Search results for: Electron backscattering diffraction (EBSD)

Authors: S. Yaglikci, B. Salgara, F. Soysal, B. Cicek

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Chemical vapor deposition method was used to produce carbon nanotubes on an iron based catalyst from acetylene. Gas-phase samples collected from the different positions of the tubular reactor were analyzed by GC/MS. A variety of species ranging from hydrogen to naphthalene were observed and changes in their concentrations were plotted against the reactor position. Briefly benzene, toluene, styrene, indene and naphthalene were the main higher molecular weight species and vinylacetylene and diacetylene were the important intermediates. Nanotube characterization was performed by scanning electron microscopy and transmission electron microscopy.

Keywords: Carbon nanotubes, chemical vapor deposition, GC/MS, species profile

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Authors: R. E. Waters, M. J. Whiting, V. Stolojan

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A method of collecting composition data and examining structural features of pearlite lamellae and the parent austenite at the growth interface in a 13wt. % manganese steel has been demonstrated with the use of Scanning Transmission Electron Microscopy (STEM). The combination of composition data and the structural features observed at the growth interface show that available theories of pearlite growth cannot explain all the observations.

Keywords: Interfaces, Phase transformations, Pearlite, Scanning Transmission Electron Microscopy (STEM).

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Authors: Kechida Ahmed, Drai Redouane, Khelil Mohamed

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In this paper we present a new approach to detecting a flaw in T.O.F.D (Time Of Flight Diffraction) type ultrasonic image based on texture features. Texture is one of the most important features used in recognizing patterns in an image. The paper describes texture features based on 2D Gabor functions, i.e., Gaussian shaped band-pass filters, with dyadic treatment of the radial spatial frequency range and multiple orientations, which represent an appropriate choice for tasks requiring simultaneous measurement in both space and frequency domains. The most relevant features are used as input data on a Fuzzy c-mean clustering classifier. The classes that exist are only two: 'defects' or 'no defects'. The proposed approach is tested on the T.O.F.D image achieved at the laboratory and on the industrial field.

Keywords: 2D Gabor Functions, flaw detection, fuzzy c-mean clustering, non destructive testing, texture analysis, T.O.F.D Image (Time of Flight Diffraction).

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Authors: Taposh Roy, Anna Paradowska, Ralph Abrahams, Quan Lai, Michael Law, Peter Mutton, Mehdi Soodi, Wenyi Yan

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In this investigation, a laser cladding process with a powder feeding was used to deposit stainless steel 410L (high strength, excellent resistance to abrasion and corrosion, and great laser compatibility) onto railhead (higher strength, heat treated hypereutectoid rail grade manufactured in accordance with the requirements of European standard EN 13674 Part 1 for R400HT grade), to investigate the development and controllability of process-induced residual stress in the cladding, heat-affected zone (HAZ) and substrate and to analyse their correlation with hardness profile during two different laser cladding directions (across and along the track). Residual stresses were analysed by neutron diffraction at OPAL reactor, ANSTO. Neutron diffraction was carried out on the samples in longitudinal (parallel to the rail), transverse (perpendicular to the rail) and normal (through thickness) directions with high spatial resolution through the thickness. Due to the thick rail and thin cladding, 4 mm thick reference samples were prepared from every specimen by Electric Discharge Machining (EDM). Metallography across the laser claded sample revealed four distinct zones: The clad zone, the dilution zone, HAZ and the substrate. Compressive residual stresses were found in the clad zone and tensile residual stress in the dilution zone and HAZ. Laser cladding in longitudinally cladding induced higher tensile stress in the HAZ, whereas transversely cladding rail showed lower tensile behavior.

Keywords: Laser cladding, residual stress, neutron diffraction, HAZ.

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Authors: A. Srion, W. Thepsuwan, N. Monmaturapoj

