Literatura académica sobre el tema "Semi-Crystalline structure"
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Artículos de revistas sobre el tema "Semi-Crystalline structure"
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Hajová, Hana, Richard Pokorný y Juraj Kosek. "Diffusion Transport in Reconstructed Semi-Crystalline Structure of Polyolefins". Macromolecular Symposia 302, n.º 1 (31 de marzo de 2011): 121–28. http://dx.doi.org/10.1002/masy.201000073.
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Moskalewicz, Tomasz, Sławomir Zimowski, Aleksandra Fiołek, Alicja Łukaszczyk, Beata Dubiel y Łukasz Cieniek. "The Effect of the Polymer Structure in Composite Alumina/Polyetheretherketone Coatings on Corrosion Resistance, Micro-mechanical and Tribological Properties of the Ti-6Al-4V Alloy". Journal of Materials Engineering and Performance 29, n.º 3 (26 de septiembre de 2019): 1426–38. http://dx.doi.org/10.1007/s11665-019-04354-y.
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Abstract This paper describes ways of improving the tribological properties of the Ti-6Al-4V titanium alloy at room and elevated temperatures by electrophoretic deposition of Al2O3/PEEK708 composite coatings and post-heat treatment. The microstructure of the coating components and the coatings was examined by scanning and transmission electron microscopy as well as x-ray diffractometry. The influence of cooling rate after heating of the coated alloy on the PEEK structure and coating surface topography was investigated. It was found that slow cooling with a furnace produced a semi-crystalline structure, whereas fast cooling in water generated an amorphous polymer structure. The semi-crystalline coatings exhibited a more developed surface topography than the amorphous ones. The coatings with a semi-crystalline structure revealed higher scratch resistance than the amorphous ones. The corrosion resistance of the uncoated and coated specimens was examined using electrochemical techniques in a 3.5 wt.% NaCl aqueous solution. Both coatings increased the corrosion resistance of the alloy. The friction and wear properties of the coated specimens against an alumina ball in dry sliding contact at room temperature and elevated temperatures of 150 and 260 °C at ball-on-disk were examined. Both amorphous and semi-crystalline coatings increased the wear resistance and decreased the friction coefficient of the titanium alloy at room temperature. In addition, the semi-crystalline coating was also very effective in improving the titanium alloy’s tribological properties at elevated temperatures. The obtained results clearly show that the composite alumina/PEEK coatings are promising for tribological applications in mechanical engineering.
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Kalwik, Aleksandra, Przemyslaw Postawa y Marcin Nabialek. "Analysis of Ageing Processes of Semi-Crystalline Materials". Materiale Plastice 57, n.º 3 (30 de septiembre de 2020): 41–51. http://dx.doi.org/10.37358/mp.20.3.5378.
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The article presents the influence of accelerated UV ageing on the structural properties of selected polymer materials. In this study, 3 types of materials from a group of thermoplastics known as PP30T, PE, POM were used. The test samples were prepared by injection moulding. In turn, an accelerated UV ageing process (600 h) was carried out in the UV Test chamber with fluorescent lamps characterized by a wavelength of 313 nm. Changes in the structure of the tested materials were observed by using an optical microscope. Measurements of gloss on the surface of primary samples that were exposed to UV rays were also taken. In addition, the structure of primary and aged samples was tested by differential scanning calorimetry (DSC). The conducted studies have demonstrated the impact of UV radiation on the changes in the surface layer of tested materials.
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Simões, Ricardo, Júlio C. Viana, Gustavo R. Dias y António M. Cunha. "Mechanical Behavior of the Lamellar Structure in Semi-Crystalline Polymers". Materials Science Forum 730-732 (noviembre de 2012): 1006–11. http://dx.doi.org/10.4028/www.scientific.net/msf.730-732.1006.
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We have employed molecular dynamics simulations to study the behavior of virtual polymeric materials under an applied uniaxial tensile load. Through computer simulations, one can obtain experimentally inaccessible information about phenomena taking place at the molecular and microscopic levels. Not only can the global material response be monitored and characterized along time, but the response of macromolecular chains can be followed independently if desired. The computer-generated materials were created by emulating the step-wise polymerization, resulting in self-avoiding chains in 3D with controlled degree of orientation along a certain axis. These materials represent a simplified model of the lamellar structure of semi-crystalline polymers, being comprised of an amorphous region surrounded by two crystalline lamellar regions. For the simulations, a series of materials were created, varying i) the lamella thickness, ii) the amorphous region thickness, iii) the preferential chain orientation, and iv) the degree of packing of the amorphous region. Simulation results indicate that the lamella thickness has the strongest influence on the mechanical properties of the lamella-amorphous structure, which is in agreement with experimental data. The other morphological parameters also affect the mechanical response, but to a smaller degree. This research follows previous simulation work on the crack formation and propagation phenomena, deformation mechanisms at the nanoscale, and the influence of the loading conditions on the material response. Computer simulations can improve the fundamental understanding about the phenomena responsible for the behavior of polymeric materials, and will eventually lead to the design of knowledge-based materials with improved properties.
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Kim, Man-Ho, Jeong-Mann Doh, Seong Chul Han, Keun Hwa Chae, Byung-Yong Yu, Kyung Tae Hong, Andrew Jackson y Lawrence M. Anovitz. "The pore wall structure of porous semi-crystalline anatase TiO2". Journal of Applied Crystallography 44, n.º 6 (4 de octubre de 2011): 1238–45. http://dx.doi.org/10.1107/s0021889811037447.
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The structure of porous TiO2prepared by electrochemical anodization in a fluoride-containing ethylene glycol electrolyte solution was quantitatively studied using small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS). The cylindrical pores along the coaxial direction were somewhat irregular in shape, were widely distributed in diameter, and seemed to have a broadly pseudo-hexagonal arrangement. The scattering from the pore wall showed a negative deviation from Porod scattering, indicating that the interface between TiO2and the pore was not sharp. A density gradient of around 40–60 Å at the pore wall (i.e.the interface between the pore and the TiO2matrix) was estimated using both constant and semi-sigmoidal interface models. This gradient may be due to the presence of fluorine and carbon partially absorbed by the pore wall from the fluoride-containing electrolyte or to sorbed water molecules on the wall. The neutron contrast-matching point between the TiO2matrix and the pores filled with liquid H2O/D2O mixtures was 51/49%(v/v) H2O/D2O, yielding an estimated mass density of 3.32 g cm−3. The specific surface area of the sample derived from the (U)SANS data was around 939–1003 m2 cm−3(283–302 m2 g−1).
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Prevorsek, D. C. "Structure of semi crystalline fibers from interpretation of anelastic effects". Journal of Polymer Science Part C: Polymer Symposia 32, n.º 1 (8 de marzo de 2007): 343–75. http://dx.doi.org/10.1002/polc.5070320119.
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Filsinger, D. H. y L. K. Frevel. "Computer Automation of Structure-Sensitive Search-Match Algorithm for Powder Diffraction Analysis". Powder Diffraction 1, n.º 1 (marzo de 1986): 22–25. http://dx.doi.org/10.1017/s0885715600011246.
