**4.3 Electrospinning of composite nanofibers**

The prepared polymer spinning solution or sol–gel solution was immediately loaded in plastic syringe of 5 ml capacity and a blunt ended 20-gauge stainless steel needle fitted in it. The nozzle equipped syringe was attached to the syringe pump. The positive electrode of high voltage power supply capable of generating DC voltages up to 40 kV attached with the needle whereas negative electrode was connected to the aluminum foil covered collecting plate. The ground electrode of the power supply was attached to a piece of flat aluminum foil used as the collector plate [57, 58]. The needle tip to collector distance was 10 cm to collect the nanofibers. The ES process was conducted in ambient air at room temperature (25 ± 2°C) having relative humidity of 65 ± 5%. A solution feeding rate was set to 1 ml/h with the help of a syringe pump. The steady deposition of nanofibers on the collector plate was ensured by frequent cleaning of nozzle clogging intermittently. The experiment was conducted by applying positive high voltage of 18 kV across the needle and the collector plate. At such

#### **Figure 3.**

*Process flowchart for the preparation of nanofibers by electrospinning method.*

environmental condition fluid jet ejected continuously from the nozzle and accelerated jet moved towards the collector plate. During this movement of jet the solvent get evaporated leaving ultra thin fibers on the collector plate. The ES process continued until all the solution in the syringe was exhausted. The complete sequence of spinning solution preparation and nanofiber synthesis, its calcination and final morphological feature are schematically represented in **Figure 3**.
