Multiwalled Nanotubes: Their Formation by Irradiating Graphite with High Doses of Electrons

Abstract

We report the production of carbon nanotubes by high dose of electron irradiation. The irradiation was performed with a 2 MeV Van de Graaff accelerator, while the irradiation conditions were the following: voltage 1.3 MeV, current 5 µA, dose rate 25 kGy/min, and total dosage 1000 kGy. The samples were analyzed in a high‐resolution transmission electron microscope. The main features observed on the samples, were huge nanotubes of several nanometer long and few nanometer wide, which are capped at one end. It is good to point out, that at this level of irradiation, we were not able to find either onion‐like or particle structures throughout the material, as it is usual in similar hexagonal structures. This behavior could be attributed to the level of irradiation used to create the nanotubes under investigation.     

Formation of NbSe2 Nanotubes by Electron Irradiation

In this work, we report the production of NbSe₂, (niobium diselenide) nanotubes by high doses of electron irradiation. The apparatus used for irradiation was a 2 MeV Van de Graaff accelerator, while the irradiation conditions were the following: voltage 1.3 MeV, current 5μA, dose rate 25 kGy/min, and total dosage 1000 kGy. Samples were analyzed with a high-resolution transmission electron microscope. The main characteristics observed were huge and very well defined nanotubes of several nm long and few nm wide, which are presumably hollow, although they are capped at one end. At this level of irradiation, we were able to find neither onion-like structure nor nanoparticles through out other areas, as it is usual in similar hexagonal structures of the dichalcogenide family.     

Formation of NbSe2 Nanotubes by Electron Irradiation

Abstract

In this work, we report the production of NbSe₂, (niobium diselenide) nanotubes by high doses of electron irradiation. The apparatus used for irradiation was a 2 MeV Van de Graaff accelerator, while the irradiation conditions were the following: voltage 1.3 MeV, current 5μA, dose rate 25 kGy/min, and total dosage 1000 kGy. Samples were analyzed with a high-resolution transmission electron microscope. The main characteristics observed were huge and very well defined nanotubes of several nm long and few nm wide, which are presumably hollow, although they are capped at one end. At this level of irradiation, we were able to find neither onion-like structure nor nanoparticles through out other areas, as it is usual in similar hexagonal structures of the dichalcogenide family.     

OPTIMIZATION OF THE ELECTRON IRRADIATION IN THE PRODUCTION OF MoTe2 NANOTUBES

In this paper, we report the study of the production of MoTe₂ (molybdenum ditelluride) samples after a high dose of electron irradition. A 2 MeV Van de Graaff accelerator was used to irradiate the sample at the following conditions: 1.3 MeV voltage, 5 μA current, 25 kGy/min dose rate, and 1000 kGy total dosage. These conditions are maintain fixed while the irradiation dosages were changed to 50, 100, 200, and 500 Mrad. The optimization of the dosage used for the production of MoTe₂ nanotubes was obtained from the analysis of the samples that were examined in a high-resolution transmission electron microscope. The most efficient production of MoTe₂ nanotubes was obtained at the range between 100 and 200 Mrad. A very typical characteristic was obtained for rotated structures with angles of 4, 5, 7, 8, and 12° observed in the diffraction pattern for MoTe₂.     

EFFECT OF ELECTRONIC IRRADIATION IN THE PRODUCTION OF NbSe2 NANOTUBES

In this work, we report the production of NbSe₂ (niobium diselenide) nanotubes formed by irradiating NbSe₂ with high doses of electron irradiation. The apparatus used for the irradiation was a 2 MeV Van de Graaff accelerator at the following conditions: voltage 1.3 MeV, current 5 μA, dose rate 25 kGy/min, and total dosage 1000 kGy. These conditions were maintained fixed while irradiation dosage was changed between 100, 250 and 500 Mrad. We observed enormous and very well defined nanotubes with a length of several nm and width of a few nm, which are hollow and capped at one end. As the level of irradiation is increased to 500 Mrad, onion-like structures were observed.     

EFFECT OF ELECTRONIC IRRADIATION IN THE PRODUCTION OF NbSe2 NANOTUBES

In this work, we report the production of NbSe₂ (niobium diselenide) nanotubes formed by irradiating NbSe₂ with high doses of electron irradiation. The apparatus used for the irradiation was a 2 MeV Van de Graaff accelerator at the following conditions: voltage 1.3 MeV, current 5 μA, dose rate 25 kGy/min, and total dosage 1000 kGy. These conditions were maintained fixed while irradiation dosage was changed between 100, 250 and 500 Mrad. We observed enormous and very well defined nanotubes with a length of several nm and width of a few nm, which are hollow and capped at one end. As the level of irradiation is increased to 500 Mrad, onion-like structures were observed.     