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AbstractThe Semi-manual Structure-sensitive SEARCH-MATCH procedure [Frevel, (1982), Anal. Chem. 54, 691–697] has been automated for the Hewlett-Packard HP 3354 Computer. The software is coded in the interpretive HP LAB BASIC II language. A core file of 1026 selected powder diffraction standards has been compiled covering the common crystalline phases encountered in industry, the ubiquitous crystalline minerals, and prototypes of the more frequently found crystal structures. Solid solutions can be readily identified.
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Lovelace, J. J., K. Narayan, J. K. Chik, H. D. Bellamy, E. H. Snell, U. Lindberg, C. E. Schutt y G. E. O. Borgstahl. "Imaging modulated reflections from a semi-crystalline state of profilin:actin crystals". Journal of Applied Crystallography 37, n.º 2 (17 de marzo de 2004): 327–30. http://dx.doi.org/10.1107/s0021889804001773.
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Modulated protein crystals remainterra incognitafor most crystallographers. While small-molecule crystallographers have successfully wrestled with and conquered this type of structure determination, to date no modulated macromolecular structures have been reported. Profilin:β-actin in a modulated semi-crystalline state presents a challenge of sufficient biological significance to motivate the development of methods for the accurate collection of data on the complex diffraction pattern and, ultimately, the solution of its structure. In the present work, fine φ-sliced data collection was used to resolve the closely spaced satellite reflections from these polymorphic crystals. Image-processing methods were used to visualize these data for comparison with the original precession data. These preliminary data demonstrate the feasibility of using fine φ-slicing to collect accurately the intensities and positions of the main and satellite reflections from these modulated protein crystals.
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Avramova, Nadka. "Amorphous and Semi-Crystalline Nylon-6: Processing and Properties". Engineering Plastics 1, n.º 4 (enero de 1993): 147823919300100. http://dx.doi.org/10.1177/147823919300100403.
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The influence of processing conditions on the structure and properties of nylon-6 are investigated. Amorphous nylon-6 is obtained and its properties are compared with those of semi-crystalline nylon-6. The kinetics of crystallization of nylon-6 depends strongly on the previous thermal prehistory of the melt. The recently observed cumulative character in the structural memory of nylon-6 is successfully applied for obtaining this polymer in a pure amorphous state. It was demonstrated that a critical temperature exists above which the “memory” of this polymer can be erased, and this critical temperature is close to the equilibrium melting temperature T m°. The value of T m ° ≍280°C was evaluated using an independent technique. Melt annealing above this temperature suppresses the crystallization process due to destruction of all crystal nuclei. Amorphous nylon-6 was obtained by ultraquenching of its melt, previously treated at a temperature above T m °, to a temperature well below the glass transition region. The ultraquenched nylon-6 is characterized by amorphous initial structure and improved mechanical properties. The thermal behaviour, crystallization and mechanical properties are investigated by differential scanning calorimetry (DSC), wide angle X ray scattering (WAXS) and mechanical testing. After drawing and annealing, the tensile strength and elasticity modulus of initially amorphous nylon-6 increase three times and the elongation at break decreases by half as compared with conventionally quenched samples. The thermal treatment in vacuum of semi-crystalline nylon-6 affects both the structure and the molecular weight. It is demonstrated that the most important factor for the improvement of mechanical properties is the orientation in the amorphous regions. The lower die initial degree of crystallinity, the better are the orientation and the mechanical properties of nylon-6. The best mechanical properties of initially amorphous nylon-6 are explained by achievement of better orientation of molecules in the amorphous regions.
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Avramova, Nadka. "Amorphous and Semi-Crystalline Nylon-6: Processing and Properties". Polymers and Polymer Composites 1, n.º 4 (enero de 1993): 261–74. http://dx.doi.org/10.1177/096739119300100403.
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The influence of processing conditions on the structure and properties of nylon-6 are investigated. Amorphous nylon-6 is obtained and its properties are compared with those of semi-crystalline nylon-6. The kinetics of crystallization of nylon-6 depends strongly on the previous thermal prehistory of the melt. The recently observed cumulative character in the structural memory of nylon-6 is successfully applied for obtaining this polymer in a pure amorphous state. It was demonstrated that a critical temperature exists above which the “memory” of this polymer can be erased, and this critical temperature is close to the equilibrium melting temperature T m°. The value of T m ° ≍280°C was evaluated using an independent technique. Melt annealing above this temperature suppresses the crystallization process due to destruction of all crystal nuclei. Amorphous nylon-6 was obtained by ultraquenching of its melt, previously treated at a temperature above T m °, to a temperature well below the glass transition region. The ultraquenched nylon-6 is characterized by amorphous initial structure and improved mechanical properties. The thermal behaviour, crystallization and mechanical properties are investigated by differential scanning calorimetry (DSC), wide angle X ray scattering (WAXS) and mechanical testing. After drawing and annealing, the tensile strength and elasticity modulus of initially amorphous nylon-6 increase three times and the elongation at break decreases by half as compared with conventionally quenched samples. The thermal treatment in vacuum of semi-crystalline nylon-6 affects both the structure and the molecular weight. It is demonstrated that the most important factor for the improvement of mechanical properties is the orientation in the amorphous regions. The lower die initial degree of crystallinity, the better are the orientation and the mechanical properties of nylon-6. The best mechanical properties of initially amorphous nylon-6 are explained by achievement of better orientation of molecules in the amorphous regions.
Tesis sobre el tema "Semi-Crystalline structure"
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Huang, Tao 1962. "Nucleation and growth of spherulitic domain structure in semi-crystalline polymer thin films". Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=34737.
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The grained patterns of semi-crystalline polymer thin films are of great scientific and industrial importance. They strongly affect polymer material properties specially the functionality in optical and electronic applications. The formation of grained pattern is the result of the nucleation-growth process. Nucleation and growth and their evolution have received much interest in the physics, materials and polymer science and engineering community. Typically domain growth associated with first order non-equilibrium phase transitions occurs via spinodal decomposition or nucleation and growth. However, the details of nucleation-growth are not well understood. The grain structure of semi-crystalline polymer systems has not been studied so far and was very poorly understood.In this work, systematic experiments have been carried out to elucidate the polymer spherulite growth mechanism, the spatio-temporal evolution of nucleation-growth and grain formation. We take spatial correlation into account and describe both geometrical and topological characteristics of the structural evolution in nucleation and growth. Physical models, computational and direct imaging methods have been developed and integrated for prediction and characterization of the microstructure formation in the semi-crystalline polymer thin films. Novel domain-spatial correlation functions and structure functions are proposed and evaluated with experimental data. Scaling relationships for nucleation-growth are explored with experimental data from both FFT imaging and the domain-spatial correlation function. Advanced grain structure analysis are proposed and evaluated in terms of the topological correlation and the grouping analysis of all the pertinent structural parameters taken together. Computational modeling based on the proposed envelop evolution equation associated with the light intensity equation and free energy equation predicts the nucleation-growth processes and grain patterns of polymer spherulitic structures. These results do not only enhance the understanding of dynamic mechanisms, but also provide reliable predictive techniques to optimize material functionality and process control.
