注镧Co-Cr合金表面氧化膜生长规律与微观结构表征

采用热重分析(TGA)方法研究了离子注镧对Co-40Cr合金在1000℃空气中的恒温氧化和循环氧化行为的影响. 用扫描电镜(SEM)和透射电镜(TEM)对表面氧化膜的微观形貌和结构进行了研究. 用二次离子质谱(SIMS)对合金表面元素铬结合能的变化情况以及氧化膜中元素镧的深度分布进行了测试, 并用激光拉曼谱(Raman)对掺杂镧引起的氧化膜内应力改变进行了测量研究.结果表明, 离子注镧后Co-40Cr合金在1000℃空气中的恒温氧化速率显著降低, 表面Cr₂O₃     

离子注钇对镍900℃高温氧化行为及氧化膜性能的影响研究

采用热重分析对纯镍及其表面离子注钇样品在900℃空气中的恒温氧化动力学规律进行了研究.用扫描电子显微镜和透射电子显微镜对含钇和不含钇氧化膜的微观形貌及结构进行了观测.用声发射方法对氧化膜在恒温生长阶段和空冷阶段的开裂与剥落进行了实时监测，根据相应的氧化膜开裂模型，对声发射信号在时域和数域上的分布情况进行了分析.结果表明离子注钇显著降低了镍的恒温氧化速率，提高了表面NiO膜的抗开裂和抗剥落性能.离子注钇提高镍抗氧化性能的原因主要是钇细化了表面NiO膜的晶粒、提高了氧化膜的高温塑性和蠕变能力，并显著降低了Ni/NiO界面缺陷的数量和大小. 关键词： 高温氧化 应力 声发射 离子注入     

纯锆上离子注入钇和镧后的表面分析

用金属蒸汽真空弧源，以40kV加速电压对纯锆样品分别进行了10¹⁶—10¹⁷/cm²的钇、镧离子注入，注入温度约为130℃.然后对注入样品进行表面分析.x射线光电子能谱分析表明，注入的钇以Y₂O₃形式存在，镧以La₂O₃形式存在.俄歇电子能谱表明，纯锆基体表面的氧化膜厚度随着离子注入剂量的增加而增加，当离子注入剂量达到10¹⁷/cm²时，氧化膜的厚度达到了最大值.卢瑟福背散射显示镧层的厚度约为30nm，同时直接观察到当离子注入剂量为(La+Y)10¹⁷/cm²时，纯锆样品表面发生了严重的溅射. 关键词： 纯锆 钇和镧离子共注入 卢瑟福背散射 x射线光电子能谱     

Fe-Cr-Al合金氧化膜形成机理电子理论研究

通过自编软件建立了Fe-Cr-Al合金表面、氧化膜/基体界面模型,采用递归法计算了合金元素在Fe-Cr-Al合金表面、氧化膜/基体界面的环境敏感镶嵌能、亲和能、结合能、态密度等电子结构参数.从电子层次系统研究了Fe-Cr-Al合金氧化膜的形成机理、稀土元素和杂质硫对氧化膜形成过程及黏附性的影响机理.研究表明Fe-Cr-Al合金中Al的偏聚驱动力远大于Y,Cr.氧化初期氧从合金表面向合金内部扩散,合金内部Al向合金表面扩散,使合金形成富铝、氧表面层;氧与Al间的亲和力较大（亲和能低）,氧原子容易与Al结合生成Al₂O₃保护膜;合金中加入Y后,Y在合金表面偏聚,抑制Al向合金表面扩散,氧化膜的横向生长得到有效控制,从而避免氧化膜皱褶形貌的发生,提高氧化膜的黏附性;合金内部的S通过扩散汇集在基体/氧化膜界面,S使界面区原子的总能增高,总态密度降低,减小了界面的稳定性,进而削弱氧化膜与合金基体的结合力. 关键词： 电子结构 高温氧化 Fe-Cr-Al合金     

Ti和蓝宝石的界面反应

在超高真空中用电子束蒸发在抛光的(1102)取向的蓝宝石(α-Al₂O₃)衬底上蒸镀500nm的Ti膜,在恒温炉中退火,然后用XRD(包括一般的和小角度的X射线衍射),AES(俄歇电子谱,包括深度剖面分布和通过界面的谱形分析)和SIMS(二次离子质谱)等表面分析技术详细研究了从室温至850℃,Ti与α-Al₂O₃的固相界面反应.结果表明室温及300℃,30min退火已有反应,Al₂O_{3< 关键词：}     

