TTP - Journal of Nano Research #3

3439925771?profile=originalSynthesis and Characterization of Mesoporous Multi-Walled Carbon Nanotubes at Low Frequencies Electromagnetic Waves

 

Authors: Hasan Soleimani, Noorhana Yahya, Noor Rasyada Ahmad Latiff, Krzysztof Koziol, B.M. Maciejewska, Beh Hoe Guan

 

Abstract: For electromagnetic absorbing and shielding applications, carbon nanotubes (CNT) are widely used due to their excellent electrical and physical properties. Fabrication of microwave absorbing materials involves the use of compounds capable of generating dielectric and/or magnetic losses when impinged by an electromagnetic wave. The presence of lattice defects e.g. vacancies and dislocations contributes to the loss and attenuation in the electromagnetic waves, which in turn remarkably enhance the absorption ability of the material. With the CVD technique which is known to produce several lattice defects in the final product, aligned MWCNTs were successfully synthesized by pyrolizing toluene and ferrocene in an inert argon environment. The morphology analysis of the aligned MWCNTs was conducted via FESEM and TEM analysis, to reveal the average length of approximately 295 μm, with diameters in the range of 60-200 nm. EDS analysis indicates the high yield of CNTs, with more than 90% in weight composition, with less than 5 % Fe impurities presence. Textural properties of MWCNTs were studied by measuring pore size and BET surface area. To understand the response of CNTs to an electromagnetic field, permeability and permittivity measurement were conducted in the frequency range of 100 Hz to 110 MHz. In conclusion, the presence of defects in MWCNTs is desirable for enhanced electromagnetic absorption ability.

 

Direct link: http://www.scientific.net/JNanoR.26.117

 

17. Hydrogen Interaction with Defects in Nanocrystalline, Polycrystalline and Epitaxial Pd Films

 

Authors: Jakub Čížek, Oksana Melikhova, Marián Vlček, František Lukáč, Martin Vlach, Patrik Dobron, Ivan Procházka, Wolfgang Anwand, Gerhard Brauer, Stefan Wagner, Helmut Uchida, Ryota Gemma, Astrid Pundt

 

Abstract: Hydrogen interaction with defects and structural development of Pd films with various microstructures were investigated. Nanocrystalline, polycrystalline and epitaxial Pd films were prepared and electrochemically loaded with hydrogen. Structural changes of Pd films caused by absorbed hydrogen were studied by in-situ X-ray diffraction combined with acoustic emission and measurement of electromotorical force. Development of defects during hydrogen loading was investigated by positron annihilation spectroscopy. It was found that hydrogen firstly fills open volume defects existing already in the films and subsequently it occupies also interstitial sites in Pd lattice. Absorbed hydrogen causes volume expansion, which is strongly anisotropic in thin films. This introduces high stress into the films loaded with hydrogen. Acoustic emission measurements revealed that when hydrogen-induced stress achieves a certain critical level rearrangement of misfit dislocations takes place. The stress which grows with increasing hydrogen concentration can be further released by plastic deformation and also by detachment of the film from the substrate.

 

Direct link: http://www.scientific.net/JNanoR.26.123

 

18. Application of Electromagnetic Waves and Dielectric Nanoparticles in Enhanced Oil Recovery

 

Authors: Hasnah Mohd Zaid, Noor Rasyada Ahmad Latiff, Noorhana Yahya, Hasan Soleimani, Afza Shafie

 

Abstract: Enhanced oil recovery (EOR) refers to the recovery of oil that is left behind in a reservoir after primary and secondary recovery methods, either due to exhaustion or no longer economical, through application of thermal, chemical or miscible gas processes. Most conventional methods are not applicable in recovering oil from reservoirs with high temperature and high pressure (HTHP) due to the degradation of the chemicals in the environment. As an alternative, electromagnetic (EM) energy has been used as a thermal method to reduce the viscosity of the oil in a reservoir which increased the production of the oil. Application of nanotechnology in EOR has also been investigated. In this study, a non-invasive method of injecting dielectric nanofluids into the oil reservoir simultaneously with electromagnetic irradiation, with the intention to create disturbance at oil-water interfaces and increase oil production was investigated. During the core displacement tests, it has been demonstrated that in the absence of EM irradiation, both ZnO and Al2O3 nanofluids recovered higher residual oil volumes in comparison with commercial surfactant sodium dodecyl sulfate (SDS). When subjected to EM irradiation, an even higher residual oil was recovered in comparison to the case when no irradiation is present. It was also demonstrated that a change in the viscosity of dielectric nanofluids when irradiated with EM wave will improve sweep efficiency and hence, gives a higher oil recovery.

 

Direct link: http://www.scientific.net/JNanoR.26.135

 

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