Effect Of Surface Oxide Layer Research Articles

Deformation mechanisms of β-Li in Mg–Li dual-phase alloy and effects of surface oxide layer

This study investigates the deformation mechanisms of β-Li micropillar prepared from a Mg–7Li dual-phase alloy with or without surface oxide layer. The β-Li micropillar with three cross-sectional sizes, 2.5 × 2.5 μm2, 4.0 × 4.0 μm2 and 5.5 × 5.5 μm2, are studied. The results show that the oxide layer improves the strength of micropillar due to the dislocation trapping effect. When increasing the micropillar size, the oxide layer having nanoporous structure becomes relatively thinner, and the strengthening effect resulting from the oxide layer decreases. Regardless of the existence of the surface oxide layer, all β-Li micropillars show continuous deformation characteristics. This is ascribed to the interactions between pre-existing dislocations and non-planar dislocations activated during compression, which induces low-angle grain boundary and effectively traps the dislocations at the central area.

Effects of surface oxide layer on fracture toughness of submicrometer-thick copper film

Effects of surface oxide layer on fracture toughness of submicrometer-thick copper film

Effects of oxide layer on adhesion and durability of titanium and transparent polyamide joint by laser joining

A joint of titanium and transparent polyamide with desirable strength was achieved by laser joining. A maximum load capacity of 3400 N was obtained from a lap joining area of 25 × 25 mm2 at a laser power of 350 W and a travel speed of 4 mm/s. The effects of surface oxide layers with different thicknesses and stability were investigated. A joint with a thick oxide layer exhibited lower load capacity due to excessive thermal degradation of polyamide caused by heat buildup inside the thick thermal insulating oxide layer. With UV exposure, more pronounced reduction in joint strength was observed in the joint with the thick oxide layer. Cracking of the oxide layers was responsible for lower strength and expected to be a result of stress from polyamide contraction combining with internal stress of the oxide layer.

NiCoCrAlYTa coatings on nickel-base superalloy substrate: Deposition by high velocity oxy-fuel spraying as well as investigation of mechanical properties and wear resistance in relation to heat-treatment duration

NiCoCrAlYTa coating, a metal-based coating, was prepared on Inconel 718 Ni-base superalloy substrate by high velocity oxy-fuel (HVOF) spraying. The as-polished NiCoCrAlYTa coating was heated at 1000 °C for different durations to afford coatings C1, C2, C3, and C4. The microstructure, element distribution, phase composition and crystalline structure of the as-deposited coating and heat-treated ones were analyzed by transmission electron microscopy, scanning electron microscopy-energy dispersive spectrometry, X-ray diffraction and electron back-scattered diffraction. Moreover, the oxidation behavior of the NiCoCrAlYTa coatings was evaluated based on isothermal oxidation kinetics as well as weight loss measurements; and the effects of surface oxide layers on the microstructure, mechanical properties as well as friction and wear behavior of the NiCoCrAlYTa coatings were investigated. Results show that the as-sprayed coating exhibits dense and uniform microstructure as well as excellent oxidation resistance. Oxide layers, mainly composed of Al2O3, Cr2O3, NiO, Y2O3, Ta2O5, NiCr2O4, and CoCr2O4, are formed on the surface of the coating upon heat-treatment in air; and the microstructure and mechanical properties of the NiCoCrAlYTa coatings as well as oxide layers are governed by heat-treatment time. Particularly, coating C3, obtained after heat-treatment of the as-polished NiCoCrAlYTa coating at 1000 °C for 50 h, exhibits greatly increased indentation hardness, elastic modulus, and wear resistance. This is because the joint functions of a compact and continuous surface oxide layer with gradient nanostructure formed after heat-treatment, and the amorphous protective layer generated on the rubbed surface of coating C3.

