Air Recirculation and Its Effect on Microfiber Spinning in Blunt-Die Melt Blowing

Sheng Xie,Guojun Jiang,Xianyan Wu,Yaping Wang,Haisu Fang,Baoqing Shentu 한국섬유공학회 2021 Fibers and polymers Vol.22 No.3

In the present work, approaches of the Computational Fluid Dynamics (CFD) simulation, the Particle ImageVelocimetry (PIV) measurement, and the spinning experiment were applied to investigate the phenomenon of air recirculation inblunt-die melt-blown airflow. Firstly, the characteristics of air recirculation were explored by CFD simulation. The simulationresults predicted that the air recirculation generated a lateral air velocity along the nose-piece direction. Then, the aircirculation was experimental verified by using PIV technique. The PIV results confirmed the predicted conclusions of CFDsimulation. Finally, the effect of air recirculation on the microfiber spinning during the melt-blown process was experimentallyinvestigated by a spinning experiment using a blunt die with nose-piece width of 2.56 mm. The spinning results indicated thatthe air circulation had a tendency of splitting the normal polymeric stream, which played negative effect on the continuity ofmicrofiber spinning. This work is expected to provide some clues to melt-blown die design and the quality control ofnonwoven products.

Melt processable polyacrylonitrile copolymer precursors for carbon fibers: Rheological, thermal, and mechanical properties

Lee, Jae Hyeok,Jin, Jeong-Un,Park, Sejoon,Choi, Dalsu,You, Nam-Ho,Chung, Yongsik,Ku, Bon-Cheol,Yeo, Hyeonuk Elsevier 2019 Journal of industrial and engineering chemistry Vol.71 No.-

<P><B>Abstract</B></P> <P>Polyacrylonitrile (PAN) copolymers containing varying amounts of methyl acrylate (MA), P(AN-<I>co</I>-MA), were synthesized as a melt-spinnable precursor of carbon fibers. The rheological properties of P(AN-<I>co</I>-MA) with MA content of 15mol% at 190°C proved to be suitable for melt-spinning and the PAN fiber was spun from an extruder. In order to prevent remelting and fusion of the fibers in the stabilization process, electron-beam irradiation of over 1500kGy was used and the melt-spun PAN fibers were successfully converted to stabilized PAN fibers by thermal treatment up to 250°C. Finally, carbon fibers (CFs) were produced by pyrolysis of the stabilized PAN fibers. The mechanical properties of the resulting-CFs were evaluated; the tensile strength, tensile modulus, and elongation at break were 1.37±0.2GPa, 110±11.1GPa, and 1.27±0.28%, respectively. These results suggest the possibility of utilizing melt-spinning as a cost-efficient method for fabrication of carbon fibers.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Poly(acrylonitrile-<I>co</I>-methylacrylate) was synthesized as a melt processible carbon fiber precursor. </LI> <LI> Thermal and rheological analysis confirmed flow characteristics suitable for melt-spinning. </LI> <LI> The precursor fibers were thermally stabilized by assistance of electron-beam irradiation without re-melting and fusion. </LI> <LI> The mechanical properties of resulting-carbon fiber were 1.37GPa in tensile strength and 110GPa in modulus, respectively. </LI> </UL> </P>

용융방사법으로 제작된 Cu1.98Se의 열전특성

탁장렬,임영수 대한금속·재료학회 2018 대한금속·재료학회지 Vol.56 No.7

Cu2Se exhibits very low thermal conductivity and the origin is known to be the "liquid-like" behavior of Cu ions around the sub-lattice of Se. Due to its very high ZT, research interest in the thermoelectric properties of this material has been increasing rapidly. However, most studies have used a conventional melting process, and, to the best of our knowledge, the melt-spinning process has not yet been employed to fabricate the Cu2Se compound. Herein, we report the thermoelectric properties of Cu1.98Se compounds prepared by melt-spinning. Depending on the cooling rate, we could control the microstructure of the melt-spun Cu1.98Se ribbons successfully. The melt-spun ribbons were consolidated using a hot press, and the thermoelectric properties of the compounds were characterized. Although the electrical conductivity of the compound decreased as compared with the Cu1.98Se compound prepared by the conventional method, an increase in Seebeck coefficient led to an improved power factor in the compound prepared by melt-spinning. Furthermore, a reduction in thermal conductivity due to the reduced contribution of electronic to total conductivity resulted in the enhancement of ZT values in the Cu1.98Se compound.

