| Abstract: | 奈米碳管(Carbon Nanotubes, CNTs) 自發現以來，不論在物性、化性或電學性質上均有顯著且非凡的表現，促使眾多學者投入研究。目前由於難以掌握其尺寸太小，及物性歧異性過大，使得奈米碳管特性無法有效應用。本研究為有效且實用CNTs，採用bottom-up之方式，將奈米碳管透過真空過濾，製成Randon buckypaper (RBP)；即將CNTs製備成一塊材薄膜。另外，在過濾時加入渦旋動力，製成一使管身向圓周對整而呈非均質特性的巴克紙Alignment buckypaper (ABP)，再透過加入少量金屬改質，改變其電阻率及介電係數，以增加其對外界物理量之作用性與靈敏性。BP基本特性量測下，首先在低溫量測實驗可知，其buckypaper呈負溫度效應，證明BP為一半導體之塊材薄膜。四點量測中，電阻率沿渦旋方向者(水平方向)隨渦旋轉速提高，而電阻率下降；垂直於渦旋方向者(垂直方向)，其電阻率卻上升。此驗證了ABP的對整排列性，可透過渦旋轉速多寡來控制。在電性量測方面，發現在2.88GHz時波傳播在水平方向 -11.19dB，垂直方向5.88GHz且與Randon buckypaper在-9.07dB在平行與垂直數值平均，此材料在2.88GHz、8.2GHz及12.06GHz皆有超過-15dB之吸收波段，也證明了其Alignment buckypaper單一材料多頻段吸收特性，可利用此薄膜特性於可調頻之通訊系統。本研究利用簡單的渦旋動力過濾，使CNTs呈方向性排列，改變了BP的電阻率及介電係數; 以渦旋動力之轉速，來控制BP的電阻率與介電係數。在電性方面，可控制排列方向來設計其吸收波段，本研究結論可望利用在通訊系統如：WiMAX，工作頻段在2.5~3.8GHz。在可見的未來，BP在半導體業與太陽綠能產業方面將大大的提高了可利用性，在通訊產業也有其長遠發展，可謂為一新興的應用材料。
Since 1991, Carbon nanotubes (CNTs) havebeen caused a worldwide wave of research interests because of its excellent characteristics ofphysical and chemical. But to the present, it’s rarely being applied to life owing to its hard-handling tiny-size and the nature of difference between each tube.In this study, in order to overcome the limit above, with the idea of bottom up, we filtrate the suspension of CNTs and make it as a sheet-like bulk material, so called random buckypaper (RBP); that make plenty of CNTs as an isotropic material, and this allows the applications of CNTs in macro-scale achieve.Besides, in order to vary the property of BP, we (1) add a vortex power to disturb suspension when filtration, that makes the direction of tube body align along the circumference, and it becomes as an alignment BP (ABP). And, (2) coat some kinds of metal oxide on it for modification, and called modify BP (MBP).According to test, RBP possesses the features of lightweight, sheet-like, robust, high specific surface area and 78 % porosity. Under four probes resistivity test, it shows thatthe resistivity of ABP along the vortex direction (horizontally) is decreased when vortex speed increased. The results were opposite when the direction is perpendicular. And, after low temperature resistance test, BP and ABPboth show the negative temperature effect phenomenon. It was assumed that BPis a semimetal material with great conductivity ability. Thus, it was considered to be an excellent material for microwave application (multi-band absorption).It would be possible of BP to make a same revolution in material history as semiconductor did (to replace ferroalloy), because of itsprecedenceelectricalproperties. |
