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The purpose of this investigation was to determine the optimal conditions for UNS N08367 electropolishing using the Taguchi method. The investigated factors were the electrolyte composition ratio, applied current density, and electrolyte temperature. Each factor was tested at three levels. Electropolishing was optimized using analysis of variance (ANOVA), signal-to-noise ratio (the smaller the better the characteristics), and surface analysis. The ANOVA results showed that among the three factors, only the electrolyte composition ratio was effective in surface planarization. The optimal conditions for electropolishing determined according to the signal-to-noise ratio were a sulfuric acid-to-phosphoric acid ratio of 2:8, a current density of 400 mA/cm2, and an electrolyte temperature of 75 °C.

Stainless steel, which is used in metallic bipolar plates, is generally known to have excellent corrosion resistance, which is achieved by forming oxide films. However, localized corrosion occurs when the oxide films are destroyed by pH and chloride ions. Particularly, since the operating condition of polymer electrolyte membrane fuel cells (PEMFCs) is strongly acidic, the reduced stability of the oxide films leads to the corrosion of the stainless steel. In this research, the electrochemical characteristics of 304L and 316L stainless steels were investigated in an accelerating solution that simulated the cathode condition of PEMFCs with chloride concentrations. Results under all experimental conditions showed that the corrosion current density of 304L stainless steel was at least four times higher than that of 316L stainless steel. Maximum damage depth was measured at 6.136 μm and 9.192 μm for 304L stainless steel and 3.403 μm and 5.631 μm for 316L stainless steel for chloride concentrations of 0 and 1000 ppm, respectively. Furthermore, 304L and 316L stainless steels were found to have uniform and localized corrosion, respectively. The differences in the electrochemical characteristics of 304L and 316L stainless steel are considered to be due to the molybdenum contained in the chemical composition of 316L stainless steel.

We report a new strategy, namely solvent-assisted curing, for developing a porous network into polymeric materials.

This study aims to predict the strength of AISI 316L steel for offshore structures due to damage to the pitting using multiple linear regression and analysis of variance. The potentiostat accelerated method was applied to cause artificial pitting damage in a 3.5% NaCl solution of pH 2 at 60 °C. The pitting damage occurred under conditions perpendicular to gravity direction, such as on a wall structure. Each pitting was measured with various parameters. Among them, the pitting intensity and mean depth were found to be significant in the 95% confidence level. It means that pitting intensity and mean depth are the greatest influencer on strength value. A multiple linear regression model was proposed for strength prediction using significant pitting parameters, and evaluated by the coefficient of determination (R2 value). As a result, the model showed a high fitness for the data (R2 = 0.8873) and considerable prediction performance.

Togni reagent II is a synthetically useful hypervalent iodine reagent for direct trifluoromethylation. Herein, we report a new reaction of Togni reagent II: α-C–H ester-functionalization of tertiary amides. This α-acyloxylation reaction proceeds smoothly in the presence of a mild base at 25–30 oC and produces moderate-to-high yields. This newly discovered reaction adds another dimension to the utility of Togni reagent II and provides direct and easy access to α-acyloxy amides and α-hydroxy amides.

Capparis spinosa L., commonly known as the caper bush, is a spiny shrub known for its edible flower buds and its use as a medicinal plant in traditional medicine. While performing bio-guided isolation of active compounds from Capparis spinosa L. leaves and buds, large amounts of bis(2-ethylhexyl) terephthalate (DEHT, a.k.a. dioctyl terephthalate or DOTP) and bis(2-ethylhexyl) phthalate (DEHP) were isolated from a fraction from the leaf extract that showed antifungal activity against Cryptococcus neoformans. The structures of these two compounds were confirmed by NMR and mass spectroscopic data, which matched with those from the standards that were purchased from Sigma-Aldrich. DEHT and DEHP are phthalic and terephthalic acid esters, the main plasticizers that are used to confer elasticity and flexibility to various fiber and plastic products. This is the first time DEHT and DEHP have been isolated from the leaves of a plant that is as commonly used as Capparis spinosa L. This study adds to the increase in the detection of plasticizers in our food and medicine sources and to the alarming concern about the potential effects of these compounds on human health.

