scholarly journals Embedding Effect on the Mechanical Stability of Pressurised Carbon Nanotubes

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Motohiro Sato ◽  
Hisao Taira ◽  
Tetsuro Ikeda ◽  
Hiroyuki Shima
Keyword(s):  
Carbon Nanotubes ◽  
Critical Pressure ◽  
Mechanical Stability ◽  
Mechanical Energy ◽  
Finite Thickness ◽  
Deformation Mode ◽  
Radial Pressure ◽  
Cross Sectional ◽  
Embedding Effect ◽  
The Continuum

We elaborate on the cross-sectional deformation of carbon nanotubes embedded into a self-contracting host medium. The continuum elastic approach is used to formulate the mechanical energy of both the embedded nanotubes and the self-contracting outer medium with finite thickness. Our formula allows us to evaluate the critical radial pressure applied on the interface between the embedded nanotube and the outer contracting medium as well as the deformation mode that arises immediately above the critical pressure. An interesting mechanical implication of the embedding effect, that is, the power-law dependence of the critical pressure on the elastic modulus of the medium, is deduced by the theoretical approach established.

scholarly journals Binding energy and mechanical stability of two parallel and crossing carbon nanotubes

2015 ◽  
Vol 471 (2180) ◽  
pp. 20150229 ◽  
Author(s):  
Junhua Zhao ◽  
Yue Jia ◽  
Ning Wei ◽  
Timon Rabczuk
Keyword(s):  
Carbon Nanotubes ◽  
Binding Energy ◽  
Mechanical Stability ◽  
Critical Length ◽  
High Accuracy ◽  
Molecular Dynamics Calculations ◽  
Continuum Modelling ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes ◽  
The Continuum

The binding energy between two parallel (and two crossing) single-walled (and multi-walled) carbon nanotubes (CNTs) is obtained by continuum modelling of the van der Waals interaction between them. The dependence of the binding energy on their diameters, number of walls and crossing angles is systematically analysed. The critical length for the mechanical stability and adhesion of the CNTs is determined by the function of E i I i , h and γ , where E i I i , h and γ are the CNTs bending stiffness, distance and binding energy between them, respectively. Checking against full atom molecular dynamics calculations show that the continuum solution has high accuracy. The established analytical solutions should be of great help for designing nanoelectromechanical devices.

Cross-Sectional Deformation in Multi-Walled Carbon Nanotubes under Hydrostatic Pressure

2016 ◽  
Vol 258 ◽  
pp. 65-68
Author(s):  
Motohiro Sato ◽  
Yu Yachi ◽  
Ikuyo Koike ◽  
Hiroyuki Shima ◽  
Yoshitaka Umeno
Keyword(s):  
Carbon Nanotubes ◽  
Deformation Mode ◽  
Md Simulations ◽  
Continuum Approximation ◽  
Cross Sectional ◽  
Multi Walled Carbon Nanotubes ◽  
Elastic Approximation ◽  
Walled Carbon Nanotubes ◽  
Critical Buckling Pressure ◽  
Deformation Modes

This contribution provides simulated results of cross-sectional deformations observed in carbon nanotubes under high pressure. Molecular dynamics (MD) simulations were performed to explore radial buckling characteristics of multi-walled carbon nanotubes, and confirmed a variety of large-amplitude deformation modes. The energetically stable deformation mode turned out to be strongly dependent on the diameter of the innermost tube and the number of concentric walls. Critical buckling pressure obtained by MD simulations was compared with that estimated from a continuum elastic approximation, by which the validity of the continuum approximation was assessed.

KALEIDOSCOPIC MODE CHANGE IN CROSS-SECTIONAL DEFORMATION OF REINFORCED CARBON NANOTUBES

2013 ◽  
Vol 27 (31) ◽  
pp. 1350179 ◽  
Author(s):  
SUNG-JIN PARK ◽  
HIROYUKI SHIMA ◽  
MOTOHIRO SATO
Keyword(s):  
Carbon Nanotubes ◽  
Elastic Medium ◽  
Multiwalled Carbon Nanotubes ◽  
Radial Pressure ◽  
Multiwalled Carbon ◽  
Cross Sectional ◽  
Mode Change ◽  
The Core ◽  
Elastic Approximation ◽  
Physical Consequences

Cross-sectional deformation of multiwalled carbon nanotubes under isotropic radial pressure is investigated in a realm of continuum elastic approximation. The nanotube we assumed is subjected to the embedment into an elastic medium and stiffener insertion into the core cavity. Combination of the two reinforcement manipulations is found to cause kaleidoscopic mode changes in the radial corrugation, in which the cylindrical walls exhibit wavy patterns along the circumferential direction. Physical consequences of the diverse corrugation patters are also discussed.

