Conductive Carbon Nanotube Films Research Articles

ウェットコーティングによるCNT透明導電フィルム

ウェットコーティングによるCNT透明導電フィルム

Carbon nanotube film interlayer for strain and damage sensing in composites during dynamic compressive loading

A major challenge in the damage assessment of materials under dynamic, high strain rate loading lies in the inability to apply most health monitoring methodologies to the analysis and evaluation of damage incurred on short timescales. Here, we present a resistance-based sensing method utilizing an electrically conductive carbon nanotube film in a fiberglass/vinyl ester composite. This method reveals that applied strain and damage in the form of matrix cracking and delamination give rise to electrical resistance increases across the composite specimen; these can be measured in real-time during high strain rate loading. Damage within the composite specimens is confirmed through pre- and post-mortem x-ray micro computed tomography imaging.

Electrically conductive superhydrophobic octadecylamine-functionalized multiwall carbon nanotube films

Electrically conductive, superhydrophobic multiwall carbon nanotube (MWCNT) thin films were prepared by direct amination of MWCNTs with up to 14wt.% of octadecylamine (ODA) by vacuum filtration method. The ODA-functionalized MWCNT films exhibit a high water contact angle of 165° and electrical conductivity of 860S/m. The liquid–air–solid interface is directly observed from above the water droplet using an optical microscope. The observation indicates that the wettability state of the MWCNTs has changed from relatively hydrophilic to superhydrophobic state upon functionalization with ODA. The fundamental mechanisms responsible for the unusual combination of surface superhydrophobicity and high electrical conductivity of the MWCNT films are described and their implications are discussed.

High-Performance Carbon Nanotube Transparent Conductive Films by Scalable Dip Coating

Transparent conductive carbon nanotube (CNT) films were fabricated by dip-coating solutions of pristine CNTs dissolved in chlorosulfonic acid (CSA) and then removing the CSA. The film performance and morphology (including alignment) were controlled by the CNT length, solution concentration, coating speed, and level of doping. Using long CNTs (∼10 μm), uniform films were produced with excellent optoelectrical performance (∼100 Ω/sq sheet resistance at ∼90% transmittance in the visible), in the range of applied interest for touch screens and flexible electronics. This technique has potential for commercialization because it preserves the length and quality of the CNTs (leading to enhanced film performance) and operates at high CNT concentration and coating speed without using surfactants (decreasing production costs).

Asymmetric deposition of manganese oxide in single walled carbon nanotube films as electrodes for flexible high frequency response electrochemical capacitors

Manganese oxide (MnO2) is a promising pseudocapacitive electrode material because of its high capacitance, abundant resource, low-cost, and environmental friendliness. However, its poor electrical and ionic conductivities and low stability hinder applications. Forming MnO2 nanocomposites with high surface area porous metal, carbon materials, or conducting polymers is a possible solution. In this work, we have developed a facile and scalable asymmetric in situ deposition method to incorporate MnO2 nanoparticles in conductive single walled carbon nanotube (SWCNT) films. The high porosity of vacuum filtrated SWCNT films accommodates pseudocapacitive MnO2 nanoparticles without sacrificing the mechanical flexibility and electrochemical stability of SWCNT films. We exposed one side of SWCNT films to acidic potassium permanganate (KMnO4) solution. The infiltrated KMnO4 solution partially etches SWCNTs to create abundant mesopores, which ensure electrolyte ions efficiently access deposited MnO2. Meanwhile, the remaining SWCNT network serves as excellent current collectors. The electrochemical performance of the SWCNT–MnO2 composite electrodes depends on the porosity of SWCNT films, pH, and concentration of KMnO4 solution, deposition temperature and time. Our optimized two-electrode electrochemical capacitor, with 1M Na2SO4 in water as electrolyte, showed a superior performance with specific capacitance of 529.8Fg−1, energy density of 73.6Whkg−1, power density of 14.6kWkg−1, excellent capacitance retention (99.9%) after 2000 charge and discharge cycles, and one of the highest reported frequency responses (knee frequency at 1318Hz). The high performance flexible electrochemical capacitors have broad applications in portable electronics and electrical vehicles, especially when high frequency response is desired.

