Inner Oxide Layer Research Articles

Developing a lithiophilic, solvent-phobic dual-functionality film for dendrite-free Li metal anodes

Li metal anodes (LMAs) are promising candidate for advanced batteries that encounters significant challenges, including electrolyte corrosion and uneven deposition. These issues not only reduce battery lifespan but also pose safety risks due to the uncontrolled growth of dendrites. Herein, we introduce a lithiophilic, solvent-phobic dual-functionality film (LSDF) designed to tackle these problems. The LSDF features an inner layer of polyethylene oxide directly applied to the LMAs and an outer layer of poly(vinylidene fluoride-co-hexafluoropropylene) facing the electrolyte. Both layers contain N-ethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, which enhances the rapid transport of Li ions. The inner layer promotes high interfacial stability, while the outer layer offers solvent resistance and Li affinity, thereby inhibiting dendrite growth and reducing side reactions. Consequently, Li||Li symmetric cells achieve stable cycling for 1650 h with a minimal overpotential of 15 mV at 3 mAh cm−2 and 3 mA cm−2. Additionally, full cells paired with LiFePO4 cathodes maintain 85 % capacity retention over 500 cycles at 1 C and demonstrate excellent rate capability. This study presents a new approach to modulate the interface of LMAs, significantly enhancing its stability for high-energy–density battery applications.

Enhanced oxidation resistance in nano-lamellar CoCrFeNiNbx (0.45 ≤ x ≤ 0.55) eutectic high entropy alloy during cyclic oxidation at 700–1100 °C

We report the superior oxidation resistance of nano-lamellar CoCrFeNiNbx (x = 0.45, 0.50, 0.55 atom ratio) eutectic high entropy alloy (EHEA) at 700–1100 °C. The as-cast microstructure comprises of nano-lamellar eutectic FCC+Laves phases. The oxidation kinetics followed the parabolic rate in between 700–800 °C, whereas, near-parabolic kinetics is followed at 900 °C. The addition of Nb improves the oxidation and spallation resistance of the EHEAs. A protective outer-oxide layer containing Cr2O3, FeCr2O4-type spinels, whereas, an inner-oxide layer containing Nb2O5, CrNbO4 were formed during oxidation. The mechanism of protection and the superiority of EHEAs as high temperature alloy are explored.

High-temperature corrosion behavior of 316 H stainless steel in lead-bismuth eutectic containing cesium

The influence of Cs on the corrosion of 316 H stainless steel pipework when exposed to liquid lead–bismuth eutectic (LBE) coolant, specifically LBE containing 0.5 wt% Cs at high temperature, is investigated. The addition of Cs in LBE can significantly accelerate the corrosion of 316 H stainless steel. Cs in LBE first destroys the Cr2O3 film on the surface of the stainless steel and reacts with Cr23C6 enriched at grain boundaries. Finally, the reaction between Cs and FeCr2O4 creates pores in inner oxide layer (IOL), thus destroying the protection provided to 316 H stainless steel by the IOL.

Construction of Ce3+ modified conversion film on oxide scale of plain steel rebars to greatly enhance the corrosion resistance

Steel rebars with oxide scale, which is usually rich of defects, are widely used in industry. On the surface of the oxide scale, it is difficult to prepare a conversion film with desirable corrosion resistance because of the acidity of conventional conversion solutions. In this work, a sol–gel solution (pH = 11) was employed to retard the diffusion of cerium ions avoiding the formation of cerium salt precipitates at room temperature. After treatments, the diffusion of cerium ions would be accelerated and a protective conversion film would form to repair natural defects on oxide scale of steel rebars at a higher temperature. This strategy can not only avoid the peeling of the oxide scale by the acid solution, but also prevent a large amount of non-uniform precipitation of the film-forming Ce3+ ions. The conversion film@oxide scale was characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curve (PPC) etc. It is found that the corrosion resistance of the prepared film@oxide scale was enhanced greatly when the concentration of added cerium ion (III) was 0.5 M, with pH adjusted to 11. After 30 days of immersion, Rct of surface treated rebar is more 180 times that of blank sample. The excellent corrosion resistance is closely related to the double-layer structure of the prepared sol-gel film, especially an about 2 nm inner layer of cerium oxide.

