• Korean Journal of Chemical Engineering
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• v.35 no.12
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• pp.2421-2429
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• 2018

Thiol-based self-assembled anchor linked to glucose oxidase (GOx) and gold nanoparticle (GNP) cluster is suggested to enhance the performance of glucose biosensor. By the adoption of thiol-based anchors, the activity of biocatalyst consisting of GOx, GNP, polyethyleneimine (PEI) and carbon nanotube (CNT) is improved because they play a crucial role in preventing the leaching out of GOx. They also promote electron collection and transfer, and this is due to a strong hydrophobic interaction between the active site of GOx and the aromatic ring of anchor, while the effect is optimized with the use of thiophenol anchor due to its simple configuration. Based on that, it is quantified that by the adoption of thiophenol as anchor, the current density of flavin adenine dinucleotide (FAD) redox reaction increases about 42%, electron transfer rate constant ($k_s$) is $9.1{\pm}0.1s^{-1}$ and the value is 26% higher than that of catalyst that does not use the anchor structure.

• Computers and Concrete
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• v.23 no.5
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• pp.361-376
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• 2019

In this research, bending analysis of a micro sandwich skew plate with isotropic core and piezoelectric composite face sheets reinforced by carbon nanotube on the elastic foundations are studied. The classical plate theory (CPT) are used to model micro sandwich skew plate and to apply size dependent effects based on modified strain gradient theory. Eshelby-Mori-Tanaka approach is considered for the effective mechanical properties of the nanocomposite face sheets. The governing equations of equilibrium are derived using minimum principle of total potential energy and then solved by extended Kantorovich method (EKM). The effects of width to thickness ratio and length to width of the sandwich plate, core-to-face sheet thickness ratio, the material length scale parameters, volume fraction of CNT, the angle of skew plate, different boundary conditions and types of cores on the deflection of micro sandwich skew plate are investigated. One of the most important results is the reduction of the deflection by increasing the angle of the micro sandwich skew plate and decreasing the deflection by decreasing the thickness of the structural core. The results of this research can be used in modern construction in the form of reinforced slabs or stiffened plates and also used in construction of bridges, the wing of airplane.

• Journal of Ocean Engineering and Technology
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• v.37 no.5
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• pp.215-224
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• 2023

While melting glaciers due to global warming have facilitated the development of polar routes, Arctic vessels require reliable anti-icing methods to prevent hull icing. Currently, the existing anti-icing method, i.e., the heating coil method, has disadvantages, such as disconnection and power inefficiency. Therefore, a carbon nanotube-based surface heating element method was developed to address these limitations. In this study, the numerical analysis of the surface heating element method was performed using ANSYS. The numerical analysis included conjugate heat transfer and computational fluid dynamics to consider the conduction solids and the effects of wind speed and temperature in cold environments. The numerical analysis method of the surface heating element method was validated by comparing the experimental results of the heating coil method with the numerical analysis results (under the -30 ℃ conditions). The surface heating element method demonstrated significantly higher efficiency, ranging from 56.65-80.17%, depending on the conditions compared to the heating coil method. Moreover, even under extreme environmental conditions (-45 ℃), the surface heating element method satisfied anti-icing requirements. The surface heating element method is more efficient and economical than the heating coil method. However, proper heat flux calculation for environmental conditions is required to prevent excessive design.

• Journal of the Korean Vacuum Society
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• v.18 no.3
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• pp.229-235
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• 2009

Millimeter-scale aligned arrays of thin-multiwalled carbon nanotube (t-MWCNT) on layered Si substrates have been synthesized by oxygen-assisted microwave plasma chemical vapor deposition (MPCVD). We have succeeded in growth of vertically aligned MWCNTs up to 2.7 mm in height for 150 min. The effect of $O_2$ and water vapour on growth rate was systematically investigated. In the case of $O_2$ gas, the growth rate was ${\sim}22{\mu}m/min$, which is outstanding growth rate comparing with those of conventional thermal CVD (TCVD). Scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), and Raman spectroscopy were used to analyze the CNT morphology, composition and growth mechanism. The role of $O_2$ gas during the CNT growth was discussed on.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.175-188
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• 2023

