Growth behavior of Cu/Al intermetallic compounds in hot‐dip aluminized copper

Hot‐dipped aluminum copper with plating auxiliary KF is introduced in this work. In this study, the intermetallic layer thickness varies with dipping temperature and time in a linear relationship. The main phases are identified to be CuAl₂ and K₃AlF₆ by means of X‐ray diffraction. The reaction equations are deduced according to the elements concentration gradient in cross section. The copper diffusion rate in liquid Al is calculated to be 1.13 × 10⁻¹² m²/s by Fick's second law in semi‐infinite solid model, and the obtained conductivity is 1.758–1.767 × 10⁻² Ω mm²/m. The results indicate that the interfacial bonding is in a good state and plating auxiliary KF aqueous solution. can significantly improve the substrate wettability. The appropriate hot‐dipping condition for the samples is 953–973 K for 4–8 s. Copyright © 2009 John Wiley & Sons, Ltd.     

垂直加热管外自由降膜流的破断特性

在较宽液膜雷诺数和进口温度范围内对垂直加热管外自由降膜流破断特性进行了实验研究。应用热物理学相似分析的方法整理实验数据，给出新的破断准则数综合关系式，并与１９９３年发表的另一些作者的结果作了比较。实验参数的变化范围如下：ｔｉｎ＝２０～９０℃，最大液膜雷诺数Ｒｅ为１．２１×１０４，最大热流密度达１．３９×１０５ｗ／ｍ２。     

石太客运专线特长隧道涌水灾害预测研究

介绍了模糊综合评判方法及其应用步骤,在分析石太客运专线特长隧道地质构造、围岩类别、降雨量、地表环境特征等因素的基础上,建立模糊综合评判矩阵对隧道涌水进行预测。结果表明,模糊综合评判方法能很好地预测隧道涌水量的大小等级。     

石油组分及其模型化合物的超分子化学作用

原油是最复杂的化学体系之一,人们对原油这种复杂的胶态分散体及其稳定性的研究兴趣与日俱增,尤其是与石油稳定性密切相关的沥青质超分子聚集体。但人们对形成沥青质超分子聚集体的主要作用力长期以来颇有争议。本文重点介绍了石油组分及其模型化合物在溶液中形成超分子聚集体的超分子化学作用研究进展。通过实验方法和理论计算证明沥青质聚集体是沥青质分子间通过氢键、π-π堆积、偶极-偶极相互作用等多种分子间弱相互作用力协同作用形成的热力学稳定结构;合成具有沥青质结构特点的纯化合物,研究它们在溶液中的行为,是提高对沥青质在液态相中自缔合行为认识的有效方法;结合现阶段的研究状况,对石油组分模型化合物的超分子化学作用研究的发展前景进行了展望。     

Rhodium(III)‐Catalyzed Enantio‐ and Diastereoselective C−H Cyclopropylation of N‐Phenoxylsulfonamides: Combined Experimental and Computational Studies

Cyclopropane rings are a prominent structural motif in biologically active molecules. Enantio‐ and diastereoselective construction of cyclopropanes through C?H activation of arenes and coupling with readily available cyclopropenes is highly appealing but remains a challenge. A dual directing‐group‐assisted C?H activation strategy was used to realize mild and redox‐neutral Rh^III‐catalyzed C?H activation and cyclopropylation of N‐phenoxylsulfonamides in a highly enantioselective, diastereoselective, and regioselective fashion with cyclopropenyl secondary alcohols as a cyclopropylating reagent. Synthetic applications are demonstrated to highlight the potential of the developed method. Integrated experimental and computational mechanistic studies revealed that the reaction proceeds via a Rh^V nitrenoid intermediate, and Noyori‐type outer sphere concerted proton‐hydride transfer from the secondary alcohol to the Rh=N bond produces the observed trans selectivity.     

