Efficient electrocatalysis at the cathode is crucial to addressing the limited stability and low rate capability of Li-O-2 batteries. This study examines the kinetic behavior of Li-O-2 batteries utilizing layered perovskite LaSrCrO4 nanowires (NWs) composed of lower oxidation states. Layered perovskite LaSrCrO4 NWs exhibited improved rate capability over a wide range of current densities and longer cycle life in Li-O-2 batteries than V-based layered perovskite (LaSrVO4) and simple perovskite (La0.8Sr0.2CrO3) NWs. X-ray photoelectron spectroscopy and electrochemical surface area analyses showed that the observed performance variations primarily stemmed from active sites such as oxygen vacancies. In situ Raman analysis showed that these active sites significantly modulate the kinetics of oxygen reduction and evolution, which are related to LiO2 intermediate adsorption. Electrochemical impedance spectroscopy showed that the active sites in layered perovskite LaSrCrO4 NWs contributed to their high charge transfer capability and reduced polarization. This study presents an appealing method for the precise fabrication and analysis of Cr-based layered perovskites, aimed at achieving highly efficient and stable bifunctional oxygen electrocatalysis.

Efficient electrocatalysis at the cathode is crucial for addressing the challenges faced by lithium-oxygen batteries (LOBs), including limited stability and low-rate capability. To develop an efficient cathode for aprotic LOBs, self-supported copper phosphide nanoarrays on carbon cloth are prepared at different heating rates via a phosphidation process using CuTCNQ nanoarrays. Different ramping rates have effects on particle size and intrinsic interaction, which in turn affect their catalytic properties. When phosphidation is carried out at a slow rate, it results in the formation of smaller, evenly distributed Cu3P particles on the nanoarrays (SG-Cu3P NAs/CC) compared to fast rate phosphidation (FG-Cu3P NAs/CC). As a result, SG-Cu3P NAs/CC exhibits lower resistance and a higher concentration of active sites than FG-Cu3P NAs/CC. The SG-Cu3P NAs/CC demonstrates LOBs with a low overpotential of 1.51 V at a high current rate of 1 mA cm(-2) and a long cycle life of 115 cycles at 0.1 mA cm(-2). The in situ Raman spectroscopy supports that Li2O2 is uniformly formed and decomposed on the SG-Cu3P NAs/CC surface. This study provides a compelling approach for the precise fabrication and analysis of binder-free, self-supported copper phosphides as highly efficient and stable materials for bifunctional oxygen electrocatalysis.

AbstractThis study aims to enhance the performance of inorganic perovskite light‐emitting diodes (PeLEDs) by incorporating porous silica (p‐SiO2) to fabricate perovskite‐composite films for electroluminescence (EL) devices. This is because, in addition to the inorganic perovskite material, composites with inherently stable materials are needed for perovskite to ensure additional external stability. The introduced p‐SiO2 particles impede the crystal growth of perovskite during the anti‐solvent assisted crystallization process, resulting in the formation of smaller CsPbBr3 crystals in the CsPbBr3/p‐SiO2 composite film. Accordingly, compared to previous CsPbBr3 films, this composite film exhibits two folds with higher photoluminescence quantum yield (PLQY) due to improved crystalline formation. Surprisingly, the CsPbBr3/p‐SiO2 composite film additionally has good water‐resistant properties because the residual cetyltrimethylammonium bromide (CTAB) molecules are extracted from the p‐SiO2 particles and are oriented at the top surface of the CsPbBr3/p‐SiO2 composite film. The EL device fabricated with this composite film exhibits outstanding luminescence efficiency, with a current efficiency (CE) of 70.06 cd A−1 and an external quantum efficiency (EQE) of 16.97%, surpassing control samples by two folds of magnitude. Furthermore, the operational stability improves approximately sevenfold compared to the control, presenting a promising strategy for advancing the field of inorganic perovskite ELs.

Energy Storage Systems (ESS) based on lithium ion battery are rapidly increasing their capacity because they can efficiently store electricity in a small area with high energy density. However, 23 fire accidents have been reported for last 21months. To date, the origin of fire has not been clearly elucidated. In this work, we investigated the origin of a fire accident through experimental field analysis and its corresponding simulation. Empirical and theoretical study reveals that the ground fault in battery string would induce high current from gird to battery modules with voltage imbalance, which is enough high to ignite fire. Therefore, it is required to protect ESS system form ground fault in battery modules.

