Removal Of Oxide Layer Research Articles

Evaluation of graphene transparent coating on copper for color and oxidation control at low temperatures

In this paper, the ability to preserve copper color was investigated by using graphene thin film coating against oxidation at 200 °C. For this purpose, graphene nano-coating was applied to the copper substrate by using chemical vapor deposition (CVD) process. Raman spectroscopy was used for the detection of the coatings. Structural investigation of the coating was performed before and after oxidation tests using optical and scanning electron microscopes. Color changes due to the formation of copper oxides were calculated using the CIE–L*a*b* color space defined by the Commission Internationale de l'Éclairage (CIE). Furthermore, the reflectance was evaluated in the UV–visible spectrum range. The results revealed that the graphene coated copper had a higher L* than the untreated copper due to the removal of oxide layer during graphene synthesis. The color change (∆E) caused by oxidation at 200 °C, in the graphene coated copper was negligible (∆E = 2.88) after 2 h, and its value was below 5 after 4 h. However, the color change on the bare copper surface was significant (∆E = 26.87) after 15 min of oxidation. The results of the present research show that the graphene coating is effective in protecting copper color. Moreover, since graphene oxidation extends from defects and grain boundaries, synthesis technique plays an important role in protecting copper against oxidation and thus preserving its color.

Effect of Remnant Carbon and Etching of Particles on Pyrolysis Bonded Silicon Carbide (PBSC)

Silicon carbide (SiC) formed through pyrolysis of preceramic polymers loaded with SiC particles has gained significant attention for applications such as coatings, composite matrix modifications, and most importantly additive manufacturing. This work presents combined synchrotron XRD, Raman spectroscopy, scanning electron microscopy, nano-indentation, and Vickers indentation of pyrolysis bonded SiC to shed light on the changes of composition and mechanical properties of these materials. Characterization was performed on samples that were heat treated ranging from the synthesis 850 °C up to 1500 °C. Pre-treatments of the powders prior to pellet synthesis, such as heat treatment and etching using a hydrofluoric acid (HF), were investigated. It is shown that the degradation of mechanical properties when exposed to higher temperatures is due to the burnout of amorphous carbon clusters remnant of the pyrolysis process of the preceramic polymer. Furthermore, prior HF etching and removal of the native oxide layer of the powders showed improved density and hardness values in the final pellets. The average Vickers hardness of the control samples were 4.59 GPa and later 3.74 GPa when exposed to 1500 °C, while the samples synthesized using powders that were etched with HF had an average hardness value of 9.37 GPa and later 6.86 GPa when exposed to 1500 °C.

Recent Advances In Silicon Carbide Chemical Mechanical Polishing Technologies.

Chemical mechanical polishing (CMP) is a well-known technology that can produce surfaces with outstanding global planarization without subsurface damage. A good CMP process for Silicon Carbide (SiC) requires a balanced interaction between SiC surface oxidation and the oxide layer removal. The oxidants in the CMP slurry control the surface oxidation efficiency, while the polishing mechanical force comes from the abrasive particles in the CMP slurry and the pad asperity, which is attributed to the unique pad structure and diamond conditioning. To date, to obtain a high-quality as-CMP SiC wafer, the material removal rate (MRR) of SiC is only a few micrometers per hour, which leads to significantly high operation costs. In comparison, conventional Si CMP has the MRR of a few micrometers per minute. To increase the MRR, improving the oxidation efficiency of SiC is essential. The higher oxidation efficiency enables the higher mechanical forces, leading to a higher MRR with better surface quality. However, the disparity on the Si-face and C-face surfaces of 4H- or 6H-SiC wafers greatly increases the CMP design complexity. On the other hand, integrating hybrid energies into the CMP system has proven to be an effective approach to enhance oxidation efficiency. In this review paper, the SiC wafering steps and their purposes are discussed. A comparison among the three configurations of SiC CMP currently used in the industry is made. Moreover, recent advances in CMP and hybrid CMP technologies, such as Tribo-CMP, electro-CMP (ECMP), Fenton-ECMP, ultrasonic-ECMP, photocatalytic CMP (PCMP), sulfate-PCMP, gas-PCMP and Fenton-PCMP are reviewed, with emphasis on their oxidation behaviors and polishing performance. Finally, we raise the importance of post-CMP cleaning and make a summary of the various SiC CMP technologies discussed in this work.

