Crystallization of glasses in the Mg-Si-O-N system

Technical Report · Wed Oct 01 00:00:00 EDT 1980

DOI:https://doi.org/10.2172/6470292· OSTI ID:6470292

Shaw, T C

Crystallization in a glass of composition 59 wt% SiO/sub 2/, 32 wt% NgO and 9 wt% Si/sub 3/N/sub 4/ was investigated in detail using the techniques of differential thermal analysis, x-ray diffraction, optical microscopy and transmission electron microscopy. Crystallization occurred mainly by internal nucleation of crystals, although some surface crystallization was also observed. Intermediate temperature heat treatments in the temperature range 1000/sup 0/C to 1300/sup 0/C crystallized the MgO rich phase of the glass to spherulites of enstatite, but had no effect on the SiO/sub 2/ rich phase. The spherulites developed at intermediate temperatures consisted of fanlike arrangements of plate-shaped enstatite grains separated by thin films of uncrystallized glass. After heating to temperatures above 1300/sup 0/C, faceted grains of enstatite were formed adjacent to the SiO/sub 2/ rich pockets by recrystallization of the spherulites. Heating to above 1300/sup 0/C also precipitated crystals of Si/sub 2/N/sub 2/O from residual glass between enstatite grains in the spherulites. Volume changes on crystallization of the glass caused porosity to form throughout the microstructure. The effect of two stage nucleation and growth heat treatments on microstructure were investigated.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6470292
• Report Number(s): LBL-11759
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALKALINE EARTH METAL COMPOUNDS
COHERENT SCATTERING
CRYSTALLIZATION
DIFFRACTION
GLASS
MAGNESIUM COMPOUNDS
NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
SCATTERING
SILICON COMPOUNDS
X-RAY DIFFRACTION