Vaithilingam Selvaraj

Electrocatalytic oxidation of formic acid and formaldehyde on nanoparticle decorated single walled carbon nanotubes

A potent catalyst has been prepared consisting of platinum (Pt), and platinum-palladium (Pt-Pd) nanoparticles supported on purified single-walled carbon nanotubes (Pt/CNT and Pt-Pd/CNT). Electrochemical characteristics of formic acid and formaldehyde oxidation on these catalysts are investigated via cyclic voltammetric analysis in mixed 0.5 M HCOOH (or 0.5 M HCHO) and 0.5 M H(2)SO(4) solutions. The results imply that the Pt-Pd/CNT electrodes exhibit a better activity than the corresponding Pt nanoparticles modified SWCNT electrodes. The modified electrode exhibits significant electrocatalytic activity towards formic acid and formaldehyde oxidation, which may be attributed due to the uniform dispersion of nanoparticles on SWCNTs and the efficacy of Pd species in Pt-Pd system. Such nanoparticles modified CNT electrodes exhibit better catalytic behavior towards formic acid and formaldehyde than the corresponding carbon electrodes, indicating that the system studied in the present work is the more promising system for use in fuel cells.

Thermal, mechanical and antibacterial properties of cyclophosphazene incorporated benzoxazine blended bismaleimide composites

Cyclophosphazene (Cp) incorporated benzoxazine (Bz) and bismaleimide (Bmi) blended (Cp–Bz–Bmi) composites were obtained through ring-opening polymerization with benzoxazine and bismaleimide polymerized via Michael addition with a phosphazene group and a Diels–Alder reaction with a polybenzoxazine group. The cyclophosphazene material was chosen as a filler to improve the thermal, mechanical, electrical resistance and antibacterial properties of Bz–Bmi composites. The results show that the addition of phosphazene can largely enhance the mechanical properties due to the strong chemical interaction between the Bz–Bmi and Cp, which was confirmed by Fourier transform infrared (FT-IR) spectroscopy. The fracture surfaces of the composites were determined by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The mechanical, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) results show that with the increasing percentage of Cp (5, 10 and 15%) in the Bz–Bmi composites, they exhibit better thermal resistance and their corresponding char yield was improved. Broadband dielectric spectroscopy (BDS) studies proved that the Cp–Bz–Bmi composites can be used as electrically resistive materials. The antibacterial properties of the Cp incorporated Bz–Bmi composites also improved due to cyclophosphazene being a bioactive material. Hence, Cp–Bz–Bmi composites are potent materials for marine coating, aerospace and microelectronic applications.

Development of halogen-free flame retardant phosphazene and rice husk ash incorporated benzoxazine blended epoxy composites for microelectronic applications

The present study is focused on the synthesis and characterization of flame retardant amine-terminated cyclophosphazene and silane functionalized rice husk ash reinforced benzoxazine blended epoxy composites as a halogen-free flame retardant material (ATCP/FRHA/Bz-Ep). FT-IR spectroscopy, scanning electron microscopy (SEM), X-ray diffraction analysis, contact angle measurements, dielectric constant, DSC, TGA, UL-94, LOI and cone calorimetry were used to characterize the surface morphology as well as the structural, electrical, thermal and flame retardant properties of the resultant ATCP/FRHA/Bz-Ep composite material. The experimental results suggested that ATCP/FRHA/Bz-Ep composites exhibit better flame retardant and dielectric performance compared to that of a neat Bz–Ep material. A plausible mechanism of the fire retardant ATCP/FRHA/Bz-Ep composite material is hypothesized based on the results of cone calorimetric, thermal and electrical analysis. From the abovementioned results, it was concluded that the ATCP/FRHA/Bz-Ep composite can be used as an electrical resistant material for electronic and microelectronic applications.

