Table of Contents

  • CHARACTERIZATION OF MECHANICAL ALLOYED Ni-Ti POWDERS

    pg(s) 11-14

    Ni-Ti system is an interesting binary system having different intermetallic compounds. NiTi is the one of them having commercial importance because of its shape memory and superelastic characteristics. In this study, effect of mechanical alloying was studied against milling time to observe powder state changes and phase formations. 35Ni-65Ti, 45Ni-55Ti and 50Ni-50Ti compositions in Ni-Ti binary system were selected, It was possible to obtain different intermetallic compounds in Ni-Ti binary system by mechanical alloying of initial Ni-Ti powders. It is also observed that, particle size and distribution measurements, XRD phase analysis, density measurements and morphological evaluation of the mechanical alloyed powders can be used for the determination of optimum conditions for obtaining desired level of alloying and final product.

  • PSEUDO-POTENTIAL CALCULATIONS OF STRUCTURAL, ELECTRONIC, ELASTIC AND PHONON PROPERTIES OF Os2YPb (Y=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn)

    pg(s) 15-17

    First-principle calculations of structural, electronic, magnetic and elastic properties Os2YPb (Y=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) are presented, using the pseudo-potential plane waves method within the local density approximation (LDA) and the gradient generalized approximation (GGA) for the exchange and correlation potential. Results are given for lattice constant, elastic constant and bulk modulus. Our results of the electronic band structure and density of states show that these compounds are conductors. We have also presented phonon spectrum for Os2YPb (Y=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn).

  • INFLUENCE OF NON-METALLIC INCLUSIONS ON THE STRENGTHENING OF STEELS UNDER LASER ACTION

    pg(s) 18-24

    Melting and crystallization of non-metallic inclusions in contact with steel matrix during laser treatment was investigated. It was shown that laser action is the method of local change of inclusion structure in the surface fused layers and also of the properties of non-metallic inclusion surface. Peculiarities of steel matrix saturation with elements of non-metallic inclusions during different regimes of laser action were investigated. It was shown the role of that process in the formation of local structure of steel matrix near non-metallic inclusions. That allows to realize possibility of transformation of the non-metallic inclusions how sources of inside local alloying of steel matrix. It was fixed that in local areas of steel matrix the liquation strengthened zones were formed. They represent different types of composite layers: gradiental zones with cascade and “spot” distribution of elements and nanohardness, dispersal zones with different types of microphases and nanophases, “tunnel” zones, and also zones with combine structure. It was shown the role of non-metallic inclusions in development of micro heterogeneous strengthening of steels under laser treatment.

  • GRAPHENE-BASED HYBRID NANOMATERIALS FOR ELECTROCHEMICAL BIOSENSORS

    pg(s) 25-28

    Nanomaterials can be combined or modified with other materials allowing the development of a great variety of composite nanomaterials and nanohybrids with new structural and functional characteristics. This article aims to show the advantages of hybrid nanomaterials as transduction, amplification and labeling elements for the construction of electrochemical biosensing platforms. Special attention will be paid to the used of graphene-based hybrid nanomaterials for biosensing.

  • RESEARCH ON THE OPTIUM TEMPERATURE REGIME FOR VACUUM OXY-NITROCARBURIZING OF AISI D2 STEEL

    pg(s) 29-32

    The present study aims to determine the optimum temperature regime for oxy-nitrocarburizing of AISI D2 steel in order to ensure high mechanical properties of both diffusion and compound zones. The examined samples are quenched and high temperature tempered in advance, thus having a hardness equivalent up to HRc 54-55 before saturation. The vacuum oxy-nitrocarburizing is held at temperatures of 500 ºС, 550 ºС and 590 ºС for 4 hours in a cycling gas flow rate. The proportion of NH3 and CO2 gases used is 90:10 volume fractions. The results of the examination are based on the analysis of X-ray diffraction patterns, cross-section microstructures and measurements of micro-hardness values on the surface and in depth of the diffusion zone. The core hardness of the substrate is also measured after the vacuum process for the purpose of establishing a possible hardness decrease after the oxy-nitrocarburizing process. Conclusions have been drawn in relation to the practice.

