Raman Singh - Academia.edu (original) (raw)
Papers by Raman Singh
Materials
The consequence of exposure to the dual environment of seawater sea sand concrete (SWSSC) on the ... more The consequence of exposure to the dual environment of seawater sea sand concrete (SWSSC) on the inner surface and seawater (SW) on the outer surface on the durability of fibre reinforced plastic (FRP) confining tubes has received very limited research attention. The durability of FRPs fabricated with different fibre types was investigated for the application of SWSSC filled tubes and SWSSC-filled double-skin tubes exposed to the external environment of SW. The colour and shininess of carbon-fibre-reinforced polymer (CFRP) surfaces generally stayed unchanged even after 6 months of exposure to the dual environment, whereas basalt-fibre-reinforced polymer (BFRP) and glass-fibre-reinforced polymer (GFRP) tubes suffered degradation. The degradation led to a ~20–30% increase in pH; however, the pH increase in the external SW was more pronounced when the internal solution was SWSSC. The extent of degradation was greater in BFRP that in GFRP. The investigation also included a specialised i...
Metals, 2021
The cold spray process is governed by the impact of high velocity feedstock particles onto a subs... more The cold spray process is governed by the impact of high velocity feedstock particles onto a substrate without melting. Hence, the bulk material properties are retained. However, it is challenging to achieve good adhesion strength. The adhesion strength depends on factors such as the cold spray process parameters, substrate conditions, coating/substrate interactions at the interface and feedstock material properties. This review examines fundamental studies concerning the adhesion mechanisms of cold spray technology and considers the effect of cold spray input parameters such as temperature, stand-off-distance, pressure, process gas, spray angle, and traverse speed of the cold spray torch on the bonding mechanism and adhesion strength. Furthermore, the effects of substrate conditions such as temperature, hardness, roughness and material on the adhesion mechanism are highlighted. The effect of feedstock properties, such as feed rate, shape and size are summarized. Understanding the e...
Research into carbon fibre reinforced polymers (CFRP)'s application to steel as a retrofitting te... more Research into carbon fibre reinforced polymers (CFRP)'s application to steel as a retrofitting technique has shown very positive results for increasing mechanical properties. However, the limitation of these materials in a corrosion inducing environment has been widely overlooked. In this study, the possible interaction of CFRP and steel in extreme weather conditions in causing localized corrosion (e.g., pitting) was investigated, with the primary aim of quantifying the pit depth and density caused by the galvanic corrosion process between the two materials. Steel tiles patched in direct contact with different varieties of CFRP were exposed to 5% NaCl solutions at two temperatures for different durations. After removal, the pit depth and pit density were analysed to determine whether galvanic conditions could indeed generate pits, which are known to initiate fatigue cracks in steels. It was observed, in this initial work, that after 4 weeks of exposure to NaCl, the pits formed from the CFRP patched specimens were not exceedingly different or critical compared to that of the control steel tiles.
Icf12 Ottawa 2009, May 3, 2013
This paper investigates the method to determine the K ISCC of grade 250 steel and simulated heat ... more This paper investigates the method to determine the K ISCC of grade 250 steel and simulated heat affected zone (SHAZ) in 30% caustic solution at 100ºC using CNT technique. Stress corrosion cracking has been confirmed using scanning electron microscope. Crack growth rate in caustic solution has been determined by CNT technique.
Interplay of microbiological corrosion and alloy
In this study, the stress corrosion cracking susceptibility of Mg-Al-Zu alloy in simulated body f... more In this study, the stress corrosion cracking susceptibility of Mg-Al-Zu alloy in simulated body fluid (SBF) was evaluated using slow strain rate test (SSRT) method. The SSRT results showed that the mechanical properties such as ultimate tensile strength and elongation-to-fracture decreased marginally (17% and 21%, respectively) in comparison with these properties in air, suggesting that stress corrosion cracking is not substantial for Mg-Al-Au alloy i simulated physiological condition.
As received recycled short milled carbon fibre (SMCF) reinforced diglycidal ether of bisphenol-A ... more As received recycled short milled carbon fibre (SMCF) reinforced diglycidal ether of bisphenol-A (DGEBA) epoxy matrix materials have been developed by ultra-sonication mixing of SMCF in epoxy then curing at room temperature for nine days. Elemental analysis, and surface chemistry of as received SMCF were examined using X-ray fluorescence (XRF), and X-ray photoelectron spectroscopy (XPS) respectively. Fourier Transform IR (FTIR) spectroscopy confirms that both in unmodified and SMCF- modified epoxies, 99% curing was achieved. In SENB sharp crack specimens tested at 2.8 mm/min, the slow crack growth region (length nearly zero for neat epoxy and maximum 1.14 mm for 10% SMCF-epoxy composite) shows intensive debonding and pull-out mechanisms. Fracture toughness (KIC) increased from 0.78 MPam0.5 for neat epoxy to 2.71 MPam0.5 for 10 weight % SMCF/epoxy composites thanks to the combined effect of fibre stereology and the debonding / pull-out mechanisms. Worth noting the flexural modulus of...
