Vickers 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. 

This chapter is focused on CS and SPS of high-purity p-SiAlON, which includes the reaction mechanism of CS the physical properties of Vickers hardness and thermal properties and the corrosion resistance properties in different atmospheres. 

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... 

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. 

In this chapter, pure and dense P-Sig Al20jN8 2S (z= 1-3) were synthesized by CS followed by SPS without any sintering additives. The Vickers hardness, thermal conductivity, and the corrosion resistance in different atmospheres were investigated for the application as high-temperature engineering materials. In summary, this study introduced an effective method to synthesize pure and dense P-SiAlON materials and showed many valuable property data, which could provide significant references for the application in fields as engineering materials. The content of this chapter is based on the author s doctoral thesis [28]. 

T. (2010) Vickers hardness of beta-SiAlON prepared by a combination... 

The octahedral pressure cells containing the samples were recovered from the multi-anvil experiment and either broken or cut in half, using a diamond wiresaw. In the latter case, the j -sialon samples were also halved in the axial direction. The specimens were then characterized with optical and scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe microanalysis (EPMA), powder X-ray diffractometry (XRD), and microhardness testing using the Vickers method. 

As mixtures of the a and polymorphs usually arise in the preparation of S13N4, in sialon preparation it is common to find mixtures of a and /3 sialons. Vickers hardness determination can be used to assess the amount of a and in a preparation because a linear correlation between and content appears to exist, as Figure 6.5 shows. The hardnesses of some and a sialons are given in Table 6.10. 

Figure 6.5. Linear dependence of Vickers hardness on the /3 -sialon content of sialon preparations. After Babini et...

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