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Mukherjee J.,CSIR - Central Electrochemical Research Institute | Chakraborty S.,CSIR - Central Electrochemical Research Institute | Chakravarty S.,National University of Singapore | Ranjan A.,DMSRDE DRDO | Das P.K.,CSIR - Central Electrochemical Research Institute
Ceramics International | Year: 2014

Liquid polycarbosilane (LPCS) derived hard coatings of silicon carbide (SiC) were deposited on Inconel alloy at three different moderately high temperatures by chemical vapour deposition. The deposited films were characterized by X-ray diffractometry and Field emission scanning electron microscopy. Liquid PCS yielded a mixture of α-SiC and β-SiC during decomposition having uniform round-shaped particles of dimension around 200-300 nm without extensive cracking and few discrete shaped particles were also found to form at higher temperature (i.e. 1100 C and 1200 C) deposited films. The coated samples showed substantial increment in hardness and fracture toughness as compared to the uncoated sample. The fracture toughness (KIC) values of the deposited films were in the range of 6.7-10.7 MPa(m) 1/2. The tribological properties and hardness of the films were also found to vary with deposition temperature. The scratch tracks of the films revealed that brittle failures occurred in all SiC coated substrates. © 2013 Elsevier Ltd and Techna Group S.r.l.All rights reserved. Source

D'Souza O.J.,Bharathiar University | Mascarenhas R.J.,St. Josephs College | Thomas T.,St. Josephs College | Basavaraja B.M.,University | And 3 more authors.
Journal of Electroanalytical Chemistry | Year: 2015

Enhanced sensitivity and electro-catalytic activity for the sensor was achieved by incorporating platinum decorated multi-walled carbon nanotubes (PtMWCNTs) into the carbon paste matrix and TritonX-100 (TX100) layered onto its surface. The modification of carbon paste electrode (CPE) using PtMWCNTs and TX100 was accomplished by employing bulk modification and drop cast methods, respectively. The electrochemical behaviour of Paracetamol (PA) at PtMWCNTs and TX100 modified CPE was investigated by cyclic voltammetry and amperometry. The electrode sensitivity for PA has shown significant variation on varying the amount of Pt nanoparticles on MWCNTs and the PtMWCNTs content in carbon paste matrix. The influence of variation of concentration, volume and time of adsorption of TX100 on the response of PA was investigated. The developed sensor was employed for the selective detection of PA using hydrodynamic amperometry at physiological pH in the presence of ascorbic acid (AA), dopamine (DA) and tryptophan (Trp). The surface morphology of the electrode was studied using FE-SEM images and the interface properties of bare and modified electrodes were investigated by electrochemical impedance spectroscopy. PtMWCNTs in combination with TX100 resulted in an impressive enhancement in the redox current with an analytical advantage of complete elimination of the interference of AA in the simultaneous determination of PA in a mixture. A lower detection limit of (17.71 ± 2.03) nM (S/N = 3) was achieved for PA. The modified electrode showed excellent reproducibility, long-term stability and antifouling effects. The practical analytical application was demonstrated by carrying out determination of PA in real samples. © 2014 Elsevier B.V. All rights reserved. Source

Debnath D.,CSIR - Central Electrochemical Research Institute | Chakraborty S.,CSIR - Central Electrochemical Research Institute | Mallick A.R.,CSIR - Central Electrochemical Research Institute | Gupta R.K.,DMSRDE DRDO | And 2 more authors.
Advances in Applied Ceramics | Year: 2015

