Surface analysis and mechanical behaviour mapping of vertically aligned CNT forest array through nanoindentation

Purpose Carbon nanotube-based architectures have increased the scientific interest owning to their exceptional performance rendering them promising candidates for advanced industrial applications in the nanotechnology field. Despite individual CNTs being considered as one of the most known strong materials, much less is known about other CNT forms, such as CNT arrays, in terms of their mechanical performance. The paper aims to discuss these issues. Design/methodology/approach In this work, thermal CVD method is employed to produce VA-MWCNT carpets. Their structural properties were studied by means of SEM, XRD and Raman spectroscopy, while their hydrophobic behavior was investigated via contact angle measurements. The resistance to indentation deformation of VA-MWCNT carpets was investigated through nanoindentation technique. Findings The synthesized VA-MWCNTs carpets consisted of well-aligned MWCNTs. Static contact angle measurements were performed with water and glycerol, revealing a rather super-hydrophobic behavior. Originality/value The structural analysis, hydrophobic behavior and indentation response of VA-MWCNTs carpets synthesized via CVD method are clearly demonstrated.

<p>The unique combination of light weight, small dimensions, structural diversity, excellent mechanical strength and remarkable electronic properties make carbon nanotubes an attractive field of discovery for a wide range of applications, from reinforcing materials to molecular sensing. The immediate problem is in reliably and reproducibly fabricating carbon nanotubes and nanotube arrays with a certain exclusive structure. The reason for this is the large number of parameters integral to nanotube growth. This thesis describes the effect of several synthesis parameters - including temperature, catalyst, and water addition - on the growth of carbon nanotubes by a thermal chemical vapour deposition method. In all instances, multi-walled nanotubes were the only carbon nanotube products observed. The chemical vapour deposition method employed here involves hexane as a volatile carbon precursor and ferrocene as a floating catalyst. The hexane is introduced into the system by passing a stream of nitrogen carrier gas through a bubbler containing the carbon precursor, while the ferrocene catalyst is positioned inside the working tube where it can evaporate gradually. The products of this method are large, vertically aligned arrays of clean multi-walled nanotubes. The second part of this thesis describes the role of the supporting layer in affecting the growth of these extended nanotube arrays. A number of substrates have been examined - both conducting and non-conducting - and the products from these were analysed. It was found that all non-conductive, metal oxide substrates used - these included quartz, alumina, glazed porcelain, Pythagoras, and also fluorite - produced extended fields of carbon nanotubes. Conversely, many conductive substrates - including nickel, molybdenum, glassy carbon, highly ordered pyrolitic graphite and nickel-iron-silicon metal alloys - produce only small amounts of carbon nanotubes. This difference is likely caused by the deactivation of the iron catalyst at high temperature due to diffusion into the substrate surface.</p>

Chapter 13 - Carbon Nanotube Sheet: Processing, Characterization and Applications

Highly uniform hole spacing micro brushes were fabricated based on aligned carbon nanotube (CNT) arrays synthesized by chemical vapor deposition method with the assistance of anodic aluminum oxide (AAO) template. Different micro brushes from CNT arrays were constructed on silicon, glass, and polyimide substrates, respectively. The micro brushes had highly uniform hole spacing originating from the regularly periodic pore structure of AAO template. The CNT arrays, serving as bristles, were firmly grafted on the substrates. The brushes can easily clean particles with scale of micrometer on the surface of silicon wafer and from the narrow spaces between the electrodes in a series of cleaning experiments. The results show the potential application of the CNT micro brushes as a cleaning tool in microelectronics manufacture field.

Various aspect ratios of CNTs reported based on alteration of annealing temperature using thermal-chemical vapor deposition (TCVD) method. Also the growth dependent and independent parameters of the carbon nanotube (CNTs) array were studied as a function of synthesis method. The FESEM images indicate that the nanotubes are approximately perpendicular to the surface of the silicon substrate and form carbon nanotubes in different aspect ratios according to the applied annealing temperature. Furthermore, due to the optimized results it can be observed that, the mechanism of the CNTs growth is still present in the annealing step as well as deposition process and the most CNTs with crystalline aspect, produced in the annealing temperature, which was optimized at 700 - 900 ˚C. This result demonstrates that the growth rate, mass production, diameter, density, and crystallinity of CNT can be controlled by the annealing temperature.

Synthesis and plasma surface functionalization of carbon nanotubes for using in advanced epoxy-based nanocomposites

The effects of Ni and Co catalysts are investigated on growth of aligned carbon nanotubes (CNTs) by thermal chemical vapor deposition (TCVD) method. It is found that the nickel catalyst has an important and strong role on the CNTs density, morphology and smaller diameter CNTs, whereas larger diameter CNTs are obtained by using cobalt catalyst lower densities. The carbon nanotubes catalyzed by Ni have the best alignment and the smoothest rather than Co catalyst in this research. The conditions were the same for synthesis of CNTs with both catalysts in this our research, but the structures were different because of the presence of different catalysts in the desired experiment. Therefore, Ni is considered the best catalyst for growth of aligned carbon nanotubes.

