soft passivating matrix of perovskites, demonstrating highly efficient and environmentally stable luminescent nanocomposites.

The aim of this work was to develop an amorphous orlistat-loaded mesoporus silica formulation using the melt-amorphisation by supercritical fluid (MA-SCF) and to investigate the effects of pressure and temperature on the pharmaceutical properties of the developed formulation. In addition, the effect of orlistat mass ratio to the mesoporus silica was also evaluated. The carbon dioxide was used as a supercritical fluid, and Neusilin&reg, UFL2 was selected as the mesoporous silica. For comparison with conventional amorphisation methods, orlistat formulations were also prepared by solvent evaporation and hot melt methods. Various pharmaceutical evaluations including differential scanning calorimetry, powder X-ray diffraction, scanning electron microscopy, specific surface area, total pore volume, and content uniformity were performed to characterise the prepared orlistat formulation. The melting point depression and the solubility of orlistat in supercritical carbon dioxide (SC-CO2) were selected for the interpretation of evaluated results in relation to temperature and pressure. The total pore volume of the prepared orlistat-loaded mesoporus silica decreased with an increasing density of SC-CO2 to about 500 g/L at a constant temperature or pressure. From these results, it was suggested that increasing the density of SC-CO2 to about 500 g/L could result in the easier penetration of CO2 into molten orlistat and lower viscosity, hence facilitating the introduction and loading of orlistat into the pores of Neusilin&reg, UFL2. However, when the density of SC-CO2 increased to more than 500 g/L, the total pore volume increased, and this may be due to the release out of orlistat from the pores of Neusilin&reg, UFL2 by the increased orlistat solubility in SC-CO2. Interestingly, as the total pore volume decreased by the filling of the drug, the drug crystallinity decreased, hence, the dissolution rate increased. Furthermore, it was shown that the most desirable mass ratio of Neusilin&reg, UFL2:orlistat for the amorphisation was 1:0.8 at an optimised supercritical condition of 318 K and 10 MPa. Compared with other amorphisation methods, only the sample prepared by the MA-SCF method was in pure amorphous state with the fastest dissolution rate. Therefore, it was concluded that the amorphous orlistat-loaded mesoporus silica prepared using MA-SCF under optimised conditions was more advantageous for enhancing the dissolution rate of orlistat than other conventional amorphisation methods.

Conventional organic light-emitting devices without an encapsulation layer are susceptible to degradation when exposed to air, so realization of air-stable intrinsically-stretchable display is a great challenge because the protection of the devices against penetration of moisture and oxygen is even more difficult under stretching. An air-stable intrinsically-stretchable display that is composed of an intrinsically-stretchable electroluminescent device (SELD) integrated with a stretchable color-conversion layer (SCCL) that contains perovskite nanocrystals (PeNCs) is proposed. PeNCs normally decay when exposed to air, but they become resistant to this decay when dispersed in a stretchable elastomer matrix; this change is a result of a compatibility between capping ligands and the elastomer matrix. Counterintuitively, the moisture can efficiently passivate surface defects of PeNCs, to yield significant increases in both photoluminescence intensity and lifetime. A display that can be stretched up to 180% is demonstrated; it is composed of an air-stable SCCL that down-converts the SELD's blue emission and reemits it as green. The work elucidates the basis of moisture-assisted surface passivation of PeNCs and provides a promising strategy to improve the quantum efficiency of PeNCs with the aid of moisture, which allows PeNCs to be applied for air-stable stretchable displays.

Graphitic carbon nitride-carbon nanofiber (g-CN-CNF) was synthesized as a bifunctional catalyst in an anion-exchange membrane water electrolyzer (AEMWE), and primary and rechargeable Zn–air cells. The g-CN-CNF catalyst shows high catalytic activity for oxygen reduction reaction and oxygen evolution reaction in half-cell, with low overpotentials and low Tafel slopes. The high activity is attributed to the synergistic effect of abundant active sites and the electrical conductivity following the pyrolysis of g-CN and CNF. As a result, AEMWE with the g-CN-CNF anode, the first application of a carbon-based catalyst, exhibits outstanding performance that is the highest record in the literature for AEMWE using a non-noble metal catalyst. In addition, the performance and durability of Zn-air cells with g-CN-CNF cathode outperform those fabricated with commercial platinum.

