梅特勒-托利多参加2012第十六届全国化学热力学和热分析学术会议

2012年10月19-22日,由中国化学会化学热力学和热分析专业委员会主办的中国化学会第十六届全国化学热力学和热分析学术会议在武汉举行。来自全国各高校、科研单位和企业界的300位代表参加。武汉大学党     

化学热力学中微积分的引入及其意义

从微积分在化学热力学理论中的应用角度出发,介绍微积分是如何被引入到化学热力学中。归纳了化学热力学状态函数的数学特性,讨论了一些重要基本概念的联系和区别,指出了微积分在化学热力学理论建立过程中的重要意义,并结合一些实例介绍了微积分原理和方法在化学热力学中的应用。     

从统计热力学角度理解重要的热力学概念

基于玻尔兹曼统计法,简要总结独立粒子的非定位系统的统计热力学基础,并应用一些实例来分析统计热力学和热力学方法之间的区别和联系,帮助学生从统计热力学角度加深对一些重要的热力学概念(如热容、吉布斯自由能、焓和化学势)的理解,建立微观物理图像,以更好地学习两部分热力学知识,并能够灵活运用于化学问题的求解中。     

前言

<正>化学热力学是物理化学的重要分支学科.化学热力学应用热力学原理研究物质体系中的化学现象和规律,依据体系的宏观可测性质和热力学函数关系判断体系的稳定性、变化的方向和变化的程度.相平衡、化学平衡、热平衡、分子构象的稳定性、分子间的聚集与解离平衡等许多重要问题都需要用化学热力学的原理和方法进行判断和解决.化学热力学的主要特点是具有坚实的理论基础,其原理具有高度的可靠性和普适性,因此对理论研究和实际应用都有重要指导意义.化学热力学的研究范畴决定了它与化学乃至化学学科以外的其     

非平衡化学反应的热力学

化学现象是由反应速率表征的,只有在非平衡条件下化学反应过程才会呈现出非零的反应速率.因此化学现象本身是一种非平衡现象,化学热力学应属于非平衡态热力学(也称不可逆过程热力学)的范畴.但是传统的化学热力学主要限于研究平衡态和可逆过程,其主要原因是长期以来整个非平衡态热力学缺乏一个较为令人满意的理论.但在最近二、三十年间非平衡态热力学取得了巨大的进展.本文简要讨论与化学反应有关的非平衡态热力学的进展.     

化学热力学的建立与发展概略

回顾化学热力学的发展历史,介绍化学热力学的近期研究成果,并指出理论结合实践才能使化学热力学更好地发展。     

花生状微/纳米CaMoO_4的表面热力学性质

采用室温反相微乳液法制备了3种不同尺寸的花生状微/纳米CaMoO4.基于纳米CaMoO4与块体CaMoO4热力学性质的本质差异,结合化学热力学基本理论及热动力学原理,推导出纳米CaMoO4摩尔表面热力学函数的关系式.在此基础上,采用原位微量热技术获得了花生状微/纳米CaMoO4的摩尔表面热力学函数.结果表明,花生状微/纳米CaMoO4的表面热力学性质变化具有尺寸效应,即随着尺寸的减小,摩尔表面焓、摩尔表面Gibbs自由能、摩尔表面熵均增加.     

不同粒度八面体纳米钼酸镉的表面热力学性质

室温条件下,采用反相微乳液法制备了一系列不同粒度的八面体纳米CdMoO4,并对其组成、结构及形貌进行了表征.基于纳米CdMoO4与块体CdMoO4热力学性质的本质差异,结合化学热力学基本理论与热动力学原理,导出了获取纳米CdMoO4表面热力学性质的关系式;在此基础上,利用原位微量热技术成功获得了所制备的不同粒度八面体纳米CdMoO4的表面热力学函数,如比表面Gibbs自由能、比表面焓和比表面熵.本文为获取纳米材料表面热力学函数提供了一种有效而普适的新方法.     

