WO3纳米材料的H2S气敏特性

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wo3-乙醇气敏材料

Temperature and acidity effects on WO 3nanostructures and gas-sensing properties of WO 3nanoplatesHuili Zhang a ,Zhifang Liu b ,Jiaqin Yang b ,Wei Guo b ,Lianjie Zhu a ,*,Wenjun Zheng b ,**aSchool of Chemistry and Chemical Engineering,Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion,Tianjin University of Technology,Tianjin 300384,PR China bDepartment of Materials Chemistry,Key Laboratory of Advanced Energy Materials Chemistry (MOE),TKL of Metal and Molecule-based Material Chemistry,Synergetic Innovation Centre of Chemical Science and Engineering (Tianjin),College of Chemistry,Nankai University,Tianjin 300071,PR ChinaA R T I C L E I N F OArticle history:Received 4January 2014Received in revised form 28May 2014Accepted 11June 2014Available online 12June 2014Keywords:Nanostructures SolvothermalElectron microscopy X-ray diffractionA B S T R A C TWO 3nanostructures were successfully synthesized by a facile hydrothermal method using Na 2WO 4Á2H 2O and HNO 3as raw materials.They are characterized by X-ray diffraction (XRD),scanning electron microscope (SEM)and transmission electron microscope (TEM).The speci ﬁc surface area was obtained from N 2adsorption –desorption isotherm.The effects of the amount of HNO 3,hydrothermal temperature and reaction time on the crystal phases and morphologies of the WO 3nanostructures were investigated in detail,and the reaction mechanism was rge amount of acid is found for the ﬁrst time to be helpful to the oriented growth of tungsten oxides,forming nanoplate-like products,while hydrothermal temperature has more in ﬂuence on the crystal phase of the product.Gas-sensing properties of the series of as-prepared WO 3nanoplates were tested by means of acetone,ethanol,formaldehyde and ammonia.One of the WO 3nanoplates with high speci ﬁc surface area and high crystallinity displays high sensitivity,fast response and distinct sensing selectivity to acetone gas.ã2014Elsevier Ltd.All rights reserved.1.IntroductionAs an n -type indirect band gap semiconductor,WO 3has attracted much attention and been studied extensively in recent years.So far,many methods have been reported for synthesis of WO 3nanomaterials with various morphologies,such as nano-plates [1–5],nanorods [6–8],nanowires [9–11],nanoparticles [12]and nano ﬁbres [13]etc .Recently,Zou et al.have prepared a new WO 3nanoplate via a simple thermal treatment process from a W-containing inorganic –organic nanohybrid precursor [14].Leaf-like WO 3nanoplatelets were fabricated via aging treatment of the precursor solutions obtained by pulsed laser ablating pure tungsten target immersed in deionized water [15].Ma et al.have prepared triclinic WO 3nanoplates by a simple hydrothermal method at various temperatures using Na 2WO 4Á2H 2O and HBF 4as precursors [1].Nimittrakoolchai and Supothina have synthesized WO 3ÁH 2O and H 2WO 4ÁH 2O platelet particles by a precipitation method using (NH 4)10W 12O 41Á5H 2O and HNO 3as precursors,and investigated the effect of nitric concentration on the yield [16].However,so far,no reference has been found concerning the effectsof both hydrothermal temperature and the amount of acid on crystal phases and morphologies of WO 3nanostructures.WO 3nanostructures could be extensively applied in electro-chromic and photochromic devices [6,17–20],lithium ion batteries [21–22],photoelectrodes [23],photocatalysts [24–26],solar energy devices [27–28],ﬁeld electron emission [29–30]and gas sensors [1,10,13,14,16,31–42]etc.Being one of the important gas-sensor materials,more and more WO 3nanomaterials with new structures or morphologies have been synthesized because the gas-sensing properties could be tuned by the structures and morphologies of the materials.For instance,WO 3nanowires [10],nano ﬁbers [13],hollow microspheres [31],nanocrystals [32,33],thin ﬁlms [34]and WO 3nanorods/graphene nanocomposites [35]have been used as the sensing materials for detection of nitrogen oxides,NH 3and ethylene.More gaseous species,such as H 2[14,34,36],ethanol [1,14,37,38],CO [14,37],H 2S [39],and ozone [37,40]could also be detected by WO 3-based nanocrystals and ﬁlms.However,so far there are few reports on acetone [14,41]and formaldehyde [14]sensing properties of WO 3nanoplates although acetone and formaldehyde are harmful to health,as common reagents widely used in industries and labs.Besides,a nanoplate-like material normally has a high sensitivityand rapid response [42]due to the effective and rapid diffusion of the analyte gas onto the entire sensing surface through the two-dimensional (2D)nanostructures.Therefore,it is worthwhile studying the gas sensing properties of the 2D WO 3nanoplates.*Corresponding author.Tel.:+862260214259;fax:+862260214252.**Corresponding author.Tel.:+862223507951;fax:+862223502458.E-mail addresses:zhulj@ (L.Zhu),zhwj@ (W.Zheng)./10.1016/j.materresbull.2014.06.0130025-5408/ã2014Elsevier Ltd.All rights reserved.Materials Research Bulletin 57(2014)260–267Contents lists available at ScienceDirectMaterials Research Bulletinj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /m a t r e s buHerein,a facile hydrothermal route was adopted for syntheses of series of WO3nanostructures.The effects of the amount of HNO3,hydrothermal temperature and reaction time on crystal phases and morphologies of WO3products were investigated and discussed.The formation mechanism of the WO3nanoplates was studied on the basis of control experiments.The gas-sensing properties of the as-prepared WO3on acetone,ethanol,formalde-hyde and ammonia were evaluated,and a nanoplate-like WO3 shows a high sensitivity,rapid response and distinct selectivity to acetone gas.2.Experimental2.1.Synthesis of WO3nanostructuresIn a typical procedure,0.3299g of Na2WO4Á2H2O(1mmol)was added into certain volume of distilled water and dissolved thoroughly under stirring.Then,certain amount of HNO3(w, 65%)was dropped into the solution and kept stirring for10min. The total volume of the solution was always kept to be25.0mL.The above mixture was transferred into a33.0mL of Teﬂon-lined stainless steel autoclave,sealed and kept in an electric oven at certain temperature for12h.The autoclave was then taken out and allowed to cool naturally to room temperature.The obtained precipitate was separated by centrifugation,washed by distilled water and absolute ethanol for three times,respectively,and dried at50 C.2.2.CharacterizationsThe XRD measurements were performed on a Rigaku D/max-2500diffractometer with Cu K a radiation(l=0.154056nm)at 40kV and100mA.The SEM images were taken with a JEOL JSM-6700F scanning electron microscope.The TEM and high resolution TEM(HRTEM)images of the WO3nanoplates were obtained on a JEOL JEM-2100F microscope operating at200kV.The N2adsorp-tion–desorption isotherm measurements were operated on a V-Sorb2800P surface area and pore size analyzer.2.3.Fabrication and test of WO3gas sensorsThe schematic illustration of the gas-sensing measurement and working principle of HW-30A system can be found in the references[1,43].The WO3nanoplates were slightly grinded with several drops of terpineol in an agate mortar.The formed slurry was coated onto an alumina tube with a diameter of1mm and length of4mm,positioned with a pair of Au electrodes and four Pt wires on both ends of