ABSTRACT Black nickel, an alloy coating of zinc and nickel, is obtained on copper substrate by pu... more ABSTRACT Black nickel, an alloy coating of zinc and nickel, is obtained on copper substrate by pulse electrodeposition from a modified Fishlock bath containing nickel sulfate, nickel ammonium sulfate, zinc sulfate and ammonium thiocyanate. A nickel undercoat of 4-5μm thickness is obtained using Watts bath to increase the corrosion resistance and adhesion of the black nickel coating. The effect of bath composition, temperature, solution pH, current density and plating time on the coating appearance and corresponding infra-red emittance of the coating is investigated systematically. Process parameters are optimized to develop a high emittance space worthy black nickel coating to improve the heat radiation characteristics. The effect of the chemistry of the plating bath on the coating composition was studied using energy dispersive X-ray analysis (EDAX) of the coatings. The 5-6 μm thick uniform jet black zinc-nickel alloy coating obtained with optimized process exhibited an emittance of 0.83 and an absorbance of 0.92. The zinc to nickel ratio of black nickel coatings showing high emittance and appealing appearance was found to be in the range 2.3 to 2.4.
ABSTRACT The E-beam evaporation technique is utilized at room temperature to deposit 90, 120 and ... more ABSTRACT The E-beam evaporation technique is utilized at room temperature to deposit 90, 120 and 150 nm thin alumina films on 75 μm thin Ti foils. As-grown films are annealed at 500, 700 and 800 °C in air. The phase structure, morphology and electronic structure of the as-grown and annealed thin films are respectively investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) techniques. The XRD results show that the as-grown thin films are amorphous. The annealed thin films show crystalline peaks corresponding to a mixture of different phases of alumina. The FE-SEM studies reveal tripod-like nanostructure and dense nanorods in the alumina thin films annealed at 700 and 800 °C, respectively. These results are explained on the basis of experimental evidences provided by the corresponding XPS studies.
Integral black anodizing and gold plating on Mg-Li alloys were developed for spacecraft thermal c... more Integral black anodizing and gold plating on Mg-Li alloys were developed for spacecraft thermal control applications. The influence of various process conditions have been investigated to optimize the process. The deposits were characterized by morphological studies, adhesion test, thickness measurement, microhardness evaluation and porosity inspection. The space worthiness of the coatings has been evaluated by humidity, thermal cycling, and thermovacuum tests and measurement of optical properties. The high solar absorptance and infrared emittance (alpha(sub S) = 0.95, epsilon(sub IR) = 0.93) value of black anodic film showed that these can be effectively utilized to improve heat radiation characteristics. The gold coating on the other hand provides the infrared emittance as low as 0.03, is extremely suitable in minimising the radiative coupling with other components within the spacecraft. Such gold mettalised surfaces with extremely low infrared emittance values are useful as radia...
ABSTRACT Adequate surface engineering of stainless steel and titanium substrates were achieved by... more ABSTRACT Adequate surface engineering of stainless steel and titanium substrates were achieved by sputtering of SiO2 and Al2O3 based films onto them. Microstructural and morphological studies of these films were carried out by field emission scanning electron microscopy and atomic force microscopy techniques. Infrared emittance (epsilon(ir)) of the films was measured by a Fourier transform infrared spectrophotometer. Nanoindentation technique was employed to evaluate nanohardness and Young's modulus of the films. The optimized bi-layer SiO2-Al2O3 film showed up to 850% increase in sir as compared to those of the bare substrates.
The 13th International Conference on Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. TRANSDUCERS '05., 2005
Pressure sensors with a metallic diaphragm and bonded strain gauge are by far the most widely use... more Pressure sensors with a metallic diaphragm and bonded strain gauge are by far the most widely used sensors in pressure measurement. In this work, we describe a method to fabricate a low power, light weight and low cost pressure sensor using aluminum diaphragm. The diaphragm is hard anodized to get insulating base over which Pt-W (Pt: 92%, W: 8%) thin
ABSTRACT Pulse electrodeposition of nanocrystalline nickel has been carried out on AA 6061 substr... more ABSTRACT Pulse electrodeposition of nanocrystalline nickel has been carried out on AA 6061 substrate from a modified Watt’s bath using saccharin as a grain refining additive. By varying the concentration of saccharin and other operating parameters, nanocrystalline nickel electrodeposits of varying average grain sizes (from 115 down to 17 nm) have been obtained. Nanoindentation was employed for studying the effect of average grain size on the mechanical and tribological properties of the electrodeposits, with emphasis on hardness, elastic modulus, wear resistance and coefficient of friction. The study confirms that the hardness of nanocrystalline nickel electrodeposits increases as the average grain size decreases and a value as high as 7?2 GPa is obtained for a coating having an average grain size of 17 nm. No inverse Hall–Petch relationship is observed for the entire range of grain sizes studied. The elastic modulus of the electrodeposits remained almost constant (between 150 and 160 GPa), irrespective of the average grain size and a coefficient of friction value of 0?25 has been obtained for a deposit having an average grain size of 17 nm.
