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Item Coconut coir pith, available in abundance especially in tropical countries, was studied as a substrate for the production of cellulase[1,4(1,3;1,4)???D?glucan 4?glucanohydrolase, EC 3.2.1.4] and ??D?glucosidase(??D?glucoside glucohydrolase, EC 3.2.1.21) in solid state fermentation. The effects of fermentation time, nutrient level, substrate particle size and inoculum size have been examined for optimal production of these enzymes by the fungal strain Aspergillus niger NCIM 1005. The highest filter paper activity (FPA) of 4.11 IU g?1, carboxyl methyl cellulose (CMCase) activity of 15·55 IU g?1 and cellobiase activity of 9·31 IU g?1 were obtained after 7 to 8 days of fermentation. Reese and Mandel's mineral solution in the substrate to mineral solution ratio of 1:10 (w/v) supported high cellulase and cellobiase activities. An inoculum size of 20–50% (v/v) based on the volume of mineral medium and substrate average particle size of 375 ?m were optimum for enzyme production. Copyright © 1994 SCI(Production of cellulases from coconut coir pith in solid state fermentation) Muniswaran, P.K.A.; Selvakumar, P.; Charyulu, N.C.L.N.1994Item Photoconductivity has been studied in cadmium selenide thin films prepared by thermal evaporation in vacuum. Attempts have been made to correlate the photoresponse with the deposition conditions. It has been observed that as-grown films, irrespective of the cadmium content, are not photosensitive and that baking in air, especially above 723 K, leads to considerable improvement in the photoconducting properties of cadmium selenide films.(Photoconductivity in vacuum deposited cadmium selenide thin films) Rajendra, B.V.; Kasturi, V.B.; Shivakumar, G.K.2004Item Effect of substrate surface roughness on wetting behaviour of vegetable oils(2009) Prabhu, K.N.; Fernades, P.; Kumar, G.Vegetable oils are mainly used in the heat treating industry due to their environmental friendliness. In the present work the effect of surface roughness on spreading of vegetable oils on stainless steel substrates was investigated. Spreading phenomenon was digitally recorded and analyzed. All of the oils under investigation exhibited power law spreading behaviour of the type: A = ktn, where A, t, k and n represent the drop base contact area, spreading time, constant and exponent, respectively. The coconut and sunflower oils exhibited accelerated kinetics owing to their lower viscosity as compared to palm and mineral oils while peanut oil showed intermediate behaviour. Viscous regime was dominant during spreading of mineral and palm oils as compared to that of coconut oil. All the oils took longer period of time on rough surfaces than on smooth surfaces to relax to the same degree of wetting. Oils spreading on rough surfaces had to overcome the additional barrier due to asperities of the rough surface. Contact angle decreased with increase in roughness supporting the Wenzel's proposition. The decrease was significant for increase in roughness from 0.25 ?m to 0.50 ?m for all oils. However, the effect was negligible with further increase in roughness particularly for high viscosity oils. A spread parameter (?) is proposed to account for the variation of contact angle with surface roughness of the substrate and momentum diffusivity of the spreading liquid. The result suggested that low viscosity liquids exhibit improved wetting characteristics during spreading on rough surfaces. A model is proposed to estimate dynamic contact angles on substrates having varying surface roughness. © 2008 Elsevier Ltd. All rights reserved.Item Thermal contact at solder/substrate interfaces during solidification(2009) Nyamannavar, S.; Prabhu, K.N.Heat flux transients at the solder/substrate interface during the solidification of Sn-37Pb and Sn-3.5Ag solder alloys against metallic substrates were estimated by the lumped heat capacitance model and the contact condition was assessed by scanning electronic microscopy (SEM). Copper substrates yielded maximum contact heat flux followed by brass and aluminium substrates. The SEM study in the solder/substrate interfacial region revealed the existence of a clear gap with the aluminium substrate. A conforming contact was obtained with copper and brass substrates. © 2009 Institute of Materials, Minerals and Mining.Item The effect of substrate temperature on the structural, optical and electrical properties of vacuum deposited ZnTe thin films(2009) Rao, G.K.; Bangera, K.V.; Shivakumar, G.K.The present paper reports the effect of substrate temperature on the structural, optical and electrical properties of vacuum deposited zinc telluride (ZnTe) thin films. X-ray diffraction (XRD) analysis of the films, deposited on glass substrates, revealed that they have cubic structure with strong (111) texture. Room temperature deposits are tellurium rich and an increase in the substrate temperature up to 553 °K results in stoichiometric films. Electrical conductivity has been observed to increase with the increase in substrate temperature, accompanied by increase in the carrier concentration and the mobility of the carriers. The optical bandgap energy and the thermal activation