Characterization of aluminum gallium oxide films grown by pulsed laser deposition

Aluminum gallium oxide (AGO) films were prepared on conventional c-plane sapphire by pulsed laser deposition (PLD). In the current PLD-AGO studies, target composition or growth temperature is usually the main deposition variable, and the other growth conditions are fixed. This would make it difficult to fully understand the theory and characterization of AGO films. In this study, several growth parameters such as target composition, gas atmosphere, laser repetition frequency, growth pressure, and substrate temperature (T_s) were all modulated to realize and optimize the AGO growth. When the (Al_xGa_1-x)₂O₃ target with the Al content larger than 20?at% was used, a serious target poisoning phenomenon occurred, leading to the extremely unstable growth rate. In comparison to the AGO film grown with argon atmosphere, the higher transparency was reached in the film prepared with oxygen atmosphere due to the relative abundance of oxygen. Because of the homogeneous oxygen reduction, the AGO film with the higher crystal quality was obtained at a higher laser repetition frequency. With an increment of growth pressure, the Al content of AGO film was increased. The growth of AGO film at the higher T_s would cause the higher bandgap value, smoother surface, and growth rate degradation. Additionally, the crystal quality of AGO film can be also improved both by increasing the growth pressure and T_s. The better characterization can be reached in the AGO film grown using the (Al_0.05Ga_0.95)₂O₃ target with oxygen atmosphere at the working pressure of 2?×?10^?1 Torr, the laser repetition frequency of 10?Hz, and the T_s of 800?°C. When the metal-semiconductor-metal photodetector fabricated with this AGO active layer, the best performance including the photocurrent of 7.56?×?10^?8 A, dark current of 1.59?×?10^–12 A, and photo/dark current ratio of 4.76?×?10⁴ (@5?V and 240?nm) were achieved.     

Nitrogen and oxygen annealing effects on properties of aluminum-gallium oxide films grown by pulsed laser deposition

Aluminum-gallium oxide (AGO) films on c-plane sapphire substrates by pulsed laser deposition are described. Both nitrogen and oxygen annealing effects on the structural and optical properties of AGO films are investigated. The AGO film shows an amorphous structure when deposited at low temperatures (≤400 °C) while a crystalline structure at 800 °C. After post annealing at 900 °C, an amorphous-to-crystalline phase transformation for the 400°C-deposited film occurs and shows the preferred β phase. The corresponding optical bandgap also increases from 5.14 eV to 5.41–5.46 eV depending on the annealing ambience. From Raman measurements, the 800°C-deposited AGO sample possesses a more stable O–Ga–O bonding compared to that of the 400°C-deposited one after annealing. Unusually, an evident increase in the nitrogen content is observed for the samples after post annealing at 900 °C in nitrogen atmosphere. The rapid dissociation of oxygen atoms may accelerate the disintegration of crystals and rearrangement, which makes the AGO film adsorb nitrogen atoms and cause the grain size to be significantly reduced. However, the extent of the nitrogen incorporation seems to have no apparent effect on the optical properties. All the AGO films show the optical transmittance over 80% in the ultraviolet–visible region with the calculated bandgaps more than 5.4 eV. Details of the mechanism about the nitrogen incorporation into the annealed AGO films via the oxygen vacancies or micro-pores will be discussed.     

ppb-Level ethanol gas sensor of porous anodic aluminum oxide at room temperature

Excessive ethanol in breath can be an indicator of alcoholism and a biomarker of liver disease. Herein, we present a novel porous aluminum anodic oxide (AAO)-based chemi-capacitive sensor that can detect ppb-levels of ethanol gas at room temperature. The oxalic acid-based porous AAO is an amorphous material contaminated with Al(OH)₃ and C₂O₄²⁻ ions (anion-contamination), which react with adsorbed ethanol gas. The optimal resonance frequency of ethanol was determined to be 500 Hz, and the response to 200 ppm ethanol at this frequency was 1.56%. Especially, the limit of detection of ppb-level (16.49 ppb) was obtained. The detection range, reliability, and selectivity of the sensor, as well as its surface properties were comprehensively investigated. The proposed sensor is promising for the detection of liver disease as well as for commercial breath ethanol analyzers.     

