Photothermal and photoacoustic investigations on certain polymers and semi conducting materials

Material synthesizing and characterization has been one of the major areas of scientific research for the past few decades. Various techniques have been suggested for the preparation and characterization of thin films and bulk samples according to the industrial and scientific applications. Material characterization implies the determination of the electrical, magnetic, optical or thermal properties of the material under study. Though it is possible to study all these properties of a material, we concentrate on the thermal and optical properties of certain polymers. The thermal properties are detennined using photothermal beam deflection technique and the optical properties are obtained from various spectroscopic analyses. In addition, thermal properties of a class of semiconducting compounds, copper delafossites, arc determined by photoacoustic technique.Photothermal technique is one of the most powerful tools for non-destructive characterization of materials. This forms a broad class of technique, which includes laser calorimetry, pyroelectric technique, photoacollstics, photothermal radiometric technique, photothermal beam deflection technique etc. However, the choice of a suitable technique depends upon the nature of sample and its environment, purpose of measurement, nature of light source used etc. The polynler samples under the present investigation are thermally thin and optically transparent at the excitation (pump beam) wavelength. Photothermal beam deflection technique is advantageous in that it can be used for the detennination of thermal diffusivity of samples irrespective of them being thermally thick or thennally thin and optically opaque or optically transparent. Hence of all the abovementioned techniques, photothemlal beam deflection technique is employed for the successful determination of thermal diffusivity of these polymer samples. However, the semi conducting samples studied are themlally thick and optically opaque and therefore, a much simpler photoacoustic technique is used for the thermal characterization.The production of polymer thin film samples has gained considerable attention for the past few years. Different techniques like plasma polymerization, electron bombardment, ultra violet irradiation and thermal evaporation can be used for the preparation of polymer thin films from their respective monomers. Among these, plasma polymerization or glow discharge polymerization has been widely lIsed for polymer thin fi Im preparation. At the earlier stages of the discovery, the plasma polymerization technique was not treated as a standard method for preparation of polymers. This method gained importance only when they were used to make special coatings on metals and began to be recognized as a technique for synthesizing polymers. Thc well-recognized concept of conventional polymerization is based on molecular processcs by which thc size of the molecule increases and rearrangemcnt of atoms within a molecule seldom occurs. However, polymer formation in plasma is recognized as an atomic process in contrast to the above molecular process. These films are pinhole free, highly branched and cross linked, heat resistant, exceptionally dielectric etc. The optical properties like the direct and indirect bandgaps, refractive indices etc of certain plasma polymerized thin films prepared are determined from the UV -VIS-NIR absorption and transmission spectra. The possible linkage in the formation of the polymers is suggested by comparing the FTIR spectra of the monomer and the polymer. The thermal diffusivity has been measured using the photothermal beam deflection technique as stated earlier. This technique measures the refractive index gradient established in the sample surface and in the adjacent coupling medium, by passing another optical beam (probe beam) through this region and hence the name probe beam deflection. The deflection is detected using a position sensitive detector and its output is fed to a lock-in-amplifIer from which the amplitude and phase of the deflection can be directly obtained. The amplitude and phase of the deflection signal is suitably analyzed for determining the thermal diffusivity.Another class of compounds under the present investigation is copper delafossites. These samples in the form of pellets are thermally thick and optically opaque. Thermal diffusivity of such semiconductors is investigated using the photoacoustic technique, which measures the pressure change using an elcctret microphone. The output of the microphone is fed to a lock-in-amplificr to obtain the amplitude and phase from which the thermal properties are obtained. The variation in thermal diffusivity with composition is studied.

