Papers by Keyword: Ca α-SiAlON

Abstract: Eu2+ Doped Ca-α-SiAlON phosphor have been synthesized from SiO2, Al2O3, CaCO3, Eu(NO3)3,carbon powders by carbothermal reduction–nitridation (CRN). Using X-ray Diffractometer (XRD) and fluorescent spectrophotometer, the influences of the phase content of the sintered samples after different soaking time at 1390°C and their luminescence properties were studied. The pure Ca-α-SiAlON:Eu2+ were prepared at processing temperatures of 1390°C in a holding time of 8 h. Ca-α-SiAlON:Eu2+ had high adsorption in the UV–visible spectral region. Two bands were observed in the emission spectrum centered at about 459 and 545 nm exited at 290nm. And two excitation bands located at about 297nm, 300-400nm were observed in the excitation spectrum with monitored at emission wavelength of 469nm or 550nm respectively. The morphology of the samples was examined via SEM, TEM. Ca/Eu co-doped α-SiAlON powders had hollow sphere morphology and it is composed of large numbers of very fine particles of around 30 to 70 nm in diameter. Elemental distribution was investigated using an EDS attached to a scanning electron microscopy (SEM). The sintered sample has a composition commonly seen for α-SiAlON.

Abstract: Ca-α-sialons with low oxygen content were fabricated at 1800°C by hot pressing. The phase and microstructure were characterized by XRD and SEM. The calculated lattice parameter reveals that 20~30% Ca2+ ions still exist in the grain boundary phase of Ca-α′. A large amount of Ca-containing liquid phase efficiently promotes the anisotropic growth of α′ grains in Ca-rich composition. Reinforced only by elongated α′ grains, the fracture toughness of Ca-α′ can reach 4.96 MPa•m1/2.

Abstract: This presented a route to utilize the Tungsten Molybdenum Bismuth Polymetallic Tailings in Shizhuyuan of Hunan province to fabricate Ca-substitued α-Sialon eco-materials. The reaction mechanism in carbothermal reduction nitridation process was widely studied by separately considering the effect of sintering temperature and soaking time. Based on the optimized conditions, a composite containing 78% Ca-based α-Sialon has been fabricated at 1600°C for 8h.

Abstract: The oxidation behavior of Ca-α-Sialon composites prepared by using the powders of α-Si3N4, AlN, Al2O3 and CaCO3 as the starting materials has been studied, for the composition Ca0.8Si8.8Al3.2O16N14.4 in the temperature range of 1200 to 1400°C for 24 to 96h in an air stream. The bending strength and weight gain of the samples before and after oxidation experiment were measured, and the phases of surfaces of the samples were examined by XRD, the microstructures of sections and surfaces of the samples were observed by SEM. The results show that the weight gain increased and the bending strength decreased as the oxidation time increased, and the oxidation layers contained bar cristobalite and glass phase at 1200°C, bubbles and glass phase at 1300°C, transparent glassy film and the pores at 1400°C, the phases of oxidation layers consisted of cristobalite, CaAl2Si2O8, and glass phase.