ZnO thin film nanostructures for hydrogen gas sensing applications

A ZnO thin film-based gas sensor was fabricated using a SiO₂/Si substrate with a platinum comb-like integrated electrode and heating element. The structural characteristics, morphology, and surface roughness of the as-grown ZnO nanostructure were investigated. The film revealed the presence of a c-axis oriented (002) phase with a grain size of 20.8 nm. The sensor response was tested for hydrogen concentrations of 50, 70, 100, 200, 400, and 500 ppm at the optimum operating temperature of 350 °C. The sensitivities towards 50 and 200 ppm of hydrogen gas at 350 °C were approximately 78% and 98%, respectively. A linear response was observed for hydrogen concentrations within the range of 50 ppm–200 ppm. These results demonstrated the potential application of the ZnO nanostructure for the fabrication of cost-effective and high-performance gas sensors.     

Photoacoustic effect of piezoelectric ZnO thin films

This paper describes the photoacoustic (PA) effect of piezoelectric ZnO thin films. The one-dimensional theory of the PA-effect was derived. The relationships between PA-signals and modulation frequency, thin film properties such as piezoelectric coefficients, dielectric constant, specific heat and thermal conductivity coefficient were obtained. The experimental results on the PA-effect of sputter-deposited ZnO thin films exhibited good agreement with the theoretical analysis. The piezoelectric stress coefficients, e₃₃ and e₃₁, of some ZnO films were determined from the PA-signals, typical values of which are 0.82 C/m² and -0.43 C/m², respectively.     

Nanostructured hybrid ZnO thin films for energy conversion

We report on hybrid films based on ZnO/organic dye prepared by electrodeposition using tetrasulfonated copper phthalocyanines (TS-CuPc) and Eosin-Y (EoY). Both the morphology and porosity of hybrid ZnO films are highly dependent on the type of dyes used in the synthesis. High photosensitivity was observed for ZnO/EoY films, while a very weak photoresponse was obtained for ZnO/TS-CuPc films. Despite a higher absorption coefficient of TS-CuPc than EoY, in ZnO/EoY hybrid films, the excited photoelectrons between the EoY levels can be extracted through ZnO, and the porosity of ZnO/EoY can also be controlled.     

纳米氧化锌脱硫剂在硫化氢去除中的潜在应用

采用两种不同路线合成了纳米氧化锌改性SBA-15的复合介孔材料,并在材料上进行了含有0.1%硫化氢气体的脱硫实验。使用氮吸附、X射线衍射、X射线能谱、透射电子显微镜和电感耦合等离子体原子发射光谱方法对实验前后的材料进行了表征。不同路线合成材料的结构、硫化氢捕集能力有较大区别。两种合成途径制备的材料(S/Z、SZ)分别较商用氧化锌脱硫剂的穿透硫容高出336%和77.3%,其中超声波辅助浸渍法制备的介孔脱硫剂的脱硫性能最佳。高效的脱硫活性源自介孔材料的高比表面积和纳米颗粒的高反应活性的共同作用。     

Semimetal graphite/ZnO Schottky diodes and their use for hydrogen sensing

A method is described for the fabrication of highly rectifying Schottky contacts on n-type ZnO (O and Zn polar face) single crystals, both bare and partially covered with Pt nanoparticles, coated with mechanically deposited colloidal graphite. A layer of Pt nanoparticles deposited by in situ pulsed electrophoretic deposition from isooctane colloid solutions is inserted between the graphite and the ZnO surface serves to dissociate hydrogen molecules in hydrogen sensing elements based on the highly rectifying Schottky barriers. The sensing elements are sensitive to gas mixtures with a low hydrogen concentration down to 10 ppm and show an extremely fast response above 1000 ppm.     

过渡金属硫化物对Claus尾气催化加氢制备硫化氢的影响

以γ-Al2O3为载体,考察了第一过渡金属亲硫元素和Cr系元素及其负载量对Claus尾气加氢生成H2S的催化活性。结果表明,经预硫化后上述负载量为10%质量分数的各元素,其催化活性按大小可以划分为4组:Ni、Co、Fe>Mo、W、Cu>Cr>Zn、Mn。针对第一组的3种元素进行物相分析表明,在反应气体积比为SO2/H2/N2=0.5/3/96.5,重量时间空速(WHSV)=6 000mL/(h.g)的强还原气氛下,Ni的催化活性相为稳定的NiS2,但Co和Fe除主晶相CoS2和FeS2外,还分别具有Co3S4和Co9S8或FeS和Fe7S8的贫硫相。     

