Abstract Cylindrical-electrode-assisted solution blowing spinning (CSBS) is a novel technique of fabricating nanofibers. In this paper, a combination of numerical simulation, theoretical analysis, and experiment is used to study the influences of CSBS airflow field and electric field on the fabrication of CSBS nanofibers for the first time. The effects of air pressure and injection speed on the morphology of CSBS fiber are studied. The research results show that the increase in air pressure will increase the centerline velocity and the centerline turbulence intensity within the effective stretching distance of the airflow. The increase in centerline velocity will result in a decrease in the diameter of CSBS fibers. There is a negative correlation between jet diameter and surface charge density of CSBS jet. The increase in air pressure will increase the stretching of the jet by the air flow, which will make the jet more likely to become thinner again because of the charge repulsion. Increasing air pressure will reduce the porosity of the nonwoven. As the injection speed increases, the diameter of CSBS fiber increases, and the porosity of the nonwoven decreases first and then increases. This work provides theoretical and experimental bases for the controllable preparation of CSBS nanofibers.
In this paper, a technology and device for large-scale fabrication of nanofibers called tiny-needle-spaced electrostatic-induction-assisted solution blowing spinning (TESBS) was developed. The air flow stretching force is used as the initial driving force for jet formation in TESBS, which avoids the electric field interference existing in the jet formation stage of multi-needle electrospinning(MES). The addition of induced electric field in TESBS solves the problem of mutual merging of jets in multi-needle solution blowing spinning (MSBS). The needle spacing of TESBS can be as small as 1mm, which is much smaller than MES (100mm) and MSBS (3mm). The substantial reduction in needle spacing can increase the arrangement density of blunt needles, thereby increasing the output of nanofibers. Compared with MSBS, the average diameter and diameter standard deviation of TESBS nanofibers can be reduced by 52.6% and 78.7%, respectively. Compared with MES, the uniformity of the TESBS nanofiber web has been significantly improved. The formula for the critical needle spacing to ensure that the TESBS jets do not merge with each other was derived. The output of 15-needle TESBS can reach as high as 3ml/min. The average diameter of TESBS nanofibers decreases with the decrease of injection speed or the increase of voltage. The distance between needle and receiver has little effect on the average fiber diameter. TESBS nanofibers with good quality and high yield have broad and bright application prospects in many fields.
Abstract Cylindrical-electrode-assisted solution blowing spinning (CSBS) is a novel method for preparing polymer nanofibers by using air-stretch and electrostatic simultaneously, which can fabricate thinner and more uniform nanofibers than the traditional solution blowing spinning (SBS). In this work, the effects of processing parameters including length of cylinder (LC), needle to cylinder distance (NCD) and left face of cylinder to collector distance (CCD) on the CSBS nanofiber diameter were investigated. The results are as follows: when the NCD decreased, the fiber diameter decreased; when the LC increased, the fiber diameter decreased; the CCD didn’t significantly affect the fiber diameter. Moreover, an orthogonal experimental design was utilized to investigate the effect of injection rate, air pressure, NCD, LC, diameter of cylinder (DC), voltage and CCD on the fiber diameter and porosity of various surface layers of nanofiber web (P1, P2, and P3). The results showed that the varied range of each properties (average diameter, standard deviation of the diameter, P1, P2, and P3) was 539.121-904.149 nm, 127.903-303.253, 71.464-85.1415%, 60.32725-75.46625%, 48.23925-70.08875%, respectively. We also found the order of the influence of the above-mentioned seven process parameters on each above properties of the nanofiber web, and the corresponding optimal spinning process parameters were listed. It is well known that the fiber diameter affects the mechanical properties of nanofibers, and porosity of nano-fiber webs is an important parameter in tissue engineering, bioengineering, and filtration. The effects of CSBS process parameters on nanofiber morphology and microstructure were investigated for the first time. The conclusion of the paper can help researchers to produce high quality CSBS nanofiber and promote the wider application of this novel technology.
Abstract An electrostatic probe differential analysis method is used to diagnose the arc current-carrying region of the sheet slanting tungsten electrode. Based on the local thermal equilibrium condition and energy transition model with charged particles collision, the temperature distribution in the current-carrying region of different welding process parameters is solved by saturated ion current. The results show that the temperature distribution range in the width direction of sheet slanting tungsten electrode expands, the arc high-temperature region shifts integrally, and the temperature in the thickness direction of sheet slanting tungsten electrode would be symmetrical. The guide effect of the hypotenuse of sheet slanting tungsten electrode for arc current and the inertia drag effect of arc would mainly change the temperature distribution. The variation of the inclination angle of the hypotenuse of sheet slanting tungsten electrode will aggravate the shift of the arc high-temperature region. The larger inclination angle will enhance the guiding effect, and then the inertia drag effect would be in a dominant position with a smaller inclination angle. With the increase of welding current, both the arc stiffness and the guiding effect would be intensified, the latter should make the arc high-temperature zone shift to the position with a small discharge gap.
A fabrication technology and equipment for nanofiber/nanosphere composite membranes (NNCMs) is proposed and named as the airflow/electrostatic method (AEM). AEM uses both air flow and induced electric field to stretch the jets. The AEM working mechanisms are proposed and verified. The electric field laws of AEM are obtained by finite‐element simulation and theoretical deduction. Compared with the airflow method (AM), the average fiber diameter, standard deviation of fiber diameter, and NNCMs, porosity of AEM can be reduced by 38.8%, 71.1%, and 87.3%, respectively. AEM can also overcome the shortcoming of the AM that cannot receive nanospheres. Compared with the electrostatic method (EM), AEM can not only fabricate NNCMs with randomly distributed nanofibers and nanospheres in one step, but also greatly improve the yield. The injection speeds of solution X and solution Y of AEM can be increased by 24 000% and 1920%, respectively, compared with that of EM. The diameters of AEM nanospheres and nanofibers increase with the increase of injection speed of solution X and solution Y, respectively. The distance between needle and receiver has little effect on the diameters of nanofibers and nanospheres. AEM NNCMs with excellent quality and high yield will be widely used in many fields.
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