Dependence of electron work function of Al-Mg alloys on surface structures and relative humidity

In many fields the determination of electronic structures of a solid material is a prerequisite in order to investigate its physical/chemical properties as well as related applications. The effect of surface structures and ambient environment on the electronic behavior is of both fundamental and practical significance. In this study, the electron work function (EWF) of Al-Mg alloys is investigated using a scanning Kelvin probe. The results show that the EWF decreases with the increase of surface smoothness, whereas surface oxidation layers would result in the increase of the EWF. Furthermore EWF is strongly dependent on the relative humidity, especially when the relative humidity is higher than 70%, implying that considerable care should be takenon such dependence in order to gain a meaningful parameter for the characterization of surface behavior.     

Surface microstructure of the oxide protective layers grown on vanadium-free Ti alloys for use in biomedical applications

In this work, we present a surface study by SFM (scanning force microscopy) of three new Ti alloys of composition (in wt%) Ti-7Nb-6Al, Ti-13Nb-13Zr and Ti-15Zr-4Nb, developed for biomedical applications. V was not included in these alloys since this element has been reported to be cytotoxic. The surface of these materials has been modified by a thermal treatment in air at 750 °C for different times. As a consequence of this treatment an oxide layer develops on the surface, resulting in both an improvement of the corrosion resistance and an increase of the roughness, which enhances the adhesion of the tissue cells to the implant. SFM has been used to characterize the surface structure and topography of the oxide layers grown on the three alloys. The surface roughness analysis obtained by SFM points to a correlation between the mean square roughness, the thickness of the oxide layer, and the α-phase/β-phase ratio in the base material.     

Effect of surface roughness on leakage current and corrosion resistance of oxide layer on AZ91 Mg alloy prepared by plasma electrolytic oxidation

The influence of the surface roughness of Mg alloys on the electrical properties and corrosion resistance of oxide layers obtained by plasma electrolytic oxidation (PEO) were studied. The leakage current in the insulating oxide layer was enhanced by increasing the surface roughness, which is a favorable characteristic for the material when applied to hand-held electronic devices. The variation of corrosion resistance with surface roughness was also investigated. The corrosion resistance was degraded by the increasing surface roughness, which was confirmed with DC polarization and impedance spectroscopy. Pitting corrosion on the passive oxide layer was also analyzed with a salt spray test, which showed that the number of pits was not affected by the surface roughness when the spray time reached 96 h.     

Effect of surface nanocrystallization induced by fast multiple rotation rolling on hardness and corrosion behavior of 316L stainless steel

A nanostructured layer was fabricated by using fast multiple rotation rolling (FMRR) on the surface of 316L stainless steel. The microstructure in the surface was characterized by transmission electron microscopy and X-ray diffraction. The effects of FMRR on the microhardness, surface roughness and corrosion behavior of the stainless steel were investigated by microhardness measurements, surface roughness measurements, potentiodynamic polarization curves and pitting corrosion tests. The surface morphologies of pitting corrosion specimens were characterized by scanning electron microscopy. The results show that FMRR can cause surface nanocrystallization with the grain size ranges from 6 to 24 nm in the top surface layer of the sample. The microhardness of FMRR specimen in the top surface layer remarkably increases from 190 to 530 HV. However, the surface roughness slightly rises after FMRR treatment. The potentiodynamic polarization curves and pitting corrosion tests indicated that the FMRR treated 316L stainless steel with a surface nanocrystallized layer reduced the corrosion resistance in a 3.5% NaCl solution and enhanced the pitting corrosion rate in a FeCl₃ solution. Possible reasons leading to the decrease in corrosion resistance were discussed.     

Influence of N~+ implantation on structure,morphology, and corrosion behavior of Al in NaCl solution

Structural and morphological changes as well as corrosion behavior of N~+ implanted Al in 0.6 M Na Cl solution as function of N~+ fluence are investigated. The x-ray diffraction results confirmed Al N formation. The atomic force microscope(AFM) images showed larger grains on the surface of Al with increasing N~+ fluence. This can be due to the increased number of impacts of N~+ with Al atoms and energy conversion to heat, which increases the diffusion rate of the incident ions in the target. Hence, the number of the grain boundaries is reduced, resulting in corrosion resistance enhancement. Electrochemical impedance spectroscopy(EIS) and polarization results showed the increase of corrosion resistance of Al with increasing N~+ fluence. EIS data was used to simulate equivalent electric circuits(EC) for the samples.Strong dependence of the surface morphology on the EC elements was observed. The scanning electron microscope(SEM)analysis of the samples after corrosion test also showed that the surfaces of the implanted Al samples remain more intact relative to the untreated Al sample, consistent with the EIS and polarization results.     