OPTIMIZATION OF THE ELECTRON IRRADIATION IN THE PRODUCTION OF MoTe2 NANOTUBES

In this paper, we report the study of the production of MoTe₂ (molybdenum ditelluride) samples after a high dose of electron irradition. A 2 MeV Van de Graaff accelerator was used to irradiate the sample at the following conditions: 1.3 MeV voltage, 5 μA current, 25 kGy/min dose rate, and 1000 kGy total dosage. These conditions are maintain fixed while the irradiation dosages were changed to 50, 100, 200, and 500 Mrad. The optimization of the dosage used for the production of MoTe₂ nanotubes was obtained from the analysis of the samples that were examined in a high-resolution transmission electron microscope. The most efficient production of MoTe₂ nanotubes was obtained at the range between 100 and 200 Mrad. A very typical characteristic was obtained for rotated structures with angles of 4, 5, 7, 8, and 12° observed in the diffraction pattern for MoTe₂.     

Formation of MoTe2 Nanotubes by Electron Irradiation

In this article, we report the study and to our knowledge the first production of MoTe₂ (Molybdenum telluride) nanotubes by irradiation with high doses of electrons. a 2 MeV Van de Graaff accelerator was used to irradiate the samples at the following conditions: 1.3 MeV voltage, 5μA current, dose rate 25 kGy/min, total dosage 1000 kGy. the samples were examined in a high-resolution transmission electron microscope. the principal characteristic observed was huge nanotubes of the order of several nm long and few nm wide, which seems to be hollow. It is necessary to point out that searching carefully through out other areas of the sample, we were not able to locate either onionlike structures or nanoparticles as it is usual to find in graphite, WS₂ or MoS₂.     

Formation of MoTe2 Nanotubes by Electron Irradiation

Abstract

In this article, we report the study and to our knowledge the first production of MoTe₂ (Molybdenum telluride) nanotubes by irradiation with high doses of electrons. a 2 MeV Van de Graaff accelerator was used to irradiate the samples at the following conditions: 1.3 MeV voltage, 5μA current, dose rate 25 kGy/min, total dosage 1000 kGy. the samples were examined in a high-resolution transmission electron microscope. the principal characteristic observed was huge nanotubes of the order of several nm long and few nm wide, which seems to be hollow. It is necessary to point out that searching carefully through out other areas of the sample, we were not able to locate either onionlike structures or nanoparticles as it is usual to find in graphite, WS₂ or MoS₂.     

Experimental and Theoretical Studies of Microstructural Instabilities in WS2 Undergoing Electron Irradiation

In this article, we report the study of WS₂ crystals after being irradiated with a high dose of electrons. A 2 MeV Van de Graaff acelerator was used to irradiate the sample at the following conditions: 1.3 MeV voltage, 5μA current, dose rate 25 kGy/min, total dosage 1000 kGy. The samples were examined in a high resolution transmission electron microscope. Three distinct structures were observed: onions layers with fullerene like structure, randomly oriented worm-like structures with their planes rotated with respect of each other by well-defined angles, and nanotube like structures. We present calculations showing that relative rotations of the sulphur layers by 2°, 4°, 5°, 8° and 16° basically have the same average energy and average energy/atom as the unrotated structure. Therefore, rotations of the layers through those angles will be favorable. Instabilities on the structure produced by the irradiation will induce rotations as well as other capricious structures resembling a knot formation.     

PRODUCTION AND CHARACTERIZATION OF MoSe2 NANOTUBES BY ELECTRON IRRADIATION

In this work, we report the production of MoSe₂ (molybdenum diselenide) nanotubes formed by irradiating the samples with high doses of electron irradiation. The irradiation was performed on a 2 MeV Van de Graff accelerator at the following conditions: voltage 1.3 MeV, current 5 µA current, dose rate 25 Kgy/min, and total dosage 1 Mgy. We observed well-defined nanotubes of several nm long and few nm wide, which suppose to be hollow and capped at one end. As the level of irradiation was increased to 1 Mgy, elongated onion-like structures were observed.     

