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Micro-Nanofabracation and Wettability of Zno Superhydrophobic Structures

Author: WangLing
Tutor: LiuChangSong
School: Qingdao Technological University
Course: Mechanical Manufacturing and Automation
Keywords: ZnO superhydrophobicity low temperature liquid phase method wettability micro-nanostructure selective growth
CLC: TB383.1
Type: Master's thesis
Year: 2008
Downloads: 113
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Abstract


ZnO materials possess excellent properties such as physics,chemic,optics and electronics as an important semiconductor material.In this thesis,ZnO micro-nanostructures with hierarchical structure were fabricated with low temperature liquid phase method.Their wettabilities were mainly discussed.In addition,ZnO micro-nanostructures were selectively grown using molecule self-assembly and photolithography techniques.The results revealed that:1.Oriented ZnO rods and micro-nanostructural ZnO spheres with hierarchical structure can be obtained through adding appropriate quantities of HF solution into the reaction solutions.When the amount of HF additives was less,H~+ played a major role to the orientation of ZnO rods;when the amount of HF additives was more,F~- was one of the main factors to tailor the microstructures of ZnO micro-nanospheres.To obtain the ZnO spheres,550-700μl HF solution(1M) should be added when the concentration of reaction solution was 0.1M;350-500μl HF additive was appropriate for 0.05M reaction solution.2.Both the reaction time and temperature have an effect on the growth of ZnO micro-nanospheres.The diameter and distribution density of spheres increased when the reaction time was prolonged up to 2 hours.When the reaction temperature was below 90℃,ZnO spheres could not grow.3.The water contact angles of the ZnO spheres films and oriented ZnO rods films are 157.1°and 151.4°,respectively.Both of them have excellent wettability photo-responsive properties.The two superhydrophobic surfaces can be transformed into superhydrophilic when irradiated by vacuum ultraviolet(VUV) for about 30 minutes,and then can be recovered to superhydrophobic when placed in dark room for about 6 days.4.The surfaces of the two ZnO different micro-nanostructures have strong adhesive force to water according to our measurement.The values were 868.3μN and 946.7μN for rods and spheres.Obviously,different microstructures can result in different adhesive forces.5.After the two surfaces of the different ZnO microstructures were modified with octadecyltrimethoxysilane(ODS),the water contact angles of them increased to 170.7° and 165.4°for ZnO spheres and rods.Also both of them have small hysteretic angles and can be reversed between superhydrophilic and superhydrophobic.6.Selective growths of ZnO microstructure were realized with organic molecule self-assembly(from bottom to up) and photolithography(from top to down) techniques. By adding some additives such as HF,Ammonium fluoride,Ammonium chloride, Ammonium nitrate,the orientation of ZnO rods can be improved when they selectively grew.Wettability of materials has attracted much interest because it will bring great convenience on our daily life as well as in many industrial and agricultural processes. Selective growth of nanomaterials is a key to realizing their practical application,such as advanced electrics,photics and MEMS devices.In this thesis,the study on the fabrication wettability of ZnO micro-nanostructures with hierarchical structure will be helpful to develop ZnO-based micro-fluidic devices.

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