Fabrication of conductive and transparent single-walled carbon nanotube films with PEDOT

Poly(3,4-ethylenedioxythiophene) is electropolymerized on a single-walled carbon nanotube film to reduce sheet resistance without causing loss in transparency.

A two-stage, self-aligned vertical densification process for as-grown CNT forests in supercapacitor applications

The method of a two-stage, self-aligned liquid densification process for carbon nanotube (CNT) forests has been demonstrated for supercapacitor electrode applications with enhanced energy density. By combining processes of mechanical bending and liquid densification, the vertical height of a 10mm×5mm in size, as-grown CNT forest on top of a silicon substrate was reduced from 320μm to 21μm in our prototype experiments. It was found that densified CNTs maintained the film continuity and the self-alignment configuration but the alignment changed into the lateral direction of the growth substrate while the CNT-silicon bottom contacts were preserved. After immersing in a liquid electrolyte, the system capacitances were measured by extracting data from the recorded cyclic voltammetry curves. Results show that, even though densified CNT forest samples had slightly reduced total capacitances as compared with samples from as-grown CNT forests, volumetric specific capacitance increased from 1.07F/cm3 to 10.7F/cm3 for densified CNT samples. As such, this two-stage, self-aligned vertical densification process could be scaled up to produce highly densified, large area, porous and conductive CNT films for potential energy storage applications.

Study of the growth of conductive single-wall carbon nanotube films with ultra-high transparency

We report a study of the growth of conductive single-wall carbon nanotube (SWCNT) films with ultra-high transparency (typically above 98% at 550 nm wavelength) on quartz substrates. Ferritin was used as the catalyst precursor and ethanol as the carbon feed. The effects of experimental parameters on film structure and performance have been investigated. Catalyst concentration and pre-annealing of the substrate after catalyst deposition seem to be important parameters to optimize the resulting films. Analysis of these trends gives further insight into the mechanism of SWCNT film growth and termination, which may contribute to more effective synthesis of SWCNT films.

Anti-scratch and transparency properties of transparent conductive carbon nanotube films improved by incorporating polyethoxysiloxane

Transparent conductive films of single-walled carbon nanotubes (SWCNTs) were fabricated by a simple method to significantly enhance anti-scratch and transparency properties by the incorporation of polyethoxysiloxane (PES). The reasons for changes in the mechanical properties and transmittance were investigated through the reflection property and morphology of thin films. With the incorporation of PES, the sheet resistance of the SWCNT thin film remained unchanged after the anti-scratch test. It was found that the transmittance of the thin films suddenly increased when the thickness of the PES layer was ca 100 nm. Although the PES incorporation resulted in a slight increase in the sheet resistance, the experimental results revealed that the sheet resistance of the SWCNT thin films with PES was lower than that of films without PES for the same transmittance due to the increase of the transmittance caused by the PES incorporation. We have demonstrated that the sheet resistance was halved at a transmittance of ∼86% due to PES incorporation. SWCNT thin films with PES showed better electrical properties than those without PES after a bend test.

Solution Processing of Highly Conductive and Transparent Single-Walled Carbon Nanotube Films: Surfactant-Free Dispersions and Non-Acidic Dopants

not Available.

Highly conductive and transparent single-walled carbon nanotube thin films fabricated by gel coating

Transparent and conductive single-walled carbon nanotube (SWCNT) films were fabricated through gel coating. A gel was formed by directly dispersing a large amount of SWCNTs in a liquid nonionic surfactant like polyoxyethylene (12) tridecyl ether without a solvent by mechanical grinding and subsequent ultrasonication. SWCNT films were obtained by coating the gels on glass substrates and subsequently removing the surfactant through heating. The SWCNT films became very thin and transparent after heating at a temperature between 480 and 520 °C. They exhibited good uniformity and a high transmittance-to-sheet resistance ratio which is attributed to the long SWCNTs dispersed in the gels. Films with a sheet resistance of around 250 Ω □−1 at 80% transmittance were obtained. The films can be easily transferred from rigid substrates like glass to flexible polymer substrates like polyethylene terephthalate.

