Thermokinetic features of the early stages of hydration of slag alkaline binders

This paper presents results of thermokinetic studies on the early stages of hydration of some slag minerals, slag alkaline binders of traditional and new-generation compounds. A possibility of adjustment and control of hardening processes through thermokinetic indices of hydration (intensity and completeness of heat evolution) for various compounds, types and quantities of the alkaline components and temperatures is proved.     

含能材料热动力学行为和热力学性质的研究进展

针对近年来含能材料热力学和热动力学分析研究方面所取得的一些进展进行了回顾和概述;对新型含能材料如含能离子盐、FOX-7及其衍生物、新型高能氧化剂及高能添加剂等的热动力学行为和热力学性质进行了系统总结.此外,介绍了目前最新的一些研究方法和理论,讨论了当前研究中存在的问题,同时对未来的发展方向进行了展望.     

连续一级反应的热动力学研究

本文把时间比法引入热动力学研究,建立了连续一级反应的热动力学研究法,并用来研究了一个连续反应体系的热动力学,验证了该方法的正确性.     

绝热式热动力学的研究II: 一级反应的热谱解析

本文采用自制的绝热式自动量热计,对两个反应体系进行了一级反应的绝热式热动力学研究.速率常数的计算结果在误差范围内,与文献值符合均好.本文还在实验数据处理中提出了局外过程热效应的线性校正法.     

细胞不同代谢类型的量热学研究 I.静息细胞有氧非生长代谢特征

The metabolic heat output of resting cells (Saccharobacter fermentatus WVB8512) has been determined by means of microcalorimetric method. The metabolic thermokinetic equation is
dp/dt=k0,k0=0
The thermochemical equations are
lntm=10.1812-6.5492×10-9C
dC/dP0=KCn n=2
The order of metabolism (n) is 2. The experimental results indicate that the heat output produced by each cell and the metabolic time depend on cell concentration and are inhibited by cell density. The metabolism presents a special kind of special inhibition effect.     

四针状纳米氧化锌的热力学函数

采用简单、温和的微乳液水热辅助法合成了尺寸、形貌均匀的四针状ZnO纳米结构,每个结构由四根长约250nm的纳米针组成．基于块体ZnO的热力学函数已知,依据热力学势函数法设计热化学循环,将纳米ZnO与块体ZnO的热力学函数进行了关联．并结合热动力学理论及过渡态理论,利用微量热技术获得了所制备的四针状纳米ZnO在298．15K下的标准摩尔生成焓、标准摩尔生成Gibbs自由能、标准摩尔熵值分别为（-329．37±0．43）kJmol-1,（-318．51±0．03）kJmol-1,（20．36±1．05）Jmol-1 K-1．     

The influence of dioxane on the hydration of bovine pancreatic α-chymotrypsin according to isothermal calorimetry and IR spectroscopy data

The influence of dioxane on the thermochemical characteristics of the hydration of bovine pancreatic α-chymotrypsin enzyme over the whole range of water thermodynamic activities was studied by comparing the isothermal calorimetry data on the thermochemistry of interaction between the enzyme and water in the presence and absence of dioxane and using the IR spectral data on the adsorption of water and organic solvent vapors on the protein.     

细胞动力学研究IV.细菌非理想生长过程的热动力学

By using LKB2277 Bioactivity Monitor, we have determined the thermogenesis power curves of four kinds of bacteria: Brucella M5(55010), 83-980, 83-981 and E. coli. We have also derived the thermokinetic equation for the process of bacterial growth, which was untypical "S" , unideal growth, as:
Ln[P•(1-P/Pm)?-1]=ln[P0•(1-P0/Pm)?-1]+kt
From this equation, the rate constants of bacterial growth k wore obtained. This thermokinetic equation is very suitable for cell growth of separated culture, in which the thermogenesis curve is untypical. The model propoted by equationl(1) has been compared with the exponential and logistic models. This thermokinetic equation is very significant for the study of bacterial limited growth and their characteristics.     

Thermokinetics of The Combustion of Carbon Containing Materials. Practical aspects of the investigations

The results of the thermokinetic analysis of the combustion of carbon containing materials in the air and oxygen have been presented. A thermokinetic model has been developed, which simplifies the current approach assuming the0-th order and zero activation energy for this process. The interpretation of the results makes possible the identification of the material (carbon carrier) of the highest reactivity toward oxygen. This material was used as a component of the insulating grease fill for the continuous slab caster (CSC) process. The application of the fill proves successful in the industrial practice. This revised version was published online in August 2006 with corrections to the Cover Date.     

