Outer TiO2 Layer Research Articles

Characteristics of oxide films on TA16 alloy after long-term exposure in simulated secondary circuit water environment of small modular reactor

Currently, little is known about the characteristics of oxide films on Ti alloys exposed to the secondary circuit water environment of small modular reactors (SMRs). In this study, multiple microstructural characterization techniques were employed to meticulously characterize the oxide film characteristics of the TA16 alloy after 6000 h and 8000 h of exposure to a simulated SMR secondary circuit water environment. The results indicate that the oxide films on the 6000 h specimen are composed of a microcrystalline anatase TiO2 interior layer and a coarse-grained anatase TiO2 exterior layer, while the oxide film on the 8000 h specimen typically consists of a microcrystalline anatase TiO2 inner layer, an NiFe2O4 middle layer, and a coarse-grained anatase TiO2 outer layer. As the corrosion time is extended to 8000 h, the presence of NiFe2O4 oxide particles can be attributed to oxide deposition by the 316L stainless steel autoclave used in the corrosion experiments, which results in the migration of Ni and Fe ions onto the surface of the Ti alloy.

Creating an extracellular matrix-like three-dimension structure to enhance the corrosion resistance and biological responses of titanium implants

Background/purposeTitanium (Ti) is extensively used in dental and orthopedic implants due to its excellent mechanical properties. However, its smooth and biologically inert surface does not support the ingrowth of new bone, and Ti ions may have adverse biological effects. The purpose is to improve the corrosion resistance of titanium and create a 3D structured coating to enhance osseointegration through a very simple and fast surface treatment. Materials and methodsThis study investigated the use of sandblasting, acid etching, and NaOH leaching to produce porous Ti implants with enhanced biological activity and corrosion resistance. ResultsThese surface modifications generated a mixed oxide layer resembling the extracellular matrix (ECM), consisting of a dense amorphous TiO2 inner layer (50–100 nm thick) and a TiO2 outer layer with interconnected pores (pore size 50–500 nm; 150–200 nm thick). The inner layer significantly improved corrosion resistance, while the hydrophilic outer layer, with its porous structure, facilitated protein albumin adsorption and promoted the attachment, proliferation, and mineralization of human bone marrow mesenchymal stem cells. ConclusionThe combined surface treatment approach of sandblasting, acid etching, and NaOH leaching offers a comprehensive solution to the challenges associated with titanium implants' biological inertness and corrosion susceptibility. By enhancing both the biological activity and corrosion resistance of Ti surfaces, this protocol holds significant promise for improving dental and orthopedic implants' success rates and longevity. Future studies should focus on in vivo assessments and long-term clinical trials to further validate these findings and explore the potential for widespread clinical adoption.

The static corrosion behaviors of gelcasted MAX phases in contaminated lead-bismuth eutectic (LBE) at 600 °C with low oxygen

The deployment of gelcasted MAX phase ceramic components in nuclear reactors is critical due to their exceptional performance. This study explores the corrosion behaviors of three gelcasted MAX phase ceramics (Ti3AlC2, Ti2AlC, and Ti3SiC2) in liquid lead-bismuth eutectic (LBE) at 600 °C under low oxygen conditions. Unique corrosion layers formed on the samples: Ti₃AlC₂ developed an Al2O3 inner layer and TiO2 outer layer, Ti₂AlC showed TiO2 grains coated with FeCr2O4 spinel, and Ti3SiC2 exhibited a composite layer of TiO2, Fe3O4, SiO2, PbO, and TiO2. LBE caused slight matrix enrichment in Ti₃AlC₂ and Ti₂AlC samples. Corrosion resistance was ranked as Ti3SiC2 > Ti3AlC2 > Ti₂AlC. Additionally, a coupled corrosion phenomenon resembling electrolytic electrodeposition between MAX phase ceramics and stainless steel was observed in contaminated LBE. This research provides novel insights into the corrosion mechanisms of MAX phases, paving the way for their application in advanced nuclear systems.