纳米晶304不锈钢高温氧化膜中Cr和Mn元素的XPS和UPS表征

利用X射线光电子能谱（XPS）和紫外光电子能谱（UPS）,对比研究了普通304不锈钢（CP-SS304）和深度轧制技术制备的块体纳米晶304不锈钢（BN-SS304）在900 ℃空气中氧化24 h后形成的高温氧化膜中Cr和Mn元素的结合能、原子百分比、价电子的相互作用和功函数,分析了BN-SS304表面电子结构的特征。结果表明：两种材料氧化膜中Cr元素以Cr3+和Cr0存在,Mn元素以Mn4+和Mn0存在,在不同溅射时间,BN-SS304氧化膜中Cr3+与（Cr3++Cr0）原子百分比和Mn4+与（Mn4++Mn0）原子百分比均低于CP-SS304氧化膜中的比值。两种材料氧化膜中价电子之间的相互作用主要有Mn—O,Cr—O,Mn0(3d和4s)和Cr0(3d和4s)。与CP-SS304相比,BN-SS304氧化膜表面价电子之间的相互作用强,其功函数比CP-SS304提高0.07 eV, BN-SS304的耐高温氧化性能增强。     

常压MOCVD生长Ga2O3薄膜及其分析

以去离子水(H₂O)和三甲基镓(TMGa)为源材料,用常压MOCVD方法在蓝宝石(0001)面上生长出β-Ga₂O₃薄膜.用原子力显微镜(AFM)、X射线衍射(XRD)以及二次离子质谱(SIMS)实验表征Ga₂O₃外延膜的质量.在X射线衍射谱中有一个强的Ga₂O₃(102)面衍射峰,其半峰全宽(FWHM)为0.25°,表明该Ga₂O₃外延膜是(102)择优取向.在二次离子质谱中除了C、H、O和Ga原子外,没有观测到其他原子.     

铌合金电子结构及其高温氧化行为

为了从电子层面揭示Nb合金高温氧化的物理本质,采用递归法计算了Nb合金的电子态密度、原子镶嵌能、亲和能等电子结构参数,探索Nb合金高温氧化机理.研究表明:氧在Nb中具备较高的扩散速率和溶解度,且氧与Nb较易发生反应,生成氧化物,这使Nb的抗高温氧化性较差.原子镶嵌能的计算结果表明,合金元素Ti,Si,Cr在基体中稳定性较低,易向Nb合金表面扩散,形成富Ti,Si,Cr的表层.合金表层中氧与Nb,Ti,Si,Cr间具有较大亲和性,可以生成相应的氧化物,形成对合金具有保护作用的氧化膜. 关键词： 递归法 高温氧化 Nb合金     

非晶态合金Fe87V3Zr10的吸氢现象

用二次离子质谱(SIMS)和穆斯堡尔谱研究了非晶态合金Fe₈₇V₃Zr₁₀的吸氢现象实验表明,H优先与Zr形成ZrH原子团,亦有部分H分别与V和Fe形成VH和FeH原子团。对吸氢影响该合金磁性的主要原因进行了分析。 关键词：     

Si-W/Si/SiO2/Si(100)的横截面电子显微镜研究

本文用横截面电子显微镜法分析了Si-W/Si/SiO₂/Si(100)在440—1000℃退火后的晶化过程,以及各个界面的变化情况.发现Si-W合金膜中,WSi₂并未优先在表面、界面处形成晶核.当退火温度不高于700℃时,反应在合金膜内发生,表面、界面起伏和缓.退火温度高达800—1000℃时,界面、表面出现原子扩散,造成剧烈的界面起伏;表面则出现小的热沟槽,Si/SiO₂界面也出现高分辨电子显微镜才能观察到的起伏.表面、界面的原子迁移的动力来源于晶界与表面、界面张力.由于SiO₂中Si—O键很稳定,不易发生Si和O在界面处的互扩散,所以Si/SiO₂界面起伏很小. 关键词：     

ESCA studies of Cr-Co alloys

ESCA examination of films formed on Cr-Co alloys after immersion in 0.1M NaCl for 24 h has shown that the thickness of passive films decreased with an increase in chromium content. Surface films consisted of chromium and cobalt oxides as Cr₂O₃ and CoO. The amount of CoO in the surface film of the alloy was decreased with an increase in chromium but Cr₂O₃ was found at a greater depth in the passive film at any composition. Cr₂O₃ was a major component of the surface film when the chromium content in the alloy was 10% or higher. Electrochemical techniques according to ASTM G59 and ASTM G5 were used for the determination of the relative corrosion rate. Both Co-10 wt.% Cr and Co-30 wt.% Cr alloys investigated showed a lower corrosion rate than the Co-5 wt.% Cr alloy. Corrosion rate measured could be correlated to the surface film composition and structure as determined by ESCA.     