Heat of hydration as a method for determining the composition of calcined gypsum

The heat of hydration of a fresh, locally produced sample of some industrial gypsum (plaster of Paris, CaSO₄ · 0.5 H₂O) was determined. An adiabatic calorimeter was used for this purpose. The obtained heat of hydration was ?9 cal g^?1, which is higher than that for the hemihydrate (?5 cal g^?1). The calculated heat of hydration for calcium sulphate hemihydrate from the known heats of formation, and using ordinary thermochemical equations, is ?5 cal g^?1. In the same manner, however, the calculated heat of hydration for the anhydrite (CaSO₄) is ?29 cal g^?1. The higher heat of hydration (?9 cal g^?1) for the tested sample than that for the ordinary hemihydrate (?5 cal g^?1) was attributed to the presence of a certain percent of anhydrite. The composition of the tested sample was proposed by applying conventional chemical and rational analyses. The present work suggests the use of the heat of hydration as a tool for determining the composition of calcined gypsum.     

The Kissinger law and isokinetic effect: Part II. Experimental analysis

On the basis of copper sulphate pentahydrate thermal dissociation, for analyzed reactions I to IV, 6 thermokinetic equations was discussed. Arrhenius law parameters were determined and the isokinetic effect (IE) and Kissinger law appearing was analyzed. It was found that only dependence resulting from isokinetic effect, in the form k _m=q/T _m, relates to the suitable thermokinetic Eq. (2) and Kissinger law in modified form (14). The confirmation was made that the possibility of determining the averaged activation energy from thermokinetic equations using suitable correction coefficients exists.This revised version was published online in November 2005 with corrections to the Cover Date.     

热动力学的研究(Ⅰ)——热动力学的理论和方法

本文根据化学反应热与反应进度的对应关系,导出了热动力学体系的基本方程和热动曲线的解析表达式。并提出了一种新的热动力学研究法。     

Determination of Kinetic Equations of Alkaline Activation of Blast Furnace Slag by Means of Calorimetric Data

The alkaline activation of blast furnace slag promotes the formation of new cement materials. These materials have many advantages over ordinary Portland cement, including high strength, low production cost and good durability. However, many aspects of the chemistry of alkaline activated slags are not yet very well understood. Some authors consider that these processes occur through a heterogeneous reaction, and that they can be governed by three mechanisms: a) nucleation and growth of the hydrated phase; b) phase boundary interactions and c) any diffusion process though the layer of hydration products. The aim of this paper was to determine the mechanism explaining the early reaction of alkaline activation of a blast furnace slag through the use of calorimetric data. A granulated blast furnace slag from Avilés (Spain) with a specific surface of 4450 cm²> g^-1 was used. The alkaline activators used were NaOH, Na₂CO₃ and a mix of waterglass (Na₂SiO₃·nH₂O and NaOH. The solution concentrations were constant (4% Na₂O with respect to the slag mass). The solutions were basic (pH 11-13). The mixes had a constant solution/slag ratio of 0.4. The thermal evolution of the mixes was monitored by conduction calorimetry. The test time was variable, until a rate of heat evolution equal to or less than 0.3 kJ kg^-1 h^-1 was attained. The working temperature was 25°C. The degree of hydration (α) was determined by means of the heat of hydration after the induction period. The law governing the course of the reaction changes at a certain degree of hydration. From a generally accepted equation, the values of α at which the changes are produced were determined. These values of α depend on the nature of the alkaline activator. Nevertheless, for high values of α, the alkaline activation of slag occurs by a diffusion process. This revised version was published online in July 2006 with corrections to the Cover Date.     

Gas-Phase Hydration Thermochemistry of Sodiated and Potassiated Nucleic Acid Bases

Hydration reactions of sodiated and potassiated nucleic acid bases (uracil, thymine, cytosine, and adenine) produced by electrospray have been studied in a gas phase using the pulsed ion-beam high-pressure mass spectrometer. The thermochemical properties, ΔH ( o ) ( n ), ΔS ( o ) ( n ), and ΔG ( o ) ( n ), for the hydrated systems were obtained from hydration equilibrium measurement. The structural aspects of the hydrated complexes are discussed in conjunction with available literature data. The correlation between water binding energies in the hydrated complexes and the corresponding metal ion affinities of nucleobases suggests that a significant (if not dominant) amount of the canonical structure of cytosine undergoes tautomerization during electrospray ionization, and the thermochemical values for cationized cytosine probably correspond to a mixture of tautomeric complexes.     