A Scalable Method for Improving Zn Crystallinity for Low-Gassing Alkaline Batteries

The corrosion of zinc particles in alkaline environments is an energetically parasitic process that produces hydrogen gas as a byproduct. This “gassing” phenomenon is thermodynamically favorable in standard zinc-alkaline battery chemistries. Building hydrogen pressure within these primary cells can eventually lead to cell rupture, leaking the high-pH electrolyte and slurry from the cell, often destroying the electronic device that the cell was meant to power. One of the particle-level variables that can control the gassing and corrosion rate is the particle crystallinity. As the crystallinity of the zinc particles is enhanced (larger grains and fewer grains per particle), a reduction in the rate of this undesirable gassing phenomenon is expected.In this study, we demonstrate a systematic method for enhancing zinc particle crystallinity by thermally growing zinc grains. Since thermally growing zinc grains requires temperature exposure above the melting point of metallic zinc, an oxide layer is first grown around the outside of the particle surface. Oxides tend to have significantly higher melting temperatures than their metallic counterparts and this is true in the zinc/zinc oxide case where the melting temperature of metallic zinc is 420 oC and the melting temperature of zinc oxide is 1975 oC. Forming a thin oxide layer around the particle allows the metallic zinc core to be recrystallized whilst simultaneously retaining the particle shape. Following the grain growth step, the oxide layer is easily washed away with a quick acetic acid treatment. Outlined in this work is a detailed study on the scalable three-step process for growing zinc grains and enhancing bulk zinc powder crystallinity by the following: 1) oxide layer formation, 2) grain growth, and 3) oxide layer removal. Following the treatment, both achievable capacity and the corrosion rate were tested. It will be shown that the higher crystallinity particles have superior performance and lower gassing than traditional Zn powders without the treatment.

Innovative Processes for a Low Impact in the Electroplating of Stainless Steel

Steel is a cheap renewable material with many interesting properties but its presence in the electroplating sector is very limited due to adhesion difficulties. Stainless steel contains approximately 10.5% chromium, which forms a surface oxide layer that passivates the steel, making it resistant to corrosion [1]. It is the presence of this surface oxide film that makes it difficult to electroplate steel. The aim of electroplating steel is to refine it by depositing nobler metals of the desired color, such as ruthenium and gold.The activation of steel involves the remotion of the oxide layer. The main method of electroplating stainless steel is generally through the deposition of nickel, but the intensive use of nickel baths makes these processes inappropriate for the sustainability paths taken by the electroplating industry. Even when nickel-based galvanizing processes are not used, it is possible that steel objects do not pass the nickel release test. This is because the steel itself contains nickel, so the removal of the surface oxide layer during the electroplating process may facilitate the release of nickel.The nickel release mechanism is not yet fully clear but bring to allergenic issues in the final product [2]. We performed a systematic study electroplating various metals and alloys on steel to evaluate which one performed better as barrier against the release of nickel and shed light on this issue.The steel substrate was characterized microscopically and spectroscopically before and after the release test. The amount of nickel was evaluated in the solution that simulates human sweat to evaluate its release in µm·cm-2·week-1 according to the standard EN 1811:2015.The authors acknowledge Regione Toscana POR CreO FESR 2014-2020 – azione 1.1.5 sub-azione a1 – Bando 1 “Progetti Strategici di ricerca e sviluppo” which made possible the projects “A.C.A.L. 4.0” (CUP 3553.04032020.158000165_1385), “A.M.P.E.R.E.” (CUP 3553.04032020.158000223_1538), “GIGA 4.0” (CUP 3553.04032020.158000105_1242) and “GoodGalv” (3647.04032020.157000060).

