• Korean Journal of Materials Research
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• v.30 no.8
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• pp.406-412
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• 2020

SrMoO₄:RE³⁺ (RE=Dy, Sm, Tb, Eu, Dy/Sm) phosphors are prepared by co-precipitation method. The effects of the type and the molar ratio of activator ions on the structural, morphological, and optical properties of the phosphor particles are investigated. X-ray diffraction data reveal that all the phosphors have a tetragonal system with a main (112) diffraction peak. The emission spectra of the SrMoO₄ phosphors doped with several activator ions indicate different multicolor emissions: strong yellow-emitting light at 573 nm for Dy³⁺, red light at 643 nm for Sm³⁺, green light at 545 nm for Tb³⁺, and reddish orange light at 614 nm for Eu³⁺ activator ions. The Dy³⁺ singly-doped SrMoO₄ phosphor shows two dominant emission peaks at 479 and 573 nm corresponding to the ⁴F_9/2→⁶H_15/2 magnetic dipole transition and ⁴F_9/2→⁶H_13/2 electric dipole transition, respectively. For Dy³⁺ and Sm³⁺ doubly-doped SrMoO₄ phosphors, two kinds of emission peaks are observed. The two emission peaks at 479 and 573 nm are attributed to ⁴F_9/2→⁶H_15/2 and ⁴F_9/2→⁶H_13/2 transitions of Dy³⁺ and two emission bands centered at 599 and 643 nm are ascribed to ⁴G_5/2→⁶H_7/2 and ⁴G_5/2→⁶H_9/2 transitions of Sm³⁺. As the concentration of Sm³⁺ increases from 1 to 5 mol%, the intensities of the emission bands of Dy³⁺ gradually decrease; those of Sm³⁺ slowly increase and reach maxima at 5 mol% of Sm³⁺ ions, and then rapidly decrease with increasing molar ratio of Sm³⁺ ions due to the concentration quenching effect. Fluorescent security inks based on as-prepared phosphors are synthesized and designed to demonstrate an anti-counterfeiting application.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.898-904
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• 2021

This experimental study aims to investigate the use of a wet electrostatic precipitator as a post-treatment device to satisfy the strict emission regulations for sulfur oxides and particulate matter (PM). The inlet/outlet of a wet electrostatic precipitator was installed in a funnel using a marine four-stroke diesel engine (STX-MAN B&W) consuming marine heavy fuel oil (HFO) with a sulfur content of about 2.1%. Measurements were then obtained at the outlet of the wet electrostatic precipitator; an optical measuring instrument (OPA-102), and the weight concentration measurement method (Method 5 Isokinetic Train) were used for the PM measurements and the Fourier transform infrared (FT-IR; DX-4000) approach was used for the sulfur oxide measurements. The experimenst were conducted by varying the engine load from 50%, to 75% and 100%; it was noted that the PM reduction efficiency was a high at about 94 to 98% under all load conditions. Additionally, during the process of lowering the exhaust gas temperature in the quenching zone of the wet electrostatic precipitator, the sulfur dioxide (SO₂) values reduced because of the cleaning water, and the reduction rate was confirmed to be 55% to 81% depending on the engine load.