HOT-PRESSING BEHAVIORS OF THE GEL AND MELT-DERIVED SODIUM-BOROSILICATE GLASS POWDERS

Na-borosilicate glasses are used widely in glass-matrix composites whi ch are produced by slurry or sol-gel infiltration followed by hot-pres sing. The hot-pressing behaviours of the glass powders are an importan t parameter in the preparation of the glass-matrix composites. The den sification and crystallization of the gel and melt-derived Na-borosili cate glass powders under hot-pressing were studied. Gel-derived powder s crystallized faster than the melt-derived powders. Cristobalite was the crystalline phase in both powders. The crystallization of the gel and melt-derived powders inhibited the viscous sintering during hot-pr essing. Viscosities of the powders were calculated at various temperat ures under isothermal hot-pressing conditions. Melt-derived powders ha d lower viscosities then the gel-derived powders. (C) 1997 Elsevier Sc ience Limited and Techna S.r.l.