the tube.After calcination at400 C for1h, the alumina tube was jointed with the measuring electric circuit.In order to improve the stability and repeatability,the gas-sensing element was aged at340 C for two weeks before the measure-ment.Acetone,ethanol,formaldehyde and ammonia with various concentrations were chosen to evaluate the gas-sensing properties of the as-prepared WO3.The sensor response is deﬁned as S=R a/R g, where R a and R g are the electrical resistance of the sensor in air and in test gas,respectively.The response and recovery time is deﬁned as the time for the sensor to reach90%of its maximum response and fall to10%of its maximum response,respectively.3.Results and discussion3.1.Effects of hydrothermal temperature and the amount of HNO3on the crystal phases and morphologies of the productsFig.1shows the crystal phase evolution of the products obtained at120 C using various amount of HNO3.When0.5mL of HNO3is used,the main product is orthorhombic WO3ÁH2O(JCPDS 43-0679)with a little impurity(Fig.1a).Increasing the amount of HNO3to1.5mL leads to the formation of a pure orthorhombic WO3ÁH2O(Fig.1b).The monoclinic phase of unhydrous WO3 (JCPDS43-1035)appears when2.5mL of HNO3is used and the relative peak intensity of this phase increases gradually by increasing the volume of HNO3until12.0mL(Fig.1c–f).When the amount of HNO3is further increased,however,no pure phase of monoclinic WO3is produced(Fig.1g and h).On the contrary,the relative intensity of the diffraction peaks of the monoclinic WO3 becomes lower,but that of the WO3ÁH2O phase becomes higher again.When the volume of HNO3reaches20.0mL,the diffraction peaks of the monoclinic WO3phase become even faint.The morphology evolution of the products prepared at120 C using various amount of HNO3is demonstrated in Fig.2.It was observed that the product’s morphology changes greatly in the low volume region of HNO3.A nanoparticle and nanorod mixture was collected when0.5mL of HNO3was used in the reaction system. Slightly increasing the volume of HNO3to1.5mL would lead to the formation of a bigﬂower-like hierarchical structure which is composed of many crossed and lapped quasi-round nanoplates with rough surfaces.The accumulated quasi-round nanoplates start dispersal and the surfaces become smooth when the volume of HNO3is increased to2.5mL.Most of the nanoplates are about 600nm in diameter and25nm in thickness.If5.0mL of HNO3is used,square-like nanoplates with a side length of around200nm and thickness of30–40nm are obtained.The surfaces of these nanoplates are rather smooth.When the volume of HNO3is in the range of 5.0–12.0mL,the products’morphologies are similar, unless the size of the nanoplate gradually becomes smaller with increasing the acid quantity.Some square-like nanoplates become a bit irregular and their surface roughness also increases if the amount of HNO3reaches15.0mL.Further increasing the amount of HNO3to20.0mL,irregularly shaped nanoplates with rather rough surfaces were obtained.This morphology is similar to that of the product in Fig.2c,unless the size is much smaller.One may notice that the phase composition of these two products(Fig.1c and h)is also similar.The other series of products were obtained at180 C,a higher hydrothermal temperature.The corresponding XRD patterns are shown in Fig.3.Orthorhombic WO3ÁH2O(JCPDS43–0679)was produced using0.5mL of HNO3.Increasing the amount of HNO3to 1.5mL leads to the formation of a mixture with most orthorhombic WO3ÁH2O and a little monoclinic WO3(JCPDS43–1035).The phase compositions of the products change dramatically withslightlyFig. 1.XRD patterns of the products prepared by hydrothermal method at120 C using various amount of HNO3:(a)0.5mL,(b)1.5mL,(c)2.5mL,(d)5.0mL,(e) 10.0mL,(f)12.0mL,(g)15.0mL and(h)20.0mL.H.Zhang et al./Materials Research Bulletin57(2014)260–267261increasing the volume of HNO 3from 1.5mL to 2.0mL.Pure monoclinic WO 3is obtained in the presence of 2.0mL of HNO 3.With further increasing the amount of HNO 3,the crystal phases of the products do not change any more.But the intensity of the diffraction peaks increases ﬁrstly and then declines slightly.The peak intensity reaches maximum using 10mL of HNO 3,which indicates the highest crystallinity of the WO 3product obtained at this condition.Thus,10mL of HNO 3is a suitable amount to obtain a pure monoclinic WO 3with a high crystallinity.The morphology evolution of the products prepared at 180 C using various amount of HNO 3is demonstrated in Fig.4.When 0.5mL of HNO 3is used,a nanoparticle –nanorod mixture (Fig.4a)is obtained,similar to the morphology of the product prepared at 120 C (Fig.2a).However,in the case of 1.5mL HNO 3,the two products prepared at these two hydrothermal temperatures have completely different morphologies.As shown in Fig.4b,the product comprises many non-uniform big rectangular blocks andplates.Slightly increasing the HNO 3–2.0mL leads to formation of WO 3nanoplates with different size,and some nanoplates accumulate with their large surfaces.When 10.0mL or 15.0mL of HNO 3is used,the product is well-dispersed nanoplates with the large surfaces exposed (Fig.4d and e).The side length and thickness of an individual nanoplate are approximately 100nm and 40nm,respectively.Changing the amount of HNO 3in the range of 10–15mL does not in ﬂuence the morphology of the products.But in case of 20.0mL HNO 3,the uniformity of the product decreases and the size of the nanoplate increases to certain extent,although its crystal phase is kept unchanged.Because both the uniformity and crystallinity of the sample prepared at 180 C using 10.0mL of HNO 3are high,its TEM and HRTEM images were taken.As shown in Fig.5a,the side length and thickness of the most WO 3nanoplates are around 100nm and 30–40nm,respectively,which is consistent with the SEM result.The clear 2D crystal lattice (Fig.5b)shows that theinterplanarFig. 2.SEM images of the products prepared by hydrothermal method at 120 C using various amount of HNO 3:(a)0.5mL,(b)1.5mL,(c)2.5mL,(d)5.0mL,(e)10.0mL,(f)12.0mL,(g)15.0mL and (h)20.0mL.262H.Zhang et al./Materials Research Bulletin 57(2014)260–267distances are 0.37and 0.38nm,corresponding to (020)and (002)crystal planes,respectively.The fast Fourier transform pattern (the inset)indicates its single crystalline nature.On the basis of above results we conclude that both hydrothermal temperature and the amount of HNO 3in ﬂuence the crystal phase and morphology of the product.Fig.6shows a summary of these two effects.Similar to the result in our previous work [1],low temperature favours the formation of WO 3ÁH 2O andhigh temperature is propitious to production of anhydrous WO 3.Increasing temperature results in dehydration of WO 3ÁH 2O,forming pure WO 3phase,even using a small volume of HNO 3(for example,2.0mL HNO 3).However,at the low hydrothermal temperature,120 C,no pure phase of WO 3was obtained even if a large volume of HNO 3was used.In the region of small volume of HNO 3,the crystal phases and morphologies of the products are found more sensitive to the change in acid quantity and reaction temperature.For instance,when 1.5mL of HNO 3was used,a hierarchical ﬂower-like hydrous WO 3was formed at 120 C,but a non-uniform rectangular block and plate-like hydrous and anhydrous WO 3mixture is the main product at 180 C.This may be attributed to different nucleation rate,diffusion rate of nanoparticles and dehydration rate at different temperatures.At high temperature,the formation rate of tungsten oxide nucleus is fast and the hydrous WO 3loses water quickly once beyond its decomposition temperature,which partially counteracts the in ﬂuence of larger amount of water on the crystal phase of the product when small volume of HNO 3is used.Moreover,the diffusion rate of nanoparticles is low at low temperature,which contributes to the formation of a big architecture.But a high diffusion rate at high temperature helps to epitaxy along certain crystal face [44].Therefore,different morphological products were produced at two hydrothermal temperatures using 1.5mL of HNO 3.When large amount of HNO 3(for instance,10mL HNO 3)is used,however,it is different from the above case.The similar morphology of the two products obtained at the twotemperaturesFig. 