Fe/Al混合膜的PLD法制备及表面分析

 采用脉冲激光气相沉积（PLD）技术制备了Fe/Al混合膜,测量了该混合膜的光电子能谱（XPS）,并采用原子力显微镜（AFM）、扫描电子显微镜（SEM）对Fe/Al混合膜作了表面分析。结果表明：Fe/Al混合膜的表面粗糙度对衬底温度有明显的依赖性, 随着衬底温度的升高,薄膜的表面逐渐变得平滑,膜层变得致密,在200 ℃衬底温度下制得了均方根（rms）粗糙度为0.154 nm、具有原子尺度光滑性的Fe/Al混合膜, 膜中Fe和Al分布比较均匀,其成分比约为1∶3,同时XPS分析也表明Fe/Al混合膜暴露在空气中后表面形成了Al₂O₃和FeO氧化层。     

Corrosion behaviors in physiological solution of cerium conversion coatings on AZ31 magnesium alloy

In this paper, a non-toxic Ce-based conversion coating was obtained on the surface of bio-medical AZ31 magnesium alloys. The micro-morphology of the coating prepared with optimal technical parameters and immersed in physiological solution (Hank's solution) in different time was observed by scanning electron microscopy (SEM), composition of the cerium conversion coating and corrosion products in Hank's solution were characterized by X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS), respectively. In addition, the corrosion property in Hank's solution was studied by electrochemical experiment and immersion test. The results show that the dense Ce-based conversion coating is obtained on the surface of AZ31 magnesium alloys in optimal technical parameters and the conversion coating consists of a mass of trivalent and tetravalent cerium oxides. The cerium conversion coating can provide obvious protection of magnesium alloys and can effectively reduce the degradation speed in Hank's solution. Also the degradation products have little influence on human body.     

Nanocrystalline soft ferromagnetic Ni-Co-P thin film on Al alloy by low temperature electroless deposition

Soft ferromagnetic ternary Ni-Co-P films were deposited onto Al 6061 alloy from low temperature Ni-Co-P electroless plating bath. The effect of deposition parameters, such as time and pH, on the plating rate of the deposit were examined. The results showed that the plating rate is a function of pH bath and the highest coating thickness can be obtained at pH value from 8 to10. The surface morphology, phase structure and the magnetic properties of the prepared films have been investigated using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and vibrating magnetometer device (VMD), respectively. The deposit obtained at optimum conditions showed compact and smooth with nodular grains structure and exhibited high magnetic moments and low coercivety. Potentiodynamic polarization corrosion tests were used to study the general corrosion behavior of Al alloys, Ni-P and Ni-Co-P coatings in 3.5% NaCl solution. It was found that Ni-Co-P coated alloy demonstrated higher corrosion resistance than Ni-P coating containing same percent of P due to the Co addition. The Ni-Co-P coating with a combination of high corrosion resistance, high hardness and excellent magnetic properties would be expected to enlarge the applications of the aluminum alloys.     

Effect of surface roughness on the development of protective Al2O3 on Fe-10Al (at.%) alloys containing 0-10 at.% Cr

The effect of alloy surface roughness, achieved by different degrees of surface polishing, on the development of protective alumina layer on Fe-10 at.% Al alloys containing 0, 5, and 10 at.% Cr was investigated during oxidation at 1000 °C in 0.1 MPa oxygen. For alloys that are not strong Al₂O₃ formers (Fe-10Al and Fe-5Cr-10Al), the rougher surfaces increased Fe incorporation into the overall surface layer. On the Fe-10Al, more iron oxides were formed in a uniform layer of mixed aluminum- and iron-oxides since the layer was thicker. On the Fe-5Cr-10Al, more iron-rich nodules developed on an otherwise thin Al₂O₃ surface layer. These nodules nucleated preferentially along surface scratch marks but not on alloy grain boundaries. For the strong Al₂O₃-forming Fe-10Cr-10Al alloy, protective alumina surface layers were observed regardless of the surface roughness. These results indicate that the formation of a protective Al₂O₃ layer on Fe-Cr-Al surfaces is not dictated by Al diffusion to the surface. More cold-worked surfaces caused an enhanced Fe diffusion, hence produced more Fe-rich oxides during the early stage of oxidation.     

Study on the solidification microstructure in AZ91D Mg alloy after laser surface melting

Laser surface melting (LSM) is known to enhance the wear and corrosion resistance of Mg alloys, but its effect on microstructural evolution of Mg alloys is not well understood. An effort has been made to study the effect of rapid solidification following LSM on the microstructural evolution of AZ91D Mg alloy. The results of X-ray diffractometry, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy indicated that the solidification microstructure in the laser-melted zone was mainly cellular/dendrite structure of primarily α-Mg phase and continuous network of β-Mg₁₇Al₁₂ phase. Numerical prediction of the laser-melted zone suggested that cooling rates increased strongly from the bottom to the top surface in the irradiated regions. An attempt has been made to correlate dendrite cell sizes of the solidification microstructure with the cooling rates in the laser-treated AZ91D Mg alloy.     

