Combusition Synthesis of Nanosized Y-Fe2O3 Structure Morphology and Bonding

A new combustion route for the synthesis of nanosized ã-Fe203 through a self-propagating combustion synthesis-using Poly (ethylene glycol) as a fuel is reported. The precursor, ferrous citrate is employed in the synthesis of Nanosized g-Fe203. The structure, morphology and bonding of as synthesized ã-Fe203 sample are characterized by X-ray diffraction (XRD), Scanning electron micrograph (SEM) and infrared (IR) techniques respectively. keywords: Nanosized ã-Fe203' Po|y (ethylene glycol), Combustion reaction and precursor.


INTRODUCTION
Interest has increased following the observation that the properties are strongly dependent on the size of particles with dramatic changes when ultrafine/nanometric sizes are acquired1^. The new synthetic routes for the preparation of Nanosized y-Fe203 are under constant investigation and some of them include the ion-exchange reaction in <x-Nafe02with benzoic acid7, co-precipitation8, thermal decomposition of metal hydrazine complexes9, through a wet chemical synthesis of successive hydrolysis, oxidation and dehydration of ferrous chloride to obtain as small as 5 nm particles'0, selective oxidation of Fe2+ and Fe3*11, thermal decomposition of lipodocracite from solid solutions12, and thermal decomposition of metal carbozylate under the controlled conditions13, and through ore beneficiation14. Many of these methods involved in the synthesis of y-Fe203 are tedious, some of them are time consuming with many reaction steps and often in many cases a small quantity of the material could be synthesized.
It is reported in literature that polyvinyl alcohol can be employed as an oxidizing agent along with urea for the synthesis of other spinel ferrites through the combustion of citrate precursor15. However, this technique has come limitations viz., use of urea as a fuel, and also that polyvinyl alcohol has a wide variation of molecula'r weight, both of these parameters would influence the combustion to undergo as a highly exothermic reaction. Hence a new fuel which can also work as a controllable oxidant in a combustible reaction generating selfpropagation is essential.
Present investigation is a new synthetic routes using new precursors for the synthesis of nanosized monophasic v-Fe203. In the present study we have employed ferrous citrate along with polyethylene glycol as an oxidant in a fixed ratio of 1:5 though a self-propagation combustion reaction16.

MATERIAL AND METHODS
Polyethylene glycol with molecular weight 4,000 was obtained commercially. All the other chemicals employed were of AR grade.

Preparation
The precursor ferrous citrate was prepared by mixing equimolar solutions of ferrous ammonium sulphate and citric acid. The precipitate of ferepus citrate obtained was filtered through sintered glass crucible and was washed with cold oxygen free distilled water and finally with dry acetone and dried under vaccum.The above precursor was mixed with polyethylene glycol in the weight ratio 1:5 and ground together in a mortar. The resultant solids were placed in a crucible and heated in the air. It was observed that polyethylene glycol first melts, forms froths and ignites to form ã-Fe203. On cooling to room temperature no traces of carbon impurities were observed in the final residue of ã-Fe203, This reaction which occurs with the evolution of lot of gases and ignites autocatalytically is called a strong self-propagating combustion reaction, as it resembles the strong combustion reaction for the preparation of SnO217.

Characterization
The powder X-ray diffraction patterns was obtained from GEOL JDX-8P or SEIMEN (Japan) X-ray diffreactometer using CoKa radiation. The morphology of the maghemite (ã-Fe203) samples prepared by mixing equimolar solutions of ferrous ammonium sulphate and citric acid. The precipitate of ferepus citrate obtained was filtered through sintered glass crucible and was washed with cold oxygen free distilled water and finally with dry acetone and dried under vaccum.The above precursor was mixed with polyethylene glycol in the weight ratio 1:5 and ground together in a mortar. The resultant solids were placed in a crucible and heated in the air. It was observed that polyethylene glycol first melts, forms froths and ignites to form ã-Fe203. On cooling to room temperature no traces of carbon impurities were observed in the final residue of ã-Fe203, This reaction which occurs with the evolution of lot  of gases and ignites autocatalytically is called a strong self-propagating combustion reaction, as it resembles the strong combustion reaction for the preparation of SnO217.