Thickness Of Oxide Layer Research Articles

Influence of Cr Content on the High-Temperature Oxidation Behavior and Mechanism of Low-Alloy Steels.

The high-temperature oxidation behavior of low-carbon steel (AISI 1015, AISI 8617, AISI 4115) was investigated over the temperature range from 600 to 1000 °C in humid air containing 25% water vapor. Mass gain of oxidation measurement was performed to study the oxidation kinetics. The microstructure, thickness, and composition of the oxide scale formed were investigated via optical microscope (OM), scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and electron probe microanalyzer (EPMA). The oxidation process was performed from 2 to 100 min. As the oxidation time increased, the trend of mass gain per unit area switched from a linear to a parabolic law, regardless of the steel grade used. As the chromium content increased, the duration of time during which the oxidation rate followed a linear relationship decreased. In the low-alloy steel with higher chromium content, the thickness of the mixed oxide layer containing Cr increased and the oxidation rate decreased at all oxidation temperatures.

Radiation-Induced Degradation Mechanism of X-Ray SOI Pixel Sensors With Pinned Depleted Diode Structure

The X-ray Silicon-On-Insulator (SOI) pixel sensor named XRPIX has been developed for the future X-ray astronomical satellite FORCE. XRPIX is capable of a wide-band X-ray imaging spectroscopy from below 1 keV to a few tens of keV with a good timing resolution of a few tens of μs. However, it had a major issue with its radiation tolerance to the total ionizing dose (TID) effect because of its thick buried oxide layer due to the SOI structure. Although new device structures introducing pinned depleted diodes dramatically improved radiation tolerance, it remained unknown how radiation effects degrade the sensor performance. Thus, this paper reports the results of a study of the degradation mechanism of XRPIX due to radiation using device simulations. In particular, mechanisms of increases in dark current and readout noise are investigated by simulation, taking into account the positive charge accumulation in the oxide layer and the increase in the surface recombination velocity at the interface between the sensor layer and the oxide layer. As a result, it is found that the depletion of the buried p-well at the interface increases the dark current, and that the increase in the sense-node capacitance increases the readout noise.

Thermomechanical evaluation of ATF fuel rods regarding irradiation effects

Fuel clad is the main barrier against the release of radioactive materials. For decades zirconium-based alloys have been used as nuclear fuel clads. Fukushima accident proposed the idea of designing and developing accident tolerant fuels (ATF). This research tries to evaluate the effect of irradiation damage on ATF clads under operating condition of a pressurized water reactor. In this work, the SiC and FeCrAl clads are investigated as two candidates for replacement with conventional cladding, Zircaloy-4. The neutronics of a WWER1000 reactor is modeled based on the Monte Carlo method. The neutronic evaluation of the core with desired clads is performed over three years in different spatial points. Using calculated neutron spectrum, the SPECTER and SPECOMP codes are applied to evaluate the damage caused by the irradiation in the term of displacement per atom (DPA). The thermomechanical evaluation of the fuel rod considering cladding irradiation effects and burnup are performed by a developed thermomechanical code. Also, stress, strain, creep, fuel-clad contact, thickness of oxide layer and … are calculated and the results are compared considering irradiation effects.

The ignition of fine iron particles in the Knudsen transition regime

A theoretical model is considered to predict the minimum ambient gas temperature at which fine iron particles can undergo thermal runaway–the ignition temperature. The model accounts for Knudsen transition transport effects, which become significant when the particle size is comparable to, or smaller than, the molecular mean free path of the surrounding gas. Two kinetic models for the high-temperature solid-phase oxidation of iron are analyzed. The first model (parabolic kinetics) considers the inhibiting effect of the iron oxide layers at the particle surface on the kinetic rate of oxidation, and a kinetic rate independent of the gaseous oxidizer concentration. The ignition temperature is solved as a function of particle size and initial oxide layer thickness with an unsteady analysis considering the growth of the oxide layers. In the free-molecular limit (small particles), the thermal insulating effect of transition heat transport can lead to a decrease of ignition temperature with decreasing particle size; however, the presence of the oxide layer slows the reaction kinetics, and its increasing proportion in the small-particle limit can lead to an increase of ignition temperature with decreasing particle size. This effect is observed for sufficiently large initial oxide layer thicknesses. The continuum transport model is shown to predict the ignition temperature of iron particles exceeding an initial diameter of 30 µm to a difference of 3% or less (30 K or less) when compared to the prediction of the transition transport model. The second kinetic model (first-order kinetics) considers a porous, non-hindering oxide layer, and a linear dependence of the kinetic rate of oxidation on the gaseous oxidizer concentration. The ignition temperature is resolved as a function of particle size with the transition and continuum transport models, and the differences between the ignition characteristics predicted by the two kinetic models are identified and discussed.

