Final Report of Minor Research Project

Transcription

1 Final Report of Minor Research Project Titled DEVELOPMENT OF FLY ASH /POLYMER COMPOSITES FOR ELECTRRONIC MATERIALS APPLICATIONS UGC Reference No: File No /10(WRO) Submitted by Dr. A. D. Dahegaonkar Department of Physics N. S. Science & Arts College Bhadrawati Dist: Chandrapur Maharashtra State 1 Page

2 1. INTRODUCTION 1.1 Conducting polymers A polymer (materials containing a long chain of molecular structures) is first and foremost an insulator. The idea that polymers or plastics could conduct electricity is considered absurd. In fact these materials are commonly used for surrounding copper wires and manufacturing the outer structures of electrical appliances that prevent human from coming in direct contact with electricity. Approximately three decades ago, scientists discovered that a type of conjugated polymer called polyacetylene could become highly electrically conductive after undergoing a structural modification process called doping. The polymer is called a conjugated polymer because of the alternating single and double bonds in polymer chain. The de-localized electrons may move around the whole system and become the charge carriers to make them conductive. This polymer can be transformed into a conducting form when electrons are removed from the backbone resulting in added to the backbone resulting in anions. Anions and cations act as charge carriers, hopping from one site to another under the influence of an electrical field, thus increasing conductivity. 1.2 Polyaniline Among the conducting polymers, polyaniline has attracted a considerable scientific interest in recent decades because of its diverse structure, low cost, good electrical properties and wide application in different field, such as microelectronics, corrosion protection, sensor and electrodes for batteries. Since these conducting polymer are usually obtained as power, they are difficult to process. 1.3 Poly (o-anisidine) The practical applications of polyaniline have been limited due to harsh chemical conditions in the synthesis and purification procedure that often lead to an inflexible polymer. To address this problem and improve processability, a diverse set of modified polymerizations have been investigated. 2 Page

3 1.4 Poly (o-toluidine) Much attention of many researchers is due to its ease of synthesis, processibility, good thermal stability and good environmental stability. MacDiarmid investigated Poly (o-toluidine) as an electrically conducting polymer, which is emerging as a promising synthetic metal. The possibility of synthesizing and doping of Poly (o-toluidine) with photonic acid dopants containing different types of counter ions is one of the key factors responsible for the versatility of this class of polymers. Photoluminescent organic molecules are a new class of compounds with interesting properties. They undergo emission over a wide range from the violet to the red. They can also be combined in several different forms to produce white light. One category of organic material with photoluminescence properties is conjugated organic polymers. 1.5 Fly ash Fly ash, a waste product of coal combustion in thermal power plant, contains many hazardous substances such as heavy metals and toxic organic compounds and thus is a major source for environment pollution. Currently in China a small percentage of this waste is mainly utilized for the manufacture of concrete, cement and brick products, and the remainder being directly buried in fly ash ponds or landfills, which is an unsatisfactory solution both from the ecological and economical points of view. As a consequence, new economical and reliable means have to be found out in order to safeguard the environment and provide useful way for its disposal. Because the fly ash contains large amount of SiO 2 and Al2O3, which are main glass network formers, many research and development investigations recently have been conducted in its utilization as a starting material for glass and glass-ceramic production. 1.6 Literature Review Conductive polymers such as polypyrrole, Polyacetylene, etc continue to be the focus of active research in diverse fields including electronics, energy storage catalysis, chemical sensing and optochemistry. Polyaniline is unique among conducting polymers in its wide range of electrical, electrochemical and optical properties as well as good stability. Polyaniline can be doped to highly conducted state by protonic acids or by electrochemical methods and show moderate conductivity upon doping. In literature survey the invention of conducting polymers has been carried into various aspects such as 3 Page

4 Developments in the field of conducting polymers, Development of Polyaniline, Synthesis, Properties, Recent trends. Fig.1.1 Books purchased under M.R.P. 2. SYNTHESIS There are different methods by which conducting polymers can be synthesized. Conducting polymers can be synthesized in the presence of different protonic acid media by different methods. The most widely accepted methods are chemical oxidative polymerization method and electrochemical method Chemical oxidative method is preferred over electrochemical polymerization because of its cost effectiveness and bulk quantity of the polymer that can be prepared during the onset of the reaction. Other techniques include solid state polymerization, plasma polymerization, precursor polymer route, template polymerization. In present investigation deals with the synthesis of conducting polymer polyaniline, poly(o-anisidine), poly(o-toulidine) and its composites with various weight percentage of fly ash. These composites have the ability to enhance their material properties with desirable mechanical and physical characteristics. One way of making these composites involves synthesizing the conductive polymer inside the matrices of conventional polymers using chemical or electrochemical polymerization. 4 Page

