Chain Model for Carbon Nanotube Bundle under Plane Strain Conditions

Carbon nanotubes (CNTs) have record high tensile strength and Young’s modulus, which makes them ideal for making super strong yarns, ropes, fillers for composites, solid lubricants, etc. The mechanical properties of CNT bundles have been addressed in a number of experimental and theoretical studies. The development of efficient computational methods for solving this problem is an important step in the design of new CNT-based materials. In the present study, an atomistic chain model is proposed to analyze the mechanical response of CNT bundles under plane strain conditions. The model takes into account the tensile and bending rigidity of the CNT wall, as well as the van der Waals interactions between walls. Due to the discrete character of the model, it is able to describe large curvature of the CNT wall and the fracture of the walls at very high pressures, where both of these problems are difficult to address in frame of continuum mechanics models. As an example, equilibrium structures of CNT crystal under biaxial, strain controlled loading are obtained and their thermal stability is analyzed. The obtained results agree well with previously reported data. In addition, a new equilibrium structure with four SNTs in a translational cell is reported. The model offered here can be applied with great efficiency to the analysis of the mechanical properties of CNT bundles composed of single-walled or multi-walled CNTs under plane strain conditions due to considerable reduction in the number of degrees of freedom

Mass transfer in the Frenkel-Kontorova chain initiated by molecule impact

The Frenkel-Kontorova chain with a free end is used to study initiation and propagation of crowdions (antikinks) caused by impact of a molecule consisting of K atoms. It is found that molecules with 1<K<10 are more efficient in the initiation of crowdions as compared to a single atom (K=1) because the total energy needed to initiate the crowdions by molecules is smaller. This happens because a single atom can initiate in the chain only sharp, fast-moving crowdions that require relatively large energy. A molecule has finite length, and that is why it is able to excite a wider crowdion with a smaller velocity and smaller energy. Our results can shed light on the atomistic mechanisms of mass transfer in crystals subject to atom and molecule bombardment

Mechanical Response of Carbon Nanotube Bundle to Lateral Compression

Structure evolution and mechanical response of the carbon nanotube (CNT) bundle under lateral biaxial compression is investigated in plane strain conditions using the chain model. In this model, tensile and bending rigidity of CTN walls, and the van der Waals interactions between them are taken into account. Initially the bundle in cross section is a triangular lattice of circular zigzag CNTs. Under increasing strain control compression, several structure transformations are observed. Firstly, the second-order phase transition leads to the crystalline structure with doubled translational cell. Then the first-order phase transition takes place with the appearance of collapsed CNTs. Further compression results in increase of the fraction of collapsed CNTs at nearly constant compressive stress and eventually all CNTs collapse. It is found that the potential energy of the CNT bundle during deformation changes mainly due to bending of CNT walls, while the contribution from the walls tension-compression and from the van der Waals energies is considerably smaller

Hydrosphere objects screening control to detect emergency oil spill

The current importance is caused by the need to improve the methodological and instrumental support, which corresponds to modern conditions and regional features, being one of the fundamental challenges before the environmental monitoring systems. Screening approach to solving this problem will become more advanced analytical tool condition monitoring of water bodies, especially those located in remote and difficult to access areas with high anthropogenic impact - oil production areas, allowing identifying quickly the occurrence of abnormal and emergency situations, leading to a negative impact on the environment, and taking more effective measures to eliminate them. The aim of the research is to prove water resources screening control methodology of remote oil production areas for detecting emergency oil spills on the example of Tomsk region. The research methods. It is proposed to use a screening approach to obtain information on the quality of natural waters, as well as timely detection of emergency situations occurred on the oil production and transportation facilities, leading to oil discharges to water bodies, together with the use of automated remote sensing methods and GIS technologies. For this purpose the environmental and geochemical conditions of water bodies in the accommodation areas of oil and gas companies were analyzed. The results and conclusions. The evaluation of the characteristic substances in the surface waters of the Ob River basin is carried out. The excess of the established water quality standards in most cases is caused by regional features of formation of their composition. The main difference of waste water composition of oil and gas complex of Siberia from the regional surface waters is expressed in rather larger content of Na+, Cl- ions, the sum of the main ions. The petroleum hydrocarbon content in produced waste water, sludge pits waters differs significantly from their concentrations in wetlands and its associated rivers and groundwater, which confirms the need to improve the effluents control and implementation of emergency early warning systems. It is necessary to use direct indicators (total petroleum hydrocarbons content by the fluorescence response) together with the indirect ones (chloride ion concentration, conductivity) as screening criteria in the accident detection methodology in oil production and transportation areas. It is caused by the peculiarities of their identification in natural aquatic environments. It was ascertained that the detection of anthropogenic oil pollution would be most reliable at concentrations from 1 mg/dm3 at a distance from the potential sources not more than 500 m