Facile Synthesis of Cu2O nanoparticle-loaded Carbon Nanotubes Composite Catalysts for Reduction of 4-Nitrophenol

2020 ◽  
Vol 16 (4) ◽  
pp. 617-624 ◽  
Author(s):  
Yao Feng ◽  
Ran Wang ◽  
Juanjuan Yin ◽  
Fangke Zhan ◽  
Kaiyue Chen ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Mechanical Stability ◽  
Catalytic Reduction ◽  
High Surface ◽  
High Surface Area ◽  
Reduction Reaction ◽  
Cycle Performance ◽  
Simple Method ◽  
Composite Catalysts ◽  
Cu2o Nanoparticles

Background: 4-nitrophenol (4-NP) is one of the pollutants in sewage and harmful to human health and the environment. Cu is a non-noble metal with catalytic reduction effect on nitro compounds, and.has the advantages of simple preparation, abundant reserves, and low price. Carbon nanotubes (CNT) are widely used for substrate due to their excellent mechanical stability and high surface area. In this study, a simple method to prepare CNT-Cu2O by controlling different reaction time was reported. The prepared nanocomposites were used to catalyze 4-NP. Methods: CNTs and CuCl2 solution were put into a beaker, and then ascorbic acid and NaOH were added while continuously stirring. The reaction was carried out for a sufficiently long period of time at 60°C. The prepared samples were dried in a vacuum at 50°C for 48 h after washing with ethyl alcohol and deionized water. Results: Nanostructures of these composites were characterized by scanning electron microscope and transmission electron microscopy techniques, and the results at a magnification of 200 nanometers showed that Cu2O was distributed on the surface of the CNTs. In addition, X-ray diffraction was performed to further confirm the formation of Cu2O nanoparticles. The results of ultraviolet spectrophotometry showed that the catalytic effect of the compound on 4-NP was obvious. Conclusions: CNTs acted as a huge template for loading Cu2O nanoparticles, which could improve the stability and cycle performance of Cu2O. The formation of nanoparticles was greatly affected by temperature and the appropriate concentration, showing great reducibility for the 4-NP reduction reaction.

scholarly journals Occupational Exposure to Carbon Nanotubes and Carbon Nanofibres: More Than a Cobweb

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 745
Author(s):  
Enrico Bergamaschi ◽  
Giacomo Garzaro ◽  
Georgia Wilson Jones ◽  
Martina Buglisi ◽  
Michele Caniglia ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Animal Studies ◽  
Chemical Properties ◽  
Biological Behavior ◽  
Cross Sectional ◽  
Carbon Nanofibres ◽  
Material Entity ◽  
Cross Sectional Design

Carbon nanotubes (CNTs) and carbon nanofibers (CNFs) are erroneously considered as singular material entities. Instead, they should be regarded as a heterogeneous class of materials bearing different properties eliciting peculiar biological outcomes both in vitro and in vivo. Given the pace at which the industrial production of CNTs/CNFs is increasing, it is becoming of utmost importance to acquire comprehensive knowledge regarding their biological activity and their hazardous effects in humans. Animal studies carried out by inhalation showed that some CNTs/CNFs species can cause deleterious effects such as inflammation and lung tissue remodeling. Their physico-chemical properties, biological behavior and biopersistence make them similar to asbestos fibers. Human studies suggest some mild effects in workers handling CNT/CNF. However, owing to their cross-sectional design, researchers have been as yet unable to firmly demonstrate a causal relationship between such an exposure and the observed effects. Estimation of acceptable exposure levels should warrant a proper risk management. The aim of this review is to challenge the conception of CNTs/CNFs as a single, unified material entity and prompt the establishment of standardized hazard and exposure assessment methodologies able to properly feeding risk assessment and management frameworks.

scholarly journals The coverage of continuum of care in maternal, newborn and child health: a cross-sectional study of woman-child pairs in Ghana

2018 ◽  
Vol 3 (4) ◽  
pp. e000786 ◽  
Author(s):  
Akira Shibanuma ◽  
Francis Yeji ◽  
Sumiyo Okawa ◽  
Emmanuel Mahama ◽  
Kimiyo Kikuchi ◽  
...  
Keyword(s):  
Child Health ◽  
Continuum Of Care ◽  
Cross Sectional Study ◽  
Health Facilities ◽  
Cross Sectional ◽  
Newborn And Child Health ◽  
Care Services ◽  
Women And Children ◽  
And Child Health ◽  
The Continuum