Engineering Structures, 2018
The use of FRP with seawater and sea sand concrete (SWSSC) holds great potential for marine and c... more The use of FRP with seawater and sea sand concrete (SWSSC) holds great potential for marine and coastal infrastructure, and concrete-filled FRP tubular columns are among the attractive forms of structural members for such applications. This paper presents a theoretical model for the compressive behaviour of seawater and sea sand concrete-filled circular FRP tubular stub columns. FRP tubes can be manufactured to possess considerable strength and stiffness in the longitudinal direction, so the behaviour of concrete-filled FRP tubes differed substantially from that of concrete columns with an FRP wrap (also referred to as "concrete-filled FRP wraps") which commonly contains fibres only in the hoop direction. Many theoretical models have been proposed for concrete-filled FRP wraps, but very limited work has been conducted on the theoretical modelling of concretefilled FRP tubes. In the present study, an existing dilation model for concrete-filled FRP wraps is combined with a biaxial stress analysis of the FRP tube so that the effect of the Poisson's ratio of the FRP tube is properly accounted for. In order to predict the buckling of the FRP tube, a maximum strain buckling failure criterion is proposed and is shown to be in reasonable agreement with the experimental results. Moreover, the load carried by the FRP tube is studied, and a simplified model is proposed to determine the load shared by the FRP tube during the entire loading process. Finally, a theoretical model for SWSSC-filled FRP tubular columns is proposed, in which the behaviour of both the concrete and the FRP tube as well as their interactions are explicitly modelled (i.e., an analysis-oriented model). The proposed model gives reasonably close predictions of the existing experimental data.
Metals, 2017
Magnesium and its alloys are attractive potential materials for construction of biodegradable tem... more Magnesium and its alloys are attractive potential materials for construction of biodegradable temporary implant devices. However, their rapid degradation in human body fluid before the desired service life is reached necessitate the application of suitable coatings. To this end, WZ21 magnesium alloy surface was modified by hexagonal boron nitride (hBN)-impregnated silane coating. The coating was chemically characterised by Raman spectroscopy. Potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) of the coated alloy in Hanks' solution showed a five-fold improvement in the corrosion resistance of the alloy due to the composite coating. Post-corrosion analyses corroborated the electrochemical data and provided a mechanistic insight of the improvement provided by the composite coating.
High Temperature Corrosion, 2016
Materials Science and Technology, 2005
The paper presents results of a laboratory investigation of the microbiological environment assis... more The paper presents results of a laboratory investigation of the microbiological environment assisted stress corrosion cracking of carbon steel in chloride solutions. Carbon steel specimens were subjected to slow strain rate testing (SSRT) in an aqueous solution of 3. 5% sodium chloride, with and without a microbiological culture. Specimens tested in the biotic (microbiological) conditions showed a considerable loss of ductility, as compared to those tested in abiotic conditions. Fractography of the specimens tested in abiotic solutions suggested features of only ductile failure (dimples), whereas those tested in biotic conditions also had features of brittle cracking. Results of SSRT tests of the specimens pre-subjected to the electrochemical conditions for hydrogen charging have indicated susceptibility of the steel to hydrogen assisted cracking, and therefore suggesting a role of microbial environment in promoting hydrogen assisted cracking.
Engineering Fracture Mechanics, 2015
For magnesium (Mg) alloys to be used as temporary biodegradable implants it is essential to estab... more For magnesium (Mg) alloys to be used as temporary biodegradable implants it is essential to establish their resistance to body fluid-assisted cracking. In this paper the fatigue behaviour of a common magnesium alloy, AZ91D, is studied in air and in modified simulated body fluid (m-SBF), and the effect of different electrochemical conditions on corrosion fatigue life is investigated. The alloy was found to be susceptible to corrosion fatigue. Results suggest inclusions and corrosion pits to be the crack initiation sites, and hydrogen embrittlement to play a dominant role in cracking of AZ91D Mg alloy in m-SBF.