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Hussein, Naji. "Enhancement of the mechanical performance of semi-crystalline polyamides by tailoring the intermolecular interaction in the amorphous phase". Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0140/document.
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L’utilisation du Polyamide 66 dans l’industrie automobile est en forte croissance car il offre à un bon compromis légèreté/propriétés mécaniques pour les applications de structure. A noter que pendant le service d’un véhicule, les pièces en polyamides sont souvent soumises à des sollicitations mécaniques très sévères aboutissant à une dégradation progressive du matériau. Récemment. E. Mourglia-Seignobos (thèse 2009), a montré que l’endommagement du polyamide 66 implique des mécanismes de cavitation et de microcraquelure dans la phase amorphe. Afin d'améliorer la durabilité de ce matériau, nous avons modifié la cohésion de sa phase amorphe via l'introduction de fonction phénolique à forte interactions intermoléculaires. Nous proposons une méthode de préparation de copolyamides bloc, à base du polyamide 66 et des noyaux phénoliques, par extrusion réactive. Nous montrons que, contrairement à la co-polycondensation classique, la structure cristalline de ces copolymères n’a pas été significativement modifiée, surtout à faible taux de PA6HIA. Les propriétés mécaniques et particulièrement la tenue en fatigue de ces copolymères dépassent largement celles du PA66. Les résultats obtenus mettent en évidence l’impact de la cohésion de la phase amorphe sur les propriétés ultimes de polymères semi-cristallins d’une part, et ouvrent la voie vers une meilleure augmentation de la durabilité de ces matériaux via le perfectionnement de leur phase cristalline d’autre partThe use of polyamides in the automotive industry has grown significantly over the last years with the demand to reduce vehicle weight and also to increase fuel efficiency. Polyamide 66 having excellent chemical resistance, mechanical strength and toughness becomes the largest engineering thermoplastic used in automotive components. These latter are often submitted to repeated stress during service and their mechanical properties decline progressively until the failure. E. Mourglia-Seignobos (thesis 2009), pointed out that damage of polyamide 66 involves voids nucleation and growth in the amorphous phase. In order to improve the durability of this material, we tailored the cohesive energy of its amorphous phase by introducing phenolic moieties offering strong intermolecular H-bonds interactions. We proposed a preparation method of block copolyamides containing aliphatic polyamide 66 and phenolic groups (PA6HIA) by reactive extrusion. Microstructural characterizations pointed out that crystalline properties of resulting copolymers are not significantly altered at low PA6HIA content and that reactive extrusion is more appropriate than the in-situ copolymerization for the preparation of these materials. We showed that PA66/6HIA copolyamides having undisturbed crystalline features exhibit superior mechanical performance than the standard PA66, particularly longer lifetime under cyclic loading. The results of this work put in evidence the impact of the amorphous phase on the ultimate properties of semi-crystalline polymers in one hand, and open the way to a better increase of the durability of these materials by improving their crystalline features in another hand
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Simmons, Stephanie. "Influence of processing on the structure and properties of semi-crystalline polymer systems : 1) biodegradable starch/poly(ethylene-vinyl alcohol) blends and 2) polyolefinic thermoplastics". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11379.
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Housseini, Joulia. "Corrélation entre la dynamique moléculaire, le polymorphisme cristallin et les propriétés électroactives des polymères à base de poly(fluorure de vinylidène) pour des applications pyroélectriques et de récupération d'énergie". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0170.
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Les polymères à base de fluorure de vinylidène (VDF) sont des matériaux électroactifs reconnus pour leurs performances fonctionnelles élevées exploitées par les effets piézoélectrique, pyroélectrique et électrocalorique. En plus de ces performances remarquables, leurs propriétés mécaniques, et notamment leur flexibilité, leur permet d’être incorporés dans des dispositifs flexibles conduisant à leur intégration dans une large gamme d'applications telles que les capteurs, le stockage d'énergie, les mémoires imprimées, la réfrigération électrocalorique, et les muscles artificiels. Les propriétés diélectriques des polymères à base de VDF sont fortement influencées par leur architecture macromoléculaire et leur structure semi-cristalline. Par conséquent, comprendre la relation entre la séquence chimique, la cristallinité et les propriétés électroactives est essentiel pour optimiser leurs performances et leur stabilité dans des applications ciblées. La modulation de leur électroactivité est directement associée au développement d’un polymorphisme cristallin, qui peut être modulé par des variations des conditions de traitement. L'objectif central de cette thèse de doctorat est de décrypter davantage les multiples structures semi-cristallines des polymères à base de VDF et de corréler le polymorphisme cristallin avec le comportement électroactif. Dans ce travail, nous avons particulièrement exploré l'intégration du copolymère P(VDF-co-TrFE) dans des dispositifs pyroélectriques, en mettant en évidence l'impact des processus de dépôt et de recuit sur la structure semi-cristalline et les propriétés pyroélectriques finales. Une combinaison de diffraction des rayons X, d’analyse enthalpique différentielle, de spectroscopie diélectrique et de mesures de cycles de polarisation a été utilisée pour optimiser la réponse pyroélectrique finale en fonction des méthodes de traitement des films. Ensuite, nous avons cherché à optimiser les systèmes P(VDF-ter-TrFE-ter-CTFE) utilisés pour la récupération d'énergie ou les applications de refroidissement en rationalisant l'impact des conditions de traitement - en mettant l'accent sur le rôle des solvants de dépôt - sur les propriétés ferroélectriques relaxeurs. Enfin, nous avons exploré l'utilisation de la spectroscopie de résonance magnétique nucléaire à l'état solide pour dévoiler la relation entre la structure macromoléculaire, le polymorphisme cristallin et les propriétés électroactives, ce qui nous permet de fournir une image plus claire de ces systèmes complexes en différenciant trois états différents d'ordonnancement dans ces matériaux : amorphe, rigide-amorphe et cristallin. En résumé, cette étude vise à établir des liens entre l'architecture macromoléculaire des polymères électroactifs et leur structure cristalline en film mince afin d'améliorer leurs fonctionnalités diélectriques pour des applications spécifiquesVinylidene Fluoride (VDF)-based polymers are well-known electroactive materials with their high output functional performance leveraged by the piezoelectric, pyroelectric, and electrocaloric effects. Besides, their outstanding electroactive properties, their ability to be incorporated into flexible devices allow them to be integrated into a broad range of applications such as sensors, energy storage, printed memories, electro caloric refrigeration, artificial muscles devices. The dielectric properties of VDF-based polymers are strongly influenced by their macromolecular architecture and semi-crystalline structure. Consequently, understanding the relationship between chemical sequence, crystallinity and electroactive properties is essential to optimize their performance and stability in targeted applications. Modulation of their electroactivity is directly associated with the development of crystalline polymorphism, which can be refined by variations in processing conditions. The central objective of this Ph.D. thesis is to further decipher the multiple semi-crystalline structures of VDF-based polymers and correlate crystalline polymorphism with electroactive behavior. In this work, we particularly delved into the integration of P(VDF-co-TrFE) copolymer into pyroelectric devices, by highlighting the impact of the casting and annealing processes on the semi-crystalline structure and the final pyroelectric properties. A combination of X-ray scattering, differential scanning calorimetry, dielectric spectroscopy and polarization cycles measurements were used to probe the structural characteristics of P(VDF-co-TrFE) layers as function of the film processing methods, leading to the optimization of the final pyroelectric response. Next, we sought at the optimization of P(VDF-ter-TrFE-ter-CTFE) systems used for energy-harvesting or cooling applications by rationalizing the impact of processing conditions – with a focus on the role of the casting solvents – on the relaxor ferroelectric properties. Finally, we have explored the use of solid state nuclear magnetic resonance spectroscopy to unravel the relationship between macromolecular structure, crystalline polymorphism and electroactive properties, which allows us to provide a clearer picture of these complex systems by differentiating three different states of ordering in these materials: an amorphous, rigid-amorphous and crystalline phases. In summary, this study aims to establish connections between the macromolecular architecture of electroactive polymers and their thin film crystalline structure to enhance their dielectric functionalities for specific applications
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Bargain, François. "Structure semi-cristalline et propriétés d'usage de films de copolymères fluorés électro-actifs : influence de la composition et de la mise en forme". Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLET007.
