• 한국자원리싸이클링학회:학술대회논문집
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• 한국자원리싸이클링학회 1999년도 제6회 산화철국제워크샵 DIGESTS OF THE INTERNATIONAL WORKSHOP ON IRON OXIDES
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• pp.1-63
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• 1999

Generation of abnormally large grains in the microstructure of small grains has been investigated on some ferrites. Some fractions of large grains were observed in the microstructure of sintered ZnFe$_2$O$_4$, Mn-ZnFe$_2$O$_4$, Fe$_3$O$_4$(in N$_2$) and MnFe$_2$O$_4$(in air). On the other hand, the large grains were not observed in NiFe$_2$O$_4$ and CoFe$_2$O$_4$, independent of calcining and sintering conditions. The large grains seem to be generated in such ferrites that are easy to vary their compositions or valencies at high temperatures. As the sintering proceeded, the number of large grains was increasing to form a continuous structure consisting of large grains, while the size of large grains did not increase remarkably. In addition, the growth of small grains was also very slow during the generation of the large grains. The large grains appeared to be suddenly generated after some induction periods. Avrami equation could be applied to the relation between net volume of large grains and sintering time. Thus, the grain boundaries may be strongly stabilized when the large grains are generated. The large grain in generated by the local activation of the stabilized grain boundaries, which is caused by the variation of compositions or valencies during sintering. It is concluded that the essence of the abnormal grain growth is not the generation of abnormally large grains, but the abnormal stabilization and the local activation of the grain boundaries.

• Journal of Ceramic Processing Research
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• 제20권1호
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• pp.63-68
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• 2019

We investigated the effects of Al2O3 addition on (1-x)Li2B4O7-xAl2O3 (LBAO; x = 0, 0.005, 0.01, 0.05, 0.07, and 0.1) glasses. The glasses were synthesized by a conventional melt-quench method. Structural transformations of the LBAO glasses were assessed via X-ray diffraction analysis. Estimations of ΔT, KGS = (Tc-Tg)/(Tm-Tc), activation energy, and the Avrami parameter were performed using differential thermal analysis and differential scanning calorimetry. An interpretation of non-isothermal kinetics of the crystallization process is presented using the modified Ozawa equation. The activation energy E increased from 3.3 to 3.5 eV for the LBAO (x < 0.01) glasses whereas those of the LBAO (x > 0.05) glasses slightly increased from 3.75 to 4.05 eV. The exponent n was estimated to be 3.9 ± 0.1 for the LBAO (x < 0.01) glasses and 3.2 ± 0.02 for the LBAO (x > 0.05) glasses. Microstructural characterization of the glassy and crystalline phases using atomic force microscopy was investigated. The effects of Al2O3 on the LBAO glasses include a decreased nucleation rate in the crystallization process and a significantly reduced crystal size.

• 한국식품과학회지
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• 제21권6호
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• pp.766-771
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• 1989

가공식품의 원료로써 잘의 가공 적성을 파악하기 위하여 아밀로오스 함량에 따라 가공용으로 육종된 8가지 품종에 대한 전분의 이화학적 특성을 조사하였다. 분리전분의 아밀로오스 함량은 $16.7{\sim}29.7%$이었으며 IR 30, Godael, Aguja 및 Lengkwang의 고 아밀로오스 품종에, Seomjinbyeo, BG-3, B개 및 Samgangbyeo는 저 아밀로오스 품종으로 분류할 수 있었다. 전분의 물 결합력과 blue value는 각각 $87.0{\sim}103.0$ 및 $0.178{\sim}0.305$이었으며 아밀로오스 함량이 증가할수록 아밀로그램의 호화온도와 break down ratio는 증가 한 반면 최고점도는 무관하였다. 0.1% 전분 현탁액의 광투과도는 저 아밀로오스 품종의 경우 $50^{\circ}C$부터 증가하기 시작하였으나 고 아밀로오스 품종은 $65^{\circ}C$이후부터 급격히 증가하였고 $75^{\circ}C$ 이상에서는 차이가 없었다. 또한 팽윤력과 용해도는 저 아밀로오스 품종에서 높게 나타났다. 한편 각종 쌀 전분겔의 노화속도상수는 Aguja 품종이 0.219로 가장 높았고 Seomjinbyeo가 0.057로 가장 낮았으며 아밀로오스 함량이 높을수록 노화속도가 빨랐다.