對流對光致質量傳輸效應的影響研究

Study of Photo Induced Mass Transport in the Presence of Convection

林銘淇(Ming-Chi Lin)

指導教授 ： 魏台輝

國立中正大學/理學院/物理學系/碩士(2015年)

摘要

在過去數年裏，我們曾分別以波長為632.8 nm的CW He-Ne雷射光和波長為532 nm的19 picosecond (ps)脈衝為光源，對濃度為7104 M與2104 M的氯鋁酞青素-乙醇溶液(簡稱ClAlPc-ethanol)進行全穿透率的量測，藉以調查溶質分子的質量傳輸效應。在以CW He-Ne雷射為光源的實驗中，我們使入射光的傳播方向垂直光學桌面(由上往下)，以減弱對流效應 [1]。
在最初的研究中，我們並不預先對樣品加以任何的擾動，亦即我們讓樣品和環境間保持完全的熱力學(thermodynamic)平衡關係。結果我們發現兩種光源所造成的質量傳輸效應有著極其不同的形式：前者所造成者是一種大家熟悉已久的熱擴散(thermal diffusion)與質量擴散(mass diffusion)過程—準靜過程(quasistatic process)；後者所造成者是一種非準靜過程(non-quasistatic process)，至今尚未有正式的學術命名。
後來，我們利用溫控平台(Instec, HCS402-01)分別控制樣品入射面與出射面的溫度，使產生約 7 K的溫差( 7 K分別意指入射面溫度高(低)於出射面溫度7 K)，然後重複以He-Ne雷射為光源的實驗，藉以探討預先存在於樣品中的對流與擴散效應對He-Ne雷射光所促成的對流與擴散效應的影響。結果我們發現溫差存在時的光穿透率低於未加溫差時的光穿透率。另方面，我們用同一溫控平台分別控制樣品入射面與出射面的溫度使產生約+5.5 K和+7.7 K的溫差，然後重複以19 ps 脈衝為光源的實驗，藉以探討預先存在於樣品中的對流與擴散效應對19 ps 脈衝所促成的質量傳輸效應的影響。結果我們發現溫差存在時的光穿透率低於未加溫差時的光穿透率。
當過去的研究全然著眼於實驗量測時，在本論文中，我們利用流體力學三大基本定律分析過去的實驗結果，特別是解釋不同條件下實驗結果的差異。在我們的理論分析中，我們以ANSYS軟體作為輔助工具，藉以模擬外加溫度梯度所造成的流體速度流場以及溫度分佈。

關鍵字

對流對光致質量傳輸效應的影響研究 ； 質量傳輸 ； 熱擴散

並列摘要

In the past few years, we have investigated the outward solute migration induced in an ethanolic solution of chloroaluminum phthalocyanine (dubbed as ClAlPc-ethanol) at two concentrations (7104 M and 2104 M) with 632.8 nm CW He-Ne laser light and 532 nm 19 picosecond (ps) laser pulses by measuring the total transmittances. To minimize the undesired convection caused by the gravitational force in combination with the buoyant force, we made the CW laser beam propagate downward perpendicularly to the optical table (from top to bottom). As a result, we found that the transmittance increase with the degree of light exposure, for both light sources, due to the outward solute migration given the sample in full thermodynamic (thermal, mechanical and chemical) equilibrium with the surrounding before light-matter interaction.
Later on, we respectively controlled the temperatures of both the entrance and exit surfaces of the sample, using a temperature controller (Instec, HCS402-01), to yield a temperature difference 7 K between both surfaces (7 K means the temperature of the entrance surface is 7 K higher (lower) than that of the exit surface) and then resumed the CW transmittance measurement at 632.8 nm. This was to explore how the temperature gradient induced convection and thermal diffusion affect the outward solute migration behaviors. As a result, we found the degree of transmittance increase is weakened in the presence of the convection and thermal diffusion.
Similarly, we respectively controlled the temperatures of both the entrance and exit surfaces of the sample, using a temperature controller (Instec, HCS402-01), to yield temperature differences 5.5 K and 7.7 K and then reconducted the 19 ps pulse transmittance measurements. This was to explore how the temperature gradient induced convection and thermal diffusion affect the outward solute migration behaviors. As a result, we found results similar to that observed in the study with CW laser light at 632.8 nm.
Based on the three fundamental laws of fluid dynamics (conservation of mass, momentum and energy respectively), we interpret in this thesis the difference between the experimental results obtained in the absence and presence of the applied temperature gradient.

並列關鍵字

Study of Photo Induced Mass Transport in the Presence of Convection ； Mass Transport ； thermal diffusion

參考文獻

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