气体传感器材料——In2O3纳米线的制备与表征

采用物理气相沉积法,以纯铟粒为原料,在980℃下Si(100)基片上通过改变气流成分制备了一系列氧化铟纳米线,并采用扫描电子显微镜、X射线衍射和透射电子显微镜对其形貌和结构进行了表征.试验表明,随着氩气中氢气含量增加,纳米线的产量降低,10%的含氢量最优.纳米线的直径在50～100nm之间,长度可达几十微米.纳米线的结构是方铁锰矿体心立方单晶结构.纳米线的生长符合VLS模型,铟起到了自催化的作用.     

SnO_2/In_2O_3纳米材料的制备及其吸附-光催化性能研究

采用水热法制备了一系列不同SnO2/In2O3比例的光催化剂,应用X射线粉末衍射(XRD)和扫描电子显微镜(FESEM)对其微观形貌和晶型进行了分析,通过紫外-可见分光光度计(UV-Vis)评价了复合材料对甲基橙(MO)溶液的吸附性能及催化活性,考察了Sn/In比例值对SnO2/In2O3样品吸附性能及光催化性能的影响。结果表明:当Sn与In摩尔比为2∶1时,对MO的吸附性能和催化性能最好。     

NO2 gas sensing responses of In2O3 nanoparticles decorated on GO nanosheets

Nanomaterials offer a wide range of applications in environmental nanotechnology. Hazardous pollutants in the environment are needed to be detected and controlled effectively to avoid human health risks. In this paper, we described the fine-controlled growth of In₂O₃ nanoparticles embedded on GO nanosheets by a facile precipitation method. The In₂O₃@GO nanocomposites exhibited outstanding gas sensing performance as compared with pure In₂O₃ nanoparticles towards NO₂. At 225 °C, the sensor displayed high selectivity, best response (78) to 40 ppm NO₂, quick response, and recovery times of 106s/42s. The improved sensing performances of the nanocomposite were attributed to large surface area, high gas adsorption-desorption capability, and the formation of p-n heterojunctions between In₂O₃ nanoparticles and GO nanosheets. The excellent gas detecting activities validate In₂O₃@GO nanocomposites as a promising candidate in the NO₂ gas sensor industry.     

Polycrystalline In2O3 and In2O3/Y2O3 photoanodes

Single crystal In₂O₃ shows promise as a photoanode for the decomposition of water. Because of various difficulties in the preparation of the single crystal material, two simple techniques were developed for the preparation of polycrystalline In₂O₃ anodes. One method involves the thermal decomposition of the nitrate while the other utilizes the chemical vapour deposition technique. Voltammograms and photoresponse spectra of these anodes are compared to the single crystal material. Among other observations, it is noted that the quantum efficiencies of the thermally decomposed films are comparable to the single crystal material. It is also shown that the on-set potential can be shifted to more negative values by forming the mixed oxide In₂O₃/Y₂O₃.     

基于CuO敏感电极的阻抗谱型NO_x传感器的研究

采用共压共烧法来制备YSZ(掺杂0.8%MnO_2)固体电解质及多孔层,使用湿浸渍技术制备敏感材料CuO,并组装成传感器。采用SEM对材料表面和断面的微观形貌进行分析,通过XRD对材料的相组成进行分析,使用电化学工作站对材料的电导率和传感器的敏感性能进行了研究。实验表明,所制得的固体电解质层和多孔层结合紧密,掺杂MnO_2的电解质电导率(800℃)达10-2的数量级,满足电解质对电导率的要求,MnO_2的掺杂可以有效降低YSZ固体电解质的烧结温度;在650℃时,随着NO2浓度逐渐升高相角逐渐增大而阻抗逐渐减小,在低频0~30Hz之间曲线区分较好。650℃时,CuO传感器对NO_2有良好的响应。     

Simulation of Filed Effect Sensor Based on Graphene Nanoribbon to Detect Toxic NO Gas

Silicon - This paper presents using density functional method to study nitrogen monoxide (NO) molecule physisorption with various concentrations on armchair graphene nanoribbon (GNR). We calculate...     

表面修饰纳米氧化铝的研究进展

综述了近年来国内外纳米氧化铝表面修饰的研究进展情况,按修饰机理区分为物理修饰和化学修饰方法,表面物理修饰方法包括吸附、包覆、辐照处理等,表面化学修饰方法包括偶联剂法、接枝法、接枝-包覆法等,文中对这些方法的特点、修饰机理以及修饰的效果进行简单介绍。     

星状Sb_2O_3纳米微粒的制备研究

室温下,在含有表面活性剂TX-100的溶液中,利用低能超声搅拌制备得到星状Sb2O3纳米颗粒,用透射电子显微镜(TEM),高分辨透射电子显微镜(HRTEM),X-射线衍射仪(XRD),扫描电子显微镜(SEM),热分析仪(TG/DTA)对样品形貌和组成进行分析,并探讨了星状Sb2O3纳米颗粒的形成机理。制备方法简单、省时并有望用于其它纳米颗粒的制备。     

