Magnetic, Dielectric and Physicomechanical Properties of Rubber Ferrite Nanocomposites

In the present study the preparation and characterisation of rubber ferrite composites containing nickel ferrite and gamma ferric oxide have been dealt with.Synthetic rubbers viz. ethylene propylene diene rubber and neoprene rubber were used for the incorporation of nickel ferrite and gamma ferric oxide for the synthesis of RFCs. Incorporation of ferrites were carried out according to a specific recipe for various loadings of the magnetic fillers. The ferrites used for the preparation of RFCs were synthesised using sol-gel method and structural characterisation was carried out. Experimental techniques like X-ray diffraction, Transmission electron microscopy and other analytical techniques were used for this. Precharaterised ferrites were then incorporated at different loading into rubber according to conventional mixing methods. The cure characteristics, mechanical, dielectric, magnetic and microwave properties of these composites were evaluated. The effect of carbon black on these properties of RFCs were carried out.

Development of novel surface coatings based on acrylic copolymers

The present study describes the preparation of Vinyl acetate-Butyl acrylate copolymer lattices of varying compositions and solid contents by semicontinuous emulsion polymerization method. This copolymer lattices were used as binder to develop a new surface coating formulation. The properties of this surface coating were improved by using nano TiO2 colloidal sol as a pigment. Antimicrobial activity of surface coatings was improved by the addition of carboxymethyl chitosan as biocide. Uniformly dispersed tyre crumb was used to give a mat finish to the coating. The mechanical properties adhesive properties, thermal properties etc. of the coatings are presented in thesis.

Synthesis of nickel–rubber nanocomposites and evaluation of their dielectric properties

Nanocomposites based on natural rubber and nano-sized nickelwere synthesized by incorporating nickel nanoparticles in a natural rubber matrix for various loadings of the filler. Structural, morphological, magnetic and mechanical properties of the compositeswere evaluated along with a detailed study of dielectric properties. Itwas found that nickel particleswere uniformly distributed in the matrix without agglomeration resulting in a magnetic nanocomposite. The elastic properties showed an improvement with increase in filler content but breaking stress and breaking strain were found to decrease. Dielectric permittivity was found to decrease with increase in frequency, and found to increase with increase in nickel loading. The decrease in permittivity with temperature is attributed to the high volume expansivity of rubber at elevated temperatures. Dielectric loss of blank rubber as well as the composites was found to increase with temperature.

Catalysis by Polymer Supported Dendrimers, their Metal Complexes and Nanoparticle Conjugates

The present thesis has described the development of some heterogeneous catalysts based on polymer supported dendrimers. Attachment of dendrimers to crosslinked polymer produced new catalysts with combined benefits of both dendrimers and heterogeneous catalysts. These were used as heterogeneous catalysts in selected reactions. All possible attempts were taken to avoid halogenated and aromatic solvents and toxic reagents. In short the present work has dealt with development of environmental friendly catalysts based on dendrimers.

Novel applications of cashew nut shell liquid in the polymer field

This research project aims at developing new applications for CNSL in the polymer field. Cashew nut shell liquid (CNSL) is a cheap agro-byproduct and renewable resource which consists mainly of substituted phenols. By using CNSL in place of phenol, phenol derived from petrochemicals can be conserved and a cheap agro-byproduct utilized.In this study CNSL based resin is prepared by condensing a mixture of phenol and CNSL with hexamethylenetetramine and the effect of P: F ratio and CNSL: P ratio on the properties of synthesized resin is studied. The adhesive properties of CNSL based resin in combination with neoprene rubber are investigated. The effect of varying the stoichiometric ratios between total phenol and formaldehyde and CNSL and phenol of the resin, resin content, choice and extent of fillers and adhesion promoters in the adhesive formulation are studied. The effect of resin on the ageing properties of various elastomers is also studied by following changes in tensile strength, elongation at break, modulus, tear strength, swelling index and acetone soluble matter. Crude CNSL and resins with different P: F ratios and CNSL: P ratios are incorporated into elastomers. Lastly, utility of CNSL based resin as binder for making particleboard is investigated.The results show that CNSL based resin is an effective ingredient in adhesives for bonding aluminium to aluminium. The resin used for adhesive fonnulation gives the best performance at 45 to 55 phr resin and a total phenol: formaldehyde of l:2.9. The resin when added at a rate of l5 phr improves ageing characteristics of elastomers with respect to mechanical properties. The reaction mixture of CNSL and hexa and the resin resulting from the condensation of CN SL, phenol and hexa can be used as effective binders for moulding particleboard.

