Thermal desorption and pyrolysis direct analysis in real time mass spectrometry of Nafion membrane

Perfluorosulfonic acid ionomer membranes have been widely used as proton conducting membranes in various electrochemical processes such as polymer electrolyte fuel cells and water electrolysis. While their thermal stability has been studied by thermogravimetry and analysis of low molecular weight products, their decomposition mechanism is little understood. In this study a newly developed methodology of thermal desorption and pyrolysis in combination with direct analysis in real time mass spectrometry is applied for Nafion membrane. An ambient ionization source and a high-resolution time-of-flight mass spectrometer enabled unambiguous assignment of gaseous products. Thermal decomposition is initiated by side chain detachment above 350°C, which leaves carbonyls on the main chain at the locations of the side chains. Perfluoroalkanes are released above 400°C by main chain scission and their further decomposition products dominate above 500 °C. DFT calculation of reaction energies and barrier heights of model compounds support proposed decomposition reactions.     

An ultrasonic study on ternary xPbO–(45-x)CuO–55B2O3 glasses

A series of xPbO–(45-x)CuO–55B₂O₃ glasses (5 ≤ x ≥ 40 mol %) were prepared by the melt-quenching technique. The X-ray diffraction (XRD) patterns of the prepared glasses are found to have amorphous structure. An extensive ultrasonic study has been made to explore the structural role of PbO and CuO in the borate network. Various elastic properties were calculated from the measured data of density and ultrasonic velocity. Ultrasonic velocity and elastic moduli revealed broad humps at about 20 mol % PbO, which are attributed to the borate anomaly. Below 20 mol % PbO, all Pb²⁺ ions are considered to be entering the borate network as a glass modifier. This results in the transforms the borate network from an open structure to a denser three-dimensional structure due to BO₃ → BO₄ conversion. Beyond 20 mol, addition of PbO results in the formation of metaborate, pyroborate, and orthoborate units with NBOs. This weakness the glass structure and decrease both ultrasonic velocity and elastic moduli. The elastic properties were predicted and quantitatively analyzed by taking into account the effect of boron coordination number on the compositional and structural parameters involved in Makishima–Mackenzie's theory, ring deformation model and bond compression model. An excellent agreement between the computed theoretical and experimental elastic moduli, micro-harness and Poisson's ratio was achieved for majority of samples.     

Chemical bond characteristics and infrared reflectivity spectrum of a novel microwave dielectric ceramic CaIn2O4 with near-zero τf

Orthorhombic-structured CaIn₂O₄ ceramics with a space group Pca2₁ were synthesized via a solid-state reaction method. A high relative density (95.6 %) and excellent microwave dielectric properties (ε_r ～11.28, Qf = 74,200 GHz, τ_f ～ ?4.6 ppm/°C) were obtained when the ceramics were sintered at 1375 °C for 6 h. The dielectric properties were investigated on the basis of the Phillips–Van Vechten–Levine chemical bond theory. Results indicated that the dielectric properties were mainly determined by the InO bonds in the CaIn₂O₄ ceramics. These bonds contributed more (74.65 %) to the dielectric constant than the CaO bonds (25.35 %). Furthermore, the intrinsic dielectric properties of the CaIn₂O₄ ceramics were investigated via infrared reflectivity spectroscopy. The extrapolated microwave dielectric properties were ε_r ～10.12 and Qf = 112,200 GHz. Results indicated that ion polarization is the main contributor to the dielectric constant in microwave frequency ranges.     

聚变堆中第一壁材料钨的紧束缚理论研究

为研究辐照时处于电子激发态下第一壁材料钨（W）的结构演化规律和热力学性质，采用紧束缚方法对聚变堆中W的物理性质进行理论研究。结果表明，体系在高能粒子辐照下诱导的电子激发导致了体系中被辐照的区域自发出现微孔、晶格急剧膨胀、熔点下降等现象。具体地，在中等电子温度（~5 000 K）以下，W的晶格膨胀主要由晶格温度驱动，但在电子温度较高时电子温度导致被辐照区域的晶格膨胀效应不可被忽略。特别是当电子温度很高（>10 000 K）时，即便晶格温度不高，电子温度也会导致很大程度晶格膨胀。这对认识聚变堆中第一壁材料W在服役过程中的物理状态十分重要。     

Scaling analysis of hydrogen flow with carbon dioxide cushion gas in subsurface heterogeneous porous media

Subsurface hydrogen (H₂) storage in geological formations is of growing interest for decarbonization. However, there is a knowledge gap in understanding the multiphase flow involved in this process, which can have a significant impact on the recovery performance of H₂. Therefore, a full-compositional modeling study was conducted to analyze potential issues and to understand the fundamental hydrodynamic mechanisms of H₂ storage. We performed a range of 2D vertical simulations at the decametre scale with a very fine cell size (0.1 m) to observe the detailed flow behaviour of H₂ with carbon dioxide (CO₂) as cushion gas in various flow regimes. Issues such as viscous instability, capillary bypassing, gas trapping and gravity segregation are analysed here. To generalize our calculations, we have validated and applied the scaling theory in the context of subsurface H₂ storage. Since this study is focused on the hydrodynamic behaviour, three dimensionless groups, including aspect factor, capillary/viscous ratio and gravity/viscous ratio were identified to correlate recovery performance between various scales in a fixed heterogeneous system. It was found that H₂ could infiltrate the cushion gas in the proximity of the injectors, meaning that CO₂ is not displaced away from the injectors in a piston-like fashion. As a result, the purity of the back produced H₂ is much degraded, particularly in a viscous-dominated scenario. On the other hand, the injected H₂ mostly accumulates at the top forming a highly restricted mixing zone with CO₂ in the gravity-dominated case. The recovery performance is therefore much improved in this case. Although the gas distribution can be significantly altered by capillary forces leading to bypassed zones, the recovery performance of H₂ is hardly influenced. This is because the back-produced H₂ recovery is not dependent on the sweep efficiency of the gas. H₂ can be back produced following the same paths which were formed during injection.     

