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1.
In this paper, a method combining the orthogonal array design and the numerical simulation is proposed to optimize the geometry parameters of the solution blowing nozzles. The centerline velocity is used to evaluate the performance of the nozzle and the characteristics of airflow fields are calculated. Three geometry parameters of the nozzle: the protrusion length of needle, the diameter of needle and the diameter of nozzle are investigated. The results show that smaller needle diameter and larger nozzle diameter will result in a higher centerline velocity, which is beneficial to fiber attenuation, whereas the effect of needle protrusion length is insignificant. The optimal geometry parameters of the nozzle achieved in this study are that the protrusion length of needle of 5 mm, the diameter of needle of 0.8 mm, and the diameter of nozzle of 4 mm. Furthermore, chitosan/PEO nanofibers are manufactured and studied with different geometry nozzles. This work can provide a better understanding of the controllable fabrication of solution blown nanofibers. 相似文献
2.
Yuman Zhou Hongbo Wang Jianxin He Kun Qi Bin Ding Shizhong Cui 《Fibers and Polymers》2018,19(10):2169-2177
Electrospinning is a simple and cost-effective method to prepare fiber with nanometer scale. More importantly, 3D flexible nanofiber yarns that fabricated by electrospinning have shown excellent application prospects in smart textiles, wearable sensors, energy storage devices, tissue engineering, and so on. However, current methods for preparing electrospinning nanofiber yarns had some limitations, including low yarn yield and poor yarn structure. In this paper, a stepped airflow-assisted electrospinning method was designed to prepare continuously twisted nanofiber yarn through introducing stepped airflow into traditional electrospinning system. The stepped airflow could not only help to improve nanofiber yield, but also good for controlling the formed nanofibers to be deposited in a small area. In addition, the experimental methods of single factor variables were used to study the effects of stepped airflow pressure, applied voltage, spinning distance, solution flow rate, air pumping volume and friction roller speed on nanofiber yarn yield, nanofiber diameter, yarn twist and mechanical property. The results showed that prepared nanofiber yarns exhibited perfect morphologies and the yield of nanofiber yarn could reach to a maximum of 4.207 g/h. The breaking strength and elongation at break of the prepared yarn could reach to 23.52 MPa and 30.61 %, respectively. 相似文献
3.
Coaxial electrospinning is an effective method to produce core-shell nanofibers, which is associated closely with the morphological stability of Taylor cone. However, the nozzle structure mainly influences the formation of Taylor cone during the coaxial electrospinning procedure. In the present work, since the numerical simulation is a novel and convenience method in the theoretical research of the coaxial electrospinning, the influence of different coaxial composite nozzle structures on Taylor cone shape was studied by ANSYS finite element simulation method. Different coaxial composite nozzle structures — concave type, flush type and convex type, were designed in this work. 2D electric field model of the nozzle structures was simulated by utilizing ANSYS finite element analysis software. The simulation results indicated that electric field intensity distribution of concave type nozzle structure was more uniform than those of the other two types. Therefore, a more stable coaxial Taylor cone was formed in the tip of concave type nozzle structure. To verify the accuracy of the simulation results, core-shell nanofibers were spun by using different coaxial composite nozzle structures. In each experiment, PAN and PVP were employed to be the shell and core solution respectively. Besides that high-speed camera was employed to monitor the coaxial electrospinning procedure. The cross-section morphology of electrospun nanofibers was characterized by scanning electron microscope (SEM). The experimental results showed that when the concave type nozzle was used in the coaxial electrospinning process, Taylor Cone morphology was more stable than other type coaxial composite nozzle structures. The cross-section morphology of electrospun fibers observed by SEM revealed that the high stability in core-shell structure also occurred in coaxial electrospinning by using concave nozzle structure. Furthermore, the simulation and experimental results verified the concave type nozzle is the better nozzle structure for coaxial electrospinning to form stable coaxial Taylor cone. 相似文献
4.
