• Title/Summary/Keyword: Nanosheet size

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The synthesis of atomically thin TiOx nanosheets with large size (원자층 두께를 갖는 대면적 TiOx 나노쉬트 합성)

  • Lee, Sang Eun;Won, Jonghan;Park, Hee Jung
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.27 no.6
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    • pp.289-294
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    • 2017
  • Films fabricated using atomic layer 2-dimensional nanosheets exhibit various physical properties depending on the size of the nanosheet. This is because the physical properties of the film depend on the interfacial properties between the sheets. Therefore, the synthesis of large-sized nanosheets is very important because it can reduce the dependency of the film on the interfacial properties. In this study, we succeeded in fabricating $TiO_x$ nanosheets with atomic layer thickness over micrometer size by using single-crystallized starting material and its chemical exfoliation. In addition, it was revealed that the mechanical agitation speed (the stirring speed of a magnetic bar) during the exfoliation step using the organic material is closely related to the nanosheet size and the colloidal concentration of the nanosheets.

The synthesis of ultrathin Nb-doped TiOx nanosheets (초박막 두께의 Nb-TiOx 나노시트 합성)

  • Lee, Sang Eun;Seo, Jun;Park, Hee Jung
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.30 no.5
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    • pp.194-199
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    • 2020
  • By controlling the composition of the metal-oxide nanosheet having a two-dimensional layered crystal structure, material properties and application can be extended. In this study, the composition of the nanosheet could be expanded from pure composition to doping composition by successfully synthesizing the TiO2 nanosheet doped with Nb. Specifically, the doping composition was designed when synthesizing the layered metal oxide as a starting material (K0.8Ti1.73-xNbxLi0.27O4, x = 0, 0.03, 0.07) and chemical exfoliation was performed. By doing this, it was possible to obtain the Nb-doped TiOy ultrathin nanosheet. The size of the nano sheet was 2 ㎛ or less based on the long length in the x-y direction, and the thickness was about 1 nm. Nb-doping was confirmed by XRD and SEM-EDS analysis.

Dielectric Properties of Ca0.8Sr1.2Nb3O10 Nanosheet Thin Film Deposited by the Electrophoretic Deposition Method

  • Yim, Haena;Yoo, So-Yeon;Choi, Ji-Won
    • Journal of Sensor Science and Technology
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    • v.27 no.1
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    • pp.1-5
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    • 2018
  • Two-dimensional (2D) niobate-based nanosheets have attracted attention as high-k dielectric materials. We synthesized strontiumsubstituted calcium niobate ($Ca_{0.8}Sr_{1.2}Nb_3O_{10}$) nanosheets by a two-step cation exchange process from $KCa_{0.8}Sr_{1.2}Nb_3O_{10}$ ceramic. The $K^+$ ions were exchanged with $H^+$ ions, and then H+ ions were exchanged with tetrabutylammonium ($TBA^+$) cations. The $Ca_{0.8}Sr_{1.2}Nb_3O_{10}$ nanosheets were then exfoliated, decreasing the electrostatic interaction between each niobate layer. Furthermore, $Ca_2Nb_3O_{10}$ nanosheets were synthesized in same process for comparison. Each exfoliated nanosheet shows a single-crystal phase and has a lateral size of over 100 nm. The nanosheets were deposited on a $Pt/Ti/SiO_2/Si$ substrate by the electrophoretic deposition (EPD) method at 40 V, followed by ultraviolet irradiation of the films in order to remove the remaining $TBA^+$ ions. The $Ca_{0.8}Sr_{1.2}Nb_3O_{10}$ thin film exhibited twice the dielectric permittivity (~60) and lower dielectric loss than $Ca_2Nb_3O_{10}$ thin films.

Effect of Hexa-methylenetetramine (HMT) on Nucleation and Growth Behaviors of Ni(OH)2 Nanosheets Produced by Electrodeposition (전착법으로 제작한 Ni(OH)2 나노 시트의 핵 형성과 성장 거동에 미치는 헥사-메틸렌테트라민(HMT)의 영향)

  • Kim, Dong Yeon;Son, Injoon;Choi, Mun-Hyun
    • Journal of the Korean institute of surface engineering
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    • v.54 no.1
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    • pp.37-42
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    • 2021
  • Electrodeposition is a synthetic method that allows fine control of the nucleation and growth factors of metals and is a suitable method for studying the nucleation and growth of Ni(OH)2. Hexa-methylenetetramine (HMT) helps to form Ni(OH)2 nanosheets by increasing the OH- of the nickel precursor solution and helps to improve the electrochemical properties of the electrode. In this study, the structural properties of Ni(OH)2 nanosheets according to the HMT concentration change using electrodeposition were studied. As the concentration of HMT increased, the size and thickness of the Ni(OH)2 nanosheet adsorbed on the surface increased and porosity increased. Also, the Scharifker-Hills nucleation theory model and experimental data were compared. In conclusion, the nanosheet shape of the HMT 7.5 mM sample electrodeposited with -0.85 V vs. Ag/AgCl grew most uniformly, and the best result was obtained as an electrode material for a pseudocapacitor.

