Editorial
Hisatoshi Kobayashi; Mikael Syväjärvi
Research Article
Rahul Palaniappan Kanthabhabha Jeya; Abdel-Hakim Bouzid
Abstract
Characterization of Teflon polymer based gaskets under expedited aging is the objective of this work. Teflon gaskets are exploited frequently as a replacement to asbestos fiber gaskets because of their excellent leak tightness and nonhazardous physical degradation properties. The research focuses profoundly ...
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Characterization of Teflon polymer based gaskets under expedited aging is the objective of this work. Teflon gaskets are exploited frequently as a replacement to asbestos fiber gaskets because of their excellent leak tightness and nonhazardous physical degradation properties. The research focuses profoundly on the adverse influence of temperature and thermal cycles on the creep and cumulative damage phenomenon under compressive load. Virgin and expanded PolyTetraFluoroEthylene (PTFE) are tested under 28 and 41 MPa of gasket stress at different temperatures. Intricate analysis of creep under coalesces of thermal ratcheting and principal stress is achieved through Universal Gasket Rig (UGR). The instigated cumulative damage is distinguishable into upper and lower bound temperature region indicating the escalation and decrease of thickness change during cycling which saturates after 12 thermal cycles for expanded PTFE while no saturation is reached for virgin PTFE in even after 20 thermal cycles. Percentage of thickness reduction at different applied stress is nearly the same for virgin PTFE whereas expanded PTFE shows largest reduction under lower stress. Compressive creep bespeaks the impact of temperature and load, thereby dictating the magnitude of ratcheting damage and contrariwise. Finally, the creep and thermal ratcheting has a proliferating effect on value of the coefficient of thermal expansion for all chosen gaskets. Copyright © 2017 VBRI Press.
Research Article
Samy K. K. Shaat; Hussein A. Dawoud
Abstract
Our novelty for the presented work is to find a simple method to study electric and dielectric properties for samples such as magnetic materials. We focus on prepare and characterize of the ferrites. During the AC measurements, we struggled to use the Lissajous figure. In addition, we have a shortage ...
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Our novelty for the presented work is to find a simple method to study electric and dielectric properties for samples such as magnetic materials. We focus on prepare and characterize of the ferrites. During the AC measurements, we struggled to use the Lissajous figure. In addition, we have a shortage of equipment for measurements. This prompted us to look for a method to be easy to use with simple devices. The Delay-Time measurement method for any two different sinusoidal waves was used to calculate the phase shift ( ) between them using an oscilloscope. The was exercised to resolve the series and the parallel of RC in AC circuit. The phasor diagram of the series and the parallel of RC in AC circuit were plotted. All the main and derived quantities of the AC circuit were calculated, such as the immittances, conductivity and dielectric parameters. The presented method is considered as a simple method comparing to other methods. Thus, it can be replaced the other methods as well as it can be used from the scientists and engineers. Our Master students already used this method and they got good results. This paper is considered to be a preliminary analysis for this simple method and we will develop it. Copyright © 2017 VBRI Press.
Research Article
Ahmed A. Al-Ghamdi; Omar A. Al-Hartomy; Falleh R. Al-Solamy; Nikolay Dishovsky; Radostin Nickolov; Nikolay Atanasov; Kamelia Ruskova
Abstract
The purpose of the study is to synthesize nanosized magnetite in situ the nanosized porous texture of activated carbons and to examine the impact of the resulting hybrid filler upon the microwave properties and electromagnetic interference shielding effectiveness of composites based on natural rubber. ...
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The purpose of the study is to synthesize nanosized magnetite in situ the nanosized porous texture of activated carbons and to examine the impact of the resulting hybrid filler upon the microwave properties and electromagnetic interference shielding effectiveness of composites based on natural rubber. The fillers have been characterized by X-ray diffraction and photoelectron spectroscopy establishing the influence of the magnetite layer on the texture characteristics. Studies have been carried out on the effect that the fillers synthesized have on the microwave properties, the real and imaginary part of the permittivity and permeability as well as on the dielectric and magnetic loss angle tangent of the composites. It has been found that filler comprising externally about 5% of magnetite phase is the most effective. The introduction of the magnetic phase contributes to the improvement in the microwave characteristics and expanding the frequency range in which the composites are of good microwave properties due to the combination of high dielectric and the high magnetic losses. Copyright © 2017 VBRI Press.
