Improved accuracy of quantitative XPS analysis using predetermined spectrometer transmission functions with UNIFIT 2004

The accuracy of quantitative XPS analysis can be improved using predetermined transmission functions. Two different calibration methods are used for estimating the transmission function T(E) of a photoelectron spectrometer, applying a survey spectra approach (SSA) and a quantified peak‐area approach (QPA) to minimize the quantification error. For the SSA method, Au, Ag and Cu spectra measured with the Metrology Spectrometer II have been used. The new QPA method was built up from Au 4f, Au 4d, Au 4p_3/2, Ag 3d, Ag 3p_3/2, Cu 3p, Cu 2p_3/2, Ge 3p and Ge 2p_3/2 standard peak areas, applying adequate ionization cross‐sections and mean free path lengths for different pass energies (10 and 50 eV), lens modes (large area, large area XL, small area 150) and x‐ray sources (Al/Mg Twin and Al Mono). In the energy range 200–1500 eV a transmission function T(E) = a₀ + b₁E (where a₀, b₁ and b₂ are variable parameters) was found to give an appropriate approximation for eight tested spectrometer settings, implementing the largest changes in the case of pass energy variations. Determination and application of the transmission functions were integrated in the XPS analysis software (UNIFIT 2004) and tested by means of an Ni90Cr10 alloy. The results demonstrate the practicability of the SSA and QPA methods, giving decreased errors of <8% in comparison with errors up to 38% obtained using Wagner's sensitivity factors. Copyright © 2005 John Wiley & Sons, Ltd.     

Charge compensation dynamics in a soluble copolymer of poly(aniline) and poly(phenylene sulfide)

Poly(phenylene sulfide phenyleneamine), PPSA, is a copolymer of poly(aniline) and poly(phenylene sulfide), soluble in conventional organic solvents as tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, and cyclohexanone. In this research, its electrochemical behavior has been studied in acetonitrile in the presence of different electrolytes, where the loss of electroactivity was observed after few cycles. In this paper, the charge compensation dynamics of PPSA is analyzed through electrochemical quartz crystal microbalance experiments and electroacoustic impedance measurements. Raman spectroscopy data have shown that once the oxidation of the sulfur atom occurs, a loss of electroactivity is observed, being not possible to recover the pristine state of the polymer. Fourier transform infrared (FTIR) and X-ray diffraction (XRD) data obtained for the fully oxidized polymer are consistent with the formation of a networked polymer due to the electrophilic attack of the positive sulfur atom on the activated aromatic rings. Electrochemical quartz crystal microbalance results clearly show that the degree of irreversibility fully depends on the chemical nature of the anions with a negligible participation of the cations of the electrolytic solution. This work is in memoriam of Prof. Dr. Francisco C. Nart, dearest friend and colleague, whose scientific skills and enthusiasm will always be remembered.     

六甲氧基甲基三聚氰胺-多元醇-丙烯酸酯混杂聚合过程热互补效应的研究

六甲氧基甲基三聚氰胺（HMMM）－多元醇－丙烯酸酯－酸催化剂的混合体系在较高温度下同时进行缩聚和自由基聚合并表现出协同效应，DSC研究结果表明，丙烯酸酯在HMMM和酸的催化作用下可在较低温度下发生自由基聚合反应，并把反应释放出来的大量的热量有效地传递给缩聚发反应，满足缩聚反应吸热的要求，从而节省固化所需要的能量，为了提高储存稳定性。本文以潜酸催化剂作为酸的来源，对该混杂聚合体系进行了研究，仍有明显的热互补效应。     

Excess heat capacities and orientational order in systems containing hexadecane isomers of different molecular structure

Using the Picker flow microcalorimeter, excess heat capacities have been obtained at 25°C throughout the concentration range for 2,2-dimethylbutane,n-hexane, and cyclohexane each mixed with a series of hexadecane isomers of increasing degrees of orientational order, as determined by depolarized Rayleigh scattering. The isomers are 2,2,4,4,6,8,8-heptamethylnonane, 6-, 4-, and 2-methylpentadecane, andn-hexadecane. Thec _p ^E values are negative, increasing rapidly in magnitude with increase of orientational order, and are not predicted by the Prigogine—Flory theory which neglects order. Values ofc _p ^E are obtained at 10, 25, and 55°C for cyclohexane +6-, 4-, and 2-methylpentadecane which with other literature data lead to the temperature dependence of the thermodynamic excess functions for cyclohexane solutions of the five C₁₆ isomers. The excess enthalpy and entropy vary with the C₁₆ isomer and with temperature, but the corresponding variation of the excess free energy is small, indicating a high degree of enthalpy-entropy compensation. This is consistent with a rapid decrease with temperature of orientational order in the C₁₆ isomers.     