... 3. JK Dennis and TE Such: 'Nickel and chromium plating', 186; 1972, London, Butterw... more ... 3. JK Dennis and TE Such: 'Nickel and chromium plating', 186; 1972, London, Butterworth's. 4. S. Jayakrishnan, M. Pushpavanam, SR Natarajan, R. Subramanian: Bull. Electrochem., 1986, 2, (3), 251. ... 19. AR Shashikala, R. Umarani, AK Sharma and SM Mayanna: Surf. ...
ABSTRACT Electrodeposition of nanocrystalline nickel on aluminium alloy AA 6061 substrate was car... more ABSTRACT Electrodeposition of nanocrystalline nickel on aluminium alloy AA 6061 substrate was carried out using cathodic square wave pulse with an on-time of 0?1 ms and an off-time of 0?9 ms from a modified Watt’s bath containing saccharin as an additive. The influences of concentration of saccharin, pH of the plating bath and average current density on the surface morphology, crystal orientation, average grain size and lattice strain were investigated. The study confirms that increase in concentration of saccharin in the plating bath as well as increase in the average current density results in a decrease in the average grain size of the deposit. pH appears to have no significant effect on the grain size of the deposit. The crystal orientation progressively changes from a strong (200) fibre structure to a (111) (200) double fibre structure as the concentration of saccharin is increased in the plating bath. It was also observed that as the grain size decreases the lattice strain of the coating increases. The space worthiness of the coating has been evaluated by humidity, thermal cycling, thermovacuum performance tests and measurement of optical properties. The coatings were characterised by scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy analysis, microhardness evaluation, adhesion, thermal stability and corrosion resistance tests.
ABSTRACT A novel galvanic conversion coating was studied on magnesium alloy AZ31B in an electroly... more ABSTRACT A novel galvanic conversion coating was studied on magnesium alloy AZ31B in an electrolyte system consisting of ammonium molybdate and magnesium chloride. The conditions of the conversion coating process and the characteristic of the coatings are studied in detail. The coatings were characterised by energy dispersive X-ray, infrared spectral and scanning electron microscopy studies. The thermoanalytical investigations have been carried out using thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). The space worthiness of the coating was evaluated by environmental tests, namely, humidity, thermal cycling, thermovacuum performance and thermal stability tests. Optical properties (solar absorptance and infrared emittance) were measured before and after each environmental test to ascertain its stability. The coating provides higher solar absorptance and infrared emittance in the order of ?0·80. The developed procedure is simple, ecofriendly and economically viable.
ABSTRACT Black nickel, an alloy coating of zinc and nickel, is obtained on copper substrate by pu... more ABSTRACT Black nickel, an alloy coating of zinc and nickel, is obtained on copper substrate by pulse electrodeposition from a modified Fishlock bath containing nickel sulfate, nickel ammonium sulfate, zinc sulfate and ammonium thiocyanate. A nickel undercoat of 4-5μm thickness is obtained using Watts bath to increase the corrosion resistance and adhesion of the black nickel coating. The effect of bath composition, temperature, solution pH, current density and plating time on the coating appearance and corresponding infra-red emittance of the coating is investigated systematically. Process parameters are optimized to develop a high emittance space worthy black nickel coating to improve the heat radiation characteristics. The effect of the chemistry of the plating bath on the coating composition was studied using energy dispersive X-ray analysis (EDAX) of the coatings. The 5-6 μm thick uniform jet black zinc-nickel alloy coating obtained with optimized process exhibited an emittance of 0.83 and an absorbance of 0.92. The zinc to nickel ratio of black nickel coatings showing high emittance and appealing appearance was found to be in the range 2.3 to 2.4.
ABSTRACT The E-beam evaporation technique is utilized at room temperature to deposit 90, 120 and ... more ABSTRACT The E-beam evaporation technique is utilized at room temperature to deposit 90, 120 and 150 nm thin alumina films on 75 μm thin Ti foils. As-grown films are annealed at 500, 700 and 800 °C in air. The phase structure, morphology and electronic structure of the as-grown and annealed thin films are respectively investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) techniques. The XRD results show that the as-grown thin films are amorphous. The annealed thin films show crystalline peaks corresponding to a mixture of different phases of alumina. The FE-SEM studies reveal tripod-like nanostructure and dense nanorods in the alumina thin films annealed at 700 and 800 °C, respectively. These results are explained on the basis of experimental evidences provided by the corresponding XPS studies.
Integral black anodizing and gold plating on Mg-Li alloys were developed for spacecraft thermal c... more Integral black anodizing and gold plating on Mg-Li alloys were developed for spacecraft thermal control applications. The influence of various process conditions have been investigated to optimize the process. The deposits were characterized by morphological studies, adhesion test, thickness measurement, microhardness evaluation and porosity inspection. The space worthiness of the coatings has been evaluated by humidity, thermal cycling, and thermovacuum tests and measurement of optical properties. The high solar absorptance and infrared emittance (alpha(sub S) = 0.95, epsilon(sub IR) = 0.93) value of black anodic film showed that these can be effectively utilized to improve heat radiation characteristics. The gold coating on the other hand provides the infrared emittance as low as 0.03, is extremely suitable in minimising the radiative coupling with other components within the spacecraft. Such gold mettalised surfaces with extremely low infrared emittance values are useful as radia...