升温速率和晶化模式对固相转化合成SAPO-5的影响

固相转化法有利于合成硅取代型磷酸铝分子筛(SAPO-5)。采用XRD、SEM、EDS表征方法研究了升温速率和晶化模式对SAPO-5分子筛结构的影响。结果表明,在高升温速率(140℃·h^-1)和低升温速率(5.8℃·h^-1)下能合成出纯SAPO-5分子筛,在中等升温速率(17.5～70℃·h^-1)下则有SAPO-34分子筛与SAPO-5伴生。此外,晶化模式对SAPO-5分子筛的形貌有显著影响。在中等升温速率下,动态晶化形成的SAPO-5分子筛为球形,静态晶化则为六边形片状,但Si的取代机制均可能为SM3取代。在高升温速率和低升温速率下,晶化模式不影响SAPO-5分子筛的形貌。而Si在动态晶化时为SM2取代,静态晶化时为SM3取代。     

铝酸盐水泥在高温和CO2气氛的水化机理研究

采用力学性能测试、X射线衍射分析、扫描电镜分析、X射线能谱分析、X射线荧光分析等现代材料分析测试方法,探索铝酸盐水泥石在高温及CO2气氛下的强度性能、物相组成、微观形貌等。结果表明：矿渣和铝酸盐水泥相互作用,影响水化过程,提高铝酸盐水泥的后期强度。铝酸盐水泥在高温及CO2气体气氛环境下养护后,强度在400 ℃以下养护不断发展,在400 ℃到达最大值,最大强度为36.39 MPa,其水泥石外层含有C2AS、C12A7等耐高温且结构致密的晶体,并且不被CO2气体腐蚀。相比于硅酸盐加砂水泥浆,铝酸盐加高温稳定剂水泥浆体更耐高温和CO2气体腐蚀。     

燃煤电厂烟气冷却器壁上沉积物分析和形成机理

选择性催化还原(SCR)系统和烟气冷却器是实现燃煤电厂节能减排的重要设备,但SCR中的氨逃逸现象对烟气冷却器的影响研究鲜有报道。本文对某电厂SCR设备后的烟气冷却器表面出现的沉积物,进行了XRD、XRF、SEM和EDS等分析研究。结果表明:沉积物的白色结晶物主要为氟硼酸铵,及其反应中间产物(氟化铵、硼酸以及氟硅酸铵),形成该结晶层的主要原因为煤中富集的氟、硼元素和SCR逃逸氨的耦合反应,该沉积物的厚度不会无限增加,但仍会影响烟气冷却器的正常运行。     

Effects of reduction of metal oxide sorbents on reactivity and physical properties during hot gas desulphurization in IGCC

In this study, the changes of physical properties and reactivity of the metal oxide sorbents were investigated under the reducing conditions of coal gas. Metal oxide sorbents are converted into metal sulphides as a result of reaction with H₂S in synthesis gas. This could cause the reduced reactivity of sorbents if the metal oxides were converted into metallic elements due to the reduction by either hydrogen or carbon monoxide. In this experiment, the changes of physical properties and reactivity of the metal oxides were investigated over the temperature range 480-700 °C. It is confirmed that the reactivity of sulphidation and the reduction of metal oxide increased with increasing temperature. Even though the sulphur capacity of the sorbents in the early stage was high, it reduced rapidly due to the progressive reduction of metal oxides as the sulphidation/regeneration process was repeated. The reduction of metal oxide and the extent of reduction were verified by measuring the amount of oxygen consumed and the amount of SO₂ produced during the regeneration of sulphidated sorbents with the aids of a gas analyser. It was concluded that the reactivity of the metal oxide sorbents was influenced by reduction with coal gas at high temperature.     

