Si<SUB>3</SUB>N<SUB>4</SUB>–TiN Nanocomposite by Nitration of TiSi<SUB>2</SUB> and Consolidation by Hot Pressing and Spark Plasma Sintering

Abstract

Homogeneous nanostructured Si3N4-TiN composite powder was obtained by nitration of a TiSi2 powder precursor in a nitrogen flow. Mechanoactivation of titanium disilicide increases the nitration rate and reduces the temperature of formation of the Si3N4 and TiN. The properties of hot pressing (HP) and spark plasma sintering (SPS) of the nanostructured Si3N4-TiN composite with Y2O3 and Al2O3 additives have been studied. In the case of the HP-prepared composite the processing conditions are sufficient to form a stable, equilibrated grain boundary framework. The SPS consolidation is extremely rapid, low-temperature process and the sintering temperature was 300-400 degrees C lower than that of the hot pressing temperature. As a result the grain boundary framework was underdeveloped. Post-sintering anneal of the SPS-prepared samples caused significant improvement of their mechanical properties. The SPS and HP-derived Si3N4-40 mass% TiN-6 mass% Y2O3-2 mass% Al2O3 nano-composite of 98.4% and 98.9% of relative density demonstrate the Vickers hardness values of 13.2 and 13.7 GPa, respectively. The grains of Si3N4 and TiN were much finer in the case of the SPS-derived ceramic composite. However, the better development of the grain boundary framework in the case of the higher temperature HP treatment in comparison to the SPS significantly reduced the advantage of nanocrystallinity. In both cases the fracture toughness was comparable even after the improvement of grain boundary framework during the SPS consolidation. The K(1c), of 7.83 MPax m(1/2) of the sample prepared according to the best SPS regime is also comparable to K(1c) of 8.30 MPa x m(1/2) of much coarser hot pressed ceramic with very similar relative density.

High‐Strength B4C–TaB2 Eutectic Composites Obtained via In Situ by Spark Plasma Sintering

“…The SPS was performed using a “Dr. Sinter” apparatus (Sumitomo, Japan) . Initially, a pressure of 20 MPa was applied to ensure sufficient electric contact between the powder tablet and the graphite die.…”

Advanced Sintering of Nano-Ceramic Materials

“…This property of SPS is of undoubted significance in the case of manufacture of bulk nanostructured parts, for which the control of grain growth is one of the major problems (H. Borodianska et al, 2008;O. Vasylkiv et al, 2008;H. Borodianska et al, 2009).…”

High-temperature reactive spark plasma consolidation of TiB2–NbC ceramic composites

“…Among the reactive consolidation techniques, spark plasma sintering (SPS) is gaining in popularity [23][24][25][26]. In a recent report on hightemperature reaction-driven spark plasma sintering (RSPS) of TiB 2 -TaC ceramics, Demirskyi et al [22] reported the formation of a hard (28 GPa) tantalum titanium carboboride phase during consolidation that involved the dissolution of titanium diboride into a newly formed (Ta,Ti)C carbide.…”