In situ fragmentation of Al/Al2O3 multilayers on flexible substrates in biaxial tension

A unique deposition approach combining atomic layer deposition (ALD) and magnetron sputtering was used to fabricate a series of thin film multilayer structures of Al (50 nm) and Al2O3 (ALD, 2.4–9.4 nm) on flexible polymer substrates without breaking vacuum. The multilayers together with 50 nm and 150 nm Al reference films were analyzed by cross-sectional TEM analysis and experimentally strained in biaxial tension to investigate their deformation behavior. Al film stresses and peak widths, measured in situ with Synchrotron X-ray diffraction, are in good agreement with post-mortem surface SEM and through-thickness FIB analysis of the multilayers. It was revealed that brittle cracking of the multilayer can be avoided, and that the lateral and through-thickness crack resistance improve as a function of decreasing oxide layer thickness. An attempt to model the full biaxial yield surface of the multilayers, which remains experimentally challenging, appears to be valid up to 2.4 nm oxide thickness. Model predictions are further compared to compression data, obtained from the unloading segments of the tensile tests. Describing the mechanical behaviour under multiaxial stress conditions is of utmost importance for a diverse understanding of these multilayers across a variety of potential carrier systems and loading cases.

Electrochemical CO2 reduction on tin and its alloys: Insights from depth-profiling X-ray photoelectron spectroscopy

Tin (Sn) and its alloys are widely used as electrodes for electrochemical CO2 reduction (EC CO2R) due to their unique p-block elemental character. In this study, we investigated the performance of Sn and Sn alloys (SnBi and SnPb) electrodes for EC CO2R under various conditions. The elemental distributions of the electrodes were examined using depth-profiling X-ray photoelectron spectroscopy (XPS) before and after EC CO2R. Our results demonstrate that Sn and its alloys can efficiently produce formate/formic acid with high Faradaic efficiency and selectivity. The Faradaic efficiency was found to be 96%, 93%, and 92% for Sn, SnBi, and SnPb electrodes, respectively, with a significant increase in formate selectivity to 99.7%. The depth profiling XPS analysis revealed substantial changes in elemental distribution, oxidation state, and oxide layer thickness after EC CO2R. Additionally, the elemental composition was found to vary with depth. The newly revealed surface elemental composition with depth and the EC CO2R performance provide valuable insights into the interfacial electronic structure of the electrodes before and after EC CO2R. These findings are crucial for developing more realistic theoretical models of the electrode and optimizing the electrochemical process for practical applications.

Effect of laser shock peening and surface mechanical attrition treatment on the oxidation resistance of a 20Cr-25Ni-Nb stainless steel

In this study, the effects of laser shock peening (LSP) and surface mechanical attrition treatment (SMAT) were comparatively investigated on the oxidation behaviors of 20Cr-25Ni-Nb stainless steel in a high-temperature (650 °C) CO2 environment up to 1000 h. The results show that the oxidation resistance of stainless steel can be improved by LSP but deteriorated by SMAT. LSP promoted the formation of a thin and uniform Cr-rich oxide layer on the 20Cr-25Ni-Nb stainless steel instead of a thick duplex oxide layer with Fe-rich outer layer and Cr-rich inner layer which appeared on the untreated sample. For the SMAT-treated sample, besides the oxide scale, a thick internal oxidation zone (IOZ) and oxides spallation were also observed. The formation of a Cr-rich oxide layer was facilitated by the enhancement of the Cr diffusion within the LSP-induced hardened layer. The unsatisfying oxidation performance of the SMAT-treated sample is due to the surface micro-cracks and significant grain refinement which synergistically contributed to the visible carburization and oxidation in a high-temperature CO2 environment.