控释肥料养分释放动力学及其机理研究 第1报 温度对包膜型控释肥料养分释放的影响

研究 4种包膜型控释肥料养分释放及温度对释放过程的影响。供试 4种肥料具有指数线形和 S线形释放特征曲线。指数线型控释肥料与 SU GIHARA方程和 S线型控释肥料与 ISHIBASHI改进方程有良好的拟合性。4种包膜型控释肥料的养分释放曲线符合初始诱导期校正参数 tau的一级反应模型。具有指数释放特征曲线包膜型控释肥料的 tau可给出零。为了养分的开始释放 ,需要一定量的水分透入包膜肥料内 ,HCRF S70需要透入的水比HCRF E5 0的多。养分释放呈指数曲线形的 HCRF E5 0和养分释放呈 S曲线形的 HCRF S70在释放机理上没有差异。与指数曲线形的 HCRF E5 0相比较 ,S曲线形的 HCRF S70养分释放推迟是由于养分开始释放时所需水分量较大。因此 ,养分释放呈 S曲线形的控释肥料的诱导期依存于温度。     

Glass forming,crystallization, and physical properties of MgO-Al2O3-SiO2-B2O3 glass-ceramics modified by ZnO replacing MgO

This study focused on the glass forming, crystallization, and physical properties of ZnO doped MgO-Al₂O₃-SiO₂-B₂O₃ glass-ceramics. The results show that the glass forming ability enhances first with ZnO increasing from 0 to 0.5 mol%, and then weakens with further addition of ZnO which acted as network modifier. No nucleating agent was used and the crystallization of studied glasses is controlled by a surface crystallization mechanism. The predominant phase in glass-ceramics changed from α-cordierite to spinel/gahnite as ZnO gradually replaced MgO. The phase type did not change; however, the crystallinity and grain size in glass-ceramics increased when the glasses were treated from 1030 °C to 1100 °C. The introduction of ZnO can improve the thermal, mechanical, and dielectric properties of the glass-ceramics. The results reveal a rational mechanism of glass formation, crystal precipitation, and evolution between structure and performance in the xZnO-(20-x)MgO-20Al₂O₃-57SiO₂-3B₂O₃ (0 ≤ x ≤ 20 mol%) system.     

Further insights into thermoelectric properties of nonstoichiometric titanium oxide fabricated by high pressure and high temperature

The present work explores the feasibility of advancing the thermoelectric properties of nonstoichiometric TiO_2?x through introducing more and more oxygen deficiencies. Compared with previous work, it is found that this compositional manipulation induces phase transition; in addition, the scattering mechanisms of both carrier and phonon have changed, resulting in the temperature-independent electrical resistivity, inferior electrical performance and an unexpected high thermal conductivity. As a consequence, a moderate zT value of 0.13 is obtained in TiO_1.72 at 600?℃. Through this work, we understand deeply about thermoelectric properties of nonstoichiometric titanium oxide by high pressure and high temperature, and further investigations about this system have been directed.     

Hybrid catalysts containing zeolite ZSM-5 and supported gallium oxide in the aromatization of n-butane

It is shown that in the aromatization of n-butane, hybrid catalysts containing irreducible oxides (silica and alumina) as co-catalysts provide aromatic yields which are almost twice that obtained with “pure” zeolite ZSM-5 zeolite. The interpretation of these results is based on the hydrogen back spillover concept. The addition of Ga₂O₃ to these co-catalysts enhances further the aromatizing performance of the hybrid catalysts. It is believed that such an additional improvement is due to the gallium species located in the interface between the two types of particles, and the Ga containing regions of the zeolite crystallites near the pore openings. This contamination results from the transfer of some partially reduced gallium oxide from the co-catalyst surface to the zeolite pores. In such a case, it is probable that the reaction is governed by the conventional bifunctional catalysis mechanism. These gallium oxide sites appear more active than the normal ones because of their location near the zeolite pore openings which enables them to react with both inward-and outward-diffusing molecules.     