This study presents a method for the fabrication of ultrafine polymeric nanobers utilizing centrifugal and electrostatic forces simultaneously. To reduce the diameter and variability of nanofibers produced from polyacrylonitrile (PAN) and poly-L-lactic acid (PLLA), a unique electro-centrifuge spinning device was designed using rotating nozzle and collector, whereas the fabrication process (spinning head) was skillfully sealed from ambient airflow. The polymer solution was continuously delivered by a rotating nozzle and the nanofibers were collected by a rotating cylindrical collector at the same rotational speed as the nozzle. Field emission scanning electron microscope (FESEM) results demonstrated that this method has a significant effect on the quality and fineness of nanofibers. The diameters of nanobers were controlled by adjusting the rotation speed of spinning head. The effect of the rotation speed on the morphology of the nanofibers fabricated by this device was also evaluated. In order to provide a useful context for the current nanofiber production method, nanofibers obtained in this method were compared with those produced by other methods. The results show that air-sealedcentrifuge-electrospinning system (ASCES) is a facile method for the fabrication nanobers with smaller diameters and high uniform structures. 相似文献
5.
Pesticides are commonly applied by using hydraulic nozzles to generate droplets. The properties of these spray droplets can influence the effectiveness and risks associated with the use of pesticides. Initial spray characteristics (initial droplet size and velocity, fan angle and spray liquid density) were therefore measured for a range of hydraulic nozzles and spray mixtures. Particle Image Velocimetry (PIV) was used to measure the spray sheet velocity.There was a significant difference between a standard hydraulic nozzle, Turbo TeeJet® and air induction nozzle for all measured spray characteristics. The standard hydraulic nozzle generated the smallest droplet sizes, the highest velocity and the highest spray liquid density. The air induction nozzle generated the largest droplet size, the slowest velocity and the lowest spray liquid density. The type of air induction nozzle and spray formulation was also found to influence spray characteristics.This work has demonstrated that initial spray characteristics such as droplet size and velocity, liquid density, fan angle and included air can vary depending on nozzle design, operating parameters and spray formulations. Initial droplet velocity was found to be significantly correlated to droplet size (Dv0.5) and spray pressure. 相似文献
6.
A simple and modified electrospinning technique was utilized to prepare aligned and heat treated Polyacrylonitrile nanofibers by using a rotating drum fixed on top of syringe needles and applying upward hot air flow which can facilitate to heat nanofibers in electrospinning zone. Polyacrylonitrile nanofibers were electrospun from its 14 wt% solution in dimethylformamide under practical conditions. Angular power spectrum analysis showed better fiber alignment with increasing take up speed, although SEM studies demonstrated wider diameters of nanofibers being produced by modified method. The glass transition temperature of all prepared samples were determined between 70 °C and 90 °C using DSC technique. The Quantitative analysis of WAXD patterns has revealed the positive effect of modified method on the degree of crystallization of nanofibers heat treated at higher take up speed. The maximum chain orientation factor of 0.27 was determined for nanofibers collected at linear velocity of 114.5 m/min in the modified set up using Raman Spectroscopy technique. 相似文献
7.
Introduced recently, electro centrifuge is a new method for nanofiber production. In the electro-centrifuge method, fibers are produced by the simultaneous use of electrical and centrifugal forces. In this research, the effective parameters in the production of PAN nanofibers diameter and the influence of each of them have been discussed. These parameters are voltage, rotation speed, flow rate of exiting solution from nozzle and viscosity of solution. Also the capability of fiber production by this method is compared with the conventional electrospinning system. Results show that a significant enhancement can be achieved by proper adjustments of the polymer solution viscosity, applied voltage, and rotational velocity in fiber production rate. To exemplify, in a PAN polymer solution, the increased production rate of electro centrifuge varied from 193 to 1200 percent, as compared with a similar electrospinning method in which the polymer concentration and applied voltage varied in a range of 13 to 16 wt% and 15 to 10 kV, respectively. 相似文献
8.