Linear Low Density Polyethylene-Biodegradability Using Bacteria from Marine Benthic Environment and Photodegradability Using Ultraviolet Light

Various compositions of linear low density polyethylene(LLDPE) containing bio-filler(either starch or dextrin)of various particle sizes were prepared.The mechanical,thermal,FTIR,morphological(SEM),water absorption and melt flow(MFI) studies were carried out.Biodegradability of the compositions were determined using a shake culture flask containing amylase producing bacteria(vibrios),which were isolated from marine benthic environment and by soil burial test. The effect of low quantities of metal oxides and metal stearate as pro-oxidants in LLDPE and in the LLDPE-biofiller compositions was established by exposing the samples to ultraviolet light.The combination of bio-filler and a pro-oxidant improves the degradation of linear low density polyethylene.The maleation of LLDPE improves the compatibility of the c blend components and thepro-oxidants enhance the photodegradability of the compatibilised blends.The responsibility studies on the partially biodegradable LLDPE containing bio-fillers and pro-oxidants suggest that the blends could be repeatedly reprocessed without deterioration in mechanical properties.

Preparation and Characterization ofHigh-k Aluminum Oxide Thin Films by Atomic Layer Deposition for Gate Dielectric Applications

Present work deals with the Preparation and characterization of high-k aluminum oxide thin films by atomic layer deposition for gate dielectric applications.The ever-increasing demand for functionality and speed for semiconductor applications requires enhanced performance, which is achieved by the continuous miniaturization of CMOS dimensions. Because of this miniaturization, several parameters, such as the dielectric thickness, come within reach of their physical limit. As the required oxide thickness approaches the sub- l nm range, SiO 2 become unsuitable as a gate dielectric because its limited physical thickness results in excessive leakage current through the gate stack, affecting the long-term reliability of the device. This leakage issue is solved in the 45 mn technology node by the integration of high-k based gate dielectrics, as their higher k-value allows a physically thicker layer while targeting the same capacitance and Equivalent Oxide Thickness (EOT). Moreover, Intel announced that Atomic Layer Deposition (ALD) would be applied to grow these materials on the Si substrate. ALD is based on the sequential use of self-limiting surface reactions of a metallic and oxidizing precursor. This self-limiting feature allows control of material growth and properties at the atomic level, which makes ALD well-suited for the deposition of highly uniform and conformal layers in CMOS devices, even if these have challenging 3D topologies with high aspect-ratios. ALD has currently acquired the status of state-of-the-art and most preferred deposition technique, for producing nano layers of various materials of technological importance. This technique can be adapted to different situations where precision in thickness and perfection in structures are required, especially in the microelectronic scenario.

Synthesis and Characterization of Novel Ionomers based on Styrene Butadiene Copolymer

