线性分析法来解热脱附动力学参数

TPD方法是研究表面常规手段之一.对于如何从实验结果获得正确的脱附动力学参数,已有不少工作发表。然而,现有方法均存在一定的适用范围,尤其是重叠谱解叠,仍然没有很好地解决。本文介绍的线性分析法,不仅适用于简单的一级和二级脱附TPD谱的解析,而且也适用于重叠谱解叠,从而为实验上确定动力学级数和复杂谱解叠提供了依据。     

Ab initio calculations of vibronic activity in phosphorescence microwave double resonance spectra of p-dichlorobenzene

The phosphorescence spectrum of p-dichlorobenzene has been calculated using multiconfiguration self-consistent-field wave functions and the quadratic response technique. Attention has been paid to the intensity distribution of the singlet–triplet (³B_1u¹A_g) transition through a number of vibronic subbands. The second order spin–orbit coupling (SOC) contribution to the spin splitting of the ³B_1u (^3*) state is found to be almost negligible, and the calculations therefore provide a good estimate for the zero-field splitting (ZFS) parameters based only on the electron spin–spin coupling expectation values. Nuclear quadrupole resonance constants for the different Cl isotopes are also calculated to accomplish the ZFS assignment. The electric dipole activity of the spin sublevels in the triplet–singlet transitions to the ground-state vibrational levels is estimated by calculations of derivatives using distorted geometries which are shifted from the equilibrium position along different vibrational modes. A vibrational analysis of the phosphorescence spectrum, based on the SOC-induced mixing of the singlet and triplet states calculated along different vibrational modes, provides reasonable agreement with experimental data.Acknowledgment O. R.-P. would like to thank the European MOLPROP network for support. The authors thank Alexander Baev for fruitful discussions. This work was supported by the Swedish Royal Academy of Science (KVA).     

Surface characterization of macroporous glycidyl methacrylate based copolymers by inverse gas chromatography

Two samples of macroporous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate), PGME, with different porosity parameters were synthesized by suspension copolymerization and modified by ring-opening reaction of the pendant epoxy groups with ethylene diamine, EDA. Inverse gas chromatography at infinite dilution was used for the determination of adsorption properties of PGME, and copolymer modified with ethylene diamine, PGME-en. Thermodynamic parameters of adsorption, dispersive components of the surface free energies, and the acid/base constants for the copolymer samples were calculated. The calculated dispersive surface energy values, , for PGME and PGME-en are comparable with the literature data for nonconductive polymers.     

Thermodynamics of complexation of lanthanides and some of transition metal ions by 5,5-dimethyl-cyclohexane-2-(2-hydroxyphenyl)-hydrazono-1,3-dione (DCPHD) and its derivatives

Summary Equilibrium betweenDCPHD,DC-4-Cl-PHD, andDC-4-Me-PHD and protons, transition, and lanthanide ions have been investigated at 30 °C by means of potentiometric titration in 75% (v/v) methanol-water mixture containing 0.10M KNO₃ as a constant ionic medium. Thermodynamic parameters (G, H and S) referring to the formation of species HL ^–,L ^––,ML ^+n–2 andML ₂ ^+n–4 (L ^–– denotes the ligand anion) have been determined in solutions. The solvent effects on the thermodynamic parameters of the complex formation are discussed in terms of differences in the donor ability of methanol and water solvents. The plots of thermodynamic parameters versus ionic potential (Z ²/r) of the lanthanide elements is not linear as expected from ionic theory. The obtained curve can be resolved in an initial group (the lighter lanthanides), an intermediate group (Sm-Dy), and a final group (the heavier ones, Tb-Lu). This behavior was explained in terms of differences in the dehydration of lighter lanthanide(III) from that of heavier ones.

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Thermodynamik der Komplexierung von Lanthaniden und einigen Übergangsmetall-Ionen mit 5,5-Dimethylcyclohexyl-2-(2-hydroxyphenyl)-hydrazono-1,3-dion (DCPHD) und seinen Derivaten

Zusammenfassung Die Gleichgewichte zwischenDCPHD,DC-4-Cl-PHD undDC-4-Me-PHD mit Protonen, Übergangsmetall- und Lanthaniden-Ionen wurden bei 30 °C mittels potentiometrischer Titration in 75% (v/v) Methanol-Wasser mit einem Gehalt an 0.10M KNO₃ als konstantem ionischem Medium untersucht. Die thermodynamischen Parameter G, H und S zur Bildung der Spezies HL ^–,L ^––,ML ^+n–2 undML ₂ ^+n–4 (L ^–– steht für das Ligandenanion) wurden in Lösung bestimmt. Die Lösungsmitteleffekte auf diese Komplexbildungsparameter werden auf Basis der Differenz im Donorvermögen von Methanol und Wasser als Solventien diskutiert. Die Diagramme der thermodynamischen Parameter gegen die ionischen Potentiale (Z ²/r) der Lanthaniden sind, wie nach der Ionentheorie zu erwarten, nicht linear. Die erhaltene Kurve läßt eine Anfangsgruppe (die leichteren Lanthaniden), eine mittlere Gruppe (Sm-Dy) und eine Endgruppe (die schwereren Lanthaniden. Tb-Lu) erkennen. Dieses Verhalten kann aus dem Unterschied im Dehydratationsverhalten erklärt werden.

