Experimentals SiAlON

Tests of a hot-pressed B4C-10%SiAlON composite demonstrated high corrosion resistance up to 500°C. Even at 500°C, almost no changes of the sample surface occurred under the experimental conditions. 

The lattice parameters of the hexagonal p-SiAlON phase were calculated from the XRD peaks ofthe products by employing the least-squares method. The lattice parameter a was calculated from (100), (110), (20 0), (2 10), (3 0 0), and (310) peaks of P-SiAlON, and the lattice parameter c was calculated from the (101) peak using the calculated a value. The bulk density of the spark-plasma-sintered (SPSed) specimens was measured according to the Archimedean principle, using distilled water as the medium. The detailed experimental procedure was published in paper [11]. 

In this part, we investigated the corrosion behavior of combustion synthesized P-SiAlONs (z = 1 - 3) in SCW. The effect of z value on the corrosion kinetics and oxide products was systemically examined. The schematic drawing of the experimental apparatus used in this study is shown in Figure 4.15. Here, the reactor is made of SUS316. The samples were exposed in SCW at a constant pressure of... 

Figures 3.89 and 3.90 show twist boundaries in SiAlON and in sapphire ceramics, respectively. In Fig. 3.89, both tilt and twist boundaries are indicated. Rows of parallel and more complex dislocations are observed. These dislocation structures are periodic. The Burgers vector determined for the dislocations are of type b = a/3 (110). The experimental results show that these twist boundaries are stable without an amorphous grain-boundary phase. It appears, according to the experimental results, that boundaries with low L misorientation possess relatively low energies and, therefore, are formed favorably during a sintering process.

A number of w-crack configurations have been experimentally observed at triple points. Figure 6.79 shows crack nucleation at grain boundaries, formed when shear stress acts along the boundaries. Here, a wedge-type cavity was formed under creep in a SiAlON-YAG ceramic in a flexural bar studied at 1170 °C. Figure 6.80 shows the cavitation strain and the total strain as functions of the normalized beam height for the applied moments of M — 0.165 N.m and M = 0.247 N.m (i.e., at the initial, maximum applied stresses of 80 and 120 MPa). Both tests were carried out at 1170 C and interrupted before failure. For M = 0.165 N.m (a = 80 MPa), the maximum cavitation strain is 20 % of the total strain, whereas for M = 0.247 N.m (b = 120 MPa), the cavitation strain... 

---