3.XRD patterns of the products prepared by hydrothermal method at 180 C using various amount of HNO 3:(a)0.5mL,(b)1.5mL,(c)2.0mL,(d)10.0mL,(e)15.0mL and (f)20.0mL.Fig.4.SEM images of the products prepared by hydrothermal method at 180 C using various amount of HNO 3:(a)0.5mL,(b)1.5mL,(c)2.0mL,(d)10.0mL,(e)15.0mL and (f)20.0mL.H.Zhang et al./Materials Research Bulletin 57(2014)260–267263clearly shows that large amount of acid is bene ﬁcial to the oriented growth of the tungsten oxides,forming nanoplates.This,on the one hand,may be related to the high degree of supersaturation of the solution,which will increase the nucleation rate and dehydration rate of H 2WO 4,and ultimately increase the reaction rate.On the other hand,the acidity of a reaction system in ﬂuences surface energies of certain crystal facets [45],which may signi ﬁcantly in ﬂuence the oriented growth of a crystal,and consequently in ﬂuence the morphology of the product.Thus,suitable amount of acid is a dominant factor to the formation of nanoplate-like morphology.However,the acidity effect on the crystal phase of the product is found weaker than that of temperature.The low nucleation rate at 120 C results in the larger size of the nanoplates (compared to the product prepared at 180 C),which accords with the crystallization principle.The low dehydration rate at the lower temperature leads to incomplete dehydration of the product,forming a mixed phase of product.Thus,a larger size of mixed phase of nanoplate was obtained at 120 C using 10mL of HNO 3.3.2.Formation mechanismBecause the product prepared at 180 C using 15.0mL of HNO 3shows the better gas-sensing property,its time-dependent crystal phase and morphology evolutions were investigated.It represents the effect of hydrothermal time on the crystal phase and morphology of a WO 3nanostructure.As shown in Fig.S1and S2in the supporting information (ESI),pure uniform orthorhombic WO 3ÁH 2O (JCPDS 43–0679)nanoplates were obtained at 1h,which were quickly transformed to WO 3nanoplates.A mixture of WO 3ÁH 2O and WO 3was collected at 1.5h and pure monoclinic WO 3(JCPDS 43-1035)nanoplates were produced at 2h.These results con ﬁrm that a hydrous WO 3was formed at the early stage of the reaction and prolonging hydrothermal time results in a quick dehydration of WO 3ÁH 2O.The corresponding chemical reactions contain:WO 2À4þ2H þ!WO 3ÁH 2O(1)WO 3ÁH 2O !WO 3þH 2O(2)This reaction process is similar to the work by Lee et al.[46,46],where the high concentrations of HNO 3(0.29–11.5mol L À1)were replaced by low concentrations of HCl (pH 2–6)and NaCl was used as a capping agent.However,WO 3nanorods were obtained in their work although a similar procedure was applied.Lee et al.believed that NaCl selectively adsorbed onto the crystal planes parallel to the c -axes of WO 3crystal nucleus to accelerate the preferential growth,resulting in the formation of 1D structure.In our case,no capping agent or directing agent was used.Besides,as shown in Fig.6,a large amount of acid is bene ﬁcial to the oriented growth of nanoplate-like tungsten oxides.Except the external factors,the intrinsic crystal structure is also an essential factor for morphology control of the product.The orthorhombic H 2WO 4consists of layers of [WO 6]octahedra,which share their four equatorial oxygen atoms.Water molecules and oxygen atoms in the axial positions of the [WO 6]octahedra form hydrogen bonds with the neighboring layers [3],as shown in Fig.S3a in the ESI.The monoclinic WO 3possesses a distorted ReO 3structure,see Fig.S3b.The layers of [WO 6]octahedra in the orthorhombic H 2WO 4and the monoclinic WO 3are similar.The shared four equatorial oxygen atoms extend forming a 2D plane structure.At high temperature,the hydrogen bonds in the layers of [WO 5(OH 2)]octahedra of the H 2WO 4were replaced by W ÀÀO ÀÀW bonds forming a three-dimensional W ÀÀO ÀÀW lattice-work and losing the crystal waters.The similarity of the WO 6octahedral sheets in H 2WO 4and WO 3results in the formation of the nanoplate-like WO 3.3.3.Gas-sensing properties and mechanismAll gas-sensing measurements were operated at 300 C.Therefore,the samples were calcined at 450 C for 2h before the gas-sensing measurements to ensure their thermal stability.The XRD patterns of the calcined WO 3samples are shown in Fig.S4in the ESI.All diffraction peaks for all the samples can be indexedtoFig. 5.(a)TEM and (b)HRTEM images of the sample prepared at 180 C using 10.0mL of HNO 3(the inset is the fast Fourier transformpattern).Fig.6.Schematic representation of the formation of the WO 3nanostructures with various morphologies and crystal phases:(a)orthorhombic WO 3ÁH 2O,(b)a mixture of orthorhombic WO 3ÁH 2O and monoclinic WO 3and (c)monoclinic WO 3,prepared at two hydrothermal temperatures using various amount of HNO 3.264H.Zhang et al./Materials Research Bulletin 57(2014)260–267monoclinic WO3(JCPDS43-1035),which indicates that pureanhydrous WO3products were obtained after the heat treatment.The SEM images of the calcined WO3samples,Fig.S5in the ESI,demonstrate that the product morphologies before and after theheat treatment are similar,which veriﬁes again that thecondensation from WO3ÁH2O to WO3is a topotactic conversion process.The synthetic conditions of the precursors,the morphol-ogies and Brunauer–Emmett–Teller(BET)surface areas of thecalcined WO3products are summarized in Table1.The gas-sensing properties of the series of WO3nanomaterialsareﬁrst evaluated by means of200ppm acetone gas(Fig.7a).Theresults show that the sensor based on the S3sample is moresensitive than the others.The response of the S2sensor is slightlylower than that of the S3sensor.The third sensitive sensor is basedon the P3sample.The high responses of the S2,S3and P3sensorsmay be attributed to their high BET surface areas,highcrystallinities and plate-like morphologies[38].The most sensitive three sensors based on the samples S2,S3and P3were then chosen to investigate the sensitivities in thepresence of various concentrations of acetone gases,from10ppmto400ppm.As shown in Fig.7b,the S3sensor always has thehigher response than the other two sensors to any concentration ofacetone gas.The responses for all the three sensors increasesigniﬁcantly with increasing the concentration of acetone gas.Forinstance,the response for the S3sensor increases from4.1to15.8with increasing the concentration of acetone from10ppm to400ppm.Fig.8a