ZnO薄膜的制备及其性能

用脉冲激光沉积(PLD)法在SiO2基片上制备了ZnO薄膜和Zn1-xMnxO薄膜。X射线衍射、原子力显微镜、紫外-可见分光光度计对ZnO薄膜的测试结果表明:薄膜具有(103)面的择优取向,表面比较平坦;SiO2基片上制备的薄膜在387nm附近存在明显的吸收边,且薄膜的吸收对基片温度变化不明显。通过对Zn1-xMnxO薄膜的吸收光谱分析得出:Mn离子的掺杂改变了ZnO薄膜的禁带宽度,随Mn离子的掺杂量的增加,薄膜禁带宽度增加;薄膜的光吸收也从直接跃迁过渡为间接跃迁过程。     

Boron and nitrogen co-doped ZnO thin films for opto-electronic applications

The transparent conductive oxides such as ZnO have been widely studied due to their potential applications. As a promising wide band gap semiconductor, ZnO thin films with various dopants are important in fabricating the photonic devices to meet the various needs. In this study, boron and nitrogen co-doped ZnO thin films were fabricated at different temperatures (100–600 °C) on sapphire (0 0 1) substrates using pulsed laser deposition technique. X-ray diffractometer, atomic force microscope, spectrophotometer and spectrometer were used to characterize the structural, morphological and optical properties of the thin films. Hall measurements were also carried out to identify the electrical properties of the thin films.     

Incorporation of hydrogen in diamond thin films

In this investigation, diamond thin films with grain size ranging from 50 nm to 1 µm deposited using hot filament chemical vapor deposition (HFCVD) have been analyzed by elastic recoil detection analysis (ERDA) for determining hydrogen concentration. Hydrogen concentration in diamond thin films increases with decreasing grain size. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) results showed that part of this hydrogen is bonded to carbon forming C–H bonding. Raman spectra also indicated the increase of non diamond phase with the decrease in crystallite size. Incorporation of hydrogen in the samples and increase of hydrogen content in nanocrystalline sample are discussed. Large separation between filament and substrate used for the synthesis of nanocrystalline film helped to understand the large incorporation of hydrogen in nanocrystalline diamond films during growth. The study addresses the hydrogen trapping in different samples and higher hydrogen concentration in nanocrystallites by considering the synthesis conditions, growth mechanisms for different grain sized diamond films and from the quality of CVD diamond films.     

国内硫化氢含量的检测方法浅析

本文按照分析原理,将天然气中硫化氢测定方法划分为物理法和化学法,包括碘量法、汞量法、亚甲基蓝法、色谱法、光谱法等。本文着重介绍了各种方法的分析原理,优势与缺点,以及目前国内最新的研究状况,并对未来硫化氢测定的发展前景作出展望。     

Electrochemical polishing of hydrogen sulfide from coal synthesis gas

An advanced process has been developed for the separation of H₂S from coal gasification product streams through an electrochemical membrane. This technology is developed for use in coal gasification facilities providing fuel for cogeneration coal fired electrical power facilities and molten carbonate fuel cell (MCFC) electrical power facilities. H₂S is removed from the syn-gas by reduction to the sulfide ion and hydrogen gas at the cathode. The sulfide ion migrates to the anode through a molten salt electrolyte suspended in an inert ceramic matrix. Once at the anode it is oxidized to elemental sulfur and swept away for condensation in an inert gas stream. The syn-gas is enriched with the hydrogen. Order of magnitude reductions in H₂S have been repeatedly recorded (100 ppm to 10 ppm H₂S) on a single pass through the cell. This process allows removal of H₂S without cooling the gas stream and with negligible pressure loss through the separator. Since there are no absorbents used, there is no absorption/regeneration step as with conventional technology. Elemental sulfur is produced as a byproduct directly, so there is no need for a Claus process for sulfur recovery. This makes the process economically attractive since it is much less equipment intensive than conventional technology.     

天然气脱除硫化氢的研究

用甲基二乙醇胺(MDEA)脱除天然气中的硫化氢,研究反应温度与MDEA浓度对脱硫效果的影响。甲基二乙醇胺最优工作温度为15～30℃,最佳浓度范围为40%～50%,原料气空速范围为1.5～3.5 h^(-1),脱硫剂空速范围为0.55～1.2 h(-1),脱硫剂空速范围为0.55～1.2 h^(-1)。与二乙醇胺(DEA)对比,在吸收温度20℃下,MDEA与DEA溶液浓度45%,DEA第180 h时硫含量>0.2 mg/L,超过二类气标准,MDEA在第276 h时硫含量>0.2 mg/L。10 mL硫含量大于二类气要求的时间增加53%,证明甲基二乙醇胺较二乙醇胺脱硫效果大幅增加,为采油厂工艺迭代提供了数据。     

Growth and photoelectrochemical behaviour of electrodeposited ZnO thin films for solar cells

