鋯金屬鹽在逆微乳膠中水解聚合反應之研究:氧化鋯奈米粒子之合成

Hydrolytic polymerization of zirconium salt solution in a reverse microemulsion: synthesis of zirconia nanoparticles

蕭博元(Bor-Yuan Hsiao)

指導教授 ： 戴怡德

國立臺灣大學/工學院/化學工程學研究所/博士(2004年)

https://doi.org/10.6342/NTU.2004.01248

摘要

摘要

本研究以water/CTAB/hexanol逆微乳膠系統配合鋯鹽溶液的水解縮合反應以合成奈米級球形氧化鋯粉體。首先進行鋯鹽溶液於逆微乳膠中的快速水解縮合反應(即逆微乳膠沈澱反應)，係將含有硝酸氧鋯與氨水的逆微乳膠在室溫下相互混合反應，形成膠狀物沈澱後再經清洗、乾燥、煆燒等步驟即可得為奈米氧化鋯粉體。由於添加氨水促使水解縮合反應迅速發生，因此兩種逆微乳膠混合後即快速的產生膠狀物沈澱，此沈澱物經由電子顯微鏡觀察發現其中包括了5~15nm的氧化鋯先驅體與界面活性劑。藉由熱分析、X光繞射等分析可知，本研究之先驅體至少需600℃煆燒溫度方可將界面活性劑等雜質燒除，而且煆燒後的氧化鋯粉體以正方晶相為主摻雜少陰蚺韐僧菕A其正方晶相比例隨逆微乳膠之水/界比(Rw)增加而下降。接著本研究以逆微乳膠沈澱反應合成釔安定化氧化鋯，發現釔安定化氧化鋯在650至1050℃的煆燒範圍內有效的控制氧化鋯晶相為正方晶相，其正方晶之結晶粒徑由16nm成長至43nm。接下來本研究將矽氨烷接枝在釔安定化氧化鋯表面，發現矽氨烷接枝煆燒後會形成Zr-O-Si的鍵結，其矽含量以EPMA技術測得僅佔1 mol%。當煆燒溫度低於1000℃，矽氨烷接枝處理可以有效抑制晶體成長保持微小晶粒與保持高比表面積。
第二部分是逆微乳膠中慢速水解縮合反應（係將含有硝酸氧鋯之逆微乳膠溶液加熱陳化促使水解縮合反應），並探討溫度對逆微乳膠穩定性的影響，反應溫度、反應時間等實驗變數對氧化鋯粉體的影響。我們發現逆微乳膠中慢速水解縮合反應，僅需60℃與數小時的反應時間即可合成球形且分散良好之水合氧化鋯奈米粒子，較傳統水解反應時間短且反應溫度也大幅降低。氧化鋯奈米粒子的粒徑與外型受反應條件的影響很大，在較低的水/界比與水/油比條件下以60℃反應可得粒徑均勻且球形之奈米級氧化鋯先驅體，此先驅體經煆燒後亦為正方晶相氧化鋯。我們發現以逆微乳膠慢速水解縮合法製備的氧化鋯粉體經煆燒後其粒徑成長快速，同時比表面積下降速度很快，由650℃的79m2/g迅速降至850℃的1.1m2/g。

關鍵字

氧化鋯 ； 水解聚合 ； 奈米粒子 ； 逆微乳膠

並列摘要

Abstract

The aim of this work is to synthesize zirconia nanoparticles using hydrolysis of zirconium salt solution in the water/CTAB/hexanol reverse microemulsion. The first part of this study is to prepare zirconia nanoparticles by means of the rapid hydrolysis reaction at room temperature caused by mixing two solutions of reverse microemulsion, one containing Zr4+ aqueous droplets and the other aqueous ammonia droplets with the same water/surfactant ratio. The resulting precipitate was recovered and characterized by using an electron microscopy (TEM and SEM). Thermal decomposition and phase transformation of the samples were characterized using thermogravimetric and differential thermal analysis (TGA/DTA), and X-ray powder diffraction (XRD) techniques. It is concluded that the precursors of zirconia about 5~15nm in size was successfully synthesized and was well dispersed in the surfactant matrix. The calcination temperature was at least 600℃ to burn out impurities and then, the precursor particles crystallized to form tetragonal phase zirconia. The resulting zirconia powder contained a higher fraction of tetragonal zirconia than the direct precipitation product did when calcination was conducted under a temperature range of 500 to 1000℃. The fraction of tetragonal zirconia decreased as the water/surfactant molar ratio (Rw) increased in this experiment.
The yttria-stabilized-zirconia (YSZ) precursors were also prepared by the rapid hydrolysis in a reverse microemulsion. The crystal structure of YSZ powder was pure tetragonal and the tetragonal crystallite sized increased sharply from 16nm to 43nm in the calcination temperatures ranging from 650 to 1050℃. Finally, the YSZ precursors were treated with hexamethyldisilazane (HMDS) so that the siloxyl groups grafted on the surface of YSZ precursors formed Zr-O-Si bonds after calcinations. The EPMA results showed that the amount of doped Si was about 1 mole%. The crystallite sizes of the HMDS-treated YSZ powder were kept smaller and rather uniform by adsorbing the siloxyl groups during calcination and thus the surface area remained high, when calcination was conducted below 1000℃.
In the second part of this study, nanosized spherical zirconia precursors were also successfully produced using slow hydrolysis method conducted by heating the zirconyl nitrate solution in the water/CTAB/hexanol microemulsion. The hydrous-zirconia particles could be synthesized at 60℃ in a few hours, which is lower and shorter than the reaction temperatures and reaction time reported by other hydrolysis processes. In addition, the particles size and shape is greatly influenced by the reaction temperature and compositions of the reverse microemulsion. For reaction temperature at 60℃ nanosized precursor with uniform size and spherical shape were produced at lower water/surfactant ratio or water/oil ratio. The resulting particles are amorphous, and they transformed into tetragonal phase after calcination. In the calcination temperatures between 650 and 850℃，the crystallite sizes greatly increased and the specific surface area reduced quickly from 79m2/g to 1.1m2/g.

並列關鍵字

hydrolysis and polymerization ； reverse microemulsion ； nanoparticles ； zirconia

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