Vickers Indentation Technique Research Articles

Influence of the Surface Topography of Titanium Dental Implants on the Behavior of Human Amniotic Stem Cells.

The dental implant surface plays a crucial role in osseointegration. The topography and physicochemical properties will affect the cellular functions. In this research, four distinct titanium surfaces have been studied: machined acting (MACH), acid etched (AE), grit blasting (GBLAST), and a combination of grit blasting and subsequent acid etching (GBLAST + AE). Human amniotic mesenchymal (hAMSCs) and epithelial stem cells (hAECs) isolated from the amniotic membrane have attractive stem-cell properties. They were cultured on titanium surfaces to analyze their impact on biological behavior. The surface roughness, microhardness, wettability, and surface energy were analyzed using interferometric microscopy, Vickers indentation, and drop-sessile techniques. The GBLAST and GBLAST + AE surfaces showed higher roughness, reduced hydrophilicity, and lower surface energy with significant differences. Increased microhardness values for GBLAST and GBLAST + AE implants were attributed to surface compression. Cell viability was higher for hAMSCs, particularly on GBLAST and GBLAST + AE surfaces. Alkaline phosphatase activity enhanced in hAMSCs cultured on GBLAST and GBLAST + AE surfaces, while hAECs showed no mineralization signals. Osteogenic gene expression was upregulated in hAMSCs on GBLAST surfaces. Moreover, α2 and β1 integrin expression enhanced in hAMSCs, suggesting a surface-integrin interaction. Consequently, hAMSCs would tend toward osteoblastic differentiation on grit-blasted surfaces conducive to osseointegration, a phenomenon not observed in hAECs.

Strength stability over loading time of zirconia-hydroxyapatite composites

Zirconia (ZrO2) and hydroxyapatite (HAp) are commonly used as materials for medical applications, especially in implants, due to their excellent mechanical properties and bioactive function. Their composites characterize with good mechanical (similar Young's modulus and compressive strength to bone) and biological properties such as: higher bioactivity and biocompatibility. In this paper 3YZrO2 -HAp composites were prepared from the nanometric powders via the wet-mixing process and the pressure-less sintering in the air atmosphere at .1150 °C. Then they were examined in terms of properties. The shrinkage was tested using a dilatometer. The structural properties of the specimens were analyzed by X-ray diffraction, Infrared (MIR) and Raman spectroscopy. The morphology of HAp and the microstructure of the 3YZrO2 -HAp composites were evaluated using TEM and SEM microscopy. The samples’ mechanical properties, such as flexural strength and the Young’s modulus, were measured using the biaxial loading method. The hardness and KIC were examined using the Vickers indentation technique. The mechanical tests showed that all the materials revealed susceptibility to subritical cracking - the higher content of HAp in the composites, the weaker tendency of slow crack growth. The bioactive modifier addition decreased the hardness and KIC of the composites and the other mechanical properties. The microstructure investigation showed that the HAp incorporation into the 3Y-ZrO2 matrix led to higher porosity and the growth of 3Y-ZrO2 grains size, as compared to 3Y-ZrO2 without addition. The XRD results confirmed the MIR and Raman ones. They revealed the HAp decomposition into β-TCP. Additionally, the phase transition of the tetragonal ZrO2(T) into the cubic ZrO2(C) was noted with the increasing HAp content in the composites. The composites’ mechanical properties met the requirements of cancellous bone and may serve as an alternative to biomaterials for bone repair and regeneration processes.

Surface modification toughening of partially stabilized zirconia ceramics: by sub-eutectoid solution annealing

In this investigation, surface modification toughening of partially stabilized zirconia ceramics, by sub-eutectoid solution annealing, has been performed. The Zr0.918Mg0.068Y0.014O1.925 designated (MZY) was prepared by mixing Magnesia Partially Stabilized Zirconia (MZ9) and Yttria Tetragonal Zirconia (TZ3Y) Polycrystal commercial powders using wet ball milling. The mechanical properties and microstructure of the MZY were investigated. XRD and SEM were used for phase analysis and microstructure examination of the sintered samples’ surfaces. The fracture toughness and hardness of the sintered compacts were determined by the Vickers indentation technique. The physical and mechanical properties of MZY were compared to those of MZ9 ceramics prepared under the same conditions. The results showed that, the Yttria addition inhibited the exaggerated growth of the tetragonal precipitates during sintering. The MZY showed a maximum in the fracture toughness of 12.9 MPa√m upon sub-eutectoid solution annealing at 1000 °C for 150 h, while the tetragonal precipitates in the MZ9 lost coherence due to their spontaneous massive transformation to the monoclinic phase via the decomposition reaction.

