Upward needleless electrospinning of nanofibers

Polyacrylonitrile (PAN) nanofibers were prepared by a needleless electrospinning method using three rotating fiber generators, cylinder, disc and coil. The effects of the spinneret shape on the electrospinning process and resultant fiber morphology were examined. The disc spinneret needed the lowest voltage to initiate fiber formation, followed by the coil and cylinder. Compared to cylinder, the disc and coil produced finer fibers with narrower diameter distribution. The productivity of a coil was 23 g/hr, which was much larger than that of the cylinder spinneret having the same length and diameter. Finite elementary method was used to analyze the electric field. Stronger electric field was found to be formed on disc and coil surface, which concentrated on the disc circumferential edge and coil wire surface, respectively. For cylinder, the high intensity electric field was mainly concentrated on the end area. Concentrated electric field on the fiber generating surface could be used to explain the better electrospinning performance of coil, which may form a new concept for designing needleless electrospinning spinnerets.

Needleless electrospinning of uniform nanofibers using spiral coil spinnerets

Polyvinyl alcohol nanofibers were prepared by a needleless electrospinning technique using a rotating spiral wire coil as spinneret. The influences of coil dimension (e.g., coil length, coil diameter, spiral distance, and wire diameter) and operating parameters (e.g., applied voltage and spinning distance) on electrospinning process, nanofiber diameter, and fiber productivity were examined. It was found that the coil dimension had a considerable influence on the nanofiber production rate, but minor effect on the fiber diameter. The fiber production rate increased with the increased coil length or coil diameter, or the reduced spiral distance or wire diameter. Higher applied voltage or shorter collecting distance also improved the fiber production rate but had little influence on the fiber diameter. Compared with the conventional needle electrospinning, the coil electrospinning produced finer fibers with a narrower diameter distribution. A finite element method was used to analyze the electric field on the coil surface and in electrospinning zone. It was revealed that the high electric field intensity was concentrated on the coil surface, and the intensity was highly dependent on the coil dimension, which can be used to explain the electrospinning performances of coils. In addition, PAN nanofibers were prepared using the same needleless electrospinning technique to verify the improvement in productivity.

Electrostatic spinning assembly

A spinneret for producing nanofibres from a viscous liquid using electrostatic spinning in an electric field is described. The spinneret includes one or more narrow annular bodies radially centred about and axially spaced along a central axis. The annular bodies may be discs, rings, or coils.

Electrostatic spinning assembly

A spinneret for producing nanofibres from a viscous liquid using electrostatic spinning in an electric field is described. The spinneret includes one or more narrow annular bodies radially centred about and axially spaced along a central axis. The annular bodies may be discs, rings, or coils.

Scaling up the production rate of nanofibers by needleless electrospinning from multiple ring

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. © 2014 The Korean Fiber Society and Springer Science+Business Media Dordrecht.

Use of airflow to improve the nanofibrous structure and quality of nanofibers from needleless electrospinning

Mass production of nanofibers from needleless electrospinning shows great potential in research and development of nanofibers. However, how to improve the electrospinning performance so as to achieve high quality nanofibers is still of great challenge. In this study, airflow has been applied to optimize upward needleless electrospinning from ring spinneret. Effects of airflow speed and the position of airflow on the nanofiber quality and production rate have been investigated. It has been found that thinner and more uniform nanofibers were produced when airflow was applied to needleless electrospinning system. It also improved the collected nonwoven membrane, resulting in better nanofibrous structure of the as-spun nanofibers. Application of airflow on needleless electrospinning would further benefit the development of mass production of nanofibers from needleless electrospinning.

On the morphology of the juvenile stages of Ampulex compressa (Fabricius 1781) (Hymenoptera, Ampulicidae)

Ampulex compressa is a cockroach-hunting ampulicid wasp. In this survey we describe its egg, mature larva, along with the 1st and 2nd larval instars and cocoon, with emphasis on the characters considered important to the phylogeny of apoid wasps. It shares the following traits with the Sphecidae: reduced head setae, absence of antennal papilla, three antennal sensilla on antennal orbit, broad and strongly emarginate labrum, and spinneret with prominent raised lips. In common with other Ampulicidae, it has integument of the body granulose and without setae, mandibles with four or five teeth and lacking basal setae, maxillary palp larger than galea and discrete parietal bands. Distinct from the other Ampulicidae, it has a deep median longitudinal groove in the area above the salivary lips, a distinct group of five sensilla on the subgenal area, and lacks spines on the spiracular peritreme. Copyright © 2006 Magnolia Press.

Redução de empeno em barra trefiladas do aço SAE 9254

In this paper we study the process of manufacture of wire drawn steel bars 9254, from rolled wire rod. These bars are used in the automotive industry for the manufacture of coil springs, which make up the system damping of several vehicles. The wire drawing process consists of the steps of pre-straightening, shot peening, drawing, cutting and polishing. The study aims to search for the configuration of process variables, which present the best result with respect to bending. To this were maintained settings prestraightening and mechanical stripping and varied angles and stringer polish being studied to replace the spinneret with a working angle, for a string with two working angles. To assist in the analysis of the results was the tool used DOE Software Minitab, which assesses the variation in results according to each parameter and the interaction parameters. It was thus possible to determine the best condition for wire drawing

Ba0.5Sr0.5Co0.8Fe0.2O3-delta ceramic hollow-fiber membranes for oxygen permeation

Setf-supported asymmetric hollow-fiber membranes of mixed oxygen-ionic and electronic conducting perovskite Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) were prepared by a combined phase-inversion and sintering technique. The starting inorganic powder was synthesized by combined EDTA-citrate complexing process followed by thermal treatment at 600 degrees C. The powder was dispersed in a polymer solution and then extruded into hollow-fiber precursors through a spinneret. ne fiber precursors were sintered at elevated temperatures to form gastight membranes, which were characterized by SEM and gas permeation tests. Performance of the hollow fibers in air separation was both experimentally and theoretically studied at various conditions. The results reveal that the oxygen permeation process was controlled by the slow oxygen surface exchange kinetics under the investigated conditions. The porous inner surface of the prepared perovskite hollow-fiber membranes considerably favored the oxygen permeation. The maximum oxygen flux measured was 0.031 mol-m(-2).s(-1) at 950 degrees C with the sweep gas flow rate of 0.522 mol(.)m(-2).s(-1). To improve the oxygen flux of BSCF perovskite membranes, future work should be focused on surface modification rather than reduction of the membrane thickness. (c) 2006 American Institute of Chemical Engineers.