The Coincidence of Mass Integrals g(α)

The idea of the generation of thermokinetic models on the basis of the analysis of kinetic equations (isothermal conditions) and thermokinetic equations (dynamic conditions) is presented. The method resembles that used in polisothermal conditions, which consists in analysis of the relation of the equilibrium conversion degree vs. temperature. The interpretation of the coincidence of mass integrals g(α) in the relation α vs. temperature has been attempted. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hydration properties of aqueous Pb(II) ion

Using density functional theory and polarized continuum models, we have determined the most probable coordination number and structure of the first hydration shell of aqueous Pb(II). The geometries and hydration free energies of Pb(H2O)(1-9)(2+) were examined and benchmarked against experimental values. The free energies of hydration of Pb(H2O)(6-8)(2+) were found to match the experimental value within 10 kcal/mol. Moreover, based upon our thermochemical results for single water addition, primary hydration numbers of 6, 7, and 8 are all thermally accessible at STP. Use of a small-core 60 electron effective core potential (ECP) with the aug-cc-pvdz-PP basis on Pb resulted in structures that are significantly less hemidirected than predicted when using the large-core 78 electron ECP and the lanl2DZ basis on the metal. Our results imply that the hemi- to holo-directed transition in Pb(II)-water complexes is driven by coordination number and not hybridization of the 6s lone-pair orbital or enhanced covalent bonding in the Pb-OH2 bond. In addition to basis set effects, the influence of different solvation models on hydration reactions has further been examined so as to determine the relative accuracy of the calculated hydration thermochemistry.     

Colloidal and Chemical Processes in Hardening Alkaline Compositions Based on Aluminosilicates and Slags: 2. Rheological Studies

The effect of slags of various basicity constituting alkaline binder compositions on their chemical (hydration) interactions with water at the earlier hardening stages, as well as the oscillation failure of forming structure under weak mechanical loading, are studied by the rheological methods. It is shown that the higher the slag basicity, the stronger the hydration interactions in alkaline binder compositions causing their hardening, all other things being equal. It is established that low-basicity slags in mixtures with natural or technogenic alkaline aluminosulicates form highly efficient low-plasticity compositions suitable for the underwater colmatage of the basements of hydraulic structures or the burial of hazardous wastes.     

Gas-phase basicities of the isomeric dihydroxybenzoic acids and gas-phase acidities of their radical cations

The thermochemical acid/base properties of the six dihydroxybenzoic acids (x,y-DHB) as prototypical matrices used in matrix-assisted laser desorption/ionization (MALDI) have been investigated. The ground-state gas-phase basicities (GB) of the six DHB isomers and the gas-phase acidities (deltaG acid) of the corresponding radical cations ([x,y-DHB]*+) have been determined by Fourier-transform ion cyclotron resonance mass spectrometry employing the thermokinetic method. The gas-phase basicities vary from 814 kJ mol-1 for the least basic isomer, 3,5-DHB, to 831 kJ mol-1 for the most basic isomer, 2,4-DHB. The obtained gas-phase acidities of the corresponding radical cations vary from 815 kJ mol-1 for the most acidic species, 3,4-DHB, to 858 kJ mol-1 for the least acidic one, 2,5-DHB. The results indicate that ground-state proton transfer from the matrix radical cations to the analyte may play a role in the ionization process of MALDI, whereas proton transfer from protonated matrix molecules can be excluded.     

Solvation of propanediol ions by water molecules in the gas phase

The thermochemical properties of protonated hydrates of 1,2- and 1,3-propanediols have been investigated using electrospray ionization-high pressure mass spectrometry. The binding enthalpies, entropies, and free energies of the stepwise hydration of protonated propanediols with one to three waters are reported. The observed negative entropy change [ΔΔS_1,3^o for the addition of the third water to 1,3-propanediol·H⁺(H₂O)₂ suggests a stable structure due to an increased number of hydrogen bonds and the loss of the intramolecular hydrogen bond in the water cluster ion. The thermochemical properties of two isomers of butanediol were also investigated in order to further elucidate the structures of the protonated propanediols.     

微量热法研究环境NaCl浓度对盐生盐杆菌生长代谢的影响

采用TAM air微量热系统和安瓿法测定了盐生盐杆菌在不同NaCl浓度中生长的生长产热曲线, 拟合得到盐生盐杆菌在不同NaCl浓度中生长的热动力学方程和热动力学参数, 并分析了盐生盐杆菌生长的各种热动力学参数与环境NaCl浓度的关系. 由此发现, 盐生盐杆菌生长的最适NaCl浓度并不是传统认为的一个宽泛的范围——3.5 mol·L^-1至约5.2 mol·L^-1 (NaCl饱和), 而是约3.9 mol·L^-1. 在环境NaCl浓度由3.9 mol·L^-1逐步升高至饱和的过程中, 盐生盐杆菌的生长代谢持续减弱. 进一步的透射电镜观察发现在近饱和的NaCl浓度中生长的盐生盐杆菌细胞发生了质壁分离, 较好地解释了微量热研究的结果. 由此对NaCl浓度变化导致嗜盐古生菌表面结构改变提出了新的解释.