Development of Best Practices for Ship Recycling Processes

Ship recycling has been considered as the best means to dispose off an obsolete ship. The current state of art of technology combined with the demands of sustainable developments from the global maritime industrial sector has modified the status of erstwhile ‘ship breaking’ involving ship scrap business to a modern industry undertaking dismantling of ships and recycling/reusing the dismantled products in a supply chain of pre owned product market by following the principles of recycling. Industries will have to formulate a set of best practices and blend them with the engineering activities for producing better quality products, improving the productivity and for achieving improved performances related to sustainable development. Improved performance by industries in a sustainable development perspective is accomplished only by implementing the 4E principles, ie.,. ecofriendliness, engineering efficiency, energy conservation and ergonomics in their core operations. The present study has done a comprehensive investigation into various ship recycling operations for formulating a set of best practices.Being the ultimate life cycle stage of a ship, ship recycling activities incorporate certain commercial procedures well in advance to facilitate the objectives of dismantling and recycling/reusing of various parts of the vessel. Thorough knowledge regarding these background procedures in ship recycling is essential for examining and understanding the industrial business operations associated with it. As a first step, the practices followed in merchant shipping operations regarding the decision on decommissioning have been and made available in the thesis. Brief description about the positioning methods and important preparations for the most feasible ship recycling method ie.,. beach method have been provided as a part of the outline of the background information. Available sources of guidelines, codes and rules & regulations for ship recycling have been compiled and included in the discussion.Very brief summary of practices in major ship recycling destinations has been prepared and listed for providing an overview of the global ship recycling activities. The present status of ship recycling by treating it as a full fledged engineering industry has been brought out to establish the need for looking into the development of the best practices. Major engineering attributes of ship as a unique engineering product and the significant influencing factors on her life cycle stage operations have been studied and added to the information base on ship recycling. Role of ship recycling industry as an important player in global sustainable development efforts has been reviewed by analysing the benefits of ship recycling. A brief synopsis on the state of art of ship recycling in major international ship recycling centres has also been incorporated in the backdrop knowledgebase generation on ship recycling processes.Publications available in this field have been reviewed and classified into five subject categories viz., Infrastructure for recycling yards and methods of dismantling, Rules regarding ship recycling activities, Environmental and safety aspects of ship recycling, Role of naval architects and ship classification societies, Application of information technology and Demand forecasting. The inference from the literature survey have been summarised and recorded. Noticeable observations in the inference include need of creation of a comprehensive knowledgebase on ship recycling and its effective implementation in the industry and the insignificant involvement of naval architects and shipbuilding engineers in ship recycling industry. These two important inferences and the message conveyed by them have been addressed with due importance in the subsequent part of the present study.As a part of the study the importance of demand forecasting in ship recycling has been introduced and presented. A sample input for ship recycling data for implementation of computer based methods of demand forecasting has been presented in this section of the thesis.The interdisciplinary nature of engineering processes involved in ship recycling has been identified as one of the important features of this industry. The present study has identified more than a dozen major stake holders in ship recycling having their own interests and roles. It has also been observed that most of the ship recycling activities is carried out in South East Asian countries where the beach based ship recycling is done in yards without proper infrastructure support. A model of beach based ship recycling has been developed and the roles, responsibilities and the mutual interactions of the elements of the system have been documented as a part of the study Subsequently the need of a generation of a wide knowledgebase on ship recycling activities as pointed out by the literature survey has been addressed. The information base and source of expertise required to build a broad knowledgebase on ship recycling operations have been identified and tabulated. Eleven important ship recycling processes have been identified and a brief sketch of steps involved in these processes have been examined and addressed in detail. Based on these findings, a detailed sequential disassembly process plan of ship recycling has been prepared and charted. After having established the need of best practices in ship recycling initially, the present study here identifies development of a user friendly expert system for ship recycling process as one of the constituents of the proposed best practises. A user friendly expert system has been developed for beach based ship recycling processes and is named as Ship Recycling Recommender (SRR). Two important functions of SRR, first one for the ‘Administrators’, the stake holders at the helm of the ship recycling affairs and second one for the ‘Users’, the stake holders who execute the actual dismantling have been presented by highlighting the steps involved in the execution of the software. The important output generated, ie.,. recommended practices for ship dismantling processes and safe handling information on materials present onboard have been presented with the help of ship recycling reports generated by the expert system. A brief account of necessity of having a ship recycling work content estimation as part of the best practices has been presented in the study. This is supported by a detailed work estimation schedule for the same as one of the appendices.As mentioned earlier, a definite lack of involvement of naval architect has been observed in development of methodologies for improving the status of ship recycling industry. Present study has put forward a holistic approach to review the status of ship recycling not simply as end of life activity of all ‘time expired’ vessels, but as a focal point of integrating all life cycle activities. A new engineering design philosophy targeting sustainable development of marine industrial domain, named design for ship recycling has been identified, formulated and presented. A new model of ship life cycle has been proposed by adding few stages to the traditional life cycle after analysing their critical role in accomplishing clean and safe end of life and partial dismantling of ships. Two applications of design for ship recycling viz, recyclability of ships and her products and allotment of Green Safety Index for ships have been presented as a part of implementation of the philosophy in actual practice.

