Key Engineering Materials Vol. 655

Abstract: Single phase LPS powders with nanosize particles were synthesized by a sol-gel process. Temperature and calcination temperature dependence of luminescence of the synthetic LPS:Ce powders were investigated under vacuum ultraviolet (VUV)-UV excitation. Luminescence intensity of LPS:Ce powders increase with calcination temperature, but it reaches the maximum at 1250 °C. Decay time of the LPS:Ce powders also slightly increasing from 27.1 to 30.5 ns as calcining temperature elevating. Both of them attribute to improved crystallization of LPS:Ce powders. Total luminescence intensity of LPS:Ce powder calcined at 1350 °C for 2 h has no noteworthy variation as the temperature rising in temperature 30-260 K range, this luminescence stability suggests that LPS:Ce would also be a good scintillator for high energy radiation detection in low temperature condition with temperature variation.

Abstract: LYSO:Ce crystal is one of efficient scintillation materials with high light output and short decay time. LYSO:Ce crystal grown by Czochralski method can be affected by annealing treatments. In present work, annealing treatments in different atmosphere (air, N₂ and H₂) were carried out on the LYSO:Ce crystals to investigate the effect on the optical and luminescence properties after annealing. The optical transmittance, excitation and emission spectrum, and the decay time have been attained at room temperature. Luminescence efficiency has been presented by the integrated area of emission spectra under ultraviolet (UV) excitation. It is found that annealing treatments almost do not affect the optical transmittance. Annealing in N₂ atmosphere has no noteworthy effect on the luminescence intensity of LYSO:Ce crystals, but increases much annealing in H₂ atmosphere, dramatically decreases the luminescence intensity after annealing in air. In addition, the decay time of LYSO:Ce crystals are affected by annealing treatment either in air or in H₂ atmosphere.

Abstract: SnS₂ nanoparticles with perfectly crystalline morphology were synthesized via a molten salt synthesis route at a relatively low temperature. The resulting SnS₂ nanoparcticles were characterized by X-ray diffraction (XRD), field scanning electron microscopy (FESEM), and UV-vis diffuse reflectance spectra (UV-vis). The observations of FESEM images showed that the sample consists of a large number of aggregates assembled with numerous nanoparticles packed into compact texture. The photocatalytic activity of the as-prepared SnS₂ samples was evaluated by the degradation of RhB aqueous solution. The effect of the molar ratio of thiourea to SnCl₂ on the photocatalytic activity was also investigated, and the result showed that the as-prepared SnS₂ sample has high photocatalytic activity efficiency in the degradation of RhB aqueous solution when the molar ratio of thiouea to SnCl₂ was 3.

Abstract: Spherical SrMoO₄:Eu³⁺ phosphors had been prepared by spray pyrolysis. The effect of the total solution concentration on phase structure, microscopic morphology and fluorescent performances of SrMoO₄: Eu³⁺ phosphor have been studied. The results showed that pure SrMoO₄ phase can be obtained at different total solution concentration; The luminous intensity of the sample was the strongest at 615nm when the total solution concentration is 0.6M. SrMoO₄: Eu³⁺ phosphor with regular spherical morphology, well dispersion and well fluorescent properties was synthesized successfully by spray pyrolysis method.

Abstract: Novel environment-friendly near-infrared reflective Y_5.2Nd_0.8MoO_12+σ pigments were fabricated by sol-gel and solid-state reaction routes, and the properties of both pigments were compared. The pigments were characterized by XRD, SEM, CIE-L*a*b* color-measurements, and UV-vis-NIR spectroscopy. The results show that pigments obtained by sol-gel routes crystallize completely at 900 °C, much lower than 1300 °C of solid-state reaction routes. Nano-size pigments fabricated by sol-gel routes possess an average grain size of ~ 50 nm, largely finer than 3 μm of solid-state reaction ones. Moreover, the sol-gel processed pigments show a higher near-infrared reflectance than solid-state reaction ones, which are 98.3 % and 91.7 %, respectively, but with a slightly light yellow color hue.

