• Title/Summary/Keyword: Nanotube

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A Study about the Strength and Microstructure of Hardened Cement Pastes Including Nanofibers (나노 섬유를 혼합한 시멘트 페이스트의 미세구조와 강도에 대한 연구)

  • Nguyen, Tri N.M;Kim, Jung Joong
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.40 no.2
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    • pp.177-182
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    • 2020
  • In this study, the effect of nanofibers in cement pastes on the compressive and tensile strength of hardened cement pastes was studied. Two types of nanofibers, nylon 66 nanofibers and carbon nanotube-nylon 66 hybrid nanofibers, were manufactured by electrospinning methodology and mixed in cement powder respectively. The specimens for experiments were prepared by water to cement ratio of 0.5 and cured in water for 28 days. The effect of nanofibers on the increase of the compressive and tensile strength were confirmed by the experimental results. The well-linking effect of nanofibers in the microstructure of the hardened cement pastes has been found by scanning electron microscope (SEM) analysis and well-explained for the increase in mechanical strength. Besides, field emission transmission electron microscope (FE-TEM) analysis and thermal gravimetric analysis (TGA) have also been conducted to analyze the properties of nanofibers as well as the microstructure of the hardened modified cement pastes.

Label-free Femtomolar Detection of Cancer Biomarker by Reduced Graphene Oxide Field-effect Transistor

  • Kim, Duck-Jin;Sohn, Il-Yung;Jung, Jin-Heak;Yoon, Ok-Ja;Lee, N.E.;Park, Joon-Shik
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.02a
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    • pp.549-549
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    • 2012
  • Early detection of cancer biomarkers in the blood is of vital importance for reducing the mortality and morbidity in a number of cancers. From this point of view, immunosensors based on nanowire (NW) and carbon nanotube (CNT) field-effect transistors (FETs) that allow the ultra-sensitive, highly specific, and label-free electrical detection of biomarkers received much attention. Nevertheless 1D nano-FET biosensors showed high performance, several challenges remain to be resolved for the uncomplicated, reproducible, low-cost and high-throughput nanofabrication. Recently, two-dimensional (2D) graphene and reduced GO (RGO) nanosheets or films find widespread applications such as clean energy storage and conversion devices, optical detector, field-effect transistors, electromechanical resonators, and chemical & biological sensors. In particular, the graphene- and RGO-FETs devices are very promising for sensing applications because of advantages including large detection area, low noise level in solution, ease of fabrication, and the high sensitivity to ions and biomolecules comparable to 1D nano-FETs. Even though a limited number of biosensor applications including chemical vapor deposition (CVD) grown graphene film for DNA detection, single-layer graphene for protein detection and single-layer graphene or solution-processed RGO film for cell monitoring have been reported, development of facile fabrication methods and full understanding of sensing mechanism are still lacking. Furthermore, there have been no reports on demonstration of ultrasensitive electrical detection of a cancer biomarker using the graphene- or RGO-FET. Here we describe scalable and facile fabrication of reduced graphene oxide FET (RGO-FET) with the capability of label-free, ultrasensitive electrical detection of a cancer biomarker, prostate specific antigen/${\alpha}$ 1-antichymotrypsin (PSA-ACT) complex, in which the ultrathin RGO channel was formed by a uniform self-assembly of two-dimensional RGO nanosheets, and also we will discuss about the immunosensing mechanism.

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Preparation of Self-Cleaning Coating Films with Nano- and Microstructure (나노마이크로 구조의 자기세정 기능성 코팅막의 제조)

