Final report

[摘要] In the DOE award, DE-FG02-00ER45823, we have used molecular dynamics (MD) computer simulations of the intergranular films (IGFs) present in alumina and silicon nitride materials to address specific questions such as: What is the atomistic structure of the glassy silicate phase? Because of the extremely thin nature of the IGF, do bulk-like glass structure and properties prevail? Does distortion exist in the silicate bonds (which affects bond strength and reactivity) and how is this structure affected by the separation distance between the crystals and/or by the composition of the IGF? Does a structural ordering caused by epitaxial adsorption occur at the IGF/crystal interface? What is the correlation length of this order perpendicular to the interface? How is this ordering affected by composition of the IGF or by the crystals in question? In all simulations, a specific number of ions in stoichiometric ratio were placed as the IGF between two similar crystals, with, in some cases, different crystallographic orientations. The IGF compositions coincided with some of those observed experimentally (calcium aluminosilicate (CAS) glasses in the alumina case, calcium silicon oxy-nitride in the nitride case). The number of ions in the IGF was varied to allow for different thicknesses, although the X and Y dimensions (parallel to the interface) were usually {approx} 50 {angstrom} x 50 {angstrom}. The IGF was melted at a high temperature between the crystals, followed by a slow quench to room temperature, where structural data were collected.

[发布日期] 2004-11-12 [发布机构] Rutgers University

[关键词] Dimensions;Silicon Nitrides;Computerized Simulation;36 Materials Science;Adsorption