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Two Lithium Disilicate (LD) glass ceramics based on SiO2-Li2O-K2O-Al2O3 system were prepared through a glass melting method. The glass rods were then fabricated into dental crowns via a hot pressing at 900˚C and 850˚C in order to study the effect of the pressing temperatures on the phase formation and microstructure of the glasses. Different samples of as cast glass and heat treated samples (600˚C and 700˚C) were used to press for investigating the effect of an initial microstructure on the hot pressing technique. Xray diffraction (XRD) and scanning electron microscopy (SEM) were performed to determine the phase formation and microstructure of the samples, respectively. XRD results show that the main crystalline structure was Li2Si2O5 by having Li3PO4, Li0.6Al0.6Si2O6, Li2SiO3, Ca5 (PO4)3F and SiO2 as minor phases. Glass compositions with different heat treatment temperatures exhibited a difference phase formations but have less effect during pressing. SEM micrographs showed the microstructure of Li2Si2O5 as lath-like shape in all glasses. With increasing the initial heat treatment temperature, the longer the lath-like crystals of lithium disilicate were increased especially when using glass heat treatment at 700˚C followed by pressing at 900˚C. This could be suggested that LD1 heat treatment at 700˚C which pressing at 900˚C presented the best formation by the hot pressing and compiled microstructure.

Keywords: Lithium disilicate, Hot pressing, Dental crown, Microstructure.

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Authors: S. U. Khan, T. Ayub, N. Shafiq

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The properties of locally produced metakaolin (MK) as cement replacing material and the comparison of reactivity with commercially available micro-silica have been investigated. Compressive strength, splitting tensile strength, and load-deflection behaviour under bending are the properties that have been studied. The amorphous phase of MK with micro-silica was compared through X-ray diffraction (XRD) pattern. Further, interfacial transition zone of concrete with micro-silica and MK was observed through Field Emission Scanning Electron Microscopy (FESEM). Three mixes of concrete were prepared. One of the mix is without cement replacement as control mix, and the remaining two mixes are 10% cement replacement with micro-silica and MK. It has been found that MK, due to its irregular structure and amorphous phase, has high reactivity with portlandite in concrete. The compressive strength at early age is higher with MK as compared to micro-silica. MK concrete showed higher splitting tensile strength and higher load carrying capacity as compared to control and micro-silica concrete at all ages respectively.

Keywords: Metakaolin, compressive strength, splitting tensile strength, load deflection, interfacial transition zone.

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Authors: B. Dikici, I. Ozdemir, M. Topuz

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The corrosion behaviour of 316L stainless steel coatings obtained by cold spray method was investigated in this study. 316L powders were deposited onto Al5052 aluminum substrates. The coatings were produced using nitrogen (N₂) process gas. In order to further improve the corrosion and mechanical properties of the coatings, heat treatment was applied at 250 and 750 °C. The corrosion performances of the coatings were compared using the potentiodynamic scanning (PDS) technique under in-vitro conditions (in Ringer’s solution at 37 °C). In addition, the hardness and porosity tests were carried out on the coatings. Microstructural characterization of the coatings was carried out by using scanning electron microscopy attached with energy dispersive spectrometer (SEM-EDS) and X-ray diffraction (XRD) technique. It was found that clean surfaces and a good adhesion were achieved for particle/substrate bonding. The heat treatment process provided both elimination of the anisotropy in the coating and resulting in healing-up of the incomplete interfaces between the deposited particles. It was found that the corrosion potential of the annealed coatings at 750 °C was higher than that of commercially 316 L stainless steel. Moreover, the microstructural investigations after the corrosion tests revealed that corrosion preferentially starts at inter-splat boundaries.

Keywords: 316L, biomaterials, cold spray, heat treatment.

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Authors: Rana Th. A. Al-Rubaye, Burcin Atilgan, Richard J. Holmes, Arthur A. Garforth

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Structured catalysts formed from the growth of zeolites on substrates is an area of increasing interest due to the increased efficiency of the catalytic process, and the ability to provide superior heat transfer and thermal conductivity for both exothermic and endothermic processes. However, the generation of structured catalysts represents a significant challenge when balancing the relationship variables between materials properties and catalytic performance, with the Na2O, H2O and Al2O3 gel composition paying a significant role in this dynamic, thereby affecting the both the type and range of application. The structured catalyst films generated as part of this investigation have been characterised using a range of techniques, including X-ray diffraction (XRD), Electron microscopy (SEM), Energy Dispersive X-ray analysis (EDX) and Thermogravimetric Analysis (TGA), with the transition from oxide-on-alloy wires to hydrothermally synthesised uniformly zeolite coated surfaces being demonstrated using both SEM and XRD. The robustness of the coatings has been ascertained by subjecting these to thermal cycling (ambient to 550oC), with the results indicating that the synthesis time and gel compositions have a crucial effect on the quality of zeolite growth on the FeCrAlloy wires. Finally, the activity of the structured catalyst was verified by a series of comparison experiments with standard zeolite Y catalysts in powdered pelleted forms.