Investigation of scale formation and degeneration of silicide coating on Nb–Si based alloy in the temperature range from 1250 °C to 1560 °C

Nb silicide coatings modified with active elements have good oxidation resistance, but there is a lack of systematic research on their oxidation behavior at high temperatures above 1250 °C. The aim of this work is to investigate the oxidation behavior of an Al–Y modified silicide coating on Nb–Si based alloy in the temperature range from 1250 °C to 1560 °C. After oxidation at 1250 °C, the scale displays a typical layered structure consisting mainly of a TiO2 outer layer, an amorphous SiO2 matrix layer embedded with TiO2 and ZrSiO4, and an inner layer consisting of SiO2 and Cr2O3. Above 1350 °C, the evaporation reaction of Cr2O3 into CrO3 (g) is significantly accelerated and Cr2O3 disappeared gradually with temperature or time. The TiO2 layers covering on the scales formed at 1250–1500 °C grow along the crystallographic orientation of [100]. The micropores formed on the surface of TiO2 should be attributed to the further oxidation of Cr2O3 into volatile oxide CrO3 (g). The scales exhibit a similar structure consisting mainly of a SiO2 glass matrix embedded with ZrSiO4 and a surface TiO2 layer until 1500 °C. Above the eutectic temperature of SiO2–TiO2 system, the scale is mainly composed of a matrix layer of SiO2–TiO2 eutectic embedded with block TiO2 particles, and a thin SiO2 interface layer at 1560 °C. The degeneration path of the (Nb,X)Si2 coating is (Nb,X)Si2 → (Ti,Nb)5Si4 → γ-(Nb,X)5Si3.

TiC and (Ti,Nb)3SiC2 based dual-layer coating on SUS430 for solid oxide fuel cell interconnects

TiC and crystalline (Ti,Nb)3SiC2 based dual-layer is prepared on SUS430 alloy by DC magnetron sputtering followed by annealing at 1000 °C for 20 h. The oxidation of TiC/TNSC coated alloy at 800 °C for 500 h follows the parabolic law with a low rate constant of 5.4 × 10−15 g2 cm−4 s−1. The formed oxide scale is composed of Cr2O3/MnCr2O4 dominated inner layer and outer layer of Nb-doped TiO2 and SiO2 uniform mixture. Owing to the barrier effect of TiC layer and dense oxide scale, outward diffusion of Cr and Mn is efficiently suppressed, resulting in the low Cr content in the outer oxide layer, which is beneficial to the reduced volatilization of Cr oxide. Furthermore, the ASR of the formed oxide scale at 800 °C is 15.87 mΩ cm2, suggesting excellent conductivity. It is concluded that the TiC/(Ti,Nb)3SiC2 coating can significantly improve the oxidation resistannce and electrical property of SUS430 alloy, endowing it potential application as SOFC interconnect protective coating.

Construction of magnetically recyclable Fe3O4/hTiO2/g-C3N4 composites for solar photocatalytic degradation of organic pollutants: Study on the performance and mechanism insight

Magnetically separable Fe3O4/hTiO2/g-C3N4 composites were successfully constructed through coating polymethylacrylic acid sacrificial interlayer by the reflux-precipitation polymerization and subsequent TiO2 outer layer by sol–gel method over magnetic Fe3O4 nanospheres, calcining process and forming composites with g-C3N4 in sequence. The formation mechanism of unique composites was proved by TEM, XPS, VSM, XRD and EDX mapping characterization. Their photocatalytic activity was investigated by the solar photodegradation of organic dyes. The results revealed the photocatalytic performance of Fe3O4/hTiO2/g-C3N4 for degrading methylene blue (95.0 %, 120 min) under simulated sunlight irradiation (Xe lamp, 500 W) was much better than g-C3N4 (71.1 %, 120 min) and Fe3O4/hTiO2 (40.3 %, 120 min). The boosted property is presumably ascribed to the synergetic interaction of multiple components and effective separation of the photoproduced electron-hole pairs between g-C3N4 and TiO2, which was verified using photocurrent and EIS analysis. On the basis of the scavenging studies of radicals (h+, •O2– and •OH), the mechanism of the boosted photocatalytic performance was put forward. The degradation pathways of methylene blue were also proposed by identifying reaction intermediates produced during photocatalysis. More significantly, the composites presented excellent magnetic responsive property owing to the magnetic Fe3O4. The superior recyclability was confirmed by cyclical photocatalytic experiments with the help of an external magnet, which is crucial for the sustainable and green application of photocatalysts.

