Capacitive humidity sensors were made of nanometer barium titanate.The pellets were prepared under different pressures between 3920N to 7850N force.The capacitance changes in three orders of magnitude in the relative ...Capacitive humidity sensors were made of nanometer barium titanate.The pellets were prepared under different pressures between 3920N to 7850N force.The capacitance changes in three orders of magnitude in the relative humidity range of 10%～98%,indicating high humidity sensitivity of the sensors.At a certain measuring frequency,the capacitance of the sensors increases as increasing of the preparation pressure,while the sensitivity of the sensors basically remains the same.The frequencies corresponding to the peaks of the dielectric loss of the sensors move to the higher frequency direction as increasing of the relative humidity.At a certain humidity,the frequencies corresponding to the peaks of the dielectric loss move to the higher frequency direction as increasing of the preparation pressure.展开更多
Poly（3-alkyl）pyrroles containing phosphonic acid groups with different alkyl segment lengths were chemical synthesized and the properties were measured by FTIR and UV-Vis spectroscopy. FTIR and UV-Vis results showed...Poly（3-alkyl）pyrroles containing phosphonic acid groups with different alkyl segment lengths were chemical synthesized and the properties were measured by FTIR and UV-Vis spectroscopy. FTIR and UV-Vis results showed that the synthesized polymers were in a low doping level through chemical polymerization. By spin-coating on the surface of substrates, the polymer can be used as a humidity sensor. The change of DC electric current of the polypyrroles varies with the chain length of the alkyl substituents. The capacitance increases with the increase of the humidity and resistance decreases with the increase of humidity. This result is different from that ofpolypyrrole without alkyl substituents due to the influence of the phosphonic acid group. The sensor showed the resistive-type at high relative humidity, and the capacitive- type at the low relative humidity. The sensor exhibited very fast response to the change of environment humidity.展开更多
Ceramic porous MgTiO3 materials have been prepared by classical solid-state route. The sintered pellets of MgTiO3 with different LiF contents were characterized for humidity-sensing application. The sintered disks of ...Ceramic porous MgTiO3 materials have been prepared by classical solid-state route. The sintered pellets of MgTiO3 with different LiF contents were characterized for humidity-sensing application. The sintered disks of these mixtures were subjected to capacitance measurements at 20℃as function of the relative humidity from which revealed that the Mixture MgTiO3 + 2% LiF (w/w) has the better characteristics. The disks were subjected to DC resistance measurements as a function of relative humidity in the range 15% - 95% RH. The selectivity of this material was discussed and compared to commercial sensor results. The response and recovery characteristics were assessed.展开更多
In this study, the fabrication and characterization of capacitive humidity sensors using cobalt-phthalocyanine （CoPc） as the active material were presented. Thin films of CoPc were deposited by drop casting on glass...In this study, the fabrication and characterization of capacitive humidity sensors using cobalt-phthalocyanine （CoPc） as the active material were presented. Thin films of CoPc were deposited by drop casting on glass substrates with pre-deposited aluminum electrodes to form A1/CoPc/A1 surface-type humidity sensors. The effect of humidity on the electrical properties of the CoPc film was investigated by measuring capacitance and resistance of the samples at four different frequencies of the applied voltage. It was observed that the capacitance of the sensor increased while the resistance decreased with raising the relative humidity. It was also found that the values of capacitance and resistance decreased with increasing frequency. The optical absorption spectra and optical band gap energy of CoPc films were measured. The structure of CoPc powder and thin films has been studied by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and atomic force microscopy （AFM）. Results of XRD studies show that the film structure is polycrystalline with the monoclinic structure while thin films have a peak for annealing temperatures with （100） orientation. Also, the surface morphology （grain size and roughness） for CoPc films have been studied by AFM.展开更多
This study presents the fabrication and characterization of novel surface-type capacitive humidity sensors using vanadyl phthalocyanine（VOPc） as the active material.The devices,which comprise three different thickne...This study presents the fabrication and characterization of novel surface-type capacitive humidity sensors using vanadyl phthalocyanine（VOPc） as the active material.The devices,which comprise three different thicknesses, have been fabricated using the thermal evaporation technique.A thin film of VOPc is deposited on thoroughly cleaned glass substrates with pre-patterned Ag electrodes.The capacitive effect of the samples under humidity has been investigated. Comparison of the samples with different thicknesses shows that the thinnest device seems more sensitive towards humidity.The humidity dependent capacitance properties of the sensor make it beneficial for use in commercial hygrometers.展开更多
