Coupling effects of water content,temperature, oxygen density,and polytetrafluoroethylene loading on oxygen transport through ionomer thin film on platinum surface in catalyst layer of proton exchange membrane fuel cell

In this work, coupling effects of water content, temperature, oxygen density, and polytetrafluoroethylene (PTFE) loading on oxygen transport through an ionomer thin film on a platinum surface in a catalyst layer of a proton exchange membrane (PEM) fuel cell are investigated using molecular dynamics approach. Taguchi orthogonal algorithm is employed to comprehensively analyze the coupling effects in a limited number of cases. It is found that the effect of operation temperature is the weakest among the four factors, which has the smallest effect index 14.4. Coupling effects including the PTFE loadings on the oxygen transfer through the ionomer thin film is uncovered. Less PTFE loadings should be beneficial for the oxygen transfer. The chemical potential gradient is considered as the major driven force for the oxygen transport through the ionomer thin film, and oxygen density is the dominating factor, significantly affecting the chemical potential in the thin film.     

Constructing the high-areal-capacity,solid-state Li polymer battery via the multiscale ion transport pathway design

The parasitic Li dendrite formation and retarded ion diffusion dynamics inhibit the deployment of solid-state batteries (SSBs) at high areal capacity loadings. Here, we present the modular design of the Li⁺ percolating network by grafting the ionic-conductive polyether amine (PEA) at the multiple scales: the PEA modified zinc hydroxystannate (PEA@ZHS) (flame retardant units) and polyamide 6 (mechanical rigid units) are coherently introduced to optimize the PEO-based solid electrolyte (PX-PEA@ZHS) with the Young's modulus (3.41 GPa), ionic conductivity (4.29 × 10⁻⁴ S cm⁻¹ at 55 °C) and flame retardancy (22% reduction of heat release rate); on the other hand, PEA molecules are grafted onto the acetylene black additive to establish the dual conductive network, endowing two orders of magnitude increase of ionic conductivity for the high-compaction cathodes. The as-integrated symmetric cell exhibits a critical current density up to 0.8 mA cm⁻² and cycling endurance for 1000 h at 0.2 mA cm⁻²; upon the SSBs assembly with the record high loading of LiFePO₄ (12.4 mg cm⁻²), the high-areal-capacity, cycling stability as well as the extreme temperature endurance till 110 °C are simultaneously realized, which inspire the rational design of commercially feasible, energy-dense, flame-resistance energy storage prototype.     

高能同步辐射光源低能束流输运线设计研究

高能同步辐射光源（HEPS）是计划在北京建造的发射度小于60 pm•rad的超低发射度光源。它由1台500 MeV直线加速器、1条500 MeV低能束流输运线、1台500 MeV～6 GeV的能量增强器、2条6 GeV的高能束流输运线、1台6 GeV的储存环以及同步辐射光束线和实验站组成。本文进行低能束流输运线的设计研究。低能束流输运线是连接直线加速器和增强器的束流传输线，在考虑建设布局限制的基础上，对两端的束流包络进行匹配，并将直线加速器产生的束流高效传输到增强器注入点。HEPS低能束流输运线设计时采用了功能分区的设计策略，设计有3个功能区，分别是消色散注入匹配区、光学参数匹配区、输出匹配区。为校正误差对束流的影响，HEPS低能束流输运线设置了8个BPM，水平和垂直各6块校正磁铁用于束流轨道校正，校正后的轨道满足束流传输要求。     

Mechanism of enhancement in magnetoresistance properties of manganite perovskite ceramics by current annealing

Studies on spintronics have provided solid evidence that the grain boundaries (GBs) in polycrystalline manganite can produce a strong extrinsic magnetoresistance (MR). This type of MR, called Low-field MR (LFMR), is larger than the intrinsic MR and can be triggered over a wide range of temperature. However, the existence of more GBs would bring about the weakening of magnetism and decrease the magnitude of MR simultaneously. Here we show that during annealing the application of electric-current to a representative ferromagnetic manganite perovskite, polycrystalline La_2/3Sr_1/3MnO₃ (LSMO), can produce more GBs and improve low-field magnetization, which leads to enhanced MR effect and field-response sensitivity as compared to the traditional-annealed sample. By using static micromagnetic models combined with the theories of spin-polarized intergrain tunneling and charge carrier hopping across domain wall, the observed enhancement of magnetoresistive response in current-annealed LSMO can be well explained.     

Transport phenomena in electrolyte solutions: Nonequilibrium thermodynamics and statistical mechanics

The theory of transport phenomena in multicomponent electrolyte solutions is presented here through the integration of continuum mechanics, electromagnetism, and nonequilibrium thermodynamics. The governing equations of irreversible thermodynamics, including balance laws, Maxwell's equations, internal entropy production, and linear laws relating the thermodynamic forces and fluxes, are derived. Green–Kubo relations for the transport coefficients connecting electrochemical potential gradients and diffusive fluxes are obtained in terms of the flux–flux time correlations. The relationship between the derived transport coefficients and those of the Stefan–Maxwell and infinitely dilute frameworks are presented, and the connection between the transport matrix and experimentally measurable quantities is described. To exemplify the application of the derived Green–Kubo relations in molecular simulations, the matrix of transport coefficients for lithium and chloride ions in dimethyl sulfoxide is computed using classical molecular dynamics and compared with experimental measurements.     