Keywords: FeCrAlloy, Structured catalyst, and Zeolite Y.

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Authors: Shiyang Zhu, Guo-Qiang Lo, Dim-Lee Kwong

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Although silicon photonic devices provide a significantly larger bandwidth and dissipate a substantially less power than the electronic devices, they suffer from a large size due to the fundamental diffraction limit and the weak optical response of Si. A potential solution is to exploit Si plasmonics, which may not only miniaturize the photonic device far beyond the diffraction limit, but also enhance the optical response in Si due to the electromagnetic field confinement. In this paper, we discuss and summarize the recently developed metal-insulator-Si-insulator-metal nanoplasmonic waveguide as well as various passive and active plasmonic components based on this waveguide, including coupler, bend, power splitter, ring resonator, MZI, modulator, detector, etc. All these plasmonic components are CMOS compatible and could be integrated with electronic and conventional dielectric photonic devices on the same SOI chip. More potential plasmonic devices as well as plasmonic nanocircuits with complex functionalities are also addressed.

Keywords: Silicon nanoplasmonics, Silicon nanophotonics, Onchip integration, CMOS

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Authors: Z. Abdolldhi, A. A. Ziaee M., A. Afshar

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In this paper the combination of thermal oxidation and electrochemical anodizing processes is used to produce titanium oxide layers. The response of titanium alloy Ti6Al4V to oxidation processes at various temperatures and electrochemical anodizing in various voltages are investigated. Scanning electron microscopy (SEM); X-Ray Diffraction (XRD) and porosity determination have been used to characterize the oxide layer thickness, surface morphology, oxide layer-substrate adhesion and porosity. In the first experiment, samples modified by thermal oxidation process then followed by electrochemical anodizing. Second experiment consists of surfaces modified by electrochemical anodizing process and then followed by thermal oxidation. The first method shows better properties than other one. In second experiment, Surfaces modified were achieved by thicker and more adherent thick oxide layers on titanium surface. The existence of an electrochemical anodized oxide layer did not improve the adhesion of thermal oxide layer. The high temperature, thermal formation of an oxide layer leads to a coarse oxide grain morphology and a complete oxidative particle. In addition, in high temperature oxidation porosity content is increased. The oxide layer of thermal oxidation and electrochemical anodizing processes; on Ti–6Al–4V substrate was covered with different colored oxide layers.

Keywords: Electrochemically anodizing, Porosity, Thermaloxidation, Ti6Al4 alloy.

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Authors: D.N Awang Sh'ri, E. Hamzah

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The deposition of diamond films on a Si3N4 substrate is an attractive technique for industrial applications because of the excellent properties of diamond. Pretreatment of substrate is very important prior to diamond deposition to promote nucleation and adhesion between coating and substrate. Deposition of nanocrystalline diamonds films on silicon nitride substrate have been carried out by HF-CVD technique using mixture of methane and hydrogen gases. Different pretreatment of substrate including chemical etching consists of hot acid etching and basic etching and mechanical etching were used to study the quality of diamond formed on the substrate. The structure and morphology of diamond coating have been studied using X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) while diamond film quality has been characterized using Raman spectroscopy. AFM was used to investigate the effect of chemical etching and mechanical pretreatment on the surface roughness of the substrates and the resultant morphology of nanocrystalline diamond. It was found that diamond film deposited on as-received, basic etched and grinded substrate shows the morphology of cauliflower while blasted and acidic etched substrates produce smooth, continuous diamond film. However, the Raman investigation did not show any deviation in quality of diamond film for any pretreatment.

Keywords: Nanocrystalline diamond, Chemical VaporDeposition, Pretreatment, Silicon Nitride

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Authors: Seyed Mohammad Hosseini, Amirhossein Moghanian

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The main purpose of this research was to design a biomimetic system by freeze-drying method for evaluating the effect of adding 5 and 10 mol. % of zinc (Zn) in 58S bioactive glass and gelatin (5ZnBG/G and 10ZnBG/G) in terms of structural and biological changes. The structural analyses of samples were performed by X-Ray Diffraction (XRD), scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR) spectroscopy. Also, 3-(4,5dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and alkaline phosphatase (ALP) activity tests were carried out for investigation of MC3T3-E1 cell behaviors. The SEM results demonstrated the spherical shape of the formed hydroxyapatite (HA) phases and also HA characteristic peaks were detected by XRD spectroscopy after 3 days of immersion in the simulated body fluid (SBF) solution. Meanwhile, FTIR spectra proved that the intensity of P–O peaks for 5ZnBG/G was more than 10ZnBG/G and control samples. Moreover, the results of ALP activity test illustrated that the optimal amount of Zn (5ZnBG/G) caused a considerable enhancement in bone cell growth. Taken together, the scaffold with 5 mol.% Zn was introduced as an optimal sample because of its higher biocompatibility, in vitro bioactivity and growth of MC3T3-E1 cells in comparison with other samples in bone tissue engineering.

