Calculation of Cu-rich part of Cu-Ni-Si phase diagram

The thermodynamic calculation of phase equilibria in the Cu-Ni-Si alloy system was carried out using the CALPHAD method. The calculations show that there are three two-phase areas and two three-phase areas in the Cu-rich parts of the isothermal section of the phase diagram at 300-600 ℃ , and the three two-phase areas are FCC-Al（Cu-rich）＋γ-Ni5Si2, FCC-Al（Cu-rich）＋δ-Ni2Si and FCC-Al（Cu-rich）＋ε-Ni3Si2, two three-phase areas are FCC-Al（Cu-rich）＋）,-Ni5Si2＋δ-Ni2Si and FCC-Al（Cu-rich）＋δ-Ni2Si＋e-Ni3Si2. For this reason, an alloy located in the Cu-rich portion may precipitate γ-Ni5Si2, δ-Ni2Si or ε-Ni3Si2; the proportion of each phase depends on the alloy composition and aging temperature. The transmission electron microscope analysis of the Cu-3.2Ni-0.75Si alloy indicates that the precipitates are mainly δ-Ni2Si with only a few γ-NisSi2 phase particles, which agrees well with the thermodynamic calculations of phase equilibria.     

纳米碳管中离散分布的金属Ni纳米线气-液/固-固填充模型

以Ni∶Cr=3∶1的双金属层作为催化剂,用C2H2为碳源气体利用化学气相沉积(CVD)法,在不同的温度下制备纳米碳管.扫描电子显微镜(SEM)和透射电子显微镜(TEM)研究制备产物发现:当制备温度高于900℃时,没有纳米碳管生成,制备温度在700～800℃之间纳米碳管中填充有一些离散分布的金属Ni纳米线,制备温度在650℃有纳米碳管生成,但是纳米碳管中没有发现纳米线的填充.通过高分辨透射电子显微镜(HRTEM)分析发现,纳米线是以液态或是粘滞液态填充进纳米碳管.根据实验结果,提出了一个在本实验条件下纳米线填充进纳米碳管的气-液/固-固V- L/S -S(vapor- liquid/solid-solid)模型,这个模型能解释一些传统的V-L-S(vapor- liquid -solid)模型不能解释的实验现象.