Materials Science and Technology, 1998
... Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, India, and in the Schoo... more ... Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, India, and in the School of Materials Science and Engineering, University of New South Wales, Sydney, Australia, Dr Tyagi, Dr Gnanamoorthy, and Dr Raj are in ... 9. RK SINGH RAMAN and AK TYAGI: Mater ...
Regions with different microstructures have been identified in the weldments of 9Cr-lMo steel. We... more Regions with different microstructures have been identified in the weldments of 9Cr-lMo steel. Weldments comprising the three regions, i.e., weld metal heat-affected zone (HAZ), and base metal, were oxidized in air at 923 K for different durations up to 500 hr. The crown area oft he weld metal was found to form a thicker oxide scale than the other regions of the weldment. When the oxidation kinetics of different regions were compared (by separating out the coupons of the HAZ and the crown and root portions of the weld metal and then oxidizing them), the crown area of the weld was found to oxidize at a much higher rate than the others. Scanning electron microscopy (SEM) was carried out to assess the morphological variations in the different regions of the weldment. The compositional variations in the scales over the different regions have been characterized by the energy-dispersive analyses of X-rays (EDX), and the results thereof have also been corroborated by secondary ion mass spectrometry (SIMS).
The synergistic influence of prior-austenite grain size and silicon content of 9Cr−1Mo steel on t... more The synergistic influence of prior-austenite grain size and silicon content of 9Cr−1Mo steel on the resistance to scale spallation has been studied in air at 773 K (for 500 hr) and 973 K (12 hr). Two steels, irrespective of their grain size and Si content, did not show spallation during oxidation at 773 K. Spallation occurred at 973 K, and fine-grain steels exhibited less spallation resistance than coarse-grain ones (in low-as well as high-Si steels). Among the four possible combinations of grain size ans Si content, the steel with low Si and fine grains showed least resistance to spallation, while the steel with high Si and coarse grains showed the best resistance. Spallation was found to initiate in the areas adjoining the oxide ridges formed at the alloy grain boundaries. Oxide scales at the ridges and within the grains were analyzed by scanning electron microscopy (SEM/EDX) and secondary-ion mass spectrometry (SIMS). These analyses suggest depletion of silicon from the areas adjoining grain boundaries, resulting in thicker scaling that triggers spallation in such areas. For similar grain-size materials, the necessary thickness for spallation was attained earlier with low-Si steel rather than in high-Si steel.
Materials Science and Engineering: A, 2006
A novel fracture mechanics technique has been employed for the determination of crack growth rate... more A novel fracture mechanics technique has been employed for the determination of crack growth rate and threshold stress intensity factor (K Iscc) for stress corrosion cracking (SCC) using small circumferential notch tensile (CNT) specimens. The technique was applied successfully for testing SCC susceptibility of spheroidal graphite (SG) cast iron in 5 M NaOH at 100 and 120 • C. Crack growth rate of SG cast iron in 5 M NaOH solution at 100 and 120 • C has been determined at different stress intensity factors (K I), and the K Iscc have been determined to be 11.2 and 9 MPa m 1/2 , respectively. The surfaces of fractured specimens have been examined by scanning electron microscopy (SEM) in order to establish intergranular propagation of stress corrosion cracks. CNT testing is a simple, relatively fast and cost-advantageous approach for generating crack growth rate and K Iscc data.
AIP Conference Proceedings, 2010
This paper presents the characterization results of nanocrystalline Zinc Oxide with different cry... more This paper presents the characterization results of nanocrystalline Zinc Oxide with different crystallite sizes prepared by mechanochemical synthesis. Nano ZnO particles of different crystallite size were synthesized by high energy milling of precursor powders for various periods of time. Diluents were added to the precursor powders to reduce the agglomeration of product phase and to avoid the spontaneous reaction of precursor powders. After the milling process, diluents were selectively leached out using distilled water. X-ray Diffraction data was used to analyze the crystallite size of the nanoparticles and also to analyze the progress of the chemical reaction during milling process. Crystallite sizes were calculated from the XRD peak broadening using the Sherrer's formula. Crystallite sizes were seen to increase at a faster rate after 5h of milling where as bellow 5h of milling, little increase was observed. This increase in crystallite size at higher milling time could be attributed to cold welding and solid state diffusion of the nano particles as a result of high energy impacts from ball to powder collision. Scanning Electron Microscope was employed to analyze the particle morphology and size distribution of the nano ZnO powders. Ultraviolet -Visible (Uv-Vis) spectroscope was employed to analyze the optical absorption of the ZnO nano particles.
