An aggregate of Eu-doped GaN columnar crystals was synthesized at 700 C and a N 2 pressure of 5 MPa at the surface of a Na-Ga melt with the addition of Eu metal. The color of the crystals was black at the melt-phase side, and changed to brown to colorless and transparent toward the gas-phase side. Energy-dispersive X-ray analysis revealed that the Eu content was 0.15 at. % at the black part and decreased gradually below <0:1 at. % at the colorless transparent part. The colorless transparent part glowed red under ultraviolet radiation. A strong emission peak associated with the intra-4 f transition of Eu 3þ from 5 D 0 to 7 F 2 was observed at 621 nm in the photoluminescence spectrum and at 624 nm in the cathodoluminescence spectrum.
In order to improve the adhesion strength of the DLC coating, Fine Particle Peening (FPP) treatment was employed as pretreatment for DLC coatings. FPP treatment was performed using SiC shot particles, and then the AISI316L steel was DLC-coated. The FPP treatment increased the surface roughness of the specimen, and a Si-rich layer was formed on the surface because of the mechanical mixing of SiC shot particles into the steel substrate. Reciprocating sliding wear tests were conducted to measure the friction coefficient. While the non-pretreated (only DLC-coated) specimens showed a sudden increase in friction coefficient resulting from delamination of the DLC coating, the pre-FPP-treated specimens maintained a low friction coefficient during the wear tests. This indicates the strong adhesion of the DLC coating of the pre-FPP-treated specimen caused by the increase in surface roughness and the presence of Si on the surface.
Abstract. In order to improve the adhesiveness of the DLC coating, Fine Particle Peening (FPP) treatment was employed as pre-treatment of the DLC coating process. FPP treatment was performed using SiC shot particles, and then AA6061-T6 aluminum alloy was DLC-coated. A SiC-rich layer was formed around the surface of the aluminum alloy by the FPP treatment because small chips of shot particles were embedded into the substrate surface. Reciprocating sliding tests were conducted to measure the friction coefficients. While the DLC coated specimen without FPP treatment showed a sudden increase in friction coefficient at the early stage of the wear cycles, the FPP/DLC hybrid treated specimen maintained a low friction coefficient value during the test period. Further investigation revealed that the tribological properties of the substrate after the DLC coating were improved with an increase in the amount of Si at the surface.
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