EFFECT OF ALKALINE SOLUTION CONCENTRATION ON THE PASSIVATION FILM OF Cu-Ni ALLOY

Passive films formed on a Cu-Ni alloy in various concentrations of alkaline environment were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy and the Mott–Schottky approach. The wide passivation range of the copper-nickel alloy was tested in alkaline solutions of three concentrations. The oxide film on the specimen has a p-type semiconductor property, while the flat band potential (EFB) decreased with increasing solution concentration. The film resistance of the passive films increased with increasing solution concentration. The pAassive films showed a duplex structure, including an inner layer of oxide (Cu2O, NiO) and an outer layer of hydroxide (Cu(OH)2, Ni(OH)2).

Optimisation of the chemical oxidation reduction process (CORD) on surrogate stainless steel in regards to its efficiency and secondary wastes

Nuclear Power is a decarbonated technology of electrical energy generation. Using nuclear energy as a power source is currently considered as the best option in the fight against climate change. But the radioactive waste generated from nuclear power plants and their related facilities are matter of concern. Though the high level and intermediate level activity wastes are contained in small volumes (≤10%), significant volumes of lower activity wastes are generated. Metallic wastes are a major component of these radioactive wastes with about 500,000 tons expected in France alone, including 130,000 tons from steam generators. Majority of these metals are made of Stainless steel 316 alloy or Inconel 600. Under the effect of the primary circuit thermal-hydraulic constraints and irradiation, these the resulting corrosion products may be activated when close to the fuel, and be transported throughout the circuit. These products can be deposited on the surface of other metal components, causing contamination of the latter. The contamination can be adsorbed on the surface but can also diffuse in the oxide layers and sub-surface. The oxide layer is composed of an inner layer of Cr oxide under a layer of Ni and Fe oxide. Chemical decontamination is preferred due to the possibility of decontamination of difficult geometries and tube bends. In order to decontaminate these materials, it is important to dissolve the oxide layers chemically and a few micrometers of base metal where it could have diffused. An existing chemical method used to treat these materials is studied in this article, Chemical Oxidation Reduction Decontamination (CORD). Surrogate steel samples were prepared using high temperature induction heating and water vapour after sample preparation and cleaning. The oxide layer was characterised before treatment of the samples in the batch method at different concentrations and its effects are observed on the dissolution of the oxide layers. A protocol is being developed for the treatment of secondary waste effluents by multi-stage precipitation with a goal to reduce the total waste volumes and thus the volumes of ion exchange resins that would otherwise be needed.

Tailoring oxidation resistance of Fe2CoCrNi0.5 based high entropy alloys by addition of alloying elements (Si, Cu and Si-Cu co-added)

Investigations about how to improve the properties of high entropy alloys (HEAs) play a key role in growing their potential for use in future industrial applications. Accordingly, this study aims to shed light on the effects of alloying elements (Si, Cu and Si-Cu co-added) on the microstructure and oxidation performance of the Fe 2 CoCrNi 0.5 based high entropy alloys. To this end, a series of high entropy alloys containing Fe 2 CoCrNi 0.5 , Fe 2 CoCrNi 0.5 Si 0.25 , Fe 2 CoCrNi 0.5 Cu 0.25 and Fe 2 CoCrNi 0.5 Si 0.25 Cu 0.25 were produced by electric current assisted sintering (ECAS) method, which is founded on the principle of simultaneous application of high-density electric current flowing through the powder mixture and uniaxial pressure within a short span of time. The oxidation test was carried out in air at 1123 K for 1200 h under cyclic conditions. The X-ray diffraction results showed that all HEAs have simple FCC solid solution phases. Among all HEAs, the oxidation resistance of the alloy exhibited an increasing trend with the Si addition and the best oxidation behavior at 1123 K for 1200 h was noted with Fe 2 CoCrNi 0.5 Si 0.25 , which experienced the least mass change of 4.72 mg cm −2 . Cu addition caused the highest mass change of 15.92 mg cm −2 and the thickest oxide scale of 38.2 µm after oxidation for 1200 h. Si addition is observed to enhance the amount of Cr-rich oxide in the scale. The oxide scale formed on HEA with Cu-added and HEA with Si-Cu co-added contained two oxide layers, including an outer layer of Fe-rich oxide and an inner layer of Cr-rich oxide, which showed continuous structure. However, the alloying elements did not play a favorable role in relieving the formation of internal oxidation. Additionally, it has been reported that Fe 2 CoCrNi 0.5 Si 0.25 HEA can exhibit high resistance to cyclic oxidation, which can be reasoned as an optimum material for structural and high-temperature applications. • Alloying element behavior has been shown to have a significant influence on the investigated properties of HEAs. • Si has proved to be effective in enhancing oxidation resistance. • Cu addition produced the thickest oxide scale. • One of the encouraging results of this investigation was the synergic effect of Si-Cu co-added.

