Department of Chemical Engineering, University of Massachusetts Lowell, One University Ave, Lowell, MA 01854, USA.
Nanoscale. 2017 Aug 31;9(34):12398-12408. doi: 10.1039/c7nr01402c.
A binary system of tin/indium (Sn/In) in the form of nanoparticles was investigated for phase transitions and structural evolution at different temperatures and compositions. The Sn/In nanosolder particles in the composition range of 24-72 wt% In were synthesized by a surfactant-assisted chemical reduction method under ambient conditions. The morphology and microstructure of the as-synthesized nanoparticles were analyzed by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD). HRTEM and SAED identified InSn and In, with some Sn being detected by XRD, but no InSn was observed. The differential scanning calorimetry (DSC) thermographs of the as-synthesized nanoparticles exhibited an endothermic peak at around 116 °C, which is indicative of the metastable eutectic melting of InSn and In. When the nanosolders were subjected to heat treatment at 50-225 °C, the equilibrium phase InSn appeared while Sn disappeared. The equilibrium state was effectively attained at 225 °C. A Tammann plot of the DSC data of the as-synthesized nanoparticles indicated that the metastable eutectic composition is about 62% In, while that of the DSC data of the 225 °C heat-treated nanoparticles yielded a eutectic composition of 54% In, which confirmed the attainment of the equilibrium state at 225 °C. The phase boundaries estimated from the DSC data of heat-treated Sn/In nanosolder particles matched well with those in the established Sn-In equilibrium phase diagram. The phase transition behavior of Sn/In nanosolders leads to a new understanding of binary alloy particles at the nanoscale, and provides important information for their low temperature soldering processing and applications.
采用表面活性剂辅助化学还原法在常温条件下制备了锡/铟（Sn/In）纳米合金，研究了不同温度和组成下的二元体系的相变和结构演变。在 24-72wt%In 的组成范围内，合成了 Sn/In 纳米焊料颗粒。采用扫描电子显微镜（SEM）、高分辨率透射电子显微镜（HRTEM）、选区电子衍射（SAED）和 X 射线衍射（XRD）对所合成纳米颗粒的形貌和微观结构进行了分析。HRTEM 和 SAED 鉴定出 InSn 和 In，XRD 检测到了一些 Sn，但未观察到 InSn。所合成纳米颗粒的差示扫描量热法（DSC）图谱在约 116°C 处显示出一个吸热峰，表明 InSn 和 In 的亚稳共晶熔化。当纳米焊料在 50-225°C 下进行热处理时，平衡相 InSn 出现，Sn 消失。在 225°C 时有效地达到了平衡状态。所合成纳米颗粒的 DSC 数据的 Tammann 图表明，亚稳共晶组成约为 62%In，而经 225°C 热处理的 DSC 数据的共晶组成则为 54%In，证实了在 225°C 时达到了平衡状态。从热处理 Sn/In 纳米焊料颗粒的 DSC 数据估算的相界与建立的 Sn-In 平衡相图中的相界吻合良好。Sn/In 纳米焊料的相变行为为纳米尺度下二元合金颗粒提供了新的认识，并为其低温焊接处理和应用提供了重要信息。