快速配体交换法制备水溶性磁性Fe3O4纳米粒子

为了获得水溶性Fe_3O_4纳米粒子,以聚乙二醇(PEG)磷酸酯为亲水性配体,在甲苯/四氢呋喃/水三元混合溶剂体系下通过快速配体交换法将油酸包覆的油溶性磁性Fe_3O_4纳米粒子转变成聚乙二醇磷酸酯包覆的水溶性Fe_3O_4纳米粒子。考察了四氢呋喃等溶剂在实现快速配体交换中所起到的作用。利用透射电子显微镜(TEM)、动态光散射(DLS)、X射线粉末衍射仪(XRD)、傅立叶红外光谱仪(FTIR)、振动样品磁强计(VSM)对磁性Fe_3O_4纳米粒子进行了分析表征。结果表明:四氢呋喃可以促进PEG磷酸酯与Fe_3O_4纳米粒子表面的有效接触并使得油酸分子从纳米粒子表面快速地脱附下来,此外,还消除了配体交换过程中出现的乳化效应。四氢呋喃的应用实现了快速配体交换法制备水溶性PEG磷酸酯包覆的磁性纳米粒子。     

酶诱发均匀沉淀法制备纳米Fe2O3

以硝酸铁和尿素为原料,草酸为掩蔽剂,室温下采用脲酶催化分解尿素诱发均匀沉淀,制备了纳米氧化铁前驱物。经TG-DTA,KFIR,XRD等测试表明,前驱物经热处理(500℃,2h)后,可得到α-Fe2O3纳米微粒,平均粒径44nm;SEM测试显示,Fe2O3粒子呈球形且大小很均匀,但存在团聚问题尚待解决。     

Metal-organic-framework-derived In2O3 microcolumnar structures embedded with Pt nanoparticles for NO2 detection near room temperature

A novel synthesis of In₂O₃ porous microcolumnar structures (MCs) by a self-sacrificial template route was carried out using MIL-68. Using a modified calcination strategy, the samples could maintain the original metal organic frame work (MOF) morphology with a high gas accessibility after a slow decomposition of organic ligands. Pt nanoparticles (NPs) were loaded on the samples before or after the MOF calcination, leading to different contact states of the Pt NPs and In₂O₃ matrix. The gas sensing properties of the samples were systematically investigated using a dynamic testing system. Particularly, sample Pt/In₂O₃ MCs-1 exhibited a superior NO₂ sensing performance near room temperature (R_g/R_a?=?44.9?at 1 part-per-million and 5.2?at 100 parts-per-billion (ppb)). The sensor resistance could recover to its baseline even at 40?°C after purging with air without any additional treatment. This can be attributed to the chemical sensitisation of the Pt NPs as well as large contents of pores and channels for gas diffusion. The introduction of humidity in the gas mixture could remarkably decrease the sensor response and recovery times owing to the ‘wet’ NO₂ adsorption mechanism. This study demonstrated a novel synthesis route of Pt-loaded In₂O₃ porous columnar structures and its potential applications in near-room-temperature detection of ppb-level NO₂.     

水泥生料中Fe2O3、Al2O3快速测定的误差分析及最佳条件选择

通过实验对水泥生料中Fe2 O3、Al2 O3 快速测定产生误差的原因进行分析 ,确定了得到稳定、准确结果的最佳条件。应用该方法对标样进行测定 ,结果的精密度及准确度均较好 ,可满足生产控制要求。     

NO reduction over La2O3 using methanol

Nitric oxide (NO) reduction by methanol was studied over La₂O₃ in the presence and absence of oxygen. In the absence of O₂, CH₃OH reduced NO to both N₂O and N₂, with selectivity to dinitrogen formation decreasing from around 85% at 623 K to 50–70% at 723 K. With 1% O₂ in the feed, rates were 4–8 times higher, but the selectivity to N₂ dropped from 50% at 623 K to 10% at 723 K. The specific activities with La₂O₃ for this reaction were higher than those for other reductants; for example, at 773 K with hydrogen a specific activity of 35 _μmol NO/s m² was obtained whereas that for methanol was 600 μmol NO/s m². The Arrhenius plots were linear under differential reaction conditions, and the apparent activation energy was consistently near 14 kcal/mol with CH₃OH. Linear partial pressure dependencies based on a power rate law were obtained and showed a near‐zero order in CH₃OH and a near‐first order in H₂. In the absence of O₂, a Langmuir–Hinshelwood type model assuming a surface reaction between adsorbed CH₃OH and adsorbed NO as the slow step satisfactorily fitted the data, and the model invoking two types of sites provided the best fit and gave thermodynamically consistent rate constants. In the presence of O₂ a homogeneous gas‐phase reaction between O₂, NO, and CH₃OH occurred to yield methyl nitrite. This reaction converted more than 30% of the methanol at 300 K and continued to occur up to temperatures where methanol was fully oxidized. Quantitative kinetic studies of the heterogeneous reaction with O₂ present were significantly complicated by this homogeneous reaction. This revised version was published online in July 2006 with corrections to the Cover Date.     