Characterization of IASCC crack tips extracted from neutron-irradiated flux thimble tube specimens in view of a probabilistic fracture model

This study reports the properties of irradiation assisted stress corrosion crack tips extracted by means of focused-ion beam from 60 to 80 dpa neutron-irradiated O-ring specimens tested under straining conditions under a pressurized-water reactor environment. Various crack tip morphologies and surrounding deformation features were analyzed as a function of applied stress, surface oxidation state and loading form - constant versus cyclic. All investigated cracks exhibit grain boundary oxidation in front of the crack tip, with the extent of oxidation being proportional to applied stress. These findings clearly demonstrate that, under the subcritical crack propagation regime, the grain boundary oxide grows faster than the crack. On the other hand, crack tips appertaining to specimens with removed oxide layer at the outer surface show comparatively less oxidation at the crack tip, which could indicate towards crack initiation from regions that exemplify lower stress, such as the O-ring inner surface. Cyclic loading is found to have a more pronounced effect on the crack tip microstructure, demonstrating increased deformation twinning and α′-martensitic transformation, which signifies towards an increased susceptibility to intergranular failure. Still, the extent of crack tip grain boundary oxidation in this case agrees well with expected values for maximum stress applied during cyclic loading. All results are interpreted based on the probabilistic subcritical crack propagation mechanism and provide strong support to a stress-driven internal oxidation model.

DDDMOSFET Performance Improvement by Gate Oxide Removal Followed by Silicided Source/Drain Formation in Gate Slots

In this work, the intentional insertion of slots in metal gate (MG) is introduced to solve the dishing issue for the double-diffused drain MOSFET (DDDMOSFET) fabrication. For traditional DDDMOSFET, the gate oxide layer in slots will be reserved to improve the device reliability, which requires an additional photomask to screen the gate/slot regions during the following sidewall formation and source/drain (S/D) implantation. This makes the process more complicated with increased cost. Without that additional photomask, it is proposed that the removal of gate oxide layer in slots can directly allow the floating S/D formation and the followed Ni silicidation there. It is demonstrated that such a novel process can not only relieve the MG dishing issue but can also effectively result in ~16% higher ON current and comparable OFF current for both N- and P-DDDMOSFETs without threshold voltage shift after applying electrical stress on gates. It is also revealed that the floating silicided S/Ds in slots have negligible influence on device breakdown characteristics. By saving one photomask, this work proposes a novel solution for the effective integration of core devices with very small feature sizes and high-voltage (HV) devices with large feature sizes in the same die, which is a common challenge for display driver chip fabrication using high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> /MG (HK/MG) technology.

Numerical Simulation of Temperature Field for Laser Removal of Oxide Layer of AlSi10Mg(Fe) Aluminum Alloy

To investigate the temperature field of the surface of AlSi10Mg(Fe) with the aluminum oxide layer being removed using pulse laser, the physical model of composite material of aluminum oxide, removed using pulse laser, and aluminum alloy is established by using COMSOL Multi-physics, which calculates the temperature field and the removal effect in the case of different laser scanning linear velocity and laser energy density by solving thermo-physics equations. The influence of different laser parameters on the removal effect is also discussed. Based on the simulation and experiment, it shows that the aluminum oxide removal effect peaks in the case of 15 j/cm2 for laser energy density.

Experimental investigation of low velocity and high temperature solid particle impact erosion wear

Next generation Concentrating Solar Power (CSP) plants utilizing solid particles as the heat transfer medium (HTM) are expected to achieve greater operational efficiencies. However, the erosion from the solid particles can cause significant damage to component materials. Low particle speeds (1–2 m/s) are proposed as a means of preventing excessive damage to containment materials. Within the current investigation, solid particle erosion of three potential containment materials, stainless-steel grade 316L, a nickel alloy (Inconel 740H), and a refractory material (Tufcrete 60 M), are examined at a particle impact speed of 1.6 m/s. CarboBead-HSP 40/70 particles, a candidate HTM for CSP systems, impact the specimens at a relatively high impact angle of 60° based on containment design criteria. Experiments were conducted at ambient temperature and 800 °C to examine erosion of the materials at very low impact speeds and determine how temperature effects erosion. Initial results revealed surprising outcomes inconsistent with available literature: ambient temperature erosion of SS316L is an order of magnitude lower than IN740H, but erosion (erosion-corrosion) of SS316L at 800 °C surpasses IN740H by two orders of magnitude. Results suggest removal of oxide layers (erosion-corrosion) is responsible for the significant erosion that was observed even at these low particle speeds.

