Diameter Of MWCNTs Research Articles

Синтез углеродных нанотрубок с помощью СВЧ излучения для модификации эластомера с улучшенной электро- и теплопроводностью

The paper presents a method of microwave influence on ferrocene C10H10Fe and graphite to obtain multilayer carbon nanotubes (MWCNTs) — designed to improve the electrical and thermophysical properties of silicon-graphite elastomer (Silagerm 8020). Diagnostics and characterisation of the synthesised MWCNTs were carried out by energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. According to SEM data, it follows that the morphology of the synthesised MWCNTs has the form of filamentous formations intertwined in bundles with the diameter of individual MWCNTs from 40 to 60 nm and length up to several microns. At the same time, the surface of most of the MWCNTs is covered with a continuous layer of iron (Fe). The EDX method also confirmed the Fe and oxygen content on the surface of the MWCNTs. XRD method identified the presence of Fe in combination with carbon in the form of Fe3C iron carbide and pure Fe iron at 44.7°. The compound Fe3C, also referred to the active phase of Fe allowing the synthesis of MWCNTs. By increasing the concentration of MWCNTs in the elastomer, an increase in thermal conductivity with percolation transition was achieved at a concentration of 8 % MWCNTs. The maximum thermal conductivity of the nanomodified elastomer was 0.48 W/(m·°C), which corresponded to the mass concentration of MWCNTs equal to 8 wt.%. At the same time, the electrical conductivity of the composite, when the MWCNTs concentration was changed from 1 to 8 %, increased in the range from 4·10–5 to 2.4 cm·cm–1 and is also due to the percolation of MWCNTs in the elastomer matrix.

Lithography-free synthesis of periodic, vertically-aligned, multi-walled carbon nanotube arrays

Until now, the growth of periodic vertically aligned multi-walled carbon nanotube (VA-MWCNT) arrays was dependent on at least one lithography step during fabrication. Here, we demonstrate a lithography-free fabrication method to grow hexagonal arrays of self-standing VA-MWCNTs with tunable pitch and MWCNT size. The MWCNTs are synthesized by plasma enhanced chemical vapor deposition (PECVD) from Ni catalyst particles. Template guided dewetting of a thin Ni film on a hexagonally close-packed silica particle monolayer provides periodically distributed Ni catalyst particles as seeds for the growth of the periodic MWCNT arrays. The diameter of the silica particles directly controls the pitch of the periodic VA-MWCNT arrays from 600 nm to as small as 160 nm. The diameter and length of the individual MWCNTs can also be readily adjusted and are a function of the Ni particle size and PECVD time. This unique method of lithography-free growth of periodic VA-MWCNT arrays can be utilized for the fabrication of large-scale biomimetic materials.

The effect of Cu content in MWCNTs synthesized by Ni - Cu @ a-C:H catalyst on the optical constants and the optical loss

In this paper, Ni-Cu NPs @ a-C:H films with different Cu content, by co-deposition of RF-sputtering and RF-plasma enhanced chemical vapor deposition (RF-PECVD) were prepared using acetylene gas and Ni and Cu targets. We studied optical constants of MWCNTs synthesized, with constant Ni content and different percentages of 5, 40 and 75 % from Cu atoms. With increase of Cu content, the average diameter of MWCNTs were increased however the RMS roughness of films were decreased. It is found that the absorption coefficients of films deposited with 5% Cu have maximum value. Also it can be seen that the minimum values of the optical band gaps of films happen in films deposited with 5% Cu. With increase of Cu content, the values of energy loss by the free charge carriers were increased however the plasma frequency ωp and free charge carriers concentration N/m* of films were decreased. The free carriers electric susceptibility χc at in films deposited with 75 % Cu has maximum value. The values of the ratio of free charge carriers concentration to effective mass, N/m*, in films deposited with 5% Cu has maximum value about of 423.731048 m−3 kg−1.