Ce–Ti oxide catalysts were synthesized using Zr doping to form fully amorphous catalysts. The Ce0.3Ti0.7O2 catalyst had fine crystalline grain on the surface of the catalyst powders throughout the particles, whereas in the case of the Zr-doped Ce–Ti oxide catalyst, the entire catalyst was in an amorphous phase. The Zr-doped Ce–Ti oxide catalyst had a well-dispersed state, and its mechanism was identified through analysis with TEM-EDS and the synchrotron radiation beam. The surface imperfection sites of the catalyst increased due to the amorphization of the Ce–Ti oxide catalyst with Zr doping. The Zr-doped catalyst exhibited much higher activity than a Ce0.3Ti0.7Ox catalyst for the selective catalytic reduction of NOx with NH3 in the temperature range from 100 to 350 °C.

Zeolite templating is a versatile synthesis route to produce various types of ordered microporous carbon. However, the synthesis thus so far has been limited to the use of wide-pore zeolites with 12-membered ring (12MR) pore mouths or more because of the diffusion limitation of organic carbon precursors. Here, we report an extension of the carbon synthesis to a 10MR zeolite, through acetylene carbonization in Li+-ion-exchanged ZSM-5 zeolite. The promoting effect of the Li+ ions on the carbon synthesis could be relevant to the carbide-forming property of the element, similar to the recently reported cases of La3+, Y3+, and Ca2+ cations in 12MR zeolites. The resultant carbon exhibited an ordered array of ultramicropores of 0.5 nm diameter, which corresponded to the thickness of the zeolite framework. Because of the ultramicroporosity, the ZSM-5-templated carbon exhibited an anomalously high value of surface-area-normalized electrical double-layer capacitance.

Anion exchange membranes (AEMs) have been studied to improve conductivity for their high performance in energy conversion systems such as reverse electrodialysis, alkaline polymer fuel cells, and redox flow batteries. The functional groups with positive charge on backbones in AEMs form ion channels, which is the most significant factor in determining the conductivity of anions through the membrane. A typical method frequently used to enhance ionic conductivity is increasing the ion exchange capacity (IEC). However, AEMs with excessive amounts of positively charged functional groups may reduce ion selectivity or increase ion crossover by weakening mechanical properties due to high water uptake and the swelling ratio. To overcome this problem, we studied in this paper the alignment of ion channels for quaternary-aminated poly (2,6-dimethyl-1,4-phenyleneoxide) (QPPO) by applying an electric field to improve conductivity while retaining ion permselectivity with reasonable mechanical properties. We observed that the conductivity of the aligned QPPO membranes was enhanced up to three times using the same ion exchange material. Further, characteristic changes in the AEMs were investigated for the aligned ion channels using X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR), and atomic force microscopy (AFM).

This study presents the structural potentials of an entire restoration technique proposed for upgrading the strength and ductility of severely damaged non-seismic columns. Three columns were prepared under concentric axial loads to examine the axial load–axial strain relationship of restored columns. Additionally, five columns subjected to a constant axial load and cyclic lateral loads were prepared to ascertain the seismic behavior of the restored columns. To simulate the entire restoration of damaged columns, non-seismic columns were initially tested up to their peak axial capacity or 80% of the flexural strength on the post-peak performance; the longitudinal and transverse reinforcing bars and concrete were then reconstructed after total removal from the initially damaged columns. The test results showed that the axial load–axial strain and lateral load–lateral displacement relationships of the restored columns exhibited pre-peak behavior that was quite similar to that of the initial non-seismic columns, whereas the slope at the post-peak branches significantly slowed down for the former columns in comparison to the latter ones. Thus, the axial and flexural strengths of the restored columns could be conservatively assessed by the procedure recommended in the ACI 318-19 provision. The restored columns displayed axial ductility and flexural displacement ductility ratios comparable to those obtained in columns strengthened using the reinforced concrete (RC) jacket with seismic details that were developed using an approach similar to the proposed restoration technique. Thus, the proposed technique shows significant potential in enhancing the seismic performance of severely damaged non-seismic columns by providing confinement to concrete cores and preventing premature buckling of longitudinal reinforcements.

