The Experts below are selected from a list of 2013 Experts worldwide ranked by ideXlab platform
Li Bao - One of the best experts on this subject based on the ideXlab platform.
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Enhanced Aerosol Particle Filtration Efficiency of Nonwoven Porous Cellulose Triacetate Nanofiber Mats
2018Co-Authors: Ratna Balgis, Hiroyuki Murata, Takashi Ogi, Makoto Kobayashi, Li BaoAbstract:Aerosol particle filtration in most penetrating particle size (MPPS) region is of great challenge for conventional nonwoven filter mats. The present work, therefore, redesigns conventional filter mats by introducing porous structure. A combination of thermally induced phase separation and breath figure mechanism was employed to synthesize porous cellulose triacetate fibers, in conjunction with the volatile solvent methylene chloride. The ambient humidity, the concentration of the polyvinylpyrrolidone (PVP) secondary polymer, and the ethanol cosolvent were all adjusted to modify the Taylor Cone formation, jet stability, and fiber porosity. After fiber formation, the PVP was removed to obtain a superhydrophobic material. To distinguish the effect of pores, the performance of porous and nonporous nanofibers having similar sizes was conducted. Tests were performed using various dust particle sizes, and the results show that the collection efficiency of the porous fibers, resulting from particle diffusion, inertial impaction, and interception, was improved. Interestingly, the efficiency of the porous fibers in the MPPS region was exceptionally enhanced (up to 95%), demonstrating that the presence of dynamic pores greatly contributes to particle capture
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synthesis of dual size cellulose polyvinylpyrrolidone nanofiber composites via one step electrospinning method for high performance air filter
Langmuir, 2017Co-Authors: Ratna Balgis, Hiroyuki Murata, Yohsuke Goi, Takashi Ogi, Kikuo Okuyama, Li BaoAbstract:Dual-size nanofibers consisting of a random mixture of nano- and submicron-size nanofibers are promising structures for specific applications such as air filters because of their increased specific surface area and low pressure drop. Synthesis of dual-size nanofibers using one-step electrospinning was reported here for the first time. The formation of well-mixed nano- and submicron-size cellulose–polyvinylpyrrolidone nanofiber composites was accomplished utilizing the physical properties of TEMPO-oxidized cellulose nanofibers (i.e., high thixotropy and high magnitude of zeta potential) and tuning the charge of the polymer jet, which influences the formation and shape of Taylor Cone, and Coulombic explosion. The dual-size nanofibers were then spun on the surface of a HEPA filter to obtain a multilayer air filter. Aerosol filtration measurements show that this multilayer air filter has an incredibly high performance, shown by the high quality factor (Qf), 0.117 Pa–1, which is 10 times the Qf of commercial H...
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Synthesis of Dual-Size Cellulose–Polyvinylpyrrolidone Nanofiber Composites via One-Step Electrospinning Method for High-Performance Air Filter
2017Co-Authors: Ratna Balgis, Hiroyuki Murata, Yohsuke Goi, Takashi Ogi, Kikuo Okuyama, Li BaoAbstract:Dual-size nanofibers consisting of a random mixture of nano- and submicron-size nanofibers are promising structures for specific applications such as air filters because of their increased specific surface area and low pressure drop. Synthesis of dual-size nanofibers using one-step electrospinning was reported here for the first time. The formation of well-mixed nano- and submicron-size cellulose–polyvinylpyrrolidone nanofiber composites was accomplished utilizing the physical properties of TEMPO-oxidized cellulose nanofibers (i.e., high thixotropy and high magnitude of zeta potential) and tuning the charge of the polymer jet, which influences the formation and shape of Taylor Cone, and Coulombic explosion. The dual-size nanofibers were then spun on the surface of a HEPA filter to obtain a multilayer air filter. Aerosol filtration measurements show that this multilayer air filter has an incredibly high performance, shown by the high quality factor (Qf), 0.117 Pa–1, which is 10 times the Qf of commercial HEPA filters
Manuel Gamerocastano - One of the best experts on this subject based on the ideXlab platform.
