Thickness Of Oxide Layer Research Articles

Development of Ternary Magnesium Alloys for Laser Powder Bed Fusion: Optimizing Oxide Layer Thickness

Magnesium alloys pose challenges in additive manufacturing, due to the difference between the melting temperature of magnesium oxide (2825 °C) on the powder particles and the boiling point of metallic magnesium (1093 °C). A promising approach to overcoming the difficulties is the reduction of the thickness of the high‐melting oxide layer on the surface of the particles. Magnesium alloys, each containing varying amounts of strontium, neodymium, and yttrium, are cast and subsequently analyzed in terms of their microstructures, mechanical properties, oxide layer thicknesses, and corrosion behavior. Alloying magnesium with strontium results in a reduction of the oxide layer thickness, which reaches a minimum of 0.5 wt% strontium content. The presence of rare earth elements increases the strength of the alloys, although the inclusion of neodymium results in an increase in the oxide layer thicknesses. On the other hand, the oxide layer thickness remains unaffected when alloying with yttrium. However, further increases in strontium content up to the monolithic phase Mg17Sr2 have been found to result in a reduced effect on the open‐circuit potential. Further studies should be conducted to investigate the suitability of strontium as an alloying element to reduce the oxide layer thickness of magnesium particles.

Research on the oxidation process of micro-boron below the melting point temperature

The ignition and combustion characteristics of boron and the energy release rate of boron-based fuel are closely related to the surface oxide layer of boron. To understand the oxidation process of boron below its melting point, the slow oxidation process of boron under different temperature and humidity storage conditions and the fast oxidation process under high-temperature conditions were investigated. The results indicate that the surface oxide layer mainly comprises boron (B), boron suboxides (BxOy), and boron trioxide (B2O3). When the degree of oxidation is low, BxOy and B are the main components. After deep oxidation, BxOy almost disappeared. The thickness and composition of the surface oxide layer vary with changes in environmental temperature, humidity, and aging time. The effect of temperature increase on the growth rate of the oxide layer thickness is significantly greater than that of moisture. With the prolongation of boron aging treatment time, the onset, end, and maximum weight gain rate temperatures of the boron thermal oxidation process all slightly decrease. As the ambient temperature increases, the formation of the oxide layer transitions from a unidirectional diffusion mechanism of oxygen into the interior of boron particles to a bidirectional diffusion mechanism of molten oxide and oxygen.

High temperature oxidation resistance behavior of Ti3SiC2/Cu composites under migration of Ti and Cu atomic

The oxidation behavior and oxidation mechanism of Ti3SiC2/Cu composites were investigated using constant temperature oxidation method. The Ti3SiC2/Cu composites were prepared at different sintering temperatures. Results showed that the relationship between the oxidation reaction rate of Ti3SiC2/Cu composites in air at 700°C∼900°C and the oxidation temperature was in accordance with the parabolic law of oxidation kinetics. The oxidation weight gain and oxide layer thickness of Ti3SiC2/Cu composites at 700 °C and 800 °C were insignificant, with oxidation reaction rates of 3.0692×10-9 kg2m-4h-1 and 6.9856×10-9 kg2m-4h-1, respectively, and the oxidation rate of Ti3SiC2/Cu composites at 900 °C was enhanced to 1.00907×10-8 kg2m-4h-1. Ti3SiC2/Cu composites oxidized at 900°C formed a protective oxide layer, which was mainly a multilayer structure composed of different kinds of oxides: the outer layer was mainly composed of TiO2; the intermediate layer mainly consisted of CuO; the inner layer mainly made up of TiO2 and SiO2.