This paper presents a development of a low-cost miniature humidity sensor with an interdigitated aluminium electrode connected in parallel on quartz substrate.Interdigitated capacitive device has been fabricated using...This paper presents a development of a low-cost miniature humidity sensor with an interdigitated aluminium electrode connected in parallel on quartz substrate.Interdigitated capacitive device has been fabricated using the photolithography method.The aluminium electrode was covered with sensitive film of a nanoporous thin film of γ-Al_(2)O_(3) made from novel solgel technique.Nanostructured thin film offers very high surface to volume ratio with distribution of micro pores for moisture detection.Pore morphologies of the film have been studied by field emission electron microscope and Xray diffraction methods.Impedance measurement of the miniature capacitive humidity sensor toward relative humidity was investigated at room temperature by Agilent 4294A impedance analyzer(Agilent,Santa Clara,CA,USA).The device exhibits short response and recovery times and good repeatability.展开更多
Multi-walled carbon nanotubes (CNTs) were grown on silicon nanoporous pillar array (Si-NPA) by thermal chemical vapor deposition method, and the structural and capacitive humidity sensing properties of CNT/Si-NPA were...Multi-walled carbon nanotubes (CNTs) were grown on silicon nanoporous pillar array (Si-NPA) by thermal chemical vapor deposition method, and the structural and capacitive humidity sensing properties of CNT/Si-NPA were studied. It was found that with the relative humidity (RH) changing from 11% to 95%, a device re-sponse of ~480% was achieved at the frequency of 50000 Hz, and a linear device response curve could be obtained by adopting longitudinal logarithmic coordinate. The response/recovery times were measured to be ~20 s and ~10 s, respectively, which indicated a rather fast response/recovery rate. The adsorption-desorption dynamic cycle experiments demonstrated the high measurement reproducibility of CNT/Si-NPA sensors. These excellent performances were attributed to the unique surface structure, morphology and chemical inertness of CNT/Si-NPA.展开更多
A novel capacitance-type relative humidity(RH) sensor based on multi-wall carbon nanotube/SiO(MWCNTs/SiO) composite film is reported.Details of the fabrication process,possible sensing mechanism and sensing characteri...A novel capacitance-type relative humidity(RH) sensor based on multi-wall carbon nanotube/SiO(MWCNTs/SiO) composite film is reported.Details of the fabrication process,possible sensing mechanism and sensing characteristics,such as linearity and sensitivity,are described.The capacitance of the MWCNTs/SiOcomposite film shows typical concentration percolation behavior with increasing MWCNT loading.At loadings below the percolation threshold(1.842wt%),the sensor capacitance increases obviously with increasing MWCNTs. The water condensed in the MWCNTs/SiOlayer can lower the percolation threshold and increase the sensor capacitance.The sensor with MWCNT concentration of 1wt%has the best properties.The sensor has a humidity sensitivity of about 673 pF/%RH and a linearity correlation of 0.98428.The response time of the sensor to RH is about 40 s and the recovery time is about 2 s.展开更多
基金The project is supported by the National Natural Science Foundation of China （60074031, 60474052）.
文摘Capacitive humidity sensors were made of nanometer barium titanate.The pellets were prepared under different pressures between 3920N to 7850N force.The capacitance changes in three orders of magnitude in the relative humidity range of 10%～98%,indicating high humidity sensitivity of the sensors.At a certain measuring frequency,the capacitance of the sensors increases as increasing of the preparation pressure,while the sensitivity of the sensors basically remains the same.The frequencies corresponding to the peaks of the dielectric loss of the sensors move to the higher frequency direction as increasing of the relative humidity.At a certain humidity,the frequencies corresponding to the peaks of the dielectric loss move to the higher frequency direction as increasing of the preparation pressure.
基金supported by the Fundamental Research Funds for the Central Universities,China(No.GK 200902008)
文摘Poly（3-alkyl）pyrroles containing phosphonic acid groups with different alkyl segment lengths were chemical synthesized and the properties were measured by FTIR and UV-Vis spectroscopy. FTIR and UV-Vis results showed that the synthesized polymers were in a low doping level through chemical polymerization. By spin-coating on the surface of substrates, the polymer can be used as a humidity sensor. The change of DC electric current of the polypyrroles varies with the chain length of the alkyl substituents. The capacitance increases with the increase of the humidity and resistance decreases with the increase of humidity. This result is different from that ofpolypyrrole without alkyl substituents due to the influence of the phosphonic acid group. The sensor showed the resistive-type at high relative humidity, and the capacitive- type at the low relative humidity. The sensor exhibited very fast response to the change of environment humidity.