The sensitization and passivation characteristics of AL-6XN heat-treated for up to 24 h at 800 °C were evaluated through double loop electrochemical potentiodynamic reactivation (2 M H2SO4 + 0.01 M KSCN +2 M NaCl solution) and cyclic potentiodynamic polarization (3.5% NaCl solution) test methods. Furthermore, the dependence between the characteristic values (Epit, Erep, and degree of sensitization) was discussed. The σ phase was precipitated at the intergranular and intragranular in AL-6XN at 800 °C. When the heat treatment time exceeded 1 hour, AL-6XN occurred rapid sensitization due to the precipitation of σ phase. In a 3.5% NaCl solution, the passivation characteristics of AL-6XN with sensitivity were very poor and depended much on the degree of sensitization.

In cancer cells, glutaminolysis is the primary source of biosynthetic precursors. Recent efforts to develop amino acid analogues to inhibit glutamine metabolism in cancer have been extensive. Our lab recently discovered many L-γ-methyleneglutamic acid amides that were shown to be as efficacious as tamoxifen or olaparib in inhibiting the cell growth of MCF-7, SK-BR-3, and MDA-MB-231 breast cancer cells after 24 or 72 h of treatment. None of these compounds inhibited the cell growth of nonmalignant MCF-10A breast cells. These L-γ-methyleneglutamic acid amides hold promise as novel therapeutics for the treatment of multiple subtypes of breast cancer. Herein we report our synthesis and evaluation of two series of tert-butyl ester and ethyl ester prodrugs of these L-γ-methyleneglutamic acid amides and the cyclic metabolite and its tert-butyl esters and ethyl esters on the three breast cancer cell lines MCF-7, SK-BR-3, and MDA-MB-231 and the nonmalignant MCF-10A breast cell line. These esters were found to suppress the growth of the breast cancer cells, but they were less potent compared to their parent L-γ-methyleneglutamic acid amides. Pharmacokinetic (PK) studies were carried out on the lead L-γ-methyleneglutamic acid amide to establish tissue-specific distribution and other PK parameters. Notably, this lead compound showed moderate exposure to the brain with a half-life of 0.74 h and good tissue distribution, such as in the kidney and liver. Therefore, the L-γ-methyleneglutamic acid amides were then tested on glioblastoma cell lines BNC3 and BNC6 and head and neck cancer cell lines HN30 and HN31. They were found to effectively suppress the growth of these cancer cell lines after 24 or 72 h of treatment in a concentration-dependent manner. These results suggest broad applications of the L-γ-methyleneglutamic acid amides in anticancer therapy.

Excellent thermal and mechanical properties of aromatic polyimides (PIs) make them attractive materials in various fields. PIs is performed using polyamic acid (PAA) precursors due to their limited solubility. However, PAAs can be easily depolymerized by moisture and heat, which can degrade the properties of PIs. Therefore, quality control of PAAs is an important task in researches and industrial applications. Here, we propose a simple, rapid, and novel method to observe the depolymerization of PAAs. The method is based on the principle that, as the molecular weight of the polymer decreases, the solution viscosity decreases, and the viscosity of the solution can be easily and rapidly measured using electrochemistry. We accelerated depolymerization by applying heat to a PAA solution and measured the change in viscosity of the solution through cyclic voltammetry. The proposed method, which also makes it possible to determine the dynamic viscosity of a polymer solution, is presented as a model system to observe state changes in various polymers.

Upconversion materials (UCMs) have been developed to convert tissue-penetrating near-infrared (NIR) light into visible light. However, the low energy conversion efficiency of UCMs has limited their further biophotonic applications. Here, we developed controlled afterglow luminescent particles (ALPs) of ZnS:Ag,Co with strong and persistent green luminescence for photochemical tissue bonding (PTB). The co-doping of Ag+ and Co2+ ions into ZnS:Ag,Co particles with the proper vacancy formation of host ions resulted in high luminescence intensity and long-term afterglow. In addition, the ALPs of ZnS:Ag,Co could be recharged rapidly under short ultraviolet (UV) irradiation, which effectively activated rose bengal (RB) in hyaluronate-RB (HA-RB) conjugates for the crosslinking of dissected collagen layers without additional light irradiation. The remarkable PTB of ZnS:Ag,Co particles with HA-RB conjugates was confirmed by in vitro collagen fibrillogenesis assay, in vivo animal wound closure rate analysis, and in vivo tensile strength evaluation of incised skin tissues. Taken together, we could confirm the feasibility of controlled ALPs for various biophotonic applications.