The role of conduction band electrons in promoting O2 adsorption to silicon interfaces

Resonance enhanced Second Harmonic Generation (SHG) was employed to assess if conduction band electrons in silicon (Si) will promote molecular adsorption of ambient species and how such adsorption depends on temperature. Experiments were performed with three types of Si (n-doped or n-Si, p-doped or p-Si, and undoped Si) at temperatures between 18 and 260 °C and under atmospheres of dry N2 and dry (cylinder) air. All Si types were covered with a 2–4 nm thick native oxide layer. Under N2, all Si types behave similarly, with SHG intensity [I(2ω)] diminishing with increasing temperature. This effect was reversible and attributed to electron–phonon scattering. In the presence of O2, I(2ω) from n-Si at room temperature is enhanced significantly. Neither p-doped Silicon (p-Si) nor undoped Si show similar effects at room temperature, with I(2ω) being independent of gas phase composition. At temperatures ≥175 °C, all three Si types behaved similarly with no dependence on atmospheric O2 content. Varying the amount of O2 above n-Si at room temperature and measuring I(2ω) suggested that O2 adsorption to n-Si could be described with a Langmuir isotherm and an adsorption energy of −0.13 ± 0.05 eV. Increasing n-Si’s oxide thickness (to 600 nm) rendered the substrate insensitive to ambient gas phase composition. Taken together, these findings support a description of Si’s surface electronic structure that is controlled by n-Si conduction band electrons backbonding into the π* orbitals of adjacent O2 and imply that these conduction band electrons can affect adsorption despite the presence of a native oxide film.

Oxidation behavior of (Hf0.2Zr0.2Ta0.2Ti0.2Me0.2)B2 (Me=Nb,Cr) high-entropy ceramics at 1200 °C in air

The oxidation behavior of (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2 and (Hf0.2Zr0.2Ta0.2Cr0.2Ti0.2)B2 high entropy boride ceramics at 1200 °C was investigated to provide insights into their microstructural evolution and oxidation mechanism. The results showed that the oxide layer thickness of (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2 was about 112 μm, much thicker than the counterpart of (Hf0.2Zr0.2Ta0.2Cr0.2Ti0.2)B2 (∼62 μm). The differences in oxidation response and oxidation resistance between these two material systems were mainly pertained to the generation of different structures of oxide layer. For the (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2 sample, the oxide layer was composed of four-layer structure (porous-dense-porous-dense). In contrast, the oxide layers of (Hf0.2Zr0.2Ta0.2Cr0.2Ti0.2)B2 sample exhibited a distinctly laminated structure.

Achieving enhanced electroless Ni-P plating on 6H-SiC substrate through optimization of plasma activation durations

This study explores the impact of plasma activation on the surface properties of 6H-SiC substrates and the subsequent characteristics of electroless nickel‑phosphorus (NiP) plating. The research investigates how varying plasma activation durations influence surface roughness, chemical composition, and plating adhesion. Plasma activation significantly increased surface roughness from 592 nm to 772 nm and the oxidation layer thickness from 5.76 nm to 32.2 nm. These changes were accompanied by corresponding decreases in water and NiP solution contact angles, indicating enhanced surface wettability. The electroless NiP plating demonstrated a progressive increase in surface roughness, and the Ra roughness reached 1319 nm. X-ray diffraction (XRD) analysis revealed a reduction in the crystallinity of the NiP layer, alongside the emergence of new phases such as Ni2P and Ni8P3, indicating alterations in the structural and chemical composition of the plating. The average thickness of the NiP plating decreased from 39.70 μm at 10 min of plasma activation to 36.12 μm at 30 min, suggesting a potential reduction in deposition efficiency with prolonged activation times. Additionally, the hardness of the NiP layer exhibited a decline from 525 HV to 502 HV, attributed to increased surface oxidation and defect formation. The adhesion quality of the plating also deteriorated with increased plasma activation time, as evidenced by significant peeling and cracking, as observed in the scratch test.

Study on Surface Quality Analysis of an Uncoated Boron Steel and Its Oxide Layer Suppression Method for Hot Stamping.

This study investigates the effects of hot stamping on boron steel surface properties, comparing uncoated steel to Al-Si-coated steel, with a focus on developing atmosphere-controlled hot stamping technology. Experiments using a hat-shaped specimen revealed that uncoated steel formed a thick oxide layer due to exposure to atmospheric oxygen at high temperatures, negatively impacting surface quality and weldability. In contrast, the Al-Si-coated steel showed no oxide formation. Although uncoated steel exhibited higher average Vickers hardness, the detrimental effects of the oxide layer on weld quality necessitate advancements in process technology. A lab-scale hot stamping simulator was developed to control atmospheric oxygen levels, utilizing a donut-shaped induction heating coil to heat the material above 1000 °C, followed by rapid cooling in a forming die. Results demonstrated that maintaining oxygen concentrations below 6% significantly reduced oxide layer thickness, with near-vacuum conditions eliminating oxide formation altogether. These findings emphasize the critical role of oxygen control in enhancing the surface quality and weldability of uncoated boron steel for ultra-high-strength automotive applications, potentially reducing manufacturing costs while ensuring part performance.