PRODUCTION AND CHARACTERIZATION OF MoSe2 NANOTUBES BY ELECTRON IRRADIATION

ABSTRACT

In this work, we report the production of MoSe₂ (molybdenum diselenide) nanotubes formed by irradiating the samples with high doses of electron irradiation. The irradiation was performed on a 2?MeV Van de Graff accelerator at the following conditions: voltage 1.3?MeV, current 5?µA current, dose rate 25?Kgy/min, and total dosage 1?Mgy. We observed well-defined nanotubes of several nm long and few nm wide, which suppose to be hollow and capped at one end. As the level of irradiation was increased to 1?Mgy, elongated onion-like structures were observed.     

Experimental and Theoretical Studies of Microstructural Instabilities in WS2 Undergoing Electron Irradiation

Abstract

In this article, we report the study of WS₂ crystals after being irradiated with a high dose of electrons. A 2 MeV Van de Graaff acelerator was used to irradiate the sample at the following conditions: 1.3 MeV voltage, 5μA current, dose rate 25 kGy/min, total dosage 1000 kGy. The samples were examined in a high resolution transmission electron microscope. Three distinct structures were observed: onions layers with fullerene like structure, randomly oriented worm-like structures with their planes rotated with respect of each other by well-defined angles, and nanotube like structures. We present calculations showing that relative rotations of the sulphur layers by 2°, 4°, 5°, 8° and 16° basically have the same average energy and average energy/atom as the unrotated structure. Therefore, rotations of the layers through those angles will be favorable. Instabilities on the structure produced by the irradiation will induce rotations as well as other capricious structures resembling a knot formation.     

Effect of electron beam treatments on degradation kinetics of polylactic acid (PLA) plastic waste under backyard composting conditions

The effects of electron beam irradiation on backyard composting behaviour of polylactic acid (PLA) polymer were evaluated. Samples (10 mm² × 0.75 mm) from thermoformed PLA drinking cups were exposed to 10 MeV electron beam irradiation at doses of 0, 72, 144 and 216 kGy. Irradiated PLA samples were placed in heat‐sealed, plastic screen and added to organic feedstock in a rotating composter within a computer‐controlled environmental chamber for 10 weeks at 35°C. Changes in weight, structural integrity and molecular weight were assessed over time. Results show that irradiation enhanced PLA breakdown. PLA weight decreased by increasing amounts as irradiation dose increased. Sample brittleness increased with irradiation dose and composting time. Finally, PLA molecular weight decreased as irradiation dose and compost time increased. Molecular weight D values for irradiated PLA were found to be about 430 kGy. After 1 week in a typical backyard composter, molecular weight D values increased to about 560 kGy and then fell to about 380 kGy after 2 weeks of composting. Samples irradiated at 216 kGy showed a reduction in weight of 9.4% after 10 weeks of composting, and a reduction of weight‐average molecular weight of 93.7% after 6 weeks. Copyright © 2008 John Wiley & Sons, Ltd.     

Electron beam irradiation of denture base materials

Electron beam irradiation can be used to influence the properties of polymers. It was the aim of this study to investigate whether PMMA denture base materials can benefit from irradiation in order to have increased fracture toughness, work of fracture or hardness. Rectangular specimens of heat-and auto-curing denture base materials were electron beam irradiated (post-cured) with 25, 100 and 200 kGy using an electron acceleration of 10 MeV or 4.5 MeV respectively. Fracture toughness, work of fracture, Vickers hardness and colour changes were measured and compared with not-irradiated specimens.The toughness, work of fracture and hardness increased using 10 MeV with a dose of 25 kGy and with 100 kGy using 4.5 MeV. However, the clinical use may not benefit from the observed small changes. Higher dosage (200 kGy) decreased the values significantly. The colour changes reached a level which was found to be not clinically acceptable. Conclusion: PMMA denture base materials do not benefit from post-curing with electron beam irradiation.     

Field Electron Emission from Layers with Very Long and Sparse Carbon Nanotubes

For carbon layers with very long and sparse nanotubes (nanofilaments) field electron emission at very low average electric field was observed. Field emission current of 10 µA was obtained at the average electric field E_av=0.16 V/µm and the value of the field amplification coefficient β reached 45,000. At high emission currents (exceeding 30-50 µA) one or several luminous nanotubes (nanofilaments) heated by the emission cuurent have been observed in the gap between the sample and the anode.     