Research Article
Doha Berraaouan; Mohamed Elmiz; Samira Salhi; AbdesselamTahani .
Abstract
Sodium Alginates are widely used in several industries as gelling agent, coagulant, thickener and encapsulation matrices. Since they can be used in aqueous solutions, it becomes more interesting to study their behavior as non-Newtonian fluids and how adding divalent cations such as calcium can influence ...
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Sodium Alginates are widely used in several industries as gelling agent, coagulant, thickener and encapsulation matrices. Since they can be used in aqueous solutions, it becomes more interesting to study their behavior as non-Newtonian fluids and how adding divalent cations such as calcium can influence it. In this work, intrinsic viscosity, apparent viscosity and rheological behavior of sodium alginate in different salt concentrations have been investigated. Obtained data have shown that the salt concentration plays a key role in the crosslinking process of this polymer. Copyright © 2017 VBRI Press.
Research Article
Meena Kumari; Manju Sikarwar; U.P. Verma
Abstract
In this paper DyMg alloy has been studied in three phases viz. B1, B2 and B3. The exchange correlation potential within the generalized-gradient approximation (GGA) of projector augmented wave (PAW) method is used. The predicted lattice constants and total energy at ambient condition, respectively ...
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In this paper DyMg alloy has been studied in three phases viz. B1, B2 and B3. The exchange correlation potential within the generalized-gradient approximation (GGA) of projector augmented wave (PAW) method is used. The predicted lattice constants and total energy at ambient condition, respectively in B1, B2 and B3 phases are 6.395, 3.772, 6.40 Å, and -24734.778, -24734.855, -24734.683 Ry. From the calculations it is evident that ground state phase of DyMg is B2, therefore, other parameters such as the bulk modulus, its pressure derivative, elastic constants and thermal properties related to B2 phase are presented in this paper. The obtained results are compared with the available experimented and theoretical data. The calculated band structure shows that this alloy no band gap. In order to obtain more information about the elastic properties other parameters such as Zener anisotropy factor, Poisson ratio, Young’s modulus and isotropic shear modulus are also presented. Thermal parameter such as Debye temperature, specific heat, Gruneisen parameter etc. has been determined as a function of pressure and temperature. Copyright © 2017 VBRI Press.
Research Article
Arehalli S Santhosh; Shadakshari Sandeep; Ningappa Kumara Swamy; Gurukar S Suresh; Jose S Melo
Abstract
In the present work, we report on green synthesis of hybrid silver nano structures using a solution of AgNO3 and leaf broth of Cassia occidentalis plant as reducing agent. The incubation of AgNO3 solution and leaf broth for 48 hrs under neutral pH and constant stirring at 150 rpm resulted in the formation ...
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In the present work, we report on green synthesis of hybrid silver nano structures using a solution of AgNO3 and leaf broth of Cassia occidentalis plant as reducing agent. The incubation of AgNO3 solution and leaf broth for 48 hrs under neutral pH and constant stirring at 150 rpm resulted in the formation of hybrid silver nanostructures comprised of silver nano particles (AgNPs) and silver nanorods (AgNRs). The bio reduction of Ag+ ions to AgNPs and AgNRs is confirmed via appearance of surface plasmon resonance peaks at 420 and 370 nm in the UV visible spectrum. The synthesized nanostructures are purified and further characterized using XRD and FT-ATR. The morphology of nanostructures is examined by SEM studies which further revealed the formation of spherical shaped AgNPs and rod shaped AgNRs. The study therefore concludes that it is possible to synthesize the AgNRs and AgNPs effectively using silver nitrate (AgNO3) solution and the leaf broth of Cassia occidentalis. However, further work is needed to establish the employability of these nanostructures in various applications. Copyright © 2017 VBRI Press.
Research Article
Prabhuodeyara M. Gurubasavaraj; Jasmith S. Charantimath
Abstract
In this work, we report the synthesis, structural characterization of Group 4 mono and bis-hydroxides and their derivatives and their catalytic properties in the Ring Opening Polymerization (ROP) of rac-Lactide. The hydroxides, and their multimetallic assemblies were characterized, using 1H NMR, 2D NMR, ...