Keywords: Scaffold, gelatin, modified bioactive glass, ALP, bone tissue engineering.

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Authors: Savvas Varitis, Panagiotis Kavouras, George Vourlias, Eleni Pavlidou, Theodoros Karakostas, Philomela Komninou

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A chromium-loaded ash originating from incineration of tannery sludge under anoxic conditions was mixed with low grade soda-lime glass powder coming from commercial glass bottles. The relative weight proportions of ash over glass powder tested were 30/70, 40/60 and 50/50. The solid mixtures, formed in green state compacts, were sintered at the temperature range of 800o C up to 1200o C. The resulting products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDXS) and micro-indentation. The above methods were employed to characterize the various phases, microstructure and hardness of the produced materials. Thermal treatment at 800o C and 1000o C produced opaque ceramic products composed of a variety of chromium-containing and chromium-free crystalline phases. Thermal treatment at 1200o C gave rise to composite products, where only chromium-containing crystalline phases were detected. Hardness results suggest that specific products are serious candidates for structural applications.

Keywords: Chromium-rich tannery residues, glass-ceramic materials, mechanical properties, microstructure

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Authors: Hoda Aleali, Nastaran Mansour, Maryam Mirzaie

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In this paper, we study the optical nonlinearities of Silver sulfide (Ag2S) nanostructures dispersed in the Dimethyl sulfoxide (DMSO) under exposure to 532 nm, 15 nanosecond (ns) pulsed laser irradiation. Ultraviolet–visible absorption spectrometry (UV-Vis), X-ray diffraction (XRD), and transmission electron microscopy (TEM) are used to characterize the obtained nanocrystal samples. The band gap energy of colloid is determined by analyzing the UV–Vis absorption spectra of the Ag2S NPs using the band theory of semiconductors. Z-scan technique is used to characterize the optical nonlinear properties of the Ag2S nanoparticles (NPs). Large enhancement of two photon absorption effect is observed with increase in concentration of the Ag2S nanoparticles using open Zscan measurements in the ns laser regime. The values of the nonlinear absorption coefficients are determined based on the local nonlinear responses including two photon absorption. The observed aperture dependence of the Ag2S NP limiting performance indicates that the nonlinear scattering plays an important role in the limiting action of the sample. The concentration dependence of the optical liming is also investigated. Our results demonstrate that the optical limiting threshold decreases with increasing the silver sulfide NPs in DMSO.

Keywords: Nanoscale materials, Silver sulfide nanoparticles, Nonlinear absorption, Nonlinear scattering, Optical limiting.

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Authors: A. Darvizeh, H. Rajabi, S. Fatahtooei Nejad, A. Khaheshi, P. Haghdoust

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In this article, biomechanical aspects of hen-s eggshell as a natural ceramic structure are studied. The images, taken by a scanning electron microscope (SEM), are used to investigate the microscopic aspects of the egg. It is observed that eggshell has a three-layered microstructure with different morphological and structural characteristics. Studies on the eggshell membrane (ESM) as a prosperous tissue suggest that it is placed to prevent the penetration of microorganisms into the egg. Finally, numerical models of the egg are presented to study the stress distribution and its deformation under different loading conditions. The effects of two different types of loading (hydrostatic and point loadings) on two different shell models (with constant and variable thicknesses) are investigated in detail.

Keywords: Eggshell, biomechanical properties, Scanning electron microscope, Numerical Modeling.