예기치 못한 탈선사고 발생 시 탈선열차에 대한 피해를 최소화하기 위한 대비로 탈선방지가드레일이나 방호벽 등의 물리적인 시설물을 설치하고 있다. 현재 국내의 방호벽의 경우 고속철도 도입 시 유럽 관행에 따라 도입하였으나, 이에 대한 설계하중 및 설치위치, 규격에 대한 기준 근거가 미약하고 정립 및 체계화되어 있지 않다. 또한, 탈선된 열차의 거동 특성에 대한 공학적 분석 및 방호시설 적용에 따른 실효성과 경제적 타당성 등을 입증할 수 있는 객관적인 자료가 전 세계적으로 미비한 실정이다. 이에 본 논문에서는 방호시설에 대한 효과입증, 방호 성능평가 기술 등을 확보하기 위한 선결과제로 국내 최초로 탈선된 열차의 거동 특성을 파악하기 위한 실대형 탈선/충돌 실험을 수행하였다. 실험차량은 주강대차를 이용하였고, 타고오름 탈선을 모사하여 탈선 이후 차륜과 레일, 체결장치, 침목 등 궤광 구성품과의 충돌거동을 분석하였다.

We investigated the effect of phosphor deposition methods on the correlated color temperature (CCT), luminous flux and thermal characteristics of packaged white light-emitting diodes (WLEDs) for use in mobile display products. For both the samples, the CCT decreased with increasing viewing angle. Phosphor sedimentation samples displayed much better angular color uniformity than phosphor dispersion samples. The phosphor sedimentation sample had higher luminous flux and luminous efficacy at 20 mA than the phosphor dispersion sample. The phosphor sedimentation sample displayed much better high-temperature/humidity (85 °C/85%) reliability and lower package temperatures compared with the phosphor dispersion sample.

We developed hybrid Ag nanodots (NDs)/Ag nanowires (NWs) electrodes for enhancing the light output power of near ultraviolet (NUV) AlGaN-based light-emitting diodes (LEDs). At 385 nm, 10-nm-thick ITOonly films deposited on p-GaN/sapphire gave a transmittance of 70%, whereas hybrid Ag NDs/Ag NWs film showed a transmittance of 47%. LEDs with ITO-only, Ag NDs/Ag NWs, and activated-Ag NDs/Ag NWs electrodes showed forward-bias voltages of 3.50, 3.65, and 3.57 V, respectively, at 20 mA. The LEDs with the ITO-only, Ag NDs/Ag NWs, and activated-Ag NDs/Ag NWs electrodes produced series resistances of 14.3, 15.2, and 14.5 U, respectively. The LEDs with the Ag NDs/Ag NWs and activated-Ag NDs/Ag NWs electrodes yielded 13.1% and 23.7% higher light output powers, respectively, at 20 mA than that produced with the ITO-only electrode. On the basis of the emission images obtained from the LEDs with 10-nmthick ITO-only, Ag NDs/Ag NWs, and activated-Ag NDs/Ag NWs electrodes, the enhanced light output power is attributed to effective current spreading and current injection. (C) 2017 Elsevier B.V. All rights reserved.

Ag nanowires (Ag NWs) were combined with a thin indium tin oxide (ITO) film as the p-type electrode in near ultraviolet (NUV) AlGaN-based light-emitting diodes (LEDs) to improve the light output power. The Ag NWs (30 +/- 5 nm in diameter and 25 +/- 5 mu m long) were dispersed in ethanol (0.3 wt%). The transmittances of 10 nm-thick ITO, ITO/Ag NWs coated at 1000 rpm, and ITO/Ag NWs coated at 3000 rpm were 98%, 90%, and 97% at 385 nm, respectively. LEDs (chip size: 300 +/- 800 mu m(2)) fabricated with the ITO/Ag NW electrode exhibited higher forward-bias voltages than the LEDs with the ITO-only electrode. However, LEDs with ITO/Ag NWs films coated at 1000 and 3000 rpm yielded 7.9 and 14.0% higher light output power, respectively, at 100 mA than the LED with ITO-only electrode. The improved output power with the ITO/Ag NWs films is attributed to an optimal trade-off between optical transmittance and current spreading. (C) 2016 Elsevier B.V. All rights reserved.