从分子图像到热力学框架——物理化学教学的探讨与实践

化学的核心是基于原子分子的图像认识世界、创造物质,化学教育需要培养学生掌握相应的思维方式。在物理化学类课程建设中,浙江大学化学系尝试把宏观化学的基本理论框架,即热力学理论建立在原子分子水平上。具体地是先简述量子化学对单个原子、分子能级结构的处理,然后利用统计热力学的基本原理,从这些量子化的能级导出宏观系统的三个基石性概念(能量、熵、温度)和一条基本定律(熵增加原理),从而建立分子图像的热力学。在教学实践中,强调直接从原子分子层面切入、弱化热机理论、理论与实验结果直接关联。在本文中,我们通过几个教学实例来分享我们的教学经验。     

关于学习物理化学的一点思考

阐述了建立知识体系的必要性。简要介绍在学习化学热力学及统计热力学时所建立的知识体系     

Sulfation of CuO,Fe2O3, MnO2, and NiO with (NH4)2SO4

An attempt has been made to calculate the free energy values for possible reactions utilising the available thermodynamic data in order to study the sulfation of CuO, Fe₂O₃, MnO₂ and NiO with (NH₄SO₄, and further trials have been made to determine the exact reaction through differential thermal analysis. There is no real correlation between the theoretical value of ΔH° and that calculated from the DTA peak, which may be due to some uncertainty in the thermodynamic values and the possibility of some side reactions.     

Investigation of phase equilibria in the systems K2SO4Sc2(SO4)3, Rb2SO4Sc2(SO4)3 and Cs2SO4Sc2(SO4)3

Phase diagrams of the systems K₂SO₄Sc₂(SO₄)₃, Rb₂SO ₄Sc₂(SO₄)₃ and Cs₂SO₄ Sc₂(SO₄)₃ have been investigated by X-ray diffraction phase analysis and differential thermal analysis techniques. A salient feature of all the systems is the formation of M₃Sc(SO₄)₃, which melt incongruently, and MSc(SO₄)₂, which on heating decompose in the solid state.     

Eu2(p-ClC6H4COO)6(C12H8N2)2配合物热分解机理及非等温动力学

The thermal decomposition behaviour of europium p-chlorobenzoate complex with 1, 10-phenanthroline and its kinetics were studied in nitrogen by non-isothermal thermogravimetry.Its thermal decomposition occurs mainly in three steps..The intermediate and residue for each step of decomposition were identified from TGcurve.The kinetic parameters were obtained from analysis of the TG-DTG curves by the Achar method.the Madhusudanan- Krishnan-Niman (MKN) method and Ozawa method respectively.The most probable mechanisms function for the first and second stage were suggested by comparing the kinetic parameters.     

Polynuclear complexes of gold(III) of the composition ([Au(S2CNR2)2][AuCl4])n (R = C4H9, R2 = (CH2)5): Synthesis, supramolecular structures, and thermal behavior

The interaction of binuclear cadmium dialkyldithiocarbamates [Cd₂(S₂CNR₂)₄] with solutions of AuCl₃ in 2M HCl gives polynuclear gold(III) complexes ([Au(S₂CNR₂)₂][AuCl₄]) _n , where R = C₄H₉ (I) and R₂ = (CH₂)₅ (II). The structures of the synthesized compounds solved by X-ray diffraction analysis are char-acterized by a complicated organization at the supramolecular level. The structures are based on polymer chains (I) and layers (II) involving isomeric cations [Au(S₂CNR₂)₂]⁺ and anions [AuCl₄]⁻. The thermal behavior of the synthesized complexes is studied by simultaneous thermal analysis including thermogravimetry and differential scanning calorimetry. The final product of the thermal transformations of the studied complexes is shown to be reduced metallic gold.     

Non-equivalent water molecules in [Ni(H2O)6](ClO4)2 and in [Ni(D2O)6](ClO4)2 in the thermogravimetric investigations

The thermal decomposition of [Ni(H₂O)₆](ClO₄)₂ and [Ni(D₂O)₆](ClO₄)₂ were studied by thermogravimetric analysis (TG) and simultaneous differential thermal analysis (SDTA) at a constant heating rate. The gaseous products of the decomposition were on-line identified by a quadrupole mass spectrometer (QMS). In both cases the process of decomposition starts at ca. 410 K and is connected with removal of water molecules in a stepwise way; at the beginning the first water molecule is lost, then the second and at higher temperature the third one. The rest of the water molecules are lost in the temperature region of ClO₄⁻ decomposition. The energy of activation of the process was calculated in both cases.     

Sulfation of Al2O3, CaO,CdO and ZnO with (NH4)2SO4

For studying the sulfation of Al₂O₃, CaO, CdO and ZnO with (NH₄)₂SO₄, free energy values have been calculated for possible reactions utilising the available thermodynamic data. Further differential thermal analysis has been carried out to find out the exact reaction. The ΔH⁰ values calculated theoretically and that from DTA peak are very close in case of CaO and ZnO, whereas in the other two cases there is no proper match. The mismatch may be due to some uncertainty in thermodynamic values and the possibility of some side reactions.     

