驟冷式化學氣相合成法製備奈米氧化鋅微粒之研究

Abstract

本研究以化學氣相合成法(CVS)產生奈米氧化鋅微粒，設計一驟冷式化學氣相合成法微粒產生系統，實驗係利用攜帶氣體(氬氣或氮氣)將蒸發鋅金屬粉末所產生的鋅蒸氣帶至反應管後端與冷卻空氣混合氧化後凝結成奈米氧化鋅微粒。本研究控制攜帶氣體流量(Qcg)與冷卻空氣流量(Qqa)，改變驟冷管於冷凝區之冷卻速率，探討不同操作條件下氧化鋅微粒的粒徑分佈情形及觀察其形貌。研究結果顯示，當Furnace 1(預熱攜帶氣體)與Furnace 2 (反應爐)的溫度分別為800 ℃及500 ℃、Qcg為1 L/min時，Qqa由1 L/min增加至5 L/min，微粒數目濃度會從2.56×107 #/cm3增加至4.28×107 #/cm3，峰值粒徑(Mode diameter, Mode)從15.26 nm下降至3.27 nm，因為當冷卻空氣流量增加時，冷凝區的冷卻速率也會增加，進而增加微粒的成核速率，導致大量的微粒形成，數目濃度增加，而微粒粒徑大小會隨著冷卻速率增加而減小，所產生的氧化鋅微粒之總數目濃度與Mode皆可以穩定5小時以上，穩定性較傳統式化學氣相合成法微粒產生系統佳。本研究所設計之微粒產生系統於Qcg為1 L/min，Qqa為5 L/min的條件下，可穩定產生Mode為3.27 nm而總數目濃度高達4.28×107 #/cm3的氧化鋅微粒，達到高純度、高濃度、可控制大小、以及能夠長時間穩定產生微粒等目的。

A stable nanoparticle generation system equipped with a dilution and quencher probe (DQP) based on chemical vapor synthesis (CVS) method was designed for zinc oxide nanoparticles (ZnO-NPs) formation by controlled cooling rate. The Zn vapor was generated from Zn powder in a tubular furnace, oxidized with oxygen in quenching air, followed by condensation nucleation, growth and coagulation to produce ZnO-NPs. The mode diameter (Mode) of the aggregates can be stabled on 3.27 nm when the flow rate of carrier gas and quenching air were 1 and 5 L/min, respectively, measured using the scanning mobility particle sizer (SMPS), which can be sustained for more than 5 hour. Morphology and crystal structure of the synthesized ZnO-NPs were studied with transmission electron microscopy (TEM). The similarly spherical-like nanoparticles were found based on TEM analyses. As a conclusion, A CVS system with a DQP could be used to produce less than 10 nm nanoparticles with good stabilization and controllability in a single-stage continuous process.