以TDS及PMIRRAS方法探討鋁合金樣品表面水氣吸附機制

Study of Water Vapor Adsorption Mechanism on Aluminum Surface by TDS and PMIRRAS

姚慕蠡(Yao, Mu Lee)

指導教授 ： 陳俊榮

國立清華大學/原子科學院/生醫工程與環境科學系/碩士(2015年)

摘要

本論文利用PMIRRAS以及TDS系統測量鋁樣品表面吸附的水氣訊號，以澄清兩種方法在測量水氣訊號上有差異的原因。在TDS實驗樣品升溫中，利用遮蔽PMIRRAS光路的方式避開加熱紅外光對PMIRRAS光譜的干擾，以確認PMIRRAS光譜測量的可信度。

從高曝水量實驗結果及低曝水量情況之TDS和PMIRRAS實驗中， PMIRRAS無法測量到高溫才從表面脫附的水氣存在，依PMIRRAS實驗原理推測，此時樣品表面吸附的水氣電偶極可能以水平方向平躺於樣品表面，實際原因值得進一步澄清。本實驗的另一結果顯示，在高與低曝水量下的TDS水氣總脫附量皆遠小於依氣體動力論(假設等向分布)所計算的水氣吸附層數，推測原因為大型載台將TDS初期樣品脫附的大量水氣吸回，或是等向氣體動力模型有修正的必要，亦或凝結係數和表面吸附量有關而導致誤差。

本論文中發現，TDS過程中的實驗數據精確度可再加改善，依實驗結果估計，若將樣品載台面積減小至約2 cm2，且載台溫度合理的控制在172~177 K 之間，來自載台的干擾比例應可降至樣品水氣訊號的10 %以下。

關鍵字

傅立葉轉換紅外光譜 ； 熱脫附質譜 ； 水分子 ； 鋁表面 ； 吸附

並列摘要

In this thesis, PMIRRAS and TDS systems were used to measure the amount of water molecules adsorbed on aluminum surface, attempting to clarify the differences between the two methods in the measurement of H2O signal. In the TDS experiment, the optical path of PMIRRAS was blocked to avoid the interference from the heating infrared source when heating the sample. The reliability of the PMIRRAS measurements was significantly improved.

In the TDS and PMIRRAS experiments, no matter high or low water coverage conditions, the PMIRRAS method was found only able to detect the water molecules with lower binding energy (i.e. desorbed at lower temperature at the TDS process), but unable to detect the water molecules adsorbed in high temperature region. It was suspected that the electric dipole of H2O molecules adsorbed on the sample surface were horizontally lied, so that the interaction of the incident p-polarized infrared with the adsorbed water molecules was greatly reduced.

Another result of the experiments showed that the total amount of water molecules desorbed during the TDS was far less than the calculated quantities of the water molecules adsorbed on the sample surface based on the gas dynamic model with isotropic distribution. The difference might attributed to the following reasons: the large-size sample holder of the experiment system re-adsorb a great deal amount of water vapor that desorbed from the sample, or the isotropic gas dynamic model is insufficient for this experiment, or that the condensation coefficient of water molecules might change with different coverages in the experiment.

It is estimated from the experimental results that the ratio of the interference from the large-size sample holder can be reduced to be <10 % of the H2O desorbed from the sample if the surface area of the holder is reduce by a factor of 250, and the holder temperature is controlled between 172~177 K.

並列關鍵字

FTIR ； TDS ； water molecules ； aluminum Surface ； adsorption

參考文獻

21.賈立凱，“以紅外光光譜儀定量真空中鋁合金表面的水氣吸附”，碩士論文，國立清華大學生醫工程與環境科學系，(2009).

16.蕭屹崴，“利用不同氧氣含量擠型之鋁合金表面熱釋氣研究”，碩士論文，國立清華大學生醫工程與環境科學所，(2012).

15.林怡君，“以極乾燥氮氣曝氣之鋁合金真空腔熱釋氣研究”，碩士論文，國立清華大學生醫工程與環境科學所，(2011).

23.林峻模，“以TDS及FTIR方法探討鋁合金樣品之水氣吸附”，碩士論文，國立清華大學生醫工程與環境科學系，(2015).

11.熊高鈺、詹哲鎧、張進春、陳慶隆、陳彥斌、許憲能、薛心白、陳俊榮，“同步加速器台灣光子源超高真空系統設計”,真空科技 21(3-4) (2008), 12-19.