Effect of surface oxide layer on fatigue crack propagation in submicrometer-thick copper films

Effect of surface oxide layer on fatigue crack propagation in submicrometer-thick copper films

銅ナノ薄膜の疲労き裂進展特性に及ぼす表面酸化層の影響

銅ナノ薄膜の疲労き裂進展特性に及ぼす表面酸化層の影響

Detection of defects in laser welding of AZ31B magnesium alloy in zero-gap lap joint configuration by a real-time spectroscopic analysis

The effect of surface oxide layer existing at the lap-joint faying surface of magnesium sheets is investigated on the keyhole dynamics of the weld pool and weld bead qualities. It is observed that by removing the oxide layer from the faying surface of the lap joint, a high quality weld can be achieved in the laser welding process. However, the presence of an oxide layer deteriorates the quality of the weld by forming pores at the interface of the two overlapped sheets. The purpose of this paper is to identify the correlation between the integrity of the weld and the interaction between the laser and material. A spectroscopy sensor was applied to detect the spectra emitted from a plasma plume during the laser welding of AZ31B magnesium alloy in a zero-gap lap joint configuration. The electron temperature was calculated by applying a Boltzmann plot method based on the detected spectra, and the correlation between the pore formation and the spectral signals was studied. The laser molten pool and the keyhole condition were monitored in real-time by a high speed charge-coupled device (CCD) camera. A green laser was used as an illumination source in order to detect the influence of the oxide layer on the dynamic behavior of the molten pool. Results revealed that the detected spectrum and weld defects had a meaningful correlation for real-time monitoring of the weld quality during laser welding of magnesium alloys.

Effects of Fine Particle Peening on Oxidation Behavior of Nickel–Titanium Shape Memory Alloy

The effects of fine particle peening (FPP) on oxidation behavior of nickel­titanium shape memory alloy (Ni­Ti alloy) were evaluated. After FPP treatment, oxidation process was performed at 300, 400 and 500°C for 30min in N2­20vol%O2 atmosphere. Surface microstructures of oxidized specimens pre-treated with FPP were characterized using scanning electron microscope (SEM), glow discharge optical emission spectroscopy (GD-OES), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction analysis (XRD). Oxide layers formed on the specimens pre-treated with FPP were thinner than those on the un-peened ones. Amorphous titanium oxides (TiO and TiO2) were formed on the un-peened specimens by oxidation process, whereas a nickel oxide (NiO) was created on the FPP-treated surface oxidized at temperature greater than 400°C as well as titanium oxides. This was because an amorphous structure created by FPP accelerated the outward growth of nickel oxide during the subsequent oxidation process. Moreover, the effects of surface oxide layers on the biocompatibility of Ni­Ti alloy were investigated. Due to the formation of a thin oxide layer which contains nickel element, the oxidized specimen pre-treated with FPP showed higher amount of nickel ion elution than that of the oxidized one during the cell culture tests. These results suggest that microstructural feature of surface oxide layer strongly affects the biocompatibility of Ni­Ti alloy. [doi:10.2320/matertrans.M2013336]

Individual Boron Nanowire Has Ultra-High Specific Young’s Modulus and Fracture Strength As Revealed by in Situ Transmission Electron Microscopy

Boron nanowires (BNWs) may have potential applications as reinforcing materials because B fibers are widely known for their excellent mechanical performance. However until now, there have been only few reports on the mechanical properties of individual BNW, and in situ transmission electron microscopy (TEM) investigations shining a light on their fracture mechanism have not been performed. In this paper, we applied in situ high-resolution TEM (HRTEM) technique to study the mechanical properties of individual BNWs using three loading schemes. The mean fracture strength and the maximum strain of individual BNWs were measured to be 10.4 GPa and 4.1%, respectively, during the tensile tests. And the averaged Young's modulus was calculated to be 308.2 GPa under tensile and compression tests. Bending experiments for the first time performed on individual BNWs revealed that their maximum bending strain could reach 9.9% and their ultimate bending stress arrived at 36.2 GPa. These figures are much higher than those of Si and ZnO nanowires known for their high bending strength. Moreover, the BNWs exhibited very high specific fracture strength (3.9 (GPa·cm(3))/g) and specific elastic modulus (130.6 (GPa·cm(3))/g), which are several dozens of times larger compared to many nanostructures known for their superb mechanical behaviors. At last, the effect of surface oxide layer on the Young's modulus, fracture strength and maximum bending strength of individual BNWs was elucidated to extract their intrinsic mechanical parameters using calculated corrections. All experimental results suggest that the present BNW are a bright promise as lightweight reinforcing fillers.

