Effect of Ga_2O_3 on Structure and Properties of Calcium Aluminate Glasses

The effect of Ga_2O_3 on the structure and properties of calcium aluminate glasses fabricated by vacuum melting process was investigated by Raman spectrum, differential scanning calorimeter（DSC）, and infrared spectrum methods. The results show that calcium aluminate glass network only consists of [AlO_4] tetrahedral units. With the gradual addition of Ga_2O_3, the quantity of [GaO_4] tetrahedral units increases. Substitution of Ga_2O_3 for Al_2O_3 results in a decrease in Tg, Tx, and Tp, and an increase in the thermal stable index ΔT. Similarly, the absorption band around 3.0 μm obviously reduces and the transparency in 4.0-6.0 μm rapidly increases with increasing Ga_2O_3 content. However, the chemical stability of calcium aluminate glasses decreases if Ga_2O_3 is introduced due to the increasing of [GaO_4] units in the glass network.

Impact of shadow glass transition on crystallization in metallic glass

The stability of glass against crystallization is of importance in practical applications and theoretical understanding of the nature of glass materials.Annealing has complicated influences on glass stability.It induces either delayed or early crystallization,depending on detailed protocols and specific materials.By interrogating the thermal behaviors of twelve metallic glasses(MGs),we find that enhanced stability is correlated to another process:the so-called shadow glass transition and its evolution.Delayed crystallization can be observed when the shadow glass transition is shifted to cross the temperature of crystallization.Concurrently,the shadow glass transition evolves to an enthalpy overshoot.Molecular dynamics simulations support these findings and suggest that the suppressed string-like motion,relating to the shadow glass transition and the enthalpy overshoot,is likely the origin of the postponed nucleation ordering and enhanced glass stability.

Thermal stability and optical properties of a novel Tm^(3+) doped fluorotellurite glass

A series of fluorotellurite glasses based on（81–x）Te O2-（10＋x）KF-9La2O3（TKL）, where x=0 mol.%, 5 mol.%, 10 mol.%, 15 mol.%, doped with 2000 ppm Tm2O3, were prepared by the conventional melt quenching method.The influence of KF content on the thermal stability and optical spectroscopic properties of the Tm3＋ doped fluorotellurite glasses were investigated by differential scanning calorimetry（DSC）, X-ray diffraction（XRD）, density measurement, Fourier transform infrared spectroscopy（FTIR）, UV-VIS-NIR optical spectroscopy and fluorescence spectroscopy.Judd-Ofelt intensity parameters of Tm3＋ in as-prepared glasses were determined and used to calculate the spontaneous emission probabilities and the radiative lifetime for the 4f-4f transitions of the Tm3＋ ions.Stimulated emission cross sections in the 1470 nm region（σse） were evaluated by Füchtbauer-Ladenburg formula.The results showed that KF substitution of Te O2 was beneficial to improving the thermal stability, decreasing glass density and reducing the content of OH related groups for the investigated fluorotellurite glasses.The glass with composition of 66 Te O2-25KF-9La2O3（named TKL25） had the longest radiative lifetime of the 3H4（361 μs） and the largest FWHM×σse value（420.07×10–28 cm3）, which made it a promising material for S-band fiber amplifiers.

Influence of alkali metal ions on thermal stability of Bi-activated NIR-emitting alkali-aluminoborosilicate glasses

We study the influence of alkali oxides on the near-infrared（NIR）-emitting thermal stability of Bi-doped R2O–Si O2–B2O3–Al2O3（R = Li, Na, K） glasses below Tg. Results show that undergoing heat treatment, remarkable luminescence quenching occurs for the glasses containing Na2 O and K2 O due to the formation of Bi metallic colloids, whereas the glass with Li2 O shows much better thermal stability. These changes can be understood by the tendency of modifier cations with lower mobility and higher tightness network to restrain the transport of Bi-related NIR-emitting centers. The results provide a scientific reference for composition design of Bi-doped optical fiber.

Treatment method of hazardous pickling sludge by reusing as glass–ceramics nucleation agent

Heavy metal containing pickling sludge（PS） is one of the by-products of the stainless-steel-making industry,which has been considered hazardous due to contained chromium and nickel.Traditional methods of PS disposing are landfill and cement solidification.This research is aimed at disposing PS by solidification/stabilization and reusing it as a nucleation agent of glass–ceramics.The crystallization behavior and the properties of a glass in the CaO–MgO–SiO2–Al2O3 system were studied by considering PS as the nucleation agent.Experimental results confirm that introducing 14 wt% PS as the nucleation agent of glass–ceramics can decrease crystallization temperature by 110.8 °C,refine the grain size by forming isometric crystals with size of 2 lm,enhance Vickers hardness by 2690 MPa and decrease water absorption from（1.21 ± 0.10） wt% to（0.04 ± 0.01） wt%.Therefore,it is reasonable to conclude that PS can be utilized as a nucleation agent to improve the crystallization and mechanical properties of the glass–ceramics.The testing results of US EPA toxicity characteristic leaching procedure（TCLP）confirm the safety of this reusing method.

Thermal and radiative characteristics of oxyfluoride glass singly doped with lanthanide ions

Rare earths-doped oxyfluoride glasses based on germanium oxide and lead fluoride were prepared from commercial raw materials. The glasses with general composition of 50GeO2-(50-x-y)PbO-yPbF2-xLnF3 (Ln=Pr3+-Yb3+), contained different concentrations of optically active dopants (x=0.2 mol.% and 2 mol.%) and PbF2 (y≤15 mol.%). The differential thermal analysis (DTA) was used to determine both thermal characteristic and thermal stability properties of the glasses in the function of the kind of dopant, its concentration, and a glass composition. Characteristic glass temperatures such as glass transition temperature (Tg), glass crystallization temperature (Tc) and temperature corresponding to the maximum of the crystallization rate (Tpc) were evaluated. On the basis of obtained results, the thermal stabilities of glasses under study were evaluated using various thermal stability criteria (Dietzel factor ?T, Saad-Poulain factors H’ and S). It was found that the increase in rare earth fluoride contents influenced thermal characteristics when the characteristic temperatures of the individual glass was shifted towards higher values. The effect of the PbF2 content and the kind of rare earth impurity on the glass stability was observed. Absorption spectra of lanthanide-doped glasses were measured at room temperature and used to determine the phenomenological intensity parameters Ωt and next, to estimate radiative properties of lanthanide ions in this matrix. Radiative transition probabilities of luminescent states of Ln3+, branching ratios and radiative lifetimes were determined. The variation of the Ωt along the lanthanide series was presented and discussed.