Vibronic intensities in centrosymmetric coordination compounds of the rare earths Part II. A vibronic crystal field-closure-ligand polarisation model and applications to the PrCl6 and UBr6 complex ions in octahedral symmetry

A symmetry adapted formalism to evaluate the vibronic intensities induced by the ungerade vibrational modes in centrosymmetric coordination compounds of the rare earths is put forward and applied to several selected electronic transitions of the PrCl³⁻₆ and UCl²⁻₆ complex ions in octahedral symmetry. This current model is based upon a modified symmetry adapted version of the combined vibronic crystal field-closure-ligand polarisation approach. This model differs from that developed in Part I of this series, in that for the vibronic crystal field contribution to the total transition dipole moment, the closure procedure is employed rather than the utilisation of a truncated basis set for the central metal intermediate electronic states. A criterion is introduced to choose an appropriate set of phases for both the electronic and the vibrational coordinates so that to ensure the right sign for the interference term (which couples together both the vibronic crystal field and the vibronic ligand polarisation contributions to the total transition dipole moment). We have focused our attention on the modulation of the intermolecular force field and a version of a modified general valence force field has been adopted. The reasons for using this formalism rather than the superposition model (SM) are fully discussed in the text. Finally, it is shown that the agreement with experiment is satisfactory for most of the components of the transitions studied, despite the apparent simplicity of our model calculation. General master equations applicable to any f^N electronic configurations are derived to show the utility and flexibility of this current formalism.     

Chemical-effect variation of Kβ/Kα X-ray intensity ratios in 3d elements

Chemical effects on Kβ/Kα X-ray intensity ratios for some Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn compounds are studied experimentally. The X-ray spectra were measured by using a Si (Li) solid state detector with high resolution. The vacancies were produced by heavily filtered ²⁴¹Am gamma rays. It is found that the Kβ/Kα X-ray intensity ratios measured with compounds deviated up to 43% from the corresponding values of the pure elements. The values for pure elements are compared with the other experimental and with theoretical values.     

纳米α-FeOOH催化剂一段法脱除COS和H2S性能的研究

利用均相沉淀法、氨水滴定法制备纳米α-FeOOH粒子，以该粒子为活性组分制备催化剂，利用微反－色谱联用活性评价技术，在常压、空速10 000 h－1、25 ℃～60 ℃温度范围内考察了纳米α-FeOOH催化剂对COS催化水解的活性。采用热重法对纳米α-FeOOH催化剂脱除H2S的性能进行了研究。结果表明：纳米α-FeOOH催化剂对COS水解在低温度、大空速下具有高的活性，系列Ⅰ和系列Ⅱ催化剂分别在60 ℃和40 ℃～45 ℃时COS转化率达到100%。在60 ℃时各种催化剂吸附H2S的能力最强，最高饱和硫容可达到21.72w%。催化剂表面能量分布不均匀，COS催化水解在低温时存在补偿效应。     

助熔剂对Y3Al5O12：Ce荧光粉性能的影响

在还原气氛下采用高温固相反应法合成了白光LED用黄色荧光粉Y3Al5O12:Ce(YAG:Ce)研究了助熔剂对YAG：Ce荧光粉发光特性的影响，。XRD的测量结果表明加入合适的助熔剂有利于YAG:Ce荧光粉的晶化，并且不引入杂相，选择BaF2和H3BO3同时使用效果要好于单独使用一种助熔剂，助熔剂的加入可增大YAG：Ce荧光粉的激发和发射光谱强度，并能有效降低荧光粉的中心粒径（D50）控制粉体的粒径分布，适用于白光LED的制造。     

Surface diffusion in reversed-phase liquid chromatography using silica gels bonded with C1 and C18 ligands of different densities

Surface diffusion in reversed-phase liquid chromatography (RPLC) using silica gels bonded with C₁ and C₁₈ alkyl ligands of different densities was studied from the viewpoints of two extrathermodynamic relationships, i.e., enthalpy-entropy compensation (EEC) and linear free energy relationship (LFER). First, according to the four methods proposed by Krug et al., the values of surface diffusion coefficient (D_s) were analyzed to confirm that an actual EEC resulting from substantial physico-chemical effects takes place for surface diffusion. Then, it was also demonstrated that a LFER is observed between surface diffusion and the retention equilibrium. The establishment of EEC and LFER suggests a mechanistic similarity of molecular migration by surface diffusion, irrespective of the alkyl chain length and the densities of C₁ and C₁₈ ligands. Finally, a thermodynamic model for the LFER based on the real EEC was used to estimate D_s values under various RPLC conditions. The D_s values can be estimated with a mean square deviation of about 25–30%. The agreement between the D_s values estimated and those experimentally measured suggests that the total mass flux by surface diffusion consists of the two contributions due to C₁ and C₁₈ ligands and that the contribution of each ligand is proportional to the ligand density.     

高管薪酬监督博弈与独立董事有效性研究

研究聚焦董事会内部沟通网络,基于独立董事信息共享机制探讨对高管薪酬的监督效果。研究发现,独立董事相互之间通过共享信息来增强对高管自利行为的抑制能力,有效降低了高管薪酬。同时,管理者权力对独立董事信息共享机制的监督效力起到调节作用,具体表现为随着管理者权力的增强,独立董事信息共享对于高管薪酬的约束作用被弱化,这一结果说明独立董事信息共享机制的监督有效性受到管理者权力的限制。研究构建了独立董事信息共享指标,并基于董事会监督博弈过程分析信息共享对高管自利行为的约束过程,最后运用A股上市公司数据加以验证。研究拓展了对独立董事监督机制的认识,为打开董事会“黑箱”、提升董事会绩效提供新视角,促进公司治理机制由静态结构研究向动态过程研究转化。