Correlations between the optical emission spectra and microstructure of microplasma coatings on aluminum 2024 alloy

Rogov, Aleksey B.; Shayapov, V. R.

doi:10.1016/j.apsusc.2012.01.097

Cited by 10 publications

(12 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Researchers have shown keen interest in raising the α-Al 2 O 3 content of the coating [74], since α-Al 2 O 3 provides hardness, stability, and wear resistance. In the bi-layer structure of Figure 1a, the dense inner layer has been found to contain more α-Al 2 O 3 than usual after soft sparking [55]. A plausible explanation for more α-Al 2 O 3 is that a thick coating retains thermal heat and allows α-Al 2 O 3 to nucleate and grow at the expense of γ-Al 2 O 3 [75].…”

Section: Amassed Oxide and Energy Consumptionmentioning

confidence: 99%

“…Researchers have employed OES in monitoring the electrolytic plasma on Al alloys. The following spectral lines are commonly analyzed; 309 nm (Al I), 396 nm (Al I), 656 nm (H α ) 486 nm (H β ), 589 nm (Na I), 777 nm (O I) [17,[53][54][55]. Under the assumption of local thermodynamic equilibrium, the intensity ratio (J ma /J nb ) of two spectral lines of the same atom can be used to extract the (plasma) electron temperature T e of a specific location, using Equation (1).…”

Section: Plasma State In Electron Temperaturementioning

confidence: 99%

See 1 more Smart Citation

Review of the Soft Sparking Issues in Plasma Electrolytic Oxidation

Tsai

Chou

2018

Metals

View full text Add to dashboard Cite

Abstract:A dense inner layer is highly valued among the surface coatings created through plasma electrolytic oxidation (PEO) treatment, because the PEO coating has been troubled by inherent porosity since its conception. To produce the favored structure, a proven technique is to prompt a soft sparking transition, which involves a sudden decrease in light and acoustic emissions, and a drop in anodic voltage under controlled current mode. Typically these phenomena occur in an electrolyte of sodium silicate and potassium hydroxide, when an Al-based sample is oxidized with an AC or DC (alternating or direct current) pulse current preset with the cathodic current exceeding the anodic counterpart. The dense inner layer feature is pronounced if a sufficient amount of oxide has been amassed on the surface before the transition begins. Tremendous efforts have been devoted to understand soft sparking at the metal-oxide-electrolyte interface. Studies on aluminum alloys reveal that the dense inner layer requires plasma softening to avoid discharge damages while maintaining a sufficient growth rate, a porous top layer to retain heat for sintering the amassed oxide, and proper timing to initiate the transition and end the surface processing after transition. Despite our understanding, efforts to replicate this structural feature in Mg-and Ti-based alloys have not been very successful. The soft sparking phenomena can be reproduced, but the acquired structures are inferior to those on aluminum alloys. An analogous quality of the dense inner layer is only achieved on Mg-and Ti-based alloys with aluminate anion in the electrolytic solution and a suitable cathodic current. These facts point out that the current soft sparking knowledge on Mg-and Ti-based alloys is insufficient. The superior inner layer on the two alloys still relies on rectification and densification of aluminum oxide.

show abstract

Section: Amassed Oxide and Energy Consumptionmentioning

confidence: 99%

Section: Plasma State In Electron Temperaturementioning

confidence: 99%

Review of the Soft Sparking Issues in Plasma Electrolytic Oxidation

Tsai

Chou

2018

Metals

View full text Add to dashboard Cite

show abstract

“…9,10,12,15 It is known that until a specific thickness H ST (for a given set of initial and boundary conditions) is reached, the common voltage and thickness behaviors are independent of the R-value. 12,15,18,27,48 Then if a current mode with appropriate R is applied, the anodic voltage begins to decrease (ΔU < 0) at a certain moment of time (t ST ) and the PEO process undergoes a transition to the soft mode. It was found that the increase in R causes an increase in ΔU magnitude and a decrease in t ST .…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…(a) decrease of anodic voltage; 8−13 (b) decrease of acoustic emission; 12,14−16 (c) decrease of light emission from discharge; 10,15,17,18 (d) a more uniform discharge distribution over the sample surface; [9][10][11]15,19,20 (e) changes in spectral properties of the light emitted by discharges; 15,18 (f) hysteresis in transient current−voltage curves. 13,16,21,22 At the same time, the following improvements can be achieved in PEO coatings due to the suitable soft sparking mode:…”

