Electropolishing of 304 stainless steel: Interactive effects of glycerol content, bath temperature, and current density on surface roughness and morphology

In this study, surface roughness of 304 stainless steel (304SS) varying from ca. 7 to 45 nm can be controlled by changing electropolishing variables in glycerol-containing baths. On the basis of the adsorbate-acceptor mechanism and the model for preferential adsorption of shielding molecules, incorporating the molecular interaction concept is helpful to explain the interactive effects of glycerol content, bath temperature, and current density on the surface roughness (Ra) and morphologies of 304SS. In order to easily understand how to control the surface roughness of 304SS in the glycerol-containing electrolyte, a simplified scheme integrating the above two mechanisms was proposed. From the atomic force microscopy (AFM) analyses, a rough surface is easily obtained by electropolishing at high bath temperatures, which endows the 304SS substrate with pores.     

Grain growth inhibition in thin nanocrystalline Au films by grain boundary diffusion and oxidation of Ti

We studied grain growth in thin nanocrystalline Au films deposited on a sapphire substrate with and without an ultrathin Ti underlayer (adhesion promoter). The samples were annealed at 200 °C for 2 h in air. The reference thin Au film without a Ti underlayer exhibited significant grain growth during annealing, whereas no changes in microstructure of the Au layer were observed in the Au/Ti bilayers. This stabilization of the microstructure of the Au layer was attributed to thermal grain boundary grooves on the Au surface filled with Ti oxide. The grooves exhibited an elongated morphology characterized by a low apparent dihedral angle value, atypical for thermal grain boundary grooves in pure metals. We demonstrated that grooves with this morphology are very efficient in pinning grain boundary motion. We also developed a quantitative model of grain boundary grooving coupled with grain boundary interdiffusion in thin bilayer films. The model predicted the formation of long, narrow grooves at the grain boundaries, which are very efficient in suppressing grain growth in nanocrystalline thin films.     

Electropolishing parameters of NiTi alloy

Electropolishing has been used in NiTi alloy in several fields for its special characteristics, but its essential details and electropolishing mechanism have not been reported yet as a demand from business competition, which, to a great degree, restricts the application and extension of the electropolishing technology. The effect of processing parameters on nitinol electropolishing was explored. Besides the electrolyte, other factors that influence the electropolishing are temperature, current density, time, spacing between anode and cathode, electrolyte stirring, etc. Studies on the effect of the temperature on the electropolishing process show that the higher the temperature is, the bigger the electropolishing rate is, following the near Gauss law. The relationship between the temperature and the surface roughness follows a near parabolic law, and the relationship between the temperature and the surface reflectivity follows a near sigmoidal law. The relationship between the electropolishing voltage and the current density follows a near cubic law, while that between the electropolishing rate and current density follows a near linear law. The relationship between the electropolishing rate and the time follows a near sigmoidal law. The practical spacing between anode and cathode is confirmed by the Hall bath experiment.     

Influence of substrate surface topography in the deposition of nanostructured diamond-like carbon films by high density plasma chemical vapor deposition

In this work, we have studied the influence of the substrate surface condition on the roughness and the structure of the nanostructured DLC films deposited by High Density Plasma Chemical Vapor Deposition. Four methods were used to modify the silicon wafers surface before starting the deposition processes of the nanostructured DLC films: micro-diamond powder dispersion, micro-graphite powder dispersion, and roughness generation by wet chemical etching and roughness generation by plasma etching. The reference wafer was only submitted to a chemical cleaning. It was possible to see that the final roughness and the sp³ hybridization degree strongly depend on the substrate surface conditions. The surface roughness was observed by AFM and SEM and the hybridization degree of the DLC films was analyzed by Raman Spectroscopy. In these samples, the final roughness and the sp³ hybridization quantity depend strongly on the substrate surface condition. Thus, the effects of the substrate surface on the DLC film structure were confirmed. These phenomena can be explained by the fact that the locally higher surface energy and the sharp edges may induce local defects promoting the nanostructured characteristics in the DLC films.     

Effect of Extrusion Profile on Surface Microstructure and Appearance of Aluminum Extrusions with Different Fe Contents

Aluminum alloy extrusions with variations in profiles and Fe-rich particles were produced using different extrusion dies and iron contents. A microstructural examination of the extrusion surface shows that the extrusion profile and iron content have a great effect on the size and number of Fe-rich particles, grain size, texture, and fraction of high-angle grain boundaries due to varying localized plastic deformation and temperature in the extrudate. After etching and anodizing, surface imperfections such as grain boundary grooves that influence the final surface appearance are formed on the extrusion surfaces. The severity of grain boundary grooves is found to be directly linked to the number of Fe-rich particles. Hence, the extrusion profile has a dramatic influence on surface imperfections and the appearance of the final anodized extrusions through its effect on the surface microstructure.     

