A Theoretical study on the charge and discharge states of Na-ion battery cathode material,Na1+xFePO4F

Na₂FePO₄F is a promising cathode material for a Na-ion battery because of its high electronic capacity and good cycle performance. In this work, first principle calculations combined with cluster expansion and the Monte Carlo method have been applied to analyze the charge and discharge processes of Na₂FePO₄F by examining the voltage curve and the phase diagram. As a result of the density functional theory calculation and experimental verification with structural analysis, we found that the most stable structure of Na_1.5FePO₄F has the P2₁/b11 space group, which has not been reported to date. The estimated voltage curve has two clear plateaus caused by the two-phase structure composed of P2₁/b11 Na_1.5FePO₄F and Pbcn Na₂FePO₄F or Na₁FePO₄F and separated along the c-axis direction. The phase diagram shows the stability of the phase-separated structure. Considering that Na₂FePO₄F has diffusion paths in the a- and c-axis directions, Na₂FePO₄F has both innerphase and interphase diffusion paths. We suggest that the stable two-phase structure and the diffusion paths to both the innerphase and interphases are a key for the very clear plateau. We challenge to simulate a nonequilibrium state at high rate discharge with high temperature by introducing a coordinate-dependent chemical potential. The simulation shows agreement with the experimental discharge curve on the disappearance of the two plateaus. © 2018 Wiley Periodicals, Inc.     

Noise analysis of an electro-optic sensor system

Optical Review - This paper describes the noise analysis of an electro-optic (EO) sensor system based on experimental and simulation results. We developed a polarization simulator of the EO sensor...     

Signal measurement system for intra-body communication using optical isolation method

In this paper, we describe an induced signal measurement on the human body for developing a high-performance transceiver of an intra-body communication system. It is important to isolate awearable transceiver from an electrical instrument for precise measurement. We have developed a probe system using an optical isolation method including a laser diode, photo-diode, and optical fiber. The probe system can be successfully applied to the precise measurement of a receiving signal power at a wearable transceiver. We verify that the experimental results agree with the simulation results based on our previous channel model of intra-body communication.     

A new Zn(II) coordination polymer with 4-pyridylthioacetate: assemblies of homo-chiral helices with sulfide sites

A coordination polymer [Zn(pyta)(OH)] (pyta = 4-pyridylthioacetate), was synthesized and structurally characterized; it is constructed by an alternating assembly of two types of homo-chiral helices, [Zn-OH] and [Zn-pyta], in which the sulfide moieties are fastened in the latter columns.     

Dielectric and electrical properties of electrorheological carbon suspensions

Measurements of electrorheological (ER) effects, dielectric properties, and electrical conductivity are made on an ER suspension composed of carbonaceous particles and silicone oil to understand the mechanism which governs the ER effect. In the frequency dependence of the dielectric permittivities, a dielectric dispersion is observed in the first-order dielectric permittivity, while in the third-order dielectric permittivity a resonance peak, which is due to shear-induced particle rotation, is recognized, showing that such dielectric properties are closely related to ER properties of the suspension. An electrical conduction mechanism, which is responsible for the ER effect, is also investigated from the dependence of dc electrical conductivity on electric-field strength and temperature.     

Effect of additives on the amination of 2-oxoglutaric acid by gamma-radiation

The effect of added substances was studied on the yield of glutamic acid produced by gamma-ray irradiation of 2-oxoglutaric acid and ammonia in aqueous solution. The contents of amino acids in the irradiated solutions were determined with amino acids analyzer. Sodium nitrate, allyl alcohol or sodium formate was used as an added substance. The yield of glutamic acid significantly decreased by the addition of nitrate, and it was little affected by the addition of allyl alcohol. In the presence of formate the yield increased from G = 0.4 (2-oxoglutaric acid 0.05M and ammonium hydroxide 2M) to G = 1.1. As a result, it was found that hydrated electron contributes on the formation of glutamic acid, but hydroxyl radical does not. The yield showed a maximum at ca. 0.1 M ammonium hydroxide concentration. These facts indicate that NH2 radical does not contribute to the formation of glutamic acid. As a reaction mechanism, it can be explained that 2-oxoglutaric acid which had been reduced by hydrated electron reacts with ammonia.     

Self-limiting nature in atomic-layer epitaxy of rutile thin films from TiCl4 and H2O on sapphire (0 0 1) substrates

The atomic-layer epitaxy of rutile thin films on sapphire (0 0 1) substrates was studied in the controlled growth of titanium oxide films by sequential surface chemical reactions using sequentially fast pressurized titanium tetrachloride (TiCl₄) and water (H₂O) vapor pulses. Optical constants and thicknesses of these rutile films were investigated in terms of vapor pressure using a variable-angle spectroscopic ellipsometer. As a result, the self-limiting nature in the atomic-layer epitaxy of rutile thin films was demonstrated clearly under various conditions of dosing reactant vapors, where growth rates were almost constant at approximately 0.077 nm/cycle (0.77 nm/min) and refractive indices were also constant at 2.59.     

The minimal energy conformations of o-benzosemiquinone anion radicals in the solvents containing the alkali metals and the alkali earth metals

The minimal energy conformations of o-benzosemiquinone anion radicals in the solvents containing the alkali metals and the alkali earth metals were calculated by using the INDO method and the molecular geometry adjusting method. Our previous calculations of o-benzosemiquinone anion radical in the lithium ion solution showed that the total energy of the minimal energy conformation in the case of the assignment |A₃| > |A₄| were lower by approximately 320 kcal/mol than that in the case of the assignment |A₃| > |A₄|. Therefore, the calculations of the minimal energy conformations of o-benzosemiquinone anion radicals in the metal ion solutions were carried out in the cases of the assignment |A₃| > |A₄|. The conformations in both assignments A₃ < A₄ < 0 and (A₃ < 0 < A₄ and |A₃| > |A₄|) were calculated. Although the metal ions were not explicitly contained in the molecular geometries, the minimal energy conformations are considered to be close to the real minimal energy conformations of o-benzosemiquinone anion radicals in the metal ion solutions. The C? O bond lengths has a good positive rank correlation with the stabilities of o-benzosemiquinone radicals in the divalent metal ion solutions and the bond angles ∠C₃C₄H₄ had a good negative rank correlation with those stabilities.     

A new method for characterizing ultrafast resonant-tunnelling diodes with electrooptic sampling

A new electrooptic sampling technique for characterizing ultrafast resonant-tunnelling diodes (RTD) is presented, in which the RTD is driven by the output of the photodiode irradiated by the same laser pulse that probes the output of the RTD. This method features a high time resolution, moderate slew rate and low heat load, which are the keys to characterizing RTD switching time. From the investigation of several factors, such as laser pulse width, interaction time between the probe pulse and electrical signal, and triggering jitter, the overall time resolution was found to be less than 1 ps. The measured switching times for In_0.53Ga_0.47As/AIAs RTDs were compared with the resistance-capacitance time constant for each device, and this confirmed that this driving method accurately measured RTD switching time at the order of 1 ps.