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Si3N2 is alpha Po structured and crystallizes in the cubic Pm-3m space group. The structure is zero-dimensional and consists of one Si3N2 cluster. Si+1.33+ is bonded in a bent 120 degrees geometry to two equivalent N2- atoms. Both Si–N bond lengths are 1.76 Å. N2- is bonded in a trigonal planar geometry to three equivalent Si+1.33+ atoms.
(Si3N2)8H2 is alpha carbon monoxide-like structured and crystallizes in the tetragonal P4mm space group. The structure is zero-dimensional and consists of one hydrogen molecule and one Si3N2 cluster. In the Si3N2 cluster, there are three inequivalent Si2+ sites. In the first Si2+ site, Si2+ is bonded in a bent 120 degrees geometry to two equivalent N+2.88- atoms. Both Si–N bond lengths are 1.76 Å. In the second Si2+ site, Si2+ is bonded in a bent 120 degrees geometry to two equivalent N+2.88- atoms. Both Si–N bond lengths are 1.77 Å. In the third Si2+ site, Si2+ is bonded in a bent 120 degrees geometry to two N+2.88- atoms. Both Si–N bond lengths are 1.76 Å. There are two inequivalent N+2.88- sites. In the first N+2.88- site, N+2.88- is bonded in a trigonal planar geometry to three Si2+ atoms. In the second N+2.88- site, N+2.88- is bonded in a trigonal planar geometry to three Si2+ atoms.
High density ceramic sinters are manufactured by coating premolded or presintered porous ceramics with a sealing material of high SiO2 porous glass or nitride glass and then sintering by hot isostatic pressing. The ceramics have excellent abrasion and corrosion resistances. Thus LC-10 (Si3N2 powder) and Y2O3-Al2O3 type sintering were mixed and molded to give a premolded porous ceramic (porosity 37%, relative bulk density 63%). The ceramic was dipped in a slurry containing high SiO2 porous glass and an alcohol solution of cellulose acetate and dried. The coated ceramic was treated in a nitrogen atmosphere and then sintered by hot isostatic pressing to give a dense ceramic sinter.