Y2O3/TiO2纳米粒子超声光催化降解邻硝基苯酚

以钛酸丁酯为原料,用溶胶——凝胶（Sol-gel）法制备了Y2O3／TiO2纳米粒子。采用X光衍射仪对粉体的粒径、物相进行了表征。研究了超声光催化协同降解水中邻硝基苯酚的效果,考察了超声波声强、反应温度和催化剂投加量对邻硝基苯酚降解速率的影响。研究结果表明：超声光催化协同降解要比单独超声波或光化学处理效果显著,证实了声光联合技术具有明显的协同效应。     

Room Temperature Radiolytic Synthesized Cu@CuAlO2-Al2O3 Nanoparticles

Colloidal Cu@CuAlO₂-Al₂O₃ bimetallic nanoparticles were prepared by a gamma irradiation method in an aqueous system in the presence of polyvinyl pyrrolidone (PVP) and isopropanol respectively as a colloidal stabilizer and scavenger of hydrogen and hydroxyl radicals. The gamma irradiation was carried out in a ⁶⁰Co gamma source chamber with different doses up to 120 kGy. The formation of Cu@CuAlO₂-Al₂O₃ nanoparticles was observed initially by the change in color of the colloidal samples from colorless to brown. Fourier transform infrared spectroscopy (FTIR) confirmed the presence of bonds between polymer chains and the metal surface at all radiation doses. Results of transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDX), and X-ray diffraction (XRD) showed that Cu@CuAlO₂-Al₂O₃ nanoparticles are in a core-shell structure. By controlling the absorbed dose and precursor concentration, nanoclusters with different particle sizes were obtained. The average particle diameter increased with increased precursor concentration and decreased with increased dose. This is due to the competition between nucleation, growth, and aggregation processes in the formation of nanoclusters during irradiation.     

Formation of N2O and (NO)2 During NO Adsorption on Au 3D Crystals

The adsorption of NO on Au 3D hemispherical crystals (field emitter tips) has been studied by means of pulsed field desorption mass spectrometry (PFDMS) under dynamic gas flow conditions and at 300 K. Local chemical probing of ~200 Au sites in the stepped surface region between the central (111) pole and the peripheral (001) plane leads to the detection of NO⁺, N₂O⁺ and (NO) species. Obviously, molecular NO adsorption on stepped Au surfaces can lead to dimerization. Nitrous oxide formation probably occurs via the dimer, (NO)₂.     

Influence of Preparation Methods of In2O3/Al2O3 Catalyst on Selective Catalytic Reduction of NO by Propene in the Presence of Oxygen

Selective catalytic reduction of NO with propene was investigated over In₂O₃/Al₂O₃ catalysts prepared by three methods, namely, a single sol-gel (SG), impregnation (IM), and co-precipitation method (CP). The catalysts were characterized by means of BET, XRD, XPS, and TPD. The maximum NO conversion over In₂O₃/Al₂ O₃ prepared by sol-gel method was 95% at 400 °C in the absence of H₂O, and the activity decreased slightly in the presence of H₂O, and it was still 76% even in the presence of H₂O and SO₂. Although the retarding effect of SO₂ on the activity was observed for the three catalysts, In₂O₃/Al₂O₃ (SG) showed relatively high activity. It is found that the high surface area and low average pore diameter are important to the catalytic activity, and the strong interaction between indium and alumina for In₂O₃/Al₂O₃ catalyst prepared by sol-gel method may be the reason of high activity for NO reduction. The reaction and surface studies showed that NO₃⁻ and partially oxidized hydrocarbons (RCOO⁻ species) are mainly intermediates, and the oxidation C₃H₆ to RCOO⁻ species maybe the key reaction process in the SCR of NO with C₃H₆.     

Enhanced Sensing Ability of Brush-Like Fe2O3-ZnO Nanostructures towards NO2 Gas via Manipulating Material Synergistic Effect

Brush-like α-Fe₂O₃–ZnO heterostructures were synthesized through a sputtering ZnO seed-assisted hydrothermal growth method. The resulting heterostructures consisted of α-Fe₂O₃ rod templates and ZnO branched crystals with an average diameter of approximately 12 nm and length of 25 nm. The gas-sensing results demonstrated that the α-Fe₂O₃–ZnO heterostructure-based sensor exhibited excellent sensitivity, selectivity, and stability toward low-concentration NO₂ gas at an optimal temperature of 300 °C. The α-Fe₂O₃–ZnO sensor, in particular, demonstrated substantially higher sensitivity compared with pristine α-Fe₂O₃, along with faster response and recovery speeds under similar test conditions. An appropriate material synergic effect accounts for the considerable enhancement in the NO₂ gas-sensing performance of the α-Fe₂O₃–ZnO heterostructures.