Y2O3 stabilized ZrO2(YSZ)thermal barrier coatings(TBCs)are prone to hot corrosion by molten salts.In this study,the microstructure of atmospheric plasma spraying YSZ TBCs is modified by laser glazing in order to impro...Y2O3 stabilized ZrO2(YSZ)thermal barrier coatings(TBCs)are prone to hot corrosion by molten salts.In this study,the microstructure of atmospheric plasma spraying YSZ TBCs is modified by laser glazing in order to improve the corrosion resistance.By optimizing the laser parameters,a^18μm smooth glazed layer with some vertical cracks was produced on the coating surfaces.The as-sprayed and modified coatings were both exposed to hot corrosion tests at 700 and 1000℃for 4 h in V2O5 molten salt,and the results revealed that the modified one had improved corrosion resistance.After hot corrosion,the glazed layer kept structural integrity,with little evidence of dissolution.However,the vertical cracks in the glazed layer acted as the paths for molten salt penetration,accelerating the corrosion of the non-modified coating.Further optimization of the glazed layer is needed in the future work.展开更多
CeO_2 stabilized ZrO_2 ultra fine nanoparticles were successfully synthesized via a simple and effective sol-gel synthetic approach by using zirconylchloride octahydrate, cerium nitrate hexahydrate, and citric acid as...CeO_2 stabilized ZrO_2 ultra fine nanoparticles were successfully synthesized via a simple and effective sol-gel synthetic approach by using zirconylchloride octahydrate, cerium nitrate hexahydrate, and citric acid as starting materials. A series of techniques, including X-ray diffraction（XRD）, thermogravimetry（TG）, differential scanning calorimetry（DSC）, Fourier transform infrared spectroscopy（FTIR）, transmission electron microscopy（TEM）, and N_2-sorption analysis, were used to characterize the structure and morphology of the asprepared samples. XRD studies indicate that the as-synthesized sample is of well crystallized tetragonal phase of CeO_2 stabilized ZrO_2 with high purity. TEM images show that the as-synthesized sample is composed of a large number of fine dispersive nanoparticles with an average size about 10 nm. The as-synthesized tetragonal CeO_2 stabilized ZrO_2 sample was heated at different temperatures in order to evaluate its thermal stability. The exprimental results reveal that the as-synthesized tetragonal CeO_2 stabilized ZrO_2 sample exhibits excellent stability without the occurrence of phase transformation.展开更多
The ZrO2 (9mol% Y2O3) coating was prepared evenly on the surface of MgO partially stabilized zirconia (Mg-PSZ) tube (oxygen sensor probe) by dipping the green Mg-PSZ tube in a ZrO2 (9mol% Y2O3) slurry and then co-fir...The ZrO2 (9mol% Y2O3) coating was prepared evenly on the surface of MgO partially stabilized zirconia (Mg-PSZ) tube (oxygen sensor probe) by dipping the green Mg-PSZ tube in a ZrO2 (9mol% Y2O3) slurry and then co-firing at 1750°C for 8 h. The double-cell method was employed to measure the electronic conductivity parameter and exam the reproducibility of the coated Mg- PSZ tube. The experimental results indicate that the good thermal shock resistance of the Mg-PSZ tube can be retained when the coating thickness is not more than 3.4 μm. The ZrO2 (9mol% Y2O3) coating reduces the electronic conductivity parameter remarka- bly, probably due to the lower electronic conductivity of Y2O,-stabilized ZrO2 than that of MgO-stabilized ZrO2. Moreover, the ZrO2 (9mol% Y2O3) coating can improve the reproducibility and accuracy of the Mg-PSZ tube significantly in the low oxygen measure- ment. The smooth surface feature and lower electronic conductivity of the coated Mg-PSZ tube should be responsible for this im- provement.展开更多
A series of CeO2–ZrO2–WO3（CZW）catalysts prepared by a hydrothermal synthesis method showed excellent catalytic activity for selective catalytic reduction（SCR）of NO with NH3 over a wide temperature of 150–550℃....A series of CeO2–ZrO2–WO3（CZW）catalysts prepared by a hydrothermal synthesis method showed excellent catalytic activity for selective catalytic reduction（SCR）of NO with NH3 over a wide temperature of 150–550℃.The effect of hydrothermal treatment of CZW catalysts on SCR activity was investigated in the presence of 10% H2O.The fresh catalyst showed above 90% NOx conversion at 201–459℃,which is applicable to diesel exhaust NOx purification（200–440℃）.The SCR activity results indicated that hydrothermal aging decreased the SCR activity of CZW at low temperatures（below 300℃）,while the activity was notably enhanced at high temperature（above 450℃）.The aged CZW catalyst（hydrothermal aging at 700℃ for 8 hr）showed almost 80% NOx conversion at 229–550℃,while the V2O5–WO3/TiO2 catalyst presented above 80% NOx conversion at 308–370℃.The effect of structural changes,acidity,and redox properties of CZW on the SCR activity was investigated.The results indicated that the excellent hydrothermal stability of CZW was mainly due to the CeO2–ZrO2 solid solution,amorphous WO3 phase and optimal acidity.In addition,the formation of WO3 clusters increased in size as the hydrothermal aging temperature increased,resulting in the collapse of structure,which could further affect the acidity and redox properties.展开更多
基金This research is sponsored by the National Natural Science Foundation of China(Grant No.51971156).