Nanocomposite of polypyrrole and alumina nanoparticles as a coating filler for the corrosion protection of aluminium alloy 2024-T3

Aluminium (Al) alloys such as 2024-T3 are widely used in industry as low weight construction materials with excellent mechanical properties. Until recently corrosion protection of Al alloys was carried out with coatings containing hexavalent chromium (Cr⁶⁺). However, Cr⁶⁺ is a health and environmental hazard and has to be replaced. Intrinsically conducting polymer (ICP) technology is the promising alternative to chromate coating technology because of good corrosion protection properties of ICPs, their moderate cost and good environmental compatibility. In this paper we report successful attempt of making nanocomposite comprised of alumina nanoparticles modified by polypyrrole for the purpose of corrosion protection of Al alloy. Modified nanoparticles were used as coating filler. Coating was designated to perform as an active barrier to electrolyte diffusion. Properties of the coating were examined by adhesion test, electrochemical impedance spectroscopy, X-rays elemental analysis, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy.     

Electron work function of Rb-Cs alloys

The temperature and concentration dependences of the electron work function (EWF) of rubidium, cesium, and nine Rb-Cs alloys are studied by the Fowler photoelectric method under the conditions of an ultra-high vacuum. It is shown that the polytherms of the electron work function for the pure components and alloys decrease by a linear law with increasing temperature. Based on the experimental data obtained, it is concluded that the concentration dependence of the EWF for the binary Rb-Cs system has a linear (additive) character within the limits of experimental error (about 1%). The presence of the azeotropic point on the state diagram of the system is not visualized in the concentration dependence of the work function.     

SEM/EDAX对腐蚀青铜器的形貌与元素分析

刮取了部分青铜器锈蚀进行了物相和成分分析,通过扫描电镜（SEM）观察青铜器锈蚀,发现锈蚀表层起鼓、发翘、瘤状突起,有的锈蚀有小脓包突起,脓包上可见小孔；扫描电镜/能谱分析（SEM/EDAX）显示腐蚀元素成分复杂,有C、O、Si、P、Sn、Cu、Pb、Ca、Fe、Al等元素；为下一步的保护工作提供了重要的参考资料.     

Deposition of duplex Al2O3/aluminum coatings on steel using a combined technique of arc spraying and plasma electrolytic oxidation

Plasma electrolytic oxidation (PEO) is a cost-effective technique that can be used to prepare ceramic coatings on metals such as Ti, Al, Mg, Nb, etc., and their alloys, but this promising technique cannot be used to modify the surface properties of steels, which are the most widely used materials in engineering. In order to prepare metallurgically bonded ceramic coatings on steels, a combined technique of arc spraying and plasma electrolytic oxidation (PEO) was adopted. In this work, metallurgically bonded ceramic coatings on steels were obtained using this method. We firstly prepared aluminum coatings on steels by arc spraying, and then obtained the metallurgically bonded ceramic coatings on aluminum coatings by PEO. The characteristics of duplex coatings were analyzed by X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The corrosion and wear resistance of the ceramic coatings were also studied. The results show that, duplex Al₂O₃/aluminum coatings have been deposited on steel substrate after the combined treatment. The ceramic coatings are mainly composed of α-Al₂O₃, γ-Al₂O₃, θ-Al₂O₃ and some amorphous phase. The duplex coatings show favorable corrosion and wear resistance properties. The investigations indicate that the combination of arc spraying and plasma electrolytic oxidation proves a promising technique for surface modification of steels for protective purposes.     

Structural changes of metallic surfaces induced by ultrasound

The effect of ultrasounds on the surface of metallic plates with cubic faced centered (Al, Ag, Cu) or hexagonal (Zn) structure was studied. Treated surfaces were strongly attacked: a micrometric roughness and a superficial oxidation (characterized by roughness measurements and scanning electron microscopy) were induced. X-ray diffraction analyses showed a preferential reorientation of the maximum density planes for both crystallographic structures.     