  • Jeong, A-Rong;Kim, Jun-Su;Yun, Jon-Do
    • Korean Journal of Materials Research
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    • v.22 no.8
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    • pp.416-420
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    • 2012
  • Recently nanoscience and nanotechnology have been studied intensively, and many plants, insects, and animals in nature have been found to have nanostructures in their bodies. Among them, lotus leaves have a unique nanostructure and microstructure in combination and show superhydrophobicity and a self-cleaning function to wipe and clean impurities on their surfaces. Coating films with combined nanostructures and microstructures resembling those of lotus leaves may also have superhydrophobicity and self-cleaning functions; as a result, they could be used in various applications, such as in outfits, tents, building walls, or exterior surfaces of transportation vehicles like cars, ships, or airplanes. In this study, coating films were prepared by dip coating method using polypropylene polymers dissolved in a mixture of solvent, xylene and non-solvent, methylethylketon, and ethanol. Additionally, attempts were made to prepare nanostructures on top of microstructures by coating with the same coating solution with an addition of carbon nanotubes, or by applying a carbon nanotube over-coat on polymer coating films. Coating films prepared without carbon nanotubes were found to have superhydrophobicity, with a water contact angle of $152^{\circ}$ and sliding angle less than $2^{\circ}$. Coating films prepared with carbon nanotubes were also found to have a similar degree of superhydrophobicity, with a water contact angle of 150 degrees and a sliding angle of 3 degrees.

Preparation of binder-free IrO2-RuO2/TiO2 nanotube electrode for DSA application. (DSA 활용을 위한 바인더를 사용하지 않은 IrO2-RuO2/TiO2 나노튜브 전극 제조)

  • Yu, Hyeon-Seok;Choe, Jin-Seop
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2018.06a
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    • pp.28-28
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    • 2018
  • 수전해(electrochemical water splitting)는 연료전지의 가역적 역반응을 이용하여 물로부터 수소와 산소를 발생시키는 기술이다. 산소는 음극에서 발생하는데, 이 때 음극 표면은 고농도의 산소 음이온 및 라디칼에 장시간 노출된다. 때문에 기계적, 화학적 내구성이 우수한 전극재를 사용할 필요가 있다. 불용성 전극 (dimensionally stable anode, DSA)은 이러한 기술적 요구사항을 잘 만족하는 상용화 된 전극이다. 티타늄이나 티타늄 합금 표면에 촉매를 미량 반복 살포하여 산화물 형태의 매우 견고한 표면을 형성함으로서 내구성을 확보한다. 그러나, 보통 DSA 제조 기법의 특징에 따라 다공성 표면 구조를 사용하지는 않기 때문에 생산 과정이 복잡하고 비용이 많이 발생하는 문제를 여전히 나타내고 있다. 본 연구는 상기 문제를 개선하기 위한 수전해용 음극 제조 기술에 관한 연구이다. 티타늄과 티타늄 합금은 동일한 양극산화 기술 적용이 가능하다는 점을 이용하여 티타늄 기판으로부터 다공성 구조를 형성함으로써 바인더의 사용을 배제하였다. 단일공정양극산화기법 (single-step anodization)을 이용하여 $IrO_2$$RuO_2$를 도핑함으로써 TiO2에 촉매능을 부여하였다. 제조된 나노튜브들의 구조적 특징을 HR-TEM (High-resolution transmission electron microscope)과 FE-SEM (Field-emission scanning electron microscope)으로 분석하고 SAED (selective area electron diffraction) 패턴을 분석하여 전극재의 결정성을 확인하였다. 알칼라인 분위기에서 일으킨 산소발생반응 (oxygen evolution reaction, OER)의 LSV (linear sweep voltammetry) 결과를 XPS (X-ray photoelectron microscoscopy) 결과와 연관지어 촉매 표면 구조와 과전압의 관계를 해석하였다. LSV 결과로부터 Tafel 분석을 연달아 수행함으로써 전극의 속도결정단계를 정의하였다. 최종적으로 사이클 테스트 통하여 DSA로써의 성능을 평가하였다.

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Effects of CNT Additions on Mechanical Properties and Microstructures of Cement (CNT 첨가량에 따른 시멘트의 역학성능 및 미세구조의 영향)

  • Oh, Sungwoo;Oh, Kyeong-seok;Jung, Sang-hwa;Chung, Wonseok;Yoo, Sung-won
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.21 no.6
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    • pp.162-168
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    • 2017
  • Carbon nanotube(CNT) is one of the promising construction materials to produce concrete with high strength and durability by adding in the concrete mixtures from various researches. Also, its superior heat conductivity can be one of the options to develop self-heating concrete. In this research, the fundamental study was conducted to investigate mechanical properties and microstructures of cement pastes and mortars by strength tests and porosity measurement with several CNT additions, which were 0 wt%, 0.115 wt%, 0.23 wt% and 0.46 wt% of CNT-cement ratio. Compressive and flexural strength test were conducted at 3, 7 and 28 days, and pore characteristics were investigated by mercury intrusion porosimetry. SEM-EDS and Thermogravimetric analysis(TGA) were conducted to prove the hydration product types and CNT dispersion in the cement matrix. As a result, even though high amount of CNT additions were caused worse performance, mixtures with 0.115 wt% of CNTs developed the similar performance with plain mixture.