文摘Y2O3 stabilized ZrO2(YSZ)thermal barrier coatings(TBCs)are prone to hot corrosion by molten salts.In this study,the microstructure of atmospheric plasma spraying YSZ TBCs is modified by laser glazing in order to improve the corrosion resistance.By optimizing the laser parameters,a^18μm smooth glazed layer with some vertical cracks was produced on the coating surfaces.The as-sprayed and modified coatings were both exposed to hot corrosion tests at 700 and 1000℃for 4 h in V2O5 molten salt,and the results revealed that the modified one had improved corrosion resistance.After hot corrosion,the glazed layer kept structural integrity,with little evidence of dissolution.However,the vertical cracks in the glazed layer acted as the paths for molten salt penetration,accelerating the corrosion of the non-modified coating.Further optimization of the glazed layer is needed in the future work.
基金Funded by the National Natural Science Foundation of China(Nos.U1304520 and U1404613)the State Key Lab of Materials Synthesis and Processing of Wuhan University of Technology for the fund support(2012-KF-5)+1 种基金the Education Department of Henan Province(2013GGJS-185)the program for New Century Excellent Talents in University(NECT-12-0655)
文摘CeO_2 stabilized ZrO_2 ultra fine nanoparticles were successfully synthesized via a simple and effective sol-gel synthetic approach by using zirconylchloride octahydrate, cerium nitrate hexahydrate, and citric acid as starting materials. A series of techniques, including X-ray diffraction（XRD）, thermogravimetry（TG）, differential scanning calorimetry（DSC）, Fourier transform infrared spectroscopy（FTIR）, transmission electron microscopy（TEM）, and N_2-sorption analysis, were used to characterize the structure and morphology of the asprepared samples. XRD studies indicate that the as-synthesized sample is of well crystallized tetragonal phase of CeO_2 stabilized ZrO_2 with high purity. TEM images show that the as-synthesized sample is composed of a large number of fine dispersive nanoparticles with an average size about 10 nm. The as-synthesized tetragonal CeO_2 stabilized ZrO_2 sample was heated at different temperatures in order to evaluate its thermal stability. The exprimental results reveal that the as-synthesized tetragonal CeO_2 stabilized ZrO_2 sample exhibits excellent stability without the occurrence of phase transformation.
文摘The ZrO2 (9mol% Y2O3) coating was prepared evenly on the surface of MgO partially stabilized zirconia (Mg-PSZ) tube (oxygen sensor probe) by dipping the green Mg-PSZ tube in a ZrO2 (9mol% Y2O3) slurry and then co-firing at 1750°C for 8 h. The double-cell method was employed to measure the electronic conductivity parameter and exam the reproducibility of the coated Mg- PSZ tube. The experimental results indicate that the good thermal shock resistance of the Mg-PSZ tube can be retained when the coating thickness is not more than 3.4 μm. The ZrO2 (9mol% Y2O3) coating reduces the electronic conductivity parameter remarka- bly, probably due to the lower electronic conductivity of Y2O,-stabilized ZrO2 than that of MgO-stabilized ZrO2. Moreover, the ZrO2 (9mol% Y2O3) coating can improve the reproducibility and accuracy of the Mg-PSZ tube significantly in the low oxygen measure- ment. The smooth surface feature and lower electronic conductivity of the coated Mg-PSZ tube should be responsible for this im- provement.
基金supported by the National Natural Science Foundation of China(Nos.U1137603,21307047)the Opening Project of Key Laboratory of Green Catalysis of Sichuan Institutes of High Education(No.LYJ1309)
文摘A series of CeO2–ZrO2–WO3（CZW）catalysts prepared by a hydrothermal synthesis method showed excellent catalytic activity for selective catalytic reduction（SCR）of NO with NH3 over a wide temperature of 150–550℃.The effect of hydrothermal treatment of CZW catalysts on SCR activity was investigated in the presence of 10% H2O.The fresh catalyst showed above 90% NOx conversion at 201–459℃,which is applicable to diesel exhaust NOx purification（200–440℃）.The SCR activity results indicated that hydrothermal aging decreased the SCR activity of CZW at low temperatures（below 300℃）,while the activity was notably enhanced at high temperature（above 450℃）.The aged CZW catalyst（hydrothermal aging at 700℃ for 8 hr）showed almost 80% NOx conversion at 229–550℃,while the V2O5–WO3/TiO2 catalyst presented above 80% NOx conversion at 308–370℃.The effect of structural changes,acidity,and redox properties of CZW on the SCR activity was investigated.The results indicated that the excellent hydrothermal stability of CZW was mainly due to the CeO2–ZrO2 solid solution,amorphous WO3 phase and optimal acidity.In addition,the formation of WO3 clusters increased in size as the hydrothermal aging temperature increased,resulting in the collapse of structure,which could further affect the acidity and redox properties.
