Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/3439
標題: Study on synthesize and properties of nanosized cobalt particles
奈米鈷粒子合成與性質研究
作者: 蔡蔚珍
Tsai, Wei-Chen
關鍵字: chemical reduction method;化學還原法;cobalt nano-particle;synthesize;magnetic;oxidation;奈米鈷粒子;合成;磁性;氧化
出版社: 化學工程學系
摘要: 
二十一世紀,奈米材料將成為材料科學領域的一個大放異彩之「明星」,在新材料、資訊、光電等各個技術範籌發揮舉足輕重的作用。神通廣大的奈米材料,及其誘人的應用前景使人們對這一嶄新的材料積極努力探索,並擴大其應用,使它為人類帶來更多的利益。
奈米磁性材料的應用相當廣範,包括磁流體、磁記錄、磁存儲器、磁光元件、磁探測器、磁致冷材料、吸波材料、細胞分離、智慧型藥物等。為此,本論文應用化學還原法以金屬離子、還原劑、及以水為溶液來合成製備粒徑均一性佳的奈米鈷粒子。首先,以氯化鈷為先驅物、聯胺為還原劑及氯化鈀為成核劑,並加入高分子型分散劑PVP,形成奈米鈷粒子;然後以PAA作為保護劑及終止反應,進而獲得穩定性良好且沒有副產物的奈米鈷粒子分散液。
從以上實驗發現:PAA分子量愈大則有利於合成後鈷粒子分散液的穩定性; PVP分子量太大則不利於奈米粒子的合成;及合成反應溫度愈高則反應速率愈快,此造成反應時間短才不會使鈷粒子的粒徑變大。另外,經由雷射粒徑分析儀及HRTEM測量得知所合成的鈷粒子其最小平均粒徑為11.8nm,且由XRD分析結果顯示其結構為面心立方體。
此外,分別以電位儀及超導量子干涉磁量儀測試得知:膠體鈷粒子的表面電位會隨著pH值的變小而下降;及平均粒徑為11.8nm鈷粒子的磁飽磁化量為±148emu/g,而在氧化過程鈷粒子會由四氧化三鈷隨著溫度上升而轉變成氧化鈷使其磁性逐漸消失。
以上研究成果可應用於下列的開發:
(1)利用奈米鈷粒子製備高性能之吸波材料;及
(2)利用奈米鈷粒子自發排列成二維奈微米結構製作量子磁碟。

The nano-materials that can yield outstanding brilliant performance have become the“Super Star” in materials science. They have prove to have decisive influence in information and photoelectric technology. Nano-materials with their alluring applications attract us to explore them in order to widen their uses and bring immense benefit to our life.
The magnetic nano-materials equip considerably extensive applications, including magnetic fluid, magnetic note, magnetic recording, magnetic light component, magnetic probe, magnetic refrigeration material, wave absorption material, cell separate, and wisdom mould medicine, etc. This thesis is to synthesize uniform cobalt nano-particles by chemical reduction method at the presence of metal ions, reduction agent, and water that serves as solvent. First, cobaltous chloride(CoCl2․6H2O), hyrazine hydrate(N2H5OH), and palladium chloride(PbCl2) were taken to serve as precursor, reduction agent, and nucleus agent, respectively, and charged surfactant of poly-vinyl pyrrolidone(PVP) was added to form cobalt nano-particles. Afterward, poly-acrylic acid(PAA) was used as the dispersant and terminator of reaction to reach stabilization and obtain cobalt nano-particle dispersion solution without other accompanied product.
The following phenomena were observed in this research. The higher molecular weight of PAA was the more stability of cobalt particles synthesis we obtained. However, PVP with higher molecular weight was unfavorable for the synthesis of nano-particles. In order to obtain the cobalt nano-particles with smaller size, the shorter reaction time was preferred. Therefore, higher reaction temperature was adopted to accelerate the synthesis. As a result, cobalt nano-particles with average diameter of 11.8nm, measured by laser particle diameter analyzer and high resolution transmission electron microscopy(HR-TEM), can be obtained. The nano-particles were characterized as face-centered cubic structure by using X-ray diffraction.
Zeta potential apparatus and superconducting quantum interference device magnetometry were also utilized to analyze the electric and magnetic force of cobalt nano-particles. It was found that the surface potential of colloid cobalt is in the solution decreased with the decreasing pH value. The saturation magnetization(Ms) value of cobalt nano with average size of 11.8 nm was about ±148emu/g. After cobalt oxidating process with higher temperature, nano cobalt was transformed to CoO from Co3O4 and lost their magnetic property.
The research result can be applied in the following exploitation:
(1) develop high performance of wave's absorption material with high performance.
(2) self-assemble nano cobalt as two-dimensional nano-structure to fabricate quantum disk.
URI: http://hdl.handle.net/11455/3439
Appears in Collections:化學工程學系所

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