Thermal and optical properties of electron beam irradiated cellulose triacetate

Cellulose triacetate (CTA) is a polymer which is widely used in a variety of applications in the field of radiation dosimetry. In the present work, CTA samples were irradiated by electron beam in the dose range 10–200 kGy. The modifications in the electron irradiated CTA samples as a function of dose have been studied through different characterization techniques such as thermogravimetric analysis, differential thermal analysis and color-difference studies. The electron irradiation in the dose range 80–200 kGy led to a more compact structure of CTA polymer, which resulted in an improvement in its thermal stability with an increase in activation energy of thermal decomposition.

Also, the variation of melting temperatures with the electron dose has been determined using differential thermal analysis (DTA). The CTA polymer is characterized by the appearance of one endothermic peak due to melting. The results showed that the irradiation in the dose range 10–80 kGy causes defects generation that splits the crystals depressing the melting temperature, while at higher doses (80–200 kGy), the thickness of crystalline structures (lamellae) is increased, thus the melting temperature increased.

In addition, the transmission of these samples in the wavelength range 200–2500 nm, as well as any color changes, was studied. The color intensity ΔE^* was greatly increased with increasing the electron beam dose, and accompanied with a significant increase in the blue color component.     

Effects of Fuel Compositions on the Structure and Yield of Flame Synthesized Carbon Nanotubes

Flame synthesis of carbon nanostructures including nanotubes on galvanized steel was investigated utilizing laminar diffusion flames of different types of fuel. Methane (CH₄), propane (C₃H₈) and acetylene (C₂H₂) were used as fuels. Distinctive carbon nanostructures were produced depending on fuel types and fuel flow rates. The qualitative and quantitative analysis of many transmission electron microscope (TEM) and scanning electron microscope (SEM) images were performed. Methane produced thin multi wall carbon nanotubes as well as nanorods and nanofibers within the fuel flow rate range of 7.18E-07 m³/s to 9.57E-07 m³/s. Propane yielded nanotubes only at the fuel flow rate of 4.20E-07 m³/s. The nanotubes synthesized by acetylene flames were of different types that included helically coiled and twisted nanotubes.     

Changes in microstructural parameters of NB4D2 silk fibres due to electron irradiation: X-ray line profile analysis

The present study is concerned with changes of microcrystalline parameters in NB4D2 (Bombyx mori) silk fibres, due to electron irradiation. The irradiation process was performed in air at room temperature using 8 MeV electron beam at different dose rates: 0, 25, 50 and 75 kGy, respectively. X-ray recording of these irradiated samples and the line profile analysis were carried out. The crystal imperfection parameters such as crystallite size 〈N〉, lattice strain (g in %) and surface weighted crystallite size (D _s) were computed and compared with other physical parameters in order to asertain the changes that have crept into these irradiated fibres. Exponential, lognormal and Reinhold functions for the column length distributions have been used for the determination of these parameters.     

Improving post irradiation stability of high density polyethylene by multi walled carbon nanotubes

Sterilization of implants and other clinical accessories is an integral part of any medical application. Although many materials are used as implants, polyethylene stands unique owing to its versatility. Carbon nanotubes are being used as a filler material to enhance the properties of polyethylene. However, the role of multi walled carbon nanotubes (MWCNTs) as an effective antioxidant and radical scavenger in resisting the deteriorating effects of sterilization is yet to be studied in detail. The present work is aimed to investigate the mechanical properties and oxidation stability of irradiated high density polyethylene (HDPE) reinforced by MWCNTs with various concentrations such as 0.25%, 0.50%, 0.75% and 1.00 wt.%. The composites were exposed to ⁶⁰Co source in air and irradiated at different dosage level starting from 25 to 100 kGy and then shelf aged for a period of 120 days prior to investigation. The loss in toughness, Young’s modulus and ultimate strength at 100 kGy for 1 wt.% MWCNTs composite were found to be 21.5%, 20.3% and 19.2%, respectively compared to that of unirradiated composite. FTIR and ESR studies confirmed the antioxidant and radical scavenging potentialities of MWCNTs with increased concentration and irradiation dosage. It was found that by the addition of 1 wt.% MWCNTs into virgin HDPE, the oxidation index of the composite at 100 kGy was decreased by 56.2%. It is concluded that the addition of MWCNTs into polyethylene not only limits the loss of mechanical properties but also improves its post irradiation oxidative stability.