Conferences

Microstructure and Conductivity of Hot-Pressed Si3N4 - TiO2 (TiH2) Composites Cooled at Different Rates

I.V.Chernyakova,
 
S.N.Zdolnik,
  

I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Krzhizhanovsky str., 3, Kyiv, 03142, Ukraine
Powder Metallurgy - Kiev: Frantsevich Institute for Problems of Materials Science NASU, 2010, #01/02
http://www.materials.kiev.ua/article/1513

Abstract

It is established that the cooling rate after hot pressing governs the crystallization and decrystallization in the Si3N4 - TiO2 (TiH2) composites. The critical cooling rate is 30 K/min for the Si3N4-TiO2 composites and 50 K/min for the Si3N4-TiH2 composites. It is shown that electrical conductivity responds to the evolution of composite microstructure as defect centers appear. The defects are located at the trap levels of 0.4±0.05–1.3±0.05 eV and differ in the mutually perpendicular directions. The best combination of properties is shown by the composites with a mono-trap level with the activation energy of 0.8 ± 0.05 eV. These energy levels supposedly belong to the thin layer of amorphous silicon. The nascent defects are probably point defects or association of point defects because of the low sensitivity of mechanical properties and strong response of electrical conductivity to the cooling rate.


CONDUCTIVITY, COOLING RATE, HOT-PRESSING PROCESS, MICROSTRUCTURE, SILICON CARBIDE, TITANIUM HYDRYDE, TITANIUM OXIDE