Topology and chemical interactions in the Li,K,Ca,Ba‖F,WO4 quinary reciprocal system and the phase complex of its LiF-LiKWO4-Li2WO4-CaWO4-BaWO4 pentatope

The Li,K,Ca,Ba‖F,WO₄ quinary reciprocal system was differentiated on the basis of graph theory with account for already known inner secants. Possible exchange and complex-formation chemical reactions that occur throughout the composition polyhedron of the system were revealed. The results of the differentiation and thermal analysis of several samples in each Phase unit block (PUB) were used to build crystallization tree of the title system. It is for the first time that the set of physicochemical methods (differential thermal analysis, visual polythermal analysis, and X-ray powder diffraction in tandem with projective thermal analysis) was used to study the LiF-LiKWO₄-Li₂WO₄-CaWO₄-BaWO₄ five-component system; this system is the stable pentatope of the Li,K,Ca,Ba‖F,WO₄ quinary reciprocal system. The coordinates of invariant points were determined. Original Russian Text ? P.A. Akhmedova, B.Yu. Gamataeva, A.M. Gasanaliev, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 5, pp. 838–850.     

Comparative thermodynamic analysis of the Pb-Au0.7Sn0.3 section in the Pb-Au-Sn ternary system

The results of comparative thermodynamic analysis of Pb-Au_0.7Sn_0.3 section in Pb-Au-Sn system are presented in this paper. Investigation was done comparatively by calorimetric measurements and thermodynamic calculation according to the general solution model. Thermodynamic parameters, such as partial and integral molar quantities, were determined at different temperatures. The comparison between experimental and calculated results showed mutual agreement. Demixing tendency of lead, presented in the positive deviation from ideal behavior, was confirmed through the study of concentration fluctuation in the long-wavelength limit. Also, chosen alloys in the investigated section were characterized using SEM-EDX analysis.     

Preparation of silane-coated TiO2 nanoparticles in supercritical CO2

Nanometric inorganic pigments are widely used as fillers for hybrid composite materials. However, these nanometric powders are hydrophilic in nature and their surface must be functionalized before use. In this work, titanium dioxide (TiO₂) nanoparticles were coated using silane coupling agents with alkyl functionality. A supercritical carbon dioxide (scCO₂) method was used for surface silanization. Five alkylalkoxysilanes with different alkyl chain length and structure were studied: methyltrimethoxy, isobutyltriethoxy, octyltriethoxy, octyldimethylmethoxy and octadecyltrimethoxysilane. The microstructure and thermal stability of deposited monolayers were characterized using thermogravimetric analysis, ATR–IR spectroscopy, transmission electron microscopy, wettability characterization and low-temperature N₂ adsorption/desorption analysis. The use of scCO₂ as a solvent provided an effective approach to functionalize individual inorganic nanoparticles due to the enhanced diffusivity of the solution molecules in the aggregates interparticle voids. The trifunctional silanes employed here yielded surfaces with better thermal stabilities and greater hydrophobicities than the used monofunctional silane.     

Thermal studies of novel molecular perovskite energetic material (C6H14N2)[NH4(ClO4)3]

(C6H(14)N2)[NH4(ClO4)3] is a newly developed porous hybrid inorganic-organic framework material with easy access and excellent detonation performances,however,its thermal properties is still unclear and severely hampered further applications.In this study,thermal behaviors and non-isothermal decomposition reaction kinetics of(C6H(14)N2)[NH4(ClO4)3] were investigated systematically by the combination of differential scanning calorimetry(DSC) and simultaneous thermal analysis methods.In-situ FTIR spectroscopy technology was applied for investigation of the structure changes of(C6H(14)N2) NH4(ClO4)3]and some selected referents for better understanding of interactions between different components during the heating process.Experiment results indicated that the novel molecular perovskite structure renders(C6H(14)N2)[NH4(ClO4)3] better thermal stability than most of currently used energetic materials.Underhigh temperature s,the stability of the cage skeleton constructed by NH4^+and ClO4^-ions determined the decomposition process rather than organic moiety confined in the skeleton.The simple synthetic method,good detonation performances and excellent thermal properties make(C6H(14)N2)[NH4(ClO4)3] an ideal candidate for the preparation of advanced explosives and propellants.