共查询到20条相似文献,搜索用时 15 毫秒
1.
H 2S gas sensing properties of BST ((Ba 0.67Sr 0.33)TiO 3)) thick films are reported here for the first time. BST ceramic powder was prepared by mechanochemical process. Thick films
of BST were prepared by screen-printing technique. The sensing performance of the films was tested for various gases. The
films were surface customized by dipping them into aqueous solutions of CuCl 2 and CrO 3 for various intervals of time. These surface modified BST films showed improved sensitivity to H 2S gas (100 ppm) than pure BST film. Chromium oxide was observed to be a better activator than copper oxide in H 2S gas sensing. The effect of microstructure and amount of activators on H 2S gas sensing were discussed. The sensitivity, selectivity, stability, response and recovery time of the sensor were measured
and presented. 相似文献
2.
Carbon dioxide gas sensors based on BaTiO3-CuO composite with different concentrations of Ag addition(1,1.5 and 2 wt%) have been prepared by stander ceramic method and sintered at 500 and 700℃ for 5 h.Electrical conductivity and gas sensing properties of the prepared samples were investigated.Electrical conductivity measurement was used to characterize the obtained sintered sensor pellets.It was found that electrical conductivity and the sensitivity to CO2 were improved with Ag addition and sintering.The correlation between Ag content at different sintering temperature and sensing characteristics towards CO2 is discussed. 相似文献
3.
In this article, we report the convenient preparation of graphene/gold nanoparticle-decorating filter membrane, which could be directly used as electrode for H 2O 2 sensing. The graphene oxide and chloroauric acid are reduced by l-ascorbic acid before covering the paper substrate. The reduced graphene oxide/gold nanoparticle-paper material is characterized by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The paper composite could be cut into piece and directly used as electrochemical sensor. The electrochemical experimental results show that the paper sensor has satisfying performances in sensing H 2O 2 with the detection limit of 15?μM and the linear range is 8.53–17.35?mM. This work would propose a novel strategy for the applications of graphene in the fields of electroanalysis and sensing. 相似文献
4.
In the present study the polyethersulphone (PES) membranes of thickness (35 ±2) μm were prepared by solution cast method.
The permeability of these membranes was calculated by varying the temperature and by irradiation of α ions. For the variation
of temperature, the gas permeation cell was dipped in a constant temperature water bath in the temperature range from 303–373
K, which is well below the glass transition temperature (498 K). The permeability of H 2 and CO 2 increased with increasing temperature. The PES membrane was exposed by a-source ( 95Am 241) of strength (1 μ Ci) in vacuum of the order of 10 −6 torr, with fluence 2.7 × 10 7 ions/cm 2. The permeability of H 2 and CO 2 has been observed for irradiated membrane with increasing etching time. The permeability increases with increasing etching
time for both gases. There was a sudden change in permeability for both the gases when observed at 18 min etching. At this
stage the tracks are visible with optical instrument, which confirms that the pores are generated. Most of pores seen in the
micrograph are circular cross-section ones. 相似文献
5.
Hydroxyapatite (HAp) biomaterial ceramic was synthesized by three different processing routes viz. wet chemical process, microwave
irradiation process, and hydrothermal technique. The synthesized ceramic powders were characterized by SEM, XRD, FTIR and
XPS techniques. The dielectric measurements were carried out as a function of frequency at room temperature and the preliminary
study on CO gas sensing property of hydroxyapatite was investigated. The XRD pattern of the hydroxyapatite biomaterial revealed
that hydroxyapatite ceramic has hexagonal structure. The average crystallite size was found to be in the range 31–54 nm. Absorption
bands corresponding to phosphate and hydroxyl functional groups, which are characteristic of hydroxyapatite, were confirmed
by FTIR. The dielectric constant was found to vary in the range 9–13 at room temperature. Hydroxyapatite can be used as CO
gas sensor at an optimum temperature near 125°C. X-ray photoelectron spectroscopic studies showed the Ca/P ratio of 1.63 for
the HAp sample prepared by chemical process. The microwave irradiation technique yielded calcium rich HAp whereas calcium
deficient HAp was obtained by hydrothermal method. 相似文献
6.
The response of Nomex sheets to some penetrants has been analyzed. The process of moisture uptake depends on the relative
humidity ( RH) of the ambient atmosphere and the initial characteristics of the polymer. In the case of common laboratory solvents, the uptake by the polymer shows an inverse dependence on the molar volume of the former. Although the calendered and the uncalendered
Nomex sheets exhibit an overall similarity in their response to various penetrants, quantitative comparison reveals distinct differences. 相似文献
7.
The characterization and ethanol gas sensing properties of pure and doped ZnO thick films were investigated. Thick films of
pure zinc oxide were prepared by the screen printing technique. Pure zinc oxide was almost insensitive to ethanol. Thick films
of Al 2O 3 (1 wt%) doped ZnO were observed to be highly sensitive to ethanol vapours at 300°C. Aluminium oxide grains dispersed around
ZnO grains would result into the barrier height among the grains. Upon exposure of ethanol vapours, the barrier height would
decrease greatly leading to drastic increase in conductance. It is reported that the surface misfits, calcination temperature
and operating temperature can affect the microstructure and gas sensing performance of the sensor. The efforts are, therefore,
made to create surface misfits by doping Al 2O 3 into zinc oxide and to study the sensing performance. The quick response and fast recovery are the main features of this
sensor. The effects of microstructure and additive concentration on the gas response, selectivity, response time and recovery
time of the sensor in the presence of ethanol vapours were studied and discussed. 相似文献
8.
