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Effect of melt spinning on the microstructure and mechanical properties of three nickel base superalloysBowman, R. R. (Randy R.) 08 1900 (has links)
No description available.
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Extrusion die design using finite element method for sheet and pipe diesHuang, Yihan January 1999 (has links)
No description available.
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Mechanisms of extrudate swell and melt fracture in SBR compoundsSirisinha, Chakrit January 1996 (has links)
The purpose of this study is to identify and quantify factors governing extrudate swell and melt fracture. In the first part, the factors which control the extrudate swell of carbon black (N330) filled styrene-butadiene rubber (SBR) compounds at various states-of-mix were investigated. State-of-mix is quantified by effective filler volume fraction (EFVF), based on an estimate of the amount of rubber immobilised in the carbon black agglomerates. Extrudate swell was found to be dominated by recoverable strain and relaxation time, which are controlled by EFVF. In contrast, shear rate and the rubber-carbon black tridimensional transient network were not found to influence extrudate swell significantly. In the second part, melt fracture of the rubber compounds was investigated in terms of surface texture wavelength. The longer the wavelength, the greater the severity of the surface disruption. It was found that wavelength was controlled strongly by state-of mix (or by EFVF). In addition, a mechanism for melt fracture of the compounds studied has been proposed, based on average energy at the extrudate surface (t.E). Lastly, the influences of additives; paraffinic processing oil, stearic acid or a mixture of predominantly calcium fatty acid soaps on extrudate swell and melt fracture were investigated. For the rubber compounds with paraffinic processing oil or stearic acid, EFVF was found to play an important role in extrudate swell. The mixture of fatty acid soaps was shown to reduce significantly extrudate swell due to the presence of wall slip. The influence of the fatty acid soaps on extrudate swell is more noticeable for extrudates obtained from long dies, in which flow is dominated by shear. The major factors shown to exert a significant influence on melt fracture for the compounds with paraffinic processing oil or stearic acid are EFVF and green strength of the extrudate. Wall slip, promoted by a mixture of fatty acid soaps, was also found to decrease the melt fracture severity, particularly for long dies in which shear stresses are dominant.
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Solid-state plasticizers for melt extrusion /Desai, Dipen. January 2007 (has links)
Thesis (Ph.D.) -- University of Rhode Island, 2007 / Typescript. Includes bibliographical references (leaves 178-184).
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Analyzing Nitrogen in Silicate Glasses by Secondary Ion Mass SpectrometryJanuary 2016 (has links)
abstract: Volcanic devolatilization is one of the major processes in the global nitrogen cycle. Past studies have often estimated the magnitude of this flux using volcanic emission measurements, which are limited to currently active systems and sensitive to atmospheric contamination. A different methodological approach requires appropriate analytical parameters for nitrogen analysis in silicate glasses by secondary ion mass spectrometry (SIMS), which have not yet been established. To this end, we analyze various ion implanted basaltic and rhyolitic glasses by SIMS. We demonstrate that water content significantly affects the ion yields of 14N+ and 14N16O−, as well as the background intensity of 14N+ and 12C+. Application of implant-derived calibrations to natural samples provide the first reported concentrations of nitrogen in melt inclusions. These measurements are from samples from the Bishop Tuff in California, the Huckleberry Ridge Tuff of the Yellowstone Volcanic Center, and material from the Okaia and Oruanui eruptions in the Taupo Volcanic Center. In all studied material, we find maximum nitrogen contents of less than 45 ppm and that nitrogen concentration varies positively with CO2 concentration, which is interpreted to reflect partial degassing trend. Using the maximum measured nitrogen contents for each eruption, we find that the Bishop released >3.6 x 1013 g of nitrogen, the Huckleberry Ridge released >1.3 x 1014 g, the Okaia released >1.1 x 1011 g of nitrogen, the Oruanui released >4.7 x 1013 g of nitrogen. Simple calculations suggest that with concentrations such as these, rhyolitic eruptions may ephemerally increase the nitrogen flux to the atmosphere, but are insignificant compared to the 4 x 1021 g of nitrogen stored in the atmosphere. / Dissertation/Thesis / Masters Thesis Geological Sciences 2016
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Efeito Hall planar e magneto impedância gigante em liga ferromagnética amorfa Co70Fe5Si15B10GONÇALVES, Lídice Aparecida Pereira January 2006 (has links)
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Previous issue date: 2006 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / 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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The Magmatic Origin and Evolution of the Oxnadalur Volcanic Complex in Northern IcelandKaiser, Jason F 01 January 2010 (has links) (PDF)
The 8-9 million year old volcanic complex of Oxnadalur is host to large-volume basalt flows, small and large volume rhyolite ash and lava flows, and a gabbroic intrusion. Both the plagioclase and pyroxene phenocrysts of the basalt are larger in size in the younger flows. The rhyolite ashes contain no primary crystals, but numerous basalt xenoliths and pumice fragments. The rhyolite lava flows are banded, with only the oldest containing phenocrysts of sanidine and plagioclase. One rhyolite flow is a mingled hybrid of two glasses, each containing plagioclase, pyroxene, and hornblende. Whole rock major and trace element analyses indicate a mixing trend among all of the units in the complex; yet abundant xenoliths in the ashes make this less data less dependable. In situ major and trace element analyses were performed via electron microprobe show two distinct populations in the variation diagrams, with the basalts and rhyolites separated by a compositional gap. Electron microprobe analyses also show that the plagioclase of the basalts and the gabbro are normally zoned with distinct calcic cores and sodic rims; this is also true for the mingled hybrid flow. Rare earth element analyses done via laser ablation inductively coupled plasma mass spectrometry, show that the phenocrysts are enriched in the light and depleted in the heavy rare earth elements. Rare earth element abundances in the glasses have a trend similar to that of ocean island basalt rather than that of mid ocean ridge basalt. Plagioclase geothermometry and amphibole geobarometry indicate that the magma chambers were replenished by new batches of melt and may have existed at a shallow level in the crust just prior to being erupted. Oxygen isotope ratios are depleted compared to those of typical mid ocean ridge basalts, typically indicating that the source melt was partially melted from a hydrothermally altered layer in the crust. As the δ18O values are whole rock, the depletion may be the result of any sub solidus interaction with low δ18O water. The data indicate that multiple shallow reservoirs evolved separately, with limited communication while being intruded by new magma throughout the lifespan of the complex.
