Loreleyn F Flores; Karem Y Tucto; Jorge A Guerra; Rolf Grieseler; Jan A Töfflinger; Andres Osvet; Miroslaw Batentschuk; Roland Weingärtner
Abstract
Amorphous silicon oxycarbide (a-SiCxOy) single doped with Yb3+ and co-doped with the couple Tb3+ - Yb3+ thin films were grown on crystalline silicon substrates by rf magnetron sputtering. The elemental composition in at. % is determined by energy dispersive spectroscopy and fourier transform infrared ...
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Amorphous silicon oxycarbide (a-SiCxOy) single doped with Yb3+ and co-doped with the couple Tb3+ - Yb3+ thin films were grown on crystalline silicon substrates by rf magnetron sputtering. The elemental composition in at. % is determined by energy dispersive spectroscopy and fourier transform infrared spectroscopy allows to investigate the chemical properties of the host. The concentration of Yb in the single doped sample was 3.5% and for the codoped samples (Yb, Tb) were (3%, 0.9%), (3.5%, 0.6%) and (4%, 0.6%), respectively. Post-deposition annealing treatments were made in order to induce optical activation of the rare earths. Conversion or absorption of high energy photons were analyzed by photoluminescence spectroscopy. The photoluminescence spectra show that for a given temperature range in the thermal annealing process, as well as for the appropriate rare earth concentrations the activation of Yb3+ and Tb3+ is enhanced. A strong reduction of the Tb3+ emission in contrast to the Yb3+ emission in the a-SiCxOy,:Tb:Yb samples at annealing temperature at 500°C suggests a energy transfer from Tb3+ to Yb3+ ions. Copyright © 2018 VBRI Press.
Jitendra Pal Singh; So Hee Kim; Weon Cheol Lim; Sung Ok Won; Keun Hwa Chae
Abstract
In the present work, we have reported the synthesis of calcium hydroxide from calcium nitrate. Synthesized nanoparticles were characterized using X-ray diffraction, scanning electron micrographs, and near edge X-ray absorption fine structure measurements. Synthesized nanoparticles exhibit tetragonal ...
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In the present work, we have reported the synthesis of calcium hydroxide from calcium nitrate. Synthesized nanoparticles were characterized using X-ray diffraction, scanning electron micrographs, and near edge X-ray absorption fine structure measurements. Synthesized nanoparticles exhibit tetragonal phase with space group P3m1. These nanoparticles exhibit almost spherical shape. Particle size of these nanoparticles are 55 nm and 69 nm for two different treatment of precursor. Microscopic studies shows that size distribution is affected by the change of thermal history. Local electronic structure measured at Ca (L- & K-) and O K-edges exhibit presence of spectral features that are characteristics of calcium hydroxide. Moreover, strength and magnitude of crystal field parameter is unaffected by thermal treatment utilized for synthesis of these materials. Copyright © 2018 VBRI Press.
Jan Trejbal; Tereza Valentová; Zdeněk Prošek
Abstract
This work focuses on a surface modification of polypropylene micro-fibers having 18 μm in diameter and 12 mm in length by means of the cold low-pressure oxygen plasma treatment. The main goal is to change fiber surface properties from hydrophobic to hydrophilic and from smooth to slightly ...
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This work focuses on a surface modification of polypropylene micro-fibers having 18 μm in diameter and 12 mm in length by means of the cold low-pressure oxygen plasma treatment. The main goal is to change fiber surface properties from hydrophobic to hydrophilic and from smooth to slightly roughened and thus to ensure a strong adhesion of their surfaces with a cement matrix. As a proper indicator of realised modifications, scanning electron microscopy (an assessment of surface roughening) and a wettability measurement with demineralized water were done. Moreover, in order to establish a time-dependent stability of the chemical changes onto fiber surfaces, the wettability measurement was repeated immediately after the treatment and with a time lag equal to 1, 7 and 30 days, when fibers were exposed to standard atmospheric conditions. To asses a rate of an adhesion between fibers and the cement matrix, mechanical four-point bending tests of prismatic cement samples (CEM I 42.5 R, w/c 0,4, dimensions 40×40×160 mm) reinforced with both reference and treated fibers were performed. SEM revealed slightly roughened fiber surfaces after plasma modifications. The treated fiber wettability with water increased almost twice, compared to reference fibers. Nevertheless, the wettability fast decreased to reference values. Copyright © 2018 VBRI Press.