Mathematical Modelling of the Dynamics of Granular Materials in a Rotating Cylinder

The current study is aimed at the development of a theoretical simulation tool based on Discrete Element Method (DEM) to 'interpret granular dynamics of solid bed in the cross section of the horizontal rotating cylinder at the microscopic level and subsequently apply this model to establish the transition behaviour, mixing and segregation.The simulation of the granular motion developed in this work is based on solving Newton's equation of motion for each particle in the granular bed subjected to the collisional forces, external forces and boundary forces. At every instant of time, the forces are tracked and the positions velocities and accelarations of each partcle is The software code for this simulation is written in VISUAL FORTRAN 90 After checking the validity of the code with special tests, it is used to investigate the transition behaviour of granular solids motion in the cross section of a rotating cylinder for various rotational speeds and fill fraction.This work is hence directed towards a theoretical investigation based on Discrete Element Method (DEM) of the motion of granular solids in the radial direction of the horizontal cylinder to elucidate the relationship between the operating parameters of the rotating cylinder geometry and physical properties ofthe granular solid.The operating parameters of the rotating cylinder include the various rotational velocities of the cylinder and volumetric fill. The physical properties of the granular solids include particle sizes, densities, stiffness coefficients, and coefficient of friction Further the work highlights the fundamental basis for the important phenomena of the system namely; (i) the different modes of solids motion observed in a transverse crosssection of the rotating cylinder for various rotational speeds, (ii) the radial mixing of the granular solid in terms of active layer depth (iii) rate coefficient of mixing as well as the transition behaviour in terms of the bed turnover time and rotational speed and (iv) the segregation mechanisms resulting from differences in the size and density of particles.The transition behaviour involving its six different modes of motion of the granular solid bed is quantified in terms of Froude number and the results obtained are validated with experimental and theoretical results reported in the literature The transition from slumping to rolling mode is quantified using the bed turnover time and a linear relationship is established between the bed turn over time and the inverse of the rotational speed of the cylinder as predicted by Davidson et al. [2000]. The effect of the rotational speed, fill fraction and coefficient of friction on the dynamic angle of repose are presented and discussed. The variation of active layer depth with respect to fill fraction and rotational speed have been investigated. The results obtained through simulation are compared with the experimental results reported by Van Puyvelde et. at. [2000] and Ding et at. [2002].The theoretical model has been further extended, to study the rmxmg and segregation in the transverse direction for different particle sizes and their size ratios. The effect of fill fraction and rotational speed on the transverse mixing behaviour is presented in the form of a mixing index and mixing kinetics curve. The segregation pattern obtained by the simulation of the granular solid bed with respect to the rotational speed of the cylinder is presented both in graphical and numerical forms. The segregation behaviour of the granular solid bed with respect to particle size, density and volume fraction of particle size has been investigated. Several important macro parameters characterising segregation such as mixing index, percolation index and segregation index have been derived from the simulation tool based on first principles developed in this work.

Investigations on the effect of excitonic confinement on nanomagnetic materials and studies on the optical properties of ferrofluids

Department of Physics, Cochin University of Science & Technology

Measurements of Electromagnetic Shielding Effect Using Htsc Materials

A simple experimental set-up is described to measure the electromagnetic shielding property of high Tc superconducting samples. Measurements were performed using HTSC materials in the form of laser ablated thin films, powders and sintered pellets. Samples used were Gd-123 in pure and doped form as well as a few Bi-based superconducting ceramics. For comparison, similar measurements were carried out on metals like aluminium, copper and μ metal. Very effective shielding was observed for HTSC materials compared to the conventional materials mentioned above. However it also depended on the sample types and poor shielding was observed for powdered HTSC material in comparison to thin films prepared by laser ablation.

