Kananbala Sharma

Influence of thermal annealing in air on the electro-optic characteristics of chemical bath deposited non-stoichiometric cadmium zinc selenide thin films

Non-stoichiometric thin films of cadmium zinc selenide were grown onto glass substrates by the chemical bath deposition technique from elemental selenium, sodium sulphite, cadmium chloride, zinc chloride, deionised water and ammonia. As-deposited films were annealed at different temperatures up to 600 K. From their deposition temperature in air, their electrical conductivity, optical properties and microstructure were evaluated. The electrical conductivity increases rapidly with increasing annealing temperature and activation energy EA for the crystallites was calculated from the Arrhenius relation. The optical absorption edge is shifted towards higher wavelengths with increasing annealing temperature. Other optical parameters such as absorption coefficient alpha , band gap Eg, refractive index n, dielectric constant epsilon and extinction coefficient k were computed from transmittance spectra. The re-growth study was also carried out from micrography obtained from optical phase contrast microscopy at different annealing temperatures and results are interpreted on the basis of grain boundaries, defects and vacancies. The fully annealed films have a hexagonal crystal structure for x or=0.6 with varying lattice constants and grain size.

Electrical Properties of CdS/Polyaniline Heterojunction

Conducting polyaniline (PANI) has been synthesized using Sol-gel technique with chemical oxidation process. Chemically prepared cadmium sulphide has been printed on pellet of conducting polyaniline using screen-printing technique. I-V characteristics of conducting polyaniline and CdS printed conducting polyaniline have been recorded at room temperature using Keithley Electrometer. The results indicated that I-V of conducting polyaniline shows non-ohmic behaviour and I-V characteristic of CdS printed PANI, a CdS/ PANI heterojunction, shows the rectification effect and confirms that a diode can be fabricated by using simple technique.

Optical properties of Cu3-xInSe2 (0.8<or=x<or=2.3) films

Thin films of CuInSe2 with varying copper content have been prepared using a solution growth technique. Optimum deposition parameters, such as pH of solution, composition of elements, deposition rate and temperature, for obtaining films suitable for semiconductor devices have been obtained. Optical properties of the films were studied extensively in the wavelength range 600-1400 nm. The variations of optical band gap, absorption coefficient, Sellmeiers parameters, refractive index and dielectric constant with copper composition x were studied. The present results agree well with the results of other studies.

Thermomechanical investigation of a thick film of aniline-formaldehyde copolymer and poly(methyl methacrylate)

A thick film of aniline-formaldehyde copolymer and PMMA is synthesized via dispersion of aniline-formaldehyde copolymer powder as filler particles in PMMA with two different concentrations. Variation of the complex elastic modulus and mechanical loss factor (tanδ) with temperature is studied. It is observed that the complex elastic modulus decreases with temperature owing to thermal expansion of films. On the other hand, tanδ increases up to a characteristic temperature beyond which it shows a decreasing trend toward melting. Transition temperature T g of sample S1 (pure PMMA) is found to be 80°C. In sample S2 (1 wt % aniline formaldehyde copolymer), the peak of tanδ at a lower temperature (66°C) corresponds to glass transition temperature T g of the PMMA matrix, while the peak of tanδ at a higher temperature (107.8°C) corresponds to T g of a polymer chain restricted by filler particles of aniline-formaldehyde copolymer. A further increase (10 wt % aniline-formaldehyde copolymer) in the concentration of filler particles of aniline-formaldehyde copolymer results in a more compact structure and a shift of T g to a higher temperature, 122.2°C. This shift in the glass transition temperature of thick films of aniline-formaldehyde copolymer and PMMA is dependent upon the concentration of filler particles in the sample.

Energy Band Gap Studies of CdS Nanomaterials

The CdS nanoparticles of different sizes are synthesized by a simple chemical method. Here, CdS nanoparticles are grown through the reaction of solution of different concentration of CdCl2 with H2S. X-ray diffraction pattern confirms nano nature of CdS and has been used to determine the size of particle. Optical absorption spectroscopy is used to measure the energy band gap of these nanomaterials by using Tauc relation. Energy band gap ranging between 3.12 eV to 2.47 eV have been obtained for the samples containing the nanoparticles in the range of 2.3 to 6.0 nm size. A correlation between the band gap and size of the nanoparticles is also established.

Morphology, miscibility and mechanical properties of PMMA/PC blends

This study deals with some results on morphology, miscibility and mechanical properties for polymethyl methacrylate/polycarbonate (PMMA/PC) polymer blends prepared by solution casting method at different concentration between 0 and 100 wt%. Dynamic storage modulus and tan δ were measured in a temperature range from 30 to 180°C using dynamical mechanical analyzer (DMA). The value of the storage modulus was found to increase with the addition of the PC in the matrix. Transition temperature of pure PMMA and pure PC is found to be 83.8 and 150°C, respectively. The result shows that the two polymers are miscible for whole concentration of PC in PMMA. The distribution of the phases in the blends was studied through scanning electron microscopy (SEM). Also the mechanical properties like elongation at break and fracture energy of the PMMA/PC blends increase with the increase in concentration of PC in PMMA.

