Mayur Patel

Interpenetrating polymer networks from castor oil based polyurethanes and poly(methyl acrylate)—IV

Abstract Castor oil and toluene-2,4-diisocyanate were reacted to form liquid prepolyurethane under various experimental conditions, varying the NCO/OH ratio. The prepolyurethanes (PPU) thus obtained were interpenetrated with methylacrylate monomer containing ethylene glycol dimethacrylate, using radical polymerization initiated by benzoyl peroxide. The PPU/MA interpenetrating polymer networks were obtained as transparent tough films by transfer moulding. They were characterized by resistance to chemical reagents, thermal behaviour and mechanical properties. The mechanothermal behaviour was studied by dynamic mechanical analysis. The morphology was examined by Scanning Electron Microscopy. Dielectric properties were studied.

Studies on Polymeric Chelates

Abstract Chelates of Cu(II), Ni(II), Co(II), Mn(II), Fe(III), Zn(II), and dioxouranium(VI) have been prepared from p-hydroxybenzoic acid (P)-urea (U)-formaldehyde (F) copolymer (PUF). The metal-ligand ratios in the chelates were established by eiemental analysis. The probable structures were elucidated on the basis of reflectance and IR spectra in conjunction with magnetic moments. These indicated a distorted octahedral structure for all the chelates except for dioxouranium(VI) chelate. Thermogravimetric analysis has been carried out to ascertain the relative thermal stability of ligand and chelates.

New chelating resins: 2-hydroxy-4-methoxyacetophenone-formaldehyde and 2-hydroxy-4-methoxyacetophenone oxime-formaldehyde

Abstract This paper describes the syntheses and characterization of chelating resins, 2-hydroxy-4-methoxyacetophenone-formaldehyde (I) and 2-hydroxy-4-methoxyacetophenone oxime-formaldehyde (II). The number-average molecular weights have been determined by vapor pressure osmometry and nonaqueous conductometric titration methods. Metal chelates of the resins with Co(II), Ni(II) and Cu(II) were prepared. Elemental analysis of the chelates indicates a metal-to-ligand ratio of 1:2. The diffuse reflectance spectra and magnetic moments of Ni(II) and Co(II) chelates show a tetrahedral structure whereas Cu(II) chelate shows a square planar structure. Infrared spectral study show that the metal ions are coordinated through the oxygen of carbonyl group in I or nitrogen of the oximino group in II, and through the oxygen of the phenolic hydroxyl group. The presence of methylene bridges in the resins is also indicated by IR spectral studies.

Characterization of SnSePb0.1 Thin Films Deposited by Flash Evaporation Technique

Tin Selenide compounds have attracted considerable attention because of their important properties useful for optoelectronics, holographic recording systems, electronic switching and infrared production and detection. Moreover, SnSe is a semiconductor with a band gap of about 1 eV that makes it potential candidate for solar cell material. Further, the optoelectronic properties of SnSe can be modified using doping of lead, copper etc. In this context, we report here results of the preparation and characterization of flash evaporated lead doped SnSe thin films. Thin films of SnSePb0.1 having thickness of 100nm and 500nm were deposited on to chemically cleaned glass substrates. The chemical composition of the deposited SnSePb0.1thin films has been evaluated using EDAX technique. The structure of SnSePb0.1was studied using low angle XRD and it shows that the deposited films are polycrystalline in nature having orthorhombic structure. Various lattice parameters along with micro strain for both 100nm and 500nm thin films have been evaluated. Electrical transport properties have been also investigated using high temperature Hall Effect measurement in the temperature range 300 400K. The decrease in the resistivity of deposited films with increasing temperature confirms the semiconducting behavior of SnSePb0.1 thin films.

Investigations on Tin Selenide Thin Film Based Schottky Barrier Diodes by I-V-T Method

Tin Selenide thin films have been deposited using thermal evaporation technique on chemically and ultrasonically cleaned glass substrates. The stoichiometry of deposited films has been studied using Energy Dispersive Analysis of X-rays (EDAX).The orthorhombic structure and polycrystalline nature of the films were also revealed by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) analysis. The well characterized thin film of SnSe was then used to fabricate Ag/p-SnSe/In Schottky barrier diode. The I-V characteristics of prepared diodes have been investigated over the temperature range of 303 K to 393 K. The forward biased I-V characteristics of prepared structure has been analyzed using TE theory and different device parameters have been evaluated and discussed in present paper. The Richardson constant was also determined from the conventional Richardson plot and it is found close to the reported value.

Preparation and Characterization of N-CdS Thin Films and its Schottky Barrier

Cadmium sulphide (CdS), a member of group II-VI semiconductors is one of the promising materials from its applications point of view. The present investigations are about the preparation, structural and optical characterization of CdS thin films and their use as Schottky diode with Aluminum. Thin films of CdS having thickness around 700nm have been deposited by thermal evaporation. The chemical composition of the deposited CdS thin films has been made using EDAX technique. The structural characterization of this films was carried out using XRD. The structure of CdS after the deposition was found to be Cubic. Also, the lattice parameters were evaluated from the XRD data. From TEM of CdS thin films, the polycrystalline nature was confirmed. Optical characterization has been carried out using UV-VIS-IR spectroscopy. The direct as well as indirect band gaps obtained are 1.64eV and 1.48eV respectively. Schottky junctions were formed by a thermal vapor-deposition of 500nm Al films on pre-coated CdS glass substrates. Diode parameters, such as the zero bias barrier height φb0, the flat band barrier height φbf and the ideality factorη, were calculated using thermionic emission theory at room temperature.

Structural and Optical Properties of e‐Beam Evaporated MX2 Thin Films

WSe2 and MoSe2 thin films were obtained by using electron beam evaporation technique at room temperature. The films were characterized by EDAX, XRD, TEM and optical absorption. The X‐ray diffraction pattern shows that prepared polycrystalline thin films have a hexagonal phase which is confirmed by TEM also. Optical properties show a direct bandgap with bandgap energy 1.89 eV and 1.98 eV for WSe2 and MoSe2 respectively.