Pearl Powder Structure And Electrophoretic Deposition Pearl Powder Bio-coating Of The Study

Nacre is a biomineral comprised of aragonite (CaCO₃) platelets and organic components. It shows excellent osteogenetic activity and bioactivity. In present paper, the structure of nacre and coating pearl powder on titanium substrate by Electrophoretic Deposition(EPD) were investigated.In the first part of the paper, microstructure of pearl powder with different size was analyzed and the platy pearl powder was prepared from the raw pearl powder. X-ray diffraction indicated that the nacre sheet was consisted of aragonite with an obvious (002) texture, while as the fine pearl powder are consisted of aragonite with small amount of calcite (one stable structure of calcium carbonate). Oxidation by NaClO makes the organic components between the plates destroyed, and the platelets of aragonite were obtained after ultrasonic treatment.Secondly, the process of preparing the pearl powder coating by EPD was investigated. The pearl powder suspension was prepared using the alcohol as the solvent and the influence of additives on the deposition was investigated. For both acetic acid and CaCl₂ additives, uniform coating was achieved under various voltage and different deposition time. The weight of the coating increases against the applied voltage and deposition time and the current deceases as the time increases during deposition. Suspension with CaCl₂ as additive is more stable and can result in higher deposition rate and more uniform coating; while suspension with acetic acid as additive can results in much higher bonding strength of the coating to the substrate. XRD and FTIR results show that the pearl coating exhibits the same characteristics as the raw pearl powder. The different influence of two addictives on the coatings was further analyzed. With the addictive of CaCl₂, more Ca²⁺ were absorbed to the pearl powder, causing the ζ potential increased and thus increased deposition rate and homogeneity of the coating. With the additive of acetic acid, more organic components in the nacre were dissolved into the suspension and under the electric field of EPD, those organic components were concurrently deposited with the nacre powder and increased the bonding strength of the coating by joining the adjacent particles.