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ipheral speed by 30% above that of SiC-Si.
The lower heat conductivity of Si3N 4 (compared with SiC-Si) increases the thermal moment which results in a negative influence on the gap profile. Therefore, the advantage of the higher stiffness, in combination with carbon, cannot be fully utilized.
For high pressure gas seals, p > 10 MPa per stage, materials with high stiffness should be used. In the group of carbide based face materials, the application of SiC, SiC-Si and Si3N 4 all DLC coated, have proven to be suitable. The dry running capability of the DLC coating and the high stiffness of silicon carbide produce gas seals capable of withstanding high pressure applications up to 300Β°C.
Using silicon nitride instead of silicon carbide as face material for the rotating face, results in an increase by 30% of the maximum peripheral speed. Even though the test results of glued composite faces (SiC-Si support + carbon graphite) were good, the dependability of this solution is questionable because the shear stiffness of the glue varies with temperature.
Further developments will focus on face material combinations using silicon carbide versus a metal rotating ring. The thermal and mechanical deformations, the dry running capability and the corrosion resistance will be thoroughly investigated.
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## General news industry. The total grant was in the region of two million US dollars. The project activities to develop certain prototypes has shown there is a potential growing market in Turkey. The type of industrial investment in advanced structural ceramic manufacturing is dependent on the m