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1.
CuO/In2O3 core–shell nanorods were fabricated using thermal evaporation and radio frequency magnetron sputtering. X-ray diffraction and transmission electron microscopy showed that both the cores and shells were crystalline. The multiple networked CuO/In2O3 core–shell nanorod sensors showed responses of 382–804%, response times of 36–54 s and recovery times of 144–154 s at ethanol (C2H5OH) concentrations ranging from 50 to 250 ppm at 300 °C. These responses were 2.3–2.8 times higher than those of the pristine CuO nanorod sensor over the same C2H5OH concentration range. The origin of the enhanced ethanol sensing properties of the core–shell nanorod sensor is discussed.  相似文献   

2.
《Ceramics International》2016,42(5):6187-6197
This paper reports on the synthesis of pristine α-Fe2O3 nanorods and Fe2O3–ZnO core–shell nanorods using a combination of thermal oxidation and atomic layer deposition (ALD) techniques; the completed nanorods were then used for ethanol sensing studies. The crystal structure and morphology of the synthesized nanostructures were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The sensing properties of the pristine and core–shell nanorods for gas-phase ethanol were examined using different concentrations of ethanol (5–200 ppm) at different temperatures (150–250 °C). The XRD and SEM revealed the excellent crystallinity of the Fe2O3–ZnO core–shell nanorods, as well as their uniformity in terms of shape and size. The Fe2O3–ZnO core–shell nanorod sensor showed a stronger response to ethanol than the pristine Fe2O3 nanorod sensor. The response (i.e., the relative change in electrical resistance Ra/Rg) of the core–shell nanorod sensor was 22.75 for 100 ppm ethanol at 200 °C whereas that of the pristine nanorod sensor was only 3.85 under the same conditions. Furthermore, under these conditions, the response time of the Fe2O3–ZnO core–shell nanorods was 15.96 s, which was shorter than that of the pristine nanorod sensor (22.73 s). The core–shell nanorod sensor showed excellent selectivity to ethanol over other VOC gases. The improved sensing response characteristics of the Fe2O3–ZnO core–shell nanorod sensor were attributed to modulation of the conduction channel width and the potential barrier height at the Fe2O3–ZnO interface accompanying the adsorption and desorption of ethanol gas as well as to preferential adsorption and diffusion of oxygen and ethanol molecules at the Fe2O3–ZnO interface.  相似文献   

3.
《Ceramics International》2016,42(16):18597-18604
Pristine and TiO2 nanoparticle-decorated Fe2O3 nanorods were synthesized via thermal oxidation of Fe thin foils, followed by the solvothermal treatment with titanium tetra isopropoxide (TTIP) and NaOH for TiO2 nanoparticle-decoration. Subsequently, gas sensors were fabricated by connecting the nanorods with metal conductors. The structure and morphology of the pristine and TiO2 nanoparticle-decorated Fe2O3 nanorods were examined via X-ray diffraction and scanning electron microscopy, respectively. The gas sensing properties of the pristine and TiO2 nanoparticle-decorated Fe2O3 nanorod sensors with regard to H2S gas were examined. The TiO2 nanoparticle-decorated Fe2O3 nanorod sensor showed a stronger response to H2S than the pristine Fe2O3 nanorod sensor. The responses of the pristine and TiO2 nanoparticle-decorated Fe2O3 nanorod sensors were 2.6 and 7.4, respectively, when tested with 200 ppm of H2S at 300 °C. The TiO2 nanoparticle-decorated Fe2O3 nanorod sensor also showed a faster response and recovery than the sensor made from pristine Fe2O3 nanorods. Both sensors showed selectivity for H2S over NO2, SO2, NH3, and CO. The enhanced sensing performance of the TiO2 nanoparticle-decorated Fe2O3 nanorod sensor compared to that of the pristine Fe2O3 nanorod sensor might be due to enhanced modulation of the conduction channel width, the decorated nanorods’ increased surface-to-volume ratios and the creation of preferential adsorption sites via TiO2 nanoparticle decoration. The dominant sensing mechanism in the TiO2 nanoparticle-decorated Fe2O3 nanorod sensor is discussed in detail.  相似文献   

4.
《Ceramics International》2017,43(10):7942-7947
Arrayed In2O3 nanosheets were synthesized directly via a two-step solution approach on an Al2O3 ceramic tube. Their morphology and structure were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–Vis absorption spectroscopy, and scanning electron microscopy (SEM). The results reveal that the length of each nanosheet is about 1 µm, the width of the bottom of nanosheet is about 200 nm. Importantly, the In2O3 nanosheets with large specific surface area possess highly sensing performance for ethanol detection. The response value to 100 ppm ethanol is about 45 at an operating temperature of 280 °C, and the response and recovery time are extremely short. It is expected that the directly grown In2O3 nanosheets with large specific surface area and excellent sensing properties will become a promising functional material in monitoring and detecting ethanol.  相似文献   

