• EDISON SW 활용 경진대회 논문집
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• 제2회(2013년)
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• pp.260-263
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• 2013

A semiconducting single-walled carbon nanotube (SWCNT) field-effect transistor (FET) in a top-gate model was constructed. The effect of different high-${\kappa}$ dielectric materials ($Al_2O_3$, $HfO_2$ and HfSiON) and various temperatures with a wide range from 50K to 500K on the performance of such nominal device were investigated. Several key device parameters including the on/off ratio of the current, transconductance ($g_m$), subthreshold swing, and carrier mobility were used to evaluate the device performance. The simulated results fit well with the experiment results previously published.

• Steel and Composite Structures
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• 제51권4호
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• pp.407-416
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• 2024

The main objective of the present paper is to investigate the nonlinear vibration of buckled beams fixed at both ends and made of Aluminium allay (Al-alloy) reinforced with randomly dispersed Single Walled Carbon Nanotube (SWNT). The Mori-Tanak (M-T) micromechanical approach is selected to predict the homogenized material properties of the beams. The differential equation of motion governing the nonlinear behavior of the Euler-Bernoulli homogeneous beam is solved using an analytical method. The influences of diverse parameters including axial load, vibration amplitude, SWNT volume fraction, SWNT aspect ratio and beam slenderness ratio on the nonlinear frequency are studied.

• 한국재료학회지
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• 제19권11호
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• pp.631-636
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• 2009

We investigated the NO gas sensing characteristics of ZnO-carbon nanotube (ZnO-CNT) layered composites fabricated by coaxial coating of single-walled CNTs with a thin layer of 1 wt% Al-doped ZnO using rf magnetron sputtering deposition. Morphological studies clearly revealed that the ZnO appeared to form beadshaped crystalline nanoparticles with an average diameter as small as 30 nm, attaching to the surface of the nanotubes. It was found that the NO gas sensing properties of the ZnO-CNT layered composites were dramatically improved over Al-doped ZnO thin films. It is reasoned from these observations that an increase in the surface-to-volume ratio associated with the numerous ZnO “nanobeads” on the surface of the CNTs results in the enhancement of the NO gas sensing properties. The ZnO-CNT layered composite sensors exhibited a maximum sensitivity of 13.7 to 2 ppm NO gas at a temperature of 200${^{\circ}C}$ and a low NO gas detection limit of 0.2 ppm in dry air.

• 대한기계학회논문집B
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• 제38권7호
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• pp.601-605
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• 2014

일반적으로 표면적/부피비가 큰 전도성 다공체는 수퍼캐패시터의 전극이나 흡수제, 유연히터 등의 다양한 분야에 적용되어 왔다. 본 논문에서는 이러한 전도성 다공성 구조의 역학적 전기적 특성을 이용하여 고감도 압력센서를 구현하였다. 탄소나노튜브 용액에 스펀지를 적셔 다공체에 전도성을 부여하였으며, 압력에 따른 전도성 다공체의 저항 변화를 측정하였다. 전도성 스펀지에 압력이 가해졌을때, 각각의 탄소나노튜브들은 서로 맞붙게 되어 저항이 최대 20%까지 줄어듦을 확인하였다. 부드럽고 탄성력이 뛰어난 탄소나노튜브 스폰지는 반복적인 압축실험에도 모양의 변형 없이 매우 빠르게 안정화되고 일정한 저항변화를 확인할 수 있었다. 또한 스펀지 압력소자를 유연소자에 적용하기 위하여 탄소나노튜브 트랜지스터와 연결하여 외부압력에 따른 전기적 특성변화를 측정하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.530-530
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• 2012

