International Journal of Materials

ISSN: 2313-0555
Volume 2, 2015

Notice: As of 2014 and for the forthcoming years, the publication frequency/periodicity of NAUN Journals is adapted to the 'continuously updated' model. What this means is that instead of being separated into issues, new papers will be added on a continuous basis, allowing a more regular flow and shorter publication times. The papers will appear in reverse order, therefore the most recent one will be on top.

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Volume 2, 2015

Title of the Paper: Experimental Performance of Hygro-Thermal Deformation of Contemporary and Historical Ceramic Bricks


Authors: Peter Šín, Jozefa Lukovičová, Gabriela Pavlendová, Marian Kubliha, Stanislav Unčík

Pages: 54-57

Abstract: This paper presents an experimental study on moisture and temperature-induced expansion of contemporary and historical bricks. Moisture expansion coefficient is determined in the moisture range from dry material to 95 % RH at temperatures 20°C and 60°C. Thermal expansion coefficient is measured in temperature range from 20°C to 60°C at moisture 0 and 35 % RH. Temperature and moisture induced length differences were measured using LVDT MACRO SENSOR SBP 375040.

Title of the Paper: Production of Multi-Walled Carbon Nanotubes via Catalytic Decomposition of Methane in the Chemical Vapor Decomposition Process


Authors: Ghazaleh Allaedini, Siti Masrinda Tasirin, Payam Aminayi, Zahira Yaakob, Meor Zainal Meor Talib

Pages: 48-53

Abstract: In this paper, carbon nanotubes (CNTs) were synthesized via vapor deposition of methane as a carbon source in the presence of Ni/MgO catalyst. The catalyst crystallinity and morphology was examined by XRD and SEM and its superior size distribution and crystallinity was confirmed. The catalytic methane decomposition was conducted in a chemical vapor deposition reactor at 900 °C. Methane, with the flow rate of 600 ml/min, was used as a carbonous gas and hydrogen and nitrogen were used at the flow rate of 500 ml/min. The obtained carbon was characterized by transmission electron microscopy (TEM) and recognized to be multi-walled carbon nanotubes with an average diameter of ~8.6 nm. The Raman spectrum confirmed a high graphitization degree

Title of the Paper: Development of Viscosity Models with the Variation of Rheology Control Agent Content and Temperature for Two Different Epoxy Resin Adhesives


Authors: F. Nihal Tüzün

Pages: 40-47

Abstract: In this study, variation of viscosity with time for three epoxy compositions used as adhesives including three different fillers was investigated by increasing the CABOSIL TS 720 content from 1 to 2, 3, 4 and 5% and decreasing the filler content as 19.9, 18.9, 17.9, 16.9 and 15.9% at the temperatures of 25, 40, 60, 70 and 800C.Variation of viscosity was also determined for two different epoxy systems as DURATEK® and SHELL resin systems consisting of DURATEK® KLM 606 A epoxy resin, DURATEK® KLM 606 B polyamide curing agent and EPIKOTE® 828 epoxy resin, EPIKURE® 3090 polyamidoamine curing agent respectively. Calcite with having three different particle diameters of 0.7, 0.9 and 10 µm , CABOSIL® TS 720 employed as rheology control agent were used as fillers in adhesives. Viscosity was measured by using HA model Brookfield type DV-II+Pro Viscometer with SC4-27 spindle at constant shear rate and viscosity models were developed for both res?n systems. It was found that viscosity of DURATEK® resin system was higher than SHELL resin system. Viscosity increased as CABOSIL® TS 720 content increased and viscosity decreased with increasing the temperature. Generally, the composition prepared by the calcite with the particle diameter of 0.7 µm gave the lowest viscosity in both resin systems.

Title of the Paper: Electromagnetic Approach to Nondestructive Testing of Fibre Concrete


Authors: Leonard Hobst, Tereza Komárková, Jiří Vala

Pages: 35-39

Abstract: Mechanical, thermal, etc. behaviour of fibre concrete structures, including (most frequently steel) fibres and a concrete matrix, is conditioned namely by i) the amount of fibres and ii) their directional distribution. Fibres should prevent quasi-brittle crack damage caused by tensile stresses and other deterioration processes, thus reliable nondestructive testing methods for i) and ii) are required. This paper presents an original electromagnetic approach based on different electromagnetic material characteristics, as magnetic permeability, dielectric permittivity and electric conductivity, of both applied materials in a composite, i. e. of (most frequently steel) fibres and concrete matrix, occurring in a special class of Maxwell equations, to the identification of i) and ii).