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characterization of the electrosprays of 1 ethyl 3 methylimidazolium bis trifluoromethylsulfonyl imide in vacuum
Physics of Fluids, 2008Co-Authors: Manuel GamerocastanoAbstract:The electrosprays of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide are composed of a complex mixture of ions and charged droplets, which can be analyzed to determine the structure of the beam and infer significant features of the electrohydrodynamic atomization. In particular, we use a combination of retarding potential and time of flight techniques to study these beams and are able to quantify the voltage drop along the Cone jet, together with the velocity and diameter of the jet at the breakup location, confirm the strong influence of viscosity and electrification in the breakup, show that the electric field in and near the Taylor Cone tip is insensitive to external electrostatic parameters, and study the spatial distribution of ions and droplets, whereby the paradoxical absence of ions in the outmost region of the beam is established. The research described in this article can be exploited in the modeling of capillary instability of charged jets: testing the results of these models is ...
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source of heavy molecular ions based on Taylor Cones of ionic liquids operating in the pure ion evaporation regime
Journal of Applied Physics, 2003Co-Authors: I Romerosanz, Fernandez J De La Mora, R Bocanegra, Manuel GamerocastanoAbstract:The full spray emitted by Taylor Cones of the ionic liquid 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMI+BF4−) held in a vacuum is investigated at room temperature by time of flight mass spectrometry. The current is composed mainly of ions under most conditions studied, but contains a small component of nanometer drops that tends to dominate the emitted mass flow. Exceptionally, drop ejection vanishes close to the smallest flow rate at which the Taylor Cone is steady. The present discovery of a stable strictly ionic regime in Taylor Cones of substances other than liquid metals owes much to earlier observations with sulfuric acid, where most but not all the current was ionic. Most striking is the fact that this purely ionic regime is obtained at an electrical conductivity K of only 1.3 S/m, much smaller than that of sulfuric acid, and smaller than that at which formamide electrolytes with K>2 S/m do still emit substantial drop currents. The ion emission includes primarily the dimer (EMI–BF4)EMI+, acc...
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direct measurement of ion evaporation kinetics from electrified liquid surfaces
Journal of Chemical Physics, 2000Co-Authors: Manuel Gamerocastano, Fernandez J De La MoraAbstract:When concentrated solutions of NaI in formamide with electrical conductivities K larger than 1.1 S/m are electrosprayed from a Taylor Cone-jet in a vacuum, ions are evaporated at substantial rates from the surface of the meniscus and the drops. This constitutes a new source of ions and nanoparticles, where the relative importance of these two contributions is adjustable. The currents of ions are measured independently from those associated with drops by a combination of stopping voltage analysis and preferential scattering in a gas background. The magnitude E of the electric field at the surface of the drops and at the apex of the Cone-jet is controlled through the electrical conductivity K of the liquid and its flow rate Q through the jet. E is related through available scaling laws for Taylor Cone-jets to the ratios K/Q or I/Q, where I is the current of drops emitted by the jet. Ion currents are very small or null at typical K/Q values used in the past. A relatively small initial ion current is attribut...
Wansheng Zhao - One of the best experts on this subject based on the ideXlab platform.
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An experimental study on the effect of parameters on the depth of crater machined by electrostatic field–induced electrolyte jet micro electrical discharge machining
Advances in Mechanical Engineering, 2016Co-Authors: Yaou Zhang, Ning Han, Xiaoming Kang, Wansheng ZhaoAbstract:Electrostatic field–induced electrolyte jet micro electrical discharge machining depends on heat generated by the periodic pulsed discharge between the workpiece and the electrolyte fine jet from the tip of Taylor Cone, induced by the intense electric field, to erode the material from the workpiece. To further investigate the characteristics of this discharge process, with the NaCl solution as the electrostatic field–induced electrolyte jet electrolyte and the silicon wafer as the workpiece, the governing factors of machining polarity, nozzle-to-workpiece distance, voltage applied between positive and negative polarities, and the effect of concentration of the electrolyte on the depth of crater after a single electrostatic field–induced electrolyte jet discharge have been studied. The experimental results show that the average depth of crater increases with the increase in the voltage applied between the nozzle and the workpiece, and increases with the increase in the concentration of the electrolyte, but decreases with the increase in the distance between the nozzle and the workpiece. The results have also demonstrated that the polarity has no clear influence on the average depth of crater after a single discharge.