WO3 layer sensitized with BiVO4 and MIL-101(Fe) as photoanode for photoelectrochemical water oxidation

Thick tungsten oxide layers were prepared electrophoretically in order to be used as photoanodes in photoelectrochemical water oxidation applications. The highest photocurrent density was obtained for a WO3 layer with thickness of ∼900 nm. Additionally, WO3/BiVO4 and WO3/BiVO4/MIL-101(Fe) heterojunctions have been fabricated using WO3 layer as substrate. WO3/BiVO4 shows an increased value of the electrochemical active surface area indicating that more sites of this photoanode are activated through the formation of the heterojunction. The small V5+ signals observed in the V 2p XPS spectra of these heterojunctions were attributed to the substitution of V5+ atoms with W6+ atoms on the surface of BiVO4. Excessive W doping of the BiVO4 film determined the decrease of the photoelectrochemical performance of WO3/BiVO4 photoanode. The significant improvement of the photoconversion efficiency of the sample decorated with MIL-101(Fe) indicated that this co-catalyst provides sites more efficiently in the photoelectrochemical process. This performance was correlated with the reduced value of the charge transfer resistance at electrode/electrolyte interface obtained from electrochemical impedance spectroscopy investigation.

Exploring thermally stable metal-oxide/SiO2 stack for metal oxide semiconductor memory and demonstration of pulse controlled linear response

We fabricated Al2O3/SiO2 stack structures with atomically thin Ti oxide layers at the interfaces using atomic layer deposition and investigated the capacitance–voltage (C–V) hysteresis of the metal-oxide-semiconductor (MOS) capacitors. We studied the effect of post-deposition annealing in the temperature range of 150 °C−500 °C on the C–V hysteresis and found that the Al2O3/SiO2-based stacks are thermally stable compared to ZrO2/SiO2- and HfO2/SiO2-based stacks. Using Al2O3/SiO2-based stacks, we investigated the impact of oxide layer thickness and gate electrode materials and studied pulse-induced current changes in MOS field-effect transistors.

Understanding the Influence of Metal Oxide Layer Thickness and Defects on Resistive Switching Behavior Through Numerical Modeling

Understanding the Influence of Metal Oxide Layer Thickness and Defects on Resistive Switching Behavior Through Numerical Modeling

Resistive Switching: Physics, Devices and Applications

Resistive Switching: Physics, Devices and Applications

Effect of particle size on ignition and oxidation of single aluminum: molecular dynamics study

Alumina nanoparticle is one of the attractive nanoparticles synthesized by the plasma method. The oxidation step in this method is challenging to explain experimentally. This work was to perform a molecular dynamics simulation to determine the oxidation mechanism of aluminum nanoparticles with different sizes and oxidation levels in the oxide layer. This work was to perform a molecular dynamics simulation to determine the oxidation mechanism of aluminum nanoparticles with different sizes and oxidation levels in the oxide layer. The simulation method employed the ReaxFF potential. The material used is aluminum nanoparticles in three different sizes (8, 12, and 16 nm) with an oxide layer thickness of 0.5 nm. Aluminum nanoparticles were given a relaxation treatment of 300 K for 1 ps and then heated to a temperature of 3250 K with a heating rate of 5×1013 K/s and cooled to 300 K. The ensemble used is a canonical ensemble with the Nose/Hoover thermostat method. The result shows that the higher the temperature applied to the system, the more oxygen molecules adsorption occurs on the surface of the oxide layer and the diffusion of oxygen to the particle core. The higher temperature applied also causes gaps, or void spaces, between the core and the shell. The reaction barrier for diffusion of oxygen also decreased significantly due to void space, and the surface of the aluminum core dissociates to the surface (alumina shell). Particles with a smaller size have a shorter ignition delay time. In addition, the smaller the particle size, the more oxygen molecules' reacted with aluminum particles in the particle core

