改善奈米二氧化鈦在水相中的分散性

Improvement of the dispersions of nanosized titanium dioxide in aqueous solution

劉怡彣(Yi-Wen Liu)

指導教授 ： 吳劍侯

國立清華大學/原子科學院/生醫工程與環境科學系/碩士(2008年)

摘要

本研究主要探討不同分散方法(包括超音波震盪法及紫外光照促進分散)對於奈米二氧化鈦懸浮液分散性質之影響。實驗中利用動態光散射儀(DLS)量測粒徑與界面電位變化及紫外光可見光光譜儀測定懸浮液吸光值變化，以進一步討論二氧化鈦在懸浮液中之分散性及安定性。探討實驗變數包括：二氧化鈦種類、光照時間、光照方式、超音波震盪時間、貯存時間等。比較未光照處理及光照處理分析結果，紫外光照能促進二氧化鈦懸浮液的分散性及安定性；結果顯示紫外光照能提升膠體的界面電位，促使懸浮液粒徑維持在200 nm以下，而且其UV-Vis吸光值也隨光照時間增加，此外，經紫外光照之樣品放置約一個月仍有不錯的懸浮性。在特性量測上，以BET、TPR、IR、XPS等儀器之分析結果與文獻對照，可知紫外光照後二氧化鈦使面OH官能基數量增加，使二氧化鈦與水溶液的濕潤性增加，促進二氧化鈦在懸浮液中的分散性及安定性。

關鍵字

二氧化鈦 ； 超親水性 ； 分散

並列摘要

Understanding the colloidal properties of nanometer-sized particles is essential to successful processing of manufactured nanophase materials. The small length scale at which particles interact presents new and unique challenges. Dispersion and stability can be difficult goals at the nanoscale. Nanoparticles always tend to agglomerate, decreasing the surface-to-volume ratio and, as a result, the free energy of the system. The force that drives the agglomeration process is the van der Waals attraction. The forces that may prevent the agglomeration and increase colloidal stability are the electrostatic and steric repulsions between the surfaces. Suspensions with strong repulsive forces between particles are generally well dispersed and stable.
A variety of techniques have been employed to increase the stability of dispersions. Simple mechanical stirring is used to break up soft agglomeration. Sonication can be used as a temporary measure to break up agglomerates, especially if they are large and the particles are weakly bonded. In a simple liquid environment, interparticle forces can be adjusted or tailored by using a suitable dispersion media, adjusting solution pH and ionic concentration, or by using surfactants or polymers that adsorb on particle surfaces. These different approaches to dispersion stabilizations can work quite well in many circumstances; however, their use is often limited.
We focused on studies of the colloidal behaviors of titanium dioxide (TiO2) nanoparticles in aqueous systems, which were analyzed by dynamic light scattering (DLS) and UV- vis spectrometry. In this study, types of titanium dioxide and effects of ultra-sonication, irradiation time, and storage time were investigated systematically. It was found that ultrasonication can help to break up agglomeration. Also, upon pretreatment of UV irradiation, the dispersion and stability of TiO2 nanoparticles in deioned water was greatly enhance by increasing the zeta potential. Furthermore, the titanium dioxide were characterized by Brunauer-Emmett-Teller (BET), X-Ray Powder Diffractometer(XRPD), temperature programmed reduction (TPR), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS). It was found that after UV irradiation, the amount of hydroxyl group increased, which induced hydrophilicity and improved the dispersion and stability of titanium dioxide.

並列關鍵字

Titanium dioxide ； Super hydrophilicity ； Dispersion

參考文獻

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