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

Thermal Conduction in Polymeric Nanofluids and Nanosolids Controlled by Interfacial Scattering:Solutions to Some Selected Problems

Dept.of Instrumentation,Cochin University of Science and Technology

Studies on the Solvent Dependence in the Reaction of a Few (Anthracen-9-yl)MethyLamines and Sulfanes with Reactive Acetylenes

The thesis entitled ‘Studies on the Solvent Dependence in the Reaction of a Few (Anthracen-9-yl)methylamines and Sulfanes with Reactive Acetylenes’ is divided into six chapters. ln Chapter l a general survey of electron transfer reactions, Diels-Alder reactions and Michael-type additions is presented. A detailed discussion on the synthesis of several (anthracen-9-yl)methylamines is presented in Chapter 2. In Chapter 3, results of preliminary photophysical studies on a few (anthracen-9yl) methylamines are compiled. A detailed discussion on extensive examination of dependence in the reaction of (anthracen-9-yl)methylamines with reactive acetylenes is presented Chapter 4. Details on the synthesis and reaction of a few (anthracen-9-yl)methylsulfanes with DMAD are described in Chapter 5.

Investigations on the structural, optical and Magnetic properties of nanostructured cerium oxide in pure and doped forms and its polymer nanocomposiets

This thesis Entitled INVESTIGATIONS ON THE STRUCTURAL, OPTICAL AND MAGNETIC PROPERTIES OF NANOSTRUCTURED CERIUM OXIDE IN PURE AND DOPED FORMS AND ITS POLYMER NANOCOMPOSITES.Synthesis and processing of nanomatelials and nanostmctures are the essential aspects of nanotechnology. Studies on new physical properties and applications of nanomaterials and nanostructures are possible only when nanostructured materials are made available with desired size, morphology,crystal structure and chemical composition.Recently, several methods have been developed to prepare pure and doped CeO2 powder, including wet chemical synthesis, thermal hydrolysis, flux method, hydrothermal synthesis, gas condensation method, microwave technique etc. In all these, some special reaction conditions, such as high temperature, high pressure, capping agents, expensive or toxic solvents etc. have been involved.Another hi gh-li ght of the present work is room temperature ferromagnetism in cerium oxdie thin films deposited by spray pyrolysis technique.The observation of self trapped exciton mediated PL in ceria nanocrystals is another important outcome of the present study. STE mediated mechanism has been proposed for CeO2 nanocrystals based on the dependence of PL intensity on the annealing temperature. It would be interesting to extent these investigations to the doped forms of cerium oxide and cerium oxide thin films to get deeper Insight into STE mechanism.Due to time constraints detailed investigations could not be canied out on the preparation and properties of free standing films of polymer/ceria nanocomposites. It has been observed that good quality free standing films of PVDF/ceria, PS/C61‘l8, PMMA/ceria can be obtained using solution casting technique. These polymer nanocomposite films show high dielectric constant around 20 and offer prospects of applications as gate electrodes in metal-oxide semiconductor devices.

Studies on Thermal structure in the seas around in India

The thesis entitled Studies on Thermal Structure in the Seas Around India. An attempt is made in this study to document the observed variability of thermal structure, both on seasonal and short-term scales, in the eastern Arabian Sea and southwestern Bay of Bengal, from the spatial and time series data sets from a reasonably strong data base. The present study has certain limitations. The mean temperatures are based on an uneven distribution of data in space and time. Some of the areas, although having a ‘full annual coverage, do not have adequate data for some months. Some portions in the area under study are having data gaps. The consistency and the coherence in the internal wave characteristics could not be examined due to non-availability of adequate data sets. The influence of generating mechanisms; other than winds and tides on the observed internal wave fields could not be ascertained due to lack of data. However, a comprehensive and intensive data collection can overcome these limitations. The deployment of moored buoys with arrays of sensors at different depths at some important locations for about 5 to 10 years can provide intensive and extensive data sets. This strong data base can afford to address the short-term and seasonal variability of thermal field and understand in detail the individual and collective influences of various physical and dynamical mechanisms responsible for such variability.