Analysis of Thermally Grown Oxides on Microperforated Copper Sheets

Copper oxides have some interesting photocatalytic properties and reasonably low price which makes them applicable as PN transistors. However, to obtain the best performance it is necessary to increase the specific working surface of materials which plays a key role in many applications. Furthermore, by ordered spacing and heterojunction formation it is possible to fabricate the systems with specific dedicated properties, like for example PN photovoltaic junction. The conducted research analyses the mechanical properties, stress distributions, and thermal stability of metal–oxide structures with such advanced geometries. Micro-perforation of thin Cu sheet was selected for the study, as it can both enhance the free surface of the substrate and decrease the number of sites of thermal stress occurrence. Both Cu-Cu2O and Cu-CuO layers were simulated using finite element analysis. The model based on fixed geometry of square shaped samples of dimensions of 156 × 156 mm was applied to thin metal plates holes-patterned covered on top by 1-3 μm thick oxide layers. On the other hand, the influence of plate thickness was found to be important in terms of structure durability. A good agreement between the simulation and the experimental data was achieved. The critical delamination temperature of c.a. 473-483 K was estimated for both oxide layers. The verification of the simulation/computation model was done by analyzing perforated and non-perforated Cu Electrolytic Tough Pitch (ETP) sheets. Two methods, FIB-TEM and surface scan using a profilometer, were selected. The first verified the decohesion of the oxide coatings from the metal support after exceeding the temperature of 523 K The issue that was also noticed is the susceptibility for peeling in the inner surface of the holes.

Effect of Batch-Annealing Temperature on Oxidation of 22MnB5 Steel during Austenitizing

In this paper, the effect of batch-annealing temperature on the oxidation of 22MnB5 steel during austenitizing was studied. When the batch-annealing temperature was decreased from 690 to 680 °C, the surface roughness of cold-rolled 22MnB5 steel decreased, which reduced the oxide layer thickness during the subsequent austenitizing process and had little effect on the mechanical properties in the cold-rolled and quenched state. This indicated that oxidation during austenitizing could be reduced by properly reducing the batch-annealing temperature without affecting the mechanical properties.

(Invited, Digital Presentation) Low-Temperature Direct Bonding of Wide-Bandgap Semiconductor Substrates

For the next-generation semiconductor devices, our research group has developed direct bonding techniques of wide-bandgap materials, including SiC, Ga2O3, and diamond. It is known that the semiconductor substrates activated by oxygen plasma can form atomic bonds at low temperatures. In this case, a thick oxide layer, which may become a thermal and electrical barrier, is formed at the bonding interface. Meanwhile, our research group demonstrated that the OH-terminated Ga2O3 and diamond substrates were directly bonded without an oxide intermediate layer. In addition, the SiC substrate dipped into the HF acid can be bonded with the Ga2O3 substrate with an ~1-nm-thick amorphous layer. The dissimilar substrates bonded through the ultra-thin intermediate layer would contribute to efficient heat dissipation and future heterojunction devices.

Investigation of Surface Oxide Layer Structure to Improve Durability of Stainless Steels Under Humidified Hydrogen

Durability of low cost stainless steels, selected from the materials widely used in other applications, was investigated under humidified hydrogen of SOFC anode condition. JIS SUS430J1L exhibited higher resistance for water oxidation. The feature came mainly from the thin Cr-rich oxide layer covering the alloy uniformly with little defects or segregations. Under humidified H2 at 700oC, Mn migrated outward and the morphology changed. Durability of the alloy seems to depend on the inner side of the surface oxide layer. Although the Cr-rich oxide layer blocked outward diffusion of metal ions, the layer could not block inward diffusion of oxygen ion completely. Improvement of the durability is possible by controlling the thickness of the surface oxide layer by the pre-heat-treatment.

Surface analysis insight note: Initial, statistical evaluation of X‐ray photoelectron spectroscopy images

With advances in instrumentation and image processing, imaging X‐ray photoelectron spectroscopy (XPS) is becoming increasingly important in surface analysis. In this Insight Note, we suggest the following three steps for the initial evaluation of XPS images: (i) Plot all the data. Possible plots here include an overlay plot, a plot of the average and standard deviation of the spectra, a waterfall plot, and a contour plot. (ii) Examine slices through the data cube at different binding energies, identifying those that show significant contrast. (iii) Examine the spectra, including their average and standard deviation, in defined regions of slices through the data that show contrast. These steps allow XPS images to be probed without the use of more sophisticated exploratory data analysis (EDA) techniques. Indeed, these steps may set the stage for additional EDA analysis of XPS images. Furthermore, they provide an initial understanding of an XPS image that stays close to the original data. Our three‐step protocol was applied to an XPS image of a region of a silicon wafer with different oxide thicknesses. This image primarily contained two types of pixels/regions: one of silicon with a thin oxide layer and the other of silicon with a thicker oxide layer. We emphasize the importance of contour plots of all the data and examining the average and standard deviation of regions of contrast in slices through the data cube.

