NiCrAlY/Al-Al2O3/Ti2AlNb高温抗氧化和力学性能研究

采用电弧离子镀技水在NiCrAlY涂层与O相Ti₂AlNb合金之间沉积不同Al:Al₂O₃比例的Al-Al₂O₃薄膜作为扩散阻挡层.研究了900℃下恒温氧化500 h后NiCrAlY/Al-Al₂O₃/Ti₂AlNb体系中Al-Al₂O₃层阻挡合金元素互扩散的行为,以及对涂层氧化动力学曲线的影响.结果表明,没有添加扩散阻挡层的NiCrAlY/Ti₂AlNb体系,涂层和基体之间的元素互扩散十分严重,涂层丧失抗氧化能力;而添加扩散阻挡层的材料体系,涂层和基体之间的元素互扩散受到抑制,涂层的长期抗高温氧化性能得到提高.对于3Al-Al₂O₃,1Al-Al₂O₃和0Al-Al₂O₃ 3种扩散阻挡层,综合比较材料体系的抗氧化性能、阻挡层阻挡涂层和基体元素互扩散能力、以及涂层和基体之间结合力,当1Al-Al₂O₃薄膜作为扩散阻挡层时,材料性能最优异.同时,本文利用扩散阻挡系数简洁定量地表示出不同Al:Al₂O₃比例阻挡层的阻挡扩散能力.     

一种可内生Al2O3扩散障的δ-Ni2Al3-Cr2O3/ Ni-Cr2O3涂层体系

通过对Ni-Cr₂O₃复合镀层620 ℃部分渗铝制备了δ-Ni₂Al₃-Cr₂O₃/Ni-Cr₂O₃涂层体系。Cr₂O₃颗粒在渗铝的过程中和Al反应生成更为稳定的Al₂O₃。1000 ℃恒温氧化20 h后发现,铝化物涂层和复合镀层内掺杂的Cr₂O₃颗粒完全转化为Al₂O₃,并在铝化物涂层/Ni镀层界面自发形成了一层Al₂O₃富集层,该富集层起扩散障作用,阻碍铝化物涂层因互扩散所致的退化。     

纳米级和微米级稀土氧化物掺杂W-La2O3-Y2O3-ZrO2 阴极尖端的组织和性能

使用粉末冶金法将纳米级(70–80 nm)和微米级(500–600 nm)稀土氧化物(La₂O₃,Y₂O₃)与钨粉混合,随后通过冷等静压、中频感应烧结、旋锻、拉拔等一系列工艺制备了W-1.5La₂O₃-0.1Y₂O₃-0.1ZrO₂(质量分数,%)材料。对含有纳米和微米尺寸稀土氧化物的阴极样品使用相同的焊接电流,分别进行了0.5、1、2 h的氩弧焊。结果表明,具有纳米级稀土氧化物的样品在焊接过程中表现出更高的工作稳定性,烧损同比降低了近85.4%。此外,随着工作时间的延长,阴极尖端不同区域的稀土氧化物聚集度显著增加。结合COMSOL Multiphysics温度模拟发现,第二相的扩散活化能降低了近34%。这是因为更为细小的第二相有效地控制了钨基体组织的演变,保留了大量晶界作为通道,促进了活性物质在电子发射过程中的扩散。     

Nb2O5/TiO2微弧氧化复合膜层微观组织和高温性能的研究

为了研究Ti6Al4V钛合金微弧氧化膜层的抗高温氧化性能,在硅酸钠电解液中添加纳米铌(Nb)颗粒制备了Nb₂O₅/TiO₂复合膜层。采用扫描电子显微镜(SEM)和X射线衍射仪(XRD)分析膜层的微观结构和相组成。结果表明：随着纳米Nb浓度增加,膜层表面微孔直径增大、数量减小,膜层中Nb元素含量逐渐增加至5at%,膜层厚度由42.28μm增加至55.48μm;膜层由锐钛矿型TiO₂、金红石型TiO₂、Al₂TiO₅、Nb₂O₅及Nb-Ti化合物组成,金红石型TiO₂峰值和Nb₂O₅峰值逐渐上升;试样增重由基体10.25 mg/cm²降低至Nb浓度为6 g/L制备膜层的2.281 mg/cm²,平均氧化速率由2.8472×10^-5 mg·cm^-2     

