Plasma electrolytic oxidation(PEO)was applied using a pulsed unipolar waveform to produce Al_(2)O_(3)−TiO_(2) composite coatings from sol electrolytic solutions containing colloidal TiO_(2) nanoparticles.The sol solut...Plasma electrolytic oxidation(PEO)was applied using a pulsed unipolar waveform to produce Al_(2)O_(3)−TiO_(2) composite coatings from sol electrolytic solutions containing colloidal TiO_(2) nanoparticles.The sol solutions were produced by dissolving 1,3,and 5 g/L of potassium titanyl oxalate(PTO)in a silicate solution.Scanning electron microscopy,energy dispersive spectrometry,X-ray diffraction,and Raman spectroscopy were applied to characterizing the coatings.Corrosion behavior of the coatings was investigated using polarization and impedance techniques.The results indicated that TiO_(2) enters the coating through all types of micro-discharging and is doped into the alumina phase.The higher level of TiO_(2) incorporation results in the decrease of surface micro-pores,while the lower incorporation shows a reverse effect.It was revealed that the higher TiO_(2) content makes a more compact outer layer and increases the inner layer thickness of the coating.Electrochemical measurements revealed that the coating obtained from the solution containing 3 g/L PTO exhibits higher corrosion performance than that obtained in the absence of PTO.The coating produced in the absence of PTO consists of γ-Al_(2)O_(3),δ-Al_(2)O_(3) and amorphous phases,while α-Al_(2)O_(3) is promoted by the presence of PTO.展开更多
Yttria-stabilized zirconia(YSZ)fiber composites are highly efficient thermal insulating materials;however,the poor thermal shock resistance limits their versatile applications.In the present study,YSZ fiber was mixed ...Yttria-stabilized zirconia(YSZ)fiber composites are highly efficient thermal insulating materials;however,the poor thermal shock resistance limits their versatile applications.In the present study,YSZ fiber was mixed directly with Al_(2)TiO_(5)fiber,which had an extremely low thermal expansion coefficient,to prepare YSZ–Al_(2)TiO_(5)(ZAT)fiber composites by compression molding and heat treatment.The minimum thermal expansion coefficient of the prepared ZAT fiber composites was measured to be 7.74×10^(−6)K^(−1),which was 26%lower than that of the YSZ fiber composites(10.42×10^(−6)K^(−1)).It was shown that the prepared ZAT fiber composites maintain the integrity after undergoing 51 thermal shock cycles between 1100℃and room temperature.Whereas,YSZ fiber composites burst immediately after only one thermal shock cycle under the same condition.In addition,the ZAT fiber composites also exhibit considerable mechanical and thermal insulating performance.展开更多
文摘Plasma electrolytic oxidation(PEO)was applied using a pulsed unipolar waveform to produce Al_(2)O_(3)−TiO_(2) composite coatings from sol electrolytic solutions containing colloidal TiO_(2) nanoparticles.The sol solutions were produced by dissolving 1,3,and 5 g/L of potassium titanyl oxalate(PTO)in a silicate solution.Scanning electron microscopy,energy dispersive spectrometry,X-ray diffraction,and Raman spectroscopy were applied to characterizing the coatings.Corrosion behavior of the coatings was investigated using polarization and impedance techniques.The results indicated that TiO_(2) enters the coating through all types of micro-discharging and is doped into the alumina phase.The higher level of TiO_(2) incorporation results in the decrease of surface micro-pores,while the lower incorporation shows a reverse effect.It was revealed that the higher TiO_(2) content makes a more compact outer layer and increases the inner layer thickness of the coating.Electrochemical measurements revealed that the coating obtained from the solution containing 3 g/L PTO exhibits higher corrosion performance than that obtained in the absence of PTO.The coating produced in the absence of PTO consists of γ-Al_(2)O_(3),δ-Al_(2)O_(3) and amorphous phases,while α-Al_(2)O_(3) is promoted by the presence of PTO.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51472144)the Shandong University Young Scholars Program(Grant No.2016WLJH27)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.2082019014)Shandong Provincial Natural Science Foundation(Grant No.ZR2020ME023)for financial support.
文摘Yttria-stabilized zirconia(YSZ)fiber composites are highly efficient thermal insulating materials;however,the poor thermal shock resistance limits their versatile applications.In the present study,YSZ fiber was mixed directly with Al_(2)TiO_(5)fiber,which had an extremely low thermal expansion coefficient,to prepare YSZ–Al_(2)TiO_(5)(ZAT)fiber composites by compression molding and heat treatment.The minimum thermal expansion coefficient of the prepared ZAT fiber composites was measured to be 7.74×10^(−6)K^(−1),which was 26%lower than that of the YSZ fiber composites(10.42×10^(−6)K^(−1)).It was shown that the prepared ZAT fiber composites maintain the integrity after undergoing 51 thermal shock cycles between 1100℃and room temperature.Whereas,YSZ fiber composites burst immediately after only one thermal shock cycle under the same condition.In addition,the ZAT fiber composites also exhibit considerable mechanical and thermal insulating performance.