energy of the films have also been evaluated. © 2009 Elsevier Ltd. All rights reserved.Item Studies on the photoconductivity of vacuum deposited ZnTe thin films(2010) Rao, K.G.; Bangera, K.V.; Shivakumar, G.K.The present paper reports the analysis of photoconductivity of vacuum deposited zinc telluride (ZnTe) thin films as a function of substrate temperature and post-deposition annealing. Detailed analyses were first carried out to understand the effect of substrate temperature and annealing on the structure, composition, optical and electrical properties of the films. The films deposited at elevated substrate temperatures showed faster and improved photoresponse. Post-deposition annealing was found to further enhance the photoresponse of the films. Attempts have been made to explain the improvement in the photoresponse on the basis of structural and compositional changes, taking place in the films, due to the substrate temperature and annealing. © 2010 Elsevier Ltd. All rights reserved.Item Wetting behaviour and evolution of microstructure of Sn-Ag-Zn solders on copper substrates with different surface textures(2010) Satyanarayan, S.; Prabhu, K.N.The effect of surface roughness on wetting behaviour and evolution of microstructure of two lead-free solders (Sn-2.625Ag-2.25Zn and Sn-1.75Ag-4.5Zn) on copper substrate was investigated. Both solders exhibited good wettability on copper substrates having rough surface and lower wettabilty on smooth surfaces. The contact angles of solders decreased linearly with increase in surface roughness of the substrate. The exponential power law, ?=exp(-K ?n), was used to model the relaxation behaviour of solders. A high intermetallic growth was observed at the interface particularly on copper substrates with rough surface texture. A thin continuous interface showing scallop intermetallic compounds (IMC) was obtained on smooth surfaces. With an increase in surface roughness, the IMC morphology changed from scallop shaped to needle type at the Sn-2.625Ag-2.25Zn solder/substrate interface and nodular to plate like IMCs for Sn-1.75Ag-4.5Zn solder matrix. Copyright © 2010 by ASTM International.Item Wetting behaviour and evolution of microstructure of Sn-Ag-Zn solders on copper substrates with different surface textures(ASTM International, 2011) Satyanarayan, S.; Prabhu, K.N.The effect of surface roughness on wetting behaviour and evolution of microstructure of two lead-free solders (Sn-2.625Ag-2.25Zn and Sn-1.75Ag-4.5Zn) on copper substrate was investigated. Both solders exhibited good wettability on copper substrates having rough surface and lower wettabilty on smooth surfaces. The contact angles of solders decreased linearly with increase in surface roughness of the substrate. The exponential power law, ?=exp(-KT -1), was used to model the relaxation behaviour of solders. A high intermetallic growth was observed at the interface particularly on copper substrates with rough surface texture. A thin continuous interface showing scallop intermetallic compounds (IMC) was obtained on smooth surfaces. With an increase in surface roughness, the IMC morphology changed from scallop shaped to needle type at the Sn-2.625Ag-2.25Zn solder/ substrate interface and nodular to plate like IMCs for Sn-1.75Ag-4.5Zn solder matrix. Copyright © 2010 by ASTM International.Item Wetting behaviour and interfacial microstructure of Sn-Ag-Zn solder alloys on nickel coated aluminium substrates(2011) Satyanarayan, S.; Prabhu, K.N.Wetting behaviours of two lead free solders (Sn-2·625Ag- 2·25Zn and Sn-1·75Ag-4·5Zn) on nickel coated aluminium substrates were investigated. Sn-2·625Ag-2·25Zn exhibited better wettability compared to Sn-1·75Ag-4·5Zn solder. Contact angles of the solders increased with increasing roughness of the substrate. The Young-Dupre equation was used to evaluate the work of adhesion of solder on the substrate. Sn-2·625Ag-2·25Zn solder exhibited higher work of adhesion than Sn-1·75Ag-4·5Zn. A thin continuous layer of Ni 3Sn was detected at the interface between Sn-2·625Ag- 2·25Zn solder and nickel coated Al substrate. Sn-1·75Ag- 4·5Zn solder exhibited scallop intermetallic compounds (IMCs) growing into the solder field as well as a thin continuous IMC in some cases. Ni 3Sn and Ni3Sn4 IMCs were observed at the interface of Sn-1·75Ag-4·5Zn solder and nickel coated Al. © 2011 Institute of Materials, Minerals and Mining.Item Hardness and electrochemical behavior of ceramic coatings on CP titanium by pulsed laser deposition(2012) Sujaya, C.; Shashikala, H.D.Thin films of alumina and silicon carbide are deposited on titanium substrate by the pulsed laser deposition technique using Nd: YAG laser. Deposited films are characterized using x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectroscopy, absorption spectroscopy and nanoindentation. Film hardness of the ceramic coating is found to be high compared to that of the substrates. Corrosion behavior of substrates after ceramic coating is studied in 3. 5% NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy measurements. Experimental results show an increase in corrosion resistance of titanium after being coated with a ceramic material. © 2012 Allerton Press, Inc.