Rhodium(III)-Catalyzed Enantio- and Diastereoselective C−H Cyclopropylation of N-Phenoxylsulfonamides: Combined Experimental and Computational Studies

Cyclopropane rings are a prominent structural motif in biologically active molecules. Enantio- and diastereoselective construction of cyclopropanes through C−H activation of arenes and coupling with readily available cyclopropenes is highly appealing but remains a challenge. A dual directing-group-assisted C−H activation strategy was used to realize mild and redox-neutral Rh^III-catalyzed C−H activation and cyclopropylation of N-phenoxylsulfonamides in a highly enantioselective, diastereoselective, and regioselective fashion with cyclopropenyl secondary alcohols as a cyclopropylating reagent. Synthetic applications are demonstrated to highlight the potential of the developed method. Integrated experimental and computational mechanistic studies revealed that the reaction proceeds via a Rh^V nitrenoid intermediate, and Noyori-type outer sphere concerted proton-hydride transfer from the secondary alcohol to the Rh=N bond produces the observed trans selectivity.     

Reaction mechanism of chitosan/acrylamides dimer: A DFT study

Environment‐sensitive hydrogel is a sensitive hydrogel that responses to outside stimuli. A new temperature‐ and pH‐sensitive hydrogel is able to been prepared by radiation polymerization or emulsion polymerization method combining with the excellent thermosensitive poly(N‐isopropyl acrylamide) (PNIPAM), and the pH‐sensitive chitosan (CS). However, it is different to understand the reaction mechanisms thoroughly unless we can obtain more details at the molecular level. In this work, the reaction mechanism of chitosan and acrylamides (AMs, that is AM or NIPAM) dimer was shed light on by using the density functional theory (DFT), to investigate all possible reaction channels and reveal the underlying nature of polymerization at the micro level. The geometric structures of all stationary points in the reaction pathways were optimized. The reaction takes place via 3 possible reaction channels, which are RCSN + AMs → RCSN/AMs, RCSO3 + AMs → RCSO3/AMs, and RCSO5 + AMs → RCSO5/AMs. Comparing the energy barriers of these reaction pathways at a higher level, RCSO5 + AMs → RCSO5/AMs is the main pathway for forming RCS/AMs. According to the variations of bond‐lengths and the corresponding vibration peaks, it is confirmed that there are intramolecular hydrogen bond interactions in RCSO3/AMs dimer and RCSO5/AMs dimer.     

高速逆流色谱法快速分离制备枸杞中莨菪亭

建立了用高速逆流色谱(HSCCC)从枸杞中快速分离莨菪亭的方法。将枸杞的乙醇提取物经D-101大孔树脂初步纯化后直接进行高速逆流色谱分离,用薄层色谱-荧光法考察了莨菪亭在不同溶剂体系中的分配情况。结果表明,最佳的溶剂体系为氯仿-甲醇-水(10:7:3, v/v/v),取上相为固定相,下相为流动相,在主机转速为850 r/min、流速为1.5 mL/min、检测波长为365 nm的条件下,从200 mg样品中一次性分离制备可得到10.2 mg纯度达到98.3%的莨菪亭。制备所得的莨菪亭与对照品的高效液相色谱(HPLC)保留时间一致,且经核磁共振氢谱、碳谱鉴定结构;纯度经HPLC法测定。研究发现,氯仿-甲醇-水(10:7:3, v/v/v)体系可连续二次进样而样品的峰形未受明显的影响。实验结果表明用薄层色谱-荧光法可快速选定HSCCC溶剂体系,进而可快速、简便地制备高纯度的莨菪亭。     

Preparation of poly(3-hexylthiophene)/graphene nanocomposite via in situ reduction of modified graphite oxide sheets

Poly(3-hexylthiophene) (P3HT)/graphene nanocomposites were facilely prepared via an in situ reduction of modified graphite oxide (mGO) in the presence of P3HT. The chemical and aggregated structures of the P3HT/mGO nanocomposites were successfully characterized by means of atomic force microscope (AFM), transmission electron microscope (TEM), photoluminescence (PL), Raman spectra, X-ray photoelectron spectroscopy (XPS) and UV-vis measurements. Coated by P3HT, reduced modified graphite oxide (re-mGO) could significantly improve their processing problem in common organic solvent. It was shown that P3HT chains were attached to re-mGO sheets closely and there existed the pi-pi interaction between P3HT and re-mGO. The P3HT/mGO nanocomposites exhibited good dispersion in chloroform and show high storage stability (>20 days). This finding provides an efficient method for fabricating a light energy conversion materials with new optical and electrical properties, combining excellent mechanics, heat-stabilization properties of graphene and excellent optical, electrical, processing and film forming properties of soluble polythiophene materials.