**4. Preparation of nanofibres using electrospinning method**

Well-controlled and high-quality ceramic nanofibers can be generated in ES process by following procedures


#### **4.1 The electrospinning solution**

Ceramic nanofibers can be obtained by direct electro-spinning of sol of only inorganic precursor metal alkoxides or metal salts dissolved in a solvent. Notable examples are synthesis of nanofibers of CeO2 [50–52], Titanium dioxide (TiO2) [53] and Al2O3/ZnO [54]. However, such synthesis shows inappropriate rheological properties and the rapid hydrolysis rates of metal alkoxides or metal salts, pose difficulties in controlling the ES process. To resolve such problems, one has to introduce a polymer matrix are added into the solution to adjust the rheological properties and catalyst is supplemented to control the hydrolysis rate of the used precursor [54]. Thus a typical spinnable precursor solution composed of metal salt or an alkoxide precursor, a polymer, an additive, and an easily volatile solvent like chloroform, ethanol, iso-propanol, water and dimethyl-formamide. The catalysts added into the solution usually stabilize the precursor and facilitate smooth electrospinning process. The catalyst are required in minute quantity but their addition in spinning solution play an key role in stabilizing the solution and the jet from the needle. The acid catalyst like acetic or hydrochloric or propionic acid is employed for adjusting both the hydrolysis and gelation rates to prevent blocking the needle mouth by solution and ensuring a continuous nanofiber synthesis [49].

At present we are discussing nanofiber synthesis using casting solution comprising precursor cerium nitrate hexahydrate and copper acetate monohydrate, PVP polymer, glacial acetic acid (3-4drops) and a solvent ethanol and water that was used for preparing green nanofibers through ES process. The details of procedure used for preparing the casting solution and green nanofibers are discussed below.

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**Figure 3.**

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

*Green Synthesis of Nanofiber and Its Affecting Parameters*

The precursors in the present nanofiber synthesis were cupric acetate monohydrate (Cu(CH3COO)2.H2O) and cerium nitrate hexahydrate (Ce(NO3)3.6H2O) and polyvinyl pyrrolidone (PVP) was the base polymer. The PVP has a remarkably large molecular weight and high solubility in polar solvents. The solvent used in the process was ethanol and de-ionized water added as co-solvent [55, 56]. The aqueous precursor solutions was prepared in dissolving Cu(CH3COO)2.H2O and cerium nitrate hexahydrate in 4 ml of deionized water and this solution was mixed ethanolic PVP solution(4 ml) for final 10% (w/v) of PVP. The mixed solution stirring continuously till complete dissolution. The 2–3 drops of acetic acid was added during magnetic sterring of solution for about 3 h at room temperature to preparing

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

*DOI: http://dx.doi.org/10.5772/intechopen.94539*

**4.2 The precursor and polymer solution**

homogeneous solution for final spinning.

**4.3 Electrospinning of composite nanofibers**
