Formation of Black Ceramic Layer on Aluminum Alloy by Plasma Electrolytic Oxidation in Electrolyte Containing Na&lt;sub&gt;2&lt;/sub&gt;WO&lt;sub&gt;4&lt;/sub&gt;

Hwang, Insung; Shin, Kihong; Lee, J. S.; Ko, Young Gun; Shin, Dong Hyuk

doi:10.2320/matertrans.m2011263

Cited by 47 publications

(14 citation statements)

References 25 publications

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“…Among the colored coatings, the black coatings with high emissivity and high absorption are highly desired for the interior components of airships, especially for electronics house packaging for thermal control applications 42–44 . Salts of transition metals such as V and W are usually used as additives to fabricate black PEO coatings 42,45,46 . However, the alloying elements from substrate metal may also play a role on the color of the PEO coatings.…”

Section: Introductionmentioning

confidence: 99%

“…[42][43][44] Salts of transition metals such as V and W are usually used as additives to fabricate black PEO coatings. 42,45,46 However, the alloying elements from substrate metal may also play a role on the color of the PEO coatings. Han et al 12 demonstrated that the oxidation of titanium substrate into low-valence oxides of titanium (Ti 2+ , Ti 3+ ) leads to black coatings.…”

Section: Introductionmentioning

confidence: 99%

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Fast formation of a black inner α‐Al₂O₃ layer doped with CuO on Al–Cu–Li alloy by soft sparking PEO process

Tian

et al. 2023

J Am Ceram Soc.

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Forming high‐temperature α‐Al2O3 phase under soft sparking is an intriguing phenomenon in plasma electrolytic oxidation (PEO) of Al alloys, which contradicts the low energy input of the process. In this study, α‐Al2O3 doped with black CuO is formed beneath an amorphous white outer layer on Al–Cu–Li alloy by PEO in a dilute silicate electrolyte under soft sparking. In comparison, reddish coatings with dominating γ‐Al2O3 are formed under the conventional plasma discharges, although blackish inner layer with α‐Al2O3 can also be exposed by heavily polishing the samples. In order to know the underlying mechanism, temperatures at the coating surface and the underlying substrate have been monitored by a thermocouple under the conventional and soft sparking PEO regimes, respectively. Interestingly, high temperatures are detected in the case of soft sparking rather than PEO with strong discharges. The formation of CuO, quartz, and cristobalite within the soft sparking coating also supports the existence of high temperature. Hence, the formation of α‐Al2O3 under soft sparking can be resolved to the conventional thermal activation mechanism, without the need of seeking other plausible explanations. Thermal condition evaluation for soft sparking PEO suggests that values of the effective thermal conductivity during PEO process for the outer layer and the barrier layer at the coating/substrate interface might be lower than ∼0.05 and ∼0.0017 W m−1 K−1, respectively. It is believed that the amorphous structure of the outer and barrier layers effectively blocks the heat dissipation, facilitating the formation of a highly wear‐resistant inner layer with α‐Al2O3, CuO, and the other high‐temperature species under soft sparking.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fast formation of a black inner α‐Al₂O₃ layer doped with CuO on Al–Cu–Li alloy by soft sparking PEO process

Tian

et al. 2023

J Am Ceram Soc.

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“…For Al alloys, Li et al [19] prepared a black MAO film on the LY12 Al alloy derived from the silicate electrolyte embracing NH 4 VO 3 . Hwang and Shin [20] obtained a sort of black film by adding Na 2 WO 4 into the phosphate electrolyte. Wang and Nie [21] invented a new blue plasma electrolytic oxidation film on wrought 2024 Al alloy.…”

Section: Introductionmentioning

confidence: 99%

The Preparation and Properties of the Brown Film by Micro-arc Oxidized on In-Situ TiB2/7050Al Matrix Composites

et al. 2020

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The brown or grayish-white color films were prepared by the micro-arc oxidation (MAO) method on in-situ TiB2/7050Al composites using these alkaline electrolytes with/without KMnO4 as an additive. The microstructure, elemental composition, chemical state and corrosion behavior have been investigated by the microstructure characterizations and electrochemistry measurements on the MAO films comparatively. The results indicated that a brown film was obtained via adding KMnO4 into the alkaline electrolyte. The coloration mechanism of the brown color can be ascribed to the existence of MnO inside the film. Furthermore, the initiation of corrosion to the Al composite was intensively hindered by the brown MAO film. Compared with the Al substrate and grayish-white film, the brown MAO film exhibited the elevated corrosion potential and reduced corrosion current. Therefore, the brown film has presented an optimized corrosion resistance for the composite.