IntroductionThe continuum of care has recently received attention in maternal, newborn and child health. It can be an effective policy framework to ensure that every woman and child receives timely and appropriate services throughout the continuum. However, a commonly used measurement does not evaluate if a pair of woman and child complies with the continuum of care. This study assessed the continuum of care based on two measurements: continuous visits to health facilities (measurement 1) and receiving key components of services (measurement 2). It also explored individual-level and area-level factors associated with the continuum of care achievement and then investigated how the continuum of care differed across areas.MethodsIn this cross-sectional study in Ghana in 2013, the continuum of care achievement and other characteristics of 1401 pairs of randomly selected women and children were collected. Multilevel logistic regression was used to estimate the factors associated with the continuum of care and its divergence across 22 areas.ResultsThroughout the pregnancy, delivery and post-delivery stages, 7.9% of women and children achieved the continuum of care through continuous visits to health facilities (measurement 1). Meanwhile, 10.3% achieved the continuum of care by receiving all key components of maternal, newborn and child health services (measurement 2). Only 1.8% of them achieved it under both measurements. Women and children from wealthier households were more likely to achieve the continuum of care under both measurements. Women’s education and complications were associated with higher continuum of care services-based achievement. Variance of a random intercept was larger in the continuum of care services-based model than the visit-based model.ConclusionsMost women and children failed to achieve the continuum of care in maternal, newborn and child health. Those who consistently visited health facilities did not necessarily receive key components of services.

scholarly journals Analysis of dynamics of a vertical cantilever in rotary coupling to the moving frame with movement limiters

2018 ◽  
Vol 241 ◽  
pp. 01021
Author(s):  
Piotr Wolszczak ◽  
Grzegorz Litak ◽  
Krystian Lygas
Keyword(s):  
Mechanical Energy ◽  
Elastic Beam ◽  
Beam Deflection ◽  
Moving Frame ◽  
Nonlinear Phenomena ◽  
Horizontal Distance ◽  
Energy Effect ◽  
Cross Sectional ◽  
Excitation Beam ◽  
Analysis Of Dynamics

The efficiency of the mechanical energy harvesting with the use of vibrating elements can be improved by synchronizing stimulation vibrations and own linear frequencies of systems as well as super or sub harmonics induced by non-linear phenomena. The article presents numerical cross-sectional study of the mechanical system. The system consists of an elastic beam set vertically, which the lower end is fixed in the rotary support, and is stimulated to move in the horizontal axis. The upper end of the beam is free but below its level there are bumpers limiting the free rotation of the beam. Numerical studies took into account the variability of the frequency and amplitude of the excitation beam movement, and horizontal distance between bumpers. Beam deflection was observed, on the basis of which the amount of energy generated by the piezo element was estimated. Nonlinear phenomena and analysis of frequency synchronization of vibrations improving the energy effect of an energy generator are presented.

The hrem observation of cross-sectional structure of carbon nanotubes

1997 ◽  
Vol 58 (11) ◽  
pp. 1887-1892 ◽  
Author(s):  
S.Q. Feng ◽  
D.P. Yu ◽  
G. Hub ◽  
X.F. Zhang ◽  
Z. Zhang
Keyword(s):  
Carbon Nanotubes ◽  
Cross Sectional ◽  
Sectional Structure ◽  
Structure Of Carbon Nanotubes

scholarly journals Multistage Mechanical Activation of Multilayer Carbon Nanotubes in Creation of Electric Heaters with Self-Regulating Temperature

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4654
Author(s):  
Alexandr Viktorovich Shchegolkov ◽  
Sung-Hwan Jang ◽  
Aleksei Viktorovich Shchegolkov ◽  
Yuri Viktorovich Rodionov ◽  
Olga Anatolievna Glivenkova
Keyword(s):  
Carbon Nanotubes ◽  
Temperature Field ◽  
Mechanical Activation ◽  
Thermal Effect ◽  
Supply Voltage ◽  
Mechanical Energy ◽  
Mechanical Action ◽  
Multilayer Carbon Nanotubes ◽  
Starting Current ◽  
Paddle Mixer

The article deals with research related to the issues of nanomodification of elastomers as a basis of electric heaters with self-regulating temperature. The effect of multistage mechanical activation of multilayer carbon nanotubes (MCNTs) with graphite on the uniformity of the temperature field distribution on the surface of nanomodified organosilicon elastomer has been studied. The influence of the stages of mechanical action on the parameters of MCNTs is revealed. It has been ascertained that for the MCNTs/graphite bulk material, which has passed the stage of mechanical activation in the vortex layer apparatus, a more uniform distribution of the temperature field and an increase in temperature to 57.1 °C at the supply voltage of 100 V are typical. The distribution of the temperature field in the centrifugal paddle mixer “WF-20B” for mixing MCNTs with graphite has been investigated. It has been found that there is also a thermal effect in addition to the mechanical action on the MCNTs in the paddle mixer “WF-20B”. The thermal effect is associated with the transfer of the mechanical energy of friction of the binary mixture MCNTs/graphite on the paddle and the walls of the vessel. The multiplicity of the starting current Ip to the nominal In (Ip/In) is 5 for the first sample, 7.5 for the second sample, and 10 for the third sample at the supply voltage of 100 V. The effect of reducing the starting current and stabilizing the temperature indicates the presence of self-regulation, which is expressed in maintaining a certain level of temperature.

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