Investigation Of Palladium-free Activation And Electroless Ni-P Plating On The Surface Of Cement-based Piezoelectric Composites

Cement based piezoelectric composite is animportant part in the Structural Health Monitoring of the eivil engineering, It has good compatibility with concrete, high strength, durability, high sensitivity and perceived low cost, so it's research can trans form the trans formation of traditional cement-based materials and promote the development of all types of civil engineering structures. Butto play the excellent piezoelectric properties of cement based piezoelectric composite, the electrodes must be well prepared on the surface. So researching a method suitable for the electrode preparation of cement based piezo electric composite is very important for the application.The multi-element piezoelectric composites were fabricated from lead zirconant-titanate ceramics?PZT-5?, Ordinary port land cementand epoxy reisn. In this paper the 1-3 type cement based piezoelectric composite were fabricated by the cut-filling method. The electrodes were prepared by palladium-free activation electroless nickel plating process. The impact of activate process and plating processon the coating performance was discussed. The studies provided basic theory for the development and application of the composites. The single factor experiment method was used to study the activation order, reducing solvent composition and main activate salt effect on the coating properties with the best roughening process and alkaline bath as the prerequisite.The main indexare the appearance of coating, deposition rate, the amount of phosphorus and corrosion resistance. The results showed that: The best process sequence of palladium-free activation electroless nickel plating on the surface of cement-based piezoelectric composites: polishing ? unoiling ? roughing ? restoring ?activation?plating; The bestactivate main saltisC₄H₆O₄Ni; The best NaBH₄ solvent was the methanol-water mixture with the methanol volume fraction of 50%.The effects of mainactivatesalt's concentration, activation temperature, activation time on the appearance of the coating, plating rate, adhesion, corrosion resistance were studied by single factor method.The recipe of the bestpalladium-free activation process and conditions of cement-based piezoelectric composites were determined using the orthogonal experimental method with the plating rate as the main index.Five sorts of additives were selected: KI, SDS, CTMAB,EDA and PEG, discussing the effects of the activation process on the coating performance to determine the best additive and concentration.The results showed that the best activation process was achieved under the conditions of C₄H₆O₄ Ni concentration of 25 g·L^-1,activation time of 10 min, and activation temperature of 35°C. For palladium activation method and improved method after activation without using palladium plating obtained was compared, the results showed that no palladium activation method by coating deposition rate higher, the coating surface morphology and corrosion resistance is better, so that palladium activation method was not suitable for cement based piezoelectric composites Electroless Nickel plating.The original basic bath were improved to give neutral bath, the single factor experiment and orthogonal experiment were used to determine the best plating process conditions. The best neutral bath formulation:NiSO₄?7H₂O: 20g/L, Na₃C₆H₅O₇?2H₂O: 12g/L, NaH₂PO₂?H₂O:30g/L, CH₃COONa: 12g/L, Na₂B₄O₇?10H₂O: 8g/L; The best plating process was obtained under the conditions of 20g·L^-1 NiSO₄ solution, 20 min plating time, 50°C plating temperature, and 8 pH value.The coating performance under the preferred activation process and plating process were analyzed, the results showed that the coating surface was smooth and bright, coating section tests showed that the thickness of coating was about 250 nm, the coating was closely combined with base material;Phosphorus content of the coating on the ceramic substrate was up to 13.21%, phosphorus content of the coating on the cement substrate was up to 12.19%, a more uniform coating composition; The surface resistivity of the coating was 0.876? · cm, which can increase the performance of the piezoelectric material effectively.