서지주요정보
알루미나에서 아노싸이트와 MgO에 의한 입자 성장 양상의 변화 = Variation of grain growth behavior induced by anorthite and MgO in $Al_2O_3$
서명 / 저자 알루미나에서 아노싸이트와 MgO에 의한 입자 성장 양상의 변화 = Variation of grain growth behavior induced by anorthite and MgO in $Al_2O_3$ / 박찬우.
저자명 박찬우 ; Park, Chan-Woo
발행사항 [대전 : 한국과학기술원, 1996].
Online Access 원문보기 원문인쇄

소장정보

등록번호

8006513

소장위치/청구기호

학술문화관(문화관) 보존서고

MMS 96021

SMS전송

도서상태

이용가능

대출가능

반납예정일

초록정보

The grain growth behaviors of ultra pure (>99.998 wt%) $α-Al_2O_3$ doped with a certain amount of anorthite and MgO have been investigated at 1650℃. In the 0.1 wt% anorthite + $Al_2O_3$, the abnormal grain growth (AGG) occurs, and all of the solid-liquid interfaces at the grain boundary junctions are observed to have faceted shapes and the singular structure. In the 0.1 wt% anorthite + 0.1 wt% MgO + $Al_2O_3$, the number of abnormally growing grains increases, and the bimodal distribution of grain size appears during the grain growth. In addition, some of the solid-liquid interfaces are observed to have rounded shapes and roughened structure, and the shapes of growing grains become quite isotropic compared to the specimen without MgO. During the sintering of $Al_2O_3$, the impurities such as CaO and $SiO_2$ form a very small amount of liquid of which composition is similar to that of anorthite, so grain boundaries and grain boundary junctions are wetted by the liquid phase. In this situation, the growth rate is controlled by the movement of grain boundary junctions, and the junctions are moved by means of dissolution/precipitation reactions at the solid-liquid interfaces. Therefore, the growth behavior of grains varies according to the structure of solid - liquid interfaces at the grain boundary junctions. If the interface energy is isotropic, the solid-liquid interfaces have rounded shapes and the atomically rough structure. The rough interface allows the continuous attachment of atoms from the liquid, and the interface mobility remains constant. Then all of the junctions can move by the dissolution/precipitation reactions, if there exist any driving forces; the normal grain growth (NGG) is expected under this condition. If the interface energy is highly anisotropic and there exist some cusps in the γ-plot of the interface energy, the solid-liquid interfaces have faceted shapes and the atomically singular structure. Without the ledge-generating sources such as screw dislocations, the grains with such singular interfaces can grow only by the 2-D nucleation. As the 2-D nucleation on a singular interface needs a driving force larger than a critical value, only the grains large enough to have capillary driving forces larger than the critical value for the 2-D nucleation can grow by dragging junctions. The growth of other grains is almost suppressed. Thus, the abnormal grain growth is expected when all of the solid-liquid interfaces at the junctions have the singular structure. The faceted shapes of liquid-solid interfaces observed at the grain boundary junctions in 0.1 wt% anorthite + $Al_2O_3$ which shows the AGG behavior confirms this predicted relationship between the singular interface structure and the AGG. The increase in the number of growing grains after the MgO doping is supposed to be due to the roughening of some solid-liquid interfaces. The roughened interfaces can grow under the capillary driving forces smaller than the critical value for the 2-D nucleation. Thus, the fraction of movable junctions increases and more grains become to be able to grow as some interfaces are roughened. Therefore, the effects of MgO are thought to increase the number of growing grains by roughening some of solid-liquid interfaces making the shapes of growing grains more isotropic. Due to these two effects, the final structure after the impingement of abnormally growing grains looks like the NGG structure.

서지기타정보

서지기타정보
청구기호 {MMS 96021
형태사항 iv, 61 p. : 삽도 ; 26 cm
언어 한국어
일반주기 저자명의 영문표기 : Chan-Woo Park
지도교수의 한글표기 : 윤덕용
지도교수의 영문표기 : Duk-Yong Yoon
학위논문 학위논문(석사) - 한국과학기술원 : 재료공학과,
서지주기 참고문헌 : p. 58-61
주제 알루미나
입자 성장
아노싸이트
MgO
Alumina
Grain Growth
Anorthite
MgO
QR CODE qr code