Intermediate and high-temperature oxidation behavior of an equiatomic TaTiCr RCCA from 800 °C to 1400 °C

This study explores the oxidation behavior of a TaTiCr refractory complex concentrated alloy (RCCA) in the temperature regime of 800–1400 °C. The oxidation kinetics were found to be proportional with temperature. However, a mechanistic shift from linear oxidation kinetics at 800 °C and 1000 °C to sub-parabolic kinetics at 1200 °C and 1400 °C was observed. This was attributed to the establishment of continuous external scales of TiO2 and Cr2O3, with fairly continuous underlying complex oxide layers at the higher temperatures. While there were morphological differences in the oxide scales depending on exposure temperature, the oxide species were all similar, primarily consisting of an outer layer of TiO2, an intermediate layer of Cr2O3, and an inner layer of rutile-structured (Cr,Ta,Ti)O2. Internal nitridation was observed in all cases, with a severe degree of internal reaction at 1400 °C, reaching a depth of 750 μm. Overall, the best performance was observed at 1200 °C, where a favorable balance of kinetics and thermodynamics promoted the most continuous oxide layers, thereby enhancing oxidation resistance.

Synthesis and properties of Ti-Al coating by high-frequency induction heated combustion

Ti-Al coatings with porosities of 1.11%− 2.28% were synthesized in situ via high-frequency induction heated combustion synthesis (HFIHCS) method within several minutes. The adiabatic temperatures at different preheating temperatures were calculated thermodynamically. The microstructure, phase composition, cross-sectional microhardness, oxidation, and corrosion resistance to molten aluminum alloy of the as-received coatings were investigated. The results showed that the Ti-Al reaction could be self-sustained when the preheating temperature reached 605 K. The combustion reaction and pore-forming mechanisms of the as-received Ti-Al coating conformed to liquid-solid reaction and thermal explosion, respectively. The coating microstructure followed a core-shell ring-shaped microstructure model, which was incomplete Ti nuclei, Ti3Al, TiAl and TiAl2 phases from inside to outside. The average microhardness of the substrate, interface and coating were 508.57, 454.54 and 377.18 HV0.2, respectively. The microhardness fluctuation was the largest at the coating-substrate interface. The oxidation kinetics of the as-received coating approximately followed a linear rate law with an oxidation rate constant of 0.3943 mg·cm−2·h−1 and a rate exponent of 1.2372. The oxide layer consisted of an outer layer of TiO2, an inner layer of nitrogen-containing compounds and a mixed layer of TiO2 and Al2O3 between them. The corrosion mechanism of the as-received Ti-Al IMC coatings in molten A380 alloy was mainly controlled by the combination of compounds formed at the liquid-solid interface and diffusion of liquid metal into the as-received Ti-Al coating, rather than by the dissolution mechanism of the as-received Ti-Al coating.

Preparation of ultrashort composite nanotubes by twin-screw extruder

The preparation of nanocomposites with controllable structure is important. There are few reports on preparation of ultrashort composite nanotubes with core–shell structure from long nanotubes, and how to maintain structural integrity and to avoid shell falling off or damaging are still challenging. Here we prepare ultrashort core–shell composite nanotubes with the outer layer of SiO2 or TiO2 and the inner layer of sulfonated PDVB by mixing their long composite nanotubes with polymer resin and shearing at a high strength with a twin-screw extruder. By contrast, using ultrasonic crushing or mechanical stirring to interrupt the composite nanotubes can destroy the SiO2 or TiO2 outer layer seriously. The method of preparing ultrashort composite nanomaterials by twin-screw extruders is very promising in the field of nanocomposite processing.

Highly oxidation-resistant Ti-Mo alloy with two-scale network Ti5Si3 reinforcement

There is keen interest in using Ti alloys as lightweight structural materials for aerospace and automotive industries. However, a long-standing problem for these materials is their poor oxidation resistance. Herein, we designed and fabricated a Ti5Si3 reinforced Ti-4(wt.%)Mo composite with two-scale network architecture by low energy milling and spark plasma sintering. It displays superior oxidation resistance at 800 °C owing to the in-situ formation of a multi-component surface layer. This oxide layer has a dense grain size gradient structure that consists of an outer TiO2 layer and an inner SiO2-padding-TiO2 layer, which has remarkable oxidation resistance and thermal stability. Furthermore, it was revealed that the hitherto unknown interaction between Ti5Si3 reinforcement and nitrogen during oxidation would contribute to the formation of a TiN nano-twin interface layer, which accommodates the thermal mismatch strain between the oxide layer and matrix. This, along with high adhesion, confers excellent thermal cycling life with no cracking or spallation during long-term oxidation. In this regard, the secure operating temperature of this new composite can be increased to 800 °C, which provides a design pathway for a new family of Ti matrix composites for high-temperature applications.

