Theory and Simulation of Fiber Texture Formation and Rheology of Carbonaceous Mesophase Fibers

2001 ◽  
Vol 709 ◽  
Author(s):  
A. D. Rey
Keyword(s):  
Liquid Crystals ◽  
High Performance ◽  
Melt Spinning ◽  
Elongational Flow ◽  
Fiber Texture ◽  
Texture Formation ◽  
Cross Sectional ◽  
Wide Range ◽  
Spinning Process ◽  
Sectional Shape

ABSTRACTCarbonaceous mesophases are discotic nematic liquid crystals that are spun into high performance carbon fibers using the melt spinning process. The spinning process produces a wide range of different fiber textures and cross-sectional shapes. Circular planar polar (PP), circular planar radial (PR) textures, ribbon planar radial (RPR), and ribbon planar line (RPL) textures are ubiquitous ones. This paper presents, solves, and validates a model of mesophase fiber texture formation based on the classical Landau-de Gennes theory of liquid crystals, adapted here to carbonaceous mesophases. The effects of fiber cross-sectional shape and elongational flow on texture formation are characterized. Emphasis is on qualitative model validation using existing experimental data [1, 2]. The results provide additional knowledge on how to optimize and control mesophase fiber textures.

scholarly journals The Effect of External Magnetic Field on Microstructure and Magnetic Properties of Melt-Spun Nd-Fe-B/Fe-Co Nanocomposite Ribbons

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Xuan Truong Nguyen ◽  
Hong Ky Vu ◽  
Hung Manh Do ◽  
Van Khanh Nguyen ◽  
Van Vuong Nguyen
Keyword(s):  
Magnetic Field ◽  
Grain Size ◽  
High Performance ◽  
Melt Spinning ◽  
Nominal Composition ◽  
Energy Product ◽  
Melt Spun ◽  
Spinning Process ◽  
Reduction Effect ◽  
Microstructure And Magnetic Properties

The ribbons Nd2Fe14B/Fe-Co were prepared with the nominal composition Nd16Fe76B8/40% wt. Fe65Co35by the conventional and the developed magnetic field-assisted melt-spinning (MFMS) techniques. Both ribbons are nanocomposites with the smooth single-phase-like magnetization loops. The 0.32 T magnetic field perpendicular to the wheel surface and assisting the melt-spinning process reduces the grain size inside the ribbon, increases the texture of the ribbon, improves the exchange coupling, and, in sequence, increases the energy product(BH)maxof the isotropic powdered samples of MFMS ribbon in ~9% by comparison with that of the ribbon melt-spun conventionally. The grain size reduction effect caused by the assisted magnetic field has also been described quantitatively. The MFMS technique seems to be promising for producing high-performance nanocomposite ribbons.

scholarly journals Structure and Properties of a Metallocene Polypropylene Resin with Low Melting Temperature for Melt Spinning Fiber Application

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 729
Author(s):  
Renwei Xu ◽  
Peng Zhang ◽  
Hai Wang ◽  
Xu Chen ◽  
Jie Xiong ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Melting Temperature ◽  
High Performance ◽  
Melt Spinning ◽  
Deep Understanding ◽  
Metallocene Catalyst ◽  
Fiber Spinning ◽  
X Ray Diffraction ◽  
Wide Range ◽  
Two Samples

An isotactic polypropylene (iPP-1) resin with low melting temperature (Tm) is synthesized by a metallocene catalyst and investigated for melt-spun fiber applications. The structure, thermal and mechanical properties, and feasibility of producing fibers of a commercial metallocene iPP (iPP-2) and a conventional Ziegler–Natta iPP (iPP-3) are carefully examined for comparison. Tm of iPP-1 is about 10 °C lower than the other two samples, which is well addressed both in the resin and the fiber products. Besides, the newly developed iPP-1 possesses higher isotacticity and crystallinity than the commercial ones, which assures the mechanical properties of the fiber products. Thanks to the addition of calcium stearate, its crystal grain size is smaller than those of the two other commercial iPPs. iPP-1 shows a similar rheological behavior as the commercial ones and good spinnability within a wide range of take-up speeds (1200–2750 m/min). The tensile property of fibers from iPP-1 is better than commercial ones, which can fulfill the application requirement. The formation of the mesomorphic phase in iPP-1 during melt spinning is confirmed by the orientation and crystallization investigation with wide angle X-ray diffraction (WAXD), which is responsible for its excellent processing capability and the mechanical properties of the resultant fibers. The work may provide not only a promising candidate for the high-performance PP fiber but also a deep understanding of the formation mechanism of the mesomorphic phase during fiber spinning.

