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Cicek, H. "Computer simulation of melt spinning." Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235356.
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Golzar, Mohammad. "Melt Spinning of the Fine PEEK Filaments." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1101380771578-37580.
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The production of fine filaments using the melt spinning process needs considerable effort. A thermoplastic melt is stretched from the spinneret under a constant take-up speed. The high performance thermoplastic PEEK is solidified in the melt spinning process in a small distance and short time. Therefore, the fine PEEK filaments in the fibre formation zone underwent a high deformation and cooling rate. To make the melt spinning process stable and to produce the fine PEEK filaments, material properties and material behaviour are examined using on-line and off-line measurements. The fibre speed measured using Laser Doppler Anemometry and simultaneous temperature measured using infrared thermography enable both the strain rate and consequently the apparent extensional viscosity to be estimated. This provides the apparent extensional viscosity over the spinning line, which can itself show the structural development of PEEK fibres in the fibre formation zone, i.e. necking and solidification phenomena. The one-dimensional fibre formation model must include both procedural and material parameters. The heat transfer coefficient was estimated using the filament temperature measurement and showed a relatively high contribution of radiation and free convection in comparison to forced convection near the spinneret. The improved model of PEEK fibre formation gave a good agreement to both temperature and speed measurements, and also confirmed the high deformation rate effect on the extensional viscosity, which could be simulated with a properly generalised Newtonian constitutive equation. The end properties of the fibres, such as as-spun filament fineness, orientation (expressed using total birefringence) and total crystallisation (examined using DSC) are investigated in relation to different spinning conditions, i.e. take-up speed, throughput and the draw down ratio. The tensile test diagram results, measuring phenomena such as the elongation at break, tenacity, and the Young modulus of elasticity are also analysed in order to complete the correlation of the above-mentioned spinning conditions to the structural properties of as-spun fine PEEK filaments. The melt spinning of fine PEEK fibres under different spinning conditions is examined with the purpose of finding the optimum take-up speed and throughputs. Other spinning conditions, such as the temperature of melt processing, and the arrangement and diameter of the spinneret holes, are changed in order to make the process more stable. The recommendations for further study can be used to further examine some aspects of this work; however, this work presents a new concept for fine PEEK melt spinning supported by spinnability examinations under different spinning conditions and the improved model of fibre formation, which is also relevant for typical industrial processing applications.
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Su, Yang. "Theoretical studies of hollow fiber spinning /." Connect to Online Resource-OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1180971638.
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Dissertation (Ph.D.)--University of Toledo, 2007.Typescript. "Submitted as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Engineering." Bibliography: leaves 200-218.
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Jia, Jun. "Melt spinning of continuous filaments by cold air attenuation." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37276.
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Traditionally ultrafine fibers below 1 dpf are produced by extrusion followed by mechanical drawing. A modified melt spinning apparatus with high-speed air nozzle was designed and fabricated to produce continuous polypropylene filaments by cold air drawing only. With this setup, the fiber is quenched and simultaneously attenuated by a symmetric cold air jet. Since the formation of fiber structure is highly dependent on the processing conditions, the new process will provide a unique operation window to study fiber attenuation and structural formation under high-speed cold air drawing. Based on computational fluid dynamics simulation results, a parametric study was carried out under different process conditions which include processing temperature, air velocity and polymer volume flow rate. Effects of changes in processing variables on the fiber diameter, molecular orientation, crystallinity, tensile strength and other properties were studied. Furthermore, a theoretical model was developed to analyze the non-isothermal fiber attenuation mechanisms. The new knowledge obtained in this study would likely yield a new process for producing innovative fiber products.
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Grove, Dale A. III. "Rheology and evolution of order in melt spinning." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/11112.
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Agarwal, Uday S. "Orientation and crystallization in melt-spinning of poly(ethylene terephthalate) based compositions." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/9975.
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Desai, Dipen. "Solid-state plasticizers for melt extrusion /." View online ; access limited to URI, 2007. http://0-digitalcommons.uri.edu.helin.uri.edu/dissertations/AAI3276980.
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Lyons, Jason Michael Ko Frank K. "Melt-electrospinning of thermoplastic polymers : an experimental and theoretical analysis /." Philadelphia, Pa. : Drexel University, 2004. http://dspace.library.drexel.edu/handle/1860/367.
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Feitosa, Francisco Riccelly P. "Obtenção e evolução da fase icosaedral quasicristalina em ligas Al-Cu-Fe e Al-Cu-Fe-B por Melt-Spinnin." Universidade Federal da Paraíba, 2009. http://tede.biblioteca.ufpb.br:8080/handle/tede/5349.
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Melt spinnng processing is one of the most common processes to obtaining quasicrystaline structures. This is because of the fast cooling rate it imposes on the system, favoring such type of structure. This work deals with the production of quasycristaline phases (Al60Cu27,5Fe12,5 e Al57Cu27,5Fe12,5B3) via melt-spinning. The alloys were initially cast via induction melting under atmospheric air, with the designed chemical composition of the quasicrystals. Hence, the ribbons were produce by melt-spinning were characterized by means of x-ray diffraction and scanning electron microscopy. The results indicate that the icosahedral ψ - Al65Cu20Fe15 phase formed in both types of starting compositions. It seams that the boron contributes to stabilize the icosahedral phase.
O processo melt-spinning por imprimir altas taxas de resfriamento, é um dos principais meios para a obtenção de ligas com estrutura quasicristalinas, sendo o primeiro método utilizado para produzir materiais quasicristalinos. Neste trabalho utilizou-se este processo para a elaboração das ligas quasicristalinas Al(60-x)Cu25Fe15Bx, Al(60-x)Cu27,5Fe12,5Bx e Al(65-x)Cu20Fe15Bx (x=0 e x=3%at de boro). As ligas foram previamente fabricadas, por fusão, em atmosfera de argônio, em forno à indução, para em seguida serem submetidas ao processo melt-spinning , onde se obteve o material na forma de fita. As amostras foram caracterizadas por difração de raios-x e microscopia eletrônica de varredura. Os resultados indicaram a formação da fase icosaedral ψ - Al65Cu20Fe15 nas composições estudadas e uma provável contribuição do boro na produção dessa fase icosaedral
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Dorsey, Kyra. "Deformation and evolution of morphology in meltblown filaments." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/11787.
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Golzar, Mohammad. "Melt spinning of fine PEEK filaments Schmelzspinnen von feinen PEEK Filamenten /." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=973384654.
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Gillen, A. G. "Rapid solidification of nickel-aluminium alloys by the melt-spinning process." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.353075.
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Manvi, Pavan Kumar [Verfasser]. "Melt spinning of carbon dioxide based thermoplastic polyurethane / Pavan Kumar Manvi." Aachen : Shaker, 2018. http://d-nb.info/1188548069/34.
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Reddy, Srinath. "Structure and properties of melt spun poly(4-methyl-1-pentene) fibers." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/10204.
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Santamarta, Martínez Rubén. "Caracterización de aleaciones base Ni-Ti producidas por solidificación rápida (melt-spinning)." Doctoral thesis, Universitat de les Illes Balears, 2002. http://hdl.handle.net/10803/9432.
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En este trabajo se ha caracterizado el efecto memoria de forma y la estabilidad térmica de la transformación martensítica ante varios tratamientos térmicos en varias aleaciones base Ni-Ti fabricadas mediante melt-spinning, un método de solidificación rápida de reciente aplicación en aleaciones con memoria de forma. Las aleaciones estudiadas pertenecen al sistema Ni-Ti, con eventuales adiciones de Cu, Hf o Zr, y han sido caracterizadas mediante varias técnicas experimentales, entre los que cabe destacar el DSC, la máquina de ensayos, el ciclado termomecánico, la difracción de rayos X, y la microscopía electrónica de transmisión. En primer lugar se han determinado las secuencias de transformación de las aleaciones, así como los parámetros de red de las fases que intervienen en la transformación. Asimismo, la microestructura inicial de las cintas fabricadas mediante melt-spinning es rica en defectos (especialmente dislocaciones y pequeños precipitados) y el tamaño de grano es significativamente más pequeño que los observados en materiales fabricados mediante métodos convencionales.
Cabe destacar que la transformación martensítica en la aleación equiatómica es la que muestra una mayor estabilidad térmica ante tratamientos térmicos severos a 500 ºC, seguida de las aleaciones con Cu, con un comportamiento intermedio, y de las composiciones con Hf y Zr, las cuales presentan la menor estabilidad térmica. A pesar de ser éstas últimas las únicas composiciones de las caracterizadas que transforman a temperaturas considerablemente por encima de la temperatura ambiente, la baja estabilidad térmica de estas últimas se manifiesta incluso con tratamientos térmicos a 300ºC. Además, tratamientos térmicos en martensita llevados a cabo en las aleaciones con Hf y Zr inducen el efecto conocido como estabilización térmica de la martensita, un efecto hasta ahora desconocido en aleaciones base Ni-Ti. Las energías de activación de este fenómeno se han estimado a partir de resultados calorimétricos. El envejecimiento en mezclas de austenita y martensita también produce estabilización térmica de la martensita por pinning (creación de defectos y/o anclajes) en las interfases martensita-austenita.
Aleaciones parcialmente amorfas pueden cristalizarse mediante tratamientos térmicos por encima de la temperatura de cristalización obtenida en el DSC, o bien por debajo de éste, de una manera controlada. La cristalización produce la aparición de pequeños cristales de martensita en las regiones que eran inicialmente amorfas, los cuales transforman a temperaturas mucho más bajas que los grandes cristales de martensita ya existentes en las cintas iniciales. Este cambio de las temperaturas de transformación se atribuye al aumento de los términos no químicos de la ecuación de balance energético de las transformaciones martensíticas termoelásticas.
Finalmente, la caracterización del efecto memoria de forma mediante ciclado termomecánico ha mostrado que las deformaciones recuperables obtenidas son del orden de las obtenidas para las aleaciones fabricadas convencionalmente. Esto certifica la posibilidad de emplear las cintas fabricadas mediante melt-spinning en aplicaciones concretas, con la ventaja de que este método produce aleaciones prácticamente listas para su utilización, sin necesidad de tratamientos mecánicos posteriores. Sin embargo, como se ha visto en este trabajo, los esfuerzos de tensión aplicados a las cintas deben limitarse con el fin de evitar la fractura prematura del material.
In the present work, the shape memory effect and the thermal stability of the martensitic transformation under various thermal treatments have been characterized on several Ni-Ti based alloys cast by melt-spinning, a novel technique on shape memory alloys. The studied alloys belong to the Ni-Ti based system, with eventual additions of Cu, Hf or Zr and have been characterized by means of DSC, mechanical testing, thermomechanical cycling, X-ray diffraction and transmission electron microscopy.
The sequences of the martensitic transformation and the lattice parameters of the melt spun ribbons have been firstly determined. Additionally, the initial microstructures show a big amount of defects (mainly dislocations and small precipitates) and small grain size in comparison to the bulk alloys.
Among all the alloys, the near-equiatomic one show the best thermal stability under severe ageing at 500 ºC, followed by the alloys with Cu and finally by the ones with Hf and Zr additions. The latter ones are the only ones exhibiting transformation temperatures well above room temperature, but their poor thermal stability is shown even at 300 ºC. Moreover, thermal treatments in martensite carried out on the the alloys with Hf and Zr reveal thermal martensite stabilization, which was a novel phenomenon in Ni-Ti based alloys; the activation energies of this process have been estimated. Ageing in mixtures of martensite and austenite on these alloys also promote the thermal martensite stabilization by pinning.
Partially amorphous melt spun ribbons can be crystallized by either thermal treatments above the crystallization temperature shown in the DSC or slightly below, in a controlled way. The crystallization promotes the apparition of small crystals from the initial amorphous regions, which transform at very low temperatures due to changes in the non-chemical terms from the energy balance equation respect to the big crystalline regions that are present in the initial state.
