ZnO films on R-sapphire substrates are prepared and characterized by x-ray diffraction and scanning electron microscopy, which indicate that the thin films are well crystallized with （1120） texture. Love wave and Ra...ZnO films on R-sapphire substrates are prepared and characterized by x-ray diffraction and scanning electron microscopy, which indicate that the thin films are well crystallized with （1120） texture. Love wave and Rayleigh wave are used for fabrications of humidity sensors, which are excited in [1100] and [0001] directions of the （1120） ZnO piezoelectric films, respectively. The experimental results show that both kinds of sensors have good humidity response and repeatability, and the performances of the Love wave sensors are better than those of the Rayleigh wave sensors at room temperature. Moreover, the theoretical calculations of the mass sensitivity of the sensors are a/so carried out and the calculated results are in good agreement with the experimental measurements.展开更多
Nonlinear impedances of two thermoacoustic stacks with ordered structures （plate-type and pipe-type） and one with a disordered structure （copper mesh） are studied. The linear resistances, nonlinear coefficients an...Nonlinear impedances of two thermoacoustic stacks with ordered structures （plate-type and pipe-type） and one with a disordered structure （copper mesh） are studied. The linear resistances, nonlinear coefficients and effective acoustic masses of the stacks are extracted from the experimental results based on an analogical model of nonlinear impedances of porous materials. The resistance and nonlinear coefficient of the disordered stack are found to be much larger than those of the ordered stacks, which have similar volume porosities. In the ordered stacks, the resistance is only marginally influenced by the length of the stack, while in the disordered stack, the resistance increases significantly with the length. These charac- teristics of the impedances of ordered and disordered stacks are explained with the minor loss theory and the tortuosity of a stack.展开更多
Nd-doping effects are investigated in TiO_(2)nanoparticles with various annealing temperatures T from 70℃ to 1100℃ by means of x-ray diffraction(XRD)and Raman scattering spectroscopy.XRD results indicate that the sa...Nd-doping effects are investigated in TiO_(2)nanoparticles with various annealing temperatures T from 70℃ to 1100℃ by means of x-ray diffraction(XRD)and Raman scattering spectroscopy.XRD results indicate that the sample shows a rutile phase at 1100℃,which changes to anatase phase at 900℃.With decreasing T down to 300℃,a significant lattice shrink is found,that is,the lattice parameter c is significantly suppressed while the a value shows a gradual decrease.With further decrease of T,the c-value shows an unexpected increase while the a-value keeps a gradual decrease.Thus,a lattice distortion takes place with changing the annealing temperature.In Raman investigation,all the Raman modes for the anatase phase show hardening behaviors with decreasing T in the range 900-300℃,and then the Eg and A1g modes show softening behaviors below 300℃,suggesting the variation of the lattice distortion.The variation of the lattice distortion at different annealing temperatures is ascribed to different depositions of Nd ions on the surface of TiO_(2)nanoparticles.展开更多
Rayleigh wave hydrogen sensors based on 128∘YX-LiNbO_(3) substrates with WO_(3) sensing layers operating at room temperature are studied.The experimental results indicate that the WO_(3) layers obtained by a sol-gel ...Rayleigh wave hydrogen sensors based on 128∘YX-LiNbO_(3) substrates with WO_(3) sensing layers operating at room temperature are studied.The experimental results indicate that the WO_(3) layers obtained by a sol-gel method have much higher sensitivities because the sensing layers produced by the sol-gel method have small grains and high roughness and porosity.It is also confirmed that in the sol-gel method,keeping WO_(3) solutions at low temperature and/or decreasing the viscosity of the solutions can decrease the grain sizes and increase the hydrogen-absorbability of the sensing layer.Under the optimized preparation conditions,the high sensitivity of the hydrogen sensors at room temperature is obtained,in which 1%hydrogen in natural air induces the frequency shift of 72 kHz at the operating frequency of 124.2 MHz.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11174142,11304160 and 11404147the National Basic Research Program of China under Grant No 2012CB921504+2 种基金the PAPD Projectthe Natural Science Foundation of Jiangsu Higher Education Institutions of China under Grant No 13KJB140008the Foundation of Nanjing University of Posts and Telecommunications under Grant No NY213018
文摘ZnO films on R-sapphire substrates are prepared and characterized by x-ray diffraction and scanning electron microscopy, which indicate that the thin films are well crystallized with （1120） texture. Love wave and Rayleigh wave are used for fabrications of humidity sensors, which are excited in [1100] and [0001] directions of the （1120） ZnO piezoelectric films, respectively. The experimental results show that both kinds of sensors have good humidity response and repeatability, and the performances of the Love wave sensors are better than those of the Rayleigh wave sensors at room temperature. Moreover, the theoretical calculations of the mass sensitivity of the sensors are a/so carried out and the calculated results are in good agreement with the experimental measurements.