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Le lien entre la structure semi-cristalline et les propriétés d’usage (mécaniques, diélectriques et électro-actives) de films de copolymères fluorés électro-actifs développés pour des applications en électronique organique imprimée a été étudié. Les matériaux investigués sont des copolymères poly(VDF-co-TrFE) et des terpolymères poly(VDF-ter-TrFE-ter-CTFE) à base de fluorure de vinylidène (VDF), trifluoroéthylène (TrFE) et chlorotrifluoroéthylène (CTFE).Les films de polymères obtenus par évaporation du solvant sont étudiés par diffraction des rayons X (SAXS-WAXS), DSC, FTIR, DMA, spectroscopie diélectrique et cycles de polarisation afin de mettre en évidence l’impact de la composition et de la mise en forme (recuit, polarisation) sur la structure et les propriétés finales du matériau. Nous montrons ainsi qu’au sein des films de copolymères, la phase ferroélectrique (FE) coexiste avec une phase ferroélectrique défective (DFE). La fraction croissante de cette phase DFE avec la teneur en TrFE permet d’expliquer l’évolution des propriétés thermiques dont la transition de Curie. Une transition structurale continue, de la phase DFE vers la phase paraélectrique (PE), en température a été mise en évidence.La teneur en termonomère CTFE influence fortement la structure cristalline et les propriétés électro-actives des films de terpolymères (disparition du caractère ferroélectrique au profit du caractère ferroélectrique relaxeur (RFE)). Nous prouvons pour la première fois l’existence d’une transition structurale continue entre la phase RFE et la phase PE au voisinage de la température ambiante. Cette transition permet d’expliquer les propriétés exacerbées de ces matériaux (constante diélectrique et déformation sous champ électrique). Enfin, des analogies de comportement entre les copolymères et les terpolymères sont discutées, notamment l’évolution des phases cristallines sous champ électrique, afin de mieux comprendre le fonctionnement de ces polymères électro-actifs pour leur futur développement au niveau industrielThe relationship between semi-crystalline structure and properties of use (mechanical, dielectric and electroactive) of fluorinated copolymer films was studied for applications in organic electronics. Investigated materials are poly(VDF-co-TrFE) copolymers and poly(VDF-ter-TrFE-ter-CTFE) terpolymers based on vinylidene fluoride (TrFE), trifluoroethylene (TrFE) and chlorotrifluoroethylene (CTFE). Polymer films, obtained after solvent evaporation, are studied by X-ray diffraction (SAXS-WAXS), DSC, FTIR, DMA, dielectric spectroscopy and polarization cycles in order to highlight the impact of composition and processing (annealing, poling) on structure and final properties of material. We showed that the ferroelectric (FE) phase coexists with the defective ferroelectric (DFE) phase in copolymer films. The increasing fraction of DFE phase with TrFE content allows explaining the evolution of thermal properties. A continuous structural transition, from DFE phase to paraelectric (PE) phase was highlighted. The CTFE termonomer content highly influences the crystalline structure and the electro-actives properties of terpolymer films (loss of ferroelectric behavior in favor of relaxor ferroelectric (RFE) behavior).We proved for the first time the existence of a continuous structural transition between RFE phase and PE phase around room temperature. This transition allows explaining exacerbated properties of these materials (dielectric constant and deformation under electric field).Finally, analogies of behavior between copolymers and terpolymers are discussed, especially the evolution of crystalline phases under electric field, in order to better understand how these electro-active materials work for their future development at industrial level
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Bargain, François. "Structure semi-cristalline et propriétés d'usage de films de copolymères fluorés électro-actifs : influence de la composition et de la mise en forme". Electronic Thesis or Diss., Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLET007.
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Le lien entre la structure semi-cristalline et les propriétés d’usage (mécaniques, diélectriques et électro-actives) de films de copolymères fluorés électro-actifs développés pour des applications en électronique organique imprimée a été étudié. Les matériaux investigués sont des copolymères poly(VDF-co-TrFE) et des terpolymères poly(VDF-ter-TrFE-ter-CTFE) à base de fluorure de vinylidène (VDF), trifluoroéthylène (TrFE) et chlorotrifluoroéthylène (CTFE).Les films de polymères obtenus par évaporation du solvant sont étudiés par diffraction des rayons X (SAXS-WAXS), DSC, FTIR, DMA, spectroscopie diélectrique et cycles de polarisation afin de mettre en évidence l’impact de la composition et de la mise en forme (recuit, polarisation) sur la structure et les propriétés finales du matériau. Nous montrons ainsi qu’au sein des films de copolymères, la phase ferroélectrique (FE) coexiste avec une phase ferroélectrique défective (DFE). La fraction croissante de cette phase DFE avec la teneur en TrFE permet d’expliquer l’évolution des propriétés thermiques dont la transition de Curie. Une transition structurale continue, de la phase DFE vers la phase paraélectrique (PE), en température a été mise en évidence.La teneur en termonomère CTFE influence fortement la structure cristalline et les propriétés électro-actives des films de terpolymères (disparition du caractère ferroélectrique au profit du caractère ferroélectrique relaxeur (RFE)). Nous prouvons pour la première fois l’existence d’une transition structurale continue entre la phase RFE et la phase PE au voisinage de la température ambiante. Cette transition permet d’expliquer les propriétés exacerbées de ces matériaux (constante diélectrique et déformation sous champ électrique). Enfin, des analogies de comportement entre les copolymères et les terpolymères sont discutées, notamment l’évolution des phases cristallines sous champ électrique, afin de mieux comprendre le fonctionnement de ces polymères électro-actifs pour leur futur développement au niveau industrielThe relationship between semi-crystalline structure and properties of use (mechanical, dielectric and electroactive) of fluorinated copolymer films was studied for applications in organic electronics. Investigated materials are poly(VDF-co-TrFE) copolymers and poly(VDF-ter-TrFE-ter-CTFE) terpolymers based on vinylidene fluoride (TrFE), trifluoroethylene (TrFE) and chlorotrifluoroethylene (CTFE). Polymer films, obtained after solvent evaporation, are studied by X-ray diffraction (SAXS-WAXS), DSC, FTIR, DMA, dielectric spectroscopy and polarization cycles in order to highlight the impact of composition and processing (annealing, poling) on structure and final properties of material. We showed that the ferroelectric (FE) phase coexists with the defective ferroelectric (DFE) phase in copolymer films. The increasing fraction of DFE phase with TrFE content allows explaining the evolution of thermal properties. A continuous structural transition, from DFE phase to paraelectric (PE) phase was highlighted. The CTFE termonomer content highly influences the crystalline structure and the electro-actives properties of terpolymer films (loss of ferroelectric behavior in favor of relaxor ferroelectric (RFE) behavior).We proved for the first time the existence of a continuous structural transition between RFE phase and PE phase around room temperature. This transition allows explaining exacerbated properties of these materials (dielectric constant and deformation under electric field).Finally, analogies of behavior between copolymers and terpolymers are discussed, especially the evolution of crystalline phases under electric field, in order to better understand how these electro-active materials work for their future development at industrial level
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Zhou, Hongxia. "Effects of Microcrystallinity on Physical Aging and Environmental Stress Cracking of Poly (ethylene terephthalate) (PET)". See Full Text at OhioLINK ETD Center (Requires Adobe Acrobat Reader for viewing), 2005. http://www.ohiolink.edu/etd/view.cgi?toledo1122315621.
