镁热还原法在不同温度下的反应路径探讨

热力学计算在冶金行业中具有重要意义。通过计算反应焓变,得到镁热还原反应能达到的最高温度为1 689 K(1 416℃)。以反应的吉布斯自由能ΔrG°为判据,得出Ti Cl4气体在液镁中的还原路径:T1 239 K(966℃),Ti Cl4→Ti Cl3→Ti;T1 239 K,Ti Cl4→Ti Cl3→Ti Cl2→Ti。     

镁热还原法在不同温度下的反应路径探讨

热力学计算在冶金行业中具有重要意义,本文通过计算反应焓变,得到镁热还原反应能达到的最高温度为1 689 K(1 416℃)。以反应的吉布斯自由能Δr G°为判据,得出Ti Cl4气体在液镁中的还原路径:T1 239 K(966℃),Ti Cl4→Ti Cl3→Ti;T1 239 K,Ti Cl4→Ti Cl3→Ti Cl2→Ti。     

关于1873K下铁液中铝脱氧平衡热力学的讨论

基于前人的实验结果和已有的热力学数据,通过热力学计算分析了Fe-Al-O三元系的反应产物、反应平衡常数,以及活度系数对铝脱氧化学平衡的影响.计算结果表明,在炼钢过程中,Fe-Al-O三元系的反应产物为Al2O3;当w[Al]0.1%时,已有的热力学数据给出的铝脱氧平衡反应曲线呈现出相似的规律(钢中w[O]随着w[Al]的增加而减少);如果采用日本学术振兴会给出的标准吉布斯自由能,并忽略二阶相互作用系数,在w[Al]接近3.5%时会给出错误解;铝脱氧的标准吉布斯自由能和相互作用系数采取Itoh的建议值,则可给出合理的结果;铝脱氧平衡曲线"上翘"的原因是一阶活度系数影响的结果,二阶相互作用系数仅减小铝氧平衡曲线"上翘"的程度.     

铅/锡/钢层状复合材料的Miedema模型和Toop模型热力学分析

在前期对铅/锡/钢层状复合材料研究为基础,为了从理论上揭示过渡金属Sn在Pb、Fe非混溶体系中所起的作用,文章借助Miedema模型和Toop模型对Pb、Sn、Fe二元及三元合金混合焓进行了计算,并对前期研究过程中铅/锡/钢层状复合材料界面出现的弥散颗粒物进行了理论解释,计算结果表明:过渡金属Sn的引入能够起到降低Pb-Fe非混溶合金体系混合焓,增大混合熵进而达到降低吉布斯自由能的目的。     

原苏联海绵钛生产技术评介

原苏联有三家万吨级海绵钛厂.它们是:乌克兰的扎波罗热钛镁联合企业、俄罗斯的别列兹尼基钛镁联合企业和哈萨克斯坦的乌斯季卡明诺哥尔斯克钛镁联合企业.三家钛厂总产能在6万吨/a以上,占世界海绵钛产能的一半.上述三家钛厂均由全苏钛科学研究院设计.该院集中了钛镁技术人员,并不断地研究新工艺、新设备,利用其成果对企业进行改造.     

TiC涂层反应标准吉布斯自由能变化的计算及其绘图

以化学气相沉积法制备TiC涂层的反应为实例,建立了TiC涂层反应的标准吉布斯自由能变化的计算模型,应用所开发的计算和绘图程序,精确地计算和绘制了TiC涂层反应的标准吉布斯自由能变化与温度关系图形.     

反应带对钛坨结构的影响

钛作为一种重要的稀有金属,具有质量轻、耐腐蚀、耐磨损的特点,广泛用于航空、航海、化工、石油等工业部门。在工业化生产海绵钛的工艺中,镁还原-真空蒸馏是最有竞争力的工艺,在海绵钛生产中占主导地位。随着设备的大型化和自动化程度的提高,镁法生产海绵钛的成本已接近民用的范围,产品质量亦逐渐提高。因此钛的应用具有广阔的前景。镁法生产海绵钛是在高温和惰性气体保护下,在密闭的反应器中用镁还原四氯化钛,得到钛和氯化镁,最后用真空蒸馏或浸出的方法除去钛坨中残留的镁和氯化镁杂质,得到纯净的海绵钛。还原过程中被镁从四氯…     

浅析还原期间提高海绵钛质量的措施

为减少海绵钛坨中杂质元素偏析,阐述了还原过程中海绵钛坨各部分的形成机理。通过合理控制反应期料速、反应液面和排镁制度等措施,可提高钛锭质量,减少爬壁钛、底皮等劣质海绵钛的产生。     

海绵钛生产中爬壁钛量的影响因素分析

首先对Kroll法海绵钛生产过程中爬壁钛的微观结构特点展开研究,进而分析爬壁钛在反应器壁处的生长过程及生成量的影响因素。研究发现,爬壁钛的生成无法避免,其生成量受MgCl_2排放前后反应界面在纵向高度的变化、液镁沿反应器壁的上爬高度及反应容器内气相TiCl_4量影响。     

辛胺萃取银的热力学研究

研究了以磺化煤油为稀释剂,辛胺为萃取剂萃取银的反应过程和热力学性质。在293.15～318.15 K的温度范围内和0.2～2.0 mol/kg的离子强度下萃取银,使用pH计测定水相的pH值,原子吸收分光光度法测定水相中的银含量,计算了萃取反应的萃取率,确定了最佳萃取条件。利用多项式拟合得到不同温度下的标准平衡常数K~?,并研究了K~?、熵、焓、吉布斯自由能与温度的关系。实验结果表明,低温和低离子强度更加有利于辛胺对银的萃取。热力学计算表明,萃取反应的吉布斯自由能、焓、熵均随着温度的降低而增加,均与温度负相关。     

Al-Si-Fe合金熔体质量作用浓度的热力学模型

基于原子分子共存理论(AMCT)建立了计算Al-Si二元熔体及Al-Si-Fe三元熔体结构单元质量作用浓度的热力学模型.针对Al-Si二元系熔体,根据FactSage热力学软件计算的活度得到生成复杂分子Al2Si和AlSi的反应的标准摩尔吉布斯自由能的表达式,进而获得了 Al-Si二元熔体中标准摩尔溶解吉布斯能变的表达...     