represents the dynamic responses of the S2,S3and P3sensors to acetone gases with various concentrations from10ppmto400ppm.Sharp rises and drops in voltage values were observedfor all concentrations of acetone gases when they were injectedand discharged,respectively.This indicates that the WO3nano-plate sensors have a wide range of acetone-detecting abilities andare of fast response and recovery speeds to acetone gases.Forexample,the response and recovery time of the S3sensor are7sand23s,respectively,for100ppm acetone gas(Fig.8b).The resultsalso show that the response increases with increasing theconcentration of acetone gas at the same operating conditions.The sensing selectivity of the S3sensor was explored bycomparing the responses of the S3sensor to acetone,ethanol,formaldehyde and ammonia gases with various concentrations.Asshown in Fig.9,the responses of the S3sensor to all the four gasesincrease gradually with increasing the concentrations of the gases.However,the order of magnitude of the responses to differentgases is quite different.It is less sensitive to ethanol and almostinsensitive to formaldehyde and ammonia,compared to acetone.Thus,the as-prepared WO3nanoplate(S3)displays a distinctsensing selectivity to acetone gas,which could be explained byconsidering its sensing mechanism.As an n-type semiconductor,the sensing mechanism of theWO3nanoplate could be explained using the classical electrondepletion theory[41,47,48].Oxygen molecules in airﬁrst physically adsorb on the surface of WO3semiconductor.The O2(ads)capturesan electron from WO3forming OÀ2(ads).At an elevated tempera-ture,the chemically adsorbed O2(ads)molecules can obtainenough energy to capture two electrons or OÀ2(ads)to capture one more electron forming OÀ(ads).Because the oxygen ionosorption depletes electrons in the conduction band,conductance of the WO3 sensor is decreased.When the WO3nanoplate sensor is exposed to the reducing gases,acetone,ethanol,formaldehyde and ammonia, the gases react with the OÀ(ads)on the surface of WO3.Referring to the references[49,50],the reactions could be expressed by the following Eqs.(3)–(6).CH2Oþ2OÀðadsÞ!CO2þH2Oþ2eÀ(3) C2H5OHþ6OÀðadsÞ!2CO2þ3H2Oþ6eÀ(4) CH3COCH3þ8OÀðadsÞ!3CO2þ3H2Oþ8eÀ(5) NH3þ5=2OÀðadsÞ!NOþ3=2H2Oþ5=2eÀ(6) The gas removes chemisorbed oxygen anions and releases electrons to the conduction band.This will decrease the amount of the surface OÀ(ads)and increase the concentration of electrons in the conduction band,which eventually increases the conductance of the WO3sensor.According to the Eqs.(3)–(5),more electrons are released with increasing carbon chain.Consequently,the response increases because of the increased conductance of the sensor. Therefore,the gas response of acetone is higher than those of ethanol and formaldehyde gases at the equivalent concentration.As it is known that WO3is an acid oxide and generally it shows relatively high response to ammonia[13,41,51,52],but this is not always the case.For instance,Yu et al.reported that the gas responses of the WO3nanorods are7.6,18and27.5for1mL of ammonia,ethanol and acetone,respectively[35].A similar result was also found by Li and his co-workers[53],where the gas responses of the WO3hollow-spheres are2.89,6.14and13.50for 500ppm of ammonia,ethanol and acetone gases,respectively. These works show that the responses of the WO3nanostructures to ammonia gases are low and much lower than those of ethanol and acetone gases at the equivalent condition,which is similar to our result.Weﬁnd that the response of the as-prepared WO3nanoplate to the alkaline gas,NH3,is lower than those of ethanol and acetone gases although it is slightly higher than that of formaldehyde.One may notice that the four gas responses(Fig.9)of the WO3 nanoplate increase with increasing the quantity of the released electrons(Eqs.3–6).This further conﬁrms the proposed sensing mechanism above.From this point of view,it is reasonable that the as-prepared WO3nanoplate shows a distinct sensing selectivity to acetone gas.The sensing performance of a material can be strongly affected by a few factors.The higher the BET surface area is,the higher the oxygen-adsorption quantity is,and the higher sensitivity the WO3 sensor has[54].High crystallinity is also beneﬁcial to highTable1The synthetic conditions of the precursors and properties of the WO3products after calcination at450 C for2h.Samples T( C)HNO3(mL)[H+](mol LÀ1)Morphologies Surface areas(m2gÀ1)P1120 5.0 2.9Nanoplate17.6P212010.0 5.8Nanoplate24.2P312012.0 6.9Nanoplate28.7P412015.08.6Nanoplate25.3S1180 2.0 1.2Big block and plate12.2S218010.0 5.8Nanoplate23.9S318015.08.6Nanoplate40.1S418020.011.5Nanoplate19.4H.Zhang et al./Materials Research Bulletin57(2014)260–267265sensitivity of a WO 3sensor [38].Therefore,the S3sensor has the highest value of acetone response due to the largest BET surface area exposed to gas and good crystallinity.Besides,the plate-like morphology of the WO 3allows for rapid diffusion of acetone molecules,which results in a fast gas-sensing response.In a word,the WO 3nanoplate (S3)is very promising for fabrication of an acetone gas sensor because of its high sensitivity,distinct selectivity and fast response to acetone gas.4.ConclusionsSeries of tungsten oxide nanostructures with different crystal phases and morphologies have been synthesized at two temper-atures by a facile hydrothermal method using various amount of HNO 3,and the formation mechanism of the WO 3nanoplate was explored based on series of time-dependant control experiments.The results show that the tungstate ﬁrst reacts with hydrion forming hydrous WO 3,followed by a dehydration rge amount of acid,high temperature and long reaction time are found generally bene ﬁcial to the formation of anhydrous WO 3nano-plates.It is worth mentioning that large amount of acid is found helpful to the oriented growth of the tungsten oxides,forming a nanoplate-like product.But the effect of acid quantity on the crystal phase of a product is weaker than that of temperature.The low dehydration rate at the low temperature (120 C)leads to incompletely dehydration of the product,forming a WO 3ÁH 2O and WO 3mixed phase of nanoplate,even if a large amount of acid (10mL)is used.At the high hydrothermal temperature (180 C)the nucleation rate,diffusion rate of nanoparticles and dehydration rate are increased signi ﬁcantly,resulting in the formation of pure monoclinic WO 3nanoplates,even if a small amount of acid (2mL)is used.The gas-sensing measurements show that the sensitivities of the sensors based on the S3,S2and P3samples are the top three in the presence of 200ppm acetone gas.The S3sensor shows a distinct selectivity and fast response to acetone gas,which implies that the WO 3nanoplate (S3)is a promising material for fabrication of an acetone gassensor.Fig.7.Response comparison of the sensors based on the samples (a)P1-P4and S1-S4in the presence of 200ppm acetone gas and (b)P3,S2and S3in the presence of various concentrations of acetonegases.Fig.8.(a)Dynamic response –recovery curves of the P3,S2and S3sensors for acetone gas detection and (b)response transients of the S3sensor to 100ppm acetone gas.R e s p o n s eConce ntration /pp mFig.9.Sensing selectivity of the S3sensor to four gases with variousconcentrations.266H.Zhang et al./Materials Research Bulletin 57(2014)260–267。

