片状花形ZnO制备及其对三甲胺的气敏性能

采用低温水热法制备了ZnO材料,通过X射线衍射仪和扫描电镜分别对其结构和形貌进行了表征,并采用气敏测试仪对所制ZnO材料对三甲胺的气敏性进行了测试. 结果表明,所得的ZnO材料具有六方纤锌矿结构,呈片状花形. 此材料在340℃,对体积分数为1.00′10?4三甲胺气体的灵敏度可达到63.72. 随着三甲胺浓度的增加,灵敏度呈现线性增加的趋势. 响应时间和恢复时间分别为4 s和21 s. 此外,该样品具有呈现良好的选择性、重复性和长期稳定性.     

碳纳米管掺杂纳米ZnO气敏元件敏感特性

采用溶胶–凝胶法合成纳米ZnO,以碳纳米管(carbonnanotube,CNT)为掺杂剂制备CNT–ZnO旁热式气敏元件样品。用X射线衍射和透射电镜分析了ZnO的结构,用扫描电镜观察CNT–ZnO气敏元件样品表面的显微形貌,研究了CNT–ZnO元件对甲醛和丙酮等气体的气敏性能。结果表明:CNT存在于平均粒径为20～30nm的ZnO晶粒间,增加了CNT–ZnO材料的气孔率。CNT–ZnO气敏元件对丙酮的灵敏度高于纯ZnO元件,掺0.6%(质量分数)CNT的ZnO气敏元件(0.6%CNT–ZnO)气敏元件对质量分数为40×10–6甲醛有最高灵敏度(15.11)。而且具有能检测低浓度甲醛气体、选择性好,响应速度快(响应时间约为15s)的优点。     

ZnO/SnS_2复合物的NO_2气敏性能

采用沉淀法合成了具有NO_2气敏性能的ZnO/SnS_2系列复合物。利用X射线衍射仪、场发射扫描电子显微镜及透射电子显微镜等测试手段对ZnO/SnS_2系列复合物进行了表征,采用静态配气法对其气敏性能进行了测试,研究了ZnO含量、工作温度、NO_2浓度等对NO_2气敏特性的影响。结果表明:加入质量分数为1%和2%的ZnO,可以有效提高Sn S2的气敏性能,其中1%ZnO/SnS_2样品对NO_2气体的灵敏度最高,相对于Cl2、SO_2等其他7种测试气体,该样品对NO_2气体具有更高的响应,其对体积浓度10×10-6的NO_2气体响应和恢复时间分别仅需7 s和49 s。这主要是由于ZnO与SnS_2之间形成异质结,有效增加了电子流动所致。     

Fe掺杂ZnO纳米纤维的制备及其乙炔气敏性能的研究

采用静电纺丝法制备了Fe掺杂ZnO纳米纤维,研究了不同浓度Fe掺杂对ZnO纳米纤维的形貌、晶体结构及乙炔气敏性能的影响。结果表明:Fe掺杂对其结构及形貌未产生影响,Fe掺杂明显提高了ZnO纳米纤维的气敏性能,Fe掺杂量为6%的ZnO纳米纤维对乙炔气体具有最佳的气敏特性,工作温度为300℃时,粉体对1000 ppm HCHO气体灵敏度达到74.61,随着乙炔气体浓度增大,Fe掺杂ZnO纳米纤维粉体的灵敏度呈上升趋势。这主要是由于Fe元素掺杂使ZnO的缺陷增多,为气敏反应提供更多的活化点,从而提高了气敏性能。     

ZnO/TiO2复合纳米材料的制备及其乙醇气敏性能研究

采用凝胶法制备了TiO_2、ZnO/TiO_2纳米材料,材料的结构和形貌分别用X射线衍射仪(XRD)、扫描电镜(SEM)等仪器进行了表征,同时研究了TiO_2、ZnO/TiO_2在常温下对乙醇气体的敏感性能。结果表明,ZnO/TiO_2复合纳米材料对乙醇气体的响应、恢复时间分别为1.5 s、1 s,相比纯TiO_2,分别提升了0.5 s、1 s,具有更加优异的气敏响应特性。     

