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1.
杜勇  韩帆 《中国稀土学报》1990,8(3):216-220
由可靠的实测相图数据,朋最小二乘法对Fe-Pr二元系进行了热力学优化及计算。优化时,液相处理为次规则溶液,而两个中间化合物Fe_(17)Pr_2和Fe_2Pr,都处理为化学计量相。给出了此系统中各相的优化热力学函数表达式。计算结果表明除液相+δ-Fe平衡外,计算相图的其他部分同实测数据符合很好。建议有必要对液相+δ-Fe平衡重新测定。  相似文献   

2.
采用相图计算(CALPHAD:Calculation of phase diagrams)方法对Zr-X(X=Li,Na,K,Sc,Hf)5个二元体系进行了相图热力学研究.基于实验数据,通过热力学优化计算获得了一套描述液相及(αZr),(βZr),(Li),(Na),(K),(αSc),(βSc),(αHf)和(βHf)相的热力学参数.Zr-Li,Zr-Na和Zr-K体系中的气相视为理想气体.与实验相图数据对比发现,本文获得的热力学参数能够准确地描述实验相平衡数据.  相似文献   

3.
采用CALPHAD方法对Al-Fe-P三元系进行了热力学评估, 并根据相关的实验数据对边际二元系Al-P进行了热力学再优化, Al-Fe和Fe-P边际二元系的热力学参数取自之前的研究并做了局部调整. 根据相图数据和热力学数据优化了Al-Fe-P三元系的热力学模型参数, 获得了体系中所有相的Gibbs自由能表达式. 所得参数之间自洽且能很好地重现Al-Fe-P体系的大部分实验相图信息. 通过驱动力判据和本文优化所得的模型参数,从热力学上解释了该体系非晶形成能力与组成之间的关系.  相似文献   

4.
改进的缔合物模型中缔合平衡的求解过程被简化,使其能够同时优化更广范围的热力学数据,包括量热、emf和相图等等数据,将其应用于KCl-MgCl2和KCl-FeCl2熔盐体系,从已有的热力学数据优化出合理的溶液模型参数,由该模型推算溶液的热力学性质,结果显示改进的缔合物模型能够很好地描述熔盐体系的非理想性质.  相似文献   

5.
综合实验相图信息和热力学数据运用CALPHAD技术优化和计算了TmCl3-ACl体系的相图。液相的吉布斯全摩尔自由能采用新改进的用于短程有序体系的以近似似化学模型进行描述。借助计算机辅助分析,一系列的热力学函数被优化得到。计算的相图和热力学参数是热力学自恰一致的。  相似文献   

6.
用循环伏安和红外光谱法对α-Fe2O3在室温LiOH溶液中的锂化行为进行研究.采用X射线衍射(XRD)、电感偶合等离子体光源的原子发射光谱(ICP)对α-Fe2O3电极在第一、二次循环中不同时段进行了跟踪分析测量.实验结果揭示:α-Fe2O3能进行少量锂化;大量的α-Fe2O3在第一次放电和充电后反应生成Fe3O4;之后,Fe3O4的锂化行为不可避免地为Fe的析出、氧化反应所限制,但在用KOH作电解质溶液的对比实验时发现:α-Fe2O3在LiOH溶液中的充放电行为与它在KOH溶液中是不同的,主要表现为,1)在LiOH溶液中,锂化和Fe析出、氧化反应协调的结果是其充放电曲线平台高度比在同碱度KOH溶液中降低了100mV左右,2)与K+对比,Li+的插入反应促进了α-Fe2O3到Fe3O4的转化.  相似文献   