WO3光电催化材料的电子结构及催化性能研究

WO3光电催化材料的电子结构及催化性能研究随着环境污染问题的加剧，寻找高效、经济、环保的治污技术成为了当今社会亟需解决的问题之一。

而光电催化技术因其具有高效、无二次污染、可再生等优点，被认为是治污技术中的一种重要手段。

而WO3作为光电催化材料的一种，因其良好的催化性能以及广泛的应用前景，受到了越来越多的研究关注。

首先，我们需要了解WO3光电催化材料的电子结构。

WO3属于过渡金属氧化物，具有独特的电子结构特征。

它的晶体结构为六方晶系，是一种正交的六方密排结构，其中W离子为六面体配位，氧离子则处于八面体配位。

在它的能带结构中，最高占据态在氧的2p轨道上，而最低未占据态则位于W的5d轨道上。

这种能带结构导致了WO3的光电催化性能，使其能够利用光的能量来激发电子的运动，产生电子空穴对并在表面产生活性物种，从而实现催化反应。

其次，我们需要探讨WO3光电催化材料的催化性能。

WO3具有优异的催化性能，特别是在光催化反应中表现突出。

研究表明，WO3的光催化剂能够产生氧化还原对，并促使废水中的有机物质在光的作用下氧化分解，从而降低废水中有机物的含量。

此外，WO3还可用于其他催化反应中，如电化学催化、化学传感器等领域。

最后，我们需要探究提高WO3光电催化材料催化性能的方法。

WO3的催化活性主要受其晶体结构、表面性质和晶格缺陷等影响。

在研究中发现，WO3晶体表面的羟基（OH-）和氧空位（O2-）是其表面活性位。

而在制备过程中，制备方式和工艺条件等也会对WO3的催化性能产生影响。

因此，通过合理的制备方式和工艺条件来构造WO3的材料形态、晶面去向和表面结构等特性，能够有效地提高其催化性能。

综上所述，WO3光电催化材料具有优异的电子结构和催化性能，具有广泛的应用前景。

同时，在研究中提高其催化性能的方法也越来越多。

相信在不久的将来，WO3光电催化材料将在各种治污领域中发挥出更加重要的作用，为我们创造一个更加美好的生活环境。

永磁同步电机,等效磁路法,工作特性曲线

Studies in Synthetic Chemistry 合成化学研究, 2017, 5(2), 7-12Published Online June 2017 in Hans. /journal/sschttps:///10.12677/ssc.2017.52002Review on Preparation and Applicationof WO3 NanomaterialsQin Zhu, Cheng Huang, Huidan Lu*College of Chemistry and Bioengineering, Guilin University of Technology, Guilin GuangxiReceived: May 14th, 2017; accepted: May 30th, 2017; published: Jun. 2nd, 2017AbstractWO3 is an important n-type semiconductor. WO3 nanomaterials can be widely applied in soler cell, electron device, photocatalysis and sensor fields, due to excellent optical and electrochemical properties. This article reviews the progress on properties, preparation and application of WO3 nanomaterials.Finally, research prospect of WO3 nanomaterials is also presented.KeywordsWO3, Property, Preparation, ApplicationWO3纳米材料的制备与应用研究进展朱琴，黄成，吕慧丹*桂林理工大学化学与生物工程学院，广西桂林收稿日期：2017年5月14日；录用日期：2017年5月30日；发布日期：2017年6月2日摘要三氧化钨(WO3)是一种重要的n型半导体材料。

气敏材料的制备及其气敏性能研究

气敏材料的制备及其气敏性能研究随着人类社会的发展，环境污染问题日益突显，如何对环境进行有效的监控和治理成为了亟待解决的问题。

其中，气体污染监测是环境监测的重要分支，而气敏材料的研究及其应用在气体污染监测方面具有重要意义。

气敏材料是一类能对某种气体或气体混合物产生敏感响应的材料，可以对气体浓度、组成等进行检测。

当前，气敏材料的种类繁多，主要包括半导体气敏材料、金属氧化物气敏材料、有机气敏材料等。

半导体气敏材料的制备通常采用溶胶-凝胶法、气相沉积法、离子束溅射法等多种方法，其中，溶胶-凝胶法由于操作简单、成本低廉、制备设备简单等优点，已成为半导体气敏材料制备的首选方法。

