大氣電漿噴塗製備碳化矽薄膜及其在製程液處理上之應用

Abstract

碳化矽具有高機械強度、良好的熱穩定性以及化學穩定性，所以被視為能承受極端環境的陶瓷膜材。在本實驗中，我們使用大氣電漿噴塗的技術來製備碳化矽塗層於純鈦基板上。相較於傳統製程，大氣電漿噴塗法具有省時以及大面積製造的優勢。然而，碳化矽易在高溫下自行分解，以至於塗層厚度以及塗層強度均不高。因此，在本實驗中，我們提出了三種方法來解決本問題。第一種是溶膠凝膠法 (Sol-gel method)，利用四乙氧基矽烷 (Tetraethoxysilane, TEOS)作為前驅物，在碳化矽粉末外層先長上二氧化矽保護層，再進行熱噴塗；再者，也是利用溶膠凝膠法，但另添加十二烷基硫酸鈉 (Sodium dodecyl sulfate, SDS) 界面活性劑，使得二氧化矽層長得更緻密；最後是添加氧化鋁，並調控碳化矽對氧化鋁的比例 (1:3、1:1、3:1)。製備完樣品後，我們用掃描式電子顯微鏡觀察樣品表面形貌；X射線繞射儀分析粉體噴塗前後成分變化；測厚儀做塗層厚度測定；百格測試比較塗層附著力強弱；抗腐蝕測試，將試片浸入pH= 0的硫酸，以及pH =14的氫氧化鈉水溶液中，並利用掃描式電子顯微鏡觀察樣品表面形貌變化。最後，測量試片純水通量以及聚苯乙烯標準溶液 (Polystyrene standard, PS standard)的阻擋率。透過本實驗可知，噴塗修飾過的碳化矽，塗層均較厚且具較高的機械強度；比較溶膠凝膠法以及機械混合氧化鋁，可以發現混合氧化鋁具有更佳的附著性，且在阻擋率測試下具較高的效能 (~ 99%)。

Silicon Carbide (SiC) is an inorganic material processing properties such as good thermal resistance, high hardness and excellent chemical resistance. Due to all these advantages, it has been regarded as one of the promising materials for membrane filtration. In this study, atmospheric plasma spraying (APS) technique was utilized to produce SiC coating onto titanium substrate. However, severe decomposition of SiC powder at high temperature heavily reduces the coating thickness and mechanical strength. Therefore, in this study, three approaches were introduced to deal with this problem. Firstly, sol-gel method was applied to create a SiO2 layer on the SiC surface. Secondly, sol-gel method with sodium dodecyl sulfate (SDS) was also applied. At last, mechanically mixed different ratio of alumina to SiC was produced. Afterwards, SEM images was utilized to investigate the morphology of both the powder and the coating surface; XRD was used to discover the variation of characteristic peaks before/after APS. Adhesion test was also conducted to understand the mechanical strength of each sample; Corrosion test was conducted as well. At last, polystyrene rejection and pure water flux were conducted to investigate the filtration efficiency of each sample. Results indicate that all these modification methods can do enhance the coating thickness and adhesion force between substrate and coating; furthermore, compared with sol-gel modified samples, samples containing alumina (Al2O3) exhibit excellent adhesion force and high polystyrene rejection (~ 99%), which can be concluded that SiC/Al2O3 sample is more suitable for water filtration application.