Influence of surface treatment on detachment of anodic films from Al–Mg alloys

Previous work of the authors has revealed detachment of anodic films during anodizing of electropolished, solid-solution Al–3 at.%Mg alloy at constant current density, with the possibility of the electropolishing pre-treatment having a significant influence on the loss of the film material. Here, anodic films were formed on a similar alloy, with pre-treatment by electropolishing, alkaline etching or mechanical polishing. The results disclose the detachment of the anodic film for all pre-treatments, thus demonstrating that prior electropolishing is not essential for initiation of detachment. However, the occurrence of detachment was sensitive to the current density, with lower current densities promoting detachment at earlier stages of growth of the anodic film for a particular pre-treatment.     

Characterization of nanocrystalline Co–W coatings on Cu substrate,electrodeposited from a citrate-ammonia bath

Cobalt–tungsten nanocrystalline coatings were electrodeposited on copper substrate using different current densities. The deposited coatings were single phase solid solution with an average grain size of about 18 nm, showing a nodular type of surface morphology. By increasing the deposition current density, the density of nodules was increased, with no obvious variation in grain size. Electrochemical impedance spectroscopy (EIS) confirmed the codeposition of tungsten through reduction of tungsten oxide film formed during the electrodeposition process. However, the role of ternary complexes in the bath cannot be ruled out, especially at lower cathodic potentials. The Co–W coating deposited at lower current densities showed higher tungsten content, microhardness, wear resistance and friction coefficient. However, this coating showed an inferior corrosion resistance. By increasing the deposition current density, a low tungsten coating with high corrosion resistant was obtained. This is attributed to the lower value of exchange current density of water reduction in the present of oxygen (i₀^H2O) achieved on the coating with lower tungsten content.     

硫代硫酸盐无氰镀银工艺及银镀层微观组织分析

采用硫代硫酸盐无氰镀银工艺,分别以 AgNO3和 AgBr 为主盐进行镀银。研究主盐含量、电流密度对Ag镀层表面质量、沉积速率和显微硬度的影响,并优化电镀参数。分析优化工艺下的Ag镀层结合强度和晶粒尺寸。结果表明：在AgNO3体系中,AgNO3最佳用量为40 g/L,最佳电流密度为0.25 A/dm2,制备的Ag镀层光亮平整,与基体结合良好,晶粒尺寸为35 nm。在AgBr体系中的最佳AgBr用量为30 g/L,最佳电流密度为0.20 A/dm2,与基体结合良好的Ag镀层的晶粒尺寸为55 nm。与AgBr体系相比,AgNO3体系适用的电镀电流密度范围较宽,制备的Ag镀层显微硬度高,晶粒尺寸小。     

永磁场磁力研磨TC11钛合金的实验研究

目的解决钛合金机械加工后表面质量差的难题。方法采用磁力研磨工艺对TC11钛合金进行了表面光整加工。以表面粗糙度为主要评价指标,研究了磁力研磨工艺参数对钛合金表面质量的影响,并对工艺参数进行了优化。采用优化后的工艺参数对钛合金进行了表面光整加工,研究了磁力研磨工艺对钛合金金相组织的影响。结果当加工间隙为3 mm时,研磨压力适宜,加工后工件表面粗糙度值最小。采用粒径为100目的磨粒使工件表面研磨加工后纹理更细,表面粗糙度值最低。提高主轴转速,工件表面材料去除率增加,当主轴转速为1500 r/min时,加工后工件表面粗糙度值最小。对比工件加工前后的金相组织,加工后试样表面组织晶粒变细,晶界增多,工件表面应力状态由张应力转变为压应力。结论实验确定了较优的工艺参数组合,即:加工间隙为3 mm,磨粒粒径为100目,主轴转速为1500 r/min。采用永磁场磁力研磨工艺,能够大幅降低TC11钛合金表面粗糙度,并使钛合金表面组织得到改善。     

Finite element analysis of stress in contacting zone of film and substrate

Based on a simplified 2D model and finite element analysis (FEA), the effects of the deposition temperature, the film thickness and the surface roughness of the substrate (Ra_s) on the value and distribution of the first principal stress in a film-substrate system were studied. The FEA results showed that the first principal stress increases with increasing deposition temperature. When the surface roughness of substrate increased, the first principal stress increases at a slowing-down rate in film and increases at an accelerated rate in substrate. With the increasing film thickness, the first principal stress decreases slowly in the film and increases rapidly in the substrate. The increased surface roughness of substrate resulted in inhomogeneous distribution of the first principal in the film-substrate system.     

