Thermodynamic properties of titanium and iron in molten silicon

Titanium and iron in silicon are known as harmful “lifetime killer” impurities, which shorten the lifetime of excited carriers in silicon solar cell and disturb power generation. Therefore, the removal of titanium and iron is one of the most important topics for the production of solar grade silicon. Thermodynamic properties of titanium and iron in molten silicon were determined at 1723 K by equilibrating molten silicon-titanium alloys or molten silicon-iron alloys with molten lead, which has a limited mutual solubility for both alloys. The activity coefficients of infinite dilution, self-interaction coefficients of titanium and iron in molten silicon, and the Gibbs energy change of mixing for silicon-titanium and silicon-iron at 1723 K relative to pure liquid silicon, titanium, and iron were determined.     

Reaction of a molten mixture of titanium,aluminum, and silicon oxides with hot-pressed silicon nitride

The formation temperature of a liquid phase and the solidification temperature of a molten mixture of Al₂O₃-TiO₂-SiO₂ oxides on a silicon nitride substrate are determined. Data are obtained for the change in kinetics. It is established that the intensity of interaction of molten Al₂O₃-TiO₂-SiO₂ with silicon nitride depends on the oxide mixture composition. With heating there are two possibilities: improvement and worsening of Si₃N₄ crystallite wetting with a liquid phase as well as solidification of the melt. The temperature range where a liquid phase exists for actual materials is about 15°C, which markedly worsens the process of structure formation with Si₃N₄ during sintering.Translated from Poroshkovaya M etallurgiya, No. 5, pp. 39–44, May, 1993.     

Thermodynamic properties of calcium hexaboride

The temperature dependence of the heat capacity of CaB₆ in the range 20–2500 K was calculated. The calculated results were confirmed by experimental measurements in the range 198–673 K, and standard enthalpy and entropy values were calculated. A recommended standard enthalpy of formation of CaB₆ was obtained from data in the literature. Equations for the thermodynamic functions of CaB₆ in the range 298.15–2500 K were obtained, which are suitable for the thermodynamic analysis of processes involving calcium hexaboride. Institute for Materials Science Problems, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8, pp. 63–66, July–August, 1997.     

高炉渣中硅、钙、镁的湿法分析

高炉渣试样用热的稀硝酸加氢氟酸分解完全后,取3份试液,其中1份试液用盐酸调节酸度后,在680nm波长处用硅钼蓝差示光度法测定二氧化硅含量,另外两份试液分别以钙指示剂和PAN指示剂指示滴定终点,用EDTA滴定法测定氧化钙及氧化钙和氧化镁合量,然后用差减法求得氧化镁的含量。用本法测定了高炉渣试样和标样中二氧化硅、氧化钙和氧化镁含量,并将本法的测定结果与X荧光光谱法的测定结果进行对照,结果表明两种方法的测定结果相符。本法测定结果的相对标准偏差≤2.7%（n=8）。     

Effects of aluminum, silicon, and boron on the dissolution rate of nitrogen into molten iron

An isotope exchange technique is employed as a method for measuring the nitrogen dissolution rate into molten iron alloys, and the effects of Al, Si, and B addition have been studied at temperatures ranging from 1873 to 2023 K. The results are compared with those of other elements such as Ti, Zr, V, and Cr. The rate of nitrogen dissolution into molten iron is shown to decrease by the addition of Al, Si, and B due to a weaker affinity for nitrogen than Fe, which is contrary to the case of Ti, Zr, V, and Cr. Among them, B shows the largest effect when their contents are lower than 1 mass pct. A reasonable correlation of the rate constant with an interaction parameter between nitrogen and each element has been observed, which can be explained by the change in the activity of the vacant site on the surface of the molten alloy. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium,” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS.     