Nafion, the most popular cation exchange membrane, was cast while charged in an electric field to enhance the proton conductivity of the membrane. This electrically modified Nafion shows dramatically increased conductivity compared to the pristine membrane. The enhancement of proton conductivity is a result of changes in the membrane nanostructure, as shown by transmission electron microscopy, X-ray diffraction, and Fourier transform-IR spectroscopy. In particular, the membrane crystallinity was increased by 7% in the electrically modified membrane. As a result of the structural changes, the conductivities were enhanced from 0.137 to 0.231 S cm−1 in the in-plane aligned membrane and from 0.111 to 0.276 S cm−1 in the through-plane aligned membrane. Furthermore, the through-plane conductivity has been calibrated using a pressure control system for accurate comparison with reference values. Through the calibration process, the membrane resistance has been separated from the measured resistance, which is the sum of the membrane and interfacial resistances. Thus, the real proton conductivity of Nafion has been calculated in the through-plane direction. In this study, we have succeeded in improving the ionic conductivity of Nafion to its highest value to the best of our knowledge. Based on our results, not only can the improved Nafion be used itself, but this technique can be applied to other kinds of ion exchange membranes for use in energy systems.

In this paper, we investigated characteristics of AlGaN/GaN high-electron mobility transistors (HEMTs) with high resistive buffer structure consisted of periodically carbon-doped (PCD) GaN buffer layer and AlGaN back barrier layer. The PCD structure was proposed for reducing undesirable trapping effects, which resulted in effective suppression of the current collapse compared to that in conventional carbon buffer structure. To further improve the dynamic performances of the device and to increase the electron confinement of the 2-D electron gas (2-DEG) channel, AlGaN back barrier was inserted between the GaN channel and the PCD buffer layer, which results in greatly improved current collapse with slightly improved 2-DEG mobility compared to those of the device without back barrier. The OFF-state leakage current of the device with back-barrier is about 2 orders lower in magnitude than that of device without back barrier, which leads to the breakdown voltage of 2 kV and figure of merit of 2.27 GV $^{2} \Omega ^{-1}$ cm−2 for the device with LGD of $10~{{\mu }}\text{m}$ , one of the highest values ever reported for the GaN-based HEMTs.

The oxygen storage capacity of amorphous CeO 2 and its mechanism were investigated in a Zr-doped MnO x -CeO 2 /TiO 2 catalyst at low temperatures. The oxygen storage capacity of several catalysts was determined by the release of lattice oxygen upon reduction of Ce 4+ to Ce 3+ . We designed a temperature programmed reduction analysis using ammonia gas to measure the amount of lattice oxygen release and identify a decrease in reaction-onset temperature from 136 °C to 75 °C upon doping the catalyst with Zr. Additional reduction was observed in Zr-doped MnO x -CeO 2 /TiO 2 and this was attributed to an increase in temperature sensitivity of thermal vibrations of the first Ce–O coordination shell. The temperature dependence of the thermal vibrations was identified by examining the behavior of the Debye–Waller factor as a function of temperature with fitting the extended X-ray absorption fine structure.

Carbon fiber-reinforced plastic has been applied in various industrial areas due to outstanding mechanic characteristics including high strength and hardness as well as light-weight. For the mechanic combination after the CFRP molding, hall processing is required. In this study, generally used carbide drill and TiAIN coating carbide drill were used to proceed the experiment. Afterwards, carbide drill where point angle was changed into 90° was manufactured while evaluating thrust force and tool wear. In the experiment of carbide drill and TiAIN coating carbide drill, thrust force was reduced when major axis rotating speed increased. However, it was not much influenced by changes in moving speed. In addition, TiAIN coating has not much influenced on the processing feature. Tools with point angle changed into were measured 90° with lower tool wear and thrust force compared to two other tools while obtaining outstanding tool performance.

The glimepiride/L-arginine (GA) binary systems were prepared at various molar ratios by using a supercritical antisolvent (SAS) process. For comparison, the GA system was also prepared by physical mixing (PM), melt quenching (MQ), and solvent evaporation (SE) methods. Analyses by DSC and PXRD showed that only the GA binary mixture at 1:1 M ratio prepared by the SAS process was a pure co-amorphous mixture with an excellent content uniformity. On the other hand, GA mixture prepared by PM and SE were not pure co-amorphous systems and contained crystalline eutectic mixture, and MQ method at 170 °C induced the decrease in drug content due to decomposition of glimepiride. The positive deviation of experimentally measured glass transition temperature (Tg) compared to predicted Tg by the Gordon Taylor equation suggests specific molecular interactions between glimepiride and L-arginine in solid-state GA co-amorphous (GACA) mixture. The intermolecular interactions between glimepiride and L-arginine in GACA system were characterized by FT-IR and solid-state NMR analyses. Improved glimepiride dissolution rate of GACA formulation were confirmed using the solubility test, contact angle measurement, and dissolution test. Furthermore, the evaluation of pharmacodynamic hypoglycemic effect demonstrated that GACA prepared by the SAS process significantly improved the therapeutic efficacy of glimepiride.

