http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Metamaterial’s Acceptable Level of Wrecked Meta-pattern
La Yunju,Jeon Ok Sung,Lee Young Jun,Park Sang Yoon,Yoo Young Joon,Lim Taekyung,Yang Keun-Hyeok 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.11
The periodic arrangement in metamaterial (MM) should be maintained to ensure the extraordinary properties, but how much periodic irregularity is allowed generally without degrading the properties is not only important for the tolerance in fabrication but interesting scientifically. We introduce the wrecked effect in MM utilizing perfect MM absorber in visible and GHz ranges. The original perfect MM properties turn out to be maintained until MM is destroyed to 10%. In the view of MM absorber, even 40% broken meta-pattern are still good for absorption higher than 93%, the criterion for perfect absorption. The wrecked pattern over 80% result in absorption of nearly 50% in both simulation and experiment, which is even higher than expected. These results can lead to broad applications at the present and in near future through more convenient and cost-effective research and development on MMs.
La, Yunju,Park, Chiyoung,Shin, Tae Joo,Joo, Sang Hoon,Kang, Sebyung,Kim, Kyoung Taek Nature Publishing Group 2014 Nature chemistry Vol.6 No.6
Analogous to the complex membranes found in cellular organelles, such as the endoplasmic reticulum, the inverse cubic mesophases of lipids and their colloidal forms (cubosomes) possess internal networks of water channels arranged in crystalline order, which provide a unique nanospace for membrane-protein crystallization and guest encapsulation. Polymeric analogues of cubosomes formed by the direct self-assembly of block copolymers in solution could provide new polymeric mesoporous materials with a three-dimensionally organized internal maze of large water channels. Here we report the self-assembly of amphiphilic dendritic–linear block copolymers into polymer cubosomes in aqueous solution. The presence of precisely defined bulky dendritic blocks drives the block copolymers to form spontaneously highly curved bilayers in aqueous solution. This results in the formation of colloidal inverse bicontinuous cubic mesophases. The internal networks of water channels provide a high surface area with tunable surface functional groups that can serve as anchoring points for large guests such as proteins and enzymes.
Tunable Metamaterial Absorber Using Ferromagnetic Resonance
La Yunju,Jeon Ok Sung,Lee Young Jun,Park Sang Yoon,Yoo Young Joon,Lim Taekyung,Yang KeunHyeok 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.11
We simulated a study on a tunable metamaterial absorber using ferrite rubber as a dielectric substrate with ferromagnetic properties. The proposed structure employs ferromagnetic resonance, which utilizes the coupling of an applied magnetic field and an incident electromagnetic wave. As the magnitude of the applied magnetic field increases, it can be seen that the absorption peak moves to a higher frequency. The adjustment of the absorption frequency using the proposed method is expected to be applied to various fields such as sensors, electronic devices and 5G communication antennas.
Pore Structure Analysis to Adsorb NOx Gas based on Porous Materials
Lim Taekyung,La Yunju,Jeon Ok Sung,Park Sang Yoon,Yoo Young Joon,Yang Keun-Hyeok 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.9
We studied the adsorption of nitrogen oxides according to various porous materials room temperature, which can effectively to adsorb the nitrogen oxides. Based on results of measuring NOx concentration, the activated carbon materials have been shown to adsorb NOx well, and they have been shown to more efficiently removing NO2, which is very harmful to the environment. In particular, in the case of the coconut activated carbon, the removal efficiency of NO and NO2 was very excellent, and the removal rate of was 30% for 100 minutes and 19.5% for 840 minutes. Our measurement results confirmed that the activated carbon materials have a very large specific surface area and pore volume. In addition, the coconut activated carbon appears to have a large specific surface area and pore volume to remove NOx over a long period of time. Based on the experimental results, it is expected to be used as a material that efficiently removes nitrogen oxides at room temperature.
