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韩国科学技术学院Suk-Joong L. Kang院士讲座通知

发布时间:2021-07-09被阅次数:10来源:材料学院

应我校材料学院王玉金教授邀请,韩国科学技术学院(Korea Advanced Institute of Science and Technology)材料科学与工程系Suk-Joong L. Kang院士将于2021712–28日在线做烧结理论学术报告,欢迎广大师生参加。

 

报告一:

题目:Basis of sintering science

时间:2021712日(星期一),16:00—17:30

腾讯会议号:960 442 988

 

摘要:

When thermal energy is applied to a powder compact, the compact is densified and the average grain size increases. The basic phenomena occurring during this process, called sintering, are densification and grain growth. To understand sintering and utilize it in materials processing, we first need to understand the fundamentals of the thermodynamics and kinetics of the two basic phenomena. In the first lecture, the process of sintering is briefly discussed and the related thermodynamics presented. The polycrystalline microstructure obtained after sintering is also characterized.

 

报告二:

题目:Solid state sintering models and densification

时间:2021714日(星期三),16:00—17:30

腾讯会议号:880 319 257

 

摘要:

Solid state sintering is usually divided into three overlapping stages-initial, intermediate and final. The initial stage is characterized by the formation of necks between particles and its contribution to compact shrinkage is limited to 2~3% at most. During the intermediate stage, considerable densification, up to ~93% of the relative density, occurs before isolation of the pores. The final stage involves densification from the isolated pore state to the final densification. For each of these three stages, simplified models are typically used: the two-particle model for the initial stage, the channel pore model for the intermediate stage, and the isolated pore model for the final stage. Although all models ignore grain growth during sintering, they do provide a means of analysing the densification process and evaluating the effects of various processing parameters. This lecture deals with sintering mechanisms and kinetics of initial stage sintering, densification models and theories at intermediate and final stage sintering. Topics of pressure-assisted sintering and constrained sintering are also included in this lecture.

 

报告三:

题目:Grain growth

时间:2021719日(星期一),16:00—17:30

腾讯会议号:256 795 832

 

摘要:

The average grain size of polycrystalline materials increases as the annealing time increases and the phenomenon of grain growth is important not only in sintering but also in other materials processes. Phenomenologically, grain growth is divided into two types: normal and abnormal (sometimes also called exaggerated) grain growth. Normal grain growth is characterized by a simple and invariable distribution of relative grain sizes with annealing time, while abnormal grain growth, which occurs by the formation of some exceptionally large grains in a matrix of fine grains, shows a bimodal grain size distribution. From the point of view of chemistry and microstructure, several cases may be considered in the study of grain growth: pure materials, materials with impurity segregation at the grain boundaries, materials with second-phase particles, materials in chemical inequilibrium, etc. Here, grain growth behavior and its theoretical basis in fully dense polycrystalline materials will be considered. Grain growth during densification of powder compacts in solid state sintering will be discussed in this lecture. The growth of grains dispersed in a liquid or solid matrix, so-called Ostwald ripening, will also be described.

 

报告四:

题目:Microstructure development and sintering of ionic compounds

时间:2021721日(星期三),16:00—17:30

腾讯会议号:207 537 174

 

摘要:

The microstructural development of a compact during sintering will mainly be discussed by analysing densification and grain growth together. At the final stage of sintering, where the pore size is usually smaller than the grain size, the pore shape, which is determined by the dihedral angle, is not the primary parameterby which microstructural development is analysed. In contrast, for pores of size comparable to or larger than the grain size, pore shape is an important parameter. Depending on the dihedral angle and ratio of pore size to grain size, pores cannot shrink unless a critical condition is satisfied as a result of grain growth. In addition, the vacancy concentration in a specific region was assumed to be determined only by the capillary pressure of the region arising from its geometry. However, the vacancy concentration in most ceramics, in particular ionic compounds, varies with the addition of dopants (also called additives, in general) and accordingly the sinterability also varies. Furthermore, depending on point defect concentration and temperature, the species that determines sinterability can also change. We will consider the densification and grain growth of ionic compounds in relation to defect chemistry, ion diffusion and ion segregation.

 

报告五:

题目:Liquid phase sintering

时间:2021728日(星期三),16:00—17:30

腾讯会议号:708 765 245

 

摘要:

When a powder compact is sintered in the presence of a liquid phase, i.e. in liquid phase sintering, the density of the compact increases and, at the same time, grains grow as in the case of solid state sintering. The phenomenon in which the average grain size increases via growth of large grains and dissolution of small grains in a matrix is referred to as Ostwald ripening. For the simplest case, Ostwald ripening has been theoretically and rigorously analysed (Lifshitz–Slyozov–Wagner (LSW) theory). The grain growth in real systems, however, is sometimes very different from the simple case, often exhibiting abnormal grain growth. This lecture describes theories of grain growth in a matrix; particular emphasis is given to recent explanations of abnormal grain growth. With respect to densification during liquid phase sintering, two theories have been proposed: the contact flattening theory and the pore filling theory. The former is basically a two-particle model, similar to that of solid state sintering. On the other hand, the latter considers both the densification and grain growth, reflecting the real phenomena that occur during liquid phase sintering. The two models and theories are critically examined in this lecture. Microstructure development during liquid phase sintering is then described.

 

报告人简介

Suk-Joong L. Kang

Distinguished Professor,

Department of Materials Science and Engineering,

Korea Advanced Institute of Science and Technology,

291 Daehak-ro, Yuseong-gu, Daejeon, 305–701,

Korea                 

E-mail: sjkang@kaist.ac.kr

 

Suk-Joong L. Kang is a Distinguished Professor in the Department of Materials Science and Engineering at the Korea Advanced Institute of Science and Technology (KAIST). He is a member of Korean Academy of Science and Technology (1996), and National Academy of Engineering of Korea (2002). He received a Dr.-Ing degree from the Ecole Centrale de Paris (1980), and a Dr. d’ Etat degree from the University of Paris VI (1985). After joining KAIST in 1980, he also served as a Visiting Professor at the Stuttgart Max-Plank-Institut (’82-’83, ’88) at Samsung Electromechanics (’93-’94), at the University of New South Wales (’01-’02) and at the University of Tokyo (’08), and as President of the Korea Institute of Ceramic Engineering and Technology (KICET) (’15-’18).

Dr. Kang has published more than 280 papers on sintering and microstructural evolution in ceramics and metals. Since 2000, he has presented over 100 invited talks at international conferences. He is the author of the text Sintering: Densification, Grain Growth and Microstructure, published in 2005. He developed the “Pore Filling Theory” of liquid phase sintering. Since the late 1990’s, Dr. Kang has particularly contributed to the understanding of microstructural evolution by structural transition and defect formation at interfaces. He introduced the concept of the mixed control of boundary migration, and deduced the mixed mechanism principle of microstructural evolution. Dr. Kang is a fellow of the American Ceramic Society and a member of the World Academy of Ceramics, President-Elect of the International Ceramic Federation (’18-’20). He also served as President of the Korean Powder Metallurgy Institute (’06), the Korean Ceramic Society (’12), and the Asia-Oceania Ceramic Federation (’13-’14), and as Editor-in-Chief of the Journal of Asian Ceramic Societies (’13-’15). He is the recipient the Sosman Award from the American Ceramic Society (’11), the Richard Brook Award from the European Ceramic Society (’15), the Helmholtz International Fellow Award from the Helmholtz Gemeinschaft (Germany) (’15), the Inchon Prize from the Inchon Memorial Foundation (’07), and the Korea Engineering Prize from the President of the Republic of Korea (’10).


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