5.
ZnSnO3 one-dimensional (1D) nanostrutures were synthesized by thermal evaporation. The morphology, crystal structure and sensing properties of the CuO-coated ZnSnO3 nanostructures to H2S gas at 100 °C were examined. Transmission electron microscopy and X-ray diffraction revealed both the ZnSnO3 nanorods and CuO nanoparticles to be single crystals. The diameters of the CuO nanoparticles on the nanorods ranged from a few to a few tens of nanometers. The gas sensors fabricated from multiple networked CuO-coated ZnSnO3 nanorods exhibited enhanced electrical responses to H2S gas compared to the uncoated ZnSnO3 nanorod sensors, showing 61.7-, 49.9-, and 31.3-fold improvement at H2S concentrations of 25, 50, and 100 ppm, respectively. The response time of the nanorod sensor to H2S gas was reduced by the CuO coating but the recovery time was similar. The mechanism for the enhanced H2S gas sensing properties of ZnSnO3 nanorods by the CuO coating is discussed.  相似文献   

6.
Mesoporous In2O3 materials were synthesized by calcining indium-organic frameworks (InOFs, CPM-5 and MIL-68), which were further successfully utilized to detect toxic HCHO vapor. By taking the intrinsic structural features of two InOF precursors into account, the surface areas of produced indium oxides were well investigated via controlling the calcination temperature. The influence of surface area on the gas sensing performance was studied in detail. Porous In2O3 prepared by heat treatment at 650 °C showed the highest responses to 50 ppm HCHO (Rg/Ra = 31.8 and 38.0, respectively; Rg, resistance in gas; Ra, resistance in air) at 210 °C, which surpass the values of all the reported In2O3 materials to date under the similar conditions. The promising HCHO-sensing properties enable these InOF-templated mesoporous In2O3 materials to be competitive candidates for detecting poisonous formaldehyde in practice.  相似文献   

7.
《Ceramics International》2016,42(8):9712-9716
A novel mixed-potential type NO2 sensor was fabricated using La10Si6O27 electrolyte and WO3 sensing electrode (SE). The sinterability of La10Si6O27 was significantly improved by the introduction of Y2O3 as sintering aid. WO3 with different morphologies prepared by the citric acid (CA) assisted hydrothermal method was examined as the sensing electrodes of the mixed-potential type NO2 sensors based on La10Si6O27 electrolyte. The results showed that 6 wt% Y2O3 added La10Si6O27 electrolyte sample could get quite dense at a temperature as low as 1500 °C. The morphologies and phase constituents of WO3 were influenced by the CA content. The sensor showed good response–recovery characteristics. Compared with the sensor based on the irregular WO3 particles or nanorods, the sensor using WO3 nanosheets-SE with hexagonal structure exhibited much higher sensitivity (195.6 mV/decade) to NO2 at 550 °C. The response signals of the sensor were slightly affected by coexistent O2 varying from 5 to 20 vol%.  相似文献   

8.
Indium oxide (In2O3) nanoparticle thin films were grown on cleaned glass substrates by the chemical spray pyrolysis technique using the precursor solution of indium nitrate (In (NO3)3). The XRD studies confirm that the films are polycrystalline In2O3, possessing cubic structure with lattice parameters, a = b = c = 10.17 Å. The optical studies show a direct optical band gap of 3.32 eV and an indirect band gap of 2.6 eV in the prepared films. The films exhibit high optical transparency >80% in the visible region, reaching a maximum of 85% at 684 nm wavelength. Further, the gas sensing properties of the films have been investigated for various concentrations of methanol in air at different operating temperatures. At 300 °C the film exhibits a very high response 99% to methanol vapor at a concentration of 40 ppm in air, which is ideal to be used as a methanol sensor. The film shows fast response and recovery to methanol vapor at higher operating temperatures. A possible methanol sensing mechanism has been proposed.  相似文献   

9.
《Ceramics International》2017,43(6):5032-5040
Nanostructured La-based perovskite oxides − LaMO3 (M=Al, Co, Fe) were synthesized by a new co-precipitation procedure using metal nitrate and carbonate salts as starting materials. X-ray diffraction and energy dispersive X-ray spectroscopic results confirmed the formation of single-phase nanocrystalline perovskite oxides with high purity. Characterizations by scanning/transmission electron microscopy and nitrogen adsorption revealed that LaAlO3 was produced in the form of rectangular porous nanorods exhibiting much larger surface area and porosity compared with densely aggregated LaCoO3 particles and loosely clustered LaFeO3 nanoparticles with cracked-egg morphologies. The materials were characterized for gas sensing towards ethanol at 200–350 °C. From gas-sensing results, the LaAlO3 sensor displayed n-type gas-sensing behaviors with considerably higher ethanol response than p-type LaFeO3 and LaCoO3 sensors, respectively. In particular, the LaAlO3 sensor exhibited a high response of 16.45–1000 ppm ethanol and excellent ethanol selectivity against NO2, SO2, CO and H2 at 350 °C. The superior gas-sensing performances could be attributed to the effective receptor function, transducer function and utility factor of LaAlO3 nanorod structures prepared by the co-precipitation method.  相似文献   