Liquid-Sn-driven lateral growth of poly-GeSn on insulator assisted by surface oxide layer

Effects of surface oxide layers on liquid-Sn-driven GeSn crystallization on insulators at various temperatures (<475 °C) are investigated. An amorphous Ge in neighborhood of patterned-Sn (<3.5 μm) becomes to polycrystalline Ge1−xSnx (x ≈ 0.025 − 0.14) after annealing at 150–475 °C, which is independent of the surface oxide thickness. Interestingly, a 50-μm-length lateral growth of polycrystalline Ge0.99Sn0.01 layers achieved by combination of thickening of the surface-oxide treated by NH4OH and annealing above melting temperature of Sn (231.9 °C). The growth length is 15 times longer than without the treatment. The advanced process promises to achieve group-IV-based optic and electronic devices on flexible substrates and Si platforms.

Effects of surface oxide layer on nanocavity formation and silver gettering in hydrogen ion implanted silicon

We have made an investigation of the surface oxide effects on nanocavity formation in hydrogen implanted silicon and the influence of resultant nanocavities on diffusion and gettering of implanted silver atoms. A wafer with a 200-nm SiO2 surface layer was implanted with 22.5 keV H ions to a dose of 1 × 1017 cm−2, yielding the concentration peak of implanted H ions at ∼140 nm below the SiO2/Si interface. Subsequently, two sets of Si samples were prepared, depending on whether the oxide layer was etched off before (Group-A) or after (Group-B) post-H-implantation annealing. As evidenced by transmission electron microscopy, Group-A samples exhibited an array of large-sized nanocavities in hexagon-like shape, extending from the surface to the depth ∼140 nm, whereas a narrow band of sphere-shaped nanocavities of small size was present around 140 nm below the surface in Group-B samples. These Si samples with pre-existing nanocavities were further implanted with Ag ions in the surface region (∼40 nm projected range) and post-Ag-implantation annealing was conducted in the temperature range between 600 and 900 °C. Measurements based on Rutherford backscattering spectroscopy revealed much different behaviors for Ag redistribution and defect accumulation in these two sets of samples. Compared to the case for Group-B Si, Group-A Si exhibited a lower concentration of residual defects and a slower kinetics in Ag diffusion as well. We discuss the role of thick surface oxide in point defect generation and recombination, and the consequence on nanocavity formation and defect retention in Si. The properties of nanocavities, e.g., their depth distribution, size, and even shape, are believed to be responsible for the observed disparities between these samples, including an interesting contrast of surface vs. bulk diffusion phenomena for implanted Ag atoms.

Effect of Surface Oxide Layer of Steel on the Tribological Characteristics of Load-bearing Additives for Multiply-Alkylated Cyclopentane Oil under High Vacuum

The tribological performance of two types of additives—alkylated phenyl phosphate and lead naphthenate—dissolved in multiply-alkylated cyclopentane was evaluated under a high vacuum using two types of ball-on-disk tribometers: a reciprocating motion tribometer under mild loading conditions and a unidirectional rotating motion tribometer under heavy loading conditions. A ball and a flat disk made of SUS440C stainless steel were used as specimens for both tribometers. The surface of the as-received flat disk specimen was covered with a thick (>40 nm) oxide layer. For the examination of the effect of the surface oxide layer on the tribological performance of the liquid lubricants under a high vacuum, another specimen with an oxide layer (approx. 4 nm thick) was prepared. The alkylated phenyl phosphate additive showed better lubrication performance with the specimen with the thicker oxide layer, but the lead naphthenate additive showed superior performance with the thinner oxide layer specimen. It is also shown that these opposite tribological characteristics are explained by the hard and soft acids and bases principle.

