Effects of defects and non-coordinating molecular overlayers on the work function of graphene and energy-level alignment with organic molecules

Bae, G.,Cha, J.,Lee, H.,Park, W.,Park, N. Pergamon Press ; Elsevier Science Ltd 2012 Carbon Vol.50 No.3

To elucidate the features of graphene as an electrode material, we studied the effect of defects and molecular overlayers on the work function of graphene using density-functional theory. We found that in-plane geometrical deformations (such as Stone-Thrower-Wales defects, carbon vacancies, and hydrogenated edges) have only a marginal effect. In contrast, intercalated alkaline atoms (K or Li) and overlayers of superhalogen species (BF<SUB>4</SUB> and PF<SUB>6</SUB>) radically change the work function. We show that the geometry of the sp<SUP>2</SUP> carbon surface remains robust after electron transfer to superhalogens, and the Fermi level could be well aligned with the energy levels of organic molecules. These methods for work function control can be used for the application of graphene materials as transparent electrodes for organic light-emitting devices.

Bonding features and associated mechanisms in kinetic sprayed titanium coatings

Bae, G.,Kumar, S.,Yoon, S.,Kang, K.,Na, H.,Kim, H.J.,Lee, C. Elsevier Science 2009 Acta materialia Vol.57 No.19

This study aims to explore the bonding features and mechanisms present in kinetic spray coatings of commercially pure titanium (CP-Ti) by linking experimental observations with finite element modeling for the purpose of optimizing the deposition process. The numerically predicted deformation features and interface thermomechanical responses of the particles adequately elucidate the deposition characteristics for different impact conditions. The formation of a porous coating by local bonding at relatively low velocity and of a very dense coating accompanied by interfacial melting at higher velocity resulted from deformation localization at high strain rates due to the relatively higher adiabacity as compared with other materials, which is one of the unique bonding mechanisms in CP-Ti. The enhanced thermal boost-up zone due to thermally accelerated adiabatic shear instability by powder preheating resulted in improved coating properties, and is essential for the optimization of economical coating processes.

Nanostructure formation and its effects on the mechanical properties of kinetic sprayed titanium coating

Bae, G.,Kang, K.,Kim, J.J.,Lee, C. Elsevier Sequoia 2010 Materials science & engineering. properties, micro Vol.527 No.23

The nanostructure formation during kinetic spraying of commercially pure titanium (CP-Ti) were studied using transmission electron microscopy (TEM) and finite element modeling (FEM) considering conductive heat transfer. The high-velocity impacted particles, subjected to severe plastic deformation (SPD), were found to be tightly bonded, and also considerably homogeneous and randomly orientated equiaxed nanograins, including some recovered grains having a low dislocation density, were found to be formed over wide areas inside the coating due to strain accumulation and the resultant thermal history enhanced by subsequent impacts of the particles. The bimodal grain structure consisting of both larger grains having high-density dislocations (>250nm) and smaller dislocation-free grains with non-equilibrium grain boundaries (<100nm) was determined to be associated with both the strain hardening and the ductile dimple fracture of the coating.

Correlation of particle impact conditions with bonding, nanocrystal formation and mechanical properties in kinetic sprayed nickel

Bae, G.,Jang, J.i.,Lee, C. Elsevier Science 2012 ACTA MATERIALIA Vol.60 No.8

Owing to the specific high-strain-rate thermomechanical characteristics of Ni particle impact in kinetic spraying, the rebound phenomenon of the impacting particles hinders the formation of the first layer and impedes successful build-up of the coating. Even at higher impact velocities, the deposition efficiency of the coating is quite low because of excessive kinetic energy, which induces the rebound and/or erosion of the highly flattened particles. This paper reports noticeably improved bonding and deposition characteristics of Ni particles resulting from suppressed equivalent (von Mises) flow stress and enhanced interface heat-up as a result of powder preheating. Experimental observations coupled with finite-element modeling (FEM) corroborate the fact that the thermally softened Ni particle is very effective for enhanced adhesive and cohesive bonding. Based on the FEM results, the thermal boost-up zone, increased by thermally accelerated adiabatic shear instability, is proposed as a crucial factor for enhancing bonding between the particles, which is essential in producing better coating properties. Moreover, nanocrystal formation (<100nm) in the coating was more pronounced than cases previously reported in the literature, mainly because of the enhanced thermal activation and straining of the severely deformed particles, which was verified by transmission electron microscopy investigations and nanoindentation tests.

