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Estimation of Surface Forces in Micro Rough Surface Contacts
Doo-In Kim,Hyo-Sok Ahn,Dong-Hoon Choi 한국트라이볼로지학회 2002 한국트라이볼로지학회 학술대회 Vol.2002 No.10
In a micro-scale contact, surface forces such as capillary force and van der Waals interaction significantly influence the contact between asperities of rough surfaces. Little is, however, known about the variation of these surface forces as a function of chemical property of the surface (hydrophilicity), relative humidity and deformation. of asperities in the real area of contact. A better understanding of these surface forces is of great necessity in order to find an optimal solution for reducing friction and adhesion of micro surfaces. We proposed an effective method to analyze capillary and van der Waals forces in nano-scale contact. In this method, Winklerian foundation model was employed to analyze the contact of rough surfaces that were obtained from atomic force microscopy (AFM) height images. Self-mated contact of diamond-like-carbon (DLC) coatings was analyzed, as an example, by the proposed model. It was shown that the capillary-force was significantly influenced by relative humidity and wet angle of the DLC surface. The deformation of asperities to a critical magnitude by external loading led to a considerable increase of both capillary and van der Waals forces.
Kim, S.H.,Lee, S.W. Elsevier Sequoia [etc.] 2008 Inorganica chimica acta Vol.361 No.1
A novel bi(thipohene)-type ligand, 1,2-bis((thiophen-3-yl)methylene)hydrazine (L), was prepared. From ligand L and silver salts AgX, three 2-D silver coordination polymers [AgL<SUB>2</SUB>].(X)[X=ClO4-,SbF6-,PF6-] could be prepared. All polymers have been constructed by van der Waals contacts.
van der Waals Layered Materials: Opportunities and Challenges
Duong, Dinh Loc,Yun, Seok Joon,Lee, Young Hee American Chemical Society 2017 ACS NANO Vol.11 No.12
<P>Since graphene became available by a scotch tape technique, a vast class of two-dimensional (2D) van der Waals (vdW) layered materials has been researched intensively. What is more intriguing is that the well-known physics and chemistry of three-dimensional (3D) bulk materials are often irrelevant, revealing exotic phenomena in 2D vdW materials. By further constructing heterostructures of these materials in the planar and vertical directions, which can be easily achieved <I>via</I> simple exfoliation techniques, numerous quantum mechanical devices have been demonstrated for fundamental research and technological applications. It is, therefore, necessary to review the special features in 2D vdW materials and to discuss the remaining issues and challenges. Here, we review the vdW materials library, technology relevance, and specialties of vdW materials covering the vdW interaction, strong Coulomb interaction, layer dependence, dielectric screening engineering, work function modulation, phase engineering, heterostructures, stability, growth issues, and the remaining challenges.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2017/ancac3.2017.11.issue-12/acsnano.7b07436/production/images/medium/nn-2017-074362_0021.gif'></P>
Boandoh, Stephen,Agyapong-Fordjour, Frederick Osei-Tutu,Choi, Soo Ho,Lee, Joo Song,Park, Ji-Hoon,Ko, Hayoung,Han, Gyeongtak,Yun, Seok Joon,Park, Sehwan,Kim, Young-Min,Yang, Woochul,Lee, Young Hee,Kim, American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.1
<P>Two-dimensional (2D) van der Waals (vdW) heterostructures exhibit novel physical and chemical properties, allowing the development of unprecedented electronic, optical, and electrochemical devices. However, the construction of wafer-scale vdW heterostructures for practical applications is still limited due to the lack of well-established growth and transfer techniques. Herein, we report a method for the fabrication of wafer-scale 2D vdW heterostructures with an ultraclean interface between layers via the aid of a freestanding viscoelastic polymer support layer (VEPSL). The low glass transition temperature (<I>T</I><SUB>g</SUB>) and viscoelastic nature of the VEPSL ensure absolute conformal contact between 2D layers, enabling the easy pick-up of layers and attaching to other 2D layers. This eventually leads to the construction of random sequence 2D vdW heterostructures such as molybdenum disulfide/tungsten disulfide/molybdenum diselenide/tungsten diselenide/hexagonal boron nitride. Furthermore, the VEPSL allows the conformal transfer of 2D vdW heterostructures onto arbitrary substrates, irrespective of surface roughness. To demonstrate the significance of the ultraclean interface, the fabricated molybdenum disulfide/graphene heterostructure employed as an electrocatalyst yielded excellent results of 73.1 mV·dec<SUP>-1</SUP> for the Tafel slope and 0.12 kΩ of charge transfer resistance, which are almost twice as low as that of the impurity-trapped heterostructure.</P> [FIG OMISSION]</BR>
안효석,장동영 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-
In micro/nano-scale contacts in MEMS and NEMS, capillary and van der Waals forces generated around contacting micro-asperities significantly influence the performance of concerning device as they are related to adhesion and stiction of interacting surfaces, In this regard, it is of prime importance to accurately estimate the magnitude of surface forces so that an optimal solution for reducing friction and adhesion of micro/nano-surfaces may be obtained. We introduce an effective method to calculate these surface forces based on topography information obtained from an atomic force microscope
안효석(Hyo-Sok Ahn),장동영(Dong-Young Jang) 한국생산제조학회 2009 한국생산제조학회지 Vol.18 No.4
In micro/nano-scale contacts in MEMS and NEMS, capillary and van der Waals forces generated around contacting micro-asperities significantly influence the performance of concerning device as they are closely related to adhesion and stiction of interacting surfaces. In this regard, it is of prime importance to accurately estimate the magnitude of surface forces so that an optimal solution for reducing friction and adhesion of micro/nano-surfaces may be obtained. We introduced an effective method to calculate these surface forces based on topography information obtained from an atomic force microscope. This method was used to calculate surface forces generated in the contact interface formed between diamond-like carbon coating and Si₃N₄ ball. This method is shown to effectively demonstrate the influence of capillary force in the contact area, especially in humid atmosphere.
