奈米尺寸之無機材固體如ZnO於水溶液中的懸浮分散性是奈米技術之製程中重要的其中一環，粒子的膠體製程目前已被廣泛地接受並已有許多工業上的應用，例如：塗層、奈米裝置、陶瓷、油漆、顏料以及醫藥。在固態微粒中高分子穩定的機制已在多處文獻中被學者們討論，雖然如此，但僅有少數人對於ZnO奈米粒子之膠體穩定性之研究進行探討。在此研究中，針對ZnO奈米粒子在懸浮水溶液並且隨著pH值的不同而觀察到有不同的沉澱量，實驗中為了得到穩定的ZnO奈米粒子懸浮水溶液，我們選取了PVAm作為分散劑，而高分子的分散效率則是透過沉澱澄清測試以及吸收度還原測量法來得知，接著再以表面電位量測法來說明高分子被吸引到ZnO奈米粒子表面之效率。此外，粒徑分布可以提供我們關於固體微粒分散程度之資訊。從此研究中，我們可以充分地了解到高分子於ZnO奈米粒子水溶液中的分散機制，我們更能清楚地得知影響高分子分散劑效率的主要原因。
在未添加PVAm的情況之下，ZnO奈米粒子分散於水中後會立即沉澱，這是因為粒子本身沒有挾帶足夠的電荷，導致粒子之間無法互相排斥，所以粒子之間的靜電排斥力無法克服凡得瓦爾力及其他因素，造成粒子與粒子傾向於聚集在一起。藉由PVAm的引入，ZnO奈米懸浮溶液之穩定性才顯著地提升，這可以透過僅有不多的ZnO奈米粒子沉澱來得以證實。另外溶液中由於PVAm的加入，ZnO的電性顛倒並且其表面電位值將變成較高的正電荷值，其中最穩定懸浮的溶液pH值為介於7與11之間，因此我們可以得知高分子沉澱之效率與懸浮水溶液的pH值有密切的關連性。

Dispersion of inorganic solid such as ZnO at nanoscale in aqueous suspension is one of the important issues in nanotechnological processes. The colloidal processing of particle has received much interest in many applications of industry such as coating, nanodevice, ceramic, paint, pigment, and pharmaceutical. The mechanism of polymeric stabilization on solid particles has been discussed in many publications. However, few researchers focused on colloidal stability of ZnO nanoparticles. In this work, aqueous suspensions of nano-ZnO powder with various pH values and amounts of dispersant are investigated. PVAm was selected as the dispersant for preparing a stable aqueous nano-ZnO suspension. The dispersion efficiency of polymer was studied by sedimentation settling test and reduction of absorbance measurement. The zeta potential measurement was used to elucidate the effect of polymeric addictive onto the surface of ZnO nanoparticles. In addition the surface charge measurement, the particle size distribution can give relatively real picture about dispersion state of solid particle. From this study we can gain better understanding of the dispersion mechanism of polymer to the ZnO nanoparticle. And we also know about the main factors influencing the effectiveness of polymeric dispersant.It was found that in the absence of poly (vinylamine); ZnO nanoparticles disperse in water completely precipitate instantly. Due to the lower zeta potential, the particles do not carry enough charge to repel each other. The electrostatic repulsion between particles is not sufficient to prevent nano-ZnO getting close and stick together because of the nature Van der Waals attraction and more likely to aggregate. By introduction of poly (vinylamine) into suspension, the stability of nano-ZnO increases significantly. It could be evidenced by the lower of ZnO nanopowder precipitation. In the presence of polymer, the surface charge of nano-ZnO shows the charge reversal and the value of zeta potential becomes further higher positive. The effectiveness of polymeric stabilization is closely related to the pH of suspension. It was found that the most stable suspension occurred at pH ranges 7 to 11.

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