Omar Chaalal; Essa Lwisa
Abstract
Many oil formations contain water having high salinity and/or high concentrations of divalent ions such as calcium or magnesium dissolved therein, and are additionally at high temperatures. Most of the available surfactants used in oil recovery operations are either ineffective in high salinity ...
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Many oil formations contain water having high salinity and/or high concentrations of divalent ions such as calcium or magnesium dissolved therein, and are additionally at high temperatures. Most of the available surfactants used in oil recovery operations are either ineffective in high salinity or high hardness waters, or incapable to stand the higher temperatures encountered in many formations. A powerful natural material that improves enhance oil reservoirs recovery through the reduction of interfacial tension and increases the volumetric sweep efficiency of fractured and /or heterogeneous oil reservoirs is introduced in this paper. The novel green surfactant for EOR is extracted from Sisyphus Spina Christi plant and Aloe Vera plant. The surfactant is 100% natural, safe and environmental friendly. It recovers more than 96% of the oil trapped in any oil reservoir. This recovery is a breakthrough in the field of enhanced oil recovery. It works at high salinity (up to 172000 ppm) and a temperature over than 90o Celsius. It can handle a bivalent ions (14000 ppm for Ca+2 and 3000 for Mg+2) and monovalent ions (57600 for ppm Na+ and 122000 ppm Cl-). The green material is mixed with the formation water and is stable over a wide range of formation temperatures and water salinities and hardness values. Copyright © 2018 VBRI Press.
Natalia Lopez-Barbosa; Johann F. Osma
Abstract
Absorption and desorption properties of poly(ethylene glycol) diacrylate (PEGDA) have seen to greatly vary depending on the molecular weight of the polymer, suggesting a dependence of the wetting phenomena on its molecular weight. Here, two sets of polymeric submicron films (140 and 190 nm) were fabricated ...
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Absorption and desorption properties of poly(ethylene glycol) diacrylate (PEGDA) have seen to greatly vary depending on the molecular weight of the polymer, suggesting a dependence of the wetting phenomena on its molecular weight. Here, two sets of polymeric submicron films (140 and 190 nm) were fabricated by free radical polymerization using Phenylbis (2, 4, 6-trimethylbenzoyl) phosphine oxide as the photoinitiator, and PEGDA (Mn 250 or 575). The films were spin coated on glass substrates to study their wetting phenomena by dynamic contact angle analysis. All films were characterized in terms of their thickness and transmittance. PEGDA Mn 250 films (Film-250) decreased the sliding time of water drops when compared to a clean glass substrate because of a decrement in the liquid-solid interface area. Nonetheless, when using PEGDA Mn 575 films (Film-575), an improvement in the adhesion forces between the coating and the drop of water was observed, avoiding the drop to slide down the substrate and leading to its later evaporation. In addition, Film-575 drastically changed their morphology after water exposure, while Film-250 remained the same. These characteristics are of special interest in environments where a response towards small amounts of water is desired, or where water evaporation is craved. Copyright © 2018 VBRI Press.
Djoko Sihono Gabriel; T. Yuri M. Zagloel; Dadang Isnandar
Abstract
Design for material value conservation in this case study was a trial implementation of design principles of plastic bag in order to minimize its value degradation and maximize its salvage value in the end of life, and therefore increase its acceptance by plastic recyclers. A Structural Equation Modelling ...
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Design for material value conservation in this case study was a trial implementation of design principles of plastic bag in order to minimize its value degradation and maximize its salvage value in the end of life, and therefore increase its acceptance by plastic recyclers. A Structural Equation Modelling (SEM) with Lisrel 8.8 software used as tool of analysis in evaluating customer acceptance of the two types of design paradigm, current and material value conservation based design. The results indicated that customer accepted both type of packaging. With final standard factor loadings, the proposed design indicated slightly better correlation coefficients: 0.46 for Ease of Information Delivery and 0.74 for Informational Content variables, better than current design with 0.44 and 0.73 coefficients. Wide spread implementation of design for material value conservation will save virgin plastic consumption for plastic packaging production, reduce plastic waste generation as well as support material resource conservation in a better condition of environment. Social and economic benefit will also be obtained as multiplier effect of material value conservation. Copyright © 2018 VBRI Press.