溶胶-凝胶法主要是将金属离子或有机物离子与适当的溶剂混合形成胶体，经过凝胶、热处理等工艺制备出气敏材料。

金属氧化物气敏材料的制备主要采用溶胶-凝胶法、物理气相沉积法、化学气相沉积法等方法。

与半导体气敏材料不同，金属氧化物气敏材料的制备通常需要高温煅烧，以提高晶体质量和敏感性。

有机气敏材料的制备主要采用溶剂聚合、原位合成、溶液法等方法，由于有机气敏材料的特殊结构以及溶液制备过程中易于控制，因此在制备过程中需要特别注意溶液粘度、聚合速率等因素。

此外，有机气敏材料的应用范围相对狭窄，多用于检测有机气体或挥发性有机化合物。

从制备过程来看，气敏材料的制备技术难度较大，需要一定的操作技能和实验经验。

另外，制备出来的气敏材料敏感性能也受到多种因素的影响，如晶体结构、纯度、晶界等。

因此，在实际应用中，需要针对具体的检测对象和检测要求进行优化和改进，以提高气敏材料的敏感性和选择性。

气敏材料的气敏性能是用来评价材料对目标气体响应的强弱及可靠性的重要指标之一。

气敏性能包括敏感度、选择性、响应时间、稳定性等指标。

其中，敏感度是评价材料检测目标气体浓度的能力，当目标气体浓度发生一定变化时，敏感度能够反映材料对浓度变化产生的响应。

选择性是评价材料检测目标气体和其他气体的区分能力，即材料对不同气体的响应差异程度。

三种纳米结构三氧化钨的气敏性研究

三种纳米结构三氧化钨的气敏性研究王新刚;郭一凡;田阳;刘丽丽;张怀龙【摘要】Utilizing ammonium metatungstate [(NH4)6W12O40] as raw material, we produced three kinds of nanostructured WO3 under the same reaction conditions by controlling the concentration of citric acid (C6H8O7). The nanostructured WO3 was characterized by XRD, SEM and TEM. Then, three kinds of gas sensors including WO 3 nanorod gas sensors, WO3 nanoplate gas sensors and WO3 nanoplate/nanorods mixing gas sensors were further manufactured. The sensitivity was measured for three kinds of nanostructured WO 3 gas sensors under the condition of acetone, ammonia and formaldehyde gas respectively. Experimental results show that the sensitivities of the three kinds of nanostructured WO3 firstly increase and then decrease with the increase of temperature at gas concentration of 1 000 ×10-6. In contrast, the sensitivity of WO3 nanoplate gas sensors is the highest among the three kinds of nanostructured WO3 for the three kinds of gases in the range of measuring temperature. The opt imum operating temperature of WO3 nanoplate gas sensor is 350 ℃, 300 ℃, 325 ℃, 250 ℃ and its maximum sensitivity is 25.4, 18.52, 30.29, 18.31 in acetone, ammonia and formaldehyde gas, respectively. The sensitivity of the three kinds of nanostructured WO3 firstly increases and then decreases with the increase of temperature in the acetone gas of 50 × 10-6 and the formaldehyde gas of 100×10-6, respectively. The sensitivityof WO3 nanoplate is obviously higher than that of other twonanostructured WO3. At the optimum operating temperature, the acetone and formaldehyde gas with lower concentration can be detected by using nanoplate WO 3 gas sensor.%试验以偏钨酸铵为钨源，采用水热法在相同的反应条件下，通过控制柠檬酸的加入量，合成了三种纳米结构的三氧化钨，并采用XRD、SEM和TEM对合成的WO3粉末进行分析。

铈掺杂WO3纳米材料气敏特性研究

（广州大学物理与电子工程学院，广东广州５００）１０６摘要：以金属ｗ粉为原料采用溶胶一凝胶法制得纳米级ＷＯ。粉体，探讨了不同ＣＯｅ。添加量对气敏特
性的影响。ＣＯｅ掺杂ｗＯ材料对挥发性有机Ｃ）而器件的工作温度
（ｎｔｕｅｏｈｓｓａｄＥｅｔｏｉｓＴｃｎｌｇ，ａｇｈｕＵｖｒｉ，ａｇｈｕ５００，ｈｎ）ＩｓｔｔｆｙｉｎｌｒｎｃｅｈｏｏｙＧｕｎｚｏｎｅｓｙＧｕｎｚｏ１０６ＣｉａｉＰｃｃｉｔＡｓａｔａｏｓａｄｔｎｓｎｔｏｉｅ（３ｏｄｒｉｓｎｅｉｄｂｏ— ｌｒｃｓｕｉｎｓｎｐｗｅｂｔｃ：Ｎｎ—ｃｌｕｇｔ —ｉｄＷＯ）ｐｗｅｓｙｔｓｅｙｓｌｅｐｏｅｓｓｇｔｇｅｏｄｒｒｅｅｒｘｈｚｇｎｕｔａｍａｒ１Ｔｅｅｅｔｆｅｉｘｄ（ｅ２ｄｉｖｎｔｎｉｖｙｆｎｌｅｉｓｓｎｅｔａｄｅｐｃａｙｓｔｉ．ｈｆｃｏｒｍｏｉＣＯ）ａｄｔｅｅｓｓｉｔｏａｄｖｅｖｓｇｔ，ｓｅｉｌｅａｆｃｕｅｉｏｈｅｔｉｆｃｉｉｉｉｅｌｔｖｌｉｒａｉｃｍｏｎｓ（Ｏｓｎｉｉｃｎｎａｃｍｎｉａｈｅｅ，ｅｈｇｅｔｅｓｉｔｉｆｕｄｔｏｏｔｅｏｇｎｃｏｐｕｄＶＣ）ａｄｓｎｆａｔｈｎｅｅｔｓｃｉｖｄｔｉｈｓｓｎｉｖｙｓｏｎａｌｇｉｅｈｔｉｏ
ｓｉｏｌｗｈａｉｇｖｌｇ．ｈｎｌｓｓｆｏｅｄｅｓｉｎＳｈｆｔｅｔｏｔｅＴｅａａｙｉｒｍｆｌ — ｍｉｓｏＥＭｅｅｌｔａｒｉｏｎａｓｐｎｅｕｏｔｏｎａｉｒｖａｓｈｔｇａｎｂｕｄｒｉｉｎｄｄｅｔｙａｄｎｅ，ｈｃｅｕｓｉｅｒａｅｉｅａｅａｅｇａｎｓｚｆｅｄｐｄＷＯｄｉｃｅｓｎｔｅｓｒａｅａｅｄｉｇＣＯ２ｗｉｈｒｓｈｎｄｃｅｓｎｔｖｒｇｒｉｉｏ —ｏｅｈｅＣ３ｎｎｒａｅｉｈｕｆｃｒａ，ａｃｍｐｒｄｗｉｈｎｏｅｎｓＣｍｐｅｍｐｄｎｅｓｅｔｏｃｐｎｌｓｓｉｄｃｔｓｔａｈｅｉｎｉｌｘｓｏａｅｔｔｅｕｄｐｄｏｅ．ｏｌｘｉｅａｃｐｃｒｓｏｙａａｙｉｎｉａｅｈｔｔｅＣｏｓｍａｎｙｅｉｔｈｉＯ３ｇａｎｂｕｄｒｗｉｈｅｕｔｎｉｃｅｓｎｇａｎｂｕｄｒｅｉｔｎｅａｄｄｃａｅｉａｎｂｕｄｒｎＷｒｉｏｎａｙ，ｈｃｒｓｌｉｎｒａｅｉｒｉｏｎａｒｓｓｃｎｅｅｓｎｇｉｏｎａｓｙａｒｙ