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Dissertation (Ph.D.)--University of Toledo, 2005.Typescript. "A dissertation [submitted] as partial fulfillment of the requirements of the Doctor of Philosophy degree in Engineering." Bibliography: leaves 231-241.
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Odarchenko, Yaroslav. "Tailoring the mesoscopic structure and orientation of semicrystalline and liquid-crystalline polymers : from 1D- to 2D-confinement". Phd thesis, Université de Haute Alsace - Mulhouse, 2012. http://tel.archives-ouvertes.fr/tel-01062091.
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Controlling the micro-structure of organic materials is crucial for a variety of practical applications such as photonics, biomedicine or the rapidly growing field of organic electronics. Recent studies have shown a possibility of tailoring the polymer structure on the nanoscale using supramolecular self-assembly under spatial confinement. Despite extensive studies already performed in this field, many questions remain open. In particular, it will be important to understand how different structure formation processes such as crystallization, LC-phase formation, microphase separation, and others occur under confinement. In the present work, we address the effect of 1D- and 2D-confinement on the structure formation for a variety of systems including segmented poly(ether-ester-amide) (PEEA) copolymers, main-chain liquid-crystalline (LC) polymers belonging to the family of poly(di-n-alkylsiloxane)s and liquid-crystalline/semicrystalline block copolymers formed through complexation of poly (2-vinylpyridine-b-ethylene oxide) (P2VP-PEO) with a wedge-shaped ligand, 4'-(3'',4'',5''-tris(octyloxy) benzamido) propanoic acid. In order to reveal the morphological diversity of the studied systems under confinement, the work was carried out on bulk materials and on thin films employing a battery of experimental methods. The main experimental techniques operational in direct and reciprocal space applied in my work are described in chapter 2. [...]
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Gref, Ruxandra. "Fractionnement par pervaporation de mélanges liquides hydro-organiques partiellement miscibles : mise en évidence du rôle de la structure cristalline des membranes denses sur leurs propriétés de transport". Vandoeuvre-les-Nancy, INPL, 1991. http://docnum.univ-lorraine.fr/public/INPL_T_1991_GREF_R.pdf.
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Nous avons étudié les particularités que manifestent, en pervaporation, les mélanges binaires dont les deux constituants ne sont pas miscibles en toute proportion. Selon la nature des interactions qui s'exercent à l'intérieur du système examiné, nous avons distingué un comportement idéal auquel s'opposent quelques cas particuliers. Nous approfondissons l'étude en choisissant une membrane idéale (acétate de cellulose) et une membrane au comportement particulier (alcool polyvinylique), parmi celles qui se rapprochent le plus des matériaux utilisés à l'échelle industrielle en pervaporation. Nous montrons que l'acétate de cellulose gonfle de manière identique dans deux phases liquides en équilibre thermodynamique. La polarisation de concentration en phase liquide est l'unique raison pour laquelle les flux partiels pourraient être différents en pervaporation. L'alcool polyvinylique est, lui, un exemple typique de matériau semicristallin. Nous avons distingué trois états différents du liquide absorbe, dont les proportions respectives dépendent de la cristallinité du polymère. Apres avoir identifié l'influence de la structure fine (cristalline) sur plusieurs autres de ses propriétés, nous avons étudié la conséquence de l'absorption d'eau sur la mobilité de ses chaines. Le modèle qualitatif élaboré à partir de l'ensemble des données permet de mieux comprendre les propriétés de perméation et de gonflement dans deux phases en équilibre thermodynamique. Finalement, nous établissons un modèle quantitatif pour la pervaporation à travers des membranes semicristallines en alcool polyvinylique. Il résulte de cette étude que l'état de l'eau une fois absorbée par un polymère hydrophile détermine le comportement de ce dernier lorsqu'il est utilisé sous forme de membrane pour traiter, par pervaporation, un mélange hydro-organique à miscibilité limitée. Nous avons souligné le rôle primordial de la cristallinité des membranes en alcool polyvinylique sur leur perméabilité en pervaporation vis-à-vis de l’eau, ainsi que des alcools étudiés (éthanol, 1-butanol et 1-octanol). Les cristallites peuvent être assimilées à des centres de réticulation multichaîne ; elles réduisent la possibilité de gonflementWe have studied the pervaporation properties of different liquid mixtures presenting a miscibility gap. Depending on inner polymer interactions, we defined an “ideal” and a particular bahaviour, and we chose to focus on one membrane of each category : Cellulose Acetate (AC) and Poly(vinyl Alcohol) (PVA), among those widely used in industry. We show that AC swells the same way in both phases in thermodynamic equilibrium, whereas PVA does not. Concentration polarization is the only mean to specifically modify one of the partial fluxes. PVA is a typical semicrystalline polymer, whose structure governs the proportions of the three possible states of soaked water. After a review of the properties ruled by the amount of crystallites in the polymer, we have build a qualitative model devoted to the permeation and swelling properties in two phases in a steady thermodynamic state. We then came to a quantitative model of the pervaporation process using PVA membranes. The result of this study is the fact that soacked water of an absorbent polymer defines its behavior when used as a membrane to pervaporate a hydro-organic mixture
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Kumar, Avinesh Avi. "Charge transport in semi-crystalline poly(3-hexylthiophene) (P3HT) structures". Thesis, Queen Mary, University of London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538659.
Texto completoLibros sobre el tema "Semi-Crystalline structure"
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Brunson, Kevin Michael. Characterization of semi-insulating polycrystalline silicon: The influence of the structural properties of SIPOS films on the electrical properties of their interfaces with crystalline silicon. Bradford, 1987.
