Journal of Nano Research Vol. 55

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Authors: Hajar Nili Ahmadabadi, Abolfazl Ghafouri-Khosrowshahi, Davoud Ahmadimoghaddam, Amir Nili-Ahmadabadi
Abstract: Gaining control over the various parameters of carbon nanotubes-(CNTs) has always been a challenge for researchers. This is because, each parameter depends on a carbon nanotube's dimensions in addition to its structure and composition. This paper aims to investigate how the thermal dependency of structural parameters -like diameter- affects the density of states (DOS). To accomplish this, the study first reviews the basic theoretical aspects of CNTs, we then present calculations of the energy band structures for armchair carbon nanotubes-(aCNTs), zigzag carbon nanotubes-(zCNTs), and chiral carbon nanotubes-(cCNTs). Finally, the study derives the DOSs to help provide an understanding of the relationship between the radial expansion of the diameter and the DOS for typical zCNTs.
Authors: Rachid Boughedaoui, Mohamed Cherif Azzaz, Mohamed Tahar Melouah, Abdennour El Mohri, M. Zergoug, Azzeddine Lounis, Mohamed Azzaz
Abstract: Nanocrystalline Fe 76 Nd 16 B 8Des échantillons d'alliage (% atomique) ont été préparés à partir de poudres élémentaires pures par fraisage mécanique à haute énergie. Les matériaux obtenus ont été caractérisés par plusieurs techniques, telles que la diffraction des rayons X (DRX), qui ont permis la dissolution du néodyme dans la phase de fer en fonction du temps de broyage; les résultats obtenus indiquent que la solution solide a été obtenue. Après 20 heures de broyage à une vitesse de 400 tr / min. La méthode d'analyse Williamson-Hall a été utilisée pour exploiter les modèles DRX enregistrés. La taille de cristallite d'environ 4,08 nm et la microstructure d'environ 2,07% ont été obtenues pour 20 heures de broyage. Les microscopes électroniques à balayage (MEB) et l'analyse EDX ont confirmé le raffinement des particules broyées en fonction du temps de broyage et de l'homogénéisation de nos poudres. L'identification de phase a également été étudiée par un calorimètre DSC dans lequel des pics de changement de phase ont été identifiés. La caractérisation magnétique a été étudiée à l'aide d'un magnétomètre à échantillon vibrant (VSM); les résultats magnétiques optimaux sont obtenus après 20 heures de broyage; la température élevée VSM indique que le matériau traité commence à perdre progressivement ses qualités magnétiques à T = 80 ° C. Au-delà de la température de Curie, le matériau est considéré comme démagnétisé. Tous les résultats trouvés ont été commentés et discutés. Au-delà de la température de Curie, le matériau est considéré comme démagnétisé. Tous les résultats trouvés ont été commentés et discutés. Au-delà de la température de Curie, le matériau est considéré comme démagnétisé. Tous les résultats trouvés ont été commentés et discutés.
Authors: Mohsen Motamedi, Amin Esfandiarpour
Abstract: Graphene is a thin sheet with special properties and complicated mechanical behavior. It’s important to study graphene experimentally and theoretically. Stone–Wales defects, cracks and atom vacancy are popular defects in carbon allotropes especially in graphene. In this paper, effect of center cracks on graphene was discussed. At first, mechanical properties of non-defected graphene sheet was obtained using molecular dynamics simulation. Comparing result with theoretical and experimental studies showing good agreements and proofing the results. Then, 8 different cracks were considered in center of graphene sheets. Stress-strain curves of defected graphene sheets with different tension strain rates were plotted. The results showed that increasing crack length lead to decreasing Young’s modulus of graphene from 870GPa to 670GPa. Also, fracture occurred in less tensile strain. In the following, structural molecular mechanics method was used to simulate cracked graphene sheets. The results showed good agreement between two methods.
Authors: Tibra Das Gupta, Dip Dutta, Muhammad Rubayat bin Shahadat
Abstract: In our present study, under uniaxial tension, atomistic simulations were conducted to explore the crack propagation mechanism of Square Nickel Plate (SNP) for two distinct shaped cracks (Rectangular and Circular) at center separately. Here, for modeling the inter-atomic potential between atoms, Embedded Atom Model (EAM) was used. In case of both types, the crack size was varied keeping a constant strain rate of 2×109 s-1 and temperature of 300 k for investigation of the effects of crack geometry and size on the behavior of crack propagation. Along with the size and geometry of crack, the effects of different strain rates (1×109, 2×109 and 4×109 s-1) and temperatures (300 K, 600 K and 900 k) were also studied. From the simulations, the declination nature of peak stress can be deduced for both of the geometries by increasing the crack size. It can also be concluded that when crack area was same, the peak stresses were higher in SNP with Circular crack than with the SNP with Rectangular one. Besides, increasing and decreasing nature of peak stress were found for two genres with the increment of strain rate and temperature separately.