Catalysis by Transition Metal Modified Ceria and Ceria-Zirconia Mixed Oxides Prepared via Sol-Gel Route

The aim of catalysis research is to apply the catalyst successfully in economically important reactions in an environmentally friendly way. The present work focuses on the modification of structural and surface properties of ceria and ceria-zirconia catalysts by the incorporation of transition metals. The applications of these catalysts in industrially important reactions like ethylbenzene oxidation, alkylation of aromatics are also investigated.Sol-gel method is effective for the preparation of transition metal modified ceria and ceria-zirconia mixed oxide since it produces catalyst with highly dispersed incorporated metal. Unlike that of impregnation method plugging of pores is not prominent for sol-gel derived catalyst materials. This prevents loss of surface area on metal modification as evident for BET surface area measurements.The powder X-ray diffraction analysis confirms the cubic structure of transition metal modified ceria and ceria-zirconia catalysts. The thermal stability is evident from TGA/DTA analysis. DR UV-vis spectra provide information on the coordination environment of the incorporated metal. EPR analysis ofCr, Mn and Cu modified ceria and a ceria-zirconia catalyst reveals the presence of different oxidation states of incorporated metal.Temperature programmed desorption of ammonia and thermogravimetric desorption of 2,6-dimethyl pyridine confirms the enhancement of acidity on metal incorporation. High a-methyl styrene selectivity in cumene cracking reaction implies the presence of comparatively more number of Lewis acid sites with some amount of Bronsted acid sites. The formation of cyclohexanone during cyclohexanol decomposition confirms the presence of basic sites on the catalyst surface.Mn and Cr modified catalysts show better activity towards ethylbenzene oxidation. A redox mechanism through oxometal pathway is suggested.All the catalysts were found to be active towards benzylation of toluene and a-xylene. The selectivity towards monoalkylated products remains almost 100%. The catalytic activity is correlated with the Lewis acidity of the prepared systems.The activity of the catalysts towards methylation of phenols depends on the strength acid sites as well as the redox properties of the catalysts. A strong dependence of methylation activity on the total acidity is illustrated.

Fabrication and Characterization of Chalcogenide nano composite based materials for Photonic device applications

In this context,in search of new materials based on chalcogenide glasses,we have developed a novel technique for fabrication of chalcogenide nano composites which are presented in this theis.The techniques includes the dissolution of bulk chalcogenide glasses in amine solvent.This solution casting method allows to retain the attractive optical properties of chalcogenide glasses enabling new fabrication routes for realization of large area thick-thin films with less cost. Chalcogenide glass fiber geometry opens new possibilities for a large number of applications in optics,like remote temperature measurements ,CO2 laser power delivery, and optical sensing and single mode propagation of IR light.We have fabricated new optical polymer fibers doped with chalcogenide glasses which can be used for many optical applications.The present thesis also describes the structural,thermal and optical characterization of certain chalocogenide based materials prepared for different methods and its applications.

Studies on Catalysis by Ordered Mesoporous SBA-15 Materials Modified with Transition Metals

To meet the challenges related to the chemical industry,development of efficient catalysts is necessary.The mesoporous materials like SBA-15 are considered as good catalyst candidates of 21st century.SBA-15 mesoporous materials are catalytically inactive,but allow the dispersion of catalytically active phases into the framework.So these materials can be considered as an interesting alternative for preparing catalytically active metal nanoparticles in-situ into it.In the present work various transition metals are incorporated to improve the catalytic activity of SBA-15 material.The fundamental aspects of the preparation,characterization and the activity studies are briefly viewed in this thesis. Systematic investigation of the physico-chemical properties and catalytic activity studies of the prepared materials were carried out and presented in this Study.