Mix-and-Match Assembly of Block Copolymer Blends in Solution
Cho, Arah,La, Yunju,Jeoung, Sungeun,Moon, Hoi Ri,Ryu, Ja-Hyoung,Shin, Tae Joo,Kim, Kyoung Taek American Chemical Society 2017 Macromolecules Vol.50 No.8
<P>The chemical structure of a block copolymer (BC?) dictates the size, shape, and function of its self-assembled structure in solution. This direct correspondence demands precision synthesis of a specific BCP with optimized structural parameters to obtain the desired nanostructures with structural and functional complexity by solution self-assembly. Here we show that the binary blends of BCPs self-assemble into the desired nanostructure in solution by adjusting the composition of the blend. By modifying the structural parameters of a binary BCP blend through control of the composition, two BCPs sharing the repeating units in both polymer blocks coassemble into the desired structures, which range from spherical micelles to inverse cubic and hexagonal mesophases. These BCP blends not only allow the direct creation of complex periodic mesoporous structures of the desired periodicity and pore size but also provide nanostructures of unprecedented morphology by simple solution self-assembly without relying on the synthesis of correspondingly designed BCPs.</P>
Cho, Arah,La, Yunju,Shin, Tae Joo,Park, Chiyoung,Kim, Kyoung Taek American Chemical Society 2016 Macromolecules Vol.49 No.12
<P>Inverse bicontinuous cubic (IBC) structures consisting of triply periodic minimal surfaces of block copolymers (BCPs) are emerging as materials of interest owing to their structural characteristics, which resemble those of their biological counterparts constructed from lipids. Solution self-assembly of amphiphilic BCPs with nonlinear architectures has recently been shown to form colloidal particles (polymer cubosomes) and macroscopic monoliths having mesoporous networks of water channels embedded in the periodic minimal surfaces of the BCP bilayers. Here we report that BCP architectures play a crucial role in controlling the packing parameter (P) of BCPs; a value greater than unity is a prerequisite for preferential self-assembly into IBC mesophases in solution. We show that the branched architecture of the polymer blocks constituting the BCP critically influences the structural parameters, such as the molecular area and, in particular, the critical length of the hydrophobic domain. Adjusting these structural parameters not only increases the P value of the BCP without depending on the asymmetry of the volume ratio of two polymer blocks (block ratio) but also dictates the lattice and periodicity of the resulting minimal surfaces of the BCPs. Our results could provide a rationale to design and synthesize amphiphilic block copolymers to directly self-assemble into periodic porous structures in solution, which could be promising materials having highly ordered mesopore networks.</P>
An, Tae Hyun,La, Yunju,Cho, Arah,Jeong, Moon Gon,Shin, Tae Joo,Park, Chiyoung,Kim, Kyoung Taek American Chemical Society 2015 ACS NANO Vol.9 No.3
<P>Solution self-assembly of amphiphilic block copolymers into inverse bicontinuous cubic mesophases is an emerging strategy for directly creating highly ordered triply periodic porous polymer nanostructures with large pore networks and desired surface functionalities. Although there have been recent reports on the formation of highly ordered triply periodic minimal surfaces of self-assembled block copolymer bilayers, the structural requirements for block copolymers in order to facilitate the preferential formation of such inverse mesophases in solution have not been fully investigated. In this study, we synthesized a series of model block copolymers, namely, branched poly(ethylene glycol)-<I>block</I>-polystyrene (bPEG-PS), to investigate the effect of the architecture of the block copolymers on their solution self-assembly into inverse mesophases consisting of the block copolymer bilayer. On the basis of the results, we suggest that the branched architecture of the hydrophilic block is a crucial structural requirement for the preferential self-assembly of the resulting block copolymers into inverse bicontinuous cubic phases. The internal crystalline lattice of the inverse bicontinuous cubic structure can be controlled <I>via</I> coassembly of branched and linear block copolymers. The results presented here provide design criteria for amphiphilic block copolymers to allow the formation of inverse bicontinuous cubic mesophases in solution. This may contribute to the direct synthesis of well-defined porous polymers with desired crystalline order in the porous networks and surface functionalities.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2015/ancac3.2015.9.issue-3/nn507338s/production/images/medium/nn-2014-07338s_0013.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn507338s'>ACS Electronic Supporting Info</A></P>
A-site Doping Effect of Multiferroic BiFeO3 Ceramics
Lim Taekyung,Jeon Ok Sung,La Yunju,Park Sang Yoon,Yoo Young Joon,Yang Keun-Hyeok 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.11
The structural, magnetic and ferroelectric properties of polycrystalline A-site ($A$ = Ho, Pr and Ce of 10%) doped BiFeO3, which were prepared by the solid-state and rapid sintering methods, have been investigated. The powder X-ray diffraction pattern reveals that all the samples show rhombohedral perovskite structure R3c. The Ho-doped BiFeO3 shows that the magnetic property is slightly increased due to compressive lattice distortion and Ho3+ ion doping effect. For the Pr and Ce doped BiFeO3, the remnant polarization and coercive field increased because Pr3+ and Ce3+ ions substitution suppressed oxygen vacancies.