5 results on '"Deng, Hui"'
Search Results
2. Highly efficient and damage-free polishing of GaN (0 0 0 1) by electrochemical etching-enhanced CMP process.
- Author
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Zhang, Linfeng and Deng, Hui
- Subjects
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GRINDING & polishing , *ELECTROLYTE solutions , *SURFACE roughness , *ETCHING - Abstract
• Electrochemical etching-enhanced CMP is proposed for efficient polishing of GaN. • Identical-site observation was conducted to study the etching behaviors of GaN. • A maximum etching rate of 1.462 μm/min has been achieved. • Sa roughness of a dia-lapped GaN surface has been reduced from 69.8 nm to 0.64 nm. An electrochemical etching-enhanced CMP process was proposed to realize the highly efficient and damage-free finishing of GaN. In this process, electrochemical etching was first used to remove the damaged layer induced by grinding or lapping, and CMP was then conducted to flatten the etched surface. The etching rate could reach 1.46 μm/min using NaOH solution as the electrolyte which was highly efficient. It was found that the etching rate and surface roughness can be balanced by adjusting the applied potential. CMP was carried out on an etched GaN sample and the surface roughness was reduced from 69.8 nm to 0.64 nm, and its surface quality was also confirmed to be desirable through photoluminescence. These results demonstrate that the proposed electrochemical etching-enhanced CMP process is highly effective and efficient to obtain a crack-free, damage-free and smooth GaN surface. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
3. Highly efficient smoothing of Inconel 718 via electrochemical-based isotropic etching polishing.
- Author
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Muhammad Ajmal, Khan, Yi, Rong, Zhan, Zejin, Ji, Jianwei, Zhang, Xinquan, and Deng, Hui
- Subjects
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GRINDING & polishing , *INCONEL , *ETCHING , *TEMPERATURE control , *SURFACE roughness , *NICKEL alloys , *PASSIVATION , *HEAT resistant alloys - Abstract
For the highly efficient and versatile polishing of metals, isotropic etching polishing (IEP), which is based on the merging of isotropic etching holes, has been developed. In this study, the feasibility and mechanism of isotropic etching polishing of nickel-based superalloy Inconel 718 (IN718) and the polishing characteristics have been studied. The potentiodynamic experiments revealed similar trends of the cathodic, passive, second passivation, and transpassive regions in all the electrolytes, while the corrosion susceptibility of IN718 successively decreased with the increasing H 2 SO 4 concentration in the electrolyte. The etching anisotropy of the IN718 precipitated with different phases can be experimentally transmuted to isotropic etching by modulating the electrolyte concentration and keeping electrolyte temperature equal or above the room temperature. Because of the positive correlation of the etching current with isotropic holes density and diameter, etching at higher currents is promoted for the rapid and proficient polishing. The surface evolution mechanism during IEP has been confirmed. The surface roughness initially increased due to the formation of etching holes, then decreased abruptly owing to the rapid merging of etching holes and finally achieved a smooth surface. The wet grounded surface of IN718 with a roughness of Sa 62.7 nm has been transformed into a mirror-like smooth surface with a roughness of Sa 0.86 nm within 300 s of IEP at optimized conditions and a high MRR of 2.73 mm3/min has been achieved. • Electrochemical-based isotropic etching polishing mechanism of Inconel 718. • Electrolyte concentration and temperature control etching anisotropy of Inconel 718. • Two phase Inconel 718 with MC carbides was polished by isotropic etching polishing. • Inconel 718 surface roughness first increased and then decreased during polishing. • Isotropic etching polishing achieved mirror-like shining Inconel 718 surface. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
4. Mechanism study of electropolishing from the perspective of etching isotropy.
- Author
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Yi, Rong, Ji, Jianwei, Zhan, Zejin, and Deng, Hui
- Subjects
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ELECTROLYTIC polishing , *CURRENT density (Electromagnetism) , *ETCHING , *SURFACE finishing , *METAL finishing , *MASS transfer , *ELECTROCHEMICAL cutting - Abstract
Electropolishing, as a damage-free and highly efficient surface finishing method, has been widely used for finishing of metal components. In this study, the electropolishing mechanism of tungsten in the electrolyte with H 2 SO 4 and CH 3 OH was investigated from the perspective of etching isotropy. The anodic dissolution behavior of tungsten demonstrated that anisotropic and isotropic etching occurred under the activation polarization and mass transfer polarization, respectively. The evolution of surface morphology, roughness, and electric current density during electropolishing has been experimentally investigated and analyzed. According to the changes in surface morphology and current density, there was a transformation from anisotropic etching to isotropic etching during the electropolishing due to the time-consuming accumulation of reactive products. The application of a pulse power supply with a duty cycle of 10% resulted in a rough surface on tungsten due to the mass transfer polarization being inhibited. Similar results were also obtained in the electrolyte with 2 wt% NaOH. The presented findings experimentally demonstrate the importance of the isotropic etching mode for electropolishing, which is of great value for further revealing the electropolishing mechanism. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
5. A generic approach of polishing metals via isotropic electrochemical etching.
- Author
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Yi, Rong, Zhang, Yi, Zhang, Xinquan, Fang, Fengzhou, and Deng, Hui
- Subjects
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METAL finishing , *SURFACE finishing , *ETCHING , *SURFACE roughness , *METALLIC surfaces - Abstract
Isotropic etching polishing (IEP), which is based on the merging of hemispherical holes that are formed by isotropic etching, is proposed in this study as a universal metal finishing approach. Modeling of the surface evolution during IEP is also carried out, and the formation of a metal surface is predicted. The etching anisotropy of titanium is experimentally studied, and the results show that isotropic etching can be realized under optimized conditions. Isotropic etching sites originate from a breakdown of the passivation layer. Both the density and growth rate of the holes are affected by the current, and a large etching current is preferred for the realization of highly efficient polishing. IEP has been shown to be effective and efficient for surface finishing of TA2. The surface Sa roughness is drastically reduced from 64.1 nm to 1.2 nm, and a maximum polishing rate of 15 μm/min is achieved under an etching current of 3 A. IEP has also been successfully applied for surface finishing of other metals, including TC4, stainless steel 304, aluminum alloy 6063 and pure nickel, demonstrating that IEP can be considered a universal approach for finishing metals. Image 1 • Isotropic etching polishing (IEP) was proposed as a general metal finishing approach. • Isotropic electrochemical etching of titanium with ultrasmooth inner surface was realized. • Sa roughness of TA2 was reduced from 64.1 to 1.23 nm with a maximum MRR of 15 μm/min. • IEP was effective for surface finishing of stainless steel, aluminum and nickel. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
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