Corrosion behaviour characterisation of 316L stainless steel and Inconel 625 in supercritical water containing hydrochloric acid and high oxygen

ABSTRACT Corrosion was currently the most crucial factor hindering the commercial development of supercritical water oxidation (SCWO) technology. Stainless steel represented by 316L and Ni-based alloy represented by Inconel 625 were performed and compared with corrosion resistance in supercritical environment with high concentrations of oxygen and chlorides. The results shown that the duplex layer was formed on two samples. The surface of 316L SS was mainly composed of loose magnetite and haematite, resulted in pitting corrosion, microcracks, and the exfoliation of oxide. The inner layer were separately a small amount of Cr2O3 oxide and FeCr2O4 spinel, which were caused by the lower content of chromium. Compared with 316L SS, the oxide film structure of Inconel 625 was composed of the outer layer of spinel and the inner layer of Cr-rich oxide. Some nodular oxides were formed, and it can be explained by the volatilisation process of chromium.

Scaling behavior of four ternary Co-20Ni-based alloys containing 3/5 wt% Al or 8/15 wt% Cr in 1 Atm O2 at 800–900 °C

The oxidation in 1 atm O2 of two Co-20Ni-yAl (y = 3,5 wt%), two Co-20Ni-xCr (x = 8,15 wt%) and a Co-20Ni alloy was studied at 800–900 °C. Except for Co-20Ni-15Cr oxidized at 900 °C, all the ternary alloys oxidized more rapidly than the binary alloy Co-20Ni at both temperatures. A thin protective oxide layer formed only on the surface of the ternary alloy Co-20Ni-15Cr by oxidation at 900 °C. In all the other cases the scales contained an outer layer of Co-Ni oxide plus an inner layer of Co-Ni oxide mixed with spinels and a zone of internal oxidation.

The formation mechanism and effect of amorphous SiO2 on the corrosion behaviour of Fe-Cr-Si ODS alloy in LBE at 550 °C

The corrosion behaviour of the newly developed Fe-Cr-Si oxide-dispersion-strengthened alloys in liquid lead–bismuth eutectic at 550 °C was microstructurally studied. The corrosion resistance was enhanced with increasing Si content, attributing to the preferred formation of amorphous SiO2 during the inward diffusion of oxygen. SiO2 promoted the formation of Cr-rich oxides that were uniformly distributed in the inner-oxide layer and matrix, thereby reducing the Fe and O diffusion coefficients and ultimately delaying the formation of the outer magnetite layer and the growth of the inner Cr-rich oxide layer while reducing interfacial defects.

Regulating magnesium combustion using surface chemistry and heating rate

The magnesium (Mg) particle surface can be used to regulate fluorination or oxidation reactions depending on the applied heating rate and Mg particle size. Magnesium particles are surrounded by a complex hydroxide shell composed of an inner layer of magnesium oxide (MgO) and outer layer of magnesium hydroxide (Mg(OH)2). As particles approach the nanoscale, the thick oxide shell (e.g., 22 nm) becomes an appreciable portion of the overall powder and can be exploited to regulate reactivity. In this study, the reactivity of 800 nm Mg particles (nMg) was compared to 44 µm Mg particles (µMg) when combined with Perfluoropolyethyer (PFPE), providing both fluorine and oxygen for Mg reactions. Experiments were performed at slow heating rates (10 °C/min) and separate experiments were performed at fast heating rates (6.0 × 105 °C/min). The slow heating rate studies used a differential scanning calorimeter (DSC) and thermogravimetric (TG) analyzer to examine reaction kinetics. The faster heating rate experiments used a hot wire to ignite a thermal run-away reaction. Powder X-ray diffraction (XRD) analysis of recovered residue at various temperatures corresponding to exothermic events in the DSC revealed reaction pathways for nMg + PFPE favoring oxidation reactions. For nMg powders, the outer Mg(OH)2 surface layer dehydrates at low temperatures (313 °C) creating highly reactive sites for surface oxidation reactions in the condensed phase leading to a higher conversion of Mg(OH)2 to MgO and greater consumption of Mg through oxidation reactions. For µMg, higher Mg(OH)2 dehydration temperatures (498 °C) stabilize µMg particles and the bulk of reactions occur at elevated temperatures and in the gas phase producing higher MgF2 concentrations. Under high heating rate conditions, MgF2 formation is favored over MgO formation for both particle sizes owing to the high reaction temperatures that promote gas phase reactions favoring MgF2 formation. Theoretical analysis using density functional theory (DFT) through cluster models for Mg(OH)2 and MgO surfaces further show that the Mg(OH)2 surface is more reactive with fluorine species than MgO, especially at elevated temperatures. The DFT results help explain the high heating rate reaction pathway that favors fluorination reactions independent of Mg particle size.