Melt-spun Liquid Core Fibers: A CFD Analysis on Biphasic Flow in Coaxial Spinneret Die

Mohammadreza Naeimirad,Ali Zadhoush 한국섬유공학회 2018 Fibers and polymers Vol.19 No.4

Simulation of co-flowing behavior in a coaxial geometry (based on the designed spin pack) has been performed using properties of two immiscible liquids to represent flowing regime while passing through the spinneret for production of liquid core fiber (LCF) by one single step high-speed melt-spinning process. Computational Fluid Dynamics (CFD) simulations confirmed the continuous liquid core channel, obtained in bicomponent melt-spinning of LCF. Also different interface morphologies could be observed: from jetting to dripping and transition core-annular regime, based on the simulation parameters, affecting the driving forces. Results showed different co-flow regimes by systematic variation in nondimensional parameters (flow rate ratio, viscosity ratio, Reynolds number, Weber number and Capillary number), individually. Also diameter of the core liquid is reduced in a logarithmic mode by increasing the outer liquid’s flow rate. Flowing morphologies at different conditions were plotted in 2D state diagrams, illustrating transition from dripping to jetting regime by changing two different parameters. This CFD analysis bears potential for simple ways of controlled jet breakup in microfluidic devices, which currently primarily rely on Rayleigh-Taylor breakup. Notably this work highlights the melt-flow regime in the spinneret to realize developed fiber core structures at different conditions during bicomponent melt-spinning. Using various materials with different properties in liquid core fiber production promises many applications for this new generation fiber in very near future.

Double magnetic entropy change peaks and high refrigerant capacity in Gd1- xHoxNi compounds in the melt-spun form

Jun-fan Jiang,Hao Ying,Tang-fu Feng,Ren-bing Sun,Xie Li,Fang Wang 한국물리학회 2018 Current Applied Physics Vol.18 No.12

Gd1-xHoxNi melt-spun ribbons were fabricated by a single-roller melt spinning method. All the compounds crystallize in an orthorhombic CrB-type structure. The Curie temperature (TC) was tuned between 46 and 99 K by varying the concentration of Gd and Ho. A spin reorientation (SRO) transition is observed around 13 K. Different from TC, the SRO transition temperature is almost invariable for all compounds. Two peaks of magnetic entropy change (ΔSM) were found. One at the higher temperature range was originated from the paramagnet-ferromagnet phase transition and the other at the lower temperature range was caused by the SRO transition. The maximum of ΔSM around TC is almost same. The other maximum of ΔSM around SRO transition, however, had significantly positive relationship with x. It reached a maximum about 8.2 J kg−1 K−1 for x=0.8. Thus double large ΔSM peaks were obtained in Gd1-xHoxNi melt-spun ribbons with the high Ho concentration. And the refrigerant capacity power reached a maximum of 622 J kg−1 for x=0.6. Gd1-xHoxNi ribbons could be good candidate for magnetic refrigerant working in the low temperature especially near the liquid nitrogen temperature range.

Effect of spinning conditions on the diameter of pitch fiber during the melt-spinning

고윤영,정진영,이영석 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.0

대량용해 Ti0.85Zr0.13(Fex-V)0.56Mn1.47Ni0.05 수소저장합금의용융방사공정을 통한 수소저장특성

김진호,한규성 한국수소및신에너지학회 2013 한국수소 및 신에너지학회논문집 Vol.24 No.5

Hydrogen storage as a metal hydride is the most promising alternative because of its relatively large hydrogen storage capacities near room temperature. TiMn2-based C14 Laves phases alloys are one of the promising hydrogen storage materials with easy activation, good hydriding-dehydriding kinetics, high hydrogen storage capacity and relatively low cost. In this work, multi-component, hyper-stoichiometric Ti0.85Zr0.13(Fex-V)0.56Mn1.47Ni0.05 C14 Laves phase alloys were prepared by a vacuum induction melting for a hydrogen storage tank. Since pure vanadium (V) is quite expensive, the substitution of the V element in these alloys has been tried and some interesting results were achieved by replacing V by commercial ferrovanadium (FeV) raw material. In addition,the melt-spinning process, which was applied to the manufacturing of some of these alloys, could make the plateau slopes much flatter, which resulted in the increase of reversible hydrogen storage capacity. The improvement of sloping properties of melt-spun Ti0.85Zr0.13(Fex-V)0.56Mn1.47Ni0.05 alloys was mainly attributed to the homogeneity of chemical composition.