Abstract: Green pigments have been synthesized. Sodium silicate, chromium oxide, lithium carbonate and quartz were used as the main raw materials to prepare (Na_0.4Li_0.6)CrSi₂O₆ emerald green pigments by solid state reaction under the non-reductive conditions. The effects of the various technological conditions, such as raw materials ratios of (Na_0.4Li_0.6)/Cr/Si, calcination temperature, holding time and the type of mineralizers, on the color presentation of the synthesized pigments were studied. XRD and SEM were employed to analyze the crystalline and structure of the synthesized pigments. Chroma value was used to characterize the color of the pigments. The results show that the optimized (Na_0.4Li_0.6)CrSi₂O₆ pigments with chroma value of L*=57.78, a*=-18.98~-18.68 and b* = 10.88~9.01 were obtained.

Abstract: To meet the requirement of ceramic pigment for ink jet printing, CoAl₂O₄ pigment was prepared by nitrate-glycine method. The effect of nitrate/glycine ratio, calcination temperature and organic sacrificial agent on the particle size and chroma of the blue pigment were considered. The results show that the particle size of the pigment increases with the increase of glycine in the ratio and the decrease of the calcination temperature. However, the increase of the calcination temperature results in the broadening of the particle size distribution of the pigment. The addition of the organic sacrificial agent contributes to decrease the particle size of the pigment, which is about 2.0 μm. The chroma of the pigment is L*=47.62、a*=9.49、b*=-51.41. The blue pigment can be used in ink jet printing.

Abstract: Single-phase ytterbium sulfides (Yb₂S₃ and YbS) were synthesized by sulfurization of Yb₂O₃ with CS₂ gas and heat treatments. Four kinds of Yb₂O₃ powders with different particle sizes and specific surface areas were employed as starting materials. When specific surface area of Yb₂O₃ powder is about 50 m²/g, a new polymorphic form Yb₂S₃ with an orthorhombic structure could be obtained by the sulfurization at 600°C for 8 hr. Single-phase hexagonal Yb₂S₃ was also synthesized form former three kinds of Yb₂O₃ powders by sulfurization above 1000 °C for 8 hr. Subsequently, the synthesized Yb₂S₃ powders were heat-treated under different conditions. Upon heat treatment at 1000 °C for 3 hr in Ar/CS₂ atmosphere, orthorhombic Yb₂S₃ phase underwent phase transition to hexagonal Yb₂S₃ phase. Moreover, XRD results showed that orthorhombic Yb₃S₄ was main phase after heat treatment at 1050°C for 8 hr under Ar atmosphere and Yb₂S₃ disappeared upon prolonged (12 hr) heat treatment. Single Yb₃S₄ phase could be obtained after treatment at 1000 °C for 3 hr, or at 1200 °C for 1 hr, under vacuum (~1.2×10^-3 Pa). YbS was formed upon treatment at 1200 °C for 5 hr. Single-phase YbS with a homogeneity range of YbS_1.11-1.15 could be synthesized by treatment at 1500 °C for 3 hr. PartialYb₂S₃ transformed to Yb₃S₄ at 1300 °C for 1 hr by spark plasma sintering.

Abstract: Effects of Ni sheath on the microstructure, mechanical properties and bubbling phenomenon during heating process of BSCCO-2223 ceramic tapes have been investigated. Ni sheath gives Bi-2223 tapes a better ability to protect ceramic core from the damage of external force. Hardness of Ni sheath is double than that of Ag sheath reached to about 70 HV. Tensile strength of the Ni-sheathed Bi-2223 tapes is also enhanced by 80%. Harder Ni sheath is also beneficial to improve the texture of the tapes. However, serious bubbling phenomenon, which can reduce the transport property of tapes, will appear during heating process owing to the bad oxygen permeability of Ni. A lower heating rate (30°C/h) is a favorite to decrease the number and size of bubbles. In addition, Ni sheath can reduce the formation rate of Bi-2223 phase which implies that longer sintering time and higher cost of fabrication will be consumed.

Abstract: The Na₂O-CaO-SiO₂-MgO-Al₂O₃-ZnO glass-ceramics was prepared from the phosphorus slag as main primary raw materials by melt quenching technique. The effects of K₂O and Al₂O₃ on crystallization behavior and structure of glass-ceramics were investigated by DSC, XRD and SEM. It is shown that the main crystalline phase is combeite (Na₄Ca₄(Si₆O₁₈)) in glass-ceramics. K₂O and Al₂O₃ do not change the main crystalline phase of glass-ceramics, but K₂O increases the crystallization temperature, Al₂O₃ increases the crystallization temperature, obviously decreases the grain size. The K₂O isometric replaces Na₂O at the same time the Al₂O₃ isometric to replace SiO₂, reduced the grain size.