7.
硝酸盐型卤水是盐湖卤水、 硝酸盐工业、 废水处理中普遍遇到的电解质溶液体系. 硝酸盐具有极高的溶解度, 实现硝酸盐型复杂电解质体系物性和相平衡的精准热力学表达依然具有挑战性. 以煤化工废水的典型体系Na+//NO3- , Cl-, SO42 - -H2O为对象, 以改进的eNRTL模型为基础, 由活度系数模型、 溶液物性模型、 物种热力学模型和固液相平衡模型构成了电解质体系的综合热力学模型. 利用二元体系的冰点、 饱和蒸汽压、 等压摩尔热容、 活度系数和渗透压系数等物性数据和三元体系等温相平衡数据, 采用多目标优化方法, 获得了表达研究体系的多温特性的12组液相特征参数和7个固相物种的热力学参数. 据此完成了3个二元体系、 3个三元体系等温相平衡的准确计算和三元、 四元完整相图的预测, 适用温度达到实验所及的全部温度范围(254.65~543.15 K); 适用浓度达到饱和程度, 其中NaNO3的浓度高达226.88 mol/kg. 三元、 四元体系的多温相图预测结果与实验数据相吻合, 并给出了9个三元、 5个四元体系零变点的完整信息.  相似文献   

8.
采用相图计算(CALPHAD)技术对LiF-CrF3体系进行了相图的优化计算.对液相分别采用置换熔体模型与缔合物模型进行描述,中间化合物Li3CrF6则采用准化学计量比化合物模型描述.模型参数的优化选取实验相平衡数据及第一性原理预测的数据,优化结果表明,缔合物模型比置换熔体模型更能准确地描述液相的实验相平衡数据.  相似文献   

9.
就Fe3++SCN-Fe(SCN)2+平衡而言,向该平衡体系中加入一定浓度的FeCl3溶液,通过改进浓度对化学平衡影响的实验和对实验的深入探究,借助实验的功能解决了平衡移动的方向、Fe(SCN)2+的浓度和溶液的颜色是如何变化的等问题,进而使学生对"外界条件对化学平衡的影响"有了更全面的认识。  相似文献   

10.
以磷酸二异辛基酯(P204)为萃取剂,CCl4为溶剂,从Fe(NO3)2水溶液中萃取铁离子,以氨的乙醇溶液反萃含铁的有机相,通过优化控制相间传质过程,获得了Fe(OH)3前驱体,经煅烧后得α-Fe2O3粉体,采用TEM、FTIR、XRD等测试技术对α-Fe2O3进行表征。 研究表明,在油水相比为1∶1,水相c(Fe3+)=0.10 mol/L(pH=3.0)、油相P204为V(P204)∶V(CCl4)=1∶3、平衡时间为20 min,Fe3+萃取率达98.44%;反萃取溶液V(氨水)∶V(乙醇)=1∶7、陈化温度约10.0 ℃,制备纳米α-Fe2O3的煅烧温度为600 ℃较宜。  相似文献   

11.
A critical evaluation and optimization of all available phase diagrams and thermodynamic data of the binary Si-RE (RE = La, Ce, Pr, Nd and Sm) systems were conducted to obtain reliable thermodynamic functions of all the phases in the systems. In the thermodynamic modelling, a systematic analysis involving the similarity and periodicity observed in the lanthanide series was applied to resolve inconsistencies in the experimental data and to estimate the unknown thermodynamic properties and phase equilibria data. The phase diagram of the Si-Sm system was predicted using this approach.  相似文献   

12.
An earlier structural model for binary silicate melts and glasses is extended to MF-BeF2 (M = Li, K) systems. The evaluation of the thermodynamic properties as well as the phase diagrams for the binary LiF-BeF2 system and the integral enthalpy of mixing of the KF-BeF2 system are carried out with this model. This thermodynamic model is based on the assumption that each alkali fluoride produces the depolymerization of BeF2 network with a characteristic free energy change. A least squares optimization program permits all available thermodynamic and phase diagram data to be optimized simultaneously. In this manner, data for these binary systems have been analysed and represented with a small number of parameters. The model predicts the chain-length distribution of polymeric ions, even though these are not explicitly treated as structural units of the model. The calculated fluoride polyanion chain-length distribution for the LiF-BeF2 system is in quantitative agreement with the predictions reported in the literature.  相似文献   