优化水热合成提高ZnMn2O4阳极的储锂性能(英文)

为探讨制备条件对过渡金属氧化物负极材料电化学性能的影响，以硝酸锌和硝酸锰为原料，采用水热法合成了过渡金属氧化物ZnMn₂O₄负极材料。通过设计4因素3水平的正交试验，系统研究反应温度、反应时间、致密度、pH值等工艺参数对合成条件的影响。X射线衍射和扫描电镜证实ZnMn₂O₄具有微米级块状结构及I41/amd空间群。在优化的制备条件下，Li/ZnMn₂O₄电池的首次放电比容量为933.1 mA·h/g，在0.1C倍率下循环100次后放电比容量仍为249.3 mA·h/g。正交优化后的样品具有良好的循环性能和倍率性能。     

Ho3+和Yb3+共掺杂La7P3O18荧光粉的合成及上转换发光性能(英文)

通过高温固相技术合成Ho³⁺和Yb³⁺共掺杂La₇P₃O₁₈上转换荧光粉。XRD结果表明,合成样品是空间群为P21/n的单斜结构的La₇P₃O₁₈晶体和少量La PO₄晶体的混合物。紫外可见漫反射光谱结果证实La₇P₃O₁₈晶体是一种光学带隙为4.10 e V的间接半导体。经980 nm激光激发,Ho³⁺和Yb³⁺共掺杂La₇P₃O₁₈荧光粉发射出Ho³⁺离子特征的蓝色(486 nm)、绿色(550 nm)和红色(661 nm)特征峰,其中,661 nm处发射峰在样品上转换发光光谱中占主导地位。此外,随着Ho³⁺和Yb³⁺掺杂量的增加,样品上转换发光强度...     

Ti(C,N)-Al2O3陶瓷基复合材料与40Cr钢辅助脉冲电流液相扩散连接

采用辅助脉冲电流液相扩散连接方法,对Ti(C,N)-Al₂O₃陶瓷基复合材料与40Cr钢进行了焊接试验,重点研究了在一定加热温度和保温时间条件下脉冲电流对界面元素分布、相结构、反应层厚度以及接头强度的影响规律.结果表明,辅助脉冲电流液相扩散连接可以实现Ti(C,N)-Al₂O₃陶瓷基复合材料的冶金结合,保温时间对焊接接头强度影响不明显,四点弯曲强度数据普遍处于146~180 MPa之间;在脉冲电流作用下,焊缝熔体中原子扩散行为、扩散路径以及扩散速率将发生显著变化,利用该特性,有助于改变界面金属间化合物的生长特性,控制焊缝中低熔点共晶组织含量,进而达到改善和提高焊接接头强度的效果.     

用于钯催化载体的P改性高孔隙率γ-Al2O3/α-Al2O3泡沫(英文)

提出了一种新方法来制备用于钯催化剂的P-γ-Al₂O₃涂层改性的α-Al₂O₃泡沫。采用聚氨酯模板法,通过优化工艺参数,使陶瓷泡沫的显气孔率达到90.28%,体积密度达到0.45 g·cm^-3,且该泡沫具有可使用强度。将掺有P元素的γ-Al₂O₃涂层涂覆在α-Al₂O₃泡沫上,然后通过超声波辅助浸渍法来装载活性催化相(Pd)。结果表明,含P涂层增加了惰性泡沫的比表面积和弱酸性位点,同时减少了强酸性位点的占比。与无涂层的泡沫相比,改性的泡沫更容易装载活性相,且装载的金属Pd不容易被氧化,CO的催化转化温度(T₅₀,T₉₀)降低了50℃左右。该研究证明了低成本改性α-Al₂O₃陶瓷泡沫在钯催化剂生产中具有极大的应用潜力。     

以Si-CaO/Al2O3-Si为连接层的C/C复合材料扩散连接接头微观组织及其剪切强度

CaO/Al₂O₃用于SiC之间的扩散连接，具有接头强度高、连接可靠等优点，但CaO/Al₂O₃与C/C复合材料的润湿性差，不宜直接用于C/C复合材料的扩散连接。为解决C/C复合材料难以焊接以及连接接头强度较低的问题，本文采用Si-CaO/Al₂O₃-Si复合夹层作为连接层，对C/C复合材料进行扩散连接，通过Si与C/C在高温下反应生成SiC以及SiC与CaO/Al₂O₃之间的相互作用，获得高强度接头。结果表明，随着保温时间的延长，接头的剪切强度先升高后下降。1500℃保温90 min的接头，剪切强度达到38.17 MPa，连接接头内部形成“富Si的过渡层-中间层-富Si的过渡层”对称结构，接头中生成的物相主要包含SiC以及由Al₂SiO₅、SiO₂、CaAl₄O₇等构成的复合玻璃相，剪切断裂主要发生在C...     