Despite wide investigation on molecular imaging contrast agents, there are still strong unmet medical needs to enhance their signal-to background ratio, brightness, photostability, and biocompatibility with multimodal imaging capability. Here, we assessed the feasibility of fluorescent nanodiamonds (FNDs) as carbon based photostable and biocompatible materials for molecular imaging applications. Because FNDs have negatively charged nitrogen vacancy (NV) centers, they can emit bright red light. FNDs were conjugated to hyaluronate (HA) for target-specific molecular imaging. HA is a biocompatible, biodegradable, and linear polysaccharide with abundant HA receptors in the liver, enabling liver targeted molecular imaging. In vitro cell viability tests revealed the biocompatibility of HA–FND conjugates and the competitive cellular uptake test confirmed their target-specific intracellular delivery to HepG2 cells with HA receptors. In addition, in vivo fluorescence lifetime (FLT) assessment revealed the imaging capability of FNDs and HA–FND conjugates. After that, we could confirm the statistically significant liver-targeted delivery of HA–FND conjugates by in vivo imaging system (IVIS) analysis and ex vivo biodistribution tests in various organs. The renal clearance test and histological analysis corroborated the in vivo biocompatibility and safety of HA–FND conjugates. All these results demonstrated the feasibility of HA–FND conjugates for further molecular imaging applications., Fluorescent nanodiamond conjugated with hyaluronate is developed as a carbon based photostable and biocompatible material for liver-targeted molecular imaging applications.

In this investigation, potentiodynamic polarization experiments were conducted on UNS S31603 and UNS N08367 in a modified green death solution, which simulates the environment of a desulfurization device (scrubber), using temperature as a variable. A Tafel analysis showed that the corrosion current density of UNS S31603 at the highest temperature (90 °C) was approximately 4.5 times higher than that of UNS N83067. A surface analysis using a scanning electron microscope revealed that pitting and intergranular corrosion occurred simultaneously in UNS S31603, whereas UNS N83067 exhibited a stronger tendency toward intergranular corrosion. After electrochemical experiments, the corrosion rates according to maximum damage depth were compared with the corrosion rates according to corrosion current density; the relationships between the two values were expressed as α values. The α values of UNS N08367 were higher than those of UNS S31603, indicating that the local damage rate of UNS N08367 was higher.

In this research, titanium nitride (TiN) was applied to grade 1 titanium as a bipolar plate for a proton exchange membrane fuel cell (PEMFC). The TiN was deposited by the arc ion plating method (AIP) to investigate the electrochemical characteristics of the anode and cathode environments in the PEMFC. The corrosion experiments were conducted in an aqueous solution of pH 3 (H2SO4 + 0.1 ppm HF, 80 °C) determined by the Department of Energy (DoE). The hydrogen gas and air were bubbled to simulate the anode and cathode environments. The potentiodynamic polarization experiment showed that there was no active peak. The potentiostatic experiment showed that the current densities of the TiN-coated specimens were less than 1 μA/cm2 in both the anode and cathode. As a result of observing the surface with an SEM before and after the potentiostatic experiment, only pinholes generated during the coating process were observed, and no corrosion damage was observed. Furthermore, electrochemical impedance spectroscopy (EIS) analysis showed that the coated specimens had a higher charge transfer resistance than the titanium substrate. In the case of interfacial contact resistance (ICR), the TiN-coated specimen displayed lower resistance than the titanium substrate and satisfied the DoE technical target of less than 10 mΩ·cm2 at 140 N/cm2.

Magnesium (Mg) and its alloys have presented a paradigm for biodegradability in the field of biomedical devices. However, biodegradation of Mg and its alloys cause the formation of hydrogen gas and...

In this paper, we studied the effects of the intersection angle between the inlet channels on the droplet diameter using a COMSOL Multiphysics® simulation. We employed the level-set method to study the droplet generation process inside a microfluidic flow device. A flow-focusing geometry was integrated into a microfluidics device and used to study droplet formation in liquid–liquid systems. Droplets formed by this flow-focusing technique are typically smaller than the upstream capillary tube and vary in size with the flow rates. Different intersection angles were modeled with a fixed width of continuous and dispersed channels, orifices, and expansion channels. Numerical simulations were performed using the incompressible Navier–Stokes equations for single-phase flow in various flow-focusing geometries. As a result of modeling, when the dispersed flow rate and the continuous flow rate were increased, the flow of the continuous flow fluid interfered with the flow of the dispersed flow fluid, which resulted in a decrease in the droplet diameter. Variations in the droplet diameter can be used to change the intersection angle and fluid flow rate. In addition, it was predicted that the smallest diameter droplet would be generated when the intersection angle was 90°.