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“…In the literature on plasma electrolytic oxidation (PEO), coloring the valve metal surface has been performed through adding either soluble metal salts − or suspended pigments in the electrolytic solution. We prefer pigment to metal salt since the pigment is more manageable in industrial practice.…”

Section: Introductionmentioning

confidence: 99%

Particle Size Influences on the Coating Microstructure through Green Chromia Inclusion in Plasma Electrolytic Oxidation

Liu

Tsai

Wang

et al. 2017

ACS Appl. Mater. Interfaces

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In an effort to color the aluminum alloy surface green via plasma electrolytic oxidation (PEO), two alkaline solutions have been employed with particulate inclusions and sodium aluminate. Electrolyte I comprises a self-made chromia pigment with a mean particle size 69 nm, whereas electrolyte II contains a commercially available pigment, GN-M, with a larger particle size 351 nm. Both pigments are oxygen deficient CrO of corundum-type structure before coating, the oxidative environment of PEO converts them into stoichiometric CrO. In electrolyte I and II, the oxides of chromium and aluminum deposit simultaneously under analogous PEO conditions, yet resulting in very different microstructures. The GN-M inclusion of large size amasses on top of the coating, while the self-made inclusion goes deep, and closely associates with alumina and pores. The oxide coating, grown in electrolyte II, consists of a top CrO-rich layer and a dense alumina layer underneath, delineated by the boundary marked with microdischarge burns. On the other hand, the self-made particulate inclusion appears to bring the electric microdischarges inside the coating and create inner pores and damages. The structure difference, caused by the difference in microdischarge locations, is attributed to shifting of the CrO-AlO interface where p-type and n-type semiconductors meet.

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Formation of Black Ceramic Layer on Aluminum Alloy by Plasma Electrolytic Oxidation in Electrolyte Containing Na<sub>2</sub>WO<sub>4</sub>

Cited by 47 publications

References 25 publications

Fast formation of a black inner α‐Al₂O₃ layer doped with CuO on Al–Cu–Li alloy by soft sparking PEO process

Fast formation of a black inner α‐Al₂O₃ layer doped with CuO on Al–Cu–Li alloy by soft sparking PEO process

The Preparation and Properties of the Brown Film by Micro-arc Oxidized on In-Situ TiB2/7050Al Matrix Composites

Particle Size Influences on the Coating Microstructure through Green Chromia Inclusion in Plasma Electrolytic Oxidation

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Formation of Black Ceramic Layer on Aluminum Alloy by Plasma Electrolytic Oxidation in Electrolyte Containing Na<sub>2</sub>WO<sub>4</sub>

Cited by 47 publications

References 25 publications

Fast formation of a black inner α‐Al2O3 layer doped with CuO on Al–Cu–Li alloy by soft sparking PEO process

Fast formation of a black inner α‐Al2O3 layer doped with CuO on Al–Cu–Li alloy by soft sparking PEO process

The Preparation and Properties of the Brown Film by Micro-arc Oxidized on In-Situ TiB2/7050Al Matrix Composites

Particle Size Influences on the Coating Microstructure through Green Chromia Inclusion in Plasma Electrolytic Oxidation

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Fast formation of a black inner α‐Al₂O₃ layer doped with CuO on Al–Cu–Li alloy by soft sparking PEO process

Fast formation of a black inner α‐Al₂O₃ layer doped with CuO on Al–Cu–Li alloy by soft sparking PEO process