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Authors: Jung-Ho Moon, Tae Kwon Ha

Abstract:

Textures of AZ31 Mg alloy sheets were evaluated by using neutron diffraction method in this study. The AZ31 sheets were fabricated either by conventional casting and subsequent hot rolling or strip casting. The effect of warm rolling was investigated using the AZ31 Mg alloy sheet produced by conventional casting. Warm rolling of 30% thickness reduction per pass was possible without any side-crack at temperatures as low as 200^oC under the roll speed of 30 m/min. The initial microstructure of conventionally cast specimen was found to be partially recrystallized structures. Grain refinement was found to occur actively during the warm rolling. The (0002),(10-10) (10-11),and (10-12) complete pole figures were measured using the HANARO FCD (Neutron Four Circle Diffractometer) and ODF were calculated. The major texture of all specimens can be expressed by ND//(0001) fiber texture. Texture of hot rolled specimen showed the strongest fiber component, while that of strip cast sheet seemed to be similar to random distribution.

Keywords: Mg alloy, texture, pole figure, ODF, neutron diffraction, warm rolling.

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Authors: K. Easawi, M. Nabil, T. Abdallah, S. Negm, H. Talaat

Abstract:

Composite nanostructures of metal core/semiconductor shell (Au/CdS) configuration were prepared using organometalic method. UV-Vis spectra for the Au/CdS colloids show initially two well separated bands, corresponding to surface plasmon of the Au core, and the exciton of CdS shell. The absorption of CdS shell is enhanced, while the Au plasmon band is suppressed as the shell thickness increases. The shell sizes were estimated from the optical spectra using the effective mass approximation model (EMA), and compared to the sizes of the Au core and CdS shell measured by high resolution transmission electron microscope (HRTEM). The changes in the absorption features are discussed in terms of gradual increase in the coupling strength of the Au core surface plasmon and the exciton in the CdS. leading to charge transfer and modification of electron oscillation in Au core.

Keywords: Nanocomposites, Plasmonics.

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Authors: Christian C. Vaso, Rinlee Butch M. Cervera

Abstract:

One of the most promising anode materials for solid oxide electrolysis cell (SOEC) application is the Sr-doped LaMnO₃ (LSM) which is known to have a high electronic conductivity but low ionic conductivity. To increase the ionic conductivity or diffusion of ions through the anode, Yttria-stabilized Zirconia (YSZ), which has good ionic conductivity, is proposed to be combined with LSM to create a composite electrode and to obtain a high mixed ionic and electronic conducting anode. In this study, composite of lanthanum strontium manganite and YSZ oxide, La_0.8Sr_0.2MnO₃/Zr_0.92Y_0.08O₂ (LSM/YSZ), with different wt.% compositions of LSM and YSZ were synthesized using solid-state reaction. The obtained prepared composite samples of 60, 50, and 40 wt.% LSM with remaining wt.% of 40, 50, and 60, respectively for YSZ were fully characterized for its microstructure by using powder X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), and Scanning electron microscope/Energy dispersive spectroscopy (SEM/EDS) analyses. Surface morphology of the samples via SEM analysis revealed a well-sintered and densified pure LSM, while a more porous composite sample of LSM/YSZ was obtained. Electrochemical impedance measurements at intermediate temperature range (500-700 °C) of the synthesized samples were also performed which revealed that the 50 wt.% LSM with 50 wt.% YSZ (L50Y50) sample showed the highest total conductivity of 8.27x10^-1 S/cm at 600 ^oC with 0.22 eV activation energy.

Keywords: Ceramics, microstructure, fuel cells, electrochemical impedance spectroscopy.

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Authors: N. Massoum, B. Bouazza, H. Tahir, C. Sayah, A. Guen Bouazza

Abstract:

to simulate the phenomenon of electronic transport in semiconductors, we try to adapt a numerical method, often and most frequently it’s that of Monte Carlo. In our work, we applied this method in the case of a ternary alloy semiconductor GaInP in its cubic form; The Calculations are made using a non-parabolic effective-mass energy band model. We consider a band of conduction to three valleys (ΓLX), major of the scattering mechanisms are taken into account in this modeling, as the interactions with the acoustic phonons (elastic collisions) and optics (inelastic collisions). The polar optical phonons cause anisotropic collisions, intra-valleys, very probable in the III-V semiconductors. Other optical phonons, no polar, allow transitions inter-valleys. Initially, we present the full results obtained by the simulation of Monte Carlo in GaInP in stationary regime. We consider thereafter the effects related to the application of an electric field varying according to time, we thus study the transient phenomenon which make their appearance in ternary material

Keywords: Monte Carlo simulation, steady-state electron transport, transient electron transport, alloy scattering.