Many practical applications of carbon nanotubes(CNTs) have been proposed and there have been attempts to utilize CNT films as transparent electrodes for solar cells and displays. Our group has considered the use of the CNT film as a thin film heater (TFH) and proposed it for the first time and reported the thermal behavior of the TFH made of single walled CNTs. However, due to the relatively high electrical resistance of the CNT film, using the TFH in application areas requiring high heat flux has been a difficult problem. To overcome this obstacle, we adopted a 'branch electrodes' concept to increase the film conductance dramatically. If two branch electrodes are inserted into a TFH whose original electrical resistance is R, the total resistance will be reduced to R/9. Because of the increased aspect ratio, the resistance of each segmented TFH will be reduced to R/3. Furthermore, since they are connected in parallel, the total resistance reduces to R/9. This could be extended to n branch electrodes, and the total resistance of the film will be reduced to R/(n+1)2, if the resistance of electrodes are negligibly small. We fabricated the heaters with different number of branch electrodes. The number of branch electrodes of the fabricated heaters are 0, 2, 4, 8 and their electrical resistance are 101.4, 39.5, 20.0, $15.4{\Omega}$, respectively. We applied 20V to each heater and monitored the temperature variations. We could achieve high heating temperature even with low voltage supply. This technique could be applied to relevant industrial applications which need high power film heater.

• Steel and Composite Structures
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• 제42권6호
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• pp.779-789
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• 2022

This work presents a non-linear cylindrical bending analysis of functionally graded plate reinforced by single-walled carbon nanotubes (SWCNTs) in thermal environment using a simple integral higher-order shear deformation theory (HSDT). This theory does not require shear correction factors and the transverse shear stresses vary parabolically through the thickness. The material properties of SWCNTs are assumed to be temperature-dependent and are obtained from molecular dynamics simulations. The material properties of functionally graded carbon nanotube-reinforced composites (FG-CNTCRs) are considered to be graded in the thickness direction, and are estimated through a micromechanical model. The non-linear strain-displacement relations in the Von Karman sense are used to study the effect of geometric non-linearity and the solution is obtained by minimization of the total potential energy. The numerical illustrations concern the nonlinear bending response of FG-CNTRC plates under different sets of thermal environmental conditions, from which results for uniformly distributed CNTRC plates are obtained as benchmarks.

• Computers and Concrete
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• 제32권1호
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• pp.75-85
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• 2023

This work utilizes simplified higher-order shear deformation beam theory (HSDBT) to investigate the vibration response for functionally graded carbon nanotube-reinforced composite (CNTRC) beam. Novel to this work, single-walled carbon nanotubes (SWCNTs) are distributed and aligned in a matrix of polymer throughout the beam, resting on a viscoelastic foundation. Four un-similar patterns of reinforcement distribution functions are investigated for the CNTRC beam. Porosity is another consideration taken into account due to its significant effect on functionally graded materials (FGMs) properties. Three types of uneven porosity distributions are studied in this study. The damping coefficient and Winkler's and Pasternak's parameters are considered in investigating the viscosity effect on the foundation. Moreover, the impact of different parameters on the vibration of the CNTRC beam supported by a viscoelastic foundation is discussed. A comparison to other works is made to validate numerical results in addition to analytical discussions. The findings indicate that incorporating a damping coefficient can improve the vibration performance, especially when the spring constant factors are raised. Additionally, it has been noted that the fundamental frequency of a beam increases as the porosity coefficient increases, indicating that porosity may have a significant impact on the vibrational characteristics of beams.

• Advances in nano research
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• 제17권4호
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• pp.323-334
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• 2024

This paper deals with the effect of non-linear volume fraction distribution of carbon nanotube in the FG-CNTRC beams on the critical buckling via a hyperbolic shear deformation theory. Here, different boundary condition was considered including hinged hinged, clamped clamped and clamped-free. Single-walled carbon nanotubes are aligned and distributed in the polymer matrix in different ways to reinforce it and the material properties of (CNTRC) beams are assumed to vary gradually along the thickness direction, following a new exponential power law distribution of (CNT). The effective material properties of nanocomposite beams are estimated using the rule of mixture. The governing equations of the mathematical models are obtained by applying Hamilton's principle. The results provided of mathematical models in this work are compared and validated with similar ones in the literature. The critical buckling loads of nanocomposite beams with different boundary conditions of linear and non-linear distribution of CNT volume fraction were obtained. The effects of several parameters, including the type of beam, the volume fraction of carbon nanotubes (CNTs), the exponent degree (n), and the aspect ratio, were investigated. The distribution non-linearity of CNT volume fraction in the beam has a significant impact on the mechanical properties, particularly in buckling behavior with different boundary conditions.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.264-264
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• 2010