Tailoring hardness behaviors of BIT-based piezoceramics via doping and annealing strategies

Bismuth titanate (BIT) piezoelectric ceramics are perceived as a strong competitor in high temperature applications. Currently, a mass of work has been done to optimize the electrical performance of the ceramic utilizing different strategies. However, little attention has been paid to the mechanical behaviors of BIT ceramics, especially the research on mechanical hardness behaviors under doping and annealing, limiting the deep understanding for ceramics and its further development of practical applications. In this work, the mechanical hardness behaviors of a type of bismuth titanate-based ceramics [Bi3.96Ce0.04Ti3-xWxNbxO12 (BCTWN)] at different doping contents and selectively annealing temperatures were investigated using nanoindentation and Vickers indentation techniques. The results show that the hardness is strongly dependent doping contents, wherein the samples with smaller grain size and higher density exhibit bigger hardness. For the poled samples, a higher annealing temperature could restore more domain walls and induce more oxygen vacancies in the samples, along with higher elastic recovery and less remanent strain, shedding extra deformation resistance to make sample harder. Moreover, a schematic of defect assistant domain wall pinning mechanism is proposed to further rationalize the enhanced deformation resistance by annealing strategy. This work helps us deep understand the deformation mechanism of BIT ceramics beneath indentation, and provides insight into tailoring mechanical hardness behaviors via doping and annealing strategies.

Crack-healing behaviour of MoSi2 dispersed Yb2Si2O7 environmental barrier coatings

MoSi2 doped Yb2Si2O7 composites were designed to extend the lifetime of Yb2Si2O7 environmental barrier coatings (EBCs) via self-healing cracks during high-temperature applications. Yb2Si2O7–Yb2SiO5–MoSi2 composites with different mass fractions were prepared by applying spark plasma sintering. X-ray diffraction results confirmed that the composites consisted of Yb2Si2O7, Yb2SiO5, and MoSi2. The thermal expansion coefficients (CTEs) of the composites increased with an increase in the MoSi2 content. The average CTE of the 15 wt% MoSi2 doped Yb2Si2O7 composite was 5.24 × 10−6 K−1, indicating that it still meets the CTE requirement of EBC materials. After being pre-cracked by using the Vickers indentation technique, the samples were annealed for 0.5 h at 1100 or 1300 °C to evaluate the crack-healing ability. Microstructural studies showed that cracks in 15 wt% MoSi2 doped Yb2Si2O7 composites were fully healed during annealing at 1300 °C. Two mechanisms may be responsible for crack healing. First, the cracks were filled with SiO2 glass formed by MoSi2 oxidation. Second, the formed SiO2 continued to react with Yb2SiO5 to form Yb2Si2O7, which can cause cracks to heal owing to volumetric expansion. The Yb2Si2O7 formation with smaller volume expansion is more beneficial.

Measurement of the Fracture Toughness and Mechanical Properties of Hydroxyapatite Using Vickers Indentation Technique

Measurement of the Fracture Toughness and Mechanical Properties of Hydroxyapatite Using Vickers Indentation Technique

Estimation of the effect of redox treatment on microstructure and tendency to brittle fracture of anode materials of YSZ–NiO(Ni) system

The effect of reduction treatment in a high-temperature (600 °C) hydrogen-containing environment on the microstructure and tendency to brittle fracture of YSZ–NiO(Ni) materials for solid oxide fuel cell anodes has been studied. To assess the crack growth resistance of the ceramics, the Vickers indentation technique was adapted, which allowed estimating the microhardness and fracture toughness of the material in the complex.The requirements for high porosity of the anodes to ensure functional properties show that the strength may be an insufficient characteristic of the bearing capacity of the anode. More structurally sensitive characteristics are needed to assess its crack growth resistance.The average levels of microhardness of YSZ–NiO ceramics in the as-sintered state and YSZ–NiO(Ni) cermets (2.0 GPa and 0.8 GPa, respectively) and their fracture toughness (3.75 MPa·m1/2 and 2.9 MPa·m1/2, respectively) were experimentally determined.It was found that the microstructure of YSZ–NiO(Ni) cermet after redox treatment is formed by a YSZ ceramic skeleton with refined Ni-phase grains combined in a network, which provides increased electrical conductivity. Along with higher porosity of the cermet, its fracture toughness is not lower than that of the one-time reduced cermet due to the implementation of the bridging toughening mechanism of fracture.The proposed treatment method allowed forming the microstructure of the anode material, resistant to crack propagation under mechanical load. The propensity of the anode material to brittle fracture on the basis of evaluation of its crack growth resistance and analysis of the microstructure and fracture micromechanism was substantiated. This result is interesting from a theoretical point of view. From a practical point of view, the developed technique allows determining the conditions of redox treatment in the technology of manufacturing fuel cell anodes