ZrO2(Y2O3)含量对Mo-12Si-8.5B-ZrO2(Y2O3)复合材料高温氧化性能的影响

为了研究ZrO₂(Y₂O₃)含量对Mo-12Si-8.5B-ZrO₂(Y₂O₃)复合材料高温氧化性能的影响，利用机械合金化与放电等离子烧结制备了ZrO₂(Y₂O₃)含量为0～10 mass%的Mo-12Si-8.5B-ZrO₂(Y₂O₃)复合材料，研究了其在800、1000和1200℃下的高温氧化行为。结果表明：复合材料在800℃时均发生显著氧化，质量损失持续增加；随着ZrO₂(Y₂O₃)含量的增加，氧化质量损失速度降低，复合材料的抗氧化能力提升；低ZrO₂(Y₂O₃)含量(0～2.5 mass%)的复合材料在1000和1200℃下具备优异的抗氧化性；高ZrO₂(Y_...     

Synthesis of tungsten oxide (W18O49) nanosheets utilizing EDTA salt by microwave irradiation method

We report the synthesis of crystalline W₁₈O₄₉ with nanosheet like morphology by low cost microwave irradiation method without employing hydrothermal process for the first time. Initially, WO₃·H₂O was synthesized using ethylenediaminetetraacetic acid (EDTA) as surface modulator. The product was annealed at 600 °C for 6 h in ambient atmosphere in order to obtain anhydrous tungsten oxide W₁₈O₄₉. Powder X-ray diffraction results confirmed the as prepared WO₃·H₂O to be orthorhombic and W₁₈O₄₉ to be monoclinic phase, respectively. Transmission electron micrographs (TEM) revealed that the W₁₈O₄₉ nanosheets have the average dimensions of the order of 250 nm in length and around 150 nm in width. UV-visible diffusion reflectance spectroscopic (DRS) studies revealed the band gap energies to be 3.28 and 3.47 eV for WO₃·H₂O and W₁₈O₄₉ samples, respectively. The growth mechanism of two dimensional W₁₈O₄₉ nanosheets is discussed.     

Preparation and electrochemical performance of nitrogen-doped carbon-coated Bi2Mn4O10 anode materials for lithium-ion batteries

To inhibit rapid capacity attenuation of Bi₂Mn₄O₁₀ anode material in high-energy lithium-ion batteries, a novel high-purity anode composite material Bi₂Mn₄O₁₀/ECP-N (ECP-N: N-doped Ketjen black) was prepared via an uncomplicated ball milling method. The as-synthesized Bi₂Mn₄O₁₀/ECP-N composite demonstrated a great reversible specific capacity of 576.2 mA·h/g after 100 cycles at 0.2C with a large capacity retention of 75%. However, the capacity retention of individual Bi₂Mn₄O₁₀ was only 27%. Even at 3C, a superior rate capacity of 236.1 mA·h/g was retained. Those remarkable electrochemical performances could give the credit to the introduction of ECP-N, which not only effectively improves the specific surface area to buffer volume expansion and enhances conductivity and wettability of composites but also accelerates the ion transfer and the reversible conversion reaction.     

Sintering and microstuctural characterization of W, Nb and Ti iron-substituted BiFeO3

The sintering behaviour and the microstructural evolution of W⁶⁺, Nb⁵⁺ and Ti⁴⁺ iron-substituted BiFeO₃ ceramics have been analyzed. The obtained results show that W⁶⁺ and Nb⁵⁺ ions interact with the secondary phases usually present in these materials, thus altering the solid state formation of the BiFeO₃ phase. In contrast, Ti⁴⁺ ions incorporate into the perovskite structure, leading to an exceptionally low proportion of secondary phases. In addition to this, BiFe_0.95Ti_0.05O₃ materials present a dense microstructure with submicronic and nanostructured grains, clearly smaller than those in the undoped materials.     