Corrigendum to ''Correlation of particle impact conditions with bonding, nanocrystal formation and mechanical properties in kinetic sprayed nickel'' [Acta Materialia 60 (2012) 3524-3535]

Bae, G.,Jang, J.i.,Lee, C. Elsevier Science 2012 Acta materialia Vol.60 No.17

The role of nitrogen in a carbon support on the increased activity and stability of a Pt catalyst in electrochemical hydrogen oxidation

Bae, G.,Youn, D.H.,Han, S.,Lee, J.S. Pergamon Press ; Elsevier Science Ltd 2013 Carbon Vol.51 No.-

Nitrogen-containing carbon materials were prepared by acetonitrile pyrolysis on carbon black and used as a support for a Pt catalyst. The Pt particles on N-containing carbon exhibited increased activity and stability in electrochemical hydrogen oxidation relative to Pt on pristine carbon black. The N-doped carbon had a graphitic structure and contained pyridinic and quaternary nitrogen species. The Pt nanoparticles were better-dispersed because of increased hydrophilicity induced by the nitrogen species. The Pt/N-containing carbon showed higher stability in a potential cycling test than Pt/C, because of an increased metal-support interaction. Using XPS and EELS mapping, we demonstrated that the metal-support interaction became stronger and more specific by adding nitrogen into carbon.

有限要蘇法에 依한 多孔板의 應力解析

呂白楡,權宅鎭,姜文明 啓明大學校 産業技術硏究所 1981 産業技術硏究所 論文報告集 Vol.3 No.-

The perforated elastic body have been dealt with the stress distribution along with stress con-centration, and boundary value. And not a few analytic studies were carried out and reported. Theoretically, the top-slab of nuclear reactor, a kind of perforated plate equipped with small hoes of regular arrangement, is too complicated to be analyzed except in particular forms of plates. In this study the boundary conditions and unit patterns of perforated plates are assumed as shown in figure 2-1 and figure 2-3. Then this unit pattern is divided into some triangular elements shown in figure 2-4. For the numerical analyses of the pattern a suitable program of F. E. M. is constructed using the stiffness matrix of Constant Strain Triangular Element. Using this program four models (ie A. B, C and D) are evaluated in this paper. And factors of stress concentration, states of stress distribution and effective elastic constants of these models are shown in graphic forms so that design of structure might be done easily. F. E. M. program of this paper may be regarded as useful to two-dimensional stress problems under the conditions shown in figure 2-3.

