| 摘要: | 高分散性碳粒子有許多可能的應用，譬如顏料、塑膠填充劑、高效電容器、電池之高效電極、甚至層析管的填充劑等。這些應用都需要有粒徑均一且高分散性的碳粒子，而且還要能控制其孔隙大小與分佈、表面性質。假若可以製作出100 nm左右的均勻碳球，最大的用途可能是作為顏料。如果可以做到50 nm左右的均勻碳粒子，還可能可以作為壓電、潤滑、導電等用途。譬如美國CleanTechnology Inc.公司發展出一種稱為Carbon NanoSphere Chain的材料，可以作為感測器或者潤滑劑用途。而美國HeadWaters Inc. 最近與日本Sumitomo Chemical合作生產一種奈米粒子形碳，主要預備添加到塑膠中以利用其導電性。當然，對於添加料，圓球形狀、高分散性、以及均勻性都是很重要的性質。 以水熱法將糖水溶液炭化製作圓球型粒子近年屢見諸文獻，但是其尺寸多半於微米級範圍。因此本篇論文的研究目的，即是在高製程效率的前提下，包括產量、產率、製作方法，設法以核種添加的方式，製備出可控制尺寸，並降低至小於60 nm且均勻分散之碳球。 我們使用葡萄糖作為碳源進行水熱合成，並以本實驗室發展之奈米氧化鈦作為碳球成核的核種。探討粒徑控制的可行性與可行之尺寸範圍，並進一步瞭解其原因。此外，我們也研究碳球經不同溫度熱處理後，其溶劑親合性與石墨化程度，粒子尺寸與形貌，表面積等性質之變化，期望能有應用的潛力。 藉由添加異質核種並控制添加量，我們成功地在95％以上的碳產率條件下，製作出約60 nm大小之碳球。不但粒徑均一且分散性良好，外貌為完整平滑的圓球形。進一步經800℃?1000℃石墨化後，尺寸還可以有約20％的降低。並且由親水性分散轉變成親油性，可輕易地分散於苯類有機溶劑中。此石墨化碳球具有約650 m2/g的表面積，若再以濕空氣活化，則可製備出具有約1500 m2/g表面積的活性碳球。 Carbon particles with high dispersity have been used as dyes and inks, supercapacitor, superelectrode in a battery, and fillers for plastic and chromatography tube. All of these applications not only require uniform and high dispersable carbon particles, but also particles of controllable pore size, distribution, and surface property. More specifically, particles of 100 nm in size can be used as dyes and inks. For applications in electric conductivity, lubrication, piezoelectric property, 50 nm particles with uniform distribution are needed. For example, American-based CleanTechnology Inc. develops a material called Carbon NanoSphere Chain, which can be used as sensor or lubricant. In addition, HeadWaters Inc. in America and Sumitomo Chemical in Japan cooperate to produce a kind of carbon nano particles, that when added to plastics, can increase its conductivity. Of course, it is important for the additives to have spherical morphology, uniform size, and high dispersity. Uniform size carbon spheres could be prepared by hydrothermal treatment of a glucose aqueous solution, but, at reasonable yield, the size is usually in the order of micron size. Therefore, the objective of this study is to establish a highly-efficient process of synthesizing 60 nm carbon spherules with superb uniformity and dispersibility by seed addition. For hydrothermal synthesis of carbon spherules, glucose is selected as the carbon source with the addition of as-synthesized TiO2 particles as seeds. Study the feasibility of controlling particle diameter and understand the possible range of the particle size variation. A detailed discussion provided explanations to size-controlling reason. Finally, solvent affinity and the degree of graphitization, size and morphology, and surface area of carbon spherules were extensively analyzed after thermal treatment. By adding appropriate seed, it was now possible to increase the nuclei and reduce the size to about 60 nm at a carbon yield of 95%. SEM analysis shows that the size of carbon spherules is very uniform and agglomeration free. The particles are in perfect spherical morphology with smooth surface. The size can be further reduced by about 20% after graphitization at 1000℃ under inert atmosphere. The graphitized spherules are hydrophobic and easily dispersed in organic solvents. It has a BET surface area of only 650 m2/g. After activation by humid air, the surface area can increase up to about 1500 m2/g. |