Materials
The consequence of exposure to the dual environment of seawater sea sand concrete (SWSSC) on the ... more The consequence of exposure to the dual environment of seawater sea sand concrete (SWSSC) on the inner surface and seawater (SW) on the outer surface on the durability of fibre reinforced plastic (FRP) confining tubes has received very limited research attention. The durability of FRPs fabricated with different fibre types was investigated for the application of SWSSC filled tubes and SWSSC-filled double-skin tubes exposed to the external environment of SW. The colour and shininess of carbon-fibre-reinforced polymer (CFRP) surfaces generally stayed unchanged even after 6 months of exposure to the dual environment, whereas basalt-fibre-reinforced polymer (BFRP) and glass-fibre-reinforced polymer (GFRP) tubes suffered degradation. The degradation led to a ~20–30% increase in pH; however, the pH increase in the external SW was more pronounced when the internal solution was SWSSC. The extent of degradation was greater in BFRP that in GFRP. The investigation also included a specialised i...
Metals, 2021
The cold spray process is governed by the impact of high velocity feedstock particles onto a subs... more The cold spray process is governed by the impact of high velocity feedstock particles onto a substrate without melting. Hence, the bulk material properties are retained. However, it is challenging to achieve good adhesion strength. The adhesion strength depends on factors such as the cold spray process parameters, substrate conditions, coating/substrate interactions at the interface and feedstock material properties. This review examines fundamental studies concerning the adhesion mechanisms of cold spray technology and considers the effect of cold spray input parameters such as temperature, stand-off-distance, pressure, process gas, spray angle, and traverse speed of the cold spray torch on the bonding mechanism and adhesion strength. Furthermore, the effects of substrate conditions such as temperature, hardness, roughness and material on the adhesion mechanism are highlighted. The effect of feedstock properties, such as feed rate, shape and size are summarized. Understanding the e...
Research into carbon fibre reinforced polymers (CFRP)'s application to steel as a retrofitting te... more Research into carbon fibre reinforced polymers (CFRP)'s application to steel as a retrofitting technique has shown very positive results for increasing mechanical properties. However, the limitation of these materials in a corrosion inducing environment has been widely overlooked. In this study, the possible interaction of CFRP and steel in extreme weather conditions in causing localized corrosion (e.g., pitting) was investigated, with the primary aim of quantifying the pit depth and density caused by the galvanic corrosion process between the two materials. Steel tiles patched in direct contact with different varieties of CFRP were exposed to 5% NaCl solutions at two temperatures for different durations. After removal, the pit depth and pit density were analysed to determine whether galvanic conditions could indeed generate pits, which are known to initiate fatigue cracks in steels. It was observed, in this initial work, that after 4 weeks of exposure to NaCl, the pits formed from the CFRP patched specimens were not exceedingly different or critical compared to that of the control steel tiles.
Icf12 Ottawa 2009, May 3, 2013
This paper investigates the method to determine the K ISCC of grade 250 steel and simulated heat ... more This paper investigates the method to determine the K ISCC of grade 250 steel and simulated heat affected zone (SHAZ) in 30% caustic solution at 100ºC using CNT technique. Stress corrosion cracking has been confirmed using scanning electron microscope. Crack growth rate in caustic solution has been determined by CNT technique.
Interplay of microbiological corrosion and alloy
In this study, the stress corrosion cracking susceptibility of Mg-Al-Zu alloy in simulated body f... more In this study, the stress corrosion cracking susceptibility of Mg-Al-Zu alloy in simulated body fluid (SBF) was evaluated using slow strain rate test (SSRT) method. The SSRT results showed that the mechanical properties such as ultimate tensile strength and elongation-to-fracture decreased marginally (17% and 21%, respectively) in comparison with these properties in air, suggesting that stress corrosion cracking is not substantial for Mg-Al-Au alloy i simulated physiological condition.
As received recycled short milled carbon fibre (SMCF) reinforced diglycidal ether of bisphenol-A ... more As received recycled short milled carbon fibre (SMCF) reinforced diglycidal ether of bisphenol-A (DGEBA) epoxy matrix materials have been developed by ultra-sonication mixing of SMCF in epoxy then curing at room temperature for nine days. Elemental analysis, and surface chemistry of as received SMCF were examined using X-ray fluorescence (XRF), and X-ray photoelectron spectroscopy (XPS) respectively. Fourier Transform IR (FTIR) spectroscopy confirms that both in unmodified and SMCF- modified epoxies, 99% curing was achieved. In SENB sharp crack specimens tested at 2.8 mm/min, the slow crack growth region (length nearly zero for neat epoxy and maximum 1.14 mm for 10% SMCF-epoxy composite) shows intensive debonding and pull-out mechanisms. Fracture toughness (KIC) increased from 0.78 MPam0.5 for neat epoxy to 2.71 MPam0.5 for 10 weight % SMCF/epoxy composites thanks to the combined effect of fibre stereology and the debonding / pull-out mechanisms. Worth noting the flexural modulus of...