Thin zinc oxide films were deposited potentiostatically from zinc nitrate aqueous solutions on ITO substrates. The influence of experimental parameters (temperature, electrolyte concentration, deposition potential) on structure and morphology of films was investigated. Deposited films were generally polycrystalline in structure, even if growth according to preferential planes occurs in certain conditions. The effect of thermal treatments in air at 150 and 350 °C was also studied. In some cases, Cl species were incorporated into deposit by adding zinc chloride to the electrolyte. A photoelectrochemical investigation, performed in neutral solution before and after thermal treatment, gives more information on film structure and reveals improvement of n-type semiconducting properties after annealing, suggesting diminution of defects and traps originated from the disordered regions of the oxide. In fact, after thermal treatment, the optical gap of the films decreases towards the value reported for the crystalline oxide. No apparent benefits in the semiconducting properties of the films were observed after incorporation of Cl species into the films.     

Nucleophilic addition of hydrogen sulfide to methyl oleate,methyl linoleate,and soybean oil

Hydrogen sulfide was added to methyl oleate, methyl linoleate, and soybean oil at −70 and 25 C in the presence of boron trifluoride. Major reaction compounds were identified by gas liquid chromatography and mass spectrometry. At −70 C with a 200 molar ratio of hydrogen sulfide to ester, the reactions were complete in 4 hr. Primary reaction product from methyl oleate was methyl 9(10)-mercaptostearate. Methyl linoleate gave ca. equal amounts of methyl 9-(2-pentyl-1-thiolan-5-yl) nonanoate and methyl 8-(2-hexyl-1-thiolan-5-yl) octanoate. At 25 C, the reaction of methyl oleate and linoleate with hydrogen sulfide was less complete, and more side reactions were noted. When equimolar amounts of methyl oleate and methyl 9(10)-mercaptostearate were reacted in the presence of boron trifluoride at 25 C, a new compound was formed, bis(methyl n-octadecanoate 9[10]-yl) sulfide. The addition of liquid hydrogen sulfide to soybean oil at −70 C in the presence of boron trifluoride yields a product which, upon saponification, acidification, and methylation analyzes by gas liquid chromatography as ca. 52% thiolan, 27% mercaptostearate, 10% palmitate, 6% stearate, and 5% unidentified compounds.     

Highly responsive hydrogen gas sensing by partially reduced graphite oxide thin films at room temperature

Novel chemo-resistive gas sensors based on reduced graphite oxide (rGO) thin films have been fabricated and evaluated for hydrogen detection. The rGO materials were thermally treated at various conditions and analyzed using X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy techniques to investigate the change of functional groups. The semiconductor type of the rGOs treated at different conditions were checked by flowing hydrogen gas at 20 cm³/min (sccm) under 10 Torr partial pressure. The rGOs treated at 70 °C in atmosphere (rGO070a), 200 °C in a vacuum (rGO200v), and 500 °C in a vacuum (rGO500v) exhibited n-type, ambipolar, and p-type behavior, respectively. The rGO500v was adopted as active sensing element without any rare metal decoration, and its sensing response to hydrogen was studied by using air as carrier gas. The rGO500v exhibited good sensitivity (～4.5%), response time (～20 s), and recovery time (～10 s) to 160 ppm hydrogen gas at room temperature.     

可脱除硫化氢的液体脱硫剂研究进展

一种可通过直接注入法注入管线中的三嗪类可脱除H2S液体脱硫剂,由于具有高效、价格低廉、易制备、抗菌、可减少低碳钢的腐蚀等特点,弥补了海上脱硫空间和成本的限制,近些年在国外海上石油辅助产品中发展迅猛,前景广阔.详细介绍了1,3,5-三(2-羟乙基)-六氢均三嗪的结构、性质、机理、工艺特点、国外应用现况,最后对其发展前景进行了展望.     

硫化氢废气制取硫酸技术的应用

本文介绍了H_2S制取H_2SO_4的原理,采用H_2S为原料,利用丹麦托普索公司的技术H_2S进行燃烧,气体经转化器进一步反应后,被蒸气吸附冷却后生成H_2SO_4。     

Nanostructured ZnO thin films by SDS-assisted electrodeposition for dye-sensitized solar cell applications

A novel ZnO with a sheet-like nanoporous morphology has been synthesized on ITO substrates by a sodium dodecyl sulfate (SDS) assisted electrodeposition method. X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were used to characterize the structures and the morphologies of ZnO nanostructures. A dye-sensitized solar cell (DSSC) is assembled with the as-prepared ZnO film electrode, and shows a power conversion efficiency of 1.969%.     

中低低变换流程半水煤气中最低硫化氢含量

简要介绍了中低低变换中Co-Mo系耐硫变换催化剂的反硫化原理及反硫化的影响因素,并论述了半水煤气中硫化氢含量、低变入口汽气比及低变催化剂热点温度,对低变催化剂反硫化影响的数据关系。