The kappa opioid receptor (KOR) is involved in the regulation of both the reward and mood processes. Recent reports find that the use of drugs of abuse increases the production of dynorphin and overall activation of KOR. Long-acting KOR antagonists, such as norbinaltorphimine (nor-BNI), JDTic, and 5'-guanidinonaltrindole (GNTI), have been shown to stop depressive and anxiety-related disorders, which are the common side effects of withdrawal that can lead to the relapse in drug use. Unfortunately, these prototypical KOR antagonists are known to induce selective KOR antagonism that is delayed by hours and extremely prolonged, and their use in humans comes with serious safety concerns because they possess a large window for potential drug-drug interactions. Furthermore, their persistent pharmacodynamic activities can hinder the ability to reverse unanticipated side effects immediately. Herein we report our studies of the lead selective, salvinorin-based KOR antagonist (1) as well as nor-BNI on C57BL/6N mice for spontaneous cocaine withdrawal. Assessment of pharmacokinetics showed that 1 is a short-acting compound with an average half-life of 3.75 h across different compartments (brain, spinal cord, liver, and plasma). Both 1 (5 mg/kg) and nor-BNI (5 mg/kg) were shown to reduce spontaneous withdrawal behavior in mice, with 1 producing additional anti-anxiety-like behavior in a light-dark transition test (however, no mood-related effects of 1 or nor-BNI were observed at the current dosing in an elevated plus maze or a tail suspension test). Our results support the study of selective, short-acting KOR antagonists for the treatment of psychostimulant withdrawal and the associated negative mood states that contribute to relapse. Furthermore, we identified pertinent interactions between 1 and KOR via computational studies, including induced-fit docking, mutagenesis, and molecular dynamics simulations, to gain insight into the design of future selective, potent, and short-acting salvinorin-based antagonists.

The purpose of this study was to identify the characteristics of blood flow in aortic coarctation based on stenotic shape structure, stenosis rate, and the distribution of the wall load delivered into the blood vessels and to predict the impact on aneurysm formation and rupture of blood vessels by using a computational fluid dynamics modeling method. It was applied on the blood flow in abdominal aortic blood vessels in which stenosis occurred by using the commercial finite element software ADINA on fluid-solid interactions. The results of modeling, with an increasing stenosis rate and Reynolds number, showed the pressure drop was increased and the velocity was greatly changed. When the stenosis rate was the same, the pressure drop and the velocity change were larger in the stenosis with a symmetric structure than in the stenosis with an asymmetric one. Maximal changes in wall shear stress were observed in the area before stenosis and minimal changes were shown in stenosis areas. The minimal shear stress occurred at different locations depending on the stenosis shape models. With an increasing stenosis rate and Reynolds number, the maximal wall shear stress was increased and the minimal wall shear stress was decreased. Through such studies, it is thought that the characteristics of blood flow in the abdominal aorta where a stenosis is formed will be helpful in understanding the mechanism of growth of atherosclerosis and the occurrence and rupture of the abdominal aortic flow.

Smart contact lenses for continuous glucose monitoring (CGM) have great potential for huge clinical impact. To date, their development has been limited by challenges in accurate detection of glucose without hysteresis for tear glucose monitoring to track the blood glucose levels. Here, long-term robust CGM in diabetic rabbits is demonstrated by using bimetallic nanocatalysts immobilized in nanoporous hydrogels in smart contact lenses. After redox reaction of glucose oxidase, the nanocatalysts facilitate rapid decomposition of hydrogen peroxide and nanoparticle-mediated charge transfer with drastically improved diffusion via rapid swelling of nanoporous hydrogels. The ocular glucose sensors result in high sensitivity, fast response time, low detection limit, low hysteresis, and rapid sensor warming-up time. In diabetic rabbits, smart contact lens can detect tear glucose levels consistent with blood glucose levels measured by a glucometer and a CGM device, reflecting rapid concentration changes without hysteresis. The CGM in a human demonstrates the feasibility of smart contact lenses for further clinical applications.

