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http://dx.doi.org/10.9713/kcer.2013.51.2.214

Plasma-mediated Hydrophobic Coating on a Silicate-based Yellow Phosphor for the Enhancement of Durability  

Jang, Doo Il (Department of Chemical and Biological Engineering, Jeju National University)
Jo, Jin Oh (Department of Chemical and Biological Engineering, Jeju National University)
Ko, Ranyoung (Department of Chemical and Biological Engineering, Jeju National University)
Lee, Sang Baek (Department of Chemical and Biological Engineering, Jeju National University)
Mok, Young Sun (Department of Chemical and Biological Engineering, Jeju National University)
Publication Information
Korean Chemical Engineering Research / v.51, no.2, 2013 , pp. 214-220 More about this Journal
Abstract
Hydrophobic coating on a silicate-based yellow phosphor ($Sr_2SiO_4:Eu^{2+}$) was carried out by using hexamethyldisiloxane (HMDSO) precursor in an atmospheric pressure dielectric barrier discharge plasma reactor, eventually to improve the long-term stability and reliability of the phosphor. The phosphor powder samples were characterized by a scanning electron microscope (SEM), a transmission electron microscope (TEM), a fluorescence spectrophotometer and a contact angle analyzer. After the coating was prepared, the contact angle of the phosphor powder increased to $133.0^{\circ}$ for water and to $140.5^{\circ}$ for glycerol, indicating that a hydrophobic layer was formed on its surface. The phosphor coated with HMDSO exhibited photoluminescence enhancement up to 7.8%. The SEM and TEM images of the phosphor powder revealed that the plasma coating led to a morphological change from grain-like structure to smooth surface with 31~46 nm thick hydrophobic layer. The light emitting diode (3528 1 chip LED) fabricated with the coated phosphor showed a substantial enhancement in the reliability under a special test condition at $85^{\circ}C$ and 85% relative humidity for 1,000 h (85/85 testing). The plasma-mediated method proposed in this work may be applicable to the formation of 3-dimensional coating layer on irregular-shaped phosphor powder, thereby improving the reliability.
Keywords
Hydrophobic Coating; Silicate Phosphor; Dielectric Barrier Discharge; Hexamethyldisiloxane;
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Times Cited By KSCI : 5  (Citation Analysis)
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