壳状氧化锌的制备及其对丙酮的敏感特性EI北大核心CSCD

采用水热法制备了壳状氧化锌。利用扫描电子显微镜、X射线衍射对样品的结构和形貌进行了表征。以该壳状氧化锌作为敏感材料制成旁热式结构的气体传感器样品,检测了样品在不同温度下对丙酮气体的灵敏度。结果表明:在300℃条件下,当丙酮的质量分数为100×10–6时,样品对丙酮气体的灵敏度为24.8,响应时间和恢复时间分别为2 s和3 s。另外,还测试了传感器对于常见干扰气体的灵敏度,表明器件具有良好的选择性。     

水热法合成ZnO∶Cd纳米棒及氢敏性研究

本文采用水热法成功的合成了纯ZnO和ZnO∶Cd纳米棒.借助扫描电子显微镜、X射线衍射仪等研究了纯ZnO和ZnO∶Cd的形貌、结构及性质。结果表明,合成的纯ZnO和ZnO∶Cd均呈六角纤锌矿纳米棒结构,Cd的掺入使得纳米棒尺寸减小、晶格发生膨胀。合成材料制成的薄膜型气敏传感器对氢气的敏感性研究表明,纯ZnO薄膜器件对氢气几乎不敏感,而ZnO∶Cd薄膜器件灵敏度较高。当工作温度为220℃时,ZnO∶Cd薄膜器件对浓度为250ppm的氢气灵敏度达到3.95,且具有良好的可重复性。     

聚丙烯酸酯-ZnO杂化材料的光催化性能研究

为了提高纳米ZnO的光催化性能,采用溶液共混法制备了聚丙烯酸酯- ZnO杂化材料,对其光催化性能进行了研究,采用FT - IR、TG -DTG对杂化材料进行了测试.结果表明:杂化材料的光催化性能优于纳米ZnO,降解率可达92.31％,随着ZnO含量增加,杂化材料的光催化性能先增加而后下降.杂化材料具有良好的重复使用性能.FI - IR分析表明在杂化材料中聚丙烯酸酯通过羧酸盐键与纳米ZnO发生杂化.UV - Vis分析表明甲基橙降解较完全.TG - DTG分析表明,杂化材料具有优良的热稳定性,杂化材料的热分解温度可达408℃.     

EuFeO_3纳米材料的制备及其气敏特性研究

以Eu_2O_3和Fe(OH)_3为反应前驱体,以NaCl为介质,采用固相反应法合成了稀土复合氧化物EuFeO_3纳米粉体。分别用XRD和TEM对粉体的物相和形貌进行了表征,并测试了其气敏性能。结果表明:反应物料于1000℃煅烧4 h可获得纯相EuFeO_3纳米粒子;在工作温度320℃时,以该纯相纳米EuFeO_3材料为基的元件对丙酮的响应强且选择性好,其灵敏度与丙酮气体的浓度的对数之间有良好的线性关系,元件对浓度为50 ppm(10~(-6))丙酮气体的灵敏度达26.2,响应-恢复时间为14 s和23 s。     

多孔ZnO-SnO_2异质结构的制备及气敏特性研究

本研究采用溶剂热法制备了SnO_2介孔球,并以此为基础,将ZnO纳米颗粒负载到其表面,最终制备了ZnO/SnO_2异质结构。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)和比表面测试(BET)对产物的晶体结构、微观形貌、元素化合态和孔结构进行了表征。气敏性能测试表明,多孔ZnO/SnO_2异质结构对三乙胺具有优异的气敏性能,对100 ppm三乙胺,灵敏度为88. 4,响应和恢复时间分别为12 s和15 s。此外,该材料对三乙胺表现出优异的选择性。从材料的多孔结构和异质结构能带匹配两方面对多孔ZnO/SnO2异质结构的作用机理进行了分析。     

水热法制备稀土元素掺杂二氧化锡及其对乙醇气敏性能

利用水热法制备了SnO2粉末及掺杂不同稀土离子的SnO2粉末. 通过XRD和气敏测试仪对其结构和性能进行了表征和测试. 结果表明,所制备的SnO2粉末呈四方金红石结构,稀土离子的掺入并没有改变SnO2的晶体结构,也无新晶相的出现. 掺杂镧的SnO2样品(SnO2:La)对乙醇有较高的气敏性. 分析了气敏机理. SnO2:La的灵敏度随着乙醇浓度的增加而增加,随温度的升高呈现波动状,且当温度在250℃时,SnO2:La对1.00′10-4乙醇的灵敏度最大,可达到101.1. 在此条件下其响应时间和恢复时间约为5 s.     

