| 姓名 |
陳可青(Ke-Ching Chen)
查詢紙本館藏 |
畢業系所 |
環境工程研究所 |
| 論文名稱 |
以HTDMA與HT DMA-APM系統探討無機鹽奈米微粒的吸溼行為
(Investigating the Hygroscopic Behavior of Inorganic Nanoparticles Using HTDMA and HT DMA-APM System)
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| 相關論文 | |
| 檔案 |
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| 摘要(中) |
依據大氣研究調查發現，粒徑界於8-100 nm的氣膠微粒廣泛存在於大氣對流層中，且多屬於凝結核之範圍，其中包含無機鹽類氣膠微粒。而這些無機鹽類微粒大多具有吸溼性，其與環境水汽間的異質成核反應對於大氣中的雲凝結核濃度、地球的輻射收支、氣膠的光學性質、甚至是人體健康皆會造成顯著的影響。
隨著相對溼度上升，無機鹽氣膠微粒(NaCl、(NH4)2SO4與混合微粒)的表面會有水膜包覆，當微粒達到潮解相對溼度(DRH)時，則會造成固液態之間的相轉變。而Russell於2002的文獻中以理論模擬之方法，提出奈米微粒DRH因受粒徑效應(表面自由能)影響會有兩個完全相反的結果，其最主要之差異來自於潮解前微粒表面是否有水膜的包覆。而本研究將針對不同粒徑、構形及化學組成的無機鹽氣膠微粒，觀察其在潮解前與水汽的交互作用關係，以探討水膜對於微粒吸溼行為的改變與影響。
截至目前為止，許多文獻也提出微粒在DRH前會受水膜之包覆而使結構更扎實且趨近於圓球狀。然而卻僅有少數研究以實驗量測之方法，透過Nano-DMA觀察到在潮解前微粒粒徑大小波動之情形。有鑑於此，本研究分別以HTDMA與APM系統即時量測微粒在不同相對溼度條件下，微粒因吸溼增長所造成的粒徑與質量變化。結合HTDMA與APM系統(合稱HT DMA-APM)所得粒徑與質量兩者數據，即可推算出微粒在潮解前因水膜包覆而造成的密度變化。本研究依據HT DMA-APM量測結果發現100 nm氯化鈉微粒在潮解前(RH=73%)約受7-8個水分子厚度的水膜包覆。水膜包覆之現象即可能改變微粒固、液相表面張力的比值，進而對奈米微粒表面自由能造成影響，以此解釋為何微粒奈米DRH會隨粒徑下降而上升。除此之外，本研究中也以半理論半經驗的多項式函數預測不同NaCl/(NH4)2SO4比例條件的內混微粒DRH，所得結果與實驗結果吻合。而有關於σc/σaq比值改變而影響微粒DRH的粒徑效應關係亦於本論文中進行探討。
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| 摘要(英) |
Particles of sizes between 8 and 100 nm in diameter are ubiquitous in the lower troposphere. The way in which these particles including the inorganic salt take up water is critical in determining their role in forming haze and clouds as well as in serving as sites for heterogeneous chemical reactions [1]. This hygroscopic growth plays a significant role in atmospheric phenomena such as cloud-droplet nucleation, earth’s radiation budget, optical properties and human health assessment.
As relative humidity increases, water would be adsorbed onto the surface of inorganic salt particles, such as pure NaCl, (NH4)2SO4 aerosols, or thier externally and internally mixed aerosols. These inorganic particles would initiate a transition from the crystalline to aqueous phase (deliquescence) at the deliquescence relative humidity (DRH). However, the current two physical models proposed in the literatures predicted opposite trend of the size effect on DRH (because of different σc/σaq ratio) [2]. Russell and Ming attributed the inconsistent predictions to the different assumptions of dry particle surface and of surface coated with a few monolayers of water molecules prior to deliquescence [1]. Therefore, for studying the hygroscopic behavior of inorganic salt particles, it is important to investigate the interactions between water and particles at or prior to DRH as well as the effects of particle size, morphology and chemical composition etc..
Many studies have claimed that the inorganic particles would start to be more compacted and spherical due to water adsorbed onto the particle surface, i.e. forming water film, at or prior to DRH. However, only few have experimentally observed the phenomena during deliquescence transition using Nano-DMA measurements [3]. Accordingly, both the hygroscopic tandem differential mobility analyzer (HTDMA, Electrostatic Classifier, TSI 3080, with DMA, TSI 3081/3085) system and the aerosol particle mass analyzer (APM, Kanomax 3601) were applied to investigate the change of particle size and mass in real time. Combining the HTDMA and APM measurements, the particle density changes caused by forming water film during deliquescence transition was observed. The measurements reveals approximately 7 to 8 monolayers of water momlecules on the surface of 100 nm crystalline sodium chloride at relative humidity 73%. This phenomenon may changes the values of σc/σaq as well as surface energy, which provides the explanation why the DRH of the nanoparticles increases as particle size decreases. In addition, we developed a semi-empirical model for predicting the CDRH of internally mixing particles at different NaCl/(NH4)2SO4 ratios, which was also validated through the experimental results. The relationship between the size effects on DRH and σc/σaq was also discussed in the thesis.