ABSTRACT Adequate surface engineering of stainless steel and titanium substrates were achieved by... more ABSTRACT Adequate surface engineering of stainless steel and titanium substrates were achieved by sputtering of SiO2 and Al2O3 based films onto them. Microstructural and morphological studies of these films were carried out by field emission scanning electron microscopy and atomic force microscopy techniques. Infrared emittance (epsilon(ir)) of the films was measured by a Fourier transform infrared spectrophotometer. Nanoindentation technique was employed to evaluate nanohardness and Young's modulus of the films. The optimized bi-layer SiO2-Al2O3 film showed up to 850% increase in sir as compared to those of the bare substrates.
The 13th International Conference on Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. TRANSDUCERS '05., 2005
Pressure sensors with a metallic diaphragm and bonded strain gauge are by far the most widely use... more Pressure sensors with a metallic diaphragm and bonded strain gauge are by far the most widely used sensors in pressure measurement. In this work, we describe a method to fabricate a low power, light weight and low cost pressure sensor using aluminum diaphragm. The diaphragm is hard anodized to get insulating base over which Pt-W (Pt: 92%, W: 8%) thin
ABSTRACT Pulse electrodeposition of nanocrystalline nickel has been carried out on AA 6061 substr... more ABSTRACT Pulse electrodeposition of nanocrystalline nickel has been carried out on AA 6061 substrate from a modified Watt’s bath using saccharin as a grain refining additive. By varying the concentration of saccharin and other operating parameters, nanocrystalline nickel electrodeposits of varying average grain sizes (from 115 down to 17 nm) have been obtained. Nanoindentation was employed for studying the effect of average grain size on the mechanical and tribological properties of the electrodeposits, with emphasis on hardness, elastic modulus, wear resistance and coefficient of friction. The study confirms that the hardness of nanocrystalline nickel electrodeposits increases as the average grain size decreases and a value as high as 7?2 GPa is obtained for a coating having an average grain size of 17 nm. No inverse Hall–Petch relationship is observed for the entire range of grain sizes studied. The elastic modulus of the electrodeposits remained almost constant (between 150 and 160 GPa), irrespective of the average grain size and a coefficient of friction value of 0?25 has been obtained for a deposit having an average grain size of 17 nm.
... 3. JK Dennis and TE Such: 'Nickel and chromium plating', 186; 1972, London, Butterw... more ... 3. JK Dennis and TE Such: 'Nickel and chromium plating', 186; 1972, London, Butterworth's. 4. S. Jayakrishnan, M. Pushpavanam, SR Natarajan, R. Subramanian: Bull. Electrochem., 1986, 2, (3), 251. ... 19. AR Shashikala, R. Umarani, AK Sharma and SM Mayanna: Surf. ...
ABSTRACT Electrodeposition of nanocrystalline nickel on aluminium alloy AA 6061 substrate was car... more ABSTRACT Electrodeposition of nanocrystalline nickel on aluminium alloy AA 6061 substrate was carried out using cathodic square wave pulse with an on-time of 0?1 ms and an off-time of 0?9 ms from a modified Watt’s bath containing saccharin as an additive. The influences of concentration of saccharin, pH of the plating bath and average current density on the surface morphology, crystal orientation, average grain size and lattice strain were investigated. The study confirms that increase in concentration of saccharin in the plating bath as well as increase in the average current density results in a decrease in the average grain size of the deposit. pH appears to have no significant effect on the grain size of the deposit. The crystal orientation progressively changes from a strong (200) fibre structure to a (111) (200) double fibre structure as the concentration of saccharin is increased in the plating bath. It was also observed that as the grain size decreases the lattice strain of the coating increases. The space worthiness of the coating has been evaluated by humidity, thermal cycling, thermovacuum performance tests and measurement of optical properties. The coatings were characterised by scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy analysis, microhardness evaluation, adhesion, thermal stability and corrosion resistance tests.
ABSTRACT A novel galvanic conversion coating was studied on magnesium alloy AZ31B in an electroly... more ABSTRACT A novel galvanic conversion coating was studied on magnesium alloy AZ31B in an electrolyte system consisting of ammonium molybdate and magnesium chloride. The conditions of the conversion coating process and the characteristic of the coatings are studied in detail. The coatings were characterised by energy dispersive X-ray, infrared spectral and scanning electron microscopy studies. The thermoanalytical investigations have been carried out using thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). The space worthiness of the coating was evaluated by environmental tests, namely, humidity, thermal cycling, thermovacuum performance and thermal stability tests. Optical properties (solar absorptance and infrared emittance) were measured before and after each environmental test to ascertain its stability. The coating provides higher solar absorptance and infrared emittance in the order of ?0·80. The developed procedure is simple, ecofriendly and economically viable.
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