Buscar texto completoCapítulos de libros sobre el tema "Semi-Crystalline structure"
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Michler, G. H. y I. Naumann. "INFLUENCE OP MOLECULAR STRUCTURE ON THE MORPHOLOGY OF SEMI-CRYSTALLINE POLYMERS". En Morphology of Polymers, editado por Blahoslav Sedláček, 329–36. Berlin, Boston: De Gruyter, 1986. http://dx.doi.org/10.1515/9783110858150-026.
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Trotignon, J. P., J. Verdu y R. Roques. "THE ROLE OF THE SKIN-CORE STRUCTURE IN THE AGEING OF SEMI-CRYSTALLINE POLYMERS". En Morphology of Polymers, editado por Blahoslav Sedláček, 297–302. Berlin, Boston: De Gruyter, 1986. http://dx.doi.org/10.1515/9783110858150-022.
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Zhang, Le, Bo Yin, Robert Fleischhauer y Michael Kaliske. "A Temperature-Dependent Viscoelastic Approach to the Constitutive Behavior of Semi-Crystalline Thermoplastics at Finite Deformations". En Creep in Structures VI, 321–34. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-39070-8_19.
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Tonelli, A. E., M. A. Gomez, Hajime Tanaka y M. H. Cozine. "Solid State 13C NMR Studies of the Structures, Conformations, and Dynamics of Semi-Crystalline Polymers". En Solid State NMR of Polymers, 81–105. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4899-2474-2_4.
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Marius, Arghirescu. "A Preonic Model of Quarks and Particles, Based on a Cold Genesis Theory". En Redefining Standard Model Particle Physics [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.109123.
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The theoretic model explains the generating of heavy quarks and of heavy particles using the known quark s(strange) and two semi-light quarks: λ±(435 MeV) and v±(∼574 MeV) resulting from a cold genesis theory1 of astro-particles’ forming, (CGT), the masses of the quarks c• (charm) and b• (bottom) of the Standard Model but also the values used by de Souza: c = 1.7 GeV and b = 5 GeV, being re-obtained as tri-quark clusters in the form: [(qq¯)q]], by a simple de-excitation reaction, with the emission of a preonic boson obtained in CGT: z0 = 34me, respective: z2 = 4z0 and zμ = 6z0- for the quarks b• and b. A similar de-excitation reaction, with emission of a preonic boson zk = n⋅z0, (n = 1÷7), representing less than 2.7% from the particle’s mass, explains the experimentally obtained masses of heavy baryons and mesons and of some multi-quark particles, with discrepancy <1% generally. The heavy current quarks result by lighter current quarks with quasi-crystalline internal structure, with trigonal/hexagonal symmetry of preonic kernels of two preonic bosons: z2 = 4z0; zπ = 7z0, the top-quark resulting as: t = 17(bb¯) + b = (7x5)⋅m(b), with a kernel of regular hexagonal polyhedron form, given by kernels of b-quarks. The model is compatible with the generation model and explains the quarks pairs forming from relativist e−- e+ jets.
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Somashekar, R. "Crystal size and distortion parameters in fibres using Wide-Angle X-ray Scattering (WAXS)". En Defect and Microstructure Analysis by Diffraction, 728–54. Oxford University PressOxford, 2000. http://dx.doi.org/10.1093/oso/9780198501893.003.0030.
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Abstract Crystal size and paracrystalline disorder of the lattice, which exist in polymer crystals, contribute to the width of the diffraction peaks. Methods have been proposed for obtaining both quantities from the intensity profile (Hosemann and Bagchi, 1962; Guinier, 1963; Vainshtein, 1966). An excellent review of Fourier methods and integral breadth methods is given by Klug and Alexander (1974). The treatments used to estimate crystal size and distortion parameters are based on the Fourier analysis of line profiles (Warren and Averbach, 1952) or on variance analysis (Wilson, 1962b, 1963, 1968; Langford, 1965, 1968). A comparison of these two methods has been given by Balzar and Ledbetter (1993a). In fact, size-strain analysis in the case of high temperature superconductors has been carried out using these methods (Balzar, 1992; Petersen et al.,1992). Fourier methods that can be used with the profile of a single reflection have been proposed (Gangulee, 1974; Mignot and Rondot, 1975; Zocchi, 1980; Nandi et al.,1984), but these again rely heavily on low order coefficients. The integral breadth methods (Ramarao and Anantharaman, 1965; Nandi and Sen Gupta, 1978; de Keijser et al.,1982) are based on the assumption that the Cauchy function determines size and that the Gaussian function gives strain. The most widely used method of de Keijser et al.(1982) gives size and strain parameters from Cauchy and Gaussian parts of the Voigt function. It has been pointed out by Balzar and Ledbetter (1993b) that the Warren-Averbach method gives surface-weighted domain sizes and a mean square strain averaged over the same distance perpendicular to the diffracting planes, whereas integral breadth gives volume-weighted domain sizes and an upper limit of strain. Several attempts have also been made to estimate crystal size distribution using the statistical approximation method (Benedetti et al.,1988; Bonetto et al.,1990; Nicolae and Emil, 1990; Espinat et al.,1993). The extent of amorphous scattering in polymer fibres has been estimated by Narten et al.(1991) casting doubts on the accuracy of existing methods of crystal size determinations. Murthy and Minor (1990) and Dokter et al.(1994, 1995) have given general procedures for evaluating amorphous scattering from X-ray diffraction scans of semi-crystalline polymers. Recently, Lee et al.(1995) have estabilished the one-to-one relationship between the structure and property of fibres using wide-angle X-ray scattering studies.
Actas de conferencias sobre el tema "Semi-Crystalline structure"
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Zhao, Y. "The structure of electrical trees in semi-crystalline polymers". En Eighth International Conference on Dielectric Materials, Measurements and Applications. IEE, 2000. http://dx.doi.org/10.1049/cp:20000525.
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Zhang, G., H. Liao, C. Coddet, H. Yu, S. G. Mhaisalkar, V. Ji y W. Huang. "Influence of Annealing Condition on Crystallization Behavior and Mechanical Properties of Thermal Sprayed PEEK Coating". En ITSC2005, editado por E. Lugscheider. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2005. http://dx.doi.org/10.31399/asm.cp.itsc2005p0732.
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Abstract Amorphous PEEK coating was prepared on Al substrate, employing flame spraying technology. The amorphous coating was subjected to annealing treatments under different conditions. Both differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) analysis revealed that the isothermally treated coating exhibited semi-crystalline structure. Coexistence of double crystal entities in semi-crystalline PEEK coating was deduced from the results obtained by DSC and WAXD measurements. Annealing temperature and holding time under this temperature affect the morphology of the minor crystal entity which is metastable. The mechanical properties of the isothermally treated coating were investigated considering coating microhardness and friction and wear properties. The variations of the coating mechanical properties were correlated with the modifications in the coating structure induced by the different annealing conditions.