Structure of Cs0.5[Nb2.5W2.5O14] analysed by focal-series reconstruction and crystallographic image processing

The structure of the oxygen sub-lattice in Cs_0.5[Nb_2.5W_2.5O₁₄] is investigated for the first time by advanced electron-optical methods. Since Cs_0.5[Nb_2.5W_2.5O₁₄] resembles the crystal structure of the so-called M1 phase of Mo–V–Nb–Te–O, which is the best catalyst for the selective oxidation of propane to acrylic acid, the structure analysis of the oxygen sub-lattice can contribute substantially to a better understanding of this catalytic process. The so far only partially known structure of the complex metal oxide Cs_0.5[Nb_2.5W_2.5O₁₄] is investigated by combining modern methods of high-resolution transmission electron microscopy with crystallographic image processing techniques. Average atom positions in the a–b plane are determined from the phase of the exit-plane wave function, which was numerically reconstructed from a focal series of spherical-aberration-corrected electron micrographs. The experimentally determined atom positions agree well with a structure model obtained by first-principles calculations for the underlying M₅O₁₄ (M = Nb, W) framework. Moreover, several deviations from the periodic structure, which may influence the catalytic properties of the structurally similar M1 phase, are observed. The obtained results demonstrate that aberration-corrected high-resolution transmission electron microscopy is a reliable alternative for the analysis of periodic structures, in particular when traditional methods for crystallographic structure determination like XRD or neutron diffraction cannot be applied.     

Sn_(0.35-0.5x)Co_(0.35-0.5x)Zn_xC_(0.30)复合材料的制备及电化学性能

采用固相烧结和球磨相结合的方法制备了锂离子电池负极复合材料Sn_0.35-0.5xCo_0.35-0.5xZn_xC_0.30 (摩尔分数x分别为0, 0.05, 0.10, 0.15和0.20), 考察了Zn添加量对材料结构和电化学性能的影响. 烧结粉末样品的XRD分析表明, 随着Zn含量的增多, 在CoSn主相基础上, 先形成少量CoSn₂相, 随后形成少量Co₃Sn₂, Zn和Sn相. 大部分 Zn原子固溶于CoSn相. 电性能分析表明, 随着Zn含量的增加, 首次放电容量和充放电效率都呈现先增加而后趋于稳定的趋势, 当x=0.15时, 首次放电容量和充放电效率都接近最大值, 分别为343 mA-h/g和73.8%; 经过 25 cyc充放电后放电容量保持了首次放电容量的87.6%. 这表明Zn原子固溶引起的晶格畸变和多种相生成导致相界数量的增多, 加快了Li⁺动力学扩散速度, 从而显著改善了电化学性能. 选择烧结粉末样品Sn_0.275Co_0.275Zn_0.15C_0.30进行球磨, 晶粒和颗粒的细化使样品的放电容量显著提升, 但对首次放电效率和循环性能改善不明显.     

Modeling Two- and Three-Stage Oxygen Tracer Experiments during High-Temperature Oxidation of Metals with a High Oxygen Solubility

The numerical tool EKINOX-Zr has been upgraded to simulate oxygen tracer experiments during the high-temperature oxidation of a metal with a high oxygen solubility limit. The penetration of ¹⁸O tracer is calculated during the dynamic evolution of the ZrO_2-x/α_{Zr(O )}/β_zr system. The numerical approach allows to explicitly take into account the variation of the tracer diffusion coefficient through the oxide scale as a function of the vacancy concentration. A classical two-stages ¹⁶O₂/¹⁸O₂ tracer experiment has been simulated. It is shown that a classical fitting procedure on the ¹⁸O concentration profile obtained for short-time experiments leads to the identification of the oxygen chemical diffusion coefficient. The second type of tracer experiment is proposed using a three-stages ¹⁶O₂/¹⁸O₂/¹⁶O₂ oxidation. It allows the direct estimation of the diffusion coefficient from the transport of ¹⁸O peak in the growing oxide scale.     