Engineering Structures, 2018
The use of FRP with seawater and sea sand concrete (SWSSC) holds great potential for marine and c... more The use of FRP with seawater and sea sand concrete (SWSSC) holds great potential for marine and coastal infrastructure, and concrete-filled FRP tubular columns are among the attractive forms of structural members for such applications. This paper presents a theoretical model for the compressive behaviour of seawater and sea sand concrete-filled circular FRP tubular stub columns. FRP tubes can be manufactured to possess considerable strength and stiffness in the longitudinal direction, so the behaviour of concrete-filled FRP tubes differed substantially from that of concrete columns with an FRP wrap (also referred to as "concrete-filled FRP wraps") which commonly contains fibres only in the hoop direction. Many theoretical models have been proposed for concrete-filled FRP wraps, but very limited work has been conducted on the theoretical modelling of concretefilled FRP tubes. In the present study, an existing dilation model for concrete-filled FRP wraps is combined with a biaxial stress analysis of the FRP tube so that the effect of the Poisson's ratio of the FRP tube is properly accounted for. In order to predict the buckling of the FRP tube, a maximum strain buckling failure criterion is proposed and is shown to be in reasonable agreement with the experimental results. Moreover, the load carried by the FRP tube is studied, and a simplified model is proposed to determine the load shared by the FRP tube during the entire loading process. Finally, a theoretical model for SWSSC-filled FRP tubular columns is proposed, in which the behaviour of both the concrete and the FRP tube as well as their interactions are explicitly modelled (i.e., an analysis-oriented model). The proposed model gives reasonably close predictions of the existing experimental data.
Metals, 2017
Magnesium and its alloys are attractive potential materials for construction of biodegradable tem... more Magnesium and its alloys are attractive potential materials for construction of biodegradable temporary implant devices. However, their rapid degradation in human body fluid before the desired service life is reached necessitate the application of suitable coatings. To this end, WZ21 magnesium alloy surface was modified by hexagonal boron nitride (hBN)-impregnated silane coating. The coating was chemically characterised by Raman spectroscopy. Potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) of the coated alloy in Hanks' solution showed a five-fold improvement in the corrosion resistance of the alloy due to the composite coating. Post-corrosion analyses corroborated the electrochemical data and provided a mechanistic insight of the improvement provided by the composite coating.
High Temperature Corrosion, 2016
Materials Science and Technology, 2005
The paper presents results of a laboratory investigation of the microbiological environment assis... more The paper presents results of a laboratory investigation of the microbiological environment assisted stress corrosion cracking of carbon steel in chloride solutions. Carbon steel specimens were subjected to slow strain rate testing (SSRT) in an aqueous solution of 3. 5% sodium chloride, with and without a microbiological culture. Specimens tested in the biotic (microbiological) conditions showed a considerable loss of ductility, as compared to those tested in abiotic conditions. Fractography of the specimens tested in abiotic solutions suggested features of only ductile failure (dimples), whereas those tested in biotic conditions also had features of brittle cracking. Results of SSRT tests of the specimens pre-subjected to the electrochemical conditions for hydrogen charging have indicated susceptibility of the steel to hydrogen assisted cracking, and therefore suggesting a role of microbial environment in promoting hydrogen assisted cracking.
Engineering Fracture Mechanics, 2015
For magnesium (Mg) alloys to be used as temporary biodegradable implants it is essential to estab... more For magnesium (Mg) alloys to be used as temporary biodegradable implants it is essential to establish their resistance to body fluid-assisted cracking. In this paper the fatigue behaviour of a common magnesium alloy, AZ91D, is studied in air and in modified simulated body fluid (m-SBF), and the effect of different electrochemical conditions on corrosion fatigue life is investigated. The alloy was found to be susceptible to corrosion fatigue. Results suggest inclusions and corrosion pits to be the crack initiation sites, and hydrogen embrittlement to play a dominant role in cracking of AZ91D Mg alloy in m-SBF.