Failure mechanism of turbine guide vane and oxide composition analysis on the surface of failure vane cracks

This study deals with the investigation of failure mechanism of turbine guide vane and the oxide composition on the surface of failure vane cracks. The material of vane is Co-based superalloy DZ40M, which has directional solidified grain structure. The investigate methods include optical microscope (OM) observation, scanning electron microscopy (SEM) observation and energy dispersive X-ray spectrometry (EDS) analysis. The results of crack morphology observation show that: the cracks are distributed at almost all the rows of cooling holes at the middle of the vane and most macroscopic morphology of cracks are transverse propagation (perpendicular to directional solidification direction). Due to the high temperature environment and action of cycle thermal stress during service, the recrystallization tissue near the cooling holes which produced by high-energy laser production process can easily become the starting point of cracks. And the cracks propagate along the grain boundaries and sub-boundaries as the large difference of thermal expansion coefficient between carbides and matrix in high temperature. The results of oxide composition analysis show that, oxide layer on the surface of cracks can be divided into two layers. The main composition of outer-oxide layer is mainly the oxides of CoO, CoCr2O4 and a small amount of Cr2O3, evenly distributed on the crack surface with about 10 μm thickness. The inner-oxide layer discontinuous distribution with spherical and needlelike morphologies, mainly composed by oxides of Cr2O3 and Al2O3, the thickness is about 30 μm.

The passivity of low-temperature carburized austenitic stainless steel AISI-316L in a simulated boiling-water-reactor environment

The passive film on low-temperature-carburized AISI-316L austenitic stainless steel was studied in an oxygenated, simulated boiling-water-reactor environment with normal water chemistry. The microstructure was studied using scanning electron microscopy, grazing-incidence X-ray diffractometry, Auger electron spectroscopy, X-ray energy-dispersive spectroscopy, and transmission electron microscopy. For non-surface engineered AISI-316L, three distinct layers were observed after exposure: an outer layer of larger nickel-oxide enriched particles with the spinel structure, an intermediate layer of small Cr-oxide-enriched hematite particles, and a compact inner layer of Cr-enriched oxide also having the spinel structure. Exposure of low-temperature-carburized AISI-316L, in contrast, resulted in only two distinct layers. These layers did not include a compact Cr-rich inner layer. Instead, the innermost layer consisted of an oxide with the spinel structure that was a mixture of Fe, Cr and Ni oxide. The outer layer on the low-temperature-carburized specimen consisted of large loosely stacked particles with the spinel structure of mixed composition. In addition to passive-film characterization, the corrosion rate was studied by monitoring mass loss. After 500 h of immersion, the mass changes measured were relatively low for all specimens indicating good adhesion and low oxidation rates.

Early stages of iron anodic oxidation: Defective growth and density increase of oxide layer

The early stages of anodic oxidation in the potentiostatic condition at the interface between a borate buffer solution at pH 8.4 and Fe(100), (110), and (111) surfaces are investigated by sub-second resolution real-time x-ray reflectometry. The growth process is composed of three stages. The electron density of the inner-oxide layer for Fe(111) after a potential step from $\ensuremath{-}0.8$ to $+0.7$ V versus Ag/AgCl in the steady-state growth, stage III (1.65 s $lt$, where $t$ denotes the time after the potential step), is 1.52 electrons/${\AA{}}^{3}$, which is close to the density of magnetite. The growth rate is proportional to ${t}^{\ensuremath{-}1}$, which follows the direct logarithmic law or point-defect model. In an earlier stage of the oxide film growth, stage II $(0.4lt\ensuremath{\le}1.65$ s), the growth rate is proportional to ${t}^{\ensuremath{-}1.5}$, while the electron density maintains the same value as that in stage III. At the first stage that can be discriminated by our time resolution, stage I $(t\ensuremath{\le}0.4$ s), the growth rate is the same as that for stage II, i.e., proportional to ${t}^{\ensuremath{-}1.5}$, while the electron density significantly decreases. The suggested structure is a highly defective spinel oxide, and defects are filled by the end of stage I; there is no signature of the growth of other phases, such as hydroxide, as the inner layer. This behavior indicates that the early stage of the oxide film growth is faster than the formation of a complete spinel layer at the iron-oxide interface. The deviation of the growth rate from the point-defect model in stages I and II is caused by the strong electric field at the iron-oxide interface.