Novel thermo-reversible zinc sulphonated ionomers based on styrene butadiene rubber (SBR), and high styrene rubber (HSH) were synthesized by sulphonation followed by neutralization with zinc. The sulphonate content of the ionomer was estimated by using x-ray fluorescence spectroscopy. Presence of sulphonate groups has been confirmed by FTIR and FTNMR spectra. The TGA results show improvement in the thermo~oxidative stability of the modified rubber. Both DSC and DMTA studies show that the incorporation of the ionic groups affect the glass rubber transition of the base polymer. lntroduction ol ionic functionality in to the base material improved the physical properties. Retention of the improved physical properties of the novel ionomers even after three repeated cycles of mixing and molding may be considered as the evidence for the reprocessability of the ionomer. Effect of particulate fillers (HAF black, silica and zinc stearate) on the properties of the zinc sulphonated styrene butadiene rubber ionomer has been evaluated. Incorporation of tillers results in improvement in mechanical properties. Zinc stearate plays the dual role of reinforcement and plasticization. The evaluation of dielectric properties of zinc sulphonated styrene butadiene rubber iorpmers at microwave frequencies reveal that the materials show conductivity at semiconductor level. The real and imaginary parts of the complex permittivity increases with increase in ionic functionality. Use of the 38.5 ZnS-SBR ionomer as a compatibiliser for obtaining the technologically compatible blends from the immiscible SBR/NBR system has been discussed.

Photonic applications of biomaterials with special reference to biopolymers and microbes

This thesis Entitled Photonic applications of biomaterials with special reference to biopolymers and microbes. A detailed investigation will be presented in the present thesis related to direct applications of biopolymers into some selected area of photonics and how the growth kinetics of an aerial bacterial colony on solid agar media was studied using laser induced fluorescence technique. This chapter is an overview of the spectrum of biomaterials and their application to Photonics. The chapter discusses a wide range of biomaterials based photonics applications like efficient harvesting of solar energy, lowthreshold lasing, high-density data storage, optical switching, filtering and template for nano s tructures. The most extensively investigated photonics application in biology is Laser induced fluorescence technique. The importance of fluorescence studies in different biological and related fields are also mentioned in this chapter.

Studies on the structural, electrical and magnetic properties of composites based on spinel ferrites

This thesis mainly deals with the preparation and studies on magnetic composites based on spinel ferrites prepared both chemically and mechanically. Rubber ferrite composites (RFC) are chosen because of their mouldability and flexibility and the ease with which the dielectric and magnetic properties can be manipulated to make them as useful devices. Natural rubber is chosen as the Matrix because of its local availability and possible value addition. Moreover, NR represents a typical unsaturated nonpolar matrix. The work can be thought of as two parts. Part l concentrates on the preparation and characterization of nanocomposites based on y-Fe203. Part 2 deals with the preparation and characterization of RFCs containing Nickel zinc ferrit In the present study magnetic nanocomposites have been prepared by ionexchange method and the preparation conditions have been optimized. The insitu incorporation of the magnetic component is carried out chemically. This method is selected as it is the easiest and simplest method for preparation of nanocomposite. Nanocomposite samples thus prepared were studied using VSM, Mossbauer spectroscopy, Iron content estimation, and ESR spectroscopy. For the preparation of RFCs, the filler material namely nickel zinc ferrite having the general formula Ni)_xZnxFez04, where x varies from 0 to 1 in steps of 0.2 have been prepared by the conventional ceramic techniques. The system of Nil_xZn"Fe204 is chosen because of their excellent high frequency characteristics. After characterization they are incorporated into the polymer matrix of natural rubber by mechanical method. The incorporation is done according to a specific recipe and for various Loadings of magnetic fillers and also for all compositions. The cure characteristics, magnetic properties and dielectric properties of these composites are evaluated. The ac electrical conductivity of both ceramic nickel zinc ferrites and rubber ferrite composites are also calculated using a simple relation. The results are correlated.

Ethylene-Propylene-Diene Terpolymer/Hexafluoropropylene-Vinylidinefluoride Elastomeric Composites: Thermal, Mechanical and Microwave Properties

In the present study, an attempt has been made to prepare composites by incorporating expanded graphite fillers in insulating elastomer matrices and to study its DC electrical conductivity, dielectric properties and electromagnetic shielding characteristics, in addition to evaluating the mechanical properties. Recently, electronic devices and components have been rapidly developing and advancing. Thus, with increased usage of electronic devices, electromagnetic waves generated by electronic systems can potentially create serious problems such as malfunctions of medical apparatus and industry robots and can even cause harm to the human body. Therefore, in this work the applicable utility of the prepared composites as electromagnetic interference (EMI) shielding material are also investigated. The dissertation includes nine chapters

