中温区Mg_(2)(Si,Sn)基热电材料因其廉价、无毒无害等优点极具发展潜力.其中,三元Mg_(2)Si_(1-x)Sn_(x)合金的电子传输性能须通过元素掺杂来进行优化,最常见的掺杂元素Bi和Sb均可以对载流子浓度、迁移率和有效质量等传输性能参数进行调...中温区Mg_(2)(Si,Sn)基热电材料因其廉价、无毒无害等优点极具发展潜力.其中,三元Mg_(2)Si_(1-x)Sn_(x)合金的电子传输性能须通过元素掺杂来进行优化,最常见的掺杂元素Bi和Sb均可以对载流子浓度、迁移率和有效质量等传输性能参数进行调节,而不同的原子置换位置会对合金的电子传输特性产生较大的影响.因此,本文采用第一性原理计算的方法,对Sb,Bi元素分别置换Si,Sn位置的缺陷形成能进行了分析,结合能带结构和态密度的变化分析其对载流子传输性能参数的影响.通过甩带快速凝固方法制备了Bi,Sb掺杂Mg_(2)Si_(1-x)Sn_(x)晶体,结合求解Boltzmann方程对电子传输性能的预测结果进行对比分析.结果表明,Bi,Sb原子均更加倾向于取代Si位,Sb原子的取代具有更低的形成能.与Bi元素相比,相同成分的Sb掺杂下载流子浓度较低,但可以提供更大的载流子有效质量,因此可以获得更高的Seebeck系数和功率因子,最高值可达–228μV/K和4.49 m W/(m·K^(2)),而Bi掺杂可以提供更高的电导率.本研究结果可以为掺杂优化Mg_(2)(Si,Sn)基合金的热电性能提供理论参考.展开更多
The effects of minor alloying elements（antimony,boron） on the recrystallization and oxidation of Mn-containing interstitial free（IF） steels were investigated using confocal scanning laser microscope（CSLM） under ...The effects of minor alloying elements（antimony,boron） on the recrystallization and oxidation of Mn-containing interstitial free（IF） steels were investigated using confocal scanning laser microscope（CSLM） under controlled atmosphere of 95% Ar and 5% H2（volume percent） at different temperatures.The results indicated that oxidation and recrystallization were primarily controlled by the grain boundaries,which moved due to release of the stored energy or acted as the fast path diffusion of alloying elements.It was found that the addition of antimony suppressed both surface oxidation and internal oxidation,whereas boron addition accelerated surface oxidation but decreased internal oxidation.The reasons caused were that the alloying elements of antimony or boron were known to segregate on the surfaces or grain boundaries to occupy the surface adsorption sites,which were expected to be less catalytic than bare iron on the transportation of alloying elements.The recrystallization was also retarded through adding minor antimony and boron elements.The oxidation kinetics of formation of grain boundary oxides were studied through calculating the areas along grain boundaries,and it was found that the areas parabolically increased with increasing time.展开更多
文摘中温区Mg_(2)(Si,Sn)基热电材料因其廉价、无毒无害等优点极具发展潜力.其中,三元Mg_(2)Si_(1-x)Sn_(x)合金的电子传输性能须通过元素掺杂来进行优化,最常见的掺杂元素Bi和Sb均可以对载流子浓度、迁移率和有效质量等传输性能参数进行调节,而不同的原子置换位置会对合金的电子传输特性产生较大的影响.因此,本文采用第一性原理计算的方法,对Sb,Bi元素分别置换Si,Sn位置的缺陷形成能进行了分析,结合能带结构和态密度的变化分析其对载流子传输性能参数的影响.通过甩带快速凝固方法制备了Bi,Sb掺杂Mg_(2)Si_(1-x)Sn_(x)晶体,结合求解Boltzmann方程对电子传输性能的预测结果进行对比分析.结果表明,Bi,Sb原子均更加倾向于取代Si位,Sb原子的取代具有更低的形成能.与Bi元素相比,相同成分的Sb掺杂下载流子浓度较低,但可以提供更大的载流子有效质量,因此可以获得更高的Seebeck系数和功率因子,最高值可达–228μV/K和4.49 m W/(m·K^(2)),而Bi掺杂可以提供更高的电导率.本研究结果可以为掺杂优化Mg_(2)(Si,Sn)基合金的热电性能提供理论参考.
基金Item Sponsored by National Natural Science Foundation of China(50902003,51172003)National Key Technology Research and Development Program in 12th Five-Year Plan of China(2010BAE00316,2011BAB02B05)
文摘The effects of minor alloying elements（antimony,boron） on the recrystallization and oxidation of Mn-containing interstitial free（IF） steels were investigated using confocal scanning laser microscope（CSLM） under controlled atmosphere of 95% Ar and 5% H2（volume percent） at different temperatures.The results indicated that oxidation and recrystallization were primarily controlled by the grain boundaries,which moved due to release of the stored energy or acted as the fast path diffusion of alloying elements.It was found that the addition of antimony suppressed both surface oxidation and internal oxidation,whereas boron addition accelerated surface oxidation but decreased internal oxidation.The reasons caused were that the alloying elements of antimony or boron were known to segregate on the surfaces or grain boundaries to occupy the surface adsorption sites,which were expected to be less catalytic than bare iron on the transportation of alloying elements.The recrystallization was also retarded through adding minor antimony and boron elements.The oxidation kinetics of formation of grain boundary oxides were studied through calculating the areas along grain boundaries,and it was found that the areas parabolically increased with increasing time.