Preparation and performance of C/Ta4HfC5-SiC composite fabricated by PIP combined with RMI process

Based on self-made Ta4HfC5 precursor, C/Ta4HfC5-SiC composite material were prepared by precursor impregnation and pyrolysis (PIP) combined with reactive melting infiltration (RMI) process. The density and open porosity of C/Ta4HfC5-SiC composite material are 2.71 ± 0.73 g/cm3 and 7.07 ± 1.29 %, respectively. Pores are distributed at multiple levels, including primarily nanopores below 40 nm, micropores between 0.04 and 8.5 μm, and a small number of macropores between 10 and 285 μm. The Ta4HfC5 phase exists in two forms: dispersed particles in the matrix and a "layered interface" on the surface of fibers within the bundle. The average bending strength, elastic modulus and fracture toughness of C/Ta4HfC5-SiC composite are 84.24 ± 8.71 MPa, 16.13 ± 5.42 GPa and 3.62 ± 0.63 MPa m1/2, respectively, showing a clear brittle fracture mode during the test. The line ablation rate and mass ablation rate of 60 s assessed by the oxyacetylene flame were 7.20 ± 0.35 μm/s and 10.84 ± 0.84 mg/s, respectively. The oxidation products such as Ta2O5, HfO2, Ta(Hf)CxOy formed by Ta4HfC5 phase during ablation present as thicker oxide layers, forming the main anti-ablation components.

An Innovative Fuel Design for HTGRs: Evaluating a 10-Hour High-Temperature Oxidation of the SiC Fuel Matrix During Air Ingress Accident Conditions

Preventing severe corrosion incidents caused by air ingress accidents in high-temperature gas-cooled reactors (HTGRs) while improving heat removal efficiency from the core is of paramount importance. To enhance both safety and efficiency, a sleeveless silicon carbide (SiC)-matrix fuel compact has been proposed. This study evaluates the 10-hour oxidation of reaction-sintered SiC (RS-SiC)-matrix fuel compact under the conditions of an air ingress accident within the temperature range of 1000 to 1400 °C. The oxidation tests were conducted in a stagnant air environment without flow. As a result, it is demonstrated that RS-SiC exhibits exceptional resistance to air oxidation up to 1400 °C, as shown by the thermogravimetric analysis (TGA), with minimal mass loss due to the oxidation of free carbon. Scanning electron microscopy with energy-dispersive X-Ray spectroscopy (SEM–EDX) analysis reveals that the morphology and thickness of the SiO2 layer formed on the RS-SiC surface vary with temperature. At 1400 °C, uniform oxide layer thickness ranging from 1.59 to 4.10 μm and localized nodule-like oxide formations of approximately 10 μm are observed. In contrast, at 1000–1200 °C, thinner oxide layers are identified, indicating that oxide growth accelerates at higher temperatures. The oxidation rates measured provide insights into the mechanisms of oxide growth.

Nanosecond pulsed laser coloring of the CrMnFeCoNi high entropy alloy

High-entropy alloys (HEAs) possess great potential for applications in the aerospace and military fields due to their excellent performance. Surface coloring can endow HEAs diverse functions. However, achieving a multi-color surface with minimal surface damage and cost remains a significant challenge. In this study, surface coloring of the CrMnFeCoNi HEA was attempted by nanosecond pulsed laser irradiation in air, and the multi-color surface was achieved. The evolution of surface color and morphology with laser parameters was analyzed. Then, five typical colors were selected, and the corresponding morphologies and chemical compositions were characterized by various techniques. The results showed that the change in oxide layer thickness as well as the formation of chromium-rich β-spinel and Cr (VI) compounds induced noticeable changes in surface color. Accordingly, complex surface patterns with various stable colors were prepared on the HEA surface, demonstrating the potential application of nanosecond pulsed laser coloring of HEAs.