Title of the Paper: Optical Properties of a Symmetric Coupled Quantum Dot Nanostructure


Authors: Ioannis Chatzopoulos, John Boviatsis, Emmanuel Paspalakis

Pages: 29-34

Abstract: We theoretically study the optical response of a symmetric double quantum dot nanostructure. We assume that each quantum dot contains only two energy levels and that the effect of tunneling is only included in the coupling of the upper levels. We then derive the optical susceptibility of the system under weak field excitation and under general initial conditions. The formula we obtain extends that of a previous work, as the effects of an initial superposition of the two lower states of the system are accounted for. We also present the form of the susceptibility for different initial states of the system.

Title of the Paper: Enhanced PSpice Model of TiO2 Memristor


Authors: Zdenek Kolka, Dalibor Biolek, Viera Biolkova

Pages: 25-28

Abstract: The present paper enhances Pickett’s model of the TiO2 memristor by modifying its Port Equation in order to eliminate a non-physical negative resistance region that occurs at higher currents. This region causes an ambiguity of the static I-V characteristic, which may bring non-convergence, numerical errors, and non-physical solutions during time-domain simulation. The modification is based on the tangential extrapolation. Full listing of the (P)Spice macromodel is provided.

Title of the Paper: Comparison of Dynamic Linear and Neural Network Models in Predicting Cement Compressive Strength


Authors: Dimitris C. Tsamatsoulis

Pages: 17-24

Abstract: A dynamic approach of two widely applied techniques has been used in predicting the typical 28-day compressive strength of Portland cement: Multiple linear regression (MLR) and artificial neural networks (ANN). Eight totally ANNs were built involving three layers with one or two nodes in the hidden layer and a cascade ANN as well, using sigmoid, hyperbolic tangent and radial basis functions. The comparison is based on the mean square residual error (MSRE) of testing sets. The ANNs of higher performance are the simplest ones, with only one node in the hidden layer and sigmoid or hyperbolic tangent function. An optimization of the future testing period was performed and the optimal value was equal to one day. Consequently the implementation of the dynamical model in the daily strength prediction needs an updating of the equations, every day that new results appear.

Title of the Paper: Magnetorheological Fluid Engine Mounts: A Review on Structure Design of Semi Active Engine Mounting


Authors: M. Z. Sariman, M. Hafiz Harun, A. K. Mat Yamin, F. Ahmad, M. R. Yunos

Pages: 6-16

Abstract: The demand for low cost, quiet operation, and increased operator comfort in automobiles and other applications requires new techniques to be developed for noise and vibration isolation. One approach to reduce noise vibration and harshness (NVH) is to develop a small low cost vibration isolator that can be used to mount components that generate vibration. Passive, semi-active and active control methods as well as different types of smart materials were studied to develop this isolator. Based on this study, the most promising approach seems to be a semi-active magnetorheological isolator. In this paper, an overview of recent advances in semi active engine mounts are presented, in term of working operation of Magnetorheological (MR) Fluid namely flow mode, shear mode, squeeze mode and mix mode. The issues are discussed with regard to the design and performance as vibration isolator device. The finding of this paper proposed the new semi active engine mounts design.

Title of the Paper: Structural Characteristics of Granulated Ferromagnetic Materials and their Average Magnetic Properties


Authors: Sandulyak A. A., Sandulyak A. V., Ershova V. A., Sandulyak D. A.

Pages: 1-5

Abstract: The new model of granular bed consisted of frac-tional cells is used to obtain parameters of its porosity. Results of researches (of magnetic permeability) of “elemen-tary” effective magnetic channel in porous are given. Such results permit to calculate a relative intensity of field between the grains. The formulae for calculating relative level of magnetizing cy-lindrical filter-matrix samples of various lengths are obtained. A considerable influence of the samples relative dimensions on this level is shown.