http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Designing Biomimetic Materials from Marine Organisms.
American Scientific Publishers 2015 Journal of nanoscience and nanotechnology Vol.15 No.1
<P>Two biomimetic design approaches that apply biological solutions to engineering problems are discussed. In the first case, motivation comes from an engineering problem and the key challenge is to find analogous biological functions and map them into engineering materials. We illustrate with an example of water pollution remediation through appropriate design of a biomimetic sponge. In the second case, a biological function is already known and the challenge is to identify the appropriate engineering problem. We demonstrate the biological approach with marine diatoms that control energy and materials at their surface providing inspiration for a number of engineering applications. In both cases, it is essential to select materials and structures at the nanoscale to control energy and materials flows at interfaces.</P>
Biomimetic sponge for photocatalytic water purification
한성민,윤성권,William T. Nichols 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.5
We report the design of a biomimetic sponge for photocatalytic purification of water. Our focus is on the hierarchical structural features that enable pollution remediation under natural conditions of sunlight irradiation and no stirring. The biomimetic sponge is created from the designed self-assembly of photoactive TiO2 nanoparticles with a natural organic molecule cyclodextrin. These materials assemble into a network of microscale fibers with lengths extending beyond millimeters. The highly interconnected nature of these fiber networks provides both the mechanical stability and large pore structure needed for water purification applications. We demonstrate that this biomimetic structure is capable of degrading a common organic pollutant and find that the percentage of TiO2 in the network structure controls the degree of pollutant degradation. In addition, the cyclodextrin in the network is seen to enhance photocatalysis through trapping of the pollutant molecules near the active titania surface. Finally, we discuss the next steps needed to mimic more faithfully the operation of a real biological sponge.
Noh, Sungwoo,Nichols, William T.,Park, Chanhwi,Shin, Dongwook Elsevier 2017 Ceramics international Vol.43 No.17
<P><B>Abstract</B></P> <P>Maximizing the proportion of active material in the composite cathode is a technical challenge for the All-Solid-State Lithium ion battery. Among viable solutions, employing a powder with minimized and uniform size distribution might be the most effective and practical solution. To address this issue, we carefully control the size of the high ionic conducting Li<SUB>2</SUB>S-P<SUB>2</SUB>S<SUB>5</SUB> solid electrolyte to a smaller and narrower size distribution than standard solid electrolyte. We show the milled electrolytes have significantly higher capacity than standard one in the composite cathode. Electrochemical impedance spectroscopy suggests that both the active material-solid electrolyte interfacial resistance and the solid electrolyte pathway resistance through the composite cathode are important. Moreover, at higher active material ratios, the resistance through ion conducting pathways becomes the most limiting factor for discharge rates. A preliminary model is suggested to guide future development of the microstructure in all-solid-state batteries.</P>
Sungwoo Noh,William T. Nichols,Lakyoung Choi,Dong-Wook Shin 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.9
Cycle performance is a technical challenge for the all-solid-state lithium ion battery because of contact loss between the activematerials and solid electrolytes. Providing an intimate adhesive contact between solid electrolyte and active materials mightbe the most effective and practical solution. To address this issue, we added PTFE powder to the composite cathode in orderto create good conducting paths for Li ions and electrons of the lithium batteries. We show the PTFE added composite cathodehas significantly better cycle performance. Electrochemical impedance spectroscopy suggests that the charge transferresistance increased as the amount of PTFE powder increased. On the other hand, differential capacity vs. voltage profilesshowed that polarization of the composite cathode was suppressed as cycle number increased in the PTFE added composites. A preliminary model is suggested to guide future development of the microstructure in all-solid-state batteries.
Chemical vapour transport synthesis and optical characterization of MoO<sub>3</sub> thin films
Lee, Young Jung,Nichols, William T,Kim, Dae-Gun,Kim, Young Do Institute of Physics [etc.] 2009 Journal of Physics. D, Applied Physics Vol.42 No.11
<P>MoO<SUB>3</SUB> thin films were successfully prepared through chemical vapour transport (CVT) deposition and post-annealing. These films showed significantly improved optical properties. It was found that the transmittance reaches 80% with low reflectivity due to improved crystallinity and removal of oxygen vacancy states. Optical analysis shows that the index of refraction is around 1.55 with a flat dispersion curve across the visible. Furthermore, the band-gap energy is estimated to be approximately 3.5 eV. These properties suggest that CVT may be an effective thin film deposition technique for low-cost, large-area deposition of molybdenum oxides for chromogenic applications.</P>
Surface Polarity-Dependent Cathodoluminescence in Hydrothermally Grown ZnO Hexagonal Rods
Lee, Won Woo,Kim, Seong Been,Yi, Jaeseok,Nichols, William T.,Park, Won Il American Chemical Society 2012 The Journal of Physical Chemistry Part C Vol. No.