Fracture behavior in electrically poled alkaline bismuth- and potassium- based lead-free piezoceramics using Vickers indentation

The fracture behavior of unpoled and electrically poled Ka0.5Na0.5NbO3 (KNN)- and Na1/2Bi1/2TiO3 (NBT)- based lead-free piezoceramics were characterized using the Vicker's indentation technique and compared with soft Pb(Zr,Ti)O3 piezoceramics. In the unpoled state, NBT-based piezoceramics demonstrate the largest fracture toughness in comparison with KNN-based and soft PZT piezoceramics due to its large intrinsic fracture toughness, which is in accordance with the previous reports. In the electrically poled state, KNN- and NBT- based piezoceramics exhibit large fracture toughness along the poling direction as opposed to perpendicular to the poling direction, with aspect ratios of 1.2 and 1.1, significantly smaller than that for PZT (1.8). The variations of the remanent strain and the process zone, which are related to the texture and the material properties during crack propagation were used to rationalize the results.

Characterization of hydroxyapatite-reduced graphene oxide nanocomposites consolidated via high frequency induction heat sintering method

ABSTRACT In this study, a solvothermal method at the temperature of 180 °C for 4 h was used for the synthesis of hydroxyapatite-reduced graphene oxide (HA-rGO) nanopowders by employing the nitrogen gas injection. To synthesize the powders, a solvent containing dimethylformamide, anhydrous ethanol, diethylene glycol, and water was used (1:1:1:2, respectively). Calcium nitrate tetrahydrate and diammonium hydrogenphosphate were used as calcium and phosphate precursors, respectively. The synthesized powders were consolidated by a high-frequency induction heat sintering method. The powders and sintered samples were then evaluated using X-ray diffraction, Raman spectroscopy, high-resolution transmission electron microscopy, Vickers indentation technique, and biocompatibility assay. The findings of this study showed that the final powders synthesized by the solvothermal method had calcium to phosphate ratio of about 1.67. The high frequency induction heat sintering method was suitable for consolidating these powders and exhibited a higher relative density than other methods. The mechanical properties of the nanocomposite were higher than those of pure HA. In biological experiments the difference of HA effect in comparison with the nanocomposite was not significant and both were biocompatible.

Effect of sintering temperature on the morphology, crystallinity and mechanical properties of carbonated hydroxyapatite (CHA)

Effect of sintering temperature on the physical and mechanical properties of synthesized B-type carbonated hydroxyapatite (CHA) over a range of temperature in CO2 atmosphere has been investigated. The B-type CHA in nano size was synthesized at room temperature by using a direct pouring wet chemical precipitation method. The synthesized CHA powders were subsequently consolidated by sintering treatment from 800 to 1100 °C. The sintered CHA samples were evaluated using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrometry, X-ray fluorescence (XRF), carbon-hydrogen-nitrogen-sulfur-oxygen (CHNS/O) elemental analyzer, Field emission scanning electron microscopy (FESEM), and Vicker's indentation technique. The results obtained from XRD and FESEM indicated that the synthesized B-type CHA powders were nanometer in size. The crystallinity and crystallite size of the sintered CHA samples were increased due to increasing sintering temperature. The heat treatment between 800 °C and 1000 °C has resulted in coarsening and increased hardness of the sintered CHA samples. However, these properties began to deteriorate when sintering beyond 1100 °C due the formation of calcium oxide.