Vinyl silane-functionalized rice husk ash-reinforced unsaturated polyester nanocomposites

Organic–inorganic hybrid nanocomposites based on vinyl silane-functionalized rice husk ash-reinforced unsaturated polyester resin were developed and characterized. Rice husk ash (RHA) is an agro product resulting from the incineration of rice husk and is used as a silica source. The present work involves the functionalization of rice husk ash using vinyl triethoxy silane reinforced with UP resin to enhance the thermomechanical properties of the UP resin. The physio-chemical, thermal, mechanical and morphological properties of the composite samples were analysed using FT-IR, differential scanning calorimetry, electron microscopy, thermogravimetric analysis, XRD and goniometry. The mechanical properties i.e., tensile strength, modulus, flexural strength, impact strength and hardness were studied and reported. The values of dielectric constant and contact angle were also studied and discussed. The vinyl silane-functionalized rice husk ash-reinforced UP resin composites possess better thermomechanical, dielectric and surface properties than those of neat UP matrix.

Studies on synthesis and characterization of surface-modified mullite fibre-reinforced epoxy nanocomposites:

The present work describes the development of epoxy composites using varying weight percentages (0.5, 1.0 and 1.5 wt%) of glycidyl-functionalized mullite (GM) fibre and diglycidyl ethers of bisphenol-A epoxy resin cured with diamino diphenyl methane. The mullite fibre was synthesized via the sol–gel method and its surface was modified with 3-glycidoxypropyltrimethoxysilane. The glycidyl functionality in the mullite fibre has been confirmed by Fourier transform infrared and thermogravimetric analyses. The data obtained from the thermal, mechanical, dielectric water absorption studies and contact angle showed that the GM fibre had a significant impact in the resultant epoxy nanocomposites compared to neat epoxy matrix. The molecular level dispersion of mullite fibres into the epoxy matrix was confirmed by the scanning electron microscopy and x-ray diffraction analyses.

Development of hexa (aminophenyl)cyclotriphosphazene-modified cyanate ester composites for high-temperature applications

The organic–inorganic hybrid of hexa(aminophenyl)cyclotriphosphazene (CPA) was synthesized by reacting hexachlorocyclotriphosphazene with 4-acetamidophenol followed by hydrolysis. The resulting product CPA was then allowed to react with 2,2-bis(4-cyanatophenyl)propane (cyanate ester) in different ratios (5, 10, and 15%) to form six-membered oxygen-linked triazine ring with formation of highly cross-linked network structure. Thermal curing behavior was confirmed using Fourier transform infrared spectroscopy analysis and thermal properties were studied using thermogravimetric analysis and differential scanning calorimetry analyses. Dielectric constant and dielectric loss were measured using impedance analyzer. Data resulted from different studies indicate that these hybrid composites can be used for high-performance thermal applications in the place of conventional cyanate esters for better performance.

Thiourea assisted hydrothermal synthesis of ZnS/CdS/Ag2S nanocatalysts for photocatalytic degradation of Congo red under direct sunlight illumination

Solar light active ternary ZnS/CdS/Ag2S nanocatalysts have been synthesized via a hydrothermal process. The crystal structure, optical, morphological and surface area of the catalyst are characterized by XRD, UV DRS, PL, FE-SEM and BET measurements. The ternary catalyst has a decreased band gap energy value compared to that of the ZnS semiconductor. The catalyst was scrutinized for its catalytic performance under direct sunlight towards the degradation of a textile dye – Congo red at different time intervals. The results confirm that the Ag2S incorporated ternary ZnS/CdS/Ag2S nanocatalyst has good photocatalytic performance under direct sunlight when compared to binary and mono semiconductor systems.

