氧化鋅奈米結晶之製備與分散; The synthesis and dispersion of ZnO nano-crystals

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Title:	氧化鋅奈米結晶之製備與分散;The synthesis and dispersion of ZnO nano-crystals
Authors:	徐志宗;Chih-Tsung Hsu
Contributors:	化學工程與材料工程研究所
Keywords:	氧化鋅;分散;dispersion;ZnO
Date:	2004-07-12
Issue Date:	2009-09-21 12:23:21 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本研究的目的為製作可分散之氧化鋅奈米結晶。我們在控制酸鹼值下，將溶於乙二醇之氯化鋅及氫氧化鈉透明溶液進行中和，形成白色乳液。由於氧化鋅在酸與鹼中溶解度都很高，故中和時之酸鹼值必須在8到10之間。假若酸鹼度控制適當，只要將中和液直接加熱即可得到分散在乙二醇中之氧化鋅奈米結晶透明分散液。在大於10wt%濃度下，分散液之可見光(600nm)穿透度大於90%，而波長小於370nm之光線則會被吸收。由吸收起始波長及粉體XRD峰寬可計算出之結晶大小約5~6nm。但實際之聚集粒子的大小則因加熱溫度與時間的不同會聚集成十到數十奈米不等。若將中和液過濾後再將濾餅加熱也可得到氧化鋅奈米結晶的分散液，不但濃度高(約27wt%)，鹽類離子的含量也較少，但粒子聚集的情況較嚴重，即使再分散到乙二醇中最多只能呈現半透明的狀態。分散液中的氧化鋅可以利用有機溶劑將凝絮、沉降、清洗後即可得到氧化鋅結晶的粉體。經過X光繞射分析，可確定產物為氧化鋅Zincite結晶。從結晶峰的半高寬估計其結晶大小也是5~6nm之間。但是因為形成粉體時未作表面保護，所以已經聚集，無法再回復成為透明分散液。 The objective of this research is to synthesis ZnO nano-crystals and to disperse it in an appropriate solvent. ZnO nanocrystals were successfully prepared by neutralizing ethylene glycol solution of Zinc chloride and sodium hydroxide under controlled the pH. A white colloidal was produced after neutralization, which turned to a transparent sol upon heating at 80oC. At a ZnO concentration of 2.5wt%, the optical transmittance of the sol can be higher than 90%. The ZnO in the transparent sol are nanocrystals, whose domain size is only about 5~6 nm calculated from the onset of UV absorption as well as powder XRD peak width. DLS analysis of the transparent sol indicated colloidal particles of about 10nm. The size and of the particles became larger as the heating temperature and time are increased. To remove the NaCl salt produced during the neutralization, the precipitation was filtered and washed. Upon heating, the filtered cake also transformed into ZnO nanocrystals. However, only a translucent sol (at 27wt%) could be obtained by this method, as the aggregation of the nanocrystals was more severe due to the high concentration. The produced ZnO nanocrystals could be collected as solid powder, by the flocculation under appropriate organic solvents. XRD analysis of the so obtained powder suggested that the ZnO formed were pure zincite crystalline about 5~6 nm domain size. The salts impurity can be further removed by washing with alcohol. However, since no surface capping was attempted, the powder thus obtained could no longer be dispersed in solvent.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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