Effects of La2O3 addition on microstructure development and physical properties of harder ZTA-CeO2 composites with sustainable high fracture toughness

The influence of La2O3 inclusion (0–3 wt%) on the microstructure, phase formation and mechanical properties of zirconia toughed alumina (ZTA) added with 5.0 wt% CeO2 was investigated. ZTA CeO2 composites were sintered at 1600 °C for 4 h. The microstructure, phase formation, density, fracture toughness and hardness properties were characterised through FESEM, Microscopy Image Analysis Software and XRD diffractometer, Archimedes principle and Vickers indentation technique, respectively. The XRD, image processing and FESEM reveal the existence of LaAl11O18. The addition of La2O3 incites the sintering, microstructure refinement, densification of ZTA-CeO2 matrix and phase transformation. Hence, the hardness of ZTA-CeO2 ceramics is increased rapidly based on refinement of Al2O3 grains, densification of ZTA-CeO2 composites and porosity reduction. It is observed that the fracture toughness is enhanced through in situ formation of elongated LaAl11O18 grains. The addition of 0.7 wt% La2O3 culminated in the achievement of the optimum findings for density (4.41 g/cm3), porosity (0.46%), hardness (1792 HV) and fracture toughness (8.8 MPa·m1/2). Nevertheless, excess La2O3 is proven to be detrimental as it displays poor mechanical properties due to the poor compactness of numerous LaAl11O18 grains, coarsening of Al2O3 grains and decline in density.

Plasma-sprayed graphene oxide reinforced alumina composite coatings on low carbon steel with improved fracture toughness, brittleness index, and microhardness

In this work, the mechanical properties of atmospheric plasma-sprayed Al2O3 and Al2O3-xGO (x = 0.5, 1.0, 1.5, and 2.0 wt%) coatings on low carbon steel was evaluated using the Vickers indentation technique, and the effects of GO addition in microhardness brittleness index and fracture toughness were investigated. The Fourier-transform infrared (FTIR) spectroscopy and Field Emission Scanning Electron Microscopy (FE-SEM) techniques were employed to analyze the microstructural characterization of the plasma-sprayed coatings and to confirm the retention of GO in the Al2O3-xGO composite after the plasma spray. It was found that the Vicker’s microhardness of as-sprayed Al2O3 is 4.148 GPa and it decreased with the increase in the addition of GO and for Al2O3-2.0GO, it is 3.305 GPa. The fracture toughness of Al2O3 is 4.86 (MPa m1/2) whereas for Al2O3-2.0GO is 16.85 (MPa m1/2). The fracture toughness has increased whereas the brittleness index has decreased as the weight percentage of GO addition is increased in the Al2O3-GO composite. Thus, the plasma-sprayed Al2O3 and Al2O3-xGO coatings suggest that 2 wt% GO addition helps in the improvement of brittleness, fracture toughness, and the microhardness.

Improving the mechanical behavior of reduced graphene oxide/hydroxyapatite nanocomposites using gas injection into powders synthesis autoclave

In this study, we show the synthesis of reduced graphene oxide/hydroxyapatite (rGO/HA) composites using a hydrothermal autoclave with argon-15% hydrogen gas injection. This both increases the hydrothermal pressure and uses hydrogen as a reductive agent in the process. The synthesized powders were then consolidated with spark plasma sintering method. The analysis of the consolidated samples included Vickers Indentation technique and cell viability. The results showed that injected gases in the autoclave produced powders with a higher crystallinity compared to synthesis without the gases. Also, hydrogen gas led to increased reduction of GO. The microscopic analysis confirmed existing graphene sheets with folding and wrinkling in the powders and indicated that various preferential directions played a role in the growth of hydroxyapatite crystals. The results showed that in general, graphene sheets increased the mechanical properties of HA. In the samples synthesized with injected gases, this increase was more significant. Interface analysis results indicate that reduced graphene oxide (rGO)/HA interface is likely coherent. These nanocomposites were biocompatible and showed some hydrophobicity compared to pure HA.

Statistical evaluation of nano-structured hydroxyapatite mechanical characteristics by employing the Vickers indentation technique

In this study, the mechanical characteristics of hydroxyapatite (HA) against the Vickers indenter under different loads were investigated. For this purpose, the HA powders were first synthesized by a one-pot solvothermal method. The powders were then subjected to consolidating by the spark plasma sintering (SPS) method for mechanical evaluation. Characterization methods used in this study included X-rays diffraction, field emission scanning electron microscopy, transmission electron microscopy, inductively coupled plasma, energy dispersive X-ray spectroscopy, and Vickers indentation technique. The findings of this study showed that the morphology of the synthesized powders by solvothermal method were rod-shaped and nanometer-sized. As the applied load increased to 2 N, the elastic modulus increased but the hardness did not change much. At a constant force, the contact depth increased with decreasing elastic modulus and hardness. Also, increasing contact depth increased the stiffness and contact area. The results of this study will be useful for investigating the mechanical properties of HA based materials.

