Low-phosporous nickel-coated carbon microcoils: Controlling microstructure through an electroless plating process

Carbon microcoils (CMCs) have been coated with a nickel-phosphorus (Ni-P) film using an electroless plating process, with sodium hypophosphite as a reducing agent in an alkaline bath. CMC composites have potential applications as microwave absorption materials. The morphology, elemental composition and phases in the coating layer of the CMCs and Ni-coated CMCs were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The effects of process parameters such as pH, temperature and coating time of the plating bath on the phosphorus content and deposition rate of the electroless Ni-P coating were studied. The results revealed that a continuous, uniform and low-phosphorous nickel coating was deposited on the surface of the CMCs for 20 min at pH 9.0, plating bath temperature 70 °C. The as-deposited coatings with approximately 4.5 wt.% phosphorus were found to consist of a mix of nano- and microcrystalline phases. The mean particle size of Ni-P nanoparticles on the outer surface of the CMCs was around 11.9 nm. The deposition rate was found to moderately increase with increasing pH, whereas, the phosphorous content of the deposit exhibited a significant decrease. Moreover, the material of the coating underwent a phase transition between an amorphous and a crystalline structure. The thickness of the deposit and the deposition rate may be controlled through careful variation of the coating time and plating bath temperature.     

β-氨基腈类化合物的合成研究进展

近年来,β-氨基腈类化合物的合成与应用有了很大的进展,引起人们的广泛关注。由于旋光纯的β-氨基腈类化合物及其衍生物是非常重要的药物合成中间体,因此新的简捷、低成本不对称合成方法的研究与开发仍然是必要的。本文比较全面而又简要地综述了β-氨基腈类化合物的合成方法,并对该领域的今后发展方向进行了展望。     

Synthesis, structures, and magnetic properties of carboxylate-bridged trinuclear complexes based on low-spin manganese(III)/iron(III) building blocks

Four linear trinuclear transition metal complexes have been prepared and characterized. The complexes [M^II(MeOH)₄][Fe^III(L)₂]₂·2MeOH (M = Fe (1) or Ni (2)), [Co^II(EtOH)₂(H₂O)₂][Fe^III(L)₂]₂·2EtOH (3), and [Mn^II(phen)₂][Mn^III(L)₂]₂·4MeOH (4) (H₂L = ((2-carboxyphenyl)azo)-benzaldoxime, phen = 1,10-phenanthroline) possesses a similar syn–anti carboxylate-bridged structure. The terminal Fe(III) or Mn(III) ions are low spin, and the central M(II) ions are high spin. Magnetic measurements show that antiferromagnetic interactions were present between the adjacent metal ions via the syn–anti carboxylate bridges. The antiferromagnetic coupling between low-spin Fe(III) and Ni(II) is unusual, which has been tentatively assigned to the structural distortion of Fe(III).     

Synthesis and inclusion properties of pillar[n]arenes

A detailed study of the reaction conditions revealed that a quantitative cyclocondensation of 1,4-dialkoxy-2,5-bis(alkoxymethyl)-benzenes to pillar[n]arenes can be achieved by catalysis of p-toluenesulfonic acid in CH₂Cl₂. Major product of this new reaction is in each case a cyclopentamer (n = 5), but small amounts of the pillar[n]arenes with n = 6, 7 and 10 can be obtained as well. Different alkoxy groups in 1- and 4-position lead to regioisomers. All cyclooligomers exist in pillar structures as pair of enantiomers, which show a racemisation at room temperature, which is fast in terms of the NMR time scale. The racemisation process occurs by rotation of the 1,4-phenylene segments in the macrocyclic rings. Pillar[n]arenes exhibit novel host–guest behavior.     

Signal moments for the short‐time Fourier transform associated with Hardy–Sobolev derivatives

The short‐time Fourier transform has been shown to be a powerful tool for non‐stationary signals and time‐varying systems. This paper investigates the signal moments in the Hardy–Sobolev space that do not usually have classical derivatives. That is, signal moments become valid for non‐smooth signals if we replace the classical derivatives by the Hardy–Sobolev derivatives. Our work is based on the extension of Cohen's contributions to the local and global behaviors of the signal. The relationship of the moments and spreads of the signal in the time, frequency and short‐time Fourier domain are established in the Hardy–Sobolev space. Copyright © 2014 John Wiley & Sons, Ltd.     