Effects of boronizing process on the surface roughness and dimensions of AISI 1020, AISI 1040 and AISI 2714

In this study, the effects of boronizing treatment on material's dimensional changes and surface roughness were investigated. The parameters chosen were substrate material composition, surface roughness before boronizing treatment, and boronizing time. The AISI 1020, AISI 1040 and AISI 2714 were chosen as substrate materials whereas Ekabor I was selected as boronizing powder. Materials were boronized at 900 °C by using a solid boronizing method for 2 or 4 h. The gradual growth of boride layer on the surface, dimensional changes and their effects on surface roughness were investigated. Variations in topographical surface roughness were determined by SEM. With the boronizing treatment, dimensional increases of the material's were observed. The dimensional increase was one fifth of boride layer thickness for AISI 1020 or AISI 1040, whereas it was one third of boride layer thickness for AISI 2714. Boronizing treatment had also a significant effect on surface roughness of materials. A “threshold roughness” term was defined in our study. This term is a surface roughness value for smooth surfaces, which received boronizing treatment. For the same material and with the same boronizing conditions, the threshold roughness value was achieved after boronizing, when surface roughness of material was below the threshold roughness value, before boronizing was applied. However, when surface roughness of a material was above that threshold roughness value, surface roughness value decreased with boronizing treatment. The thereshold roughness value depended on substrate material composition and boronizing parameters.     

Mechanical Properties of Ternary Sn-In-Ag Ball-Grid Array Assemblies at Ambient and Elevated Temperatures

The mechanical behavior of a ternary Sn-15In-2.8Ag ball-grid array assembly was evaluated at ambient and elevated temperatures. The maximum stress of the Sn-15In-2.8Ag ball-grid array assembly decreased as the temperatures increased and the strain rates decreased. An irregular brittle NiSnIn intermetallic layer formed at the SnInAg/Au/Ni/Cu interface, resulting in decreased bond strength of the joints. The Arrhenius diagram of the Sn-15In-2.8Ag ball-grid array assembly at a constant stress of 16 MPa consists of two straight lines intersecting at 50 °C, which indicates that two kinds of creep mechanism controlled the Sn-15In-2.8Ag ball-grid array assembly deformation. The AuIn₂ intermetallics and grain boundaries acted as the location for nucleation of the creep voids, which induced reduction of the solder’s cross-sectional area and led the Sn-15In-2.8Ag ball-grid array assembly to fail rapidly with a transgranular creep fracture.     

NUMERICAL CHARACTERIZATION OF CURRENT-INDUCED CHANGES IN SURFACE MORPHOLOGY OF THIN Ag FILMS

The changes in surface topography of thin conducting Ag films under high-density current condition are studied by optical and scanning tunnelling microscopy (STM). It is established that the loss of conductivity in specimens occurs through depletion of the material due to their overheating and electromigration process. It has been shown that the r.m.s. roughness, the fractal dimension of voids and the fractal dimension of the surface allow complete numerical characterization of surface topography changes in thin Ag films.     

电解抛光工艺对 AP1000 管座焊接表面的改善作用

研究了AP1000上封头CRDM管座用焊接镍基合金的电解抛光工艺条件,探讨了电解抛光对其表面粗糙度和应力的改善作用。结果表明:焊接镍基合金的抛光电流密度应控制在0.3~0.5 A/cm2之间,抛光时间宜为2~5 min;电解抛光使表面拉应力大幅度减少,甚至产生压应力,这可抑制焊接镍基合金应力腐蚀开裂的发生。     

Effect of Ag nanoparticles on the electron energy structure and electrical properties of poly(p-phenylene vinylene) (PPV)

The effects of inorganic nanoparticles on a conjugated polymer were investigated by measuring the electronic properties of poly(p-phenylene vinylene) (PPV) and PPV/Ag nanocomposites. Through hybridization, an enhancement in current density was achieved with PPV/Ag nanocomposites due to an increase in the electron affinity with Ag nanoparticle content. Furthermore, roughening of the surface morphology was observed with incorporation of Ag nanoparticles. This roughness induces an enhanced applied field at the thinner region of the film and an increase in the surface area with a resulting increase of electron injection, leading to current enhancement.     

