SiGe合金氧化层中的纳米结构

在硅锗合金衬底上采用氧化等制膜方式生成零维和二维的纳米结构样品 ,用高精度椭偏仪 (HPE)、卢瑟福背散射谱仪 (RBS)和高分辨率扫描透射电子显微镜 (HR -STEM)测量样品的纳米结构 ,并采用美国威思康新州立大学开发的Rump模拟软件对卢瑟福背散射谱 (RBS)中的CHANNEL谱和RANDOM谱分别进行精细结构模拟 ,测量并计算出纳米氧化层与锗的纳米薄膜结构分布 ,并且反馈控制加工过程 ,优化硅锗半导体材料纳米结构样品的加工条件 .在硅锗合金的氧化层表面中首次发现纳米锗量子点组成的纳米盖帽薄膜 ( 2nm) 。

铝合金表面氧化物激光清洗机理研究进展

激光清洗作为21世纪新兴的清洗技术,以其独有的高精度、环保节能等优势,很大程度契合了当前可持续发展的要求。在归纳众多试验和理论研究的基础上,以激光能量密度为变量,重点综述了随着激光能量密度的变化,激光去除铝合金表面氧化层的不同机理,包括热机械膨胀、熔化蒸发、相爆炸、蒸发压力冲击、等离子体冲击,传统意义上的清洗机理“热烧蚀”应被理解为一种实验观察到的现象。介绍了当前激光清洗机理研究中常用手段,包括高速摄像和热力学模拟。介绍了当前激光清洗机理分析中遇到的一些困难,包括升温过程的复杂性和微观清洗过程的难观测性等。在此基础上,介绍了不同清洗机理作用下的铝合金表面质量变化,包括表面粗糙度及烧蚀坑形貌。对清洗机理与应用之间的联系进行说明,包括激光清洗对样品表面性能(如硬度、耐蚀性等)的影响。同时针对激光作用过程中涉及的多因素耦合作用进行了说明,包括各种能量场耦合,以及因界面声阻抗不同而产生的拉应力等对清洗过程的影响。最后提出当前制约激光清洗技术发展存在的一些问题,并对激光清洗技术的发展方向进行了展望。

铝合金微弧氧化层耐海水冲蚀性能的研究

采用失重法研究了冲刷速度和温度对铝合金微弧氧化层在海水中冲刷腐蚀速率的影响,结合对试样表面腐蚀形貌的观察,对铝合金微弧氧化层在海水中冲蚀行为进行了分析。结果表明,铝合金微弧氧化层在海水中的耐蚀性与海水的冲蚀速度和海水的温度有密切联系,微弧氧化层的耐蚀性随冲蚀速度的增大和冲蚀温度的升高而降低。

Corrosion of in-situ grown Mg Al-LDH coating on aluminum alloy

Mg Al-layered double hydroxides（LDH） coatings were fabricated by the in-situ hydrothermal treatment method on the AA5005 aluminum alloy.The characteristics of the coatings were investigated by XRD,FT-IR,SEM and EDS.The effect of the p H value of the solution on the formation of the LDH coatings was studied.The optimum p H value of the solution was 10.0.The corrosion resistance of the LDH coatings was studied using potentiodynamic polarization tests and electrochemical impedance spectrum（EIS）.The results demonstrate that the LDH coatings,characterized by platelets vertically to the substrate surface possess excellent corrosion resistance.The influence of the hydrothermal crystallization time on the corrosion resistance was evaluated.Prolonging the crystallization time can increase the corrosion resistance of the obtained LDH coatings.The anticorrosion mechanism of the LDH coatings was discussed.

