Studies Of Electroless Plating Ni-P On Piezoelectric Ceramic And Properties Of The Coatings

In order to meet the requirement of some special properties of piezoelectric ceramic (such as electric conductivity, corrosion resistance, sonic property and so on), Electroless plating Ni-P on PZT ceramic were studied in this paper. The effect of the composition and pH in alkali baths on the films' properties was researched by measuring the depotision rate and adhesive strength of the coatings. The perpendicular design methods were employed to optimize the acid EN baths. The structure and composition of the films electroless-plated in acid and alkali baths were measured separately. The polarization curves and AC impedance of the coatings were investigated. The effects of heat-treatment temperature on the properties of Ni-P films were measured at 200 癈, 300 癈, 400 癈, 500 癈 respectively.From the results of EDAX, we found that P content was about 10.2 % in the acid Ni-P coating, and 9.12 % in the alkali Ni-P film. The acid and alkali Ni-P films were confirmed to be amorphous state by X-ray diffraction patterns. The coatings had excellent adhesive strength. The adhesive strength of the acid film was stronger than that of the alkali film. The experiments of the weigh loss showed the corrosion resistance of the coating in synthetic seawater was excellent.The adhesive strength and corrosion resistance were better at 200 癈 heat-treatment. With increasing the heat-treatment temperature, the adhesive strength and corrosion resistance of the films declined. Thecoating had transformed from amorphous state to crystalline state at 300 heat-treatment. Electrochemical experiments showed the coatings were active dissolved and corrosion was homogeneous. Single capacitance semicircles on EIS of the coatings in synthetic seawater were observed under corrosion potential (except the coating heat-treated at 200 )The cavitation rate decrease slightly with increasing heat-treatment temperature. The adhesive strength and cavitation resistance of the coating followed down by enhanced ultrasonic strength. The alkali coating had better cavitation resistant ability than that of the acid coating.The PZT ultrasonic transducer had been fabricated and was applied in the ultrasonic humidifier. At the same time the cavitation test was studied, which show that the film had good cavitation resistant ability.