ISSN:
1013-9826
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Reaction bonded MgSiN2 (RBMSN) was prepared by direct nitridation of aSi/Mg2Si/Mg/Si3N4 powder compact in a temperature range of 1350-1550°C. The oxygen contentof MgSiN2 was in the range of 0.4 – 0.6 wt%. A thermal stability examination showed that MgSiN2is stable up to 1400°C at 0.1 MPa N2 pressure. The activation energy of decomposition calculatedfrom the temperature dependence of weight loss is [removed info]H = 383 kJ⋅mol-1. The time dependence andnitrogen pressure dependence of MgSiN2 decomposition was also investigated at constanttemperature. MgSiN2 is stable at 1560°C in 0.6 MPa nitrogen atmosphere. Using these experimentaldata together with the heat capacity published in a literature the Gibbs free energy of formation ofMgSiN2 was calculated in a temperature range 300-2500 K.Dense MgSiN2 ceramics or MgSiN2/Si3N4 composites with fluorine-based additives wereprepared by hot pressing. The composite materials had a 4-point bending strength of 427 MPa andVickers hardness (HV1) of 20.8 GPa, respectively. The indentation fracture toughness was 5.3MPa.m1/2, due to the presence of elongated β-Si3N4 grains. The dielectric constant of dense reactionbonded MgSiN2 at 100 kHz was 9.5-10, while that of MgSiN2/Si3N4 composite in a wide range 50 –6000, depending on composition and heat treatment
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/01/51/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.317-318.857.pdf
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