<P>Vertically oriented ZnO hexagonal rod arrays were produced by site-specific hydrothermal growth. These ZnO nanostructures possess well-defined surfaces composed of Zn-terminated (0001) planes (for the top surface) and nonpolar {101̅0} planes (for the rectangular side faces), thereby providing an opportunity to investigate the correlation between surface structures and local optical properties. The cathodoluminescence (CL) spectra of various sized ZnO rods revealed that the ratio of the deep-level emission (DLE) to the near-band-edge emission (NBE) peak intensities increased continuously with increasing diameter, which is contradictory to the general trend that the DLE increases by enhancing the surface-to-volume ratio. From the CL spectral mapping, significant NBE quenching was observed at the Zn-terminated (0001) surface, whereas the DLE was bright for every surface. Based on these observations, the anomalous behavior observed in our ZnO rods can be attributed to the surface polarity-dependent NBE characteristics. We have also shown that the surface defects associated with the NBE quenching could be eliminated by appropriate thermal annealing.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-1/jp209834d/production/images/medium/jp-2011-09834d_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp209834d'>ACS Electronic Supporting Info</A></P>
High performance all-solid-state lithium-sulfur battery using a Li<sub>2</sub>S-VGCF nanocomposite
Eom, Minyong,Son, Seunghyeon,Park, Chanhwi,Noh, Sungwoo,Nichols, William T.,Shin, Dongwook Pergamon Press 2017 Electrochimica Acta Vol. No.
<P><B>Abstract</B></P> <P>In lithium-sulfur batteries, cyclability is often strongly limited by a high interfacial resistance caused by poor contact between the active material and electron and lithium ion transporting materials. Here, we develop a Li<SUB>2</SUB>S-VGCF (Vapor Grown Carbon Fiber) nanocomposite positive electrode for an all-solid-state lithium-sulfur battery that significantly improves cyclability. The Li<SUB>2</SUB>S-VGCF nanocomposite is prepared by a solution-based technique with subsequent heat-treatment in order to control the formation of Li<SUB>2</SUB>S nanocrystals within the VGCF electron conducting matrix. The small, well-dispersed Li<SUB>2</SUB>S nanocrystals offer a large contact area with the solid electrolyte and electron conducting carbon in the composite cathode. To further improve conductivity, the composite cathode employs a multi-dimensional approach with long 1-D VGCF fibers supporting long distance electron transport and 0-D carbon powder enhancing the contact area with the Li<SUB>2</SUB>S active material at lower total carbon content. In the all-solid-state batteries, the highest initial capacity of 469mhA∙g<SUP>−1</SUP> is obtained at conditions of 500°C during heat-treatment. Activation of Li<SUB>2</SUB>S is observed during the first 10 cycles. Subsequently, the capacity gradually increased up to 600mAh∙g<SUP>−1</SUP> (g of Li<SUB>2</SUB>S). The optimized cell exhibits excellent cyclic performance through 20 cycles and a Coulombic efficiency of ∼100%.</P>
Simple, Large-Scale Patterning of Hydrophobic ZnO Nanorod Arrays
Kim, Seong Been,Lee, Won Woo,Yi, Jaeseok,Park, Won Il,Kim, Jin-Sang,Nichols, William T. American Chemical Society 2012 ACS APPLIED MATERIALS & INTERFACES Vol.4 No.8
<P>Here we describe a simple, versatile technique to produce large-scale arrays of highly ordered ZnO nanorods. Patterning of three distinct ZnO crystal morphologies is demonstrated through use of different ZnO seed layers. Array formation is accomplished through a simple variation on nanosphere lithography that imprints a thickness variation across a PMMA mask layer. The area of exposed seed layer is controlled through etching time in an oxygen plasma. Subsequent hydrothermal growth from the patterned seed layer produces high-quality ZnO crystals in uniform arrays. The high uniformity of the patterned array is shown to induce a high contact angle hydrophobic state even without the need for chemical modification of the ZnO surface. This technique provides a straightforward way to integrate the optical and electrical properties of high-quality ZnO nanorods with the tunable fluidic properties at the surface of well-ordered arrays.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2012/aamick.2012.4.issue-8/am3007142/production/images/medium/am-2012-007142_0007.gif'></P>