A gel was formed when a aqueous solution of BaCl 2, NbF 5 and citric acid in stoichiometric ratio is heated on a water bath. This gel on decomposition at 600°C yielded the nano crystallites
of BaNb 2O 6, as confirmed by X-ray diffraction study (XRD). This is a much lower temperature as compared to that prepared by traditional
solid state method (1000°C) as reported for the formation of BaNb 2O 6. Transmission electron microscopic (TEM) investigations revealed that the average particle size is 50 nm for the calcined
powders. The room temperature dielectric constant at 1 kHz is found to be 1000. The ferroelectric hysteresis loop parameters
of these samples were also studied. 相似文献
9.
Growth of Hg 1-xCd xTe epitaxial films by a new technique called asymmetric vapour phase epitaxy (ASVPE) has been carried out on CdTe and CZT
substrates. The critical problems faced in normal vapour phase epitaxy technique like poor surface morphology, composition
gradient and dislocation multiplication have been successfully solved. The epitaxial films have been electrically characterized
by using the Hall effect and capacitance-voltage ( C-V) measurements. 相似文献
10.
Herein we report the preparation of SnO 2 nanomatierials by chemical precipitation, sol-gel and dissolution-pyrolysis. Furthermore, we studied their sensing properties. The composition, crystal structure and ceramic microstructure of the powders obtained are characterized by X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The results show SnO 2 fabricated through the three methods has rutile structure and the sizes of spherical particles are below 30 nm. From the result, we can also know that the thick films deposited onto alumina substrates show different morphology, and which are fabricated by dissolution-pyrolysis has fibrous structure. We investigate the sensitivities, response and recovery times of the three sensors. The results of gas sensing measurement show that SnO 2-based sensor prepared by dissolution-pyrolysis method has high sensitivity, quick response and recovery behavior to the gases we studied. It also has wider range of working temperature that is from 25 to 400 °C compared with SnO 2-based sensor fabricated by the other two methods. 相似文献
11.
Abstract. Cubic spinels of composition, LiMg yMn 2-yO 4, with y = 0.0, 0.05, 0.1, 0.15 and 0.2, were synthesized by a modified Pechini process using polyethylene glycol and citric
acid. The phase formation and/or crystallization of the precursors were studied by thermal analysis. Products were characterized
by X-ray diffraction and SEM analysis. Coin cells were fabricated with lithium as the anode and LiMg yMn 2-yO 4 as the cathode in an electrolyte of 1 M LiPF 6 in a 1: 1 (v/v) mixture of EC and DEC. The charge-discharge studies were performed and the results were compared with materials
prepared by a solid state thermal method. 相似文献
12.
Nano-crystal embedded PbO-P 2O 5 glass has been prepared and characterized by XRD and TEM measurements. The ultrasonic velocity and attenuation measured within
the temperature range 80–300 K show significant structure and interesting feature with the presence of nano-crystalline region.
The glass samples were prepared by melt-quench method and nano-crystals of different sizes were produced by heat treatment
of the glasses for different durations of heating. All the processes were carried out at or above glass transition temperature.
A theoretical model that takes account of the effects of thermally activated relaxation, anharmonicity as well as microscopic
elastic inhomogeneities arising out of fluctuations has been successfully applied to interpret the variation of ultrasonic
velocity and attenuation data. An interesting outcome of this application has been to propose a method for the determination
of the size of nano-crystals from the ultrasonic attenuation data. 相似文献
13.
The coupling effect and synergistic effect between the two metal elements of the bimetallic oxide make it has unique electrical characteristics and gas-sensitive properties, but it has the limitation of low conductivity. In this paper, the bimetallic oxide Zn2SnO4 was decorated with reduced graphene oxide (rGO) to increase its electrical conductivity and promote charge transfer during gas adsorption, which enhances the response and shortens the response time of the bimetallic oxide gas sensor. The high-performance ammonia sensor based on Zn2SnO4/rGO nanocomposite material was prepared by environmentally friendly hydrothermal method and spin coating technology. The structure and properties of composite materials were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The ammonia sensing performance of Zn2SnO4/rGO nanocomposite sensor was tested at room temperature, including the dynamic response, response/recovery time, selectivity, repeatability, long-term stability. It showed a good sensing response to ammonia (22.94 for 100 ppm), and a fast response/recovery time (20 s/27 s). Finally, the response mechanism of Zn2SnO4/rGO nanocomposite sensor is explained. The enhanced ammonia sensing properties of Zn2SnO4/rGO nanocomposite sensor were ascribed to the synergistic effect and p–n heterojunction between Zn2SnO4 and rGO. 相似文献
14.