Measuring tensile strength of nanofibers using conductive substrates and dynamic mechanical analyzer
Though the tensile strength of nanofibers is essential to determine their application fields, few studies have been conducted
on this topic, due to the difficulties involved in the preparation of single nanofiber tensile specimens, the manipulation
of the clamping device, and the sensing of the nano- force and strain. A bundle testing method was employed in this work to
measure the tensile strength of nanofibers. For this purpose, a conductive substrate was designed to hold several thousand
nanofibers extruded from a spinning nozzle and align them uniaxially during the electrospinning process. This substrate was
designed for a dynamic mechanical analyzer (DMA), because most DMAs are equipped with fine sensors sensitive enough to measure
a very small force and strain. Nylon 6 nanofibers were electrospun and collected on the substrate. Then, they were elongated
simultaneously in the DMA until they were fractured, showing that the aligned nanofibers have superior tensile strength and
modulus compared to their counterpart microfibers and thus suggesting that polymeric nanofibers have the potential to be used
as reinforcement fibers for composite materials. 相似文献
9.
A novel electrospinning system for the mass production of nanofibers using a moving conventional yarn as the spinneret was designed. In the process of electrospinning, a large number of jets were ejected from the surface of the polymer liquid carried by the yarn. The effects of conductivity, surface structure and fineness of the yarn on the morphology and productivity of the obtained nanofibers were discussed in the research. Results indicate that the productivity of nanofibers can be increased up to 1.17 g/h with our method, which is a more than fourfold enhancement compared to less than 0.3 g/h with the method of single-needle electrospinning. Both issues of needle clogging in needle electrospinning and intense solvent evaporation due to the open solution surface in most needleless electrospinning techniques can be avoided. 相似文献
10.
Mass production of nanofibers is crucial in both laboratory research and industry application of nanofibers. In this study, multiple ring spinnerets have been used to generate needleless electrospinning. Multiple polymer jets were produced from the top of each ring in the spinning process, resulting in thin and uniform nanofibers. Production rate of nanofibers increased gradually with the increase of the number of rings in the spinneret. Spinning performance of multiple ring electrospinning, namely the quality and production rate of the as-spun nanofibers, was dependent on experimental parameters like applied voltage and polymer concentration. Electric field analysis of multiple ring showed that high concentrated electric field was formed on the surface of each ring. Fiber diameter together with production rate of needleless electrospinning was dependent on the strength and distribution of the electric field of the spinneret. Needleless electrospinning from multiple ring can be further applied in both laboratory research and industry where large amount of nanofibers must be employed simultaneously. 相似文献
11.
Hongbo Chen Haoyi Li Xiaolu Ma Wanlin He Jing Tan Weimin Yang 《Fibers and Polymers》2016,17(4):576-581
A cone-shape spinneret with air-suction assisted was used for the production of ultrafine fibers by melt electrospinning. The influence of the applied voltages on the number of jets and the effects of the different types of air flow (air blowing and air suction) on the fiber bundle were studied. It was demonstrated that the breadth of the diameter distribution of the fibers decreases markedly and the production rate was also improved when air suction and higher applied voltages were applied. Therefore this new melt electrostatic spinning equipment can meet the need of some special applications and industrial mass production of nanofibers. 相似文献
12.
Ruaa Yaseen Hammoudi Al-Mezrakchi 《Fibers and Polymers》2018,19(1):105-115
An integrated experimental and modeling approach was utilized to study scalable production of nanofibers via electrospinning. Two concepts have been investigated to study the fabrication of PAN nanofibers, which are needle-based and orifice-guided electrospinning to utilize the optimum setup. Moreover, it was observed that the natural flow rate of electrospinning does not scale linearly with number of needles (unlike polymer processing methods such as dry spinning), which was explained based on the partial pressure of the solvent vapor, peculiar to multi-needle setup, and the stress relaxation in the solution. In addition, it was demonstrated that the minimum voltage required to continuously electrospun fibers increases as the distance between needles is reduced, which was explained by the shielding effect of neighboring needles and elucidated by the Finite Element Analysis (FEA) models. Nano-fibers with diameters less than 100 nm were produced in this investigation. 相似文献
13.
