Effects of surface treatment methods on the phase changes in zirconia

Aim: In this study, zirconia was subjected to various surface treatments, namely, Al₂O₃ sandblasting, CoJet, and coating; the effects of these methods were investigated with the use of SEM, EDX, and XRD. Coating of zirconia surface with silica using the ultrasonic spray method is performed for the first time in this study. The present results are particularly important for the conduct of future studies. Methodology: Eighty-four zirconia samples were used for the XRD (n=28), SEM (n=28), and EDX (n=28) analyzes. Commercial semi-sintered discs (Kuraray-Noritake Katana HT10 14 mm, Japan) were used in this study. The size of the zirconia samples (i.e., 6 mm in diameter and 3 mm in height) was designed in a computer environment, factoring in the degree of shrinkage following sintering. The dimensions of the sintered samples were determined with a digital caliper. Four surface treatments were employed in this study. Results: The surfaces of the zirconium samples subjected to different surface treatments were investigated. The SEM and EDX images of the treated zirconia were taken at 80×, 250×, 1000×, 10,000×, and 20,000× magnifications and then compared with those of the untreated sintered samples. The XRD analysis results showed that the intensity of the peaks of the zirconium oxide samples at the 2θ range of 20°–40° varied from the tetragonal phase to the monoclinic phase along the surface. Conclusion: The sandblasting and CoJet surface treatments caused mechanical changes on the surface of the zirconia samples, and Al₂O₃ particles were detected on the surface, as shown by the SEM and EDX analysis results. The XRD analysis results for the blasting group differed the most from the results for the control group; by contrast, the results for the ultrasonic spray group were nearly the same to those for the control group.