Study on Exploration of Azeotropic Point of Pb-Sb Alloys by Vacuum Distillation and Ab Initio Molecular Dynamic Simulati
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INTRODUCTION
ENORMOUS Pb-based alloys such as Pb-Sb and Pb-Sn have been accumulated from tin smelters and the recycle of secondary metals. Furthermore, high-effective utilization of secondary resource and the increasing demand for Sb have got considerable interest in the separation of Pb-based alloys. However, there are some serious problems in conventional methods such as low recovery of metals, high energy consumption, and evident environment pollution.[1,2] Dai et al.[3–7] have studied the separation of high-lead-antimony alloys (Sb ~ 90 pct, Pb ~ 10 pct) by vacuum distillation, showed that the method is feasible, and the effect is better. However, an abnormal phenomenon in the process separation of Pb-Sb alloys has been reported. Zhang[8] found that there was no BINGYI SONG and LINGXIN KONG, Ph.D. Candidates, WENLONG JIANG, Lecturer, BIN YANG, XIUMIN CHEN, BAOQIANG XU, and DACHUN LIU, Professors, are with the National Engineering Laboratory for Vacuum Metallurgy, Kunming University of Science and Technology, No 253#, Xuefu Road, Kunming, 650093, P.R. China, and with the Key Laboratory for Nonferrous Vacuum Metallurgy of Yunnan Province, Kunming 650093, P.R. China, and also with the State Key Laboratory of Complex Nonferrous Metal Resources Clear Utilization, Kunming University of Science and Technology. Contact e-mail: jiangwlkg@ foxmail.com YONGNIAN DAI, Academician, is with the National Engineering Laboratory for Vacuum Metallurgy, Kunming University of Science and Technology. Manuscript submitted July 8, 2014. Article published online July 25, 2016 5214—VOLUME 47A, OCTOBER 2016
difference of the Sb content between in vapor phase and liquid phase, while Sb content was 22 wt pct at 1073 K (800 C); meanwhile, similar conclusions were presented by Yang[7] and Hu,[9] and they pointed out that Sb and Pb simultaneously evaporated into vapor phase when Sb content was 20 to 25, and 23 wt pct at 1073 K (800 C), respectively. Furthermore, Kroll[10] also proposed that there existed an azeotropy at a certain composition (about 75 pct Pb), viz. the metal and the metal vapor had the same composition. The experimental results quoted above indicate that the presence of azeotropes causes the appearance of separating manifolds of various ingredients, which prevents the obtainment of fractions of the required composition. Above studies focused on their experiments, unfortunately, there are not many researches on their theoretical researches, especially the molecular dimension of the simulation. Kumar[11] have reported the structure and stability of liquid Pb-Sb alloys determined by the Kumar-Samarin technique of centrifuging liquid metals. It was observed that liquid Pb-Sb alloys in the composition ranges 0 to 5 and 65 to 100 at pct Sb were stable and can be regarded as a colloidal dispersion of lead- and antimony-rich clusters in monatomic matrices. Guo[12] have measured electrical resistivity and viscosity of Pb-Sb alloys to investigate Peierls distortion behavior in the melts, which indicated that abnormal structure trans
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