铁磷和硼硅酸盐熔体对耐火材料的腐蚀性能

耐火材料的选择对放射性核废料的玻璃化过程是至关重要的,本文采用动态耐火材料腐蚀速度技术比较了铁磷模拟放射性核废料熔体和硼硅酸盐熔体DWPF的腐蚀性质,测量在1000至1300℃之间进行。在铁磷熔体中,致密氧化铝和氧化铬耐火材料有最低的熔线腐蚀速度,二氧化硅、锆英石和AZS耐火材料的腐蚀速度比较高。同时,氧化铝和氧化铬耐火材料在铁磷熔体中的腐蚀速度小于它们在硼硅酸盐熔体DWPF中的腐蚀速度。对氧化铬耐火材料来说,其在三种含有模拟HLW废料的铁磷熔体中的熔线腐蚀速度小于0.1mm/day。按照DWPF熔化器的设计标准,Alumina和Zircon商品耐火材料可以用来熔化多种HLW废料。     

铁磷模拟HLW熔体的腐蚀性能

在铁磷模拟ＨＬＷ熔体和硼硅酸盐熔体ＤＷＰＦ内测量了六种耐火材料的动态腐蚀速度,测量在 １０００～１３００℃之间进行,在铁磷熔体中,致密氧化铝和氧化铬耐火材料有最低的熔线腐蚀速度,二氧化硅、锆英石和ＡＺＳ耐火材料的腐蚀速度比较高．同时,氧化铝和氧化铬耐火材料在铁磷熔体中的腐蚀速度小于它们在硼硅酸盐熔体ＤＷＰＦ中的腐蚀速度．对氧化铬耐火材料来说,其在三种含有模拟ＨＬＷ废料的铁磷熔体中的熔线腐蚀速度＜０．１ｍｍ／ｄａｙ．可以认为商品制造的致密氧化铝和氧化铬耐火材料是可以用来熔化很多铁磷ＨＬＷ废料的,甚至可以熔化含有１６ｗｔ％氧化钠的ＨＬＷ废料．     

微注塑成型充模流动中的表面张力EI北大核心

微尺度通道中的高聚物熔体流动行为与宏观熔体流动有许多不同。基于对微注塑成型中的熔体充模流动特性的理论分析,建立了微小通道中熔体流动的表面张力模型,并以不同的表面张力系数和不同接触角,对矩形微通道中的熔体流动速度分布进行了数值模拟。结果表明,接触角小于90°时,熔体在通道壁面附近具有最大速度;接触角大于90°时,熔体在壁面处具有最大速度。无表面张力时,熔体填充流动所需时间明显长于有表面张力时的填充时间,即表面张力对微小通道中的熔体流动具有促进作用。     

微注塑成型充模流动中的表面张力

微尺度通道中的高聚物熔体流动行为与宏观熔体流动有许多不同。基于对微注塑成型中的熔体充模流动特性的理论分析,建立了微小通道中熔体流动的表面张力模型,并以不同的表面张力系数和不同接触角,对矩形微通道中的熔体流动速度分布进行了数值模拟。结果表明,接触角小于90°时,熔体在通道壁面附近具有最大速度;接触角大于90°时,熔体在壁面处具有最大速度。无表面张力时,熔体填充流动所需时间明显长于有表面张力时的填充时间,即表面张力对微小通道中的熔体流动具有促进作用。     

悬浮区熔法中线圈中心厚度对电磁场的影响

为提高悬浮区熔(FZ)法的成晶率，使用模拟计算软件深入研究FZ硅单晶的生长过程。本文通过Comsol Multiphysics软件模拟FZ炉内的电磁场，分析不同线圈中心厚度对于电磁场的影响。随着线圈中心厚度增加，熔化的多晶硅表面电磁能量减小，而熔体自由表面电磁能量增加。如果线圈中心厚度过小，较小熔体自由表面电磁能量会导致穿过线圈的多晶硅棒中心区域不熔化；如果线圈中心厚度过大，较小熔化的多晶硅表面电磁能量使熔化的多晶硅减少，引起熔体自由表面形状改变。之后，本文使用中心厚度为1 mm、1.5 mm和2 mm线圈生长6英寸硅单晶，发现线圈中心厚度为1.5 mm时，线圈产生的电磁场更有利于硅单晶生长。     

基于传热凝固模型金属熔体滴落、铺展温度变化分析

运用有限体积法对金属微熔体滴落、铺展成形温度变化进行数值模拟。在考虑熔体滴落过程中和周围环境存在热交换作用的前提下,采用凝固UDF模型,成功模拟了固定坐标点金属Sn60%-Pb40%熔体以及固定节点金属Al熔体滴落和与基板壁面进行碰撞铺展的温度梯度变化。结果表明:金属熔体在滴落过程中,由外表面向内层逐渐凝固,而且各个区域凝固速度不同,即熔体外表面向中心温度下降梯度逐渐减小。     

