Upconversion and Near Infrared Emission of Rare Earth Ions in Chalcohalide Glass at the Early Stage of Crystallization

Nd^(3+),Er^(3+)ions doped 0.9(Ge_(0.25)Ga_(0.10)S_(0.65))-0.1CsBr chalcohalide glass were prepared via melt-quenching method,and heat treated at 360℃ in high purity Ar gas atmosphere for different hours for the early stage of crystallization.The effect of heat treatment durations on visible upconversion luminescence and near infrared emission from Nd^(3+)ions and Er^(3+)ions were investigated.The specimens kept amorphous status until the heat treatment duration extended to 10 hours,for Ga_(2)S_(3) nano-crystal formation in glass matrix.The stark splitting in visible upconversion luminescence center at 600 nm from Nd^(3+)ions weakened,and disappeared,and the shape of infrared emission centered at 1550 nm from Er^(3+)ions changed,with the heat treatment duration increased.The lifetime of Nd^(3+):^(4)F_(3/2) level and Er^(3+):^(4)I_(13/2) level dropped,then increased with heat treatment duration increased.X-ray diffraction patterns and transmission electron microscope images confirmed the amorphous state and Ga_(2)S_(3) nano-crystals formation in glass matrix.The rare earth ions local environment changes with heat treatment duration were proposed,based on the emission and lifetime changes.This research will be helpful for the understanding of rare earth doped chalcohalide crystallization mechanism and processes.

The Curing for Modified Vinyl Ester Resin by Hexamethylene Diisocyanate and Its Influence on Performances

The commercial vinyl ester resins(VER)was modified by diphenylmethane diisocyanate(MDI)to enhance its toughness,which is called MVER.Hexamethylene diisocyanate(HDI),a common curing agent for polyurethane(PU),was found to be a reactive agent for MVER and can contribute to the toughness of MVER.Based on present experiment results,the crosslinking mechanism of MVER and HDI system is very similar to that of PU.The FTIR result shows the-NCO of HDI can react with the-OH of MVER.The microstructure of material prepared by MVER and HDI was characterized by NMR,and it was revealed that the unique microstructure leads to the good performances.The different content of HDI has an influence on the microstructure,and the microstructure gradually reduces the toughness and mechanical performances of the MVER cured with increasing concentration of reactive curing agent(HDI).This feature is consistent with a maximum in toughness as a function of the additive(HDI)content,followed by a rapid deterioration in toughness at higher concentrations.The toughness exhibits the maximum at such an HDI concentration(20wt%).Therefore,the special curing agent(HDI)and reactive mode is very important to the microstructure and mechanical properties of material.Furthermore,there should be other reactions which contribute to the curing and microstructure of the material,which needs the further research.