采用Al和C脱氧钢液平衡氧含量的热力学分析

对标准大气压强下的[Al]-[O]平衡和不同压强下[C]-[O]平衡进行了热力学计算,得到了钢液中[O]含量的最小理论值.温度一定的条件下,采用[Al]脱氧时钢液中[Al]和[O]呈U型关系;过小或过大的[Al]含量对减少钢液中[O]均不利;提高温度可进一步降低[Al]脱氧条件下的钢液中[O]含量的最小理论值.对[C]脱氧而言,温度一定的条件下,提高真空度可提高[C]的脱氧能力;且随着钢液中[C]的增加,钢液中[O]呈减少趋势.温度为1873 K,真空度100 Pa时,钢液中[C]含量大于0.0015%的条件下,[C]的脱氧能力大于[Al]的脱氧能力.利用实际数据分别对[Al]脱氧和[C]脱氧平衡曲线最低值理论公式验证,且与实际结果均符合较好.     

Thermodynamic properties of molten PbO−SiO2 systems

Thermodynamic properties of the molten PbO?SiO₂ systems were determined by electromotive force measurements employing solid electrolytes. The experiments were carried out in the temperature range 900° to 1000°C on the galvanic cells \(Pb_{(l)} + PbO_{(l)} \left| \begin{gathered} Electrolyte \\ ZrO_2 \times CaO \\ \end{gathered} \right|Pb_{(l)} + PbO - SiO_{2(l)} \) From the results the activities of PbO and SiO₂, the partial and integral free energies, entropies, and heats of mixing were determined. These experimental results are interpreted and compared with previous experimental data. Based on the present data and according to the model of Toop and Samis,¹the activity coefficients of the free oxygen ion O^2? concentration is reduced.     

X射线荧光光谱法测定生石灰中钙、镁、硅、硫

介绍了用X射线荧光光谱仪测定生石灰中Ca ,Mg ,Si和S含量的方法。通过条件试验 ,确定了各元素的最佳测定条件 ,同时探讨了研磨样品时间对X射线荧光强度和分析曲线的影响、放置时间对样品含量的影响。实践证明 ,该方法快捷、简便、准确。RSD在 0 . 0 17%～ 0 .93 %之间     

Thermodynamic properties of dilute solutions of magnesium in zinc

Concentration cells of the type: Mg(s) |MgCl₂ in (LiCl-KCl)_eut(l) |Mg-Zn(l) have been employed for a study of the thermodynamic properties of dilute Mg-Zn alloys in the range from 0.01 < X_Mg < 0.17 and at temperatures below the melting point of Mg, 922 K. The data were discussed in terms of the Krupkowski formulae, Wagner's linear relations of In γ_Mg vs X_Mg and Darken's quadratic formalism. This research was done at the Institute of Inorganic Chemistry, The Technical University of Norway, Trondheim, Norway.     

Experimental and modeling studies of the thermal conditions and magnesium,iron, and copper content on the morphology of the aluminum silicon eutectic in hypoeutectic aluminum silicon alloys

Hypoeutectic aluminum silicon alloys without and with additions of magnesium, copper, iron, and strontium have been cast in a mold, giving directional solidification from a chill. Detailed temperature measurements have been carried out. Solidification modeling based on front tracking of the microstructure growth fronts allowed identification of the time and temperature at which the dendrite tips and the first eutectic pass the thermocouples. The undercooling, growth rate, and thermal gradients at the dendritic and eutectic growth fronts were derived. The effect of varying thermal parameters and alloy compositions on the microstructure was investigated. Compared to the binary alloy, a coarser eutectic was observed in the alloys with magnesium, iron, and/or copper. The coarsening is explained as a result of the transition from a eutectic forming at one specific temperature, to a eutectic forming over a temperature range. The former is likely to grow as a plane front, whereas the latter is likely to form an interdendritic eutectic mushy zone.     

火焰原子吸收光谱法测定含硅铝合金中微量铬铜镁铁

采用NaOH-H2O2-HNO3溶解试样,以SrCl2为释放剂,标准加入法以消除基体及试液进样的物理化学干扰,建立了火焰原子吸收光谱法连续测定Cr,Cu,Mg,Fe的方法。优化了仪器测定条件,并对可能存在的元素进行了干扰试验。结果表明,测定3μg/mL Cr,Cu,10μg/mL Mg和4μg/mL Fe时,100μg/mL Na+,K+,80μg/mL Ca2+,50μg/mL Zn2+,Mn2+,Pb2+,Cd2+和30μg/mL Ni2+,Co2+没有干扰;100μg/mL Cr,Cu,Mg,Fe之     

Thermodynamic properties of liquid alloys of gadolinium with silicon

Powder Metallurgy and Metal Ceramics - Partial heats of mixing for gadolinium and silicon in the binary system Gd–Si are measured by means of a high-temperature isoperibolic calorimeter in...     