Oligo(p-Phenylenevinylene) Derived Organogels: A Novel Class of Functional Supramolecular Materials

The main objective of the present study is to have a detailed investigation on the gelation properties, morphology and optical properties of small π-conjugated oligomers. For this purpose we have chosen oligo(p-phenylenevinylene)s (OPVs), a class of molecules which have received considerable attention due to their unique optical and electronic properties. Though a large number of reports are available in the literature on the self-assembly properties of tailor made OPVs, none of them pertain to the design of nanostructures based on organogels. In view of this, we aimed at the creation of functional chromophoric assemblies of π-conjugated OPVs through the formation of organogels, with the objective of crafting nanoscopic assemblies of different size and shape thereby modulating their optical and electronic properties.In order to fulfill the above objectives, the design and synthesis of a variety of OPVs with appropriate structural variations were planned. The design principle involves the derivatization of OPVs with weak H-bonding hydroxymethyl end groups and with long aliphatic hydrocarbon side chains. The noncovalent interactions in these molecules were expected to lead the formation of supramolecular assembly and gels in hydrocarbon solvents. In such an event, detailed study of gelation and extensive analysis of the morphology of the gel structures were planned using advanced microscopic techniques. Since OPVs are strongly fluorescent molecules, gelation is expected to perturb the optical properties. Therefore, detailed study on the gelation induced optical properties as a way to probe the nature and stability of the selfassembly was planned. Apart from this, the potential use of the modulation of the optical properties for the purpose of light harvesting was aimed. The approach to this problem was to entrap an appropriate energy trap to the OPV gel matrix which may lead to the efficient energy transfer from the OPV gel based donor to the entrapped acceptor. The final question that we wanted to address in this investigation was the creation of helical nanostructures through proper modification of the OPV backbone With chiral handles.The present thesis is a detailed and systematic approach to the realization of the above objectives which are presented in different chapters of the thesis.

Investigations of Optical Interaction Processes in Certain Photonic Materials Using Z-scan and Thermal Lens Techniques

International School of Photonics, Cochin University of Science and Technology

Functionalized Silicon Polymers: Novel Materials for Catalysis

Dept.of Applied Chemistry,Cochin University of Science and Technolgy

Dielectric properties of certain biological materials at microwave frequencies.

In the medical field, microwaves play a larger role for treatment than diagnosis. For the detection of diseases by microwave methods, it is essential to know the dielectric properties of biological materials. For the present study, a cavity perturbation technique was employed to determine the dielectric properties of these materials. Rectangular cavity resonators were used to measure the complex permittivity of human bile, bile stones, gastric juice and saliva. The measurements were carried out in the S and J bands. It is observed that normal and infected bile have different dielectric constant and loss tangent. Dielectric constant of infected bile and gastric juice varies from patient to patient. Detection and extraction of bile stone with possible method of treatment is also discussed.

Packaging materials for shrimp, fish and fish products, their properties, selection and effect of different packaging materials on their shelf life

Packaging is important not only in extending the shellife of fish and fishery products but also improving their marketability. In the recent years, significant development have taken place in the packaging industry. During the past decade in India, there is almost a packaging revolution with the availability of variety packaging materials, thus generating better packaging consciousness in other producer/manufacturing industries. But unfortunately, such realisation is not forthcoming in the fisheries sector and packaging techniques for local and export trade continues to be on traditional lines with their inherent drawbacks and limitations. Better packaging ensures improved quality and presentation of the products and ensures higher returns to the producer. Among several packaging materials used in fishery industry, ISI specifications had been formulated only for corrugated fibre board boxes for export of seafoods and froglegs. This standard was formulated before containersiation came into existance in the export of marine products. Before containerisation, the standards were stringent in view of the rough handling, transportation and storage. Two of the common defects reported in the master cartons exported from India are low mechanical strength and tendency to get wet. They are weakened by the deposits of moisture caused by temperature fluctuations during loading, unloading and other handling stages. It is necessary to rectify the above defects in packaging aquatic products and hence in the present study extensive investigations are carried out to find out the reasons for the damage of master cartons, to evolve code of practice for the packaging oi frozen shrimp for exports, development of alternative style of packaging for the shipping container, development of suitable consumer packaging materials for fish soup powder, cured dried mackeral, fish pickles in oil and frozen shrimp. For the development of suitable packaging materials, it is absolutely essential to know the properties of packaging materials, effect of different packaging materials on theirshelf life and their suitability for food contact applications.