Nozzle-collector distance

In addition to solution properties, the stmcture (especially, the fiber diameter) of electrospun nanofibers also can be controlled by selectively adjusting the electrospinning operational conditions, such as voltage, nozzle diameter, nozzle-collector distance, solution flow rate, and motion of the collector. 

Nozzle diameter also is an important operational parameter in controlling the fiber diameter. A decrease in nozzle diameter typically leads to smaller fiber diameters and fewer beads. However, if the nozzle diameter is too small, it may not be possible to extrude the spinning solution through the nozzle to form nanofibers. 

The distance between the nozzle and collector has a direct influence on both the flight time and electric field strength. During the electrospinning of polymer 

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Different types of collectors have also been designed to collect nanofibers in different forms. Figure 13.5A shows a circular metal or plastic collector, which can collect nanofibers on the surface of the iimer wall. The diameter of the circular collector determines the nozzle-collector distance, which is an important parameter for determining the nanofiber structure. The eircular collector is suitable for batch production of nanofibers. A nanofiber sheet collector is shown in Figure 13.5B. In this case, nanofibers are collected onto a porous substrate (such as textile fabric, paper, or other porous membranes) placed on the top of the collector. A suction force is used to assist the formation of a uniform nanofiber sheet (or nonwoven) on the surface of the porous substrate. The sheet collector is suitable for continuous production of nanofibers. Figure 13.5C shows a yam collector. Nanofibers are collected in a water bath and the use of a rotating roller allows the collection of continuous yams of nanofibers. 

Operational conditions, snch as rotating speed, spinneret diameter, nozzle diameter, nozzle-collector distance, etc., also affect the structure of centrifugally sptmnanofibers. 

Nozzle-Collector Distance—The distance between the nozzle and collector has a direct influence on the flight time of the liquid jet. When a solution is used as the spinning fluid, a minimum nozzle-collector distance is required so the liquid jet can have sufficient time for most of the solvent to be evaporated before reaching the collector. In addition, when the nozzle-collector distance increases, the liquid jet will have a longer distance to travel and this favors the fiber diameter reduction (This applied to both solution and melt). However, when the nozzle-collector distance is too large, the liquid jet may not be able to reach the collector due to the insufficient centrifugal force. 

The organic molecules from the GC are seeded in a hydrogen or helium supersonic beam and enter the vacuum chamber through a ceramic nozzle. The distance from the top of the nozzle to the surface is roughly 5 mm. In the vacuum chamber, the beam collides with ReOa or Pt surface for efficient positive ion production. The surface is always at a positive potential of 200 V against the collector electrode. The kinetic energy of the sample molecule, which is proportional to the nozzle... 

Polymer solution fed at speed of 2.8 pj/min through needles with an outer diameter of 0.7 mm. A 9 kv voltage applied between the two needles while nozzle distance was 10 cm. The tip to collector distance was 15 cm. 

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