Effects of a Solid Solution Outer Layer of TiO2 on the Surface and Electrochemical Properties of LiNi0.6Co0.2Mn0.2O2 Cathodes for Lithium-Ion Batteries through the Use of Thin-Film Electrodes

Thin-film electrodes are considered to be desirable for understanding the detailed surface characteristics of active materials for rechargeable batteries. This study attempts to elucidate the effects of a solid solution outer layer (SSOL) of TiO2 on the surface and electrochemical properties of LiNi0.6Co0.2Mn0.2O2 (NCM622) cathodes by using thin-film electrodes synthesized by a spin-coating technique. The SSOL phase is induced on the NCM622 thin-film surface by a post-annealing process after the TiO2 coating using atomic layer deposition. Structural and morphological analyses revealed that the bare NCM622 thin-film electrode without a thin SSOL has a spinel-like derivative phase induced by an oxygen vacancy at the surface, which is considered to be the crucial factor for the poor electrochemical properties of Ni-rich NCM. In particular, additional measurements including in situ Raman spectroscopy revealed that the spinel-like derivative phase rapidly makes the surface structure become corrupt and change to the amorphous state during electrochemical reactions. In contrast, the oxygen vacancy can be eliminated by forming a SSOL phase at the surface of the NCM622 thin-film through the rapid migration of Ni, Ti, and O atoms during the post-annealing process, significantly enhancing the structural stability, which ultimately improves the electrochemical performance, including cyclability and Coulombic efficiency.

Hierarchical Carbon Nanofibers@Nickel Phosphide Nanoparticles for High‐Performance Supercapacitors

The design and synthesis of novel active materials as the capacitor electrodes is of great significance to fabricate high‐performance supercapacitors, namely those with large and stable capacitances as well as high power and energy densities. Herein, binder‐free and hierarchical carbon nanofibers@nickel phosphide nanoparticles are grown in a chemical vapor deposition reactor, where Ni5TiO7 nanowires and a TiO2 outer layer are in situ converted into interconnected nickel phosphide nanoparticles and a TiC layer, respectively. The initially formed hierarchical nickel phosphide nanoparticles boost the catalytic growth of CNFs, leading to the generation of a 3D interconnected texture, which features a high specific surface area and excellent conductivity. The combination of this nanocomposite as a capacitor electrode with redox electrolyte of 0.05 m Fe(CN)63−/4− generates a specific capacitance of 59.3 mF cm−2 at a current density of 5 mA cm−2. This capacitor electrode exhibits 95% of its initial capacitance even after 10 000 charging/discharging cycles. The as‐fabricated supercapacitor device offers an energy density of as high as 27.4 Wh kg−1 accompanied with a power density of 7.25 kW kg−1. The proposed method thus provides an approach to produce binder‐/current‐collector‐free capacitor electrodes, which can be utilized to fabricate high‐performance supercapacitors.

A High-Efficiency TiO2/ZnO Nano-Film with Surface Oxygen Vacancies for Dye Degradation.

Photocatalytic degradation of organic pollutants in water is a highly efficient and green approach. However, the low quantum efficiency is an intractable obstacle to lower the photocatalytic efficiency of photocatalysts. Herein, the TiO2/ZnO heterojunction thin films combined with surface oxygen vacancies (OVs) were prepared through magnetron sputtering, which was designed to drive rapid bulk and surface separation of charge carriers. The morphology and structural and compositional properties of films were investigated via different techniques such as SEM, XRD, Raman, AFM, and XPS. It has been found that by controlling the O2/Ar ratio, the surface morphology, thickness, chemical composition, and crystal structure can be regulated, ultimately enhancing the photocatalytic performance of the TiO2/ZnO heterostructures. In addition, the heterojunction thin film showed improved photocatalytic properties compared with the other nano-films when the outer TiO2 layer was prepared at an O2/Ar ratio of 10:35. It degraded 88.0% of Rhodamine B (RhB) in 90 min and 90.8% of RhB in 120 min. This was attributed to the heterojunction interface and surface OVs, which accelerated the separation of electron–hole (e–h) pairs.

Mechanical Behavior of Bi-Layer and Dispersion Coatings Composed of Several Nanostructures on Ti13Nb13Zr Alloy.

