Development of a novel theory of pressure-induced nucleation in supercritical carbon dioxide
Development of a novel theory of pressure-induced nucleation in supercritical carbon dioxide
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DOI：
10.1039/d2ce00187j
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发表时间：
2022-03-17
期刊：
影响因子：
3.1
通讯作者：
Yang，Ming-Zhe
中科院分区：
文献类型：
--
作者：
Wang，Qi-Bo;Xu，Qin-Qin;Yang，Ming-Zhe
在化学气相沉积和原子层沉积等自下而上的方法中，成核是制备二维材料的基础。超临界流体沉积(SCFD)技术由于其优良的物理化学性质和可调的溶剂功率，可能为这些技术提供一种替代技术。然而，由于超临界流体的非理想性，经典成核理论不适用于超临界流体中的成核。建立了由非挥发溶质和超临界CO2组成的稀溶液体系，提出了压力诱导超临界相成核理论。新定义的溶质-溶剂关联函数在这一特殊过程中对成核驱动力有很大影响，特别是在过饱和度较小时。研究还发现，在高温高压下，成核势垒低，有利于形核。以MoO_2(Acac)_2为溶质，scCO_2为溶剂，进行了相应的实验，验证了理论的正确性。用静态平衡法准确测定了MoO2(Acac)2的溶解度。过饱和度、温度和压力对形核的影响与用该理论预测的结果是一致的。用PI-SCPN计算的成核率与实验值进行了比较，结果吻合较好，误差在一个数量级以内。
Nucleation is the basis of the fabrication of two-dimensional materials in the bottom-up methods such as chemical vapor deposition and atomic layer deposition. Supercritical fluid deposition (SCFD) might provide an alternative to these techniques owing to the excellent physicochemical properties and adjustable solvent power of supercritical fluids. However, classical nucleation theory (CNT) was not suitable for the nucleation in supercritical fluid (SCF) because of the non-ideality of SCF. Herein, a dilute solution system composed of a nonvolatile solute and supercritical CO2 (scCO2) was established and the theory of pressure-induced supercritical phase nucleation (PI-SCPN) was proposed. A newly defined solute–solvent correlation function was found to influence the nucleation driving force a lot in this particular process, especially when the supersaturation was small. It was also found that at high temperature and high pressure, the barrier of nucleation was low, which was conducive to the formation of a nucleus. Furthermore, the corresponding experiments were conducted using MoO2(acac)2 as the solute and scCO2 as the solvent to verify the proposed theory. The solubility of MoO2(acac)2 was accurately measured by the static equilibrium method. The influence of supersaturation, temperature and pressure on nucleation was found to be consistent with that predicted using the proposed theory. The nucleation rates calculated by PI-SCPN were compared to the experimental values, showing good agreement, and the errors were within one order of magnitude.