10.
《Ceramics International》2016,42(5):6136-6144
In the present work, α-Fe2O3 nanoparticles were successfully synthesized by Pechini sol–gel (PSG) method following annealing at 550 °C. The morphology and microstructure of the prepared α-Fe2O3 nanoparticles were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman analysis. The electrical and sensing properties were also investigated. The α-Fe2O3 based sensor showed good sensitivity and selectivity towards ethanol at the optimal temperature of 225 °C. Moreover, the sensor displayed good electrical and sensing stability. These results suggest the potential applications of α-Fe2O3 synthesized by Pechini sol–gel method as a sensor material for ethanol detection.  相似文献   

11.
《Ceramics International》2016,42(14):15889-15896
Well-defined three-dimensional (3D) hierarchical tin dioxide (SnO2) nanoflowers with the size of about 200 nm were successfully synthesized by a simple template-free hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption-desorption analyses were used to characterize the structure and morphology of the products. The as-synthesized full crystalline and large specific surface area SnO2 nanoflowers were assembled by one-dimensional (1D) SnO2 nanorods with sharp tips. A possible self-assembly mechanism for the formation the SnO2 nanoflowers was speculated. Moreover, gas sensing investigation showed the sensor based on SnO2 nanoflowers to exhibit high response and fast response-recovery ability to detect acetone and ethanol at an operating temperature lower than 200 °C. The enhancement of gas sensing properties was attributed to their 3D hierarchical nanostructure, large specific surface area, and small size of the secondary SnO2 nanorods.  相似文献   

12.
Zn2SnO4-core/ZnO-shell nanorods were synthesized using a two-step process: synthesis of Zn2SnO4 nanorods the thermal evaporation of a mixture of ZnO, SnO2, and graphite powders, followed by atomic layer deposition (ALD) of ZnO. The nanorods were 50–250 nm in diameter and a few to a few tens of micrometers in length. The cores and shells of the nanorods were face-centered cubic-structured single crystal Zn2SnO4 and wurtzite-structured single crystal ZnO, respectively. The multiple networked Zn2SnO4-core/ZnO-shell nanorod sensors showed a response of 173–498% to NO2 concentrations of 1–5 ppm at 300 °C. These response values are 2–5 times higher than those of the Zn2SnO4 nanorod sensor over the same NO2 concentration range. The NO2 sensing mechanism of the Zn2SnO4core/ZnO-shell nanorods is discussed.  相似文献   

13.
Indium oxide (In2O3) porous nanoplates (PNPs) were synthesized by an ethylenediamine-assisted hydrothermal process followed by calcination at 270 °C. Compared with In2O3 non-porous nanoplates (NPs) obtained at higher temperature (500 °C), PNPs possessed a high value of specific surface area (156.9 m2 g 1) and a meso-microporous structure. As-synthesized In2O3 PNPs showed a superior activity for photocatalytic decomposition of an emerging persistent organic pollutant-perfluorooctanoic acid (PFOA), the decomposition half-life of PFOA was shortened to 4.4 min.  相似文献   

14.
《Ceramics International》2016,42(3):3762-3768
Indium oxide (In2O3) is a n-type semiconductor with various applications in thin film coatings, on the basis of its optical properties, and in gas sensing equipment, due to its high sensitivity to various oxides such as COx and NOx. In this study, a synthesis process for obtaining In2O3 nanoparticles is examined. The precursor used is indium nitrate hydrate (InN3O9·H2O) because of its high solubility in water. By dissolving the nitrate salt in a PVA (polyvinyl alcohol) solution, the precursor is dispersed homogeneously, which reduces the agglomeration of the resulting powder. Calcination at a low temperature of 200–250 °C burns out the organic materials of the PVA with NOx gas emission and allows the oxidation of the indium, resulting in indium oxide nanoparticles. The influence of the PVA solution characteristics and the heat treatment temperature on the powder morphology and size was analyzed by using SEM, TEM, XRD, TGA/DSC, and four point BET for a specific surface area analysis. The measured specific surface area varies from 3 m2/g to 76 m2/g depending on the calcination temperature, and the particle size of the synthesized powders is under 10 nm for the samples heat treated at 300 °C.  相似文献   