Synthesis and Mechanical Properties of Zirconia–Yttria Matrices/Alumina Short Fibre Composites

Yttria tetragonal zirconia polycrystals (YTZP)/alumina short fibre (Al2O3-SF) composites were prepared by wet ball milling. Three different commercial powders of YTZP containing 2, 2.5 and 3 mol% of yttria (denoted as TZ2Y, TZ2.5Y and TZ3YA, respectively) were used as matrices, reinforced with 20 wt% Al2O3-SF. The effect of sintering conditions on the mechanical properties of the composites was studied. XRD and SEM techniques were used for the characterization of the prepared composites. The fracture toughness and hardness were determined by the Vickers indentation technique. The bend strength was measured using a four-point bending test machine. The results showed that both strength and toughness increase with yttria content. The TZ3YA/20 wt% Al2O3-SF composite showed bend strengths up to 760 MPa and fracture toughness of 9.2 MPa√m upon pressureless sintering at 1600 °C. Higher values of the bend strength, up to 855 MPa, were obtained for the post-sintered hipped composites at 1500 °C. The high bend strength and fracture toughness, KIC, result from strong fibre matrix interface. The toughening mechanisms were found to comprise transformation toughening, domain switching and crack deflection toughening. The addition of Al2O3-SF to the matrices of low yttria content was invaluable due to its high monoclinic content upon sintering.

The influence of metal phase composition on microstructure and mechanical properties of Al2O3-Cu-Cr ceramic metal composites

Ceramic metal composites from the ternary Al2O3-Cu-Cr system were fabricated with the use of the slip casting method. Densities of the obtained composites with 15 vol.% of metal content and different percentage composition of Cu and Cr were examined by the Archimedes method. The samples’ microstructures, observed by scanning electron microscope, were analysed with image analysis program in order to determine size distribution of the metallic areas in the structure. Phase composition of the sintered samples was examined by X-ray diffraction analysis. Vickers hardness of the samples was tested along with their fracture toughness with the use of the Vickers indentation technique. The conducted research revealed the correlation between the microstructure and mechanical properties of the obtained specimens. It has demonstrated the possibility of manufacturing composites from ternary system with the use of the slip casting method. It was revealed that the addition of the chromium particles to the metallic phase enhances hardness of the composites. Also, the metallic phase composition of the samples affects mechanism of the crack propagation in the material. Although the mechanical properties have been improved, it was found that the density of the samples was not satisfying and the need for further analysis has been identified.

Femtosecond Pulsed Laser Deposition of Chromium Diboride-Rich Thin Films

Chromium borides are promising candidates for several structural applications including protective coatings for materials exposed to corrosive and abrasive environments. In this paper the pulsed laser deposition of chromium diboride-rich thin films has been carried out in vacuum by using a frequency doubled Nd:glass laser with a pulse duration of 250 fs. The films have been deposited at different substrate temperatures and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. Lastly, the film’s hardness has been studied by Vickers indentation technique. The results indicate that only the films deposited at a substrate temperature of 500 °C are crystalline and formed by chromium diboride, together with a certain amount of boron and chromium, which suggests that, as main mechanism, a process taking place on the surface from atoms and ions from the gas phase. This hypothesis has been confirmed by the study of the plasma produced by the ablation process.

Mechanical properties of lithium metasilicate after short-term thermal treatments

