Both green and residual bending strength of the dip-coat layer composed of ZrO2 (CaO) powder and colloi-dal zirconiz sol binder are sutdied and the effects of process factrs on the strength of dip-coat layer are inter...Both green and residual bending strength of the dip-coat layer composed of ZrO2 (CaO) powder and colloi-dal zirconiz sol binder are sutdied and the effects of process factrs on the strength of dip-coat layer are interpreted,using the results of TG-DTA ,TMA and SEM analyses of the fracture morphology of the coating layer and following the strength theory for porous body.展开更多
A microporous zirconia membrane with hydrogen permeance about 5 × 10-8mol·m-2·s-1·Pa-1, H2/CO2 permselectivity of ca. 14, and excellent hydrothermal stability under steam pressure of 100 k Pa was f...A microporous zirconia membrane with hydrogen permeance about 5 × 10-8mol·m-2·s-1·Pa-1, H2/CO2 permselectivity of ca. 14, and excellent hydrothermal stability under steam pressure of 100 k Pa was fabricated via polymeric sol–gel process. The effect of calcination temperature on single gas permeance of sol–gel derived zirconia membranes was investigated. Zirconia membranes calcined at 350 °C and 400 °C showed similar single gas permeance, with permselectivities of hydrogen towards other gases, such as oxygen, nitrogen, methane, and sulfur hexa fluoride, around Knudsen values. A much lower CO2permeance（3.7 × 10-9mol·m-2·s-1·Pa-1）was observed due to the interaction between CO2 molecules and pore wall of membrane. Higher calcination temperature, 500 °C, led to the formation of mesoporous structure and, hence, the membrane lost its molecular sieving property towards hydrogen and carbon dioxide. The stability of zirconia membrane in the presence of hot steam was also investigated. Exposed to 100 k Pa steam for 400 h, the membrane performance kept unchanged in comparison with freshly prepared one, with hydrogen and carbon dioxide permeances of 4.7 × 10-8and ~ 3 × 10-9mol·m-2·s-1·Pa-1, respectively. Both H2 and CO2permeances of the zirconia membrane decreased with exposure time to 100 k Pa steam. With a total exposure time of 1250 h, the membrane presented hydrogen permeance of 2.4 × 10-8mol·m-2·s-1·Pa-1and H2/CO2 permselectivity of 28, indicating that the membrane retains its microporous structure.展开更多
Fused salt accelerated hot corrosion is quite common in gas turbines, fossil fuelled devices, waste inclinators, pyrochemical systems, etc. Presence of fused salt on metal surface dissolves their existing oxide layer....Fused salt accelerated hot corrosion is quite common in gas turbines, fossil fuelled devices, waste inclinators, pyrochemical systems, etc. Presence of fused salt on metal surface dissolves their existing oxide layer. This results in an increase in oxidation rate of the metal. Since, zirconia coating is well recognized for corrosion protection under high temperature oxidative environment, we have developed zirconia coating on 9Cr1Mo ferritic steel and their oxidation performance was evaluated in LiCl-NaCl and Na2SO4-K2SO4 salts deposit system in air atmosphere at 650?C and 850?C, respectively. Before coating development, zirconium based sol was synthesized using zirconium (IV) propoxide as a precursor. Oxidation test results indicated that the zirconia coated specimens shows more than two times higher corrosion resistance in LiCl-NaCl and three time higher corrosion resistance in Na2SO4-K2SO4 salt deposit, respectively.展开更多
The influence of solvent and the rate of addition of water on the characteristics of alumina-zirconia powders obtained by sol-gel method were investigated. The Al2O3-ZrO2 powders (1:1 molar ratio) were prepared using ...The influence of solvent and the rate of addition of water on the characteristics of alumina-zirconia powders obtained by sol-gel method were investigated. The Al2O3-ZrO2 powders (1:1 molar ratio) were prepared using aluminum tri-sec-butoxide and zirconium n-propoxide as precursors. Ethanol (EtOH), isopropanol (iPrOH) and isobutanol (iBuOH) were used as solvents. The Al2O3-ZrO2 powders were characterized by nitrogen physisorption (SBET), Fourier transformed infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Prepared oxides calcined at 700℃ showed high specific surface area (200 - 240 m2/g). Obtained results suggest that the homogeneity of the mixed oxides is favored by using a water addition rate of 0.06 and 0.10 mL/min with ethanol as solvent.展开更多