聚合物熔体复杂流动时形变的研究

为了研究聚合物流体在圆形通道中的流动，设定不同的速度、温度以及圆柱体在流道中的不同位置，分别进行实验，并对其数值模拟。实验和数值模拟的结果表明，我们可以得到熔体流动形变的轨迹，并用Ｃａｒｒｅａｕ－Ｙａｓｕｄａ和Ｍａｘｗｅｌｌ以及ＰＴＴ模型描述和比较聚合物熔体在流动中的形变。     

硅砂原料对无碱铝硼硅玻璃熔化特性的影响

研究了硅砂原料对无碱铝硼硅酸盐玻璃(即TFT-LCD基板玻璃)熔化特性的影响。结果表明:玻璃熔制过程中"富硅氧层"的出现与石英砂颗粒粒径有关,当粒径小于75微米时,玻璃熔化质量良好;石英砂颗粒形态对于熔解特性也很重要,最佳的颗粒形态为圆形,并且粒径分布范围要相对集中,处于较窄区域。     

分子动力学模拟在冶金熔渣中的应用进展

冶金熔渣是由多种氧化物组成的熔体,常见的有硅酸盐熔渣和铝酸盐熔渣.冶金熔渣具有绝热保温、防止二次氧化、吸收钢液中夹杂物、去除钢液中有害元素等重要作用,制备性能优良的熔渣是实现冶金流程节能减排和绿色发展的重要保证,为此有必要系统地研究冶金熔渣的熔体结构和性质.目前,采用模拟实验直接研究高温熔渣熔体结构和性质的限制因素较多,分子动力学模拟可以弥补实验研究方面的不足.由于冶金熔渣种类繁多、复杂多变,如何在冶金熔渣的微观结构与宏观性质之间建立广泛的关联是当今国内外学者的研究重点.分子动力学模拟可以获得熔渣中不同粒子对的键长、键角、配位数等完整的熔体结构数据.基于此,研究者利用熔体结构的聚合度建立了多组元熔渣黏度与熔体结构单元的定量关系.此外,熔渣的电导率与熔体结构中离子的扩散能力有关,可以通过Nernst-Einstein关系式建立电导率和熔体结构之间的关系.本文综述了分子动力学模拟在冶金熔渣中应用的相关研究.首先,对分子动力学模拟在冶金熔渣中的模拟过程进行了介绍.然后,分别详述了分子动力学模拟技术在硅酸盐熔渣和铝酸盐熔渣中的应用现状.最后,总结了现有的问题,并对分子动力学模拟在冶金熔渣中的应用进行了展望.     

熔体内重力对流速度场的实验研究及其理论分析

应用最近开发的高温光学实时观察法研究了铌酸钾熔体的重力对流现象．通过加热直径为2．5mm的圆环形坩埚,形成厚度为0．2mm的圆形KNbO₃熔液．实验测量了熔体内温度和流体速度的分布,并从理论上对速度场的分布给出了定量分析．     

聚合物熔体粘弹性本构方程

概述了聚合物熔体粘弹性本构方程的发展历程，给出了有代表性的线性粘弹性和非线性粘弹性本构方程的各种形式的数学表达式，讨论了它们的特点及应用范围，旨在为聚合物熔体流动数值模拟中本构方程的选择提供帮助。     

Viscosities of Multicomponent Silicate Melts at High Temperatures

In the present work; the viscosities in the quaternaries CaO–Fe _n O–MgO–SiO₂, Fe _n O-MgO–MnO–SiO₂, and CaO–MgO–MnO–SiO₂ and the quinary CaO–Fe _n O–MgO–MnO–SiO₂ were studied. The experimental technique employed was the well-established rotating cylinder method, using a Brookfield digital viscometer mounted over a specially designed graphite furnace. Generally, iron crucibles were used along with iron spindles. Periodic calibrations of the experimental setup were made using the standard reference slag recommended by the European Union. The measurement's were carried out up to a maximum temperature of 1773 K in all cases. The reliability of the measurements were checked at different rotation speeds as well as during thermal cycling, and excellent reproducibility of the results was noted. The experimental viscosity values were incorporated into a viscosity model. Equations based on the model for calculating the viscosities of the quarternary systems CaO–Fe _n O–MgO–SiO₂, Fe _n O–MgO–MnO–SiO₂, and CaO–MgO–MnO–SiO₂ and the quinary system CaO–Fe _n O–MgO–MnO–SiO₂ are provided.     

The Existence of an Immiscibility Region in the U-Zr-O System

This paper is devoted to the study into the structure of core melts of reactors such as water-moderated water-cooled power reactors. The quenching method is used to experimentally investigate the structure of U-Zr- O melts with an atomic ratio of U/Zr = 1.2–1.6 at a temperature of 2773 K. It is found that, for the most probable compositions of U-Zr-O melts under conditions of heavy accident with the Zr oxidation level above 30%, no separation of the corium melt into immiscible liquids is observed.     

