Photoluminescence Properties Of Products Research Articles

Carbothermal Reduction Nitridation of Fly Ash, Diatomite and Raw Illite: Formation of Nitride Powders with Different Morphology and Photoluminescence Properties

Rare-earth-doped SiAlON and Si3N4 materials from aluminosilicate starting materials have been reported to show superior photoluminescence (PL) properties. Three different starting materials, including pulverized coal furnace fly ash, diatomite and raw illite, were used for synthesis of nitride materials. The phase and morphology evolution of these products were carefully monitored at the low temperature range of 1350 °C to 1450 °C by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and Fourier-transform infrared spectroscopy (FT-IR). The PL properties of Eu-doped nitride products were also comparatively characterized. The results show that the type of starting material affects the phase composition and the photoluminescence properties of products. The existence of aluminum and alkali metals could effectively promote nitridation reactions. Aluminum in the starting materials led to the formation of different aluminum-rich nitride phases. Thus, β-SiAlON could be achieved at a much lower temperature (1350 °C) using raw illite or fly ash containing the proper amount of aluminum. Additionally, excess aluminum led to the formation of corundum and 15R-SiAlON. The products from pulverized coal furnace fly ash had more prismatic particles, and the products from diatomite had more fibrous particles. With the progress of the nitridation process, the fibers were increased, becoming longer and straighter, and the prismatic particles were more obvious. The presence of aluminum in the starting materials led to a blue shift in the photoluminescence spectrum.

Impacts of Si particle size and nitrogen pressure on combustion synthesis of Eu2 +-doped α-SiAlON yellow phosphors

Herein, a facile combustion synthesis strategy (CS) was constructively developed for the highly-efficient preparation of SiAlON based phosphors. Yellow light emitting behavior was endued to the Ca-α-SiAlON ceramic powders by doping of Eu2+. The Si average particle size and nitrogen pressure were known to play vital roles in the CS reaction. The distinct impacts of these two important processing parameters on the phase composition, microstructure and photoluminescence properties of products were firstly thoroughly studied in the CS system of Ca-α-SiAlON:Eu2+ phosphors. The experimental results demonstrated that the comprehensive properties of as-synthesized phosphors would be evidently promoted by the utilization of appropriate Si particle size and nitrogen pressure, respectively 4μm and 5MPa in this system. The phosphors were featured with high phase purity, good state of crystallization, favorable uniformity and equiaxed morphology. A strong yellow emission was peaked at 576nm under excitation of near-UV or blue light.

Fluorescence Studies on Thiol‐Functional Polystyrene‐CdS Nanocomposites

Thiol‐functional polystyrene‐CdS nanocomposites have been prepared via an in‐situ method. The products were characterized in detail. The photoluminescence properties of products were also studied. The thiol fraction in thiol‐functional polystyrene can be controlled by the copolymerization of styrene and 4‐chloromethylstyrene. So, the CdS content in polymer and the photoluminescence properties of nanocomposites can be tuned up quantificationally. Results show that the fluorescence of nanocomposites depends on the CdS content. The charge‐transfer mechanism of nanocomposites accords with ligand‐to‐metal charge‐transfer (LMET) model. These nanocomposites can be used as potential optical materials.