滿洲語 音韻史硏究를 위하여 (基二) : 淸文啓蒙 異施淸字 硏究

成百仁 명지대학교 1975 明大論文集 Vol.8 No.-

「청문계몽」권지일은 (1) 만주십이자두단자연자지남, (2) 철운청자, (3) 만주외단자, (4) 만주외연자, (5) 청자얼운법, (6) 이시청자, (7) 청서운필선후 로 구성되어 있다. (7)을 제외하고는 모두 만주어 및 만주어로 표기된 한자차용어들의 발음에 관한 것들이다. (1)은 만주어의 기본적인 음적을 심이항목으로 나누어 한자로 주음하고 각각 그 음절들을 포함하고 있는 청어단어의 용예를 들고 있다. 특히 제2자두에서 제이십자두까지는 대개 3~5개의 단어를 (합계 36개) 예시하고 그 단어들을 한자로 주음하고 있다. (2) 는 「j」및「w」계의 이중모음을 포함하는 음절들을 수록하고 한자로 주음하여 높은 것인데 이 음절들은 문자상 (1)의 두 자두 즉 두 음절의 복합으로 이루어져 있다. 다라서 (2)는 이 음절들은 문자상 (1)의 두 자두 즉 두 음절의 복합으로 이루어져 있다. 따라서 (2)는 십이자두에서 누락된 음절의 추가라고 볼 수 있다. (3)(4)와 다른 점은 음절을 표기한 문자가 (1) 에서 이미 제시한 자두들로 구성되었다는 점이다. 만주문자는 비록 음운문자이지만 그들은 문자글 음절단위로 인식하고 있다. 이것은 반드시 중국문자 내지는 중국운학의 영향이라고만 생각할 수 없는 전통을 가지고 있는 듯이 보인다. (2)의 「철운청자」에 수록된 음절들 속에는 액면 그대로 받아들 일 수 없는 많은 문제가 있다. 가령 tuwa와 같은 문자상 두 음절의 종합이 만주엉 어휘들속에서 언제나 독와절로 [twa]였느냐 하는 문제가 있다. 이러한 문제는 여기서 길게 다룰 성질의 것이 못되지만 만주어학상의 하나의 어려운 문제인 것이다. (3)의 「만주어단자」의 항목은 심칠자 즉 십칠개의 음절로 구성되어 있다. 이 항목은 그 내용으로 보나 manju tulergi emteli hergen 「만주외단자」라는 이름으로 보나 외래어 표기를 위한 음절을 모은 것이 아닌가 하는 생각이 들기도 한다. 사실 그 내용은 중국계 차용어를 표기하는데 전용하는 단자들에 틀림 없다. 만주어속의 중국어 차용어는, 만주문자가 17세기 초에 쓰이기 시작했다고 해서, 17세기부터 차용된 것은 아니다. 매우 오랜 세월동안 다각적인 경로로 차용된 것이다. 중국천지로 뛰어 들어간 만주족의 언어표기에 나타난 차용어는 갈피를 잡을 수 없이 그 한계가 모호하다. 이 점을 「청문계몽」의 저자는 무척 고심하고 있다. (3)의 내용이 결과적으로는 모두 중국어표기용 음절로 구성되어 있으나, 무격은 (3)을 외래적 요소로 인식하고 있었던 것은 아니다. 단지 만주문어 기록속에 나타나는 십이자두나 칠운청자외의 음절을 수록한 것에 불과하다. 이러한 견해는 (4)를 보면 명백해진다.

만문당안 (基二) : 康熙·雍正朝의 奏摺·皇旨 K'ang-hsi·Yung-cheng Period

成百仁 명지대학교 국어국문학과 1977 明知語文學 Vol.9 No.-

Organic Complementary Circuits: Remarkable Enhancement of Hole Transport in Top‐Gated N‐Type Polymer Field‐Effect Transistors by a High‐k Dielectric for Ambipolar Electronic Circuits (Adv. Mater. 40/2012)

Baeg, Kang‐,Jun,Khim, Dongyoon,Jung, Soon‐,Won,Kang, Minji,You, In‐,Kyu,Kim, Dong‐,Yu,Facchetti, Antonio,Noh, Yong‐,Young WILEY‐VCH Verlag 2012 Advanced Materials Vol.24 No.40

<P>On page 5433, Yong‐Young Noh, Antonio Facchetti, Kang‐Jun Baeg, and co‐workers report that high performance ambipolar complementary inverters and ring oscillators are provided by a remarkable enhancement of both hole injection and transport for n‐channel dominant N2200 OFETs. The significant enhancement of hole mobility in N2200 OTFTs is attributed to the strong dipoles in fluorinated high‐k gate dielectric blend of P(VDF‐TrFE):PMMA. </P>