Cu—ZSM—5分子筛表面铜离子的价态研究

以吸附ＣＯ红外光谱结合ＴＰＲ谱详细表征了经真空自还原及用不同还原剂还原的Ｃｕ－ＺＳＭ－５分子筛样品，考察了表面铜离子的价态分布情况及其影响因素，得知铜在Ｃｕ－ＺＳＭ－５是还原的。用不同方法进行氧化和还原时的难易程度不同。研究了用不同方法进行氧化还原时铜的价态转变条件和铜离子在不同价态间氧化还原循环的可逆性。     

复合卤化物中钐价态的异常变化及其稳定性

复合卤化物中钐价态的异常变化及其稳定性孙淑清，石春山（中国科学院长春应用化学研究所稀土化学与物理开放实验室长春１３００２２）关键词钐，价态，复合卤化物，光谱Ｓｍ２＋离子在红区和红外区可以产生４ｆ６组态内的ｆ－ｆ跃迁锐线发射和４ｆ５５ｄ组态的ｄ－ｆ跃迁...     

混合价态铜(Ⅰ，Ⅱ)配合物的合成与结构

本文概述了铜(Ⅰ,Ⅱ)混合价态配合物的化学进展,总结了这类配合物的合成方法及其结构特征。     

固态化合物中铕的价态研究进展

介绍了近年来关于变价稀土元素Ｅｕ价态研究的最新进展,总结了Ｅｕ＾２＋的价态稳定和转换及其与基质结构,取代离子半径电荷,共掺杂稀土离子电子构型之间的关系和规律。     

环境监测中的元素价态分析

本文主要评述了10多年来环境监测中约15种元素价态分析的现状。内容涉及到分光光度、原子光谱、电化学以及色谱等分析方法。     

Cu—La,Cu—Ce系的热力学

利用推荐的相图及最新发表的热力学实验数据,对Cu—La、Cu—Ce两个二元系进行了优化处理,所得结果与实验数据颇为一致。     

热力学标准态

热力学标准态姚天扬（南京大学化学系２１００９３）在化学热力学中标准状态（简称标准态ＳｔａｎｄａｒｄＳｔａｔｅ）是一个重要而抽象难懂的概念，它贯穿整个化学热力学。波及化学动力学及统计热力学。本文将从物理化学教学角度对标准态作一较全面的论述。标准态概念化...     

原子的价态电负性与价键轨道特性

电负性概念自Pauling提出以来,在化学学科中得到了广泛的应用,相继出现了多种经验或半经验的计算方法。Allred等将原子核作用于价电子的静电力定义为原子的电负性,使得电负性具有较直观的物理含义,是最广泛采用的标度之一。Mulliken将原子电负性定义为该原子的第一电离势和第一电子亲和能的平均     

样品价态对激光气化产生Cu/Cl团簇的组成和稳定性的影响

研究团控的形成条件、形成机理是目前团簇科学中的一个热点领域［‘］．产生气相团簇的方法主要有Knudsen高温炉扩散法、粒子溅射法、激光气化／分子束法、直接激光气化法·因为不需要另加缓冲气体，直接激光气化法【刀具有对体系真空要求较低，装置简单，容易和飞行时间质谱结     

二氮杂菲分光光度法分析温泉水中铁的价态

使用UV–2100型分光光度计,在二氮杂菲质量浓度为1 g/L、乙酸铵缓冲溶液(pH 4.2)用量为10 m L、显色时间为15 min的条件下,于510 nm处对温泉水中铁的价态进行分析。Fe(Ⅱ)测定结果的相对标准偏差为1.61%(n=20),被测温泉水中总铁加标回收率为98.42%~104.36%,Fe(Ⅱ)的加标回收率为95.25%~102.88%。该法可用于温泉水中铁的价态分析。     

Transition State Thermodynamics of Lipid Bilayers Characterized by Differential Scanning Calorimetry

The laboratory experiment presented in this paper focuses on using differential scanning calorimetry to determine the calorimetric enthalpy and cooperativity of the gel to liquid crystalline phase transition in hydrated lipid bilayers as a function of cholesterol content. The procedure and analysis are appropriate for junior-and senior-level physics and biophysical chemistry courses in the undergraduate curriculum. The laboratory is used to emphasize the use of thermodynamic data to obtain information about structure-function relationships in biological systems. The experimental results are directly related to the authors ongoing research in lipid bilayer structure characterization and applications of hydrated lipid bilayers as model systems for the interpretation of MRI contrast. The laboratory is easily modified to study the effects of other conditions, such as degree of hydration, pH, and composition, on the thermodynamic behavior of lipid bilayers.     

