Metal contact quenching mechanism of sintered SrAl2O4:Eu2+, Dy3+ composite coating

simple and economic coating monitoring technology. The light-emitting properties of the novel coating can serve as an indicator layer, which warns when the coating has worn off, replacing or recoating is necessary [7]. When we inspect on coating with a hand-held UV-lamp, the yellowgreen light of SrAl2O4:Eu, Dy3+ will disappear. It means that the functional coating is worn out and that recoating is needed [8]. The Cu-14Al-X/SrAl2O4:Eu, Dy3+ composite coating has been successfully prepared by vacuum pressure-assisted sintering method. But the phosphorescent particles are quenched bucause of the preparation method, which will be harmful to the indication of the coating. The quenching behavior of phosphors has been previously studied. For example, Chithambo [9] reported thermal quenching of SrAl2O4:Eu,Dy with an activation energy and Mothudi [10] proposed hole trap levels when the SrAl2O4:Eu, Dy3+ phosphors annealed at different temperatures. Ju Guifang [11] proposed the concentration quenching of Eu2+ is attributed to competitive capturing of electrons with traps. Yang XF [12] studied quenching on iron impurity in Eu2+, Dy3+ doped strontium aluminates phosphor and explained that iron displace the aluminum and form Fe–O bond. However, most of researches focus on the fluorescent quenching mechanism in the synthesis process. To the best of our knowledge, the report on quenching mechanism of SrAl2O4:Eu, Dy3+ coupled with the wear-resistant materials is rare. In this work, luminescent composite coatings doped with rare earth phosphorescence were fabricated by vacuum pressure-assisted sintering. There are five types of composite coatings, which formed by luminescent powders dispersed throughout different matrixes (Cu, Fe, Ni, Mn and Cu-14Al-X). The sintered temperatures and metal contact were investigated in details; also the quenching mechanism of phosphor is discussed in composite coating. Abstract The self-sensing tribological composite coating (Cu-14Al-X/SrAl2O4:Eu, Dy3+) for wear indicator is quenched because of vacuum pressure-assisted sintering method, which do harm to the monitoring of coating. In this paper, we constructed a model to explain the quenching mechanism of SrAl2O4:Eu, Dy3+ in alloy coatings. The initial electron concentration and the energy level structures were studied. The results show that contact quenching rather than the traditional thermal quenching is the most important influencing factor for SrAl2O4:Eu, Dy3+. The contact metal in coatings can be as a defect level and dissipation center of electron transition, the quenching process could be well explained by the model we proposed.