In a series of (Ca2–x/2–yEuy□x/2)(Si1–xPx)O4 (x = 0.06, 0.02 ≤ y ≤0.5), various color-emitting phosphors were successfully synthesized by a solid-state reaction. These phosphors were characterized by photoluminescence (PL) spectroscopy, X-ray powder diffractometry, transmission electron microscopy, and X-ray absorption fine structure spectroscopy. We evaluated the effect of heat treatment on PL properties with various annealing temperatures at 1373–1773 K for 4 h before/after reduction treatment from Eu3+ to Eu2+. In the red-emitting (Ca1.95Eu3+0.02□0.03)(Si0.94P0.06)O4+δ phosphor, the highest PL intensity exhibited when it was annealed at 1773 K. On the other hand, in the green-emitting (Ca1.95Eu2+0.02□0.03)(Si0.94P0.06)O4 phosphor, the highest PL intensity was realized when it was annealed at 1473 K and consequently treated under a reductive atmosphere. With increasing annealing temperature, the emission peak wavelength steadily decreased. Furthermore, with increasing Eu2+ content, the emission peak wavelength increased, with the color of emitting light becoming yellowish. Thus, the PL properties of the phosphors were affected by both the structural change from β to α’L, which occurred by heat treatment, and the amount of doped Eu ions.
Friction and wear properties of the copper/carbon/RB ceramics (Cu/C/RBC) composite were investigated under electrical current with and without arc-discharge. The weight fraction and the mean diameter of RB ceramics powder were 5 wt% and 4.9 µm, respectively, in the Cu/C/RBC composite. Friction tests were conducted with the block-on-ring friction apparatus. The Cu/C/RBC and the copper/carbon (Cu/C) composite, the conventional pantograph slider material of a railway current collector, were used as block specimens. Under electrical current without arc-discharge, the Cu/C/RBC composite showed 98% reduction in the specific wear rate of the block specimen, 23% reduction in that of the ring specimen, and 75% reduction in the friction coefficient over the conventional Cu/C composite. Under electrical current with arc-discharge, the Cu/C/RBC composite showed the wear resistance to arc-discharge equivalent to the conventional Cu/C composite.
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