Improvement of fretting fatigue strength by carbon monoxide and catalyst activation under chemomechanical effects of fretting

It is known that the fretting fatigue strength in hydrogen (H2) gas is lower than that in air. The objective of this study is to mitigate the hydrogen effect during the fretting fatigue test in H2 gas by adding carbon monoxide (CO) to the H2 environment. The expected CO effect was reduction in the hydrogen uptake into the material following deactivation of the catalytic surface where H2 molecules dissociate into H atoms. However, an unexpected result, which was unique in fretting, was obtained. The fretting fatigue test using JIS SUS304 austenitic stainless steel was performed in H2, argon (Ar), 2 vol% CO mixed H2, and 2 vol% CO mixed Ar gases. The fretting fatigue strengths in the CO-mixed gases were significantly improved. For instance, the fretting fatigue life at σa = 240 MPa was 8.8 × 105 cycles in the H2 and 107 cycles or longer in the CO mixed H2. The cause of the improved fretting fatigue strength was the formation of amorphous carbon between the contacting surfaces during the fretting. The carbon reduced the tangential force coefficient between the contacting surfaces from around 0.6 in the H2 to 0.2 or less in the CO mixed H2. The reduced tangential force resulted in improvement of the fretting fatigue strength. Although the detailed mechanisms of the carbon deposition were unclear, it is plausible that the catalytic action of the metal surface for the CO decomposition into C and O was activated by the effect of fretting, such as removal of the surface oxide layer and other chemomechanical effects.

Three-dimensional finite element simulation and experimental validation of sliding wear

Wear tests involving thousands of operating cycles can be impractical and costly. Therefore, the use of numerical methods to predict surface evolution due to wear can be a good alternative. A generalised three-dimensional finite element (FE) method is presented here to determine the wear of mechanical components. The method is tested and validated against the results obtained from the ball on disc sliding tests performed on different materials and in different conditions, with the aim to predict the wear profiles of the ball and disc. The wear simulation procedure is, for simplicity, based on Archard’s wear law and is implemented in a commercial FE package, ABAQUS. The developed methods are appropriate for 3D surfaces and the wear profiles are based on the accurate determination of the contact pressure. The surface evolutions of both contacting bodies are calculated simultaneously. The generation of artificial roughening of the worn surfaces due to numerical restrictions of element sizes is minimised using a local smoothening procedure. The developed methods are compared with the results obtained for reciprocating sliding tests, which result in wear of few microns wear depths, and continuous sliding tests, which result in tens of microns wear depths. The results were generally in good agreement with the test, with the maximum discrepancy of ∼ 10% in all indicators used, considering the statistical error margin of the tests. The developed method is versatile and applicable to a wide range of sliding wear tests. The model can be updated to consider both more complex material descriptions and to incorporate tribofilm or oxide layer growth or removal.

Study of transient events during the full-system chemical decontamination operation of the Kori-1 nuclear power plant

The Kori-1 nuclear power plant (NPP), a Westinghouse 2-loop pressurized water reactor in Korea, permanently ceased operations on June 18, 2017. Before the main decommissioning activities, full chemical decontamination of primary systems will be performed to secure the safety of workers and minimize the quantity of radioactive waste. In this study, the steady and transient flow characteristics for the chemical decontamination operations were analyzed via a simulation using the Multidimensional Analysis of Reactor Safety, KINS Standard version. Then, based on the accumulated flow mass released from the reactant cooling systems during transient events, the radioactivity levels were estimated using the oxide layer removal ratio obtained from the chemical decontamination experiment. The loss of residual heat removal, steam generator tube rupture (SGTR), power-operated relief valve open (PORV Open), and combination of SGTR and PORV Open simulations were investigated in terms of the transient events. Finally, a strategy for managing transient events during the full-system chemical decontamination operation of the Kori-1 NPP is proposed.

