In practical applications,noble metal doping is often used to prepare high performance gas sensors,but more noble metal doping will lead to higher preparation costs.In this study,CeO_(2)/ZnO-Pd with low palladium cont...In practical applications,noble metal doping is often used to prepare high performance gas sensors,but more noble metal doping will lead to higher preparation costs.In this study,CeO_(2)/ZnO-Pd with low palladium content was prepared by ultrasonic method with fast response and high selectivity for acetone sensing.With the same amount of palladium added,the selectivity coefficient of CeO_(2)/ZnO-Pd is 1.88 times higher than that of the stirred sensor.Compared with the pure PdO-doped CeO_(2)/ZnO-PdO material,the content of Pd in CeO_(2)/ZnO-PdO is about 30%of that in CeO_(2)/ZnO-PdO,but the selectivity coefficient for acetone is 2.56 times higher.The CeO_(2)/ZnO-Pd sensor has a higher response(22.54)to 50×10^(−6) acetone at 300℃and the selectivity coefficient is 2.57 times that of the CeO_(2)/ZnO sensor.The sensor has a sub-second response time(0.6 s)and still has a 2.36 response to 330×10^(−9) of acetone.Ultrasonic doping makes Pd particles smaller and increases the contact area with gas.Meanwhile,the composition of n-p-n heterojunction and the synergistic effect of Pd/PdO improve the sensor performance.It shows that ultrasonic Pd doping provides a way to improve the utilization rate of doped metals and prepare highly selective gas sensors.展开更多
Nickel ferrite nano-powders were prepared by microwave radiating low-temperature solid-state reaction method, and then modified with Ag by dipping method. The crystal structure and morphology of the samples were chara...Nickel ferrite nano-powders were prepared by microwave radiating low-temperature solid-state reaction method, and then modified with Ag by dipping method. The crystal structure and morphology of the samples were characterized by means of X-ray diffraction（XRD）, scanning electron microscopy （SEM） and X-ray photoelectron spectroscopy （XPS）. The gas sensing properties of the samples were also investigated. The results reveal that the Ag, as amorphous structure, can efficiently prevent the reuniting and growing-up of nanosized NiFe2O4 grains, and 1.5% Ag modified NiFe2O4 sensor has a better sensitivity, up to 43, for acetone gas than 1.5%Ag mixed NiFe2O4 sensor prepared by low-temperature solid-state reaction, at an optimal working voltage of 4.5 V. The quick response time （1 s） and fast recovery time （～10 s） are the main characteristics of this sensor.展开更多
Numerical simulation based on phase field method was developed to describe the solidification of two-dimensional isothermal binary alloys. The evolution of the interface morphology was shown and the effects of phase f...Numerical simulation based on phase field method was developed to describe the solidification of two-dimensional isothermal binary alloys. The evolution of the interface morphology was shown and the effects of phase field parameters were formulated for succinonitrile-acetone alloy. The results indicate that an anti-trapping current(ATC) can suppress many trapped molten packets, which is caused by the thickened interface. With increasing the anisotropy value from 0 to 0.05, a small circular seed grows to develope secondary dendritic, dendritic tip velocity increases monotonically, and the solute accumulation of solid/liquid interface is diminished distinctly. Furthermore, with the increase of the coupling parameter value, the interface becomes unstable and the side branches of crystals appear and grow gradually.展开更多
基金Project(2023JJ10005)supported by the Natural Science Foundation of Hunan Province,ChinaProjects(51772082,51804106)supported by the National Natural Science Foundation of China。
文摘In practical applications,noble metal doping is often used to prepare high performance gas sensors,but more noble metal doping will lead to higher preparation costs.In this study,CeO_(2)/ZnO-Pd with low palladium content was prepared by ultrasonic method with fast response and high selectivity for acetone sensing.With the same amount of palladium added,the selectivity coefficient of CeO_(2)/ZnO-Pd is 1.88 times higher than that of the stirred sensor.Compared with the pure PdO-doped CeO_(2)/ZnO-PdO material,the content of Pd in CeO_(2)/ZnO-PdO is about 30%of that in CeO_(2)/ZnO-PdO,but the selectivity coefficient for acetone is 2.56 times higher.The CeO_(2)/ZnO-Pd sensor has a higher response(22.54)to 50×10^(−6) acetone at 300℃and the selectivity coefficient is 2.57 times that of the CeO_(2)/ZnO sensor.The sensor has a sub-second response time(0.6 s)and still has a 2.36 response to 330×10^(−9) of acetone.Ultrasonic doping makes Pd particles smaller and increases the contact area with gas.Meanwhile,the composition of n-p-n heterojunction and the synergistic effect of Pd/PdO improve the sensor performance.It shows that ultrasonic Pd doping provides a way to improve the utilization rate of doped metals and prepare highly selective gas sensors.
基金Project (2006BS04035) supported by the Youth Scientific Research Foundation of Shandong Province, China
文摘Nickel ferrite nano-powders were prepared by microwave radiating low-temperature solid-state reaction method, and then modified with Ag by dipping method. The crystal structure and morphology of the samples were characterized by means of X-ray diffraction（XRD）, scanning electron microscopy （SEM） and X-ray photoelectron spectroscopy （XPS）. The gas sensing properties of the samples were also investigated. The results reveal that the Ag, as amorphous structure, can efficiently prevent the reuniting and growing-up of nanosized NiFe2O4 grains, and 1.5% Ag modified NiFe2O4 sensor has a better sensitivity, up to 43, for acetone gas than 1.5%Ag mixed NiFe2O4 sensor prepared by low-temperature solid-state reaction, at an optimal working voltage of 4.5 V. The quick response time （1 s） and fast recovery time （～10 s） are the main characteristics of this sensor.
基金Projects(50331040 60171034) supported by the National Natural Science Foundation of China
文摘Numerical simulation based on phase field method was developed to describe the solidification of two-dimensional isothermal binary alloys. The evolution of the interface morphology was shown and the effects of phase field parameters were formulated for succinonitrile-acetone alloy. The results indicate that an anti-trapping current(ATC) can suppress many trapped molten packets, which is caused by the thickened interface. With increasing the anisotropy value from 0 to 0.05, a small circular seed grows to develope secondary dendritic, dendritic tip velocity increases monotonically, and the solute accumulation of solid/liquid interface is diminished distinctly. Furthermore, with the increase of the coupling parameter value, the interface becomes unstable and the side branches of crystals appear and grow gradually.
