Yttrium이 첨가된 BaTiO₃에서 형성된 core/shell 구조에서 shell의 TCC 거동: 독립적 관찰

전상채,Jeon, Sang-Chae 한국결정성장학회 2020 한국결정성장학회지 Vol.30 No.3

MLCC(Multi-Layer Ceramic Capacitor)의 유전체 층에 사용되는 BaTiO₃ 입자는 안정한 TCC(Temperature Characteristics of Capacitance) 거동을 갖기 위해 core/shell 구조를 갖는다. 지금까지 shell의 특성은 core/shell 구조의 전체 특성에서 유추해 왔다. 이는 core/shell 구조가 겨우 수 ㎛의 작은 크기로 shell 특성만 구별해서 측정하기가 어렵기 때문이다. 본 실험에서는 micro-contact법을 이용하여 확산쌍 시편의 계면에 형성된 확대된 core/shell 구조에 Pt 전극을 증착하여 35~135℃ 에서 shell 영역의 독립적인 TCC 거동을 측정하였다. 그 결과, 65℃에서 최대 유전율 값을 갖는 완만한 피크의 확산 상전이(Diffusion Phase Transition) 거동인 core의 특성과 구별되는 거동을 관찰하였으며, 이는 core/shell 구조의 온도-유전거동을 묘사하는 모델링에서 실험 자료로 활용될 것으로 본다. Grains in the BaTiO₃, which is used for a dielectric layer in MLCC(Multi-Layer Ceramic Capacitor) are necessary to form core/shell structure for a stable TCC(Temperature Coefficient of Capacitance) behavior. The shell property has been deduced from the whole TCC behavior of core/shell structure due to its tiny size, ~ few ㎛. This study demonstrates the individual TCC behavior of the shell phase measured by micro-contact measurement in a temperature range between 35 and 135℃. Pt electrode pairs deposited on an enlarged core/shell structure in a diffusion couple sample made the measurement possible. As a result, the DPT (Diffusion Phase Transition) behavior of the shell phase was revealed as a different TCC behavior from that of the core: a broad peak with T_m at 65℃. This would be also useful experimental data for a modelling that depicts dielectric-temperature behavior of core/shell structure.

Core-shell 구조의 Au/TiO₂ 나노 미립자의 합성 및 특성 평가

유연태,Paul Mulvaney 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.9

Au/TiO$_2$ core-shell 구조 나노 미립자가 졸-겔법에 의해서 제조되었고, TiO$_2$ shell의 형상과 결정성이 TEM과 UV-Vis. absorption spectrometer에 의해서 조사되었다. Au/TiO$_2$ core-shell 나노 미립자는 Au 콜로이드 에탄올 수용액 중에서 TOAA(Titanium Oxide Acethylacetonate)의 가수분해에 의해 합성될 수 있었다. Au 나노 미립자의 표면에 형성된 TiO$_2$ shell의 두께는 약 1 nm이었다. TiO$_2$ shell의 결정성을 조사하기 위하여. TiO$_2$가 피복된 Au 콜로이드 에탄올 용액에 254 nm의 자외선과 $^{60}$Co의 방사선을 조사하였다. Au 나노 미립자의 surface plasmon 현상은 방사선이 조사되었을 때만 나타났고, 이 결과로부터 TiO$_2$ shell은 비정질 상태임을 알 수 있었으며, Au의 분산성 향상을 위해 표면에 처리된 MUA(Mercaptoundecanoic Acid)층은 전자의 이동을 방해하는 장애물로 작용하지 않음을 확인할 수 있었다. Au/TiO$_2$ core-shell structure nanoparticles were synthesised by sol-gel process, and the morphology and crystallinity of TiO$_2$ shell were investigated by TEM and UV-Vis. absorption spectrometer. Au/TiO$_2$ core-shell structure nanoparticles could be prepared by the hydrolysis of TOAA (Titanium Oxide Acethylacetonate) in Au colloid ethanol solution with $H_2O$. The thickness of TiO$_2$ shell on the surface of Au particles was about 1 nm. To investigate the crystallinity of TiO$_2$ shell, UV light with 254 nm and radioactive lay of $^{60}$ CO were irradiated on the TiO$_2$ coated Au colloid ethanol solution. The surface plasmon phenomenon of Au nanoparticles appeared only when the radioactive lay was irradiated on the TiO$_2$ coated Au colloid ethanol solution. From these results, it was found that the TiO$_2$ shell was amorphous and the MUA (Mercaptoundecanoic Acid) layer on the Au particle for its dispersion didn't act as an obstacle to disturb the movement of electron onto the surface of Au particle.