Finally, the shape memory effect characterized by thermomechanical cycling show recoverable strains similar to the ones in bulk alloys, which demonstrate that the melt spun ribbons may be used in potential applications when using reduced tensional stress in order to avoid an early fracture.
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Palardy, Genevieve. "Aspects of the melt spinning of fibres from carbon nanotube- nylon nanocomposites." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107732.
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Carbon nanotubes (CNT) have experienced growing popularity in the past two decades. The field of advanced composite materials has developed quite an interest in using them for high performance applications, such as into thermoplastic fibres. However, a review of the literature showed that there was a lack of understanding between the rheological behavior of CNT-filled polymer and the processability of such materials through melt spinning. In this work, a methodology to incorporate carbon nanotubes (CNT) into thermoplastic fibres and to relate mechanical properties, fibre quality and viscosity was developed. Multi-walled nanotubes (MWNT) were combined into a polyamide 12 (PA12) matrix through melt compounding and twin-screw extrusion. Pellets containing 0 wt%, 0.5 wt%, 1.0 wt%, 2.0 wt%, 5.0 wt% and 10.0 wt% MWNT were produced. Their rheological behaviour was investigated and spinnability and processability criteria were developed based on the loss factor and the relative viscosity. They both predicted that masterbatches containing more than 2.0 wt% CNT would be unsuitable for the production of high quality MWNT/PA12 fibres. The pellets were subsequently melt spun with a capillary rheometer at winding speeds of 41 m/min and 152 m/min. The tensile properties of as-spun filaments were measured with a micro-tensile testing machine. The results showed that the maximum Young's modulus was reached between 0 wt% and 1.0 wt% CNT, exhibiting an increase of 17%. Morphological observations revealed that there was a link between the decrease of elastic modulus and loss of surface quality for filaments containing more than 1.0 wt% MWNT. To further improve the fibres' mechanical properties, post-drawing parameters were systematically investigated: temperature, drawing speed and elongation. The best improvements in terms of elastic modulus and tensile stress were measured for the following post-drawing conditions: 140C and 500% elongation, regardless of drawing speed. The elastic modulus (E) and tensile stress values of MWNT/PA12 fibres were improved by at least 300% after post-drawing. Compared to pure PA12 fibres post-drawn under the same conditions, E increased by up to 45% and the tensile stress by up to 62%, for fibres containing 5.0 wt% MWNT. It was confirmed through electron microscopy and X-ray diffraction that these enhancements were caused by uniform nanotube dispersion, the improvement of surface quality and the alignment of the polymer chains along the fibre axis, controlled by the post-drawing temperature and elongation. Control of the mechanical properties with the post-drawing parameters shows that this method gives the opportunity to tailor CNT-fibres to meet specific demands.Les nanotubes de carbone (CNT) ont connu une vague de popularité depuis les 20 dernières années. L'industrie des matériaux composites a développé un intérêt marqué pour leur utilisation dans des applications haute performance, telles que les fibres thermoplastiques. Par contre, une revue de la litérature a démontré qu'il y avait un manque d'information concernant le lien entre le comportement rhéologique des CNT-polymères et la facilité de fabrication par filage à l'état fondu. Dans ce travail, une méthodologie détaillée pour incorporer des nanotubes de carbone (CNT) dans des fibres thermoplastiques et relier leurs propriétiés mécaniques à leur qualité de surface et leur viscosité a été développée. Des nanotubes à multiples parois (MWNT) ont été incorporés dans une matrice de polyamide 12 (PA12) par extrusion bi-vis. Des granules contenant 0%, 0.5%, 1.0%, 2.0%, 5.0% et 10.0% de CNT par masse ont été formulées. Leur comportement rhéologique a été investigué des critères de prodédé par filage ont été développés, basés sur la viscosité relative et le facteur de perte. Ils ont tout deux prédit que des formulations contenant plus de 2.0% de CNT par masse seraient inadéquates pour la production de fibres MWNT/PA12 de qualité. Les granules ont été par la suite filées par fusion avec un rhéomètre capillaire à des vitesse de filage de 41 m/min et 152 m/min. Les propriétés en tension des filaments ont été mesurées avec une machine de test micro-tension. Les résultats ont démontrés que le module d'Young a augmenté d'une valeur maximale de 17% entre 0 et 1.0% de CNT. Des observations morphologiques ont révélées qu'il y avait un lien entre la diminution du module d'élasticité et le fini de surface de filaments contenant plus de 1.0% MWNT. Pour davantage augmenter les propriétés mécaniques, des paramètres de post-étirement ont été investigués systématiquement: température, vitesse d'étirement et elongation. Les meilleures améliorations en terme de module d'élasticité et de contrainte en tension ont été mesurées pour les paramètres suivants: 140C et 500% d'élongation, peu importe la vitesse d'étirement. Le module d'élasticité et la contrainte en tension ont augmenté d'au moins 300% après le post-traitement. Ces propriétés ont augmenté de 45% et 62%, respectivement, pour les fibres contenant 5.0% MWNT, comparées aux fibres pures de PA12 étirées selon les mêmes conditions. Il a été confirmé par microscopie électronique et diffraction aux rayons X que ces gains ont été causés par la distribution plus uniforme des nanotubes, l'amélioration du fini de surface et l'alignement des chaînes de polymère le long des fibres, contrôlés par la temperature et l'élongation. Le contrôle des propriétés mécaniques avec les paramètres de post-étirement démontre que cette méthode s'avère fort prometteuse pour confectionner des fibres selon des applications spécifiques.
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Pérez, Isaac Rodríguez. "Produção de estruturas porosas contendo nanopartículas de prata e silício por Melt Spinning." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/159240.
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No presente trabalho estudou-se uma nova rota para obter nanopartículas de prata e silício aleatoriamente dispersas em uma matriz nanoporosa de nanotubos de óxido de alumínio sobre alumínio. Além disso, estudou-se a aplicação deste novo material como ânodo em células a combustível alcalinas com etanol como combustível, usando a prata como catalisador na eletroxidação do etanol e da produção de H2. O processo proposto consiste na solidificação rápida mediante melt spinner de uma liga de alumínio-prata rica em alumínio (95.25% em peso de alumínio) para obter uma solução sólida supersaturada. Posteriormente foi feita uma anodização porosa em ácido oxálico e estudo eletroquímico em meio alcalino por meia hora. A morfologia da liga obtida foi caracterizada por Microscopia Eletrônica de Varredura, Difração de Raios-X, Microscopia Eletrônica de Transmissão equipado com Espectrometria de Raios X Dispersiva em Energia e avaliado o desempenho como ânodo mediante ensaios de voltametria cíclica Os resultados obtidos confirmam que o desenvolvimento de um novo processo para produzir nanopartículas cristalinas de prata com um tamanho que varia de 4 a 120 nm, com 95% delas entre 4 e 87 nm. A partir dos estudos eletroquímicos concluiu-se que a liga de Al-Ag produzida exibe um comportamento semelhante ao alumínio puro em NaOH 0.1 M e NaOH 0.1 M com 1 M de etanol. A reação entre o alumínio e o meio alcalino produz uma camada de hidrogênio que impede que a prata catalise a eletroxidação do etanol. Portanto, conclui-se que a liga de alumínio-prata produzida não é um material viável como ânodo em células a combustível alcalinas de etanol direto. Portanto, foi avaliado o método de produção de nanopartículas para uma liga Al-Si eutética (14.2% em peso). Esta liga com nanopartículas de silício apresentou um incremento no desempenho na produção de H2 de 17% comparado à liga Al-Si eutética sem o tratamento térmico.In the present work a new route to obtain silver nanoparticles randomly dispersed in a porous Al2O3 nanotube matrix layer on aluminum was studied. Moreover, the use as an anode in alkaline fuel cells (AFC) with ethanol as combustible was studied, using the prepared surfaces as a catalyzer for the electrooxidation of ethanol. The developed process consists of the rapid solidification (quenching) through melt spinning of an aluminum-silver alloy (92.25 %wt. Al) to obtain a supersaturated solid solution, followed by a porous anodization in oxalic acid and electrochemical treatment in alkaline medium. The morphology of the alloy was characterized by Scanning Electron Microscopy, X-Ray Diffraction, Transmission Electron Microscopy and Energy Dispersive X. Ray Spectrometry and the performance of the ethanol electrooxidation was tested though cyclic voltammetry The obtained results confirm that this process produces crystalline silver nanoparticles with a size varying from 4 to 120 nm with 95% of the particles between 4 and 87 nm. The electrochemical study showed that the produced alloy exhibits a similar behavior to that of pure aluminum in the tested mediums. The reaction between the aluminum and the alkaline medium produces a gaseous hydrogen layer that impedes the catalytic action of silver on the ethanol oxidation. Moreover, it was concluded that the produced alloy is not a viable material for the use as anode for direct ethanol AFCs. Therefore, the nanoparticle production method was tested for an Al-Si near-eutectic alloy (14.2 %wt.). This alloy with silicon nanoparticles showed an increase in the performance of H2 production rate of 17% compared to that of the regular Al-Si near-eutectic alloy.
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Hsiao, Hsien-Fu. "Mechanical behavior and heat transfer in polymer fiber melt-spinning and drawing processes." Connect to resource, 1997. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osuosu1243349868.
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Sharifikolouei, Elham [Verfasser], and Joachim P. [Akademischer Betreuer] Spatz. "Fabrication of metal microfibers by melt-spinning / Elham Sharifikolouei ; Betreuer: Joachim P. Spatz." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://d-nb.info/1211090507/34.
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Bowman, R. R. (Randy R. ). "Effect of melt spinning on the microstructure and mechanical properties of three nickel base superalloys." Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/11301.
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Yu, Jianger. "Establishing the Conditions for Stable Extrusion of Melt Spun Polyacrylonitrile with Water Based Plasticizers." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/90287.
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Polyacrylonitrile (PAN) fiber is one of the most important synthetic fibers in the world because it is a precursor to carbon fiber. Compared to the traditional solution spinning process, the melting spinning process of PAN is less costly and can further reduce the price of PAN fiber. This dissertation is concerned with the objective of establishment of conditions (temperature, plasticizer type, and plasticizer composition) that a PAN copolymer is able to be stable melt spun with water based plasticizers. More specifically, PAN/water/acetonitrile (70/15/15) mixture is considered as reference sample in this study because it was proposed in a BASF patent in which it was claimed it could be stably melt spun. We are looking for a more benign plasticizer so that the use of acetonitrile can be avoided and PAN can still be stably melt spun.
To achieve this objective, the first step is to measure the melting point (Tm) of PAN copolymer with various plasticizers and compositions by using differential scanning calorimetry (DSC). The results indicate the Tm of PAN copolymer can be reduced to around 160 oC with water only as a plasticizer, which is lower than the degradation temperature of PAN (180 oC). Moreover, using a water/ethanol mixture and water/acetonitrile as plasticizers can further reduce the melting point of PAN to 150 oC and 135 oC, respectively.
The second step is conducting rheological measurements on the PAN/plasticizers mixture. A pressure chamber was designed and attached to the capillary rheometer in order to prevent the foaming and evaporation of plasticizers during the viscosity experiments. Both steady-shear and time-dependent viscosity measurements were conducted. The rheological measurement results indicate that PAN can keep stable for more than 120 minutes with all plasticizers under 170 oC, and it starts to degrade in 60 minutes at 180 oC, except samples plasticized with 30 wt% of water (which keep stable for 120 minutes as well). The steady-shear viscosity results indicate the shear-thinning behavior is observed for the PAN/plasticizer mixtures at a temperature ranging from 170 oC to 190 oC and provide the fundamental viscosity data which can be applied to the extrusion process. In conclusion, the rheological measurements show PAN/Water (70/30 wt%) at 180 oC and PAN/EtOH/Water (70/15/15) at 170 oC are two potential systems for carrying out the PAN melt spinning process.