自重湿陷性黄土地基预钻孔浸水处理的可靠度设计方法

为解决传统预浸水法存在的浸水时间长、浸水处理范围难以确定等不足,基于土体中水分运移规律,依据可靠度理论、极限状态设计方法及复合 Poisson 过程原理,提出一种消除黄土湿陷性的处理浸水方法——预钻孔浸水法。给出了利用预钻孔浸水法对自重湿陷性黄土地基进行浸水时,水平向及竖直向浸水影响范围的确定模型;在此基础上结合达西定律给出了浸水孔设计参数如孔深、孔间距及浸水孔个数的确定方法。结合铜川某工程,设计进行了现场预钻孔浸水试验,对该方法的合理性进行了验证,并通过现场钻探、现场勘探、室内湿陷性试验等方法对该方法的处理效果进行了评价。该浸水方法具有浸水时间短、浸水影响范围可根据浸水孔布设进行控制等优点,且浸水处理效果良好,完全符合施工要求。     

基于心流理论的民艺体验产品设计要素研究

目的 探索民艺体验产品的设计方法，帮助用户实现沉浸式体验，提高用户对民艺产品的认同感，促进民艺的活态传承。方法 以竹编体验产品为例，通过用户观察、访谈并以用户体验地图的方式提取出“乌镇竹编”民艺产品在用户体验上的优点和痛点，结合心流理论，提出民艺体验产品的设计策略，同时优化“乌镇竹编”民艺体验产品。结论 经用户测试验证，最优的民艺体验产品除了要具备符合现代审美、工艺流程简化以及材料工具模块化等特征之外，还应具备以下设计要素:产品选择层次化、目标设置精细化、学习形式交互化、背景知识通俗化、作品分享社区化。     

Swapping catalytic active sites from cationic Ni to anionic F in Fe–F–Ni3S2 enables more efficient alkaline oxygen evolution reaction and urea oxidation reaction

Electrolysis of water for producing hydrogen instead of traditional fossil fuels is one of the most promising methods to alleviate environmental pollution and energy crisis. In this work, Fe and F ion co-doped Ni₃S₂ nanoarrays grown on Ni foam substrate were prepared by typical hydrothermal and sulfuration processes for the first time. Density functional theory (DFT) calculation demonstrate that the adsorption energy of the material to water is greatly enhanced due to the doping of F and Fe, which is conducive to the formation of intermediate species and the improvement of electrochemical performance of the electrode. The adsorption energy of anions (F and S) and cations (Fe and Ni) to water in each material was also calculated, and the results showed that F ion showed the most optimal adsorption energy of water, which proved that the doping of F and Fe was beneficial to improve the electrochemical performance of the electrode. It is worth noting that the surface of Fe–F–Ni₃S₂ material will undergo reconstruction during the process of water oxidation reaction and urea oxidation reaction, and amorphous oxides or hydroxides in situ would be formed on the surface of electrode, which are the real active species.     

Yttrium doped covalent triazine frameworks as promising reversible hydrogen storage material: DFT investigations

Through Density Functional Theory (DFT) simulations, we have explored the possibility of yttrium (Y) doped Triazine (Covalent Triazine Frameworks i.e., CTF-1) to be a promising material for reversible hydrogen storage. We have found that Y atom strongly bonded on Triazine surface can adsorb at the most 7H₂ molecules with an average binding energy of ?0.33 eV/H₂. This boosts the storage capacity of the system to 7.3 wt% which is well above the minimum requirement of 6.5 wt% for efficient storage of hydrogen as stipulated by the US Department of Energy (DoE). The structural integrity over and above the desorption temperature (420 K) has been entrenched through Molecular Dynamics simulations and the investigation of metal-metal clustering has been corroborated through diffusion energy barrier computation. The mechanism of interactions between Y and Triazine as well as between H₂ molecules and Y doped Triazine has been explored via analyses of the partial density of states, charge density, and Bader charge. It has been perceived that the interplay of H₂ molecules with Y on Triazine is Kubas-type of interaction. The above-mentioned analysis and outcomes make us highly optimistic that Y doped Triazine could be employed as reversible hydrogen storage material which can act as an environmentally friendly alternate fuel for transport applications.     

Generalized differential quadrature analysis of MHD mixed convective motion of Casson fluids past an isothermal irregular slender geometry via Cattaneo–Christov's approach

Classical Fourier's theory is well-known in continuum physics and thermal sciences. However, the primary drawback of this law is that it contradicts the principle of causality. To explore the thermal relaxation time characteristic, Cattaneo–Christov's theory is adopted thermally. In this regard, the features of magnetohydrodynamic (MHD) mixed convective flows of Casson fluids over an impermeable irregular sheet are revealed numerically. In addition, the resulting system of partial differential equations is altered via practical transformations into nonlinear ordinary differential equations. An advanced numerical algorithm is developed in this respect to get higher approximations for temperature and velocity fields, as well as their corresponding wall gradients. For validating our numerical code, the current outcomes are compared with the available literature results. Moreover, it is revealed that the velocity field is more prominent in the suction flow situation as compared with the injection flow case. It is also found that the Casson fluid is hastened in the case of lower yield stress. Larger values of thermal relaxation parameters create a lessening trend in the temperature distribution and its related boundary layer breadth.