Catalytic properties of oxide nanoparticles applied in gas sensors

A series of gas sensing layers based on indium oxide doped with gold were prepared by using the aerosol technology for deposition as the active contact layer in a metal oxide semiconductor capacitive device. The interaction between the measured species and the insulator surface was quantified as the voltage changes at a constant capacitance of the device. The sensor properties were investigated in the presence of H₂, CO, NH₃, NO, NO₂ and C₃H₆ at temperatures between 100–400 °C. Significant differences in the morphology of the layer and its sensitivity were noted for different preparation methods and different gas environments.     

The effect of confined spherulite morphology of high-density polyethylene and polypropylene on their gas barrier properties in multilayered film systems

Confined crystallization of high-density polyethylene (HDPE) in multilayer films is studied in this paper. A new cyclic olefin copolymer (COC), HP030, is co-extruded with HDPE by a layer multiplying technique. The number of layers and layer compositions are changed to study the effect of layer thickness on the crystalline morphology of the HDPE layers under confinement. Atomic force microscopy (AFM) is used to investigate the crystalline morphology of the HDPE layers. MOCON (Minneapolis, MN, commercial instrument) units are employed to measure both oxygen permeability and water vapor transport rate (WVTR) of these co-extruded HDPE/HP030 multilayer films. We report that when the HDPE layer nominal thickness is about 290 nm in the HDPE/HP030 multilayer films, the HDPE layer effective gas barrier property is improved approximately 2 times for oxygen and 5 times for water vapor. This is the result of confined spherulite morphology of HDPE, which increases the tortuosity for gas to diffuse through the films. Similar phenomenon is found for polypropylene (PP), when PP is co-extruded against polycarbonate (PC). The same experiments as for HDPE are conducted to confirm that PP spherulites have been confined by PC in PP/PC multilayer films. We discover that the confined spherulites of PP improve its gas barrier properties as well.     

The crystallization behavior and mechanical properties of polylactic acid in the presence of a crystal nucleating agent

The crystallization behavior of polylactic acid (PLA) was studied in the presence of a crystal nucleating agent, ethylenebishydroxystearamide (EBH). The crystallization rate and crystallinity were significantly increased with addition of EBH. The isothermal crystallization half-time at 105°C was decreased from 18.8 minutes for neat PLA to 2.8 minutes for PLA with 1.0 wt % of EBH. The crystallinity of PLA with 1.0 wt % EBH was about 35% after 5-minute annealing at 105°C. Like neat PLA, the double melting peaks were also observed for nucleated PLA. The changes of the double melt peaks were investigated with various crystallization temperatures, heating rates, and annealing times. The heat deflection temperature (HDT) of nucleated PLA was up to 93°C after annealing. The correlation between crystallinity and HDT was demonstrated. A percolation threshold of crystallinity was found corresponding to HDT. The crystal size of nucleated PLA was significantly decreased with addition of EBH. The mechanical properties of annealed PLA blends simultaneously; showed improved modulus and impact strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

硼掺杂Co3O4海胆状微球的制备及其乙醇气敏强化机制

四氧化三钴（Co₃O₄）是一种p型半导体,可作为气体传感材料。非金属硼（B）具有吸电子特性,将其与p型半导体气敏材料进行掺杂,可增加材料的空穴载流子浓度,从而提高材料的气敏性能。本文以六水合硝酸钴[Co(NO₃)₂·6H₂O]、硼酸（H₃BO₃）和尿素[CO(NH₂)₂]为原料,采用低温一步水热法成功制备了B掺杂Co₃O₄海胆状微球。通过X射线衍射仪（XRD）、扫描电镜（SEM）、透射电镜（TEM）、X射线光电子能谱仪（XPS）和拉曼光谱仪（Raman）对掺杂B前后的Co₃O₄进行结构表征,探究B掺杂对其气敏性能的影响。结果表明：B掺杂对Co₃O₄材料的气敏性能有明显的强化作用。当掺杂摩尔比为Co∶B=8∶1时,B-Co₃O₄对1×10⁵μg/L乙醇的最佳工作温度为180℃,灵敏度响应达到26.8,是相同条件下纯Co₃O₄的4.4倍。B-Co₃O₄在较低的工作温度下,具有良好的灵敏度、选择性和稳定性,是一种性能优良的气敏材料。     