13.
Further studies of the ternary phase diagram Al-Zn-Sn have been carried out by X-ray diffraction at various temperatures and by thermodilatometry in order to confirm our earlier experimental results which have been refuted by some recent work based on thermodynamic optimization. These new results, in particular the change with temperature of the crystallized fraction for Al-Zn-Sn mixtures containing up to 31.5 mass% of tin, confirm our previous results on the existence of a significant retrograde miscibility of tin in a solid solution α′ss (in the temperature range 286 to 335°C) which protrudes into the ternary system starting from the Al-Zn binary up to a tin concentration of about 50 mass%. This disagreement between theory and experiment highlights the difficulties of a thermodynamic optimization approach based on solid state solubilities in the binary systems and on ternary liquidus data which disregards the ternary interaction parameters in the solid state. Besides, this experimental study highlights the difficulties in understanding the phenomena which depend on phase stabilities. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

14.
By using the CALPHAD technique, an optimization of the binary EuCl3–MCl (M = Na, K, Rb, Cs) systems has been carried out. To describe the Gibbs energies of liquid phases in these systems the new modified quasi-chemical model was used in the pair-approximation for short-range ordering. From the measured phase equilibrium data and the experimental thermo-chemical properties, the EuCl3–MCl phase diagrams were optimized and calculated. A set of thermodynamic functions has been optimized based on an interactive computer-assisted analysis. The calculated phase diagrams and thermodynamic data are self-consistent.  相似文献   

15.
The MgO-P2O5 and CaO-P2O5 systems have been thermodynamically assessed based on the available phase diagram and thermodynamic data using the Calculation of Phase Diagram (CALPHAD) method. The liquid phase is described by the modified quasichemical model with the pair approximation, which takes short-range ordering in liquid solution into account. The PO43- is considered as the basic building unit of P2O5 in the liquid solution since the maximum short-range ordering occurs at the M3(PO4)2 (M = Mg, Ca) composition. All intermetallic phases are treated as stoichiometric compounds and the phase transformations are considered. A set of self-consistent model parameters is obtained to describe the thermodynamic property of every phase in these two binary systems, by which the published phase diagram, enthalpy, entropy, and activity data are reproduced well within experimental error limits. The present study can be used as a basis for the development of a thermodynamic database of molten slag system for the steelmaking dephosphorus process.  相似文献   

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17.
《Thermochimica Acta》2004,414(2):197-202
Thermodynamic modelling of the Ca-Pb system was carried out. The thermodynamic parameters were determined using available experimental information: phase diagram data and thermodynamic quantities. For this system, the liquid phase was described from the association model with the “Ca2Pb” associated complex. The calculations well restore experimental values. All the results so-obtained (optimised thermodynamic parameters and calculated phase diagram) are reported in this paper and discussed.  相似文献   

18.
The MgO–NiO–SiO2 system has been studied by a combination of thermodynamic modeling and experimental measurements of phase equilibria. A complete literature review, critical evaluation and thermodynamic modeling of phase diagrams and thermodynamic properties of all oxide phases in the MgO–NiO–SiO2 system at 1 atm total pressure are presented. To resolve the contradictions in the literature data, a new experimental investigation has been carried out over the temperature range from (1400 to 1650) °C using an equilibration and quenching technique followed by electron probe X-ray microanalysis (EPMA). Tie-lines between olivine and monoxide, olivine and proto-pyroxene, liquid and olivine and liquid and cristobalite have been measured. The whole set of experimental data, including the new experimental results and previously published data, has been taken into consideration in thermodynamic modeling of oxide phases in the MgO–NiO–SiO2 system. The Modified Quasichemical Model has been used for the liquid phase. A simple random mixing model with a polynomial expansion of the excess Gibbs energy has been used for the monoxide solid solution. The models for olivine and proto-pyroxene were developed within the framework of the Compound Energy Formalism. The optimized model parameters reproduce all available thermodynamic and phase diagram data within experimental error limits.  相似文献   

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