Al—Si—Fe三元合金熔体组元活度的解析

将Ａｌ－Ｓｉ－Ｆｅ三元合金熔体中组元Ａｌ的过剩偏摩尔自由能表达成多项式函数的形式,再由组成该三元系的三个二元子系以及三元系部分实验结果作为边界条件确定多项式中的参数Ａｊｋ值。根据Ｇｉｂｂｓ－Ｄｕｈｅｍ方程导出了计算体系过剩摩尔自由能多项式中的参数Ｆｊｋ值,由Ａｊｋ和Ｆｊｋ值求得组元Ｓｉ、Ａｌ的过剩偏摩尔自由能的表达式,并用上述解析表达式计算出了整个液相区域内各组元的等活度线     

Thermodynamic properties of SnSb2Te4 ternary compounds

The Gibbs free energy, enthalpy, and entropy of formation for tin monotelluride from its solid compounds and for the ternary compound SnSb₂Te₄ from SnTe and Sb₂Te₃ are determined by measuring the emf of galvanic cells. The thermodynamic functions of ternary compound formation from pure components (solid tin, antimony, and tellurium) are calculated. The enthalpy of formation for tin monotelluride is in good agreement with the results of calorimetric measurements.     

Electromotive Force Measurements in the Ternary System Bi-In-Zn

The thermodynamic properties of the ternary Bi-In-Zn system were determined with the electromotive force (EMF) method using a liquid electrolyte. Four different cross sections with constant In/Bi ratios of 1:2, 1:1, 2:1, and 9:1 were applied to measure the thermodynamic properties of the ternary system in the temperature range between the liquidus temperature of the alloys and 973 K (700 °C). Zinc was added in steps of 5 at. pct from 5 to 90 pct. The partial free energies of Zn in liquid Bi-In-Zn alloys were determined as a function of concentration and temperature. The integral Gibbs free energy and the integral enthalpy of the ternary system at 873 K (600 °C) were calculated by Gibbs–Duhem integration. The ternary interaction parameters were evaluated using the Redlich–Kister–Muggianu polynomials.     

Thermodynamics of nanocrystalline platinum

Nanocrystalline materials are not in thermodynamical stable equilibrium. Excess Gibbs free energy is the thermodynamic driving force for recovery towards stable equilibrium. Recovery of nanocrystalline platinum is discussed in terms of the pathway of excess Gibbs free energy during annealing. Calorimetric measurements yield the excess enthalpy and specific heat. The excess entropy is calculated and found to be linearly dependent upon grain boundary free volume, as is the excess enthalpy, thus scaling with the literature values for general large-angle grain boundaries in platinum. From these results it is possible to calculate how excess Gibbs free energy evolves as recovery proceeds with increasing temperature.     

Thermodynamic Study of Titanium Oxycarbide

Titanium oxycarbide was synthesized through carbothermic reduction of TiO₂ and sintering of TiO and TiC. The combustion enthalpy and specific heat capacity of oxycarbide were measured by differential scanning calorimetry (DSC). The mixing enthalpy and Gibbs free energy of the reaction?0.5TiO + 0.5TiC = TiC_0.5O_0.5, consequently, was calculated based on the preceding measured data. The Gibbs free energy obtained was in good agreement with those results obtained by the equilibrium measurements.     

联合法海绵钛生产中主要杂质分析及其控制

论述了联合法海绵钛生产中主要杂质(Fe,Si,Cl,C,N,O)的来源、分布及其对产品质量的影响,对比分析了国内外海绵钛产品质量存在差异的原因,从原料(TiCl4、镁锭、氩气)、设备(反应器)、操作工艺(加料制度、散热体系)等方面分析了减少杂质含量的控制措施。     

Oxidation of titanium disilicide in A. Nonisothermal regime

Differential-thermal and thermogravimetric analyses are used to study the oxidation of titanium disilicide in a nonisothermal regime in the temperature range 300–1250 K with a heating rate in air of 10 deg/min. Experimental results are compared with theoretical Criado curves. An oxidation mechanism is established. The activation energy for oxidation is calculated: E = 127.03 kJ/mole, and thermodynamic parameters are calculated for activation, i.e., entropy, Gibbs free energy, enthalpy: ΔS^# = ?165.54 J/(mole · K), ΔG^# = 277.53 kJ/mole, ΔH^# = 119.47 kJ/mole, respectively.     

High-temperature thermodynamic characteristics of Ho5Ge3

The enthalpy of Ho₅Ge₃ is measured by drop calorimetry between 463 and 2314 K for the first time. The temperature dependences of enthalpy, heat capacity, entropy, and Gibbs free energy are plotted and, enthalpy and entropy of melting are calculated.