  • INVESTIGATION OF DIFFERENT ABLATION TIMES ON THE FORMATION OF ZINC OXIDE NANOPARTICLES SYNTHESIZED BY LIQUID-PHASE PULSED LASER ABLATION TECHNIQUE

    pg(s) 3-5

    This work was focused for studying the effect of ablation time on the producing ZnO nanoparticles by Liquid –Phase Pulsed Lase Ablation (LP-PLA) of Zn metal plate in the aqueous environment of cetyl trimethyl ammonium bromide (CTAB) with molarity (10-2 M) using Q-Switched Nd:YAG pulsed laser has wavelength= 1064 nm, Rep. rate= 10 Hz, Pulse duration =6 ns and laser energy 170 mJ. The effect of ablation time on the optical and structure of ZnO was studied is characterized by UV-visible absorption. UV-visible absorption spectrum has four peaks at 219, 232,242,249 nm for ablation time (5, 10, 15, and 20 min) respectively, our results show that UV–visible spectra show a blue shift in the presence of CTAB with decrease the ablation time and blue shift indicated to get smaller size of nanoparticles. The blue shift in the absorption edge indicates the quantum confinement property of nanoparticles. Also FTIR transmittance spectra of ZnO2 nanoparticles prepared in these states show a characteristic ZnO absorption at 435–445cm−1.

  • THE SYNTHESIS, THERMAL AND STRUCTURAL CHARACTERIZATION OF POLYVINYLCHLORIDE/GRAPHENE OXIDE (PVC/GO) COMPOSITES

    pg(s) 33-36

    In this study, the thermal and structural changes were observed in polyvinylchloride / graphene oxide (PVC/GO) composites in different amounts of 0.1, 0.3, 0.5 and 1 wt.%. To this aim, GO was prepared from natural graphite by Hummers method. XRD results of GO indicated that the interlayer distance increased from 0.33 nm to 0.88 nm. Energy Dispersive Spectroscopy (EDS) analysis results showed that oxygen content increased from 22.59 % to 47.95 % after the oxidation process. These features suggested that the GO sample, mainly oxygen-containing functional groups, was oxidized. PVC/GO composites were prepared by colloidal blending. XRD results of all composites indicated the GO layers well-dispersed in polymer matrix. SEM analysis revealed that the composites with 0.1 and 0.5 wt. % GO filler exhibited a uniform composite with highly porous and micro porous morphology respectively. TGA and DSC analysis showed that the use of minimum amount of GO in PVC matrix did not provide an important improvement on the thermal stability of the examined composites.

  • STUDY OF HIGH TEMPERATURE ABRASIVE WEAR BEHAVIOR OF VERMICULAR AND NODULAR CAST IRONS

    pg(s) 37-39

    This paper examines the influence of the graphite morphology on the high temperature abrasive wear behavior of vermicular and nodular cast irons, having same hardness. Wear tests were conducted on a 240-mesh Al2O3 abrasive paper at various temperatures in between 25 and 450 °C. The results showed that in all cases, the nodular cast iron exhibits a higher wear resistance than the vermicular cast iron. Generally the examined vermicular and nodular cast irons exhibit the highest resistance to abrasion at 150°C.

  • ELECTRONIC, ELASTIC AND VIBRATIONAL PROPERTIES OF Cu2TMAl (TM=Sc, Ti, Cr) FROM FIRST-PRINCIPLES CALCULATIONS

    pg(s) 6-7

    The structure, electronic, elastic and vibrational properties of the Cu2TMAl (TM=Sc, Ti, Cr) Heusler compounds have been investigated in detail by employing an ab initio pseudopotential method and a direct method within a generalized gradient approximation (GGA-PBE) of the density-functional theory (DFT) scheme. Calculated lattice parameter values are in excellent agreement with recent experiments. In the present study, Cu2ScAl and Cu2TiAl does not show any magnetic moments, whereas the Cu2CrAl has magnetic moment of 2.95 μB per formula unit. From electronic band structures we have found that these compounds have a metallic nature. The elastic constants Cij are computed using the total energy variation versus strain technique. The calculated elastic constants and bulk modulus are reported and compared with earlier available theoretical calculations. Phonon frequency for Cu2TMAl (TM=Sc, Ti, Cr) Heusler compounds have been computed and plotted along with high symmetry directions.

  • STRUCTURAL, ELECTONIC, ELASTIC, PHONON AND THERMAL PROPERTIES OF L12 INTERMETALLIC COMPOUNDS BASED ON IRIDIUM (Ir3Hf)

    pg(s) 8-10

    We present ab initio calculations of the structural, electronic structures, elastic, thermodynamic and vibrational properties of the Ir3Hf compound in the L12 structure. The calculated lattice constants, bulk modulus, and first-order pressure derivative of the bulk modulus are reported for the L12 structure and compared with the earlier values. The elastic constants (C11, C12 and C44) in L12 phase for Ir3Hf compound is calculated using the energy-strain method. The calculated elastic constants satisfy the mechanical stability criterion. Electronic band structures and partial and total densities of states have been derived for Ir3Hf. The band structures show metallic character; the conductivity is mostly governed by Ir 5d states. The phonon-dispersion curves and phonon total density of states based on the linear-response method have been investigated for this compound. Temperature variations of specific heat capacity in the range of 0–1000 K are obtained using the quasi-harmonic model.