5 Fig. 2.1 Weight Balance Fig. 2.3 Hot Air Oven Fig. 2.2 Synthesis process Fig. 2.4 Prepared Samples =========================================================.There are many reports pertaining to the chemical preparation of conductive polymer composites without using any insulating polymer. The most preferred method for synthesis of PANI composites is to use either HCL or H 2SO4 with ammonium peroxydisulfate as an oxidant. In these approaches monomer is polymerized in the presence of commercially available 5 Page

6 inorganic acid particles which act as colloidal substrate for the precipitating polymer nuclei leading to the formation of conducting polymer-inorganic oxide composites.among different conducting polymers polyaniline is chosen as a matrix polymer because of its high stability, easy processability,low cost and wide utility. 3. CHARACTERIZATION Characterization of a material is an important step after its synthesis because it gives useful parameters in determining the properties of polymers. The characterization of conducting polymer composites required various lab techniques which are to be used to determine the structure and properties. Chemical characterizations required to determine the oxidation states. Physical characterization consists of spectroscopic analysis using Fourier Transform Infra Red (FT-IR) and UV-visible spectrophotometer; structural analysis using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM); thermal analysis using Thermogravimtric Analysis (TGA), Thermal Differential Analysis (DTA) and Differential Scanning Calerometry (DSC). Physico-chemical methods involve the application of electroanalytical techniques like Cyclic Voltammetry (CV). \ A single method may not provide much information, but a combination of two or three methods can give us fairly good knowledge about structure of conducting polymer semiconductor composites. In present investigation, the following useful techniques have been used to investigate the synthesized materials. Scanning Electron Microscopy UV - visible spectroscopy X-Ray Diffraction Fourier Transform Infra Red The aim of the present chapter is to explore the composition of synthesized conducting polymer fly ash composites by using these techniques and each technique has been well explained with introduction, theoretical aspects and finally results and discussion came out from the analysis. 6 Page

7 4. ELECTRIC AND DIELECTRIC PROPERTIES 4.1 Conductivity Measurement The electrical conductivity of polyaniline, poly(o-anisidine), poly(o-toulidine), FA and its composites with various weight percentage of FA measurements were carried out Department of physics N S Science & Arts College Bhadrawati in by four probe resistivity measurement setup as shown in figure 4.2.The whole four probes set-up consist of separate three units Model produced by Scientific Equipment Roorkee. Four probe set up consist of separate three units. Fig. 4.1: Experimental set up of the Four-Probe method 4.2 Dielectric Properties: Dielectric constant measurement are one of the most popular methods of evaluating solid materials, such as electric insulators and polymers, because dielectric constant measurement can be performed easier than chemical analysis techniques. We can evaluate not only the electrical characteristics, but also the physical characteristics, the structure of elements and their density can be derived from measured dielectric constant information. 7 Page

8 5. FUTURE SCOPE OF THE WORK Conducting polymers are becoming of increasing important for a variety of applications. However, still more research is needed to ascertain their use in sensors,electronic devices, photovoltaic devices, electroluminescence, molecular electronics, as catalyst supports low conducting coatings for high voltage transmission cables and for the anodic protection of steel against corrosion. Moreover, there is very great potential to use them in the virtually unexplored biomedical applications. Another versatile area from the technological point of view is the studies on composites containing conducting polymers and an inert polymer matrix. Fly ash utilization is being promoted as an "eco-friendly solution". It is certainly a use of an otherwise useless and potentially hazardous waste. We have not found any data to indicate any environmental problems with fly ash utilization. This could be a result of inadequate focus on the problem, But nor have we found any data that actually absolves fly ash products of potential environmental contamination. In fact, most proponents of fly ash products do not seem to have given this aspect any serious thought. Studies examining the environmental and health effects due to leachates from such applications are hard to come by. ``At the moment we are in the process of studying whether utilization of fly ash will have any human health or environmental effects or not. We are generating data for 3 years after which we can confidently say that fly ash is environment friendly says Vimal Kumar Director of Fly Ash Mission. For a number of meaningful applications, electrical conductivity is potentially one of the most important properties of a material. Usually, raw FA is rich in aluminosilicate materials(mullite, quartz, and alumina) and has a high electrical resistivity of the order of Ω.cm or even higher. In comparison, porcelain, which is made from aluminosilicate materials (clay, quartz, alumina and feldspar) too, and is used in the high-tension ceramic insulators, has an electrical resistivity of the order of 1013Ω.cm. This implies that FA can possibly be used as a raw material in high-tension insulators applications, although not much work has been done along this direction. On the other hand, based on the requirements, the electrical properties of FA can be significantly modified, for example, by blending it into composites of suitable material, such as a conducting polymer. FA showed dielectric constant of the order of 10 which can be best suitable material for capacitor fabrication and the samples of fly ash is of great scientific and technological interest. 8 Page

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