Hard facing with Nickel/cobalt based alloys for steel substrates are widely used for high temperature and pressure applications in chemically reactive environments due to their good corrosion and wear resistance prope...Hard facing with Nickel/cobalt based alloys for steel substrates are widely used for high temperature and pressure applications in chemically reactive environments due to their good corrosion and wear resistance properties. In the present research, the ceramic material, i.e., zirconium, is coated on a hypoeutectic cast iron substrate to improve its corrosion and wear resistance. The substrate was coated with zirconium by sol-gel process as well as by the plasma spray process for comparison purpose. Results of the research indicated that the successful deposition of zirconium on the cast iron substrate by sol-gel deposition technique had improved both corrosion and wear resistance of cast iron. SEM analysis revealed that the coating was denser without any internal cracks indicating the soundness of deposition. Also, sol-gel process of coating indicated better wear resistance as compared with plasma spray coated cast iron. Thus, zirconium coating on the substrate has made cast iron sound (without any surface defects) along with excellent corrosion and wear resistance properties. This has made cast iron suitable for structural and automotive applications.展开更多
Carbon microspheres were firstly prepared using glucose （C6H12O6 ） as the starting materials by hydrotherreal carbonization. Then hollow ZrB2 spheres were successfully synthesized using zirconium oxychloride （ ZrCl...Carbon microspheres were firstly prepared using glucose （C6H12O6 ） as the starting materials by hydrotherreal carbonization. Then hollow ZrB2 spheres were successfully synthesized using zirconium oxychloride （ ZrClO2 · 8H2O）, boric acid （ H3BO3 ） by a combined solgel and boro/carbothermal reduction method, and the prepared carbon microspheres as the template. The effects of the reaction temperatures （1 200, 1 300, 1 400 and 1 500 ℃, respectively） and contents of carbon microspheres （ n （ C ） ： n （ ZrO2 ＋ B2O3） is 5. 0, 5. 5, 6. 0 and 6. 5, respectively） on the synthesis of hollow ZrB2 spheres were studied. The prepared carbon microspheres have smooth sugrace and good hollow structure by hydrothermal nitridation. Increase of reaction temperature and excessive carbon microspheres can greatly promote the formation of hollow ZrB2 spheres. The optimized reaction temperature and molar ratio of n （C）/ n （ ZrO2 ＋ B2O3 ） were 1 500 ℃ and 6.5, respectively.展开更多
Extensive research on environmentally complaint sol-gel coatings is currently underway for a wide range of applications. Sol-gel technology combines the synergistic properties of inorganic and organic components to de...Extensive research on environmentally complaint sol-gel coatings is currently underway for a wide range of applications. Sol-gel technology combines the synergistic properties of inorganic and organic components to design nanostructured coating materials with advanced physical properties. Through a judicious choice of precursors and additives improved performances, such as chemical resistance or pH stability, it can be achieved. This is of particular interest for copper rich AA 2024-T3 aluminium alloys used on aircraft, where increase in local pH occurs at corrosion sites. This work focuses on improving the alkaline stability and anticorrosion properties of such a sol-gel coatings on AA2024-T3 by incorporating aluminium functionality into hybrid materials prepared from hydrolysis and condensation of 3-methacryloxypropyltrimethoxysilane, zirconium n-propoxide and zirconium/alkoxide precursors. Dynamic light scattering technique was used to study the particle size nature of the sol-gel materials in colloidal form. X-ray photoelectron spectroscopy was used to study the oxidation state of the aluminium and zirconium at the sol-gel coating surface. Field emission scanning electrochemical microscopy coupled with energy dispersive spectroscopy was used to assess the microstructural features. Electrochemical characterisations employing potentiodynamic scanning and electrochemical impedance spectroscopy were performed to investigate the anticorrosion performance of the hybrid sol-gel coatings. The best anti-corrosive protection of AA2024-T3 in an alkaline saline solution (pH = 10) was achieved with materials containing 10 mol% and 15 mol% aluminium doped sol-gel coatings. This study shows that presence of aluminium has a positive effect on alkaline stability of the coatings and is a potential green candidate for the protective coatings on aerospace alloys.展开更多
文摘Hard facing with Nickel/cobalt based alloys for steel substrates are widely used for high temperature and pressure applications in chemically reactive environments due to their good corrosion and wear resistance properties. In the present research, the ceramic material, i.e., zirconium, is coated on a hypoeutectic cast iron substrate to improve its corrosion and wear resistance. The substrate was coated with zirconium by sol-gel process as well as by the plasma spray process for comparison purpose. Results of the research indicated that the successful deposition of zirconium on the cast iron substrate by sol-gel deposition technique had improved both corrosion and wear resistance of cast iron. SEM analysis revealed that the coating was denser without any internal cracks indicating the soundness of deposition. Also, sol-gel process of coating indicated better wear resistance as compared with plasma spray coated cast iron. Thus, zirconium coating on the substrate has made cast iron sound (without any surface defects) along with excellent corrosion and wear resistance properties. This has made cast iron suitable for structural and automotive applications.
