Alumina coating was formed on AA7075 aluminum alloy by micro arc oxidation（MAO） method and its corrosion and stress corrosion cracking（SCC） behaviors were examined in 3.5%（mass fraction） NaCl solution.Electroche...Alumina coating was formed on AA7075 aluminum alloy by micro arc oxidation（MAO） method and its corrosion and stress corrosion cracking（SCC） behaviors were examined in 3.5%（mass fraction） NaCl solution.Electrochemical impedance spectroscopy（EIS） was used to evaluate the degradation of the coating as a function of immersion time and was modeled with appropriate equivalent circuits.Constant load stress corrosion cracking（SCC） results followed by post-test metallographic observations demonstrated the usefulness of MAO coating to avoid the premature failure of the alloy due to severe localized corrosion initiated by Cu-and Fe-rich intermetallic phases.展开更多
Maraging steels have excellent combination of strength and toughness and are extensively used for a variety of aerospace applications. In one such critical application, this steel was used to fabricate shear screws of...Maraging steels have excellent combination of strength and toughness and are extensively used for a variety of aerospace applications. In one such critical application, this steel was used to fabricate shear screws of a stage separation system in a satellite launch vehicle. During assembly preparations, one of the shear screws which connected the separation band and band end block has failed at the first thread. Microstructural analysis revealed that the crack originated from the root of the thread and propagated in an intergranular mode. The failure is attributed to combined effect of stress and corrosion leading to stress corrosion cracking.展开更多
A series of five chalcone derivatives with different substituents in para and meta posions have been synthesized, and single crystals were successfully grown in aceton solution by slow evaporation solution growth tech...A series of five chalcone derivatives with different substituents in para and meta posions have been synthesized, and single crystals were successfully grown in aceton solution by slow evaporation solution growth technique (SESGT). Single crystal X-ray studies revealed that all the crystals crystallized in noncentrosymmetric space group with their molecular dipoles perfectly aligned in a direction-favorable for large nonlinear optical effects. Kurtz powder tests revealed that all five materials have second-harmonic-generating properties with maximum efficiencies of approximately 14 times that of urea standard. UV-vis-NIR spectroscopy and thermogravimetric analyses are also presented for all of the reported materials. Among the five chalcones, high quality single crystals of 4-Methoxy-4'-chlorochalcone were grown by SESGT, and its crystalline perection were studied by using a high resolution X-ray diffractometry (HRXRD).展开更多
Single crystals of the NLO material L-Prolinium tartrate (LPT) have been grown in the presence and absence of picric acid, by slow evaporation technique. Good quality crystals were harvested within 30 days. The grown ...Single crystals of the NLO material L-Prolinium tartrate (LPT) have been grown in the presence and absence of picric acid, by slow evaporation technique. Good quality crystals were harvested within 30 days. The grown crystals were characterized by single crystal X-ray diffraction. The quality of the crystals grown in the presence and absence of picric acid was examined by high resolution X-ray diffractometry (HRXRD). Fourier transform infrared spectroscopy (FTIR) and Fourier transform Raman spectroscopy were used to confirm the presence of the functional groups of L-Prolinium tartrate and the absence of picric acid in the crystals. The thermal stability and the trend of decomposition of the grown crystals were analyzed by thermo gravimetric analysis (TGA). The influence of picric acid on the second harmonic generation efficiency was studied by Kurtz and Perry method. It was observed that the SHG efficiency increased by about 2.3 times compared to that of normal LPT crystals. The results are discussed in detail.展开更多
In present investigation,samples from wastewaters of electroplating industry were collected and analyzed for the concentration of Cu heavy metal.For the synthesis of copper nanoparticles,Pseudomonas stutzeri bacterial...In present investigation,samples from wastewaters of electroplating industry were collected and analyzed for the concentration of Cu heavy metal.For the synthesis of copper nanoparticles,Pseudomonas stutzeri bacterial strain was used.The bacterial strain was isolated from soil and found that it produced 50-150 nm sized cubical copper nanoparticles from electroplating waste water.The nanoparticles have been characterized by UV-visible Spectrophotometer,X-ray diffraction,Scanning Electron Microscopy and Energy Dispersive X-ray Analysis.展开更多
文摘Alumina coating was formed on AA7075 aluminum alloy by micro arc oxidation（MAO） method and its corrosion and stress corrosion cracking（SCC） behaviors were examined in 3.5%（mass fraction） NaCl solution.Electrochemical impedance spectroscopy（EIS） was used to evaluate the degradation of the coating as a function of immersion time and was modeled with appropriate equivalent circuits.Constant load stress corrosion cracking（SCC） results followed by post-test metallographic observations demonstrated the usefulness of MAO coating to avoid the premature failure of the alloy due to severe localized corrosion initiated by Cu-and Fe-rich intermetallic phases.
文摘Maraging steels have excellent combination of strength and toughness and are extensively used for a variety of aerospace applications. In one such critical application, this steel was used to fabricate shear screws of a stage separation system in a satellite launch vehicle. During assembly preparations, one of the shear screws which connected the separation band and band end block has failed at the first thread. Microstructural analysis revealed that the crack originated from the root of the thread and propagated in an intergranular mode. The failure is attributed to combined effect of stress and corrosion leading to stress corrosion cracking.
文摘A series of five chalcone derivatives with different substituents in para and meta posions have been synthesized, and single crystals were successfully grown in aceton solution by slow evaporation solution growth technique (SESGT). Single crystal X-ray studies revealed that all the crystals crystallized in noncentrosymmetric space group with their molecular dipoles perfectly aligned in a direction-favorable for large nonlinear optical effects. Kurtz powder tests revealed that all five materials have second-harmonic-generating properties with maximum efficiencies of approximately 14 times that of urea standard. UV-vis-NIR spectroscopy and thermogravimetric analyses are also presented for all of the reported materials. Among the five chalcones, high quality single crystals of 4-Methoxy-4'-chlorochalcone were grown by SESGT, and its crystalline perection were studied by using a high resolution X-ray diffractometry (HRXRD).
文摘Single crystals of the NLO material L-Prolinium tartrate (LPT) have been grown in the presence and absence of picric acid, by slow evaporation technique. Good quality crystals were harvested within 30 days. The grown crystals were characterized by single crystal X-ray diffraction. The quality of the crystals grown in the presence and absence of picric acid was examined by high resolution X-ray diffractometry (HRXRD). Fourier transform infrared spectroscopy (FTIR) and Fourier transform Raman spectroscopy were used to confirm the presence of the functional groups of L-Prolinium tartrate and the absence of picric acid in the crystals. The thermal stability and the trend of decomposition of the grown crystals were analyzed by thermo gravimetric analysis (TGA). The influence of picric acid on the second harmonic generation efficiency was studied by Kurtz and Perry method. It was observed that the SHG efficiency increased by about 2.3 times compared to that of normal LPT crystals. The results are discussed in detail.
基金the financial support given to this research from the Department of Science&Technology,New Delhi under the NSTI(SR/S5/NM-22/2006)Scheme.
文摘In present investigation,samples from wastewaters of electroplating industry were collected and analyzed for the concentration of Cu heavy metal.For the synthesis of copper nanoparticles,Pseudomonas stutzeri bacterial strain was used.The bacterial strain was isolated from soil and found that it produced 50-150 nm sized cubical copper nanoparticles from electroplating waste water.The nanoparticles have been characterized by UV-visible Spectrophotometer,X-ray diffraction,Scanning Electron Microscopy and Energy Dispersive X-ray Analysis.
