Effect of powder loading on the excitation temperature of a plasma jet in DC thermal plasma spray torch

G. Shanmugavelayutham,V. Selvarajan,P.V.A. Padmanabhan,K.P. Sreekumar,N.K. Joshi 한국물리학회 2007 Current Applied Physics Vol.7 No.2

A DC non-transferred mode plasma spray torch was fabricated for plasma spheroidization. The eect of powder-carrier gas and pow-der loading on the temperature of the plasma jet generated by the torch has been studied. The experiment was done at dierent inputparticles in the size range from 40 to 100l m were processed. The temperature of the jet was estimated after owing powder-carrier gasonly into the plasma jet and with powder-carrier gas feeding powder into the ame. On introduction of powder-carrier gas and powderloading the temperature of the jet was found to decrease appreciably down to 11%. The temperature of the plasma jet was estimatedusing the Atomic Boltzmann plot method.

In-flight particle behaviour and its effect on co-spraying of alumina?titania

G. Shanmugavelayutham,V. Selvarajan,T.K. Thiyagarajan,P.V.A. Padmanabhan,K.P. Sreekumar,R.U. Satpute Y. Zhai 한국물리학회 2006 Current Applied Physics Vol.6 No.1

The present paper investigate and illustrate the importance of plasmaparticle interaction in controlling the plasma spray processwhile spraying aluminatitania powder blend. Plasma sprayed coatings of aluminatitania (6040l m) have been prepared at dier-chemical composition of aluminatitania coatings, prepared at low input power, is signicantly dierent from that of the feed stockpowder. Coating composition progressively approaches that of the feedstock powder at higher power inputs. Experimental resultsare explained in terms of the in-ight behaviour of alumina and titania particles in the plasma jet using a one-dimensional model topredict the thermal state of the particles. In particular, the eect of particle size and input power are considered in this study.

Preparation of bovine hydroxyapatite by transferred arc plasma

C.P. Yoganand,V. Selvarajan,O.M. Goudouri,K.M. Paraskevopoulos,Junshu Wu,Dongfeng Xue 한국물리학회 2011 Current Applied Physics Vol.11 No.3

Hydroxyapatite (Ca_10(PO_4)_6(OH)_2, abbreviated as HA) is a kind of bioactive material that has received considerable attention over the past decades as an implant material due to its excellent biocompatability for clinical applications. In this work, Hydroxyapatite was obtained by plasma processing of the natural bovine bones by Transferred arc plasma (TAP) processing at 5 kW in argon plasma for different processing times (i.e. 30, 45, 60, 90 and 120 s). The TAP synthesized HA bioceramic was characterized by XRD, FTIR,SEM-EDX and TG-DTA analysis. The effect of TAP processing time on the preparation of organic free HA from bovine bone was studied. The study indicated that TAP processing for 30, 45 and 60 s were insuf-ficient for removal of organics from the natural bovine bone. Organic free bovine HA was obtained for 90 s TAP processing with a Ca/P ratio of 1.93 comparable with commercially available natural HA-Endobon powder. Whereas 120 s of processing resulted in trivial thermal decomposition of HA in to its constituent phases. Thus our present investigation suggested that HA production from bovine bone using TAP processing is a time effective advantageous method in comparison to the annealing method.

Glow discharge plasma-induced immobilization of heparin and insulin on polyethylene terephthalate film surfaces enhances anti-thrombogenic properties

Pandiyaraj, K.N.,Selvarajan, V.,Rhee, Y.H.,Kim, H.W.,Shah, S.I. Elsevier 2009 Materials science & engineering. C, Materials for Vol.29 No.3

Polyethylene terephthalate (PET) films were treated with DC glow discharge plasma followed by graft copolymerization with acrylic acid (AA) and polyethylene glycol (PEG). The obtained PET-PEG was coupled to heparin or insulin molecules. The surfaces were then characterized by contact angle measurements, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The surface energies of the modified PET films were estimated using contact angle measurements, and the changes in crystallinity of the plasma-modified PET film surfaces were investigated by X-ray diffraction (XRD) analysis. The blood compatibilities of the surface-modified PETs were examined by in vitro thrombus formation, whole blood clotting time, platelet contact and protein adsorption experiments. The results revealed that the contact angle value decreased and that the interfacial tension between the modified PET films and blood protein was drastically diminished compared to unmodified PET film. The XPS results showed that the PET-AA surface containing carboxylic acid and the immobilized PET surface containing both carboxylic acid and amino groups exhibited a hydrophilic character, and AFM results showed marked morphological changes after grafting of AA, PEG and biomolecule immobilization. Heparin and insulin-coupled PET surfaces exhibited much less platelet adhesion and protein adsorption than the other surface-modified PET film surfaces.

CaO–MgO–SiO2 glass ceramics: Transferred arc plasma (TAP) synthesis and microstructural characterization

C.P. Yoganand,V. Selvarajan,Luca Lusvarghi 한국물리학회 2009 Current Applied Physics Vol.9 No.4

