受高斯白噪声影响的有限化学反应体系的随机热力学——外噪声对化学反应体系影响的有效热力学量度

通过分析噪声对跃迁概率的不同影响,借助Novikov定理及MSR理论,建立了受多源白噪声影响的有限化学反应体系的有效主方程及有效熵平衡方程,导出非平衡定态时这类噪声体系熵产生的一般表达式,揭示涨落熵产生的统计内涵及噪声贡献,并针对非宏观量级的外噪声,借助扰动按分布参数分离法及有效主方程的Kramers-Moyal展开,进一步对简单加合性噪声建立了非平衡定态宏观稳定性判据的随机模拟,论证了噪声对化学反应体系定态稳定性的弱化作用.     

Multipole expansion of diatomic overlap

A systematic extension of Ruedenberg's expansion formula is applied to evaluate two-electron integrals occurring in calculations on molecular structure. Minimum STO basis sets are used for all SCF-calculations within the framework of the MEDO-method (Multipole Expansion of Diatomic Overlap). The errors due to this approximation scheme are almost negligible compared to those introduced by the truncated basis set: LiH, Li₂ and N₂ are chosen as examples.     

Resistivity and Thermal Expansion (4.2–820 K) of Skutterudites after Severe Plastic Deformation via HPT

Thermoelectric materials with a high figure of merit, ZT, are the essential basis to build thermoelectric generators, which can directly convert heat into electricity. Severe plastic deformation (SPD) via high-pressure torsion (HPT) was successfully applied to enhance ZT of ball-milled and hot-pressed skutterudites as well as to produce bulk nanostructured skutterudites directly from powders. SPD introduces many defects into the sample and in parallel the crystallite size is significantly reduced. During measurement-induced heating these defects anneal partially out, and the grains grow. In this work for the first time systematically the changes of the temperature-dependent electrical resistivity and of thermal expansion were compared. It could be shown that for p- and n-type skutterudites, being hot-pressed and HPT-processed as well as directly HPT-processed from compacted powder, these changes occur more or less simultaneously within the same temperature ranges. This evaluation gives a much deeper insight into the thermoelectric behavior of HPT samples under the influence of changing temperature.     

RP-HPLC study of redox equilibria in vanadium-PAR binary and ternary systems: Direct determination of vanadium in steel

The reversed-phase high-performance liquid Chromatographic (RP-HPLC) behaviour of the binary chelates of V(V) and V(IV) with 4-(2-pyridylazo) resorcinol (PAR) and ternary chelates of vanadium with PAR and auxiliary ligands: hydrogen peroxide, hydroxylamine, tartrate and citrate were studied using a C₁₈ column. The complex double-peak chromatograms of V(IV)/V(V)-PAR systems were studied and the origin of each peak was proved. Vanadium in ternary systems with PAR and hydrogen peroxide was found exclusively in V(V)-H₂O₂-PAR complex (single peak on the chromatogram) despite its initial oxidation state. The double role of hydroxylamine (complex agent and reductor) in vanadium systems with PAR was confirmed: in the V(V) system three species were identified (V(V)-PAR, V(V)-NH₂OH-PAR and V(IV)-PAR), but in the V(IV) system only two: V(IV)-PAR and V(V)-NH₂OH-PAR. Citrate and tartrate giving single peak were found as auxiliary ligands in ternary V(V) systems of analytical importance. Due to its masking potential towards iron (III) ions, citrate was chosen as the most suitable third component of a ternary vanadium system with PAR, to form the basis of an RP-HPLC method for direct determination of V in steel.     