Characterization of zirconium oxides part I: Raman mapping and spectral feature analysis

Abstract Raman mapping of sectioned zirconium cladding oxides was performed to analyze different spectral features before and after breakaway, as well as between zirconium and its alloys Zr-2.65Nb, Zry-3, and Zry-4. Oxide phase composition, or percent tetragonality, was defined to compare tetragonal to monoclinic zirconia. Percent tetragonality was spatially mapped to support distinction of zirconia phase distribution. A tetragonal-rich layer was seen at the metal/oxide interface, while post-breakaway samples exhibited increased amount of tetragonal phase in the bulk of their oxides. Spatial mapping of spectral peak location and half-width at half-maximum was accomplished to distinguish differences in stability mechanisms of tetragonal-rich zirconia phase. Shifts in monoclinic peak positions provided mapping of relative stress state, supporting the differences in stabilization of tetragonal phase near the metal/oxide interface and tetragonal phase in the bulk of the oxide. Tetragonal phase near the metal/oxide interface is stabilized through support of oxygen sub-stoichiometry and compressive stress. Tetragonal phase observed in the bulk of the oxide is stabilized through oxygen sub-stoichiometry, void of compressive stress. A linear trend between percent tetragonality and stress state was determined. This resulted in a connection between mechanism of tetragonal to monoclinic phase transformation and a cladding's ability to resist oxidation and breakaway. Poor performing samples displayed greater stress gradients, driven by lattice mismatch at the metal/oxide interface, as well as between tetragonal and monoclinic phase boundaries. Tetragonal phase at the metal/oxide interface for superior performing samples have reduced epitaxial growth of tetragonal grains, lowering compressive stress gradients and provided more resistant inner-oxide layers. With increased utility of Raman spectroscopy for characterizing zirconium cladding materials, different degradation mechanisms can be further understood.

Fabrication of a double-layered Co-Mn-O spinel coating on stainless steel via the double glow plasma alloying process and preoxidation treatment as SOFC interconnect

To improve oxidation resistance, prevent Cr evaporation and maintain appropriate electrical conductivity of AISI 430 stainless steel (430 SS) as the solid oxide fuel cells' (SOFCs) interconnect, a double-layered Co-Mn-O spinel coating is fabricated successfully on 430 SS via a simple double glow plasma alloying process (DGPA) followed by heating in the air (preoxidation treatment). The double-layered Co-Mn-O spinel coating is composed of a thick MnCo2O4 spinel outlayer and a thin mutual-diffused (MnCoFe)3O4 oxide innerlayer. The isothermal and cyclic oxidation measurements are used to investigate the oxidation resistance, and the ASR test is performed to evaluate the conductivity for the coated and uncoated specimens. The coated specimen has a lower oxidation kinetics rate constant (9.0929 × 10−4 mg2 cm−4 h−1) than the uncoated one (1.900 × 10−3 mg2 cm−4 h−1) and the weight gain of the coated specimen (0.84 mg cm−2) is less than that of bare steel (1.29 mg cm−2) after 750 h oxidation. Meanwhile, the coated specimen holds a lower area specific resistance (0.029 Ω cm2) compared to the uncoated one (2.28 Ω cm2) after 408 h oxidation. Furthermore, the compact Co-Mn-O spinel coating can effectively impede Cr-volatilization. Additionally, the probable mechanism of the Co-Mn alloy conversion into spinel and the electronic conduction behavior in the spinel are discussed. The effects of mutual-diffused oxide innerlayer on oxidation behavior and conductivity are investigated.

Inhibition of in-stent restenosis after graphene oxide double-layer drug coating with good biocompatibility.