Dual oxygen and Ir oxide regeneration of glucose oxidase in nanostructured thin film glucose sensors

A nanoparticulate iridium oxide (IrOx) thin film has been developed as a redox-active matrix material for an advanced generation glucose biosensor, in which IrOx serves as the non-physiological mediator, replacing oxygen in the enzymatic re-oxidation of glucose oxidase (GOx). Ethanolic solutions of Nafion and an Ir sol were mixed with an aqueous GOx solution and then deposited on a Au support. The Ir nanoparticles were then oxidized electrochemically to IrOx and the resulting films (IrOx-GOx-Nafion) were tested for their glucose response in both oxygen- and argon-saturated solutions, with the oxygen content in both solutions monitored by a Pt electrode. The sensors that are regenerated largely by O₂ are characterized by a Michaelis-Menten K^′m value of ∼30 mM or more and i_max values of at least 20 μA cm⁻². Under fully deareated conditions, the sensors lose only ∼50% of their response to glucose, clearly indicating that a dual oxygen-regeneration and IrOx mediation mechanism is operative for the biosensor under these conditions. Under optimized conditions, involving a controlled GOx:Ir ratio, only the Ir oxide sites in the film serve to mediate GOx regeneration, giving K^′m (10-15 mM) and i_max values that are independent of the O₂ content of the solution.     

干燥温度对纳米氧化石墨烯/PHBH复合膜结构及性能的影响

通过溶液浇铸法制备得到纳米氧化石墨烯（GO）/聚羟基丁酸-羟基己酸酯（PHBH）复合膜,利用SEM、XRD、DSC、拉伸测试、阻隔测试及透明度测试等检测手段,研究了不同干燥温度对复合膜结构及性能的影响,优化了制备工艺。结果表明：随着干燥温度的升高,GO在PHBH中的分散性以及复合膜的结晶度、断裂伸长率和阻隔性先增加后减小,而拉伸强度及透光率则随温度的增加而增加。当干燥温度为45℃→55℃梯度升温时,GO在PHBH中均匀分散,且复合膜的断面光滑,有良好的结晶度、热稳定性、力学及阻隔性能,其拉伸强度、断裂伸长率可分别达到20.11MPa、17.47%,且透氧系数及水蒸气透过系数分别为48cm³/(m²·d)、13.33g/(cm²·d),综合性能优于其他干燥温度下的复合膜。     

Effect of crystallization and interface formation mechanism on mechanical properties of film‐insert injection‐molded poly(propylene) (PP) film/PP substrate

A previous study has shown that the adhesion between the film and substrate of film‐insert injection‐molded poly(propylene) (PP) film/PP substrate was evident with the increases in barrel temperature and injection holding pressure. In this second part of the research work, the crystallinity at the interfacial region (i.e., region between the film and the injected substrate) was extensively studied using FTIR imaging, polarized light microscopy, and DSC in an attempt to determine the level of influence that crystallinity has on the interface and bulk mechanical properties. Consequently, a more thorough and clearer picture of the influence of the inserted film on the interfacial crystallinity and subsequently the substrate mechanical properties, such as peel strength and impact strength, has been revealed. The initial proposition that crystallinity could enhance film–substrate interfacial bonding has been confirmed, judging from the higher peel strength with increasing crystallinity at the interfacial region. Nevertheless, the change in crystallinity was not only confined to the interfacial region. With the film acting as heat‐transfer inhibitor between the injected resin and the mold wall, the total crystal structure of the substrate was substantially altered, which subsequently affected the bulk mechanical properties. The lower impact strength of film‐insert injection‐molded samples compared to that of samples without film inserts provided evidence of how the film could impart inferior properties to the substrate. The difference in cooling rate between the substrate and film might also cause other defects such as warpage and/or residual stress build‐up within the product. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 294–301, 2005     