Oxidation behavior of Zr-containing Ti_2AlNb-based alloy at 800°C

The oxidation behavior of Ti?22Al?(27?x)Nb?xZr (x=0, 1, 6) alloys at 800 °C for exposure time up to 100 h was examined. It is shown that oxidation rate of experimental alloys obeys the parabolic kinetics. Ti?22Al?26Nb?1Zr alloy demonstrates more excellent oxidation resistance than the other two alloys. The main oxidation products are TiO2, Al2O3 and AlNbO4 phases for all these alloys. For the Ti?22Al?26Nb?1Zr alloy, Zr addition can modify the growth mechanism of oxide scale, which can effectively hinder the diffusion of oxygen. Whereas, reaction of Zr with oxygen leads to the formation of ZrO2 precipitates for the Ti?22Al?21Nb?6Zr alloy, which promotes the oxygen ingress into the substrate. Meanwhile, oxidation affected zones, including internal-oxidation layer and oxygen-enriched zone, are present beneath the outmost oxide scale. The difference in these zones is derived from the phase constitution in the starting Ti?22Al?(27?x)Nb?xZr (x=0, 1, 6) alloys.

Growth and corrosion behaviors of thin anodic alumina membrane on AA5083 Al-Mg alloy in incalescent medium

A self-ordered porous film was fabricated on aluminum alloy in a ternary boric-sulfuric-oxalic acid electrolyte system. By means of voltage–time response, the oxidation process as well as the growth efficiency was studied. Field emission scanning electron microscopy（FE-SEM） was adopted to reveal the morphological and microstructural features of as-fabricated oxide layers. The corrosion protection properties of the films were investigated by electrochemical impedance spectroscopy and potentiodynamic polarization measurements. The results showed that increasing the concentration of the double ionic layer located at the oxide interface could accelerate the film growth rate. The anodic oxidative layer with thickness of 8-9 μm and pore diameter of 10-14 nm maintains the pattern and topography of workpieces, compared with the overall closed film with hierarchical structure. Both samples exhibited much lower corrosion current density after boil water sealing. Meanwhile, a superior stability could be achieved through raising the ambient temperature.

Oxidation behavior of RE-modified nickel-based superalloy between 950℃ and 1150℃ in air

A new Ni-based superalloy Ni48Cr28W5Co3Mn1Si1.6 was developed and the influence of a trace amount of rare earth (RE) metal addition on the oxidation resistance of this alloy was investigated. Isothermal oxidation behavior was investigated at 950?1150 °C in air, and then analyzed using scanning electronic microscopy and X-ray diffraction. The results showed that oxidation mass gain kinetics of the samples with and without RE elements follow the parabolic law. The effect of 0.20% RE on oxidation resistance is relatively small, and the oxidation rate constant of the alloy modified with 0.20% RE addition decreases by 5.9%?9.0%. Oxidation at 950?1150 °C for 100 h results in the formation of MnCr2O4, Cr2O3 and SiO2. A continuous and protective MnCr2O4 spinel layer forms as outer layer. The continuous middle oxide layer is confirmed to be Cr2O3, and the innermost layer consists of discontinuous SiO2.

Effects of current density on microstructure and properties of plasma electrolytic oxidation ceramic coatings formed on 6063 aluminum alloy

Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density on microstructure and properties of the PEO coatings were studied. It was found that pore density of the coatings decreased with increasing the current density. The tribological and hardness tests suggested that the ceramic coating produced under the current density of 15 A/dm2showed the best mechanical property, which matched well with the phase analysis. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves proved that the coating obtained under 15 A/dm2 displayed the best anti-corrosion property, which was directly connected with morphologies of coatings.

硫化物和硫/磷化合物的添加方式对石脑油热裂解结焦影响的研究

以石脑油为裂解原料,考察了硫化物和硫/磷化合物的添加方式对热裂解结焦行为的影响。采用Raman光谱、XRD、SEM和XPS等检测手段表征了HP40试样的氧化层和焦炭的形貌与结构。结果表明,原料连续注入硫化物条件下,磷化物的加入使得焦炭结构改变,显示出优异的抗结焦效果。硫化物和硫/磷化合物预处理导致氧化层中Fe含量升高,抑制结焦效果有限。硫/磷预处理与原料连续注入硫/磷化合物联合方式与原料连续注入硫/磷化合物方式的抗结焦效果接近,但前者在初期的抑制效果更明显。所有添加方式都会引起结焦层中无定形焦炭含量升高,焦炭的石墨化程度降低。热裂解焦炭缩合程度较高,硫化物和硫/磷化合物减少了催化结焦的生成,在一定程度上提高了焦层中氢含量。