형태-껍질-구조(Morph-Shell-Structure)와 형태통사론(Morphosyntax)

김양진 ( Kim Ryan-gjin ) 한말연구학회 2021 한말연구 Vol.- No.61

The purpose of this paper is to examine the aspect in which the lexical category of Korean has a lexical morph-shell according to the expansion of [[[[noun] adjective] intransitive verb] transitive verb]. Through this Morph-Shell-Structure, we tried to show that the principle of expansion of the morphology can be applied to the syntax in the same way as the mirror image principle. In Korean, which is an agglutinative language, some shell-structures appear as morphemes. Even considering the blanks of the paradigmatic relation and syntagmatic relation, Lexical morph-shell-structure in the developmental dimension could be confirmed. Afterwards, we will examine how this morph-shell structure is implemented in languages other than Korean, and how it is correlated and reflected with the syntactic structure of the target language.

Static analysis of a radially retractable hybrid grid shell in the closed position

Jianguo Cai,Chao Jiang,Xiaowei Deng,Jianfeng Zhao,Yixiang Xu 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.6

A radially retractable roof structure based on the concept of the hybrid grid shell is proposed in this paper. The single-layer steel trusses of the radially foldable bar structure are diagonally stiffened by cables, which leads to a single-layer lattice shell with triangular mesh. Then comparison between the static behavior between the retractable hybrid grid shell and the corresponding foldable bar shell with quadrangular mesh is discussed. Moreover, the effects of different structural parameters, such as the rise-to-span ratio, the bar cross section area and the pre-stress of the cables, on the structural behaviors are investigated. The results show that prestressed cables can strengthen the foldable bar shell with quadrangular mesh. Higher structural stiffness is anticipated by introducing cables into the hybrid system. When the rise-span ratio is equal to 0.2, where the joint displacement reaches the minimal value, the structure shape of the hyrbid grid shell approaches the reasonable arch axis. The increase of the section of steel bars contributes a lot to the integrity stiffness of the structure. Increasing cable sections would enhance the structure stiffness, but it contributes little to axial forces in structural members. And the level of cable prestress has slight influence on the joint displacements and member forces.

Composted Oyster Shell as Lime Fertilizer Is More Effective Than Fresh Oyster Shell

LEE, Young Han,ISLAM, Shah Md. Asraful,HONG, Sun Joo,CHO, Kye Man,MATH, Renukaradhya K.,HEO, Jae Young,KIM, Hoon,YUN, Han Dae Japan Society for Bioscience, Biotechnology, and A 2010 Bioscience, Biotechnology, and Biochemistry Vol.74 No.8

<P>Physio-chemical changes in oyster shell were examined, and fresh and composted oyster shell meals were compared as lime fertilizers in soybean cultivation. Structural changes in oyster shell were observed by AFM and FE-SEM. We found that grains of the oyster shell surface became smoother and smaller over time. FT-IR analysis indicated the degradation of a chitin-like compound of oyster shell. In chemical analysis, pH (12.3±0.24), electrical conductivity (4.1±0.24 dS m<SUP>−1</SUP>), and alkaline powder (53.3±1.12%) were highest in commercial lime. Besides, pH was higher in composted oyster shell meal (9.9±0.53) than in fresh oyster shell meal (8.4±0.32). The highest organic matter (1.1±0.08%), NaCl (0.54±0.03%), and moisture (15.1±1.95%) contents were found in fresh oyster shell meal. A significant higher yield of soybean (1.33 t ha<SUP>−1</SUP>) was obtained by applying composted oyster shell meal (a 21% higher yield than with fresh oyster shell meal). Thus composting of oyster shell increases the utility of oyster shell as a liming material for crop cultivation.</P>