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Li, Shuangshan, Mathew Wynn y Navid Zobeiry. "A Machine Learning Framework for In-Situ Microstructural and Kinetics Analysis of Thermoplastic Composites While Processing Under a Polarized Microscope". En ASME 2023 Aerospace Structures, Structural Dynamics, and Materials Conference. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/ssdm2023-105758.
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Abstract There has been a significant increase in thermoplastic composite applications in aerospace in recent years. Semi-crystalline thermoplastics like polyetheretherketone (PEEK) nucleate and grow crystalline structures called spherulites. Addition of carbon fibers forms a crystal structure called transcrystallinity. Processing parameters such as thermal uniformity, dwell time, and temperature history influence crystallinity and crystal morphology in thermoplastic composites. To investigate crystal morphology, neat PEEK and PEEK-carbon fiber composite samples are melted and cooled down while observed under a polarizing light microscope with a heating stage. A classification machine learning model based on the YOLOv3 algorithm is developed and applied to microscopy images to determine spherulite size and count in real-time. A segmentation model based on the U-Net algorithm is used to separate spherulites that have grown and impinged. The impingement of these crystal structures creates boundaries that are difficult to detect in the micrograph. The U-Net model is also used to identify transcrystalline regions that nucleate from carbon fibers. The use of these models in situ provides a unique real-time perspective of the kinetics of different crystals that form in varying processing parameters, part geometries, and reinforcement types.
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Zhang, G., H. Liao, M. Cherigui y C. Coddet. "Effect of Substrate Surface Topography and Temperature on Millimeter and Micrometer Sized Splat Formation and on Thermal Contact Resistance". En ITSC2006, editado por B. R. Marple, M. M. Hyland, Y. C. Lau, R. S. Lima y J. Voyer. ASM International, 2006. http://dx.doi.org/10.31399/asm.cp.itsc2006p0923.
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Abstract Flame sprayed PEEK (poly-ether-ether-ketone) coatings, with an amorphous structure, were subjected to isothermal treatments with annealing temperatures from 180 to 300 °C and holding time from 1 to 30 min. The coating structures were studied by means of DSC (Differential Scanning Calorimetry) and XRD (X-Ray Diffraction) analyses. All annealed coatings exhibit semi-crystalline structures. Coexistence of thick and thin lamellae in the spherulites of annealed coatings can be deduced from the analysis results. The Knoop hardness and the interfacial adhesion of the coatings were examined. The annealed coatings exhibit higher hardness than the amorphous ones. The formation of the thick lamellae is the determinant factor for improving the coating hardness. However, the annealed coatings exhibit a weak adherence to the substrate. Some fissures or spherical porosities could be observed, in certain zones, on the coating/substrate interface. The formation of these fissures and porosities could be ascribed to the coating residual stress and the big volume contraction during the crystallisation that occurred under the annealing condition.
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Özten, Almila, Fatih Sargın, Kürşat Kanbur, Alperen Kızılöz y Ahmet Türk. "Investigation of Triton X-100 Use in PVA Nanofiber Production". En 6th International Students Science Congress. Izmir International Guest Student Association, 2022. http://dx.doi.org/10.52460/issc.2022.044.
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Polyvinylalcohol (PVA) is a hydrophilic, non-toxic, and biocompatible semi-crystalline biomaterial. Today, PVA nanofibers are widely used in the field of biomaterials, as they provide high surface area and a favorable environment for the growth of cells. PVA nanofibers are used in the construction or repair of scaffold types for tissue engineering applications, thanks to positive effect of their three-dimensional structure on cell proliferation and growth. In addition, the use of PVA nanofiber structures in many areas such as drug release, wound dressing, filters and soft tissue applications is becoming widespread. The electrospinning method, which is frequently preferred in the production of polymer nanofibers, draws attention with its low cost and easy application. In the electrospinning method, nanofiber structure is formed by applying high voltage to the polymer solution prepared at a predetermined rate, and nanofiber mat production is carried out by depositing it in a collector. However, structural problems such as bead structure encountered in nanofiber mat production prevent homogeneous nanofiber formation. Various surface agents are used in nanofiber mats to obtain a homogeneous fiber structure, to prevent defects in nanofibers and as a result to increase the mechanical properties of PVA nanofibers. In this study, it is aimed to determine the effect of Triton X-100 surface agent that used in the production of PVA nanofibers. For this purpose, firstly, the rheological effect of Triton X-100 surface agent on nanofiber properties was determined. Then, the effect on the morphological properties of nanofibers produced with Triton X-100 surface agent was investigated. The results revealed that varying Triton X-100 amounts cause changes in the nanofiber structure.
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Li, Chang-Jiu, Guan-Jun Yang y Cheng-Xin Li. "Development of the Particle Interface Bonding in Thermal Spray Coatings for Expanding High Performance Applications". En ITSC 2012, editado por R. S. Lima, A. Agarwal, M. M. Hyland, Y. C. Lau, C. J. Li, A. McDonald y F. L. Toma. ASM International, 2012. http://dx.doi.org/10.31399/asm.cp.itsc2012p0047.
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Abstract Thermally sprayed coatings are formed through the successive impact of molten droplets and/or semi-molten particles followed by flattening, rapid cooling, and solidification. Individual droplets flatten to form splats of several micrometers in thickness upon impact and result in the formation of a coating that has a lamellar structure with limited interface bonding. The inclusion of semi-molten particles in the coating modifies its microstructure. The bonding between particles dominates coating properties and performance. This review paper examines the bonding formation at the interface between thin lamellae in the coating. The effect of spray parameters on the bonding ratio is presented to reveal the main droplet parameters controlling bonding formation. It is shown that spray particle temperature dominates the bonding formation more than particle velocity. Significant increases in ceramic particle temperature are not possible due to the inherent characteristics of thermal spray processing; therefore, the bonding ratio is limited to a maximum of about 32%. On the other hand, it was found that through controlling the surface temperature of coating prior to molten droplet impact, the bonding at the lamellar interface can be significantly increased. Consequently, with the proper selection of deposition conditions and control of surface temperature, the bonding ratio of ceramic deposits can be altered from a maximum of 32% for a conventional deposit to the maximum of 100%. Such wide adjustability of lamellar bonding extends the applicability of plasma spray coatings to applications requiring different microstructures and properties. Moreover, this bonding control makes it possible to fabricate porous surfaces and structures through the deposit of surface-molten particles, to deposit high temperature abradable ceramic coatings, and to form super-hydrophobic surfaces. Furthermore, the ability to deposit coatings with complete interface bonding allows crystalline structure control of individual splats through epitaxial grain growth.
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Kalia, Karun y Amir Ameli. "Interfacial Bond Strength of Various Rigid/Soft Multi-Materials Printed via Fused Filament Fabrication Process". En ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/smasis2020-2298.
