Antony Ananth

Time dependence of ethylene decomposition and byproducts formation in a continuous flow dielectric-packed plasma reactor

This work investigated the decomposition of ethylene in a continuous flow dielectric-packed bed plasma reactor filled with various packing materials at atmospheric pressure and room temperature. When compared to the case without any packing material, the reactor filled with packing materials remarkably facilitated the plasma-induced decomposition of ethylene in the order of α-alumina>silica>zirconia>glass wool (GW). Under identical condition, the increase in the decomposition efficiency (DE) with increasing the specific energy input was more rapid in the plasma reactor filled with the packing materials than in the blank plasma reactor. In the early stage, almost complete decomposition of ethylene was observed with the α-alumina, but after a certain period of time, the DE decreased with time. Unlike the α-alumina, the other packing materials examined did not show any significant deterioration in the decomposition over time during 10-h operation. After the regeneration of the used packing materials by using the plasma in the presence of oxygen, the original decomposition performance was nearly recovered. The decrease in the BET surface area due to the formation of polymer deposits was observed in the used α-alumina and silica; however the surface area was almost regained by the regeneration. While no other byproducts except carbon oxides and N2O were detected with the α-alumina and silica, methane, acetylene, formaldehyde and N2O were identified in the effluent gas with the zirconia and GW packing materials.

Dielectric Barrier Discharge (DBD) Plasma Assisted Synthesis of Ag2O Nanomaterials and Ag2O/RuO2 Nanocomposites

Silver oxide, ruthenium oxide nanomaterials and its composites are widely used in a variety of applications. Plasma-mediated synthesis is one of the emerging technologies to prepare nanomaterials with desired physicochemical properties. In this study, dielectric barrier discharge (DBD) plasma was used to synthesize Ag2O and Ag2O/RuO2 nanocomposite materials. The prepared materials showed good crystallinity. The surface morphology of the Ag2O exhibited “garland-like” features, and it changed to “flower-like” and “leaf-like” at different NaOH concentrations. The Ag2O/RuO2 composite showed mixed structures of aggregated Ag2O and sheet-like RuO2. Mechanisms governing the material’s growth under atmospheric pressure plasma were proposed. Chemical analysis was performed using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Thermogravimetric analysis (TGA) showed the thermal decomposition behavior and the oxygen release pattern.

Defect-induced metallic-to-semiconducting transition in multilayer graphene

We investigate the electrical transport properties of multilayer graphene (MLG) following irradiation with Ar plasma. The plasma induces defects, including vacancies, voids, and nanoholes, which altered the resistance of the MLG. The resulting defect-rich MLG device exhibits an asymmetric ambipolar behavior, with a strong p-doping effect, which considerably deteriorates the electron conductivity, implies defect generation on the MLG surface. The pristine MLG was metallic; however, the resulting defect-rich MLG following plasma treatment exhibited a semiconductor-like temperature dependence of the resistance. Thus, MLG with morphological disorder exhibits a metallic-to-semiconductor transition in the resistance as a function of temperature.

Effects of in situ and ex situ formations of silica nanoparticles on polyethersulfone membranes

This study deals with the observed changes in the structure and performance of polyethersulfone (PES) membranes due to in situ formation and ex situ addition of silica particles (SiO2). Hydrolysis and condensation of tetraethyl orthosilicate (TEOS) inside the PES polymer matrix and the reaction of TEOS with ammonium hydroxide were chosen to form in situ and ex situ SiO2 formations, respectively. The resultant structure confirmed by X-ray diffraction for the composite PES membranes showed the retention of the amorphous nature even after the addition of SiO2. The FTIR study revealed the functional groups corresponding to silica networks with enhanced OH signatures on the surface of the composite membranes. Field emission scanning electron microscopic images showed the variation in the surface and cross-sectional structures for the pure and composite membranes. Considerable reduction in the thickness of the skin, difference in the pore structure and ‘finger-like’ cross-sectional morphology with the presence of SiO2 was observed in PES membranes. Both SiO2/PES composite membranes were showed a minor change in their glass transition temperature (Tg). The ex situ methodically formed composite membrane displayed an increase in the pure water flux and decrease in bovine serum albumin rejection as compared to in situ and pure PES membranes. These kinds of composite membranes can be utilized for water treatment applications demanding higher water flux.