An application of nanoparticle technology is carbon nanotube (CNT). CNT gives more some advantages than the other materials. These advantages make the research about CNT have many attentions. This research aims to determine the better type of catalyst supported between natural zeolit and y type zeolit in CNT synthesis from ethanol using CVD (chemical vapor deposition) method with Fe - Co as the catalysts. In addition, the research aims to determine the optimum concentration of acid in CNT purification. In CNT synthesis using CVD method, the carbon source that obtained from the ethanol was reacted with H 2 gas and Co - Fe catalysts. Fe - Co catalyst was impregnated in catalyst supported and dried in oven at 80 0 C for one day and then it was calcinated in furnace at 500 0 C on the air flow for 60 minutes. The synthesis process was done that the catalyst was put on the ceramic boat and entered in the quartz reactor. The reactor was vacuumed by vacuum pump. The N 2 gas was flowed with flow rate 200 cm 3 /minutes in room temperature. The furnace was flamed and set at 900 0 C. Ethanol was flowed into the reactor and the flow rate of the N 2 gas was decreased to 6,19 cm 3 /minutes and H2 began to be flowed, then it was reacted for 30 minutes. Acid contacted method was used to purification CNT. The nitrate acid was diluted up to obtain 3N, 2N and 1N nitrate acid. These nitrate acid were mixed with CNT in beaker glass for 10 minutes, then they were put into oven for 24 hours. The CNT from synthesis process and CNT from purification process were analyzed by Scanning Electron Microscopy (SEM). The results of the research show that natural zeolit is better than y type zeolit for CNT synthesis from ethanol of CVD method with Fe - Co catalyst and the optimum acid concentration in purification of CNT by acid contacted method was 3N. Keywords: CNT, synthesis, purification, SEM, ethanol

In this article, we describe a simple method to reversibly tune the wetting properties of vertically aligned carbon nanotube (CNT) arrays. Here, CNT arrays are defined as densely packed multi-walled carbon nanotubes oriented perpendicular to the growth substrate as a result of a growth process by the standard thermal chemical vapor deposition (CVD) technique.1,2 These CNT arrays are then exposed to vacuum annealing treatment to make them more hydrophobic or to dry oxidation treatment to render them more hydrophilic. The hydrophobic CNT arrays can be turned hydrophilic by exposing them to dry oxidation treatment, while the hydrophilic CNT arrays can be turned hydrophobic by exposing them to vacuum annealing treatment. Using a combination of both treatments, CNT arrays can be repeatedly switched between hydrophilic and hydrophobic.2 Therefore, such combination show a very high potential in many industrial and consumer applications, including drug delivery system and high power density supercapacitors.3-5 The key to vary the wettability of CNT arrays is to control the surface concentration of oxygen adsorbates. Basically oxygen adsorbates can be introduced by exposing the CNT arrays to any oxidation treatment. Here we use dry oxidation treatments, such as oxygen plasma and UV/ozone, to functionalize the surface of CNT with oxygenated functional groups. These oxygenated functional groups allow hydrogen bond between the surface of CNT and water molecules to form, rendering the CNT hydrophilic. To turn them hydrophobic, adsorbed oxygen must be removed from the surface of CNT. Here we employ vacuum annealing treatment to induce oxygen desorption process. CNT arrays with extremely low surface concentration of oxygen adsorbates exhibit a superhydrophobic behavior.

Development of carbon nanotube-based gas sensors for NO x gas detection working at low temperature

Synthesis and Characterization of High Yield Multiwalled Carbon Nanotubes by Ternary Catalyst

Zero reflection and complete light absorption are required in a wide range of applications ranging from sensing devices to solar heaters and photoelectrodes. However, simultaneously satisfying the requirements of the broadband spectrum, omnidirectionality, polarization insensitivity, and scalability is very challenging. Combining the light-trapping characteristics of microscale copper nanowires (Cu NWs) with the unique optical properties of carbon nanotubes (CNTs), we experimentally demonstrate a novel perfect absorber that has an average total reflectance of 0.75% over the broad 400–1000 nm wavelength range and an average specular reflectance as low as 0.1%. Importantly, our cactus-like, hierarchical structure retains a similar performance independently of light polarization and for a broad range of incident angles. We furthermore developed a model that elucidates how the Cu NW and CNT components synergistically contribute to the suppression of both specular and diffuse reflections while maximizing light absorption. Thanks to the scalability of the fabrication process, on the basis of the thermal oxidation and chemical vapor deposition methods, our broadband and omnidirectional perfect absorber exhibits a large potential for boosting the performance of many light-harnessing devices.

Synthesis and growth of carbon nanotubes (CNTs) from C2H2 by thermal chemical vapour deposition (TCVD) using a mixture of different gases were investigated. A thin film of nickel was coated as catalyst on silicon substrates by ion beam sputtering technique. Various parameters such as thickness of oxide layer and time, as well as reduction temperature were investigated in view of obtaining the best conditions for CNTs growth. C2H2 was very effective as carbon feedstock and NH3 pretreatments were crucial steps towards obtaining a high density of nucleation sites for CNTs growth by inhibiting amorphous carbon generation in the initial stage of the synthesis. The substrate oxide layer was analysed by secondary ion mass spectrometry. The prepared CNTs were confirmed by Raman spectroscopy and were further characterised using scanning electron microscopy and transmission electron microscopy.

Field emission properties of carbon nanocoils synthesized on stainless steel

Controlling the formation of nanoparticles for definite growth of carbon nanotubes for interconnect applications