Section: ■ Introductionmentioning

confidence: 99%

The Role of Cathodic Current in Plasma Electrolytic Oxidation of Aluminum: Phenomenological Concepts of the “Soft Sparking” Mode

2017

View full text Add to dashboard Cite

A comprehensive analysis of experimental data relating to so-called "soft sparking" mode of plasma electrolytic oxidation (PEO) has been undertaken. The transition to the soft sparking mode is accompanied by a number of characteristic effects, such as a decrease in anodic voltage, acoustic and light emission, increase in hysteresis in transient current-voltage curves, improved uniformity of the discharge distribution on the surface, disappearance of atomic lines, and development of continuous radiation in the optical emission spectra. An explanation of the main features of PEO process operated under soft sparking conditions is proposed assuming the existence of a specific narrow region in the coating thickness, where the main anodic voltage drops. Because of high electric field in this "active zone", both anodic oxidation of the metal substrate and high-energy processes may take place. According to this assertion, the soft sparking mode of PEO is caused by cathodic polarization (a) eliminating the potential barrier at the oxide-electrolyte interface due to local acidification and (b) increasing electric field at the metal-oxide interface during subsequent anodic half-cycle due to narrowing of low-conductive part within the active zone. Based on this consideration, it is possible to account for the main characteristic phenomena accompanying the PEO process on aluminum under alternating polarization.

show abstract

“…A through-hole amorphous alumina coating with the thickness that reaches hundreds of microns [22] can be produced by anodizing technology. Unfortunately, the thermal conductivity is poor [23]. Restricted by thermodynamics, the phase transition temperature (1150 • C) of amorphous alumina to α-alumina is much higher than the liquefaction temperature (660 • C) of aluminum [24].…”

Section: Materials Dielectric Strength (Kv/mm) Thermal Conductivity (mentioning

confidence: 99%

Fabrication of a Thick Crystalline Al2O3 Coating with Insulation and High Thermal Conductivity via Anodic Oxidation and Subsequent Mic Arc Discharge Treatment

Song

Jiang

2020

Coatings

View full text Add to dashboard Cite

Amorphous Al2O3 coating with a thickness of 143 μm was firstly prepared by anodic oxidation, then the amorphous Al2O3 was transformed into crystalline Al2O3 through applying micro arc discharge. The crystal structure of the Al2O3 coatings was analyzed with an X-ray diffractometer. Results indicated that the coating consisted of amorphous and crystalline Al2O3. The microstructure of the coating was characterized by scanning electron microscopy, which showed that the coating had a compact structure. The thermal conductivity of the coating was 23.7 W/m·K, which is significantly higher than that of amorphous Al2O3 coating. The total and specific breakdown voltages of the coating were 3.85 kV and 26.92 kV/mm, which is suitable to apply for high power LED heat sink substrate.

show abstract

Correlations between the optical emission spectra and microstructure of microplasma coatings on aluminum 2024 alloy

Cited by 10 publications

References 28 publications

Review of the Soft Sparking Issues in Plasma Electrolytic Oxidation

Review of the Soft Sparking Issues in Plasma Electrolytic Oxidation

The Role of Cathodic Current in Plasma Electrolytic Oxidation of Aluminum: Phenomenological Concepts of the “Soft Sparking” Mode

Fabrication of a Thick Crystalline Al2O3 Coating with Insulation and High Thermal Conductivity via Anodic Oxidation and Subsequent Mic Arc Discharge Treatment

Contact Info

Product

Resources

About