We compared the ionic properties of yttria-stabilized zirconia (YSZ) thin films prepared by atomic layer deposition (ALD) using various oxidants including water, oxygen, and ozone. Cross-plane conductivity measurements were performed at low temperature (50°C) and high temperature (450°C) using AC impedance spectroscopy. As a result, we have confirmed that the conductivity of ALD YSZ films below 300°C is greater by several orders of magnitude compared to the nano-scale YSZ thin films synthesized by other conventional techniques. Among the ALD YSZ samples, ALD YSZ fabricated using water showed the highest conductivity while ALD YSZ fabricated using ozone showed the lowest. We have analyzed this result in relation with grain morphology characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM), and the chemical binding states measured by X-ray photoelectron spectroscopy (XPS).

We report high-performance solid-oxide fuel cells (SOFCs) with silver cathodes surface-treated using yttria-stabilized zirconia (YSZ) nano-particulates fabricated by atomic layer deposition (ALD). Fuel cell tests are conducted on gadolinia-doped ceria electrolyte pellets with a platinum anode at 250-450 degrees C. In our tests, the fuel cell performance of the SOFCs with an optimized ALD YSZ surface treatment is close to that of SOFCs with porous Pt, which is known as the best performing catalyst in the low-temperature regime. Electrochemical impedance spectroscopy confirms that the performance enhancement is due to improved electrode kinetics by the increase in charge transfer reaction sites between the surface of supporting silver and the ALD-YSZ particulates. Fuel cell durability tests shows that the ALD YSZ surface treatment improves the long-term stability. X-ray photoelectron spectroscopy also confirms that the ALD YSZ capping prevents reduction of the surface silver oxide and destruction of the mesh morphology. (C) 2015 Elsevier B.V. All rights reserved.

We report on the performance of thin-film yttria-stabilized zirconia (YSZ) synthesized by atomic layer deposition (ALD) at temperatures of 50-525 degrees C. Electrochemical impedance spectroscopy (EIS) was used for conductivity measurements. Relatively high conductivity values were observed in the low-temperature region when compared to reference values of YSZ synthesized by other methods. To investigate the conduction mechanism, various experimental variables were modified during the electrical measurements, including the ratio of yttria to zirconia in the ALD YSZ films and the atmospheric conditions. To relate the electrical properties to the structural characteristics, the crystallinity and microstructure were investigated using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Finally, the suitability of an ALD YSZ membrane as the electrolyte of micro solid oxide fuel cells was evaluated. An open circuit voltage of almost 1 V and decent power output were successfully measured below 100 degrees C. (C) 2014 Published by Elsevier B.V.

The nucleon resonance spectrum is important to understand fundamental information of non-perturbative QCD. In spite of a lot of efforts to search for the nucleon resonances in photoproduction and hadronic reactions, “missing resonance” problem is unsolved yet. Recently electron/photon beam facilities are providing high-precision data of two-pion production because most of high mass nucleon resonances strongly decay into ππN final state with large branching ratio. It, however, shows that many nucleon resonances still have fair or poor star rating in the status of the nucleon resonances in the Particle Data Group. At present, the πN a ππN and πNaKY reactions, which are free from the electromagnetic interactions, are lacking because few measurements done about three decades ago with limited statistics. It is highly required to be measuring high precision πN a ππN reaction as well as πNaKY reaction to understand N states. In this moment, J-PARC is the best facility where these reactions can be measured precisely. The J-PARC E45 collaboration proposed to measure the πNaππN and πNaKY reactions with a hyperon time-projection-chamber (HypTPC) at the J-PARC hadron experimental facility [1]. In this presentation, we will discuss detector’s R&D and the sensitivity of the E45 experiment.

We present a viable method to enhance the current efficiency of organic light-emitting diodes (OLEDs) by imprinting cylindrical nanopatterns (NPs) onto a glass substrate. Herein, OLEDs equipped with an optimum NP array having a diameter of 300 nm and a periodic distance of 500 nm show a 33.4% improvement in current efficiency compared with a device without NPs. The light extraction efficiency of OLEDs was enhanced using a nanopatterned glass substrate, without any electrical degradation owing to the formation of NPs on opposite sides of the organic layers. In addition, top-emitting OLEDs can be fabricated easily by patterning the encapsulation glass.