溶胶-凝胶法制备氧化钨薄膜的研究

溶胶-凝胶法制备氧化钨薄膜的研究刘英;王兵;王速【摘要】H The WO3 thin film was prepared on ceramic substrate by sol-gel method using sodium tungstate as raw material,and then be annealed at 500℃.The structure and morphology of WO3 were characterized by X-ray diffraction(XRD)and scanning electron microscopy(SEM).The results showed that the film surface travels as nano-porous structure.And then,the gas sensing properties of WO3 thin film to NO2, H2 and alcohol were also researched.WO3 showed a better sensitivity to NO2 than to H2 and alcohol.%本文以钨酸盐为原料利用溶胶凝胶法，在陶瓷衬底制备WO3敏感薄膜，于500℃退火。

接着对制备好的薄膜进行X射线衍射与电子显微测试，观察到薄膜表面呈较规则的纳米多孔结构。

接着对NO2、H2、乙醇等气体进行敏感测试，测试证明薄膜对H2、乙醇敏感性较差，对NO2敏感性良好。

【期刊名称】《电子测试》【年(卷),期】2016(000)016【总页数】2页(P160-160,156)【关键词】WO3纳米薄膜;溶胶-凝胶法;气体敏感【作者】刘英;王兵;王速【作者单位】广东宁源科技园发展有限公司，526000;广东宁源科技园发展有限公司，526000;广东宁源科技园发展有限公司，526000【正文语种】中文本文旨在改善溶胶-凝胶法制造工艺，利用后期热处理制造出具有介孔结构的纳米WO3薄膜。

纳米WO3的性质及应用

纳米WO3的性质及应用摘要：WO3是一种过渡金属半导体，位于元素周期表第 6 周期 VI B 族，带隙约为2.6eV，有着非常丰富的物理化学性能，本文就WO3性质及应用作一个简要的综述，并展望其发展方向。

关键词：WO3，性质，应用1 引言WO3是带隙约为2.6eV的过渡金属半导体，是一种重要的功能材料，因其优越的物理化学性能成为研究的热点。

WO3位于元素周期表第 6 周期 VI B 族，在自然界以钨华或钨赭石矿物态存，在空气和氧气中煅烧钨酸或仲钨酸铵，可以得到三氧化钨。

WO3的结构类似于ReO3的晶体，它的结构单元是钨离子位于八面体的中心，六个氧原子构成一个正八面体的顶点[1]。

退火温度和退火时间以及掺杂都对WO3的晶相有很大的改变。

WO3常见的晶系有单斜晶系，正交晶系，立方晶系和六方晶系。

WO3因其优越的物理化学性能在传感器，光电器件，太阳能电池，光催化等领域都有广泛的应用。

本文在前人研究的基础上就WO3的结构性质及应用作简要的概述。

2 性质及应用WO3的密度为7.2~7.4 g/cm3，沸点1700~2000℃之间，高于800℃时显著升华，三氧化钨不溶于除氢氟酸以外所有的无机酸，但易溶于碱金属氢氧化物的水溶液和碱金属氢氧化物及碳酸盐的溶体中。

水热法制备WO3的过程中很容易带上结晶水而得到WO3.nH2O，对其进行退火就能脱水得到WO3，很多科学家在上个世纪都对带结晶水的WO3进行过研究，发现其与WO3的性质并无不同。

2.1 气敏性能WO3具有很好的气敏性能，是一种很好的气敏材料，利用这一性质，可以制作为气敏传感器。

研究表明，氧化钨基气敏材料能准确检测出H2S，O3，NH3，NO2等，被认为最有前景的气敏材料之一。

WO3纳米材料由于比较面积大，所以具有较强的吸附功能，当它与空气中的H2、NH3接触时，会发生如下反应[2]：A+为H、Na等阳离子，当阳离子注入透明的WO3薄膜时， WO3的颜色由淡黄变为深蓝，AxWO3是含W5+的钨青铜。