碱熔-电感耦合等离子体原子发射光谱法测定钒渣中钒硅钙镁铝锰铬钛磷

钒渣是制备钒氧化物、钒金属材料等高钒基体产品的关键原料,快速准确掌握其成分含量是调控工艺参数、确保产品质量的前提条件.使用化学湿法检测效率低、周期长,而X射线荧光光谱法(XRF)难以满足微量元素测定需要,为此建立了碱熔-电感耦合等离子体原子发射光谱法(ICP-AES)同时测定钒渣中V、Si、Ca、Mg、Al、Mn、Cr...     

Thermodynamic measurements in molten Pb-Sn alloys

The reversible galvanic cell: Sn(l), SnO₂(s)/CaO-ZrO₂/Pb-Sn(l), SnO₂(s) (electrolyte) was employed to determine the thermodynamic properties of liquid Pb-Sn alloys in the composition range ofX _sn from 0.1 to 0.9 and in the temperature range of 875 to 1100 K. The activities of both tin and lead exhibit only moderate positive deviations from the respective Raoult’s law lines and do not agree with the values reported in the literature.S ^E , as calculated by combiningH ^E values of Kleppa andF ^E values determined in this investigation, are positive and range from 0 to 0.139 eu. S. K. DAS, formerly M. Tech. Student, Department of Metallurgical Engineering, Indian Institute of Technology, Kanpur, India This paper is based on a portion of a thesis submitted by S. K. DAS in partial fulfillment of the requirements of the M. Tech. degree at the Indian Institute of Technology, Kanpur.     

Study of the reduction of UO2 by magnesium or calcium dissolved in molten chlorides

The reduction of solid UO₂ to uranium by magnesium or calcium dissolved in their molten chlorides has been studied. The rate of reduction per unit area of UO₂ surface, at constant temperature and concentration of reductant in the molten chloride, was found to increase with time to a constant value. The rate of reduction per unit area was observed to be proportional to the concentration of reductant in the molten salt. The small increase observed in the reaction rate over the temperature range 750° to 850°C, suggests that the reduction is controlled by transport of the reductant to the reaction site. Solidified salt, containing UO₂ pellets which had been partially reduced, was sectioned, polished, and examined microscopically. The products of the reduction reaction form concentric layers around the UO₂ pellets. Layers of metallic uranium and oxide containing small amounts of dispersed salt alternated with layers of salt containing small amounts of metallic uranium and oxide. The layers ruptured, presumably because the volume of the products, uranium and oxide, is greater than the volume of the UO₂. Therefore, an impervious layer did not form on the oxide surface to inhibit the reduction reaction.     

X射线荧光光谱法测定白云石、石灰石中氧化钙、氧化镁和二氧化硅

将白云石、石灰石标准样品直接压片, 通过灼烧减量对氧化钙、氧化镁和二氧化硅含量进行校正, 根据其含量与强度的对应关系绘制校准曲线, 建立了X射线荧光光谱法(XRF)测定白云石、石灰石中这3种主要成分的方法。对一部分试样直接压片测定, 同时另一部分试样进行灼烧减量试验, 可大大节约标准样品的用量。灼烧时间试验表明, 试样在1 100 ℃下灼烧0.5 h就可达到恒重;粒度试验表明, 样品粒度大于200目时可消除粒度效应的影响。用CaO和MgO含量进行基体校正, 可消除其对低含量SiO₂的影响;采用经验系数法可消除元素间的吸收-增强效应。精密度试验结果表明, 氧化钙、氧化镁和二氧化硅测定结果的相对标准偏差(n=8)在0.038%~3.5%之间;对石灰石和白云石标准样品和实际样品进行准确度考察, 测定值与认定值或滴定法的测定值一致。