Increasing resolution of selectivity in alkene hydrogenation via diffusion length in core-shell MFI zeolite

Jia, Xicheng,Jeong, Yanghwan,Baik, Hionsuck,Choi, Jungkyu,Yip, Alex C.K. Elsevier 2018 CATALYSIS TODAY - Vol.314 No.-

<P><B>Abstract</B></P> <P>We designed a core-shell zeolite structure comprises of palladium-deposited ZSM-5 core and silicalite-1 (S-1) shell which favors selectivity towards light olefin in hydrogenation via increased diffusion length. A well designed S-1/Pd/ZSM-5 core-shell structure was prepared via secondary crystallization of S-1 layer on the Pd/ZSM-5 core. The catalytic and selectivity performance of the S-1/Pd/ZSM-5 composite was evaluated in catalytic hydrogenation of alkenes in liquid phase. The synthesized S-1/Pd/ZSM-5 gives a much higher selectivity towards 1-hexene (87%) over cyclohexene (13%) even though both reactants are able to enter the 10-membered ring channels of the core-shell structure. The zeolitic core-shell composite also showed an increasing selectivity towards 1-hexene over 1-heptene as the S-1 layers built up, even though both are linear alkenes with similar kinetic diameter that are accessible to the MFI framework. In this work, we demonstrate a strong correlation between the thickness of the S-1 shell layer and the selectivity towards light olefins due to faster mass transfer rate. The design of the core-shell MFI structure is a new example of how selectivity in a zeolite-catalyzed reaction can be changed and enhanced without relying on typical molecular size exclusion process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A synthesis method for a core-shell S-1/Pd/ZSM-5 composite is reported. </LI> <LI> The S-1 shell can distinguish alkenes with similar size/shape via diffusion length. </LI> <LI> Selectivity of MFI zeolite can be augmented without changing the pore size. </LI> <LI> The core-shell design broadens the applications of MFI in selective reactions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

The actuation equation of macro-fiber composite coupled plate and its active control over the vibration of plate and shell

Tu, Jianwei,Zhang, Jiarui,Zhu, Qianying,Liu, Fan,Luo, Wei Techno-Press 2018 Structural monitoring and maintenance Vol.5 No.2

Plate and shell structure is widely applied in engineering, i.e. building roofs, aircraft wings, ship platforms, and satellite solar arrays. Its vibration problem has become increasingly prominent due to the tendency of lightening, upsizing and flexibility. As a new smart material with great actuating force and toughness, macro-fiber composite (MFC) is composed of piezoelectric fiber and epoxy resin basal body, which can be directly pasted onto the surface of plate and shell and is suitable for vibration control. This paper deduces the actuation equation of MFC coupled plate in different boundary conditions, an equivalent finite element modeling method is proposed which uses MFC actuating force as the applied excitation, and on this basis the active control simulation and experiment of MFC over plate and shell structure vibration are accomplished. The results indicate that MFC is able to implement effective control over plate and shell structure vibration in multi-band range. The comparison between experiment and simulation proves that the actuation equation deduced herein, effective and practicable, can be applied into the simulation calculation of MFC vibration control over plate and shell structure.

