電場/電磁場誘發鍍鎳碳纖維配向於環氧樹脂基材之研究及其在燃料電池雙極板之應用

Abstract

材料混摻纖維能改善原基底材料物理性質之不足，藉由成形過程中控制纖維配向以少量纖維達成其成品的異方向性性能需求。本研究利用具高導電性鍍鎳碳纖維與優異物理性質的環氧樹脂，成形具有異方向物理性質之矩形薄板。研究中設計製作了一個電場與電磁場產生裝置，在澆注成形之固化過程中進行電場與電磁場處理，以探討在不同外場處理下，對成形品鍍鎳碳纖維配向之影響。第一部分實驗主要是探討使用電場與電磁場處理對其纖維配向之影響，實驗過程中使用光學顯微鏡(OM)進行其纖維配向觀察，並以穿透導電性量測裝置作為其纖維配向佐證實驗。電場實驗結果顯示，使用電場誘發其纖維配向於環氧樹脂材料，在不產生電荷轉移與聚集的情況下，其纖維是不會滿足電泳特性完成聚集與配向，因此使用電場誘發其纖維配向於環氧樹脂控制處理，對於真實高導電性能需求產品之量產是較不適宜的。電磁場實驗結果顯示，在提供其系統磁通量密度(0.069Tesla)、詴片厚度2mm、纖維含量0.5wt％、長度1mm與該樹脂黏度下，其纖維幾乎是完全垂直磁場方向整齊排列。在與沒有配向處理詴片相比較，可量測到其詴片穿透導電性(200MΩ以下)數目，由原本的18.75％提升至84.37％。在使用實驗參數為纖維含量0.4、0.6、0.8wt％、長度2mm下，其詴片可量測到穿透導電性隨著其纖維含量提升而遞減，由100％、75％至72.9％，導電範圍由25、125遞增至250Ω。因此如果能適當的提升其系統磁通量密度，對於使用電磁場誘發纖維配向，在製造與開發具有異方向性性能需求產品上的可行性是很高的。 由於尚未有對使用電磁場誘發鍍鎳碳纖維配向控制於環氧樹脂，並將其應用在燃料電池雙極板製作之研究報告，第二部分實驗，主要是探討其纖維配向於環氧樹脂矩形薄板穿透方向，在燃料電池雙極板應用之可行性，並藉由銑床加工其複合材料與石墨板蛇形流場，再以單一電池發電性能進行比較。研究結果得知，其複合材料在美國能源局(DOE)對於燃料電池雙極板，熱性質，氣體滲透率與耐腐蝕性的要求都是通過標準的。在使用纖維含量0.4wt％、長度2mm與磁通量密度(0.069Tesla)下，成形(63×54×2 mm)雙極板與石墨雙極板單一電池發電性能比較結果得知，其複合材料雙極板最高發電功率密度只有石墨板的1％，2.1mW。主要是其複合材料雙極板的穿透阻抗遠大於石墨板所造成。由於本研究所始使用的複合材料其帄面導電性是超過200MΩ，會讓此複合材料雙極板構成發電主要還是其雙極板穿透導電性所提供的導電通路。因此使用導電纖維配向於燃料電池雙極板穿透方向，對於燃料電池雙極板之應用具有一定的可行性。

Physical properties are tunable by mixing fibers into the base material. Product anisotropy is achieved by controlling fiber alignment during the formation process. The researchers in this study manufactured a rectangular plate with anisotropic physical properties. The plate contained nickel-coated carbon fiber of high electrical conductivity and epoxy resin with a supreme physical property. An electrical and electromagnetic field generator was designed and fabricated to modulate electric and electromagnetic fields during solidification in the casting process. This study investigated fiber alignment of nickel-coated carbon products under the influence of different force fields. In the first section of experiments, the effects of electric and electromagnetic fields on fiber alignment were examined. This study utilized Optical microscopy (OM) to observe alignment of fibers, and penetrative conductivity measurement devices for fiber alignment verification were used. The researchers treated epoxy resin with an electric field to induce fiber alignment. Electric field experiments revealed that, the fibers did not satisfy electrophoresis properties and failed to aggregate and align when no electrical transition and aggregation occurred. The procedure of using the electric field to induce fiber alignment in epoxy resin is not applicable for mass production of virtual products with high electrical conductivity. The results of electromagnetic field experiments demonstrated that nearly all fibers aligned perpendicular to the magnetic field under certain conditions: such as, system magnetic flux density 0.069 Tesla, specimen thickness 2 mm, fiber content 0.5 wt percentage, length 1 mm, and certain resin viscosity. Compared to specimens that did not undergo aligning treatment, the penetrative conductivity (under 200MΩ) increased from 18.75% to 84.37%. The study used the experimental conditions fiber density 0.4, 0.6, and 0.8wtpercentage, length 2mm. The penetrative conductivity decreased while the fiber content increased. Fiber content ranged from 100%, 75%, and 72.9%with changed conductivity from 25, 125, and 250 Ω. The method of inducing fiber alignment with electromagnetic fields is applicable to the manufacture and development of products requiring anisotropic properties under certain levels of enhancement of system magnetic flux density. Research reports on fiber alignment control of nickel-coated carbon and its application in manufacturing fuel cell bipolar plates are nonexistent. The second phase of the experiment focused on whether the procedure of fiber alignment along the penetration direction of the epoxy resin rectangular plate is applicable to fuel cell bipolar plates. The researchers milled the composite and graphite plates to create serpentine flow fields. These two materials were compared for single cell power generation performance. Results showed that the composite of interest qualified under the Department of Energy (DOE) requirements for thermal properties, gas permeability, and corrosion resistance for fuel cell bipolar plates. The maximum power density of the composite bipolar plate was 1% (2.1mW) of the graphite counterpart under the conditions of fiber content 0.4 wt%, length 2 mm, magnetic flux density 0.069 Tesla, and plate dimensions of 63×54×2 mm. The maximum power density results were due to the greater penetrative resistance of the composite bipolar plate. The researchers utilized composite material with a planar conductivity of greater than 200MΩ; therefore, the electricity generated was mainly due to the conductive current provided by the penetrative conductivity of the bipolar plate. The study concludes that the procedure of conductive fiber alignment along with penetrative direction of fuel cell bipolar plates may be used in fuel cell applications.