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CONTENTS
Volume 4, Number 1, March 2016
 

Abstract
Superparamagnetic iron oxide nanoparticles (Nps), composed of magnetite, Fe3O4, or maghemite,r-Fe2O3, core and biocompatible polymer shell, such as dextran or chitozan, have recently found wide applications in magnetic resonance imaging, contrast enhancement and hyperthermia therapy. For different diagnostic and therapeutic applications, current attempt is focusing on the synthesis and biomedical applications of various ferrite Nps, such as CoFe2O4 and MnFe2O4, differing from iron oxide Nps in charge, surface chemistry and magnetic properties. This study is focused on the synthesis of manganese ferrite, MnFe2O4, Nps by most commonly used chemical way pursuing better control of their size, purity and magnetic properties. Co-precipitation syntheses were performed using aqueous alkaline solutions of Mn(II) and Fe(III) salts and NaOH within a wide pH range using various hydrothermal treatment regimes. Different additives, such as citric acid, cysteine, glicine, polyetylene glycol, triethanolamine, chitosan, etc., were tested on purpose to obtain good yield of pure phase and monodispersed Nps with average size of <_20 nm. Transmission electron microscopy (TEM), X-ray diffraction, energy dispersive X-ray spectroscopy (EDX), Mössbauer spectroscopy down to cryogenic temperatures, magnetic measurements and inductively coupled plasma mass spectrometry were employed in this study.

Key Words
manganese ferrite; nanoparticles; hydrothermal synthesis; phase purity; magnetic properties

Address
Marija Kurtinaitiene, Kestutis Mazeika, Simonas Ramanavicius, Vidas Pakstas and Arunas Jagminas: State Research Institute Centre for Physical Sciences and Technology, Savanoriu 231, LT-02300 Vilnius, Lithuania

Abstract
A low cost environmentally benign surface coating binder is highly desirable in the field of material science. In this report, castor oil based hyperbranched polyester/bitumen modified fly ash nanocomposites were fabricated to achieve the desired performance. The hyperbranched polyester resin was synthesized by a three-step one pot condensation reaction using monoglyceride of castor oil based carboxyl terminated pre-polymer and 2,2-bis (hydroxymethyl) propionic acid. Also, the bulk fly ash of paper industry waste was converted to hydrophilic nano fly ash by ultrasonication followed by transforming it to an organonano fly ash by the modification with bitumen. The synthesized polyester resin and its nanocomposites were characterized by different analytical and spectroscopic tools. The nanocomposite obtained in presence of 20 wt% styrene (with respect to polyester) was found to be more homogeneous and stable compared to nanocomposite without styrene. The performance in terms of tensile strength, impact resistance, scratch hardness, chemical resistance and thermal stability was found to be improved significantly after formation of nanocomposite compared to the pristine system after curing with bisphenol-A based epoxy and poly(amido amine). The overall results of transmission electron microscopic (TEM) analysis and performance showed good exfoliation of the nano fly ash in the polyester matrix. Thus the studied nanocomposites would open up a new avenue on development of low cost high performing surface coating materials.

Key Words
bio-based materials; hyperbranched polyesters; nano fly ash; nanocomposites; thermosets

Address
Deepshikha Bhagawati, Suman Thakur and Niranjan Karak: Advanced Polymer and Nanomaterial Laboratory, Center for Polymer Science and Technology, Department of Chemical Sciences, Tezpur University, Tezpur, Assam, India

Abstract
This article is concerned with the free vibration problem for chiral double-walled carbon nanotube (DWCNTs) modelled using the non-local elasticity theory and Euler Bernoulli beam model. According to the governing equations of non-local Euler Bernoulli beam theory and the boundary conditions, the analytical solution is derived and two branches of transverse wave propagating are obtained. The numerical results obtained provide better representations of the vibration behaviour of double-walled carbon nanotube, where the aspect ratio of the (DWCNTs), the vibrational mode number, the small-scale coefficient and chirality of double-walled carbon nanotube on the frequency ratio (xN) of the (DWCNTs) are significant. In this work, the numerical results obtained can be used to predict and prevent the phenomenon of resonance for the forced vibration analyses of double -walled carbon nanotubes.

Key Words
free vibration; double-walled carbon nanotube; frequency ratio; chirality; non-local

Address
Kaddour Rakrak: Laboratoire de Modélisation et Simulation Multi-échelle, Université de Sidi Bel Abbés, Algerie; Département de Physique, Faculté des Sciences, Université Hassiba benbouali, Chlef, Algerie
Mohamed Zidour: Laboratoire des Matériaux et Hydrologie, Université de Sidi Bel Abbés, BP 89 Cité Ben M\'hidi, 22000 Sidi Bel Abbés, Algerie; Université Ibn Khaldoun, BP 78 Zaaroura, 14000 Tiaret, Algerie
Houari Heireche, Abdelmoumen Anis Bousahla and Awda Chemi: Laboratoire de Modélisation et Simulation Multi-échelle, Université de Sidi Bel Abbés, Algerie

Abstract
Data of Raman spectroscopy from graphene and few-layer graphene (FLG) irradiated by SEM electron beam in the range of energies 0.2 -30 keV are presented. The obvious effect of damaging the nanostructures by all used beam energies for specimens placed on insulator substrates (SiO2) was revealed. At the same time, no signs of structural defects were observed in the cases when FLG have been arranged on metallic substrate. A new physical mechanism of under threshold energy defect production supposing possible formation of intensive electrical charged puddles on insulator substrate surface is suggested.

Key Words
few-layer graphene; radiation effects; electric charged puddles

Address
Nazim R. Guseinov, Gulzhan A. Baigarinova and Arkady M. Ilyin: Open access National Nanolab, Kazakh National University, 71 Farabi Str., Almaty, Republic of Kazakhstan

Abstract
This paper investigates the effects of thermal load and shear force on the buckling of nanobeams. Higher-order shear deformation beam theories are implemented and their predictions of the critical buckling load and post-buckled configurations are compared to those of Euler-Bernoulli and Timoshenko beam theories. The nonlocal Eringen elasticity model is adopted to account a size-dependence at the nano-scale. Analytical closed form solutions for critical buckling loads and post-buckling configurations are derived for proposed beam theories. This would be helpful for those who work in the mechanical analysis of nanobeams especially experimentalists working in the field. Results show that thermal load has a more significant impact on the buckling behavior of simply-supported beams (S-S) than it has on clamped-clamped (C-C) beams. However, the nonlocal effect has more impact on C-C beams that it does on S-S beams. Moreover, it was found that the predictions obtained from Timoshenko beam theory are identical to those obtained using all higher-order shear deformation theories, suggesting that Timoshenko beam theory is sufficient to analyze buckling in nanobeams.

Key Words
buckling; nanobeams; higher-order beam theories; nonlocal elasticity; thermal loads

Address
M.A. Eltaher: Department of Mechanical and Mechatronics Engineering, University of Waterloo, Canada; Department of Mechanical Design and Production Engineering, Zagazig University, Egypt
M.E. Khater: Department of Systems Design Engineering, University of Waterloo, Canada; Department of Mechanical Engineering, KFUPM, Dhahran 31261, KSA
S. Park and E. Abdel-Rahman: Department of Systems Design Engineering, University of Waterloo, Canada
M. Yavuz: Department of Mechanical and Mechatronics Engineering, University of Waterloo, Canada


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