Understanding of the correlation between work function and surface morphology of metals and alloys

Abstract The relationships between material behaviors and its structures are extremely complicated, and the understanding of these relationships is of much significance for revealing the physical, chemical and mechanical properties of various materials. In this study, the change of the work function (WF) of metals and alloys as a function of surface roughness was investigated by scanning Kelvin probe, with the aim of understanding the inherent correlation between the WF and surface morphology using a simple and intuitive way. It was demonstrated that at the rough surface of Cu and Ag, the sharp micro/nanostructures induced a lower WF, just as the lightning rod effect providing a direct and fast path for electron transport. While for Al and Mg alloys, the rough surface resulted in an increase of the WF owing to the effect of surface oxide layers, just as the anti-lightning rod effect providing a protected layer to confine the electron transport.

High speed camera investigation of the impingement of single water droplets on oxidized high temperature surfaces

This study investigates the influence of oxide layer over the hot surfaces on the behavior of single droplets impacting the high temperature surfaces using high speed camera. In the present work, an experimental apparatus was installed where direct contact between mono-dispersed water droplet and solid hot surface in the presence of different values of oxide layer (4.5, 6.7, 9.4 and 12.6 μm) over the hot surface was experimentally investigated. The droplets size and its velocity were controlled independently. The results presented the effects of surface oxide layer, droplet velocity, droplet size and surface superheating on the hot solid–liquid contact wettability time and on the maximum droplet spread diameter on the hot surface. Empirical correlations are presented describing the hydrodynamic characteristics of an individual droplet impinging on a heated surface and concealing the affecting parameters for surface oxidation phenomena in such process. Also, the comparison between the obtained results at oxidation phenomena and the results due to others at non oxidation phenomena shows the effect of surface oxidation phenomena on the behavior of single droplet impacting the high temperature surface. These experimental observations provide the validation data required for multi-phase modeling of these phenomena by computational fluid dynamics (CFD) (e.g. Volume of Fluid (VOF) modeling) methods.

Effect of surface oxide layer on deuterium permeation behaviors through a type 316 stainless steel

Abstract Effect of surface oxide layer on the hydrogen isotope permeation was studied. Iron oxide was uniformly formed in the oxide layer, although chromium was limited at the interface between the oxide layer and bulk SS-316. The permeation behavior of deuterium for oxidized SS-316 was compared with that for unoxidized SS-316 at temperature range of 333–673 K. The deuterium permeability for the oxidized SS-316 was reduced 1/10–1/20 times as high as that for unoxidized one. However, the activation energy of deuterium permeation as gas form for oxidized SS-316 was almost the same as that for unoxidized SS-316 and was 0.64 eV, which was almost consistent with the sum of activation energies for diffusion and solubility. This fact indicates that the deuterium permeation is diffusion limited. The permeability of deuterium as water form was almost constant even if heating temperature is high, showing that the deuterium was permeated through bulk SS-316 and react with oxygen at the oxide layer as water desorption, which is controlled by the permeation flux of deuterium and oxygen concentration on the surface of oxide layer in downstream side.

Effect of Surface Oxide Layer on Mechanical Properties of Single Crystalline Silicon

AbstractFatigue fracture under cyclic loading of single crystal silicon (SCS) is concerned and fatigue properties and mechanism are investigated widely. Surface oxide is considered to have an important role on fatigue fractures. In this paper, the tensile testing of SCS whose surface was intentionally oxidized and the effect of the oxide thickness on the mechanical properties were reported. After fabrication of SCS specimens, they were oxidized in dry oxidization at 1100 ºC. Quasi-static tensile testing of SCS specimens with no, 100-nm-oxide, and 200-nm-oxide thick oxide was performed. As the results, the deviation in fracture strain was decreased by oxidation, and the fracture origin was observed to be the inner silicon part. These results might be caused by the decrease of surface roughness and defects formation by oxygen precipitation during thermal oxidation.