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［］尼科利斯，．３Ｇ．Ｉ普里戈京著，徐锡申等译．非平衡系统的自组织，北京：科学出版社，８：９ — ０．１６４６５０９
中图分类号：Ｐ２２２Ｔ１．文献标识码：Ａ
用于检测微量Ｈｓ２气体的Ｓ０元件具有相当ｎ２高的灵敏度，但响应－恢复时间较长，选择性的提高也受限制。本文用化学沉淀法合成了ｘｔ％Ｓ２ｗ．ｉ一０ｗｏ（＝，，，０１）￣ｘ０３５１，５纳米粉体，研制出一系列烧
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维普资讯
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化学研究与应用
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维普资讯
化学研究与应用
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图２中ａｂ分别为纯ｗｏ粉体及掺杂比例、３为５ｉ２３％Ｓ一粉体的ＴＭ照片，０ｗｏＥ放大倍数为５万倍，比例计算后可知，ｗｏ粉体的平均粒按纯３径大约为４ｎ，２ｉ２３４ｎｌ５％Ｓ一ｏｗｏ粉体的平均粒径为３．ｎｌ２５ｎ，粒度均匀。２２材料的气敏性能．由图３可知，元件的灵敏度先是随着工作温度的升高逐渐增大，当工作温度为１０Ｉ时，８ｃ＝各元件的灵敏度达到该掺杂条件下的最大值，随后当
＝
上３０Ｉ老化２０ｈ２ｃ下＝４。
气敏性能的测试采用静态配气法，测试气体有ＨＳＮ－、ＨＯ、酮、２、Ｉ５Ｈ丙１３汽油、甲苯等，元件的加热电压可在较大范围内调节，负载电阻为可换插卡式，义元件的灵敏度Ｓ＝Ｒ／。Ｒ、ｇ定ａ船ａＲ分别为元件在空气和被测气体中的电阻。
３８７
化学研究与应用
第１卷６
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图２Ｓ２Ｗｏ粉体的ＴＭ照片ｉ－３ｏＥ
Ｆｇ．ＴＭｍａｅｆＳＯ２ＷＯ３ｐｗｅｓｉ２Ｅｉｇｓｏｉ－ｏｄｒ
温度继续升高时，元件灵敏度开始降低。这是由于元件的气敏性能不仅与基体材料有关，同气还体与材料的表面作用息息相关【。元件工作温度２Ｊ较低时元件的表面活性较低，化学吸附氧太少，与气体的作用较弱，因而灵敏度较低；由于Ｈｓ２是一种强还原性气体，温度过高时元件表面的氧化反应速度过快会限制ＨＳ气体的扩散，得元件表２使面被测气体的浓度很小，会引起灵敏度降低。同样该元件较其它ＨＳ气敏元件的最佳工作温度有很２大降低，元件工作温度越低，与环境温差越小，元件的阻值受环境温度的影响越小，实用性越强Байду номын сангаас 。３
掺杂量为３５１％时，强峰在左侧，、、０最当掺杂量为１％时最强峰移至右侧，５这是因为掺杂量不同时，在ｗｏ晶格内的分布有所不同，Ｓ３当掺杂
量增加到一定程度时，３ｗｏ的结合状态发生了变化，出现一定的定向性。随着掺杂量的增加，ＲＸＤ结型气敏元件，工作温度为１￣掺杂量为５８Ｃ，０％的其中１％ｓ２３图谱的５ｉ一ｏｗｏ气敏元件对Ｈｓ２有很高的灵敏度和选择性，响应一谱有一定的宽化现象，宽化现象较为明显，这是由于Ｓ的掺杂在一定恢复快，而且工作温度较低，有较好的应用价值。程度上抑制了ｗｏ晶粒的生长，３随着掺杂量的增１实验方法加，粉体粒径变小而引起的。由Ｓｅｅ公式计算ｈｒｒｒ得粉体的晶粒尺寸２．４４．８ｎｌＸＤ谱一１３ — ２２ｎ与Ｒ１１气敏材料的合成．在一定量的钨酸铵（学纯）化中加去离子水，致。加热至６ｃ使其溶解，ｏＩ＝在此条件下将正硅酸乙酯、无水乙醇、盐酸（分析纯）比例混合加入其按中，不断搅拌，形成黄色沉淀，过滤、洗涤、烘干、６０Ｃ０￣高温下煅烧５ｈ自然冷却，，研磨制得ｘｔ％ｗ．（，，，，５的ｓ２３０３５１１）ｉ．气敏粉体材料。００ｗｏ１２气敏元件的制作及气敏性能测试．取ｓ２３体材料少许，ｉ一粉０ＷＯ加入粘合剂磨匀，到已制好的带有金电极和铂引线的氧化铝涂细瓷管上，烘干、０ｃ下焙烧１ｈ冷却后在瓷管６ｏＩ＝，中间串入电阻丝并焊接到六腿管座上，在老化台
数为００５Ｅ气体灵敏度达到了９，．％ＨＳ０３是同样温度下其它元件的３～７倍。这是由于添加适量的ｓ抑制了晶粒的生长，减小粉体粒径，增大了比表面积之故。但随着掺杂量的增加，有部分会ｓ分布在ｗｏ晶粒表面，碍了晶粒表面对被３阻测气体的吸附一吸过程，解因而影响材料的气敏性能。尽管掺杂量为１％、５０１％时粉体粒径比掺杂量为５％时小，但其气敏性能却降低了，明５说％的掺杂为最佳掺杂量。气敏元件在相同环境中对被检测气体有较好的灵敏度，其它气体没有灵敏度或灵敏度较小对选择性较好。最佳掺杂量５ｉ２３敏元件％Ｓ０一ｗｏ气１０８ ℃下对ＨＳ丙酮、２、汽油、甲苯、精、气等六酒氨种气体的灵敏度，中，酮、其丙氨气的体积分数为００％，．１其余气体体积分数为００５．０％。该元件对Ｈｓ灵敏度为９）２（３以外的几种气体灵敏度很小，其抗干扰能力强，选择性很好。响应时间￡为元件接触被测气体后，载电负阻Ｒ．的电压由Ｉ上变化到＋９％（ｘＵ）ＯＵ— ０所需的时间，复时间ｔｖ元件脱离被测气体恢为ｒｅ后，载电阻Ｒ的电压由负Ｌ恢复到＋１％０（ｘＵ）Ｕ — ０所用的时间，为元件在空气中时负载电阻上的电压值，为元件在被测气体中时负载电阻上的电压值。环境温度３ｃ，度５％ＲＯ【湿＝０Ｈ，为１０【５Ｓ２３气敏元件对体积分数为８ｃ％ｉ一＝０ｗｏ００５２气体的响应一复曲线显示元件接触．％ＨＳ０恢被测气体后，阻值降低，负载电压升高，响应较快，反之，离被测气体后，脱负载电压降低，电阻升高。计算得响应时间ｉｓ５ｓ恢复时间ｔ＝２，＝，ｒｅ３ｓ说明元件响应一恢复较快，有较好的实用价值。
ＷＯ纳米材料的ＨＳ气敏特性３２
魏少红张岩２牛新书，，
（．１安阳师范学院化学系，河南安阳４５０；．５００２平顶山工学院化学系，河南平顶山４７０；６００３河南师范大学化学与环境科学学院，．河南新乡４３０）５０２
关键词：三氧化钨；硫化氢；气敏特性
［］１钱逸泰，结晶化学导论，合肥：中国科技大学出版社，１９：６７．９９２ —２７７
３７７．６ —３０［］３全宝富，孙良彦，吴家琨，传感器技术，９，）１—１．１６（：９３５９
［］２徐甲强，刘艳丽，牛新书，无机材料学报，０，（）２２１２：０７
参考文献：
［］玖平，久里，１徐罗徐启旺．Ｉ四川大学学报（自然科学