Studies On Preparation And Structure And Property Of Polymer/(SrAl₂O₄: Eu～(2+), Dy～(3+)) Coated With Si And Al Composite Luminescent Materials

SrAl₂O₄:Eu²⁺,Dy³⁺ luminescent material takes aluminates as the base, Eu²⁺ ionsas the activator, Dy³⁺ ions as the co-activator, and is functional inorganic materialswith strong luminescence at the yellow/green region, long afterglow time and noradio element. But SrAl₂O₄:Eu²⁺,Dy³⁺ is easy to hydrolyze in a humid place. Thehydrolysis reaction will result in a going down of the luminescent ability of thematerials till no light and lose its value.Because the SrAl₂O₄:Eu²⁺,Dy³⁺ is easy to hydrolyze, the polymer/SrAl₂O₄:Eu²⁺,Dy³⁺ composite luminescent materials were prepared throughemulsion polymerization. Although there is much water in a general emulsionpolymerization, we realized mainly to prepare the polyacrylate/SrAl₂O₄:Eu²⁺,Dy³⁺composite luminescent materials through grafting polyacrylate onto the surface ofSrAl₂O₄:Eu²⁺,Dy³⁺ by in-situ emulsion polymerization in the paper. Polymericmaterials, which are a type of widely used materials, of course, have manyadvantages such as abundant in source, low density, good performance in mechanic,electric, and optic properties, stable to chemicals, and easy in processing. When theobtained polyacrylate/SrAl₂O₄: Eu²⁺,Dy³⁺ composite luminescent materials were usedin plastic matrix such as low-density polyethylene (LDPE), it will modify the materials' water-resistance, processing performance, and improve the compatibilitybetween the luminescent materials and the matrix. The major research works are asfollows:SrAl₂O₄:Eu²⁺,Dy³⁺coated with Si and Al were prepared by the sol-gel route,and the influence of the mass of TEOS, two type of catalyst and pH of the system onthe reaction were studied. The result of fluorescence (FL) spectra and the apparatusof testing photo-luminescence measurement indicate that the coated sample has thesimilar luminescent properties to that of the uncoated. The size, compositions,microstructure, texture and surface morphology of the binary films containing Si andAl elements were investigated by XPS, XRD, SEM, BET and LSD. Water-resistanceof the coated and uncoated samples was evaluated by measuring the pH of water inwhich they were dispersed. The results show that the size of the coated sample isabout 30μm, a thin dense binary film containing Si and Al elements forms on thesurface of the uncoated sample and combines to its surface through chemical bond,which can enhance the uncoated sample's stability under water-containing condition.According to the results listed above, the principle of how to coat SrAl₂O₄:Eu²⁺,Dy³⁺with Si and Al was studied.SrAl₂O₄:Eu²⁺,Dy³⁺ coated with Si and Al were modified by the silicanecoupling agent(MAPS), making the surface of SrAl₂O₄:Eu²⁺,Dy³⁺ coated with Si andAl hydrophobic, which is crucial to ensure that acrylate monomers or styrenemonomer can react on the surface of SrAl₂O₄:Eu²⁺,Dy³⁺. The structure of themodified SrAl₂O₄:Eu²⁺,Dy_<sup>3+ coated with Si and Al was characterized by means ofFTIR, XPS, SEM and TG-DTG respectively. The results show that the amount of thecoupling agent grafted on the surface of SrAl₂O₄:Eu²⁺,Dy³⁺ coated with Si and Al isabout 0.34%. The results of the fluorescence (FL) spectra and thephoto-luminescence measurement indicate that the modified sample has the similarluminescent properties to that of SrAl₂O₄:Eu²⁺,Dy³⁺.The polymer/SrAl₂O₄: Eu²⁺,Dy³⁺ coated with Si and Al were firstly prepared byemulsion polymerization by using acrylate monomers and styrene monomer. The result of the experiment shows that the emulsifier concentration was far more thanthe CMC of the emulsifier. The reason is that the size of SrAl₂O₄:Eu²⁺,Dy³⁺ coatedwith Si and Al was about 30μm (D (0.5)) and the density of it is very high.Emulsified and dispersed functions of the emulsifier were important equally, so theemulsifier concentration was far more than the CMC of the emulsifier. The structureof polymer/ (SrAl₂O₄:Eu²⁺,Dy³⁺) coated with Si and Al composite luminescentmaterials was characterized by means of FTIR,TG-DTG, SEM,XRD and XPSrespectively, and the luminescent properties were measured by fluorescence (FL)spectra and the apparatus of testing photo-luminescence. The results show thatorganic parts are combined onto the surface of the inorganic parts through chemicalbond. Compared with SrAl₂O₄:Eu²⁺,Dy³⁺, Polymer/ (SrAl₂O₄:Eu²⁺,Dy³⁺) coatedwith Si and Al composite luminescent materials still kept good luminescentproperties. Water-resistance of composite luminescent materials was evaluated bymeasuring the pH of water in which they were dispersed. The result indicates thatthe composite luminescent materials can improve the water-resistance ofSrAl₂O₄:Eu²⁺,Dy³⁺. Based on the results listed above, the formation mechanism ofthe composite luminescent materials was probed.The polyacrylate/SrAl₂O₄:Eu²⁺,Dy³⁺ coated with Si and Al was used in plasticmatrix such as low-density polyethylene (LDPE) to prepare luminescent plastics.The luminescent properties of the luminescent plastic were measured byfluorescence (FL) spectra and the apparatus of testing photo-luminescence. Theresults show a good luminescent performance.The result of SEM indicates that thecomposite luminescent materials can improve the compatibility between theluminescent materials and the matrix.