Laser induced thermal lens and near infrared absorption studies of ch overtones in some organic compounds

Vibrational overtone spectroscopy of X-H (X=C,N,O) containing molecules is an area of recent interest. The spectroscopic studies of higher vibrational levels yield valuable informations, regarding,the molecular structure, intra- and inter-molecular interactions, radiationless transitions, intra-molecular vibrational relaxations, multiphoton excitations and chemical reactivities, which cannot be z obtained by other spectroscopic methods. This thesis presents the results of experimental investigations on the overtone spectra of some organic compounds in the liquid phase for the characterization of CH bonds. The spectra in the fifth overtone region (1fiV=6) are recorded using a dual beam thermal lens setup and the lower overtones (.AV=2-5) are recorded spectrophotometrically.The thesis is presented in six chapters.

Photoacoustic investigation of the optical and thermal properties of selected amorphous chalcogenide semiconductors

This thesis work has mainly concentrated on the investigation of the ,optical and thermal properties of binary semiconducting chalcogenide glasses belonging to the AivB¥5x and AZBXEX families. The technique used for these studies is a relatively new one namely, the photoacoustic (PA) technique. This technique is based on the detection of acoustic signal produced in an enclosed volume when the sample is irradiated by an intensity modulated radiation. The signal produced depends upon the optical properties of the sample, and the thermal properties of the sample, backing material and the surrounding gas. For the present studies an efficient signal beam gas-microphone PA spectrometer, consisting of a high power Xenon lamp, monochromator, light beam chopper, PA cell with microphone and lock-in amplifier, has been set up. Two PA cells have been fabricated: one for room temperature measurements and another for measurements at high temperatures. With the high temperature PA cell measurements can be taken upto 250°C. Provisions are incorporated. in both the cells to change the volume and to use different backing materials for the sample. The cells have been calibrated by measuring the frequency response of the cells using carbon black as the sample

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.

Development of solar air heaters & thermal energy storage system for drying applications in food processing industries

In the present work, the author has designed and developed all types of solar air heaters called porous and nonporous collectors. The developed solar air heaters were subjected to different air mass flow rates in order to standardize the flow per unit area of the collector. Much attention was given to investigate the performance of the solar air heaters fitted with baffles. The output obtained from the experiments on pilot models, helped the installation of solar air heating system for industrial drying applications also. Apart from these, various types of solar dryers, for small and medium scale drying applications, were also built up. The feasibility of ‘latent heat thermal energy storage system’ based on Phase Change Material was also undertaken. The application of solar greenhouse for drying industrial effluent was analyzed in the present study and a solar greenhouse was developed. The effectiveness of Computational Fluid Dynamics (CFD) in the field of solar air heaters was also analyzed. The thesis is divided into eight chapters.

On the Tailoring of Magnetic Properties of Fe-Based Alloy Thin Films by Swift Heavy Ion Irradiation and Thermal Annealing

The development of new materials has been the hall mark of human civilization. The quest for making new devices and new materials has prompted humanity to pursue new methods and techniques that eventually has given birth to modern science and technology. With the advent of nanoscience and nanotechnology, scientists are trying hard to tailor materials by varying their size and shape rather than playing with the composition of the material. This, along with the discovery of new and sophisticated imaging tools, has led to the discovery of several new classes of materials like (3D) Graphite, (2D) graphene, (1D) carbon nanotubes, (0D) fullerenes etc. Magnetic materials are in the forefront of applications and have beencontributing their share to remove obsolescence and bring in new devices based on magnetism and magnetic materials. They find applications in various devices such as electromagnets, read heads, sensors, antennas, lubricants etc. Ferromagnetic as well as ferrimagnetic materials have been in use in the form of various devices. Among the ferromagnetic materials iron, cobalt and nickel occupy an important position while various ferrites finds applications in devices ranging from magnetic cores to sensors.