The Structure and Thermomechanical Properties of Blends of Trans-polyisoprene with Cis-polyisoprene

The present work reports the structural and thermomechanical properties of cis- and trans-polyisoprene blends. These blends have been prepared using the solution casting method. The effect of blending on thermomechanical properties such as glass transition temperature, damping and storage modulus and mechanical properties such as toughness, elastic modulus, tensile strength and elongation of present blends has been studied. Besides these, the effect of blending on structure has also been studied. It was observed that elastic moduli, tensile strength and toughness of the TPI/CPI blends decreases with increased CPI percentage. The study also presents a relation between Tg and crystallinity.

Mechanical Characterization of Polymethyl Methacrylate and Polycarbonate Blends

Blends of Poly methyl methacrylate (PMMA) and Polycarbonate (PC) were prepared using solution casting method in five different concentrations (0%, 25%, 50%, 75%, and 100% by weight) using dichloromethane (CH2Cl2) as a solvent. The mechanical properties were studied by Dynamic Mechanical Analyser (DMA). Stress‐strain scan have been used to study the tensile strength and Youngs modulus for these blends. It has been observed that complex modulus decreases with temperature due to the thermal expansion of the film of polymer blend. The result obtained for variation of Tan δ and modulus with concentration indicates about the degree of miscibility of this blends. Glass transition temperature of pure PMMA is found to be at 136 °C because it is highly isotactic in nature. It is observed that Tg of the blend shifts towards the lower temperature with the increase of concentration of PC. Blending of PMMA and PC improves the mechanical properties such as Youngs modulus and tensile strength. The Youngs modulus, ultimate strength and tensile strength increases with the increase in concentration of PC upto 50% and then decreases on further increase in concentration. The value of Youngs modulus and tensile strength is found to be highest at 50% concentration.Blends of Poly methyl methacrylate (PMMA) and Polycarbonate (PC) were prepared using solution casting method in five different concentrations (0%, 25%, 50%, 75%, and 100% by weight) using dichloromethane (CH2Cl2) as a solvent. The mechanical properties were studied by Dynamic Mechanical Analyser (DMA). Stress‐strain scan have been used to study the tensile strength and Youngs modulus for these blends. It has been observed that complex modulus decreases with temperature due to the thermal expansion of the film of polymer blend. The result obtained for variation of Tan δ and modulus with concentration indicates about the degree of miscibility of this blends. Glass transition temperature of pure PMMA is found to be at 136 °C because it is highly isotactic in nature. It is observed that Tg of the blend shifts towards the lower temperature with the increase of concentration of PC. Blending of PMMA and PC improves the mechanical properties such as Youngs modulus and tensile strength. The Youngs modulus, ulti...

Morphological effects on mechanical properties of polystyrene-polyvinylchloride blends

The morphological effects on mechanical properties of polystyrene/polyvinylchloride (PS/PVC) polymer blends were investigated through dynamic mechanical analyzer. Study reveals that the peaks of Tan δ curves of pure PVC and pure PS samples fall at temperatures 58.9 ± 0.2°C and 113.1 ± 0.1°C, respectively. Tan δ curves of 30, 50 and 70-wt% of PVC blends show two peaks indicating the immiscibility of PS/PVC blend. It has been observed that peak falling at lower temperature side shifts towards the higher temperature with the increase of PS concentration and the other one which falls at higher temperature side shifts towards lower temperature side with the increase of PVC concentration in PS/PVC blends. The variation in mechanical performance is attributed to the polymer domain interactions resulting from the different morphologies of various blend compositions.

Structural and Electrical Characterization of Protonic Acid Doped Polyaniline

Polyaniline doped with different protonic acids were chemically synthesized using ammonium persulfate (APS) as an oxidant. These samples were characterized through X‐ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, which confirms the amorphous nature and acid doping, respectively. Electrical conduction in these samples has been studied through the measurement of I‐V characteristics at room temperature as well as in the temperature range from 313 K to 413 K. So obtained characteristic curves were found to be nonlinear. The conductivity of phosphoric acid doped polyaniline sample is higher as compared to HCl doped polyaniline and pure polyaniline. Temperature dependence of conductivity suggests a semiconducting nature with increase in temperature. Activation energies have been found to be 50.86, 25.74 and 21.05 meV for pure polyaniline (base), polyaniline doped with hydrochloric, phosphoric acid, respectively.