可控表面磷原子修饰提升超细W2C纳米颗粒电解水析氢反应性能

研究高活性和稳定性的非贵金属基析氢催化剂对解决当前能源危机和环境污染问题具有重要意义.碳化钨具有与贵金属Pt类似的d带电子结构,因而成为一类新兴的非贵金属析氢催化剂,受到广泛关注.磷掺杂是提高催化剂析氢活性的有效方法之一,然而目前最常见的构筑磷掺杂方法是使用多金属氧酸盐(POMs,如H3PW12O40),其固定的W/P原子比导致W2C中的掺杂浓度难以调控,并且磷掺杂主要是进入碳载体而不是碳化物本身,从而导致无法明确杂原子对其电催化析氢活性的贡献.本文采用植酸(PA)为磷源设计合成了可控磷掺杂W2C纳米颗粒,并探讨了催化剂组分、杂原子掺杂位置与析氢性能之间的关系.深入研究了磷掺杂碳化钨(WCP)的化学结构和析氢活性.与原始的W2C催化剂相比,WCP具有更高的本征活性、更快的电子转移速率和更多的活性位数量,并且在酸性和碱性条件下均表现出较好的析氢性能.特别是过电位为-200 mV时,WCP催化剂的本征活性在酸性和碱性条件下分别为0.07和0.56 H2 s-1,高出纯W2C(0.01和0.05 H2 S-1)数倍.同时,在电流密度为-10 mA cm-2时,优化后的WCP催化剂在酸性和碱性条件下的析氢过电位分别降低了96和88 mV.XPS及EDS元素分析结果表明,随磷源添加量增加,磷掺杂从碳化钨表面逐渐向内部扩散,进一步说明磷取代位置与析氢活性之间的构效关系,高浓度的表面磷取代可以加速质子捕获过程,从而显著提高其析氢活性,而过量的内部磷取代会破坏W2C结构,降低电子转移速率,从而导致析氢性能下降.利用密度泛函理论计算深入研究了WCP具有较好析氢性能的原因,与内部磷取代相比,表面磷取代会使碳化钨表现出更合适的氢吸附自由能,并且更加有效地降低了氢释放势垒,从而优化了析氢反应动力学.综上,本文为元素掺杂工艺提供了新的思路,同时研究了表面异质原子对析氢活性的关键作用,为该类催化材料的构效关系研究提供了新思路.     

Synthesis and electrochemical properties of P2-Na<Subscript>2/3</Subscript>Ni<Subscript>1/3</Subscript>Mn<Subscript>2/3</Subscript>O<Subscript>2</Subscript>

The pure phase P2-Na_2/3Ni_1/3Mn_2/3O₂ was synthesized by a solid reaction process. The optimum calcination temperature was 850 °C. The as-prepared product delivered a capacity of 158 mAh g^?1 in the voltage range of 2–4.5 V, and there was a phase transition from P2 to O2 at about 4.2 V in the charge process. The P2 phase exhibited excellent intercalation behavior of Na ions. The reversible capacity is about 88.5 mAh g^?1 at 0.1 C in the voltage range of 2–4 V at room temperature. At an elevated temperature of 55 °C, it could remain as an excellent capacity retention at low current rates. The P2-Na_2/3Ni_1/3Mn_2/3O₂ is a potential cathode material for sodium-ion batteries.     

Pollution characteristics of ambient PM2.5-bound PAHs and NPAHs in a typical winter time period in Taiyuan

The pollution characteristics of ambient fine particulate matter（PM2.5） containing polycyclic aromatic hydrocarbons（PAHs） and nitrated PAHs（NPAHs） in samples collected during a typical winter time period in Taiyuan of China were investigated.The obtained results revealed that the mean mass concentrations of PM2.5,SPAHs（sum of 16 PAHs） and SNPAHs（sum of 3 NPAHs） on PM2.5were161.4 mg/m3,119.8 ng/m3and 0.446 ng/m3,respectively.Diagnostic ratios of PAHs and NPAHs implied that coal consumption might be the main source of the PM2.5pollution.The measured PM2.5mass concentrations,BaP equivalent toxicity（28.632 ng/m3） and individual carcinogenicity index（3.14 10 5） were much higher than those of the recommended safety standards.