Scanning electron microscopy (SEM) images were taken for the reference state and potential conditions. These images show that the copolymer strands have more and larger voids when plasticized with water only compared to those plasticized with water/acetonitrile and water/ethanol mixture. In this case, PAN/EtOH/Water (70/15/15) at 170 oC is considered to be the most benign system for that PAN melt spinning.Doctor of Philosophy
The melt spinning process of polyacrylonitrile (PAN) has been studied in the past few decades. Compared to the traditional solution spinning process, it does not require toxic organic solvents. The major problem of the PAN melt spinning process is the melting point (Tm) of PAN is much higher than its degradation temperature. However, by adding plasticizers the Tm of PAN can be significantly reduced, which makes PAN melt spinning feasible. In this work we discuss the feasibility of the melt spinning process of polyacrylonitrile (PAN) copolymer plasticized with water based plasticizers by using differential scanning calorimetry (DSC) and rheological methods. The objective is to use water only as a plasticizer to melt spin PAN under specific conditions (composition, temperature etc). The melting point and rheological measurements have been conducted by DSC and a modified capillary rheometer, respectively, for this plasticized system. The DSC results show that the melting point of the PAN copolymer can be reduced below the degradation temperature of PAN, and the rheological results show that the PAN copolymer can be extruded with a reasonable viscosity at 15-20 o v above its melting point, and also the stability and viscosity are strongly dependent on temperature and the plasticizer type and content. Furthermore, the Scanning electron microscopy (SEM) images show the copolymer strands extruded from PAN/H2O mixture have many more and larger voids than PAN/H2O/EtOH mixture. In conclusion, the results indicate that the most appropriate condition for PAN melt spinning is PAN/H2O/EtOH mixture of 70/15/15 wt% ratio at a temperature of 170 oC
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GONÇALVES, Lídice Aparecida Pereira. "Efeito Hall planar e magneto impedância gigante em liga ferromagnética amorfa Co70Fe5Si15B10." Universidade Federal de Pernambuco, 2006. https://repositorio.ufpe.br/handle/123456789/1381.
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Foi descoberto um sistema mel-spinning para produção de fitas metálicas. O sistema consiste essencialmente de um forno de radio-freqüência, operando com 8kVA de potência e em 450 kHz, o qual é utilizado para fundir a liga precursora e um volante de cobre usado para resfriamento da liga fundida...
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Soroudi, Azadeh. "Melt Spun Electro-Conductive Polymer Composite Fibers." Doctoral thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-3590.
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One interesting approach is the development of conductive polymer composite fibers for innovative textile applications such as in sensors, actuators and electrostatic discharge. In this study, conductive polymer composite fibers were prepared using several different blends containing conductive components: a conjugated polymer (polyaniline-complex) and/or carbon nanotubes. Different factors such as processing parameters, the morphology of the initial blends and the final fibers, fiber draw ratio and material selection were studied separately to characterize their effects on the fiber properties. In binary blends of PP/polyaniline-complex, the processing conditions, the matrix viscosity and the fiber draw ratio had substantial effects on the electrical conductivity of the fibers and linearity of resistance-voltage dependence. These factors were associated with each other to create conductive pathways through maintaining an appropriate balance of fibril formation and breakage along the fiber. The blend morphology was defined as the initial size of the dispersed conductive phase (polyaniline-phase), which depended on the melt blending conditions as well as the PP matrix viscosity. Depending on the initial droplet phase size, an optimum draw ratio was necessary to obtain maximum conductivity by promoting fibril formation (sufficient stress) and preventing fibril breakage (no excess stress) to create continuous pathways of conductive phase. Ternary blend fibers of PP/PA6/polyaniline-complex illustrated at least three-phase morphology with matrix/core-shell dispersed phase style. When ternary fibers were compared to binary fibers, the former could combine better mechanical and electrical properties only at a specific draw ratio; this showed that draw ratio was a more determinant factor for the ternary fibers, as both conductivity and tensile strength depended on the formation of fibrils from the core-shell droplets of the PA6/polyaniline-complex through the polypropylene matrix. The achieved maximum conductivity so far was in the range of 10 S/cm to 10 S/cm, which for different samples were observed at different fiber draw ratios depending on the mixing conditions, the matrix viscosity or whether the fiber was a binary or ternary blend. To improve the properties, PP/polyaniline-complex blends were filled with CNTs. The CNTs and the polyaniline-complex both had an increasing effect on the crystallization temperature and the thermal stability of PP. Furthermore, the maximum conductivity was observed in samples containing both CNTs and polyaniline-complex rather than the PP with either one of the fillers. Although increasing the content of CNTs improved the conductivity in PP/CNT fibers, the ease of melt spinning, diameter uniformity and mechanical properties of fibers were adversely affected. Diameter variation of PP/CNT as-spun fibers was shown to be an indication of hidden melt-drawings that had occurred during the fiber extrusion; this could lead to variations in morphology such as increases in the insulating microcracks and the distance between the conductive agglomerates in the drawn parts of the fiber. Variations in morphology result in variations in the electrical conductivity; consequently, the conductivity of such inhomogeneous fiber is no longer its physical property, as this varies with varying size.Thesis to be defended in public on Friday, May 20, 2011 at 10.00 at KC-salen, Kemigården 4, Göteborg, for the degree of Doctor of Philosophy.
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Repka, Michael Andrew. "Physical-mechanical and chemical properties of topical films produced by hot-melt extrusion /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Dearing, Neil. "An analysis of ferromagnetic shape memory alloys produced by melt spinning, sputtering and pulsed laser deposition." Thesis, University of Hull, 2010. http://hydra.hull.ac.uk/resources/hull:2739.
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Ferromagnetic shape memory alloys (FSMA) have recently attracted much interest and research because of their large magnetic-field induced strain. Strains of up to 10% have been reported in single crystals of Ni2MnGa at room temperature. The mechanism of twin boundary motion is understood to be responsible for the strain in FSMA's and theoretically allows for a full crystal lattice distortion strain, which is 10% in the case of orthorhombic martensites and 5-6% in the case of tetragonal martensites. These strains however are only achievable in single crystals and much smaller strains have been observed in polycrystalline samples. Here, competition of the randomly orientated grains restrict the cooperative twin boundary motion that is evident in single crystals.Melt spun ribbons are often highly textured and may offer a method of producing ribbons in a form useful as a start material for applications, i.e. basis of a useful 'bulk' compact form. Magnetic and structural properties of melt spun Ni-Mn-Ga have previously been reported. Applied magnetic field has been shown to affect the transformation strain on cooling. Ni-Mn-Ga alloys form a Heusler (L21) lattice which, on cooling, undergoes a diffusionless transformation beginning at the martensite start temperature Ms into either a tetragonal ororthorhombic martensite, both of which are highly twinned. The reverse transformation begins at the austenite start temperature As and both transformations occur over a range of approximately 10K. The type of martensite formed depends strongly on the composition of the sample and its thermal history. The influence of atomic order in Ni-Mn-Ga alloys has also been studied. It has been found that the degree of atomic order plays a large part in determining the martensitic transition temperature. This temperature is suppressed significantly in the disordered B2 structure where there is little correlation of the Mn and Ga atoms at the body center. Ni2MnGa undergoes a B2 to L21 (Heusler) transition at 1071K on cooling. In this work the structural and magnetic properties of melt spun Ni-Mn-Ga ribbons are presented and the effect of an applied magnetic field on the transformation strain is shown for the case of annealed ribbons under tensile stress.It is the intention of this work to explore the properties of melt-spun ribbons of the ferromagnetic shape memory alloys Ni-Mn-Ga and Ni-Fe-Ga with the addition of Tb. A range of compositions of both alloys have been created and analysed for both structural and magnetic properties. Melt spun ribbons are usually either amorphous or nanocrystalline, so the effect of heat treatments to both relieve stress and re-crystallise the ribbons is also explored. This provides some insight into how the crystal structure and magnetic properties evolve with annealing temperature. Thin films of these ferromagnetic shape memory alloys were also produced by both sputtering and pulsed laser deposition in order to characterise their behaviour and gain some insight into the growth conditions necessary to successfully produce thin films of ferromagnetic shape memory alloys. This was done because thin films grown at low temperatures can have similar properties to the melt spun ribbons, in that they are nanocrystalline or amorphous. It was hoped that producing and analysing these thin films would yield some more information about the behaviour of polycrystalline ferromagnetic shape memory alloys.
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Kotze, Tyrone. "The influence of heat transfer limitations on the properties of PET yarn produced by melt spinning." Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/5304.
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Includes abstract.Includes bibliographical references (leaves 121-126).
The production of synthetic yarns requires a cost efficient process whilst simultaneously incorporating process methods which ultimately lead to a high quality fibre. A critical part of the production process is the spinning of the molten polymer into individual filaments which are brought together to form the filament bundle. During this process a quench air stream is blown across the filament bundle to aid in cooling the molten polymer. Here, heat transfer limitations may cause inter-filament property variations, which will adversely affect the quality of the yarn. This thesis focuses on the development of a model which allows for an a priori prediction of the influence of major process variables on the degree of fibre property uniformity. Fibre quality is characterised by the high degree of uniformity in the properties which affect the structural features of the yarn. Yarn morphology is dictated by the degree of crystallinity and molecular alignment of the polymer macro-molecules parallel to the fibre axis. These properties are strongly influenced by online tensile stress and local temperature which are, in turn, affected by heat transfer effects between the quench air and filament surface. A model that predicts the influence of heat transfer limitations on the uniformity of the as-spun fibre is therefore needed. Previous research in this field is limited with most work focussed on single filament model development. In this investigation, a monofilament model developed by previous workers (Jarecki et al., 2000) is integrated into a multifilament framework. This model assumes Newtonian behaviour of the polymer with viscosity strongly dependent on local temperature and crystallinity. The development of the multifilament model involves dividing the spinning zone into a number of cells, in which the filament properties are modelled using the monofilament model. The change in quench air temperature is estimated by means of an energy balance incorporating air flow terms and heat transfer through forced convection from the filament surface. A novel iteration approach is proposed in which the temperature of the quench air exiting each cell is iterated for until convergence is met. In simplifying the model, it was found that uniform quench air flow profile could be assumed, since the quench flow channel length was found to fall far short of the length required for turbulent flow to develop. However, it is known that increased contact time for heat transfer would occur if air were dragged down with the filament. Although modelling this effect is beyond the scope of the project, the heat transfer gradients are worsened by air-dragging and hence the model presented in this thesis reveals whether polymer uniformity is possible even under the best possible flow patterns. A negative result therefore indicates that non-uniformity will definitely occur.
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Crisci, Jean-Pierre. "Élaboration de fils métalliques fins par trempe depuis l'état liquide : paramètres et mécanismes (In Rotating Liquid Melt Spinning)." Vandoeuvre-les-Nancy, INPL, 1991. http://www.theses.fr/1991INPL125N.
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L'étude présentée dans ce mémoire porte sur un procédé d'élaboration de fils métalliques fins par trempe depuis l'état liquide (IRLMS), appliqué à deux alliages à base de fer : l'un à bas point de fusion (fe75Si10b15% at), l'autre à haut point de fusion (fe75Cr17Ni7Al1%pds). La méthodologie employée lors de l'étude paramétrique a permis de déterminer, dans chacun des cas, l'influence des paramètres sur la géométrie des fils et de définir une démarche conduisant aux conditions optimales de coulée du point de vue de la circularité, de la régularité, et de la longueur des fils (les principaux paramètres étant la température de coulée, la vitesse du jet, l'angle d'entrée du jet dans la nappe de liquide de refroidissement, la nature et la vitesse de déplacement de ce dernier. . . ). Les principaux résultats révèlent un comportement différent pour les deux alliages. Les interactions mécaniques et thermiques entre le jet de métal liquide et le liquide de refroidissement ont été abordées, démontrant la présence de caléfaction autour du jet. Pour chacun des alliages, l'analyse des mécanismes de refroidissement a mis en évidence les corrélations entre les paramètres de coulée, la nature du liquide de trempe, le mode de refroidissement et le fil obtenu (du point de vue de sa géométrie et de sa structure)
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Alshammari, Ohud. "EFFECT OF ANNEALING ON THE MICROSTRUCTURE AND MAGNETIC PROPERITES OF SELECTED (Ni-Mn-Ga) MELT-SPUN RIBBONS." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1464184585.
