DOI: 10.5176/2251-1857_M312.43
Authors: Tsunehisa SUZUKI, Mutsuto KATO
Abstract: Carbon nanotubes (CNTs) as reinforcements are
increasingly attracting scientific and technological interest
because of their unique chemical and physical properties for
producing composites of metallic and non-metallic constituents.
Ni-based CNT composite coatings formed by using electroless
codeposition and electrocodeposition have good friction and wear
properties improved by codepositing CNTs in the matrix.
However, surface roughness of the Ni-CNT composite coatings is
very bad because of large nodules by codepositing CNT
aggregates in Ni matrix. In the present work, surface roughness
of electroplated Ni-CNT composite coatings were improved by
sonication with various frequencies (28kHz, 60kHz) and various
amplitudes of displacement of ultrasonic vibration. In horn
sonication method, sonicator horn was immersed in the Ni
sulfamate plating bath. The vibrating surface of the horn was
parallel to the substrate surface and vibration in the direction
was vertical to the substrate surface. Dynamic light scattering
results indicated that the dispersion state of CNT suspension is
also improved by sonication. Large size CNT aggregates
decreased by high frequency vibration (60 kHz), especially.
Surface roughness decreased with increasing the vibration
velocity. Improvement of the surface roughness could be
independent of frequency and amplitude of vibration. There was
no nodule of CNT aggregates at the surface electroplated with
sonication of 0.2m/s of vibration velocity at vibrating surface of
horn. Cristal orientation and crystal size of Ni matrix of Ni-CNT
composite coating was analyzed by X-ray diffraction. In terms of
crystal orientation, Ni matrix became completely random with
increasing frequency of vibration. The random crystal nickel
could be concerned to well-dispersed CNT in the matrix.
Keywords: Carbon nanotube; sonication; composite coating;
electroplating;
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