Study on the fretting wear performance of oxide layer and Cr coating on zirconium alloy in high-temperature water

Grid-to-rod fretting wear is an important factor causing the fuel failure in nuclear power plants. Accident tolerant fuel (ATF) Cr coating and oxide ceramic coating have been developed to improve the fretting wear performance. In this research, two different oxide layers and Cr coating were prepared on zirconium (Zr) alloy, and the fretting wear performance were studied. The morphology, microstructure, tribo-corrosion reaction, and wear characteristics were analyzed. The oxide layer formed at high-temperature pressurized water (HTPW) has the lowest wear rate of 0.11 × 103 μm3/Nm due to the high hardness and compact structure, which leads to the corresponding friction pairs presenting the highest wear rate of 8.42 × 103 μm3/Nm. The wear depth of oxide layer formed at HTPW is about 5 times lower than that of as-received Zr alloy, and it is also less than the thickness of oxide layer. The oxide layer formed at HTPW after fretting has a larger thickness than the initial state because the plastic deformation layer caused by shear stress can quickly oxidize to zirconia in high-temperature water, and the wear rate of oxide layer is lower than the formation rate of oxide layer. The wear mechanism of two different oxide layers is delamination and abrasive wear, and that of Cr coating is abrasive wear and fatigue wear.

Oxidation anisotropy of 4H-SiC wafers during chemical-mechanical polishing

4H silicon carbide (4H-SiC) wafers are widely used in high-power, high-temperature, and high-frequency electronics owing to their excellent physical and electrical properties. In the processing of 4H-SiC wafers, chemical-mechanical polishing (CMP) is commonly employed to realize atomic-scale smoothness, damage-free surface, and global planarization. The CMP process is the synergy of wet oxidation and mechanical grinding, whose efficiency significantly relies on the oxidation process. Therefore, understanding the wet oxidation mechanism of Si face and C face of 4H-SiC wafers is critical to high-efficiency double-side CMP. In this work, the anisotropic CMP performance of Si face and C face of 4H-SiC wafers are investigated. It has been found that the material removal rate of the C face is 2–3 times that of the Si face. The thicknesses of the transient oxide layer on the C face and Si face are 8.71 nm and 3.50 nm, respectively. X-ray photoelectron spectroscopy analysis reveals that the oxygen content on the C face is higher than that on the Si face after wet KMnO4 oxidation. This indicates that the C face of 4H-SiC is easier to oxidize, which results in more oxides that that on the Si face of 4H-SiC. Our work shows that accelerating the oxidation of the Si face of 4H-SiC wafers during the simultaneous double-sided CMP process is crucial for the efficient polishing of 4H-SiC wafers.

Evaluation of the corrosion and oxidation resistance of NiCoCrAlY cladding on CMSX-4 by laser cladding

This study uses laser cladding to investigate the hot corrosion and oxidation behavior of CMSX-4 claddes with NiCoCrAlY powder. High-temperature oxidation tests were conducted at 1050°c for 50, 100, 150, and 200 h on 4 samples, while 6 samples underwent hot corrosion testing at 850°c for 6 h. The innovative application of laser cladding enables the creation of a γ′ and β interdendritic phase microstructure. High-temperature oxidation tests reveal a growth rate of 0.05 μm/h in oxide layer thickness between 50 and 200 h, accompanied by a surface weight increase rate of approximately 0.8 mg/cm2.h. The oxide layer's regeneration, continuity, and density are observed at 200 h, highlighting the innovative potential of this technique. Fracture oxidation is observed at 150 h in some TGO layer regions, but at 200 h of oxidation, the TGO layer's regeneration, continuity, and dense TGO was observed at the cladding interface. The TGO forms at 1050°c consist of Al2O3, Cr2O3, and CoO oxides, with Al2O3 as the main oxide phase. The study's findings demonstrate the ability of laser cladding to enhance the thermal protection of CMSX-4, showcasing a promising innovation in the field.

