The electronic structures and optical properties, the atomic population, bond lengths, band structures and density of states (DOS) of undoped and doped rare earth elements (Y, La) in γ-Si_3N_4 have been calculated by means of plane wave pseudo-potential method (PWP) with generalized gradient approximation (GGA).

Based on the calculations, we analyzed the influence of pressure on the optical and mechanical properties γ-Si_3N_4, which indicates that γ-Si_3N_4 is quite suitable for applications under high pressure.

Fabrication and Simulation of Silicon-on-Insulator Structure with Si_3N_4 as a Buried Insulator;

Three experimental schemes were executed to validate the feasibility of producing the V-bearing HRB400 bar with Si_3N_4 alloy as nitrogen alloy reagent.

Synthesis of silicon nitride powder is the basis of fabrication of Si_3N_4 ceramics.

silicon nitride (Si_3N_4) ceramics were bonded by the adhesive, and the bonded specimens were heat-treated within 300～800℃ subsequently.

The addition of the dispersant can make the isoelectric point of silicon nitride slurry move ahead,and make the slurry become better.

The crack resistance behaviour of two kinds of silicon nitride ceramics which have different microstructure was determined, and the crack closure (bridging) stress distribution in the wake region of the crack tip was also estimated.

This paper deals with an experimental study on the surface roughness of Si 3N 4 ceramics by WEDM-HS.

Three kinds of sintering aids MgO, Al 2O 3+AlN and Y 2O 3+AlN are chosen and effect of them and their contents on mechanical properties of pressurelessly sintered (1 800℃×3 h) Si 3N 4 is investigated.