Sb2S3 nanorods/porous-carbon composite from natural stibnite ore as high-performance anode for lithium-ion batteries

To avoid the high purity reagents and high energy consumption involved in the manufacturing of lithium-ion battery anode materials, Sb₂S₃ nanorods/porous-carbon anode was prepared by remodeling natural stibnite ore with porous carbon matrix via a simple melting method. Due to the nanostructure of Sb₂S₃ nanorods and synergistic effect of porous carbon, the Sb₂S₃ nanorods/porous-carbon anode achieved high cyclic performance of 530.3 mA·h/g at a current density of 100 mA/g after 150 cycles, and exhibited a reversible capacity of 130.6 mA·h/g at a high current density of 5000 mA/g for 320 cycles. This shows a great possibility of utilizing Sb₂S₃ ore as raw material to fabricate promising anodes for advanced lithium-ion batteries.     

Isotope exchange studies of oxidation mechanisms in nickel-base superalloys using FIB-SIMS techniques

The thermo-mechanical stability of the oxide layer that grows between the metallic bond coat and the ceramic top coat on superalloy turbine blades determines the lifetime of the system. Understanding the mechanisms of oxidation of the bond coat that is applied to the superalloy is key to improving the performance of the thermal barrier coatings. FIB-SIMS (Focused Ion Beam-Secondary Ion Mass Spectrometry) techniques in conjunction with tracer diffusion experiments represent a powerful tool in characterizing this oxide layer. This paper presents the results of oxidation studies on single crystal nickel-base superalloys/bond coat systems. In these studies, a two-stage oxidation experiment is used where ¹⁸O₂ serves as a tracer element during the second stage oxidation. The aluminium oxide grown in ¹⁶O₂ during the first stage oxidation represents an initial layer of oxide. Mass spectra collected by FIB-SIMS reveal the counter mass transportation of inward oxygen diffusion and outward diffusion of aluminium. New oxide formation during the second stage oxidation under an ¹⁸O₂ enriched environment is observed at both the gas/oxide interface as well as the oxide/superalloy interface. FIB-SIMS scanning enables high-resolution isotope maps, in particular ¹⁸O⁻, to be captured. These confirm the existence of new oxide forming at the oxide/superalloy interface with clear indications of short circuit diffusion paths through the existing oxide. These data allow the diffusion mechanisms for different superalloy/bond coat systems to be identified and contrasted, allowing the role of alloying additions to be elucidated.     

Core–shell structures in pressureless-sintered undoped Pb(Fe2/3W1/3)O3 ceramics

Core–shell structures have been found by both scanning and transmission electron microscopy in undoped Pb(Fe_1/3W_2/3)O₃ ceramics when a solid-state-reacted powder of stoichiometric composition was sintered at 800°C. The presence of superlattice reflections of the {1/2 1/2 1/2}-type, often termed F-spots, indicates that the existence of nanoscale ordered domains of 2–5 nm size in both core and shell is due to chemical ordering of the B-site cations with alternating Fe³⁺ and W⁶⁺ along the <111> direction. The ceramic is densified by the assistance of a low-temperature liquid eutectic at ∼690°C. A formation mechanism of core–shell structures in Pb(Fe_1/3W_2/3)O₃ ceramic is proposed. It can be described by solution-reprecipitation and phase transformation subsequently to perovskite Pb(Fe_1/3W_2/3)O₃, involving at least two intermediate phases which are formed at temperatures below and above the low-temperature liquid eutectic point and related to pyrochlore (Pb₂FeWO_6.5). The cores are characterised by “black dots” and contain relatively Fe-excess. The shells exhibiting featureless contrast are free of “black dots” but contain W-excess relative to the cores. Long term sintering at 800°C has facilitated the inward diffusion of W⁶⁺ to the grain interior when the distribution of the B-site cations is improved. As a result, the shell increases its size at the expense of the core.     

ZrO2(ZrB2)活性扩散障界面演变行为的研究

本实验采用电子束物理气相沉积(Electron Beam Physical Vapor Deposition, EB-PVD)技术在镍基单晶合金Rene N5基体上制备出N5/(ZrB₂+ZrO₂)/ NiCrAl和N5/ZrO₂/ NiCrAl两组试样。然后,同时对其进行900℃/5h恒温氧化和1000℃/250h、1000℃/300h及1000℃/350h循环氧化,并采用SEM、EDS分析方法研究了界面演变行为及退化失效行为,结果表明,ZrB₂的加入对活性扩散障界面反应的生成速率有一定的延缓,但不影响具有阻扩散功能的Al₂O₃扩散障层的最终形成;并且,ZrB₂的加入提高了活性扩散障结构的服役寿命,改变了活性扩散障结构的失效方式。