scholarly journals Microstructure Evolution and Mechanical Properties of Melt Spun Skutterudite-based Thermoelectric Materials

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 984 ◽  
Author(s):  
Huiyuan Geng ◽  
Jialun Zhang ◽  
Tianhong He ◽  
Lixia Zhang ◽  
Jicai Feng
Keyword(s):  
Mechanical Properties ◽  
Spinodal Decomposition ◽  
Microstructure Evolution ◽  
Thermoelectric Materials ◽  
High Performance ◽  
Melt Spinning ◽  
Bending Strength ◽  
Annealed Sample ◽  
Submicron Scale ◽  
Spinning Process

The rapid solidification of melt spinning has been widely used in the fabrication of high-performance skutterudite thermoelectric materials. However, the microstructure formation mechanism of the spun ribbon and its effects on the mechanical properties are still unclear. Here, we report the microstructure evolution and mechanical properties of La–Fe–Co–Sb skutterudite alloys fabricated by both long-term annealing and melt-spinning, followed by sintering approaches. It was found that the skutterudite phase nucleated directly from the under-cooled melt and grew into submicron dendrites during the melt-spinning process. Upon heating, the spun ribbons started to form nanoscale La-rich and La-poor skutterudite phases through spinodal decomposition at temperatures as low as 473 K. The coexistence of the micron-scale grain size, the submicron-scale dendrite segregation and the nanoscale spinodal decomposition leads to high thermoelectric performance and mechanical strength. The maximum three-point bending strength of the melt spinning sample was about 195 MPa, which was 70% higher than that of the annealed sample.

Study on On the Cross-Sectional Shape Change of the Profiled Fiber along the Spinning Path in Melt Spinning

2012 ◽  
Vol 602-604 ◽  
pp. 1804-1807
Author(s):  
Yue Wang ◽  
Wu Shan Cheng ◽  
Ming Hong Wang
Keyword(s):  
Numerical Simulation ◽  
Physical Properties ◽  
Melt Spinning ◽  
Shape Change ◽  
Deformation Degree ◽  
Cross Sectional ◽  
The Cross ◽  
Profiled Fibers ◽  
Sectional Shape ◽  
Profiled Fiber

The cross-sectional shape of profiled fibers has made obvious influence on fibers physical properties. The fiber profiled factor is an index used to estimate the deformation degree of profiled fibers. Based on the equations of melt-spinning dynamics and deformation, a numerical simulation program for calculating the fiber profiled factor along the spinning path was developed. A numerical simulation for calculating the fiber profiled factor along the spinning path of trilobal fibers in the PET melt spinning was performed. The simulation result graph of the fiber profiled factor along the spinning path is close to the final average fiber profiled factor measured in the spinning experiment under the same condition.

Analytical description of the scattering of cellulose nanocrystals in tracheid wood cells

2010 ◽  
Vol 43 (2) ◽  
pp. 256-263 ◽  
Author(s):  
Malte Ogurreck ◽  
Martin Müller
Keyword(s):  
Cellulose Nanocrystals ◽  
Microfibril Angle ◽  
Analytical Description ◽  
Fiber Texture ◽  
Cell Axis ◽  
Cross Sectional ◽  
Scattering Geometry ◽  
Sample Orientation ◽  
Additional Level ◽  
Sectional Shape