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Melt Fracture of PolystyreneLidorikis, Stathis 09 1900 (has links)
<p> A high-pressure nitrogen-driven viscometer has been used to study the melt fracture of polystyrene. The polystyrene samples used differed in molecular weight and molecular weight distribution. The weight average molecular weight (Mw) ranged from 97,200 to 1.8 x 10^6 and the distribution breadth (Mw/Mn) from 1.06 to 9.21. Results obtained indicate that the critical shear stress varies linearly with 1/Mw, increases slightly with temperature and is independent of the polydispersity of polymers. This type of behaviour is satisfactorily explained in terms of Graessley's entanglement theory.</p> / Thesis / Master of Engineering (MEngr)
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Melt Processing of Metastable Acrylic Copolymer Carbon PrecursorsBortner, Michael J. 08 December 2003 (has links)
This thesis is concerned with the development of engineering technologies that facilitate melt spinning of carbon fiber precursors in both an environmentally sound and cost effective manner. More specifically, methods were developed to avoid a degradative process in acrylonitrile copolymers (typically used in textiles and as carbon fiber precursors) that occurs as melt spinning temperatures are approached. The following set of analyses was developed to define the rheological properties required for a melt processable acrylic copolymer suitable for use as a carbon fiber precursor, and accordingly facilitated development of a processing window: measurement of steady shear viscosity as a function of both temperature and time, measurement of the magnitude of the complex viscosity (|η*|) as a function of temperature using a temperature sweep, and measurement of the angular frequency dependence of |η*|. Through a systematic screening process, the following properties were identified to afford melt spinnable acrylic precursors suitable for conversion to carbon fibers: emulsion polymerization, 85-88 mole % acrylonitrile, 11-14 mole % methyl acrylate, 1 mole % acryloyl benzophenone, intrinsic viscosity < 0.6 dL/g, steady shear viscosity ≤ 1000-2000 Pa*s at a shear rate (γ) of 0.1 s⁻¹, viscosity increases ≤ 45% over a period of 1800 seconds at 200-220°C and γ=0.1 s⁻¹. Use of the rheological analyses assisted in development of a melt spinnable carbon fiber precursor, which resulted in carbon fibers possessing a tensile strength and modulus of approximately 1.0 and 120 GPa, respectively.
A second approach was evaluated using carbon dioxide (CO₂) to plasticize AN copolymers to an extent that facilitates processing at reduced temperatures, below where thermal degradation is significant. A batch saturation method to absorb CO₂ in AN copolymers was developed. Differential scanning calorimetry and thermogravimetric analyses were used to measure the glass transition temperature (T<sub>g</sub>) reduction and amount of absorbed CO₂ (respectively). A pressurized rheometer and measurement procedure was designed to obtain viscosity measurements of saturated AN copolymers. Up to 6.7 wt. % CO₂ was found to absorb into a 65 mole % AN copolymer with the saturation method used, resulting in a 31°C glass transition temperature (T<sub>g</sub>) reduction, 60% viscosity reduction, and 30°C potential processing temperature reduction. It was found that CO₂ can absorb into copolymers containing up to 90 mole % AN (with the absorption methods used) with the following results (for a 90/10 mole % AN/MA copolymer): 3.0 wt. % uptake, 27°C T<sub>g</sub> reduction, 56% viscosity reduction, and potential processing temperature reduction of 9°C. Via estimates of the required pressure, sealing fluid flow rate, and length of a pressure chamber to prevent foaming of the saturated polymer melt during extrusion, melt spinning of saturated AN copolymers appears feasible. / Ph. D.
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Establishing the Conditions for Stable Extrusion of Melt Spun Polyacrylonitrile with Water Based PlasticizersYu, Jianger 18 June 2019 (has links)
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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