電化學法探討單晶碳化矽在濃鹽酸下的腐蝕行為

Electrochemical Corrosion of Single Crystal Silicon Carbide in the HCl

本實驗主要是利用電化學之直流測試法與交流阻抗法，探討碳化矽單品的腐蝕行為。直流測試法通常只能測試得腐蝕電壓與腐蝕電流，而利用交流阻抗法則可分析受腐蝕物的腐蝕系統。碳化矽於氧化氣氛下，表面產生一層SiO2薄膜以保護其不再繼續受腐蝕。本實驗探討碳化矽在濃鹽酸液中的腐蝕行為，包括其受濃鹽酸侵蝕而產生孔蝕的情形與電雙層、鈍化膜於腐蝕過程中所扮演的角色，藉由電極（碳化矽）表面所產生的電阻與電容變化，判斷電極表面所產生鈍化膜之耐蝕性與吸附性，並研究其對腐蝕時間之影響。由直流測試法中施予特定電壓與電流值時可觀察到碳化矽腐蝕行為。而利用交流阻抗法測定技術，即為變更交流頻率反應，則可將腐蝕液、鈍化膜、碳化矽間的電容值與阻抗值以一組等效電路模擬之。並藉由所得的電路數據，轉換成以頻率值和阻抗值互為函數的Bode圖，或為複數阻抗值表示方式的Nyquist圖，再由各圖中解釋各項數據所代表的意義。溶液阻抗值的定值現象、SiO2鈍化膜阻抗值的週期性變化、與各項電容值充放電的影響，均在本研究中詳加以討論。

Single crystal silicon carbide (SiC) is corroded in the concentrated hydrochloride acid (12M HCl). The corrosion behavior of SiC has been delineated by applying A.C impedance techniques and D.C polarization measurements. Silicon dioxide (SiO2) film acting as a protective barrier will form on the surface of silicon carbide in the corrosive environments. Impedance spectroscopy expressed in Bode and Nyquist plots has been carried out to show the corrosion behavior of SiC. The impedance data was simulated to obtain an equivalent circuit, from which the values of the pore resistance, capacitance, and relative permittivity of protective SiO2 film where estimated .Plots of each parameters against reaction time are discussed to explain the interaction. Direct-current polarization of this system confirms the inferration derived from impedance study. It is observed that the SiO2 film on the SiC is formed and faded repeatedly to the end of reaction.