Control of electrical to thermal conductivity ratio for <i>p</i>-type La_xFe₃CoSb₁₂ thermoelectrics by using a melt-spinning process

Son, Geonsik,Lee, Kyu Hyoung,Park, Hae-Woong,Caron, Arnaud,Kim, Il-Ho,Lee, Soonil,Choi, Soon-Mok Elsevier 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.729 No.-

<P><B>Abstract</B></P> <P>In this work we improved the thermoelectric figure of merit <I>ZT</I> in a La<SUB>x</SUB>CoFe<SUB>3</SUB>Sb<SUB>12</SUB> (x = 0.80, 0.85, 0.90) skutterudite system by applying a conductivity ratio (electrical to thermal) control method based on the phonon-glass electron-crystal (PGEC) approach. Polycrystalline bulks of La<SUB>x</SUB>CoFe<SUB>3</SUB>Sb<SUB>12</SUB> were prepared by melt-spinning and subsequent spark plasma sintering. Based on the thermoelectric transport properties and microstructural analysis, we found that large amount of La-filler (x ≥ 0.9) in the La<SUB>x</SUB>CoFe<SUB>3</SUB>Sb<SUB>12</SUB> system is necessary to increase the conductivity ratio required to improve the thermoelectric properties in the La<SUB>x</SUB>CoFe<SUB>3</SUB>Sb<SUB>12</SUB> system. Resultantly, the maximum <I>ZT</I> value of 0.87 was obtained at 723 K in the heavily filled La<SUB>0.9</SUB>CoFe<SUB>3</SUB>Sb<SUB>12</SUB>. We discuss our results on the basis of the filling level dependence of the rattling effect and on the formation of the skutterudite single phase. We also confirm that a large amount of La-filling level is necessary to meet the electrical neutrality condition of the <I>p</I>-type La<SUB>x</SUB>CoFe<SUB>3</SUB>Sb<SUB>12</SUB> skutterudite system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nanocrystalline of La<SUB>x</SUB>CoFe<SUB>3</SUB>Sb<SUB>12</SUB> samples were prepared by melt-spinning and SPS sintering. </LI> <LI> The conductivity ratio is a critical parameter to determine thermoelectric performance. </LI> <LI> Large amount of La filler is necessary to increase the conductivity ratio. </LI> <LI> Rattling effect by La filler is confirmed to be the main mechanism for phonon scattering. </LI> </UL> </P>

Investigation of PdTe2 phase segregation on thermoelectric properties of n-type Bi2Te2.7Se0.3 fabricated by melt-spinning technique for possible carrier filtering effect

Dong Ho Kim,Hyun-Sik Kim,Seokown Hong,Ju Hyeong Lee,Jae Gwan Han,Hong Sik Cho,Se Woong Lee,Sang-il Kim 대한금속·재료학회 2021 ELECTRONIC MATERIALS LETTERS Vol.17 No.5

Influence of secondary phases of PdTe2in n-type thermoelectric Cu0.008Bi2Te2.7Se0.3alloys on their thermoelectric propertieswas investigated through in situ phase separation by melt spinning process. The phase segregation of PdTe2in theCu0.008Bi2Te2.7Se0.3matrix were successfully induced by using the melt spinning process. Since heterointerfaces of PdTe2and Cu0.008Bi2Te2.7Se0.3form potential barriers, low energy carrier filtering effect could be expected; however, the powerfactor and effective mass decreased with the PdTe2addition, which implies that the carrier filtering effect did not occur. Thepotential barrier of 0.06 eV expected at the interfaces between PdTe2and Cu0.008Bi2Te2.7Se0.3matrix seems not to inducecarrier energy filtering effect. However, further investigation based on single parabolic band model shows that the non-degeneratemobility and quality factor B are enhanced by PdTe2addition, suggesting that the further optimization of the carrierconcentration would increase zT further in PdTe2-added Cu0.008Bi2Te2.7Se0.3samples. This implies that the favorable carrierfiltering effect could be attained by further controlling the optimal carrier concentration even with small barrier heights.

Poly(ethylene 2,6-naphthalene dicarboxylate) 섬유의 고속방사에 따른 미세구조 형성과 물성

조현혹,이화경,김주애,Takeshi Kikutani 한국섬유공학회 2001 한국섬유공학회지 Vol.38 No.11

PEN fibers of two different molecular weights. low and high, were prepared by high-speed melt spinning. The fine structure and physical properties of PEN fibers were investigated with various techniques such as wide-angle X-ray diffraction, birefringence, density. DSC, dynamic viscoelasticity, and tensile testing. From the WAXD test, PEN fibers of high molecular weight was found to have a reflection peak associated with orientation-induced crystallization that started to appear at take up velocities above 3km/min. In this region, the crystalline structure was dominated by $\beta$ form crystal. This tendency was also confirmed by DSC thermogram, density, and birefringence data. In the DSC thermograms, the melting peak shifted to higher temperature with increasing take-up velocity, while the area of cold crystallization peak decreased. Especially, the temperature of melting peak increased remarkably with increasing take-up velocity in the range of 2$65^{\circ}C$ to 298$^{\circ}C$ for PEN fibers of high molecular weight. Mechnaical properties of the two PEN fibers were relatively improved by the high-speed melt spinning at higher spinning speeds. However, the initial modulus and tenacity of PEN fibers of high molecular weight decreased slightly at the take-up velocity of 7km/min.