Joel Espino-Portillo; Dora A. Cortés-Hernández; José C. Escobedo-Bocardo; Héctor J. Sánchez; Mirna M. G. Saldívar-Ramírez; Laura E. De-León-Prado
Abstract
The effect of mixed ferrites nature and that of several coatings on the magnetic properties and thus, on the heating ability of nanoparticles, was studied. The Mg0.4Ca0.6Fe2O4 and Mn0.5Ga0.5Fe2O4 ferrites, synthesized by sol-gel method, followed by heat treatment, were coated with oleic acid + Pluronic® ...
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The effect of mixed ferrites nature and that of several coatings on the magnetic properties and thus, on the heating ability of nanoparticles, was studied. The Mg0.4Ca0.6Fe2O4 and Mn0.5Ga0.5Fe2O4 ferrites, synthesized by sol-gel method, followed by heat treatment, were coated with oleic acid + Pluronic® F-127, carboxymethyl-dextran sodium or polyvinylpyrrolidone. An average particle size of 12 and 15 nm was obtained for the Mg-Ca and Mn-Ga ferrites, respectively. Samples, before and after coating, revealed a heating capacity over 42°C and a superparamagnetic behaviour. The compounds accomplished the requirements of heating ability and specific absorption rate for magnetic hyperthermia treatment. The Mn0.5Ga0.5Fe2O4 system was more efficient than the Mg0.4Ca0.6Fe2O4 system. Copyright © 2018 VBRI Press.
Alejandro Zuleta; Andrés Valencia-Escobar; Carlos Rodríguez
Abstract
The high requirements of Bicycle Motocross (BMX) race conditions demands on the bicycle frame complex dynamic and static loads states by which it is expected that frames to experience high levels of stress and strain. To build efficient bike frames in terms of performance, weight and quality, it is necessary ...
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The high requirements of Bicycle Motocross (BMX) race conditions demands on the bicycle frame complex dynamic and static loads states by which it is expected that frames to experience high levels of stress and strain. To build efficient bike frames in terms of performance, weight and quality, it is necessary to analyse systematically its response against different loads. The aim of this work is to perform the design of a BMX frame for the national team of Colombia, including the microstructural and mechanical characterization of the initial bicycle frame as complement for the macrostructural characterization of the frame in static conditions. The components of the bike frame were exanimated using optical emission spectrometry, metallographic examinations, microhardness measurements and mechanical tests. It was found that significant differences of the grain sizes of the samples were reflected in the deformation values measured in the frame showing a high structural anisotropy. Despite this, the microhardness and mechanical resistance values the results show coherence between them. In Addition, safety coefficient of the four of the components of the bicycle frame was calculated finding that coefficient values was the calculated safe factor was 4.27. Copyright © 2018 VBRI Press
Mykhaylo Romanyuk; Martina Avalos; Edgardo R. Benavidez; Elena Brandaleze
Abstract
The application of IF steels in the automotive industry has increased significantly due to their excellent deep drawability. The chemical composition, the microstructure, the precipitation phenomena and texture of the material determine the mechanical properties. This paper proposes, a more profound ...
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The application of IF steels in the automotive industry has increased significantly due to their excellent deep drawability. The chemical composition, the microstructure, the precipitation phenomena and texture of the material determine the mechanical properties. This paper proposes, a more profound study of some aspects related to the application of high plastic deformation, as well as its relation with the formation of fine grain structures, texture, precipitates and grain boundaries interaction. The structure of an IF steel plate with ultra-low carbon was characterized using optical microscopy and scanning electron microscopy (SEM). A ferritic structure with very fine and recrystallized grains containing high number of triple point was observed. The precipitation kinetic of the steel was simulated applying Fact Sage 7.1. The main precipitates predicted are: TiN and TiS, these types of second phases improve the drawability behaviour. The formability aptitude of the sheet was evaluated by different mechanical tests: Hole Expansion, Erichsen and n-r determination. Finally, yield strength, tensile strength, percentage elongation and average r-value results, are correlated with the structural information. A strong (111) <110> recrystallization texture confirms the high formability of the IF steel sheet. Copyright © 2018 VBRI Press.
Elena Brandaleze; Martina Avalos; Mykaylo Romanyuk
Abstract
Steel wires under severe cold drawing deformation, develop high strength (5-6 GPa) and ductility. For these reasons it is relevant to increase the knowledge on the structural evolution and deformation mechanisms involved during wire drawing process, due to their critical applications such as bridges, ...
