The continuous production of macroscale filaments of 17 μm in diameter comprising aligned TEMPO-oxidized cellulose nanofibrils (CNFs) is conducted using a fieldassisted flow-focusing process. The effect of an AC external field on the material's structure becomes significant at a certain voltage, beyond which augmentations of the CNF orientation factor up to 16% are obtained. Results indicate that the electric field significantly contributes to improve the CNF ordering in the bulk, while the CNF alignment on the filament surface is only slightly affected by the applied voltage. X-ray diffraction shows that CNFs are densely packed anisotropically in the plane parallel to the filament axis without any preferential out of plane orientation. The improved nanoscale ordering combined with the tight CNF packing yields impressive enhancements in mechanical properties, with stiffness up to 25 GPa and more than 63% (up to 260 MPa), 46% (up to 2.8%), and 120% (up to 4.7 kJ/m 3 ) increase in tensile strength, strain-to-failure, and toughness, respectively. This study demonstrates for the first time the control over the structural ordering of anisotropic nanoparticles in a dynamic system using an electric field, which can have important implications for the development of sustainable alternatives to synthetic textiles.
This paper presents a numerical investigation of characteristics and processes in the worldwide unique type of thermal plasma generator with combined stabilization of arc by argon flow and water vortex, the so-called hybrid-stabilized arc. The arc has been used for spraying of ceramic or metallic particles and for pyrolysis of biomass. The net emission coefficients as well as the partial characteristics methods for radiation losses from the argon–water arc are employed. Calculations for 300–600 A with 22.5–40 standard litres per minute (slm) of argon reveal transition from a transonic plasma flow for 400 A to a supersonic one for 600 A with a maximum Mach number of 1.6 near the exit nozzle of the plasma torch. A comparison with available experimental data near the exit nozzle shows very good agreement for the radial temperature profiles. Radial velocity profiles calculated 2 mm downstream of the nozzle exit show good agreement with the profiles determined from the combination of calculation and experiment (the so-called integrated approach). A recent evaluation of the Mach number from the experimental data for 500 and 600 A confirmed the existence of the supersonic flow regime.
The real-time computational simulation of arc melting process with considering complex interactions and solid-liquid mushy zone in molten anode has been successfully conducted to provide the fundamental data for highly economical performance of arc melting process. The configuration of molten anode predicted by realistic numerical model shows the quantitative agreement with the experimental data. The effects of sulfur content concentration in molten metal, arc current and cathode vertex angle on the welding structure is discussed in detail. Finally, the heat exchange efficiency and molten cross-sectional area are evaluated under different arc currents and cathode vertex angles for optimum welding process with high efficiency.KEY WORDS: arc melting system; complex interactions; mushy zone; real-time computational simulation.(8) Evaporation, deformation and charge on the molten anode surfaces are neglected for simplicity. (9) Evaporation, melting and deformation on the cathode surface are neglected for simplicity. Under these assumptions, the governing equations for arc and electrodes region are presented as follows.Conservation c Ar c Ar The initial conditions of arc melting process are the steady thermofluid fields of arc without melting anode. Table 1 shows the system configuration and operating conditions. The thermofluid field is solved by SemiImplicit-Method for Pressure Linked Equation (SIMPLE) method 14) using Tri Diagonal-Matrix Algorithm (TDMA). The electromagnetic field is solved by SOR method. In this study, 90 grid points are adopted in both axial and radial directions. The thermodynamic and transport properties of argon, tungsten and stainless steel are given as a function of temperature. 10,[15][16][17][18][19][20][21] The viscosity in the solid-liquid mushy zone is as a function of liquid fraction. Numerical Conditions and Procedures 22) Numerical Results and DiscussionFigures 2(a) and 2(b) show the effect of sulfur content on the temperature fields of arc and molten pool. The steady state of molten pool is obtained approximately 20 s after arc generation. It is found that sulfur content does not affect the arc flow so much even near interface, however, the welding structure changes drastically by sulfur content. In the case of low sulfur content in SUS304 as shown in Fig. 2(a), the molten metal spreads outward. On the other hand, in the case of high sulfur content in SUS304, the molten pool penetrates downward in the core region.Figures 3(a) and 3(b) show the four kinds of driving forces which affects surface flow induced on the molten pool corresponding as shown in Figs. 2(a) and 2(b). In the case of low sulfur content in SUS304, shear force resulting from cathode jet is stronger at the inner molten region but surface tension is stronger at the outer molten region. Then, total driving force shows positive at the inner molten region but negative at the outer one, which induce the outward and inward flows correspondingly. On the other hand, in case of high sulfur content in SUS304, surface tension...
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