基金financially supported by National Natural Science Foundation of China(General program,51272188,51472184,51472185)State Basic Research Development Program of China(973 Program,2014CB660802)+1 种基金Natural Science Foundation of Hubei Province,China(Contract No.2013CFA086)Foreign cooperation projects in Science and Technology of Hubei Province,China(Contract No.2013BHE002)
文摘Carbon microspheres were firstly prepared using glucose （C6H12O6 ） as the starting materials by hydrotherreal carbonization. Then hollow ZrB2 spheres were successfully synthesized using zirconium oxychloride （ ZrClO2 · 8H2O）, boric acid （ H3BO3 ） by a combined solgel and boro/carbothermal reduction method, and the prepared carbon microspheres as the template. The effects of the reaction temperatures （1 200, 1 300, 1 400 and 1 500 ℃, respectively） and contents of carbon microspheres （ n （ C ） ： n （ ZrO2 ＋ B2O3） is 5. 0, 5. 5, 6. 0 and 6. 5, respectively） on the synthesis of hollow ZrB2 spheres were studied. The prepared carbon microspheres have smooth sugrace and good hollow structure by hydrothermal nitridation. Increase of reaction temperature and excessive carbon microspheres can greatly promote the formation of hollow ZrB2 spheres. The optimized reaction temperature and molar ratio of n （C）/ n （ ZrO2 ＋ B2O3 ） were 1 500 ℃ and 6.5, respectively.
文摘Extensive research on environmentally complaint sol-gel coatings is currently underway for a wide range of applications. Sol-gel technology combines the synergistic properties of inorganic and organic components to design nanostructured coating materials with advanced physical properties. Through a judicious choice of precursors and additives improved performances, such as chemical resistance or pH stability, it can be achieved. This is of particular interest for copper rich AA 2024-T3 aluminium alloys used on aircraft, where increase in local pH occurs at corrosion sites. This work focuses on improving the alkaline stability and anticorrosion properties of such a sol-gel coatings on AA2024-T3 by incorporating aluminium functionality into hybrid materials prepared from hydrolysis and condensation of 3-methacryloxypropyltrimethoxysilane, zirconium n-propoxide and zirconium/alkoxide precursors. Dynamic light scattering technique was used to study the particle size nature of the sol-gel materials in colloidal form. X-ray photoelectron spectroscopy was used to study the oxidation state of the aluminium and zirconium at the sol-gel coating surface. Field emission scanning electrochemical microscopy coupled with energy dispersive spectroscopy was used to assess the microstructural features. Electrochemical characterisations employing potentiodynamic scanning and electrochemical impedance spectroscopy were performed to investigate the anticorrosion performance of the hybrid sol-gel coatings. The best anti-corrosive protection of AA2024-T3 in an alkaline saline solution (pH = 10) was achieved with materials containing 10 mol% and 15 mol% aluminium doped sol-gel coatings. This study shows that presence of aluminium has a positive effect on alkaline stability of the coatings and is a potential green candidate for the protective coatings on aerospace alloys.
