Enhancing impurities removal from Si by controlling crystal growth in directional solidification refining with Al-Si alloy
Enhancing impurities removal from Si by controlling crystal growth in directional solidification refining with Al-Si alloy
复制标题
铝硅合金定向凝固精炼中通过控制晶体生长来提高硅中的杂质去除率
DOI：
10.1016/j.jallcom.2019.153300
复制
发表时间：
2019
影响因子：
6.2
通讯作者：
Wenhui Ma
中科院分区：
文献类型：
--
作者：
Guoyu Qian;Liyuan Sun;Hang Chen;Zhi Wang;Kuixian Wei;Wenhui Ma
本文尝试采用“素料”原理来提高硅（Si）纯度，即控制固液界面和Si晶体生长方式，以增强Al-Si合金定向凝固精炼中Si中杂质的去除。建立了Si晶体生长与杂质去除之间的关系，发现随着Si晶体从块状Si、多孔Si、针状Si向Al-Si共晶合金的有序演化，金属杂质去除率（小于95%到大于99%）逐渐下降。对于块状硅，可以去除 99.5% 以上的金属杂质。然而，硼（B）和磷（P）的去除却呈现相反的趋势。根据构成过冷原理，基于凝固界面硅原子质量守恒来评价晶体硅的生长和界面形貌，并用于解释杂质去除的机理。通过改变温度梯度（降低速率）、硅合金成分（硅含量）和固液界面传热模式（以坩埚壁与底部之间的有效传热面积比（LA）表示）来实现硅晶体生长的控制。当LA值为0.1时，在0.05 mm/min的下降速率下获得了更加稳定和平坦的液固界面和45%的块体Si，可以大大增强杂质的去除。
In this paper, the principle of “plain materials” was attempted to advancing silicon (Si) purity, i.e., controlling solid-liquid interface and Si crystal growth pattern to enhance impurities removal from Si in directional solidification refining with Al-Si alloy. The relationship between Si crystal growth and impurity removal was established, and it was found that the removal ratio of metal impurities (less than 95% to more than 99%) gradually decreased with the order evolution of Si crystal from bulk Si, porous Si, acicular Si to Al-Si eutectic alloy. More than 99.5% of metallic impurities could be removed in the case of bulk silicon. However, the removal of boron (B) and phosphorus (P) showed the opposite trend. According to the principle of constitutional supercooling, the crystal Si growth and interface morphology were evaluated based on the conservation of mass of silicon atoms at the solidification interface, which was also used to explain the mechanism of impurities removal. Control of silicon crystal growth was achieved by changing the temperature gradient (lowering rate), Si alloy composition (Si content) and the heat transfer mode of solid-liquid interface that was expressed in terms of the effective heat transfer area ratio between wall and bottom of crucible (LA). A more stable and flat liquid-solid interface and 45% bulk Si was obtained at a lowering rate of 0.05 mm/min when the value of LA was 0.1, which can greatly enhance the removal of impurities.