含酰胺结构超低膨胀聚酰亚胺薄膜的热膨胀行为

采用联苯二酐与3种含酰胺结构二胺制备了具有不同取代基团的聚酰胺-酰亚胺薄膜,考察了酰胺结构对薄膜力学、耐热及尺寸稳定性的影响,研究了聚集态结构与薄膜热膨胀行为的关系和规律.该系列薄膜具有超高强度和优异的耐热性能,拉伸强度高达280. 5 MPa,玻璃化转变温度在389～409℃,并在30～300℃温度范围内表现出超低负膨胀,热膨胀系数(CTE,ppm/℃,即106cm·cm-1·℃-1)在-3. 05～-1. 74ppm/℃之间.聚集态分析结果表明,酰胺结构使分子链间形成了强氢键相互作用,分子链在薄膜面内方向高度有序取向,并在膜厚方向堆积更为紧密,使薄膜表现出热收缩现象.通过不同体积大小的取代基团进一步调控分子链间相互作用及排列堆积,可实现薄膜在高温下近乎零尺寸形变,为设计制备超低膨胀聚合物基板材料提供了新思路.     

Compatibility Range in Polymer Mixtures. An approach using analogue calorimetry and group contribution procedures

The mixing enthalpies of blends of polymethylmethacrylate (PMMA) with poly(styrene-co-acrylonitrile) (SAN) were investigated by analogue calorimetry through the determination of the excess enthalpies of pseudobinary model mixtures corresponding to the addition of methyl-i-butyrate to a binary mixture of acetonitrile or propionitrile plus toluene or ethylbenzene. A group contribution procedure, based on UNIQUAC equation, was also devised and the polymeric mixing enthalpies were calculated from properly defined group contributions. Enthalpies for polymeric interactions were introduced into the Flory-Huggins equation and the miscibility window of PMMA-SAN mixtures was calculated. The results show a qualitative agreement with the experimental miscibility data and indicate that both the analogue calorimetry and the group contribution procedures yield correct results when acetonitrile, and not propionitrile, is chosen as the model for the polyacrylonitrile repeat unit of the copolymer. This revised version was published online in July 2006 with corrections to the Cover Date.     

Association Model and Its Representation of Phase Equilibria and Excess Enthalpies of Alcohol, Aniline, and Acetonitrile Mixtures

An association model is presented to describe vapor–liquid equilibria,liquid–liquid equilibria, and excess enthalpies of binary and ternary liquid solutionscontaining alcohols, aniline, and/or acetonitrile using the concepts of linearself-association of associated components and of solvation between unlike molecules.Calculated results also show that the model works well in representing thethermodynamic properties for alcohol + aniline, alcohol + acetonitrile, andalcohol + alcohol mixtures.     

Systeme Binaire AgNO3-LiNO3. Diagramme de phases et proprietes thermodynamiques des mélanges a l’etat liquide

To study the coherence of thermodynamic data of the AgNO₃-LiNO₃ -RbNO₃ ternary system, phase diagram of the binary system AgNO₃ -LiNO₃ has been obtained between 303 and 550 K by direct and differential thermal analysis technique. This system is characterized by an eutectic point (25% mol. LiNO₃ , 445±1 K) and a plateau due to the solid-solid transition in AgNO₃ at 434±1 K. In the solid state the solubility of each component in the other seems to be nil or negligible (no more than a few percents). Using other thermodynamic data, the excess properties of the binary liquid (AgNO₃ - LiNO₃ ) were calculated at 623 K. This revised version was published online in August 2006 with corrections to the Cover Date.     

An Empirical Approach for Estimating the Density of Multicomponent Aqueous Solutions Obeying the Linear Isopiestic Relation

An empirical approach is presented for the density of aqueous multicomponentsolutions conforming to the linear isopiestic relation. This approach can be usedto estimate the densities of multicomponent systems from data on the constituentbinary subsystems at the same water activity. Predicted and measured densitiesfor 22 mixtures have been compared, using the simple Young's rule, theisopycnotic mixing rule of Teng and Lenzi, and the present method. The present methodand Young's rule give the most accurate predictions for strong electrolyte mixtureswithout common ions and for the mixtures with strong ion complexes, respectively.There is no universal best method for the strong electrolyte mixtures with commonions. An extensive comparison has also been given between apparent molarvolume predictions by Young's rule and by the new method. The two rules arerelatively better for the strong electrolyte mixtures without common ions andmixtures containing the transition metal chlorides, respectively. However, neitheris universally better for mixtures of strong common-ion electrolytes.