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Yang, Jinhai. "Phase Morphology and Orientation Development of Polymer Blends in Melt Processing." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1200460579.
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Shan, Haifeng. "Structure development in melt spinning, cold drawing and cold compression of poly(ethylene-co-octene) with different octene content." Akron, OH : University of Akron, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1137341440.
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Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Engineering, 2006."May, 2006." Title from electronic dissertation title page (viewed 10/11/2006) Advisor, James L. White; Committee members, Avraam I. Isayev, Thein Kyu, Darrell H. Reneker, Shing-Chung "Josh" Wong; Department Chair, Sadhan C. Jana; Dean of the College, Frank N. Kelley; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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LOYOLA, G. V. "Distribuição de anisotropia e efeitos de curvatura observados por espectroscopia Mössbauer em metais amorfos magnetostrictivos obtidos por Melt-Spinning." Universidade Federal do Espírito Santo, 2011. http://repositorio.ufes.br/handle/10/7422.
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Previous issue date: 2011-09-30Neste trabalho estudamos: (i) o efeito de reorientação da magnetização induzida por tensão (curvatura) em bicamadas Al x/ Metglas, onde Metglas é o material magnetostrictivo Fe78B13Si9 (Metglas 2605S2), Al é o material de cobertura e x é a espessura (~microns). (ii) As anisotropias fora do plano com medidas Mössbauer em função do campo magnético em tricamadas Ni x/ FINEMET/ Ni x, onde FINEMET é o material magnetostrictivo Fe73. 5Cu1Nb3Si13.5B9, Ni é o material de cobertura. Induzimos tensão através do acoplamento de materiais com diferentes coeficientes de expansão térmica e estudamos o efeito de reorientação magnética através da espectroscopia Mössbauer, já que as intensidades relativas das linhas de absorção (I_23) de uma fase magnética, medidas por espectroscopia Mössbauer, dependem das direções entre a magnetização média da amostra e o feixe de raios-γ incidente. Realizamos medidas Mössbauer com o feixe de raios-γ incidindo perpendicularmente ao plano das bicamadas e tricamadas estudadas, consequentemente obtivemos informações da distribuição média de magnetização nas fitas em questão. Como principais resultados concluímos que (i): existe uma linha de tensão nula que se desloca em função da curvatura fazendo resultar em tensões médias não nulas (ii) a reorientação magnética ocorre principalmente devido ao efeito de curvatura (iii) 95% da fração com anisotropia perpendicular para a fita magnetostrictiva FINEMET possui valores de 0 a 3kJ/m3 e notamos também que o restante do volume perpendicular, cerca de 5%, apresenta anisotropias superiores a 12kJ/m3 associadas a defeitos e irregularidades provenientes do processo de produção. (iv) Volume perpendicular substancialmente aumentado devido a tensão induzida pela deposição da camada de Ni.
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Pandana, Dushyanth V. "Study of structure development during melt spinning of isotactic polypropylene fibers using Raman spectroscopy and wide angle x-ray diffraction simultaneously." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1181250628/.
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Lukesle, Václav. "Modul ohřevu elektrozvlákňovací elektrody." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-221046.
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The thesis deals with the principal heating design of the electrospinning electrode. These electrodes are fed with high voltage (tens of kV), which is an essential part of the device for the nanofibres production. This thesis presents the research of possible solutions of the heating and also it analyzes some principles of the nanofibre production. Furthermore, the work presents electrical schematics and PCB of the heating module. The aim of this work is to propose such a solution of heating that makes spinning from melt realizable in the device for 4SPIN ® nanofibres production.
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Ouvrard, Blanche. "Matériaux conducteurs à haute limite d’élasticité dans le système Cu-Mg : élaboration, caractérisation et modélisation." Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14860/document.
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Les alliages conducteurs à haute tenue mécanique sont utilisés dans de nombreux domaines tels que le transport, l’énergie et l’industrie électronique. La demande en ces matériaux est croissante. Les alliages Cu-Be constituent à l’heure actuelle les matériaux conducteurs les plus résistants mais posent un problème de toxicité et de coût. Pour proposer une alternative à ces derniers, nous avons étudié des alliages Cu-Mg hypo-eutectiques. Deux voies de synthèse ont été utilisées afin d’obtenir des composites endogènes possédant une combinaison originale de propriétés structurelles et fonctionnelles : le refroidissement conventionnel et la solidification rapide par melt-spinning. Les microstructures obtenues ont en commun la présence d’agrégats eutectiques et diffèrent principalement par la dimension des paramètres métallurgiques tels que la taille de grains et la distance interlamellaire. Les systèmes présentent des forces motrices de transformation de phases importantes conduisant à une précipitation au cours d’un maintien thermique. L’investigation des propriétés mécaniques et électriques des alliages Cu-Mg montre que ces dernières égalent celles des alliages Cu-Be. En complément de l’approche expérimentale, nous avons adapté deux modèles : un modèle thermocinétique pour décrire l’évolution temporelle de la microstructure qui a lieu à haute température et un modèle mécanique permettant de rationaliser l'influence des paramètres microstructuraux sur les propriétés mécaniques et électriquesCopper-based high strength conductive alloys are used in a myriad of applications such as transport, energy and electronic industries. The demand for these materials is booming. The strongest conductive alloy is based on the Cu-Be system which has the disadvantage of toxicity and cost. In an attempt to find an alternative to these, we have developed hypoeutectic Cu-Mg alloys. Two synthesis routes were applied to produce endogenous compounds with a unique combination of structural and functional properties: the conventional cooling and the rapid solidification by melt-spinning. The obtained microstructures share the presence of eutectic aggregates and differ mainly by the size of the metallurgical parameters such as grain size and interlamellar distance. The two systems provide high driving forces for phase transformations leading to precipitation during aging. The investigation of the mechanical and electrical properties of Cu-Mg alloys shows that they are equal to those of the Cu-Be alloys. In addition to experimental approach, we have adapted two models: a thermo-kinetic one to describe time evolution of the microstructure which takes place at high temperature and a mechanical one to rationalize the influence of microstructural parameters on mechanical and electrical properties
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Owen, Aaron. "ASSISTED DEVELOPMENT OF MESOPHASE PITCH WITH DISPERSED GRAPHENE AND ITS RESULTING CARBON FIBERS." UKnowledge, 2018. https://uknowledge.uky.edu/me_etds/126.
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The efficacy of dispersed reduced graphene oxide (rGO) as a nucleation site for the growth of mesophase in an isotropic pitch was investigated and quantified in this study. Concentrations of rGO were systematically tested in an isotropic petroleum and coal-tar pitch during thermal treatments and compared to pitch without rGO. The mesophase content of each thermally treated pitch was quantified by polarized light point counting. Further characterization of softening temperature and insolubles were quantified. Additionally, the pitches with and without rGO were melt spun, graphitized, and tensile tested to determine the effects of rGO on graphitized fiber mechanical properties and fiber morphology.
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Ochin, Patrick. "La Solidification Rapide : Relation élaboration, microstructure et propriétés d'un alliage." Habilitation à diriger des recherches, Université Paris-Est, 2010. http://tel.archives-ouvertes.fr/tel-00512464.
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« La solidification rapide : relation Elaboration – Microstructure et Propriétés d'un alliage » RESUME Si les propriétés intrinsèques des matériaux dépendent de la force des liaisons chimiques, qui ne peuvent être modifiées, il est bien connu que leurs propriétés extrinsèques dépendent de la microstructure. Les métallurgistes disposent de moyens techniques pour contrôler relativement bien cette microstructure et aussi faire en sorte que les propriétés associées correspondent aux besoins du cahier des charges de l'application. Classiquement, partant du lingot élaboré par fusion, des traitements thermomécaniques plus ou moins complexes engendrent la microstructure. Mais il est bien clair que les possibilités d'évolution de la microstructure dépendent dramatiquement de l'état initial de l'alliage. C'est ici qu'interviennent les techniques basées sur la solidification rapide. Elles vont engendrer des microstructures initiales pouvant être très différentes de celles qui sont conventionnelles, et qui pourront, par traitements thermomécaniques, aboutir à des microstructures finales également très différentes. Les méthodes de solidification rapide d'alliages métalliques ou céramiques ont pour but principal d'étendre ou de modifier les limites des domaines d'équilibre thermodynamique, ou d'obtenir de nouvelles structures atomiques, ce qui n'est généralement pas accessible par des méthodes dites conventionnelles de solidification. Les produits élaborés se caractérisent par exemple par réduction de taille de grains, par la précipitation d'une phase secondaire plus fine et homogène Ces procédés permettent dans le même temps d'obtenir les matériaux directement à partir de l'état fondu, sous la forme de produits minces finis ou dans un état intermédiaire, tels que des rubans (10 à 80 μm) par « planar flow casting PFC » (flot planaire), des tôles fines (de 200 μm à 3 mm d'épaisseur (en production industrielle) par « twin roll casting TRC» (coulée entre rouleaux) ou encore mais plus rarement des fils (100 à 200 μm de diamètre) par « In rotating water melt spinning INROWASP». J'ai dans ce manuscript décrit les méthodes et techniques d'élaboration que j'utilise en développant quelques aspects thermodynamiques et cinétiques tout en révélant l'essentiel des informations techniques. Un ensemble d'exemples tirés de mes travaux en collaboration et dans le cadre de projets de recherche internes au laboratoire, nationaux et internationaux illustrent ces techniques, notamment les verres métalliques massifs, les quasicristaux, les alliages à magnétorésistance géante, et particulièrement les alliages à mémoire de forme. Les relations entre d'une part la méthode de préparation, qui inclut la technique de fusion, de solidification, les traitements associés thermo-mécaniques, et d'autre part les caractéristiques structurales, microstructurales ainsi que les propriétés mécaniques et fonctionnelles ont été mises en évidence. Le choix de méthodes de production par solidification rapide, comme je l'ai écrit, peut dans certaines conditions autoriser l'obtention d'une phase qu'on ne peut pas obtenir par refroidissement classique (< 103 KS-1) ou, par l'abaissement de la taille de grains, optimiser certaines caractéristiques mécaniques. Néanmoins comme le montrent certains résultats mitigés sur les alliages à mémoire de forme, ces méthodes ne sont en aucun cas une panacée aux problèmes rencontrés comme le manque de ductilité à température ambiante. Le problème de la mise en forme à froid qu'on rencontre dans nombres d'alliages intermétalliques ou les verres métalliques ne sont pas ou seulement partiellement résolus par ces procédés. Mais la production en une seule ou un nombre limité d'étapes d'objets finis ou semi-finis reste un élément économique appréciable de ces méthodes. Les phases quasicristallines stables thermodynamiquement ainsi que les verres métalliques massifs ne nécessitent pas des vitesses de refroidissement supérieures à 103 KS-1 et peuvent être obtenus par des méthodes de préparation ce qui nécessite certaines précautions (c.a.d. par exemple sans contamination chimique) mais à vitesse de refroidissement classique. Néanmoins dans ce cas il a été démontré que seule une méthode de solidification rapide (telle que le melt spinning ou l'atomisation gazeuse) permet d'une part d'obtenir la précision compositionnelle requise et d'autre part d'atteindre, après traitement thermique, une qualité structurale de la phase optimale (cas des quasicristaux). En ce qui concerne les verres métalliques ces techniques nous permettent d'étudier plus facilement la capacité à l'amorphisation, la formulation et la déformation à froid de ces alliages : par exemple les essais de nanoindentations sur les rubans ou les tôles hypertrempées qui nous autorisent à remonter aux mécanismes de déformation des alliages massifs. L'obtention d'une précipitation de dispersoïdes nanométriques dans la matrice amorphe (VMM) ou la matrice paramagnétique des alliages magnétorésistifs à l'étude, n'est possible qu'en utilisant ces techniques.