文摘Ceramic porous MgTiO3 materials have been prepared by classical solid-state route. The sintered pellets of MgTiO3 with different LiF contents were characterized for humidity-sensing application. The sintered disks of these mixtures were subjected to capacitance measurements at 20℃as function of the relative humidity from which revealed that the Mixture MgTiO3 + 2% LiF (w/w) has the better characteristics. The disks were subjected to DC resistance measurements as a function of relative humidity in the range 15% - 95% RH. The selectivity of this material was discussed and compared to commercial sensor results. The response and recovery characteristics were assessed.
文摘In this study, the fabrication and characterization of capacitive humidity sensors using cobalt-phthalocyanine （CoPc） as the active material were presented. Thin films of CoPc were deposited by drop casting on glass substrates with pre-deposited aluminum electrodes to form A1/CoPc/A1 surface-type humidity sensors. The effect of humidity on the electrical properties of the CoPc film was investigated by measuring capacitance and resistance of the samples at four different frequencies of the applied voltage. It was observed that the capacitance of the sensor increased while the resistance decreased with raising the relative humidity. It was also found that the values of capacitance and resistance decreased with increasing frequency. The optical absorption spectra and optical band gap energy of CoPc films were measured. The structure of CoPc powder and thin films has been studied by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and atomic force microscopy （AFM）. Results of XRD studies show that the film structure is polycrystalline with the monoclinic structure while thin films have a peak for annealing temperatures with （100） orientation. Also, the surface morphology （grain size and roughness） for CoPc films have been studied by AFM.
文摘This study presents the fabrication and characterization of novel surface-type capacitive humidity sensors using vanadyl phthalocyanine（VOPc） as the active material.The devices,which comprise three different thicknesses, have been fabricated using the thermal evaporation technique.A thin film of VOPc is deposited on thoroughly cleaned glass substrates with pre-patterned Ag electrodes.The capacitive effect of the samples under humidity has been investigated. Comparison of the samples with different thicknesses shows that the thinnest device seems more sensitive towards humidity.The humidity dependent capacitance properties of the sensor make it beneficial for use in commercial hygrometers.
文摘This paper presents a development of a low-cost miniature humidity sensor with an interdigitated aluminium electrode connected in parallel on quartz substrate.Interdigitated capacitive device has been fabricated using the photolithography method.The aluminium electrode was covered with sensitive film of a nanoporous thin film of γ-Al_(2)O_(3) made from novel solgel technique.Nanostructured thin film offers very high surface to volume ratio with distribution of micro pores for moisture detection.Pore morphologies of the film have been studied by field emission electron microscope and Xray diffraction methods.Impedance measurement of the miniature capacitive humidity sensor toward relative humidity was investigated at room temperature by Agilent 4294A impedance analyzer(Agilent,Santa Clara,CA,USA).The device exhibits short response and recovery times and good repeatability.
基金Supported by the National Natural Science Foundation of China (Grant No. 10574112)
文摘Multi-walled carbon nanotubes (CNTs) were grown on silicon nanoporous pillar array (Si-NPA) by thermal chemical vapor deposition method, and the structural and capacitive humidity sensing properties of CNT/Si-NPA were studied. It was found that with the relative humidity (RH) changing from 11% to 95%, a device re-sponse of ~480% was achieved at the frequency of 50000 Hz, and a linear device response curve could be obtained by adopting longitudinal logarithmic coordinate. The response/recovery times were measured to be ~20 s and ~10 s, respectively, which indicated a rather fast response/recovery rate. The adsorption-desorption dynamic cycle experiments demonstrated the high measurement reproducibility of CNT/Si-NPA sensors. These excellent performances were attributed to the unique surface structure, morphology and chemical inertness of CNT/Si-NPA.
文摘A novel capacitance-type relative humidity(RH) sensor based on multi-wall carbon nanotube/SiO(MWCNTs/SiO) composite film is reported.Details of the fabrication process,possible sensing mechanism and sensing characteristics,such as linearity and sensitivity,are described.The capacitance of the MWCNTs/SiOcomposite film shows typical concentration percolation behavior with increasing MWCNT loading.At loadings below the percolation threshold(1.842wt%),the sensor capacitance increases obviously with increasing MWCNTs. The water condensed in the MWCNTs/SiOlayer can lower the percolation threshold and increase the sensor capacitance.The sensor with MWCNT concentration of 1wt%has the best properties.The sensor has a humidity sensitivity of about 673 pF/%RH and a linearity correlation of 0.98428.The response time of the sensor to RH is about 40 s and the recovery time is about 2 s.
