The molybdenum powders with average particle size of 3 μm were coated with copper by electroless plating. The influence of pretreatment, solution composition and plating conditions on electroless copper plating was s...The molybdenum powders with average particle size of 3 μm were coated with copper by electroless plating. The influence of pretreatment, solution composition and plating conditions on electroless copper plating was studied. The copper-coated molybdenum powders were examined by SEM and XRD. Results indicate that a series of optimization methods is used to add activated sites before electroless copper plating. Taking TEA and EDTA as chief and assistant complex agents respectively, 2,2＇-bipyridyl and PEG as double stabilizers, the Mo powders are coated with copper successfully with little Cu20 contained, at the same time, Mo-Cu composite powders with copper content of 15 - 85 wt% can be obtained. The optimal values of pH, temperature and HCHO concentration are 12 -13, 60 -65 ℃ and 22 -26 mL/L, respectively.展开更多
A comparative study of amorphous electroless Ni-W-P coatings on mild steel substrate treated by a high power diode laser and furnace annealing was presented.Effects of different laser operating parameters and furnace-...A comparative study of amorphous electroless Ni-W-P coatings on mild steel substrate treated by a high power diode laser and furnace annealing was presented.Effects of different laser operating parameters and furnace-annealing conditions on microstructures,in terms of crystallisation,pores formation and grain growth,were investigated using SEM/EDX and XRD. Corrosion behaviours of these coatings before and after various treatments were evaluated with anodic polarisation in 0.5 mol/L H2SO4 solution.The results show that the furnace-annealing produces either a mixture of nanocrystallined Ni and amorphous phases or precipitated Ni3P phase distributed in nanocrystallined Ni-based matrix,depending on annealing temperatures,whilst the laser treatment under the operating conditions only produces nanocrystallined Ni-based matrix with Ni3P precipitates.Corrosion performance of the coatings treated by both the laser and the furnace-annealing is dependent on the annealing temperature and laser operating conditions.Corrosion mechanisms of various treated-coatings were discussed in the consideration of phase constitutes and proportion,grain sizes of both Ni and Ni3P phases,pores formation and residual stresses.展开更多
Fe/Si3N4 composite powder was synthesized by the heterogeneous precipitation-thermal reduction process,and then pressed into flakes under a pressure of 10 MPa.Flakes were sintered by pressureless and hot-pressing at 1...Fe/Si3N4 composite powder was synthesized by the heterogeneous precipitation-thermal reduction process,and then pressed into flakes under a pressure of 10 MPa.Flakes were sintered by pressureless and hot-pressing at 1 600℃under 0.1 MPa N2. The chemical composition,phases and microstructure of composite powder and sintered flakes were investigated by energy dispersive spectroscopy(EDS),X-ray diffraction(XRD),scanning electron microscopy(SEM)and transmission electron microscopy (TEM).The results show that the structure of composite powders is Si3N4 coated by nano Fe.The crystal phases of sintered flakes by pressureless are Fe(Si)compound,SiC and Si3N4.The crystal phases of the sintered samples by hot-pressing are Fe,Fe(Si) compound and Si3N4.It is found that crystal phases flakes obtained by pressureless and hot-pressing are very different.展开更多
基金Sponsored by the National Natural Science Founation of China(Grant No.50301017)
文摘The molybdenum powders with average particle size of 3 μm were coated with copper by electroless plating. The influence of pretreatment, solution composition and plating conditions on electroless copper plating was studied. The copper-coated molybdenum powders were examined by SEM and XRD. Results indicate that a series of optimization methods is used to add activated sites before electroless copper plating. Taking TEA and EDTA as chief and assistant complex agents respectively, 2,2＇-bipyridyl and PEG as double stabilizers, the Mo powders are coated with copper successfully with little Cu20 contained, at the same time, Mo-Cu composite powders with copper content of 15 - 85 wt% can be obtained. The optimal values of pH, temperature and HCHO concentration are 12 -13, 60 -65 ℃ and 22 -26 mL/L, respectively.
基金Project(Y2006F40) supported by the Natural Science Foundation of Shandong Province, ChinaProject(N00003) supported by UK Northwest Science Council through Northwest Laser Engineering Consortium (NWLEC)
文摘A comparative study of amorphous electroless Ni-W-P coatings on mild steel substrate treated by a high power diode laser and furnace annealing was presented.Effects of different laser operating parameters and furnace-annealing conditions on microstructures,in terms of crystallisation,pores formation and grain growth,were investigated using SEM/EDX and XRD. Corrosion behaviours of these coatings before and after various treatments were evaluated with anodic polarisation in 0.5 mol/L H2SO4 solution.The results show that the furnace-annealing produces either a mixture of nanocrystallined Ni and amorphous phases or precipitated Ni3P phase distributed in nanocrystallined Ni-based matrix,depending on annealing temperatures,whilst the laser treatment under the operating conditions only produces nanocrystallined Ni-based matrix with Ni3P precipitates.Corrosion performance of the coatings treated by both the laser and the furnace-annealing is dependent on the annealing temperature and laser operating conditions.Corrosion mechanisms of various treated-coatings were discussed in the consideration of phase constitutes and proportion,grain sizes of both Ni and Ni3P phases,pores formation and residual stresses.
基金Project(50804016)supported by the National Natural Science Foundation of China
文摘Fe/Si3N4 composite powder was synthesized by the heterogeneous precipitation-thermal reduction process,and then pressed into flakes under a pressure of 10 MPa.Flakes were sintered by pressureless and hot-pressing at 1 600℃under 0.1 MPa N2. The chemical composition,phases and microstructure of composite powder and sintered flakes were investigated by energy dispersive spectroscopy(EDS),X-ray diffraction(XRD),scanning electron microscopy(SEM)and transmission electron microscopy (TEM).The results show that the structure of composite powders is Si3N4 coated by nano Fe.The crystal phases of sintered flakes by pressureless are Fe(Si)compound,SiC and Si3N4.The crystal phases of the sintered samples by hot-pressing are Fe,Fe(Si) compound and Si3N4.It is found that crystal phases flakes obtained by pressureless and hot-pressing are very different.
