The catalytic activity of amorphous Ni_63 Zr_32 La_5 ribbon for hydrogenation of ethyne to ethylene can be greatly enhanced when the alloy ribbon is pretreated with dilute acid solution,heated under negative atmospher...The catalytic activity of amorphous Ni_63 Zr_32 La_5 ribbon for hydrogenation of ethyne to ethylene can be greatly enhanced when the alloy ribbon is pretreated with dilute acid solution,heated under negative atmosphere pressure and subjected to hydrogen reduction successively. The change of surface state of the ribbon during the activation has been analysed by AES and XPS. The surface of as-received ribbon is covered with a thin film of La_2 O_3. After pretreatment. the surface concentrations of both Ni and Zr increase obviously, whereas the surface concentration of La decreases markedly.Finally, on the surface of activated catalyst the Ni and NiO disperse finely on the matrix consisting of oxides of both Zr and La and a small amount of fluorides of Zr and La.展开更多
With the rapid development of modern industries,the high-temperature piezoelectric sensors that can work in extreme environments are in great demand.In this work,langasite(La_(3)Ga_(5)SiO_(14),LGS),as a high-temperatu...With the rapid development of modern industries,the high-temperature piezoelectric sensors that can work in extreme environments are in great demand.In this work,langasite(La_(3)Ga_(5)SiO_(14),LGS),as a high-temperature piezoelectric crystal with stable electro-elastic performance,is used as core element,and air and porous Al_(2)O_(3) are selected as backing layers respectively to prepare two kinds of high-temperature acoustic emission(AE)sensors.The detection sensitivities at 25–500℃ are analyzed by the ball falling test and Hsu–Nielsen experiment.Under the condition of 25–500℃,the received amplitude signals by both sensors are maintained above 90 dB stimulated by the ZrO_(2) ceramic ball dropping.In the Hsu–Nielsen experiment,as the temperature rising from 25℃ to 500℃,the signal amplitude of sensor with air backing layer decays from 447 mV to 365 mV,while the signal amplitude varies from 270 mV to 203 mV for the sensor with porous Al_(2)O_(3) backing layer.Signiffcantly,compared with the bandwidth of the air-backing sensor(37–183 kHz),the sensor with porous Al_(2)O_(3) backing layer broadens bandwidth to 28–273 kHz.These results show that both these AE sensors have strong and stable response ability to AE signals at high-temperature of 500℃.Therefore,piezoelectric AE sensor based on LGS has great potential application in the ffeld of high-temperature structural health monitoring.展开更多
A novel non-contact optical thermometer,qualified with high sensitivity and temperature resolution,is urgently needed for temperature measuring of micro devices,moving objects and specific severe environments.Hence,a ...A novel non-contact optical thermometer,qualified with high sensitivity and temperature resolution,is urgently needed for temperature measuring of micro devices,moving objects and specific severe environments.Hence,a series of dual-emitting La_(5)Si_(2)BO_(13):Ce^(3+),Eu^(2+)phosphors were synthesized.The two ions show diverse responses with the changing in temperature.The variational emissions of Ce^(3+)and Eu^(2+)can be converted to FIR(fluorescence intensity ratio)signals.The maximal absolute sensitivity Sa and relative sensitivity Sr reach up to 0.07526%/K and 3.2241%/K,respectively.It is worthy noting that the Sa and Sr possess the same variation tendency and both have high values in the low temperature region(293-373 K),showing the great temperature measuring property especially in low temperature region.The temperature sensing characteristics are superior to the results of most previous reports.The energy transfer(ET)process is certified to occur from Ce^(3+)to Eu^(2+)ions.These studies indicate that La_(5)Si_(2)BO_(13):Ce^(3+),Eu^(2+)phosphor could have a good prospect for optical thermometry.展开更多
文摘The catalytic activity of amorphous Ni_63 Zr_32 La_5 ribbon for hydrogenation of ethyne to ethylene can be greatly enhanced when the alloy ribbon is pretreated with dilute acid solution,heated under negative atmosphere pressure and subjected to hydrogen reduction successively. The change of surface state of the ribbon during the activation has been analysed by AES and XPS. The surface of as-received ribbon is covered with a thin film of La_2 O_3. After pretreatment. the surface concentrations of both Ni and Zr increase obviously, whereas the surface concentration of La decreases markedly.Finally, on the surface of activated catalyst the Ni and NiO disperse finely on the matrix consisting of oxides of both Zr and La and a small amount of fluorides of Zr and La.
基金supported by the Shandong Provincial Natural Science Foundation(Grant No.ZR2020KA003)the Project of“20 Items of University”of Jinan(Grant No.T202009)+1 种基金Shandong Provincial Key Research and Development Plan(Grant No.2022CXPT045)the Primary Research&Development Plan of Shandong Province(Grant No.2019JZZY010313).
文摘With the rapid development of modern industries,the high-temperature piezoelectric sensors that can work in extreme environments are in great demand.In this work,langasite(La_(3)Ga_(5)SiO_(14),LGS),as a high-temperature piezoelectric crystal with stable electro-elastic performance,is used as core element,and air and porous Al_(2)O_(3) are selected as backing layers respectively to prepare two kinds of high-temperature acoustic emission(AE)sensors.The detection sensitivities at 25–500℃ are analyzed by the ball falling test and Hsu–Nielsen experiment.Under the condition of 25–500℃,the received amplitude signals by both sensors are maintained above 90 dB stimulated by the ZrO_(2) ceramic ball dropping.In the Hsu–Nielsen experiment,as the temperature rising from 25℃ to 500℃,the signal amplitude of sensor with air backing layer decays from 447 mV to 365 mV,while the signal amplitude varies from 270 mV to 203 mV for the sensor with porous Al_(2)O_(3) backing layer.Signiffcantly,compared with the bandwidth of the air-backing sensor(37–183 kHz),the sensor with porous Al_(2)O_(3) backing layer broadens bandwidth to 28–273 kHz.These results show that both these AE sensors have strong and stable response ability to AE signals at high-temperature of 500℃.Therefore,piezoelectric AE sensor based on LGS has great potential application in the ffeld of high-temperature structural health monitoring.
基金Project supported by Natural Science Foundation of Zhejiang Province,China(LY19E020005)Science and Technology Innovation Platform and Talent Plan of Zhejiang(2017R52037)。
文摘A novel non-contact optical thermometer,qualified with high sensitivity and temperature resolution,is urgently needed for temperature measuring of micro devices,moving objects and specific severe environments.Hence,a series of dual-emitting La_(5)Si_(2)BO_(13):Ce^(3+),Eu^(2+)phosphors were synthesized.The two ions show diverse responses with the changing in temperature.The variational emissions of Ce^(3+)and Eu^(2+)can be converted to FIR(fluorescence intensity ratio)signals.The maximal absolute sensitivity Sa and relative sensitivity Sr reach up to 0.07526%/K and 3.2241%/K,respectively.It is worthy noting that the Sa and Sr possess the same variation tendency and both have high values in the low temperature region(293-373 K),showing the great temperature measuring property especially in low temperature region.The temperature sensing characteristics are superior to the results of most previous reports.The energy transfer(ET)process is certified to occur from Ce^(3+)to Eu^(2+)ions.These studies indicate that La_(5)Si_(2)BO_(13):Ce^(3+),Eu^(2+)phosphor could have a good prospect for optical thermometry.