Materials Science and Technology, 1998
... Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, India, and in the Schoo... more ... Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, India, and in the School of Materials Science and Engineering, University of New South Wales, Sydney, Australia, Dr Tyagi, Dr Gnanamoorthy, and Dr Raj are in ... 9. RK SINGH RAMAN and AK TYAGI: Mater ...
Regions with different microstructures have been identified in the weldments of 9Cr-lMo steel. We... more Regions with different microstructures have been identified in the weldments of 9Cr-lMo steel. Weldments comprising the three regions, i.e., weld metal heat-affected zone (HAZ), and base metal, were oxidized in air at 923 K for different durations up to 500 hr. The crown area oft he weld metal was found to form a thicker oxide scale than the other regions of the weldment. When the oxidation kinetics of different regions were compared (by separating out the coupons of the HAZ and the crown and root portions of the weld metal and then oxidizing them), the crown area of the weld was found to oxidize at a much higher rate than the others. Scanning electron microscopy (SEM) was carried out to assess the morphological variations in the different regions of the weldment. The compositional variations in the scales over the different regions have been characterized by the energy-dispersive analyses of X-rays (EDX), and the results thereof have also been corroborated by secondary ion mass spectrometry (SIMS).
The synergistic influence of prior-austenite grain size and silicon content of 9Cr−1Mo steel on t... more The synergistic influence of prior-austenite grain size and silicon content of 9Cr−1Mo steel on the resistance to scale spallation has been studied in air at 773 K (for 500 hr) and 973 K (12 hr). Two steels, irrespective of their grain size and Si content, did not show spallation during oxidation at 773 K. Spallation occurred at 973 K, and fine-grain steels exhibited less spallation resistance than coarse-grain ones (in low-as well as high-Si steels). Among the four possible combinations of grain size ans Si content, the steel with low Si and fine grains showed least resistance to spallation, while the steel with high Si and coarse grains showed the best resistance. Spallation was found to initiate in the areas adjoining the oxide ridges formed at the alloy grain boundaries. Oxide scales at the ridges and within the grains were analyzed by scanning electron microscopy (SEM/EDX) and secondary-ion mass spectrometry (SIMS). These analyses suggest depletion of silicon from the areas adjoining grain boundaries, resulting in thicker scaling that triggers spallation in such areas. For similar grain-size materials, the necessary thickness for spallation was attained earlier with low-Si steel rather than in high-Si steel.
Materials Science and Engineering: A, 2006
A novel fracture mechanics technique has been employed for the determination of crack growth rate... more A novel fracture mechanics technique has been employed for the determination of crack growth rate and threshold stress intensity factor (K Iscc) for stress corrosion cracking (SCC) using small circumferential notch tensile (CNT) specimens. The technique was applied successfully for testing SCC susceptibility of spheroidal graphite (SG) cast iron in 5 M NaOH at 100 and 120 • C. Crack growth rate of SG cast iron in 5 M NaOH solution at 100 and 120 • C has been determined at different stress intensity factors (K I), and the K Iscc have been determined to be 11.2 and 9 MPa m 1/2 , respectively. The surfaces of fractured specimens have been examined by scanning electron microscopy (SEM) in order to establish intergranular propagation of stress corrosion cracks. CNT testing is a simple, relatively fast and cost-advantageous approach for generating crack growth rate and K Iscc data.
AIP Conference Proceedings, 2010
This paper presents the characterization results of nanocrystalline Zinc Oxide with different cry... more This paper presents the characterization results of nanocrystalline Zinc Oxide with different crystallite sizes prepared by mechanochemical synthesis. Nano ZnO particles of different crystallite size were synthesized by high energy milling of precursor powders for various periods of time. Diluents were added to the precursor powders to reduce the agglomeration of product phase and to avoid the spontaneous reaction of precursor powders. After the milling process, diluents were selectively leached out using distilled water. X-ray Diffraction data was used to analyze the crystallite size of the nanoparticles and also to analyze the progress of the chemical reaction during milling process. Crystallite sizes were calculated from the XRD peak broadening using the Sherrer's formula. Crystallite sizes were seen to increase at a faster rate after 5h of milling where as bellow 5h of milling, little increase was observed. This increase in crystallite size at higher milling time could be attributed to cold welding and solid state diffusion of the nano particles as a result of high energy impacts from ball to powder collision. Scanning Electron Microscope was employed to analyze the particle morphology and size distribution of the nano ZnO powders. Ultraviolet -Visible (Uv-Vis) spectroscope was employed to analyze the optical absorption of the ZnO nano particles.