Tracheid cells are complex structures. The cellulose nanocrystals are wound in helices around the tracheid cell axis. The microfibril angle describes the angle between the cellulose crystals and the cell axis. Furthermore, the cross-sectional shape of tracheids varies widely, ranging from square to round. These parameters affect the scattering geometry and thus the experimental scattering signal. In an experiment, the macroscopic sample orientation relative to the beam is a further variable. Here, a description is presented that allows the calculation of azimuthal scattering patterns for anyhklreflection from cellulose nanocrystals in tracheid cells of any orientation. Additionally, this model can be used to describe fibrillar aggregates with an additional level of organization that surpasses an ideal fiber texture, for example pairs of twisted fibers.

scholarly journals Transient Confinement of the Quaternary Tetramethylammonium Tetrafluoroborate Salt in Nylon 6,6 Fibres: Structural Developments for High Performance Properties

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2938
Author(s):  
Ahmed Dawelbeit ◽  
Muhuo Yu
Keyword(s):  
Phase Transitions ◽  
High Performance ◽  
Melt Spinning ◽  
Structural Phase ◽  
Tensile Modulus ◽  
High Strength ◽  
Strength Properties ◽  
Nylon 6,6 ◽  
Spinning Process ◽  
Hot Drawing

A temporary confinement of the quaternary tetramethylammonium tetrafluoroborate (TMA BF4) salt among polyamide molecules has been used for the preparation of aliphatic polyamide nylon 6,6 fibres with high-modulus and high-strength properties. In this method, the suppression or the weakening of the hydrogen bonds between the nylon 6,6 segments has been applied during the conventional low-speed melt spinning process. Thereafter, after the complete hot-drawing stage, the quaternary ammonium salt is fully extracted from the drawn 3 wt.% salt-confined fibres and the nascent fibres are, subsequently, thermally stabilized. The structural developments that are acquired in the confined-nylon 6,6 fibres are ascribed to the developments of the overall fibres’ properties due to the confinement process. Surprisingly, unlike the neat nylon 6,6 fibres, the X-ray diffraction (XRD) patterns of the as-spun salt-confined fibres have shown diminishing of the (110)/(010) diffraction plane that obtained pseudohexagonal-like β’ structural phase. Moreover, the β’ pseudohexagonal-like to α triclinic phase transitions took-place due to the hot-drawing stage (draw-induced phase transitions). Interestingly, the hot-drawing of the as-spun salt-confined nylon 6,6 fibres achieved the same maximum draw ratio of 5.5 at all of the drawing temperatures of 120, 140 and 160 °C. The developments that happened produced the improved values of 43.32 cN/dtex for the tensile-modulus and 6.99 cN/dtex for the tensile-strength of the reverted fibres. The influences of the TMA BF4 salt on the structural developments of the crystal orientations, on the morphological structures and on the improvements of the tensile properties of the nylon 6,6 fibres have been intensively studied.

Influence of Morphology on Flow Law Characteristics in Open-Cell Foams: An Overview of Usual Approaches and Correlations

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Prashant Kumar ◽  
Frédéric Topin
Keyword(s):  
High Performance ◽  
Pore Space ◽  
Cross Sectional ◽  
Open Cell ◽  
Industrial Systems ◽  
Wide Range ◽  
Open Cell Foam ◽  
Successful Design ◽  
Open Cell Foams ◽  
Flow Law

Foam structures have been a subject of intensive research since the last decade. The pore space in open-cell foam is interconnected, forming perforated channels of varying cross-sectional areas where fluid can flow. Knowledge of pressure drop induced by these foam matrices is essential for successful design and operation of high-performance industrial systems. In this context, analytical correlations were derived for the determination of Darcian permeability (KD) and Forchheimer inertia coefficient (CFor) in open-cell foams of different strut shapes. It has been shown that the flow law characteristics are strongly dependent on strut shape, strut characteristic dimension, and length. The applicability of new correlations was examined by comparing and validating the numerical and experimental flow law characteristics data against the predicted ones. An excellent agreement has been observed for the foam structures of different materials and variable texture in a wide range of porosity and Reynolds number.

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