Stability of Rare-Earth Oxychloride Phases: Bond Valence Study

The crystal structures of the tetragonal rare earth (RE) oxychlorides, REOCl (RE=La-Nd, Sm-Ho, and Y) were studied by X-ray powder diffraction measurements, Rietveld analyses, and bond valence calculations. The tetragonal structure (space group P4/nmm, No. 129, Z=2) is stable for all but Er-Lu oxychlorides, which possess a hexagonal structure. The tetragonal structure consists of alternating layers of (REO)_nⁿ⁺ complex cations and Xⁿ⁻ anions, where the rare earth is coordinated to four oxygens and four plus one chlorines in a monocapped tetragonal antiprism arrangement. The Rietveld analyses yielded a coherent series of structural parameters. Preferred orientation and microabsorption effects were found significant. The evolution of interatomic distances and bond angles indicated that the reason for the preferred structure changing from tetragonal to hexagonal is the strain in the chlorine layer. The bond valence parameter B for the RE-O bonds had to be recalculated due to the covalent nature of the (REO)_nⁿ⁺ unit. The results obtained with the new parameter confirmed the strains in the chlorine layer to be the cause for the phase transition.     

Intermediate Valence Behavior of Yb2Cu9Al8

Intermediate valence behavior is frequently observed in materials containing Ce, Yb, Eu, Sm, or Tm. In the current work, we report synthesis and characterization of Yb₂Cu₉Al₈ (Th₂Zn₁₇ structure type). Its intermediate valence behavior can be described by an excitation energy E_ex/k_B = 319 K and a spin fluctuation temperature T_sf = 60 K. The valence state of Yb is estimated to be close to 2.04 for the low-temperature region. The valence gradually evolves to the value of 2.80 at T = 400 K. The specific heat coefficient of γ_exp = 59 mJ · mol_Yb^–1 · K^–2 indicates a moderate effective mass enhancement, together with finite density of states at the Fermi level. The latter is also confirmed by the band structure calculations.     

Thermodynamics of the Cu(II) adsorption on thin vanillin-modified chitosan membranes

In this work, low-density vanillin-modified thin chitosan membranes were synthesized and characterized. The membranes were utilized as adsorbent for the removal of Cu(II) from aqueous solutions. The experimental data obtained in batch experiments at different temperatures were fitted to the Langmuir and Freundlich isotherms to obtain the characteristic parameters of each model. The adsorption equilibrium data fitted well with the Langmuir model (average R² > 0.99). Interactions thermodynamic parameters (Δ_intH, Δ_intG, and Δ_intS), as well as the interaction thermal effects (Q_int) were determined from T = (298 to 333) K. The thermodynamic parameters, the Dubinin–Radushkevick equation and the comparative values of Δ_intH for some Cu(II)–adsorbent interactions suggested that the adsorption of Cu(II) ions to vanillin-chitosan membranes show average results for both the diffusional (endothermic) and chemical bonding (exothermic) processes in relation to the temperature range studied.     

关于热力学自发过程及其判据的讨论

文章指出现有各种自发过程的判据都是在指定的约束条件下才能应用,缺乏普适性是自发过程定义多样化的引发原因。在无约束条件下将热力学第一定律代入总熵判据得出并分析讨论了总熵判据的另一种形式,结合自发过程的特点总结出了热力学变化过程中能量变化的本质,给出了自发过程的通用定义。进一步指出原总熵判据只能分辨可逆与不可逆,不能分辨自发与非自发。文章给出的总熵判据的另一种形式——封闭系统任意过程的做功能力判据具有分辨自发与非自发的能力。通过理论研讨和实际应用表明,做功能力判据与总熵判据完全等价,在相应约束条件下可还原为当前热力学中各类方向判据。填补了常见的变温过程和变压过程在以前的教科书中无自发和非自发判据的空白。以前教科书中由于自发过程定义和解释的混乱而出现的一些疑难问题,在通用定义和做功能力判据面前都能得到满意的解答。