Gravity Effects on Combustion Synthesis of Glasses

The Combustion Synthesis technique has been used to produce glasses based on B2O3-Al2O3-MgO and CaO-Al2O3. The combustion characteristics of these combustion synthesis reactions using both small cylindrical pellets (SCP) and large spherical pellets (LSP) are presented. Low density pellets (approx. 35% of their theoretical density) were used, which made synthesis of low exothermic combustion reactions possible. Microstructural analysis of reacted samples was carried out to identify the glass-forming compositions. The effects of gravity on the glass formation were studied aboard the KC-135 using SCP samples. Gravity seemed to have such obvious effects on the combustion characteristics that the wave velocity was lower and the Width of the combustion wave was larger under reduced gravity conditions. Samples produced under low gravity also had more enhanced vitrification than those on ground, while some systems also exhibited lower combustion temperatures. It was also found that the container significantly affects both the combustion characteristics and microstructure. Substantially more divitrification occurred at the area which was in contact with the support (container)