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Steel wires under severe cold drawing deformation, develop high strength (5-6 GPa) and ductility. For these reasons it is relevant to increase the knowledge on the structural evolution and deformation mechanisms involved during wire drawing process, due to their critical applications such as bridges, cranes and tire cord. This paper presents a comparative study of steel wires (0.84%C) at different deformation stages. The product presents a normal behaviour under torsion test, the mentioned test is normally used to corroborate the wire aptitude. The main objective of the study is to increase the knowledge on the structural evolution after cold drawn considering the deformation mechanisms, cementite dissolution, and epsilon carbide precipitation. The microstructural study was carried out applying light and scanning electron microscopy (SEM-EBSD). The structural information was correlated with results of differential thermal analysis (DTA) and FactSage simulation. The structural study verified the presence of curling phenomenon in the wires. The interlaminar spacing (l) and the thickness of cementite lamellae in wires cold drawn from 8 mm up to 2 mm of diameter was determined. Finally, the dynamic strain aging, which is promoted by cementite destabilization and the precipitation of epsilon carbide was studied. Copyright © 2018 VBRI Press.
S. Rajesh; K. Thyagarajan; Vasudeva Reddy Minnam Reddy
Abstract
Zinc Sulfide nanophosphor (ZnS) nanophosphor doped with 2 mol % Dysprosium (Dy) and co-doped with (2 – 6) mol % Manganese (Mn) was successfully prepared by cost-effective chemical co-precipitation method using polyvinylpyrrolidone (PVP) as the capping agent. The effects of dopant and co-dopant ...
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Zinc Sulfide nanophosphor (ZnS) nanophosphor doped with 2 mol % Dysprosium (Dy) and co-doped with (2 – 6) mol % Manganese (Mn) was successfully prepared by cost-effective chemical co-precipitation method using polyvinylpyrrolidone (PVP) as the capping agent. The effects of dopant and co-dopant concentrations on the various properties of ZnS were investigated by various characterizations like Powder X-ray Diffraction (PXRD) studies confirmed the cubic zinc blende structure of ZnS and no impurity peaks corresponding to Dy doping and Co-doped by Mn was observed. Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDAX) confirmed the presence of dopant Dy and co-dopants Mn in the prepared ZnS. Photoluminescence (PL) studies on Dy doped Mn and co-doped ZnS nanophosphor indicated that the emission wavelength 605 nm is tunable in the range of 400–650 nm with the incorporation of doped Dy and Co-doped Mn into ZnS host lattice with the excitation wavelength of 320 nm. Blue color of ZnS doped Dy by enhances to orange color due to co-doped with Mn ions. The chromaticity co-ordinates (CIE) and Correlated color temperature (CCT) of the phosphor were shows enhancement of blue to orange region; hence, it is useful for the fabrication of orange component of WLEDs and display applications. Copyright © 2018 VBRI Press.
Nasrullah Shah; Touseef Rehan; Muhammad Balal Arain; Rabia Tabassum
Abstract
The addition of appropriate additives can change the properties of the polymer matrix. Nanocomposites are useful because of its high aspect ratio. Selection of additives which can make a cheaper and multifunctional material is one of the major issues. ZnO nanoparticles can be used as an additive in preparing ...
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The addition of appropriate additives can change the properties of the polymer matrix. Nanocomposites are useful because of its high aspect ratio. Selection of additives which can make a cheaper and multifunctional material is one of the major issues. ZnO nanoparticles can be used as an additive in preparing biocompatible and biodegradable nanocomposite which would have several analytical and biomedical applications. ZnO nanoparticles are multifunctional materials and in recent years they drawn an increasing attention because of its physical and chemical stability, high catalysis activity, effective antibacterial and bactericide function and intensive UV and IR absorption. Hence considering the above reasons, in the present study the incorporation of different amounts of ZnO powder inside the P oly(acrylonitrile-co-acrylic acid) is done by a low cost physico-mechanical method to prepare polymer nanocomposite for multiple purposes. The as synthesized ZnO based Poly(acrylonitrile-co-acrylic acid) composite sheets were characterized by various analytical techniques such as FTIR, Raman Spectroscopy, SEM, XRD and TGDTA. The analyses indicated the uniform dispersion of ZnO nanoparticles inside the polymer matrix resulted in crystalline structure which resulted in improved thermal stability and low water holding capacity and swelling ratio. The as synthesized nanocomposites were effectively utilized for biological activities. Copyright © 2018 VBRI Press.