Differences of thermal decomposition behaviors and combustion properties between CL-20-based propellants and HMX-based solid propellants

Journal of Thermal Analysis and Calorimetry - Differences of thermal decomposition characteristics and combustion properties between CL-20-based propellants and HMX-based propellants were...     

Structural damage detection using convolutional neural networks combining strain energy and dynamic response

Meccanica - Based on the classification ability of a convolutional neural network (CNN), this paper proposes a structural damage detection method in which a CNN is used to classify the location and...     

DFT mechanistic study of the H2‐assisted chain transfer copolymerization of propylene and p‐methylstyrene catalyzed by zirconocene complex

DFT computations have been performed to investigate the mechanism of H₂‐assisted chain transfer strategy to functionalize polypropylene via Zr‐catalyzed copolymerization of propylene and p‐methylstyrene (pMS). The study unveils the following: (i) propylene prefers 1,2‐insertion over 2,1‐insertion both kinetically and thermodynamically, explaining the observed 1,2‐insertion regioselectivity for propylene insertion. (ii) The 2,1‐inserion of pMS is kinetically less favorable but thermodynamically more favorable than 1,2‐insertion. The observation of 2,1‐insertion pMS at the end of polymer chain is due to thermodynamic control and that the barrier difference between the two insertion modes become smaller as the chain length becomes longer. (iii) The pMS insertion results in much higher barriers for subsequent either propylene or pMS insertion, which causes deactivation of the catalytic system. (iv) Small H₂ can react with the deactivated [Zr]?pMS?PP_n facilely, which displace functionalized pMS?PP_n chain and regenerate [Zr]? H active catalyst to continue copolymerization. The effects of counterions are also discussed. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 576–585     

Brake Orbits of First Order Convex Hamiltonian Systems with Particular Anisotropic Growth

Combining the dual least action principle with Mountain-pass lemma,we obtain the existence of brake orbits for first-order convex Hamiltonian systems with particular anisotropic growth.     

Tracking the atomic pathways of Pt3Ni-Ni(OH)2 core-shell structures at the gas-liquid interface by in-situ liquid cell TEM

Using the in-situ liquid cell transmission electron microscopy, the three-stage growth of Pt_3Ni-Ni(OH)_2 core-shell structures at the gas-liquid interfaces was clearly observed, which consists of(1) a thermodynamically driven Pt_3Ni alloy core by the monomer attachment,(2) a nickel(Ni) shell formation due to the depletion of the Pt salt precursor, and(3) the oxidation and of the Ni shell into Ni(OH)_2 flakes. We also further observed the nucleation and growth of the Ni(OH)_2 flakes on an existing layer either at the middle part or at the step edge. More interestingly, the dynamic transformation among a Pt_3Ni alloy, Ni clusters and Ni(OH)_2 flakes was also imaged even at a high electron dose rate.     

Energy,exergy and economic (3E) evaluation of the photovoltaic/thermal collector-assisted heat pump domestic water heating system for different climatic regions in Turkey

Journal of Thermal Analysis and Calorimetry - In this study, the energy, exergy and economic (3E) analyses were performed for the photovoltaic/thermal collector-assisted heat pump domestic water...     

Continuous Transport of Zn(II) by Ammonium Chloride Media via Supported Liquid Membrane System

With the gradual depletion of traditional zinc resources, the full use of various non-traditional zinc-containing resources has received intensive attention. However, the efficient recovery of zinc ions with low concentrations remains challenging. Here efficient and continuous recovery of zinc ions in ammoniacal chloride media by a flat supported liquid membrane system is achieved, using Cyanex923 and TBP mixed extractant as the membrane phase. This article discusses the synergistic effect between Aliquat336, Cyanex923 and TBP, the effects of feed pH, total ammonia concentration, Cl⁻ concentration and temperature on Zn(II) transport.     