Initial oxidation stages on FeCr(100) and FeCr(110) surfaces

Simultaneous LEED and AES are used to follow early stages of oxidation of monocrystalline FeCr(100) and (110) between 700 and 900 K in the oxygen pressure range 10^?9–10^?6 Torr. A chromium-rich oxide region at the alloy/oxide interface is observed, which exhibits different surface structures on oxidized FeCr(100) and FeCr(110). The chromium concentration in this initially formed oxide film is found to be enhanced by low oxygen pressures or high temperatures. During further oxidation different behaviours are observed on FeCr(100) and FeCr(110), which are explained by assuming different ion permeabilities through the initial chromium rich oxide regions on the two surface planes. On FeCr(110) surfaces oxidation is initiated on chromium enriched (100) facets at 800 K or below. At 900 K a film consisting of rhombohedral Cr₂O₃ or (Fe, Cr)₂O₃ is epitaxially growing with its (001) plane parallel to the alloy (110) face. On FeCr(100) surfaces the chromium rich oxide region next to the substrate is of fcc type. As soon as the diffusion of iron from the alloy to the gas/oxide interface is observable, a spinel type oxide is formed and connected with the location of iron in tetrahedral lattice sites. Closer to the fcc lattice the spinel oxide consists of FeCr₂O₄ or a solid solution of FeCr₂O₄ and Fe₃O₄ whereas next to the gas phase the oxide is pure Fe₃O₄.     

Physico-chemical investigations on selected gallium doped lanthanum chromites

Investigations on lanthanum gallium chromium mixed oxides of the compositions La_1.0Ga_0.2Cr_0.8O_3−d and La_0.9Ga_0.2Cr_0.8O_3-d are presented regarding their structure, redox stability, conductivity and catalytic activity for the oxidation of propene. The mixed oxide has perovskite-type structure, high redox stability, an electronic p-type conductivity and low catalytic activity. If the perovskite-type compound has a deficiency of lanthanum, the electronic conductivity, surface area and catalytic activity are significantly higher. The catalytic activity is likely comparable to that of gold. Similar to gold electrodes of solid electrolytes, oxygen electrodes formed with gallium doped lanthanum chromite show a relatively high sensitivity to hydrocarbons such as propene at temperatures of about 700 °C. The mixed oxide is possibly suitable as electrode material for exhaust gas sensors using oxide-ion conducting solid electrolytes. Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, September 13–20, 1998.     

Characterization of Cr/SiO2 catalysts and ethylene polymerization by XPS

Cr/SiO₂ catalysts with 1 or 3 wt.% Cr loadings and different chromium precursors were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). A method to determine chromium species in the sample was developed through the decomposition of the Cr 2p XPS spectrum in Cr⁶⁺ and Cr³⁺ standard spectra. The results of the binding energy from the Cr 2p region and of the distribution of chromium species allowed to evaluate the dynamic photo-reduction of the surface chromium species during XPS analysis. Photo-reduction of surface Cr⁶⁺ to Cr³⁺ species was verified for all samples supported in silica, depending on the precursor and chromium content. Bulk CrO₃ and Cr₂O₃ standards did not reveal variation in the binding energy of Cr 2p_3/2, but a physical mixture of CrO₃ with SiO₂ presented photo-reduction. The behavior of this mixture resembled to the catalysts and suggests the participation of the surface hydroxyls of silica in the photo-reduction process. XPS intensity measurements for assessing dispersion of chromium oxide were used to compare the calcined and reduced catalysts to different chromium precursors. Polyethylene chains were detected by in situ XPS, while oligomerization products were not observed.     

AgI(Cr2O3)复合离子导体的光谱研究

本文研究了AgI(Cr₂O₃)复合离子导体的红外吸收光谱,近紫外、可见反射光谱。发现复合离子导体的两种谱图均与纯AgI,Cr₂O₃的不同。红外吸收光谱在882—889cm^-1处有一新吸收峰。电子谱中,AgI从430nm开始向长波方向表现的光离解特性消失。本来Cr₂O₃由配位场效应而引起的d—d吸收跃迁以410nm,530nm为中心的反射谱带,现在410nm处的谱带消失。530nm处的谱带稍有红移,且随加入Cr₂O₃量的增多而强度减弱。代之以整个紫外、可见区的较强吸收。对此,结合透射电子显微镜的分析,用双声子耦合和介质的变形极化以及配位场理论对AgI(Cr₂O₃)复合离子导体的声子谱和电子谱进行了解析。 关键词：     

Investigation of the electronic structure of La1−x(M2+)xCrO3, Cr2O3 and La2O3 by X-ray photoelectron spectroscopy

The electronic structures of lanthanum chromites, pure and doped with magnesium and strontium, have been studied in comparison with Cr₂O₃ and La₂O₃ through the use of X-ray photo-electron spectroscopy. The main peaks and satellites of inner and outer electrons are properly assigned. The band structure of LaCrO₃ is determined by using the XPS data and a calculation based on point charge model. The partially filled Cr(3d) band is localized. The conduction is mainly extrinsic. The measured Fermi-level is close to the valence band indicating a low activation energy in agreement with the results of conductivity measurements.     