Polycrystalline 3Y-TZP/Al2O3 tetragonal zirconia fiber was obtained by the pyrolysis of gel fibers using zirconium oxychloride octahydrate（ZOC） as the raw material. The spinnable zirconia sol was prepared by electro...Polycrystalline 3Y-TZP/Al2O3 tetragonal zirconia fiber was obtained by the pyrolysis of gel fibers using zirconium oxychloride octahydrate（ZOC） as the raw material. The spinnable zirconia sol was prepared by electrolyzing the zirco-nium oxychloride octahydrate（ZOC） solution in the presence of acetic acid and sugar（ sucrose, glucrose or fructose） , in which the molar ratios of CH3 COOH/ZOC and sugar/ZOC were 1.0-4.0 and 0.2-0.4, respectively. The pre- pared tetragonal zireonia fibers sintered at different temperatures showed smooth and crack-free surfaces with diame, ters of 5-10 μm. The addition of Al2O3 enhanced the sintering process and prevented the crystals from growing. Thermogravimetric analysis（TG）, X-ray diffraction （ XRD ）, Fourier transform infrared spectroscopy（FTIR）, and scanning electron microscope（SEM） techniques were used to characterize the prepared fibers.展开更多
zirconia-based nanostructured coatings were deposited on AA2024 to improve the corrosion resistance properties. Three different nanostructured coatings, namely, zirconia–benzotriazole, zirconia–alumina–benzotriazol...zirconia-based nanostructured coatings were deposited on AA2024 to improve the corrosion resistance properties. Three different nanostructured coatings, namely, zirconia–benzotriazole, zirconia–alumina–benzotriazole, and zirconia–yttria–benzotriazole, were applied on AA2024 via a sol–gel method using the dip-coating technique. Next, the coatings were annealed at 150°C after each dipping period. The phases and morphologies of the coatings were investigated using grazing incidence X-ray diffraction(GIXRD), Fourier transform infrared spectroscopy(FT-IR), field emission scanning electron microscopy(FESEM), and atomic force microscopy(AFM). The corrosion properties were evaluated using electrochemical methods, including polarization and electrochemical impedance techniques in 3.5 wt% NaCl solution. The obtained results confirm the formation of homogeneous and crack free zirconia-benzotriazole-based nanostructured coatings. The average roughness values for zirconia-benzotriazole, zirconia-alumina-benzotriazole, and zirconia-yttria-benzotriazole nanostructured coatings were 30, 8, and 6 nm, respectively. The presence of alumina as a stabilizer on zirconia coating was found to have a beneficial impact on the stability of the corrosion resistance for different immersion times. In fact, the addition of alumina resulted in the dominance of the healing behavior in competition with the corrosion process of zirconia-benzotriazole nanostructured coating.展开更多
文摘Both green and residual bending strength of the dip-coat layer composed of ZrO2 (CaO) powder and colloi-dal zirconiz sol binder are sutdied and the effects of process factrs on the strength of dip-coat layer are interpreted,using the results of TG-DTA ,TMA and SEM analyses of the fracture morphology of the coating layer and following the strength theory for porous body.
基金Supported by the National Natural Science Foundation of China(21276123,21490581)the National High Technology Research and Development Program of China(2012AA03A606)+3 种基金State Key Laboratory of Materials-Oriented Chemical Engineering(ZK201002)the Natural Science Research Plan of Jiangsu Universities(11KJB530006)the "Summit of the Six Top Talents" Program of Jiangsu Provincea Project Funded by the Priority Academic Program development of Jiangsu Higher Education Institutions(PAPD)
文摘A microporous zirconia membrane with hydrogen permeance about 5 × 10-8mol·m-2·s-1·Pa-1, H2/CO2 permselectivity of ca. 14, and excellent hydrothermal stability under steam pressure of 100 k Pa was fabricated via polymeric sol–gel process. The effect of calcination temperature on single gas permeance of sol–gel derived zirconia membranes was investigated. Zirconia membranes calcined at 350 °C and 400 °C showed similar single gas permeance, with permselectivities of hydrogen towards other gases, such as oxygen, nitrogen, methane, and sulfur hexa fluoride, around Knudsen values. A much lower CO2permeance（3.7 × 10-9mol·m-2·s-1·Pa-1）was observed due to the interaction between CO2 molecules and pore wall of membrane. Higher calcination temperature, 500 °C, led to the formation of mesoporous structure and, hence, the membrane lost its molecular sieving property towards hydrogen and carbon dioxide. The stability of zirconia membrane in the presence of hot steam was also investigated. Exposed to 100 k Pa steam for 400 h, the membrane performance kept unchanged in comparison with freshly prepared one, with hydrogen and carbon dioxide permeances of 4.7 × 10-8and ~ 3 × 10-9mol·m-2·s-1·Pa-1, respectively. Both H2 and CO2permeances of the zirconia membrane decreased with exposure time to 100 k Pa steam. With a total exposure time of 1250 h, the membrane presented hydrogen permeance of 2.4 × 10-8mol·m-2·s-1·Pa-1and H2/CO2 permselectivity of 28, indicating that the membrane retains its microporous structure.