Global interest in hydrogen energy is increasing as an eco-friendly future energy that can replace fossil fuels. Accordingly, a next-generation hydrogen production technology using microorganisms, nuclear power, etc. is being developed, while a lot of time and effort are still required to overcome the cost of hydrogen production based on fossil fuels. As a way to minimize greenhouse gas emissions in the hydrocarbon-based hydrogen production process, methane direct decomposition technology has recently attracted attention. In order to improve the economic feasibility of the process, the simultaneous production of value-added carbon materials with hydrogen can be one of the most essential aspects. For that purpose, various studies on catalysis related to the quality and yield of high-value carbon materials such as carbon nanotubes (CNTs). In terms of process technology, a number of the research and development of fluidized-bed reactors capable of continuous production and improved gas-solid contact efficiency has been attempted. Recently, methane direct decomposition technology using a fluidized bed has been developed to the extent that it can produce 270 kg/day of hydrogen and 1000 kg/day of carbon. Plus, with the development of catalyst regeneration, separation and recirculation technologies, the process efficiency can be further improved. This review paper investigates the recent development of catalysts and fluidized bed reactor for methane direct pyrolysis to identify the key challenges and opportunities.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.123-123
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• 2003

탄소나노튜브는 지금까지의 많은 연구를 통해 다양한 분야에 대한 응용 가능성이 확인되었으며, 그 중에서도 특히 탄소나노튜브를 이용한 전계방출표시소자(carbon nanotube field emission display, CNT-FED)는 상용화를 눈앞에 두고 있는 상황이다. 본 연구에서는 탄소나 노튜브를 합성할 수 있는 여러 가지 방법 중에서 열화학기상증착법(thermal chemical vapor deposition, thermal CVD)을 이용하여 유리기판 위에 탄소나노튜브를 합성하였다. Electron beam evaporation으로 유리기판 위에 전극층으로 Cr을 150nm를 증착하고 연속하여 촉매층인 Invar(Fe-53%Ni-6%Co 합금)를 10nm의 두께로 형성하였다. 사진식각으로 Cr층을 line 패턴한 후 Cr line 내의 Invar층을 line 및 dot 패턴하였다. 나노튜브 합성을 위해 480-58$0^{\circ}C$까지 진공분위기 또는 질소 분위기에서 20분간 승온한 후 CO(150sccm)와 H$_2$(1200sccm)를 주입하여 20분간 성장시키고 질소 분위기에서 냉각시켰다. 성장된 탄소나노튜브는 SEM, TEM, Raman spectroscopy 등을 통하여 구조 및 형상분석을 하였다. 진공승온의 경우 탄소불순물인 a-C이 많은 양 증착 되었으며 탄소나노튜브는 온도에 따라 1-5$\mu\textrm{m}$의 두께로 성장하였으나, 질소분위기 승온의 경우는 a-C이 거의 증착되지 않았으며 나노튜브의 두께가 10-20$\mu\textrm{m}$였다. 본 연구에서는 diode구조를 갖는 탄소나노튜브 에미터의 수명예측을 위해 여러 가지 가속측정조건에서 전계방출 특성을 연구하였다. Anode와 cathode 간의 간격을 400$\mu\textrm{m}$로 유지한 diode 구조에 대해 $10^{-6}$ torr 이하의 진공에서 전계방출을 측정하였다. 100 line의 에미터를 60Hz의 주파수에서 1/100 duty로 구동하였으며, duty비 증가에 따라 pulse의 on-time을 고정하고 frequency를 변화시켰다. dc까지 duty비가 증가됨에 따라 방출전류의 양이 선형적으로 증가하였다. 전압을 일정하게 고정시키고 각 duty비에서 시간에 따라 방출전류를 측정한 결과 duty비가 높을수록 방출전류가 시간에 따라 급격히 감소하였다. 각 duty비에서 방출전류의 양이 1/2로 감소하는 시점을 에미터의 수명으로 볼 때 duty비 대 에미터 수명관계를 구해 높은 duty비에서 전계방출을 시킴으로써 실제의 구동조건인 낮은 duty비에서의 수명을 단시간에 예측할 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.152-152
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• 2008