Effect of the diameter of MWCNTs on shape memory and mechanical properties of polyurethane composites

The work reported herein, effect of diameter of reinforced (MWCNTs) on shape memory and mechanical properties of shape memory thermoplastic polyurethane (SMTPU) composites. The composites containing 1 wt.% reinforced having three different MWCNTs outer diametre (OD = 10–20 nm, OD = 30–50 nm, and OD= > 50 nm) with the same length (10–30 μm) were prepared through melt mixing route by using micro-compounder followed by Injection moulding. Shape memory and mechanical properties both were significantly improved for composites. Thicker MWCNTs (at same length) leads to a less number of MWCNTs at a given wt.%, result in less percolated network and larger distance between the indivisual MWCNTs which alter the shape memory and mechanical properties. Furthermore, with increasing the diameter of reinforced MWCNTs at a same wt.% in polyurethane matrix the properties were decreased.

Entropy optimization in CNTs based nanomaterial flow induced by rotating disks: A study on the accuracy of statistical declaration and probable error

BackgroundCNTs (Carbon nanotubes) being allotropes of carbon, made of graphene and diameters of single and multi-walls carbon nanotubes are typically 0.8 to 2 nm and 5 to 20 mn, although diameter of MWCNTs can exceed 100 nm. Carbon nanotubes lengths range from less than 100 nm to 0.5 m. Their impressive structural, electronic and mechanical attributes subject to their small size and mass, their high electrical and thermal conductivities, and their strong mechanical potency. CNTs based materials are successfully applied in medicine and pharmacy subject to their huge surface area that is proficient of conjugating or adsorbing with a wide variety of genes, drugs, antibodies, vaccines and biosensors etc. Therefore, we have presented a theoretical study about mathematical modeling of CNTs based viscous material flow between two rotating disks. Both types of nanotubes i.e., SWCNTs and MWCNTs are considered. Xue model is used for the mathematical modeling. Fluid flow is due to rotating disks. Main focus here is given to probable error and statistical declaration. Entropy is calculated for both single and multi-walls nanotubes. MethodNonlinear PDEs are first converted into ODEs and then computed for homotopy convergent solutions. Results and conclusionStatistical declaration and probable error for skin friction and Nusselt number are numerically computed and discussed through Tables. From obtained outcomes it is concluded that magnitude of skin friction increases at both disks surface for higher values of Reynolds number, lower stretching parameter and porosity parameter while it decays for both of disks versus larger rotation parameter. Nusselt number or heat transfer rate also enhances at both disks in the presence of radiation and Reynolds number while it decays against Eckert number.

Durable superamphiphobic coatings repelling both cool and hot liquids based on carbon nanotubes

Superamphiphobic coatings have wide potential applications in many fields, however, preparation of superamphiphobic coatings with low sliding angles and high durability is very challenging. Here, we report a facile spray-coating method for the preparation of durable superamphiphobic coatings repelling both cool and hot liquids from polyperfluoroalkylsilane-modified multiwalled carbon nanotubes (MWCNTs@fluoroPOS). The MWCNTs@fluoroPOS suspensions were preparation by hydrolytic condensation of 1H,1H,2H,2H-perfluorodecyltrichlorosilane (PFDTES) and tetraethoxysilane (TEOS) on the surface of MWCNTs. The suspensions and the superamphiphobic coatings were characterized using a variety of analytical techniques such as scanning electron microscopy, transmitting electron microscopy and X-ray photoelectron spectroscopy. The effects of the diameter of MWCNTs, and the concentrations of MWCNTs, TEOS and PFDTES on wettability and microstructure of the coatings were also investigated. The coatings show high contact angles and low sliding angles for water and organic liquids of low surface tension such as n-hexadecane, toluene and n-decane. The coatings even exhibit excellent superamphiphobicity for hot water and hot organic liquids up to 80°C, which is seldom achieved according to the previous literatures. Moreover, the coatings feature high mechanical, chemical and environmental durability, and are applicable onto various substrates. The simple method, the high superamphiphobicity to both cool and hot liquids, and the excellent durability of the coatings have paved the way for their practical applications in various fields, e.g., anti-icing, anti-oil climbing and oil transportation, etc.

Durable, Transparent, and Hot Liquid Repelling Superamphiphobic Coatings from Polysiloxane-Modified Multiwalled Carbon Nanotubes.