Dry sliding wear behavior and mechanism of AM60B alloy at 25-200 ℃

Dry wear tests under atmospheric conditions at 25-200 °C and loads of 12.5-300 N were performed for AM60B alloy. The wear rate increases with increasing the load; the mild-to-severe wear transitions occur under the loads of 275 N at 25 °C, 150 N at 100 °C and 75 N at 200 °C, respectively. However, as the load is less than 50 N, the wear rate at 200 °C is lower than that at 25 °C or 100 °C. In mild wear regimes, the wear mechanisms can be classified into abrasive wear, oxidation wear and delamination wear. Delamination wear prevailed as the mild-to-severe wear transition starts to occur; the delamination occurs from the inside of matrix. Subsequently, plastic-extrusion wear as severe wear prevails accompanied with the transition. The thick and hard tribo-layer postpones the mild-to-severe wear transition due to restricting the occurrence of massive plastic deformation of worn surfaces.

Non-isothermal oxidation and ignition prediction of Ti-Cr alloys

The non-isothermal oxidation behavior and oxide scale microstructure of Ti-Cr alloy （0≤w（Cr）≤25%） were studied from room temperature to 1723 K by thermogravimetric analysis （TGA）, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The influencing mechanism of chromium on the oxidation resistance of Ti-Cr alloys was discussed. The results show that the oxidation resistance of the alloys decreases with Cr below a critical chromium content wC and increases above wC; above 1000 K, the oxidation kinetics obeys parabolic rule and titanium dominates the oxidation process; after oxidation, the oxygen-diffusing layer is present in the alloy matrix, the oxide scale is mainly composed of rutile whose internal layer is rich in chromium, and chromium oxides separated out from TiO2 near the alloy-oxide interface improve the oxidation resistance. Ignition of metals and alloys is a fast non-isothermal oxidation process and the oxidation mechanism of Ti-Cr alloys during ignition is predicted.

镁合金微弧氧化表面处理研究进展

应用微弧氧化可在镁合金表面生成氧化陶瓷膜层,增强镁合金的耐腐蚀性。本文首先对镁合金微弧氧化表面处理进行了概述,介绍了对几种镁合金基体进行微弧氧化处理的相关研究,并对镁合金微弧氧化膜生物活性的研究进行了简述,最后总结了镁合金微弧氧化技术的优点及存在的一些不足。

Enhanced corrosion resistance of micro-arc oxidation coated magnesium alloy by superhydrophobic Mg-Al layered double hydroxide coating

To further enhance the corrosion resistance of the porous micro-arc oxidation(MAO) ceramic layers on AZ31 magnesium alloy, superhydrophobic Mg-Al layered double hydroxide(LDH) coating was fabricated on MAO-coated AZ31 alloy by using in-situ growth method followed by surface modification with stearic acid. The characteristics of different coatings were investigated by XRD, SEM and EDS. The effect of the hydrothermal treatment time on the formation of the LDH coatings was studied. The results demonstrated that the micro-pores and cracks of MAO coating were gradually sealed via in-situ growing LDH with prolonging hydrothermal treating time. Electrochemical measurement displayed that the lowest corrosion current density, the most positive corrosion potential and the highest impedance modulus were observed for superhydrophobic LDH/MAO coating compared with those of MAO coating and LDH/MAO coating. Immersion experiment proved that the superhydrophobic LDH/MAO coating with the active anti-corrosion capability significantly enhanced the long-term corrosion protection for MAO coated alloy.