탄소나노튜브(carbon nanotube) 필름은 낮은 전기저항, 높은 투명도, 우수한 기계적 강도 및 유연성, 열적 안정성 등의 뛰어난 특성을 가지고 있다. 본 연구에서는 다양한 계면활성제로 분산시킨 수용액으로부터 제조된 단일벽 탄소나노튜브(single-walled CNT) 필름의 면저항(sheet resistance) 특성을 비교하였다. 먼저 나노튜브의 분산을 위해 널리 사용되는 계면활성제인 sodium dodecyl sulfate(SDS)를 기준으로 탄소나노튜브의 양, 원심분리 시간, 초음파 세기 및 시간 등의 최적 공정조건을 정한 후 각 계면활성제에 대해 분산을 위한 최적 첨가량을 알아내어 계면활성제 별로 탄소나노튜브 수용액을 제조하였다. 다양한 계면활성제로 분산된 단일벽 탄소나노튜브 수용액을 알루미나 재질의 필터에 정량적으로 vacuum-filtration하여 필름을 만들었다. 이 필름들의 면저항을 측정함으로써 계면 활성제에 따른 전기적 특성의 차이를 관찰하였다. 본 연구에서 사용한 여러 가지 계면활성제 중 sodium dodecylbenze nesulfonate (NaDDBS)를 사용하여 만든 필름이 가장 낮은 면저항을 나타내었으며, 이는 NaDDBS가 단일벽 탄소나노 튜브 다발들을 개개의 튜브로 잘 분산시키기 때문인 것으로 생각된다.

• Science of Emotion and Sensibility
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• v.24 no.4
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• pp.129-138
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• 2021

This study aimed to determine the effects of the shape and attachment position of stretchable textile sensors coated with carbon nanotube on their performance when used to measure children's joint movements. Moreover, the child-safe requirements for fabric motion sensors are established. The child participants were advised to wear integrated clothing equipped with the sensors of various shapes (rectangular and boat-shaped) and attachment positions (at the knee and elbow joints or 4 cm below the joints). The voltage change induced by the elongation and contraction of the fabric sensors was determined for arm and leg flexion-extension motions at 60 deg/s (three measurements of 10 repeats each for 60°and 90°angles, for a total of 60 repetitions). Their dependability was determined by comparing the fabric motion sensors to the associated acceleration sensors. The experimental results indicate that the rectangular-shaped sensor affixed 4 cm below the joint is the most effective fabric motion sensor for measuring children's arm and leg motions. In this study, we designed a textile sensor capable of tracking children's joint motion and analyzed the sensor shape and attachment position on motion sensing clothing. We demonstrated that flexible fabric sensors integrated into garments may be used to detect the joint motions of the human body.

• Electrical & Electronic Materials
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• v.12 no.7
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• pp.7-11
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• 1999

Fully sealed field emission display in size of 4.5 inch has been fabricated using single-wall carbon nanotubes-organic vehicle com-posite. The fabricated display were fully scalable at low temperature below 415$^{\circ}C$ and CNTs were vertically aligned using paste squeeze and surface rubbing techniques. The turn-on fields of 1V/${\mu}{\textrm}{m}$ and field emis-sion current of 1.5mA at 3V/${\mu}{\textrm}{m}$ (J=90${\mu}{\textrm}{m}$/$\textrm{cm}^2$)were observed. Brightness of 1800cd/$m^2$ at 3.7V/${\mu}{\textrm}{m}$ was observed on the entire area of 4.5-inch panel from the green phosphor-ITO glass. The fluctuation of the current was found to be about 7% over a 4.5-inch cath-ode area. This reliable result enables us to produce large area full-color flat panel dis-play in the near future. Carbon nanotubes (CNTs) have attracted much attention because of their unique elec-trical properties and their potential applica-tions [1, 2]. Large aspect ratio of CNTs together with high chemical stability. ther-mal conductivity, and high mechanical strength are advantageous for applications to the field emitter [3]. Several results have been reported on the field emissions from multi-walled nanotubes (MWNTs) and single-walled nanotubes (SWNTs) grown from arc discharge [4, 5]. De Heer et al. have reported the field emission from nan-otubes aligned by the suspension-filtering method. This approach is too difficult to be fully adopted in integration process. Recently, there have been efforts to make applications to field emission devices using nanotubes. Saito et al. demonstrated a car-bon nanotube-based lamp, which was oper-ated at high voltage (10KV) [8]. Aproto-type diode structure was tested by the size of 100mm $\times$ 10mm in vacuum chamber [9]. the difficulties arise from the arrangement of vertically aligned nanotubes after the growth. Recently vertically aligned carbon nanotubes have been synthesized using plasma-enhanced chemical vapor deposition(CVD) [6, 7]. Yet, control of a large area synthesis is still not easily accessible with such approaches. Here we report integra-tion processes of fully sealed 4.5-inch CNT-field emission displays (FEDs). Low turn-on voltage with high brightness, and stabili-ty clearly demonstrate the potential applica-bility of carbon nanotubes to full color dis-plays in near future. For flat panel display in a large area, car-bon nanotubes-based field emitters were fabricated by using nanotubes-organic vehi-cles. The purified SWNTs, which were syn-thesized by dc arc discharge, were dispersed in iso propyl alcohol, and then mixed with on organic binder. The paste of well-dis-persed carbon nanotubes was squeezed onto the metal-patterned sodalime glass throuhg the metal mesh of 20${\mu}{\textrm}{m}$ in size and subse-quently heat-treated in order to remove the organic binder. The insulating spacers in thickness of 200${\mu}{\textrm}{m}$ are inserted between the lower and upper glasses. The Y\ulcornerO\ulcornerS:Eu, ZnS:Cu, Al, and ZnS:Ag, Cl, phosphors are electrically deposited on the upper glass for red, green, and blue colors, respectively. The typical sizes of each phosphor are 2~3 micron. The assembled structure was sealed in an atmosphere of highly purified Ar gas by means of a glass frit. The display plate was evacuated down to the pressure level of 1$\times$10\ulcorner Torr. Three non-evaporable getters of Ti-Zr-V-Fe were activated during the final heat-exhausting procedure. Finally, the active area of 4.5-inch panel with fully sealed carbon nanotubes was pro-duced. Emission currents were character-ized by the DC-mode and pulse-modulating mode at the voltage up to 800 volts. The brightness of field emission was measured by the Luminance calorimeter (BM-7, Topcon).