Preparation of PSf/D2EHPA/CNTs Beads Immobilized with Carbon Nanotubes and Di-(2-ethylhexyl)-phosphoric acid on Polysulfone and Removal Characteristics of Sr(II) (Polysulfone에 Di-(2-ethylhexyl)-phosphoric acid와 Carbon Nanotubes를 고정화한 PSf/D2EHPA/CNTs 비드의 제조와 Sr(II)의 제거 특성)

  • Lee, Min-Gyu;Yun, Jong-Won;Suh, Jung-Ho
    • Korean Chemical Engineering Research
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    • v.55 no.6
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    • pp.854-860
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    • 2017
  • PSf/D2EHPA/CNTs beads were prepared by immobilizing extractant di-(2-ethylhexyl)- phosphoric acid (D2EHPA) and adsorbent carbon nanotubes (CNTs) on polysulfone (PSf), and the adsorption characteristics of Sr(II) on the beads were studied. The morphological characteristics of the prepared PSf/D2EHPA/CNTs beads were observed by scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), and Fourier transform infrared spectrometer (FTIR). The equilibrium time for the removal of Sr(II) by PSf/D2EHPA/CNTs beads was 60 min. The experimental kinetic data followed pseudo-second-order model more than pseudo-first-order kinetics model. The maximum removal capacity of Sr(II) obtained from Langmuir isotherm was 4.75 mg/g. The removal efficiencies of Sr (II) by PSf/D2EHPA/CNTs beads were improved 2.5 times by adding the adsorbent CNTs more than by using only the extractant D2EHPA.

뉴로모픽 시스템용 시냅스 트랜지스터의 최근 연구 동향

  • Nam, Jae-Hyeon;Jang, Hye-Yeon;Kim, Tae-Hyeon;Jo, Byeong-Jin
    • Ceramist
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    • v.21 no.2
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    • pp.4-18
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    • 2018
  • Lastly, neuromorphic computing chip has been extensively studied as the technology that directly mimics efficient calculation algorithm of human brain, enabling a next-generation intelligent hardware system with high speed and low power consumption. Three-terminal based synaptic transistor has relatively low integration density compared to the two-terminal type memristor, while its power consumption can be realized as being so low and its spike plasticity from synapse can be reliably implemented. Also, the strong electrical interaction between two or more synaptic spikes offers the advantage of more precise control of synaptic weights. In this review paper, the results of synaptic transistor mimicking synaptic behavior of the brain are classified according to the channel material, in order of silicon, organic semiconductor, oxide semiconductor, 1D CNT(carbon nanotube) and 2D van der Waals atomic layer present. At the same time, key technologies related to dielectrics and electrolytes introduced to express hysteresis and plasticity are discussed. In addition, we compared the essential electrical characteristics (EPSC, IPSC, PPF, STM, LTM, and STDP) required to implement synaptic transistors in common and the power consumption required for unit synapse operation. Generally, synaptic devices should be integrated with other peripheral circuits such as neurons. Demonstration of this neuromorphic system level needs the linearity of synapse resistance change, the symmetry between potentiation and depression, and multi-level resistance states. Finally, in order to be used as a practical neuromorphic applications, the long-term stability and reliability of the synapse device have to be essentially secured through the retention and the endurance cycling test related to the long-term memory characteristics.