ObjectivesThe properties of lithium-silicate dental glass-ceramics are very sensitive to heat treatments which are conducted after CAD/CAM (Computer Aided Design/Computer Aided Machining) processing. In particular, temperature variations inside the furnace chamber which may occur between different models of furnaces may result in altered mechanical properties of these materials. In this work, the effect of thermal treatment parameters on the transformation of lithium metasilicate (Li2SiO3) into lithium disilicate (Li2Si2O5) and on the resulting mechanical properties has been investigated. MethodsLithium metasilicate samples. containing 59 vol% of amorphous phase, were thermal treated under vacuum at 820 °C for up to 9 min or at 840 °C for 7min (as control group). The samples were characterized by X-ray diffraction analysis using the Rietveld refinement and scanning electron microscopy. Hardness and fracture toughness (n = 30 indentations/group) were evaluated by the Vickers indentation technique. The elastic properties were measured by the Impulse Excitation Technique and the flexural strength (n = 15/group) was measured using the piston-on-three-ball (P–3B) testing assembly. Complementary Weibull statistic were conducted as statistical analysis. ResultsThe results indicate a progressive reduction of the Li2SiO3 phase with increasing isothermal holding time at 820 °C until the conversion into Li2Si2O5, is completed for treatments longer than 7 min. A complete transformation of Li2SiO3 into Li2Si2O5 has also been observed for the control group of samples treated at 840 °C for 7min. Samples of the control group exhibited hardness, fracture toughness, Young's modulus and Poisson ratio 5.76 ± 0.17 GPa, 1.60 ± 0.03 MPa m1/2, 100.3 GPa e 0.21, respectively. The reduction of the thermal treatment temperature to 820 °C reduced the fracture toughness and the Young's modulus between 5-10%. Furthermore, the fracture strength was significantly reduced by approximately 71%, because of the lower amount of elongated Li2Si2O5 grains and higher amount of residual amorphous phase. ConclusionIn general, the glass-ceramic material containing residual amorphous phase associated with various crystalline phases, presented a reduction of its mechanical properties in relation to the lithium disilicate glass-ceramic. The reasons for these differences in the mechanical behavior are discussed by analyzing the influences of different phenomena such as thermal expansion anisotropy, residual stresses, amorphous phase content and microstructure on the properties.

Role of addition of La2O3 on the phase contents, microstructure and mechanical properties of ZTA-MgO ceramics

Abstract Addition of MgO into Zirconia Toughened Alumina (ZTA) enhanced the Vickers hardness (1710 HV) but reduced the fracture toughness (3.38 MPa.m1/2). The reason is attribute to the formation of MgAl2O4 phase in the ZTA-MgO system. Hence, the La2O3 was added to ZTA-MgO compounds to acquire both high hardness and fracture toughness. The mixtures were prepared with addition of La2O3 (0.1 wt.% to 10.0 wt.%) to ZTA/1.0 wt% MgO. The mixtures were pressed to a rectangular bar of (54*12*5) mm3 at 1600 oC for 4 hrs. The characterisation of phase contents, microstructure, density, porosity and mechanical properties were done through XRD, SEM, Archimedes principle and Vickers indentation technique, respectively. The optimum La2O3 addition was between (0.7 wt. % - 1.0 wt.%) for better fracture toughness of ZTA ceramics with a reasonable high hardness. The addition of La2O3 has a significant effect on the formation of finer Al2O3 grains, creating strong interface between the Al2O3 grains and LaAl11O8 grains result in denser ZTA-MgO ceramics of hardness of 2028 HV. Also, the presence of rodlike LaAl11O8 and/or LMA grains in the ZTA-MgO ceramics improved the fracture toughness up to 6.67 MPa.m1/2.

Microstructure and fracture toughness of a WC-Fe cemented carbide layer produced by a diffusion-controlled reaction

To improve the mechanical properties of the surface of iron-based alloys, a tungsten carbide-iron (WC-Fe) cemented carbide layer is produced on an alloy by adopting an isothermal annealing process, which was performed at 1050 °C for 4 h. By deeply etching the obtained sample, the morphologies of the WC ceramic grains in the WC-Fe hardmetal layer are characterized via scanning electron microscopy. The present results reveal three distinct morphologies consisting of rectangular, triangular prism and multi-layered shapes. Furthermore, the mechanical properties and fracture toughness of the WC-Fe layer are investigated through combined nanoindentation and Vickers indentation techniques. Nanoindentation testing is performed in a load range of 100 to 450 mN. Based on the data collected from the nanoindentation results, the average values of the hardness, Young' modulus and deformation ratio are evaluated, and the fracture toughness is determined to have a value of 3.08 MPa·m½ at 450 mN. In the Vickers indentation technique, however, by identifying the crack type and choosing the appropriate model, the fracture toughness is calculated to be 1.85–3.44 MPa·m½ at applied loads ranging from 0.98 to 4.9 N. The obtained fracture toughness results exhibit good consistence between the nanoindentation and Vickers indentation methods.