In order to study the effect of the structure of vortex tube on the yarn performance in jet vortex spinning, 8 groups of vortex tube structure were designed, and the corresponding 3D computational fluid dynamic models were established to numerically simulate the airflow in the nozzle. Through analysis of the characteristics of air flow inside the different nozzles, such as pressure distribution and velocity vectors, the motion of drafted fibers and performances of yarns were discussed. Simulation results show that when the structure of vortex tube has a transition region between the cylindrical and conical cavity (CCT) and the outlet of jet orifice is located at the junction of cylindrical and transition cavity, the airflow state within the nozzle has a large negative pressure with appropriate axial and tangential velocity, which is conducive to the formation of the open-ends of fibers and twisting, and the yarn quality turns out to be better. Spinning experiment results prove that the yarn strength reaches the maximum value, while the unevenness of breaking strength meets the minimum, and the other yarn properties are superior, which shows a good agreement with the simulation results. Thus, the numerical simulation can provide the theoretical as well as quantitative reference for the vortex tube design in the coming future. 相似文献
14.
Nanofibers definitely hold great advantage and promise in filtration as they have very high specific surface area, which ensures greater probability of capturing the particles and hence, the filtration efficiency of the nanofiber filter media is high. Electrospun nanofibers are prohibitively expensive due to extremely low production rate. With recent advances in melt blowing technology, nanofibers could be produced at production rate few orders of magnitude higher than that of conventional single syringe electrospinning and hence, quite cost effective. Influence of air pressure and die to collector distance (DCD) were studied on the number average fiber diameter for the nanofibers as well as the performance properties of the nonwoven webs, each factor at three discrete levels. The nanofibers were as fine as 260 nm. A very encouraging observation of the study is very high values of quality factor observed for nanofiber nonwoven filter media. In order to compare the filtration efficiency of different nanofiber nonwoven media samples with different basis weight, a novel term of specific filtration efficiency is proposed and was found that the specific filtration efficiency with the increase in DCD or air pressure. 相似文献
15.
Effects of formulation on spray nozzle performance for applications from ground-based boom sprayers 总被引：1，自引：0，他引：1
The performance of agricultural spray nozzles has components relating to the droplet size and velocity distributions within the spray, spray structure, entrained air characteristics and the spray volume distribution pattern. The interaction of these physical performance parameters has been shown to influence target retention, efficacy and the risk of drift. Results from a number of studies have also shown that the physical properties of the spray liquid have a substantial effect on spray formation such that changes in formulation type can give changes in spray characteristics that would be equivalent to doubling the flow rate through conventional hydraulic flat fan nozzles. The interactions between the physical properties of the spray liquid and the characteristics of the spray formed is a function of nozzle design. However, analysis of a large data set for a range of types of hydraulic pressure nozzle has shown that sprays formed from liquids based on emulsions generally have a coarser droplet size distribution compared with sprays formed from surfactant solutions. Although some correlation between dynamic surface tension and viscosity with spray droplet size has been established, the results from work reviewed in this paper suggest that other factors also influence the spray formation process. Air induction and twin-fluid nozzles mix air and liquid in the spray formulation process to produce droplets with air inclusions. These nozzle designs have been found to have a performance that is more sensitive to changes in spray liquid properties compared with hydraulic pressure nozzles and to exhibit trends that are different from those of conventional nozzle types. 相似文献
16.
Studies on reduction of yarn hairiness by nozzles in ring spinning and winding by airflow simulation
Reduction of yarn hairiness by nozzles in ring spinning and winding is a new approach. Simulation of the airflow pattern inside
the nozzles provides useful information about actual mechanism of hairiness reduction. The swirling air current inside the
nozzles is capable of wrapping the protruding hairs around the yarn body, thereby reducing yarn hairiness. Since production
rate of winding is very high and the process itself increases yarn hairiness any method to reduce the hairiness of yarns at
this stage is a novel approach. A CFD (computational fluid dynamics) model has been developed to simulate the airflow pattern
inside the nozzles using Fluent 6.1 software. In this study, both S- and Z-type nozzles having an axial angle of 50° and diameter
of 2.2 mm were used for simulation studies. To create a swirling effect, four air holes of 0.4 mm diameter are made tangential
to the inner walls of the nozzles. S- and Z-twisted yarns of 30 tex were spun with and without nozzles and were tested for
hairiness, tensile and evenness properties. The total number of hairs equal to or exceeding 3 mm (i.e. the S3 values) for
yarn spun with nozzle is nearly 49–51 % less than that of ring yarns in case of nozzle-ring spinning, and 15 % less in case
of nozzle-winding, while both the yarn types show little difference in evenness and tensile properties. Upward airflow gives
best results in terms of hairiness reduction for nozzle-ring and nozzle wound yarns compared to ring yarns. Yarn passing through
the centre of the nozzle shows maximum reduction in S3 values. 相似文献
17.
