B_20_3-Na_20_3-A1_20_3系のゲルの熱的安定性とガラス化領域(<小特集>セラミック材料小特集号)

概要

論文の詳細を見る
The thermal stability of gels in the B_2O_3-Na_2O_3-Al_2O_3 System Was evaluated by two methods., (1) observation of the change of amorphous region after heating up to 200〜800℃ at a heating rate of 1℃/min and keeping for 2 h, and (2) determination of the crystallization temperature T_c from the DTA curve of gels with heating rate of 5℃/min and calculation of the ratio of T_c to the liquidus temperature T_l, T_c/T_l. After heating gels up to 800℃, the original gel region, which extends over a wide area including Al_2O_3 Was reduced to only a small amorphous region near the Al_2O_3 rich area. The T_c /T_l ratio showed the highest value of more than 0.8 in the composition range B_2O_3=55〜90 mol% and Al_2O_3=0〜20 mol%, while it was less than 0.6 value in the Al_2O_3 rich composition area. The compositional dependence of T_c/T_l ratio was compared with the variation of the glass-forming region obtained from melt at various cooling rates Q in the range of logQ=-2 to 5. It was recognized that the gel region having a high T_c/T_l value corresponds to a stable glass region obtainable under slow cooling. It seems that some close relationship exists between the T_c/T_l of a gel and the critical cooling rate Q* for glass formation of a melt having the same composition.
社団法人日本材料学会の論文
1992-05-15