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| 關鍵字(中) |
★ 奈米微粒
★ 吸溼
★ 無機鹽 |
關鍵字(英) |
★ nanoparticles
★ hygroscopic
★ inorganic |
| 論文目次 |
致謝 III
摘要 V
Abstract III
目錄 VII
圖目錄 XI
表目錄 XIV
符號說明 XVI
一、前言 2
1.1 研究源起 2
1.2 研究目的 2
1.3 研究方法與內容 3
二、文獻回顧 6
2.1 異相核凝結 6
2.1.1 凝結核的來源與分類 6
2.2 氣膠微粒與環境水氣間的交互作用(氣膠微粒的吸溼特性) 9
2.3 氣膠微粒的吸溼參數 10
2.3.1 潮解相對溼度(DRH, Deliquescence Relative Humidity) 10
2.3.2 微粒吸溼生長因子(GF, Growth Factor) 11
2.3.3 吸溼性參數Kappa(κ) 11
2.4 氣膠微粒吸溼影響因子 13
2.4.1 氣膠微粒構形(Morphology) 14
2.4.2 氣膠微粒的大小(Size)與化學組成(Chemical composition) 15
2.4.2.1 凱爾文效應(Kelvin effect) 15
2.4.2.2 溶質效應(Raoult′s Law) 16
2.5 無機混合性氣膠微粒的吸溼特性 18
2.6 氣膠微粒吸溼行為對人體健康與環境之衝擊 19
2.6.1 大氣能見度(氣膠光學性質) 19
2.6.2 氣膠微粒的沉降機制 20
2.6.3 氣候變遷 21
2.6.4 人體健康 22
2.7 氣膠微粒吸溼之量測方法 23
2.7.1 秤重法 23
2.7.2 EDB(ElectroDynamic Balance) 24
2.7.3 HTDMA(Hygroscopicity Tandem Differential Mobility Analyzer System) 25
三、研究方法與實驗設備 29
3.1 研究流程 29
3.2 各項變因控制及測定需求 31
3.3 氣膠微粒吸溼量測系統介紹 32
3.3.1 氣膠微粒吸溼量測系統- HTDMA 32
3.3.2 氣膠微粒吸溼量測系統- HT DMA-APM 35
3.4 混合性氣膠微粒產生系統 36
3.4.1 外部混合微粒產生系統 37
3.4.1.1 定量輸出霧化器原理(Constant Output Atomizer) 38
3.4.2 內部混合微粒產生系統 39
3.4.2.1 定量輸出霧化器(Constant Output Atomizer) 41
3.4.2.2 高溫爐(Furnace) 41
3.4.2.3 定量輸出霧化器-高溫爐(Constant Output Atomizer - Furnace) 43
3.4.2.4 電噴霧(Electrospray) 43
3.5 氣膠微粒收樣系統-構形確認 45
3.6 氣膠微粒表面積量測-即時微粒構形監測 46
3.7 氣膠微粒收樣及檢測分析系統-化學組成確認 48
3.8 物質種類及基本性質 49
四、無機鹽氣膠微粒吸溼相關理論介紹 50
4.1 潮解相對溼度(Deliquescence Relative Humidity, DRH) 50
4.2 粒徑效應(Size effect) 52
4.3 微粒吸溼生長因子 55
4.4 內部混合無機鹽氣膠微粒之潮解相對溼度(CDRH) [33] 56
4.5 κv- Köhler theory 57
4.6 質量型吸溼性參數κm 59
五、結果與討論 61
5.1 氣膠微粒吸溼量測系統驗證 61
5.1.1 HTDMA實驗系統驗證 61
5.1.1.1 氯化鈉(NaCl)微粒吸溼量測結果 62
5.1.1.2 硫酸銨((NH4)2SO4))微粒吸溼量測結果 64
5.1.2 APM實驗系統驗證 65
5.2 粒徑對於氣膠微粒潮解相對溼度的影響 66
5.3 不同產生源對於氣膠微粒潮解相對溼度的影響 69
5.4 外部混合氣膠微粒的吸溼行為 74
5.4.1 外部混合氣膠微粒濃度比例 74
5.4.2 外部混合氣膠微粒吸溼量測結果 77
5.4.3 粒徑對外部混合氣膠微粒吸溼行為的影響 81
5.5 內部混合氣膠微粒的吸溼行為 83
5.5.1 內部混合氣膠微粒化學組成 83
5.5.2 內部混合氣膠微粒吸溼量測結果 84
5.5.3 不同產生源對內混微粒吸溼行為的影響 91
5.6 微粒粒徑吸溼成長因子(GFD)之預測 96
5.6.1 潮解相對溼度下的微粒吸溼成長因子 96
5.6.2 純物質微粒的κv值 97
5.6.3 內混微粒的κv值 99
5.6.4 粒徑對於微粒κv值的影響 100
5.7 微粒吸溼之質量分析 102
5.7.1 微粒在潮解前後的質量變化 104
5.7.2 HT DMA-APM系統量測結果 106
5.7.3 純物質微粒的κm值 108
5.7.4 內混微粒的κm值 110
5.7.5 粒徑對於微粒κm值的影響 111
5.7.6 κv與κm的比較 113
6.1 結論 115
6.2 建議與未來展望 117
參考文獻 120
委員意見回覆 133
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| 參考文獻 |
1. Russell, L.M. and Y. Ming, Deliquescence of small particles. The Journal of chemical physics, 2002. 116(1): p. 311-321.
2. Biskos, G., et al., Nanosize effect on the deliquescence and the efflorescence of sodium chloride particles. Aerosol Science and Technology, 2006. 40(2): p. 97-106.
3. Romakkaniemi, S., et al., Adsorption of water on 8-15 nm NaCl and (NH4) 2SO4 aerosols measured using an ultrafine tandem differential mobility analyzer. The Journal of Physical Chemistry A, 2001. 105(35): p. 8183-8188.
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| 指導教授 |
蕭大智(Ta-Chih Hsiao)
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審核日期 |
2014-12-1 |
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