The resonant oscillation of a sessile droplet on the electrohydrodynamic (EHD) jetting nozzle was studied using a series of sinusoidal and square pulse voltage signal. At small amplitude oscillations, the lowest mode resonant frequency depended on a contact angle and the explicit relationship was developed assuming one-dimensional standing capillary wave. When the meniscus was oscillated with a higher voltage amplitude for jetting, its height became maximum at the phase delay of about π/2 from the maximum applied voltage signal, which can be predicted in a harmonic oscillator model. In addition, there existed an effective resonant frequency where the meniscus oscillation was amplified quickly to initiate a jetting earlier, and the jetting continued every cycle afterwards. Therefore, the resonant oscillation would be effectively used for high speed printing of a simple regular pattern where the jetting should occur at a constant frequency.

In this study, we present a theoretical model for an oscillating meniscus along with changing the volume of the sessile droplet on the electrohydrodynamic nozzle under various voltage waveforms, supported by experimental data. The transient volume change of the sessile droplet upon step electric pressure was modeled by a one-dimensional flow. The meniscus oscillation upon cyclic electric pressure was analyzed by a harmonic oscillator model. By combining these two models, the behavior of the sessile droplet, under a bi-directional square voltage pulse train with a different bias voltage, was analyzed. It is expected that this theoretical model can provide effective information in optimizing the voltage waveform for drop-on-demand electrohydrodynamic jetting.

We demonstrated a diketopyrrolopyrrole (DPP)-based alternating copolymer (i.e., PDTTDPP) which contains planar dithieno[3,2-b:2′,3′-d]thiophene (DTT) unit and high effectiveness in the fabrication of solution-based polymer nanowires (PNWs). PDTTDPP was found highly crystalline and exhibited optimized energy levels for p-type semiconductor. The electrical properties of single PNWs such as specific resistivity (ρ) and photoresponsivity (R) were investigated by measuring the dark current and photocurrent under visible and near-infrared lights. These electrical properties were compared for high (HA-PNW) and low (LA-PNW) aspect ratio PNWs produced using two different preparation methods such as membrane wetting method and self-assembly in a dilute solution. The measured responsivity (R) values of single HA-PNW at +40 V are 134 and 114 A W−1 at 632 and 830 nm, respectively. In contrast, the R values of LA-PNW under identical conditions were determined to range from 0.55 A W−1 to 0.65 A W−1 (λ = 632 nm) and from 0.61 A W−1 to 0.73 A W−1 (λ = 830 nm) at a +40 V bias voltage, which are significantly lower than those of HA-PNW-based devices.

The first demonstration of polymer nanowire (PNW) crystals based on a diketopyrrolopyrrole-based copolymer (i.e., PDTTDPP), and their application to field-effect transistors (FETs) is reported. Remarkably, transmission electron microscopy and selected area electron diffraction analyses of the PNW reveal its single-crystalline (SC) nature. FETs fabricated of a SC PNW exhibit a maximal charge carrier mobility of ≈7.00 cm(2) V(-1) s(-1) , which is almost one order of magnitude higher than that of the thin-film transistors made of the same polymer (PDTTDPP).

New diketopyrrolopyrrole (DPP)-containing conjugated polymer such poly (benzothieno[3,2-b]benzothiophene-2,5-bis(2-octyldodecyl)-6-(thiophen-2-yl)pyrrolo [3,4-c]pyrrole-1,4(2H,5H)-dione) was successfully synthesized via Horner-Emmons condensation. The polymer showed a low bandgap energy (E-g = 1.56eV) in a film state. The polymer also exhibits good solubility in common organic solvents and good self-film-forming properties. The semiconducting properties of the polymer synthesized herein were evaluated in organic thin film transistors (OTFTs). The polymer exhibits charge carrier mobilities as high as 3.0 x 10(-3) cm(2)V(-1)s(-1) (I-on/off = 10(5)) after thermal annealing at 200 degrees C for 10min, which is three times higher than that of thin film transistor made of the pristine film.