Papers by Keyword: Nd₂O₃

Abstract: Li₂O-Al₂O₃-SiO₂ glass-ceramics doped with Nd₂O₃ were prepared by the melting method. The effects of Nd₂O₃ on the crystallization behavior of Li₂O-Al₂O₃-SiO₂ glass-ceramics were studied by DTA, XRD and SEM. With the increase of Nd₂O₃ content, the glass crystallization temperature arised. The SEM result indicates that the main crystal phase of Li₂O-Al₂O₃-SiO₂ glass-ceramics doped with Nd₂O₃ is β-quartz solid solution, for without doping Nd₂O₃ it is β-spodumene solid solution. These results shows that the crystallization temperature increases significantly by doping Nd₂O₃, and phase transition from β-quartz to β-spodumene is suppressed. The grain size increases with the increase of Nd₂O₃ content.

Abstract: Si and C of rice rusk were used as silica source and pore-forming agent to prepare cordierite-mullite ceramics at 1380°C for 5 h soaking. The Nd2O3 additive was added to improve the sintering properties. The bending strength, porosity, and thermal expansion coefficient were measured. The composition was characterized by X-ray diffraction (XRD). The microstructures of the sintered samples were observed by scanning electron microscopy (SEM). The cordierite-mullite ceramic doped with 2% Nd2O3 have high prorosity and low thermal expansion coefficient, its bending strength reaches 20.55 MPa. The addition of Nd2O3 decreases the mullite formation temperature to 1200 °C

Abstract: Nd--sialons with the stoichiometric composition and extra 2wt.% addition of Nd2O3 in Nd0.333Si10Al-2ON15 were synthesized by hot-press sintering. The longtime oxidation resistance of the two ceramics at high temperature was investigated. The oxidation process is very similar, i.e. the weight gain increases linearly at primary stage, and then tends to be constant with prolonging the oxidation time. The oxidation kinetic obeys the parabolic rate law. Inward diffusion of oxygen into ceramics and outward diffusion of metal cations is the main oxidation mechanism. Due to the variation of the content of the added rare earth oxide, the oxidation performance of the two Nd--sialon ceramics are also different.

Abstract: Nd--sialons with the stoichiometric composition of Nd0.333Si10Al¬2ON15 were obtained by hot-press sintering at 1800°C for 1h. The thermal shock behavior of the Nd--sialons was examined by a water-quenching technique. The influence of the thermal shock temperature difference (T) and cycle times on the residual strength was evaluated. Equiaxed -sialon grains formed together with a small amount of intergranular phase M (Nd2Si3-xAl¬xO3+xN4-x) and -sialon phase. The residual strength after a thermal shock tended to decrease gradually with increasing T above 500°C. However, the specimens exhibited an improved residual strength (~94% of the room temperature strength) after a thermal shock of T=1100°C. The residual strength presented a gradual decrease with increasing the thermal shock cycle times at T=1100°C, and was still remained ~55% of the room temperature strength after 11-time cycle. It is contributed to the surface oxidation which may results in the healing of surface cracks and the generation of surface compressive stresses.

Abstract: Series of multi-component glass systems of the following chemical composition SiO2-Na2O-CaO-Nd2O3 with an increasing of rare earth concentration, the effect of Nd2O3 on the optical properties of the glass systems is investigated. On the basis of the measure values of densities and refraction, Nd3+ ion concentration in glasses and several other physical properties were determined. The absorption coefficient, both direct and indirect optical energy gaps, and Urbach energy are evaluated using the absorption edge calculations. The different factors that play a role for controlling the refractive indices such as electronic polarizability, bridging and non-bridging oxygen, and optical basicity are discussed in accordance with the obtained index data. The non-crystalline phase identified basing on X-ray diffraction analysis.

Abstract: Fully dense ZrO2-TiN composites containing 1.75-2 mol %Y2O3, 1 mol% Y2O3 and 1 mol% Nd2O3 stabilizers, small amounts of Al2O3, and electrical conductive TiN particles (40-70 vol%) have been produced by hot pressing and spark plasma sintering at 1550°C. Although the intrinsic hardness of TiN (1400 kg/mm²) is higher than that of t-ZrO2 (1200 kg/mm²), the decreasing hardness trend can be attributed to the larger TiN grain size with the higher TiN content. Since TiN is more brittle, the fracture toughness decreases with increasing TiN content. Transformation toughening has been attributed as the main toughening mechanism as a result of fracture toughness decreasing with the transformability. Spark Plasma sintering temperature was too high for mechanical properties and hydrothermal stability of the mixed stabilized composites. The transformability decreases so hydrothermal stability increases linearly with increasing TiN content as a result of smaller volume fraction of t-ZrO2 grains becoming susceptible to hydrothermal transformation due to the shielding effect of the present TiN grains.