Indentation size effect in aqueous electrophoretic deposition zirconia dental ceramic
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Indentation size effect in aqueous electrophoretic deposition zirconia dental ceramic Lei Wang1,a), Isaac Asempah2, Xu Li2, Sheng-Qi Zang3, Yan-Fei Zhou2, Jie Ding2, Lei Jin3,b) 1
Stomatology Department, Nanjing General Hospital, Medical School, Nanjing University, Nanjing 210002, People’s Republic of China; and National Demonstration Center for Experimental Materials Science and Engineering Education, Jiangsu University of Science and Technology, Zhenjiang 212003, People’s Republic of China 2 National Demonstration Center for Experimental Materials Science and Engineering Education, Jiangsu University of Science and Technology, Zhenjiang 212003, People’s Republic of China 3 Stomatology Department, Nanjing General Hospital, Medical School, Nanjing University, Nanjing 210002, People’s Republic of China a) Address all correspondence to these authors. e-mail: [email protected] b) e-mail: [email protected] Received: 25 June 2018; accepted: 16 November 2018
Highly dense zirconia dental ceramic coatings were fabricated by aqueous electrophoretic deposition (EPD) and subsequently sintered between 1250 and 1450 °C. Microstructural examination revealed that aqueous EPDZrO2 coatings possessed a tetragonal phase structure and the grain size increased with increasing sintering temperature. Nanoindentation study proved that the aqueous EPDZrO2 coating also had excellent mechanical properties. The effect of different applied loads on hardness and elastic modulus of the 1350 °C-sintered sample at room temperature was investigated by the method of progressive multicycle measurement nanoindentation. The simulative experiment proved that hardness of aqueous EPDZrO2 exhibited reverse indentation size effect (ISE) behavior and then displayed the normal ISE response. The analysis indicates that the reverse ISE is attributed to the relaxation of surface stresses resulting from indentation cracks at small loads and normal ISE is caused by geometrically necessary dislocations. The tetragonal–monoclinic stress-induced phase transformation during nanoindentation is the primary cause of dental zirconia failures.
Introduction Zirconia ceramic has a wide variety of clinical applications, such as fixed dental prostheses (FDPs), root posts, and implant abutments in reconstructive dentistry [1, 2, 3, 4, 5]. It is highly suitable for dental use because of its high mechanical properties, natural tooth appearance, no cytotoxicity, reduction in bacterial adhesion, and low corrosion potential [6, 7, 8]. It provides an alternative for both dentists and laboratory workers [9]. These digital procedures replaced sensitive manual work as a result. It was much easier and more accurate to digitize implant positions, plan and design restorations virtually on a computer, and manufacture the restoration directly by milling [10]. Briefly, the process starts from a die or wax pattern by optical or contact scanners. Afterward, an enlarged restoration is designed by computer software (CAD) and then a presintered ceramic blank is milled by computer-aided machining. T
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