摘要
為了提升化學、印刷、油墨等工業在先進應用領域的發展，生產具特殊功能之奈米材料變得極需開發的關鍵技術。奈米粉體自身的團聚、粉體與基材的結合力較弱等問題，限制奈米粉體在工業上的應用，也使得奈米粉體的優異特性無法充分發揮。濕式研磨即是消除奈米粉體於液相中團聚現象的方法之一。為了避免於研磨過程中發生粉體再次凝聚，須加入適當之分散劑或助劑，當助磨劑。本研究成功地以實驗型批次濕式奈米粉體研磨/分散設備，添加不同分散劑與穩定劑，在顆粒表面達成化學與物理方式之雙層吸附，獲得在水相中安定分散之氧化鐵(Fe3O4)奈米磁流體。選擇不同分散劑包括：聚丙烯酸鈉(Poly(acrylic acid sodium salt), PAANa)、聚甲基丙烯酸鈉(Poly(methacrylic acid sodium salt), PMAANa)、聚乙烯亞胺(Poly(ethyleneimine), PEI)作為分散劑與穩定劑。探討分散劑種類、添加劑量及分子量對粒徑分布、表面電位及流變性質之間的影響，找出最適合之分散條件，以得到高固含量、長時間穩定之氧化鐵奈米磁流體。利用穿透式電子顯微鏡，X-ray繞射光譜，粒徑與表面電位儀，動態光散射儀，震動樣品磁測量儀等儀器，分析其物化特性。實驗結果發現，經研磨分散後，顆粒有較高的表面電位，且粒徑分布變窄。並發現以PEI當分散劑的分散效果有限，推測其主因為其分子結構中具有大量的胺基產生強烈的氫鍵作用力，使分散劑分子無法發揮靜電穩定作用。藉由震動樣品磁測量儀在室溫下分析氧化鐵奈米流體的磁性質，發現流體具有無磁殘留量及無矯頑力之超順磁特性，飽和磁化量約為19~22 emu/g(Fe3O4)。
關鍵詞：濕式研磨、分散、氧化鐵、奈米磁流體
Abstract
To enhance the state-of-the-art chemical, paint- and printing inks industries and to meet the needs of the production of nanoparticles with specific functional properties in the future, further development of wet grinding technology is necessary. This investigation deals with a comprehensive analysis of the dispersion behavior of magnetite(Fe3O4) powders in order to determine the exact conditions for mixing and grinding dense superparamagnetic nanofluids by the novel wet beads mill. During the grinding procedure, due to the high surface energy of particles, particles tend to flocculate and not to disperse in aqueous solution. To avoid the phenomena of flocculation of particles, we can add dispersants in the grinding procedure since dispersants tend to attach on particle surface. The effects of dispersants, including Poly(acrylic acid sodium salt) (PAANa), Poly(methacrylic acid sodium salt) (PMAANa) and Poly(ethyleneimine) (PEI), on the dispersion phenomena of Fe3O4 powders in aqueous solution was investigated. The effect of polymer molecular weight on dispersion was also studied. The degree of dispersion of powders was evaluated from the measurements of average particles size and zeta potential. The size and morphology of nanoparticles were observed by Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Dynamic Light Scattering (DLS), Zeta Potential (Zeta) and Vibrating Sample Magnetometer (VSM). In all dispersed systems, the flocculation of Fe3O4 particles was decreased obviously after the grinding procedure. The dispersion phenomena of Fe3O4 particles were explained by the adsorption of the polymer on particle surface and the increase of zeta potential. The size of nanoparticles was decreased after the grinding procedure. Furthermore, the dispersion effect caused by the dispersant PEI was limited, and we speculated that the main reason for this is that its molecular structure has a large number of amine, which enable hydrogen bond forces to produce powder aggregation. Magnetic measurement revealed the fluids were superparamagnetic with a saturation of 19~22 emu/g(Fe3O4).
Keywords: Wet Beads Mill、Dispersion、Magnetite、Magnetic Nanofluids