Although encouraging progress in the field of superamphiphobic coatings has been obtained, the superamphiphobic coatings with high durability, transparency, and repellency to hot liquids are very rare. Here, durable, transparent, and hot liquid-repelling superamphiphobic coatings were successfully prepared using polysiloxane-modified multiwalled carbon nanotubes (MWCNTs@POS) as the templates. The hydrolytic condensation of n-hexadecyltrimethoxysilane (HDTMS) and tetraethoxysilane on the surface of MWCNTs formed MWCNTs@POS, which are highly dispersible in toluene. The superamphiphobic coatings were prepared by spray-coating the homogeneous suspension of MWCNTs@POS in toluene onto glass slides, calcination in air to form the silica nanotubes (SNTs), and then modification with 1H,1H,2H,2H-perfluorodecyltrichlorosilane in dry toluene. The changes in the surface microstructure, surface chemical composition, and wettability were characterized by various techniques such as scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. It was found that the microstructures of the SNTs have great influences on superamphiphobicity and transparency of the coatings and can be regulated by the concentration of HDTMS and the diameter of MWCNTs. The SNTs with tunable wall thickness and diameter could be obtained using the method. The superamphiphobic coatings showed high contact angles and low sliding angles for various cool and hot liquids of different surface tensions. The superamphiphobic coatings also exhibited high transparency and comprehensive durability.

Structural, Morphological, Photovoltaic and Electron Transport Properties of ZnO Based DSSC with Different Concentrations of MWCNTs

This study highlights the structural, morphological, photovoltaic and electron transport properties of zinc oxide-multi-walled carbon nanotubes (ZnO-MWCNTs) based dye-sensitized solar cell (DSSC) prepared at different concentrations of 0.0, 0.1, 0.3 and 0.5 wt.%. The ZnO-MWCNTs thin films were prepared by a chemical bath deposition method. X-ray diffraction (XRD) analysis proved the formation of hexagonal wurtzite of the samples. The crystallite sizes, D of ZnO-MWCNTs was measured varies from 21 nm to 11 nm. The oat-like ZnO nanoflakes structure and the presence of MWCNTs were captured by field-emission scanning electron microscopy (FESEM) analysis. Transmission electron microscopy (TEM) analysis measured the inner (~6.81 nm) and outer (~28.31 nm) diameter of MWCNTs. The optimum concentration of 0.1 wt.% MWCNTs produced the highest photocurrent density, Jsc of 13.5 mA/cm2, open-circuit voltage, Voc of 0.149 V, fill factor, FF of 0.406 and power conversion efficiency, PCE of 0.817 %. Optimum doping of 0.1 wt.% MWCNTs generated short electron lifetime, τeff of 0.67 ms, low effective electron chemical diffusion coefficient, Deff of 9.5 x 10-8 cm2 s-1 and higher electron recombination rate, keff of 1497.48 s-1. The addition of MWCNTs has influenced the structural, morphological, photovoltaic and electron transport properties of ZnO-MWCNTs based DSSC.

Polysiloxane/multiwalled carbon nanotubes nanocomposites and their applications as ultrastable, healable and superhydrophobic coatings

Superhydrophobic coatings with high water contact angles, ultralow sliding angles, excellent stability and good healing capability were prepared by spray-coating the homogeneous suspensions of the fluorine-free polysiloxane/multiwalled carbon nanotubes (POS/MWCNTs) nanocomposites onto various substrates and cured for a period of time. The nanocomposites were synthesized by hydrolytic co-condensation of n-hexadecyltriethoxylsilane and tetraethoxysilane in the presence of acid activated MWCNTs. The nanocomposites composed of POS-modified MWCNTs and free POS are highly dispersible in various alkanes and arenes. The nanocomposites and their coatings were characterized using a wide range of electron microscopy and other analytical techniques. In addition, the effects of various parameters, e.g., acid activation of MWCNTs, diameter of MWCNTs, spray-coating density and annealing temperature, on superhydrophobicity and morphology of the coatings were investigated. Moreover, the stability and healing capability of the coatings were studied. The coatings show negligible change in CAs and maintain low SAs after various harsh stability tests, e.g., intensive sand abrasion from a height of 300cm. Also, the slightly damaged coatings are healable with the help of toluene and annealing. The mechanisms for the excellent stability and good healing capability were proposed. The ultrastable, healable and superhydrophobic POS/MWCNTs coatings are very promising for various practical applications.