Effect of H2S on the corrosion behavior of austenitic and martensitic steels in supercritical CO2 at 550 °C and 20 MPa for Brayton cycle system

Corrosion of alloy materials significantly influences the stability and efficiency of the supercritical carbon dioxide (S-CO2) Brayton cycle. In this study, we investigated the corrosion behavior of the austenitic alloy SP2215 and the martensitic alloy X19CrMoNbVN11-19 (X19) in S-CO2 at 550°C and 20 MPa. The effect of impurities, H2S, on corrosion behavior was studied. After 900 hours, SP2215 formed a 1.1 μm thick oxide layer (Cr2O3). X19 formed a loose and porous double oxide layer of 4.1 μm (outer: Fe3O4, inner: FeCr2O4). After H2S doping, SP2215 had an oxide layer of 6.2 μm (FeS, SiO2, and Cr2O3), while X19 was 9.8 μm (outer: Fe3O4, SiO2, FexSy and Fe2O3, inner: FeCr2O4, Fe2SiO4 and Cr2S3). Metal sulfides formed and the corrosion layer thickened. This indicates that H2S not only changes the corrosion mechanism but also aggravates the corrosion. However, the corrosion of CO2 is dominant. SP2215 has better corrosion resistance than X19.

Bond-associated non-ordinary state-based peridynamics for simulating damage evolution of thermal barrier coatings in aero-engine turbine blades

The failure mode of thermal barrier coatings (TBC) systems in aeroengine turbine blades is very complex because of the harsh service conditions. A peridynamic (PD) model is established to simulate the damage evolution of TBC with uniform thermally grown oxide (TGO) growth under cycle load. The peridynamic differential operator is introduced to solve the zero-energy mode, and thermo-elastic deformation is considered. Moreover, the influence of high-temperature holding time, initial oxide layer thickness, and interface morphology on the evolution of the stress distribution and interface damage is discussed. The newly proposed PD model can effectively capture the interface cracking of TBC systems and it is conducive to the study of the failure of TBC systems.

Controlling the digital-to-analog switching in HfO2-based memristors via modulating the oxide thickness

The HfO2-based memristors have been acknowledged as a highly potential candidate for nonvolatile memory and neuromorphic computing applications. However, the analog resistive switching behavior of the HfO2-based memristors still needs improvement. In this work, Cu/HfO2/Pd devices with different oxide layer thicknesses were prepared by the magnetron sputtering process. The resistance switching characteristics related to oxide layer thickness were explored, revealing significant differences in the forming, SET, and RESET characteristics depending on oxide thickness. The conduction mechanism of the Cu/HfO2/Pd memristors is mainly attributed to the space charge limited current (SCLC) model. Thinner devices tend to show a more abrupt SET behavior and larger SET voltage, while thicker devices exhibit more gradual SET behavior and a lower SET voltage. In addition, as the thickness of the oxide layer increases, the Cu/HfO2/Pd memristors transition from digital resistive switching to analog resistive switching. The formation and rupture of oxygen vacancy filaments are predominant in thicker device, and the shape of the conduction filaments has been proposed as responsible for the abrupt and gradual changes in resistive switching. This work demonstrates that the thickness of the oxide layer plays an important role in engineering digital logic and neuromorphic behavior in HfO2-based memristors.

Surface Structure Formation in Plasma Cutting of Aluminum and Titanium Alloys Using Direct Current Straight and Reverse Polarity

Abstract The structural features and phase composition are examined in near-surface layers of specimens of Al-Mg, Al-Cu-Mg alloys and commercially pure titanium obtained by plasma cutting using direct current straight polarity (DCSP) and direct current reverse polarity (DCRP). It is found that the flows of molten metal ejected by the gas stream from the cut cavity during cutting form the fusion and heat-affected zones, whose structural morphology, phase composition, and thickness depend on both the selected material and the cutting mode. The fusion zone is thicker in specimens cut using DCRP than in those cut with DCSP. The thickness of the adjacent heat-affected zone is also the largest in the mode that provides a thicker fused layer. Aluminum alloy specimens cut in ambient air are characterized by the presence of oxygen in the near-surface layers. The lowest degree of oxidation is observed in Al-Mg alloy. Oxygen penetrates into the fused layer to a depth of 350–500 μm in Al-Cu-Mg and up to 200–250 μm in Al-Mg alloy. In titanium alloy, the thickness of oxide layers does not exceed 100–150 μm during straight polarity cutting and 200–250 μm during reverse polarity cutting. A thin brittle layer of TiO and TiO2 oxides is formed on the titanium alloy surface. It is shown that the generation of “water mist” around the plasma jet when cutting materials of all types with DCRP leads to a more intensive oxidation of metal, less thermal effect on the material, and reduced roughness of the cut face.

