Cycling performance of a lithium-ion polymer cell assembled by in-situ chemical cross-linking with fluorinated phosphorous-based cross-linking agent

Lithium-ion polymer cells composed of a carbon anode and a LiCoO₂ cathode are assembled with a gel polymer electrolyte cured by in-situ chemical cross-linking with novel cross-linking agents. The strong interfacial adhesion between the electrodes and the porous polyethylene membrane by the chemical cross-linking results in the stable capacity retention of the cell. However, a reduction in the ionic mobility in both the electrolyte and the electrodes adversely affects the high rate performance of the cell. These results imply that proper control of the cross-linking density in the cell is imperative for achieving good capacity retention and high rate performance of the cell.     

Low-frequency noise in ambipolar carbon nanotube transistors

Low-frequency noise measurements on individual single-walled carbon nanotube transistors exhibiting ambipolar characteristics have been carried out. With a polymer electrolyte as gate medium, low-frequency noise can be monitored in both p- and n-channel operation of the same nanotube under the same chemical environment. 1/ f noise in the p-channel of polymer electrolyte gated nanotube transistor is similar to that of back gate operation. However, most devices exhibit significantly larger noise amplitude in the n-channel operation that has a distinct dependence on the threshold voltage. A nonuniform energy distribution of carrier trapping/scattering sites is considered to explain these observations.     

Double S-Shaped Polarization – Voltage Curve and Negative Capacitance from Al2O3-Hf0.5Zr0.5O2-Al2O3 Triple-Layer Structure

The negative capacitance (NC) effect, recently discovered in a fluorite-based ferroelectric thin film, has attracted great attention as a rescue to overcome the scaling limitations of the conventional memory and logic devices of highly integrated circuits. The NC effect manifesting an S-shaped polarization–voltage (P–V) curve is initially interpreted by a 1-dimensional Landau Ginzburg Devonshire (LGD) model. However, a series of recent studies have found that this effect can also be explained by the inhomogeneous stray field energy (ISE) model. In this study, by extending the ISE model in the ferroelectric (FE)-dielectric (DE) layered structure, an analytical model that considers the influence of the interfacial screening charge distribution is presented. This model showed that the NC effect in the FE-DE heterostructure can be manifested in various forms other than a single S-shaped P–V curve. In particular, a double S-shaped P–V curve is expected from the fully compensated anti-parallel domain structure, confirmed experimentally in the actual Al₂O₃/(Hf_0.5Zr_0.5)O₂/Al₂O₃ triple-layer structure. Furthermore, to reveal the origin of the double S-shaped P–V curve, a multidomain LGD model is presented. It is confirmed that this phenomenon is attributed to the evolution of inhomogeneous stray field energy.     

Statistical kinetic modeling procedure for cationic polymerization and its application to polyisobutylene

A statistical modeling procedure is established for carbocation polymerization with the characteristics of living with chain transfer. A single state model is suggested for cases of narrow molecular weight distribution, whereas a multi-state model is claimed for cases of broad distribution. In the multi-state case, it is demonstrated how the overall kinetics can be derived using the expectations and variances of the kinetic parameters rather than those of individual states, thereby simplifying the modeling step. Although the expectation and variance do not follow the relationship of the Arrhenius equation, a procedure is given for how to account for temperature dependence. The proposed statistical method minimizes the number of parameters to identify and therefore is expected to help establish a model with fewer experiments. The whole procedure is demonstrated through an experimental study of isobutylene polymerization.     

High-Performance Ammonia Protonic Ceramic Fuel Cells Using a Pd Inter-Catalyst

This study reports the performance and durability of a protonic ceramic fuel cells (PCFCs) in an ammonia fuel injection environment. The low ammonia decomposition rate in PCFCs with lower operating temperatures is improved relative to that of solid oxide fuel cells by treatment with a catalyst. By treating the anode of the PCFCs with a palladium (Pd) catalyst at 500 °C under ammonia fuel injection, the performance (peak power density of 340 mW cm⁻² at 500 °C) is approximately two-fold higher than that of the bare sample not treated with Pd. Pd catalysts are deposited through an atomic layer deposition post-treatment process on the anode surface, in which nickel oxide (NiO) and BaZr_0.2Ce_0.6Y_0.1Yb_0.1O_3–δ (BZCYYb) are mixed, and Pd can penetrate the anode surface and porous interior. Impedance analysis confirmed that Pd increased the current collection and significantly reduced the polarization resistance, particularly in the low-temperature region (≈500 °C), thereby improving the performance. Furthermore, stability tests showed that superior durability is achieved compared with that of the bare sample. Based on these results, the method presented herein is expected to represent a promising solution for securing high-performance and stable PCFCs based on ammonia injection.     