基金supported by the National Basic Research Program of China(Grant No.2012CB921504)the National Natural Science Foundation of China(GrantNos.11374154,10904067,and 11174142)+2 种基金the Ph.D.Programs Foundation of Ministry of Education of China(Grant No.20090091120050)the PriorityAcademic Program Development of Jiangsu Higher Education Institutions,Chinathe Fundamental Research Funds for the Central Universities of Ministryof Education of China(Grant No.1101020402)
文摘Nonlinear impedances of two thermoacoustic stacks with ordered structures （plate-type and pipe-type） and one with a disordered structure （copper mesh） are studied. The linear resistances, nonlinear coefficients and effective acoustic masses of the stacks are extracted from the experimental results based on an analogical model of nonlinear impedances of porous materials. The resistance and nonlinear coefficient of the disordered stack are found to be much larger than those of the ordered stacks, which have similar volume porosities. In the ordered stacks, the resistance is only marginally influenced by the length of the stack, while in the disordered stack, the resistance increases significantly with the length. These charac- teristics of the impedances of ordered and disordered stacks are explained with the minor loss theory and the tortuosity of a stack.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10874087,11074124 and 10904052,Jiangsu Provincial Natural Science Foundation under Grant No 200921555the China Postdoctoral Science Foundation under Grant No 201003575.
文摘Nd-doping effects are investigated in TiO_(2)nanoparticles with various annealing temperatures T from 70℃ to 1100℃ by means of x-ray diffraction(XRD)and Raman scattering spectroscopy.XRD results indicate that the sample shows a rutile phase at 1100℃,which changes to anatase phase at 900℃.With decreasing T down to 300℃,a significant lattice shrink is found,that is,the lattice parameter c is significantly suppressed while the a value shows a gradual decrease.With further decrease of T,the c-value shows an unexpected increase while the a-value keeps a gradual decrease.Thus,a lattice distortion takes place with changing the annealing temperature.In Raman investigation,all the Raman modes for the anatase phase show hardening behaviors with decreasing T in the range 900-300℃,and then the Eg and A1g modes show softening behaviors below 300℃,suggesting the variation of the lattice distortion.The variation of the lattice distortion at different annealing temperatures is ascribed to different depositions of Nd ions on the surface of TiO_(2)nanoparticles.
基金by the National Natural Science Foundation of China under Grant No 11174142,and the National Basic Research Program of China under Grant No 2012CB921504.
文摘Rayleigh wave hydrogen sensors based on 128∘YX-LiNbO_(3) substrates with WO_(3) sensing layers operating at room temperature are studied.The experimental results indicate that the WO_(3) layers obtained by a sol-gel method have much higher sensitivities because the sensing layers produced by the sol-gel method have small grains and high roughness and porosity.It is also confirmed that in the sol-gel method,keeping WO_(3) solutions at low temperature and/or decreasing the viscosity of the solutions can decrease the grain sizes and increase the hydrogen-absorbability of the sensing layer.Under the optimized preparation conditions,the high sensitivity of the hydrogen sensors at room temperature is obtained,in which 1%hydrogen in natural air induces the frequency shift of 72 kHz at the operating frequency of 124.2 MHz.