Research on the Microstructure Characteristics and Mechanical Properties of Autogenous and Non-autogenous Laser Beam Welded AA2195 Joints Without Removal of Surface Oxide Layers

Research on the Microstructure Characteristics and Mechanical Properties of Autogenous and Non-autogenous Laser Beam Welded AA2195 Joints Without Removal of Surface Oxide Layers

Laser beam brazing of aluminum alloys in XHV-adequate atmosphere with surface deoxidation by ns-pulsed laser radiation

Laser beam brazing is an established manufacturing process due to its low heat input and esthetically appealing seams. However, brazing of materials with high oxygen affinity, such as aluminum alloys, requires the removal of surface oxides prior to the brazing process, commonly through the application of chemical fluxes that may be harmful to the environment and to health. The approach presented here dispenses with the use of fluxes and involves oxide layer removal by means of ns-pulsed laser radiation within an atmosphere that is adequate to an extreme high vacuum (XHV) in regard to the oxygen content. By doping the process gas with monosilane (SiH4), an oxygen content equivalent to an extreme high vacuum with an oxygen partial pressure below 10−20 mbar is realized. Hence, a subsequent reoxidation is actively prevented so that wetting of the base material by the filler material and consequent diffusion processes are enabled. The wetting angle between filler material and material is used to evaluate the effectiveness of laser-based deoxidation under an XHV-adequate atmosphere.

Mid-infrared Fourier-transform spectrometer based on metamaterial lateral cladding suspended silicon waveguides.

Integrated mid-infrared micro-spectrometers have a great potential for applications in environmental monitoring and space exploration. Silicon-on-insulator (SOI) is a promising platform to tackle this integration challenge, owing to its unique capability for large volume and low-cost production of ultra-compact photonic circuits. However, the use of SOI in the mid-infrared is restricted by the strong absorption of the buried oxide layer for wavelengths beyond 4 µm. Here, we overcome this limitation by utilizing metamaterial-cladded suspended silicon waveguides to implement a spatial heterodyne Fourier-transform (SHFT) spectrometer operating at wavelengths near 5.5 µm. The metamaterial-cladded geometry allows removal of the buried oxide layer, yielding measured propagation loss below 2 dB/cm at wavelengths between 5.3 and 5.7 µm. The SHFT spectrometer comprises 19 Mach-Zehnder interferometers with a maximum arm length imbalance of 200 µm, achieving a measured spectral resolution of 13 cm-1 and a free spectral range of 100 cm-1 at wavelengths near 5.5 µm.

Взаимосвязь электронной и атомной структуры пассивированных поверхностей n-InP(100)

Photoluminescence, Raman spectroscopy and X-ray photoelectron spectroscopy are used to study electronic and atomic structure of n-InP(100) surfaces treated with different sulfide solutions. It is shown that the sulfide treatment causes removal of the native oxide layer from the semiconductor surface and formation of the passivating layer consisting of In−S chemical bonds with the structure dependent on the solution composition and atomic arrangement at the initial surface of the semiconductor. This is accompanied by an increase in photoluminescence intensity and narrowing of the surface depletion layer. Atomic structure of the passivating layer determines the total dipole that modifies the depth distribution of the bands potentials and thus the surface electronic structure.

Correlation of the electronic and atomic structure at passivated n-InP(100) surfaces

Photoluminescence, Raman spectroscopy and X-ray photoelectron spectroscopy are used to study electronic and atomic structure of n-InP(100) surfaces treated with different sulfide solutions. It is shown that the sulfide treatment causes removal of the native oxide layer from the semiconductor surface and formation of the passivating layer consisting of In-S chemical bonds with the structure dependent on the solution composition and atomic arrangement at the initial surface of the semiconductor. This is accompanied by an increase in photoluminescence intensity and narrowing of the surface depletion layer. Atomic structure of the passivating layer determines the total dipole that modifies the depth distribution of the bands potentials and thus the surface electronic structure. Keywords: surface modification, sulfur passivation, Raman spectroscopy, photoluminescence, X-ray photoelectron spectroscopy.