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In this work, we report the synthesis, structural characterization of Group 4 mono and bis-hydroxides and their derivatives and their catalytic properties in the Ring Opening Polymerization (ROP) of rac-Lactide. The hydroxides, and their multimetallic assemblies were characterized, using 1H NMR, 2D NMR, Elemental Analysis, and Single crystal XRD. These complexes were used as catalysts for ring opening polymerization of rac-Lactide. All complexes exhibit varied activity in the polymerization but produce heterotactic polylactide in high yield. These polymers were further characterized by 13C NMR.A tendency toward formation of heterotactic polylactide was observed in the bulk polymerizations. Copyright © 2017 VBRI Press.
Research Article
Pradosh K. Sahoo; G. Mangamma; M. Kamruddin; S. Dash; Ashok K. Tyagi
Abstract
In the present work ZnO dendritic nanostructures (NS) were synthesized by sol-gel and spin coating methods over silicon (100) substrate. The phase purity was confirmed by XRD. Grain size was found to be less than 10 nm. The vibrational modes of the nano ZnO wurtzite structure were observed by laser Raman ...
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In the present work ZnO dendritic nanostructures (NS) were synthesized by sol-gel and spin coating methods over silicon (100) substrate. The phase purity was confirmed by XRD. Grain size was found to be less than 10 nm. The vibrational modes of the nano ZnO wurtzite structure were observed by laser Raman spectroscopy. Raman spectra revealed asymmetrically broadened red shift of E2 (high) optical phonon mode which accrues from contribution of Non-Brillouin Zone (NBZ) phonons. The shift in the peak is attributed to the quantum mechanical confinement of phonon due to their nano grains as inferred from XRD and morphological studies by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). SEM and AFM images revealed the leaf like dendrite structures having several branches. Possible growth mechanism has been discussed in line with the synthesis. Box counting method was implemented to determine the fractal dimension (D) and the value of D is found to be ~1.6±0.1. This work will be useful in designing novel optoelectronic devices and sensors from ZnO nanostructures (NS) exhibiting complex morphology. Copyright © 2017 VBRI Press.
Research Article
Veena Choudapur; A. B. Raju; Arvind Bennal
Abstract
The studies on luminescent II-VI semiconducting nanomaterials have attracted widespread attention, due to their potential applications in optoelectronic and biophotonic devices. Amongst II-VI group semiconductor nanoparticles, ZnS Nano Particles with large exciton binding energy and wide direct bandgap ...
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The studies on luminescent II-VI semiconducting nanomaterials have attracted widespread attention, due to their potential applications in optoelectronic and biophotonic devices. Amongst II-VI group semiconductor nanoparticles, ZnS Nano Particles with large exciton binding energy and wide direct bandgap at room temperature have drawn considerable attention for exploring its interesting optoelectronic properties. In this paper, high band gap Zinc Sulphide nanocrystals are prepared by simple Co-precipitation method at different concentrations of precursors, and the role of sulphur concentration on structural and optical properties is studied. The Zinc Sulphide nanomaterial was prepared using low cost precursors and de ionised water as solvent without using any capping agents. As synthesized Zinc Sulphide nanocrystals were characterized by using X-ray diffraction (XRD), Energy Dispersive Spectroscopy analysis, UV-Visible Spectrophotometry, Photoluminescence, Scanning electron Microscopy (SEM) and Ellipsometry. X-ray diffraction studies revealed that as prepared of ZnS nanocrystals are Polycrystalline with Cubic phase with preferential orientation along (111) direction. The crystallite size of the order of 5-11nm were obtained. EDAX pattern confirms the presence of Zinc and Sulfur. From optical absorption measurements, it has been observed that the direct optical band gap energy increases from 4.4 to 5.2eV with decrease in sulphur concentration in ZnS and exhibit large quantum confinement effect. Ellipsometry was carried out to measure optical constants of ZnS thin film. The electrical conductivity of the film is measured for the film coated on ITO glass by two probe methods. Copyright © 2017 VBRI Press.
Research Article
Meena .; Annu Sharma; Sanjeev Aggarwal; Pawan K. Sharma
Abstract
Bio-degradable polymers such as starch, chitosan, cellulose etc which are extracted from renewable resources are attracting increasing interest in the recent years due to their environmentally friendly nature, low cost and high availability. In the present work, synthesis of colloidal silver nanoparticles ...