Triple-function Hydrated Eutectic Electrolyte for Enhanced Aqueous Zinc Batteries

Aqueous rechargeable zinc-ion batteries (ARZBs) are impeded by the mutual problems of unstable cathode, electrolyte parasitic reactions, and dendritic growth of zinc (Zn) anode. Herein, a triple-functional strategy by introducing the tetramethylene sulfone (TMS) to form a hydrated eutectic electrolyte is reported to ameliorate these issues. The activity of H₂O is inhibited by reconstructing hydrogen bonds due to the strong interaction between TMS and H₂O. Meanwhile, the preferentially adsorbed TMS on the Zn surface increases the thickness of double electric layer (EDL) structure, which provides a shielding buffer layer to suppress dendrite growth. Interestingly, TMS modulates the primary solvation shell of Zn²⁺ ultimately to achieve a novel solvent co-intercalation ((Zn-TMS)²⁺) mechanism, and the intercalated TMS works as a “pillar” that provides more zincophilic sites and stabilizes the structure of cathode (NH₄V₄O₁₀, (NVO)). Consequently, the Zn||NVO battery exhibits a remarkably high specific capacity of 515.6 mAh g⁻¹ at a low current density of 0.2 A g⁻¹ for over 40 days. This multi-functional electrolytes and solvent co-intercalation mechanism will significantly propel the practical development of aqueous batteries.     

CO2 Hydroboration: Impact of the Boryl Moieties on the Reactivity of Four Bis(boryl)acetal Compounds toward 2,6-Diisopropylaniline

The hydroboration of CO₂ into bis(boryl)acetal (BBA) compounds is an important transformation, since it enabled to selectively reduce CO₂ by 4e^- and to subsequently use the BBA compounds as C₁ and C_n sources. However, the influence of the nature of the boryl moieties on the reactivity of BBA compounds has not been evaluated so far. In the present study, four BBA compounds – including two new ones – were reacted with 2,6-diisopropylaniline to afford the expected imine. Significant differences in the rate of the reaction from minutes to weeks have been observed depending on the BBA used, showing the importance of the nature of the boryl moieties. Theoretical investigations enabled to propose a mechanism involving the addition of the aniline to the BBA as the rate-determining step and to determine that the steric hindrance of the BBA compounds is the main factor driving the rate of this condensation reaction.     

调控碳材料的功函数以大幅度提升其电催化氧还原性能

氧的电催化还原反应是燃料电池装置与金属空气电池的阴极反应,具有重大的研究意义.在众多的非铂催化剂中,碳材料因其低廉的价格以及独特的物理化学性质受到了广泛的关注.自从发现氮掺杂的碳纳米阵列具有优异的氧还原活性后,不同类型的氮掺杂的碳也得到了深入研究.例如近年来兴起的由金属有机框架衍生的氮掺杂的碳材料,兼具丰富的氮位点及良好的三维结构.氮的掺杂对碳原子具有电子调控的作用,是其高氧还原活性的根本原因.本文对金属有机框架衍生的氮掺杂的碳材料进行进一步的电子结构的优化,以提升催化性能.功函是电子逸出表面所需的最少的能量,是材料的电子结构性质之一,其对氧还原反应的影响也有报道,早期以理论计算为基础,探究氧气分子在碳材料表面的解离能与氮掺杂的碳的表面功函的关系,后续则采用开尔文探针显微镜,直接测量了不同元素掺杂的碳表面功函,并建立起功函与氧还原动力学的线性关系.本文通过控制碳材料的功函来调节其电子结构.铯是一种经典的给电子物质,通过将电子注入到掺杂材料表面来降低其功函.因此,本文通过CsCO₃与2-甲基咪唑、Zn(NO₃)₂煅烧形成铯修饰的氮掺杂碳.电镜及XRD均观察不到所得材料中铯的存在,证明碳层中无大颗粒团聚的铯物种.EDS元素分布图表明,铯在碳层中呈原子级均匀分布.Raman谱结果表明,碳的G带发生明显的位置偏移,证明其面内电子结构发生了明显的改变.XPS结果证明铯成功与氮原子配位,通过铯氮键将电子注入到碳骨架.UPS则最终显示,经过铯的修饰,碳表面功函从4.25 eV下降到3.6 eV.表面功函的降低有利于氧气分子的解离,也调节OOH^*中间体的吸附,使其吸附的自由能更接近最优值.材料改性后氧还原性能明显提升,起始电位达到0.91 V vs RHE,半波电位达到0.83 V vs RHE,均接近商业Pt/C催化剂.氧还原反应的动力学电流密度随功函的降低而增大,验证了前人的结论.本文提供了一个较为新颖的电子结构调控策略,为设计新的氧还原催化剂提供了新的思路.