Glasses with the composition, (Sm 2
O
3)
x
( ZnO) (40-x)( TeO
2) (60), were prepared by conventional melt quenching method. The density, molar volume, and optical energy band gap of these glasses
have been measured. The refractive index, molar refraction and polarizability of oxide ion have been calculated by using Lorentz-Lorentz
relations. Optical absorption spectra of these glasses were recorded in the range 300–700 nm at room temperature. The oxide
ion polarizabilities deduced from two different quantities, viz. refractive index and optical energy band gap, agree well
compared with other glasses. The nonlinear variation of the above optical parameters with respect to samarium dopant has been
explained. 相似文献
15.
A semiconductor ethanol sensor was developed using ZnO–CuO and its performance was evaluated at room temperature. Hetero-junction sensor was made of ZnO–CuO nanoparticles for sensing alcohol at room temperature. Nanoparticles were prepared by hydrothermal method and optimized with different weight ratios. Sensor characteristics were linear for the concentration range of 150–250 ppm. Composite materials of ZnO–CuO were characterized using X-ray diffraction (XRD), temperature-programmed reduction (TPR) and high-resolution transmission electron microscopy (HR-TEM). ZnO–CuO (1:1) material showed maximum sensor response ( S = Rair/ Ralcohol) of 3.32 ± 0.1 toward 200 ppm of alcohol vapor at room temperature. The response and recovery times were measured to be 62 and 83 s, respectively. The linearity R2 of the sensor response was 0.9026. The sensing materials ZnO–CuO (1:1) provide a simple, rapid and highly sensitive alcohol gas sensor operating at room temperature. 相似文献
16.
Free-standing TiO 2–SiO 2/polyaniline (TS/PANI) composite nanofibers were prepared by electrospinning, in situ polymerization and calcination method. The effect of tetra- n-butyl titanate (TBT) in the electrospinning solution on the morphology and the ammonia sensing properties of TS/PANI composite nanofibers were investigated. The obtained nanofibers were characterized by scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, thermo-gravimetric analysis and gas sensor test system. It is proved that too much TBT in the solution would make the fibrous morphology and ammonia sensing properties worse. Gas sensing tests showed that the TS/PANI composite nanofibers ammonia sensor can work at room temperature and possess ideal response values, selectivity and repeatability. With the increase in TiO 2 content in the TS nanofibers, the ammonia sensing properties were improved because of the increase in P–N heterojunctions formed between TiO 2 and PANI in the sensors. 相似文献
17.
Solid adsorbents have shown great promise for control of particulate and non-particulate matter and as gas sensing devices
in recent times. In the present study, adsorption of environmental toxic pollutant such as lead ions on solid adsorbents viz.
α-Fe 2O 3 and fly ash, are reported. Considerable adsorption was observed on fly ash when compared to α-Fe 2O 3 surface. These studies are characterized by employing solid state and solution studies. 相似文献
18.
The present paper describes the alcohol sensing characteristics of spin coated SnO 2 thin film deposited by using sol-gel process. The sensitivity of the film was measured at different temperatures and different
concentrations of alcohol at ppm level. Alcohol detection result shows peak sensitivity at 623 K. The variation of sensitivity
and ethanol concentration has shown a linear relationship up to 1150 ppm and after that it saturates. The response time measurement
of the sensor was also observed and it was found that the response time is 30 sec. The results obtained favour the sol-gel
process as a low cost method for the preparation of thin films with a high sensing characteristic. 相似文献
19.
CdIn 2O 4 sensor with high sensitivity and excellent selectivity for H 2S gas was synthesized by using sol-gel technique. Structural, electrical and gas sensing properties of doped and undoped CdIn 2O 4 thick films were studied. XRD revealed the single-phase polycrystalline nature of the synthesized CdIn 2O 4 nanomaterials. Since the resistance change of a sensing material is the measure of its response, selectivity and sensitivity was found to be enhanced by doping different concentrations of cobalt in CdIn 2O 4 thick films. The sensor exhibits high response and selectivity toward H 2S for 10 wt.% Co doped CdIn 2O 4 thick films. The current-voltage characteristics of 10 wt.% Co doped CdIn 2O 4 calcined at 650 °C shows one order increase in current with change in the bias voltage at an operating temperature of 200 °C for 1000 ppm H 2S gas. 相似文献
20.
Hydroxyterminated polybutadiene (HTPB) based porous polyurethaneurea (PUU) membranes were prepared. The porosity was developed
by incorporation of lithium chloride into polymer matrix with subsequent leaching of the same in hot water. Scanning electron
microscopic analysis of the prepared membrane surfaces was performed. The pervaporation performance of the synthesized membrane
was studied with aqueous 4-nitrophenol solution as feed. The effects of various parameters on 4-nitrophenol separation factor
and total as well as 4-nitrophenol flux were studied. Polyurethaneurea membrane was found to permeate 4-nitrophenol selectively
with high separation factors for the organic component. Pore size and number of pores on the surface of the membrane were
calculated from SEM image of the membranes. Effects of pore size and porosity on pervaporation flux were also investigated. 相似文献
|