ABSTRACT
The interaction between colloidal SiO(2) particles and the surface of ZnS-type phosphors has been studied. The green emitting phosphor ZnS:Cu,Al,Au applied in color television tubes was chosen as a model compound. After the surface of the phosphor particles (d(50)=5.0 µm) was treated in different manners like washing with H(2)O, HCl, or H(2)O(2) as well as precoating with colloidal ZnO particles (d(50)=81 nm), colloidal SiO(2) particles (d(50)=207 nm) were added. Thereafter, the amount of adhered SiO(2) was investigated based on SEM and ESCA analysis. By ESA measurements the surface charge of the colloids and the differently treated ZnS materials was investigated. Based on the experimental results it can be concluded that colloidal SiO(2) particles adhere sufficiently only if ZnO is present on the ZnS surface. The SiO(2) particles are located on top of the ZnO. Finally, the attractive interactions in the system ZnS-ZnO-SiO(2) are discussed in more detail. Copyright 2000 Academic Press.
ABSTRACT
Chemical and physical aspects of the adhesion of colloidal ZnO particles (d(50)=81 nm) on the surface of ZnS-type phosphors have been studied. Here, the green-emitting phosphor ZnS:Cu,Al,Cu (d(50)=5.0 µm) applied in TV screens was chosen as model compound. The ZnS material was pretreated in various ways (H(2)O, HCl, H(2)O(2)) and reacted thereafter with a suspension containing colloidal ZnO particles. Analytical investigations (SEM, ESCA) have shown that the adhesion of colloidal ZnO particles is strongly affected by the degree of hydrolysis of the ZnS surface. Electroacoustic investigations (ESA) prove that both types of surfaces, hydrolyzed ZnS as well as colloidal ZnO, are positively charged. Even so, adhesion of ZnO particles is encouraged very much under these conditions, indicating that secondary attractive forces (electrostatic interaction, chemical bonding) determine the amount of colloidal ZnO adhered on a ZnS-type phosphor. Copyright 2000 Academic Press.