Corrosion resistance of Mg−Al LDH/Mg(OH)2/silane−Ce hybrid coating on magnesium alloy AZ31

An environmentally-friendly hybrid coating on AZ31 magnesium alloy substrates was reported.The synergic effect was studied on Mg−Al-layered double hydroxide Mg−Al LDH/Mg(OH)2-coated AZ31 magnesium alloy via an in-situ steam coating process and a subsequent combined surface modification of bis-[triethoxysilylpropyl]tetrasulfide(BTESPT)silane and Ce(NO3)3.The microstructure and composition characteristics of the hybrid coatings were investigated by means of X-ray diffraction(XRD),scanning electronic microscopy(SEM),Fourier transform infrared spectrophotometry(FT-IR)and X-ray photoelectron spectroscopy(XPS).The corrosion resistance of the coated samples was evaluated by potentiodynamic polarization(PDP),electrochemical impedance spectrum(EIS)and hydrogen evolution rate during immersion in 3.5 wt.%NaCl solution.The results show an improved corrosion resistance of the alloy in the presence of BTESPT silane and Ce(NO3)3.This is most likely due to the synergistic effect of steam coating and silane coating to enhance the barrier properties of hybrid coating.In addition,the formation mechanism and anti-corrosion mechanism of coatings were discussed.

Oxidation behavior and mechanism of porous nickel-based alloy between 850 and 1000 °C

The oxidation behavior and mechanism of a porous Ni?Cr?Al?Fe alloy in the temperature range from850to1000°Cwere investigated by optical microscopy,scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS),X-raydiffraction(XRD)analyses and X-ray photoelectron spectroscopy(XPS).The results show that the oxidation kinetics at950and1000°C of this porous alloy is pseudo-parabolic type.Complex layers composed of external Cr2O3/NiCr2O4and internalα-Al2O3areformed on the surface of the oxidized porous alloys.γ?phases favor the formation of NiO/Cr2O3/NiCr2O4during the initial oxidation.Many fast diffusion paths contribute to the development of the oxide layers.The decrease of the open porosity and the permeabilitywith exposure time extending and temperature increasing can be controlled within a certain range.

In-situ layered double hydroxides on Mg−Ca alloy:Role of calcium in magnesium alloy

Mg−Al layered double hydroxides(LDHs),produced on cast Mg−xCa(x=0.5,0.8,2.0,wt.%)alloys by an in-situ growth method,showed good corrosion resistance compared to the bare magnesium substrate.The influence mechanism of the second phase(Mg_(2)Ca)on LDHs production was investigated.Increasing Ca content increased the amount of Mg_(2)Ca,decreasing the grain size and the corrosion rate of the alloys.The increased amount of the second phase particles and the grain refinement promoted the growth of LDHs,and thus led to the decreasing of corrosion rate of the Mg−xCa alloys with LDHs.A higher Mg_(2)Ca amount resulted in forming fluffy LDHs.Due to the dual effects of the second phase(Mg_(2)Ca)for LDHs growth and microgalvanic corrosion,LDHs/Mg−0.8Ca showed the lowest corrosion rate.

Preparation and corrosion resistance of superhydrophobic coatings on AZ31 magnesium alloy

In order to improve the corrosion resistance of the Mg alloys, the superhydrophobic coatings on AZ31 Mg alloy wereprepared by a two-step process of micro-arc oxidation treatment and superhydrophobic treatment in stearic acid ethanol solution. Theeffects of voltages, frequencies and treatment time on the contact angle of the superhydrophobic treated sample were investigated.The results showed that with increasing the voltage, frequency and treatment time, all of the contact angles of the superhydrophobictreated sample increased first, and then decreased, reaching the maximum values at 350 V, 1000 Hz and 5 min, respectively. Theoptimal superhydrophobic coating was mainly composed of MgO and Mg2SiO4 phases, with the pore diameter of ～900 nm, thethickness of ～6.86 μm and the contact angle of 156.96°. The corrosion current density of the superhydrophobic AZ31 sampledecreased by three orders of magnitude, and the amount of hydrogen evolution decreased by 94.77% compared with that of the AZ31substrate sample.