文摘Fused salt accelerated hot corrosion is quite common in gas turbines, fossil fuelled devices, waste inclinators, pyrochemical systems, etc. Presence of fused salt on metal surface dissolves their existing oxide layer. This results in an increase in oxidation rate of the metal. Since, zirconia coating is well recognized for corrosion protection under high temperature oxidative environment, we have developed zirconia coating on 9Cr1Mo ferritic steel and their oxidation performance was evaluated in LiCl-NaCl and Na2SO4-K2SO4 salts deposit system in air atmosphere at 650?C and 850?C, respectively. Before coating development, zirconium based sol was synthesized using zirconium (IV) propoxide as a precursor. Oxidation test results indicated that the zirconia coated specimens shows more than two times higher corrosion resistance in LiCl-NaCl and three time higher corrosion resistance in Na2SO4-K2SO4 salt deposit, respectively.
文摘The influence of solvent and the rate of addition of water on the characteristics of alumina-zirconia powders obtained by sol-gel method were investigated. The Al2O3-ZrO2 powders (1:1 molar ratio) were prepared using aluminum tri-sec-butoxide and zirconium n-propoxide as precursors. Ethanol (EtOH), isopropanol (iPrOH) and isobutanol (iBuOH) were used as solvents. The Al2O3-ZrO2 powders were characterized by nitrogen physisorption (SBET), Fourier transformed infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Prepared oxides calcined at 700℃ showed high specific surface area (200 - 240 m2/g). Obtained results suggest that the homogeneity of the mixed oxides is favored by using a water addition rate of 0.06 and 0.10 mL/min with ethanol as solvent.
基金Supported by National High Technology Research and Development Program of China(No.2002AA2040).
文摘Polycrystalline 3Y-TZP/Al2O3 tetragonal zirconia fiber was obtained by the pyrolysis of gel fibers using zirconium oxychloride octahydrate（ZOC） as the raw material. The spinnable zirconia sol was prepared by electrolyzing the zirco-nium oxychloride octahydrate（ZOC） solution in the presence of acetic acid and sugar（ sucrose, glucrose or fructose） , in which the molar ratios of CH3 COOH/ZOC and sugar/ZOC were 1.0-4.0 and 0.2-0.4, respectively. The pre- pared tetragonal zireonia fibers sintered at different temperatures showed smooth and crack-free surfaces with diame, ters of 5-10 μm. The addition of Al2O3 enhanced the sintering process and prevented the crystals from growing. Thermogravimetric analysis（TG）, X-ray diffraction （ XRD ）, Fourier transform infrared spectroscopy（FTIR）, and scanning electron microscope（SEM） techniques were used to characterize the prepared fibers.
文摘zirconia-based nanostructured coatings were deposited on AA2024 to improve the corrosion resistance properties. Three different nanostructured coatings, namely, zirconia–benzotriazole, zirconia–alumina–benzotriazole, and zirconia–yttria–benzotriazole, were applied on AA2024 via a sol–gel method using the dip-coating technique. Next, the coatings were annealed at 150°C after each dipping period. The phases and morphologies of the coatings were investigated using grazing incidence X-ray diffraction(GIXRD), Fourier transform infrared spectroscopy(FT-IR), field emission scanning electron microscopy(FESEM), and atomic force microscopy(AFM). The corrosion properties were evaluated using electrochemical methods, including polarization and electrochemical impedance techniques in 3.5 wt% NaCl solution. The obtained results confirm the formation of homogeneous and crack free zirconia-benzotriazole-based nanostructured coatings. The average roughness values for zirconia-benzotriazole, zirconia-alumina-benzotriazole, and zirconia-yttria-benzotriazole nanostructured coatings were 30, 8, and 6 nm, respectively. The presence of alumina as a stabilizer on zirconia coating was found to have a beneficial impact on the stability of the corrosion resistance for different immersion times. In fact, the addition of alumina resulted in the dominance of the healing behavior in competition with the corrosion process of zirconia-benzotriazole nanostructured coating.
