構形與微粒的物理及化學特性息息相關，於製藥業、粉體工業、大氣科學等相關應用皆可扮演重要的影響因子。許多研究已指出氣膠微粒的構形會因降濕與結晶過程的不同而改變。在微粒降濕風化過程相關研究中，HT-DMA (Hygroscopic Tandem Differential Mobility Analyzer)為一常用之實驗系統，然而此系統無法確切得知微粒的構形與密度。因此本研究利用APM (Aerosol Particle Mass Analyzer，Kanomax 3601)量測氣膠微粒的質量分佈，結合HT-DMA量測微粒之電移動度粒徑，解析經歷不同降濕過程的無機鹽氣膠微粒之有效密度及動力形狀因子，藉以表徵及量化微粒之構形的變化。 研究結果顯示，液態無機鹽氣膠之降濕過程中，溶劑的揮發與溶質擴散之交互關係主導著乾燥後微粒的構形。於極度乾燥環境時，溶劑快速的揮發，傾向使無機鹽微粒呈現不規則形狀；反之，慢速乾燥利於溶質擴散堆積，易形成球狀結構。然而液態氣膠的乾燥為一極為複雜之過程，溶質之種類 ( 氯化鈉與硫酸銨 )、濃度，甚至氣膠粒徑之不同皆可能影響研究結論。因此，本研究結合擴散方程式與柯勒理論，模擬液珠的乾燥歷程；並應用無因次參數-佩雷數(Peclet number)量化溶劑揮發與溶質擴散之競爭行為，揭示微粒於不同參數設置之生成機制。 此外，為探究不同乾燥條件所形成之奈米無機鹽微粒的雲凝結核活化能力，本研究亦結合HT-DMA與CCNC (Cloud Condensation Nuclei Counter, DMT 100)，量測經歷不同乾燥速率之無機鹽氣膠微粒的雲凝結核活化率。結果更指出，微粒之活化率可隨著物質、乾燥條件而有不同之變化趨勢。 ;Morphology of aerosol particles are related to their physical and chemical properties which may play an important role in pharmaceuticals, powder industry, and atmospheric science. Rich literature has shown dried particle shape depend on the dehydration condition and crystallization process. Hygroscopic tandem differential mobility analyzers (HT-DMA) are generally used to study the hygroscopic behavior of aerosol particles, however, it cannot provide the information about particle morphology and density. Therefore, in this study, in addition to a hygroscopic tandem differential mobility analyzer (HT-DMA) system, a hygroscopic coupled tandem DMA and aerosol particle mass analyzer (APM) were integrated. The former size change and latter mass was. The mass and diameter changes were used to derive the particle effective density and calculated dynamic shape factor which characterize particle shape. The experimental results indicated that the solvent evaporation and solute diffusion dominated the morphology of the dried particles in dehydration process. In extreme dry condition, the particle tended to form in irregular shape due to the fast remove of solvent. In contrast, there was more sufficient time for the solute diffusion in slow drying and the particle formed in spherical shape. However, drying and crystallization of aqueous aerosol particle were complicated process. Numerous factors such as materials, solute concentration, and particle size could affect the dried particle morphology. Thus, in order to investigate the dehydration process of aerosol particle, this study combined the diffusion equation and Köhler theory. In addition, quantifying the competitive relationship between solvent evaporation and solute diffusion by the dimensionless parameter : Peclet number and revealing the mechanism of particle formation in different experimental parameters setup. To understand the ability of nanoparticles to activate as cloud condensation nuclei in different drying condition. This study also conducted the HT-DMA-CCNC measurement and showed the activated fraction could vary in different experimental setup.