Titanium implants are commonly used because of several advantages, but their surface modification is necessary to enhance bioactivity. Recently, their surface coatings were developed to induce local antibacterial properties. The aim of this research was to investigate and compare mechanical properties of three coatings: multi-wall carbon nanotubes (MWCNTs), bi-layer composed of an inner MWCNTs layer and an outer TiO2 layer, and dispersion coatings comprised of simultaneously deposited MWCNTs and nanoCu, each electrophoretically deposited on the Ti13Nb13Zr alloy. Optical microscopy, scanning electron microscopy, X-ray electron diffraction spectroscopy, and nanoindentation technique were applied to study topography, chemical composition, hardness, plastic and elastic properties. The results demonstrate that the addition of nanocopper or titanium dioxide to MWCNTs coating increases hardness, lowers Young’s modulus, improves plastic and elastic properties, wear resistance under deflection, and plastic deformation resistance. The results can be attributed to different properties, structure and geometry of applied particles, various deposition techniques, and the possible appearance of porous structures. These innovative coatings of simultaneously high strength and elasticity are promising to apply for deposition on long-term titanium implants.

On the adsorption kinetics and mechanism of enhanced photocatalytic activity of Fe3 O4 -SiO2 -TiO2 core-multishell nanoparticles against E. coli.

In the present study, a Fe3 O4 -TiO2 (FT) core-shell and a core-multishell structure of Fe3 O4 -SiO2 -TiO2 (FST) were synthesized, and their bactericidal capability was investigated on Escherichia coli (E. coli). Scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV-vis), X-ray diffraction, Brunauer-Emmett-Teller, zeta potential, and fluorimetry were carried out to characterize properties of synthesized nanoparticles. An efficiency of 98% adsorption and harsh bacterial damage was observed when E. coli was put in contact with FST. Weaker adsorption of bacteria in contact with FT demonstrated that heterojunction has destructive effects on nanostructure. Further investigation proved that more OH were produced on the surface of FST, which is a sign of its longer lifetime. Moreover, results revealed that the presence of SiO2 in the structure caused enhanced coverage, surface area, and porosity in TiO2 outer layer, all of which have positive effects on adsorption. However, UV-vis showed smaller band gap for FT. It suggests that although photoactivity of FST is less influenced by light absorption, it possesses more e/h lifetime for generation of reactive oxygen species. Results point to the importance of SiO2 as an obstacle of heterojunction on both adsorption and photoactivity. It was also proposed that increasing band gap in FST can be attributed to the porosity of SiO2 that causes suppression of TiO2 nanocrystallite growth.

A three-layered multifunctional photoactive core-shell gadolinium based nanocomposite

Multifunctional composite structures play an important role in biomedical applications, where many side effects can be eliminated and the therapy can be more effective. In this research, Gd ions and TiO2 were chosen to develop a potential material with image contrast enhancement behavior and photocatalytic properties. Such a unique combination would have the potential to be used as an efficient theranostic agent. Silica nanospheres were synthesized as a biocompatible platform through microemulsion method. The gadolinium carbonate layer was first formed around the silica cores, which can be transformed to Gd2O3 via calcination at 1000 °C. The outer TiO2 layer was deposited through controlled precipitation from TBOT as the precursor. The thickness of each layer was controlled by controlling the amount of its corresponding precursor. FESEM was used for morphological observations and the ultimate multilayer nanocomposite was confirmed using high resolution TEM. XRD and FTIR techniques were used to confirm the successful formation of each layer. The final nanocomposite particles with different layers thickness have an average diameter in the range of 47–76 nm. The nanocomposites were photoactive and able to decompose methylene blue by 45% after being exposed to UV radiation. The photocatalytic effect increased with TiO2 thickness and UV exposure time.

Facile and Effective Fabrication of Highly UV-Resistant Silk Fabrics with Excellent Laundering Durability and Thermal and Chemical Stabilities.

