Radical Chemistry and Reaction Mechanisms of Propane Oxidative Dehydrogenation over Hexagonal Boron Nitride Catalysts

Although hexagonal boron nitride (h‐BN) has recently been identified as a highly efficient catalyst for the oxidative dehydrogenation of propane (ODHP) reaction, the reaction mechanisms, especially regarding radical chemistry of this system, remain elusive. Now, the first direct experimental evidence of gas‐phase methyl radicals (CH₃^.) in the ODHP reaction over boron‐based catalysts is achieved by using online synchrotron vacuum ultraviolet photoionization mass spectroscopy (SVUV‐PIMS), which uncovers the existence of gas‐phase radical pathways. Combined with density functional theory (DFT) calculations, the results demonstrate that propene is mainly generated on the catalyst surface from the C?H activation of propane, while C₂ and C₁ products can be formed via both surface‐mediated and gas‐phase pathways. These observations provide new insights towards understanding the ODHP reaction mechanisms over boron‐based catalysts.     

阵列微电极研究Nd~(3+)对金属铜在3.5% NaCl溶液中腐蚀电化学行为的影响

利用阵列微电极技术测量了金属铜的自腐蚀电位、阻抗及表面腐蚀产物膜层载流子密度,并结合扫描电子显微镜,研究了Nd3+对金属铜在3.5%(w)NaCl溶液中腐蚀电化学行为的影响.结果表明,加入Nd3+使得金属铜表面生成的腐蚀产物膜层的形貌及结构发生了变化,腐蚀产物膜层变薄,腐蚀产物由片状结构转变为粒状结构,颗粒均匀分散分布;Nd3+的存在使得金属铜表面各区域的电位方差由0.034下降为0.026,阻抗标准方差由32805下降为6940,电位及阻抗分布趋于均匀化,有利于抑制局部腐蚀的发生;并且加入Nd3+将造成金属铜表面绝大部分区域腐蚀产物膜层的半导体类型由n型转变为p型,表面腐蚀产物膜层载流子密度标准方差由1.89×1017上升为4.10×1017,载流子密度分布趋于不均匀.     

Light modulation and coupling and rugby‐shaped resonators based on polymer fiber waveguide junctions

We report a systematic study of the dependence of the output efficiency and scattering efficiency on crossing angle, guided wavelength, and junction size in polymer nanofiber waveguide junctions. The junctions were assembled by using poly(trimethylene terephthalate) nanofibers (PNFs) with diameters of 200–800 nm under an optical microscope with the assistant of micromanipulators. A Chinese character and an SU pattern based the PNF junction technique have been demonstrated, moreover, the junction technique has also been expanded to various elastic substrates instead of glass substrate with high robustness. To further demonstrate the ability of modulating light of using the junction technique, we fabricated rugby‐shaped microresonators based on the polymer fiber junction, which exhibited high Q factor up to 10⁵. Furthermore, the microresonators can incorporate dyes or quantum dots into them, acting as active devices. We believe that the polymer fiber junction technique would provide a versatile platform for investigating light modulation or light matter interaction in various cavities with different configuration. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 833–840     

Gas-kinetic scheme with discontinuous derivative for low speed flow computation

The present paper concerns the improvement of the gas-kinetic scheme (GKS) for low speed flow computation. In the modified GKS scheme, the flow distributions with discontinuous derivatives are used as an initial condition at the cell interface for the flux evaluation. This discontinuity is determined by considering both the flow characteristic and grid’s resolution. Compared with GKS method with a continuous slope for the flow variables at a cell interface, the new scheme is more robust and accurate. In the under resolved flow computation, the new scheme presents much less numerical oscillation. The extension of the current scheme to unstructured mesh is straightforward. To validate the method, both computations of 2D lid-driven cavity flow and 3D flow past a sphere are performed. The numerical results validate the current method.     