铝电解惰性阳极近10年发展状况

铝电解惰性阳极的研究和应用对环境、能源和国民经济有着深远的影响.概述了近10年来4种铝电解惰性阳极的最新进展,评述了它们各自的优点及存在的问题,面临的挑战及应用前景.其中金属陶瓷、金属合金和梯度材料是当前研究的重点.尽管它们的设计方案不同,其原理都是利用金属改善阳极的导电导热性、抗热震性和可加工性;陶瓷或在阳极表面形成陶瓷以抵抗熔融冰晶石的腐蚀.     

High-Temperature Containerless Viscosity Measurement by Gas-Film Levitation

The gas levitation process development program has, so far, been focused mainly on contact-free manipulation, on molding and shaping of liquids, on high-temperature contact-free treatment, and on shaping and solidification of interesting materials for scientific and technical purposes. Recently proposed by Parayre for viscosity measurements, this process eliminates the perturbing effects of the container, in particular, that of crystallization when studying supercooled liquids. The method consists of extracting viscosity values from the damped decay of perturbed liquid drops floating on a gas-film. An apparatus has been designed and developed for viscosity values higher than 1 Pa·s and at temperatures up to 2000°C. The method was applied to a silicate glass of industrial interest containing 70 wt% per cent of SiO₂, with viscosities ranging from 10² to 10⁶ Pa·s. Experimental results are compared with the Vogel–Fulcher–Tamann law for viscosity predictions. This paper demonstrates the industrial and scientific interest of this new method for viscosity determinations, which can be used for the working and softening points of any glass. These results may lead to a better understanding of network-forming or network-modifying behavior in oxide glasses.     

采用无容器凝固技术研究过冷熔体热物理性质

深过冷是获得特殊性能亚稳材料的一种非常重要的手段,采用无容器凝固技术可以在较低的冷却速度下实现并保持较长时间熔体的深过冷,使过冷熔体热物理性质参数的测量成为可能.介绍了电磁悬浮、助熔剂处理等几种常用的无容器凝固技术,阐述了它们在测量过冷熔体比热容等热物理性质方面的应用,同时综述了过冷状态下熔体比热容等热物理性质的研究现状,并展望了今后的发展趋势.     

Graphite Nucleation in Cast Iron Melts Based on Solidification Experiments and Microstructure Simulation

Microstructure strongly influences the mechanical properties of cast iron. By inoculating the melt with proper inoculants, foreign substrates are brought into the melt and eventually the graphite can crystallize on them. The elements and substrates that really play a role for nucleation are yet unknown. Until now there is very little knowledge about the fundamentals of nucleation, such as composition and morphology of nuclei. In this work we utilized EN-GJL-200 as a base material and examined several produced specimens. The specimens were cast with and without inoculants and quenched at different solidification states. Specimens were also examined with a high and low oxygen concentration, but the results showed that different oxygen contents have no influence on the nucleation in cast iron melts. Our research was focused on the microscopic examination and phase-field simulations. For studying the samples we applied different analytical methods, where SEM-EDS, -WDS were proved to be most effective. The simulations were conducted by using the software MICRESS, which is based on a multiphase-field model and has been coupled directly to the TCFE3 thermodynamic database from TCAB. On the basis of the experimental investigations a nucleation mechanism is proposed, which claims MnS precipitates as the preferred site for graphite nucleation. This theory is supported by the results of the phase-field simulations.     

高分子熔体的各向异性内部结构流变模型EI

提出了一个高分子熔体内部结构流变模型，采用大分子构象张量表述，并结合经典弹性力学与大分子动力学求得自由能各向异性唯象表达式，运用Ｈａｍｉｌｔｏｎｉａｎ／ＰｏｉｓｏｎＢｒａｃｋｅｔ方法从自由能函数和耗散张量推导建立了高分子构象张量动力学方程与相应的应力张量表达式。ＬＤＰＥ和ＰＳ在简单剪切流场中的粘弹特性的模拟结果与实验数据进行了分析对比，两者基本相符。本文还预测和讨论了上述流体大分子构象的变化过程以及各向异性参数的作用。     

Measurements of thermophysical properties by contactless modulation calorimetry

Contactless modulation calorimetry was applied to measure the specific-heat of glass forming eutectic Zr alloys in the stable and undercooled liquid under microgravity conditions during the space shuttle IML-2 mission. The experimental method is described. leading to a quantitative determination of the specific heat from measured temperature modulations. In addition, the enthalpy of Vision of the specimen and the total hemispherical emissivity can be obtained. The data on ZrNi₃₆, permit calculation of the thermodynamic functions in the stable and undercooked melt as well as estimation of the ideal glass transition temperature.Paper presented at the Fourth International Workshop on Subsecond Thermophysics, June 27–29, 1995, Köln, Germany.