쉘 구조물의 유한요소해석에 대하여

이필승(Lee Phill-Seung),노혁천(Noh Hyuk-Chun) 대한토목학회 2007 대한토목학회논문집 A Vol.27 No.3A

본 논문에서는 최근 주요 연구들을 토대로 쉘 구조물의 유한요소해석에 대하여 중요한 개념들과 그 연관관계를 고찰한다. 감절점 쉘 유한요소의 수학모델인 기본쉘수학모델을 살펴본다. 쉘 구조물의 두께가 얇아짐에 따라 일어나는 쉘 구조문제의 세가지 극한거동들(휨지배거동, 막지배거동, 혼합지배거동)에 대한 쉘의 점근거동 이론을 소개하고 점근거동을 유한요소해석을 통해 찾아내는 방법을 알아본다. 유한요소해의 오차를 s-norm으로 평가하는 방법을 소개하고 이를 이용하여 쉘 유한요소의 잠김현상이 유한요소해의 수렴곡선에 어떻게 나타나는지 살펴본다. 쉘 구조물의 유한요소해석에서 균일최적수렴의 개념을 논의한다. 마지막으로 이상적인 쉘 유한요소의 조건을 알아보고 쉘 유한요소의 성능평가를 위한 방법론을 제시한다. Based on recent research works, important concepts on the finite element analysis of shell structures and the relations among them are presented in this paper. We review the basic shell mathematical model, which is the underlying mathematical model of the continuum mechanics based shell finite elements. The asymptotic theory of shell structures then is reviewed and we present how to evaluate the asymptotic behavior in finite element solutions. S-norm is introduced as an error measure of finite element solutions and we show "locking" in the convergence curves of shell finite element solutions. We discuss the concept of "uniform optimal convergence" in finite element analysis of shells. We finally summarize requirements on ideal shell finite elements and propose how to perform benchmark tests of shell finite elements.

Transient energy flow in ship plate and shell structures under low velocity impact

Liu, Z.S.,Swaddiwudhipong, S.,Lu, C.,Hua, J. Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.20 No.4

Structural members commonly employed in marine and off-shore structures are usually fabricated from plates and shells. Collision of this class of structures is usually modeled as plate and shell structures subjected to dynamic impact loading. The understanding of the dynamic response and energy transmission of the structures subjected to low velocity impact is useful for the efficient design of this type of structures. The transmissions of transient energy flow and dynamic transient response of these structures under low velocity impact are presented in the paper. The structural intensity approach is adopted to study the elastic transient dynamic characteristics of the plate structures under low velocity impact. The nine-node degenerated shell elements are adopted to model both the target and impactor in the dynamic impact response analysis. The structural intensity streamline representation is introduced to interpret energy flow paths for transient dynamic response of the structures. Numerical results, including contact force and transient energy flow vectors as well as structural intensity stream lines, demonstrate the efficiency of the present approach and attenuating impact effects on this type of structures.

Effect of structure of Pd@Fe core–shell cubes on the enhancement of H2 conversion in direct reaction of H2 and O2

XIAO XIANGYUN,이석호,Geun-Ho Han,Kyong Ryol Tag,안재평,Hong-Kyu Kim,이관영,유태경 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.122 No.-

Structure engineering is an integrated strategy to regulate the performance of nanoparticles for variouscatalytic reactions, since the nanoparticle composition, shape, and interface affect the reaction activityand selectivity. Herein, we report a simple synthesis of clear core–shell structured Pd@Fe nanocubes withdifferent shell thicknesses, which exhibit higher H2 conversion efficiency in direct hydrogen peroxidegeneration compared with ordinary Pd cubes. This result can be attributed to two main reasons: (i)the conformal growth of the Fe oxide shell consisting of loose structured Fe3O4 favors H2 penetration,and (ii) the capping agent (Br) on the Pd–Fe3O4 interface that blocks the Pd active sites is removed duringthe shell formation. Therefore, the Fe oxide shell of the Pd@Fe nanoparticles not only helps maintainingthe morphology of the nanoparticles but also increases the number of active sites on the inner coresurface, confirming the advantage of the core–shell structure.