Synthesis of carbon nanosheets using RF thermal plasma (유도 열플라즈마를 이용한 카본나노시트 합성)

  • Lee, Seung-Yong;Ko, Sang-Min;Koo, Sang-Man;Hwang, Kwang-Taek;Han, Kyu-Sung;Kim, Jin-Ho
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.24 no.5
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    • pp.207-212
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    • 2014
  • An ultrathin sheet-like carbon nanostructure provides an important model of a two-dimensional graphite structure with strong anisotropy in physical properties. As an easy and cheap route for mass production, RF thermal plasma synthesis of freestanding carbon nanosheet from $CH_4$ (Methane) and $C_3H_8$ (Propane) is presented. Using vapor synthesis process with RF inductively thermal plasma, carbon nanosheets were obtained without catalysts and substrates. The synthesized carbon nanosheets were characterized using transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analysis. The carbon nanosheets synthesized using methane and propane generally showed 5~6 and 15~16 layers with a wrinkled morphology and size of approximately 100 nm.

Relation between the Concentration of Hexagonal Boron Nitride Nano-Sheets Dispersed in Pure Water and Their Width and Height (초순수 용매 내 육방정 질화붕소 나노시트의 농도와 크기의 관계)

  • Cho, Dae-Hyun;Park, Miyoung;Ha, Seonghun
    • Tribology and Lubricants
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    • v.35 no.6
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    • pp.343-349
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    • 2019
  • According to a report in 2011, hexagonal boron nitride demonstrated good solubility in pure water, even without surfactants or organic functionalization. Hexagonal boron nitride nanosheets are an effective lubricant additive, and their solubility in pure water has motivated lubrication engineers to utilize aqueous solutions containing these nanosheets as water-based lubricants. In this study, we measure the width and height of the hexagonal boron nitride nanosheets dispersed in pure water by using the Zetasizer and atomic force microscopy. Without surfactants or functionalization, aqueous solutions containing 0.10, 0.07, 0.05, and 0.01 wt% of hexagonal boron nitride nanosheets are synthesized via sonication-assisted hydrolysis. The Zetasizer provides only a one-dimensional size of approximately 410 nm, regardless of the concentration of the solution. Thus, it does not allow the estimation of the shape of the nanosheet. To acquire the three-dimensional size of the nanosheets, atomic force microscopy is employed. The aqueous solutions containing 0.10, 0.07, 0.05, and 0.01 wt% of the hexagonal boron nitride nanosheets show average values of 740, 450, 700, and 610 nm in width, and 37, 26, 33, and 32 nm in thickness, respectively. No significant trend is observed between the concentration of the solution and size of the nanosheets. Therefore, when preparing a water-based lubricant, it may be appropriate to adjust conditions such as ultrasonication time rather than the concentration.

Development of Mixed Conducting Ceramic Membrane for High Purity Hydrogen and Carbon Production from Methane Direct Cracking (복합전도성 세라믹 분리막의 탄화수소 직접분해에 의한 고순도 수소와 탄소 제조)

  • Kim, Ji-Ho;Choi, Duck-Kyun;Kim, Jin-Ho;Cho, Woo-Seok;Hwang, Kwang-Taek
    • Transactions of the Korean hydrogen and new energy society
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    • v.22 no.5
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    • pp.649-655
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    • 2011
  • Methane direct cracking can be utilized to produce $CO_x$ and $NO_x$-free hydrogen for PEM fuel cells, oil refineries, ammonia and methanol production. We present the results of a systematic study of methane direct cracking using a mixed conducting oxide, Y-doped $BaZrO_3$ ($BaZr_{0.85}Y_{0.15}O_3$), membrane. In this paper, dense $BaZr_{0.85}Y_{0.15}O_3$ membrane with disk shape was successfully sintered at $1400^{\circ}C$ with a relative density of more 93% via addition of 1 wt% ZnO. The ($BaZr_{0.85}Y_{0.15}O_3$) membrane is covered with Pd as catalyst for methane decomposition with an DC magnetron sputtering method. Reaction temperature was $800^{\circ}C$ and high purity methane as reactant was employed to membrane side with 1.5 bar pressure. The $H_2$ produced by the reaction was transported through mixed conducting oxide membrane to the outer side. In addition, it was observed that the carbon, by-product, after methane direct cracking was deposited on the Pd/ZnO-$BaZr_{0.85}Y_{0.15}O_3$ membrane. The produced carbon has a shape of sphere and nanosheet, and a particle size of 80 to 100 nm.