안효석(Hyo-Sok Ahn),장동영(Dong-Young Jang) 한국생산제조학회 2008 한국생산제조시스템학회 학술발표대회 논문집 Vol.2008 No.5
In micro/nano-scale contacts in MEMS and NEMS, capillary and van der Waals forces generated around contacting micro-asperities significantly influence the performance of concerning device as they are related to adhesion and stiction of interacting surfaces. In this regard, it is of prime importance to accurately estimate the magnitude of surface forces so that an optimal solution for reducing friction and adhesion of micro/nano-surfaces may be obtained. We introduce an effective method to calculate these surface forces based on topography information obtained from an atomic force microscope.
부유부상 공정에 있어서 표면 에너지의 역할 - 부유부상 효율에 있어 고형 입자의 표면 에너지 및 극성성분의 중요성 -
이학래,박일,이용민,이진희,조중연,한신호,Lee, Hak-Rae,Park, Il,Lee, Yong-Min,Lee, Jin-Hee,Cho, Joong-Yeon,Han, Sin-Ho 한국펄프종이공학회 2002 펄프.종이기술 Vol.34 No.3
The object of this study was to determine the surface energy of hydrophobically modified micro-crystalline cellulose (MCC) with AKD and evaluate the effect of surface energy of the solid particles dispersed in aqueous medium on flotation efficiency. Especially to eliminate the complication derives from the diverse parameters of solid particles including particle size, type, etc. MCC's modified with AKD have been used. The surface energy Parameters were calculated from advancing contact angles of apolar and polar liquids on MCC pellets using the Lifshitz-van der Waals acid-base (LW:AB) approach. Total surface energy of hydrophobic MCC ranged from 46.19 mN/m to 48.60 mN/m. The contribution of the acid-base components to the total surface energy ranged form 13% to 17% for hydrophobic MCC's. The effect of surface characteristics on the flotation efficiency was evaluated. It was shown that there exist critical values of surface energies to increase flotation efficiency. Total surface energy and polar component of solid particles should be lower than 47 mN/m and 7 mN/m, respectively, for effective removal in the flotation process.
Huh, H.S.,Kim, S.H.,Yun, S.Y.,Lee, S.W. Pergamon Press 2008 Polyhedron Vol.27 No.4
One silver discrete compound [AgL<SUP>1</SUP><SUB>2</SUB>](PF<SUB>6</SUB>) and four silver coordination polymers or networks, [Ag<SUB>2</SUB>L<SUP>2</SUP><SUB>3</SUB>](PF<SUB>6</SUB>)<SUB>2</SUB>, [Ag<SUB>2</SUB>L<SUP>2</SUP><SUB>3</SUB>](ClO<SUB>4</SUB>)<SUB>2</SUB>, [Ag<SUB>2</SUB>L<SUP>2</SUP><SUB>2</SUB>](BF<SUB>4</SUB>)<SUB>2</SUB>, and [Ag<SUB>2</SUB>L<SUP>2</SUP>(NO<SUB>3</SUB>)<SUB>2</SUB>], were prepared by layer diffusion, where L<SUP>1</SUP> is 1,2-bis(thiophen-2-ylmethylene)hydrazine and L<SUP>2</SUP> is 1,2-bis(furan-2-ylmethylene)hydrazine.