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DYNA

versão impressa ISSN 0012-7353

Resumo

MOLINA, JAROL  e  HOYOS, BIBIAN. EFFECT OF PULSE CURRENT WAVEFORMS IN NANOCRYSTALLYNE ELECTRODEPOSITION. Dyna rev.fac.nac.minas [online]. 2009, vol.76, n.157, pp.153-161. ISSN 0012-7353.

A mathematical model has been developed for describing the effect of pulse current wave forms on size and hardness of electroplated nanocrystals. The model relates in a direct form the typical wave variables (frequency, duty cycle and peak current) with harness of generated deposits by means of direct current and by four pulse current wave forms: rectangular, ramp up, ramp down and triangular. The results of the model were evaluated for duty cycles of 20 and 80%, with frequencies of 50 and 150 Hz and peak currents of 4 and 8 kA/m2.The model predicts that small increases in the concentration overpotential drives to increase the nucleation rate significantly, diminishing the growth of the nanocrystals and generating a hardness increase. The increase of the duty cycle and the wave’s frequency produces a behavior increasingly close to that produced by direct current, with a diminution in the nanocrystals hardness. Any modification in the waveform variables that increases the peak current produces higher hardness values.

Palavras-chave : Pulse current; electroplating; nucleation; growth; Mathematical model.

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