Dan Yu Jiang

Fabrication and Spectroscopic Investigation of La2Hf2O7-Based Phosphors

Phase-pure crystalline La2Hf2O7 doped with activators were directly synthesized through combustion process and glycine as a fuel. The basic luminescent properties of Eu, Tb, Pr, Ce or Ti in La2Hf2O7 were investigated. Luminescence was not observed in La2Hf2O7:Ce, probably due to the luminescence of Ce being completely quenched by the impurities in La2Hf2O7. All the other activators doped La2Hf2O7 samples show bright luminescence under UV excitation.

Luminescent Properties of Eu3+-Doped HfO2 Powders Prepared by Combustion

Scintillators are ideal candidates used in detectors for X-ray ,γ-ray and high energy ray , and have been widely applied in nuclear medicine , high energy physics ,geologic survey , security inspection and material flaw detection. The high density of HfO2 is an attractive compound for host lattice activated by rare earth for applications as scintillating materials. This paper reported the synthesis of Eu3+ doped HfO2 nanopowders by chemical self-combustion method at low temperature. Analytical grade Eu(NO3)3 and high pure HfOCl2 were used as raw materials. The requisite amount of urea and glycine as the mixed fuel were added to the mixed solution. A little EDTA was used as a complexant. The mixed solution was dried at 200°C, and fired at 450°C. The powders synthesized by self-combustion were then calcined at 800°C to profit the crystal growth and improve the luminescent properties. XRD, TEM were employed to analyze the phase composition and the characteristics of as-obtained powders. The TEM images display typical nano-structured morphology of Eu3+ doped HfO2. Analysis of XRD indicates that Eu3+ doped HfO2 nanopowders are cubic phase. The excitation and emission spectra were analyzed by the fluorescence photometer. There are two peaks in emission spectra .One is at 595nm, and another is at 614nm. The luminescent properties also reveal the structure of cubic phase.

Combustion Synthesis of Nanosized Y2Hf2O7 and Lu2Hf2O7 Powders

Y2Hf2O7 and Lu2Hf2O7 precursor powders are prepared by nitrate solution combustion method with various fuels at 450°C, respectively. Phase evolution of the synthesized powders was determined by X-ray diffraction (XRD) techniques. Single-phase cubic Y2Hf2O7 and Lu2Hf2O7 crystalline powders were obtained by calcining the resultant combustion ash at 800°C for 2h. By controlling the pH of the nitrate solution, the type of fuel and the ratio of fuel/nitrate, nanosized powders can be obtained. The crystallite size of resultant powders is much related to the combustion flame temperature, which can be controlled by controlling the type of fuel and adjusting the fuel-to-oxidizer ratio. The influence of the ratio of reactants and the type of fuel on the properties of the final products was investigated. The crystal size and morphology were analyzed by TEM.

Measuring Mechanical Properties of Zirconia Dental Crowns by Nanoindentation

Mechanical properties of dental materials are increasingly studied via nanoindentation testing. Due to the excellent mechanical properties, 3-mol%-Yttria-Stabilized Tetragonal Zirconia (3Y-TZP) has become an attractive high-toughness core material for fixed dental restorations. In this paper, the mechanical properties of 3Y-TZP were studied by nanoindentation. The continuous stiffness measurement (CSM) and the single load/unload cycle test controlled by displacement and load respectively were performed with a Berkovich indenter.

The Anti-Erosion Properties of Pyrochlore Simulated Waste Forms

MCC-1 static short-term corrosion tests were performed to pyrochlore simulated waste forms in deionized water, at 90°C. Experimental results show that pyrochlore simulated waste forms has a good anti-leaching property. Both the normalized mass loss rate and the normalized mass loss of element Ce decrease with soaking time increasing in the short test. The corrosion process is co-dominated by the leaching agent and the corrosion temperature.

Corrosion Behaviors of Borosilicate Glasses in Various Leaching Agents

Static short-term corrosion tests were performed to two kinds of borosilicate glasses in deionized water, at 70°C and 150°C, respectively. Same corrosion experiments were also carried out in other leaching agents, such as simulated under ground water of Beishan, sulfuric acid solution (pH=0.5) and potassium hydroxide solution (pH = 13). Experimental results show that both leaching agent and corrosion temperature co-dominate the corrosion process, and the temperature plays more important role. At low temperature of 70°C, the corrosion reaction is controlled by the ion diffusing in DIW at earlier stage. While in PHS, network hydrolysis reaction is the main corrosion mechanism.

The Exploring Research of the Determination Method of Magnesium Oxide Hydration

Magnesium oxide is one of the most important raw materials in the refractory industry due to its high melting point (2800oC), corrosion resistance in the basic environment, and low cost. Nevertheless, magnesium oxide reacts easily with water to produce magnesium hydrate, which is followed by a large volumetric expansion, limiting its application in refractory industry. As the hydration of MgO is very important either in theory or in industrial production of magnesium, in this paper, the influence of temperature, residence time, as well as the impact of the solid content on MgO hydration and the kinetics of hydration reaction was evaluated to optimize the determination method of magnesium oxide hydration in refractory industry.

Synthesis of Ultrafine Lu2Hf2O7/Tb Phosphor by Solution Combustion Process

Ultrafine terbium-doped Lu2Hf2O7/Tb phosphor powders are prepared by a solution combustion process using glycine and urea as fuel. Phase evolution of the synthesized powder is determined by X-ray diffraction (XRD) techniques. Single-phase cubic Lu2Hf2O7/Tb crystalline powder is obtained by calcining the amorphous materials at 800oC and no intermediate phase is observed. Transmission electronic microscope (TEM) morphology shows that the resultant Lu2Hf2O7/Tb powders have uniform size and good homogeneity. The photoluminescence (PL) spectra of Tb3+ substituted for Lu3+ in Lu2Hf2O7 with different content has been measured on samples calcined at 1000oC.

Synthesis and Photo-Catalytic Performance of ZnO/Graphene Composites

Zinc acetate dehydrate and Graphene oxide (GO) were employed as raw materials, the ZnO/Graphene composites were simply and quickly synthesized by solvothermal reaction at 180°C for 12 h. The phase structure and morphologies of the as-obtained composites were characterized and observed by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). Using RhB solution simulated dye wastewater, the composites’ photo-catalytic performance were preliminary tested and observed with the visible light irradiation. The results indicated that the concentrations of zinc acetate and the mass ratio of zinc acetate dihydratio and graphene oxide all had an impact on the photo-degradation rate. The photo-degradation rate of the composites prepared with the concentrations of zinc acetate of 0.01 mol/L was higher than that of zinc acetate of 0.001 mol/L. The mass ratio of zinc acetate dehydratio and graphene oxide of 4:1 was higher than that of 8:1.

Structure and Luminescence Characteristics of Terbium Hydroxide Nanosheets Doped with Eu3

Eu3+ doped terbium hydroxide nanosheets were successfully synthesized from layer compound of Tb2(OH)5NO3·1.5H2O doped by Eu3+. Firstly layer compound of Tb2(OH)5NO3·1.5H2O doped by Eu3+ was obtained by hydrothermal reaction at 1200 . After ion exchange reaction with SDS under the microwave condition, the layer space of the compound increases from 0.907 nm to 2.34 nm. Furthermore stable nanosheet sol was obtained after exfoliation under ultrasonic condition. At the mean time we discovered that microwave and ultrasonic method can greatly shorten the preparation time. The structure of layer compound and the morphology of nanosheets were determined by XRD and TEM. The luminescence properties of terbium hydroxide nanosheets doped with Eu3+ were examined; the relationship between structure and spectra was discussed