Studies on High- Tc Superconductors with Inequivalent Conducting Layers

The thesis deals with the study of super conducting properties of layered cuprates within the frame work of a modified Lawrence-Doniach (LD) model. The thesis is organized in seven chapters. Chapter I is a survey of the phenomena and theories of conventional superconductivity which can serve as a springboard for launching the study of the new class of oxide superconductors and it also includes a chronological description of the efforts made to overcome the temperature barrier. Chapter II deals with the structure and properties of the copper oxide superconductors and also the experimental constraints on the theories of high te:::nperature superconductivity. A modified Lawrence-Doniach type of phenomenological model which forms the basis of the presnt study is also discussed. In chapter III~ the temperature dependence of the upper critical field both parallel and perpendicular to the layers is determined and the results are compared with d.c. magnetization measurements on different superconducting compoilllds. The temperature and angular dependence of the lower critical field both parallel and perpendicular to the layers is also discussed. Chapters IV, V and VI deal with thermal fluctuation effects on superconducting properties. Fluctuation specific heat is studied in chapter IV. Paraconductivity both parallel and perpendicular to the layers is discussed in chapter V. Fluctuation diamagnetism is dealt with in chapter VI. Dimensional cross over in the fluctuation regime of all these quantities is also discussed. Chapter VII gives a summary of the results and the conclusions arrived at.

Thermal characterisation of dye-intercalated K-10 montmorillonite ceramics using photoacoustic technique

Thermal diffusivity (TD) measurements were performed on some industrially important dyes – auramine O (AO), malachite green and methylene blue (MB) – adsorbed K-10 montmorillonites using photoacoustic method. The TD value for the dye-adsorbed clay mineral was observed to change with a variation in dye concentration. The contribution of the dye towards TD was also determined. The repeatedly adsorbed samples with MB and AO exhibited a lower TD than the single-adsorbed samples. TD values of sintered MB samples were also obtained experimentally. These sintered samples exhibit a higher TD, although they show a trend similar to that of non-sintered pellets. A variation in dye concentration and sintering temperature can be used for tuning the TD value of the clay mineral to the desired level

Thermal characterization of methylene blue intercalated montmorillonites by photoacoustic technique

Thermal diffusivity (TD) measurement on commercial K-10 and KSF montmorillonites was carried out by photoacoustic technique. The TD of the montmorillonites after methylene blue adsorption changed with the dye concentration. The repeatedly adsorbed samples showed a lesser TD than the single adsorbed samples. After methylene blue adsorption the acid leached K-10 samples showed well defined changes in TD when compared to the ordered KSF samples

Optical and Thermal Properties of Diethyl-(2R, 3R) (1)-tartrate Based Chiral Polyurethanes with Main Chain Amido Chromophores

The toluene diisocyanate based optically active chiral polyurethanes were synthesized according to the symmetry conditions. The noncentrosymmetric (both charge asymmetry and spatial asymmetry) environment were attained by the incorporation of the chiral units (diethyl-(2R,3R)(þ)-tartrate) and donor-acceptor building blocks in the main chain which induce a helical conformation in the macromolecular chain. A series of optically active polyurethanes containing chiral linkages in the polymer back bone have been synthesized by using DBTDL catalyst by incorporating the amido diols which were obtained by the aminolysis of e-caprolactone by using the diamines, diaminoethane, diaminobutane, and diaminohexane respectively. The effect of incorporation of the chiral molecule diethyl-(2R,3R)(þ)-tartrate on the properties of polyurethanes was studied by changing the chromophores and also by varying the chiral-chromophore composition. Various properties of polyurethanes were investigated by UV, Fluorescence, TG/DTA, XRD, polarimetric techniques, Kurtz-Perry powder techniques, etc.