Faheem A. Sheikh Nasser A. M. Barakat Muzafar A. Kanjwal S. J. Park Hern Kim Hak Yong Kim 《Fibers and Polymers》2010,11(3):384-390
Gallium arsenide (GaAs) does have superior electronic properties compared with silicon. For instant, it has a higher saturated
electron velocity and higher electron mobility. Weak mechanical properties and high production cost are the main drawbacks
of this interesting semiconductor. In this study, we are introducing production of GaAs nanofibers by electrospinning methodology
as a very low cost and yielding distinct product technique. In general, nano-fibrous shape is strongly improving the physical
properties due to the high surface area to volume ratio of this nanostructure. The mechanical and environmental properties
of the GaAs compound have been modified since GaAs nanofibers have been produced as a core inside a poly(vinyl alcohol) (PVA)
shell. GaAs/PVA nanofibers were prepared by electrospinning of gallium nitrate/PVA solution in presence of arsenic vapor.
The whole process was carried out in a closed hood equipped with nitrogen environment. FT-IR, XPS, TGA and UV-Vis spectroscopy
analyses were utilized to confirm formation of GaAs compound. Transmission electron microscope (TEM) analysis has revealed
that the synthesized GaAs compound is crystalline and does have nano-fibrous shape as a core inside PVA nanofibers. To precisely
recommend the prepared GaAs nanofiber mats to be utilized in different applications, we have measured the electric conductivity
and the band gap energies of the prepared nanofiber mats. Overall, the obtained results affirmed that the proposed strategy
successfully remedied the drawbacks of the reported GaAs structures and did not affect the main physical properties of this
important semiconductor. 相似文献
18.
Well-aligned PMIA nanofiber mats were fabricated by electrospinning and then hot-stretching along the fiber axis was used to improve the mechanical properties of nanofibers in this paper. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Differential scanning calorimetry (DSC) were used to characterize the morphology and properties of nanofibers. The results showed that the nanofibers became thinner and better alignment than the as-spun nanofibers after hotstretching, and the average diameter of the nanofibers decreased with the increasing of the tensile force. In the same time, hotstretching improved the crystallinity and T g of the as-spun PMIA nanofibers. The tensile strength and modulus of the hotstretched nanofiber mats peaked at ca.50 % and ca.196 % respectively at the tensile force of 12 N compared with the as-spun nanofiber mats. 相似文献
19.
The synthesis of titanium dioxide nanofibers with 200–300 nm diameter was presented. The new inorganic-organic hybrid nanofibers
were prepared by sol-gel processing and electrospinning technique using a viscous solution of titanium isopropoxide (TiP)/poly(vinyl
acetate) (PVAc). Pure titanium dioxide nanofibers were obtained by high temperature calcination of the inorganic-organic composite
fibers. SEM, FT-IR, and WAXD techniques were employed to characterize these nanofibers. The titanium dioxide nanostructured
fibers have rougher surface and smaller diameter compare with PVAc/TiP composite nanofibers. The anatase to rutile phase transformation
occurred when the calcination temperature was increased from 600 °C to 1000 °C. 相似文献
20.
Hidekazu Sato Kyu-Oh Kim Han-Ki Kim Byoung-Suhk Kim Yuji Enomoto Ick-Soo Kim 《Fibers and Polymers》2010,11(8):1123-1127
We reported the preparation and characterization of the poly(vinyl alcohol) (PVA)/BaSO4 hybrid nanofibers prepared by normal and ultrasonic electrospinning, respectively. Compared to normal electrospinning, BaSO4 particles in the resultant PVA/BaSO4 hybrid nanofibers prepared by ultrasonic electrospinning were well-dispersed without severe agglomerations, as confirmed by scanning electron microscopy (SEM) analysis. X-ray diffraction (XRD) analysis indicated that typical crystalline peaks of PVA and BaSO4 particles were dramatically decreased by ultrasonication during electrospinning. Moreover, the size of BaSO4 aggregates became smaller. 相似文献