A New Member of Giant Polyoxomolybdate Containing Bridging Hydroxylamine Moieties: Synthesis and Crystal Structure of (NH4)4Na2[MoVI 36O108(NH2OH)2(OH)6(H2O)12]⋅35H2O

A new member of giant polyoxomolybdate containing bridging hydroxylamine groups has been unexpectedly obtained during the preparation of the material of {Mo₅₇V₆}, (NH₄)₄Na₂[Mo^VI ₃₆O₁₀₈(NH₂OH)₂(OH)₆(H₂O)₁₂]35H₂O. The title compound crystallizes in the monoclinic space group P2(1)/n, a=16.7886(2), b=18.4309(3), c=24.49950(10) Å, =99.58°, V=7475.18(15) ų, Z=2, and D _calc =2.817. Each giant cluster anion [Mo^VI ₃₆O₁₀₈(NH₂OH)₂(OH)₆(H₂O)₁₂]^6– ({Mo ₃₆ (NO) ₂ }) consists of two large [Mo^VI ₁₅O₅₀(MoO)⁴⁺ ₂(-NH₂OH)(-OH)(t-OH)₂(t-OH₂)₆]^5– ({Mo₁₇} units linked together by two {MoO₂}²⁺ centers; these anions {Mo ₃₆ (NO) ₂ } are further connected via distorted mono-capped pentagonal-pyramidal sodium into a three-dimensional structure with channels that filled with lattic water molecules and NH⁺ ₄ ions.     

Development of a Validated HPLC Method for Analysis of Astragaloside II, Paeonol, and Osthole in Snake Wine

A gradient-elution RP-HPLC method has been established for simultaneous determination of astragaloside II, paeonol, and osthole in the snake wine. The compounds were separated on a Polaris C₁₈ column (150 mm × 4.6 mm i.d., 5-µm particles); compounds were eluted with a gradient prepared from acetonitrile and 0.01 M phosphate buffer, pH 6.8. The detection wavelengths were 205, 274, and 323 nm from 0–10 min, 10–13 min, and 13–20 min, respectively. Linear quantitative calibration plots were obtained over the concentration ranges 2–200 µg mL^?1 for astragaloside II and 0.1–50 µg mL^?1 for paeonol and osthole. Average recoveries for astragaloside II, paeonol, and osthole were 96.32%, 96.89%, and 97.12%, respectively, and the respective RSD were 1.45%, 1.13%, and 1.17%. The method was found to be precise with RSD values in the ranges 0.87–1.91% for intra-day assays and 1.03–2.43% for inter-day assays. This method was efficient with high reproducibility and accuracy. Different batches of snake wine were analyzed by use of the method.     

求解对流占优问题的无网格自适应稳定化方案

应用标准的无网格方法求解对流占优问题时会出现非物理的数值伪振荡现象,采用MF-SUPG、MFGLS、MFSGS等稳定化方法可以有效地消除数值伪振荡.因此本文基于无网格径向点插值法提出了一种自适应布点方案,并分别与MFSUPG、MFGLS、MFSGS方法相结合.数值模拟表明:当扩散系数较小时,三种稳定化方法均可以有效地消除对流占优问题大部分区域的数值伪振荡,但稳定化后其解在边界处仍有振荡存在,而结合自适应方案后的三种稳定化方法均可以彻底地消除数值伪振荡,且具有计算精度高、稳定性好、算法实施简单、前后处理方便.     

Effect of deposition temperature on boron-doped carbon coatings deposited from a BCl3-C3H6-H2 mixture using low pressure chemical vapor deposition

A mixture of propylene, hydrogen and boron trichloride was used to fabricate boron-doped carbon coatings by using low pressure chemical vapor deposition (LPCVD) technique. Effect of deposition temperature on deposition rate, morphologies, compositions and bonding states of boron-doped carbon coatings was investigated. Below 1273 K, the deposition rate is controlled by reaction dynamics. The deposition rate increases with increasing deposition temperature. The activation energy is 208.74 kJ/mol. Above 1273 K, the deposition rate decreases due to smaller critical radius r_c and higher nuclei formation rate J with increasing temperature. Scanning electron microscopy shows that the structure changes from glass-like to nano-laminates with increasing deposition temperature. The boron concentration decreases with increasing deposition temperature, corresponding with increasing carbon concentration. The five types of bonding states are B-C, B-sub-C, BC₂O, BCO₂ and B-O. B-sub-C and BC₂O are the main bonding states. The reactions are dominant at all temperatures, in which the B-sub-C and PyC are formed.     

Uniform design and regression analysis of LPCVD boron carbide from BCl3-CH4-H2 system

Boron carbide was prepared by low pressure chemical vapor deposition (LPCVD) from BCl₃-CH₄-H₂ system. The deposition process conditions were optimized through using a uniform design method and regression analysis. The regression model of the deposition rate was established. The influences of deposition temperature (T), deposition time (t), inlet BCl₃/CH₄ gas ratio (δ), and inlet H₂/CH₄ gas ratio (θ) on deposition rate and microstructure of the coatings were investigated. The optimized deposition parameters were obtained theoretically. The morphologies, phases, microstructure and composition of deposits were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman micro-spectroscopy, transmission electron microscopy (TEM), energy dispersive spectra (EDS), and Auger electron spectra (AES), the results showed that different boron carbides were produced by three kinds of deposition mechanisms.     

金刚石膜/多孔硅复合材料的性能表征

提出了一种新颖的多孔硅表面钝化技术,即采用微波等离子体辅助的化学气相沉积（MPCVD）方法在多孔硅上沉积金刚石薄膜。采用原子力显微镜（AFM）、扫描电子显微镜（SEM）、X射线衍射仪（XRD）、拉曼光 谱仪和荧光分光度计对多孔硅及金刚石膜的表面形貌、结构和发光特性进行了表征。结果表明采用微波等离子体化学气相沉积法可在多孔硅基片上形成均匀、致密、性能稳定且对可见光具有全透性的金刚石膜。金刚石膜与多孔硅的复合,大大稳定了多孔硅的发光波长和强度,同时增强了多孔硅的机械强度。     

Generation of Nanoparticle,Atomic‐Cluster,and Single‐Atom Cobalt Catalysts from Zeolitic Imidazole Frameworks by Spatial Isolation and Their Use in Zinc–Air Batteries

The size effect of transition‐metal nanoparticles on electrocatalytic performance remains ambiguous especially when decreasing the size to the atomic level. Herein, we report the spatial isolation of cobalt species on the atomic scale, which was achieved by tuning the zinc dopant content in predesigned bimetallic Zn/Co zeolitic imidazole frameworks (ZnCo‐ZIFs), and led to the synthesis of nanoparticles, atomic clusters, and single atoms of Co catalysts on N‐doped porous carbon. This synthetic strategy allowed an investigation of the size effect on electrochemical behavior from nanometer to Ångström dimensions. Single‐atom Co catalysts showed superior bifunctional ORR/OER activity, durability, and reversibility in Zn–air batteries compared with the other derivatives and noble‐metal Pt/C+RuO₂, which was attributed to the high reactivity and stability of isolated single Co atoms. Our findings open up a new avenue to regulate the metal particle size and catalytic performance of MOF derivatives.     

MATLAB在运动学中的应用

仿真处理了著名的PASCAL摆线问题,并求解了摆线的运动学参数(以矩阵形式输出);仿真一个很难凭空想象其绝对运动轨迹的点的合成运动,并用编制的通用程序探索它的美妙轨迹;仿真了椭圆尺规机构的运动过程.仿真结果可作为教学演示,使抽象的力学生动活泼起来.