Optical and thermal characterization of dye intercalated montmorillonites and rare earth doped materials

The advent of high optical quality transparent nano—structured glasses, the so-called transparent glass ceramics or vitroceramics disclosed the possibility of producing nano-sized photonic devices based on rare-earth doped up—converters. Transparent glass ceramics have been investigated as hosts for lanthanide ions envisioning the production of materials that are easy to shape and with high performance for photonic applications. Rare earth doped glasses have been extensively studied due to their potential applications in optical devices such as solid state lasers and optical fibers. Various photothermal and optical techniques have been successfully applied for the thermal and optical characterization of these rare earth doped materials. In the present thesis, the effective thermal parameters like thermal diffusivity and thermal effusivity of complex materials for various applications have been investigated using photothermal methods along with their optical characterization utilising the common optical absorption as well as fluorescence spectroscopic techniques. These sensitive optical procedures are also essential for exploiting these materials for further photonic applications.

Studies on Elastomer Blends with special reference to NBR/Butyl, NR/Butyl and NBR/EPDM Blends

The distribution of curing agents and fillers in the constituents of an elastomer blend is an important factor which determines the curing behaviour and vulcanizate properties of the blend. The distribution of curatives and fillers largely depends on the nature of elastomers. The curatives tend to migrate preferentially to the rubber of higher unsaturation and/or higher polarity, and reinforcing fillers tend to get distributed in the low viscosity phase, resulting in inferior mechanical properties of the blends. The thesis suggests several methods for improving mechanical properties of blends like NBR/butyl, NR/butyl, NBR/EPDM and NR/.

Design and development of compact printed ultra wide band antennas

In recent years, there is a visible trend for products/services which demand seamless integration of cellular networks, WLANs and WPANs. This is a strong indication for the inclusion of high speed short range wireless technology in future applications. In this context UWB radio has a significant role to play as an extension/complement to existing cellular/access technology. In the present work, three major types of ultra wide band planar antennas are investigated: Monopole and Slot. Three novel compact UWB antennas, suitable for poratble applications, are designed and characterized, namely 1) Ground modified monopole 2) Serrated monopole 3) Triangular slot The performance of these designs have been studied using standard simulation tools used in industry/academia and they have been experimentally verified. Antenna design guidelines are also deduced by accounting the resonances in each structure. In addition to having compact sized, high efficiency and broad bandwidth antennas, one of the major criterion in the design of impulse-UWB systems have been the transmission of narrow band pulses with minimum distortion. The key challenge is not only to design a broad band antenna with constant and stable gain but to maintain a flat group delay or linear phase response in the frequency domain or excellent transient response in time domain. One of the major contributions of the thesis lies in the analysis of the frequency and timedomain response of the designed UWB antennas to confirm their suitability for portable pulsed-UWB systems. Techniques to avoid narrowband interference by engraving narrow slot resonators on the antenna is also proposed and their effect on a nano-second pulse have been investigated

Growth of metal and semiconductor nanostructures for nonlinear optical applications

Nonlinear optics has been a rapidly growing field in recent decades since the invention of lasers. The systematic progress in the laser technology increases our efficiency in the generation and control of coherent optical radiations. Nonlinear optics is based on the study ofeffects and phenomena related to the interaction of intense coherent light radiation with matter. Compared to other light sources laser radiation can provide high directionality, high monochromaticiry, high brightness and high photon degeneracy. At such a very intense incident beam, the matter responds in a nonlinear manner to the incident radiation fields, which endows the media :1 characteristic to change the refractive index or absorption coe fflcient of the media or the wavelength, or the frequency of the incident electromagnetic waves. This thesis encompasses the fabrication of nonlinear optical devices based on semiconductor and metal nanostructures. The presented work focus on the experimental and theoretical discussions on nonlinear optical effects especially nonlinear absorption and refraction exhibitted by metal and semiconductor nanostructures