Indentation SiAlON

The bulk densities of all the materials were determined using Archimedes method (AS 1774.5, 1979). The Vickers indentation technique was used to measure the hardness in each case. The applied load in the Vickers hardness tests was 10 kg for silicon nitrides and sialons. However, using the same load produced severe lateral cracking in silicon carbides around indents, which prevented the accurate measurement of the diagonals of indents. Therefore the load was reduced to 0.3 kg for silicon carbide samples. 

Xie ZH, Hoffman M, Moon RJ, Munroe PR, Cheng YB (2004) Subsurface indentation damage and mechanical characterization of a-sialon ceramics. J Am Ceram Soc 87 2114—2124... 

The Vickers hardness of polished CS-SPSed P-SiAlON compacts was measured using a Vickers microhardness tester with a diamond indenter of regular pyramid with an opposite angle of 136°. The experiments were performed under the loads between 0.981 N (0.1kg) and 19.614N (2.0kg) at room temperature. The dwell time for each load was 20 s. An average of at least five readings at different locations of the specimen surfaces was taken for each specimen. The Vickers hardness GPa) was calculated according to Equation 4.4... 

Figure 4.8 shows the measured as a function of indentation load for the CS-SPSed P-SiAlON (z= 1-3). The variation ofwith applied indentation test load for all samples shows that decreases with the increase of apphed load at low load region. It reaches a saturation value at higher loads when F > 4.903 N for z = 1 and 2. However, for z = 3, the ISE is more clear than that of z = 1 and 2. Also, as the figure shows, decreases with the increase in z value. At the max applying... 

As the conclusion for CS-SPSed P-SiAlON, the Vickers hardness ranges between 14.7 and 17.6 GPa due to different z values under the indentation load of 19.614 N. 

Until now, no details have been reported of indentation fracture toughness (K c-ICL) measurements on pure y-Si3N4. However, in the case of the spinel-sialon y-Si2A10N3, mean Kic-ICL values of 4.6MPam were reported at indentation loads of 0.5 and 1.0 kg [51]. 

Yield and absolute hardness, 72 Y-sialon glass density, 229 Knoop hardness, 229 Modulus, 229 Young s modulus of AljOj, 241, 259-261 anisotropy in /3-AI2O3, 281 of B4C, 228, 241 and bond type, 172 and crack depth, 155 and cracking, 147 of CrjCj, 302 of germanium, 252 of glass, 238 and hardness, 72 hardness ratio, 179 from Knoop indents, 180 mismatch stress, 273 of MgO, 241, 269 and penetration depth, 47, 240 and plasticity parameter, 241 and residual impression parameter, 240... 

A. L. Yurkov and R. C. Bradt, Load Dependence of Hardness of SIALON Based Ceramics, in Fracture Mechanics of Ceramics, Vol 11, Eds. R. Bradt et al., (Plenum Press, NY, 199S), pp. 369 378. P. M. Sargent, Use of the Indention Size Effect on Microhardness for Materials Characterization, in Microindentation Techniques in Materials Science and Engineering, ASTM STP 889, eds. P. J. Blau and B. R. Lawn, (ASTM, West Conshohocken, PA, 1986), pp. 160 174. 

A. L.Yurkov, E. Breval, R. C. Bradt, Cracking During Indentation in Sialon-Based Ceramics Kinetic Microhardness and Acoustic Emission, J. Mat Sci. Lttrs., 15,987-990 (1996). 

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