Hydrogen Isotope Absorption in Unary Oxides and Nitrides with Anion Vacancies and Substitution

The absorption states of hydrogen isotopes in various ceramic materials were investigated by density functional theory. For pristine ceramic materials, main-group oxides do not form any bond with a hydrogen atom. However, transition metal oxides form hydroxyl groups and absorb hydrogen atoms. Main-group and transition metal nitrides form ionic bonds between a hydrogen atom and the surrounded cation. For anion-deficient ceramic materials, hydrogen atoms are negatively charged because of excess electrons induced by anion vacancies, and ionic bonds form with the surrounded cation, which stabilizes the hydrogen absorption state. N substitutional doping into oxides introduces an electron hole, while O substitutional doping into the nitrides introduces an excess of electrons. Therefore, hydrogen isotopes form covalent bonds in N-substituted oxides, and form hydride ions in O-substituted nitrides. Thus, Al₂O₃, SiO₂, CrN, and TiN are promising materials as hydrogen permeation barriers.     

在线萃取分析系统快速测定水体中阴离子表面活性剂

以国标方法 GB 7494-1987为依据,采用直线模组自动控制系统和基于多通阀的复杂管路切换技术,实现对阴离子表面活性剂的在线、连续、多样品萃取分析.结果表明,阴离子洗涤剂在线萃取分析系统在0.1~2.0 mg/L质量浓度范围内,标准曲线的线性相关系数为0.999 9,检出限为0.035 mg/L,实际样品加标回收率为80%~115%,相对标准偏差在0.57%~5.73%之间,每个样品的实际检测周期为25 min,样品最大检测位数为20位.全自动萃取分析系统整个萃取过程完全密闭,且可恒温恒湿,操作过程试验人员不会接触三氯甲烷试剂,整个萃取分析流程较手动萃取快速高效,完全满足水样批量分析及实时监测的要求.     

碳棒涂膜电极流动注射法测定环境水样中的阴离子表面活性剂

采用自制碳棒PVC涂膜阴离子表面活性剂电极 ,建立了测定环境水样中阴离子表面活性剂的流动注射电位分析新方法。电极膜最佳组成 :THDA DBS 5mg ,DBS 0 .4mL,NB 0 .3mL ,PVC粉 0 .2g;电极线性响应范围 1× 1 0 - 3～ 1× 1 0 - 6 mol L。以 0 .0 1mol LKCl溶液作载流 ,流速 6.6mL min ,进样体积 2 0 0 μL,分散管长 2 0cm ,采样频率 5 0～ 80次样 h。测定 1 0 - 3、1 0 - 4 mol LDBS溶液 ,RSD≤ 3 .1 2 % (n=7) ,回收率 88.0 %～ 1 0 5 .0 %。电极易制作 ,成本低 ,FIA流路简单 ,操作方便 ,且克服了直接电位法电位飘移大的缺点 ,有较好的实用性     

Nanoscale structural order from the atomic pair distribution function (PDF): There's plenty of room in the middle

Emerging materials of scientific and technological interest are generally complex and often nanostructured: they have atomic orderings that extend on nanometer length-scales. These can be discrete nanoparticles; bulk crystals with nanoscale chemical or displacive order within them; mesoporous materials that are bulk materials containing nanoscale holes; and nanocomposites that are intimate heterogeneous mixtures of nano-sized constituents. As always, a quantitative knowledge of the atomic structure within these materials is a prerequisite to understanding and engineering their properties. Traditional crystallographic methods for obtaining this information break down at the nanoscale, sometimes referred to as “the nanostructure problem”. We describe here some emerging methods for studying nanoscale structure. We present some examples of recent successes. Finally, we discuss future directions and opportunities and draw attention to limitations and potential problems.     