Effect of laser texturing pattern on Ti6Al4V tribocorrosion in a physiological solution

Laser texturing is a process that alters a material’s surface properties by modifying its morphology, which can improve properties like adherence, wettability, thermal and electrical conductivity and friction. Here, the effect of laser texturing was studied on an alpha-beta titanium alloy (Ti6Al4V) biomedical material. Two types of patterned surfaces, cross-hatch with varying scan-line separations, Δx = 100, 180 and 280 µm and dimples of 200 µm size, were prepared on the surface of alpha-beta titanium alloy by laser technology. Prepared samples were characterised for their surface properties, such as corrosion, wear-induced corrosion, friction and wettability. Electrochemical and tribocorrosion properties in a physiological solution were studied on the samples with different texture densities of cross-hatch pattern and dimples and compared to the as-received alpha-beta titanium alloy surface. Corrosion rate decreased for laser-textured samples, especially for cross-hatch texture (down to 1 µm/year for Δx = 180 µm) when compared to the as-received alpha-beta titanium alloy surface due to the changed laser-induced surface film and wetting properties. Friction coefficient slightly decreased for all laser-textured surfaces, most noticeably for cross-hatch patterns, from 0.38 (as-received) down to 0.34 (Δx = 180 and 280 µm). The main contribution to total wear in physiological solution increased due to the mechanical wear, which is governed by the removal of the surface oxide layer induced by laser texturing.

Gradient Microstructure Induced by Surface Mechanical Attrition Treatment in Grade 2 Titanium Studied Using Positron Annihilation Spectroscopy and Complementary Methods.

Microstructural changes in grade 2 titanium generated by surface mechanical attrition treatment (SMAT) were studied using positron annihilation lifetime spectroscopy and complementary methods. A significant increase in the mean positron lifetime indicated many lattice defects introduced by SMAT. Two positron lifetime components were resolved in the positron lifetime spectra measured. The longer lifetime revealed the presence of vacancy clusters containing about 3 or 4 vacancies, while the shorter one was attributed to the annihilation of positrons trapped at dislocations. The changes of the positron lifetime indicated a decreasing dislocation density and the presence of a deeper layer with a higher concentration of vacancy clusters at the distance from the treated surface for which the microhardness approached the value for the strain-free matrix. Electrochemical impedance spectroscopy showed the positive effect of SMAT on the corrosion resistance of the titanium studied in a saline environment also after removal of the original oxide layer that was formed during the SMAT.

Research on the mechanism of laser removal for the oxide layer in TA15 titanium alloy by analyzing in-situ high-speed camera and product characteristics

The natural oxide film of TA15 titanium alloy hinders its serviceability for subsequent process applications. Nanosecond pulsed laser removal of oxide layers is feasible, while the nanosecond scale and high pulse number cause challenges for mechanistic studies. Therefore, we research the laser removal mechanism of the oxide layer in TA15 titanium alloy by analyzing in-situ high-speed camera and product characteristics in this paper. As the energy density (E) increases, the fluctuation degree of the molten pool intensifies. Below 17.5 J/cm2, only the molten pool and plasma variations were observed. With 17.5 J/cm2 and above, ejected block and splash occurred. As E increases, it causes the surrounding blocks to move or even “expand” before breaking. It is demonstrated the existence of the boundary between the pure thermal mechanism and the thermal-inpact mechanism between 8.75 J/cm2 to 17.5 J/cm2. The vaporization pressure was obtained by the finite difference method and the transition threshold was fitted as 14.08 J/cm2. The block ejection velocity was coincided by calculating the buckling velocity. The collection of process products also verified the in-situ camera results for the transition mechanism. Below 17.5 J/cm2, only TiO2 particles with hundred nanometer to micron sizes were collected. With 17.5 J/cm2 and above, the number of particles increased and the blocks are collected. In addition, flocculent agglomerates wrapped around particles and block agglomerates with attached particles appeared. The morphology and composition of the products were discussed with the variation of energy input.