Oxidation behavior and failure mechanisms of enamel coatings at different temperature

This work studies the prolonged high-temperature oxidation behavior and failure mechanisms of enamel coatings at three distinct temperatures: 600 °C, 800 °C, and 1000 °C. The evolution of the coating’s microstructural morphology was characterized, and the kinematics of porosity, crystal precipitation, and oxide layer thickness were measured. The results indicated that at 600 °C and 800 °C, the coatings exhibit strong oxidation resistance and retain their mechanical integrity. However, at 1000 °C, the coatings rapidly deteriorate due to formation of Cr microcrystalline bands and the diffusion of oxidation layer, leading to volume expansion and element segregation. These factors result in the formation of voids and stress concentrations. The precipitation of crystals further exacerbates localized stress and microcracks, increasing the brittleness and enlarging the stress concentration areas, ultimately causing coating spallation. The effects of cooling rate on the long-term oxidation lifetime of the coatings were also examined. The findings of this work suggest that the temperatures below 800 °C are suitable for long-term application of the enamel coatings, while exposure to 1000 °C results in their rapid failure.

Low-frequency noise in the Double SOI (DSOI) MOSFETs with back-gate control

In this paper, the impact of the back-gate voltage (Vb ) on the low-frequency (1/f) noise is evaluated for the 180 nm double silicon-on-insulator (DSOI) NMOS, fabricated with various thicknesses of first buried oxide (BOX1) layer (145/50 nm). Both positive and negative Vb increased the measured normalized drain current power spectral density (PSD) for more than ten-fold in DSOI standard devices with 145 nm BOX1, while the normalized PSD decreases with Vb going up in devices with 50 nm BOX1. By comparing with CNF+CMF model, interface trap density and the Coulomb scattering coefficient are extracted with the back-gate voltage applied. The interface trap density increases in standard devices for both positive and negative Vb , but decreases with increasing back-gate biasing from -10 V to 10 V in devices with 50 nm BOX1. The interface trap density shows a similar back-gate coupling effect with threshold voltage under the influence of different thickness of BOX1. The CNF and CMF noise variation under back-gate voltage can be explained by the significant fluctuation in drain current.

Hydrodynamic Flexible Spindle (HydroFlex) Polishing of turbine blade internal cooling channels for oxide removal

Internal cooling channels are essential to turbine blades for high efficiency power generation. Effective removal of aluminum oxide build-up in turbine blade cooling channels is of critical importance to refurbishment and prolonged service life of turbine blades. Conventional internal polishing processes, including abrasive flow machining, chemical polishing, and electrical discharge machining cannot effectively remove the oxide layer within the internal cooling channels due to the complex geometry with high aspect ratio and diameter variation and the electric insulation of the oxide layer. In this case study, we investigated the application of a novel hydrodynamic flexible-spindle (HydroFlex) polishing process to remove the oxide layer within the internal cooling channels of an Inconel 738 turbine blade that was taken out of serve due to oxide build-up. For a 350 mm long cooling channel featured with an inner diameter transition from ϕ4 mm to ϕ2.5 mm, within 12 min, at the grinding wheel rotational speed of 50,000 rpm and 30,000 rpm, HydroFlex was able to completely remove the 14.31 µm thick oxide layer off from the wall of the turbine blade internal cooling channel, improve the channel circularity by 54.7 %, and decrease the channel surface roughness by up to 64.3 %. The results demonstrated the effectiveness of HydroFlex in polishing complex internal cooling channels of turbine blades for oxide removal and potential blade service life extension.