涂层导体用Ni-7%W合金基带的织构分析

采用先进的放电等离子烧结技术(SPS)制备Ni7W合金初始坯锭,通过优化高能球磨和烧结工艺以及后续和热处理工艺制备出高度立方织构的Ni7W合金基带.利用电子背散射衍射(EBSD)技术对Ni7W合金基带的晶粒取向、晶界特征等信息进行采集和分析,对其织构进行了表征.该基带无需抛光,即可获得高花样质量的电子背散射衍射图像.EBSD测试结果表明:该Ni7W基带表面10°以内立方织构晶粒质量分数高达99.4%,10°以内晶界长度质量分数为93.6%,具有高质量的立方织构.     

Electropolishing of 316L stainless steel for anticorrosion passivation

316L stainless steel is deemed an indispensable material in the semiconductor industry. In many instances, the surface of the production equipment needs to be treated for low-corrosion passivation, good finish, weldability, and cleanliness. The process characteristics of electropolishing meet these requirements well. The current study investigates the effects of the major processing parameters on the anticorrosion performance and the surface roughness. The electrolyte with 10% water content and a ratio between H₂SO₄ and H₃PO₄ of 4 and 6 has been proven to be successful, showing no corrosion pitting points on the specimen surface. The electrolyte temperature of 85±10 °C and the electrical current density of 0.5 to 1.0 A/cm² are found to be optimal. The processing time beyond 3 to 5 min produces no further improvement. The addition of 10% glycerin provides a very fine surface (maximum roughness of 0.05 μm), while the anticorrosion performance is deteriorated. The results obtained are useful for the manufacture of the semiconductor equipment.     

Characterization of the alumina scale formed on a commercial MCrAlYHfSi coating

A commercial NiCoCrAlYHfSi coating deposited on a Ni-base superalloy substrate was characterized before and after high temperature oxidation. The combination of Y, Hf and Si additions is reported to improve coating performance. Advanced characterization techniques including scanning-transmission electron microscopy were used to study the segregation behavior of Y and Hf ions to the alumina grain boundaries after 200 h at 1050 °C and 100 and 200 h exposures at 1100 °C. After both exposure times, two distinct oxide layers were observed. The outer transient layer included many Y- and Hf-rich oxide particles. The inner layer consisted of columnar α-Al₂O₃ grains normal to the surface of the coating. Segregation of Y and Hf ions was found on the alumina grain boundaries as has been observed in model alloys with similar compositions. Isothermal exposures for up to 200 h at 1050° and 1100 °C caused a minimal increase in surface roughness. However, 200 1-h cycles at 1100 °C resulted in a more significant increase in surface roughness.     

工业纯镁内部疲劳微裂纹的热扩散性愈合

采用单向对称拉压低周疲劳疗法在具有等轴晶的工业纯镁试样中引入了微米级的内部裂纹,裂纹主要位于晶内和穿晶位置,宽度为0.5-15μm,长宽比分布在10-35之间,在623K对疲劳试样进行2,4和6.5h的真空退火处理,SEM观察表明：晶内疲劳微裂纹纵剖面二维形态发生了主要由表面扩散控制的形态变化,由初始的扁椭圆形演化成多个球洞定向排列的形态;穿晶疲劳微裂纹纵剖面二维形态则在表面和晶界扩散的耦合作用下首先在晶界处分隔成两部分,并在晶界上留下了一个空洞,在退火处理的后期阶段,空洞收缩消失,引起空洞间距的增大并引起试样密度少量恢复。     

Adhesion characteristics of copper thin film deposited on PET substrate by electron cyclotron resonance-metal organic chemical vapor deposition

The adhesion characteristics of Cu/C:H films on the pretreated PET (polyethylene terephthalate) substrate prepared by ECR-MOCVD with a periodic DC bias system were investigated in the aspect of surface energy, surface morphology, roughness, and adhesion force. For a chromo-sulfuric acid pretreatment, the surface roughness of PET substrate was increased up to a maximum value at 60 min of acid-soaking time, followed by a gradual decrease for longer acid-soaking times. The changes of surface energy by various pretreatment methods (such as Ar-ion implantation, O₂ plasma, chromo-sulfuric acid, and sandblasting) barely affected on the adhesion force because the pretreated PET was changed into hydrophobic surface through ECR-plasma polymerization of hfac (1,1,1,5,5,5-hexafluoro-2,4-pentandione) ligand of copper precursor. The acid pretreatment followed by ECR-deposition was confirmed as an effective method for the good adhesion of copper thin film on PET substrate at room temperature. The adhesion force of deposited metallic films primarily depended on the surface roughness of the pretreated substrate, and there was no strong correlation between the surface energy of the pretreated PET and the adhesion force of deposited Cu/C:H films.