Photodegradation and antibacterial studies of ZnS enwrapped fly ash nanocomposite for multipurpose industrial applications

A ZnS-enwrapped amine-functionalized fly ash nanocomposite (ZnS/A-FA) has been prepared by using various weight percentages of amine functionalized fly ash, zinc nitrate hexahydrate and sodium sulphide through wet chemical synthesis method. The synthesized ZnS/A-FA photocatalyst is characterized using XRD, UV-visible DRS, PL, FT-IR, FE-SEM, EDX, elemental mapping, HR-TEM, TGA and BET techniques. The BET surface area results conclude that the fly ash-supported ZnS has a higher surface area of 153.5 m2 g−1 than that of bare ZnS (68.5 m2 g−1). The photocatalytic activity of the ZnS/A-FA nanocomposite has been investigated for the degradation of methylene blue (MB) dye under UV irradiation. The percentage dye degradation experiments are conducted by varying the weight percentage of A-FA supported ZnS to 0.25%, 0.5%, 1%, 2% and 3%. In addition, kinetic studies are carried out by varying the pH, catalyst dosage of ZnS-enwrapped A-FA nanocomposite and dye concentration. From the results, it has been concluded that the fly ash-supported ZnS shows higher catalytic activity compared to that of bare ZnS nanoparticles. Further, one weight percent A-FA-supported ZnS nanocomposite exhibits higher photocatalytic performance when compared to other ratios. The antibacterial properties of A-FA, bare ZnS and the ZnS/A-FA nanocomposite are studied against Gram-positive and Gram-negative bacteria. From the antibacterial studies, it has been found that the ZnS-enwrapped A-FA material exhibits good antibacterial activity compared to that of A-FA and bare ZnS nanoparticles. Hence, ZnS-enwrapped fly ash is a promising photocatalyst for waste water treatment, dye degradation and antibacterial applications.

Development of a polybenzoxazine/TSBA-15 composite from the renewable resource cardanol for low-k applications

The current work describes the synthesis of a novel cardanol-based benzoxazine monomer (CBz) from the renewable resource cardanol using caprolactamdiamine (CPLDA) by a solvent-free method. Thiol-functionalized mesoporous silica (TSBA-15) was incorporated into the cardanol-based benzoxazine matrix (PCBz) and the structure of thiol-functionalized mesoporous silica/cardanol based polybenzoxazine(TSBA-15/PCBz) composite was confirmed by FT-IR and NMR analysis. The surface morphology of TSBA-15/PCBz was determined using SEM and TEM. From the TEM results, it was observed that the dispersion of thiol-functionalized mesoporous silica into PCBz forms a fibrous material containing free volume. The thermal properties of this fibrous materials were studied by using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The thermal properties were observed to depend on the weight percentage of the TSBA-15 material. Dielectric data obtained from impedance analysis shows that the TSBA-15/PCBz composites have lower dielectric constant values, and dielectric loss than that of neat PCBz material. The results indicate that TSBA-15/PCBz composites obtained in a renewable manner from waste cardanol can find applications in microelectronics as electrical resistors.

Pt and Pt-Sn nanoparticles decorated conductive polymer-biowaste ash composite for direct methanol fuel cell

The present work is focused on the synthesis of platinum (Pt)and platinum-tin (Pt-Sn) nanoparticles decorated poly(aniline)-rice husk ash (PANI-RHA) composite by the chemical reduction of their respective metal salts. The obtained Pt/PANI-RHA and Pt-Sn/PANI-RHA composites were characterized by FT-IR, XRD, SEM, EDAX and HR-TEM analysis. Platinum nanoparticles were also decorated on RHA and PANI for comparative studies. The synthesized electrocatalysts have been subjected to electrooxidation of methanol by cyclic voltammetry. It has been concluded that the Pt nanoparticles decorated PANI-RHA composite exhibits a remarkable enhancement for the electrochemical oxidation of methanol when compared with Pt/PANI and Pt/RHA composites. So, PANI-RHA composite has proven to be a good supporting material for alcohol fuel cell applications. Further, Pt-Sn bimetallic nanoparticles decorated PANI-RHA composite exhibit a remarkable enhancement for the electrochemical oxidation of methanol compared to that of Pt/PANI-RHA catalyst. Hence, the above results suggest that Pt-Sn/PANI-RHA composite is a potent and low cost electrocatalyst for fuel cell industries.