Abstract
The objective of this study is to investigate a novel chemical method, which is not found in the literature, to synthesize nickel fibers. This chemical method utilizes nickel salt solution as a precursor, hydrazine in an alkaline solution as a reducing agent, and other necessary additives, such as surface active agents, to obtain the claimed nickel fibers under the influence of magnetic field. We believed that ultra-fine nickel powders were first produced by chemical reduction, and subsequently grew into fibers along the direction of magnetic field. The diameters of these fibers were strongly affected by the starting pH of the precursor solution, varying from 50 mm to around 1 mm when pH was changed from 11.5 to 14.0. On the other hand, when the magnetic field was above 50 Oe (Oersted), we could easily obtain fibers with length over 5 cm.The effectiveness of nickel fiber/ABS composite as an electromagnetic interference (EMI) shielding material was also investigated in this work. We used nickel fiber as the filler, ABS as the polymeric matrix to get a composite for EMI applications. The mixing was done by the solvent method using chloroform and the composite was made into thin film. The effects of fiber diameter and fiber strength on the shielding effectiveness were studied. Deviations of experimental shielding effectiveness from theoretical predictions were thought to be due to the non-uniform distribution of fibers in the composites. The addition of a coupling agent helps the bonding between nickel fiber and polymer matrix of ABS as well as the uniformity of the composites. As a result, the mechanical strength and EMI shielding effectiveness of the composites increased accordingly, and the best SE (~45 dB) at a thickness of 250μm was reached in this work.