The characterization of Cr secondary oxide phases in ZnO films studied by X-ray spectroscopy and photoemission spectroscopy

X-ray absorption near-edge structure (XANES), X-ray emission spectroscopy (XES), and X-ray photoemission spectroscopy (XPS) were used to characterize the Cr secondary oxide phases in ZnO films that had been prepared using a co-sputtering method. Analysis of the Cr L_3,2-edge XANES spectra reveals that the intensity of white-line features decreases subtly as the sputtering power increases, indicating that the occupation of Cr 3d orbitals increases with Cr concentration in (Zn, Cr)O films. The O K-edge spectra show that the intensity of XANES features of (Zn, Cr)O films is lower than those of ZnO film, suggesting enhanced occupation of O 2p-derived states through O 2p-Cr 3d hybridization. The XES and XPS spectra indicate that the line shapes in the valence band of (Zn, Cr)O films are quite different from those of ZnO and that the Cr₂O₃ phase dominates the spinel structure of (Zn, Cr)O films increasingly as the Cr sputtering power is increased. Over all results suggest that the non-ferromagnetic behavior of (Zn, Cr)O films can be attributed to the dominant presence of Cr₂O₃, whereas the bulk comprise phase segregations of Cr₂O₃ and/or ZnCr₂O₄, which results them the most stable TM-doped ZnO material against etching.     

Corrosion behavior and composition analysis of chromate passive film on electroless Ni-P coating

A passive film was formed on electroless Ni-P coating (ENPC) in a bath of K₂Cr₂O₇ 30 g/l. XPS and electrochemical methods were employed to analyze its chemical compositions and corrosion behaviors. The potentiodynamic polarization tests indicated the corrosion current of the passivated sample was 1/30 that of as-plated ENPC. The XPS analysis illustrated the film comprised Cr, Ni and O. The film thickness was evaluated to be a few nanometers according to the sputtering rate of Ar⁺ ion. High-resolution XPS spectra suggested that the detected Cr in film was in the form of trivalent compounds, Cr₂O₃ and Cr(OH)₃.     

Oxidation behavior and mechanism of powder metallurgy Rene95 nickel based superalloy between 800 and 1000 °C

The oxidation behaviors of powder metallurgy (PM) Rene95 Ni-based superalloy in the temperature range of 800-1000 °C are investigated in air by virtue of isothermal oxidation testing, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the oxidation kinetics follows a square power law as the time extends at each temperature. The oxidation layers are detected to be composed of Cr₂O₃, TiO₂ and a small amount of NiCr₂O₄. The cross-sectional morphologies indicate that the oxidation layer consists of three parts: Cr-rich oxide layer, Cr and Ti duplex oxide layer, and oxidation affected zone. Theoretical analyses of oxidation kinetics and thicknesses of oxidation layers confirm that the activation energy of oxidation of PM Rene95 superalloy is 165.32 kJ mol⁻¹ and the oxidation process is controlled by diffusions of oxygen, Cr, and Ti. Accordingly, a diffusion-controlled mechanism is suggested to understand the oxidation behaviors of PM Rene95 superalloy at elevated temperatures.     

Constituted oxides/nitrides on nitriding 304, 430 and 17-4 PH stainless steel in salt baths over the temperature range 723 to 923 K

The progressively developed oxides and nitrides that form on nitriding 304, 430 and 17-4 PH stainless steel are analysed by X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) in this study. The experimental results show that the Cr contents and matrix structures (ferrite, austenite and martensite) play an important role in forming FeCr₂O₄, Cr₂O₃ and Fe₂O₃ oxides as well as nitrides. After a short immersion time, oxides of Cr₂O₃ and FeCr₂O₄ form in nitride films on 304 stainless steel samples. Fe₂O₃ oxide will subsequently form following an increasing immersion time. For the 430 stainless steel, Cr₂O₃ predominately forms after a short dipping time which hinders the growth of the nitride layer. As a result, this sample had the thinnest nitride film of the three for a given immersion time. After the formation of oxides, both CrN and Cr₂N were detected near the surface of the nitride films of three samples while Cr₂N phases formed in the deeper zone. The greatest amount of Fe₂O₃ oxide among the three samples was obtained on the nitriding 17-4 PH stainless steel which also had a high intensity count of N 1s.