As the most favored high-quality biopolymer, silk fiber is widely used in the textile and medical industries owing to its impressive mechanical properties, wear comfort properties, and biocompatibility. However, its photoinstability, chemical instability, and thermal instability seriously hinder its utilization in luxurious fashionable apparels. Therefore, we herein report the preparation of an ultrathin and uniform TiO2-Al2O3 cloth with a thickness of just six in a thousand of fiber on silkworm silk fiber via atomic layer deposition. In this ultrathin composite cloth, the outer TiO2 layer acts as a sacrificial ultraviolet (UV) absorbent to dissipate large amounts of UV energy. Free radicals and electrons generated by the TiO2 layer are effectively blocked outside the surface of the bulk silk fiber by the inner insulating Al2O3 layer. The excellent UV-resistance of the modified silk fiber was confirmed by a lack of fade in the silk fabric after exposure to UV light for 60 min (equal to continuous exposure to strong sunlight for 3285 days). Compared with silk fiber, the tenacity of the prepared SF-200Al2O3-800TiO2 increased by 18.9% even after sunlight exposure. In addition, both the chemical and thermal stabilities of the modified silk fiber were improved. This technology is expected to have potential applications in various fields, such as high-end fabric development and smart materials, and will further guide material design for future innovations in functional fibers and devices.

Substrate oxidation enhances the electrochemical production of hydrogen peroxide

Hydrogen peroxide (H2O2) is electrochemically produced via oxygen (O2) reduction on a carbon cathode surface. In order to enhance the production of H2O2, anodic loss pathways, which significantly reduce the overall H2O2 production rate, should be inhibited. In this study, we investigate the effects of organic electron donors (i.e., typical chemical contaminants) on the anodic loss pathways of H2O2 in a single-cell electrochemical reactor that employs an anode composed of TiO2 over-coated on a mixed-metal oxide ohmic contact catalyst, Ir0.7Ta0.3O2, deposited on a Ti-metal that is coupled with a graphite rod cathode in a sodium sulfate (Na2SO4) electrolyte that is saturated with oxygen (O2). Organic electron donors are shown to enhance the electrochemical production of H2O2, while simultaneously undergoing oxidative degradation. The observed positive effect of organic electron donors on the electrochemical production of H2O2 is due in part to a preferential adsorption of organic substrates on the TiO2 outer layer of the anode. The sorption of the organic electron donors inhibits the formation of surficial titanium hydroperoxo species (Ti-OOH) on the anode surface. The organic sorbates also act as scavengers of surface-bound hydroxyl radical Ti-OH. As a result, the decomposition of H2O2 on the anode surface is significantly reduced. The cathodic production rate of H2O2 at low pH is enhanced due to proton coupled electron transfer (PCET) to O2, while the anodic decomposition of H2O2 is inhibited due to electrostatic interactions between negatively-charged organic substrates and a positively-charged outer surface of the anode (TiO2 pHzpc = 5.8) at low pH.

H2 generation using Pt nanoparticles encapsulated in Fe3O4@SiO2@TiO2 multishell particles

Metal nanoparticles contained in core-shell nanostructures have emerged as well-defined heterogeneous catalysts. Such particles with a magnetite-supported core could also be easily separated in liquid phase reactions. Herein, we report a synthetic encapsulating method for Pt nanoparticles on magnetic multishell particles for use as a magnetically separable, thermally stable, and easily recyclable catalyst in liquid phase reactions. Fe3O4@SiO2-Pt@TiO2 catalysts exhibited high catalytic activity and stability during recycling in H2 generation tests using the NaBH4 solution. While the Fe3O4@SiO2-Pt catalyst without a TiO2 outer-layer not only exhibited high catalytic activity, but also exhibited very unstable performance during recycling tests due to the detachment of Pt nanoparticles from core-shell particles. Therefore, a thin TiO2 layer at the outer shell of the Fe3O4@SiO2-Pt@TiO2 catalysts was found to enhance the catalytic stability and recyclability for multiple reaction runs.

High-Temperature Corrosion of Ti–46Al–6Nb–0.5W–0.5Cr–0.3Si–0.1C Alloy in N2/0.1%H2S Gas

Ti–46Al–6Nb–0.5W–0.5Cr–0.3Si–0.1C alloy was corroded at 800–1100 °C for 200 h in N2/0.1%H2S gas to characterize its corrosion behavior in an aggressive H2S-containing environment. The alloy displayed superior corrosion resistance because Ti and Al preferentially reacted with impurity oxygen in the gas to form TiO2 and Al2O3. It corroded primarily by outward diffusion of Ti, Al, W, and Cr in addition to inward transport of sulfur, nitrogen, and oxygen. Scales were adherent and consisted of an outer TiO2 layer, an intermediate Al2O3 layer, and an inner (TiO2, Al2O3)-mixed layer. TiN and Ti2AlN formed at the scale/matrix interface where sulfur, Nb, W, and Cr segregated.