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an experimental study on the effect of parameters on the depth of crater machined by electrostatic field induced electrolyte jet micro electrical discharge machining
Advances in Mechanical Engineering, 2016Co-Authors: Yaou Zhang, Ning Han, Xiaoming Kang, Wansheng ZhaoAbstract:Electrostatic field–induced electrolyte jet micro electrical discharge machining depends on heat generated by the periodic pulsed discharge between the workpiece and the electrolyte fine jet from the tip of Taylor Cone, induced by the intense electric field, to erode the material from the workpiece. To further investigate the characteristics of this discharge process, with the NaCl solution as the electrostatic field–induced electrolyte jet electrolyte and the silicon wafer as the workpiece, the governing factors of machining polarity, nozzle-to-workpiece distance, voltage applied between positive and negative polarities, and the effect of concentration of the electrolyte on the depth of crater after a single electrostatic field–induced electrolyte jet discharge have been studied. The experimental results show that the average depth of crater increases with the increase in the voltage applied between the nozzle and the workpiece, and increases with the increase in the concentration of the electrolyte, but decreases with the increase in the distance between the nozzle and the workpiece. The results have also demonstrated that the polarity has no clear influence on the average depth of crater after a single discharge.
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the tool electrode investigation of electrostatic field induced electrolyte jet e jet electrical discharge machining
The International Journal of Advanced Manufacturing Technology, 2016Co-Authors: Yaou Zhang, Ning Han, Xiaoming Kang, Kevin Wilt, Wansheng ZhaoAbstract:This investigation addresses concerns in micro-electrical discharge machining (EDM) such as high tool electrode preparation cost, tool electrode wear, and tool electrode compensation by proposing a new electrostatic field-induced electrolyte jet tool electrode. This method utilizes the theory that in a strong direct current electric field, the electrolyte at the capillary tube outlet can form a Taylor Cone based on the balance of electric field force and surface tension. Coupled with the increase of electric field intensity, a very fine jet can eject from the tip of the Taylor Cone, and this induced charge on the tip leads to a discharge to the workpiece which can remove debris from the workpiece surface. After the discharge, the induced charge at the tip is neutralized, leading to the surface tension outweighing the electric field force and the withdrawal of the fine jet. As a result, the cyclic pulse discharge process is generated. During the process, the tip of the fine jet serves as the tool electrode. This paper identifies this cyclic pulse electrolyte jet tool electrode generation and discharge process in action and tests the machining ability of this tool electrode on a silicon wafer. This electrolyte jet tool is also shown to have no wear or compensation issues, and the cost compared to conventional EDM is shown to be small.
Darrell H Reneker - One of the best experts on this subject based on the ideXlab platform.
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corona discharge from electrospinning jet of poly ethylene oxide solution
Polymer, 2009Co-Authors: Sureeporn Tripatanasuwan, Darrell H RenekerAbstract:Abstract Corona discharges from electrospinning jets were observed and photographed at the tip of the Taylor Cone, and in a cylindrical region around the jet, a few millimeters below the tip. The corona discharge was also faintly visible to a dark adapted eye. At the position at which the cylindrical corona discharge became apparent, typical conditions were a jet diameter of 30 μm, an applied potential of 12 kV, and a calculated radial electric field of 400 kV/cm, The calculated electric field required to create a corona in air around a metal wire of the same diameter, calculated from Peek's empirical formula, was only about 200 kV/cm. The cross sectional shape of some segments of the electrospun fibers had two or three lobes. The lobes often separated, and formed smaller fibers.
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Taylor Cone and jetting from liquid droplets in electrospinning of nanofibers
Journal of Applied Physics, 2001Co-Authors: Alexander L Yarin, Sureeporn Koombhongse, Darrell H RenekerAbstract:Sessile and pendant droplets of polymer solutions acquire stable shapes when they are electrically charged by applying an electrical potential difference between the droplet and a flat plate, if the potential is not too large. These stable shapes result only from equilibrium of the electric forces and surface tension in the cases of inviscid, Newtonian, and viscoelastic liquids. In liquids with a nonrelaxing elastic force, that force also affects the shapes. It is widely assumed that when the critical potential φ0* has been reached and any further increase will destroy the equilibrium, the liquid body acquires a conical shape referred to as the Taylor Cone, having a half angle of 49.3°. In the present work we show that the Taylor Cone corresponds essentially to a specific self-similar solution, whereas there exist nonself-similar solutions which do not tend toward a Taylor Cone. Thus, the Taylor Cone does not represent a unique critical shape: there exists another shape, which is not self-similar. The exp...