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Yan, Xiang. "Design of biphasic polymeric fiber from melt-spinning charged with nanoparticles : effects of the formulation and the fillers localization, to obtain a functionalized fiber at surface level." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1I084.
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Le but de ce travail est de développer des filaments fonctionnels de polypropylène (PP) poreuses mais aussi des microfibres de PP par filage voie fondu de mélange de polymères immiscibles PP/Poly(vinyl-alcool) (PVA) après extraction sélective de la phase de PVA. Le premier objectif est de déterminer le ratio optimal entre le PP et le PVA afin d’obtenir la filabilité du mélange et de localiser les charges à l’interface du mélange biphasique. Les charges utilisées sont à la fois des nanoparticules de silices modifiées ainsi que des particules Janus à base de kaolinite, favorisant la localisation à l’interface. Les morphologies et les localisations des charges ont été analysées à la fois sur des joncs extrudés ainsi que sur des fibres. Le travail s’est concentré principalement sur des ratios de polymères permettant d’obtenir des fibres de PP poreuses, mais un travail exploratoire a permis de déterminer les conditions d’obtention de microfibres de PP. Le ratio PP/PVA avec 70 % de PP et 30 % de PVA en masse est la formulation idéale pour fabriquer ces fibres poreuses. La localisation des nanocharges de silice dans le mélange biphasique est principalement contrôlée par la thermodynamique du mélange, et en fonction des tensions de surface des nanosilices, la localisation à l’interface a pu être obtenue. De plus, les particules Janus permettent une voie alternative afin d’obtenir une localisation à l’interface, qui apportent un renforcement mécanique de la formulation. La faisabilité de la production de microfibres via l’inversion de phase PVA/PP avec l’ajout de nanocharges a été démontréeThe work aims to make the functional porous polypropylene (PP) fibers as well as PP microfibers, by the melt spinning of PP-poly(vinyl alcohol) (PVA) blends followed with the selective phase extraction of PVA. The objective is to first find out the optimal ratio of PP and PVA for fabrication of multifilament yarns by melt spinning, and to localize the filler at the biphasic interface. The fillers include not only the homogenously modified silica nanoparticles, but also the kaolinite Janus particles. The concomitant morphology evolution of the extrudates and fibers were observed. The work mainly discusses about the fabrication of porous fibers, but also makes an exploratory experiment to reverse the ratio to fabricate the microfibers. It was found that the ratio of two polymers as 70 wt.%/30 wt.% is an ideal formula for fabricating the porous fibers. Both of the two fillers are successfully tailored at the biphasic interface. The localization of silica nanoparticles within the biphasic can be fixed by the thermodynamic control, and one of the sorts has been dominantly localized at the biphasic interface. In addition, the Janus particles provide an alternative way to have the interface localization, which even helps the mechanical enhancement. The feasibility of microfiber production with the embedment of the fillers was also demonstrated
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Ranganathan, Sathees. "Rapid solidification behaviour of Fe and Al based alloys." Doctoral thesis, KTH, Materialvetenskap, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11325.
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Rapid solidification experiment on Fe-Cr-Mo-Mn-Si-C alloy was performed to investigate metastable phases formed during the solidification. A wide range of cooling rate was used to analyse the sample from melt spinning technique (~107 K/s) to water quenching method (~102 K/s). A single phase featureless structure was obtaind initially in the melt spinning experiment for 77Fe-8Cr-6Mn-5Si-4C alloy. Reduction of C and addition of Mo led to form a complete featureless structure for 2.85 mm rod for 72.8Fe-8Cr-5Mo-6Mn-5Si-3.2C. Subsequent investigation of influence of Mo, Cr and Mn on the single phase featureless structure concludes that 7.5 mm thick complete featureless phase could be formed at 63.8Fe-15Cr-7Mo-6Mn-5Si-3.2C alloy composition. In a separate attempt, powder samples of 40 μm dia. size complete featureless powders were produced for three slightly different compostions for the same alloy system. Characterisation of the featureless phases reveals that it could be a single phase metastable structure of ε phase or austenitic solid solution with high amount of alloying element dissolved in it. Subsequent heat treatment of this featureless phase of the rod and the powder at different temperatures formed bainitic ferrite with fine carbides dispersed in the austenitic matrix. Hardness values measured on featureless phase found to have influenced by the alloying element specially Mo, Cr and Mn. In an attempet to improve clean melting condition to extend the featureless phase and to form amorphous, an elliptic short arc lamp vaccum furnace was designed with 10 kW lamp power. Around 30 g of iron based alloy system was melted and cast as a 7 mm rod sample in a copper mould. Design details of new mirror and the lamp furnace are presented. In a separate study, influence of the melt temperature on Al-Y and Al-Si alloys were investigated by levitaion casting in a silver mould at around 2000 K/s cooling rate. Plate like structure of Al8Y3 primary phase was observed at low melt temperature with small percentage of peritectic transformation of Al8Y3 and liquid melt into Al9Y2. A pre-dentritic star like crystal of Al3Y was observed in a fine eutectic matrix at very high melt temperature. Amount and number of primary Si crystals formed in a unit area during the solidification increases as the melt temperature increases.QC 20100805
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Jemt, Gardell Emma, and Hannah Racklin. "Från plagg till plagg." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-10469.
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De senaste decennierna har visat på en stor ökning av den textila konsumtionen som följd av efterfrågan, samtidigt som den textila återvinningen idag är nästintill obefintlig. Detta leder till att mycket av det textila materialet deponeras istället för att återvinnas, vilket innebär ett stort slöseri av redan befintlig råvara som skulle kunna användas till att skapa nytt textilt material. Genom att undersöka olika återvinningsmetoder och -processer skulle denna råvara kunna användas på nytt. Examensarbetet är en del av forskningsprojektet ”Från spill till guld” som leds av forskningsinstitutet Swerea IVF. Forskningsprojektets utgångspunkt är att minimera produktionsspill och att höja dess värde inom bland annat textilindustrin. Examensarbetet syftar till att undersöka termomekanisk återvinning av plagg gjorda av polyamid 6.6 (PA6.6) och elastan, smältspinna filament samt formspruta provstavar från denna nya polymerblandning utan att separera fibrerna. Andra syftet är att även hitta en lösning för produkterna som undersöks i detta examensarbete kan återvinnas i sin helhet, så att ingen demontering av produkterna ska behövas. Fyra olika plagg undersöktes i examensarbetet bestående av materialblandningen PA6.6 och elastan. Analyser av de fyra olika plaggen genomfördes för att fastställa materialen. Hela plagg tillverkade i de olika materialen klipptes eller maldes ned och smältes sedan om genom kompoundering, därefter tillverkades granulat. Materialen testades i spinnbarhet genom smältspinningsförsök, sedan smältspanns eller formsprutades materialen. Resultaten från smältspinningsförsöken analyserades i ljusmikroskop för att avgöra om elastanen är termoplastiskt eller inte då detta är en avgörande faktor vid smältspinning. Olika tester gjordes på materialen för att undersöka deras eventuella kemiska nedbrytning som resultat av kompoundering. Resultatet visade att smältspinning och formsprutning inte är möjligt från denna polymerblandning. Ett antagande kan göras att återvinningen inte fungerade på grund av PA6.6:s höga smälttemperatur, då elastanen antagligen bryts ned vid denna höga temperatur, vilket förstör materialet. Slutsatsen blir då att smältspinning och formsprutning inte är möjligt utifrån denna polymerblandning, men återvinning till plastdetaljer kan produceras vid kompounderingsstadiet och återanvändas i annan industri än textilindustrin. Potential finns för återvinning av plagg till plagg om ändringar görs under processens gång och om elastanen identifieras som termoplastisk eller inte.The latest decades have shown a large increase in textile consumption as a result of demand, at the same time the textile recycling today is almost non-existent. This means that much of the textiles are used for landfill rather than being recycled, which generates a large waste of raw material that could be used to create new textiles. By exploring various recycling methods and processes this raw material could be used again. This thesis is part of a research project, “From Waste To Gold”, which is led by the research institute Swerea IVF. The research projects foundation is to minimize production waste and to increase its value in areas such as textile industries. This thesis’ foundation is to examine the mechanical recycling of garments made by polyamide 6.6 (PA6.6) and spandex, melt spin filaments and produce injection moulded samples from this new polymer blend, without separating the fibres. The other foundation is to find a solution for the products that are examined in this thesis so they could be recycled as a unit, no disassembly of the products would be necessary Four different garments was examined in this thesis, the materials were a combination of PA6.6 and spandex. Different analyses were made on the four different garments. Whole garments from the different materials were cut or milled and then re melted through compounding, after compounding granulates was made. The materials spin ability was tested through melt spinning trials, then the materials were either melt spun or injection moulded. The results from the spinning trials was analysed in a light microscope to examine if the spandex were thermoplastic or not, as this is a crucial factor when melt spinning. Various tests were conducted to analyse their chemical degradation after the compounding. The results from the melt spinning and injection moulding showed that it was not possible to recycle this polymer combination this way. An assumption can be made that the recycling methods did not work because of the high melt temperature of PA6.6, the spandex assumes to decompose at this high temperature and therefore destroys the material. The conclusion is that melt spinning and injection moulding is not possible to conduct with this polymer combination, but recycling to plastic details could be done at the compound stage and then be used in some other industry, not in the textile industry. There are potential for garment-to-garment recycling if changes are made during the recycling processes and if the spandex could be identified as a thermoplastic or a non-thermoplastic.
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Kudla, Christian. "Strukturell komplexe intermetallische Phasen : Untersuchungen an binären und ternären Phasen der Systeme Ag-Mg und Ag-Ga-Mg." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1201041427278-30978.
