A Simulation of the Contact Angle for Organic Vapors to Cause the Same Probability of the Heterogeneous and Homogeneous Nucleation

本文以古典核凝理論模擬計算微粒固－液接觸角在多大時，均相與非均相核凝在單位時間單位體積產生臨界胚核數目的核凝速率（以下稱之為核凝概率）相當。此臨界接觸角可用以判斷蒸氣在過飽和狀態下，在某一微粒濃度時，非均相與均相核凝何者先發生。模擬計算了水及12類族有機蒸氣，結果顯示，微粒半徑愈大，核凝概率愈低時，臨界接觸角愈大，亦即較利於非均相核凝的優先發生。在核凝概率低於某一特定值，溫度愈低，臨界接觸角愈大；核凝概率高於此一特定值，則溫度愈高，臨界接觸角愈大。亦即在此兩種情況下利於非均相核凝的優先發生。物質之間的模擬比較，在均相過飽和度方面，對於低極性有機蒸氣，同類族物質的的過飽和度隨acentric factor增加而加，符合corresponding state理論的預測。臨界接觸角方面，除了醇、酸、酯和氯甲烷等類族外，對於其他類族，同一類族內的有機蒸氣，模擬所得到的臨界接觸角幾乎相同，符合corresponding state correlation。

關鍵字

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並列摘要

The classical nucleation theory was employed to calculate the value of contact angle between solid and liquid at which the same number of critical nuclei per unit volume per unit time (nucleation probability) was produced by homogeneous and heterogeneous nucleation. Such a critical contact angle can used to judge whether heterogeneous or homogeneous is going to happen first in a system containing a supersaturated vapor and particles. Water and 12 families of organic compounds were tested. The simulation shows that the critical contact angle increases with the particle size, and decreases with the nucleation probability. Large critical angle favors heterogeneous nucleation. As a nucleation probability is less than a certain value, the lower the temperature is, the larger the critical contact angle is; but at a nucleation probability higher than the value, the higher the temperature is, the larger the critical contact angle is. For different compounds, supersaturations required for the organic vapors in the same family with low dipole moment increase with acentric factor, in agreement with that predicted by the corresponding state correlation. An approximately same critical contact angle is observed for organic vapors in the same family except for families of alkanol, acid, ester and chloromethane, this observation is in agreement with the corresponding state correlation.

並列關鍵字

Homogeneous nucleation ； Heterogeneous nucleation ； Supersaturation ； contact angle ； Corresponding state

國際替代計量

A Simulation of the Contact Angle for Organic Vapors to Cause the Same Probability of the Heterogeneous and Homogeneous Nucleation

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