15.
Cylinder- and cake-like Cr2O3 with a rhombohedral structure were fabricated using the hydrothermal and microemulsion methods, respectively. It is found that surface areas, surface Cr6 + and oxygen adspecies concentrations, and low-temperature reducibility of cake-like Cr2O3 were much higher or better than those of the bulk counterpart. The cake-like Cr2O3 sample showed the best catalytic performance for toluene combustion, giving the T50% and T90% of 229 and 240 °C at SV = 20,000 mL/(g h), respectively. The excellent catalytic performance of cake-like Cr2O3 was associated with its oxygen adspecies concentration and good low-temperature reducibility.  相似文献   

16.
In2O3 nanoparticles are coated on the surfaces of single-walled carbon nanotubes (SWCNTs) by a successive ionic layer adsorption and reaction process. The thickness of the In2O3 nanoparticle film is tuned by controlling the number of coating cycles. The electric field around the In2O3-coated SWCNTs is compared with that of pristine SWCNTs. Field enhancement of the In2O3-coated SWCNTs is confirmed by conductive atomic force microscopy at low electric field (contact mode: 1 V to −1 V) and also field emission (FE) analysis at high electric field (0–4.2 V/μm). The uniformity and emission stability are also measured via FE analysis. Near infrared and X-ray photoemission spectroscopy data are suggested to explain the charge transfer, bandgap change between the In2O3 nanoparticles and SWCNTs, and the electric field enhancements in the In2O3-coated SWCNTs at both low and high electric field.  相似文献   

17.
Sintering of Cr2O3 was performed at 1530°C under low pO2 close to the Cr–Cr2O3 equilibrium generated by H2/H2O gas mixtures. Addition of 1 wt%ZrO2 and 0·1 wt%MgO increases the density of Cr2O3 from 97% TD to nearly full density. Rapid densification and the higher density are attributed to the appearance of a transient CrO liquid phase as a result of the presence of ZrO2 and MgO under the sintering conditions. A grain size reduction is also achieved owing to the presence of ZrO2 particles and the possible formation of a MgCr2O4 spinel at grain boundaries. There is no connection between densification and loss of material due to evaporation. ©  相似文献   

18.
The (ZnO)kIn2O3 system is interesting for applications in the fields of thermoelectrics and opto-electronics. In this study we resolve the complex homologous phase evolution with increasing temperature in polycrystalline ceramics for k = 5, 11 and 18 and its influence on the microstructural development and thermoelectric properties. The phase formation at temperatures above 1000 °C is influenced by the local ZnO-to-In2O3 ratio in the starting-powder mixture. While the Zn5In2O8 equilibrium phase for k = 5 is formed directly after sintering at 1200 °C, the formation of the k = 11 and k = 18 equilibrium phases proceeds at higher temperatures by diffusion between the initially formed phases, the lower k Zn5In2O8/Zn7In2O10 and the higher k ZnkIn2Ok+3 (9 < k < ∞). Such phase formation affects the sintering and grain growth, and consequently, with the degree of structural and compositional homogeneity, also the thermoelectric characteristics of the (ZnO)kIn2O3 ceramics.  相似文献   

19.
《Ceramics International》2016,42(7):8565-8571
A new micro gas sensor based on the TiO2 nanorod arrays (NRAs) was developed and its response properties to oxygen (O2) at room temperature were investigated. The micro sensor combined a pair of micro interdigitated electrodes realized by the MEMS process and sensing materials based on the TiO2 NRAs. The TiO2 NRAs were selectively grown on the patterned straps of Ti/Pd films through the acid vapor oxidation (AVO) process. Relationship between the morphology of the TiO2 NRAs and reaction temperatures was analyzed with the scanning electronic microscopy (SEM) and X-ray diffraction (XRD). The results indicate that the diameters of the TiO2 NRs enlarged as the reaction temperature increased from 140 °C to 180 °C. The TiO2 NRAs sensors showed a good response to O2 at room temperature (25 °C) due to the large specific surface areas of the TiO2 NRs and the TiO2 NR/NR junctions. The TiO2 NRAs sensors prepared at 140 °C for 3 h exhibited better response properties to O2 at room temperature with a fast response and recovery time. The research indicates that the TiO2 NRAs prepared by the simple AVO process is a good choice for detecting O2 at room temperature.  相似文献   

20.
In this research, hydrothermal‐calcination route was applied to synthesize In2O3 nanoparticles for gas sensor application. Hydrothermal synthesis with duration of 5 h at 180°C resulted in In(OH)3 nanorods. Then, in the calcination step, considering controlled rate of heating and temperature, In2O3 nanoparticles with rough surfaces were obtained. In the next step, these nanoparticles were deposited by low frequency AC electrophoretic deposition between the interdigitated electrodes to fabricate gas sensor. Deposition in the frequency of 10 kHz resulted in the chained nanoparticles in the interelectrode space. At the end, gas sensitivity measurements were conducted at 150°C–300°C and revealed that fabricated sensor had fast response and recovery times to NO2 gas.  相似文献   

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