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Bio-degradable polymers such as starch, chitosan, cellulose etc which are extracted from renewable resources are attracting increasing interest in the recent years due to their environmentally friendly nature, low cost and high availability. In the present work, synthesis of colloidal silver nanoparticles and subsequently Ag-starch nanocomposite films were carried out via a green process. For synthesis of Ag nanoparticles water, soluble starch and fructose have been used as solvent, reducing agent and stabilizing agent respectively. The effect of varying concentration of colloidal Ag nanoparticles on the optical and structural properties of starch was investigated. The structural analysis of the nanocomposites was carried out using Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). Size of the Ag nanoparticles from TEM micrograph comes out to be 10.75 ± 0.8 nm in the starch matrix. UV-visible absorption was further utilized to ascertain various optical constants like optical energy gap, Urbach’s energy, optical conductivity etc. The optical energy gap of starch decreases from 4.08 eV to 2.21 eV for Ag-starch nanocomposite film containing 0.50 wt% of Ag nanoparticles and the Urbach’s energy increases from 0.77 eV to 1.37 eV. Copyright © 2017 VBRI Press.
Research Article
Govind Reddy.Y; Sadananda Chary.A; Awasti. A.M; Narender Reddy.S
Abstract
The composite solid electrolyte systems, (1-x)Pb(NO3)2:xCeO2 (x= 0, 0.02, 0.03, 0.04, 0.05 and 0.08), have been investigated by XRD for structural properties, SEM with EDS for morphological studies and Electrical properties through impedance spectroscopy. The frequency and temperature dependence of ac ...
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The composite solid electrolyte systems, (1-x)Pb(NO3)2:xCeO2 (x= 0, 0.02, 0.03, 0.04, 0.05 and 0.08), have been investigated by XRD for structural properties, SEM with EDS for morphological studies and Electrical properties through impedance spectroscopy. The frequency and temperature dependence of ac conductivity, dielectric constant and dielectric loss were measured between the temperatures 30oC to 340oC in the frequency range 1Hz to 10MHz. The complex impedance data is analyzed in conductivity, permittivity and electric modulus formalism in order to through light on transport mechanism. Variation of ac conductivity against frequency suggests the response obeying universal power law. The dynamics of conducting ion is studied through Jonscher’s Universal power law. The parameters of n and A of Jonscher’s Universal law suggest these values are strongly temperature sensitive. The variation of dielectric permittivity, loss, and modulus spectra were found to be consistent with conductivity. Impedance, dielectric and modulus analysis had indicated the non-Debye behavior in these composites. The relaxation phenomena were observed in all formalisms. Copyright © 2017 VBRI Press.
Research Article
Sourabh Biswas; Sam Allison; S. Habib Alavi; Sandip P. Harimkar
Abstract
In the present investigation, effect of laser melting with and without simultaneous application of ultrasonic vibrations on electrochemical properties of 2024 aluminum alloy is investigated. The electrochemical behavior of the laser melted specimens was studied using open-circuit and potentiodynamic ...
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In the present investigation, effect of laser melting with and without simultaneous application of ultrasonic vibrations on electrochemical properties of 2024 aluminum alloy is investigated. The electrochemical behavior of the laser melted specimens was studied using open-circuit and potentiodynamic polarization measurements. Subsequently, investigation of the corrosion films was performed using scanning electron microscopy. It was observed that the laser melted specimens exhibited significant improvement in open circuit potential (both with and without simultaneous ultrasonic vibration application). The open circuit potential of the laser melted specimen without ultrasonic vibrations was observed to be more stable compared to the laser melted specimen with ultrasonic vibrations. It was observed that the corrosion mechanism undergoes a transition from pitting to uniform corrosion in the laser treated specimen, particularly in the laser melted specimen without ultrasonic vibrations. However, the extensive agitations due to ultrasonic vibrations in the melt pool appear to restrict Cu migration to grain boundaries that result in porous and relatively inefficient passive layer formation in laser processed samples with application of ultrasonic vibrations. This behavior was also observed in the potentiodynamic polarization studies that showed that the laser melted specimen without ultrasonic vibrations exhibited lower corrosion current and corrosion rate compared to the laser melted specimen with ultrasonic vibrations as well as the as received substrate. Copyright © 2017 VBRI Press.