Micromagnetic Simulation of Damped Oscillatory Behavior of Domain Wall Propagation in Sinusoidal Ferromagnetic Nanowire

We have investigated a damped oscillatory behavior of domain wall propagation in wavy nanowires under an external field higher than the Walker breakdown field using micromagnetic simulation. In nanowires having sinusoidal edge distortions with variation of wavelengths, domain wall has been observed to pseudomorphically follow the sinusoidal wires with keeping an intrinsic transformational frequency of inner wall spin structure. Oscillation amplitude of the domain wall position decreases as the wavelength of the wire decreases by an interaction between the periodically distributed spins and the propagating domain wall. Oscillatory behavior of the domain wall position is found to decay in a wire having the wavelength well matching with an intrinsic transformational frequency of the propagating domain wall.      

Improvement strategy for edge waviness in roll bending process of corrugated sheet metals

This paper focuses on the corrugated thin-walled sheet metal in the roll bending process. The main defect that appears in corrugated panels subjected to high amounts of bending deformation is a wavy edge. Edge defects are caused by excessive longitudinal stress and strain near the edge of the plate, and local edge buckling may occur when some critical value of the bending radius is exceeded. This paper proposes two different approaches to avoid a wavy edge for a formed panel: excessive stress on the edge region is restrained by controlling the length of the cross-sectional end of the corrugated panel while considering the stress distribution, and the bending radius in each forming step is determined by considering the strain limit at which the initial edge waviness occurs to avoid excessive compression at particular steps. The experimental and numerical results indicated that the two proposed design strategies can minimize wavy edges in the formed shape.     

Ruthenium Nanoparticles on Cobalt‐Doped 1T′ Phase MoS2 Nanosheets for Overall Water Splitting

2D MoS₂ nanostructures have recently attracted considerable attention because of their outstanding electrocatalytic properties. The synthesis of unique Co–Ru–MoS₂ hybrid nanosheets with excellent catalytic activity toward overall water splitting in alkaline solution is reported. 1T′ phase MoS₂ nanosheets are doped homogeneously with Co atoms and decorated with Ru nanoparticles. The catalytic performance of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is characterized by low overpotentials of 52 and 308 mV at 10 mA cm^?2 and Tafel slopes of 55 and 50 mV decade^?1 in 1.0 m KOH, respectively. Analysis of X‐ray photoelectron and absorption spectra of the catalysts show that the MoS₂ well retained its metallic 1T′ phase, which guarantees good electrical conductivity during the reaction. The Gibbs free energy calculation for the reaction pathway in alkaline electrolyte confirms that the Ru nanoparticles on the Co‐doped MoS₂ greatly enhance the HER activity. Water adsorption and dissociation take place favorably on the Ru, and the doped Co further catalyzes HER by making the reaction intermediates more favorable. The high OER performance is attributed to the catalytically active RuO₂ nanoparticles that are produced via oxidation of Ru nanoparticles.     

J resistance behavior in functionally graded materials using cohesive zone and modified boundary layer models

This paper describes elastic–plastic crack growth resistance simulation in a ceramic/metal functionally graded material (FGM) under mode I loading conditions using cohesive zone and modified boundary layer (MBL) models. For this purpose, we first explore the applicability of two existing, phenomenological cohesive zone models for FGMs. Based on these investigations, we propose a new cohesive zone model. Then, we perform crack growth simulations for TiB/Ti FGM SE(B) and SE(T) specimens using the three cohesive zone models mentioned above. The crack growth resistance of the FGM is characterized by the J-integral. These results show that the two existing cohesive zone models overestimate the actual J value, whereas the model proposed in the present study closely captures the actual fracture and crack growth behaviors of the FGM. Finally, the cohesive zone models are employed in conjunction with the MBL model. The two existing cohesive zone models fail to produce the desired K–T stress field for the MBL model. On the other hand, the proposed cohesive zone model yields the desired K–T stress field for the MBL model, and thus yields J _R curves that match the ones obtained from the SE(B) and SE(T) specimens. These results verify the application of the MBL model to simulate crack growth resistance in FGMs.