Full textAbstract:
Im Rahmen der Dissertation wurden Komplexe Intermetallische Phasen (KIP) in den Systemen Ag-Mg und Ag-Ga-Mg dargestellt und charakterisiert. KIP sind Verbindungen, die sich grundlegend von einfachen Metallen unterscheiden. Große Elementarzellen, ein hierarchisch strukturierter Aufbau und inhärente Fehlordnung sind wesentliche Charakteristika. Empirisch wird zudem eine Häufung von strukturchemisch verwandten KIP (Ähnlichkeitsregel) in der Nähe von definierten Zusammensetzungen beobachtet (Häufungsregel). Obwohl nur wenig über die physikalischen Eigenschaften dieser Verbindungsklasse bekannt ist, zeigen neueste Untersuchungen, dass sie interessante Eigenschaften wie ungewöhnliches plastisches Verhalten und Pseudo-Bandlücken in der elektronischen Zustandsdichte in Höhe der Fermi-Energie aufweisen können. Diese Arbeit zeigt exemplarisch, dass in der Chemie der KIP durchaus einfache Regeln (Häufungs-, Ähnlichkeits-, Valenzelektronenkonzentrationsregel) genutzt werden können, um neue Verbindungen mit vorgegebenen geometrischen Baueinheiten aufzufinden. Vereinfachende Annahmen, wie die Aussage, dass zweikomponentige Mackay-Cluster keine Fehlordnung aufweisen oder dass ein Mackay-Cluster maximal 92 Valenzelektronen enthält, erwiesen sich hingegen als falsch. Die Untersuchungen haben gezeigt, dass eine Kombination verschiedener Synthesemethoden notwendig ist. Insbesondere hat sich das Schmelzspinnverfahren, das zur Darstellung kristalliner magnesiumreicher Legierungen angewandt und modifiziert wurde, bei der phasenreinen Synthese der Verbindungen bewährt. Die Entwicklung von Spritzdüsen aus Tantal ermöglichte die kontaminationsfreie Verarbeitung der Mg-haltigen Legierungen. Die Bestimmung der Kristallstrukturen inklusive der Fehlordnungsphänomene war für das Verständnis der Stabilität der KIP entscheidend. Da häufig zwischen verschiedenen Modellen zur Beschreibung der Fehlordnung entschieden werden musste, waren neben präzisen Beugungsdaten genaue Untersuchungen der Präparate mittels chemischer Analytik, Metallographie und WDX hinsichtlich der Zusammensetzung aller Phasen erforderlich. Der magnesiumreiche Teil des binären Phasendiagramms Ag-Mg wurde neu bestimmt. Dabei wurden zwei bislang unbekannte Phasen dargestellt. Die fünf magnesiumreichen Phasen kristallisieren innerhalb eines schmalen Bereichs von nur 9 At.-% Mg. Die Kristallstrukturen dieser Phasen wurden unter besonderer Berücksichtigung der Fehlordnungsphänomene untersucht. Die Verbindungen sind strukturchemisch verwandt und lassen sich den I3-Cluster-Phasen zuordnen. Ag2Mg5 kristallisiert ohne Fehlordnung im Al5Co2-Typ. Die Kristallstrukturen von Ag7Mg26 und Ag17Mg54 lassen sich als fcc bzw. bcc Anordnungen von Mackay-Clustern beschreiben. Es handelt sich um die ersten bekannten binären Phasen, in denen innerhalb von isolierten Mackay-Clustern Substitutionsfehlordnung auftritt. AgMg4 kristallisiert hexagonal in einem eigenen Strukturtyp. Das I3-Cluster-Netzwerk füllt den gesamten Raum bis auf einen annähernd zylindrischen Bereich um 0, 0, z, in dem eine Atom-Split-Position aus drei Lagen vorliegt. Lokal liegen drei unterschiedliche Koordinationspolyeder vor, deren Stapelabfolge in der Kristallstruktur von AgMg4 zufällig ist, jedoch mit kurzreichweitiger Korrelation. Es konnte gezeigt werden, dass sich AgMg4 in eine Tieftemperaturphase umwandelt, in der die Polyeder vermutlich langreichweitig unter Bildung einer Überstruktur ordnen. Der Phasenbestand des ternären Systems Ag-Ga-Mg wurde untersucht und die Kristallstrukturen von sechs neuen Phasen bestimmt. Des weitern wurde eine Verbindung im System Ga-Mg-Pd charakterisiert. Anhand der Strukturtypen Al3Ir und Cu3P sowie den Verbindungen Ag0,55Ga0,45Mg3, Ga4,62Mg13,38Pd7 und Ag1,31Ga1,89Mg7,80 wurde gezeigt, wie die Variation von Strukturmotiven durch geringe Abweichungen von idealer Symmetrie zu zunehmend komplexeren Kristallstrukturen führt, die sich stets von Packungen des Edshammarpolyeders ableiten lassen. Drei ternäre Phasen vom I3-Cluster-Typ konnten identifiziert werden: Neben ternären Varianten der Phasen Ag7Mg26 und Ag17Mg54 kristallisiert Ag0,59Ga0,41Mg2 metastabil im NiTi2-Typ. In den strukturchemisch verwandten Phasen Ag6Ga12Mg11 und Ag21Ga74Mg44 bilden die Mg Atome Netzwerke mit Clatrath-II- bzw. Clatrath-IV-Topologie, die mit Ikosaedern und Frank-Kasper-Polyedern aus Ag und Ga gefüllt sind. Diese Phasen werden wahrscheinlich durch das e/a-Verhältnis der gesamten Struktur im Sinne einer Hume-Rothery-Regel stabilisiert.
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Ohorodniichuk, Viktoriia. "Influence de la nanostructuration sur les propriétés thermoélectriques des matériaux masifs de type p à base de (Bi, Sb, Te)." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0266/document.
Full textAbstract:
Ce travail a été réalisé en collaboration avec EDF R&D, dans le cadre d’une convention CIFRE-ANRT, l’objectif étant d’améliorer le coefficient de performance de pompes à chaleur thermoélectriques (PACTEs) pour des "Bâtiments Basse Consommation". Les PACTEs présentent de nombreux avantages environnementaux, le désavantage étant leur faible performance. Ainsi l'objectif de ce travail a été d'examiner la possibilité d'améliorer, par nanostructuration les performances des semi-conducteurs utilisés dans les modules thermoélectriques des PACTEs. Nos travaux se sont concentrés sur les solutions solides à base de Sb2-xBixTe3, celles-ci étant, selon l’état-de-l’art, les plus performantes pour l’application visée. La nanostructuration a été réalisée par la technique de trempe sur roue (technique de refroidissement rapide de liquides) de matériaux synthétisés auparavant à l'état liquide dans des tubes en quartz. Les moyens de caractérisation (DRX, MEB, MET, METHR) ont permis de corréler les changements structurels avec la variation des propriétés thermiques et électriques (le pouvoir thermoélectrique, la résistivité électrique, l'effet de Hall, la conductivité thermique) mesurées sur de larges gammes de température (5-460 K). L'influence favorable de la nanostructuration par la diminution de conductivité thermique a été prouvée. Nous avons montré la forte dépendance des propriétés thermoélectriques des matériaux étudiés avec la concentration de défauts et la stœchiométrie. Le dopage avec du Te a été examiné comme une possibilité de contrôler le niveau de la concentration des porteurs de charge. L'idée de créer des niveaux d'impuretés résonantes par un dopage au Sn s’est montrée infructueuse, vraisemblablement en raison de la structure de bande complexe du composé ternaire. Néanmoins, des valeurs du facteur de mérite adimensionel ZT de près de 1,2 ont été obtenues pendant ce travailThis work results from the collaboration between IJL and EDF R&D performed under a CIFRE-ANRT convention, in order to improve the coefficient of performance of thermoelectric heat pumps (THPs). THPs attracted attention of EDF due to its numerous environmental advantages, but the main drawback remains its low performance. The objective of our work was thus to investigate the possibility to enhance the performance of the semiconductors used in the thermoelectric modules of the THPs, by nanostructuration. The research was concentrated on the Sb2-xBixTe3-based solid solutions, the most effective materials for the application sought. The nanostructuration was performed by applying the melt-spinning technique (rapid quenching from a melt on a water-cooled cupper wheel) to the material synthesised beforehand from liquid state in quartz tubes. The means of characterisation (XRD, SEM, TEM, HRTEM) gave the possibility to correlate the structural changes with the variation of the thermal and electrical properties (thermoelectric power, electrical resistivity, Hall effect, thermal conductivity) measured over a wide temperature range (5-460 K). The favourable influence of nanostructuration through the decreasing of thermal conductivity was proved. A high dependence of the thermoelectric efficiency of the studied materials on the concentration of defects and stoichiometry is shown. Doping with Te was investigated as a possibility to control the resulting level of the charge carrier concentration. The idea of creating resonant impurity levels by Sn-doping was shown to be non-conclusive presumably due to the complex band structure of the ternary compounds. Nevertheless, relatively high values of the dimensionless TE figure of merit, close to 1.2, were obtained during this work
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Kudla, Christian. "Strukturell komplexe intermetallische Phasen : Untersuchungen an binären und ternären Phasen der Systeme Ag-Mg und Ag-Ga-Mg." Doctoral thesis, Technische Universität Dresden, 2007. https://tud.qucosa.de/id/qucosa%3A24048.
Full textAbstract:
Im Rahmen der Dissertation wurden Komplexe Intermetallische Phasen (KIP) in den Systemen Ag-Mg und Ag-Ga-Mg dargestellt und charakterisiert. KIP sind Verbindungen, die sich grundlegend von einfachen Metallen unterscheiden. Große Elementarzellen, ein hierarchisch strukturierter Aufbau und inhärente Fehlordnung sind wesentliche Charakteristika. Empirisch wird zudem eine Häufung von strukturchemisch verwandten KIP (Ähnlichkeitsregel) in der Nähe von definierten Zusammensetzungen beobachtet (Häufungsregel). Obwohl nur wenig über die physikalischen Eigenschaften dieser Verbindungsklasse bekannt ist, zeigen neueste Untersuchungen, dass sie interessante Eigenschaften wie ungewöhnliches plastisches Verhalten und Pseudo-Bandlücken in der elektronischen Zustandsdichte in Höhe der Fermi-Energie aufweisen können. Diese Arbeit zeigt exemplarisch, dass in der Chemie der KIP durchaus einfache Regeln (Häufungs-, Ähnlichkeits-, Valenzelektronenkonzentrationsregel) genutzt werden können, um neue Verbindungen mit vorgegebenen geometrischen Baueinheiten aufzufinden. Vereinfachende Annahmen, wie die Aussage, dass zweikomponentige Mackay-Cluster keine Fehlordnung aufweisen oder dass ein Mackay-Cluster maximal 92 Valenzelektronen enthält, erwiesen sich hingegen als falsch. Die Untersuchungen haben gezeigt, dass eine Kombination verschiedener Synthesemethoden notwendig ist. Insbesondere hat sich das Schmelzspinnverfahren, das zur Darstellung kristalliner magnesiumreicher Legierungen angewandt und modifiziert wurde, bei der phasenreinen Synthese der Verbindungen bewährt. Die Entwicklung von Spritzdüsen aus Tantal ermöglichte die kontaminationsfreie Verarbeitung der Mg-haltigen Legierungen. Die Bestimmung der Kristallstrukturen inklusive der Fehlordnungsphänomene war für das Verständnis der Stabilität der KIP entscheidend. Da häufig zwischen verschiedenen Modellen zur Beschreibung der Fehlordnung entschieden werden musste, waren neben präzisen Beugungsdaten genaue Untersuchungen der Präparate mittels chemischer Analytik, Metallographie und WDX hinsichtlich der Zusammensetzung aller Phasen erforderlich. Der magnesiumreiche Teil des binären Phasendiagramms Ag-Mg wurde neu bestimmt. Dabei wurden zwei bislang unbekannte Phasen dargestellt. Die fünf magnesiumreichen Phasen kristallisieren innerhalb eines schmalen Bereichs von nur 9 At.-% Mg. Die Kristallstrukturen dieser Phasen wurden unter besonderer Berücksichtigung der Fehlordnungsphänomene untersucht. Die Verbindungen sind strukturchemisch verwandt und lassen sich den I3-Cluster-Phasen zuordnen. Ag2Mg5 kristallisiert ohne Fehlordnung im Al5Co2-Typ. Die Kristallstrukturen von Ag7Mg26 und Ag17Mg54 lassen sich als fcc bzw. bcc Anordnungen von Mackay-Clustern beschreiben. Es handelt sich um die ersten bekannten binären Phasen, in denen innerhalb von isolierten Mackay-Clustern Substitutionsfehlordnung auftritt. AgMg4 kristallisiert hexagonal in einem eigenen Strukturtyp. Das I3-Cluster-Netzwerk füllt den gesamten Raum bis auf einen annähernd zylindrischen Bereich um 0, 0, z, in dem eine Atom-Split-Position aus drei Lagen vorliegt. Lokal liegen drei unterschiedliche Koordinationspolyeder vor, deren Stapelabfolge in der Kristallstruktur von AgMg4 zufällig ist, jedoch mit kurzreichweitiger Korrelation. Es konnte gezeigt werden, dass sich AgMg4 in eine Tieftemperaturphase umwandelt, in der die Polyeder vermutlich langreichweitig unter Bildung einer Überstruktur ordnen. Der Phasenbestand des ternären Systems Ag-Ga-Mg wurde untersucht und die Kristallstrukturen von sechs neuen Phasen bestimmt. Des weitern wurde eine Verbindung im System Ga-Mg-Pd charakterisiert. Anhand der Strukturtypen Al3Ir und Cu3P sowie den Verbindungen Ag0,55Ga0,45Mg3, Ga4,62Mg13,38Pd7 und Ag1,31Ga1,89Mg7,80 wurde gezeigt, wie die Variation von Strukturmotiven durch geringe Abweichungen von idealer Symmetrie zu zunehmend komplexeren Kristallstrukturen führt, die sich stets von Packungen des Edshammarpolyeders ableiten lassen. Drei ternäre Phasen vom I3-Cluster-Typ konnten identifiziert werden: Neben ternären Varianten der Phasen Ag7Mg26 und Ag17Mg54 kristallisiert Ag0,59Ga0,41Mg2 metastabil im NiTi2-Typ. In den strukturchemisch verwandten Phasen Ag6Ga12Mg11 und Ag21Ga74Mg44 bilden die Mg Atome Netzwerke mit Clatrath-II- bzw. Clatrath-IV-Topologie, die mit Ikosaedern und Frank-Kasper-Polyedern aus Ag und Ga gefüllt sind. Diese Phasen werden wahrscheinlich durch das e/a-Verhältnis der gesamten Struktur im Sinne einer Hume-Rothery-Regel stabilisiert.