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Authors: Adriana Souza M. Batista, Cláubia Pereira, Luiz O. Faria

Abstract:

The irradiation of polymeric materials has received much attention because it can produce diverse changes in chemical structure and physical properties. Thus, studying the chemical and structural changes of polymers is important in practice to achieve optimal conditions for the modification of polymers. The effect of gamma irradiation on the crystalline structure of poly(vinylidene fluoride) (PVDF) has been investigated using differential scanning calorimetry (DSC) and X-ray diffraction techniques (XRD). Gamma irradiation was carried out in atmosphere air with doses between 100 kGy at 3,000 kGy with a Co-60 source. In the melting thermogram of the samples irradiated can be seen a bimodal melting endotherm is detected with two melting temperature. The lower melting temperature is attributed to melting of crystals originally present and the higher melting peak due to melting of crystals reorganized upon heat treatment. These results are consistent with those obtained by XRD technique showing increasing crystallinity with increasing irradiation dose, although the melting latent heat is decreasing.

Keywords: Differential scanning calorimetry, gamma irradiation, PVDF, X-ray diffraction technique.

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Authors: A. Abdikian

Abstract:

Using the linearized quantum hydrodynamic model (QHD) and by considering the role of quantum parameter (Bohm’s potential) and electron exchange-correlation potential in conjunction with Maxwell’s equations, electromagnetic wave propagation in a single-walled carbon nanotubes was studied. The electronic excitations are described. By solving the mentioned equations with appropriate boundary conditions and by assuming the low-frequency electromagnetic waves, two general expressions of dispersion relations are derived for the transverse magnetic (TM) and transverse electric (TE) modes, respectively. The dispersion relations are analyzed numerically and it was found that the dependency of dispersion curves with the exchange-correlation effects (which have been ignored in previous works) in the low frequency would be limited. Moreover, it has been realized that asymptotic behaviors of the TE and TM modes are similar in single wall carbon nanotubes (SWCNTs). The results show that by adding the function of electron exchange-correlation potential lead to the phenomena and make to extend the validity range of QHD model. The results can be important in the study of collective phenomena in nanostructures.

Keywords: Transverse magnetic, transverse electric, quantum hydrodynamic model, electron exchange-correlation potential, single-wall carbon nanotubes.

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Authors: Z. Ž. Lazarević, D. L. Sekulić, V. N. Ivanovski, N. Ž. Romčević

Abstract:

NiFe2O4 (nickel ferrite), ZnFe2O4 (zinc ferrite) and Ni0.5Zn0.5Fe2O4 (nickel-zinc ferrite) were prepared by mechanochemical route in a planetary ball mill starting from mixture of the appropriate quantities of the Ni(OH)2/Fe(OH)3, Zn(OH)2/Fe(OH)3 and Ni(OH)2/Zn(OH)2/Fe(OH)3 hydroxide powders. In order to monitor the progress of chemical reaction and confirm phase formation, powder samples obtained after 25 h, 18 h and 10 h of milling were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), IR, Raman and Mössbauer spectroscopy. It is shown that the soft mechanochemical method, i.e. mechanochemical activation of hydroxides, produces high quality single phase ferrite samples in much more efficient way. From the IR spectroscopy of single phase samples it is obvious that energy of modes depends on the ratio of cations. It is obvious that all samples have more than 5 Raman active modes predicted by group theory in the normal spinel structure. Deconvolution of measured spectra allows one to conclude that all complex bands in the spectra are made of individual peaks with the intensities that vary from spectrum to spectrum. The deconvolution of Raman spectra allows to separate contributions of different cations to a particular type of vibration and to estimate the degree of inversion.

Keywords: Ferrites, Raman spectroscopy, IR spectroscopy, Mössbauer measurements.

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Authors: Bassam M. Abunahel, Nurul Zahirah Noor Azman, Munirah Jamil

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The effect of needle diameter on the morphological structure of electrospun n-Bi₂O₃/epoxy-PVA nanofibers has been investigated using three different types of needle diameters. The results were observed and investigated using two techniques of scanning electron microscope (SEM). The first technique is backscattered SEM while the second is secondary electron SEM. The results demonstrate that there is a correlation between the needle diameter and the morphology of electrospun nanofibers. As the internal needle diameter decreases, the average nanofiber diameter decreases and the fibers get thinner and smoother without agglomeration or beads formation. Moreover, with small needle diameter the nanofibrous porosity get larger compared with large needle diameter.