The redox properties of CeO2-WO3 mixed oxide supported on multi-walled carbon nanotubes (MWCNTs) and TiO2 were investigated in terms of valence state and active oxygen species. Ce–W/CNT and Ce–W/TiO2 were synthesized by impregnation method to support CeO2-WO3 mixed oxide on CNTs and TiO2. The interplanar distance of CeO2 in Ce–W/CNT was measured to be 0.316 nm by TEM and SAED pattern analysis, which was larger than that of Ce–W/TiO2 (0.310 nm), indicating the lattice expansion due to Ce3+ formation. Since the F2g and Ov peaks in Raman spectrum of Ce–W/CNT were broader than those of Ce–W/TiO2, it implied the increased oxygen vacancies of CeO2 supported on CNTs. In XPS analysis, Ce3+/(Ce4++Ce3+) ratios in Ce–W/CNT and Ce–W/TiO2 were 42.28% and 28.60%, and Oα/(Oα+Oβ) ratios were 29.07% and 17.29%, respectively. The redox properties of the catalysts were investigated by H2-TPR analysis. The reduction peak of Ce–W/CNT shifted to a lower temperature compared to Ce–W/TiO2, and H2 consumption increased by 1.91 mmol/g, increasing the redox properties. The reduction in the valence state of Ce4+ was caused by charge transfer between CNT and CeO2-WO3 mixed oxide, and the reduction promoted the formation of oxygen vacancies and active oxygen species.

In this study, the effect of a vanadium addition on the fracture and wear resistance of indefinite chilled cast iron (ICCI) was investigated. The possibility of cracks in the roll is greatly influenced by the microstructural properties. Indefinite chilled cast iron used as a material consists of a martensite, Fe3C, and graphite. A large amount of Fe3C is deposited to improve wear resistance. However, cracks propagate easily due to the Fe3C. To overcome this disadvantage, the effect of vanadium was investigated by adding vanadium content of 1.3 %, 2.6 %, and 4.3 %. For analysis of the effects of vanadium, the volume fraction and distribution of carbide and graphite formed during solidification are measured. As a result of microstructure analysis, the addition of vanadium element crystallizes vanadium carbide in high-hardness precipitates, providing excellent wear resistance. In addition, due to the finely distributed but discontinuous Fe3C, it is difficult for the crack to propagate, thus increasing the flexural strength.

Dielectric properties of x (Na 0.5 K 0.5 )NbO 3 –(1− x )BaTiO 3 ( x =0.00 and 0.06) specimens were investigated in terms of changes in local atomic structure, according to the phase transition by elevating the overall temperature. A 0.06(Na 0.5 K 0.5 )NbO 3 –0.94BaTiO 3 (NKN–BT) specimen exhibited enhanced temperature stability along with an increased dielectric constant. The degree of reduction in tetragonality ( c / a ) at the Curie temperature was smaller in NKN–BT compared to that in pure BaTiO 3 , as calculated by Rietveld refinement. From a comparison of the pre-edge region in the Ti K -edge, it was determined that the off-center displacement of the Ti atom was also raised to 13.4% through NKN substitution, with a change in local orientation from the [001] to the [111] directions. The substitution by NKN, which has a different ionic radius and electrical charge compared with BaTiO 3 , causes structural distortion of the TiO 6 octahedra in the NKN–BT lattice, resulting in local polarization. These structural changes lead to the temperature stability of the dielectric constant and an overall improvement in the electrical properties of BaTiO 3 .

Indium-tin oxide is considered a highly promising mixed-metal oxide system, because it shows good performance in various industrial processes. Therefore, it will be of great importance to explore the possibility of obtaining new In-Sn oxides with controlled contents whose properties could be tailored. However, In or Sn content in In-Sn oxides has generally been restricted to

The thermal expansion and ionic conduction of 15 mol% CaO-stabilized zirconia (CSZ) with added Al2O3 were investigated. Specimens with 0.5 and 1 mol% Al2O3 maintained the cubic phase, and the thermal diffusivity increased from 0.499 to 0.661 mm2/s with a 1 mol% addition. The addition of 5 mol% caused a decrease in the thermal diffusivity (0.609 mm2/s) with the formation of the monoclinic phase. The thermal expansion coefficient of the CSZ decreased, and the thermal diffusivity increased with the addition of Al2O3. The ionic conductivity was increased up to the addition of 1 mol% due to scavenging of siliceous by Al2O3, while the 5 mol% addition showed a decrease in conductivity with the formation of the intergranular phase.