Nanocomposites and nanomaterials

Features of thermochemical processing and consolidation of nanocrystalline powders in microwaves (2,45 GHz)
Zgalat-Lozynskyy O.B.
Department of Thermomechanical Treatment of High-Melting-Point Materials, Institute for Problems of Materials Science of the NAS of Ukraine. 3, Krzhyzhanovkogo str., Kyiv-03142, Ukraine. 
E-mail: zgalatlozynskyy@gmail.com

Application of microwave (MW) for thermochemical treatment of titanium nitride and silicon nitride nanopowders is a very effective way to reduce the amount of oxygen in the treated material. MW heat treatment at moderate temperatures facilitates the passage of reducing reactions and nitration for nanopowders and mixtures based on silicon nitride. Nanopowders after MW-heat treatment at 250-300 °C characterized by the oxygen content decreasing on 60 - 30% compared to its content in the initial powders. For nanopowders of silicon nitride simultaneously with a decreasing of oxygen amount more than 2 times, there is an increase in the amount of nitrogen in the material by 1.7% by weight [1].
The principle of powder composition formation by the type of "chessboard" for microwave sintering are developed. The "chessboard" principle of composition formation means that the components with different microwave penetration depth are homogeneously distributed in the volume of the material [2]. The consolidation process of high-melting-point wearproof nanocomposites by MW sintering was investigated. After consolidation in microwaves TiN- Si3N4 nanocomposites exhibited a density of ~ 99% of theoretical and fine-grained structure with a grain size of ~30 nm for Si3N4 and ~100 nm for TiN The mechanical properties of this nanocomposite were HV = 21.2 ± 0.5 GPa and K1c = 4.9 MPa·m1/2.

1.	Zgalat-LozynskyyO., KolesnichenkoV., ZamulaM. et al. Thermochemical microwave treatment of refractory nanopowders // Powder Metall Met C+.- 2013.-52.-P. 137-143.
2.	Simms S., Fusco V.F. Chessboard reflector for RCS reductionn // Elec. Let. – 2008. –44, 4. – P.316 - 317