基底温度对中阶梯光栅厚铝膜质量的影响

大尺寸中阶梯光栅具有大孔径和极高的衍射级次,可以实现普通光栅难以达到的极高光谱分辨率。中阶梯光栅通常是利用刻划机在厚铝膜上刻划而成,所以制备大面积均匀性的高质量铝膜刻划基底是实现高性能大尺寸中阶梯光栅的关键因素。在较厚铝膜的制备工艺中,基底温度是至关重要的工艺参数。本文通过电子束热蒸发镀铝工艺在不同基底温度下制备了厚铝膜样品,并利用原子力显微镜、扫描电镜等手段从宏观和微观尺度详细分析了基底温度对铝膜质量的影响。铝膜平均晶粒尺寸从100℃时的264.34 nm增大到200℃时的384.97 nm和300℃时的596.35 nm,表面粗糙度Rq从100℃时的34.7 nm增长到200℃时的58.9 nm和300℃时的95.1 nm。结果表明,随着基底温度的升高表面粗糙度迅速增大,铝膜的表面质量严重退化。     

Electrochemical machining of super-hydrophobic Al surfaces and effect of processing parameters on wettability

Super-hydrophobic aluminum (Al) surfaces were successfully fabricated via electrochemical machining in neutral NaClO₃ electrolyte and subsequent fluoroalkylsilane (FAS) modification. The effects of the processing time, processing current density, and electrolyte concentration on the wettability, morphology, and roughness were studied. The surface morphology, chemical composition, and wettability of the Al surfaces were investigated using scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), white-light interferometry, roughness measurements, X-ray diffraction (XRD), Fourier-transform infrared spectrometry (FTIR), and optical contact angle measurements. The results show that hierarchical rough structures and low surface energy films were present on the Al surfaces after electrochemical machining and FAS modification. The combination of the rough structures and the low surface energy materials plays a crucial role in achieving super-hydrophobicity. Compared with the anodic oxidation and chemical etching method, the method proposed in our work does not require strong acid or alkali, and causes less harm to the environment and operators but with high processing efficiency. The rough structures required by the super-hydrophobic surfaces were obtained at 30-s processing time and the best super-hydrophobicity with 164.6^° water contact angle and 2^° tilting angle was obtained at 360 s. The resulting super-hydrophobic Al surfaces have a long-time stability in air and an excellent resistance to corrosive liquids.     

Influence of surface topography on the secondary electron yield of clean copper samples

Secondary electron yield (SEY) due to electron impact depends strongly on surface topography. The SEY of copper samples after Ar-ion bombardment is measured in situ in a multifunctional ultrahigh vacuum system. Increasing the ion energy or duration of ion bombardment can even enlarge the SEY, though it is relatively low under moderate bombardment intensity. The results obtained with scanning electron microscopy and atomic force microscopy images demonstrate that many valley structures of original sample surfaces can be smoothed due to ion bombardment, but more hill structures are generated with stronger bombardment intensity. With increasing the surface roughness in the observed range, the maximum SEY decreases from 1.2 to 1.07 at a surface characterized by valleys, while it again increases to 1.33 at a surface spread with hills. This phenomenon indicates that hill and valley structures are respectively effective in increasing and decreasing the SEY. These obtained results thus provide a comprehensive insight into the surface topography influence on the secondary electron emission characteristics in scanning electron microscopy.     

The Influence of Powder Properties and Tabletting Conditions on the Surface Roughness of Tablets

Tablets of five different compression formulations were investigated for their surface roughness using scanning electron microscopy and non-contact laser profilometry. It was found that the composition of a formulation not only influenced the tabletting properties of the powder mixtures, but also the surface properties of the final product. The addition of larger quantities of very brittle materials such as dibasic calcium phosphate dihydrate increased the surface roughness of tablets. An increase in tabletting pressure reduced the tablet surface roughness. Tablets were found to have smoother edges than faces, presumably due to the comparatively higher shear stress at the die walls and a polishing effect during tablet ejection. The assessment of surface roughness in three dimensions appeared more powerful than a simple line profile measurement.     

Fractal study of Ni–Cr–Mo alloy for dental applications: effect of beryllium

Different Ni-based alloys with various compositions were prepared by varying the amounts of beryllium. Effect of the amount of beryllium added to the alloy on its corrosion in an electrolyte solution of artificial saliva was investigated. Fractal dimension was used as a quantitative factor for surface analysis of the alloys before and after storage in the artificial salvia. The fractal dimensions of the electrode surfaces were determined by means of the most reliable method in this context viz. time dependency of the diffusion-limited current for a system involving “diffusion towards electrode surface”. The results showed that increase of the beryllium amount in the alloy composition significantly increases the alloy corrosion. It is accompanied by increase of the fractal dimension and roughness of the electrode surface, whereas a smooth and shiny surface is required for dentures. From the methodology point of view, the approach utilized for fractal analysis of the alloy surfaces (Au-masking of metallic surfaces) is a novel and efficient method for study of denture surfaces. Generally, this approach is of interest for corrosion studies of different metals and alloys, particularly where changes in surface structure have a significant importance.