Current common analgesics are mediated through the mu or kappa opioid receptor agonism. Unfortunately, selective mu or kappa receptor agonists often cause harmful side effects. However, ligands exhibiting dual agonism to the opioid receptors, such as to mu and kappa, or to mu and delta, have been suggested to temper undesirable adverse effects while retaining analgesic activity. Herein we report an introduction of various 6,5-fused rings to C2 of the salvinorin scaffold via an ester linker. In vitro studies showed that many of these compounds have dual agonism on kappa and mu opioid receptors. In vivo studies on the lead dual kappa and mu opioid receptor agonist demonstrated supraspinal thermal analgesic activity while avoiding anxiogenic effects in male mice, thus providing further strong evidence in support of the therapeutic advantages of dual opioid receptor agonists over selective opioid receptor agonists.

Magnesium (Mg) and its alloys have presented a paradigm for biodegradability in the field of biomedical devices. However, biodegradation of Mg and its alloys cause the formation of hydrogen gas and basic molecules in the body. Here we developed a surface modification method for Mg implants by double-coating with osteogenic dexamethasone (Dex)-loaded black phosphorus (BP) and poly(lactide

In this study, electroless nickel (EN) plating was performed with stabilizer concentration to improve cavitation erosion resistance of gray cast iron under marine environment. Cavitation erosion tests were carried out in natural seawater solution in accordance with modified ASTM G32 . The change of stabilizer concentration affected the plating rate, P content, and average crystal size of EN coating. The decrease of the plating rate with the stabilizer concentration and the flake-shaped graphite exposed to the gray cast iron surface negatively affected the cavitation erosion and corrosion prevention. In particular, cavitation erosion damage of EN coating was accelerated due to combined galvanic corrosion when the EN coating was destroyed and the substrate was exposed under the cavitation erosion environment.

In this paper, the effect of lead nitrate stabilizer concentration on the electroless nickel (EN) plating properties of gray cast iron was investigated in a sulfuric acid plating bath. The specific critical stabilizer concentration was found to vary the EN coating properties. At the critical stabilizer concentration or more, plating rate and the chemical composition of the EN coating were changed because the deposition of Ni and P was inhibited by excessive stabilizer concentration. The surface morphology of the EN coating was strongly influenced by the plating rate change with the stabilizer concentration and the galvanic coupling effect due to the microstructure of the substrate. The crystallinity of the EN coating tended to increase with increasing stabilizer concentration. As a result, the EN plating properties of gray cast iron were greatly affected by the stabilizer concentration in the plating bath and the microstructure of the substrate.

Diabetic retinopathy is currently treated by highly invasive repeated therapeutic injections and surgical interventions without complete vision recovery. Here, a noninvasive smart wireless far red/near-infrared (NIR) light emitting contact lens developed successfully for the repeated treatment of diabetic retinopathy with significantly improved compliance. A far red/NIR light emitting diode (LED) is connected with an application-specific integrated circuit chip, wireless power, and communication systems on a PET film, which is embedded in a silicone elastomer contact lens by thermal crosslinking. After in vitro characterization, it is confirmed that the retinal vascular hyper-permeability induced by diabetic retinopathy in rabbits is reduced to a statistically significant level by simply repeated wearing of smart far red/NIR LED contact lens for 8 weeks with 120 µW light irradiation for 15 min thrice a week. Histological analysis exhibits the safety and feasibility of LED contact lenses for treating diabetic retinopathy. This platform technology for smart LED contact lens would be harnessed for various biomedical photonic applications.

Background: Wilson disease (WD) is a genetic disorder of copper storage, resulting in pathological accumulation of copper in the body. Because symptoms are generally related to the liver, chelating agents capable of capturing excess copper ions after targeted delivery to the liver are highly required for the treatment of WD. Methods: We developed hyaluronate - black phosphorus (HA-BP) conjugates for capturing copper ions accumulated in the liver for the treatment of WD.Results: HA-BP conjugates showed high hepatocyte-specific targeting efficiency, selective copper capturing capacity, excellent biocompatibility, and biodegradability. HA enhanced the stability of BP nanosheets and increased copper binding capacity. In vitro cellular uptake and competitive binding tests verified targeted delivery of HA-BP conjugates to liver cells via HA receptor mediated endocytosis. The cell viability test confirmed the high biocompatibility of HA-BP conjugates.Conclusion: HA-BP conjugates would be an efficient copper chelating agent to remove accumulated copper in the liver for the WD treatment.