High temperature scaling of Ni-15Cu-5Al alloy in 1×10^5 Pa pure oxygen

The oxidation of the ternary alloy Ni-15Cu-5Al in 1 × 105 Pa pure oxygen at 700 ℃ and 800 ℃ was studied. The results show that the behavior of the Ni-rich alloy is similar to that of the binary Ni-Al alloy with the same Al content in the form of an external NiO layer coupled to the internal oxidation of aluminium. The presence of 15%(mole fraction) Cu cannot modify substantially the values of relevant parameters affecting the transition from the internal to the external oxidation of aluminium. The presence of 5 % Al reduces the oxidation rate of the corresponding Ni-Cu alloy during the whole oxidation stages, though 5 % Al is still insufficient to form protective external alumina scales.

Electrochemically formed PtFeNi alloy nanoparticles on defective NiFe LDHs with charge transfer for efficient water splitting

Efficient and stable bifunctional electrocatalysts for water splitting is essential for producing hydrogen and alleviating huge energy consumption.Meanwhile,charge transfer engineering is an efficient approach to modulate the localized electronic properties of catalysts and tune the electrocatalytic performance.Herein,we tactfully fabricate PtFeNi alloys/NiFe layered double hydroxides(LDHs)heterostructure by an easily electrochemical way with a small amount of Pt.The experimental and theoretical results unravel that the charge transfer on the alloy clusters modulated by the defective substrates(NiFe LDHs),which synergistically optimizes the adsorption energy of the reaction intermediates.The electrocatalyst exhibits an ultra‐low overpotential of 81 and 243 mV at the current density of 100 mA cm^(–2) for hydrogen evolution and oxygen evolution,respectively.Furthermore,the overall water splitting indicates that PtFeNi alloys/NiFe LDHs presents an ultra‐low overpotential of 265 and 406 mV to reach the current density of 10 and 300 mA cm^(–2),respectively.It proves that the PtFeNi alloys/NiFe LDHs catalyst is an excellent dual‐function electrocatalyst for water splitting and promising for industrialization.This work provides a new electrochemical approach to construct the alloy heterostructure.The prepared heterostructures act as an ideal platform to investigate the charge re‐distribution behavior and to improve the electrocatalytic activity.

Corrosion and antimicrobial property of TiO_(2)/Cu_(2)O and TiO_(2)/Cu_(2)O@CeO_(2)micro-arc oxidation coatings on Ti-6Al-4V alloys in natural seawater

Microarc oxidation is an effective surface treatment for improving certain properties of metals and their alloys.In this paper,TiO_(2)/Cu_(2)O and TiO_(2)/Cu_(2)O@CeO_(2)coatings were prepared on Ti-6Al-4V by microarc oxidation.Thecoatings exhibited good corrosion resistance and antimicrobial properties.X-ray diffraction(XRD),scanning electronmicroscopy(SEM),and 3D laser confocal were used to characterize the coatings.The properties of TiO_(2)/Cu_(2)O and TiO_(2)/Cu_(2)O@CeO_(2)coatings were analyzed,including microstructure,surface roughness,corrosion resistance,andantimicrobial properties.The electrochemical results showed that the coatings prepared by microarc oxidation hadenhanced corrosion resistance compared to the substrate.The antibacterial properties of TiO_(2)/Cu_(2)O and TiO_(2)/Cu_(2)O@CeO_(2)coating against Pseudomonas aeruginosa were evaluated by fluorescence microscopy and plate counting.The antibacterial rate of TiO_(2)/Cu_(2)O@CeO_(2)coating was up to 99.70%.In summary,the TiO_(2)/Cu_(2)O and TiO_(2)/Cu_(2)O@CeO_(2)coatings prepared by microarc oxidation have a potential application background in the field of marine corrosionprotection and biofouling.