Ethanol sensor based on ZnO and Au-doped ZnO nanowires

ZnO nanowires and Au-doped ZnO nanowires were prepared by oxidation reaction. The oxidation was performed by heating zinc powder and a mixture of zinc and 1 wt% gold powder which was pressed into a tube shape at 600 °C for 24 h. The ethanol sensors based on ZnO nanowires were simply fabricated by applying silver electrode at each end of the tube and inserting a coil heater into the tube. The ethanol sensing properties of ZnO nanowires were observed from the resistance change under ethanol vapor atmosphere. By considering the sensitivity and response time, the optimum operating temperature of the ethanol sensor was found to be 240 °C. Also, it was found that the sensitivity of the sensor based on Au-doped ZnO nanowires exhibits higher value than that of the sensor based on undoped ZnO nanowires.     

Effect of dilute concentrations of Sm on the temperature‐dependent electrical and dielectric properties of ZnO

Compounds of undoped and samarium (Sm) doped ZnO have been prepared by standard solid‐state reaction method. X‐ray diffraction (XRD), Williamson‐Hall (W‐H) analysis, Transmission Electron Microscopy (TEM), temperature‐dependent electrical and dielectric studies have been done to characterize these materials. Inclusion of Sm as dopant in hexagonal wurtzite ZnO changes the lattice parameters to a small extent with some Sm aggregation at higher concentration. Also, the mean particle sizes of ZnO:Sm compounds showed an inter‐correlation with the Scherrer method, W‐H analysis as well as with TEM results. The electrical resistivity depicts an exponential decay and metal‐semiconductor transition (MST) at ~300 K for the pristine sample whereas there is large decrement in the resistivity with Sm doping. The analysis of σ_ac of ZnO suggests that the power law is obeyed and indicated an increase in the ac conductivity with Sm content. The mechanism behind this type of conductivity is elucidated by small polaron tunneling (SPT) model of conductivity. The dependence of ln dc on the temperature inverse shows that the traps of electrons are thermally activated such that low and high temperature activation energies confirm the presence of vacancies and interstitials of both O and Zn ions. Thus, a high value of dielectric constant makes these materials suitable for high frequency and charge storage device applications.     

Enhancement of optical,dielectric and transport properties of (Sm,V) co-doped ZnO system and structure-property correlations

In this work, V-doped and (Sm, V) co-doped ZnO samples have been synthesized using ball milling method followed by heat treatment. The dependence of structural, optical, electrical and dielectric properties of V:ZnO samples on the Sm doping concentration has been explored. The structural properties have been studied by means of X-ray diffraction (XRD) and Rietveld refinement. Oxidation states of the elements present in the samples are determined using X-ray photoelectron spectroscopy. Raman spectra of the samples further verified the observations obtained from XRD. The crystallite size and microstrain have been estimated from the Williamson-Hall analysis. Microstrain increases from 0.814 × 10^?3 to 1.01 × 10^?3 with increase in the Sm doping level. The morphology of the grains is significantly affected by the Sm doping. The enhancement of defect density with Sm doping is responsible for the observed red shift (3.29–3.19 eV) in the band gap. The frequency dependence of the dielectric properties has been studied at various fixed temperatures ranging from 25 to 350 °C. The increase in real dielectric constant with dopant content indicates the enhancement of energy storage capacity. The ac conductivity follows Jonscher's power law and it increases up to 1 mol% Sm concentration. Further increase in Sm extent leads to the decrease in ac conductivity. The impedance spectroscopy has been performed to understand electrical behavior of samples and Cole-Cole plots are fitted against the equivalent circuit model. The electrical activation energy values for conduction and relaxation vary in the range: 0.281–0.269 eV and 0.260–0.243 eV, respectively.     

A novel hydrazine electrochemical sensor based on a carbon nanotube-wired ZnO nanoflower-modified electrode

ZnO nanoflowers were synthesized by a simple process (ammonia-evaporation-induced synthetic method) and were applied to the hydrazine electrochemical sensor. The prepared material was characterized by means of scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) and was then immobilized onto the surface of a glassy carbon electrode (GCE) via multi-walled carbon nanotubes (MWCNTs) to obtain ZnO/MWCNTs/GCE. The potential utility of the constructed electrodes was demonstrated by applying them to the analytical determination of hydrazine concentration. An optimized limit of detection of 0.18 μM was obtained at a signal-to-noise ratio of 3 and with a fast response time (within 3 s). Additionally, the ZnO/MWCNTs/GCE exhibited a wide linear range from 0.6 to 250 μM and higher sensitivity for hydrazine than did the ZnO modified electrode without immobilization of MWCNTs.     