An inorganic route to decorate graphene oxide with nanosilica and investigate its effect on anti‐corrosion property of waterborne epoxy

This paper reported an inorganic route that uses potassium silicate, which is one type of alkali silicate as an inorganic modifier, taking advantage of its instability and water condensation to decorate graphene oxide (GO) with nano‐SiO₂. The ingredients of prepared nanocomposites were characterized by Fourier‐transform infrared spectroscopy (FT‐IR) and X‐ray photoelectron spectroscopy (XPS), and the thermodynamic property was tested by thermal gravimetric analysis (TGA). Scanning electron microscopy (SEM) was used to observe the morphology of SiO₂‐GO nanocomposites. All the analyses above revealed the nano‐SiO₂ (<100 nm) was deposited on the surface of GO by chemical bonds. In the meantime, the dispersion test illustrated that nano‐SiO₂ played an important role in improving the dispersity of GO. The effect of SiO₂‐GO nanocomposites on barrier and corrosion protection performance of SiO₂‐GO nanocomposites was tested by immersion experiment and electrochemical impedance spectroscopy (EIS). The results indicated that GO was helped to block the corrosion of aggressive medium; moreover, SiO₂‐GO nanocomposites had the best anticorrosion performance and the slowest rate of corrosion because of its good dispersity with waterborne epoxy coatings.     

Ladder-type Diindenopyrazine Based Conjugated Copolymers for Organic Solar Cells with High Open-circuit Voltages

A ladder-type diindenopyrazine （IPY） was synthesized and used as a building block for constructing conjugated copolymers. Three copolymers based on the IPY moiety were obtained via the Suzuki coupling reaction with dif- ferent monomers, including 4,7-dithien-2-yl-2,1,3-benzothiadiazole （DBT）, 5,8-dithien-2-yl-2,3-diphenylquinoxa- line （DTQ）, and 5,8-dithien-2-yl-2,3-di（4-fluorophenyl）quinoxaline （DFTQ）. The obtained polymers were charac- terized by 1H NMR spectroscopy, UV-Vis absorption spectroscopy, cyclic voltammetry, and gel permeation chro- matography （GPC）. Owing to the four solubilizing alkyl chains on the IPY unit, all the three copolymers have good solubility in common solvents. These polymers have deep-lying HOMO energy levels in the range of-5.55-5.60 eV, and exhibit field-effect mobilities as high as 0.006 cm2.V-l.s i. Photovoltaic applications of these polymers as light-harvesting and hole-conducting materials were investigated in conjunction with [6,6]-phenyl-C6rbutyric acid methyl ester （PC61BM）. Both conventional and inverted devices were fabricated based on these three polymers. A power conversion efficiency （PCE） of 2.53% and a high open-circuit voltage of 1.00 V were obtained under simu- lated solar light AM 1.5 G （100 mW/cm2） from an inverted solar cell with an active layer containing 25 wt% lad- der-type IPY containing copolymer （PIPYDTQ） and 75 wt% PC61BM. Moreover, a high open-circuit voltage of 1.02 V and a PCE of 2.40% were achieved from a conventional solar cell based on PIPYDTQ.     

TC4钛合金及40Cr钢破片中绝热剪切带的TEM分析

 对含有约热剪切带（ASB）的TC4钛合金及40Cr钢破片作了扫描电镜（SEM）和透射电镜（TEM）分析。结果表明，TC4钛合40Cr钢中的ASB是由平均直径不到0.3 μm的微晶组成，微晶列有一定择优取向，电子衍射花样表现为不连续的环状。ASB内位错密度均很低，其邻近基体区含有高密度位错，ASB内没有察到相变发生。     

爆炸金属管的绝热剪切断裂宏观研究

本文介绍了45号钢、TC4钛合金及WTG05钨合金三种金属管在内部爆炸载荷下的宏观剪切断裂行为,并对此作了一些初浅的分析,提到了实验中发现的钛合金的一种反常单向性剪切起裂现象,同时发现该钨合金在爆炸应变率下表现为脆性断裂。