Novel aluminosilicate hollow sphere as a catalyst support for methane decomposition to COx-free hydrogen production

Novel Ni and Co supported on aluminosilicate hollow sphere catalysts were investigated to decompose methane into CO and CO2 free hydrogen and carbon nanotube. The hollow sphere structure was prepared by reverse microemulsion method and then Ni and Co were loaded by the impregnation method. The fresh catalysts and deposited carbon were characterized by several microscopic and spectroscopic techniques. The catalytic results showed that the Co based catalyst exhibited higher activity and durability at longer reaction time, due to the higher number and distribution of metal sites. The hollow sphere structure of the support could protect the metal particles against aggregation during the catalytic reactions. Accordingly, higher metal dispersion, stabilization and catalytic performance were achieved. The formation of nickel silicate is the main reason for the lower decomposition activity of Ni based catalyst at longer reaction time. TEM and Raman spectroscopic data revealed that the Co-based catalyst produced a relatively uniform diameter of MWCNTs with higher crystallinity and graphitization degree compared to the Ni-based catalyst.

Effect of nitrogen and hydrogen on the growth of multiwall carbon nanotubes on flexible carbon cloth using thermal chemical vapor deposition

In this study, the effect of various mixture fluxes of nitrogen (N2) and hydrogen (H2) on carbon nanotube (CNT) synthesis grown on flexible carbon cloth using thermal chemical vapor deposition (thermal CVD) with ethylene (C2H4) as the carbon source and nickel (Ni) as the catalyst was investigated. Field emission scanning electron microscopy (FE-SEM) was utilized to study the morphology of CNTs on flexible carbon cloths with various N2 and H2 inlet flow rates. The results indicate that average diameter of MWCNTs decreases with increasing H2 and N2 flow rates; however, the density of CNTs increases first and then decreases with increasing H2 and N2 flow rates. On the other hand, in our field emission experiments, the result indicates that the field emission is strongly dependent on the density and geometry of MWCNTs. In addition, we also found that the contact electrical conductance measurement is an easy method to predict the field emission characteristics of MWCNTs.

Preparation, magnetic and electromagnetic properties of polyaniline/strontium ferrite/multiwalled carbon nanotubes composite

Strontium ferrite particles were firstly prepared by sol–gel method and self-propagating synthesis, and then the polyaniline/strontium ferrite/multiwalled carbon nanotubes composites were synthesized through in situ polymerization approach. Structure, morphology and properties of the composite were characterized by various instruments. XRD analysis shows that the output of PANI increases with the increase of the content of MWCNTs, due to the large surface area of MWCNTs. Because of the coating of PANI, the outer diameter of MWCNTs increases from 10nm to 20–40nm. The electrical conductivity of the composites increases with the amount increase of MWCNTs and reaches 7.2196S/cm in the presence of 2g MWCNTs. The coercive force of the composites prepared with 2g MWCNTs is 7457.17Oe, which is much bigger than that of SrFe12O19 particles 6145.6Oe, however, both the saturation magnetization and the remanent magnetization of the composite become much smaller than those of SrFe12O19 particles. The electromagnetic properties of the composite are excellent in the frequency range of 2–18GHz, which mainly depend on the dielectric loss in the range of 2–9GHz, and mainly on the magnetic loss in the range of 9–18GHz.

Microwave electromagnetic properties of multiwalled carbon nanotubes filled with Co nanoparticles

Multiwalled carbon nanotubes filled with face centered cubic Co nanoparticles (MWCNTs/Co) were successfully prepared by a chemical reducing method. The average outer diameter of MWCNTs is about 40 nm and the size of Co nanoparticles is in the range from 5 to 20 nm. The relative permeability and permittivity spectra of MWCNTs/Co resin composites with 50 wt % powders were measured in the frequency range of 0.1–18 GHz. Three resonance absorption peaks are observed in the μ″−f spectrum: the peak around 5.0 GHz can be attributed to natural resonance, while the other two appear around 10.6 and 16.9 GHz are induced by exchange resonance. It is found that the peak with minimum reflection loss (RL) value moves to lower frequencies and the RL value increases from 4.2 to 10.1 dB with the increase of the absorber’s thickness from 2 to 6 mm.