Effect of surface oxide layer on activation performance of hydrogen storage alloy TiMn 1.25Cr 0.25

The activation performance of TiMn 1.25Cr 0.25 alloy without and with exposure to air prior to activation was compared at P=1 MPa and T=293 K and the possible underlying mechanism was discussed. The alloy, which has not been exposed to air before activation, can be activated with ease under moderate activation conditions. However, with increasing duration of exposure, its full activation became more difficult. X-ray photoelectron spectroscopy and Auger electron spectroscopy results show about 4– 7 nm thick oxide layer on the surface of the air-exposed samples, which implies that formation of surface oxide layer may play an important role in controlling activation. As indicated by scanning electron microcopy, the activation process of the alloy is closely related with fragmentation of alloy particles. According to X-ray diffraction results, activation leads to expansion of the crystal lattice of the alloy and the expanded structure would not be restored even after hydrogen desorption, which benefits the decrease in activation energy for hydrogen absorption and desorption and makes the process easy.

Effect of aluminium oxide caps on hillock formation in aluminium alloy films

The effect of surface oxide layers on thermally induced hillock formation was examined in AlTa and AlCu alloy films. An anodic oxide or a sputter-deposited oxide layer was intentionally formed on the top of the Al alloy films, and subsequently annealed in a vacuum of less than 1×10−4 Pa. Hillock formation on the encapsulated films, the dependence of hillock density on types and thickness of the oxides, and film stresses were investigated. It was observed that hillocks preferentially formed under the oxides and extruded out of the films, breaking through them. SEM and cross-sectional TEM micrographs revealed hillock growth along with the oxide/metal interface and deformation of the surface oxides following the change of surface topography by hillock formation. More than 100 nm in thickness of anodic oxide caps or a 230-nm thick sputter oxide were necessary to suppress hillock formation. An identical hillock density was obtained in each Al alloy film with encapsulation up to 62 nm in thickness, independent of the thickness and type of the oxide cap. The results indicate that surface conditions are unlikely to determine hillock density, and hillock suppression in the encapsulated films was presumably achieved by lower film stresses at elevated temperature resulting from higher initial tensile stresses induced by anodization and a smaller gradient of the stress-temperature curve of the metal/oxide multilayered films.

FTIR-RAS Studies of the Coordination of Surface Oxide Layers of Copper with Poly(acrylonitrile)

The effect of surface oxide layers on the coordination of polyacrylonitrile (PAN) to copper has been investigated by infrared reflection-absorption spectroscopy. It has been found that side-on coordination can be formed for PAN on copper surface preoxidized at 200°C for 30 min. On the other hand, no coordination is observed for PAN adsorbed on freshly cleaned copper which had been heated at 200°C for 90 min in vacuum. However, the side-on coordination is also found on the freshly cleaned copper after an additional heating at 180°C for 90 min in air. We proposed that these results are likely due to the variation in chemical reactivity of copper in different oxidation states. It has also been found that the side-on coordination of copper to C ≅ N groups can facilitates the cyclization of PAN at lower temperatures.

Effect of surface oxide layers on deuterium permeation through stainless steels with reference to outgassing reduction in ultra- to extremely high vacuum

Hydrogen is a dominant outgassing species from stainless steel vacuum chambers in ultra- to extremely high vacuum. Oxidation of stainless steel surfaces has been known to reduce the outgassing. The oxide layer formed on the stainless steel surface is expected to serve as a diffusion barrier for hydrogen diffusing from the bulk. In the present study the effects of oxidation on the outgassing rate, on hydrogen thermal desorption spectra, on surface contamination and on deuterium permeation and diffusion characteristics through the stainless steels are summarized. Discussion is given to the role of the surface oxide layer in outgassing reduction as well as to the effect of thickness and chemical compositions on reduction in hydrogen permeability and diffusion. The surface oxide formed in the present study appears to serve as the diffusion barrier for hydrogen and is found to decrease the deuterium permeability to 1 2 – 1 3 of the unoxidized one by lowering the diffusion coefficient. The most effective oxide is proposed to be Cr-rich oxide with 100–200Å thickness.