Nano Al <sub> 2 </ Sub> O <sub> 3 </ Sub> Alkaline Composite Plating Nickel

Due to the special characters of nano particles, electroless composite plating could obtain new properties. But this should be based on the even dispersion of nano particles in the composite coating. As a result, three requirements must be met: first, nano particles without hard agglomeration;second, excellent dispersion of nano particles during electroless plating;third, uniform deposition of nano particles into the coating.In these preconditions, experiments were carried out to study the nano-Al₂O₃ electroless composite plating. Firstly, the dispersion of nano-Al₂O₃ was investigated, which was based on the distribution of particles after ultrasonic treatment and by adding several different surface-active reagents;then, the dispersion of the as-received nano-Al₂O₃ powders from different companies was compared. Results showed that the dispersion of the nano-Al₂O₃ particles was better when temperature was increased, but particles agglomerated when temperature was too high. The hard agglomeration of nano particles couldn't be dispersed by ultrasonic wave, emulsify trimming, some disseminating agents such as PEG, PVA, PMAA—NH₄ of different density and ion absorption. To obtain even dispersion composite coatings, the nanometer particle must with better dispersion. Nano-Al₂O₃ powders from different companies should be used in solutions with different pH values to get best dispersion. It was indicated that the nano-Al₂O₃ powders received from Nanotec Corp. were best dispersed with a mean diameter of 130nm in alkali plating solution when pH value was 9.Then, the appearance, microstructure and properties of the composite coating were studied, The alkali nickel electroless plating solution was preferred, using the hypophosphite (NaH₂PO₂H₂O) as the reductant, and the plating was implemented at 60℃. The coating with high content of phosphorus was aimed. The glass substrate was pretreated by self-assembly. The plating rate was determined by measuring the weight gain after plating. The appearance of the plating was determined by scanning electron microscopy. The X-ray diffraction pattern and differential thermal analysis apparatus were used to analyze the phase of the powders, and the distribution of thenano particles was determined by transmission electron microscopy.To study the influence of nano particles on the appearance of the coating, electroless plating was implemented on glass substrate. Before electroless plating, substrates were pretreated by two methods respectively: two-step process and self-assembly. Results indicated that the appearance of the coating on substrate pretreated by self-assembly was better than that pretreated by two-step process. And for self-assembly pretreatment, when it was carried out assisted with ultrasonic, abrighter nickel coating with better cohesion could be obtained.To study the influence of the nano-A^Os particles on the configuration, property and crystallization of the coating, composite electroless plating was implemented on steel substrate. The effect of temperature, plating time and pH value on the microstructure and property of the coating was investigated as well. As a result, the coating containing nano-AhC^ particles was obtained, and its hardness was obviously increased. It was showed that nano-A^C^ particles accelerated the crystallization of the composite coatings.