Ratna Balgis - One of the best experts on this subject based on the ideXlab platform.
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Enhanced Aerosol Particle Filtration Efficiency of Nonwoven Porous Cellulose Triacetate Nanofiber Mats
2018Co-Authors: Ratna Balgis, Hiroyuki Murata, Takashi Ogi, Makoto Kobayashi, Li BaoAbstract:Aerosol particle filtration in most penetrating particle size (MPPS) region is of great challenge for conventional nonwoven filter mats. The present work, therefore, redesigns conventional filter mats by introducing porous structure. A combination of thermally induced phase separation and breath figure mechanism was employed to synthesize porous cellulose triacetate fibers, in conjunction with the volatile solvent methylene chloride. The ambient humidity, the concentration of the polyvinylpyrrolidone (PVP) secondary polymer, and the ethanol cosolvent were all adjusted to modify the Taylor Cone formation, jet stability, and fiber porosity. After fiber formation, the PVP was removed to obtain a superhydrophobic material. To distinguish the effect of pores, the performance of porous and nonporous nanofibers having similar sizes was conducted. Tests were performed using various dust particle sizes, and the results show that the collection efficiency of the porous fibers, resulting from particle diffusion, inertial impaction, and interception, was improved. Interestingly, the efficiency of the porous fibers in the MPPS region was exceptionally enhanced (up to 95%), demonstrating that the presence of dynamic pores greatly contributes to particle capture
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synthesis of dual size cellulose polyvinylpyrrolidone nanofiber composites via one step electrospinning method for high performance air filter
Langmuir, 2017Co-Authors: Ratna Balgis, Hiroyuki Murata, Yohsuke Goi, Takashi Ogi, Kikuo Okuyama, Li BaoAbstract:Dual-size nanofibers consisting of a random mixture of nano- and submicron-size nanofibers are promising structures for specific applications such as air filters because of their increased specific surface area and low pressure drop. Synthesis of dual-size nanofibers using one-step electrospinning was reported here for the first time. The formation of well-mixed nano- and submicron-size cellulose–polyvinylpyrrolidone nanofiber composites was accomplished utilizing the physical properties of TEMPO-oxidized cellulose nanofibers (i.e., high thixotropy and high magnitude of zeta potential) and tuning the charge of the polymer jet, which influences the formation and shape of Taylor Cone, and Coulombic explosion. The dual-size nanofibers were then spun on the surface of a HEPA filter to obtain a multilayer air filter. Aerosol filtration measurements show that this multilayer air filter has an incredibly high performance, shown by the high quality factor (Qf), 0.117 Pa–1, which is 10 times the Qf of commercial H...
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Synthesis of Dual-Size Cellulose–Polyvinylpyrrolidone Nanofiber Composites via One-Step Electrospinning Method for High-Performance Air Filter
2017Co-Authors: Ratna Balgis, Hiroyuki Murata, Yohsuke Goi, Takashi Ogi, Kikuo Okuyama, Li BaoAbstract:Dual-size nanofibers consisting of a random mixture of nano- and submicron-size nanofibers are promising structures for specific applications such as air filters because of their increased specific surface area and low pressure drop. Synthesis of dual-size nanofibers using one-step electrospinning was reported here for the first time. The formation of well-mixed nano- and submicron-size cellulose–polyvinylpyrrolidone nanofiber composites was accomplished utilizing the physical properties of TEMPO-oxidized cellulose nanofibers (i.e., high thixotropy and high magnitude of zeta potential) and tuning the charge of the polymer jet, which influences the formation and shape of Taylor Cone, and Coulombic explosion. The dual-size nanofibers were then spun on the surface of a HEPA filter to obtain a multilayer air filter. Aerosol filtration measurements show that this multilayer air filter has an incredibly high performance, shown by the high quality factor (Qf), 0.117 Pa–1, which is 10 times the Qf of commercial HEPA filters
