Date of Award

5-2004

Document Type

Thesis

Degree Name

Master of Materials Science and Engineering (MMatSE)

Department

Materials Science

First Advisor

Dr. Mahmood Alawy Mohsin

Second Advisor

Dr. Ahmed Galal Helmy

Third Advisor

Richard Jon es

Abstract

The performance of materials in general depends on their properties. There is a continuous need of new materials to meet the technological revolution that was witnessed by the end of last century. In this work, a new class of materials was synthesized. The host matrix is an Organic Conducting Polymer (OCP) of either poly(3-methylthiophene) (PMT) or poly(aniline) (PAN). The synthesis of OCP is achieved using electrochemical methods of applying constant potential or cyclic voltammetry at a platinum or graphite substrate in an acetonitrile containing tetra-alkyl-ammonium salt. The set up is three-electrode system of a platinum counter electrode and a silver/silver chloride reference electrode. The thickness of the OCP film was controlled by the amount of charge passing through the cell. Thus, different thickness of OCP was synthesized using the above method. Inorganic layer was then added to the OCP host matrix using two different approaches. The first is based on electrochemical deposition of platinum particles with different size and spatial distribution within the OCP matrix, while the second uses a sol-gel approach to dip coat the OCP film. The resulting hybrid/composite material was studied using electrochemical techniques such as cyclic voltammetry (CV) to study the general characteristic of the redox behavior of the film and electrochemical impedance spectroscopy (EIS) to characterize the charge transfer processes and capacitive nature of the material. Two important findings were discovered the first is that the OCP layer retained its electrochemical characteristics known for this class of materials; the second is the considerable increase in the capacitive nature of the film upon inclusion of the inorganic layer. The highest value of capacity was achieved with a "sandwich" type hybrid film. The film was constructed as PMT/sol-gel/PMT or sol-gel/PMT/sol-gel system interfaced with an electrolytic phase. The first "sandwich" type material showed high promising value of capacitance that make it a good candidate for future use as rechargeable battery system. All electrochemical/electronic parameters calculated were using a numerical/graphical method and the data were fitted to equivalent circuit models.

The thermal stability of the resulting hybrid/composite materials was examined using Thermal and Differential Gravimetric Analyses (TGA and DTGA). The results proved that the inorganic layer incorporated into the film, rendered the material more stable and retarded the weight loss considerably upon applying the heating protocol. On the other hand the morphology of the resulting film was examined using Scanning Electron Microscopy (SEM) and the pictures recorded showed the formation of inorganic particles in the sub-micron dimension as well as inorganic clustered structures. The spatial distribution of these particles and clustered layers were homogeneously spread over and within the OCP film. These observations were successfully related to the observed electrochemical/electronic parameters obtained by CV and EIS measurements. The incorporation of the metallic elements such as Pt, Fe, and Ce was confirmed from the extended diffraction of X-rays (EDAX) with relatively small concentrations that might be further studied for catalytic conversion purposes. The latter study would be extreme importance towards applications in the area of treatment of wastes and chemical conversions. This is beyond the scope of the present work and will be suggested for further investigations. X-ray diffraction (XRD) measurements shows that the structure of the OCP was maintained and the appearance of inorganic particle inclusion with estimated dimensions in the range between 130 nm and 550 nm. Fourier Transform InfraRed (FTIR) measurements were made on the as-grown films to examine the molecular structure of this new class of materials. The results showed that the structure of the OCP was maintained with the appearance of new bands indicating the presence of the inorganic moieties.

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