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Thoss, Franziska. "Amorphe, Al-basierte Anodenmaterialien für Li-Ionen-Batterien." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-119680.
Full textAbstract:
Hochleistungsfähige Lithium-Ionen-Batterien sind insbesondere von der hohen spezifischen Kapazität ihrer Elektrodenmaterialien abhängig. Intermetallische Phasen sind vielversprechende Kandidaten für alternative Anodenmaterialien mit verbesserten spezifischen Kapazitäten (LiAl: 993 Ah/kg; Li22Si5: 4191 Ah/kg) gegenüber den derzeit vielfach verwendeten Kohlenstoff-Materialien (LiC6: 372 Ah/kg). Nachteilig ist jedoch, dass die kristallinen Phasenumwandlungen während der Lade-Entlade-Prozesse Volumenänderungen von 100-300% verursachen. Durch die Sprödigkeit der intermetallischen Phasen führt dies zum Zerbrechen des Elektrodenmaterials und damit zum Kontaktverlust. Um Lithiierungs- und Delithiierunsprozesse ohne kristalline Phasenumwandlungen zu realisieren und somit große Volumenänderungen zu vermeiden, wurden amorphe Al-Legierungen untersucht. In amorphe, mittels Schmelzspinnen hergestellte Legierungen (Al86Ni8La6 und Al86Ni8Y6) kann beim galvanostatischen Zyklieren nur sehr wenig Li eingelagert werden. Da kristalline Phasenumwandlungen im amorphen Zustand nicht möglich sind, wird für die Diffusion und Einlagerung von Li-Ionen ein ausreichendes freies Volumen im amorphen Atomgerüst benötigt. Die Dichtemessung der Legierungen zeigt, dass dieses freie Volumen für eine signifikante Lithiierung nicht ausreichend ist. Wird Li bereits in die amorphe Ausgangslegierung integriert, können Li-Ionen auf elektrochemischem Wege aus ihr entfernt und auch wieder eingebaut werden. Die neuartige Legierung Al43Li43Ni8Y6, die Li bereits im Ausgangszustand enthält, konnte mittels Hochenergiemahlung als amorphes Pulver hergestellt werden. Verglichen mit den Li-freien amorphen Legierungen Al86Ni8La6 bzw. Al86Ni8Y6 und ihren kristallisierten Pendants zeigt diese neu entwickelte, amorphe Legierung eine signifikant höhere Lithiierungsfähigkeit und erreicht damit eine spezifische Kapazität von ca. 800 Ah/kg bezogen auf den Al-Anteil. Durch den Abrieb des Stahlmahlbechers enthält das Pulver Al43Li43Ni8Y6 einen Fe-Anteil von ca. 15 Masse%. Dieses mit Fe verunreinigte Material zeigt besonders bei niedrigen Laderaten eine bessere Zyklenstabilität als ein im abriebfesten Siliziumnitrid-Becher gemahlenes Pulver der gleichen Zusammensetzung. Mittels Mössbauerspektroskopie wurde nachgewiesen, dass das Pulver z.T. oxidisches Fe enthält. Dieses kann über Konversionsmechanismen einen Beitrag zur spezifischen Kapazität leistenHigh-energy Li-ion batteries exceedingly depend on the high specific capacity of electrode materials. Intermetallic alloys are promising candidates to be alternative anode materials with enhanced specific capacities (LiAl: 993 Ah/kg; Li22Si5: 4191 Ah/kg) in contrast to state-of-the-art techniques, dominated by carbon materials (LiC6: 372 Ah/kg). Disadvantageously the phase transitions during the charge-discharge processes, induced by the lithiation process, cause volume changes of 100-300 %. Due to the brittleness of intermetallic phases, the fracturing of the electrode material leads to the loss of the electrical contact. In order to overcome the huge volume changes amorphous Al-based alloys were investigated with the intension to realize the lithiation process without a phase transformation. Amorphous powders (Al86Ni8La6 and Al86Ni8Y6) produced via melt spinning and subsequent ball milling only show a minor lithiation during the electrochemical cycling process. This is mainly caused by the insufficient free volume, which is necessary to transfer and store Li-ions, since phase transitions are impossible in the amorphous state. If Li is already integrated into the amorphous alloy, Li-ions can easily be removed and inserted electrochemically. The new alloy Al43Li43Ni8Y6 contains Li already in its initial state and could be prepared by high energy milling as an amorphous powder. Compared with the Li-free amorphous alloys Al86Ni8La6 or Al86Ni8Y6 and their crystalline counterparts, this newly developed amorphous alloy achieves a significantly higher lithiation and therefore reaches a specific capacity of 800 Ah/kg, based on the Al-content. By the abrasion of the steel milling vials the powder contains a wear debris of 15 mass% Fe. This contaminated material shows a better cycling stability than a powder of the same composition, milled in a non-abrasive silicon nitride vial. By means of Mössbauer spectroscopy has been shown that the wear debris contains Fe oxides. This may contribute to the enhancement of the specific capacity about conversion mechanisms
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Kalinichenka, Siarhei. "Rascherstarrte nanokristalline Magnesiumlegierungen für die Wasserstoffspeicherung." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-79095.
Full textAbstract:
Im Rahmen der vorliegenden Arbeit sind die Struktur und die Wasserstoffsorptionseigenschaften neuer nanokristalliner, hydridbildender magnesiumbasierter Legierungen, die mittels Rascherstarrung (Melt-Spinning Verfahren) hergestellt wurden, untersucht worden. Der Schwerpunkt der Arbeit bestand in der Erforschung der Vorgänge während der Aktivierung und der zyklischen Hydrierung/Dehydrierung der rascherstarrten Mg-Legierungen. Zusätzlich wurde das Gefüge, das sich nach der Kristallisation, Aktivierung bzw. Hydrierung einstellt, seine Erhaltung und Auswirkung auf das H2-Speicherverhalten (Struktur-Eigenschafts-Beziehungen) untersucht.
Die für die Verbesserung der Kinetik des H2-Speicherverhaltens angestrebte Nanostruktur konnte nach der Hydrierung der rascherstarrten Legierungen erreicht werden. Die REM-, TEM- sowie EFTEM (EELS)-Untersuchungen zeigten, dass ein Y-Zusatz zu Mg-basierten Legierungen zu einer sehr feinen (ca. 50 nm) und homogenen Verteilung von Y-Hydriden im Gefüge der rascherstarrten Bänder führt. Mg2Ni-Hydride bilden dagegen größere Körner im Größenbereich von 2-3 µm. Bei den Cu-haltigen Legierungen wurde eine Koexistenz von Mg2NiH4 und MgCu2 in direkter Nachbarschaft nachgewiesen.
Detaillierte Untersuchungen der Wasserstoffabsorption haben gezeigt, dass die Chemisorption während des linearen Anfangsbereiches des Hydrierungsverlaufes geschwindigkeitsbestimmend ist. Nach dem linearen Hydrierungsverlauf ist die Hydrierungskinetik von der Wasserstoffdiffusion durch eine geschlossene Hydridschicht beeinflusst.
Mit dem breiten Spektrum der Untersuchungen (REM, EELS, TEM, HP-TGA, DSC, in situ-Synchrotron-XRD) als auch durch gezielte Variation der Zusammensetzungen wurden neue und grundlegende Erkenntnisse zum H2-Speicherverhalten der rascherstarrten Mg-basierten Legierungssysteme gewonnen. Besondere Beachtung verdient die Mg90Ni8Y1,6SE0,4-Legierung. Durch die Möglichkeit einer einfachen Herstellung, ihre schnelle Reaktionskinetik, ihren hohen Wasserstoffgehalt (bis zu 5,6 Gew.%) und ihre gute Zyklenstabilität eignet sich diese Legierung zur sicheren, volumeneffizienten sowie leichtgewichtigen Speicherung von Wasserstoff. Damit kann Wasserstoff gespeichert, transportiert und als CO2-freier Sekundärenergieträger in stationären und mobilen Anwendungen eingesetzt werden.
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Bao, Cuimin. "Étude sur la définition du terme "amorphe" par l'analyse comparative de rubans de Pd82 Si18 en termes de production, structure, microstructure, qualité et propriétés mécaniques." Thesis, Vandoeuvre-les-Nancy, INPL, 2007. http://www.theses.fr/2007INPL068N/document.
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Depuis leur découverte, un travail de recherche important a été développé sur la production, la structure, la microstructure, les propriétés et les applications des alliages métalliques amorphes. Cependant, la question de ce qui est entendu exactement par le terme « amorphe » n’est pas considérée dans la majorité des études publiées. Or, il n’existe pas de verres réels représentant un désordre parfait comme il n’existe pas de cristaux réels avec une structure parfaitement ordonnée. Il est difficile de donner une définition précise sans donner les limites d’échelle et la technique de détection de cette non-cristallinité. L’étude est une interrogation, pour un alliage particulier, sur le terme « amorphe » en fonction de l’échelle et de la technique. Cette étude comporte une analyse des conditions de préparation d’échantillons amorphes de mêmes compositions. Des techniques complémentaires de détection de leurs différences, en particulier à l’échelle de la structure et de la microstructure ont été utilisées. Des échantillons Pd82Si18 d’épaisseurs différentes ont été produits par solidification ultra rapide sur roue, avec différents paramètres, tels que la vitesse de rotation de la roue, la pression du gaz d’éjection, les dimensions de l’orifice d’éjection, la température de trempe et l’existence ou non d’un traitement thermique du liquide avant la trempe, etc. Les échantillons ont été ensuite analysés avec plusieurs techniques, telles que la diffraction des rayons X et des neutrons, la diffusion des neutrons aux petits angles, la microscopie électronique à transmission, la calorimétrie, les essais mécaniques, la fractographie par microscopie électronique à balayageSince their discovery, an important research work has been developed on the production, the structure, the microstructure, the properties and the applications of amorphous metallic alloys. However, the question of what is exactly meant by the term “amorphous” is not considered in most of the reported studies. As a matter of fact, there exist no real glasses representing a perfect disorder, as there exist no real crystals with a perfectly ordered structure. It is thus difficult to give a precise definition without giving the limitations in scale and in detection of this non-crystallinity. The aim the study is an interrogation, in the case of a specific alloy, on the term “amorphous” as a function of the two directions of reference given above (the scale and the technique). This study thus contains an analysis of the conditions of synthesis of amorphous samples of similar compositions. Furthermore, complementary detection techniques of their differences at the scale of the structure and microstructure have been used. Samples of Pd82Si18 of different thickness have been produced by melt-spinning with different parameters, such as the rotation speed of the wheel, the pressure of the gas, the dimensions of the nozzle, the quenching temperature and the existence or not of a heat treatment of the melt before quench. The samples have been analysed by various techniques such as diffraction of standard X rays and of neutrons, small angle neutrons scattering, transmission electron microscopy, calorimetry, mechanical tests and fractography by scanning electron microscopy
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Persson, M. (Maria). "3D woven scaffolds for bone tissue engineering." Doctoral thesis, Oulun yliopisto, 2014. http://urn.fi/urn:isbn:9789526206967.
