석탄 바닥재로 제조된 유리의 결정화 거동 분석
The crystallization behavior of glass made from coal bottom ash
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초록
화력 발전소에서 발생하는 석탄 바닥재에 Na2O와 Li2O가 첨가된 결정화 유리를 제조하고, 비등온 열분석법을이용하여 결정성장 거동을 분석하였다. 온도에 따른 결정화 분율 및 결정화 속도 변화를 계산한 결과, 결정화가 50 % 진행된 온도는 DTA 상의 결정 발열피크 Tp 보다 약간 높게 나타났으며, 결정화가 가장 빠르게 진행되는 온도는 Tp와 거의 일치함을 알 수 있었다. Kissinger 식을 이용하여 결정화 활성화 에너지(262 kJ/mol), Avrami 상수 (1.7) 그리고 진동수(5.7 × 1016/s)를 계산하였으며, 이로부터 nepheline 결정 성장은 주로 1~2 차원적 표면 결정화 경향을 보이지만, 동시에 내부결정화도 어느 정도 나타날 것으로 예측되었다. 실제 미세구조 관찰에서 수지(dendrite)상의 표면 결정화가 상당히 일어났고동시에 낮은 분율의 내부 결정도 생성된 것이 확인되어, Kissinger 식에 의해 예측된 결과가 본 연구에서 제조된 결정화 유리의 거동과 일치함을 알 수 있었다.
Abstract
The glass-ceramics made from the mixture of coal bottom ash, produced from a thermal power plant mixed with Na2O and Li2O was fabricated and their crystallization behavior was studied using a non-isothermal analyzing method. The temperature for 50 % crystallization was higher than the exothermic peak temperature Tp at DTA curve and the quickest crystallization temperature was much the same as Tp as identified from the relationships of crystallized fraction and crystallization rate with temperature. By using Kissinger equation describing a crystallization behavior, the activation energy (262 kJ/mol), the Avrami constant (1.7) and the frequency (5.7 × 1016/s) for crystallization were calculated from which the nepheline crystal could be expected as showing an 1~2-dimensional surface crystallization behavior mainly with some bulk crystallization tendency at the same time. The actual observation of microstructure using SEM showed the considerable amount of surface crystals of dendrite and the bulk crystals with low fraction, so the prediction by the Kissinger equation was in accord with the crystallization behavior of glass-ceramics fabricated in this study.
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