The Mechanism of Initiation of the Anionic Polymerization of Acrylonitrile with 14C-Labeled Lithium Alkoxides in Dimethylformamide

Investigations of the anionic polymerization of acrylonitrile in dimethylformamide initiated with ¹⁴C-labeled lithium tertiary butoxide have shown that the tertiary butoxide group is not incorporated into the polymer chain, Comparison with the initiation behavior of other lithium alkoxides has indicated that the amount of incorporation of the alkoxyl groups from the anionic lithium alkoxide initiators depended on the basicity of the alkoxide group. A new initiation mechanism is proposed which involves as initiator an active center which consists of an electron donor-acceptor complex of the lithium alkoxide with the solvent dimethylformamide and the acrylonitrile monomer.     

Anionic polymerization of acrylates. II. Polymerization of 2-ethylhexyl acrylate initiated by butyllithium/lithium-tert-butoxide system in tetrahydrofuran and its mixtures with toluene

The anionic polymerization of 2-ethylhexyl acrylate (EtHA) initiated with the complex butyllithium/lithium-tert-butoxide (BuLi/t-BuOLi) was investigated at ?60°C in a medium of various solvating power, i.e., in mixtures of toluene and tetrahydrofuran and in neat tetrahydrofuran. With increasing amount of THF in the mixture the attainable limiting conversion of polymerization decreases; the monomer can be polymerized quantitatively only in a toluene/THF mixture (9/1). Molecular weights of the polymers thus obtained, their distribution, and initiator efficiency are not appreciably affected by the polymerization medium. The molecular weight distribution of the products is medium-broad (M_w/M_n = 2–2.4), with a hint of bimodality. The ¹H-¹³C-NMR, and IR spectra suggest that during the polymerization there is neither any perceptible reesterification of the polymer with the alkoxide nor transmetalation of the monomer with the initiator. In a suitable medium, autotermination of propagation proceeds to a limited extent only, predominantly via intramolecular cyclization of propagating chains; in a medium with a higher content of polar THF, it prevails and terminates propagation before the polymerization of the monomer has been completed. © 1992 John Wiley & Sons, Inc.     

用矩分析法研究流动注射分析中化学反应对试样分散的影响

根据串联釜模型和统计矩分析法，通过实验证实了化学反应对分散度的影响；在同一流路中有化学反应的峰宽和二阶矩均比无化学反应的增大。并证明了二阶矩与１／４峰高处峰宽的平方成线性关系。同时给出了一个计算响应曲线统计矩的简易方法。     

表面增强拉曼光谱结合主成分分析快速筛查食品接触材料中多环芳烃

建立了表面增强拉曼/主成分分析快速筛查食品接触材料中4种多环芳烃的分析方法。采用纳米银溶胶作为增强基底,碘化钾为絮凝剂,实现了4种多环芳烃（芘、荧蒽、苯并［b］荧蒽、苯并［k］荧蒽）的表面增强拉曼分析。针对食品接触材料中4种多环芳烃拉曼谱峰重叠难以鉴别区分的问题,采用主成分分析法分别对同浓度多环芳烃、不同浓度多环芳烃以及多环芳烃混合样品进行分析。结果表明,4种多环芳烃均可得到较好的鉴别。该方法成功用于食品接触材料迁移液中4种多环芳烃的快速筛查。     

Probing multiple melting behaviors in poly(ethylene naphthalene 2,6‐dicarboxylate) with different thermal histories by simultaneous wide‐angle and small‐angle X‐ray scattering

A simultaneous wide‐angle and small‐angle X‐ray scattering study of two poly(ethylene naphthalene 2,6‐dicarboxylate) samples crystallized from the glassy state at different annealing temperatures for different annealing times was carried out with synchrotron radiation. Either single or dual melting was induced in the samples, as confirmed by differential scanning calorimetry (DSC). The correlation function and interface distribution function were calculated to evaluate microstructural parameters such as the long spacing, the thickness of the amorphous and crystalline phases, and the width of the size distributions. The sample with dual melting behavior exhibited an abrupt increase of all microstructural parameters at temperatures above the melting of the lowest endotherm, whereas the sample revealing a single melting endotherm did not show such a sudden change. This finding agrees with the concept that the appearance of two melting peaks in DSC traces can be explained by the dual lamellar stacking model. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 881–894, 2001