Keywords: Needle diameter, fiber diameter, agglomeration, porosity, SEM.

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Authors: Nazli Darkhal

Abstract:

The use of gems and ornaments has been common in Iran since the beginning of history. The prosperity of the country, the wealth, and the interest of the people of this land in a luxurious and glorious life, combined with beauty, have always attracted the attention of Iranian people to gems and jewelry. Iranians are famous in the world for having a long history of collecting and recognizing precious stones. In this case, we can use the unique treasure of national jewelry. Raman spectroscopy method is one of the oscillating spectroscopy methods that is classified in the group of nondestructive study methods, and like other methods, in addition to several advantages, it also has disadvantages and problems. Micro Raman spectroscopy is one of the different types of Raman spectroscopy in which an optical microscope is combined with a Raman device to provide more capabilities and advantages than its original method. In this way, with the help of Raman spectroscopy and a light microscope, while observing more details from different parts of the historical sample, natural or artificial pigments can be identified in a small part of it. The EDX (Energy Dispersive X ray) electron microscope also functions as the basis for the interaction of the electron beam with the matter. The beams emitted from this interaction can be used to examine samples. In this article, in addition to introducing the micro-Raman spectroscopy method, studies have been conducted on the structure of three samples of existing stones in the historic citadel of Bam. Using this method of study on precious and semi-precious stones, in addition to requiring a short time, can provide us with complete information about the structure and theme of these samples. The results of experiments and gemology of the stones showed that the selected beads are agate and jasper, and they can be placed in the chalcedony group.

Keywords: Bam citadel, precious stones, semi-precious stones, Raman spectroscopy, scanning electron microscope.

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Authors: Oyugi Ngure Robert, Tabitha A. Amollo, Kallen Mulilo Nalyanya

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Nanomaterials have attracted significant attention in research because of their exemplary properties, making them suitable for diverse applications. This paper reports the successful synthesis as well as the structural and optical properties of silver sulfide-reduced graphene oxide (Ag2S-rGO) nanocomposite. The nanocomposite was synthesized by the chemical reduction method. Scanning electron microscopy (SEM) showed that the reduced graphene oxide (rGO) sheets were intercalated within the Ag2S nanoparticles during the chemical reduction process. The SEM images also showed that Ag2S had the shape of nanowires. Further, SEM energy dispersive X-ray (SEM EDX) showed that Ag2S-rGO is mainly composed of C, Ag, O, and S. X-ray diffraction analysis manifested a high crystallinity for the nanowire-shaped Ag2S nanoparticles with a d-spacing ranging between 1.0 Å and 5.2 Å. Thermal gravimetric analysis (TGA) showed that rGO enhances the thermal stability of the nanocomposite. Ag2S-rGO nanocomposite exhibited strong optical absorption in the UV region. The formed nanocomposite is dispersible in polar and non-polar solvents, qualifying it for solution-based device processing. Thus, the surface plasmon resonance effect associated with metallic nanoparticles, strong optical absorption, thermal stability crystallinity and hydrophilicity of the nanocomposite suits it for solar energy conversion applications.

Keywords: Silver sulfide, reduced graphene oxide, nanocomposite, structural properties, optical properties.

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Authors: Prakash Chand, Anurag Gaur, Ashavani Kumar

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In the present study, we have synthesized Cr and Fe doped zinc oxide (ZnO) nanostructures (Zn1-δCraFebO; where δ = a + b = 20%, a = 5, 6, 8 & 10% and b = 15, 14, 12 & 10%) via sol-gel method at different doping concentrations. The synthesized samples were characterized for structural properties by X-ray diffractrometer and field emission scanning electron microscope and the optical properties were carried out through photoluminescence and UVvisible spectroscopy. The particle size calculated through field emission scanning electron microscope varies from 41 to 96 nm for the samples synthesized at different doping concentrations. The optical band gaps calculated through UV-visible spectroscopy are found to be decreasing from 3.27 to 3.02 eV as the doping concentration of Cr increases and Fe decreases.

Keywords: Nanostructures, Optical Properties, Sol-gel method.

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Authors: Wisutmethangoon S., Pannaray S., Plookphol T., Wannasin J.