In this paper, synthesis of CaO–MgO–SiO2 glass ceramic using transferred arc plasma (TAP) processing method is illustrated. Homogeneous mixture of 51.6% SiO2, 35.6% CaO and 12.8% MgO prepared by dry mixing in a ball mill was kept in the anode well (which is the melting bed) of the 10 kW transferred arc plasma torch. It was melted in plasma at an operating power of 5 kW (by varying the processing time for 3, 5 and 8 min). The melt was cooled to solidify by applying forced air on it. The resulting samples were characterized for microstructure and phase composition. The phases were identified by scanning electron microscopy (SEM), using the back-scattered electron (BSE) image mode and X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX). The microstructure was examined using optical microscopy (OM) and scanning electron microscopy. The micro-hardness, density and porosity measurements for the synthesized samples were carried out. Differential thermal analysis (DTA) was performed to study the thermal evolution. The results show the formation of diopside phase in the transferred arc plasma melted CaO–MgO–SiO2 glass ceramic system achieved with in a quite considerable short time of plasma processing. The method indicated that TAP technique could be a promising, time saving and onestep manufacturing process for the production of functional bulk glass ceramics. In this paper, synthesis of CaO–MgO–SiO2 glass ceramic using transferred arc plasma (TAP) processing method is illustrated. Homogeneous mixture of 51.6% SiO2, 35.6% CaO and 12.8% MgO prepared by dry mixing in a ball mill was kept in the anode well (which is the melting bed) of the 10 kW transferred arc plasma torch. It was melted in plasma at an operating power of 5 kW (by varying the processing time for 3, 5 and 8 min). The melt was cooled to solidify by applying forced air on it. The resulting samples were characterized for microstructure and phase composition. The phases were identified by scanning electron microscopy (SEM), using the back-scattered electron (BSE) image mode and X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX). The microstructure was examined using optical microscopy (OM) and scanning electron microscopy. The micro-hardness, density and porosity measurements for the synthesized samples were carried out. Differential thermal analysis (DTA) was performed to study the thermal evolution. The results show the formation of diopside phase in the transferred arc plasma melted CaO–MgO–SiO2 glass ceramic system achieved with in a quite considerable short time of plasma processing. The method indicated that TAP technique could be a promising, time saving and onestep manufacturing process for the production of functional bulk glass ceramics.

Influence of bias voltage on diamond like carbon (DLC) film deposited on polyethylene terephthalate (PET) film surfaces using PECVD and its blood compatibility

Pandiyaraj, K.N.,V. Selvarajan,Heeg, J.,Junge, F.,Lampka, A.,Barfels, T.,Wienecke, M.,Rhee, Y.H.,Kim, H.W. Elsevier 2010 Diamond and related materials Vol.19 No.7

In this paper, diamond like carbon (DLC) films were coated on polyethylene terephthalate (PET) film substrate as a function of biasing voltage using plasma enhanced chemical vapour deposition. The surface morphology of the DLC films was analyzed by scanning electron microscopy and atomic force microscopy. The chemical state and structure of the films were analyzed by X-ray photoelectrons spectroscopy and Raman spectroscopy. The micro hardness of the DLC films was also studied. The surface energy of interfacial tension between the DLC and blood protein was investigated using contact angle measurements. In addition, the blood compatibility of the films was examined by in vitro tests. For a higher fraction of sp<SUP>3</SUP> content, maximum hardness and surface smoothness of the DLC films were obtained at an optimized biasing potential of -300V. The in vitro results showed that the blood compatibility of the DLC coated PET film surfaces got enhanced significantly.

Investigation on surface properties of TiO2 films modified by DC glow discharge plasma

K. Navaneetha Pandiyaraj,V. Selvarajan,Matteo Pavese,Polycarpos Falaras,Dimitrios Tsoukleris 한국물리학회 2009 Current Applied Physics Vol.9 No.5

In the present work, TiO2 films deposited on polyethylene terephthalate substrates by dip coating technique were subsequently treated by DC glow discharge plasma as a function of discharge potential. Hydrophilicity of these TiO2 film surfaces was analyzed by contact angle measurements. Atomic force microscopy (AFM) revealed changes in surface morphology of the plasma treated TiO2 films. Modifications in structural and chemical composition of the TiO2 films were detected by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The blood compatibility of TiO2 films was studied by in vitro investigation which includes thrombus formation and whole blood clotting time analysis (WBCT). It was found that the plasma treatment results in blood compatibility enhancement attributed to the structural, chemical and morphological properties of the modified film surfaces.

Influence of metal powder shape on drag coefficient in a spray jet

S. Kumar,Hyuntaek Na,이창희,V. Selvarajan 한국물리학회 2009 Current Applied Physics Vol.9 No.3

In plasma spraying, particle shape, size, distribution and density are the important factors to be considered in order to ensure high spray efficiency and better coating properties. In the present work, nickel, iron and aluminium irregular powders in the size range from 50 to 63 lm were spheroidized using thermal plasma processing. The spheroidization experiments have been carried out at different gas flow rates and plasma torch power levels. The sphericity was analyzed using shape factor. Drag coefficients of the powders were estimated using Reynolds number and sphericity of the powders in plasma. For irregular particles, the drag coefficient is higher than that of the spherical because of its large area of contact with plasma. The temperature dependent on drag coefficient is also discussed. Increasing temperature increases the drag coefficient of the powder particles injected in to the plasma jet. Increasing plasma jet temperature changes the density and viscosity of the plasma which affects the particle’s drag coefficient in the plasma. The results are reported and discussed. In plasma spraying, particle shape, size, distribution and density are the important factors to be considered in order to ensure high spray efficiency and better coating properties. In the present work, nickel, iron and aluminium irregular powders in the size range from 50 to 63 lm were spheroidized using thermal plasma processing. The spheroidization experiments have been carried out at different gas flow rates and plasma torch power levels. The sphericity was analyzed using shape factor. Drag coefficients of the powders were estimated using Reynolds number and sphericity of the powders in plasma. For irregular particles, the drag coefficient is higher than that of the spherical because of its large area of contact with plasma. The temperature dependent on drag coefficient is also discussed. Increasing temperature increases the drag coefficient of the powder particles injected in to the plasma jet. Increasing plasma jet temperature changes the density and viscosity of the plasma which affects the particle’s drag coefficient in the plasma. The results are reported and discussed.