Free-Standing Highly Conductive Transparent Ultrathin Single-Walled Carbon Nanotube Films

Transparent and conductive single-walled carbon nanotube (SWNT) films are of great importance to a number of applications such as optical and electronic devices. Here, we describe a simple approach for preparing free-standing highly conductive transparent SWNT films with a 20-150 nm thickness by spray coating from surfactant-dispersed aqueous solutions of SWNTs synthesized by an improved floating-catalyst growth method. After the HNO(3) treatment, dipping the SWNT films supporting on glass substrates in water resulted in a quick and nondestructive self-release to form free-standing ultrathin SWNT films on the water surface. The obtained films have sufficiently high transmittance (i.e., 95%), a very low sheet resistance (i.e., ∼120 Ω/sq), and a small average surface roughness (i.e., ∼3.5 nm for a displayed 10 × 10 μm area). Furthermore, the floating SWNT films on the water surface were easily transferred to any substrates of interest, without intense mechanical and chemical treatments, to preserve their original sizes and network structures. For example, the transferred SWNT films on poly(ethylene terephthalate) films are mechanically flexible, which is a great advantage over conventional indium-tin oxide (ITO) and therefore strongly promise to be "post ITO" for many applications.

Fast and Efficient Purification for Highly Conductive Transparent Carbon Nanotube Films

A combination of thermal oxidation and thermal recovery was used to obtain transparent single-walled carbon nanotube (SWCNT) films with low sheet resistance. The process resulted in the effective removal of impurities and healing of defects in the SWCNTs, thus markedly increasing their conductivity. SWCNT samples before and after the process were analyzed by Raman spectroscopy, scanning and transmission electron microscopy, thermogravimetric analysis, contact angle measurement, and transparent conductive film fabrication. Following purification, the sheet resistance decreased from 5380 to 187 Ω/sq at 80% optical transmittance and at a wavelength of 550 nm. The process requires a short time of about 3 h and produces 30% yield of the as-produced sample.

시분해 테라파 분광학을 이용한 고전도성 탄소나노튜브 박막의 광학계수 측정

본 연구에서는 전도성이 매우 높은 탄소나노튜브 박막을 제작하고 테라파 영역에서의 광학상수를 측정하였다. 탄소나노튜브박막은 스핀코팅법 또는 진공여과법을 이용하여 연성플라스틱 기판 위에 증착되었다. 테라파 영역의 전자파 투과율은 박막의 두께조절을 통해 가능하며, 산처리 등의 후속공정을 통해서도 조절이 가능하다. 시분해 테라파 투과파의 진폭과 위상 측정을 통해유전상수를 포함한 광학상수의 스펙트럼을 측정하였다. 이를 통해 탄소나노튜브 박막이 Drude 자유전자 모델에 잘 부합하며, 높은 플라즈마 진동수를 가지는 등, 우수한 금속의 특성을 가지고 있음이 밝혀졌다. 또한 산처리 전후 유전상수가 변화하는 것을 직접확인할 수 있었다. 마지막으로 셀룰로즈 멤브레인에 증착된 CNT 필름의 경우엔 기판의 효과가 제거된 광학계수 측정이 가능함을 보여준다. We performed time-domain terahertz (THz) spectroscopy to determine optical constants of highly conductive carbon nanotube (CNT) films. The CNT films have been fabricated on a flexible plastic substrate by using spin-coating or vacuum filtration. We found that the transmission of THz waves can be controlled by manipulating the thickness of the films and by post-treatments. From amplitude and phase information of the transmitted THz waves, we obtain optical constants such as refractive indices and dielectric constants of the CNT films. The frequency dependent dielectric constants show good metallic behaviors, relevant to the Drude free electron models with high plasma frequencies. It is also found that the dielectric constants are higher for the acid-treated films. Finally, the frequency dependent dielectric constants which are free from substrate effects have been demonstrated by using CNT films deposited on cellulose membranes.