The distribution of oxygen in submicron silicon powders produced by ultrafine grinding

The distribution of oxygen in submicron silicon powders produced by ultrafine grinding was studied as a function of grinding time, grinding liquid composition, air exposure during the grinding experiments and post-grinding handling. Grinding in isopropyl alcohol resulted in relatively low oxygen concentrations. Here, a maximum SiO2 oxide layer thickness of 0.24 nm was calculated for a product with a total oxygen concentration of 3.35 wt%, a mean particle size of 122 nm and a BET specific surface area of 72 m2/g. When excluding the contribution from adsorbed or trapped grinding liquid and alkoxy groups the layer thickness was reduced to 0.07 nm. The addition of ion exchange water to the isopropyl alcohol produced a non-linear increase in the oxygen concentration. The effect of exposure to air during drying was small compared to the effect of exposure to air during the grinding process or during heat treatment at higher temperatures.

Zero-Dimensional Ignition Model of Boron Agglomerates.

Boron primarily exists in the form of agglomerates in ramjet combustion chambers. However, the model used to predict the ignition time of boron agglomerates is usually based on the single-particle assumption, resulting in inaccurate predictions. This study aims to develop a numerical model that can accurately describe the ignition of boron agglomerates. The model is based on the ignition model of a single particle boron proposed by the group of Kuo. Thiele modulus and effectiveness factor are introduced to represent the diffusion resistance of reaction gases in the pores of boron agglomerates. The model includes the necessary physical processes to accurately predict the ignition time. The rates of evaporation and heterogeneous reactions involved in the oxide layer removal process are corrected based on the fact that the diffusion rate of (BO)n in the liquid oxide layer equals to its consumption rate at the oxide-air interface. To evaluate the accuracy of the model, the obtained results for ignition time are compared with experimental data, showing reasonable consistency between them. The model is then applied to investigate the ignition characteristics of boron agglomerates. Parameters, such as initial average pore diameter, oxide layer thicknesses, initial particle diameter, O2 concentration, H2O concentration, and environmental pressure, are studied for their effects on the ignition time. In summary, the boron ignition model established in this study is a powerful tool to investigate the ignition mechanisms and characteristics of boron agglomerates. It can be further coupled with flow analysis for the detailed simulation of turbulent combustion in ramjet combustors.

Oxidation Property of a Fourth-Generation Powder Metallurgy FGH4108 Nickel-Based Superalloy

Isothermal oxidation kinetics of a fourth-generation powder metallurgy FGH4108 nickel-based superalloy is investigated at 800 °C to 1100 °C by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). At 800 °C and 900 °C, the oxidation kinetic curves of the FGH4108 superalloy follow parabolic law. At 1000 °C, the oxidation kinetic curve follows cubic law. At 1100 °C, the oxidation kinetic curve has two distinct parts: the first part follows a parabolic law, and the second one obeys a linear law. Cross-sectional morphologies and elemental distributions show that the oxide film consists of two parts at 800 °C: the outer layer is a continuous dense protective Cr2O3 oxide film, and the inner layer is a discontinuous Al2O3 oxide layer. At 900–1100 °C, the oxides consist of three layers: the outermost is the oxides of Cr2O3 and TiO2, the middle is a continuous oxide of Al2O3, and the innermost is dotted oxides of TiO2. The thickness of the inner TiO2 oxide layer increases with the increase of oxidation temperature. On this basis, the oxidation behavior of the FGH4108 superalloy at high temperatures is confirmed to be controlled by the diffusion of Cr, Al, Ti, and O. From the aspect of oxidation resistance, the long-term service temperature of the FGH4108 superalloy should not exceed 1000 °C.