Authors: Belkacem Kadari, Aicha Bessaim, Abdelouahed Tounsi, Houari Heireche, Abdelmoumen Anis Bousahla, Mohammed Sid Ahmed Houari
Abstract: This work presents the buckling investigation of embedded orthotropic nanoplates by using a new hyperbolic plate theory and nonlocal small-scale effects. The main advantage of this theory is that, in addition to including the shear deformation effect, the displacement field is modeled with only three unknowns and three governing equation as the case of the classical plate theory (CPT) and which is even less than the first order shear deformation theory (FSDT) and higher-order shear deformation theory (HSDT). A shear correction factor is, therefore, not required. Nonlocal differential constitutive relations of Eringen is employed to investigate effects of small scale on buckling of the rectangular nanoplate. The elastic foundation is modeled as two-parameter Pasternak foundation. The equations of motion of the nonlocal theories are derived and solved via Navier's procedure for all edges simply supported boundary conditions. The proposed theory is compared with other plate theories. Analytical solutions for buckling loads are obtained for single-layered graphene sheets with isotropic and orthotropic properties. The results presented in this study may provide useful guidance for design of orthotropic graphene based nanodevices that make use of the buckling properties of orthotropic nanoplates. Verification studies show that the proposed theory is not only accurate and simple in solving the buckling nanoplates, but also comparable with the other higher-order shear deformation theories which contain more number of unknowns. Keywords: Buckling; orthotropic nanoplates; a simple 3-unknown theory; nonlocal elasticity theory; Pasternak’s foundations. * Corresponding author;
Authors: Faruk Ahmeti, Kasif Teker
Abstract: Optical resonator biosensors have emerged as one of the most sensitive and practical microsystem biodetection technology. Here, we have developed a model for an optical microring resonator to be used as an ultrasensitive biosensor. A linear correlation between increasing the radius of the microring and the red shift in the resonance wavelengths has been observed. In fact, resonance shifts for very small changes in microring radius, as low as 10 nm, have been detected. Furthermore, sensing capability of the resonator has been simulated by introducing TiDO2 nanoparticles and protein molecules to the resonator surface by varying both thickness and effective refractive index of the attached layer such that the layer size has been changed from 10 nm to 100 nm with an increment of 10 nm. We have observed readily detectable unique resonance shifts for both TiDO2 nanoparticles and protein molecules. Moreover, effective medium approach has been implemented in order to account for refractive index fluctuations in sensing medium. As a consequence, combination of optical resonators with microfluidics could produce a simple-to-operate, portable and robust diagnostic tool enabling new insights into biomolecular function and recognition.
Authors: Nonofo M.J. Ditshego
Abstract: A highly sensitive low-doped ZnO nanowire field effect transistor (NWFET) biosensor has been fabricated and measured. The low doped biosensor with NWFET transducer was used to sense charge of the following substances: lysozyme (LYSO), phosphate buffered saline (PBS), bovine serum albumin (BSA). It achieved maximum sensitivity of -543.2 % for the PBS-LYSO protein and 13,069 % for the PBS-BSA protein. These results were achieved because the electrical measurement and characterisation was focused on the charge effect of the LYSO and BSA acting on the ZnO nanowire subthreshold region. The nano-fabrication process is stable and reproducible. The high sensitivity of the ZnO NWFET biosensor can be exploited for selective analyte detection by functionalizing the nanowire surface with antibodies and/or other biomolecular probe molecules.
Authors: C. Usha, Palanichamy Vimala
Abstract: In this paper, we propose the analytical modeling for fully depleted surrounding gate TFET surrounding gate tunneling field effect transistor with single metal gate. This model comprises the surface potential using 2-D Poisson’s equation and drain current with the effects of oxide thickness, silicon thickness as radius, drain voltage, gate metal work function, and assuming channel is fully depleted. The model is tested using TCAD Simulation Tool.
Authors: Feng Duan, Wei Jia Yang, Xin He, Jia Yi Jiang, Wan Yu Zhu, Da Xue Xia
Abstract: In this work, we fabricated a flexible silver nanowires (Ag NWs)/graphene transparent conducting film on polyethylene terephthalate (PET) substrate, which was applied in an electrochromic device. The graphene layer was coated on the surface of the Ag NW film utilizing the electrostatic adsorption in order to improve the stability of the metallic nanowire layer and the performance of the electrochromic device. The Ag NWs/graphene composite film exhibited an optical transmittance of 82.5% at 550 nm and a sheet resistance of 57.5 Ω/sq. With the concentration of the adsorbed graphene increased, the transmittance and conductivity of the composite film both decreased. Furthermore, the lifetime of the electrochromic devices based on the tungsten oxide (WO3) thin film and the Ag NW/graphene composite electrodes was greatly extended, compared to that utilizing the pristine Ag NW electrodes. The results indicate that the introduction of the graphene layer could protect the Ag NW film from corrosion of the electrolyte layer, and greatly improve the lifetime and cycle numbers of the electrochromic device. Key words: silver nanowire; graphene; transparent electrode; electrochromic devices

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