Production of Ultrahigh‐Molecular‐Weight Polyethylene/Pristine MWCNT Composites by Half‐Titanocene Catalysts

MWCNT/ Ultrahigh-molecular-weight polyethylene (UHMWPE) composites, where pristine MWCNTs are well dispersed in the UHMWPE matrices, are produced using MWCNT/half-titanocene hybrids as catalysts. The diameter of the UHMWPE-coated MWCNT strands produced is about 30–70 nm, while the diameter of the pristine MWCNTs used is 10–15 nm. UHMWPE composites with a molecular weight greater than 2 × 106 are produced. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Functionalization of Multi‐Walled Carbon Nanotubes with Poly(2‐ethyl‐2‐oxazoline)

AbstractMulti‐walled carbon nanotubes (MWCNTs) were successfully functionalized with water‐soluble poly(2‐ethyl‐2‐oxazoline) (PEOX) through a polymer wrapping process. Pristine MWCNTs were first treated with nitric acid (HNO3) at 120 °C for 24 hours. The resulting carboxylated MWCNTs were then mixed with 10 wt.% PEOX in ethanol, followed by sonication using a horn‐type sonicator for 30 min and stirring at room temperature for 24 hours. Thereafter, unreacted free polymer was washed out repeatedly by centrifugation with an excess amount of ethanol. Scanning electron microscopy exhibited that the diameter of MWCNTs increased approximately by 10 nm after the functionalization of MWCNT with PEOX. Thermogravimetric analysis showed that approximately 15 wt.% polymer was incorporated in the functionalized MWCNTs. The functionalized MWCNTs gave excellent and stable dispersion in water as well as other organic solvents such as ethanol and DMF.

Effect of purification treatment on adsorption characteristics of carbon nanotubes

Carbon nanotubes are novel materials with porous-rich structures and superior adsorption characteristics. In this report, multi-walled carbon nanotubes with different diameter were synthesized by thermal chemical vapor deposition. Amorphous carbon particles were highly removed by thermal oxidation process. Microwave digestion acidic procedure was used to dissolve metal catalysts and open tip of carbon nanotubes. The opened-end multi-walled carbon nanotubes are expected to be much more porous with more gas adsorption sites. The results indicated that the BET surface area decreases with their increasing of diameter of MWCNTs. The effective surface area of carbon nanotubes processed by thermal annealing treatment can increase with the increasing temperatures of 300 °C, 400 °C and 450 °C. Similarly, effective surface area of carbon nanotubes processed by microwave digestion acidic treatment can also increase with increasing processing time. Nitric acid can effectively absorb microwave energy and rapidly dissolve impurities in the carbon nanotubes during digestion process. The surface area increased about 30% with 20 min microwave digestion treatment time. However, microwave digestion acidic and thermal annealing treatments not only remove metallic catalysts and amorphous carbon particles and also increase effective surface area and the extent of purification of carbon nanotubes.

Investigation on preparation of multiwalled carbon nanotubes by DC arc discharge under N 2 atmosphere

MWCNTs and SWCNT bands were prepared and carbon nanostructures were formed by DC arc discharge under N 2 atmosphere. The effects of nitrogen pressure and flow rate on the yield and morphology of CNTs, and morphology of carbon nanostructures were investigated separately. SEM, HR-TEM, EDX in SEM and TEM, and XRD were performed to characterize the products. It was found that MWCNTs and SWCNTs bands exist in the inner core of the cathode deposit, but the former one is the main product. The suitable N 2 atmosphere should be in the region of 200–300 Torr, and the N 2 flow rate should be smaller than 350 mL/min. The inner diameter and the length of growth of MWCNTs obviously increases with the increase of the N 2 pressure from 0 to 900 Torr, but the change of outside diameter of MWCNTs does not show a good regularity. Both the inner and outside diameters of MWCNTs slightly decrease with the increase of the N 2 flow rate from 0 to 1000 mL/min. Right angle structure of SWCNT band and graphite layers in MWCNT was observed. It is very possible that a little amount of nitrogen atoms has doped into MWCNTs. Several different carbon nanostructures were observed in the products collected from the different parts in the DC arc discharge apparatus.