ZrB2-SiC composites were prepared by hot pressing with different sources of SiC to study the effect of SiC with different morphology on densification, microstructure, phase composition and mechanical properties like hardness, fracture toughness and tribological properties (namely, scratch resistance, wear parameters) and thermal behaviour of the composites. Three different ZrB2-SiC composites, i.e. ZrB2-SiCP (polycarbosilane derived SiC), ZrB2-SiCC (SiC from CUMI, India) and ZrB2-SiCH (SiC from H. C. Starck, Germany), were studied. It is found that ZrB2-SiCC composite shows highest hardness (19·13 GPa) and fracture toughness (5·30 MPa m1/2 at 1 kgf load) in comparison with other composites. Interconnected network, better contiguity between grains of ZrB2-SiC composites and impurity content in starting powders can play significant roles for achieving high mechanical, tribological and thermal properties of the composites. Coefficient of friction and wear parameters of all ZrB2-SiC composites are very low, and thermal conductivity of ZrB2-SiC composites varied from 52·71 to 65·53 W (m K)-1 (ZrB2-SiCP), 54·30 to 71·55 W (m K)-1 (ZrB2-SiCC) and 64·25 to 88·02 W (m K)-1 (ZrB2-SiCH), respectively and also calculate the interfacial resistance of all the composites. © 2015 Institute of Materials, Minerals and Mining. Source

Chakraborty S.,CSIR - Central Electrochemical Research Institute | Debnath D.,CSIR - Central Electrochemical Research Institute | Mallick A.R.,CSIR - Central Electrochemical Research Institute | Gupta R.K.,DMSRDE DRDO | And 3 more authors.
International Journal of Refractory Metals and Hard Materials | Year: 2015

Abstract ZrB2-SiCp (w/w 80:20) composites were spark plasma sintered at 1900, 2000 and 2100 °C with ton = 50 ms and toff = 5 ms conditions under 50 MPa pressure for 15 min. SiC was obtained by in situ pyrolysis of polycarbosilane during sintering. The FTIR spectra of semi-pyrolysed ZrB2-SiCp powder showed that pre-ceramic PCS polymeric bands such as Si-CH2-Si, Si-CH3 and Si-H weakened and few characteristic bands like Si-C, Si-O and C = C peaks appeared strong in the spectra. In ZrB2-SiCP composition, uniform distribution of ZrB2 and secondary SiC phases were found in the sintered sample. The interfaces between hexagonal ZrB2 and needle shaped SiC were found in high resolution bright field TEM images. The Vickers' micro-hardness, fracture toughness (measured by DCM) of ZrB2-SiCp composite sintered at 2000°C achieved up to 16.22 GPa and 3.69 MPa√m, respectively. The critical energy release rate (GIC) value was 27.46 J·m- 2 implying that the composite resists fracture during indentation. Wear resistance coefficient and wear rate values of all the composites were found to be very low. Thermal conductivity values of all the composites varied from 78.09 to 57.20 W/m·K in 100°C to 1000°C range. © 2015 Elsevier Ltd. Source

Valiyaneerilakkal U.,National Institute of Technology Calicut | Singh A.,DMSRDE DRDO | Singh K.,National Institute of Technology Calicut | Subash C.K.,National Institute of Technology Calicut | And 3 more authors.
Applied Physics A: Materials Science and Processing | Year: 2014

A metal–ferroelectric–insulator–semiconductor (MFIS) structure has been made using poly(vinylidene difluoride–trifluoroethylene)/barium titanate [P(VDF–TrFE)/BaTiO3] nanocomposite as ferroelectric layer, on silicon/silicon dioxide (Si/SiO2) substrate. Different concentrations of BaTiO3 were added to P(VDF–TrFE) polymer using bath sonication method, and the films were prepared using spin coating method. The structure was annealed to 120 °C for 2 h and then the top aluminium electrode was deposited by thermal evaporation method. Capacitance–voltage shows an increase in accumulation capacitance as the BaTiO3 nanoparticle concentrations increases. Dielectric constant was estimated from the capacitance voltage (C–V) characteristics and found to be changing as the concentration of BaTiO3 is varied. Polarization–electric field analyses show hysteresis behaviour of the nanocomposite. A comparison of MFIS and metal–ferroelectric–semiconductor structures was done with varying ferroelectric film thicknesses. All these results suggest that this polymer nanocomposite can be a promising material which can be used in non-volatile memory devices. © 2014, Springer-Verlag Berlin Heidelberg. Source

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