Synthesis of Carbon Nanotubes Supported PtCo Electrocatalysts and Its Characterization for the Cathode Electrode of PEMFC (탄소나노튜브에 담지된 PtCo 촉매 제조 및 PEMFC Cathode 전극 특성)

  • Jung, Dong-Won;Park, Soon;Kang, Jung-Tak;Kim, Jun-Bom
    • Korean Journal of Materials Research
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    • v.19 no.5
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    • pp.233-239
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    • 2009
  • The electrocatalytic behavior of the PtCo catalyst supported on the multi-walled carbon nanotubes (MWNTs) has been evaluated and compared with commercial Pt/C catalyst in a polymer electrolyte membrane fuel cell(PEMFC). A PtCo/MWNTs electrocatalyst with a Pt:Co atomic ratio of 79:21 was synthesized and applied to a cathode of PEMFC. The structure and morphology of the synthesized PtCo/MWNTs electrocatalysts were characterized by X-ray diffraction and transmission electron microscopy. As a result of the X-ray studies, the crystal structure of a PtCo particle was determined to be a face-centered cubic(FCC) that was the same as the platinum structure. The particle size of PtCo in PtCo/MWNTs and Pt in Pt/C were 2.0 nm and 2.7 nm, respectively, which were calculated by Scherrer's formula from X-ray diffraction data. As a result we concluded that the specific surface activity of PtCo/MWNTs is superior to Pt/C's activity because of its smaller particle size. From the electrochemical impedance measurement, the membrane electrode assembly(MEA) fabricated with PtCo/MWNTs showed smaller anodic and cathodic activation losses than the MEA with Pt/C, although ohmic loss was the same as Pt/C. Finally, from the evaluation of cyclic voltammetry(CV), the unit cell using PtCo/MWNTs as the cathode electrocatalyst showed slightly higher fuel cell performance than the cell with a commercial Pt/C electrocatalyst.

Properties of PP/MWCNT Nanocomposite Using Pellet-Shaped MWCNT (펠렛형 MWCNT를 사용한 PP/MWCNT 나노복합체 물성 연구)

  • Jeong, Dong-Seok;Nam, Byeong-Uk
    • Polymer(Korea)
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    • v.35 no.1
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    • pp.17-22
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    • 2011
  • Polypropylene/multi-walled carbon nanotube(PP/MWCNT) composites along with various MWCNT contents up to 20 wt% were prepared by a twin screw extruder. Nanocomposites having 20 wt% MWCNT as a master batch(M/B) were diluted with PP by way of melt compounding. The electrical/thermal conductivity, morphology, thermal/viscoelastic/mechanical properties were investigated with the variation of MWCNT contents. Also, we compared some properties between 1-step PP/MWCNT and the diluted PP/MWCNT composites. The percolation threshold of electrical and thermal conductivity was measured at about 3 wt% MWCNT. And conductivity of diluted PP/MWCNT composites were superior to those of PP/MWCNT composites. The non-isothermal crystallization temperature and thermal decomposition temperature appeared at higher temperatures with increasing MWCNT contents. Morphology showed that length of MWCNT in diluted PP/MWCNT composites was shortened by twice melt blending, which contributed to improve the tensile strength of PP/MWCNT composites.

Improved Performance of CdS/CdTe Quantum Dot-Sensitized Solar Cells Incorporating Single-Walled Carbon Nanotubes

  • Shin, Hokyeong;Park, Taehee;Lee, Jongtaek;Lee, Junyoung;Yang, Jonghee;Han, Jin Wook;Yi, Whikun
    • Bulletin of the Korean Chemical Society
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    • v.35 no.10
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    • pp.2895-2900
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    • 2014
  • We fabricated quantum dot-sensitized solar cells (QDSSCs) using cadmium sulfide (CdS) and cadmium telluride (CdTe) quantum dots (QDs) as sensitizers. A spin coated $TiO_2$ nanoparticle (NP) film on tin-doped indium oxide glass and sputtered Au on fluorine-doped tin oxide glass were used as photo-anode and counter electrode, respectively. CdS QDs were deposited onto the mesoporous $TiO_2$ layer by a successive ionic layer adsorption and reaction method. Pre-synthesized CdTe QDs were deposited onto a layer of CdS QDs using a direct adsorption technique. CdS/CdTe QDSSCs had high light harvesting ability compared with CdS or CdTe QDSSCs. QDSSCs incorporating single-walled carbon nanotubes (SWNTs), sprayed onto the substrate before deposition of the next layer or mixed with $TiO_2$ NPs, mostly exhibited enhanced photo cell efficiency compared with the pristine cell. In particular, a maximum rate increase of 24% was obtained with the solar cell containing a $TiO_2$ layer mixed with SWNTs.