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Abstract Bone tissue engineering has become a rapidly expanding research area because it offers a promising new approach for bone repair and regeneration. Compared to traditional autograft and allograft procedures, bone tissue engineering techniques based on the use of scaffolding materials in combination with autogenous stem cells can eliminate problems of donor site morbidity associated with the harvest of bone tissue, and its short supply. Clearly, the choices of material as well as a scaffold design that enhance bone regeneration are major challenges in the tissue engineering approach. Fibers in the micro-range in combination with textile-based technologies are consider as potential routes for the production of complex scaffolds since they can be used to generate a wide range of morphological structures and geometrically varied structures with high precision. Therefore in this thesis the specific objects were to: (i) develop a biocompatible composite fiber from poly(lactic acid) (PLA) and hydroxyapatite (HA) by melt spinning, (ii) design a 3D textile scaffold utilizing weaving and (iii) evaluate the scaffolds’ performance as a bone substitute material in vitro. In the present study PLA/HA composite fibers were successfully produced, and found to possess sufficient mechanical strength even at high loading concentrations (i.e. 20wt %), to be useful in a textile process. In addition, the material was shown to be biocompatible and the presence of HA in the PLA composite significantly enhanced the initial cell attachment. In a 3D woven scaffold, bone marrow derived human mesenchymal stem cells (hMSCs) differentiated into osteoblasts and mineralized bone formation in vitro was observed through-the-thickness of the scaffold. Taken together, these results indicate the potential feasibility of PLA/HA composite fiber in a 3D woven scaffold for use as a bone substitute material in tissue engineering applicationsTiivistelmä Luupuutosten korvaaminen kudosteknologisesti on kehittynyt nopeasti ja tutkimustulokset tarjoavat lupaavia mahdollisuuksia tuottaa uutta luuta luupuutosalueelle. Perinteisiin potilaan omasta luusta tehtyihin luusiirteisiin ja pankkiluusiirteisiin verrattuna potilaan omat kantasolut voivat vähentää ongelmia, joita ovat siirremateriaalin rajallinen saatavuus ja vieraan kudoksen aiheuttamat reaktiot. On tärkeä etsiä hyviä materiaaleja, joista voidaan valmistaa sellaisia kolmiulotteisia (3D) rakenteita, joilla tehostetaan luun paranemista ja uuden luun muodostumista. Kutomalla tuotetut tukirakenteet mahdollistavat kantasolusiirteille kolmiulotteisuuden, jota voidaan säädellä monipuolisesti ja tarkasti. Tämän väitöstutkimuksen tarkoituksena oli: (i) kehittää bioyhteensopiva kuitu maitohappopolymeeristä poly lactic acid (PLA) ja hydroksiapatiitista (HA) kuituekstruusiolla, (ii) suunnitella ja kutoa tästä kuidusta 3D tekstiilirakenne, ja (iii) tutkia sen toimivuus ja ominaisuudet luunmuodostusta tukevana materiaalina soluviljelyolosuhteissa. Tämä tutkimus osoittaa, että PLA kuitua voidaan seostaa hydroksiapatiitilla, ja PLA/HA kuidut ovat mekaanisesti kestäviä sisältäessään jopa 20 painoprosenttia hydroksiapatiittia. Siten kuidut ovat tekstiilin valmistuksessa käyttökelpoisia. Lisäksi materiaali osoittautui bioyhteensopivaksi, ja hydroksiapatiitti paransi solujen tarttumista PLA kuituun viljelyn alkuvaiheessa. Ihmisen luuytimestä peräisin olevat sidekudoksen kantasolut (hMSCs) erilaistuivat soluviljelmässä luuta muodostaviksi soluiksi eli osteoblasteiksi, ja tuottivat mineralisoitunutta luun väliainetta kautta koko kudotun tukirakenteen. Johtopäätöksenä on, että PLA/HA yhdistelmäkuitua voidaan kutoa kolmiulotteiseksi tukirakenteeksi, ja sitä on mahdollista käyttää apuna korvattaessa luupuutoksia kudosteknologian keinoin
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Tajul, Islam Mollah Mohammad. "Experimental study on Temperature regulating bi-component fibres containing paraffin wax in the core." Thesis, Högskolan i Borås, Institutionen Textilhögskolan, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-19749.
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Putting on or taking off clothes helps the body to stay within the comfortable temperature range (toavoid shivering or sweating) at different activity levels and ambient conditions. Clothes with built-inthermo-regulating properties would mean maintained comfort without putting on or taking off clothesthat frequently. Integration of phase change materials (PCMs) in clothes is one way of achievingthermo-regulating properties. When the body temperature goes up, the PCM melts and absorbs theheat from the body in the form of latent heat (cooling effect). When the temperature drops, the PCMcrystallizes and the stored heat is released again (warming effect).Research on thermo regulating fibres of the bi-component type containing PCM in the core has beenconducted at Swerea IVF in Mölndal, Sweden, for some time. It has been found that high molecularweight HDPE is a suitable viscosity modifier for hydrocarbon waxes used as PCM. The preparation ofcore materials has so far been done in a batch wise fashion in the way that molten wax has beensoaked into pelletized HDPE at around 180°C during prolonged times followed by melt compoundingin a Brabender batch kneader (0.3 kg per batch). Besides being very impractical for larger productionvolumes the method involves long residence times at high temperatures which may induce thermaldegradation reactions. The objective of the present diploma (master’s thesis) work was to develop acontinuous mixing method to produce PCM/HDPE blends and to test the resulting material in bicomponentfibers with a Nylon (PA6) sheath and to characterize the resulting fiber properties in termsof strength and latent heat.It was proven possible to compound HDPE with large amounts (70%) of octadecane (PCM) on aBrabender twin screw extruder. HDPE was metered to the extruder hoper by means of a screw feederand wax was continuously fed to the hoper in the liquid state by means of a heated membrane pump.To facilitate mixing HDPE in form of powder instead of pellets was used. The extruded threads weresolidified in a water bath followed by granulation. Bi-component fibers were successfully producedfrom such materials. Fibers containing 15 to 42% Octadecane were produced showing heat of fusionsin the range 26 to 86 J/g and tenacities in the range 33 to 16 cN/tex. The heat of fusion of the fiberscompares favorable with existing commercial products showing values in the range 5-15 J/g (acrylicand cellulosic fibres containing microencapsulated hydrocarbon waxes). The peak melting point ofoctadecane measured by DSC was found to be depressed some 4-5°C in the fibers compared to pureoctadecane (28°C). Such a melting point depression is important to consider when choosing type ofhydrocarbon wax.Program: Magisterutbildning i textilteknologi
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Peixoto, Erilaine Barreto. "Estudo dos processos de cristalização em fitas magnéticas amorfas." Universidade Federal de Sergipe, 2015. https://ri.ufs.br/handle/riufs/5355.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESIn this work, we study the crystallization process in the Fe40Ni40P14B6 and Fe76.5Cu1Nb3Si13.5B6 amorphous magnetic ribbons fabricated by melt spinning technique. The effect of crystallization on the magnetic properties is studied via MvsH data at room temperature carried out to as-cast and heated samples. X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TGA), magnetization of the magnetic field (MvsH) and magnetization versus temperature (MvsT) are reported. The values of Curie temperatures determined via TGA measurements are in agreement with that estimated via MvsT data. DSC measurements are carried out in isothermal and non-isothermal modes, and from the non-isothermal results, we define the temperatures of the isotherms. These isothermal data were fitted using the Johnson-Mehl-Avrami (JMA) model to Fe40Ni40P14B6 ribbon yielding an Avrami exponent, m > 2.5, to isothermal curves in the onset of crystallization process and 1.5 < m < 2.5 to intermediate regions of crystallization process. It is worth to comment that we are able to fit the non-isothermal curves for using the JMA model. XRD measurements taken after TGA measurement (T = 800oC) allow us to identify nanoparticles with Fe-Ni-based and Fe3B0.82P0.18 crystallographic phases to Fe40Ni40P14B6 ribbon and nanoparticles with Fe3Si crystallographic phase to the case of Fe76.5Cu1Nb3Si13.5B6 ribbon. The MvsH data are consistent with the crystallization processes which take place in amorphous magnetic materials.
Neste trabalho, nós estudamos os processos de cristalização em fitas magnéticas amorfas de Fe40Ni40P14B6 e Fe76.5Cu1Nb3Si13.5B6 fabricadas através da técnica de melt spinning. As medidas das curvas de MvsH a temperatura ambiente nas fitas como produzidas e tratadas termicamente permitiram estudar o efeito da cristalização nas propriedades magnéticas. As amostras foram caracterizadas através de medidas de difração de raios X (DRX), calorimetria exploratória diferencial (DSC), termogravimetria (TGA), magnetização em função do campo magnético (MvsH) e magnetização em função da temperatura (MvsT). Medidas de TGA mostraram-se eficazes para determinação da temperatura de Curie desses materiais, confirmadas pelas medidas de MvsT. Nós também realizamos medidas de DSC nos modos isotérmicos e não isotérmicos e, a partir dos resultados não isotérmicos, nós definimos as temperaturas de realização das isotermas. Em seguida, o modelo de Johnson-Mehl-Avrami (JMA) foi aplicado para a fita de Fe40Ni40P14B6. Para esses dados, o modelo JMA foi satisfeito e o valor do expoente de Avrami foi de m > 2.5 na região onde a curva de fluxo de calor aumenta e 1.5 < m < 2.5 nas regiões intermediárias entre o início do aumento da curva e pico de cristalização. Para as curvas não isotérmicas, o modelo de JMA não foi satisfeito. Para a fita de composição Fe76.5Cu1Nb3Si13.5B6 o modelo de JMA não foi testado. As medidas de DRX realizadas na fita de Fe40Ni40P14B6 após tratamento térmico identificaram fases nanocristalinas a base de Fe-Ni e contendo Fe3B0.82P0.18 e para a fita de Fe76.5Cu1Nb3Si13.5B6 a fase Fe3Si foi observada. As medidas de MvsH confirmaram as mudanças nas propriedades magnéticas de acordo com as frações cristalizadas dos materiais.
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Wade, Mary E. "Engineering of Elastomeric Biomaterials and Biomimicry of Extracellular Matrix for Soft Tissue Regeneration." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1478000902817738.
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Štulrajterová, Lujza. "Vlastnosti vláken na bázi polyhydroxybutyrátu." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2018. http://www.nusl.cz/ntk/nusl-376819.
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Táto práca sa zaoberá zvlákňovaním biopolymérov z taveniny. V teoretickej časti sú zhrnuté doterajšie poznatky o zvlákňovaní poly(3-hydroxy butyrátu) (PHB) a poly(mliečnej kyseliny) (PLA). Následne boli zvláknené polymérne zmesi na báze PHB s rôznym zložením, čo umožnilo štúdium vplyvu PLA, zmäkčovadiel a ich množstva na vlastnosti pripravených vlákien. Boli použité tri komerčné zmäkčovadlá (ATBC, PEG, A6) a dva experimentálne syntetizované. Zvláknenie bolo prevedené na troch rôznych zvlákňovacích linkách. Konvenčné zvlákňovacie linky s odťahovými rýchlosťami nad 150 m/min sa preukázali ako nevhodné pre spracovanie našich zmesí. Kvôli nedostatočnej pevnosti taveniny sú potrebné nízke odťahové rýchlosti. Boli pripravené vlákna s dĺžiacim pomerom 6,4; ktoré boli následne analyzované pomocou GPC, MDSC a ťahovej skúšky. Na základe nameraných teplôt skelného prechodu zmäkčovadlá ATBC a PEG vykázali lepšiu schopnosť zmäkčiť skúmané PLA/PHB zmesi. Vlákna obsahujúce A6 vykazovali najvyššiu pevnosť v ťahu (250 MPa) a modul pružnosti (2,7 GPa). Nakoniec bol skúmaný vplyv starnutia, tepla a vriacej vody na mechanické vlastnosti týchto vlákien.