CO2 laser beam modulating for surface texturing machining

Laser texturing is a novel technique that may be used to texture a cold roller in the process of manufacturing high quality steel sheets. With the aim of improving the quality of the textured roller by using a CO₂ laser, a new laser beam modulating device is proposed. An optical beam expander with a fast rotating chopper system is designed. The laser pulse is split into two parts by the chopper blades; one is the preheating pulse that is reflected onto optical loop mirrors; the other is the directly transmitted pulse that creates the craters at the preheated spots. The preheating beam focus spot size and position can be adjusted. The focusing characteristics and optical parameter compensation for the flying optics are investigated. The heat transfer and melt process of laser texturing are numerically simulated. The effects of the double pulses on the texturing are analyzed. The effect of preheating the sample ahead of the laser texturing pulse is examined. The surface profile and bump hardness show improvements by using this approach.     

Synthesis and photophysical properties of europium pentafluorinated β-diketonate complexes

Research on Chemical Intermediates - Two pentafluorinated β-diketone ligands, 4,4,5,5,5-pentafluoro-1-(4-methoxyphenyl)pentane-1,3-dione (PFMP) and 4,4,5,5,5-pentafluoro-1-(4-dimethyl...     

Rapid Interception of CnF2n+1(O)SO. Radical with Copper-Based Carbene: A Novel Access to Perfluoroalkanesulfinate Ester

In this communication, an unprecedented interception of C_nF_2n+1(O)SO^. radical with a copper-based carbene has been established. Distinguished by wide substrate scopes and mild reaction conditions, this novel radical–carbene coupling reaction (RCC reaction) provides a fundamentally different and mechanistically interesting strategy for the synthesis of perfluoroalkanesulfinate esters.     

Spectroscopic and theoretical optical properties of indoleninyl-substituted dibenzotetraaza[14]annulenes

Two new macrocyclic dibenzotetraaza[14]annulene (DBTAA) compounds with indolenine ( 5 ) and pyridoindolenine ( 6 ) moieties were synthesized and characterized by spectroscopy. Both DBTAAs exhibit strong UV-Vis absorption properties in the Soret band region. The theoretical second-order nonlinear optical property, electric dipole moment (μ), dispersion-free dipole polarizability (α) and first hyper-polarizability values were calculated by density functional theory and time dependent density functional theory. The ab-initio quantum mechanical calculation by time-dependent Hartree-Fock method was utilized to investigate the dynamic dipole polarizabilities, dynamic second-order, static, and dynamic third-order (γ) hyper-polarizabilities of the DBTAAs. The configuration interaction technique of all doubly occupied molecular orbitals possesses theoretically defined single-photon absorption (OPA) specifications for the examined structures. The computed maximum OPA wavelengths on both macrocyclic compounds coincide with the preceding measurement outcomes.     

Visible-Light-Induced Vicinal Dichlorination of Alkenes through LMCT Excitation of CuCl2

This work demonstrates photoredox vicinal dichlorination of alkenes, based on the homolysis of CuCl₂ in response to irradiation with visible light. This catalysis proceeds via a ligand to metal charge transfer process and provides an exciting opportunity for the synthesis of 1,2-dichloride compounds using an inexpensive, low-molecular-weight chlorine source. This new process exhibits a wide substrate scope, excellent functional group tolerance, extraordinarily mild conditions and does not require external ligands. Mechanistic studies show that the ready formation of chlorine atom radicals is responsible for the facile formation of C−Cl bonds in this synthetic process.     

Engineering Carbon Distribution in Silicon-Based Anodes at Multiple Scales

The successful commercialization of promising silicon-based anode materials has been hampered by their poor cycling stability caused by the huge volume change. Integration of the carbon matrix with silicon-based (C/Si-based) anode materials has been demonstrated to be a powerful solution to achieve satisfactory electrochemical performance. This minireview aims to outline recent developments on C/Si-based composites, with the emphasis on the importance of carbon distribution at multiple scales. In addition, the forms of the carbon framework (carbon sources and doping of heteroatoms) have been summarized. Particularly, a novel C/Si-based hybrid with carbon distributed at the atomic scale has been highlighted.     

Lattice-confined Ru clusters for hydrogen oxidation reaction with high CO-tolerance

正Hydrogen has been considering as a promising renewable energy source and a viable alternative for fossil-fuels in the future [1,2]. Hydrogen oxidation reaction (HOR) and its reverse reaction are two significant reactions for applying hydrogen as electrochemical energy. On the other hand,platinum is believed to be the best electrocatalyst for HOR,although several drawbacks including high cost, scarcity,low CO tolerance, and depressed catalytic activities in alkaline environments, hinder the development of hydrogen application [1]. Hence, it is highly desired to develop Pt-free HOR catalysts with high activity, high stability, low cost, and good resistance to CO poisoning [3].     

石墨毡载纳米δ-MnO2高性能除铵净水材料研究

首先制备了α-MnO₂纳米花簇、β-MnO₂纳米针和δ-MnO₂微米颗粒三种不同晶型的MnO₂粉末材料,对其结构、形貌及吸附除铵能力进行了表征和测试.结果表明,层间距（7.2Å）大于NH₄⁺直径（2.96Å）和水合NH₄⁺直径（6.62Å）的δ-MnO₂相比其他两种晶型的MnO₂有更高的NH₄⁺吸附量;接着研究采用KMnO₄原位氧化还原法在石墨毡（GF）上直接生长超薄δ-MnO₂纳米片（MnO₂NPs）阵列构筑了石墨毡载纳米MnO₂（MnO₂NPs/GF）多级结构材料,制备简单,无须成型造粒就可直接用作除铵净水材料,研究结果表明,MnO₂NPs/GF不仅具有较高的吸附量（15 mg·g^－1）与良好的选择性,同时还展现了优异的快速吸附和稳定的循环使用性能.MnO₂NPs/GF对水中NH₄⁺的吸附符合准二级动力学模型,其吸附等温线符合Langmuir吸附等温式,是吸附-离子交换法除铵的理想材料.