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Abstract Layered multi-materials of dissimilar polymers and their nanocomposites offer new opportunities as smart materials and structures. A critical aspect of such structures is the quality of interlayer adhesion between dissimilar polymer matrices. This work reports the development of asymmetric double cantilever beam (ADCB) specimens of dissimilar polymers and its use in the analysis and understanding of their interlayer adhesion in 3D-printed rigid/soft interfaces. Acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polylactic acid (PLA) were chosen as the rigid polymers and combined with thermoplastic polyurethane (TPU) as the soft component. 3D-printed ADCB specimens were loaded under opening mode, until fracture, to obtain the load-displacement data and the fracture surfaces were analyzed using optical microscopy. ABS/TPU/ABS and PC/TPU/PC material combinations resulted in a more stable crack growth with a high peak load indicating a relatively good interfacial adhesion. The high nozzle temperatures of ABS and PC and their amorphous nature contributed to a good layer-to-layer fusion during 3D printing. However, PLA/TPU/PLA specimens exhibited an unstable crack growth behavior with a pure adhesive failure mode and a significantly lower peak load. This poor interfacial bond strength was correlated to the relatively low nozzle temperature of PLA and its semi-crystalline structure. The maximum loads in ABS/TPU/ABS and PC/TPU/PC specimens were found to be ∼2.5 times greater than that of PLA/TPU/PLA ones. The method provides a valuable tool in quantifying interlayer adhesion quality in printed dissimilar polymers and their functional nanocomposites.
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WYNN, MATHEW, KUAN-TING CHEN y NAVID ZOBEIRY. "CHARACTERIZING THERMAL DEGRADATION IN SEMI-CRYSTALLINE THERMOPLASTIC COMPOSITES". En Proceedings for the American Society for Composites-Thirty Eighth Technical Conference. Destech Publications, Inc., 2023. http://dx.doi.org/10.12783/asc38/36599.
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Semi-crystalline thermoplastic composites, such as carbon fiber-reinforced polyetheretherketone (PEEK) and polyetherketoneketone (PEKK), are processed and consolidated while melted at high temperatures. During cool-down, polymer chains fold into lamellar structures at the nanoscale to form crystalline morphology. These lamellar structures radiate from a nucleus, creating spherulitic structures in bulk polymers, and transcrystallinity in fiber reinforced polymers. A certain amount of thermal degradation occurs when the thermoplastic matrix is melted, and the amount of degradation is a factor of several parameters such as melting temperature, time at melt, and whether the material is processed in an inert environment such as nitrogen. One form of degradation that occurs in the matrix is cross-linking and oxidation. In this case, the polymer chain breaks and new bonds form between chains or within the chain. Moreover, thermal degradation affects crystallization, the lamellar thickness and spacing, and overall degree of crystallinity. The spacing between lamellar structures can be measured through Small Angle X-ray Scattering (SAXS) at nanoscale, while the degree of crystallinity can be found using Wide Angle X-ray Scattering (WAXS). To study thermal degradation, the effect of melting temperature, environmental condition, and reprocessing was investigated on samples of neat PEEK, as well as carbon-fiber PEKK prepreg. Additionally, these samples were thermally cycled multiple times, and repeats were performed for each condition. Degree of crystallinity, spacing, and lamellar thickness were measured using an x-ray scattering system. To study underlying physics and correlations, a probabilistic Machine Learning (ML) framework was used for regression. Using this approach, different thermal degradation mechanisms for neat resin and prepreg samples were demonstrated at the nanoscale. The differences were explained in terms of crystallinity and nucleation around fibers in prepreg. This framework provides a unique holistic understanding of crystal formation and degradation, which affects the reprocessability and end-part properties of semicrystalline thermoplastic composites.
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Fayyad, Eman, Aboubakr Abdullah, Mohamed Hassan, Abdul Rasheed Pathath, Khaled Mahmoud, George Jarjoura y Zoheir Farhat. "Novel Electroless Deposited Corrosion – Resistant and Anti-Bacterial NiP–TiNi Nanocomposite Coatings". En Qatar University Annual Research Forum & Exhibition. Qatar University Press, 2020. http://dx.doi.org/10.29117/quarfe.2020.0009.
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From acidic NiP electroless bath, the co-deposition of TiNi nanoparticles in the NiP matrix to form novel NiP-TiNi nanocomposite coatings (NCCs) on top of API X100 carbon steel using several concentrations of TiNi nanoparticles (0.2, 0.4 and 0.8 g L-1 in the bath) is successfully achieved. The influence of the TiNi nanoparticles on the composition, deposition rate, thickness, and morphology of the NiP coating are investigated before and after annealing at 400 oC. The addition of TiNi nanoparticles into the NiP matrix led to the transform of the amorphous structure of the as-plated NiP into a semi-crystalline one. The microhardness of the composite coating significantly enhances with increasing TiNi concentration up to 0.4 g L-1 and further improvement takes place after heat treatment. The electrochemical impedance spectroscopy (EIS) and the colony counting method are carried out to assess the corrosion protection and antibacterial properties, respectively, of the as-deposited and the annealed coatings. The results demonstrate that there is an optimum concentration for the addition of TiNi (0.4 g L-1), which offers the composite coating with the highest corrosion protection that reaches to about 98 %. Below and beyond this concentration as well as after heat treatment, the improvement in the corrosion protection of the composite coatings slightly decreases. Besides, the NiP–TiNi NCCs have effective antibacterial properties as it decreased the cell viability of Escherichia coli from 100 to 19%.
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Pramod, K. y Ramesh Babu Gangineni. "Structural phase study in un-patterned & patterned PVDF semi-crystalline films". En SOLID STATE PHYSICS: Proceedings of the 58th DAE Solid State Physics Symposium 2013. AIP Publishing LLC, 2014. http://dx.doi.org/10.1063/1.4872845.
Texto completoInformes sobre el tema "Semi-Crystalline structure"
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Pisani, William, Dane Wedgeworth, Michael Roth, John Newman y Manoj Shukla. Exploration of two polymer nanocomposite structure-property relationships facilitated by molecular dynamics simulation and multiscale modeling. Engineer Research and Development Center (U.S.), marzo de 2023. http://dx.doi.org/10.21079/11681/46713.
Texto completoResumen
Polyamide 6 (PA6) is a semi-crystalline thermoplastic used in many engineering applications due to good strength, stiffness, mechanical damping, wear/abrasion resistance, and excellent performance-to-cost ratio. In this report, two structure-property relationships were explored. First, carbon nanotubes (CNT) and graphene (G) were used as reinforcement molecules in simulated and experimentally prepared PA6 matrices to improve the overall mechanical properties. Molecular dynamics (MD) simulations with INTERFACE and reactive INTERFACE force fields (IFF and IFF-R) were used to predict bulk and Young's moduli of amorphous PA6-CNT/G nanocomposites as a function of CNT/G loading. The predicted values of Young's modulus agree moderately well with the experimental values. Second, the effect of crystallinity and crystal form (α/γ) on mechanical properties of semi-crystalline PA6 was investigated via a multiscale simulation approach. The National Aeronautics and Space Administration, Glenn Research Center's micromechanics software was used to facilitate the multiscale modeling. The inputs to the multiscale model were the elastic moduli of amorphous PA6 as predicted via MD and calculated stiffness matrices from the literature of the PA6 α and γ crystal forms. The predicted Young's and shear moduli compared well with experiment.