本文關鍵詞：改性對硅膠納米通道內流體傳輸特性影響研究　出處：《中南林業(yè)科技大學》2017年碩士論文　論文類型：學位論文

  更多相關文章： 硅膠 改性 納米通道 表面效應 納米流動

【摘要】：微/納機電系統(tǒng)是微/納米技術的重要分支,材料在微/納機電系統(tǒng)中的性質和行為相對宏觀尺度會發(fā)生不可忽視的變化。硅膠微粒內部空腔與微粒表面具有納米級的輸送通道,而改性后其通道壁面的化學組成也發(fā)生本質上的改變,改性后硅膠納米通道所具有的“表面效應”會對流體水在納米通道中的傳輸行為產(chǎn)生重大影響。因此,研究改性對硅膠納米通道內流體傳輸特性的影響,對硅膠改性及其在微納機電系統(tǒng)中的應用具有一定的理論指導意義。本文基于分子動力學方法建立了納米流動模型,對流體水在硅膠納米通道內的密度、速度、偶極取向分布進行模擬計算。分析了流體水與壁面間氫鍵的形成,并對流體水在納米通道內的擴散行為和粘度性質進行了研究。首先,研究了改性對硅膠納米通道潤濕性的影響規(guī)律。計算了納米通道內流體水的密度、速度以及電偶極矩取向分布,發(fā)現(xiàn)羥基化通道壁面呈強親水性,而改性后硅烷化通道壁呈強疏水性,流體滑移長度與改性層烷基鏈長呈線性關系;羥基化納米通道使得流體水偶極取向較為有序,與水分子間存在較強的氫鍵作用,而改性后硅烷化通道壁面使得流體水取向角變得相對無序,與水分子無氫鍵作用。其次,研究了改性對硅膠納米通道內流體擴散行為的影響。計算了流體水的均方位移與擴散系數(shù),發(fā)現(xiàn)流體水在羥基化硅膠納米通道內的擴散系數(shù)遠小于在硅烷化納米通道內的擴散系數(shù),但都要小于體相水,改性后硅膠納米通道壁面特征的“表面效應”對流體水的傳輸占主導作用。進一步研究了納米通道內流體水的局部擴散系數(shù),結果表明納米通道內流體水的局部擴散系數(shù)與其到壁面的距離相關。最后,研究了改性對硅膠納米通道內流體粘度性質的影響。計算了流體水的粘度值,發(fā)現(xiàn)在羥基化硅膠納米通道內流體的粘度值幾乎為體相水的11倍;而改性后硅烷化納米通道內流體水的粘度值僅為羥基化納米通道內流體水粘度的1/5左右,約為體相水的2倍,并隨著改性程度的增強,流體水在硅烷化納米通道內的粘度值逐漸減小;進一步探討了納米通道內流體局部粘度的分布狀況,結果顯示納米通道內流體水的局部粘度值與其到壁面的距離相關。
[Abstract]:Micro / nano electromechanical system is an important branch of micro / nano technology. The properties and behaviors of materials in micro / nano electromechanical systems can not be ignored on a macro scale. There are nano-scale transport channels in the cavity and surface of silica gel particles. The chemical composition of the modified channel wall also changed substantially. The "surface effect" of the modified silica gel nanochannel will have a significant impact on the transport behavior of fluid water in the nanochannel. The effect of modification on the fluid transport characteristics in silica gel nanochannels was studied. It has a certain theoretical significance for the modification of silica gel and its application in micro / nano electromechanical system. Based on the molecular dynamics method, a nano flow model is established, which can be used to determine the density and velocity of water in silica gel nanochannels. The dipole orientation distribution was simulated and the formation of hydrogen bond between fluid water and wall was analyzed. The diffusion behavior and viscosity properties of fluid water in nanochannels were studied. The effect of modification on the wettability of silica gel nanochannels was studied. The density, velocity and electric dipole moment orientation distribution of fluid water in the nanochannels were calculated, and it was found that the hydroxy channel wall was strongly hydrophilic. The hydrophobicity of the modified silanized channel wall and the linear relationship between the fluid slip length and the alkyl chain length of the modified layer were observed. The hydroxy nanochannels make the water dipole orientation of the fluid more orderly and have strong hydrogen bond with the water molecules, while the wall surface of the modified silanized channel makes the water orientation angle of the fluid become relatively disordered. Secondly, the effect of modification on the diffusion behavior of silica gel nanochannels was studied. The mean square displacement and diffusion coefficient of fluid water were calculated. It is found that the diffusion coefficient of water in hydroxylated silica gel nanochannels is much smaller than that in silanized nanochannels, but is smaller than that of bulk phase water. The "surface effect" of the wall characteristics of modified silica gel nanochannels plays a dominant role in the transport of fluid water. The local diffusion coefficient of fluid water in nanochannels is further studied. The results show that the local diffusion coefficient of fluid water in nanochannels is related to the distance from the surface to the wall. Finally, the influence of modification on the viscosity properties of silica gel nanochannels is studied, and the viscosity value of fluid water is calculated. It is found that the viscosity of the hydroxy silica gel nanochannels is almost 11 times that of the bulk water. The viscosity of water in the modified silanized nanochannels was only about 1/5 of that in the hydroxylated nanochannels, about 2 times that of the bulk water, and with the increase of the degree of modification. The viscosity of water decreases gradually in silanized nanochannels. The distribution of the local viscosity of the fluid in the nanochannel is further discussed. The results show that the local viscosity of the fluid water in the nanochannel is related to the distance from the water to the wall.
【學位授予單位】：中南林業(yè)科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TH-39;TB383.1

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