Synthesis of Polyaniline-Graphite Nano-Composites

M. A. Gadyal^*1, K. S. Venkatesh²

¹Department of Materials Science Gulbarga University, Gulbarga.

²Research Guide,Department of Materials Science Gulbarga University, Gulbarga.

DOI : http://dx.doi.org/10.13005/msri/120114

ABSTRACT:

The polyaniline belongs to the group of electronically conducting polymers. The graphite is anisotropic, being a good electrical and thermal conductor within the layers. One of the more important groups of materials in our lives today is composite material. The nano-composites provide reinforcing efficiency because of their high aspect ratios In this paper, synthesis and characterization polyaniline- graphite as a novel eco-friendly nano-composite material is reported.

KEYWORDS: Polyaniline; graphite; nano-material; composites

Copy the following to cite this article: Gadyal M. A, Venkatesh K. S. Synthesis of Polyaniline-Graphite Nano-Composites. Mat.Sci.Res.India;12(1)

Copy the following to cite this URL: Gadyal M. A, Venkatesh K. S. Synthesis of Polyaniline-Graphite Nano-Composites. Mat.Sci.Res.India;12(1). Available from: http://www.materialsciencejournal.org/?p=1668

Introduction

Materials science studies the fundamental physical and chemical basis for the controlled combination of atoms to form new compounds, phases, and micro structures, as well as the characterization of the resulting structures and their properties. One of the more important groups of materials in our lives today is composite material. The man made composite materials, that are a three-dimensional combination of at least two chemically distinct materials, with a distinct interface separating the components, created to obtain properties that cannot be achieved by any of the components acting alone¹.

Composite materials have many advantages over monolithic materials, because their mechanical, chemical and electrical properties can be tailored as per the requirements for particular applications. Sometimes the properties of a composite can be strikingly different from the properties of the constituent materials. For example, two materials with positive thermal expansion coefficients can be combined to create a porous structure to give a composite with a negative thermal expansion coefficient².

Usually, composite materials have the components, called the matrix and the filler. The matrix is the component that holds the filler together to form the bulk of the material. It usually consists of various epoxy type polymers but other materials may also be used. The filler is the material that has been impregnated in the matrix to lend its advantage (physical and chemical change) to the composite. The four main manmade composite groups are: metal matrix composites polymer matrix composites, ceramic matrix composites and conducting composites. The conducting composites are the mixture of conducting and insulating phases or the mixture of high and low conducting materials².

The electrical properties of these conducting composite materials are of great technological and scientific interest. The electrical conductivity of such materials can be altered to a few orders of magnitude by increasing the conducting phase above the percolation threshold. Such dramatic changes in the electrical properties can be utilized for various applications.

The discovery of electrically conducting polymers, inventers A. Heeger, A. MacDiarmid and H. Shirakawa awarded with the Nobel Prize in chemistry in the year 2000. The three winners established that polymer plastics could be made highly conducting by suitable doping³. Certain conjugated organic polymers such as polyaniline, polypyrrole poly-p-phenylene, polythiophene and polyacetylene show very high value of conductivity⁴.

The Polyaniline (PANI) belongs to the group of electronically conducting polymers, which are of great interest for practical applications at present. Conductive PANI has been studied extensively because of its ease of synthesis. It can be synthesize by chemically or electrochemically. The numerous methods employed to synthesize this material have produced several products, which differ in their nature and properties and must represent the result of multitude of polymerization mechanisms of aniline. The aniline polymers are on limelight because of their environmental stability, controllable electrical conductivity and interesting redox properties associated with the nitrogen atoms in the main chain. The PANI has numerous applications^5,6.

Graphite (GRA) is a naturally occurring, steel-gray to black, crystalline form. The graphite consists of carbon layers and each carbon layer is called graphene layer. The graphite is anisotropic, being a good electrical and thermal conductor within the layers and a poor electrical and thermal conductor perpendicular to the layers. The carbon atoms in graphite are strongly bonded together in layers. Because the bonds between the layers are weak, other atoms can easily fit between them ^7,8.

Since many important chemical and physical interactions are governed by surfaces and surface properties, a nanostructured material can have substantially different properties from a larger-dimensional material of the same composition. In the case of particles and fibers, the surface area per unit volume is inversely proportional to the material’s diameter, thus, the smaller the diameter, the greater the surface area per unit volume^9,10.11.In the present work, nano-composites containing two different weight % of graphite powder filler material were synthesized and XRD and SEM analysis were done.

Materials and Methods

Natural flake graphite with an average diameter of 500 µm washed with acetone and  dried for three days.  The  solution  of  0.2 M  aniline (C 6H 5NH 2)  and  0.1 M  ammonium  persulphate  [(NH4) ₂– S₂O₈] was prepared in 1 M HCl in two separate flasks using  triple  distilled  water and the measured quantity of graphite powder is added[7-10].  These  solutions  were  slowly  mixed  under  continuous  stirring  at  room  temperature,  the  initial  colorless solution slowly turned green. After completion of the  reaction,  the  resultant  product  was  repeatedly  washed in  Buchner  funnel  with  distilled  water  till  filtered  solution turned  from  acidic  to  neutral.  Finally,  it  was  washed  with acetone  to  remove  low-molecular  weight  intermediates  of aniline  (brown  colored  solution).  The  dried  material  was grinded  to  fine  powder  and  stored  in  a  sealed  bottle  for further processing.

The two samples of weight percentage of ratio PANI:GRA=90.55:9.45 and 80.762:19.238 are prepared from above mentioned procedure.

Results

The X-ray diffraction (XRD) patterns were obtained using CuKa radiation at a scanning rate of 2.0mm/min., using a voltage of 45 kV and a current of 40 mA. Fig. 1a and 1b shows the X-ray diffraction patterns of as-prepared PANI:GRA=90.55:9.45 and 80.762:19.238 composites respectively.  In Fig.1a one diffraction peak is located at θ= 13.2603º  and in Fig.1 b  the diffraction peak is located at θ=13.2712º.

Figure1a: XRD pattern of PANI:GRA=90.55:9.45   Click here to View figure

 

Figure1b: XRD pattern of PANI:GRA=80.762:19.238     Click here to View figure

 

The figures 2a and 2b are the respective SEM images of the PANI: GRA=90.55:9.45 and 80.762:19.238 composites.

Figure2a: SEM image of PANI:GRA=90.55:9.45   Click here to View figure

 

Figure2b: SEM image of PANI:GRA=807625:19.238   Click here to View figure

 

Discussion

From the XRD pattern particle sizes were determined using  FWHM method. The sizes were 20.8985 nm and 18.447 nm of PANI:GRA 90.55:9.45  and 80.762:19.238 composites respectively. The SEM analysis that the samples appear like two dimensional sheets. From the histogram the mean diameter of first sample was 22.28 nm with standard deviation 1.9 nm and for second sample was 21.22 nm with standard deviation 1.7 nm. Polyaniline-graphite composites of different weight percentage  were prepared in powder form and analysis reveals the particle are nano in size. Hence we succeed in synthesis of  nano-composites of polyaniline and graphite.

Acknowledgement

This work was supported by research center, Department of materials science, Gulbarga University Gulbarga (Karnataka –India).

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