www.elsevier.com/locate/jmbbm Available online at www.sciencedirect.com Research Paper Nano-scale mechanical properties and behavior of pre-sintered zirconia Abdur-Rasheed Alao, Ling Yin n School of Engineering & Physical Sciences, James Cook University, Townsville, QLD 4811, Australia article info Article history: Received 16 January 2014 Received in revised form 27 March 2014 Accepted 31 March 2014 Available online 15 April 2014 Keywords: Pre-sintered zirconia Loading rate Material behavior Mechanical properties Nanoindentation In situ SPM abstract This paper reports on the mechanical properties and material behavior of pre-sintered zirconia using nanoindentation with in situ scanning probe microscopy. Indentation contact hardness, H c , and Young's modulus, E, were measured at loading rates of 0.1– 2 mN/s and 10 mN peak load to understand the loading rate effect on its properties. Indentation imprints were analyzed using in situ scanning probe imaging to understand the indentation mechanisms. The average measured contact hardness was 0.92–1.28 GPa, independent of the loading rate (ANOVA, p40.05). Young's moduli showed a loading rate dependence, with average 61.25 GPa and a great deviation at a low loading rate of 0.1 mN/s, which was twice the average moduli at the loading rates of 0.5–2 mN/s. Extensive discontinuities and the largest maximum penetration, final and contact depths were also observed on the load–displacement curves at the lowest loading rate. These phenomena corresponded to microstructural compaction (pore closure and opening) and kink band formation, indicating the loading rate dependence for microstructural changes during nanoindentation. The in situ scanning probe images of indentation imprints show plastic deformation without fracture at all loading rates, compaction at the low loading rate and pore filling at the high loading rate. The mechanical behavior studied provides physical insight into the abrasive machining responses of pre-sintered zirconia using sharp diamond abrasives. & 2014 Elsevier Ltd. All rights reserved. 1. Introduction Zirconia is widely used in engineering, medicine and dentistry as ferrules in optic fiber connectors (Yin et al., 2004a), sensors, environmental filters, and mechanical components (Chintapalli et al., 2012), orthopedic joints and bones (Piconi and Maccauro, 1999), dental implants, crowns and bridges (Yin et al., 2003), due to its excellent mechanical properties and biocompatibility. Sintered zirconia can be machined using precision machining technology, requiring expensive high-stiffness and high preci- sion machines (Chen et al., 2005; Huang et al., 2004; Yin and Huang, 2004a, 2004b, 2008; Yin et al. 2004a, 2005). Meanwhile, the martensitic tetragonal to monoclinic phase transformation during machining, its sintered solid makes zirconia more susceptible to ageing, thereby putting its products at risk of a catastrophic failure (Silva et al., 2010; Zarone et al., 2011). Thus, http://dx.doi.org/10.1016/j.jmbbm.2014.03.019 1751-6161/& 2014 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ61 7 4781 6254. E-mail address: ling.yin@jcu.edu.au (L. Yin). journal of the mechanical behavior of biomedical materials 36 (2014) 21–31