不同气氛下Ca-Fe二元助剂改变高硅铝煤灰熔融温度的规律和机制

准格尔高硅铝煤灰熔融温度（AFT）高,易引发液态排渣气化炉排渣口堵塞问题,需添加助熔剂降低AFT。利用灰熔融温度测试仪研究了不同质量比CaO/Fe₂O₃（Ca/Fe）助剂的助熔效果,结合热机械分析仪、热重-示差扫描量热仪、XRD以及热力学计算对比分析了氩气气氛与弱还原气氛下Ca-Fe协同助熔机理。研究发现,弱还原与氩气气氛下,AFT均随Ca/Fe增加先降低后升高,在Ca/Fe=1/1时AFT最低,但弱还原气氛下Ca-Fe的助熔效果优于氩气气氛。不同Ca-Fe助剂煤灰在变形温度（DT）、软化温度（ST）、半球温度（HT）和流动温度（FT）时对应的收缩程度差异较大,并且氩气气氛下熔融温度范围（DT~FT）内灰柱的收缩速率显著高于弱还原气氛下的收缩速率。氩气与弱还原气氛下煤灰的收缩过程均可分为三个阶段,且其收缩程度依次递增,但弱还原气氛下第一、二阶段收缩程度较氩气气氛下高。进一步研究表明第一阶段的收缩主要以化学反应引起的固相烧结为主,第二阶段以初始液相形成的液相烧结为主,而第三阶段的收缩行为最终决定煤灰的AFT。高温矿物演化行为显示莫来石和钙长石单独存在时AFT很高,但两者可以与含铁组分形成低共熔物降低AFT,并且Fe²⁺可以促进低共熔物的形成,促使弱还原气氛下低共熔物的生成温度低于氩气气氛下的。     

不同气氛下Ca-Fe二元助剂改变高硅铝煤灰熔融温度的规律和机制

准格尔高硅铝煤灰熔融温度（AFT）高,易引发液态排渣气化炉排渣口堵塞问题,需添加助熔剂降低AFT。利用灰熔融温度测试仪研究了不同质量比CaO/Fe₂O₃（Ca/Fe）助剂的助熔效果,结合热机械分析仪、热重-示差扫描量热仪、XRD以及热力学计算对比分析了氩气气氛与弱还原气氛下Ca-Fe协同助熔机理。研究发现,弱还原与氩气气氛下,AFT均随Ca/Fe增加先降低后升高,在Ca/Fe=1/1时AFT最低,但弱还原气氛下Ca-Fe的助熔效果优于氩气气氛。不同Ca-Fe助剂煤灰在变形温度（DT）、软化温度（ST）、半球温度（HT）和流动温度（FT）时对应的收缩程度差异较大,并且氩气气氛下熔融温度范围（DT~FT）内灰柱的收缩速率显著高于弱还原气氛下的收缩速率。氩气与弱还原气氛下煤灰的收缩过程均可分为三个阶段,且其收缩程度依次递增,但弱还原气氛下第一、二阶段收缩程度较氩气气氛下高。进一步研究表明第一阶段的收缩主要以化学反应引起的固相烧结为主,第二阶段以初始液相形成的液相烧结为主,而第三阶段的收缩行为最终决定煤灰的AFT。高温矿物演化行为显示莫来石和钙长石单独存在时AFT很高,但两者可以与含铁组分形成低共熔物降低AFT,并且Fe²⁺可以促进低共熔物的形成,促使弱还原气氛下低共熔物的生成温度低于氩气气氛下的。