In this study, we designed a double layer-coated vascular stent of 316L stainless steel using an ultrasonic spray system to achieve both antiproliferation and antithrombosis. The coating included an inner layer of graphene oxide (GO) loaded with docetaxel (DTX) and an outer layer of carboxymethyl chitosan (CMC) loaded with heparin (Hep). The coated surface was uniform without aggregation and shedding phenomena before and after stent expanded. The coating treatment was able to inhibit the adhesion and activation of platelets and the proliferation and migration of smooth muscle cells, indicating the excellent biocompatibility and antiproliferation ability. The toxicity tests showed that the GO/DTX and CMC/Hep coating did not cause deformity and organ abnormalities in zebrafish under stereomicroscope. The stents with GO double-layer coating were safe and could effectively prevent thrombosis and in-stent restenosis after the implantation into rabbit carotid arteries for 4–12 weeks.

Influence Mechanism of Cu on High Temperature Oxidation Behavior of Titanium Alloys

The oxidation behavior and mechanism of Ti-Cu alloys (0≤w(Cu)≤20%) in the temperature range of 1000°C～1300°C are studied by thermogravimetric analysis(TGA) combined with SEM, EDS and XRD analysis methods. The results show that the oxidation rates of Ti-Cu alloys increase sharply when the temperature rises above 1000°C. The oxidation products have a three-layer structure, from the outside to the inside, which are dense outer oxide layer of TiO2, porous inner oxide layer of low valence oxide of Ti and Cu-enriched layer. With the increase of the temperature, the thicknesses of oxide layers of Ti-Cu alloy increase and the Cu-enriched phase increases gradually and melts. The melting Cu-enriched phase flows to the oxidation surface along the grain boundaries of the oxide layer. The high temperature oxidation resistance of Ti-Cu alloys declines with the increase of Cu content. The main reason is that more liquid Cu-enriched phase is formed and flows to the oxidation surface along the oxide grain boundaries in the Ti-Cu alloy, and Ti and O ions can diffuse more easily along the liquid Cu-enriched phase, which increases the oxidation rates.

Corrosion-Resistant Porous Alumina Formed via Anodizing Aluminum in Etidronic Acid and Its Pore-Sealing Behavior in Boiling Water

Alkaline corrosion-resistant porous alumina was fabricated by anodizing aluminum in etidronic acid, and its hydration behavior during pore sealing in boiling water was investigated. High-purity aluminum plates were anodized in sulfuric, oxalic, citric, and etidronic acid solutions. Anodizing with etidronic acid caused stable growth of a uniform, porous alumina layer at a high voltage of approximately 200 V. This porous alumina possessed a thick barrier layer with an inner layer of pure aluminum oxide and exhibited a 10-fold increase in the corrosion resistance in a 2.5 M sodium hydroxide solution. When the porous alumina film formed by sulfuric acid anodizing was immersed in boiling water, plate-like hydroxide scales rapidly formed on the whole surface, and the pores were sealed within 10 min. In the case of etidronic acid, the hydroxides formed at the bottom of the pores in the initial stage of immersion, and the thickness of the hydroxide layer gradually increased with the immersion time. The porous layer was completely sealed by long-term immersion. Although the barrier layer was reduced to approximately 80% of its original size due to hydration, a thick barrier layer was still maintained at the bottom of the pores after immersion.

A duplex coating composed of electrophoretic deposited graphene oxide inner-layer and electrodeposited graphene oxide/Mg substituted hydroxyapatite outer-layer on carbon/carbon composites for biomedical application

A duplex coating composed of electrophoretic deposited graphene oxide (GO) inner-layer and electrodeposited GO/Mg substituted hydroxyapatite (MH) outer-layer was prepared on carbon/carbon composites (CC). The morphology and microstructure of GO-GO/MH coating were researched by Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy. The bonding strength between GO-GO/MH coating and CC substrate was investigated by shear test. The in-vitro bioactivity of GO-GO/MH coating was analyzed by simulated body fluid (SBF) immersion test. The results demonstrated that electrophoretic deposited GO inner-layer was successfully introduced on CC and could serve as an interlayer between CC and following electrodeposited GO/MH outer-layer. GO/MH outer-layer presented a flake morphology with 150–250 nm in thickness and 1.5–2.5 µm in width, exhibiting porous three-dimensional networks structure uniformly. The shear test showed that the bonding strength between the duplex coating and CC reached 7.4 MPa, which was 80.49% higher than that of single-layered MH coating without GO. The duplex coating could induce the formation of flocculent and chapped apatite after SBF immersion, which demonstrated the in-vitro bioactivity of the duplex coating. These results suggested that GO-GO/MH coating might be a promising candidate in the field of biomaterials, especially for implant coatings.