Single-walled carbon nanotubes (SWCNTs) were grown on a Si wafer by using thermal chemical vapor deposition (t-CVD). We investigated the effect of the catalyst deposition rate on the types of CNTs grown on the substrate. In general, smaller islands of catalyst occur by agglomeration of a catalyst layer upon annealing as the catalyst layer becomes thinner, which results in the growth of CNTs with smaller diameters. For the same thickness of catalyst, a slower deposition rate will cause a more uniformly thin catalyst layer, which will be agglomerated during annealing, producing smaller catalyst islands. Thus, we can expect that the smaller-diameter CNTs will grow on the catalyst deposited with a lower rate even for the same thickness of catalyst. The 0.5-nm-thick Fe served as a catalyst, underneath which Al was coated as a catalyst support as well as a diffusion barrier on the Si substrate. The catalyst layers were. coated by using thermal evaporation. The deposition rates of the Al and Fe layers varied to be 90, 180 sec/nm and 70, 140 sec/nm, respectively. We prepared the four different combinations of the deposition rates of the AI and Fe layers. CNTs were synthesized for 10 min by flowing 60 sccm of Ar and 60 sccm of $H_2$ as a carrier gas and 20 sccm of $C_2H_2$ as a feedstock at 95 torr and $810^{\circ}C$. The substrates were subject to annealing for 20 sec for every case to form small catalyst islands prior to CNT growth. As-grown CNTs were characterized by using field emission scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, UV-Vis NIR spectroscopy, and atomic force microscopy. The fast deposition of both the Al and Fe layers gave rise to the growth of thin multiwalled CNTs with the height of ${\sim}680\;{\mu}m$ for 10 min while the slow deposition caused the growth of ${\sim}800\;{\mu}m$ high SWCNTs. Several radial breathing mode (RBM) peaks in the Raman spectra were observed at the Raman shifts of $113.3{\sim}281.3\;cm^{-1}$, implying the presence of SWCNTs (or double-walled CNTs) with the tube diameters 2.07~0.83 nm. The Raman spectra of the as-grown SWCNTs showed very low G/D peak intensity ratios, indicating their low defect concentrations.

• Structural Engineering and Mechanics
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• 제53권3호
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• pp.497-517
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• 2015

In this study, nonlocal nonlinear buckling analysis of embedded polymeric temperature-dependent microplates resting on an elastic matrix as orthotropic temperature-dependent elastomeric medium is investigated. The microplate is reinforced by single-walled carbon nanotubes (SWCNTs) in which the equivalent material properties nanocomposite are estimated based on the rule of mixture. For the carbon-nanotube reinforced composite (CNTRC) plate, both cases of uniform distribution (UD) and functionally graded (FG) distribution patterns of SWCNT reinforcements are considered. The small size effects of microplate are considered based on Eringen's nonlocal theory. Based on orthotropic Mindlin plate theory along with von K$\acute{a}$rm$\acute{a}$n geometric nonlinearity and Hamilton's principle, the governing equations are derived. Generalized differential quadrature method (GDQM) is applied for obtaining the buckling load of system. The effects of different parameters such as nonlocal parameters, volume fractions of SWCNTs, distribution type of SWCNTs in polymer, elastomeric medium, aspect ratio, boundary condition, orientation of foundation orthtotropy direction and temperature are considered on the nonlinear buckling of the microplate. Results indicate that CNT distribution close to top and bottom are more efficient than those distributed nearby the mid-plane for increasing the buckling load.