Water transport according to temperature and current in PEM water electrolyzer

Recently, various studies have been conducted on hydrogen energy as a means of replacing conventional fuels. Polymer electrolyte membrane water electrolyzers (PEMWEs) are being studied as a means of producing hydrogen for renewable energy. The PEMWE can be operated over a wider range than other types of water electrolyzers and can be connected to a renewable energy source, such as solar or wind. However, further studies are required because the water accompanying the hydrogen in the cathode presents a problem regarding hydrogen purity and storage. The phenomenon of water transport which is occurred on the PEMWE is analyzed by electro-osmotic drag and diffusion in the membrane. Electro-osmotic drag coefficients which are calculated by mass flow rate of discharged water with hydrogen are compared to the results of previous studies. The results of Electro-osmotic drag coefficient are different from previous studies at each operating condition. This difference is considered to be caused by the capacity of PEMWE such as active area and the number of cell.     

以物理气相传输法自支撑生长氮化铝单晶的表征

本文提出了以物理气相传输法自支撑生长氮化铝单晶的新方法，此方法可以在氮化铝烧结体表面一次性获得大量生长的氮化铝单晶。本研究中，在2373–2523 K的温度条件下经过100 h生长的氮化铝单晶，其最大尺寸为7 × 8 × 12 mm3，典型直径为5–7 mm。这些原生晶体的表面形貌及结晶质量分别通过扫描电子显微镜、拉曼光谱和高分辨X射线衍射进行表征分析。其中，拉曼光谱E2峰位的半高全宽为5.7 cm-1，高分辨X射线衍射得到的对称摇摆曲线的半高全宽为93.6角秒。经过选择性化学腐蚀后的晶体，其表面的平均腐蚀坑密度为7.5 × 104 cm-2。逸出气体分析和辉光放电质谱分析结果表明，碳和氧为晶体内部的主要杂质元素，含量分别为28 ppmw和120 ppmw。此方法为高质量氮化铝单晶的获取提供了一个新的途径，这些单晶可以被切成晶片作为后续氮化铝同质外延生长的优良籽晶。使用这些小的籽晶，我们首次成功制备出了直径高达60 mm的氮化铝单晶体/晶圆，并具有良好的深紫外光透过性。     

Influence of Pluronic coating formulation on iron oxide nanoparticle transport in natural and oil-impacted sandy aquifer media

Targeted delivery of nanoparticles has the potential to enhance remediation and characterization of sites contaminated with non-aqueous phase liquids (NAPLs) by ensuring delivery of treatment or contrast agents to the NAPL/water interface. For a targeted delivery technique to be successful, nanoparticles must be capable of transporting through porous media and binding to NAPLs under relevant geological conditions. In this study, successful targeted delivery of nanoparticles to sandy aquifer material mixed with crude oil was achieved using an active targeting technique based on an amphiphilic polymer coating. It was determined that the molecular structure and concentration of the nanoparticle coating greatly influenced the recovery of nanoparticles injected into saturated columns. Coatings with longer polymer molecules and lower polymer concentrations reduced recovery, and the nanoparticle coating formulation could be adjusted to improve transport while maintaining targeted binding behaviour. This study demonstrated that nanoparticle retention in oil-impacted sand exceeded that of clean sand in flow through experiments, indicating that a nanoparticle targeted delivery strategy for soil contaminated with LNAPLs such as crude oil is possible under the experimental conditions explored.     

Optimizing the stability and electrical transport properties of CeNbO4+δ-based oxide ceramics by regulating oxygen ion content

CeNbO_4+δ ceramics have attracted extensive research interest because of their unique mixed ion-electron transport characteristics and interesting structure-functional characteristics caused by the difference in oxygen ion content. Although the change of oxygen ion content brings rich redox properties, it also causes serious crystal transformation and abnormal electrical transport properties. In order to obtain stable structure and excellent electrical transport properties, the directional regulation of the oxygen ion content has been realized through introducing Al₂O₃ and high temperature aging. After 600 h of aging at 1073 K, the prepared composite ceramics not only obtain a stable structure without crystal transformation, but also show good negative temperature coefficient (NTC) thermistor characteristics in the temperature range of 473 K–1273 K, in which the linear fitting maximum Pearson's r of the relationship between lnρ and 1000/T can reach 99.97%. The proposed method provides a new thought for the design and application of high-temperature electronic ceramics.     

Significance of interface barrier at electrode of hematite hydroelectric cell for generating ecopower by water splitting

Recent increase in energy demand and associated environmental degradation concern has triggered more research towards alternative green energy sources. Eco‐friendly energy in facile way has been generated from abundantly available iron oxides using only few microliters of water without any external energy source. Hydroelectric cell (HEC) compatible to environment benign, low cost oxygen‐deficient mesoporous hematite nanoparticles has been used for splitting water molecules spontaneously to generate green electricity. Hematite nanoparticles have been synthesized by coprecipitation method. Chemidissociated hydroxyl group presence on hematite surface has been confirmed by infrared spectroscopy (IR) and X‐ray photoelectron spectroscopy (XPS). Surface oxygen vacancies in nanostructured hematite have been identified by transmission electron microscopy (TEM), XPS, and photoluminescence (PL) measurement. Hematite‐based HEC delivers 30 mA current with 0.92 V emf using approximately 500 μL water. Maximum off‐load output power 27.6 mW delivered by 4.84 cm² area hematite‐based HEC is 3.52 times higher than reported 7.84 mW power generated by Li‐magnesium ferrite HEC. Electrochemistry of HEC in different irreversible polarization loss regions has been estimated by applying empirical modeling on V‐I polarization curve revealing the reaction and charge transport mechanism of cell. Tafel slope 22.7 mV has been calculated by modeling of activation polarization overvoltage region of 0.11 V. Low activation polarization indicated easy charge/ion diffusion and faster reaction kinetics of Ag/Zn electrode owing to lesser energy barrier at interface. Dissociated H₃O⁺ ions diffuse through surface via proton hopping, while OH^? ions migrate through interconnected defective crystallite boundaries resulting into high output cell current.