Electrical properties of transparent conducting carbon nanotube films

Single walled-carbon nanotube (SWCNT) thin film is one of the candidates for the next-generation flexible and transparent conductive thin film, which is a crucial component in various applications such as electrodes of flat-panel displays, solar cells, light emitting diodes, and touch panels. An intensive research work is underway to develop thin and flexible SWCNT films. The most important requirement of an SWCNT thin film is that it should show a low sheet resistance coupled with a high transparency. In this work, thin films of SWCNTs are prepared by vacuum filtration. The electrical properties of the as-prepared, annealed and HNO3-treated SWCNT films have been investigated. It is found that the square resistance can be significantly changed upon anneal and HNO3-treatment. A room-temperature ethanol alcohol sensor based on the SWCNT film has also been demonstrated.

Removal of the Residual Surfactants in Transparent and Conductive Single-Walled Carbon Nanotube Films

Photocatalysis and Fenton reaction treatments were first employed to eliminate the residual surfactants in the single-walled carbon nanotubes (SWNTs) films without destroying the intrinsic structure of SWNTs. The removal of the surfactants was verified by Raman and XPS spectra. After the treatments, the conductance of SWNTs films was enhanced by a factor of 2.5. Taking a SWNTs film with transparency of 90.6% at 550 nm and resistance of 4.3 kΩ/◻, for example, the sheet resistance decreased to 2.0 kΩ/◻, while the transmittance increased by 0.3% after the treatment.

Effect of annealing and HNO 3-treatment on the electrical properties of transparent conducting carbon nanotube films

Thin films of single-walled carbon nanotubes (SWCNTs) were prepared by vacuum filtration. The electrical behavior of the as-prepared, annealed and HNO 3-treated SWCNT thin films was investigated. The results demonstrated that the post-treatments play an important role in modifying the electrical properties of the SWCNT thin films. The changes in the electrical properties upon annealing and HNO 3-treatment were attributed to the chemical–charge-transfer. A room-temperature ethanol alcohol sensor based on the SWCNT film has been demonstrated.

Ultra Smooth, Large Area, High Uniformity, Conductive Transparent Single-Walled Carbon Nanotube Films for Photovoltaics Produced by Ultrasonic Spraying

not Available.

Continuous and Scalable Fabrication of Transparent Conducting Carbon Nanotube Films

We report an industrially scalable, fast, and simple process for the large scale fabrication of optically transparent and electrically conducting thin films of single-walled carbon nanotubes (SWNT). Purified, pristine HiPco SWNTs were dispersed in water at high concentrations with the help of surfactants, rod-coated into uniform thin films, and doped by various acids. We show how to combine different surfactants to make uniform dispersions with high concentration of SWNTs and optimal rheological behavior for coating and drying, including preventing dewetting and film rupture that has plagued earlier attempts. Doping by fuming sulfuric acid yielded the films with best performance (sheet resistance of 100 and 300 Omega/sq for respective transparency of 70% and 90%). We use a figure of merit (FOM) plot for an immediate evaluation and comparison of the performance and microstructure of CNT films produced by different methods. Further scientific engineering will pave the way to the deployment of CNT films in commercial applications.

Nanolithographic patterning of transparent, conductive single-walled carbon nanotube films by inductively coupled plasma reactive ion etching

The authors report successful patterning of transparent, conductive single-walled carbon nanotube films down to 100nm lateral dimensions by photolithography or e-beam lithography and subsequent O2 plasma etching using an inductively coupled plasma reactive ion etching (ICP-RIE) system. They systematically study the effect of ICP-RIE etch parameters, such as substrate bias power, chamber pressure, and substrate cooling, on the nanotube film etch rate and etch selectivity. They also characterize the effect of the linewidth etched on the nanotube film etch rate for widths ranging from 50μm down to 100nm. Furthermore, by fabricating standard four point probe structures using the patterning capability developed, the authors investigate the effect of different resist processes on the resistivity of patterned single-walled carbon nanotube films and the effect of ICP reactive ion etching on the resistivity of partially etched nanotube films. In addition, they demonstrate that using an ICP-RIE system provides significant advantages, such as faster etch rates and better etch selectivity, over conventional parallel plate RIE plasma systems, making it possible to pattern lateral features as small as 100nm in nanotube films. The simple and efficient “top-down” patterning capability developed in this article could open up many opportunities for integrating single-walled nanotube films into a wide range of electronic and optoelectronic devices.