Dimethylammonium dimethyldithiocarbamate‐accelerated sulfur vulcanization. I. Thermal stability and reactions with curatives

To investigate its thermal stability and reactivity towards other accelerators dimethylammonium dimethyldithiocarbamate ((dma)dmtc) was heated at programmed heating rates in sealed and open pans in a differential scanning calorimeter and on a thermobalance. (Dma)dmtc was heated on its own, in rubber compounds and in mixes with tetramethylthiuram disulfide, zinc dimethyldithiocarbamate, and ZnO. In open systems (dma)dmtc readily sublimes at temperatures well below its melting point, and it is almost as rapidly lost when compounded on its own with rubber. No decomposition is observed at vulcanization temperatures and (dma)dmtc is unreactive towards tetramethylthiuram disulfide and zinc dimethyldithiocarbamate. Moisture does not promote its decomposition. Reaction with ZnO to give zinc dimethyldithiocarbamate is restricted to the surface of ZnO particles. (Dma)dmtc is soluble in water in which it dissociates. It must be concluded that when its is included in formulations, (dma)dmtc, per se, would act as a vulcanization accelerator; it does not decompose to dimethyldithiocarbamic acid and dimethylamine, both of which are known accelerators. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3067–3073, 2001     

簇状氧化锌纳米棒的合成及其光催化性能研究

采用醋酸锌和氨水为原料、水作为溶剂,以水热法在80℃条件下反应20 h制备出了簇状氧化锌纳米棒,用XRD、SEM分别分析了制备产物的物相和形貌。以ZnO纳米棒为光催化剂对有机染料甲基橙进行了光催化降解实验,研究了甲基橙溶液初始浓度和催化剂添加量对光催化的影响。结果表明,合成的氧化锌纳米棒均为六方晶系铅锌矿结构;产物为从中心发散的簇状纳米棒结构,纳米棒直径分布均匀且分散性好,每个簇由几十个纳米棒组成,每个纳米棒平均直径约为150 nm,长度约为5μm。制备的ZnO有良好的光催化性能。     

Sm掺杂ZnO QDs的制备及其荧光性能研究

通过研究不同碱/锌、钐/锌物质的量比制备了分散性良好的Sm掺杂氧化锌量子点（ZnO QDs）。通过紫外可见光谱（UV-vis）、X射线衍射（XRD）、场致发射透射电子显微镜（TEM）、能量色散X射线谱（EDS）、X射线光电子能谱（XPS）对样品做了表征。研究结果表明,n（Zn）∶n（OH^-）=1∶1、Sm掺杂量为4%（物质的量分数）时制备的ZnO QDs在383 nm紫外光激发下的荧光发射强度最强。并发现稀土钐离子的掺杂与ZnO QDs的氧空位（OV）形成有关。Sm掺杂后的ZnO QDs的氧空位浓度比未掺杂的高,且ZnO QDs氧空位的浓度越大,其荧光发射强度越强。     

A hydroxylamine electrochemical sensor based on electrodeposition of porous ZnO nanofilms onto carbon nanotubes films modified electrode

A novel route (electrodeposition) for the fabrication of porous ZnO nanofilms attached multi-walled carbon nanotubes (MWCNTs) modified glassy carbon electrodes (GCEs) was proposed. The morphological characterization of ZnO/MWCNT films was examined by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The performances of the ZnO/MWCNTs/GCE were characterized with cyclic voltammetry (CV), Nyquist plot (EIS) and typical amperometric response (i-t). The potential utility of electrodes constructed was demonstrated by applying them to the analytical determination of hydroxylamine concentration. An optimized limit of detection of 0.12 μM was obtained at a signal-to-noise ratio of 3 and with a fast response time (within 3 s). Additionally, the ZnO/MWCNTs/GCE exhibited a wide linear range from 0.4 to 1.9 × 10⁴ μM and higher sensitivity. The ease of fabrication, high stability, and low cost of the modified electrode are the promising features of the proposed sensor.