     

The ion product of H2O,dissociation constants of H2CO3 and pitzer parameters in the system Na+/H+/OH−/HCO 3 − /CO 3 2- /ClO 4 − /H2O at 25°C

The ion product of water and the dissociation constants of carbonic acid have been determined in 0.1, 1.0, 3.0, and 5.0M NaClO₄ at 25°C. The ion product of water K _w ^' has been evaluated by emf measurements with a combined glass electrode in NaClO₄ solutions containing 0.001–0.1M HCLO₄ or NaOH. The product K _H ^' K _l ^' K ₂ ^' of the Henry constant for CO₂ and the dissociation constants for H₂CO₃ have been determined by titration of carbonate solutions equilibrated with pCO₂ =10^–3.52 atm, and K ₂ ^' has been evaluated by potentiometric titration and by measuring the H⁺ concentration at fixed HCO ₃ ^– and CO ₃ ^2- concentrations. The ion interaction (Pitzer) equations are applied to describe the constants K _w ^' , K ₂ ^' and K _H ^' H ₁ ^' K ₂ ^' as a function of the NaClO₄ concentration. The experimental data are used to evaluate the mixing parameters _{i/ClO 4} and _{i/ClO 4} ^-/Na⁺ fori = OH ^-,HCO ₃ ^- andCO ₃ ^2-     

Principal component analysis of carbon-13 substituent-induced chemical shifts of some unsaturated compounds

Principal component analysis (PCA) is applied to 32 disubstituted unsaturated compounds (Y–CH₂–X): cyanides, oximes and propenes; bearing 12 -substituents: F, Cl, Br, I, OMe, OEt, SMe, SEt, NMe₂, NEt₂, Me, and Et. The experimental ¹³C chemical shifts for the -carbon and functional carbon atoms are correlated with theoretically derived molecular properties, i.e. partial charges, electronegativity, hardness, dipole moments and the nuclear repulsion energies. In the first PCA, the clustering of these three classes of organic compounds occurred mostly because of the chemical shifts and partial charges, and also of the dipole moments, hardness and electronegativity parameters as confirmed by loading graph. A strong grouping is observed in the second PCA, showing the chemical shift dependence on the type of heteroatom substituents. Therefore, sulfur, nitrogen, oxygen and neutral groups exhibit four types of C-13 SCS influences, indicating that the heteroatom (Y) properties play a significant role on the effects on chemical shifts. The -halogenated compounds represent a very heterogeneous group due to possible orbital interactions between the functional group and the substituent. The third PCA shows the grouping of F, Cl, Br and I derivatives, confirming the second PCA results that same halogen presents the same or very similar effects on the chemical shifts.     

Lattice Thermal Transport in the Homogeneous Cage-Like Compounds Cu3VSe4 and Cu3NbSe4: Interplay between Phonon-Phase Space,Anharmonicity, and Atomic Mass

Understanding the correlation between crystal structure and thermal conductivity in semiconductors is very important for designing heat-transport-related devices, such as high-performance thermoelectric materials and heat dissipation in micro-nano-scale devices. In this work, the lattice thermal conductivity ( ) of the cage-like compounds Cu₃VSe₄ and Cu₃NbSe₄ was investigated by experimental measurements and first-principles calculations. The experimental of Cu₃NbSe₄ is approximately 25 % lower than that of Cu₃VSe₄ at 300 K. The relevant important physical parameters, including the sound velocity, heat capacity, weighted phonon phase space (W), and third-order force constants along with atomic mass were theoretically analyzed. It is found that W is the dominant parameter in determining the , and the other factors only play a minor role. The physical origin is the relatively “soft” lattice of Cu₃NbSe₄ with heavier atomic mass. This research provides deep insight into the correlation between the thermal conductivity and crystal structure and paves the way for discovering high-performance thermal management device and thermoelectric materials with intrinsically low .     

Composting of urban solid residues (USR) by different dispositions

The thermal behavior and non-isothermal kinetics of thermal decomposition of three different kinds of composting of the USR like: stack with drilled PVC tubes (ST), revolved stack (SR) and stack with material of structure (SM), from the usine of composing of Araraquara city, Săo Paulo state, Brazil, within a period of 132 days of composting were studied. Results from TG, DTG and DSC curves obtained on inert atmosphere indicated that the cellulosic fraction present, despite the slow degradation during the composting process, is thermally less stable than other substances originated from that process. Due to that behavior, the cellulosic fraction decomposition could be kinetically evaluated through non-isothermal methods of analysis. The values obtained were: average activation energy, Ea=248, 257 and 259 kJ mol^-1 and pre- exponential factor, logA=21.4, 22.5, 22.7 min^-1, to the ST, SR and SM, respectively. From Ea and logA values and DSC curves, Málek procedure could be applied, suggesting that the SB (Šesták-Berggren) kinetic model is the appropriated one to the first thermal decomposition step. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dielectric studies of binary mixtures of n -propyl alcohol and ethylenediamine

Dielectric constant (ε’) and dielectric loss (ε") of n-propyl alcohol (PA), ethylenediamine (EDA) and their binary mixtures, for different mole fractions of ethylenediamine have been experimentally measured at 11.15 GHz microwave frequency. Values of density (ρ), viscosity (η) and square refractive index (n _D ² ) of binary mixtures as well as those of pure liquids are reported. Excess square refractive index, viscosity and activation energy of viscous flow have also been estimated. These parameters have been used to explain the formation of complexes in the system.     

AN/St悬浮共聚体系中AN在水/油两相间分配及其对共聚物组成的影响

研究了丙烯腈/苯乙烯(AN/St)悬浮共聚体系中AN在水/油两相间的分配及其对AN/St共聚物组成的影响.结果表明,AN分配于水/油两相间,使油相AN的含量低于相同单体配料比的本体聚合,导致生成的AN/St共聚物组成偏离本体共聚.为了准确预测进而控制AN/St悬浮共聚物的组成,提出了在考虑AN相分配的基础上计算AN/St悬浮共聚物组成的模型.计算结果与实验值一致,计算中用到的油相实际竞聚率与本体聚合相同,但该悬浮聚合的表观竞聚率随水/油比的变化而发生较大改变.