Balram Tripathi

Enhancement of hydrogen gas permeability in electrically aligned MWCNT-PMMA composite membranes.

The multi-walled carbon nanotube (MWCNT) dispersed polymethylmethacrylate (PMMA) composite membranes have been prepared for hydrogen gas permeation application. Composite membranes are characterized by Raman spectroscopy, optical microscopy, X-ray diffraction, electrical measurements and gas permeability measurements. The effect of electric field alignment of MWCNT in PMMA matrix on gas permeation has been studied for hydrogen gas. The permeability measurements indicated that the electrically aligned MWCNT in PMMA has shown almost 2 times higher permeability for hydrogen gas as compare to randomly dispersed MWCNT in PMMA. The enhancement in permeability is explained on the basis of well aligned easy channel provided by MWCNT in electrically aligned sample. The effect of thickness of membrane on the gas permeability also studied and thickness of about 30microm found to be optimum thickness for fast hydrogen gas permeates.

Microstructure change in poly(ethersulfone) films by swift heavy ions

PES membrane of thickness 25 microm was irradiated by Cl(9+) ions of energy 100 MeV at IUAC, New Delhi. Microstructure changes due to exposure to high-energy ions were investigated by Fourier transform infrared (FTIR) and ultraviolet/visible (UV/vis) absorption spectroscopies, X-ray diffraction technique and by dynamic mechanical analysis (DMA). A significant loss of crystallinity is observed by the XRD data. Particle size or grain size calculated using Scherrer formula indicates measurable change in particle size of irradiated samples. The polymer chain scissions and structure degradations are expected to occur for irradiated samples. Optical properties of the films were changed due to irradiation that could be clearly seen in the absorption spectra. FTIR does not show the remarkable change in the irradiated samples, but there is some change in the surface roughness observed by AFM.

Transport through track etched polymeric blend membrane

Polymer blends of polycarbonate (PC) and polysulphone (PSF) having thickness, 27 μm, are prepared by solution cast method. The transport properties of pores in a blend membrane are examined. The pores were produced in this membrane by a track etching technique. For this purpose, a thin polymer membrane was penetrated by a single heavy ion of Ni7+ of 100 MeV, followed by preferential chemical etching of the ion track. Ion permeation measurements show that pores in polymeric membrane are charged or neutralized, which depends upon the variation in concentration of the solvent. TheV-Icurve at concentration, N/10, shows that the pores are negatively charged, whereas at concentration, N/20, the linear nature ofV-I curve indicates that the pores approach towards neutralized state and on further concentration, N/40, the pores become fully neutralized, consequently the rectifier behaviour of pores has been omitted.The gas permeability of hydrogen and carbon dioxide of this membrane was measured with increasing etching time. The permeability was measured from both the sides. Permeability at the front was larger than the permeability at the back which shows asymmetric behaviour of membranes.

Effect of Electric Field Alignment of MWCNT in PMMA Matrix for Hydrogen Gas Purification

The composite membranes of multi‐walled carbon nanotube (MWCNT) and polymethylmethacrylate (PMMA) were prepared by solution cast method. The MWCNT was dispersing a very low concentration (0.1 wt %) in PMMA matrix. Alignment of MWCNT in PMMA matrix has been performed by inducing a DC electric field at different voltage parameter varying from 350 V/cm to 1250 V/cm. The MWCNT/PMMA composites were characterized by gas permeation and electrical measurement before and after electric field alignment. The effect of electric field alignment has been studied on gas permeation measurements for gas purification applications. These measurements indicate the enhancement in gas permeability due to the aligned of MWCNT in PMMA matix as compare to randomly dispersed MWCNT. I–V characteristics measurement also indicates that aligned MWCNT/PMMA composite membrane exhibits electron tunneling conductivity.

Ni+7 Ion Beam Effect on Ag Doped ZnS Nanocrystals Embedded in PMMA Matrix

Semiconductor nanocrystals (NCs) have received much interest for their optical and electronic properties. When these NCs dispersed in polymer matrix, brightness of the light emission is enhanced due to their quantum dot size. Silver doped Zinc Sulphide NCs were synthesized through chemical route method. The synthesized NCs are characterized by XRD. The effect of Ag doping and Swift heavy ion irradiation on optical properties of nanocomposite polymer films is analyzed by Photoluminescence (PL) and UV measurements. The XRD results show that Ag doped ZnS was grown in the hexagonal phase of about 10 nm size as calculated by Scherer formula. These NCs were dispersed in PMMA matrix by solution cast method and irradiated by swift heavy ion (SHI) (Ni+7 ion beam, 100 MeV). The UV‐Vis measurement show a red shift in optical absorption and band gap decreases after irradiation with respect to pristine nanocomposite polymer film. Photoluminescence shows the enhancement in luminescence intensity after irradiation.

OPTICAL AND DYNAMIC MECHANICAL CHARACTERIZATION OF THIN FILM POLYMER NANOCOMPOSITES

Polymer composites in various forms and configuration are being developed in an effort to provide lighter weight construction, better optical and thermal properties to maintain adequate strength and stability. To this end thin film polymer (PMMA) nanocomposites synthesized for purpose of influencing optical luminescence using CdS nanocrystals as filler without incurring losses in mechanical properties, were examined to determine elastic modulus and degree of dispersion. Optical absorption spectroscopy has been used for finding discrete energy levels in CdS/polymer.