• Proceedings of the Technology Innovation Conference
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• 2005.06a
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• pp.69-91
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• 2005

나노 기술은 국가와 기업 차원에서 전략적으로 활발하게 연구, 개발되고 있는 분야로 기술과 산업 전 분야에 걸쳐 있으며 계속 확대되고 있다. 이중 탄소나노튜브는 약 10년여 전부터 활발히 연구되고 있으며, 소재, 소자 등 나노 기술의 전 분야에 걸쳐서 적용될 수 있는 물질로 현재까지 실용화된 기술이나 제품이 많이 나오지는 않았으나 앞으로 다양한 적용분야가 창출될 전망이다. 그러나 전략적인 기술 개발을 위한 연구는 미비한 실정이다. 전략적이고 효과적인 기술 개발의 대안으로 특허 분석(patent analysis)이 제시되고 있으며 나노 기술에 대한 전반적인 특허 분석은 각 기업 연구소나 국가 연구소에서 진행되어 왔으나, 여기서 도출된 정보만으로는 전략적인 문제들을 분석하기에는 미흡하였다. 따라서 전략적인 기술 개발을 위한 특허 분석의 필요성이 제기되고 있다. 이에 본 연구에서는 특허의 인용(citation) 정보를 이용하여 특허와 특허 사이의 관계를 분석하고 이를 바탕으로 관련된 특허를 군집화(clustering) 하여 각 군집의 특성을 살펴보았다. 먼저 탄소나노튜브에 관한 특허를 USPTO 자료를 통해 추출하고, 이 특허들이 인용한 특허들을 추출하여 각 특허들이 어느 정도로 관련이 되어 있는가를 상관 행렬(correlation matrix)을 이용하여 조사하였다. 인용 특허의 분석은 기초 기술 분야에 이르기까지 광범위하게 조사하여 기술별로 특허를 군집화 하였을 뿐만 아니라, 특허 출원인 정보도 활용하여 군집화 하였다. 이를 통하여 기술별, 특허 출원인 별로 특허의 군집을 만들어서 각 군집의 특성을 도출하였고, 마지막으로 각 군집의 특성에 맞게 기술 개발측면에서 전략적인 시사점을 도출하였다. 각각의 군집들은 시간이 지날수록 확대, 통합되는 결과를 보이고 있으며, 융합기술화 되고 있다. 군집을 이루는 주요한 특성으로는 출원인 정보가 큰 비중을 차지하였으며, 이는 출원인의 기술 개발 전략과 이에 따른 기술개발경로나 특허 전략과 관련이 있는 것으로 나타났다. 다양한 기술에 관하여 군집의 크기가 계속 확대되고 있는 경향을 보이고 있기 때문에, 앞으로 지속적인 연구를 통하여 향후 특허 관리와 특허 전략에 적용할 수 있도록 하는 것이 중요하다.