Abstract:

2024 Aluminum alloy was squeezed cast by the Gas Induced Semi Solid (GISS) process. Effect of artificial aging on microstructure and mechanical properties of this alloy was studied in the present work. The solutionized specimens were aged hardened at temperatures of 175°C, 200°C, and 225°C under various time durations. The highest hardness of about 77.7 HRE was attained from specimen aged at the temperature of 175°C for 36h. Upon investigation the microstructure by using transmission electron microscopy (TEM), the S’ phase was mainly attributed to the strengthening effect in the aged alloy. The apparent activation energy for precipitation hardening of the alloy was calculated as 133,805 J/mol.

Keywords: 2024 aluminum alloy, Gas induced semi solid, T6 heat treatment, Aged hardening, Transmission electron microscopy.

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Authors: S. Palaniyappan, P. K. Chennam, M. Trautmann, H. Ahmad, T. Mehner, T. Lampke, G. Wagner

Abstract:

In structural-health monitoring of fiber reinforced plastics (FRPs), every single inorganic fiber sensor that are integrated into the bulk material requires an electrical insulation around itself, when the surrounding reinforcing fibers are electrically conductive. This results in a more accurate data acquisition only from the sensor fiber without any electrical interventions. For this purpose, thin nano-films of aluminium oxide (Al₂O₃)-based electrical-insulation coatings have been fabricated around the Silicon Carbide (SiC) single fiber sensors through reactive DC magnetron sputtering technique. The sputtered coatings were amorphous in nature and the thickness of the coatings increased with an increase in the sputter time. Microstructural characterization of the coated fibers performed using scanning electron microscopy (SEM) confirmed a homogeneous circumferential coating with no detectable defects or cracks on the surface. X-ray diffraction (XRD) analyses of the as-sputtered and 2 hours annealed coatings (825 & 1125 ˚C) revealed the amorphous and crystalline phases of Al₂O₃ respectively. Raman spectroscopic analyses produced no characteristic bands of Al₂O₃, as the thickness of the films was in the nanometer (nm) range, which is too small to overcome the actual penetration depth of the laser used. In addition, the influence of the insulation coatings on the mechanical properties of the SiC sensor fibers has been analyzed.

Keywords: Al2O3 insulation coating, reactive sputtering, SiC single fiber sensor, single fiber tensile test.

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Authors: Rana Th. A. Al-Rubaye, Arthur A. Garforth

Abstract:

This work details the generation of thin films of structured zeolite catalysts (ZSM–5 and Y) onto the surface of a metal substrate (FeCrAlloy) using in-situ hydrothermal synthesis. In addition, the zeolite Y is post-synthetically modified by acidified ammonium ion exchange to generate US-Y. Finally the catalytic activity of the structured ZSM-5 catalyst films (Si/Al = 11, thickness 146 0m) and structured US–Y catalyst film (Si/Al = 8, thickness 230m) were compared with the pelleted powder form of ZSM–5 and USY catalysts of similar Si/Al ratios. The structured catalyst films have been characterised using a range of techniques, including X-ray diffraction (XRD), Electron microscopy (SEM), Energy Dispersive X–ray analysis (EDX) and Thermogravimetric Analysis (TGA). The transition from oxide-onalloy wires to hydrothermally synthesised uniformly zeolite coated surfaces was followed using SEM and XRD. In addition, the robustness of the prepared coating was confirmed by subjecting these to thermal cycling (ambient to 550oC). The cracking of n–heptane over the pellets and structured catalysts for both ZSM–5 and Y zeolite showed very similar product selectivities for similar amounts of catalyst with an apparent activation energy of around 60 kJ mol-1. This paper demonstrates that structured catalysts can be manufactured with excellent zeolite adherence and when suitably activated/modified give comparable cracking results to the pelleted powder forms. These structured catalysts will improve temperature distribution in highly exothermic and endothermic catalysed processes.

Keywords: FeCrAlloy, Structured catalyst, and Zeolite Y, Zeolite ZSM-5.

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Authors: B. Ghosh, H. Sahoo, K. K. Mondal

Abstract:

Propagation of arbitrary amplitude nonlinear Alfven waves has been investigated in low but finite β electron-positron-ion plasma including full ion dynamics. Using Sagdeev pseudopotential method an energy integral equation has been derived. The Sagdeev potential has been calculated for different plasma parameters and it has been shown that inclusion of ion parallel motion along the magnetic field changes the nature of slow shear Alfven wave solitons from dip type to hump type. The effects of positron concentration, plasma-β and obliqueness of the wave propagation on the solitary wave structure have also been examined.

Keywords: Alfven waves, Sagdeev potential, Solitary waves.

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