This study investigated influence of sensitization on the mechanical properties of AISI 304 stainless steel. The small and tensile specimens were isothermally aged at 650 °C for up to 1000 hours. Microstructure and precipitates of these specimens were characterized by scanning electrode microscope with energy dispersive X-ray spectroscopy. The degree of sensitization of aged specimens was measured by double loop electrochemical potentiodynamic reactivation method. The tensile test was conducted to evaluate mechanical properties of these specimens. With the progress of aging, the degree of sensitization value drastically increased to more than 50% as Cr-rich carbides were precipitated in the austenite grain boundaries. Also, the mechanical properties were degraded, and fracture mode drastically changed from ductile to brittle. As a result, the surface damage and degradation of mechanical properties were correlated with the degree of sensitization value.

Electroless nickel plating (ENP) was performed to prevent the cavitation erosion damage of gray cast iron in the marine environment. The effect of the changes in the pH of a plating bath on the ENP coating characteristics, corrosion resistance and the cavitation erosion damage behavior in natural seawater were examined. The results showed that the pH of the plating bath had a significant effect on the plating rate, crystallinity, composition, and microhardness of the ENP coating. The corrosion resistance of ENP coating was greatly affected by the plating rate and the microstructure of the substrate. The cavitation erosion damage behavior depended on the crystallinity of the ENP coating. Once the substrate is exposed by the cavitation erosion of ENP coating, it is accompanied by galvanic corrosion, which accelerates the damage. Furthermore, the cavitation erosion damage mechanism of ENP coating was investigated.

In this study, the characteristics of cavitation-erosion resistance of 316L stainless steel after plasma ion nitriding at various temperatures were investigated in natural seawater. Plasma ion nitriding was performed with N₂ and H₂ at a ratio of 1:4 from 400 to 500 °C for 10 hours. Micro-Vickers hardness measurement showed that the mechanical properties were improved by increasing hardness due to the formation of expanded austenite (S-phase) at 400 °C and 450 °C and γ'-Fe₄N and CrN phases at 500 °C. In the cavitation-erosion test, weight loss and damage rate decreased with increasing nitriding temperatures up to 450 °C, while the depth of damage was found to be increased at 500 °C. The lowest weight loss and damage depth were obtained at 450 °C, which measured the thickest layer of γN phase. At 500 °C, cavitation-erosion damage was significantly occurred due to the internal residual stress accumulated during the plasma ion nitriding.

Anodization using an electrolyte, oxygen plasma method, chemical oxidation method and oxide coating method through CVD are generally used to generate oxide film. Among them, alloys other than pure metals are mainly used since anodization using aluminum is important for strength and workability. Even if an alloy is made of the same alloy, the film formation rate and characteristics greatly vary depending on the degree of dispersion of the additive element. In particular, anodization using an electrolyte has been studied for a long time in industrial applications and attracted attention in various fields because cost reduction, high productivity, and application to complex shapes are possible. In this study, electrochemical experiment was conducted to select the optimal surface modification current density to have excellent corrosion resistance in a marine environment using 5083-O aluminum alloy. The result of experiment showed that the current flow and the formation of a thick barrier layer affected the electrochemical characteristics according to the pore diameter; however, the corrosion current density was significantly lower when anodization was performed.

In this study, the oxidation and sulfidation characteristics of modified 9Cr 1Mo steels according to Cr-rich M23C6 distributed in grain boundaries in the N2-O2-CO2-SO2 atmosphere at 650 °C were analyzed. The oxidation kinetic was obeyed by the parabolic law. The oxide layer presented a three-layer structure consisting of hematite, magnetite, and Fe Cr spinel from the outside. In the initial oxidation stage, Cr-rich M23C6 exposed to the surface acted as nuclei of Cr-rich oxide. However, it is thought to hardly effect on the growth of the outer oxide layer. The Cr-rich M23C6 distributed in grain boundaries preferentially formed a Cr2O3 layer at the oxide/matrix interface, and internal oxidation characteristics were shown to be different depending on the presence or absence of SO2 in the atmosphere.